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Sample records for carbon molecular sieves

  1. Carbon fiber composite molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, T.D.; Rogers, M.R.; Williams, A.M.

    1996-06-01

    The removal of CO{sub 2} is of significance in several energy applications. The combustion of fossil fuels, such as coal or natural gas, releases large volumes of CO{sub 2} to the environment. Several options exist to reduce CO{sub 2} emissions, including substitution of nuclear power for fossil fuels, increasing the efficiency of fossil plants and capturing the CO{sub 2} prior to emission to the environment. All of these techniques have the attractive feature of limiting the amount of CO{sub 2} emitted to the atmosphere, but each has economic, technical, or societal limitations. In the production of natural gas, the feed stream from the well frequently contains contaminants and diluents which must be removed before the gas can enter the pipeline distribution system. Notable amongst these diluent gasses is CO{sub 2}, which has no calorific value. Currently, the pipeline specification calls for <2 mol % CO{sub 2} in the gas. Gas separation is thus a relevant technology in the field of energy production. A novel separation system based on a parametric swing process has been developed that utilizes the unique combination of properties exhibited by our carbon fiber composite molecular sieve (CFCMS).

  2. Coal-based carbons with molecular sieve properties

    Energy Technology Data Exchange (ETDEWEB)

    El-Wakil, A.M.; Youssef, A.M.; Tollan, K.A. (Mansoura Univ. (Egypt))

    1991-01-01

    Carbon molecular sieves are used extensively in gas chromatography for the separation of permanent gases and light hydrocarbons. Carbon molecular sieves also find commercial application for the manufacture of pure hydrogen from hydrogen-rich gases such as coke-oven gas, and for the separation of air by the pressure-swing adsorption technique. The objective of this investigation was to prepare carbons from Maghara coal, recently available on the commercial market. Coal-based carbons, if they possess molecular sieve properties, are superior to molecular sieve carbons from agricultural by-products because they have more satisfactory mechanical properties.

  3. Copper modified carbon molecular sieves for selective oxygen removal

    Science.gov (United States)

    Sharma, Pramod K. (Inventor); Seshan, Panchalam K. (Inventor)

    1992-01-01

    Carbon molecular sieves modified by the incorporation of finely divided elemental copper useful for the selective sorption of oxygen at elevated temperatures. The carbon molecular sieves can be regenerated by reduction with hydrogen. The copper modified carbon molecular sieves are prepared by pyrolysis of a mixture of a copper-containing material and polyfunctional alcohol to form a sorbent precursor. The sorbent precursors are then heated and reduced to produce copper modified carbon molecular sieves. The copper modified carbon molecular sieves are useful for sorption of all concentrations of oxygen at temperatures up to about 200.degree. C. They are also useful for removal of trace amount of oxygen from gases at temperatures up to about 600.degree. C.

  4. Copper crystallite in carbon molecular sieves for selective oxygen removal

    Science.gov (United States)

    Sharma, Pramod K. (Inventor); Seshan, Panchalam K. (Inventor)

    1993-01-01

    Carbon molecular sieves modified by the incorporation of finely divided elemental copper useful for the selective sorption of oxygen at elevated temperatures. The carbon molecular sieves can be regenerated by reduction with hydrogen. The copper modified carbon molecular sieves are prepared by pyrolysis of a mixture of a copper-containing material and polyfurfuryl alcohol to form a sorbent precursor. The sorbent precursors are then heated and reduced to produce copper modified carbon molecular sieves. The copper modified carbon molecular sieves are useful for sorption of all concentrations of oxygen at temperatures up to about 200.degree. C. They are also useful for removal of trace amount of oxygen from gases at temperatures up to about 600.degree. C.

  5. Carbon molecular sieves for air separation from Nomex aramid fibers.

    Science.gov (United States)

    Villar-Rodil, Silvia; Martínez-Alonso, Amelia; Tascón, Juan M D

    2002-10-15

    Activated carbon fibers prepared from aramid fibers have proved to possess outstanding homogeneity in pore size, most of all when Nomex aramid fiber is used as precursor. Taking advantage of this feature, microporous carbon molecular sieves for air separation have been prepared through carbon vapor deposition of benzene on Nomex-derived carbon fibers activated to two different burnoff degrees. Carbon molecular sieves with good selectivity for this separation and showing acceptable adsorption capacities were obtained from ACFs activated to the two burnoff degrees chosen. PMID:12702417

  6. Effect of processing on carbon molecular sieve structure and performance

    KAUST Repository

    Das, Mita

    2010-11-01

    Sub-micron sized carbon molecular sieve (CMS) materials were produced via ball milling for subsequent use in hybrid material formation. A detailed analysis of the effects of the milling process in the presence of different milling environments is reported. The milling process apparently alters the molecular scale structure and properties of the carbon material. Three cases: unmilled, air milled and nitrogen milled, were analyzed in this work. The property changes were probed using equilibrium sorption experiments with different gases. Furthermore, WAXD and BET results also showed differences between milling processes. Finally in order to improve the interfacial polymer-sieve region of hybrid membranes, the CMS surface was chemically modified with a linkage unit capable of covalently bonding the polymer to the sieve. A published single-wall carbon nanotube (SWCNTs) modification method was adopted to attach a primary aromatic amine to the surface. Several aspects including rigidity, chemical composition, bulky groups and length were considered in selecting the preferred linkage unit. Fortunately kinetic and equilibrium sorption properties of the modified sieves showed very little difference from unmodified samples, suggesting that the linkage unit is not excessively filling or obstructing access to the pores of the CMSs during the modification process. © 2010 Elsevier Ltd. All rights reserved.

  7. Production of carbon molecular sieves from Illinois coal

    Science.gov (United States)

    Lizzio, A.A.; Rostam-Abadi, M.

    1993-01-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for application in the separation of gas molecules that vary in size and shape. A study is in progress at the Illinois State Geological Survey to determine whether Illinois basin coals are suitable feedstocks for the production of CMS and to evaluate their potential application in gas separation processes of commercial importance. Chars were prepared from Illinois coal in a fixed-bed reactor under a wide range of heat treatment and activation conditions. The effects of various coal/char pretreatments, including coal demineralization, preoxidation, char activation, and carbon deposition, on the molecular sieve properties of the chars were also investigated. Chars with commercially significant BET surface areas of 1500 m2/g were produced by chemical activation using potassium hydroxide as the activant. These high-surface-area (HSA) chars had more than twice the adsorption capacity of commercial carbon and zeolite molecular sieves. The kinetics of adsorption of various gases, e.g., N2, O2, CO2, CH4, CO and H2, on these chars at 25??C was measured. The O2/N2 molecular sieve properties of one char prepared without chemical activation were similar to those of a commercial CMS. On the other hand, the O2/N2 selectivity of the HSA char was comparable to that of a commercial activated carbon, i.e., essentially unity. Carbon deposition, using methane as the cracking gas, increased the O2/N2 selectivity of the HSA char, but significantly decreased its adsorption capacity. Several chars showed good potential for efficient CO2/CH4 separation; both a relatively high CO2 adsorption capacity and CO2/CH4 selectivity were achieved. The micropore size distribution of selected chars was estimated by equilibrium adsorption of carbon dioxide, n-butane and iso-butane at O??C. The extent of adsorption of each gas corresponded to the effective surface area contained in pores with diameters greater than 3

  8. Carbon Molecular Sieve Membrane (CMSM) for Industrial Gas Separation

    Institute of Scientific and Technical Information of China (English)

    WANG Kean; Haraya Kenji

    2003-01-01

    Membrane separation is an environmental benign technology for 21st century, and is developing quickly to replace the conventional distillation process. Carbon molecular sieve membrane (CMSM) was synthesized through the controlled pyrolysis of polyimide films. The CMSM is symmetric in structure and presents strong sieving effect towards gas molecules of slightly different diameters. The microstructure of CMSM was manipulated through the thermal treatment program and further modified through activation vapor/chemical depositions. It is demonstrated that CMSM can be synthesized/modified for specific gas mixtures, such as O2/N2, CO2/CH4, C3H6/C3H8, and ect. The pore size distribution, relationship between the permeance & selectivity on CMSM for the separation of some gas pairs was also investigated.

  9. Use of Carbon Fiber Composite Molecular Sieves for Air Separation

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Frederick S [ORNL; Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL; Burchell, Timothy D [ORNL

    2005-09-01

    A novel adsorbent material, 'carbon fiber composite molecular sieve' (CFCMS), has been developed by the Oak Ridge National Laboratory. Its features include high surface area, large pore volume, and a rigid, permeable carbon structure that exhibits significant electrical conductivity. The unique combination of high adsorptive capacity, permeability, good mechanical properties, and electrical conductivity represents an enabling technology for the development of novel gas separation and purification systems. In this context, it is proposed that a fast-cycle air separation process that exploits a kinetic separation of oxygen and nitrogen should be possible using a CFCMS material coupled with electrical swing adsorption (ESA). The adsorption of O{sub 2}, N{sub 2}, and CO{sub 2} on activated carbon fibers was investigated using static and dynamic techniques. Molecular sieving effects in the activated carbon fiber were highlighted by the adsorption of CO{sub 2}, a more sensitive probe molecule for the presence of microporosity in adsorbents. The kinetic studies revealed that O2 was more rapidly adsorbed on the carbon fiber than N{sub 2}, and with higher uptake under equilibrium conditions, providing the fiber contained a high proportion of very narrow micropores. The work indicated that CFCMS is capable of separating O{sub 2} and N{sub 2} from air on the basis of the different diffusion rates of the two molecules in the micropore network of the activated carbon fibers comprising the composite material. In response to recent enquires from several potential users of CFCMS materials, attention has been given to the development of a viable continuous process for the commercial production of CFCMS material. As part of this effort, work was implemented on characterizing the performance of lignin-based activated carbon fiber, a potentially lower cost fiber than the pitch-based fibers used for CFCMS production to date. Similarly, to address engineering issues

  10. Carbon dioxide sorption in a nanoporous octahedral molecular sieve

    International Nuclear Information System (INIS)

    We have performed first-principles density functional theory calculations, incorporated with van der Waals interactions, to study CO2 adsorption and diffusion in nanoporous solid—OMS-2 (Octahedral Molecular Sieve). We found the charge, type, and mobility of a cation, accommodated in a porous OMS-2 material for structural stability, can affect not only the OMS-2 structural features but also CO2 sorption performance. This paper targets K+, Na+, and Ba2+ cations. First-principles energetics and electronic structure calculations indicate that Ba2+ has the strongest interaction with the OMS-2 porous surface due to valence electrons donation to the OMS-2 and molecular orbital hybridization. However, the Ba-doped OMS-2 has the worst CO2 uptake capacity. We also found evidence of sorption hysteresis in the K- and Na-doped OMS-2 materials. (paper)

  11. Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membranes

    Science.gov (United States)

    Koh, Dong-Yeun; McCool, Benjamin A.; Deckman, Harry W.; Lively, Ryan P.

    2016-08-01

    Liquid-phase separations of similarly sized organic molecules using membranes is a major challenge for energy-intensive industrial separation processes. We created free-standing carbon molecular sieve membranes that translate the advantages of reverse osmosis for aqueous separations to the separation of organic liquids. Polymer precursors were cross-linked with a one-pot technique that protected the porous morphology of the membranes from thermally induced structural rearrangement during carbonization. Permeation studies using benzene derivatives whose kinetic diameters differ by less than an angstrom show kinetically selective organic liquid reverse osmosis. Ratios of single-component fluxes for para- and ortho-xylene exceeding 25 were observed and para- and ortho- liquid mixtures were efficiently separated, with an equimolar feed enriched to 81 mole % para-xylene, without phase change and at ambient temperature.

  12. Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membranes.

    Science.gov (United States)

    Koh, Dong-Yeun; McCool, Benjamin A; Deckman, Harry W; Lively, Ryan P

    2016-08-19

    Liquid-phase separations of similarly sized organic molecules using membranes is a major challenge for energy-intensive industrial separation processes. We created free-standing carbon molecular sieve membranes that translate the advantages of reverse osmosis for aqueous separations to the separation of organic liquids. Polymer precursors were cross-linked with a one-pot technique that protected the porous morphology of the membranes from thermally induced structural rearrangement during carbonization. Permeation studies using benzene derivatives whose kinetic diameters differ by less than an angstrom show kinetically selective organic liquid reverse osmosis. Ratios of single-component fluxes for para- and ortho-xylene exceeding 25 were observed and para- and ortho- liquid mixtures were efficiently separated, with an equimolar feed enriched to 81 mole % para-xylene, without phase change and at ambient temperature. PMID:27540170

  13. Structure–performance characterization for carbon molecular sieve membranes using molecular scale gas probes

    KAUST Repository

    Rungta, Meha

    2015-04-01

    © 2015 Elsevier Ltd. All rights reserved. Understanding the relationship between carbon molecular sieve (CMS) pore structure and corresponding gas separation performance enables optimization for a given gas separation application. The final pyrolysis temperature and starting polymer precursor are the two critical parameters in controlling CMS performance. This study considers structure and performance changes of CMS derived from a commercially available polymer precursor at different pyrolysis temperatures. As reviewed in this paper, most traditional characterization methods based on microscopy, X-ray diffraction, spectroscopy, sorption-based pore size distribution measurements etc. provide limited information for relating separation performance to the CMS morphology and structural changes. A useful alternative approach based on different sized gases as molecular scale probes of the CMS pore structure was successfully used here in conjunction with separation data to provide critical insights into the structure-performance relationships of the engineered CMS.

  14. Carbon-fiber composite molecular sieves for gas separation

    Energy Technology Data Exchange (ETDEWEB)

    Jagtoyen, M.; Derbyshire, F.; Kimber, G.; Fei, Y.Q. [Univ. of Kentucky Center for Applied Energy Research, Lexington, KY (United States)

    1995-08-01

    The progress of research in the development of novel, rigid, monolithic adsorbent carbon fiber composites is described. Carbon fiber composites are produced at ORNL and activated at the CAER using steam or CO{sub 2} under different conditions, with the aims of producing a uniform degree of activation through the material, and of closely controlling pore structure and adsorptive properties The principal focus of the work to date has been to produce materials with narrow porosity for use in gas separations.

  15. Mesoporous molecular sieve catalysts

    DEFF Research Database (Denmark)

    Højholt, Karen Thrane

    This thesis deals with a very specific class of molecular sieves known as zeolites. Zeolites are a class of crystalline aluminosilicates characterised by pores or cavities of molecular dimensions as part of their crystal structure. In this work zeolites were modified for the use and understanding...

  16. Production of carbon molecular sieves from palm shell through carbon deposition from methane

    Directory of Open Access Journals (Sweden)

    Mohammadi Maedeh

    2011-01-01

    Full Text Available The possibility of production of carbon molecular sieve (CMS from palm shell as a waste lignocellulosic biomass was investigated. CMS samples were prepared through heat treatment processes including carbonization, physiochemical activation and chemical vapor deposition (CVD from methane. Methane was pyrolyzed to deposit fine carbon on the pore mouth of palm shell-based activated carbon to yield CMS. All the deposition experiments were performed at 800 ºC, while the methane flow rate (100, 200, 300 mL min-1 CH4 diluted in 500 mL min-1 N2 and deposition time (30 to 60 min were the investigated parameters. The textural characteristics of the CMSs were assessed by N2 adsorption. The largest BET surface area (752 m2 g-1, micropore surface area (902.2 m2 g-1 and micropore volume (0.3466 cm3 g-1 was obtained at the CH4 flow rate of 200 mL min-1 and deposition time of 30 min. However, prolonging the deposition time to 45 min yielded in a micropouros CMS with a narrow pore size distribution.

  17. Carbon-fiber composite molecular sieves for gas separation

    Energy Technology Data Exchange (ETDEWEB)

    Jagtoyen, M.; Derbyshire, F. [Univ. of Kentucky, Lexington, KY (United States)

    1996-08-01

    This report describes continuing work on the activation and characterization of formed carbon fiber composites. The composites are produced at the Oak Ridge National Laboratory (ORNL) and activated at the Center for Applied Energy Research (CAER) using steam, CO{sub 2}, or O{sub 2} at different conditions of temperature and time, and with different furnace configurations. The general aims of the project are to produce uniformly activated samples with controlled pore structures for specialist applications such as gas separation and water treatment. In previous work the authors reported that composites produced from isotropic pitch fibers weighing up to 25g can be uniformly activated through the appropriate choice of reaction conditions and furnace configurations. They have now succeeded in uniformly activating composites of dimensions up to 12 x 7 x 6 cm, or up to about 166 gram - a scale-up factor of about six. Part of the work has involved the installation of a new furnace that can accommodate larger composites. Efforts were made to achieve uniform activation in both steam and CO{sub 2}. The authors have also succeeded in producing materials with very uniform and narrow pore size distributions by using a novel method involving low temperature oxygen chemisorption in combination with heat treatment in N{sub 2} at high temperatures. Work has also started on the activation of PAN based carbon fibers and fiber composites with the aim of producing composites with wide pore structures for use as catalyst supports. So far activation of the PAN fiber composites supplied by ORNL has been difficult which is attributed to the low reactivity of the PAN fibers. As a result, studies are now being made of the activation of the PAN fibers to investigate the optimum carbonization and activation conditions for PAN based fibers.

  18. Fabrication variables affecting the structure and properties of supported carbon molecular sieve membranes for hydrogen separation

    KAUST Repository

    Briceño, Kelly

    2012-10-01

    A high molecular weight polyimide (Matrimid) was used as a precursor for fabricating supported carbon molecular sieve membranes without crack formation at 550-700°C pyrolysis temperature. A one-step polymer (polyimide) coating method as precursor of carbon layer was used without needing a prior modification of a TiO 2 macroporous support. The following fabrication variables were optimized and studied to determine their effect on the carbon structure: polymeric solution concentration, solvent extraction, heating rate and pyrolysis temperature. Two techniques (Thermogravimetric analysis and Raman spectroscopy) were used to determine these effects on final carbon structure. Likewise, the effect of the support was also reported as an additional and important variable in the design of supported carbon membranes. Atomic force microscopy and differential scanning calorimetry quantified the degree of influence. Pure gas permeation tests were performed using CH 4, CO, CO 2 and H 2. The presence of a molecular sieving mechanism was confirmed after defects were plugged with PDMS solution at 12wt%. Gas selectivities higher than Knudsen theoretical values were reached with membranes obtained over 650°C, showing as best values 4.46, 4.70 and 10.62 for H 2/N 2, H 2/CO and H 2/CH 4 ratio, respectively. Permeance values were over 9.82×10 -9mol/(m 2Pas)during pure hydrogen permeation tests. © 2012 Elsevier B.V.

  19. Sorbate Transport in Carbon Molecular Sieve Membranes and FAU/EMT Intergrowth by Diffusion NMR

    OpenAIRE

    John J. Low; Sesh Prabhakar; Sergey Vasenkov; Douglas B. Galloway; Mayumi Kiyono-Shimobe; Steven A. Bradley; Koros, William J.; Amrish Menjoge; Rohit Kanungo; Robert Mueller

    2012-01-01

    In this paper we present and discuss selected results of our recent studies of sorbate self-diffusion in microporous materials. The main focus is given to transport properties of carbon molecular sieve (CMS) membranes as well as of the intergrowth of FAU-type and EMT-type zeolites. CMS membranes show promise for applications in separations of mixtures of small gas molecules, while FAU/EMT intergrowth can be used as an active and selective cracking catalyst. For both types of applications diff...

  20. Solid-phase reversible trap for [ sup 1 sup 1 C]carbon dioxide using carbon molecular sieves

    CERN Document Server

    Mock, B H; Mulholland, G T

    1995-01-01

    A simple, maintenance-free trapping technique which concentrates and purifies no-carrier-added sup 1 sup 1 CO sub 2 from gas targets is described. The trap requires no liquid nitrogen cooling and has no moving parts besides solenoid valves. It employs carbon molecular sieves to adsorb sup 1 sup 1 CO sub 2 selectively from gas targets at room temperature. Nitrogen, O sub 2 , CO, NO and moisture in the target gas which could interfere with subsequent radiochemical steps are not retained. Trapping efficiency of 1 g of sieve for sup 1 sup 1 CO sub 2 from a 240 cm sup 3 target gas dump and helium flush cycle is <99%, and the adsorbed sup 1 sup 1 CO sub 2 is recovered quantitatively as a small concentrated bolus from the carbon sieve trap by thermal desorption. This durable trap has performed reliably for more than 1 y with a single charge of carbon sieve. It has simplified the production, and improved the yields of several sup 1 sup 1 C-radiochemicals at this laboratory.

  1. Carbon molecular sieve membranes derived from Matrimid® polyimide for nitrogen/methane separation

    KAUST Repository

    Ning, Xue

    2014-01-01

    A commercial polyimide, Matrimid® 5218, was pyrolyzed under an inert argon atmosphere to produce carbon molecular sieve (CMS) dense film membranes for nitrogen/methane separation. The resulting CMS dense film separation performance was evaluated using both pure and mixed N2/CH4 permeation tests. The effects of final pyrolysis temperature on N 2/CH4 separation are reported. The separation performance of all CMS dense films significantly exceeds the polymer precursor dense film. The CMS dense film pyrolyzed at 800 C shows very attractive separation performance that surpasses the polymer membrane upper bound line, with N 2 permeability of 6.8 Barrers and N2/CH4 permselectivity of 7.7 from pure gas permeation, and N2 permeability of 5.2 Barrers and N2/CH4 permselectivity of 6.0 from mixed gas permeation. The temperature dependences of permeabilities, sorption coefficients, and diffusion coefficients of the membrane were studied, and the activation energy for permeation and diffusion, as well as the apparent heats of sorption are reported. The high permselectivity of this dense film is shown to arise from a significant entropic contribution in the diffusion selectivity. The study shows that the rigid \\'slit-shaped\\' CMS pore structure can enable a strong molecular sieving effect to effectively distinguish the size and shape difference between N2 and CH4. © 2013 Elsevier Ltd. All rights reserved.

  2. A Pilot-Scale System for Carbon Molecular Sieve Hollow Fiber Membrane Manufacturing

    KAUST Repository

    Karvan, O.

    2012-12-21

    Carbon molecular sieve (CMS) membranes offer advantages over traditional polymeric membrane materials, but scale-up of manufacturing systems has not received much attention. In the recent decade, there has been a dramatic increase in fundamental research on these materials with a variety of applications being studied. The results from a pilot-scale CMS production system are presented. This system was designed based on extensive laboratory research, and hollow fiber membranes produced in this system show similar performance compared to membranes produced using a smaller bench-scale system. After optimizing the system design, a 93% recovery of the precursor fibers for use in membrane module preparation were obtained. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Correlation Between Pyrolysis Atmosphere and Carbon Molecular Sieve Membrane Performance Properties

    KAUST Repository

    Kiyono, Mayumi

    2011-01-01

    Carbon molecular sieve (CMS) membranes have attractive separation performance properties, greatly exceeding an "upper bound" trade-off curve of polymeric membrane performance. CMS membranes are prepared by pyrolyzing polymers, well above their glass transition temperatures. Multiple factors, such as polymer precursor and pyrolysis protocol, are known to affect the separation performance. In this study, a correlation observed between pyrolysis atmosphere and CMS separation performance properties is discussed. Specifically, oxygen exposure during the pyrolysis process is the focus. The theory and details of the oxygen exposure and development of a new CMS preparation method using oxygen as a "dopant" will be described with a strong correlation observed with separation performance for CMS membranes prepared with various polymer precursors. In addition, study of possible mass transfer limitations on the oxygen "doping" process will be described to clarify the basis for the equilibrium-based interpretation of doping data. The method is also explored by changing the pyrolysis temperature. © 2011 Elsevier B.V.

  4. Production of carbon molecular sieves from Illinois coal. Technical report, March 1, 1994--May 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Lizzio, A.A.; Rostam-Abadi, M.; Feizoulof, C.A.; Vyas, S.N.

    1994-09-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois coal is a suitable feedstock for the production of CMS and to evaluate the potential application of the products in commercial gas separation processes. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II, the optimal char preparation conditions determined in Phase I are being applied to production of larger quantities of CMS in a 2 in. ID batch fluidized-bed reactor (FBR) and a 4 in. ID continuous rotary tube kiln (RTK). In the previous reporting period, an invention disclosure describing a novel CMS preparation technique (oxygen deposition) was prepared and submitted to Research Corporation Technologies for evaluation. During this reporting period, work continued on the development of the oxygen deposition process. Carbon deposition as a means to narrow pore size was also investigated. Pound quantities of CMS were prepared from IBC-102 coal in the TRK. A meeting was arranged between the ISGS and Carbo Tech Industieservice GmbH, one of two companies in the world that produce CMS from coal, to discuss possible shipment of Illinois coal to Germany for CMS production. A secrecy agreement between the ISGS and Carbo Tech is in preparation. Several large scale char production runs using Industry Mine coal were conducted in an 18 in. ID batch and 8 in. ID continuous RTK at Allis Mineral Systems, Milwaukee, WI. The molecular sieve properties of the chars have yet to be determined.

  5. Microwave regeneration of molecular sieves

    International Nuclear Information System (INIS)

    Molecular sieve driers have been included in the design of tritium handling systems for fusion reactors. In these systems there is a need to maintain extremely low exit dew points from the driers as well as a capability to rapidly reduce tritium concentrations following an accident. The required capacity of the driers is very high. The conventional method of regenerating these sieves after a water adsorption cycle is with hot air. However, because water is rapidly heated by microwave energy, this technology may be suitable for decreasing the bed regeneration time and hence may allow reduced capital and operating costs associated with a smaller bed. The present study was conducted to obtain preliminary information on the technical feasibility of regenerating molecular sieves with microwave energy. The study concentrated on Type 4A molecular sieve with a few tests on Type 13X sieve and also a silica gel adsorbent

  6. Sorbate Transport in Carbon Molecular Sieve Membranes and FAU/EMT Intergrowth by Diffusion NMR

    Directory of Open Access Journals (Sweden)

    John J. Low

    2012-02-01

    Full Text Available In this paper we present and discuss selected results of our recent studies of sorbate self-diffusion in microporous materials. The main focus is given to transport properties of carbon molecular sieve (CMS membranes as well as of the intergrowth of FAU-type and EMT-type zeolites. CMS membranes show promise for applications in separations of mixtures of small gas molecules, while FAU/EMT intergrowth can be used as an active and selective cracking catalyst. For both types of applications diffusion of guest molecules in the micropore networks of these materials is expected to play an important role. Diffusion studies were performed by a pulsed field gradient (PFG NMR technique that combines advantages of high field (17.6 T NMR and high magnetic field gradients (up to 30 T/m. This technique has been recently introduced at the University of Florida in collaboration with the National Magnet Lab. In addition to a more conventional proton PFG NMR, also carbon-13 PFG NMR was used.

  7. Carbon molecular sieve gas separation membranes based on an intrinsically microporous polyimide precursor

    KAUST Repository

    Ma, Xiaohua

    2013-10-01

    We report the physical characteristics and gas transport properties for a series of pyrolyzed membranes derived from an intrinsically microporous polyimide containing spiro-centers (PIM-6FDA-OH) by step-wise heat treatment to 440, 530, 600, 630 and 800 C, respectively. At 440 C, the PIM-6FDA-OH was converted to a polybenzoxazole and exhibited a 3-fold increase in CO2 permeability (from 251 to 683 Barrer) with a 50% reduction in selectivity over CH4 (from 28 to 14). At 530 C, a distinct intermediate amorphous carbon structure with superior gas separation properties was formed. A 56% increase in CO2-probed surface area accompanied a 16-fold increase in CO2 permeability (4110 Barrer) over the pristine polymer. The graphitic carbon membrane, obtained by heat treatment at 600 C, exhibited excellent gas separation properties, including a remarkable CO2 permeability of 5040 Barrer with a high selectivity over CH4 of 38. Above 600 C, the strong emergence of ultramicroporosity (<7 Å) as evidenced by WAXD and CO2 adsorption studies elicits a prominent molecular sieving effect, yielding gas separation performance well above the permeability-selectivity trade-off curves of polymeric membranes. © 2013 Elsevier Ltd. All rights reserved.

  8. Adsorption and double layer charging in molecular sieve carbons in relation to molecular dimensions and pore structures

    International Nuclear Information System (INIS)

    The pore structure of a fibrous carbon molecular sieve was studied by adsorption of molecular probes. Mild activation steps enabled the graduated opening of critical pore dimensions in the range 3.1-5.0 A, which keeps adsorption selectivity between molecules differing by 0.2 A in cross section diameter, to be considerably greater than 100/1. High adsorption stereospecificity over a wide pore dimension range enabled the studied adsorbates to be ordered in a sequence of increasing critical molecular dimension. Estimation of molecular dimensions by various experimental methods was discussed and their relevance to nonspherical molecules was evaluated. Polar molecules assume different dimensions depending on whether the carbon surface was polar (oxidized) or not. Hydrogen acquires, surprisingly, large width in accordance with its high liquid molar volume. Adsorbent-adsorbate interactions play a crucial role in determining molecular dimensions. Adsorption of ions from aqueous solutions into the developed ultramicropores of fibrous carbon electrodes was also studied. The dependence of the double layer capacitance and the charging rate on the pore critical dimension and on surface oxidation was studied using linear potential sweep voltametry. (Author)

  9. Mixed Matrix Carbon Molecular Sieve and Alumina (CMS-Al2O3) Membranes

    Science.gov (United States)

    Song, Yingjun; Wang, David K.; Birkett, Greg; Martens, Wayde; Duke, Mikel C.; Smart, Simon; Diniz da Costa, João C.

    2016-07-01

    This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a formation of carbon molecular sieve (CMS) structures, reaching the lowest average pore sizes of ~5 Å at carbonisation temperatures of 700 °C. The combination of vacuum-assisted impregnation and carbonisation led to the formation of mixed matrix of CMS and α-alumina particles (CMS-Al2O3) in a single membrane. These membranes were tested for pervaporative desalination and gave very high water fluxes of up to 25 kg m-2 h-1 for seawater (NaCl 3.5 wt%) at 75 °C. Salt rejection was also very high varying between 93-99% depending on temperature and feed salt concentration. Interestingly, the water fluxes remained almost constant and were not affected as feed salt concentration increased from 0.3, 1 and 3.5 wt%.

  10. Separation of radioactive krypton from carbon dioxide and oxygen with molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Forsberg, C. W.

    1977-10-01

    In the reprocessing of HTGR nuclear fuels, the off-gas cleanup system generates a stream containing about 1 percent krypton, 90+ percent CO/sub 2/, and various amounts of O/sub 2/, N/sub 2/, and xenon. The krypton is radioactive and must be separated from the CO/sub 2/ before it is bottled or zeolite-encapsulated for final disposal. A series of theoretical and experimental investigations to find the best method for separating CO/sub 2/ and krypton under the required conditions showed that 5A molecular sieves near O/sup 0/C and 1.01 x 10/sup 5/ Pa (1 atm) provided the most effective separation. Molecular sieves are powerful solid adsorbents for CO/sub 2/ but weak adsorbents for krypton. For a typical expected CO/sub 2/-O/sub 2/-krytpon gas mixture, a molecular sieve bed adsorbs the CO/sub 2/, allows the O/sub 2/ to pass freely through the bed, and concentrates the krypton before it exits the bed. The process selected and investigated is called frontal analysis gas chromatography.

  11. Carbon Molecular Sieve Membrane (CMSM) for Industrial Gas Separation

    Institute of Scientific and Technical Information of China (English)

    WANGKean; HaravaKenji

    2003-01-01

    Membrane separation is an enviroranental benign technology for 21st century, and is developing quickly to replace the conventional distillation process. Carbon raolecular sieve membrane (CMSM) was synthesized through the contndled pyrolysis of polyimide films. The CMSM is synanetric in structure and presents strong sieving effect towards gas molecules of slightly different diameters. The microstructure of CMSM was manipulated through the thermal treatment program and further modified through activation vapor/chemical depositions. It is demonstrated that CMSM can be synthesized/modified for specific gas mixtures, such as O2/N2, CO2/CH4, C3H6/C3H8, and ect. The pore size distrilmfion, relationship between the permeance & selectivity on CMSM for the separation d some gas pairs was also investigated.

  12. Matrimid® derived carbon molecular sieve hollow fiber membranes for ethylene/ethane separation

    KAUST Repository

    Xu, Liren

    2011-09-01

    Carbon molecular sieve (CMS) membranes have shown promising separation performance compared to conventional polymeric membranes. Translating the very attractive separation properties from dense films to hollow fibers is important for applying CMS materials in realistic gas separations. The very challenging ethylene/ethane separation is the primary target of this work. Matrimid® derived CMS hollow fiber membranes have been investigated in this work. Resultant CMS fiber showed interesting separation performance for several gas pairs, especially high selectivity for C2H4/C2H6. Our comparative study between dense film and hollow fiber revealed very similar selectivity for both configurations; however, a significant difference exists in the effective separation layer thickness between precursor fibers and their resultant CMS fibers. SEM results showed that the deviation was essentially due to the collapse of the porous substructure of the precursor fiber. Polymer chain flexibility (relatively low glass transition temperature (Tg) for Matrimid® relative to actual CMS formation) appears to be the fundamental cause of substructure collapse. This collapse phenomenon must be addressed in all cases involving intense heat-treatment near or above Tg. We also found that the defect-free property of the precursor fiber was not a simple predictor of CMS fiber performance. Even some precursor fibers with Knudsen diffusion selectivity could be transformed into highly selective CMS fibers for the Matrimid® precursor. To overcome the permeance loss problem caused by substructure collapse, several engineering approaches were considered. Mixed gas permeation results under realistic conditions demonstrate the excellent performance of CMS hollow fiber membrane for the challenging ethylene/ethane separation. © 2011 Elsevier B.V.

  13. Carbon molecular sieve dense film membranes derived from Matrimid® for ethylene/ethane separation

    KAUST Repository

    Rungta, Meha

    2012-04-01

    Development of dense film carbon molecular sieve (CMS) membranes for ethylene/ethane (C 2H 4/C 2H 6) separation is reported. A commercial polyimide, Matrimid®, was pyrolyzed under vacuum and inert argon atmosphere, and the resultant CMS films were characterized using pure C 2H 4 and C 2H 6 permeation at 35 °C, 50 psia feed pressure. The effects on C 2H 4/C 2H 6 separation caused by different final vacuum pyrolysis temperatures from 500 to 800 °C are reported. For all pyrolysis temperatures separation surpassed the estimated \\'upper bound\\' solution processable polymer line for C 2H 4 permeability vs. C 2H 4/C 2H 6 selectivity. C 2H 4 permeability decreased and selectivity increased with increasing pyrolysis temperature until 650-675 °C where an optimum combination of C 2H 4 permeability ∼14-15 Barrer with C 2H 4/C 2H 6 selectivity ∼12 was observed. A modified heating rate protocol for 675 °C showed further increase in permeability with no selectivity loss. CMS films produced from argon pyrolysis showed results comparable to vacuum pyrolysis. Further, mixed gas (63.2 mol% C 2H 4 + 36.8 mol% C 2H 6) permeation showed a slightly lower C 2H 4 permeability with C 2H 4/C 2H 6 selectivity increase rather than a decrease that is often seen with polymers. The high selectivity of these membranes was shown to arise from a high \\'entropic selection\\' indicating that the \\'slimmer\\' ethylene molecule has significant advantage over ethane in passing through the rigid \\'slit-shaped\\' CMS pore structure. © 2011 Elsevier Ltd. All rights reserved.

  14. Carbon Molecular Sieve Membrane as a True One Box Unit for Large Scale Hydrogen Production

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Paul

    2012-05-01

    IGCC coal-fired power plants show promise for environmentally-benign power generation. In these plants coal is gasified to syngas then processed in a water gas-shift (WGS) reactor to maximize the hydrogen/CO{sub 2} content. The gas stream can then be separated into a hydrogen rich stream for power generation and/or further purified for sale as a chemical and a CO{sub 2} rich stream for the purpose of carbon capture and storage (CCS). Today, the separation is accomplished using conventional absorption/desorption processes with post CO{sub 2} compression. However, significant process complexity and energy penalties accrue with this approach, accounting for ~20% of the capital cost and ~27% parasitic energy consumption. Ideally, a one-box process is preferred in which the syngas is fed directly to the WGS reactor without gas pre-treatment, converting the CO to hydrogen in the presence of H{sub 2}S and other impurities and delivering a clean hydrogen product for power generation or other uses. The development of such a process is the primary goal of this project. Our proposed "one-box" process includes a catalytic membrane reactor (MR) that makes use of a hydrogen-selective, carbon molecular sieve (CMS) membrane, and a sulfur-tolerant Co/Mo/Al{sub 2}O{sub 3} catalyst. The membrane reactor's behavior has been investigated with a bench top unit for different experimental conditions and compared with the modeling results. The model is used to further investigate the design features of the proposed process. CO conversion >99% and hydrogen recovery >90% are feasible under the operating pressures available from IGCC. More importantly, the CMS membrane has demonstrated excellent selectivity for hydrogen over H{sub 2}S (>100), and shown no flux loss in the presence of a synthetic "tar"-like material, i.e., naphthalene. In summary, the proposed "one-box" process has been successfully demonstrated with the bench-top reactor. In parallel we have successfully designed and

  15. Application of molecular sieves in the fractionation of lemongrass oil from high-pressure carbon dioxide extraction

    Directory of Open Access Journals (Sweden)

    L. Paviani

    2006-06-01

    Full Text Available The aim of this work was to study the feasibility of simultaneous process of high-pressure extraction and fractionation of lemongrass essential oil using molecular sieves. For this purpose, a high-pressure laboratory-scale extraction unit coupled with a column with four different stationary phases for fractionation: ZSM5 zeolite, MCM-41 mesoporous material, alumina and silica was employed. Additionally, the effect of carbon dioxide extraction variables on the global yield and chemical composition of the essential oil was also studied in a temperature range of 293 to 313 K and a pressure range of 100 to 200 bar. The volatile organic compounds of the extracts were identified by a gas chromatograph coupled with a mass spectrometer detector (GC/MS. The results indicated that the extraction process variables and the stationary phase exerted an effect on both the extraction yield and the chemical composition of the extracts.

  16. Gas Separation Performance of Carbon Molecular Sieve Membranes Based on 6FDA-mPDA/DABA (3:2) Polyimide

    KAUST Repository

    Qiu, Wulin

    2014-02-23

    6FDA-mPDA/DABA (3:2) polyimide was synthesized and characterized for uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes. The membranes were characterized with thermogravimetric analysis, FTIR spectroscopy, wide-angle X-ray diffraction, and gas permeation tests. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes were discussed in relation to pyrolysis protocols. The uncross-linked polymer membranes showed high CO 2/CH4 selectivity, whereas thermally crosslinked membranes exhibited significantly improved CO2 permeability and excellent CO2 plasticization resistance. The CMS membranes showed even higher CO2 permeability and CO2/CH4 selectivity. An increase in the pyrolysis temperature resulted in CMS membranes with lower gas permeability but higher selectivity. The 550 °C pyrolyzed CMS membranes showed CO2 permeability as high as 14 750 Barrer with CO 2/CH4 selectivity of approximately 52. Even 800 °C pyrolyzed CMS membranes still showed high CO2 permeability of 2610 Barrer with high CO2/CH4 selectivity of approximately 118. Both polymer membranes and the CMS membranes are very attractive in aggressive natural gas purification applications. Permeating through: Polyimide-based uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes are prepared. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes are discussed in relation to pyrolysis protocols. Both the polymer and CMS membranes are very attractive in aggressive natural gas purification applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Ni(II) decorated nano silicoaluminophosphate molecular sieves-modified carbon paste electrode as an electrocatalyst for electrooxidation of methanol

    Indian Academy of Sciences (India)

    SEYED KARIM HASSANINEJAD-DARZI; MOSTAFA RAHIMNEJAD; SEYEDEH ELHAM MOKHTARI

    2016-06-01

    In this work, we reported amethod for the synthesis of nanosized silicoaluminophosphate (SAPO) molecular sieves that are important members of zeolites family. The synthesized SAPO was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) as well as infrared (IR) techniques. Then, the modified carbon paste electrode was prepared by nano SAPO molecular sieves and nickel (II) ion incorporated at this electrode. The electrochemical behaviour of the modified electrode (Ni-SAPO/CPE) towards the oxidation of methanol was investigated by cyclic voltammetry and hronoamperometry methods. It has been found that the oxidation current is extremely increased by using Ni-SAPO/CPE compared to the unmodified Ni-CPE, it seems that Ni$^{2+}$ inclusion into nano SAPO channels provides the active sites for catalysis of methanol oxidation. The effect of some parameters such as scan rate of potential, concentration of methanol, amount of SAPO was investigated on the oxidation of methanol at the surface of modified electrode. The values of electron transfer coefficient, charge-transfer rate constant and electrode surface coverage for the Ni(II)/Ni(III) couple in the surface of Ni-SAPO/CPE were found to be 0.555, 0.022 s$^{−1}$ and 5.995 $\\times$ 10$^{−6}$ mol cm$^{−2}$, respectively. Also, the diffusion coefficient and the mean value of catalytic rate constant for methanol and redox sites of modified electrode were obtained to be $1.16\\times 10^{−5}$ cm$^2$ s$^{−1}$ and $4.62\\times 10^4$ cm$^3$ mol$^{−1} s$^{−1}$, respectively. The good catalytic activity, high sensitivity, good selectivity and stability and easy in preparation rendered the Ni-SAPO/CPE to be a capable electrode for electrocatalytic oxidation of methanol.

  18. Production of carbon molecular sieves from Illinois coal. Final technical report, 1 September, 1992--31 August 1993

    Energy Technology Data Exchange (ETDEWEB)

    Lizzio, A.A.; Rostam-Abadi, M. [Illinois State Geological Survey, Champaign, IL (United States)

    1993-12-31

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois Basin coals are a suitable feedstock for the production of CMS and to evaluate the potential application of these products in commercial gas separation processes. In Phase 1 of this project, gram quantities of char were prepared from Illinois coal in a fixed-bed reactor under a wide range of pyrolysis and activation conditions. Chars having surface areas of 1,500--2,100 m{sup 2}/g were produced by chemical activation using potassium hydroxide (KOH) as the chemical activant. These high surface area (HSA) chars had more than twice the adsorption capacity of commercial molecular sieves. The kinetics of adsorption of various gases, e.g., O{sub 2}, N{sub 2}, CO{sub 2}, CH{sub 4}, and H{sub 2}, on these chars at 25 C was determined. Several chars showed good potential for efficient O{sub 2}/N{sub 2}, CO{sub 2}/CH{sub 4} and CH{sub 4}/H{sub 2} separation. In Phase 2 of this project, larger quantities of char are being prepared from Illinois coal in a batch fluidized-bed reactor and in a continuous rotary tube kiln. The ability of these chars to separate binary gas mixtures is tested in an adsorption column/gas chromatography system. Oxygen and nitrogen breakthrough curves obtained for selected chars were compared to those of a commercial zeolite. Selected chars were subjected to a nitric acid oxidation treatment. The air separation capability of nitric acid treated char was strongly dependent on the outgassing conditions used prior to an O{sub 2}/N{sub 2} adsorption experiment. An outgassing temperature of 130--160 C produced chars with the most favorable air separation properties. 61 refs.

  19. Production of carbon molecular sieves from Illinois coal; [Quarterly] technical report, September 1, 1993--November 30, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Lizzio, A.A.; Rostam-Abadi, M. [Illinois State Geological Survey, Champaign, IL (United States); Vyas, S.N. [Indian Institute of Technology, Bombay (India)

    1994-03-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois Basin coal is a suitable feedstock for the production of CMS and to evaluate the potential application of these products in commercial gas separation processes. In Phase I of this project, gram quantities of char were produced from IBC-102 coal in a fixed-bed reactor under a wide range of pyrolysis and activation conditions. Chars having surface areas. of 1500--2100 m{sup 2}/g were produced by chemical activation using potassium hydroxide as the activant. These high surface area chars had more than twice the adsorption capacity of commercial molecular sieves. The kinetics of adsorption of various gases, i.e., O{sub 2}, N{sub 2}, CO{sub 2}, CH{sub 4} and H{sub 2} on these chars at 25{degree}C was studied. Several chars showed good potential for efficient O{sub 2}/N{sub 2}, CO{sub 2}/CH{sub 4}, CO{sub 2}/H{sub 2} and CH{sub 4}/H{sub 2} separation; both high adsorption capacities and selectivities were achieved. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II, the optimal preparation conditions determined in Phase I will be applied to production of larger quantities of CMS in a batch fluidized-bed reactor (FBR) and continuous rotary tube kiln (RTK).

  20. An efficient synthesis of graphenated carbon nanotubes over the tailored mesoporous molecular sieves by chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: ► Tailored 3D cubic Ni/KIT-6 with large pores was synthesized successfully. ► The new hybrid g-CNTs in large scale were synthesized using Ni/KIT-6 by CVD method. ► The use of mesoporous material by CVD method would be an ideal choice to prepare g-CNTs at reasonable cost. ► This type of g-CNTs might be a new avenue for nano-electronic applications. - Abstract: The new hybrid of graphenated carbon nanotubes (g-CNTs) was superior to either CNTs or graphene. Mesoporous 3D cubic Ni/KIT-6 were synthesized hydrothermally through organic template route and then were used as catalytic template for the production of g-CNTs using acetylene as a carbon precursor by chemical vapor deposition (CVD) method. The deposited new hybrid carbon materials were purified and analyzed by various physico-chemical techniques such as XRD, TGA, SEM, TEM and Raman spectroscopy techniques. The graphitization of CNTs was confirmed by TGA and HRTEM studies. Thermal stability, surface morphology, and structural morphology of these materials were revealed by TGA, SEM and TEM analysis, respectively. Moreover, the tailored mesoporous Ni/KIT-6 molecular sieves were found to possess better quality and massive quantity of g-CNTs produced compared to other catalytic template route

  1. An efficient synthesis of graphenated carbon nanotubes over the tailored mesoporous molecular sieves by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Atchudan, R. [Department of Applied Chemistry, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Department of Chemistry, CEG Campus, Anna University, Chennai 600025 (India); Joo, Jin., E-mail: joojin@knu.ac.kr [Department of Applied Chemistry, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Pandurangan, A., E-mail: pandurangan_a@yahoo.com [Department of Chemistry, CEG Campus, Anna University, Chennai 600025 (India)

    2013-06-01

    Highlights: ► Tailored 3D cubic Ni/KIT-6 with large pores was synthesized successfully. ► The new hybrid g-CNTs in large scale were synthesized using Ni/KIT-6 by CVD method. ► The use of mesoporous material by CVD method would be an ideal choice to prepare g-CNTs at reasonable cost. ► This type of g-CNTs might be a new avenue for nano-electronic applications. - Abstract: The new hybrid of graphenated carbon nanotubes (g-CNTs) was superior to either CNTs or graphene. Mesoporous 3D cubic Ni/KIT-6 were synthesized hydrothermally through organic template route and then were used as catalytic template for the production of g-CNTs using acetylene as a carbon precursor by chemical vapor deposition (CVD) method. The deposited new hybrid carbon materials were purified and analyzed by various physico-chemical techniques such as XRD, TGA, SEM, TEM and Raman spectroscopy techniques. The graphitization of CNTs was confirmed by TGA and HRTEM studies. Thermal stability, surface morphology, and structural morphology of these materials were revealed by TGA, SEM and TEM analysis, respectively. Moreover, the tailored mesoporous Ni/KIT-6 molecular sieves were found to possess better quality and massive quantity of g-CNTs produced compared to other catalytic template route.

  2. High-performance carbon molecular sieve membranes for ethylene/ethane separation derived from an intrinsically microporous polyimide

    KAUST Repository

    Salinas, Octavio

    2015-11-18

    An intrinsically microporous polymer with hydroxyl functionalities, PIM-6FDA-OH, was used as a precursor for various types of carbon molecular sieve (CMS) membranes for ethylene/ethane separation. The pristine polyimide films were heated under controlled N2 atmosphere at different stages from 500 to 800 °C. All CMS samples carbonized above 600 °C surpassed the polymeric ethylene/ethane upper bound. Pure-gas selectivity reached 17.5 for the CMS carbonized at 800 °C with an ethylene permeability of about 10 Barrer at 2 bar and 35 °C, becoming the most selective CMS for ethylene/ethane separation reported to date. As expected, gravimetric sorption experiments showed that all CMS membranes had ethylene/ethane solubility selectivities close to one. The permselectivity increased with increasing pyrolysis temperature due to densification of the micropores in the CMS membranes, leading to enhanced diffusivity selectivity. Mixed-gas tests with a binary 50:50 v/v ethylene/ethane feed showed a decrease in selectivity from 14 to 8.3 as the total feed pressure was increased from 4 to 20 bar. The selectivity drop under mixed-gas conditions was attributed to non-ideal effects: (i) Competitive sorption that reduced the permeability of ethylene and (ii) dilation of the CMS that resulted in an increase in the ethane permeability.

  3. Controllable deformation of salt water-filled carbon nanotubes using an electric field with application to molecular sieving

    Science.gov (United States)

    Ye, Hongfei; Zheng, Yonggang; Zhang, Zhongqiang; Zhang, Hongwu; Chen, Zhen

    2016-08-01

    Precisely controlling the deformation of carbon nanotubes (CNTs) has practical application in the development of nanoscale functional devices, although it is a challenging task. Here, we propose a novel method to guide the deformation of CNTs through filling them with salt water and applying an electric field. With the electric field along the axial direction, the height of CNTs is enlarged by the axial electric force due to the internal ions and polar water molecules. Under an electric field with two mutually orthogonal components, the transverse electric force could further induce the bending deformation of CNTs. Based on the classical rod and beam theories, two mechanical models are constructed to verify and quantitatively describe the relationships between the tension and bending deformations of CNTs and the electric field intensity. Moreover, by means of the electric field-driven tension behavior of CNTs, we design a stretchable molecular sieve to control the flow rate of mixed gas and collect a single high-purity gas. The present work opens up new avenues in the design and fabrication of nanoscale controlling units.

  4. Controllable deformation of salt water-filled carbon nanotubes using an electric field with application to molecular sieving.

    Science.gov (United States)

    Ye, Hongfei; Zheng, Yonggang; Zhang, Zhongqiang; Zhang, Hongwu; Chen, Zhen

    2016-08-01

    Precisely controlling the deformation of carbon nanotubes (CNTs) has practical application in the development of nanoscale functional devices, although it is a challenging task. Here, we propose a novel method to guide the deformation of CNTs through filling them with salt water and applying an electric field. With the electric field along the axial direction, the height of CNTs is enlarged by the axial electric force due to the internal ions and polar water molecules. Under an electric field with two mutually orthogonal components, the transverse electric force could further induce the bending deformation of CNTs. Based on the classical rod and beam theories, two mechanical models are constructed to verify and quantitatively describe the relationships between the tension and bending deformations of CNTs and the electric field intensity. Moreover, by means of the electric field-driven tension behavior of CNTs, we design a stretchable molecular sieve to control the flow rate of mixed gas and collect a single high-purity gas. The present work opens up new avenues in the design and fabrication of nanoscale controlling units. PMID:27335235

  5. Production of carbon molecular sieves from Illinois coal. [Quarterly] technical report, December 1, 1993--February 28, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Lizzio, A.A.; Rostam-Abadi, M. [Illinois State Geological Survey, Champaign, IL (United States); Vyas, S.N. [Indian Institute of Technology, Bombay (India)

    1994-06-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois coal is a suitable feedstock for the production of CMS and to evaluate the potential application of the products in commercial gas separation processes. In Phase I of this project, gram quantities of char were produced from IBC-102 coal in a fixed-bed reactor under a wide range of pyrolysis and activation conditions. The kinetics of adsorption of various gases, i.e., O{sub 2}, N{sub 2}, CO{sub 2}, CH{sub 4} and H{sub 2}, on these chars at 25{degree}C was studied. Several chars showed good potential for efficient O{sub 2}/N{sub 2}, CO{sub 2}/CH{sub 4}, CO{sub 2}H{sub 2} and CH{sub 4}/H{sub 2} separation; both high adsorption capacities and selectivities were achieved. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II, the optimal char preparation conditions determined in Phase I are applied to production of larger quantities of CMS in a batch fluidized-bed reactor (FBR) and a continuous rotary tube kiln (RTFK).

  6. OZONE REACTION WITH N-ALDEHYDES (N=4-10), BENZALDEHYDE, ETHANOL, ISOPROPANOL, AND N-PROPANOL ADSORBED ON A DUAL-BED GRAPHITIZED CARBON/CARBON MOLECULAR SIEVE ADSORBENT CARTRIDGE

    Science.gov (United States)

    Ozone reacts with n-aldehydes (n = 4 - 10), benzaldehyde, ethanol, isopropanol, and n-propanol adsorbed on a dual-bed graphitized carbon/carbon molecular sieve adsorbent cartridge. Destruction of n-aldehydes increases with n number and with ozone concentration. In some samp...

  7. Ethylene/ethane permeation, diffusion and gas sorption properties of carbon molecular sieve membranes derived from the prototype ladder polymer of intrinsic microporosity (PIM-1)

    KAUST Repository

    Salinas, Octavio

    2016-01-05

    Fine-tuning the microporosity of PIM-1 by heat treatment was applied to develop a suitable carbon molecular sieve membrane for ethylene/ethane separation. Pristine PIM-1 films were heated from 400 to 800 °C under inert N2 atmosphere (< 2 ppm O2). At 400 °C, PIM-1 self-cross-linked and developed polar carbonyl and hydroxyl groups due to partial dioxane splitting in the polymer backbone. Significant degradation occurred at 600 °C due to carbonization of PIM-1 and resulted in 30% increase in cumulative surface area compared to its cross-linked predecessor. In addition, PIM-1-based CMS developed smaller ultramicropores with increasing pyrolysis temperature, which enhanced their molecular sieving capability by restricted diffusion of ethylene and ethane through the matrix due to microstructural carbon densification. Consequently, the pure-gas ethylene permeability (measured at 35 °C and 2 bar) decreased from 1600 Barrer for the pristine PIM-1 to 1.3 Barrer for the amorphous carbon generated at 800 °C, whereas the ethylene/ethane pure-gas selectivity increased significantly from 1.8 to 13.

  8. Vitrification of spent mordenite molecular sieves

    International Nuclear Information System (INIS)

    Vitrification of cesium loaded inorganic ion exchangers (mordenite type molecular sieves/zeolite AR-1) was studied empolying borosilicate glass systems. Direct vitrification of aluminosilicates is rather difficult mainly on account of volatility of cesium at processing temperatures of 1100 degC-1300 degC. In the borosilicate glass system, oxides of lead, sodium and zinc along with boric oxide were employed as major glass formers. Homogeneous glass matrix was obtained incorporating simulated composition of mordenite along with oxides of sodium, lead and boron at the processing temperature of 950 degC. The waste oxide loading up to 50% on dry weight basis was incorporated in this glass formulation. Partial replacement of PbO by TeO2, Bi2O3 and CaF2 resulted in lowering of the processing temperature and also increasing homogeneity of matrix. Based on these results, a glass matrix was prepared with actual cesium AR-1 molecular sieves with processing temperature limited to 925 degC. Powdered samples of glass matrix were subjected to leaching as per ASTM-1285 Product Consistency Test in high purity water at 90 degC for 28 days. The normalised cesium leach rate of this glass was found to be 3.92 x 10-6 g/cm2/day, which is comparable to sodium borosilicate glass matrices currently in use for immobilisation of high level waste. The molecular sieves are also amenable to immobilization in cement matrix. As expected, there is substantial volume reduction by factor 3 in vitrification compared to their immobilization in cementious matrices. Also the quantity of cesium leached from vitrified product was nearly 10,000 times lower compared to cement based matrix. Vitrification of mordenite molecular sieves would lead to high capacity utilisation of zeolite AR-1 for the treatment of low and intennediate levelliquid effluents. (author)

  9. Preparation of a carbon molecular sieve and application to separation of N{sub 2}, O{sub 2} and CO{sub 2} in a fixed bed

    Energy Technology Data Exchange (ETDEWEB)

    Soares, J.L.; Jose, H.J.; Moreira, R.F.P.M. [Univ. Federal de Santa Catarina, Florianopolis, SC (Brazil). Dept. of Chemistry and Food Engineering

    2003-03-01

    The emission of CO{sub 2} from power plants that burn fossil fuels is the major cause of the accumulation of CO{sub 2} in the atmosphere. The separation of CO{sub 2} from CO{sub 2}/air mixtures can play a key role in alleviating this problem. This separation can be carried out by using suitable adsorbents, such as carbon molecular sieves. In this work, a CMS was prepared by deposition of polyfurfuryl alcohol polymer on activated carbon. After deposition of the polymer, the material was carbonized at 800{sup o}C for 2 hours. This material was used to separate O-2/N-2 mixtures and CO{sub 2} in a fixed bed at room temperature. Experimental breakthrough curves obtained were fitted to theoretical models in order to establish the main mechanisms of mass transfer. The breakthrough curves showed that it is possible to separate O{sub 2}, N{sub 2} and CO{sub 2}. The shape of the breakthrough curves was not influenced by the total flow, indicating that the gas contact for the gas mixture was good. The experimental data were fitted to theoretical models and it was established that the main mechanism of mass transfer was intraparticle diffusion.

  10. Preparation of a carbon molecular sieve and application to separation of N2, O2 and CO2 in a fixed bed

    Directory of Open Access Journals (Sweden)

    Soares J.L.

    2003-01-01

    Full Text Available The emission of CO2 from power plants that burn fossil fuels is the major cause of the accumulation of CO2 in the atmosphere. The separation of CO2 from CO2/air mixtures can play a key role in alleviating this problem. This separation can be carried out by using suitable adsorbents, such as carbon molecular sieves. In this work, a CMS was prepared by deposition of polyfurfuryl alcohol polymer on activated carbon. After deposition of the polymer, the material was carbonized at 800masculineC for 2 hours. This material was used to separate O2/N2 mixtures and CO2 in a fixed bed at room temperature. Experimental breakthrough curves obtained were fitted to theoretical models in order to establish the main mechanisms of mass transfer. The breakthrough curves showed that it is possible to separate O2, N2 and CO2. The shape of the breakthrough curves was not influenced by the total flow, indicating that the gas contact for the gas mixture was good. The experimental data were fitted to theoretical models and it was established that the main mechanism of mass transfer was intraparticle diffusion.

  11. Octahedral molecular sieve sorbents and catalysts

    Science.gov (United States)

    Li, Liyu [Richland, WA; King, David L [Richland, WA

    2010-04-20

    Octahedral molecular sieve sorbents and catalysts are disclosed, including silver hollandite and cryptomelane. These materials can be used, for example, to catalyze the oxidation of CO.sub.x (e.g., CO), NO.sub.x (e.g., NO), hydrocarbons (e.g., C.sub.3H.sub.6) and/or sulfur-containing compounds. The disclosed materials also may be used to catalyze other reactions, such as the reduction of NO.sub.2. In some cases, the disclosed materials are capable of sorbing certain products from the reactions they catalyze. Silver hollandite, in particular, can be used to remove a substantial portion of certain sulfur-containing compounds from a gas or liquid by catalysis and/or sorption. The gas or liquid can be, for example, natural gas or a liquid hydrocarbon.

  12. Direct Synthesis of Dimethyl Carbonate from CO2 and CH3OH Using 0.4 nm Molecular Sieve Supported Cu-Ni Bimetal Catalyst

    Institute of Scientific and Technical Information of China (English)

    陈惠玲; 王栓紧; 肖敏; 韩冬梅; 卢一新; 孟跃中

    2012-01-01

    The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by BET, XRD (X-ray diffraction), TPR (temperature programmed reduction), IR (infra-red adsorption), NH 3-TPD (temperature programmed desorption) and CO 2-TPD (temperature programmed desorption) techniques. The results showed that the surface area of catalysts decreased with increasing metal content, and the metals as well as Cu-Ni alloy co-existed on the reduced catalyst surface. There existed interaction between metal and carrier, and moreover, metal particles affected obviously the acidity and basicity of carrier. The large amount of basic sites facilitated the activation of methanol to methoxyl species and their subsequent reaction with activated carbon dioxide. The catalysts were evaluated in a continuous tubular fixed-bed micro-gaseous reactor and the catalyst with bimetal loading of 20% (by mass) had best catalytic activities. Under the conditions of 393 K, 1.1 MPa, 5 h and gas space velocity of 510 h 1 , the selectivity and yield of DMC were higher than 86.0 % and 5.0 %, respectively.

  13. A controllable molecular sieve for Na+ and K+ ions.

    Science.gov (United States)

    Gong, Xiaojing; Li, Jichen; Xu, Ke; Wang, Jianfeng; Yang, Hui

    2010-02-17

    The selective rate of specific ion transport across nanoporous material is critical to biological and nanofluidic systems. Molecular sieves for ions can be achieved by steric and electrical effects. However, the radii of Na(+) and K(+) are quite similar; they both carry a positive charge, making them difficult to separate. Biological ionic channels contain precisely arranged arrays of amino acids that can efficiently recognize and guide the passage of K(+) or Na(+) across the cell membrane. However, the design of inorganic channels with novel recognition mechanisms that control the ionic selectivity remains a challenge. We present here a design for a controllable ion-selective nanopore (molecular sieve) based on a single-walled carbon nanotube with specially arranged carbonyl oxygen atoms modified inside the nanopore, which was inspired by the structure of potassium channels in membrane spanning proteins (e.g., KcsA). Our molecular dynamics simulations show that the remarkable selectivity is attributed to the hydration structure of Na(+) or K(+) confined in the nanochannels, which can be precisely tuned by different patterns of the carbonyl oxygen atoms. The results also suggest that a confined environment plays a dominant role in the selectivity process. These studies provide a better understanding of the mechanism of ionic selectivity in the KcsA channel and possible technical applications in nanotechnology and biotechnology, including serving as a laboratory-in-nanotube for special chemical interactions and as a high-efficiency nanodevice for purification or desalination of sea and brackish water. PMID:20102186

  14. Olefins-selective asymmetric carbon molecular sieve hollow fiber membranes for hybrid membrane-distillation processes for olefin/paraffin separations

    KAUST Repository

    Xu, Liren

    2012-12-01

    In this paper, the development of asymmetric carbon molecular sieve (CMS) hollow fiber membranes and advanced processes for olefin/paraffin separations based on the CMS membranes are reported. Membrane-based olefin/paraffin separations have been pursued extensively over the past decades. CMS membranes are promising to exceed the performance upper bound of polymer materials and have demonstrated excellent stability for gas separations. Previously, a substructure collapse phenomenon was found in Matrimid ® precursor derived CMS fiber. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM precursors were selected as potential new precursors for carbon membrane formation. Defect-free asymmetric 6FDA-DAM and 6FDA/BPDA-DAM hollow fibers were successfully fabricated from a dry-jet/wet-quench spinning process. Polymer rigidity, glass-rubber transition and asymmetric morphology were correlated. CMS hollow fiber membranes produced from 6FDA-polymer precursors showed significant improvement in permeance for ethylene/ethane and propylene/propane separations. Further studies revealed that the CMS membranes are olefins-selective, which means the membranes are able to effectively separate olefins (ethylene and propylene) from paraffins (ethane and propane). This unique feature of CMS materials enables advanced hybrid membrane-distillation process designs. By using the olefins-selective membranes, these new processes may provide advantages over previously proposed retrofitting concepts. Further applications of the membranes are explored for hydrocarbons processes. Significant energy savings and even reduced footprint may be achieved in olefins production units. © 2012 Elsevier B.V.

  15. Adsorption of hydrogen and deuterium on modified molecular sieves

    International Nuclear Information System (INIS)

    The adsorption characteristics of hydrogen isotopes on 5A, ZSM-5 and their modified molecular sieves were studied at liquid nitrogen temperature with volumetric method. The effects of modification methods such as transition metal salt loading and ball milling on the adsorption behavior were discussed. It is observed that the adsorption amounts on the modified molecular sieves are reduced. but some modifications contribute to the separation between H2 and D2. (authors)

  16. Crystalline molecular sieves and their synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Kuehl, G.H.

    1989-03-21

    A synthetic crystalline silliceous molecular sieve material has the structure of zeolite ZSM-5, zeolite ZAM-12 or zeolite ZSM-12 and contains aluminum and at least tow elements selected from the group consisting of boron, gallium and iron in its anionic framework. The crystalline material has a composition on an anhydrous basis and in terms of moles of oxides per mole of silica expressed the formula: a R/sub 2//sub ///sub n/O : b Fe/sub 2/O/sub 3/ : c B/sub 2/O/sub 3/: d Ga/sub 2/O/sub 3/ : e Al/sub 2/O/sub 3/ : SiO/sub 2/ wherein R is at least one cation having the valence n, and a = (1.0+/- 0.2)(b+c+d+e); b = 0 to 0.05; c = 0 to 0.05; d = 0 to 0.05; e = 0.00003 to 0.02; b+c+d+e = 0.005 to 0.05; b+c+d greater than or equal to 0.00047; and wherein only one of b, c and d can be 0. When in the ammonium form, the crystalline material has a TPAD (temperature-programmed ammonia desorption) peak of from greater than 300/sup 0/C to less than 390/sup 0/C and a TPAD half-height width from greater than 135/sup 0/C to less than 155/sup 0/C.

  17. Molecular Sieve Bench Testing and Computer Modeling

    Science.gov (United States)

    Mohamadinejad, Habib; DaLee, Robert C.; Blackmon, James B.

    1995-01-01

    The design of an efficient four-bed molecular sieve (4BMS) CO2 removal system for the International Space Station depends on many mission parameters, such as duration, crew size, cost of power, volume, fluid interface properties, etc. A need for space vehicle CO2 removal system models capable of accurately performing extrapolated hardware predictions is inevitable due to the change of the parameters which influences the CO2 removal system capacity. The purpose is to investigate the mathematical techniques required for a model capable of accurate extrapolated performance predictions and to obtain test data required to estimate mass transfer coefficients and verify the computer model. Models have been developed to demonstrate that the finite difference technique can be successfully applied to sorbents and conditions used in spacecraft CO2 removal systems. The nonisothermal, axially dispersed, plug flow model with linear driving force for 5X sorbent and pore diffusion for silica gel are then applied to test data. A more complex model, a non-darcian model (two dimensional), has also been developed for simulation of the test data. This model takes into account the channeling effect on column breakthrough. Four FORTRAN computer programs are presented: a two-dimensional model of flow adsorption/desorption in a packed bed; a one-dimensional model of flow adsorption/desorption in a packed bed; a model of thermal vacuum desorption; and a model of a tri-sectional packed bed with two different sorbent materials. The programs are capable of simulating up to four gas constituents for each process, which can be increased with a few minor changes.

  18. Mesoporous Molecular Sieves as Supports for Metathesis Catalysts

    Science.gov (United States)

    Balcar, Hynek; Cejka, Jirí

    Mesoporous molecular sieves represent a new family of inorganic oxides with regular nanostructure, large surface areas, large void volumes, and narrow pore size distribution of mesopores. These materials offer new possibilities for designing highly active and selective catalysts for olefin metathesis and metathesis polymerization. Siliceous sieves MCM-41, MCM-48, SBA-15, and organized mesoporous alumina (OMA) were used as supports for preparation of new molybdenum and rhenium oxide catalysts, as well as for heterogenization of well-defined homogeneous catalysts.

  19. Carbon fiber composite molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, T.D.; Rogers, M.R. [Oak Ridge National Lab., TN (United States)

    1997-12-01

    Monolithic adsorbents based on isotropic pitch fibers have been developed jointly by ORNL and the University of Kentucky, Center for Applied Energy Research. The monoliths are attractive for gas separation and storage applications because of their unique combination of physical properties and microporous structure. Currently at ORNL the monoliths are produced in billets that are 10 cm in diameter and 25 cm in length. The monolithic adsorbent material is being considered for guard bed applications on a natural gas (NG) powered device. In order for the material to be successful in this application, one must attain a uniform activation to modest micropore volumes throughout the large monoliths currently being produced. Here the authors report the results of a study directed toward attaining uniform activation in these billets.

  20. 负载Co介孔分子筛催化热解乙醇制备纳米碳管%Preparation of carbon nanotubes by ethanol pyrolysis on loaded Co mesoporous molecular sieve

    Institute of Scientific and Technical Information of China (English)

    张丽; 赵谦; 纪美茹; 贾佳

    2013-01-01

    以硅酸钠为原料,CTAB为模板剂,水热法合成MCM-41介孔分子筛,采用浸渍法制备负载钴的介孔分子筛(Co/MCM-41),并将其作为催化剂,CVD法热解无水乙醇制备CNTs.利用XRD、TEM、比表面积和孔径分布测定和Raman光谱等方法对所合成的介孔分子筛和纳米碳管进行了表征.结果表明:所制备的Co/MCM-41样品具有典型的MCM-41的介孔结构;当热解反应温度为750℃下所制备出的纳米碳管的品质最好.%MCM-41mesoporous molecular sieve was synthesized by hydrothermal method using cetyltri-methyl ammonium bromide as template and sodium silicate as raw material, respectively. And Co-loaded mesoporous molecular sieve (Co/MCM-41) was prepared by the wet impregnation method with cobalt chloride solution. The chemical vapor deposition method was employed to catalytically synthesize carbon nanotubes (CNTs) using Co/MCM-41 as catalytic template and alcohol as carbon source. The physicochemical properties of the obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 physical adsorption and Raman spectroscopy, respectively. The results show that the Co/MCM-41 sample possesses a typical mesoporous framework of MCM-41. The Co/MCM-41 mesoporous molecular sieve with high specific surface area was successfully synthesized under hydrothermal condition. These mesoporous materials have good mesoporous ordering. When the reaction temperature is 750 ℃ , the resulting CNTs are of high quality.

  1. Double rotation NMR studies of zeolites and aluminophosphate molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Jelinek, R. [California Univ., Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

    1993-07-01

    Goal is to study the organization and structures of guest atoms and molecules and their reactions on internal surfaces within pores of zeolites and aluminophosphate molecular sieves. {sup 27}Al and {sup 23}Na double rotation NMR (DOR) is used since it removes the anisotropic broadening in NMR spectra of quadrupolar nuclei, thus increasing resolution. This work concentrates on probing aluminum framework atoms in aluminophosphate molecular sieves and sodium extra framework cations in porous aluminosilicates. In aluminophosphates, ordering and electronic environments of the framework {sup 27}Al nuclei are modified upon adsorption of water molecules within the channels; a relation is sought between the sieve channel topology and the organization of adsorbed water, as well as the interaction between the Al nuclei and the water molecules. Extra framework Na{sup +} cations are directly involved in adsorption processes and reactions in zeolite cavities.

  2. Carbon molecular sieve CMSCH4 for adsorptive concentration of methane%CMSCH4浓缩甲烷碳分子筛吸附剂

    Institute of Scientific and Technical Information of China (English)

    史乃弘

    2014-01-01

    A novel carbon molecular sieve CMSCH4 for adsorptive concentration of methane was prepared, and its performances for concentrating methane from the mixtures containing methane were evaluated in a two column experimental installation. The results showed that for the mixed gas of V(CH4)/V(N2)/V(O2)=5/79/16,φ(CH4) in the product gas was up to 28% with φ(O2) of below 0.5%and methane recovery of 34.8%;for the mixed gas of V (CH4)/V (N2)=30/7,φ (CH4) in the product gas could be up to 94.1% with methane recovery of 34.8%; and for the mixed gas of V (CH4)/V (CO2)=50/50, φ (CH4) and φ (CO2) in methane and CO2 product gases could be up to 98.5%and 93.7%with methane and CO2 recovery of 94.7%and 97.3%, respectively. The adsorbent CMSCH4 had high separation coefficients which made it excellent for removing nitrogen, oxygen and/or carbon dioxide from the gases containing methane and them, and showed great potential for concentrating methane from low concentration coal mine methane, biogas and landfill gas by PSA process.%制备了新型专用浓缩甲烷碳分子筛吸附剂CMSCH4,并利用双塔评价装置评价了其从含甲烷的混合气浓缩甲烷的性能。结果显示:对V(CH4)/V(N2)/V(O2)=5/79/16的混合气可浓缩为φ(CH4)=28%、φ(O2)<0.5%的成品气,甲烷回收率34.8%;对V(CH4)/V(N2)=30/70的混合气可浓缩为φ(CH4)=94.1%的成品气,甲烷回收率35.8%;对V(CH4)/V(CO2)=50/50的混合气可浓缩为φ(CH4)=98.5%的成品气和φ(CO2)=93.7%的成品气,甲烷与CO2回收率分别为94.7%和97.3%。新开发的CMSCH4碳分子筛浓缩甲烷吸附剂具有高分离系数,提供了良好的除氮、脱氧和脱碳功能,成为PSA技术浓缩低浓度煤层气和沼气、垃圾填埋气提纯甲烷极有发展前途的吸附剂。

  3. Adsorption properties of the SAPO-5 molecular sieve

    KAUST Repository

    Hu, Enping

    2010-09-09

    The adsorption properties of an aluminophosphate molecular sieve, SAPO-5, were measured for a number of gases and vapors, including N2, water, isopropanol, and xylenes. The data showed that SAPO-5 is quite hydrophobic and has a strong selectivity of o-xylene over its isomers m- and p-xylene. © 2010 American Chemical Society.

  4. Preparation and structure characterization of nanospherical MCM- 41 molecular sieves

    Directory of Open Access Journals (Sweden)

    CHEN Ting

    2013-04-01

    Full Text Available Nanospherical MCM-41 molecular sieves have been synthesized by using hexadecyl trimethyl ammonium bromide (CTAB as templates and tetraethyl orthosilicate (TEOS as silicon sources. XRD,SEM,FT-IR,TEM,and N2 adsorption-desorption isotherms were used to investigate the effects of the reaction temperature and aging time on the morphology and structure of the samples. The results show that the nanospherical MCM-41 particles can be obtained at reaction temperatures between 20 to 80℃. With the reaction temperature increasing,the diameter of the nanospheres increases. When the reaction temperature reaches 110℃,MCM-41 molecular sieves exhibit irregular particle morphology. With the aging time of 0-15 h,the dispersion of nanospherical MCM-41 molecular sieves is very good. However,as the aging time increases,the particle size is also increased,while agglomeration is also more serious. Besides,the optimal synthesis conditions of the nanospherical MCM-41 molecular sieves were obtained by analyzing their formation mechanism.

  5. A SAPO-11 Silicoaluminophosphate Molecular Sieve with Stable Crystal Structure

    Institute of Scientific and Technical Information of China (English)

    Yue Ming LIU; Feng Mei ZHANG; Hai Hong WU; Hai Jiao ZHANG; Jian Guo YANG; Xing Tian SHU; Ming Yuan HE

    2004-01-01

    A SAPO-11 silicoaluminophosphate molecular sieve with stable crystal structure was synthesized for the first time. After removing template by calcination, its crystal space group still retains Icm2 which the as-synthesized has. The catalyst deriving from the present SAPO-11materials shows higher isomerization selectivity and higher paraffin hydroisomerization yield than those reported elsewhere.

  6. Synthesis and spectroscopic studies of vanadium-containing molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Sayari, A.; Moudrakovski, I.; Reddy, K.M. [Universite Laval, Quebec (Canada)] [and others

    1995-12-01

    New vanadium containing large pore and mesoporous molecular sieves with ZSM-12 and MCM-41 structures were synthesized and characterized by variety of chemico-physical methods. All samples showed promising properties in the oxidation of organic substrates by hydrogen peroxide. Based on EPR and multinuclear NMR data a possible mechanism of vanadium incorporation into the lattice of the molecular sieves is proposed. It is shown, that part of vanadium incorporates the lattice during the hydrothermal synthesis. Incorporation of the other part takes place during high temperature calcination through interaction with hydroxyl groups at defect sites. The local coordination of vanadium in these materials has been examined by EPPI and {sup 51}V NMR. In calcined samples, vanadium was coordinated to four oxygen atoms in tetrahedral symmetry and could be easily converted from V(5+) to V(4+) and vice versa. Possible models of the local environment of vanadium will be proposed, and catalytic properties presented.

  7. Preparation and structure characterization of nanospherical MCM- 41 molecular sieves

    OpenAIRE

    Chen, Ting; WEI Yiting; Guo, Yajun; CHU Lianfeng; Guo, Yaping

    2013-01-01

    Nanospherical MCM-41 molecular sieves have been synthesized by using hexadecyl trimethyl ammonium bromide (CTAB) as templates and tetraethyl orthosilicate (TEOS) as silicon sources. XRD,SEM,FT-IR,TEM,and N2 adsorption-desorption isotherms were used to investigate the effects of the reaction temperature and aging time on the morphology and structure of the samples. The results show that the nanospherical MCM-41 particles can be obtained at reaction temperatures between 20 to 80℃. With the reac...

  8. Modified molecular sieves: stationary phase for the gas chromatographic separation of hydrogen isotopes

    International Nuclear Information System (INIS)

    Gas chromatographic separation of hydrogen isotopes on different molecular sieves at liquid nitrogen temperature has been investigated. Normal molecular sieves 5A, 13X and AW500 are not satisfactory for the purpose both in the partially dehydrated as well as totally dehydrated state. Molecular sieve 4A in partially dehydrated state separated H2 and D2 while H2 and HD are not well resolved. Iron exchanged or coated molecular sieves 4A, 5A, 13X and AW500 in the partially dehydrated state separated the isotopic mixtures H2, HD, D2 and H2, HT, T2. The resolution varied depending on the amount of iron content and the residual moisture in the molecular sieves. Good separations were obtained on 15% Fe coated molecular sieve 5A and 5% Fe coated molecular sieve 4A. (author). 18 refs., 6 figs., 3 tabs

  9. Unexpected Molecular Sieving Properties of Zeolitic Imidazolate Framework-8

    KAUST Repository

    Zhang, Chen

    2012-08-16

    We studied molecular sieving properties of zeolitic imidazolate framework-8 (ZIF-8) by estimating the thermodynamically corrected diffusivities of probe molecules at 35 °C. From helium (2.6 Å) to iso-C 4H 10 (5.0 Å), the corrected diffusivity drops 14 orders of magnitude. Our results further suggest that the effective aperture size of ZIF-8 for molecular sieving is in the range of 4.0 to 4.2 Å, which is significantly larger than the XRD-derived value (3.4 Å) and between the well-known aperture size of zeolite 4A (3.8 Å) and 5A (4.3 Å). Interestingly, because of aperture flexibility, the studied C 4 hydrocarbon molecules that are larger than this effective aperture size still adsorb in the micropores of ZIF-8 with kinetic selectivities for iso-C 4H 8/iso-C 4H 10 of 180 and n-C 4H 10/iso-C 4H 10 of 2.5 × 10 6. These unexpected molecular sieving properties open up new opportunities for ZIF materials for separations that cannot be economically achieved by traditional microporous adsorbents such as synthetic zeolites. © 2012 American Chemical Society.

  10. Nanoscale octahedral molecular sieves: Syntheses, characterization, and applications

    Science.gov (United States)

    Liu, Jia

    The major part of this research consists of studies on novel synthesis methods, characterization, and catalytic applications of nanoscale manganese oxide octahedral molecular sieves. The second part involves studies of new applications of bulk porous molecular sieve and layered materials (MSLM), zeolites, and inorganic powder materials for diminishing wound bleeding. Manganese oxide octahedral molecular sieves (OMS) are very important microporous materials. They have been used widely as bulk materials in catalysis, separations, chemical sensors, and batteries, due to their unique tunnel structures and useful properties. Novel methods have been developed to synthesize novel nanoscale octahedral molecular sieve manganese oxides (OMS) and metal-substituted OMS materials in order to modify their physical and chemical properties and to improve their catalytic applications. Different synthetic routes were investigated to find better, faster, and cheaper pathways to produce nanoscale or metal-substituted OMS materials. In the synthetic study of nanosize OMS materials, a combination of sol-gel synthesis and hydrothermal reaction was used to prepare pure crystalline nanofibrous todorokite-type (OMS-1) and cryptomelane-typed (OMS-2) manganese oxides using four alkali cations (Li+, K+, Na +, Rb+) and NH4+ cations. In the synthesis study of nanoscale and metal-substituted OMS materials, a combination of sol-gel synthesis and solid-state reaction was used to prepare transition metal-substituted OMS-2 nanorods, nanoneedles, and nanowires. Preparative parameters of syntheses, such as cation templates, heating temperature and time, were investigated in these syntheses of OMS-1 and OMS-2 materials. The catalytic activities of the novel synthetic nanoscale OMS materials has been evaluated on green oxidation of alcohols and toluene and were found to be much higher than their correspondent bulk materials. New applications of bulk manganese oxide molecular sieve and layered materials

  11. Kinetics of Cyclohexanone Ammoximation over Titanium Silicate Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    李永祥; 吴巍; 闵恩泽

    2005-01-01

    An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading,and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H202 decomposition reaction Inust be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.

  12. Itegrated Test and Evaluation of a 4-Bed Molecular Sieve (4BMS) Carbon Dioxide Removtal System (CDRA), Mechanical Compressor Engineering Development Unit (EDU), and Sabitier Engineering Development Unit (EDU)

    Science.gov (United States)

    Knox, James C.; Campbell, Melissa; Murdoch, Karen; Miller, Lee A.; Jeng, Frank

    2005-01-01

    Currently on the International Space Station s (ISS) U.S. Segment, carbon dioxide (CO2) scrubbed from the cabin by a 4-Bed Molecular Sieve (4BMS) Carbon Dioxide Removal Assembly (CDRA) is vented overboard as a waste product. Likewise, the product hydrogen (H2) that will be generated by the Oxygen Generation Assembly (OGA) planned for installation will also be vented. A flight experiment has been proposed that will take the waste CO2 removed from the cabin, and via the catalytic Sabatier process, reduce it with waste H2 to generate water and methane. The water produced may provide cost and logistics savings for ISS by reducing the amount of water periodically re-supplied to orbit. To make this concept viable, a mechanical piston compressor and accumulator were developed for collecting and storing the CO2 from the CDRA. The compressor, accumulator and Sabatier system would be packaged together as one unit and referred to as the Carbon Dioxide Reduction Assembly (CRA). Testing was required to evaluate the performance of a 4BMS CDRA, compressor, accumulator, and Sabatier performance along with their operating rules when integrated together. This had been numerically modeled and simulated; however, testing was necessary to verify the results from the engineering analyses. Testing also allowed a better understanding of the practical inefficiencies and control issues involved in a fully integrated system versus the theoretical ideals in the model. This paper presents and discusses the results of an integrated engineering development unit test.

  13. Evaluation of Strontium Selectivity by Sandia Octahedral Molecular Sieves (SOMS).

    Energy Technology Data Exchange (ETDEWEB)

    Rigali, Mark J.; Stewart, Thomas Austin

    2016-01-01

    Sandia National Laboratories has collaborated with Pleasanton Ridge Research Company (PRRC) to determine whether Sandia Octahedral Molecular Sieves (SOMS) and modified SOMs materials can be synthesized in large batches and produced in granular form. Sandia National Laboratories tested these SOMS and its variants based in aqueous chemical environments for an application-based evaluation of material performance as a sorbent. Testing focused primarily on determining the distribution coefficients (K d ) and chemical selectivity SOMs for alkali earth (Sr) ions in aqueous and dilute seawater solutions. In general the well-crystallized SOMS materials tested exhibited very high K d values (>10 6 ) in distilled water but K d values dropped substantially (%7E10 2 -10 3 ) in the dilute seawater (3%). However, one set of SOMS samples (1.4.2 and 1.4.6) provided by PRRC yielded relatively high K d (approaching 10 4 ) in dilute seawater. Further examination of these samples by scanning electron microscopy (SEM) revealed the presence of at least two phases at least one of which may be accounting for the improved K d values in dilute seawater. Evaluation of Strontium Selectivity by Sandia Octahedral Molecular Sieves (SOMS) January 20, 2016

  14. Transformation of metal-organic frameworks for molecular sieving membranes

    Science.gov (United States)

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-04-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively.

  15. High pressure pure- and mixed-gas separation of CO2/CH4 by thermally-rearranged and carbon molecular sieve membranes derived from a polyimide of intrinsic microporosity

    KAUST Repository

    Swaidan, Raja

    2013-11-01

    Natural gas sweetening, one of the most promising venues for the growth of the membrane gas separation industry, is dominated by polymeric materials with relatively low permeabilities and moderate selectivities. One strategy towards improving the gas transport properties of a polymer is enhancement of microporosity either by design of polymers of intrinsic microporosity (PIMs) or by thermal treatment of polymeric precursors. For the first time, the mixed-gas CO2/CH4 transport properties are investigated for a complete series of thermally-rearranged (TR) (440°C) and carbon molecular sieve (CMS) membranes (600, 630 and 800°C) derived from a polyimide of intrinsic microporosity (PIM-6FDA-OH). The pressure dependence of permeability and selectivity is reported up to 30bar for 1:1, CO2:CH4 mixed-gas feeds at 35°C. The TR membrane exhibited ~15% higher CO2/CH4 selectivity relative to pure-gas feeds due to reductions in mixed-gas CH4 permeability reaching 27% at 30bar. This is attributed to increased hindrance of CH4 transport by co-permeation of CO2. Interestingly, unusual increases in mixed-gas CH4 permeabilities relative to pure-gas values were observed for the CMS membranes, resulting in up to 50% losses in mixed-gas selectivity over the applied pressure range. © 2013 Elsevier B.V.

  16. Mesoporous molecular sieve MCM-41 synthesis from fluoride media

    Directory of Open Access Journals (Sweden)

    F. S. Bastos

    2011-12-01

    Full Text Available A study of the synthesis of MCM-41 mesoporous molecular sieves in fluoride media, having no alkaline metal ions, was performed by changing the gel composition and crystallization temperature and time. X-ray diffraction and nitrogen adsorption analyses showed that highly ordered MCM-41 samples were obtained from gels with a NH4OH/SiO2 molar ratio in the 3.25-4.3 range (room temperature synthesis or in the 4.3-20 range (24 hours at 373 K. During calcination, unit cell shrinkage, caused by high temperature polycondensation of the SiOH groups, was observed for all samples. The samples synthesized at high temperature (373 K or using low pH gels (7.5 underwent lower unit cell shrinkage than those obtained at room temperature or high pH (9.0, indicating that the former samples had lower SiOH groups content than the latter. These highly-ordered samples showed large surface area (ca. 1100 m²/g and pore volume (ca. 0.80 cm³/g, also presenting a narrow pore size distribution. Due to higher silicate polycondensation and a thicker pore wall, the samples synthesized at 373 K were more hydrothermally stable than those obtained at room temperature.

  17. Magnetic properties of iron loaded MCM-48 molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Elias, Veronica R. [Centro de Investigacion y Tecnologia Quimica, Universidad Tecnologica Nacional, Facultad Regional Cordoba. Cordoba (Argentina); CONICET (Argentina); Oliva, Marcos I. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Cordoba (Argentina); IFEG-CONICET (Argentina); Vaschetto, Eliana G. [Centro de Investigacion y Tecnologia Quimica, Universidad Tecnologica Nacional, Facultad Regional Cordoba. Cordoba (Argentina); Urreta, Silvia E., E-mail: urreta@famaf.unc.edu.a [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Cordoba (Argentina); Eimer, Griselda A. [Centro de Investigacion y Tecnologia Quimica, Universidad Tecnologica Nacional, Facultad Regional Cordoba. Cordoba (Argentina); CONICET (Argentina); Silvetti, Silvia P. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Cordoba (Argentina)

    2010-11-15

    Mesoporous molecular sieves of MCM-48 type were loaded with iron by the wet impregnation method, using Fe(III) nitrate or Fe(II) sulfate aqueous solutions as Fe sources, to obtain a magnetic porous composite. The iron loaded materials were characterized by XRD, N{sub 2} adsorption and DRUV-vis and compared with the Si-MCM-48 host. Their magnetic properties were studied by measuring the hysteresis loops up to 1.5 T at different temperatures (5-300 K) and by magnetization vs. temperature curves following the conventional zero field cooling (ZFC) and field cooling (FC) protocols. Materials with high structure regularity and surface area are obtained, which exhibit a mixed paramagnetic and superparamagnetic behavior, arising in isolated iron ions inserted in the host framework, and in small iron oxide clusters or nanoparticles forming inside the pores, respectively. Larger hematite particles (8-13 nm) grown on the external surface provide a quite small ferromagnetic contribution to the hysteresis loop.

  18. Preparation of carbon nanotubes by ethanol pyrolysis using Co-containing mesoporous molecular sieve as catalyst%含钴介孔分子筛催化热解乙醇制备纳米碳管

    Institute of Scientific and Technical Information of China (English)

    张丽; 纪美茹; 赵谦; 田军

    2012-01-01

    以CTAB为模板剂,硅酸钠、氯化钴为原料,通过水热法合成含钴介孔分子筛(Co-MCM-41).以所合成的Co-MCM-41做催化剂,采用化学气相沉积(CVD)法催化热解乙醇制备纳米碳管.通过XRD、FT-IR、TEM、N2吸附-脱附和Raman光谱等分析手段对所合成的介孔分子筛和纳米碳管进行了表征.结果表明:合成的Co-MCM-41样品具有MCM-41的介孔结构,比表面积较大且介孔有序性较好.以所合成的含钴介孔分子筛催化热解乙醇制备出管径均匀、管壁较厚、顶端开口的多壁纳米碳管.%Co-MCM-41 mesoporous molecular sieves were synthesized by hydrothermal method using cetyltrimethyl ammonium bromide as template and sodium silicate and cobalt chloride as raw materials, respectively. Carbon nanotubes ( CNTs) were synthesized by chemical vapor deposition ( CVD) method using the Co-MCM-41 as a catalytic template by the pyrolysis of ethanol at atmospheric pressure. The physicochemical properties of the obtained samples were characterized by X-ray diffraction ( XRD) , Fourier transform infrared spectroscopy ( FT-IR) .transmission electron microscopy ( TEM ) , N2 physical adsorption and Raman spectroscopy, respectively. The results show that the Co-MCM-41 samples possess a typical mesoporous framework of MCM-41. These mesoporous materials have high specific surface area and good mesoporous ordering. The open-ended and high purification CNTs with uniform diameter and thicker wall were successfully synthesized.

  19. Molecular sieve sampling of CO2 from decomposition of soil organic matter for AMS radiocarbon measurements

    International Nuclear Information System (INIS)

    A molecular sieve based procedure has been established for sampling CO2 of decomposing soil organic matter for AMS radiocarbon measurements. The sampling and desorption lines are capable to produce well measurable (>1 mg) AMS targets.

  20. Adsorption Characteristics of H2 on Molecular Sieves 5A at 77 K

    Institute of Scientific and Technical Information of China (English)

    XIA; Ti-rui; YANG; Hong-guang; LIU; Wen-jun; LIU; Zhen-xing; ZHAO; Wei-wei; HAN; Zhi-bo

    2013-01-01

    With the aim of applying cryogenic molecular sieves bed(CMSB)to a tritium extraction system(TES)for ITER TBM,adsorption characteristics of H2 on a molecular sieve at 77 K was investigated by a volumetric method.The adsorption isotherms for H2 in a pressure range between about 1 and 103 Pa was shown in Fig.1,and alkaline treatment(CaA includes not only Na+but also Ca2+)improved the adsorption

  1. Cryogenic Adsorption of Low-concentration Hydrogen on 5A Molecular Sieve Bed

    Institute of Scientific and Technical Information of China (English)

    LIU; Zhen-xing; YANG; Hong-guang; XIA; Ti-rui; ZHAN; Qin; YANG; Li-ling

    2013-01-01

    The separation of low-concentration hydrogen isotopes from helium is a processing step that is required for ceramic lithium breeding blanket processing.In this study,the adsorption of low-concentration hydrogen from helium carrier was measured using 5A molecular sieve fixed bed in the cryogenic condition.The adsorption performances of hydrogen on 5A molecular sieve were discussed.The effect of the different

  2. Carbon molecular sieve membranes for gas separation

    OpenAIRE

    Briceño Mejías, Kelly Cristina

    2012-01-01

    Membrane separations are simple, energy efficient processes, which can be economically competitive with traditional separation technologies. In the case of gas separation both dense and porous materials have been developed for different application where hydrogen production is one of the most important niches of development. Hydrogen is being one of the most important vectors to develop alternative clean power generation sources. Nowadays, a lot of processes require the fabrication of pure hy...

  3. Tritium recovery from helium purge stream of solid breeder blanket by cryogenic molecular sieve bed. 2. Regeneration operation of cryogenic molecular sieve bed

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Yoshinori; Enoeda, Mikio; Nishi, Masataka [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Regeneration operation is a very important operation, because it is the most influential factor for deciding the net operation cycle time and the minimum dimension of Cryogenic Molecular Sieve Bed (CMSB). However, the experimental data of CMSB regeneration operation was not so sufficient that even the optimum regeneration procedure could not be decided yet. This work was focused on getting the primary information about various regeneration procedures. (author)

  4. Preparation of Molecular Sieve Catalyst and Application in the Catalytic Oxidation Treatment of Waste Water

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Citric acid is an important additive in foods, cosmetics, medicine and so on, but it discharges about 10 ton of factory effluent when 1 ton of citric acid is produced. The COD of the factory effluent is near 20000 mg/L. The treatment of citric acid factory effluent is a serious problem in environmental chemistry. It is found that molecular sieve support metal complexes have high catalytic activity in aerobic oxidation of alkene [1,2]. In this paper, a kind of molecular sieve catalyst was prepared. The catalyst was used for the treatment of citric acid factory effluent by method of catalytic oxygen oxidation.

  5. Development of design information for molecular-sieve type regenerative CO2-removal systems

    Science.gov (United States)

    Wright, R. M.; Ruder, J. M.; Dunn, V. B.; Hwang, K. C.

    1973-01-01

    Experimental and analytic studies were conducted with molecular sieve sorbents to provide basic design information, and to develop a system design technique for regenerable CO2-removal systems for manned spacecraft. Single sorbate equilibrium data were obtained over a wide range of conditions for CO2, water, nitrogen, and oxygen on several molecular sieve and silica gel sorbents. The coadsorption of CO2 with water preloads, and with oxygen and nitrogen was experimentally evaluated. Mass-transfer, and some limited heat-transfer performance evaluations were accomplished under representative operating conditions, including the coadsorption of CO2 and water. CO2-removal system performance prediction capability was derived.

  6. Dehydrogenative Aromatization of Saturated Aromatic Compounds by Graphite Oxide and Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    张轩; 徐亮; 王希涛; 马宁; 孙菲菲

    2012-01-01

    Graphite oxide (GO) has attracted much attention of material and catalysis chemists recently. Here we describe a combination of GO and molecular sieves for the dehydrogenative aromatization. GO prepared through improved Hummers method showed high oxidative activity in this reaction. Partially or fully saturated aromatic compounds were converted to their corresponding dehydrogenated aromatic products with fair to excellent conversions and selectivities. As both GO and molecular sieves are easily available, cheap, lowly toxic and have good tolerance to various functional groups, this reaction provides a facile approach toward aromatic compounds from their saturated precursors

  7. Synthesis and chemistry of chromium in CrAPO-5 molecular sieves

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Schoonheydt, R.A.

    1994-01-01

    CrAPO-5 molecular sieves were synthesized hydrothermally starting with different Cr precursors and Cr and template contents. The behavior of Cr was investigated spectroscopically by diffuse reflectance spectroscopy (d.r.s.) and electron spin resonance (e.s.r.). In the gels, Cr 3+ and Cr 8+ are prese

  8. Preparation of Mesoporous Molecular Sieves Al-MSU-S Using Ionic Liquids as Template

    Institute of Scientific and Technical Information of China (English)

    YU Xin-Yu; LIU Cai-Hua; YANG Jian-Guo; WU Hai-Hong; WU Peng; HE Ming-Yuan

    2006-01-01

    Mesoporous molecular sieves Al-MSU-S has been prepared from the precursor of zeolite Y using ionic liquids l-hexadecane-3-methylimidazolium bromide (CMIMB) as a template in basic medium, which exhibited larger pore diameter, pore volume and surface area than that synthesized using cetyl trimethyl ammonium bromide (CTAB)template.

  9. Synthesis of Mesoporous Silica and Ti-containing Molecular Sieves via A Novel Assembly

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Thermally stable mesoporous silica and Ti-containing molecular sieves have been synthesized at mild temperature using low-cost and biodegradable---amphoteric tetradecyl betaine as template. The physicochemical characterizations proved that Ti(Ⅳ) could be incorporated in the mesoporous struture.

  10. Experiments for the Undergraduate Laboratory that Illustrate the Size-Exclusion Properties of Zeolite Molecular Sieves

    Science.gov (United States)

    Cooke, Jason; Henderson, Eric J.

    2009-01-01

    Experiments are presented that demonstrate the size-exclusion properties of zeolites and reveal the reason for naming zeolites "molecular sieves". If an IR spectrometer is available, the adsorption or exclusion of alcohols of varying sizes from dichloromethane or chloroform solutions can be readily demonstrated by monitoring changes in the…

  11. Aminopropyl-modified mesoporous molecular sieves as efficient adsorbents for removal of auxins

    Energy Technology Data Exchange (ETDEWEB)

    Moritz, Michał, E-mail: michal.moritz@put.poznan.pl [Poznan University of Technology, Faculty of Chemical Technology, Institute of Chemistry and Technical Electrochemistry, Berdychowo 4, 60-965 Poznań (Poland); Geszke-Moritz, Małgorzata, E-mail: Malgorzata.Geszke-Moritz@amu.edu.pl [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-03-15

    Graphical abstract: Adsorption of indole-3-acetic acid (IAA) on aminopropyl-modified mesoporous sieves. - Highlights: • Four types of mesoporous molecular sieves were used as sorbents for removal of auxins. • SBA-15, MCF, PHTS and SBA-16 were grafted with (3-aminopropyl)triethoxysilane. • The adsorption capacity of modified materials was higher as compared to pure silicas. • Surface modification and pore volume play important role in adsorption process. - Abstract: In the present study, mesoporous siliceous materials grafted with 3-aminopropyltriethoxysilane (APTES) were examined as sorbents for removal of chosen plant growth factors (auxins) such as 1-naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). Four different types of mesoporous molecular sieves including SBA-15, PHTS, SBA-16 and MCF have been prepared via non-ionic surfactant-assisted soft templating method. Silica molecular sieves were thoroughly characterized by nitrogen adsorption–desorption analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The maximum adsorption capacity (Q{sub max}) for NAA, IAA and IBA was in the range from 51.0 to 140.8 mg/g and from 4.3 to 7.3 mg/g for aminopropyl-modified adsorbents and pure silicas, respectively. The best adsorption performance was observed for IAA entrapment using both APTES-functionalized SBA-15 and MCF matrices (Q{sub max} of 140.8 and 137.0 mg/g, respectively) which can be ascribed to their larger pore volumes and pore diameters. Moreover, these silicas were characterized by the highest adsorption efficiency exceeding 90% at low pollutant concentration. The experimental points for adsorption of plant growth factors onto aminopropyl-modified mesoporous molecular sieves fitted well to the Langmuir equation.

  12. 氧化钾/SBA-15催化合成碳酸二正丁酯%SYNTHESIS OF DIBUTYL CARBONATE BY TRANSESTERIFICATION OVER MESOPOROUS MOLECULAR SIEVE K2O/SBA-15

    Institute of Scientific and Technical Information of China (English)

    崔晓燕; 沈健

    2011-01-01

    以介孔分子筛SBA-15为载体,浸渍KNO3后经过焙烧,制得K2O/SBA-15固体碱催化剂.通过XRD,N2等温吸附脱附和IR等测试手段对试样进行了分析.研究了K2O/SBA-15催化碳酸二甲酯(DMC)与正丁醇(n-BuOH)酯交换合成碳酸二正丁酯(DBC)的反应.结果表明:当K2O负载量为2%,反应时间2 h,反应温度180℃,n(正丁醇)∶n(DMC)为3.0,m(催化剂)∶m(原料)为0.08时,DMC转化率最大为89.6%,DBC 收率为58%,DBC选择性为64.7%.并且K2O/SBA-15催化剂重复使用多次仍具有较好的催化效果.%K2O/SBA-15 as the solid base catalyst was synthesized bu loading potassium on mesoporous sieve SBA-15.The sample has been characterized by XRD, N2 adsorption desorption and IR.The study on the synthesis of dibutyl carbonate from dimethyl carbonate and butanol has been done.The experimental results showed that when the loaded mount of K2 O was 2 %, reaction time was 2 h, reaction temperature was 180 ℃ ,n(n-butanol): n(dimethyl carbonate) was 3 and the ratio of catalyst to raw material was 8%, the highest conversion of dimethyl carbonate was 89.6%, the yield of DBC was 58%, the selectivity to DBC was 64.7%.The results also showed that the K2O/SBA-15 could be reused with good catalytic effect.

  13. Preparation of Molecular Sieve Catalyst and Application in the Catalytic Oxidation Treatment of Waste Water

    Institute of Scientific and Technical Information of China (English)

    WANG; RongMin

    2001-01-01

    Citric acid is an important additive in foods, cosmetics, medicine and so on, but it discharges about 10 ton of factory effluent when 1 ton of citric acid is produced. The COD of the factory effluent is near 20000 mg/L. The treatment of citric acid factory effluent is a serious problem in environmental chemistry.  It is found that molecular sieve support metal complexes have high catalytic activity in aerobic oxidation of alkene [1,2]. In this paper, a kind of molecular sieve catalyst was prepared. The catalyst was used for the treatment of citric acid factory effluent by method of catalytic oxygen oxidation.  ……

  14. Removal of Nitrogen Oxides in Diesel Engine Exhaust by Plasma Assisted Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper reports the studies conducted on removal of oxides of nitrogen (NOx) from diesel engine exhaust using electrical discharge plasma combined with adsorbing materials such as molecular sieves. This study is being reported for the first time. The exhaust is taken from a diesel engine of 6 kW under no load conditions. The characteristic behavior of a pulse energized dielectric barrier discharge reactor in the diesel exhaust treatment is reported. The NOx removal was not significant (36%) when the reactor without any packing was used. However, when the reactor was packed with molecular sieves (MS -3A, -4A & -13X), the NOx removal efficiency was increased to 78% particularly at a temperature of 200 o C. The studies were conducted at different temperatures and the results were discussed.

  15. Catalytic Performance of Al-MCM-48 Molecular Sieves for Isopropylation of Phenol with Isopropyl Acetate

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethyl-ammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffraction patterns and transmission electron microscopy images. The catalytic performance of the materials was evaluated in the vapor phase isopropylation of phenol with isopropyl acetate. Phenol conversion decreased with the increase in the Si/Al ratio of the catalysts. The major reaction product was 4-isopropyl phenol with 78% selectivity. The delocalization of phenolic oxygen electron pair over the aromatic ring promoted para-selective alkylation. Such delocalization could be aided by the hydrophilic surface of the molecular sieves. Although an ester was used as the alkylating agent, phenyl isopropyl ether was not formed in the reaction.

  16. [Removal Characteristics of Elemental Mercury by Mn-Ce/molecular Sieve].

    Science.gov (United States)

    Tan, Zeng-qiang; Niu, Guo-ping; Chen, Xiao-wen; An, Zhen

    2015-06-01

    The impregnation method was used to support molecular sieve with active manganese and cerium components to obtain a composite molecular sieve catalyst. The mercury removal performance of the catalyst was studied with a bench-scale setup. XPS analysis was used to characterize the sample before and after the modification in order to study the changes in the active components of the catalyst prepared. The results showed that the catalyst carrying manganese and cerium components had higher oxidation ability of elemental mercury in the temperature range of 300 degrees C - 450 degrees C, especially at 450 degrees C, the oxidation efficiency of elemental mercury was kept above 80%. The catalyst had more functional groups that were conducive to the oxidation of elemental mercury, and the mercury removal mainly depended on the chemical adsorption. The SO2 and NO in flue gas could inhibit the oxidation of elemental mercury to certain extent. PMID:26387298

  17. Evaluation of RTV as a Moldable Matrix When Combined With Molecular Sieve and Organic Hydrogen Getter

    Energy Technology Data Exchange (ETDEWEB)

    Knight, J. A.

    2011-12-01

    This work was undertaken in an effort to develop a combined RTV 615/3Å molecular sieve/DEB molded component. A molded RTV 615/3Å molecular sieve component is currently in production, and an RTV 615/DEB component was produced in the past. However, all three materials have never before been combined in a single production part, and this is an opportunity to create a new component capable of being molded to shape, performing desiccation, and hydrogen gettering. This analysis looked at weapons system parameters and how they might influence part design. It also looked at material processing and how it related to mixing, activating a dessicant, and hydrogen uptake testing.

  18. Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes

    OpenAIRE

    Martínez Sánchez, Mª Cristina; Corma Canós, Avelino

    2011-01-01

    The increasing environmental concern and promotion of “green processes” are forcing the substitution of traditional acid and base homogeneous catalysts by solid ones. Among these heterogeneous catalysts, zeolites and zeotypes can be considered as real “green” catalysts, due to their benign nature from an environmental point of view. The importance of these inorganic molecular sieves within the field of heterogeneous catalysis relies not only on their microporous structure and the related shap...

  19. Photocatalytic Properties of Nb/MCM-41 Molecular Sieves: Effect of the Synthesis Conditions

    OpenAIRE

    Caterine Daza Gomez; J. E. Rodriguez-Paez

    2015-01-01

    The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of niobium incorporation. The synthesized Nb-MCM-41 ceramic powders were characterized using the spectroscopic techniques of infrared spectroscopy (IR), Raman spectroscopy, X-ray diffract...

  20. Preparation and Characterization of Single Crystals of MAPO-43 Molecular Sieve

    Institute of Scientific and Technical Information of China (English)

    Jian Jun LI; Guo Dong LI; Chun Yu XI; Jie Sheng CHEN

    2004-01-01

    Large single crystals of MAPO-43 molecular sieve have been synthesized hydrothermally using dimethylamine as the template. The typical molar composition of the starting mixture was 1.0P2O5 : 0.54Al2O3: 0.8MgO: 8.5CH3NHCH3: 0.68HF: 180H2O. The sample was characterized by XRD, TGA, DTA and IR.

  1. Design Through Simulation of a Molecular Sieve Column for Treatment of MON-3

    Science.gov (United States)

    Swartz, A. Ben; Wilson, D. B.

    1999-01-01

    The presence of water in propellant-grade MON-3 is a concern in the Aerospace Industry. NASA Johnson Space Center (JSC), White Sands Test Facility (WSTF) Propulsion Department has evaluated many types of molecular sieves for control of iron, the corrosion product of water in Mixed Oxides of Nitrogen (MON-3). In 1995, WSTF initiated laboratory and pilot-scale testing of molecular sieve type 3A for removal of water and iron. These tests showed sufficient promise that a series of continuous recycle tests were conducted at WSTF. Periodic samples of the circulating MON-3 solution were analyzed for water (wt %) and iron (ppm, wt). This test column was modeled as a series of transfer units; i. e., each unit represented the height equivalent of a theoretical plate. Such a model assumes there is equilibrium between the adsorbent material and the effluent stream from the unit. Operational and design parameters were derived based on the simulation results. These parameters were used to predict the design characteristics of a proposed molecular sieve column for removal of water and iron from MON-3 at the NASA Kennedy Space Center (KSC). In addition, these parameters were used to simulate a small, single-pass operation column at KSC currently used for treating MON-3. The results of this work indicated that molecular sieve type 3A in 1/16 in. diameter pellets, in a column 2.5 ft. in diameter, 18 ft. in height, and operated at 25 gpm is adequate for the required removal of water and iron from MON-3.

  2. Stability of Y/MCM-48 composite molecular sieve with mesoporous and microporous structures

    Directory of Open Access Journals (Sweden)

    Qian Zhao

    2014-12-01

    Full Text Available Y/MCM-48 composite molecular sieve was hydrothermally synthesized at different crystallization temperatures and crystallization times using ethyl orthosilicate as Si source and cetyltrimethyl ammonium bromide as template with the aid of fluoride ions and was characterized by X-ray diffraction, N2 physical adsorption technique, scanning electron microscopy and transmission electron microscopy. The thermal, hydrothermal, acidic, and basic stabilities of the Y/MCM-48 composite were investigated. The results show that Y/MCM-48 composite molecular sieve with meso- and microporous structures was synthesized successfully at 120 °C for 36 h. The Y/MCM-48 composite has the surface area of 864 m2/g and the average pore size is ca. 2.48 nm. The bi-porous structure in composite molecular sieve still maintains its stability even after thermal treatment at 800 °C for 4 h or hydrothermal treatment at 100 °C for 48 h. After treatment in 1 mol/L hydrochloric acid solution or 1 mol/L sodium hydroxide solution for 48 h, the Y/MCM-48 composite exhibits good acidic stability. The acidic stability is superior to the basic stability at the same treatment time.

  3. Synthesis and characterization of a new microporous cesium silicotitanate (SNL-B) molecular sieve

    Energy Technology Data Exchange (ETDEWEB)

    NYMAN,MAY D.; GU,B.X.; WANG,L.M.; EWING,R.C.; NENOFF,TINA M.

    2000-03-20

    Ongoing hydrothermal Cs-Ti-Si-O-H{sub 2}O phase investigations has produced several new ternary phases including a novel microporous Cs-silicotitanate molecular sieve, SNL-B with the approximate formula of Cs{sub 3}TiSi{sub 3}O{sub 9.5}{center_dot}3H{sub 2}O. SNL-B is only the second molecular sieve Cs-silicotitanate phase reported to have been synthesized by hydrothermal methods. Crystallites are very small (0.1 x 2 microns) with a blade-like morphology. SNL-B is confirmed to be a 3-dimensional molecular sieve by a variety of characterization techniques (N{sub 2} adsorption, ion exchange, water adsorption/desorption, solid state CP-MAS NMR). SNL-B is able to desorb and adsorb water from its pores while retaining its crystal structure and exchanges Cs cations readily. Additional techniques were used to describe fundamental properties (powder X-ray diffraction, FTIR, {sup 29}Si and {sup 133}/Cs MAS NMR, DTA, SEM/EDS, ion selectivity, and radiation stability). The phase relationships of metastable SNL-B to other hydrothermally synthesized Cs-Ti-Si-O-H{sub 2}O phases are discussed, particularly its relationship to a Cs-silicotitanate analogue of pharmacosiderite, and a novel condensed phase, a polymorph of Cs{sub 2}TiSi{sub 6}O{sub 15}(SNL-A).

  4. A Pervaporation Study of Ammonia Solutions Using Molecular Sieve Silica Membranes

    Directory of Open Access Journals (Sweden)

    Xing Yang

    2014-02-01

    Full Text Available An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV, benchmarked against vacuum membrane distillation (VMD. Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor downstream and long-term performance. A modified low-temperature membrane evaluation system was utilized, featuring the ability to capture and measure ammonia in the permeate. It was found that the silica membrane with confirmed molecular sieving features had higher water selectivity over ammonia. This was due to a size selectivity mechanism that favoured water, but blocked ammonia. However, a cobalt doped silica membrane previously treated with high temperature water solutions demonstrated extraordinary preference towards ammonia by achieving up to a 50,000 mg/L ammonia concentration (a reusable concentration level measured in the permeate when fed with 800 mg/L of ammonia solution. This exceeded the concentration factor expected by the benchmark VMD process by four-fold, suspected to be due to the competitive adsorption of ammonia over water into the silica structure with pores now large enough to accommodate ammonia. However, this membrane showed a gradual decline in selectivity, suspected to be due to the degradation of the silica material/pore structure after several hours of operation.

  5. A pervaporation study of ammonia solutions using molecular sieve silica membranes.

    Science.gov (United States)

    Yang, Xing; Fraser, Thomas; Myat, Darli; Smart, Simon; Zhang, Jianhua; Diniz da Costa, João C; Liubinas, Audra; Duke, Mikel

    2014-01-01

    An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV), benchmarked against vacuum membrane distillation (VMD). Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor downstream and long-term performance. A modified low-temperature membrane evaluation system was utilized, featuring the ability to capture and measure ammonia in the permeate. It was found that the silica membrane with confirmed molecular sieving features had higher water selectivity over ammonia. This was due to a size selectivity mechanism that favoured water, but blocked ammonia. However, a cobalt doped silica membrane previously treated with high temperature water solutions demonstrated extraordinary preference towards ammonia by achieving up to a 50,000 mg/L ammonia concentration (a reusable concentration level) measured in the permeate when fed with 800 mg/L of ammonia solution. This exceeded the concentration factor expected by the benchmark VMD process by four-fold, suspected to be due to the competitive adsorption of ammonia over water into the silica structure with pores now large enough to accommodate ammonia. However, this membrane showed a gradual decline in selectivity, suspected to be due to the degradation of the silica material/pore structure after several hours of operation. PMID:24957120

  6. MOLECULAR SIEVES AS CATALYSTS FOR METHANOL DEHYDRATION IN THE LPDMEtm PROCESS

    Energy Technology Data Exchange (ETDEWEB)

    Andrew W. Wang

    2002-04-01

    Several classes of molecular sieves were investigated as methanol dehydration catalysts for the LPDME{trademark} (liquid-phase dimethyl ether) process. Molecular sieves offer a number of attractive features as potential catalysts for the conversion of methanol to DME. These include (1) a wide range of acid strengths, (2) diverse architectures and channel connectivities that provide latitude for steric control, (3) high active site density, (4) well-investigated syntheses and characterization, and (5) commercial availability in some cases. We directed our work in two areas: (1) a general exploration of the catalytic behavior of various classes of molecular sieves in the LPDME{trademark} system and (2) a focused effort to prepare and test zeolites with predominantly Lewis acidity. In our general exploration, we looked at such diverse materials as chabazites, mordenites, pentasils, SAPOs, and ALPOs. Our work with Lewis acidity sought to exploit the structural advantages of zeolites without the interfering effects of deleterious Broensted sites. We used zeolite Ultrastable Y (USY) as our base material because it possesses a high proportion of Lewis acid sites. This work was extended by modifying the USY through ion exchange to try to neutralize residual Broensted acidity.

  7. Cerium modified Y/SBA-15 composite molecular sieve catalyzed synthesis ofn-butyl acetate

    Institute of Scientific and Technical Information of China (English)

    史春薇; 吴文远; 边雪; 裴明远; 赵杉林; 陈平

    2016-01-01

    A novel Ce-Y/SBA-15 catalyst was prepared by modifying HY/SBA-15 microporous-mesoporous composite molecular sieve with cerium using the impregnation method. The characterization results from scanning electron microscopy/energy dispersive X-ray dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and X-ray fluorescence (XRF) studies indi-cated that the Ce-modified catalyst maintained the microporous-mesoporous structure of Y/SBA-15. The Ce ions were found to be uniformly dispersed in the pores of the molecular sieve without aggregation. The results from pyrolysis coupled-Fourier transform in-frared spectroscopy (Pyridine-FTIR) and temperature programmed desorption of ammonia (NH3-TPD) showed that the loading of ce-rium caused the hydroxyl group in the catalyst to display stronger Bronsted acidity. The efficiency of the modified Ce-Y/SBA-15 catalyst was evaluated by using it to catalyze the synthesis ofn-butyl acetate. The optimal synthesis conditions were determined by orthogonal experiments. The highest esterification yield of 94.4% was obtained when the reaction time was 2.0 h, with acid/alcohol molar ratio of 1:1.2, and catalyst loading of 10 wt.%. The results in this study demonstrated that the loading of cerium and the structure of Y/SBA-15 microporous-mesoporous composite molecular sieve helped in improving the catalytic activity of this acidic catalyst.

  8. Thermal and hydrothermal stability of ZrMCM-41 mesoporous molecular sieves obtained by microwave irradiation

    Indian Academy of Sciences (India)

    T S Jiang; Y H Li; X P Zhou; Q Zhao; H B Yin

    2010-05-01

    ZrMCM-41 mesoporous molecular sieves were synthesized by using the zirconium sulfate as zirconium source and using cetyltrimethyl ammonium bromide as a template under microwave irradiation condition. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma (ICP) technique, Fourier transform infrared spectroscopy (FT-IR) and N2 physical adsorption, respectively. The effect of the different initial ZrO2 : SiO2 molar ratio, the different thermal treatment temperature and hydrothermal treatment time on textural property was investigated. The results show that the obtained products possess a typical mesoporous structure of MCM-41 and have specific surface areas in the range of 598.1 ∼ 971.4 m2/g and average pore sizes in the range of ca. 2.46 ∼ 3.43 nm. On the other hand, the BET specific surface area and pore volume of the synthesized ZrMCM-41 mesoporous molecular sieve decrease with the increased amount of zirconium incorporated in the starting material, the rise of thermal treatment temperature and the prolonging of hydrothermal treatment time, the mesoporous ordering deteriorates. The mesoporous structure of the ZrMCM-41 mesoporous molecular sieve still retains after calcination at 750°C for 3 h or hydrothermal treatment at 100°C for 6 days, however, the mesoporous ordering is poor.

  9. Aromatization of n-hexane by platinum-containing molecular sieves. 1. Catalyst preparation by the vapor phase impregnation method

    Energy Technology Data Exchange (ETDEWEB)

    Suk Bong Hong; Mielczarski, E.; Davis, M.E. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States))

    1992-03-01

    A vapor phase impregnation method with Pt(acac){sub 2} has been developed and used to load Pt into aluminosilicate (KL, BaKL, NaY, CsNaY, cubic and hexagonal polytypes of faujasite, ZSM-12, and SSZ-24) and aluminophosphate (AlPO{sub 4}-5 and VPI-5) molecular sieves. Pt-containing molecular sieves are characterized by XRD,TPD, elemental analysis, {sup 13}C MAS NMR, TEM, and H{sub 2} chemisorption. {sup 13}C MAS NMR, TEM, and H{sub 2} chemisorption measurements reveal that Pt can be loaded into the micropores of molecular sieves with both charged and neutral frameworks. Pt impregnated into zeolites and aluminophosphates by this method does not migrate to the exterior surface of the molecular sieve catalysts at n-hexane aromatization reaction conditions of atmospheric pressure and temperatures between 460 and 510 C.

  10. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  11. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  12. Molecular sieve supported ionic liquids as efficient adsorbent for CO2 capture

    OpenAIRE

    Yang Na; Wang Rui

    2015-01-01

    [NH3e-mim][BF4], [OHe-mim][BF4] and [HOEAm] were selected and supported onto molecular sieves NaY, USY, SAPO-34 and MCM-41, to prepare supported ionic liquids. It was found that [NH3e-mim][BF4]/NaY has excellent CO2 adsorption performance, with adsorption capacity of 0.108 mmolCO2/g. This paper investigates the optimal adsorption conditions and recyclability of [NH3e-mim][BF4]/NaY. The results show that [NH3e-mim][BF4]/NaY has good CO2 adsorption under the ...

  13. Stabilization of ferroelectricity in KNO3 embedded into MCM-41 molecular sieves

    International Nuclear Information System (INIS)

    Measurements of the linear permittivity and third-order harmonic generation were carried out for KNO3 loaded molecular sieves MCM-41 with pores of 37 and 26 A in comparison with bulk potassium nitrate. The samples were warmed up to 423 and 463 K from room temperature. The ferroelectric phase III was shown to occur upon cooling in both nanocomposites after warming till 463 K when it emerges also in bulk KNO3. Nanoconfinement led to the pronounced broadening of the temperature range of ferroelectricity. While under the thermal conditions when phase III does not arise in bulk KNO3, ferroelectricity was found only within pores of 26 A.

  14. Ti-modified Mesoporous Molecular Sieves Containing both Selective Oxidation and Photocatalysis Centers

    Institute of Scientific and Technical Information of China (English)

    GUO Zong-ying; HE Jing; David G. Evans; DUAN Xue; ZHU Yue-xiang; XIAO Tian-cun

    2004-01-01

    Mesoporous molecular sieves possessing high mesopore volumes and large specific surface areas were prepared and characterized by means of XRD, low temperature N2 adsorption-desorption measurements,FT IR, Raman, UV-visible diffuse reflectance and XPS spectroscopy. The materials contain both framework and extra-framework Ti centers which exhibit selective oxidation catalytic activity and photocatalytic activity respectively. The catalysis of selective oxidation was studied with the hydroxylation of benzene with hydrogen peroxide and photochemical activity was studied by the yields of · OH and H2O2, respectively.

  15. Hydroxylation of phenol over MeAPO molecular sieves synthesized by vapor phase transport

    Science.gov (United States)

    Shao, Hui; Chen, Jingjing; Chen, Xia; Leng, Yixin; Zhong, Jing

    2016-07-01

    In this study, MeAPO-25 (Me = Fe, Cu, Mn) molecular sieves were first synthesized by a vapor phase transport method using tetramethyl guanidine as the template and applied to hydroxylation of phenol. The zeolites were characterized by XRD, SEM, FT-IR, and DR UV-Vis. As a result, MeAPO-21 and MeAPO-15 were synthesized by changing the Me/Al ratio. UV-Visible diffuse reflectance study suggested incorporation of heteroatoms into the framework and FT-IR study also supported these data. Effects of heteroatoms, contents of Me in MeAPO-25, reaction temperature, phenol/H2O2 mole ratios, reaction time and concentration of catalyst on the conversion of phenol, as well as on the selectivity were studied. FeAPO-25 exhibited a high catalytic activity at the mole ratio of FeO and Al2O3 equal to 0.1 in the synthesis gel, giving the phenol conversion of 88.75% and diphenols selectivity of 66.23% at 60°C within 3 h [ n(phenol)/ n(H2O2) = 0.75, m(FeAPO-25)/ m(phenol) = 7.5%]. Experimental results indicated that the FeAPO-25 molecular sieve was a fairly promising candidate for the application in hydroxylation of phenol.

  16. Molecular sieve/sulfonated poly(ether ketone ether sulfone) composite membrane as proton exchange membrane

    Science.gov (United States)

    Changkhamchom, Sairung; Sirivat, Anuvat

    2012-02-01

    A proton exchange membrane (PEM) is an electrolyte membrane used in both polymer electrolyte membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFCs). Currently, PEMs typically used for PEMFCs are mainly the commercially available Nafion^ membranes, which is high cost and loss of proton conductivity at elevated temperature. In this work, the Sulfonated poly(ether ketone ether sulfone), (S-PEKES), was synthesized by the nucleophilic aromatic substitution polycondensation between bisphenol S and 4,4'-dichlorobenzophenone, and followed by the sulfonation reaction with concentrated sulfuric acid. The molecular sieve was added in the S-PEKES matrix at various ratios to form composite membranes to be the candidate for PEM. Properties of both pure sulfonated polymer and composite membranes were compared with the commercial Nafion^ 117 membrane from Dupont. S-PEKES membranes cast from these materials were evaluated as a polymer electrolyte membrane for direct methanol fuel cells. The main properties investigated were the proton conductivity, methanol permeability, thermal, chemical, oxidative, and mechanical stabilities by using a LCR meter, Gas Chromatography, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy, Fenton's reagent, and Universal Testing Machine. The addition of the molecular sieve helped to increase both the proton conductivity and the methanol stability. These composite membranes are shown as to be potential candidates for use as a Proton Exchange Membrane (PEM).

  17. Dynamics of ferrocene in molecular sieves probed by Mossbauer spectroscopy and nuclear resonant scattering

    International Nuclear Information System (INIS)

    A detailed study on the slow dynamics of ferrocene in the unidimensional channels of the molecular sieves SSZ-24 and AlPO4-5 has been carried out, using Moessbauer spectroscopy (MS), nuclear forward scattering (NFS) and synchrotron radiation-based perturbed angular correlations (SRPAC). In both host systems, anisotropic rotational dynamics is observed above 100 K. For SSZ-24, this anisotropy persists even above the bulk melting temperature of ferrocene. Various theoretical models are exploited for the study of anisotropic discrete jump rotations for the first time. The experimental data can be described fairly well by a jump model that involves reorientations of the molecular axis on a cone mantle with an opening angle dependant on temperature.

  18. 催化氧化脱硫分子筛催化剂研究进展%Research progress of molecular sieve catalyst for catalytic oxidative desulfurization

    Institute of Scientific and Technical Information of China (English)

    宋华; 穆金城

    2011-01-01

    The advance in catalytic oxidative desulfurization over molecular sieve, including TS molecular sieve catalyst, SBA molecular sieve catalyst, HMS molecular sieve catalyst, MCM molecular sieve catalyst, ZSM-5 molecular sieve catalyst, and aluminophosphate molecular sieve catalyst is summarized. Among these molecular sieve catalysts, SBA, HMS, MCM, aluminophosphate mesoporous molecular sieves catalysts have higher desulfurization rate of macromolecule sulfides and therefore have good prospect. The research of molecular sieve catalyst for oxidative desulfurization should be focused on developing large pore size general molecular sieve, investigating the mechanism and reducing the cost of oxidative desulfurization.%综述了催化氧化脱硫分子筛催化剂的研究进展.介绍了TS分子筛催化剂、SBA分子筛催化剂,HMS分子筛催化剂、MCM分子筛催化剂、ZSM-5分子筛催化剂和磷酸铝分子筛催化剂上油品的氧化脱硫方法,其中SBA、HMS、MCM和磷酸铝介孔分子筛催化剂对大分子的硫化物脱除率较高,具有很好的发展前景.今后分子筛催化氧化脱硫技术研究的重要方向是进一步开发通用性好的大孔径分子筛,研究脱硫机理和降低成本.

  19. Exploring meso-/microporous composite molecular sieves with core-shell structures.

    Science.gov (United States)

    Qian, Xufang F; Li, Bin; Hu, Yuanyuan Y; Niu, Guoxing X; Zhang, D Yahong H; Che, Renchao C; Tang, Yi; Su, Dangsheng S; Asiri, Abdullah M; Zhao, Dongyuan Y

    2012-01-16

    A series of core-shell-structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM-5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant-directed sol-gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15-100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso-/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4-3.0 nm in diameter) to zeolite micropores (≈0.51 nm). The short-time kinetic diffusion efficiency of benzene molecules within pristine ZSM-5 (≈7.88×10(-19)  m(2)  s(-1)) is almost retainable after covering with 75 nm-thick mesoporous silica shells (≈7.25×10(-19)  m(2)  s(-1)), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core-shell composite shows greatly enhanced adsorption capacity (≈1.35 mmol  g(-1)) for large molecules such as 1,3,5-triisopropylbenzene relative to that of pristine ZSM-5 (≈0.4 mmol  g(-1)) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core-shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Brønsted acid sites). The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core-shell structure over pristine ZSM-5. Insight into the core-shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes. PMID

  20. Changes in the molecular sieve of glomerular basement membrane in rats with aminonucleoside nephrosis.

    Directory of Open Access Journals (Sweden)

    Takaya,Yasumasa

    1980-02-01

    Full Text Available Isolated and purified glomerular basement membranes (GBM of normal and aminonucleoside (PAN nephrosis rats were observed by electron microscopy after negative staining. Although GBM of normal rats appeared as a molecular sieve with uniform pores, GBM of nephrotic rats showed enlargement and elongation of the pores. For an average of fifty pores, the long dimension was 40.4+/-10.7 A and the short dimension 13.8+/-3.6 A in nephrosis whereas the long dimension was 12.3+/-2.5 A and the short dimension 8.4+/-1.0 A in normal rats. Changes in the pores in GBM were thought to result in increased permeability of serum protein and hence proteinuria.

  1. Synthesis, characterization, and catalytic properties of stable mesoporous molecular sieve MCM-41 prepared from zeolite mordenite

    International Nuclear Information System (INIS)

    Mesoporous molecular sieves (denoted as M-MCM-41) with ordered hexagonal structure have been successfully synthesized from the assembly of precursors from preformed zeolite Mordenite with CTAB surfactant micelle in alkaline media. The samples were characterized by XRD, N2 adsorption, IR and DTG. The materials exhibit highly hydrothermal stability, as compared with conventional MCM-41. Characterization results indicate that the mesoporous walls of M-MCM-41 contain the secondary building units similar to those in microporous crystal of zeolite Mordenite. In catalytic dealkylation of C10+ aromatic hydrocarbon, M-MCM-41 shows higher activities in comparison with Mordenite and MCM-41, which would be ascribed to the combination of advantages of both MCM-41 (large pores) and Mordenite (strong acidity). Furthermore, this synthesis strategy could be used as a new general method for the preparation of hydrothermally stable mesoporous aluminosilicate materials under alkaline conditions

  2. Efficient adsorption of phenanthrene by simply synthesized hydrophobic MCM-41 molecular sieves

    Science.gov (United States)

    Hu, Yun; He, Yinyun; Wang, Xiaowen; Wei, Chaohai

    2014-08-01

    Hydrophobic molecular sieve MCM-41 including surfactant template was synthesized by a simple method. The adsorption properties of this material toward phenanthrene were studied. The effects of adsorbent dose and pH value on the adsorption process as well as the adsorption mechanism and reuse performance were investigated. The template-containing MCM-41 showed a significant adsorption for phenanthrene, due to its hydrophobicity created by the surfactant template in MCM-41. The solution pH had little effect on the adsorption capacity. The adsorption kinetic could be fitted well with pseudo-second-order kinetic model. The adsorption equilibrium was fitted well by the linear model, and the adsorption process followed the liquid/solid phase distribution mechanism. The thermodynamic results indicated that the adsorption was a spontaneous and exothermic process.

  3. Mesoporous Molecular Sieves Based Catalysts for Olefin Metathesis and Metathesis Polymerization

    Science.gov (United States)

    Balcar, Hynek; Čejka, Jiří

    Heterogeneous catalysts for olefin metathesis using different types of (i) siliceous mesoporous molecular sieves, and (ii) organized mesoporous alumina as supports are reported. The catalysts were prepared either by spreading of transition metal oxidic phase on the support surface or by immobilizing transition metal compounds (mostly organometallic) on the support. The activity of these catalysts in various types of metathesis reactions (i.e. alkene and diene metathesis, metathesis of unsaturated esters and ethers, RCM, ROMP and metathesis polymerization of alkynes) was described. The main advantages of these catalysts consist generally in their high activity and selectivity, easy separation of catalysts from reaction products and the preparation of products free of catalyst residue. The examples of pore size influence on the selectivity in metathesis reactions are also given.

  4. A Simple Approach for Synthesis of TAPO-11 Molecular Sieve with Controllable Space Group

    Institute of Scientific and Technical Information of China (English)

    Yue Ming LIU; Huan Yan ZHANG; Hai Jiao ZHANG; Hai Hong WU; Peng WU; Ming Yuan HE

    2006-01-01

    A TAPO-11 molecular sieve with the space group Icm2 was synthesized successfully.The samples with different space group were controlled simply only by adjusting the crystallization temperature (CT) in the hydrothermal system. In the system of gel with a molar composition of 0.7R: xTiO2: P2O5: Al2O3: 30H2O, where x is 0.01-0.10 and the R is a mixture of di-n-propylamine and diisopropylamine as templates. When CT was between 150-160℃, the calcined sample showed the space group of Icm2, while it showed Pna21 at CTlarger than 190℃.The characterizations of UV-Vis and FT-IR confirmed that Ti was incorporated into the AEL framework successfully.

  5. Photocatalytic Properties of Nb/MCM-41 Molecular Sieves: Effect of the Synthesis Conditions

    Directory of Open Access Journals (Sweden)

    Caterine Daza Gomez

    2015-08-01

    Full Text Available The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of niobium incorporation. The synthesized Nb-MCM-41 ceramic powders were characterized using the spectroscopic techniques of infrared spectroscopy (IR, Raman spectroscopy, X-ray diffraction (XRD, and transmission electron microscopy (TEM. The photodegradation capacity of the powders was studied using the organic molecule, methylene blue. The effect of both the method of synthesis and the percentage of niobium present in the sample on the photodegradation action of the solids was determined. The mesoporous Nb-MCM-41 that produced the greatest photodegradation response was obtained using the sol-gel method and 20% niobium incorporation.

  6. Syntheses of Ferrocenyl Schiff Bases Using Molecular Sieves and AlCl3 as Catalysts

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In order to study the donor ability of ferrocenylimines as directing ortho metalation group(DMG) to lithium alkylide to prepare planar chiral ferrocene, a series of ferrocenyl schiff bases were synthesized by new methods using molecular sieves(0.4nm) and AlCl3 as catalysts. The reaction periods were reduced using these two catalysts in contrast with Al2O3, which was a traditional method used in the literature. In addition, as an important feature of these schiff bases, we found that they were unstable as oils in air or when filtrated through silica gel, but were stable as solids. The structures of the new compounds were confirmed by IR, 1H NMR and HRMS.

  7. Manganese oxide octahedral molecular sieves as insertion electrodes for rechargeable Mg batteries

    KAUST Repository

    Rasul, Shahid

    2013-11-01

    Magnesium has been inserted electrochemically into manganese oxide octahedral molecular sieves (OMS-5 MnO2) at room temperature. Discharge/charge profiles show that a large amount of Mg, i.e., 0.37 Mg/Mn can be inserted electrochemically using 1 M Mg(ClO4)2/AN electrolyte when OMS-5 is prepared in presence of acetylene black. X-ray diffraction analysis and discharge/charge profiles verify that a solid state solution reaction takes place upon Mg insertion into the host lattice with concurrent reduction of Mn4+ to Mn2+. However, upon each reduction of Mn by Mg insertion and resultant dissolution into electrolyte, decrease in the active compound occurs consequently. A low intrinsic electronic conductivity of OMS-5 was suggested to play a vital role in Mg insertion into the host. © 2013 Elsevier Ltd.

  8. Isopropylation of benzene with 2-propanol over substituted large pore aluminophosphate-based molecular sieves

    Indian Academy of Sciences (India)

    K Joseph Antony Raj; V R Vijayaraghavan

    2004-03-01

    Large pore aluminophosphate-based molecular sieves like AlPO4-5, MAPO-5, MnAPO-5 and ZAPO-5 were synthesised hydrothermally using triethylamine as a structure directing agent. These materials were characterised by X-ray diffraction (XRD), 27Al and 31P MAS-NMR, ICP-MS, -butylamine- TPD, BET and SEM. The catalytic performance of these materials was tested for isopropylation of benzene with 2-propanol at 250, 300, 350 and 400°C. The products were cumene, -DIPB (-diisopropylbenzene) and -DIPB (-diisopropylbenzene). MnAPO-5 was found to be more active than the other catalysts. Maximum conversion (20%) was noted at 350°C over MnAPO-5. The selectivity to DIPB was found to decrease with time on stream but the selectivity to cumene showed an increase after 3 h of time on stream.

  9. Ionothermal synthesis process for aluminophosphate molecular sieves in the mixed water/ionic liquid system.

    Science.gov (United States)

    Zhao, Zhenchao; Zhang, Weiping; Xu, Renshun; Han, Xiuwen; Tian, Zhijian; Bao, Xinhe

    2012-01-21

    The synthesis process of aluminophosphate AlPO(4)-11 molecular sieve in the mixed water/1-butyl- 3-methylimidazolium bromide ([bmim]Br) ionic liquid was investigated by XRD, multinuclear solid-state NMR, scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). It was observed that a tablet phase, named SIZ-2, was formed at the early stage of crystallization. During crystallization metastable SIZ-2 with an incompletely condensed framework phosphorus disappeared gradually, and the phosphorous species became fully condensed through hydroxyl reaction with tetrahedral aluminum to form thermodynamically stable AlPO(4)-11 in the final product. It was found that [bmim]Br, acting as the structure-directing agent, was occluded into the AlPO(4)-11 channel.

  10. Thermal decomposition of poly(ethylene terephthalate)/mesoporous molecular sieve composites

    Institute of Scientific and Technical Information of China (English)

    RUN Mingtao; ZHANG Dayu; WU Sizhu; WU Gang

    2007-01-01

    The nonisothermal and isothermal degradation processesofpoly(ethyleneterephthalate)/mesoporous molecular sieve (PET/MMS) composites synthesized by insitu polymerization were studied by using thermogravimetric analysis in nitrogen.The nonisothermal degradation of the composite is found to be the first-order reaction.An isoconversional procedure developed by Ozawa is used to calculate the apparent activation energy (E),which is an average value of about 260 kJ/mol with the weight conversion from 0% to 30%,and is higher than that of neat PET.Isothermal degradation results are confirmed with the nonisothermal process,in which PET/MMS showed higher thermal stability than neat PET.The polymer in mesoporous channels has more stability due to the protection of the inorganic pore-wall.These results indicate that mesoporous MMS in PET/MMS composites improve the stability of the polymer.

  11. Inorganic fluoride uptake as a measure of relative compatibility of molecular sieve desiccants with fluorocarbon refrigerants

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, A.P.; Blackwell, C.S. [UOP, Tarrytown, NY (United States)

    1995-12-31

    The fluoride content of molecular sieve desiccants after exposure to R-32 in compatibility tests indicates the extent of the reaction of refrigerant with desiccant. The objective is to determine this fluoride content in a way that reports fluorine that has reacted with the desiccant, not fluorine that is present as adsorbed refrigerant. A conditioning procedure is described to remove adsorbed refrigerant by displacement with water vapor. The efficacy of this procedure is substantiated by {sup 19}F NMR spectroscopy. The conditioned desiccant undergoes pyrohydrolysis at a high temperature (975 C, 1787 F) to remove reacted fluorine as HF. Fluoride is determined in the resulting condensate using an ion-selective electrode. The ability of this technique to report accurate fluoride values is confirmed with standard reference materials.

  12. The effects of zeolite molecular sieve based surface treatments on the properties of wool fabrics

    International Nuclear Information System (INIS)

    Wool is a natural composite fiber, with keratin and keratin-associated proteins as the key molecular components. The outermost surface of wool fibers comprises a hydrophobic lipid layer that can lead to unsatisfactory processing and properties of fabric products. In this study, molecular sieve 5A, a Na+ and Ca2+ exchanged type A zeolite with a 1:1 Si:Al ratio was integrated onto the surface of wool using 3-mercaptopropyl trimethoxy silane. The resultant surface morphology, hydrophilicity and mechanical performance of the treated wool fabrics were then evaluated. Notably, the surface hydrophilicity of wool was observed to increase dramatically. When wool was treated with a dispersion of 2 wt% acetic acid, 2.5 wt% zeolite and 0.3 wt% or more silane, the water contact angle was observed to decrease from an average value of 148° to 0° over a period of approximately 30 s. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, with infrared spectroscopic evaluation indicating strong bonding of the dealuminated zeolite to wool keratins. This application of zeolite showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite-based treatment is a potentially efficient approach to increasing the surface hydrophilicity and modifying other key surface properties of wool and wool fabrics

  13. Molecular sieving action of the cell membrane during gradual osmotic hemolysis

    Energy Technology Data Exchange (ETDEWEB)

    MacGregor, R.D. II

    1977-05-01

    Rat erythrocytes were hemolyzed by controlled gradual osmotic hemolysis to study cell morphology and hemoglobin loss from individual cells. Results suggest that each increase in the rate of loss of a protein from the cells during the initial phases of controlled gradual osmotic hemolysis is caused by the passage of a previously impermeable species across the stressed membrane. Similarly, during the final stages of controlled gradual osmotic hemolysis, each sharp decrease in the rate of loss of a protein corresponds to the termination of a molecular flow. A theoretical model is described that predicts the molecular sieving of soluble globular proteins across the stressed red cell membrane. Hydrophobic interactions occur between the soluble proteins and the lipid bilayer portion of the cell membrane. A spectrin network subdivides the bilayer into domains that restrict the insertion of large molecules into the membrane. Other membrane proteins affect soluble protein access to the membrane. Changes in the loss curves caused by incubation of red cells are discussed in terms of the model.

  14. The effects of zeolite molecular sieve based surface treatments on the properties of wool fabrics

    Science.gov (United States)

    Carran, Richard S.; Ghosh, Arun; Dyer, Jolon M.

    2013-12-01

    Wool is a natural composite fiber, with keratin and keratin-associated proteins as the key molecular components. The outermost surface of wool fibers comprises a hydrophobic lipid layer that can lead to unsatisfactory processing and properties of fabric products. In this study, molecular sieve 5A, a Na+ and Ca2+ exchanged type A zeolite with a 1:1 Si:Al ratio was integrated onto the surface of wool using 3-mercaptopropyl trimethoxy silane. The resultant surface morphology, hydrophilicity and mechanical performance of the treated wool fabrics were then evaluated. Notably, the surface hydrophilicity of wool was observed to increase dramatically. When wool was treated with a dispersion of 2 wt% acetic acid, 2.5 wt% zeolite and 0.3 wt% or more silane, the water contact angle was observed to decrease from an average value of 148° to 0° over a period of approximately 30 s. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, with infrared spectroscopic evaluation indicating strong bonding of the dealuminated zeolite to wool keratins. This application of zeolite showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite-based treatment is a potentially efficient approach to increasing the surface hydrophilicity and modifying other key surface properties of wool and wool fabrics.

  15. Aplicação catalítica de peneiras moleculares básicas micro e mesoporosas Catalytic applications of basic micro and mesoporous molecular sieves

    Directory of Open Access Journals (Sweden)

    Leandro Martins

    2006-04-01

    Full Text Available Catalysis by solid acids has received much attention due to its importance in petroleum refining and petrochemical processes. Relatively few studies have focused on catalysis by bases and even les on using basic molecular sieves. This paper deals with the potential application of micro and mesoporous molecular sieves in base catalysis reactions. The paper is divided in two parts, the first one dedicated to the design of the catalysts and the second to some relevant examples of catalytic reactions, which find a huge field of applications essentially in the synthesis of fine chemicals. Here, recent developments in catalysis by basic molecular sieves and the perspectives of applications in correlated catalytic processes are described.

  16. Speciation of copper diffused in a bi-porous molecular sieve

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.-H. [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Paul Wang, H., E-mail: wanghp@mail.ncku.edu.t [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Sustainable Environmental Research Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Wei, Y.-L. [Department of Environmental Science and Engineering, Tunghai University, Taichung 40704, Taiwan (China); Chang, J.-E. [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Sustainable Environmental Research Center, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2010-07-21

    To better understand diffusion of copper in the micro- and mesopores, speciation of copper in a bi-porous molecular sieve (BPMS) possessing inter-connecting 3-D micropores (0.50-0.55 nm) and 2-D mesopores (4.1 nm) has been studied by X-ray absorption near edge structure (XANES) spectroscopy. It is found that about 77% (16% of CuO nanoparticles and 61% of CuO clusters) and 23% (CuO{sub ads}) of copper can be diffused into the meso- and micropores, respectively, in the BPMS. At least two diffusion steps in the BPMS may be involved: (i) free diffusion of copper in the mesopores and (ii) diffusion-controlled copper migrating into the micropores of the BPMS. The XANES data also indicate that diffusion rate of copper in the BPMS (4.68x10{sup -5} g/s) is greater than that in the ZSM-5 (1.11x10{sup -6} g/s) or MCM-41 (1.17x10{sup -5} g/s).

  17. Molecular sieve supported ionic liquids as efficient adsorbent for CO2 capture

    Directory of Open Access Journals (Sweden)

    Yang Na

    2015-01-01

    Full Text Available [NH3e-mim][BF4], [OHe-mim][BF4] and [HOEAm] were selected and supported onto molecular sieves NaY, USY, SAPO-34 and MCM-41, to prepare supported ionic liquids. It was found that [NH3e-mim][BF4]/NaY has excellent CO2 adsorption performance, with adsorption capacity of 0.108 mmolCO2/g. This paper investigates the optimal adsorption conditions and recyclability of [NH3e-mim][BF4]/NaY. The results show that [NH3e-mim][BF4]/NaY has good CO2 adsorption under the condition of 20°C and 20% ILs loading amount. By vacuum heating, CO2 adsorption capacity reaches 0.451mmolCO2/g at fifth runs and reduces to 0.29mmolCO2/g at tenth runs. The structure and characterization of the [NH3e-mim][BF4]/NaY was examined by FT-IR, XRD, SEM and TG-DSC. TG-DSC also shows that it has good thermostability below 50°C.

  18. Vapour phase alkylation of ethylbenzene with -butyl alcohol over mesoporous Al-MCM-41 molecular sieves

    Indian Academy of Sciences (India)

    V Umamaheswari; M Palanichamy; Banumathi Arabindoo; V Murugesan

    2002-06-01

    The alkylation of ethylbenzene with -butyl alcohol was studied over Al-MCM-41 (Si/Al = 50 and 90) and Al, Mg-MCM-41 (Si/(Al + Mg) =50) in the vapour phase from 200 to 400°C. The products were --butylethylbenzene (--BEB), --butylvinylbenzene (--BVB) and --butylethylbenzene ( --BEB). Ethylbenzene conversion decreased with increase in temperature and increase in the ethylbenzene content of the feed. The reaction between the freely diffusing ethylbenzene in the channel and the -butyl cations remaining as charge compensating ions yielded --BEB. --BVB, an unexpected product in this investigation, was produced by dehydrogenation of --BEB over alumina particles present in the channels of the molecular sieves. Adsorption of ethylbenzene on Brønsted acid sites and its subsequent reaction with very closely adsorbed -butyl cations proved to be necessary to obtain --BEB. Though --BEB was obtained, the corresponding --butylvinylbenzene was not observed in this study. Study of time durations indicated rapid and slow catalyst deactivation at lower and higher streams respectively.

  19. Efficient adsorption of phenanthrene by simply synthesized hydrophobic MCM-41 molecular sieves

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Simply synthesized template-containing MCM-41 is used for phenanthrene adsorption. • Template-containing MCM-41 has much higher adsorption capacity than pure MCM-41. • The adsorption process follows the liquid/solid phase distribution mechanism. - Abstract: Hydrophobic molecular sieve MCM-41 including surfactant template was synthesized by a simple method. The adsorption properties of this material toward phenanthrene were studied. The effects of adsorbent dose and pH value on the adsorption process as well as the adsorption mechanism and reuse performance were investigated. The template-containing MCM-41 showed a significant adsorption for phenanthrene, due to its hydrophobicity created by the surfactant template in MCM-41. The solution pH had little effect on the adsorption capacity. The adsorption kinetic could be fitted well with pseudo-second-order kinetic model. The adsorption equilibrium was fitted well by the linear model, and the adsorption process followed the liquid/solid phase distribution mechanism. The thermodynamic results indicated that the adsorption was a spontaneous and exothermic process

  20. Efficient adsorption of phenanthrene by simply synthesized hydrophobic MCM-41 molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yun, E-mail: huyun@scut.edu.cn; He, Yinyun; Wang, Xiaowen; Wei, Chaohai

    2014-08-30

    Graphical abstract: - Highlights: • Simply synthesized template-containing MCM-41 is used for phenanthrene adsorption. • Template-containing MCM-41 has much higher adsorption capacity than pure MCM-41. • The adsorption process follows the liquid/solid phase distribution mechanism. - Abstract: Hydrophobic molecular sieve MCM-41 including surfactant template was synthesized by a simple method. The adsorption properties of this material toward phenanthrene were studied. The effects of adsorbent dose and pH value on the adsorption process as well as the adsorption mechanism and reuse performance were investigated. The template-containing MCM-41 showed a significant adsorption for phenanthrene, due to its hydrophobicity created by the surfactant template in MCM-41. The solution pH had little effect on the adsorption capacity. The adsorption kinetic could be fitted well with pseudo-second-order kinetic model. The adsorption equilibrium was fitted well by the linear model, and the adsorption process followed the liquid/solid phase distribution mechanism. The thermodynamic results indicated that the adsorption was a spontaneous and exothermic process.

  1. New methods in encapsulation of complexes in molecular sieve zeolites of the type FAU-Y

    International Nuclear Information System (INIS)

    Tetrabenzoporphyrazine (phthalocyanine) complexes of various metals, such as iron, cobalt and nickel, as a guest for encapsulation in molecular sieve zeolites of the type FAU-Y synthesized and purified with different methods such as Suxhlet apparatus, purification with 98% H2SO-4 and... (over 90% yield). In order to have soluble complexes in water, where is a prerequisite for presence in the synthesis phase of zeolite, direct sulfonation process selected and the best results on Co Pc obtained. Synthesis of the host acts presence of Co Pc(SO3Na)4 and in contrast with a blank, revealed that the host acts independently. With a different method (ship in the bottle), Ni Pc in two different temperatures, inside the super cage of FAU-Y synthesized. Spectroscopic data revealed that a distortion in the planar geometry of the complex has been occurred, so that, it is effective on the physicochemical properties. From spectroscopic data, also, information about fraction of encapsulated complexes inside the cages, obtained, products, characterized by instrumental devices like x-ray diffraction, DRS, IR, UV and ..

  2. Synthesis, Characterization and Application of N-Ti/13X/MCM-41 Mesoporous Molecular Sieves.

    Science.gov (United States)

    Tao, Hong; Nguyen, Nhat-Thien; Hei, Xiao-Hui; Nguyen, Cong Nguyen; Tsai, Hsiao-Hsin; Chang, I-Cheng; Chang, Chang-Tang

    2016-06-01

    Di-n-butyl phthalate (DBP) is a type of phthalate ester. In recent years, an increasing number of studies have examined the removal of DBP. In this study we use a composite material of N-Ti/13X/MCM-41, synthesized by nitrogen, molecular sieve 13X, tetrabutyl orthotitanate and tetraethyl orthosilicate as raw materials, CTAB as a structural template and tetrabutyl titanate and urea under hydrothermal conditions. The optimized experimental conditions, such as the amount of material, reaction time, pH value and initial concentration were tested. The surface areas of N-Ti/13X/MCM-41 were found to be 664 m2g(-1). TEM micrographs revealed N-Ti/13X/MCM-41 is consisting of aggregates of spherical particles, similar with standard synthesized MCM-41 (Mobil Composition of Matter No. 41). Through photocatalytic degradation experiments, the optimum degradation efficiency of DBP was more than 90% at a pH 6.0 with catalyst dosing of 0.15 g L(-1). PMID:27427754

  3. Covalent Anchoring of Chloroperoxidase and Glucose Oxidase on the Mesoporous Molecular Sieve SBA-15

    Directory of Open Access Journals (Sweden)

    Martin Hartmann

    2010-02-01

    Full Text Available Functionalization of porous solids plays an important role in many areas, including heterogeneous catalysis and enzyme immobilization. In this study, large-pore ordered mesoporous SBA-15 molecular sieves were synthesized with tetraethyl orthosilicate (TEOS in the presence of the non-ionic triblock co-polymer Pluronic P123 under acidic conditions. These materials were grafted with 3 aminopropyltrimethoxysilane (ATS, 3-glycidoxypropyltrimethoxysilane (GTS and with 3 aminopropyltrimethoxysilane and glutaraldehyde (GA-ATS in order to provide covalent anchoring points for enzymes. The samples were characterized by nitrogen adsorption, powder X-ray diffraction, solid-state NMR spectroscopy, elemental analysis, diffuse reflectance fourier transform infrared spectroscopy and diffuse reflectance UV/Vis spectroscopy. The obtained grafted materials were then used for the immobilization of chloroperoxidase (CPO and glucose oxidase (GOx and the resulting biocatalysts were tested in the oxidation of indole. It is found that enzymes anchored to the mesoporous host by the organic moieties can be stored for weeks without losing their activity. Furthermore, the covalently linked enzymes are shown to be less prone to leaching than the physically adsorbed enzymes, as tested in a fixed-bed reactor under continuous operation conditions.

  4. Cryptomelane(KxMn8-xO16): Natural active octahedral molecular sieve(OMS-2)

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Xiangtan manganese deposit (XTM) used to be considered a supergene oxide manganese ore in South China. We reported a new identification of the naturally outcropping cryptomelane by examining the physical, chemical and structural features of the XTM supergene oxide manganese ore. The MnO2 content was over 90%, K2O more than 3%, and water from 2.2%-3.1% which is similar to one in zeolite. The cell parameters of the cryptomelane were given as a0 = 0.9974 nm, b0 = 0.2863 nm, c0 = 0.9693 nm and β91.47(. There was a larger pseduotetragonal tunnel in the natural cryptomelane that was formed by [MnO6] octahedral double chains with aperture of 0.462×0.466 nm2, filled with K cations resulting in some Mn3+ substituting for Mn4+ to balance the negative charges of structure. The finding is important not only for prospecting manganese resources in South China, but also in application of octahedral molecular sieve of natural cryptomelane as that developed in the tetragonal molecular sieve of natural zeolite over the past century. The XTM cryptomelane (OMS-2) may be the real mineral of the active octahedral molecular sieve in nature.

  5. Synthesis and characterization of Co (Ni or Cu)-MCM-41 mesoporous molecular sieves with different amount of metal obtained by using microwave irradiation method

    International Nuclear Information System (INIS)

    Co (Ni or Cu)-MCM-41 mesoporous molecular sieves with different amount of metal were synthesized by using cetyltrimethyl ammonium bromide as a template and by a novel microwave irradiation method. These samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and N2 physical adsorption. The experimental results show that Co (Ni or Cu)-MCM-41 mesoporous molecular sieves were successfully synthesized. When the as-synthesized samples were calcined at 550 deg. C for 10 h, the template was effectively removed. Under microwave irradiation condition, Co-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 745.7-1188.8 m2/g and average pore sizes in a range of 2.46-2.75 nm; Ni-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 625.8-1161.3 m2/g and average pore sizes of ca. 2.7 nm; Cu-MCM-41 mesoporous molecular sieves have specific surface areas in a range of 601.6-1142.9 m2/g and average pore sizes in a range of 2.46-2.76 nm. On the other hand, with increasing the introduced metal amount, the specific surface area and pore volume of the synthesized Co (Ni or Cu)-MCM-41 mesoporous molecular sieves became small, and the mesoporous ordering of the samples became poor. Under the comparable synthesis conditions, the synthesized Co-MCM-41 mesoporous molecular sieve has a bigger specific surface area and a more uniform pore distribution as compared with the synthesized Ni-MCM-41and Cu-MCM-41 mesoporous molecular sieves

  6. A New Strategy for the Synthesis of 3-Acyl-coumarin Using Mesoporous Molecular Sieve MCM-41 as a Novel and Efficient Catalyst

    Institute of Scientific and Technical Information of China (English)

    HERAVI,Majid M; POORMOHAMMAD,Nargess; BEHESHTIGA,Yahia Sh; BAGHERNEJAD,Bita; MALAKOOTI,Reihaneh

    2009-01-01

    3-Acyl-coumarins were obtained in high yields from ortho-hydroxybenzaldehydes and ethyl acetoacetate or ethyl benzoylacetate in acetonitrile in the presence of a catalytic amount of mesoporous molecular sieve MCM-41. 3-Acyl-coumarins were obtained in high yields from ortho-hydroxybenzaldehydes and ethyl acetoacetate or ethyl benzoylacetate in acetonitrile in the presence of a catalytic amount of mesoporous molecular sieve MCM-41.

  7. Analysis of the Sensitivity of K-Type Molecular Sieve-Deposited MWNTs for the Detection of SF6 Decomposition Gases under Partial Discharge

    Directory of Open Access Journals (Sweden)

    Xiaoxing Zhang

    2015-11-01

    Full Text Available Sulfur hexafluoride (SF6 is widely utilized in gas-insulated switchgear (GIS. However, part of SF6 decomposes into different components under partial discharge (PD conditions. Previous research has shown that the gas responses of intrinsic and 4 Å-type molecular sieve-deposited multi-wall carbon nanotubes (MWNTs to SOF2 and SO2F2, two important decomposition components of SF6, are not obvious. In this study, a K-type molecular sieve-deposited MWNTs sensor was developed. Its gas response characteristics and the influence of the mixture ratios of gases on the gas-sensing properties were studied. The results showed that, for sensors with gas mixture ratios of 5:1, 10:1, and 20:1, the resistance change rate increased by nearly 13.0% after SOF2 adsorption, almost 10 times that of MWNTs sensors, while the sensors’ resistance change rate with a mixture ratio of 10:1 reached 17.3% after SO2F2 adsorption, nearly nine times that of intrinsic MWNT sensors. Besides, a good linear relationship was observed between concentration of decomposition components and the resistance change rate of sensors.

  8. Catalyzing the oxidation of sulfamethoxazole by permanganate using molecular sieves supported ruthenium nanoparticles.

    Science.gov (United States)

    Zhang, Jing; Sun, Bo; Huang, Yuying; Guan, Xiaohong

    2015-12-01

    This study developed a heterogeneous catalytic permanganate oxidation system with three molecular sieves, i.e., nanosized ZSM-5 (ZSM-5A), microsized ZSM-5 (ZSM-5B) and MCM-41, supported ruthenium nanoparticles as catalyst, denoted as Ru/ZSM-5A, Ru/ZSM-5B and Ru/MCM-41, respectively. The presence of 0.5gL(-1) Ru/ZSM-5A, Ru/ZSM-5B and Ru/MCM-41 increased the oxidation rate of sulfamethoxazole (SMX) by permanganate at pH 7.0 by 27-1144 times. The catalytic performance of Ru catalysts toward SMX oxidation by permanganate was strongly dependent on Ru loading on the catalysts. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses confirmed that Ru catalyst acted as an electron shuttle in catalytic permanganate oxidation process. Ru(III) deposited on the surface of catalysts was oxidized by permanganate to its higher oxidation state Ru(VII), which could work as a co-oxidant with permanganate to decompose SMX and was then reduced to its initial tri-valence. During the successive runs, Ru/ZSM-5A could not maintain its catalytic activity due to the deposition of MnO2, which was the reductive product of permanganate, onto the surface of Ru/ZSM-5A. Thus, the regeneration of partially deactivated Ru catalysts by reductant NH2OH⋅HCl or ascorbic acid was proposed. Ru/ZSM-5A regenerated by NH2OH⋅HCl displayed comparable catalytic ability to its virgin counterpart, while ascorbic acid could not completely remove the deposited MnO2. A trace amount of leaching of Ru into the reaction solution was also observed, which would be ameliorated by improving the preparation conditions in the future study. PMID:26196405

  9. High-flux water desalination with interfacial salt sieving effect in nanoporous carbon composite membranes

    CERN Document Server

    Chen, Wei; Zhang, Qiang; Fan, Zhongli; Huang, Kuo-Wei; Zhang, Xixiang; Lai, Zhiping; Sheng, Ping

    2016-01-01

    Nanoporous carbon composite membranes, comprising a layer of porous carbon fiber structures with an average channel width of 30-60 nm grown on a porous ceramic substrate, are found to exhibit robust desalination effect with high freshwater flux. In three different membrane processes of vacuum membrane distillation, reverse osmosis and forward osmosis, the carbon composite membrane showed 100% salt rejection with 3.5 to 20 times higher freshwater flux compared to existing polymeric membranes. Thermal accounting experiments found that at least 80% of the freshwater pass through the carbon composite membrane with no phase change. Molecular dynamics simulations revealed a unique salt rejection mechanism. When seawater is interfaced with either vapor or the surface of carbon, one to three interfacial atomic layers contain no salt ions. Below the liquid entry pressure, the salt solution is stopped at the openings to the porous channels and forms a meniscus, while the surface layer of freshwater can feed the surface...

  10. Effect of the thermal and hydrothermal treatment on textural properties of Zr-MCM-41 mesoporous molecular sieve

    International Nuclear Information System (INIS)

    Zr-containing mesoporous molecular sieves were synthesized by hydrothermal method using cetyltrimethyl ammonium bromide as a template and sodium silicate and zirconium sulfate as raw materials. The structure and morphology of the synthesized samples were characterized via various physicochemical methods, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, solid state nuclear magnetic resonance (29Si MAS-NMR) techniques, thermal gravimetric-differential scanning calorimeter (TG-DSC) and N2 physical adsorption, respectively. The effect of the different initial ZrO2:SiO2 molar ratio, the different thermal treatment temperature and the different hydrothermal treatment time on textural property was investigated. The experimental results reveal that the as synthesized samples possess a typical mesoporous structure of MCM-41. On the other hand, the specific surface area and pore volume of the synthesized Zr-MCM-41 mesoporous molecular sieve decrease with the increase of the amount of zirconium incorporated in the starting material, the rise of thermal treatment temperature and the prolonging of hydrothermal treatment time, the mesoporous ordering becomes poor. Also, when the molar ratio of ZrO2:SiO2 in the starting material is 0.1, the mesoporous structure of the Zr-MCM-41 mesoporous molecular sieve still retains after calcination at 750 deg. C for 3 h or hydrothermal treatment at 100 deg. C for 6 d, and have specific surface areas of 423.9 and 563.9 m2/g, respectively.

  11. Spray-dried powders enhance vaginal siRNA delivery by potentially modulating the mucus molecular sieve structure

    Directory of Open Access Journals (Sweden)

    Wu N

    2015-08-01

    Full Text Available Na Wu,1,2,* Xinxin Zhang,2,* Feifei Li,2 Tao Zhang,2 Yong Gan,2 Juan Li1 1School of Pharmacy, China Pharmaceutical University, Nanjing, People’s Republic of China; 2Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, People’s Republic of China *These authors contributed equally to this work Abstract: Vaginal small interfering RNA (siRNA delivery provides a promising strategy for the prevention and treatment of vaginal diseases. However, the densely cross-linked mucus layer on the vaginal wall severely restricts nanoparticle-mediated siRNA delivery to the vaginal epithelium. In order to overcome this barrier and enhance vaginal mucus penetration, we prepared spray-dried powders containing siRNA-loaded nanoparticles. Powders with Pluronic F127 (F127, hydroxypropyl methyl cellulose (HPMC, and mannitol as carriers were obtained using an ultrasound-assisted spray-drying technique. Highly dispersed dry powders with diameters of 5–15 µm were produced. These powders showed effective siRNA protection and sustained release. The mucus-penetrating properties of the powders differed depending on their compositions. They exhibited different potential of opening mesh size of molecular sieve in simulated vaginal mucus system. A powder formulation with 0.6% F127 and 0.1% HPMC produced the maximum increase in the pore size of the model gel used to simulate vaginal mucus by rapidly extracting water from the gel and interacting with the gel; the resulting modulation of the molecular sieve effect achieved a 17.8-fold improvement of siRNA delivery in vaginal tract and effective siRNA delivery to the epithelium. This study suggests that powder formulations with optimized compositions have the potential to alter the steric barrier posed by mucus and hold promise for effective vaginal siRNA delivery. Keywords: siRNA delivery, vaginal administration, spray-dried powders, mucus penetration, molecular sieve effect

  12. Physicochemical properties of CuAlMCM-41 and CuNbMCM-41 mesoporous molecular sieves

    International Nuclear Information System (INIS)

    The texture and surface properties of copper-containing aluminosilica and niobiosilica mesoporous molecular sieves of MCM-41 type, in which all elements were introduced during the synthesis, have been studied by means of XRD, N2 adsorption, H2TPR, FTIR combined with pyridine and NO adsorption as well as the skeletal region, and the test reaction. The results were compared with those obtained earlier for Cu post synthesis exchanged AlMCM41 and NbMCM-41. All results and this comparison allow the suggestion that copper is partially located in the skeleton of both MCM-41 materials, which exhibit redox and acidic properties. (author)

  13. ZSM -5分子筛在甲醇转化制烯烃领域应用的研究进展%Research progress in the application of ZSM-5 molecular sieves in the methanol-to-olefin field

    Institute of Scientific and Technical Information of China (English)

    冯琦瑶; 邢爱华; 张新锋; 姜继东

    2016-01-01

    综述了 ZSM -5分子筛在甲醇制烯烃反应特别是在甲醇制丙烯反应中的应用。介绍在接近工业反应条件下甲醇在 ZSM -5分子筛上生成烯烃的反应机理,在较高反应温度下高碳数烯烃裂解是导致轻烯烃形成的主要反应路径;分析 ZSM -5分子筛酸性及粒径对产品选择性及催化剂寿命的影响,由于 ZSM -5分子筛酸性较强,直接用于甲醇制烯烃反应时低碳烯烃的选择性不高,而粒径小的 ZSM -5分子筛扩散性能好,因而丙烯选择性得到提高。重点介绍小晶粒 ZSM -5分子筛的研究进展,指出目前 ZSM -5分子筛的研究方向一是对其进行酸性改性,二是制备酸度适中、粒径合适和具有介孔的多级结构 ZSM -5分子筛。%The application of ZSM-5 molecular sieves for methanol-to-olefin(MTO)reaction,especially for methanol-to-propylene( MTP)reaction was reviewed. The reaction mechanism of methanol-to-olefin over ZSM-5 molecular sieves under the commercial condition was introduced. The main formation path of light olefins was the cracking of high carbon number olefins under higher reaction temperatures. Moreo-ver,the effects of the acidity and particle size of ZSM-5 molecular sieves on the selectivity to the product and catalyst life were analyzed. When it was directly applied in MTO reactions,the selectivity to light ole-fins was low because of its strong acidity of ZSM-5 molecular sieves,but ZSM-5 molecular sieves with smaller particle size led to higher selectivity to propene because its diffusion property was improved. Fur-thermore,the research progress in small grain ZSM-5 molecular sieves was focused on. It is pointed out that the main research directions for ZSM-5 molecular sieves are:one is the acid modification of ZSM-5 molecular sieves,the other is the preparation of ZSM-5 molecular sieves with suitable acidity,appropriate particle size and hierarchical structure with meso-pores.

  14. 合成多级孔分子筛的研究进展%Research advance in synthesis of hierarchical molecular sieves

    Institute of Scientific and Technical Information of China (English)

    刘晓玲; 姜健准; 张明森

    2016-01-01

    Constructing hierarchical molecular sieves is an important method to enhance accessibility of molecular sieves and the research hotspot in catalytic field. A great number of synthetic methods for adjusting the pore structure of hierarchical molecular sieves were developed. The synthetic researches on hierarchical molecular sieves were reviewed from three different aspects as follows:demetalization,in-situ crystallization and recrystallization. Demetalization mainly included steaming treatment and chemical treatment. In-situ crystallization included hard template and soft template methods. Recrystallization was a method of synthesizing hierarchical molecular sieves,which was obtained by the alkali treatment of zeo-lite crystal under the existence of surfactants. In addition,the prospect of hierarchical molecular sieves was also outlined.%构建多级孔分子筛是提高分子筛扩散性能的重要手段,是目前催化领域研究的热点之一。多级孔分子筛的合成方法较多,从脱除骨架元素、原位合成和重结晶3个方面综述近年来多级孔分子筛的合成研究。脱除骨架元素主要有蒸汽处理和化学处理;原位合成法主要包括硬模板法和软模板法;重结晶是分子筛晶体经碱溶解后在表面活性剂条件下自组装形成多级孔分子筛,并对多级孔分子筛的发展前景进行展望。

  15. Crosslinkable mixed matrix membranes with surface modified molecular sieves for natural gas purification: I. Preparation and experimental results

    KAUST Repository

    Ward, Jason K.

    2011-07-01

    Dense film mixed matrix membranes (MMMs) comprised of SSZ-13 dispersed in a crosslinkable polyimide (PDMC) were fabricated and evaluated for carbon dioxide/methane separations. MMMs containing 25% (w/w) as-received (AR) SSZ-13 exhibited a carbon dioxide permeability of 153 Barrers with a carbon dioxide/methane ideal selectivity of 34.7 at 65. psia and 35 °C. This represents a permeability enhancement of 129% and a decline in selectivity of 4.7% over neat PDMC (PCO2=66.9 Barrers, αCO2/CH4=36.4). A sieve surface modification procedure was developed with the aim of improving SSZ-13/PDMC MMM transport properties. MMMs containing 25% (w/w) surface modified (SM) SSZ-13 exhibited a carbon dioxide permeability of 148 Barrers and carbon dioxide/methane selectivity of 38.9 at 65. psia and 35 °C, representing enhancements in both permeability and selectivity of 121% and 6.9%, respectively. Mixed gas permeation analyses of MMMs containing SM-SSZ-13 using a 10% carbon dioxide/90% methane mixture shows that permeability and selectivity enhancements of 47% and 13%, respectively, over neat PDMC are possible at 700. psia and 35 °C. © 2011 Elsevier B.V.

  16. Gas-Transport-Property Performance of Hybrid Carbon Molecular Sieve−Polymer Materials

    KAUST Repository

    Das, Mita

    2010-10-06

    High-performance hybrid materials using carbon molecular sieve materials and 6FDA-6FpDA were produced. A detailed analysis of the effects of casting processes and the annealing temperature is reported. Two existing major obstacles, sieve agglomeration and residual stress, were addressed in this work, and subsequently a new membrane formation technique was developed to produce high-performing membranes. The successfully improved interfacial region of the hybrid membranes allows the sieves to increase the selectivity of the membranes above the neat polymer properties. Furthermore, an additional performance enhancement was seen with increased sieve loading in the hybrid membranes, leading to an actual performance above the upper bound for pure polymer membranes. The membranes were also tested under a mixed-gas environment, which further demonstrated promising results. © 2010 American Chemical Society.

  17. Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule [South Kazakhstan State University, 5, Tauke Khan Avenue, 160012 Shymkent (Kazakhstan)

    2015-05-15

    In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested.

  18. Laboratory test and evaluation report of the essex model 60C-0037-2 molecular sieve oxygen generating system

    Science.gov (United States)

    Squire, Brendan E.; Bruckart, James E.; Quattlebaum, Martin; Johnston, Leslie W.

    1993-06-01

    The Essex Model 60C-0037-2 Molecular Sieve Oxygen Generating System was tested for environmental and electromagnetic interference/compatibility under the U.S. Army Program for Testing and Evaluation of Equipment for Aeromedical Operations. The tests were conducted using current military and industrial standards and procedures for environmental tests and electromagnetic interference/compatibility and human factors. The Essex Model 60C-0037-2 performed properly in the test environments. The oxygen concentration produced by the unit depends on the compressed air pressure, oxygen flow, and vent pressure. A separate oxygen concentration analyzer would be required to determine the oxygen concentration for patient use. The unit produces a significant amount of noise while operating.

  19. Synthesis of an extra-large molecular sieve using proton sponges as organic structure-directing agents

    Science.gov (United States)

    Martínez-Franco, Raquel; Moliner, Manuel; Yun, Yifeng; Sun, Junliang; Wan, Wei; Zou, Xiaodong; Corma, Avelino

    2013-01-01

    The synthesis of crystalline microporous materials containing large pores is in high demand by industry, especially for the use of these materials as catalysts in chemical processes involving bulky molecules. An extra-large–pore silicoaluminophosphate with 16-ring openings, ITQ-51, has been synthesized by the use of bulky aromatic proton sponges as organic structure-directing agents. Proton sponges show exceptional properties for directing extra-large zeolites because of their unusually high basicity combined with their large size and rigidity. This extra-large–pore material is stable after calcination, being one of the very few examples of hydrothermally stable molecular sieves containing extra-large pores. The structure of ITQ-51 was solved from submicrometer-sized crystals using the rotation electron diffraction method. Finally, several hypothetical zeolites related to ITQ-51 have been proposed. PMID:23431186

  20. Encapsulation of Eu(TTA)3 into MCM-41 Mesoporous Molecular Sieve by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The rare earth complex Eu(TTA)3 was successfully encapsulated into MCM-41 mesoporous molecular sieve by the addition of the complex into the sol-gel mixture for the synthesis of MCM-41 mesoporous material under microwave radiation. The as-synthesized MCM-41-hosted Eu(TTA)3 mesophase was confirmed to possess hexagonally ordered mesostructure and a uniform crystal size of about 30 nm with XRD and HRTEM techniques. Moreover, the IR spectrum, photoluminescence effect and fluorescence lifetime of the Eu(TTA)3/MCM-41 hybrid were also studied. An increase in Stokes' shift and no change in luminescence lifetime were observed to the resultant mesophase in comparison with Eu(TTA)3 in ethanol solution.

  1. Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

    Science.gov (United States)

    Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule

    2015-05-01

    In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested.

  2. Molecular simulations of supercritical fluid permeation through disordered microporous carbons.

    Science.gov (United States)

    Boţan, Alexandru; Vermorel, Romain; Ulm, Franz-Josef; Pellenq, Roland J-M

    2013-08-13

    Fluid transport through microporous carbon-based materials is inherent in numerous applications, ranging from gas separation by carbon molecular sieves to natural gas production from coal seams and gas shales. The present study investigates the steady-state permeation of supercritical methane in response to a constant cross-membrane pressure drop. We performed dual control volume grand canonical molecular dynamics (DCV-GCMD) simulations to mimic the conditions of actual permeation experiments. To overcome arbitrary assumptions regarding the investigated porous structures, the membranes were modeled after the CS1000a and CS1000 molecular models, which are representative of real microporous carbon materials. When adsorption-induced molecular trapping (AIMT) mechanisms are negligible, we show that the permeability of the microporous material, although not significantly sensitive to the pressure gradient, monotonically decreases with temperature and reservoir pressures, consistent with diffusion theory. However, when AIMT occurs, the permeability increases with temperature in agreement with experimental data found in the literature. PMID:23886335

  3. Isomorphous substitution of Mn(II), Ni(II) and Zn(II) in AlPO-31 molecular sieves and study of their catalytic performance

    Indian Academy of Sciences (India)

    V Umamaheswari; C Kannan; Banumathi Arabindoo; M Palanichamy; V Murugesan

    2000-08-01

    Isomorphously substituted molecular sieves, MAPO-31, NAPO-31 and ZAPO-31, were prepared under mild hydrothermal conditions from gels containing sources of aluminium, phosphorus, appropriate metal and dipropylamine (DPA), presumably acting as a structure-directing template. They were characterized by XRD, FTIR, TGA, inductively coupled plasma (ICP), ESR, Brunauer, Emmett, Teller (BET) and diffusion reflectance spectroscopy (DRS) techniques. In the XRD, the peak at 2 = 16 7° of the metal substituted AlPO-31 is more intense than that of pure AlPO-31 suggesting preferential occupation of the plane corresponding to it as compared to other planes. The O-H stretch in the IR spectra of the metal-substituted molecular sieves is blue-shifted with respect to the parent AlPO-31 molecular sieves possibly due to metal substitution. The g values obtained from the ESR spectra of MAPO-31 and NAPO-31 also substantiate framework substitution. Ethylation of toluene was carried out between 300 and 450°C over the above catalysts as a model test reaction. The high toluene conversion over metal-substituted molecular sieves proves the isomorphic substitution of metal ions in the AlPO-31 framework.

  4. Effect of lipase immobilization on resolution of (R, S)-2-octanol in nonaqueous media using modified ultrastable-Y molecular sieve as support.

    Science.gov (United States)

    Dai, Dazhang; Xia, Liming

    2006-07-01

    The lipase from Penicillium expansum PED-03 (PEL) was immobilized onto modified ultrastable-Y (USY) molecular sieve and the resolution of (R, S)- 2-octanol was carried out in a bioreactor in nonaqueous media by the immobilized lipase. It was found that the conversion rate, enantiomeric excess (ee) value, and enantioselectivity (E) value of the resolution catalyzed by PEL immobilized on modified USY molecular sieve were much higher than those of the reaction catalyzed by free PEL and PEL immobilized on other supports. Immobilized on modified USY molecular sieve, the PEL exhibited obvious activity within a wider pH range and at a much higher temperature and showed a markedly enhanced stability against thermal inactivation, by which the suitable pH of the buffer used for immobilization could be "memorized." The conversion rate of the reaction catalyzed by PEL immobilized on modified USY molecular sieve reached 48.84%, with excellent enantioselectivity (average E value of eight batches >460) in nonaqueous media at "memorial" pH 9.5, 50 degrees C for 24 h, demonstrating a good application potential in the production of optically pure (R, S)-2-octanol. PMID:16891665

  5. X-Ray Imaging of SAPO-34 Molecular Sieves at the Nanoscale : Influence of Steaming on the Methanol-to-Hydrocarbons Reaction

    NARCIS (Netherlands)

    Aramburo, Luis R.; Ruiz-Martinez, Javier; Sommer, Linn; Arstad, Bjornar; Buitrago-Sierra, Robison; Sepulveda-Escribano, Antonio; Zandbergen, Henny W.; Olsbye, Unni; de Groot, Frank M. F.; Weckhuysen, Bert M.

    2013-01-01

    The effect of a severe steaming treatment on the physicochemical properties and catalytic performance of H-SAPO-34 molecular sieves during the methanol-to-hydrocarbons (MTH) reaction has been investigated with a combination of scanning transmission X-ray microscopy (STXM), catalytic testing, and bul

  6. Applications and Related Mechanisms of Molecular Sieves in Medicine%分子筛在医学领域的应用及作用机制

    Institute of Scientific and Technical Information of China (English)

    陈炳鹏; 王卓鹏; 柳菁菁; 王金成; 于吉红

    2011-01-01

    Molecular sieves are a class of inorganic materials with regular channels or cavities of molecular dimensions. Besides their important industrial uses, molecular sieves have promising applications in medical field due to their special structural features, excellent biological activity, biological stability and biocompatibility. Recently, natural zeolites have been explored to be used as adjuvant in anticancer therapy; as antibacterial agents, silver zeolite and NO-loaded zeolite demonstrate powerful anti-infective activities; with their high adsorption capabilities and tunable surface properties, mesoporous molecular sieves have been tested as drug carriers in drug delivery system; molecular sieves can also be used in other aspects such as blood-clot, thrombolysis and so on. This paper reviews the recent progress on medical applications of molecular sieves. The re-lated mechanisms are discussed as well.%分子筛具有特殊的多孔结构、优异的生物活性、生物稳定性及生物相容性.大量的临床应用研究表明,分子筛可用作抗肿瘤治疗的佐剂、抗微生物治疗及药物的载体、快速凝血剂和防止血栓制剂等,在医学领域有着广泛的应用前景.本文详细介绍了分子筛在医学领域应用的进展及作用的相关机制.

  7. Molecular sieve of the rat glomerular basement membrane: a transmission electron microscopic study of enzyme-treated specimens.

    Directory of Open Access Journals (Sweden)

    Ichiyasu,Akira

    1988-12-01

    Full Text Available Isolated rat glomerular basement membrane was treated with elastase and observed by transmission electron microscopy. The treatment with elastase revealed the fundamental structure of the glomerular basement membrane quite clearly, and enabled the observation of a sieve structure within the glomerular basement membrane. This sieve structure may play a major role in the filtration of blood as well as in the production of urine. Treatment with antibody showed that the sieve was mainly constituted of type IV collagen.

  8. Research on Synthesis of the L-Lactide Catalyzed by Molecular Sieve%分子筛催化L-丙交酯的合成研究

    Institute of Scientific and Technical Information of China (English)

    欧阳春平; 胡生平; 王瑀; 杨名; 张政朴

    2012-01-01

    Lactide was the intermediate of PLA synthesized via the ring-opening polymerization. L-lactide was prepared by L-lactic acid as the material, ZnO as the condensation dehydration catalysts, ZSM-5 molecular sieve as the cracking catalyst. The influence of different amounts of ZSM-5 molecular sieve cracking catalyst in L-lactide yield was studied. The determination for physical and chemical properties of products proved that there was no influence for L-lactide after adding the molecular sieve as cracking catalysts. The results showed that the proper amount of molecular sieve catalysts could shorten the reaction time, improve the crude yield of L-lactide, however, the excess of ZSM-5 molecular seive effected the ultimate yield of L-lactide.%丙交酯是开环聚合制备聚乳酸的中间体.以L-乳酸为原料,氧化锌为缩合脱水催化剂,ZSM-5分子筛作裂解催化剂合成L-丙交酯.研究ZSM-5分子筛裂解催化剂的不同用量对丙交酯产率的影响.通过对产物理化性能的测定,表明加入分子筛做裂解催化剂后不影响L-丙交酯的性质.通过对反应时间测定及反应粗产率的计算,表明适量地加入分子筛能缩短反应时间,提高反应粗产率,然而过多的ZSM-5分子筛影响L-丙交酯的最终产率.

  9. Ionothermal Synthesis of MnAPO-SOD Molecular Sieve without the Aid of Organic Structure-Directing Agents.

    Science.gov (United States)

    Liu, Hao; Tian, Zhijian; Wang, Lei; Wang, Yasong; Li, Dawei; Ma, Huaijun; Xu, Renshun

    2016-02-15

    An SOD-type metalloaluminophosphate molecular sieve (denoted as SOD-Mn) was ionothermally synthesized by introducing manganese(II) cations into the reaction mixture via MnO-acid or MnO2-reductant reactions. Composition and structure analyses results show that two kinds of manganese(II) cations exist in the SOD-Mn structure. Part of the manganese(II) cations isomorphously substitute the framework aluminum(III) with a substitution degree of ∼30%. The rest of the manganese(II) cations occupy a fraction of the sod cages in their hydrated forms. A comprehensive investigation of the synthesis parameters, crystal sizes, and crystallization kinetics indicates that the in situ released hydrated manganese(II) cations direct the formation of SOD-Mn. Such structure-directing effect may be inhibited by both the fluorination of manganese(II) cations and the water accumulation during crystallization. In the fluoride anion-containing reaction mixture with a low ionic liquid content, the crystallization process is strongly suppressed, and large SOD-Mn single crystals of over 200 μm in size are yielded. SOD-Mn is free from organics and shows improved thermal stability compared with metalloaluminophosphates synthesized by using organic structure-directing agents.

  10. Effect of the Si/Zr molar ratio on the synthesis of Zr-based mesoporous molecular sieves

    International Nuclear Information System (INIS)

    Highly ordered Zr-based mesoporous molecular sieves were synthesized via a surfactant-templated method and the effect of the Si/Zr molar ratio on the crystalline structure, textural properties and surface acidity were studied by XRD, FTIR, TEM and 29Si MAS-NMR techniques. FTIR spectra show that the intensity of the band around 890 cm-1 which corresponds to the vibration of Si-O-Zr bond was increased with increasing of the zirconium content, therefore, this band may be used as an indicator of the degree of the zirconium incorporation into the Si-framework. When the zirconium content increased in the materials, the Q3/Q4 value obtained from 29Si MAS-NMR was linearly increased, whereas, the intensity the XRD peaks was gradually reduced; as a result, the pore wall thickness of the resultant materials was gradually increased, the surface area and the structural regularity were diminished. In order to obtain Zr-MCM-41 with highly ordered mesostructure and large surface area, proper Si/Zr molar ratio is a key factor, e.g., Si/Zr should be no less than 10. It was also found that the Bronsted acid sites which resulted from charge unbalance or local structure deformation due to the Zr4+ incorporation into the vicinity of the hydroxyls carrying silicon were created on the surface of the Zr-MCM-41 solids; strong Bronsted acidity could be formed on the solid with high zirconium content

  11. Host-guest chemistry of Cu2+/Histidine complexes in molecular sieves

    NARCIS (Netherlands)

    Mesu, Jan Gijsbert

    2005-01-01

    The high activity and selectivity of enzymes have inspired many scientists to study the structure and working mechanism of bio-molecular complexes. Also in the catalysis community this subject is of topical interest, as it may provide inspiration for the development of a new generation of bio-inspir

  12. Influence of Molecular Sieve Supported Metal Oxides on the Desulfurization in Catalytic Cracking of Sulfur-containing Model Compounds and Hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    申宝剑; 李海丽; 李会峰; 鲍晓军; 周小虹

    2003-01-01

    Zn, La, Zr, Sn and Ti loaded molecular sieves were prepared by impregnation method. Conversions of benzothiophene and dibenzothiophene over the metal oxides modified ultra stable zeolite Y(USY), ZSM-5, β and MSU-2 molecular sieve catalysts were investigated by means of micro-activity test (MAT) experiments. The results showed that Zn and La loaded catalysts were better than the other metals, and ZSM-5 with lower SiO2/Al2O3 mole ratio showed better results than those with higher SiO2/Al2O3 as far as desulfurization reaction is considered. A comparison of the desulfurization activities of the La/Zn-USY catalyst with USY catalyst indicated that the bimetal loaded USY catalyst gave good products selectivity when sulfur containing heavy oil was used as the feedstock. The sulfur content in gasoline fraction was decreased by 25%, and there was no loss in the Research Octane Number.

  13. Host-guest chemistry of Cu2+/Histidine complexes in molecular sieves

    OpenAIRE

    Mesu, Jan Gijsbert

    2005-01-01

    The high activity and selectivity of enzymes have inspired many scientists to study the structure and working mechanism of bio-molecular complexes. Also in the catalysis community this subject is of topical interest, as it may provide inspiration for the development of a new generation of bio-inspired catalyst materials. Functionalization of inorganic substrates, such as zeolites, with transition metal ion (TMI) complexes offers the possibility to design new materials with a high potential to...

  14. An Empiric Linear Formula between the Internal Tetrahedron Symmetric Stretch Frequency and the Al Content in the Framework of KL Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    Nong Yue HE; Chun YANG; Jian Xin TANG; Peng Feng XIAO; Hong CHEN

    2003-01-01

    KL molecular sieves with different framework compositions were secondarily synthesized by substituting Si for Al with a solution of (NH4)2SiF6. The internal tetrahedron symmetric stretch frequency, at ν770 cm-1, is linear with the molar fraction of Al (XAl= Al/(Si+Al)) in the framework of KL samples: XAl = -7.309×10-3 (υ770-760) + 0.3242.

  15. An improved process for the synthesis of VPI-5 molecular sieve

    Indian Academy of Sciences (India)

    N Venkatathri

    2003-04-01

    VPI-5 was synthesized with lesser time duration. The synthesized sample was characterized by XRD, SEM, FT-IR, TG/DTA, 27Al and 31P MASNMR techniques, which shows that the synthesized sample was highly crystalline. Carbon and nitrogen analyses reveal that the sample contains no template molecules, however, TG/DTA analysis shows the presence of physisorbed template molecules. MASNMR results show the presence of three different types of aluminium and phosphorous. Two of them were present as in tetrahedral and the remaining one is present in octahedral environment.

  16. SAPO分子筛的合成及影响因素的研究进展%Advance in study in synthetic and influences of SAPO molecular sieve

    Institute of Scientific and Technical Information of China (English)

    汪颖军; 吴红玉; 吴红姣; 张莹莹; 朱光宇

    2011-01-01

    The synthesis methods of SAPO molecular sieve, including hydrothermal synthesis synthesis, gas phase crystallization,liquidoid crystallization, microwave radiation, poikilothermal ageing methods, ultrasonic synthesis, temperarure profile methods and so on, is summarized in this paper. The effects of the composition of the reaction mixture, templates, pH, media, the crystallization temperature and time for synthesis of SAPO molecular sieve were discussed. Finally, the prospects of synthesis methods of SAPO molecular sieves were outlined.%本文综述了SAPO分子筛的主要合成方法,包括水热合成法、气相晶化法、液相晶化法、微波合成法、变温陈化法、超声合成法、程序升温法等方法.讨论了反应物的组成、模板剂、酸碱度、介质、晶化温度、晶化时间等因素对SAPO分子筛合成的影响.最后对SAPO分子筛合成方法进行了展望.

  17. A study of the thermal activation of synthetic zeolites (molecular sieve) for gas-solid chromatography

    International Nuclear Information System (INIS)

    The thermal activation of synthetic zeolites from two sources has been investigated with reference to the adsorption chromatography of inorganic gases. It was found that the heats of adsorption for oxygen and carbon monoxide increased with activation temperature. Limits of detection for oxygen in argon and conversely argon in oxygen were determined as well as the chromatographic stability of the activated zeolite. The practical implications and importance of the results are discussed and the application to the analysis of fast reactor blanket gas is mentioned. An explanation is proposed for the adsorption behaviour of these activated materials, based on an electrostatic mechanism, and this has suggested a reason for the separation characteristics of oxygen and argon on polar zeolites. Further work is identified including the investigation of energy states of the oxygen molecule adsorbed on activated zeolite by means of ultra-violet photoelectron spectroscopy. (author)

  18. Energy-efficient hydrogen separation by AB-type ladder-polymer molecular sieves

    KAUST Repository

    Ghanem, Bader

    2014-07-19

    The synthesis, microstructures, and exceptional gas transport properties of two new soluble ladder polymers, polymers of intrinsic microporosity (TPIM-1 and TPIM-2) containing triptycene moieties substituted with branched isopropyl and linear propyl chains at the 9,10-bridgeheads were reported. The precursor A-B monomers were modified with an o -difluoride functionality for enhanced activation for nucleophilic aromatic substitution. In a Schlenk tube, a mixture of the A-B monomer, 18-crown-6, anhydrous DMF and anhydrous potassium carbonate was stirred at 155 °C under nitrogen atmosphere for 20 min followed by the addition of toluene. The reaction was continued for another 45 min and more toluene was added. After another 45 min the reaction mixture was cooled to room temperature and poured into methanol. Slow evaporation of filtered, dilute 3-5 wt% chloroform solutions from a leveled glass plate yielded isotropic polymer films. Dry membranes were soaked in methanol for 24 h, air-dried, and then heated at 120°C for 24 h under high vacuum to remove any traces of residual solvent. TPIM-1 exhibits simultaneous boosts in permeability and selectivity, which highlights the significant potential of an isopropyl-substituted triptycene moiety as a contortion center for ladder PIMs.

  19. ADSORPTION BEHAVIOUR OF n-PARAFFINS CONTAINED IN NAPHTHA ON THE BED WITH BINDERLESS 5A MOLECULAR SIEVE%石脑油中正构烷烃在无黏结剂5A分子筛床层中的吸附行为研究

    Institute of Scientific and Technical Information of China (English)

    孙辉; 沈本贤; 焦鑫

    2011-01-01

    在固定床吸附分离实验装置上对比研究石脑油中正构烷烃在无黏结剂和有黏结剂5A分子筛床层中的吸附行为.结果表明,随着碳数的增加,各正构烷烃穿透床层的时间增加.与有黏结剂5A分子筛床层相比,无黏结剂5A分子筛床层具有更高的正构烷烃吸附容量,床层穿透时的油筛比(原料油与分子筛质量比)更大.在吸附温度300℃、石脑油进料空速90 h-1的条件下,无黏结剂5A分子筛对石脑油中正构烷烃的动态吸附容量较有黏结剂5A分子筛高34.5%.正构烷烃在无黏结剂5A分子筛床层中的传质段长度小于有黏结剂5A分子筛床层,无黏结剂5A分子筛床层的有效利用率更高.%Adsorption of n-paraffins contained in naphtha on 5A molecular sieve pellets with/without binder was studied on a fixed bed adsorption device. The results indicated that the adsorption breakthrough times of various n-paraffins increased with the increase of n-paraffins' carbon number. As compared with molecular sieve with binder, the adsorption bed of binderless 5A molecular sieve showed higher adsorption capacities for n-paraffins; at an adsorption temperature of 300 ℃ and a space velocity of 90 h-1, the dynamic adsorption capacity of binderless 5A molecular sieve was 34.5 % higher than that of molecular sieve with binder,which indicated that more naphtha feed could be processed or less molecular sieve pellets should be packed. Furthermore,the mass-transfer zone of bed with binderless 5A molecular sieve was shorter, which suggested that the effective using rate of this adsorption bed was higher.

  20. A Cu/Al-MCM-41 mesoporous molecular sieve: application in the abatement of no in exhaust gases

    Directory of Open Access Journals (Sweden)

    M. S. Batista

    2005-09-01

    Full Text Available Propane oxidation and reduction of NO to N2 with propane under oxidative conditions on a Cu-Al-MCM-41 mesoporous molecular sieve and Cu-ZSM-5 zeolites were studied. Both types of catalysts were prepared by ion exchange in aqueous solutions of copper acetate and characterised by X-ray diffraction (XRD, nitrogen sorption measurement, diffuse reflectance ultra-violet spectroscopy (DRS-UV, diffuse reflectance infra-red Fourier transform spectroscopy (DRIFTS of the adsorption of CO on Cu+ and temperature-programmed reduction with hydrogen (H2-TPR. The NO reduction was performed between 200 and 500 ºC using a GHSV = 42,000 h-1. H2-TPR data showed that in the prepared Cu-Al-MCM-41 all the Cu atoms are on the surface of the mesopores as highly dispersed CuO, which results in a decrease in specific surface area and in mesopore volume. H2-TPR together with DRIFTS data provided evidence that in Cu/ZSM-5 catalysts, Cu atoms are found as two different Cu2+ cations: Cualpha2+ and Cubeta2+, which are located on charge compensation sites, and their thermo-redox properties were different from those of Cu atoms in Cu-Al-MCM-41. The specific activity of the Cu2+ exchangeable cations in Cu-ZSM-5, irrespective of their nature, was much greater than that of the Cu2+ in Cu-Al-MCM-41, where they are found as CuO.

  1. Comparative studies of Zr-based MCM-41 and MCM-48 mesoporous molecular sieves: Synthesis and physicochemical properties

    International Nuclear Information System (INIS)

    Two surfactant-templated synthetic routes are developed for the preparation of new types of mesoporous molecular sieves, Zr-MCM-41 and Zr-MCM-48, using different Si sources but keeping the same zirconium precursor (zirconium-n-propoxide). When fumed silica was used as Si precursor, a Zr-MCM-48 material of cubic structure was formed with a surface area of 654.8 m2/g and an unimodal pore diameter distribution. It shows low stability: after calcination at 600 deg. C, the ordered structure was transformed into a relatively disordered worm-like mesostructure with many defects and silanol groups. The use of tetraethyl orthosilicate as Si source led to the formation of a Zr-MCM-41 mesoporous solid, which had good thermal stability and a highly ordered hexagonal arrangement, with a surface area 677.9 m2/g and an uniform pore diameter distribution. Fourier transform infrared (FT-IR) characterization and 29Si NMR analysis confirm that zirconium ions indeed incorporated into the framework of the solid. The in situ FT-IR spectroscopy of pyridine adsorption reveals that both, Lewis and Broensted acid sites, were formed on the surface of these mesoporous materials. The strength and number of the Broensted acid sites of the Zr-MCM-48 solid were greater than those of the Zr-MCM-41, due to a lower degree of condensation reaction during the synthesis that led to more structural defects in the framework and more silanol groups stretching from the solid surface

  2. Current Understanding of Cu-Exchanged Chabazite Molecular Sieves for Use as Commercial Diesel Engine DeNOx Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Feng; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2013-11-03

    Selective catalytic reduction (SCR) of NOx with ammonia using metal-exchanged molecular sieves with a chabazite (CHA) structure has recently been commercialized on diesel vehicles. One of the commercialized catalysts, i.e., Cu-SSZ-13, has received much attention for both practical and fundamental studies. For the latter, the particularly well-defined structure of this zeolite is allowing long-standing issues of the catalytically active site for SCR in metal-exchanged zeolites to be addressed. In this review, recent progress is summarized with a focus on two areas. First, the technical significance of Cu-SSZ-13 as compared to other Cu-ion exchanged zeolites (e.g., Cu-ZSM-5 and Cu-beta) is highlighted. Specifically, the much enhanced hydrothermal stability for Cu-SSZ-13 compared to other zeolite catalysts is addressed via performance measurements and catalyst characterization using several techniques. The enhanced stability of Cu-SSZ-13 is rationalized in terms of the unique small pore structure of this zeolite catalyst. Second, the fundamentals of the catalytically active center; i.e., the chemical nature and locations within the SSZ-13 framework are presented with an emphasis on understanding structure-function relationships. For the SCR reaction, traditional kinetic studies are complicated by intra-particle diffusion limitations. However, a major side reaction, nonselective ammonia oxidation by oxygen, does not suffer from mass-transfer limitations at relatively low temperatures due to significantly lower reaction rates. This allows structure-function relationships that are rather well understood in terms of Cu ion locations and redox properties. Finally, some aspects of the SCR reaction mechanism are addressed on the basis of in-situ spectroscopic studies.

  3. Catalytic degradation of Acid Orange 7 by manganese oxide octahedral molecular sieves with peroxymonosulfate under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Lian; Sun, Binzhe; Wei, Mingyu; Luo, Shilu; Pan, Fei; Xu, Aihua [School of Environmental Engineering, Wuhan Textile University, Wuhan 430073 (China); Li, Xiaoxia, E-mail: lixxwh@163.com [School of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073 (China)

    2015-03-21

    Highlights: • OMS-2/PMS/Vis system could efficiently catalyze the degradation of organic dyes. • The system showed much higher activity than that of OMS-2/PMS and OMS-2/Vis. • The OMS-2 catalyst exhibited stable performance for multiple runs. • Sulfate radicals were suggested to be the major reactive species in the system. • The radicals production might involve the redox cycle of Mn(IV)/Mn(III) and Mn(III)/Mn(II). - Abstract: In this paper, the photodegradation of Acid Orange 7 (AO7) in aqueous solutions with peroxymonosulfate (PMS) was studied with manganese oxide octahedral molecular sieves (OMS-2) as the catalyst. The activities of different systems including OMS-2 under visible light irradiation (OMS-2/Vis), OMS-2/PMS and OMS-2/PMS/Vis were evaluated. It was found that the efficiency of OMS-2/PMS was much higher than that of OMS-2/Vis and could be further enhanced by visible light irradiation. The catalyst also exhibited stable performance for multiple runs. Results from ESR and XPS analyses suggested that the highly catalytic activity of the OMS-2/PMS/Vis system possible involved the activation of PMS to sulfate radicals meditated by the redox pair of Mn(IV)/Mn(III) and Mn(III)/Mn(II), while in the OMS-2/PMS system, only the redox reaction between Mn(IV)/Mn(III) occurred. Several operational parameters, such as dye concentration, catalyst load, PMS concentration and solution pH, affected the degradation of AO7.

  4. LIQUID ADSORPTION KINETICS OF n-PARAFFINS IN NAPHTHA ON 5A MOLECULAR SIEVE%石脑油中正构烷烃在5A分子筛上液相吸附动力学特性

    Institute of Scientific and Technical Information of China (English)

    曹君; 沈本贤; 刘纪昌

    2012-01-01

    设计双阀门液相吸附动力学测定装置测定正构烷烃在5A分子筛上的液相吸附动力学数据,分别考察吸附温度、正构烷烃碳数以及正构烷烃初始浓度对石脑油中正构烷烃在5A分子筛上吸附速率的影响.结果表明:随着吸附温度和正构烷烃初始浓度的增加,正构烷烃在分子筛上的吸附速率变快;而随着正构烷烃碳数的变化,正构烷烃在分子筛上的吸附速率变化不明显.分别以异辛烷、甲基环己烷和甲苯为溶剂考察石脑油中不同非正构烷烃组分对正构烷烃在5A分子筛上吸附特性的影响.结果表明,石脑油中不同非正构烃类对正构烷烃在5A分子筛上吸附速率影响从大到小的顺序为:芳香烃类>环烷烃类>异构烃类.采用Arrhenius公式对实验数据拟合的结果表明,以芳香族化合物为溶剂时正构烷烃在5A分子筛上的扩散阻力最大.%The kinetics data for the liquid adsorption of n-paraffins on 5A molecular sieve was determined by a self-designed double-valve apparatus, and the influences of adsorption temperature, carbon number and initial concentration of n-paraffins on the liquid adsorption kinetics of n-paraffins on 5A molecular sieve were studied. Results showed that the adsorption rate of n-paraffin on 5A molecular sieve increased with the increase of adsorption temperature and initial n-paraffin concentration. The effect of n-paraffin carbon number on the adsorption rate was not significant. Furthermore, the influence of various non-normal paraffin components in naphtha, such as iso-octane,methyl cyclohexane and toluene, on the liquid adsorption kinetics of w-paraffins on 5A molecular sieve was investigated as well. Test results indicated that the influence of non-normal paraffin components on the adsorption rate of n-paraffins was as follows :aromatics>cycloparaffins >iso-paraffins. Results of Arrhenius formula for data fitting showed that the maximum diffusion resistance of

  5. Mesoporous molecular sieve catalysts

    OpenAIRE

    Højholt, Karen Thrane; Nielsen, Michael Brorson; Fehrmann, Rasmus

    2011-01-01

    Denne afhandling omhandler en specifik klasse af molekylesier, nemlig zeolitter. Zeolitter, der er en klasse af krystallinske aluminosilikater, er kendetegnet ved, at deres krystalstruktur indeholder kanaler og hulrum i samme størrelsesorden som små molekyler. I dette projekt er zeolitter blevet modificeret til brug i udvalgte katalytiske reaktioner, hvorved der også er opnået en dybere forståelse af reaktionerne. Zeolitter er hovedsageligt blevet modificeret med hensyn til porøsitet. Desuden...

  6. Evaluation of INL Supplied MOOSE/OSPREY Model: Modeling Water Adsorption on Type 3A Molecular Sieve

    Energy Technology Data Exchange (ETDEWEB)

    Pompilio, L. M. [Syracuse University; DePaoli, D. W. [ORNL; Spencer, B. B. [ORNL

    2014-08-29

    The purpose of this study was to evaluate Idaho National Lab’s Multiphysics Object-Oriented Simulation Environment (MOOSE) software in modeling the adsorption of water onto type 3A molecular sieve (3AMS). MOOSE can be thought-of as a computing framework within which applications modeling specific coupled-phenomena can be developed and run. The application titled Off-gas SeParation and REcoverY (OSPREY) has been developed to model gas sorption in packed columns. The sorbate breakthrough curve calculated by MOOSE/OSPREY was compared to results previously obtained in the deep bed hydration tests conducted at Oak Ridge National Laboratory. The coding framework permits selection of various options, when they exist, for modeling a process. For example, the OSPREY module includes options to model the adsorption equilibrium with a Langmuir model or a generalized statistical thermodynamic adsorption (GSTA) model. The vapor solid equilibria and the operating conditions of the process (e.g., gas phase concentration) are required to calculate the concentration gradient driving the mass transfer between phases. Both the Langmuir and GSTA models were tested in this evaluation. Input variables were either known from experimental conditions, or were available (e.g., density) or were estimated (e.g., thermal conductivity of sorbent) from the literature. Variables were considered independent of time, i.e., rather than having a mass transfer coefficient that varied with time or position in the bed, the parameter was set to remain constant. The calculated results did not coincide with data from laboratory tests. The model accurately estimated the number of bed volumes processed for the given operating parameters, but breakthrough times were not accurately predicted, varying 50% or more from the data. The shape of the breakthrough curves also differed from the experimental data, indicating a much wider sorption band. Model modifications are needed to improve its utility and

  7. ZSM-5-SBA-15复合分子筛的制备%Preparation of ZSM-5-SBA-15 Composite Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    刘鹏; 沈健

    2015-01-01

    The micro-mesoporous composite molecular sieves of ZSM-5–SBA-15 were synthesized via a post synthesis. The influences of mass ratio of ZSM-5/SBA-15, crystallization time, acid content and calcination temperature on the preparation of the composite molecular sieves were investigated. The ZSM-5–SBA-15 prepared at the mass ratio of ZSM-5/SBA-15 of 0.2, crystallization time of 18 h, acid content of 20 mL and calcination temperature of 550 ℃ has a conversion rate of methanol of 94.93%and a selectivity of para-xylene of 45.46%. The acidity on the surface of ZSM-5 is reduced by mesoporous molecular sieve of nonvalent SBA-15, thus improving the selectivity of para-xylene.%采用后合成法合成了 ZSM-5–SBA-15微介孔复合分子筛,考察了 m(ZSM-5)/m(SBA-15)、晶化时间、盐酸量、焙烧温度对烷基化催化性能的影响。在 m(ZSM-5)/m(SBA-15)=0.2,晶化时间为18 h,盐酸量为20 mL,焙烧温度为550℃条件下,合成的复合分子筛催化剂的甲醇转化率为94.93%,对二甲苯选择性为45.46%。惰性 SBA-15介孔分子筛抑制了 ZSM-5外表面酸性,提高了对二甲苯的选择性。

  8. 钛硅分子筛催化环己酮氨肟化反应动力学%Kinetics of Cyclohexanone Ammoximation over Titanium Silicate Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    李永祥; 吴巍; 闵恩泽

    2005-01-01

    An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading,and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H2O2 decomposition reaction must be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.

  9. Synthesis of 4A Molecular Sieves from Poor Quality Coal Gangue%劣质煤矸石合成4A沸石分子筛

    Institute of Scientific and Technical Information of China (English)

    孔德顺; 连明磊; 范佳鑫; 李琳

    2013-01-01

    In order to synthesize 4A molecular sieves from poor quality high iron and silica concentrations coal gangue,the gangue was calcined at 350 ℃ for 2 h,then the hydrochloric acid whose concentration was 20% was added into the metakaolin overdose in 10% and leached at 90 ℃ for 2 h,the iron leaching ratio was 95.1%,the alumina leaching ratio was 10% of the total; the removed iron gangue was calcined at 750 ℃ for 2 h,the carbon and other organic matter were removed and the kaolin transformed into amorphous metakaolin; the sodium hydroxide was added to the 750 ℃ calcined gangue powder with the ratio m(gangue) ∶ m(sodium hydroxide) =1 ∶ 1,then the mixture was calcined at 400 ℃ for 2 h,quartz and other matters turned into soluble sodium silicate and sodium aluminosilicate,so the high activity raw material were obtained,then the synthesis system of 4A molecular sieves was formed by n(SiO2)/n(Al2O3)=2.0,n(Na2O)/n(SiO2)=1.7and n(H2O)/n(Na2O)=45,the system was aging at 40 ℃ for 2 h,crystallization by hydrotherrnal method at 95 ℃ for 4 h,the crystal products were characterized by XRD,SEM and other method,the results showed that the products were pure 4A molecular sieves with complete crystal form,the average particle size was at about 1 μm,the Ca2+ exchange capacity was 296 mg CaCO3/g dry zeolite.%为了利用高铁高砂型劣质煤矸石来合成4A沸石分子筛,先将该煤矸石在350℃煅烧2h,然后加入过量10%的浓度为20%的盐酸,在90℃的条件下酸浸3h,除铁率为95.1%,铝元素浸出率为总铝含量的1 0%;将除铁后的煤矸石粉在750℃煅烧2h后,煤矸石中的炭等有机质被除去、高岭石转变为无定形态的偏高岭石;然后向该750 ℃煤矸石煅烧粉中按照m(煤矸石)∶m(氢氧化钠)=1∶1的比例加入氢氧化钠,混匀后在400℃恒温2h,煅烧粉中的石英等成分转变为可溶于水的硅酸钠和硅铝酸钠,因此获得了高活性的原料;合成4A沸石分子筛

  10. Efficient Improving the Activity and Enantioselectivity of Candida rugosa Lipase for the Resolution of Naproxen by Enzyme Immobilization on MCM-41 Mesoporous Molecular Sieve

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2015-09-01

    Full Text Available Lipase from Candida rogusa was immobilized on MCM-41 mesoporous molecular sieves in a trapped aqueous-organic biphase system for the resolution of racemic naproxen methyl ester. It was interesting that the activity and enantioselectivity of the immobilized lipase were improved significantly relative to the free enzyme. The proportion of water (ml/support (g has a dramatic influence on the activity and enantioselectivity of lipase immobilized onto MCM-41 molecular sieves. It was also found that the activity of immobilized lipase was more sensitive to pH value and temperature than the free one. Higher pH value will increase the activity but decrease the enantioselectivity of the immobilized lipase. The enantioselectivity of the immobilized lipase was not altered significantly within the range of tested temperature. The immobilized lipase can be reused for at least 8 batches without significant lose of activity with the aid of methanotrophic bacteria to eliminate the methanol produced during the resolution process.

  11. New Molecular Sieves for Adsorbing Tobacco Specific Nitrosamines%吸附烟草特有亚硝胺的分子筛新材料

    Institute of Scientific and Technical Information of China (English)

    朱建华

    2012-01-01

    烟草特有亚硝胺(TSNA)属于强致癌物,是吸烟导致癌症的重要因素.如何在成分复杂的环境烟气里吸附亚硝胺成为环境保护的难题.文章综述了近年来的研究进展,剖析了分子筛形貌对TSNA吸附的影响,讨论了液相吸附TSNA的新材料,并展望特定分子筛新材料的发展方向.%Tobacco specific nitrosamines (TSNA) are well-recognized carcinogens, and TSNA in smoke causes health hazard by smoking. How to adsorb TSNA in tobacco smoke with complex composi- tion becomes the challenge facing environment protection. In this article some latest research progress in adsorption of TSNA by new molecular sieves are reviewed. The special effect of molecular sieves morphol- ogy on the adsorption of TSNA in tobacco smoke is described, and the new functional adsorbents to trap the TSNA in aqueous tobacco extract solution are introduced. Finally the development of new functional materials to eliminate the pollution of TSNA is prospected.

  12. Effect of the Si/Ce molar ratio on the textural properties of rare earth element cerium incorporated mesoporous molecular sieves obtained room temperature

    International Nuclear Information System (INIS)

    Rare earth Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized via a direct and nonhydrothermal method at room temperature from sodium silicate and ammonium cerium (IV) nitrate as raw materials. Cetyltrimethyl ammonium bromide (CTAB) was used as a template. The resultant samples were characterized by means of powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet-visible spectroscopy (UV-vis) and N2 physical adsorption, respectively. The effect of the Si/Ce molar ratio on the crystalline structure and textural properties of CeMCM-41 was also investigated. The experimental results show that ordered CeMCM-41 mesoporous molecular sieves were successfully synthesized at room temperature and the resultant mesoporous materials have specific surface areas in the range of 594-1369 m2/g and average pore sizes in the range of ca. 2.5-2.8 nm. It has been found that the structural properties are strongly related to the amounts of cerium incorporation. When the cerium content increased in the samples, the intensity of the peak (1 0 0) was gradually reduced, and the surface area and structural regularity were diminished.

  13. Molecular sieve as an economical route for the removal of hydrogen sulfide (H/sub 2/S) and tetrahydrothiophene(THT) from natural gas for fuel cell applications

    International Nuclear Information System (INIS)

    The removal of hydrogen sulfide (H/sub 2/S) and tetrahydrothiophene (THT) from the natural gas has been studied by employing two kinds of sorbents, i. e., compounds of sulfur-absorbing and sulfur-adsorbing materials. For the removal of sulfur compounds, a system was designed, established and operated for 2000 hours. Determination of the life-cycle assessment and feasibility of material's effectiveness were also carried out. The same experiment was repeated by using a substitute (molecular sieve) and the treated gas coming out of the cleaning system was examined every 4-hour-run time by Drager gas detector pump (DGDP) for the presence of H/sub 2/S and THT. The results were very encouraging for this material. The molecular sieve is found highly economical as a single material with a simple design when compared with the set of sorbents tried earlier. The sulfur-free natural gas is required as feedstock for the production of hydrogen gas which will be consumed by the proton exchange membrane fuel cells for smooth functioning, keeping in view the high efficiency of the system. (author)

  14. Application of a molecular sieve in the drying of solid insulation in energized power transformers; Aplicacao de peneira molecular na secagem da isolacao solida em transformadores de potencia energizados

    Energy Technology Data Exchange (ETDEWEB)

    Mello, Julio C.P.; Silva, Carlos A. [Eletropaulo Metropolitana e Eletricidade de Sao Paulo S.A. (AES ELETROPAULO), SP (Brazil)], E-mails: julio.pereira@aes.com, carlos.alves@aes.com; Wilhelm, Helena M.; Mattoso, Mauricio; Piovezan, Natalia; Fernandes, Paulo O. [DIAGNO - Materiais e Meio Ambiente Ltda (Brazil)], E-mails: mattoso@diagno.srv.br, natalia@diagno.srv.br, fernandes@diagno.srv.br; Hossri, Jose Henrique C. [Universidade de Sao Paulo (IEE/USP), SP (Brazil). Instituto de Eletrotecnica e Energia], E-mail: henrique.hossri@iee.usp.br; Galdeano, Claudio A.; Silva Junior, Milton M. [MGM - Consultoria e Diagnosticos em Equipamentos Eletricos Ltda, Campinas, SP (Brazil)], E-mails: laudio@mgmdiag.com.br, junior@mgmdiag.com.br

    2011-10-15

    The main objective of this study was to assess a new adsorbent material to remove water from insulating mineral oil (IMO) in transformers during operation (while energized). A process for recovery of the adsorbent material, aiming at its reuse was also tested. The results indicated that it is possible to remove water from IMO in energized transformers safely and with remote online monitoring, using a molecular sieve, recyclable by steam washing. (author)

  15. 高稳定性介孔分子筛的合成与表征%SYNTHESIS AND CHARACTERIZATION OF HIGHLY STABILIZED MESOPOROUS MOLECULAR SIEVES

    Institute of Scientific and Technical Information of China (English)

    姜廷顺; 赵谦; 陆路德; 殷恒波

    2006-01-01

    Highly stabilized mesoporous molecular sieves were synthesized by the hydrothermal method using natural clay and sodium silicate as raw materials and cetyltrimethyl ammonium bromide as a template. The samples were characterized by means of X-ray diffraction, transmission electron microscopy, specific Surface area analysis, Fourier transform infrared spectroscopy and N2 physical adsorption. The results show that the synthesized mesoporous molecular sieve has a specific surface area over 550 m2/g and an average pore size of 2.72 nm. The pore structure is not damaged after calcination at 850 ℃ for 3 h or hydrothermal treatment at 100 ℃ for 10 d. The mesoporous ordering is improved, but the pores contract and the specific surface area decreases after hydrothermal treatment. The stability of the synthesized mesoporous molecular sieves is enhanced because natural clay was used as a raw material.%以天然黏土和硅酸钠为原料、十六烷基三甲基溴化铵为模板剂,水热法合成了有序性好的高稳定性介孔分子筛.用粉末X射线衍射、透射电镜、Fourier变换红外光谱和比表面积孔径分析等方法对所合成的介孔分子筛进行了表征.结果表明:所合成的介孔分子筛的比表面积大于550m2/g,平均孔径为2.72nm.样品经850℃焙烧3 h,100℃水热处理10 d,介孔分子筛的介孔结构没有被破坏,并且热处理使孔发生收缩,比表面积减小,水热处理使介孔的有序性变得更好,天然黏土为原料提高了介孔分子筛的水热稳定性.

  16. Preparation,characterization,and catalytic performance of a novel methyl-rich Ti-HMS mesoporous molecular sieve with high hydrophobicity

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel methyl-rich Ti-containing hexagonal mesoporous silica (Ti-HMS) molecular sieve with high hydrophobicity has been prepared by a two-step method involving co-condensation followed by vapor-phase methyl grafting.The sample was characterized by XRD,N2 adsorption,FTIR,UV-visible and 29Si NMR spectroscopies,TG,ICP-AES,and hydrophilicity measurements,and its catalytic performance was evaluated using the epoxidation of cyclohexene as a probe reaction.The Ti-HMS material retains a typical mesoporous structure and compared with a co-condensed Ti-HMS prepared in a one-step method possesses more methyl groups and higher hydrophobicity,and also exhibits better catalytic activity and selectivity.

  17. Metal cation sensing material based on the assembly of meso-terakis(4-N,N,N-trimethylamiophenyl) porphyrin and mesoporous molecular sieve MCM-41

    Institute of Scientific and Technical Information of China (English)

    ZHANG Huidong; SUN Yinghui; ZHANG Ping; YE Kaiqi; ZHANG Jingying; WANG Yue

    2005-01-01

    The metal cation sensing material was prepared by entrapment of a water-soluble porphyrin compound, mesoterakis(4-N,N,N-trimethylamiophenyl) porphyrin (TTMAPP), in mesoporous molecular sieve MCM-41. The powder X-ray diffraction (XRD) spectra results demonstrated that after the introduction of TTMAPP, the ordered channel arrangement of MCM-41 remained. The assembly material, TTMAPP/MCM-41, exhibited a typical absorption feature of porphyrin compound. Emission spectrum study revealed that the introduction of zinc (II) cation resulted in the formation of a new emission peak at 600 nm for TTMAPP/MCM-41, while the presence of copper (II) cation at low concentration led to that the luminescent intensity of TTMAPP/MCM-41 was obviously reduced by 68.42%. The experiment results demonstrated that TTMAPP/MCM-41 is a cation sensing materials with good performance.

  18. A New Class of Octahedral Molecular Sieve Materials for the Selective Removal and Sequestration of {sup 90}Sr{sup 2+}

    Energy Technology Data Exchange (ETDEWEB)

    NYMAN,MAY D.; NENOFF,TINA M.; TRIPATHI,AKHILESH; PARISE,JOHN B.; MAXWELL,ROBERT S.; HARRISON,WILLIAM T.A.

    2000-07-14

    The structure of Na{sub 16}Nb{sub 12.8}Ti{sub 3.2}O{sub 44.8}(OH){sub 3.2} {center_dot} 8H{sub 2}O, a member of a new family of Sandia Octahedral Molecular Sieves (SOMS) having a Nb/Na/M{sup IV} (M= Ti, Zr) oxide framework and exchangeable Na and water in open channels, was determined from Synchrotron X-ray data. The SOMS phases are isostructural with variable M{sup IV}:Nb(1:50--1:4) ratios. The SOMS are extremely selective for sorption of divalent cations, particularly Sr{sup 2+}. The ion-exchanged SOMS undergo direct thermal conversion to a perovskite-type phase, indicating this is a promising new method for removal and sequestration of radioactive Sr-90 from mixed nuclear wastes.

  19. 一种新型自动深冷及活化分子筛的吸附泵设计%Design of a new adsorption pump with cryogenically refrigerated and automatically activated molecular sieve

    Institute of Scientific and Technical Information of China (English)

    邓云伟; 李军格; 杜卫星

    2012-01-01

    设计实现了一种新型自动深冷及活化分子筛的吸附泵.进行了吸附能力设计,采用基于PLC(可编程逻辑控制器)软硬件为核心的电气系统,方便地实现了对分子筛吸附泵的液氮自动输送以维持液氮量及分子筛活化的远程控制,有利于操作者操作和安全保障.验证实验结果表明,该分子筛吸附泵能快速吸附泄漏到密封容器里的有害气体,且吸附效果良好.%A new adsorption pump was designed and manufactured by applying the design technique of adsorption ability of molecular sieve. The hardware and software of the PLC (programmable logic controller) were used as the kernel of the electric system, which was applied to refrigerate cryogenically the molecular sieve by supplying and automatic -maintaining of the volume of the liquid nitrogen and activate the molecular sieve by heating the heater in the pump. The electric system made the pump operation easier and safer for operators. Further experiments demonstrated effectively rapid adsorption ability of the molecular sieve pump to deleterious gas leaked into the sealed box.

  20. Analysis on Properties and Test Methods of New Molecular Sieve Material——Standard of Molecular Sieve 4A%浅析新型分子筛材料的性能及检验方法——4A分子筛的标准化

    Institute of Scientific and Technical Information of China (English)

    朱琳; 王鹏飞; 邓琦; 顾艳

    2011-01-01

    As a new material,molecular sieve 4A has excellent properties of adsorption,separation,and dispersion.It is widely used in chemical industry,paint industry,automotive industry and modern medicine,etc.The new standard,HG/T 2524-2010 molecular sieve 4A ,may cause confusion sometimes,since it is used in many fields.This paper introduces some new information of the standard including the main technical performance and the test methods,and may help users to operate properly.%4A分子筛作为一种新型材料,具有很好的吸附、分离、分散等性能,广泛应用于化工、涂料、日化、汽车及现代医学等领域.由于涉及领域较多,新修订的HG/T 2524-2010《4A分子筛》标准在使用过程中可能会遇到一些问题.本文对该标准进行了解读与介绍,包括主要技术性能和检验方法,可以帮助各领域标准应用者正确运用标准,以达到预期目的.

  1. Crosslinkable mixed matrix membranes with surface modified molecular sieves for natural gas purification: II. Performance characterization under contaminated feed conditions

    KAUST Repository

    Ward, Jason K.

    2011-07-01

    Mixed matrix membranes (MMMs) composed of the crosslinkable polyimide PDMC and surface modified (SM) SSZ-13 have recently been shown to enhance carbon dioxide permeability and carbon dioxide/methane selectivity versus neat PDMC films by as much as 47% and 13%, respectively (Part I). The previous film characterization, however, was performed using ideal, clean mixed gas feeds. In this paper, PDMC/SSZ-13 MMMs are further characterized using more realistic mixed gases containing low concentrations (500 or 1000. ppm) of toluene as a model contaminant. Mixed matrix membranes are shown to outperform pure PDMC films in the presence of toluene with 43% greater carbon dioxide permeability and 12% greater carbon dioxide/selectivity at 35 °C and 700 psia feed pressure. These results suggest that MMMs-in addition to exhibiting enhanced transport properties-may mitigate performance degradation due to antiplasticization effects. Moreover, the analyses presented here show that the reduction in separation performance by trace contaminant-accelerated physical aging can be suppressed greatly with MMMs. © 2011 Elsevier B.V.

  2. Dynamical Sieve of Eratosthenes

    OpenAIRE

    Mateos, Luis A.

    2012-01-01

    In this document, prime numbers are related as functions over time, mimicking the Sieve of Eratosthenes. For this purpose, the mathematical representation is a uni-dimentional time line depicting the number line for positive natural numbers N, where each number n represents a time t. In the same way as the Eratosthenes' sieve, which iteratively mark as composite the multiples of each prime, starting at each prime. This dynamical prime number function P(s) zero-cross all composite numbers depa...

  3. Lacunar fractal photon sieves

    OpenAIRE

    Gimenez, Fernando; Furlan, Walter D.; Monsoriu, Juan A.

    2007-01-01

    We present a new family of diffractive lenses whose structure is based on the combination of two concepts: photon sieve and fractal zone plates with variable lacunarity. The focusing properties of different members of this family are examined. It is shown that the sieves provide a smoothing effect on the higher order foci of a conventional lacunar fractal zone plate. However, the characteristic self-similar axial response of the fractal zone plates is always preserved.

  4. Application of computational fluid dynamics for the simulation of cryogenic molecular sieve bed absorber of hydrogen isotopes recovery system for Indian LLCB-TBM

    Energy Technology Data Exchange (ETDEWEB)

    Gayathri Devi, V.; Sircar, A.; Sarkar, B. [Institute of Plasma Research, Bhat, Gandhinagar, Gujarar (India)

    2015-03-15

    One of the most challenging tasks in the design of the fuel cycle system lies in the effective design of Tritium Extraction System (TES) which involves proper extraction and purification of tritium in the fuel cycle of the fusion reactor. Indian Lead Lithium cooled Ceramic Breeder Test Blanket Module (LLCB-TBM) would extract hydrogen isotopes through Cryogenic Molecular Sieve Bed (CMSB) adsorber system. A prototype Hydrogen Isotopes Recovery System (HIRS) is being developed to validate the concepts for tritium extraction by adsorption mass transfer mechanism. In this study, a design model has been developed and analyzed to simulate the adsorption mass transfer kinetics in a fixed bed adsorption column. The simulation leads primarily to effective design of HIRS, which is a state-of-the-art technology. The paper describes the process simulation approach and the results of Computational Fluid Dynamics (CFD) analysis. The effects of different operating conditions are studied to investigate their influence on the hydrogen isotopes adsorption capacity. The results of the present simulation study would be used to understand the best optimized transport phenomenon before realizing the TES as a system for LLCB-TBM. (authors)

  5. Towards operando characterisation by powder diffraction techniques of molecular sieves; Vers la caracterisation operando de tamis moleculaires par diffraction par les poudres

    Energy Technology Data Exchange (ETDEWEB)

    Pichon, C.; Palancher, H. [Institut Francais du Petrole, 69 - Vernaison (France); Palancher, H.; Hodeau, J.L.; Berar, J.F. [Laboratoire de Cristallographie (CNRS), BP 38 - Grenoble (France); Berar, J.F. [D2AM- CRG francaise (ESRF), 38 - Grenoble (France)

    2005-07-01

    Working molecular sieves imply numerous and various atoms and for their characterisation we need chemical selective probes. Thus they can be studied either by neutron powder diffraction or by anomalous X-ray powder diffraction techniques to extract structural information. We will illustrate the complementarities of these methods in the analysis of two different chemical processes on X-type zeolite. In the first case, a fully exchanged barium X-type zeolite was, firstly, characterised by neutron powder diffraction after an ex situ preparation step. During the preparation step, the sample was saturated with a mixture of heavy water and deuterated para-xylene. The selectivity of neutron diffraction for light elements allows the precise location of both water and xylene molecules. In the second example, an X-type zeolite exchanged by both strontium and rubidium cations was studied during the dehydration process. The in situ structural characterisation was performed by recording, for each state of the zeolite (hydrated, dehydrated), three X-ray powder patterns. Two of them were measured at an energy close to the absorption edge of each compensating cation (Sr{sup 2+} and Rb{sup +}) and one far from both absorption edges. The chemical selectivity of resonant diffraction allows an accurate determination of the distribution of compensating cations (location, distribution and mobility) during the dehydration process. Finally a comparison of some specificities and limitations of both methods are summarized. (authors)

  6. Alkane sorption in molecular sieves: The contribution of ordering, intermolecular interactions and sorption on Brondsted acid sites

    NARCIS (Netherlands)

    Eder, Florian; Lercher, Johannes A.

    1997-01-01

    Distinct molecular ordering of sorbed alkanes is observed in MFI zeolites when the chain length of the alkane is similar to the length of the zig-zag channels (i.e., with n-hexane and n-heptane). In contrast, sorbate-sorbate interactions lead to an increase of the heat of adsorption with increasing

  7. Fluorescent carbon dot–molecular salt hydrogels

    OpenAIRE

    Cayuela, Angelina; Kennedy, Stuart R.; Soriano, Laura; Jones, Christopher D.; Valcárcel, M.; Steed, Jonathan W.

    2015-01-01

    The incorporation of functionalised carbon nanodots within a novel low molecular weight salt hydrogel derived from 5-aminosalicylic acid is reported. The carbon dots result in markedly enhanced gelation properties, while inclusion within the hydrophobic gel results in a dramatic fluorescence enhancement for the carbon nanomaterials. The resulting hybrid CD gels exhibit a useful sensor response for heavy metal ions, particularly Pb2+.

  8. Logic control of molecular sieve purification system of 65000m3· h-1 air separation plant%65000m3·h-1空分设备分子筛纯化系统逻辑控制

    Institute of Scientific and Technical Information of China (English)

    朱玉芹

    2012-01-01

    The structure and technical process of molecular sieve purification system of 65000m3/ an air separation plant of Hebi coal and electeicity 600 ktpa methanol project are briefed, automatic valve closing / opening logical control of molecular sieve purification system, automatic / manual operation sequence control program,implementation of the sequence control program and optimized reform of the sequence control configuration program of the molecular sieve absorber in accordance with site operation conditions are described.%简介鹤壁煤电股份有限公司化工分公司空分厂65000m3·h-1空分设备分子筛纯化系统结构和工艺流程,介绍分子筛纯化系统阀门自动开关控制逻辑、顺控程序自动/手动运行、顺控程序执行过程,以及根据现场生产运行实际情况,对分子筛吸附器顺控组态程序进行的优化改进.

  9. 改性条件下X型分子筛对甲醛吸附性能的研究%The Study on Adsorption Properties of Modified Molecular Sieve Material to Formaldehyde

    Institute of Scientific and Technical Information of China (English)

    肖艳华; 王银叶; 骆永娜; 张宏伟

    2012-01-01

    Indoor formaldehyde pollution has aroused much attention around the world in recent years. A kind of adsorbent named modified molecular sieve was developed, which can adsorb formaldehyde efficiently. The adsorption properties of the X small grain zeolite were studied in the conditions of different modification, such as microwave, calcination and drying. The results showed that formaldehyde adsorption efficiency were 99. 51% , 85. 25% and 61. 63% , respectively, at different modification of microwave , calcination and drying. The influences of modification conditions on the adsorption properties of zeolites were analyzed, with the help of FTIR infrared spectral. As the result of microwave, the molecular vibrational energy transferred from inside to outside through the molecular sieve tunnel, which was called " internal heating" . Under such condition, the molecular sieve cavity was dredged completely, the energy barrier formaldehyde diffusion overcoming was reduced, and the activity point of molecular sieve was increased, but the supercage structure of molecular sieve was not changed. As for calcining modification, the thermal energy transferred from outside to inside, that was called "exterior heating". But the molecular sieve cavity was not dredged completely. The FTIR analysis showed that Si-0 key (1448 cm-1 ) of the molecular sieve was changed, meanwhile, the Si = O= Si key (693 cm ) was generated. Therefore, the structure of the zeolite was changed by calcining.%针对目前国内外室内空气中甲醛污染严重问题,研制高效吸附甲醛材料-改性分子筛.以X型小晶粒分子筛为主体,研究其在烘干、煅烧和微波改性条件下对甲醛气体的吸附性能.结果表明:微波、煅烧和烘干分子筛对甲醛的吸附效率分别为99.51%、85.25%和61.63%.借助FTIR红外光谱分析了不同改性条件对分子筛吸附性能的影响.微波使分子的振动能量从分子筛孔道内向外传递,形成的是“内加热

  10. Oxidative dehydrogenation of propane over vanadium based catalysts supported on Y molecular sieve%Y分子筛负载V基催化剂的丙烷氧化脱氢性能

    Institute of Scientific and Technical Information of China (English)

    范爱鑫; 张聚华

    2016-01-01

    以 Y 分子筛为载体,采用浸渍法制备不同 V 含量的 V/ Y 系列催化剂,并考察其丙烷氧化脱氢制丙烯的催化性能。通过 BET、XRD、H2- TPR 和 NH3- TPD 等技术对催化剂的物化性能进行表征。结果表明,Y 分子筛具有大比表面积和窄孔径分布的特点,使负载的 V 能够形成高分散和孤立态V—O物种,负载的 V 物种堵塞了 Y 分子筛的小孔孔道,同时 Y 分子筛的弱酸性位有助于丙烷的吸附,对晶格氧活化丙烷起到了协同作用,负载 V 质量分数6%时,催化效果最好。%Using Y molecular sieve as the support,vanadium supported Y molecular sieve catalysts(V/ Y) with different vanadium contents were prepared by the impregnation method,and their catalytic perform-ance in the oxidative dehydrogenation of propane to propene was investigated. The catalysts were charac-terized by BET,XRD,H2-TPR and NH3-TPD. The results showed that Y molecular sieve possessed large specific surface area and narrow pore size distribution,which enabled vanadium to form highly dispersed and isolated state V—O species;the loading vanadium species blocked the small pore channels of Y molecular sieve;at the same time,the weak acid sites of Y molecular sieve was helpful to propane adsorp-tion,and had synergistic effect on propane activation by lattice oxygen. V/ Y catalyst with 6wt% vanadium exhibited better catalytic performance.

  11. HZSM-5/MCM-41 composite molecular sieves for the catalytic cracking of endothermic hydrocarbon fuels: nano-ZSM-5 zeolites as the source

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Yu; Jiao, Qingze; Li, Hansheng, E-mail: hanshengli@bit.edu.cn; Wu, Qin; Zhao, Yun; Sun, Kening, E-mail: sunkn@bit.edu.cn [Beijing Institute of Technology, School of Chemical Engineering and the Environment (China)

    2014-12-15

    A series of HZSM-5/MCM-41 composite molecular sieves (HZM-Ns (x)) were prepared by employing nano-ZSM-5 zeolites with the SiO{sub 2}/Al{sub 2}O{sub 3} ratios (x) of 50, 100 and 150 as the source. These materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, N{sub 2} adsorption–desorption measurement, and NH{sub 3} temperature-programmed desorption. The catalytic cracking of endothermic hydrocarbon fuels over the HZM-Ns with n-decane as model was evaluated at atmospheric pressure and 500 °C. The effect of the parent zeolite, mesopore and SiO{sub 2}/Al{sub 2}O{sub 3} ratio on the structure, acidity, and catalytic performance of HZM-Ns was investigated. The HZM-Ns exhibited a skeletal matrix with nano-sized HZSM-5 particles (200–300 nm) with a controllable acidity well dispersed in and microporous–mesoporous hierarchical pores. The mesoporous structure improved the diffusion of the reactants and products in the pores, and the HZSM-5 nanoparticles uniformly dispersed in the MCM-41 matrix supplied a proper acidity, shorter channels, and a higher specific surface area for reaction. These resulted in a high catalytic activity, a high selectivity to light olefins and a long lifetime for n-decane catalytic cracking. The HZM-N (150) exhibited the excellent conversion, a high selectivity to light olefins and a long lifetime due to low diffusion resistance, high specific surface area, and appropriate acid distribution and strength, with the increasing SiO{sub 2}/Al{sub 2}O{sub 3} ratio.

  12. THE CAPACITY EXPANSION OF A MOLECULAR SIEVE DEWAXING COMPLEX%分子筛脱蜡联合装置扩能改造

    Institute of Scientific and Technical Information of China (English)

    刘升

    2001-01-01

    为使抚顺石油化工公司石油三厂分子筛脱蜡联合装置生产正构烷烃能力由120 kt/a 扩大到1 50 kt/a,对装置进行了改造。加热炉改用无机热管式空气预热器,引风机、鼓风机改用变频 技术,使加热炉热效率提高7.2个百分点;采用浙江工业大学 DJ-Ⅲ型复合塔盘对抽余液塔 、抽出液塔、脱 C10塔、脱 C13塔的内构件进行技术改造。改造后的工业标定 结果表明,产量可达155 kt/a 且产品质量可满足要求,装置能耗降低14.75%。%The normal paraffin production capacity of the molecular sieve dewaxing complex at No. 3 Refinery of Fushun Petrochemical Company was expanded from 120 kt/a to 150 kt/a by some equipment change. Heating pipe type air preheater was used in the heating furnace and the frequency modulation technique was employed in the induced draft fan and the air blower, which increased the heat furnace efficiency by 7.2%. Th e extraction and raffination column trays were also replaced by DJ-Ⅲ type comp lex trays, which were developed by Zhejiang University of Technology. After the revamping, th e normal paraffin production was up to 155 kt/a, and the energy consumption decr eased by 14.75%.

  13. Efeitos da incorporação de peneiras moleculares 3A, 4A, 5A e 13X em membranas compósitas de quitosana/poli(vinil álcool Effect of molecular sieves 3A, 4A, 5A and 13X incorporation on the chitosan/poly(vinyl alcohol composites membranes

    Directory of Open Access Journals (Sweden)

    Denice Schulz Vicentini

    2010-01-01

    Full Text Available The composite membranes prepared via incorporation of 12.5% of molecular sieves 3A, 4A, 5A and 13X into chitosan/poly(vinyl alcohol (1:1. The composite membranes were immersed in the cross-linker sulfuric acid in order to acquire high proton conductivity for applications in electrolytes in PEMCF and DMF. The influence of the molecular sieves on the structural, optical, thermal, mechanical, morphologic and protonic conductivity properties and water/methanol swelling degree of membranes were investigated.

  14. Microfluidic sieve valves

    Science.gov (United States)

    Quake, Stephen R; Marcus, Joshua S; Hansen, Carl L

    2015-01-13

    Sieve valves for use in microfluidic device are provided. The valves are useful for impeding the flow of particles, such as chromatography beads or cells, in a microfluidic channel while allowing liquid solution to pass through the valve. The valves find particular use in making microfluidic chromatography modules.

  15. Carbon Isotope Chemistry in Molecular Clouds

    Science.gov (United States)

    Robertson, Amy N.; Willacy, Karen

    2012-01-01

    Few details of carbon isotope chemistry are known, especially the chemical processes that occur in astronomical environments like molecular clouds. Observational evidence shows that the C-12/C-13 abundance ratios vary due to the location of the C-13 atom within the molecular structure. The different abundances are a result of the diverse formation pathways that can occur. Modeling can be used to explore the production pathways of carbon molecules in an effort to understand and explain the chemical evolution of molecular clouds.

  16. Effect of H3PW12O40 impregnation on Sn-MCM-41 mesoporous molecular sieves and their physico-chemical properties

    International Nuclear Information System (INIS)

    Graphical abstract: The wide angle XRD shows the well dispersion of HPWA in Sn-MCM-41. It enhances the total acidity of the material. The acidity of the material is correlated with sulfone selectivity. The FT-IR of dibenzothiophene and product shows the formation of sulfone (DBTO2). - Highlights: • To enhance the total acidity of Sn-MCM-41 TPA is impregnated. • FT-IR and 31P MAS NMR confirms the HPWA intact on Sn-MCM-41. • EDAX shows the presence of W and P on Sn-MCM-41. • In ODS formation of sulfone was confirmed by FT-IR and 1H NMR. • The order of the catalytic activity of the catalysts are 18HSnM > 28HSnM > 8HSnM. - Abstract: Si-Sn-MCM-41 (Si/Sn = 110) mesoporous molecular sieve was synthesized by hydrothermal sol–gel method using cetyltrimethylammonium bromide (CTAB) as surfactant and SnCl4·5H2O as a metal source. To generate surface acidity of Si-Sn-MCM-41, 12-tungstophosphoric acid (HPWA) is impregnated on it. The acidity of HPWA loading on Sn-MCM-41 was investigated by temperature programmed desorption of NH3. The diffused reflectance spectra of ultraviolet radiation, Raman spectra, FT-IR, 29Si-MAS NMR and 31P-MAS NMR techniques revealed the intact of α-Keggin anions on Sn-MCM-41. The wide angle XRD results showed that the HPWA is well dispersed on the support. The total acidity was enhanced with increase in loading of H3PW12O40. The catalytic activity was examined in desulfurization of dibenzothiophene in vapor phase system. Among the catalysts 18% HPWA loaded Sn-MCM-41 showed good catalytic activity in desulfurization at 325 °C. The HPWA/Sn-MCM-41 are a suitable solid acid catalyst for converting organic sulfur into insoluble sulfone

  17. SBA-15分子筛用于组装二溴对氯偶氮胂%USE OF MOLECULAR SIEVE SBA - 15 FOR INCORPORATION OF DIBROMOCHLORO-ARSENAZO

    Institute of Scientific and Technical Information of China (English)

    翟庆洲; 于辉; 蔡建岩; 秦亮

    2006-01-01

    Molecular sieve (SBA - 15)-(dibromochloro-arsenazo, DBC-ASA) host-guest composite materials were prepared by a liquid-phase grafting method using the calcined SBA- 15 molecular sieve as the host material, the DBC-ASA solution as the guest material, and water as the medium. The composite materials (SBA- 15)-(DBC-ASA) were characterized by X-ray diffraction(XRD), Fourier transform infrared(FTIR)spectra, solid state diffuse reflectance absorption spectra, and luminescence studies. The XRD results show that the molecular sieve framework in the (SBA- 15)-(DBC-ASA) host-guest composite materials is retained, and is highly ordered. The FTIR spectra indicate that the framework of the SBA- 15 molecular sieve is retained when a small amount of DBC-ASA is incorporated into it, the order degree of the molecular sieve decreases when a large amount of DBC-ASA is incorporated into it. The solid state diffuse reflectance absorption spectra show that DBC-ASA is located in the channel of the SBA - 15 molecular sieve, and the channel of SBA - 15 has stereoconfinment. The luminescence spectra show a strong non-radiation transition processes in the prepared samples, and this results in very strong electron-photon interaction causing a charge transfer transition. The Stokes displacement takes place and the spectrum bands broaden.%以煅烧的分子筛SBA-15为主体材料,二溴对氯偶氮胂(dibromochloro-arsenazo,DBC-ASA)作客体材料,以水为介质,用液相移植法制备了(SBA-15)-(DBC-ASA)主客体复合材料.用粉末X射线衍射、Fourier变换红外光谱、固体扩散漫反射吸收光谱及发光研究表征了所制得的复合材料(SBA-15)-(DBC-ASA)的性质.X射线衍射结果表明:(SBA-15)-(DBC-ASA)主客体复合材料分子筛骨架存在且有序度高.红外光谱分析表明:较低量的DBC-ASA引入SBA-15分子筛中,分子筛骨架结构仍然存在,但引入量较大时,分子筛的骨架有序度明显降低.固体扩散漫反射吸收光谱研

  18. Phase zone photon sieve

    Institute of Scientific and Technical Information of China (English)

    Jia Jia; Xie Chang-Qing

    2009-01-01

    A novel diffractive optical element, named phase zone photon sieve (PZPS), is presented. There are three kinds of phase plates in PZPSs: PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve (PS) when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography.

  19. 载人航天用TC-5A和TC-13X分子筛的研制及评价%Development and Evaluation of TC-5A and TC-13X Molecular Sieve in Manned Spacecraft

    Institute of Scientific and Technical Information of China (English)

    胡宏杰; 冯安生; 韩永强; 董文平; 刘宏召; 金梅; 张秀峰; 郭庆宏

    2013-01-01

    Objective To develop molecular sieves for manned spacecraft and evaluate their effectiveness.Methods Shaping,drying,baking,recrystalization,re-exchange and re-baking were adopted in the development of the molecular sieves.The static and dynamic behavior were tested by isothermal adsorption and by four-bed molecular sieves system.Results The TC-5A CO2 adsorption capacity was 19.7% and TC-13X moisture capacity was 29.15%.The kinetic experiments in four-bed molecular sieve system (4BMS) showed that the dew point at the outlet of drying bed was kept below-40 ℃ and the CO2 removal capacity was 2.17 ~6.17 kg/d when the regeneration temperatures of adsorption bed and drying bed were 280 ℃ and 120 ℃ respectively.Conclusion TC-5A and TC-13X can be used in 4BMS to remove CO2 effectively in a space capsule with three crew members.%目的 研制载人航天专用分子筛,并进行应用效果评价.方法 分子筛产品的研制采用造粒、烘干、焙烧、二次晶化、二次交换和二次焙烧技术,并通过等温吸附和4床分子筛试验进行静态动态性能评价.结果 研制的TC-5A和TC-13X分子筛产品,CO2和H2O的静态吸附能力分别达到19.7%和29.15%,在4床分子筛动态试验中,吸附床再生温度280℃,干燥床达120℃,干燥床出口空气露点小于-40℃,吸附床CO2动态处理能力为2.17 ~6.17 kg/d.结论 TC-5A和TC-13X分子筛应用于4床分子筛CO2处理系统,能够保证系统稳定运转,CO2处理量可满足3人密闭生存空间对CO2浓度控制的需要.

  20. Ultrasound- and Molecular Sieves-Assisted Synthesis, Molecular Docking and Antifungal Evaluation of 5-(4-(Benzyloxy)-substituted phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thiones.

    Science.gov (United States)

    Nimbalkar, Urja D; Tupe, Santosh G; Seijas Vazquez, Julio A; Khan, Firoz A Kalam; Sangshetti, Jaiprakash N; Nikalje, Anna Pratima G

    2016-01-01

    A novel series of 5-(4-(benzyloxy)substituted phenyl)-3-((phenyl amino)methyl)-1,3,4-oxadiazole-2(3H)-thione Mannich bases 6a-o were synthesized in good yield from the key compound 5-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione by aminomethylation with paraformaldehyde and substituted amines using molecular sieves and sonication as green chemistry tools. The antifungal activity of the new products was evaluated against seven human pathogenic fungal strains, namely, Candida albicans ATCC 24433, Candida albicans ATCC 10231, Candida glabrata NCYC 388, Cryptococcus neoformans ATCC 34664, Cryptococcus neoformans PRL 518, Aspergillus fumigatus NCIM 902 and Aspergillus niger ATCC 10578. The synthesized compounds 6d, 6f, 6g, 6h and 6j exhibited promising antifungal activity against the tested fungal pathogens. In molecular docking studies, derivatives 6c, 6f and 6i showed good binding at the active site of C. albicans cytochrome P450 enzyme lanosterol 14 α-demethylase. The in vitro antifungal activity results and docking studies indicated that the synthesized compounds have potential antifungal activity and can be further optimized as privileged scaffolds to design and develop potent antifungal drugs. PMID:27171073

  1. Carbon-based ion and molecular channels

    Science.gov (United States)

    Sint, Kyaw; Wang, Boyang; Kral, Petr

    2008-03-01

    We design ion and molecular channels based on layered carboneous materials, with chemically-functionalized pore entrances. Our molecular dynamics simulations demonstrate that these ultra-narrow pores, with diameters around 1 nm, are highly selective to the charges and sizes of the passing (Na^+ and Cl^-) ions and short alkanes. We demonstrate that the molecular flows through these pores can be easily controlled by electrical and mechanical means. These artificial pores could be integrated in fluidic nanodevices and lab-on-a-chip techniques with numerous potential applications. [1] Kyaw Sint, Boyang Wang and Petr Kral, submitted. [2] Boyang Wang and Petr Kral, JACS 128, 15984 (2006).

  2. 分子筛负载硫化镉光催化降解罗丹明B的研究%CdS Loaded on molecular sieve for photocatalytic degradation of Rhodamine B

    Institute of Scientific and Technical Information of China (English)

    王学文; 周力

    2012-01-01

    CdS Loaded on SiO, molecular sieve is prepared via a wet chemical method, CdS-SiO2 for photocatalytic degradation of organic pollutant Rhodamine B, compared to that of pure CdS, the CdS loaded on the molecular sieve shows a higher photocatalytic activity in a degradation process of Rhodamine B aqueous solution under visible light irradiation.%采用湿化学法制备了分子筛多孔二氧化硅负载硫化镉光催化材料CdS-SiO2,用于可见光降解有机污染物罗丹明B.结果表明,相比单相的硫化镉,分子筛负载的硫化镉表现出更高的光催化效率,且光降解后催化剂沉淀回收后仍可表现出较高的光催化降解能力.

  3. 负载金属氧化物分子筛催化氧化模拟汽油的脱硫研究%Oxidative Desulfurization of Simulated Gasoline over Metal Oxide-loaded Molecular Sieve

    Institute of Scientific and Technical Information of China (English)

    陈兰菊; 郭绍辉; 赵地顺

    2007-01-01

    A simulated gasoline consisting of model sulfur compounds of thiophene (C4H4S) and 3-methythiophene (3-MC4H4S) dissolved in n-heptane was tested for the oxidative desulfurization in the hydrogen peroxide (H2O2)and formic acid oxidative system over metal oxide-loaded molecular sieve. The effects of the oxidative system,loaded metal oxides, phase transfer catalyst, the addition of olefin and aromatics on sulfur removal were investigated in details. The results showed that the sulfur removal rate of simulated gasoline in the H2O2/formic acid system was higher than in other oxidative systems. The cerium oxide-loaded molecular sieve was found very active catalyst for oxidation of simulated gasoline in this system. The sulfur removal rates of C4H4S and 3-MC4H4S were enhanced when phase transfer catalyst (PTC) was added. However, the sulfur removal rate of simulated gasoline was reduced with the addition of olefin and aromatics.

  4. Molecular transport: Catch the carbon dioxide

    Science.gov (United States)

    Kirchner, Barbara; Intemann, Barbara

    2016-05-01

    Understanding the minute details of CO2 transport is key to finding new technologies that reduce the hazardous levels of CO2 in our atmosphere. Now, the observation that the transport of CO2 in molten calcium carbonate occurs faster than standard molecular diffusion brings us one step closer.

  5. Hydrothermal synthesis of NaY molecular sieve from coal-series kaolin by acid-leaching dealuminization%煤系高岭土酸浸脱铝水热合成NaY分子筛

    Institute of Scientific and Technical Information of China (English)

    蒋荣立; 陈文龙; 赵锐先; 王茜

    2012-01-01

    以煤系高岭土为原料,经煅烧、酸浸脱铝工艺,首次在酸浸偏高岭土-碱水热反应体系中合成了NaY分子筛.采用XRD,SEM对所合成样品进行表征,考察了体系中碱度、硅铝比、老化过程、晶化过程对NaY分子筛合成的影响.结果表明:该水热反应体系适宜的碱度条件为n(H2O)/n(Na2O)=80,碱度过高或过低均会出现P型分子筛杂相.适宜的硅铝配比为n(SiO2)/n(Al2O3)=6.4;老化有助于生成纯相、结晶度好的NaY分子筛,其适宜的老化温度为50℃、老化时间为4h.晶化温度过高或晶化时间过长易转晶生成P型杂相,适宜的晶化条件是晶化温度为85℃、晶化时间为24h.在该反应体系中反应原料由偏高岭土酸浸脱铝后获得,产物结晶度较高,无杂晶,晶形完整,粒度为2μm左右.%Taking coal-series kaolin as the material, the high-silica NaY molecular sieve was synthesized firstly in the hydrothermal reaction system of acid-leaching metakaolinite-alkali af- ter calcination and acid-leaching processes. The product was charactered by XRD and SEM. The effects of various hydrothermal conditions, including the molar ratios of n(SiO2)/ n(A12O3), aging process and crystallizing process on NaY molecular sieve synthesizing were in- vestigated. The results show that the proper alkalinity condition is molar ratios n(H20)/ n(Na2O)=80. The higher or lower alkalinity will cause molecular sieve impurity phase. The optimum n(SiO2)/n(A12O3) is 6.4. Theaging process contributes to generate pure and good crystallinity NaY molecular sieve, and the proper aging temperature and time are 50 ℃ and 4 h, respectively. The higher crystallizing temperature or longer crystallizing time will easily cause crystal transformation and yield P molecular sieve impurity phase. The proper crystalli- zing temperature and time are 85 ℃ and 24 h, respectively. The reaction material is easily yiel- ded by acid-leaching only once and the 2/

  6. Preparation of the Fine-crystal NaA Molecular Sieve by Grinding Method%NaA型小晶粒沸石分子筛的研磨制备

    Institute of Scientific and Technical Information of China (English)

    齐晓勇; 王前; 徐会君; 张建春; 杜庆洋

    2015-01-01

    In order to investigate the method to produce NaA molecular sieve in large scale,the fine-crystal NaA molecu-lar sieve was prepared by grinding method using NaA zeolite as raw materials and NaCl as grinding aids. The phase composi-tion,morphology,particle distribution and surface area of NaA molecular sieve before and after grinding were characterized by SEM,BET,and Laser Particle Size Analyzer,and Cd2+ exchange capacity was determined. The results showed that the particle size of NaA molecular sieve was decreased from 3 μm to 0. 98 μm,the surface area was increased from 12. 306 m2/g to 27. 997 m2/g,and Cd2+exchange capacity was enhanced from 294 mg/g to 352 mg/g after grinding under conditions of rotating speed 400 r/min,w(NaCl) ∶ w(NaA) of 12 ∶ 1,mass ratio between ball and powder 7 ∶ 1 for 7 h. Therefore,the dry grinding method is a novel method for mass production of NaA molecular sieve,with easy operating and low cost.%为了探索NaA型小晶粒沸石分子筛的大规模生产方式,以偏高岭石水热转化法合成的NaA型沸石分子筛为原料、NaCl为助磨剂,采用研磨法进行了小晶粒NaA分子筛制备试验,用SEM、BET和激光粒度分析仪对研磨前后样品的形貌、粒度分布及比表面积进行了表征,并测定了研磨前后样品的钙离子交换容量。结果表明,在转速为400 r/min、NaCl与NaA质量比为12∶1、球料质量比为7∶1、研磨时间为7 h的条件下,可将标称粒径为3μm、比表面积为12.306 m2/g、镉离子交换容量为294 mg/g的NaA分子筛研磨至平均粒度为0.98μm、比表面积为27.997 m2/g、镉离子交换容量为352 mg/g的小晶粒NaA分子筛。因此,干法研磨工艺是小晶粒NaA分子筛大规模生产的易操作、低成本新工艺。

  7. Degradation of toluene by cryptomelane molecular sieve under the assistance of plasma%隐钾锰矿分子筛协同等离子体降解甲苯

    Institute of Scientific and Technical Information of China (English)

    李云霞; 胡淑恒; 朱承驻; 陈天虎; 邹雪华; 袁玉袭

    2015-01-01

    文章通过回流法和固相法合成了隐钾锰矿八面体分子筛OM S‐2催化剂,用BET‐N2吸脱附曲线、X射线衍射、H2‐TPR和透射电镜等方法对催化剂进行了表征。在常温常压下,将OMS‐2催化剂涂覆在等离子放电管的余辉区,甲苯先经过介质阻挡放电(dielectric barrier discharge ,DBD )得到初步降解;在余辉区, OMS‐2吸附DBD产生的长寿命活性物种和臭氧进一步催化氧化甲苯。结果表明:OMS‐2与DBD等离子体相结合可显著提高甲苯的转化效率;催化剂的合成方法对催化剂表面性质和催化氧化性能有显著影响,回流法制备的OM S‐2对甲苯转化率(η)、CO2选择性、尾气中O3产生量及能量效率(Φ)等性能的影响表现更优异。%Manganese oxide octahedral molecular sieve(OMS‐2) for toluene catalytic combustion is syn‐thesized by solvent‐free solid‐state and refluxing synthesis methods .BET‐N2 ,XRD , H2‐TPR and TEM techniques are applied to characterize catalysts .At room temperature and atmospheric pressure , the OMS‐2 catalyst is coated on the afterglow section of the discharge tube .After the initial degrada‐tion of toluene by dielectric barrier discharge (DBD) ,OMS‐2 can adsorb and catalyze long‐lived active species and ozone produced by DBD for further removal of toluene .The results show that OMS‐2 and DBD plasma can significantly improve the conversion efficiency of toluene .Preparation method of cat‐alyst has a significant impact on the surface properties and catalytic performance of catalyst . The OMS‐2 catalyst prepared by refluxing method has excellent performance with regard to toluene remov‐al efficiency (η) ,carbon oxide selectivity ,amounts of O3 in tail gas and energy efficiency (Φ) .

  8. On sieve bootstrap prediction intervals.

    OpenAIRE

    Andrés M. Alonso; Peña, Daniel; Romo Urroz, Juan

    2003-01-01

    In this paper we consider a sieve bootstrap method for constructing nonparametric prediction intervals for a general class of linear processes. We show that the sieve bootstrap provides consistent estimators of the conditional distribution of future values given the observed data.

  9. 煤系高岭土酸浸脱铝水热合成NaX分子筛%Hydrothermal Synthesis of NaX Molecular Sieves from Coal-series Kaolin by Leaching Dealuminization

    Institute of Scientific and Technical Information of China (English)

    孔德顺; 连明磊; 范佳鑫; 李琳

    2013-01-01

    The coal series kaolin was turned into metakaolin by calcination at 750℃for 2 h, then the hydrochloric acid whose concentration was 20%was added into the metakaolin overdose in 10%and leached at 90℃for 2 h, the alumina leaching ratio was 72.6%;then the synthesis system of NaX molecular sieves was that n(SiO2)/n(Al2O3) being 3.0, n(Na2O)/n(SiO2) being 1.9 and n(H2O)/n(Na2O) being 40, aging at room temperature for 24 h, adding 10%NaX molecular sieve raw powder of theoretical output as seeds, crystallization by hydrothermal method at 95℃for 9 h, the products were purer NaX molecular sieves.%将煤系高岭土在750℃下煅烧2 h,使其转变为偏高岭土,加入过量10%质量分数为20%的盐酸在90℃下酸浸2 h,氧化铝溶出率达到72.6%;合成NaX分子筛的体系组成是:n(SiO2)/n(Al2O3)为3.0、n(Na2O)/n(SiO2)为1.9、n(H2O)/n(Na2O)为40,室温老化24 h后,加入理论产量10%的NaX分子筛原粉作为晶种,在95℃水热条件下晶化9 h,得到晶化产物,产物为较纯净的NaX分子筛。

  10. Analysis and treatment of trouble of molecular sieve purification system of 21000 m^3/h air separation plant%21000m^3/h空分设备分子筛纯化系统故障分析及处理

    Institute of Scientific and Technical Information of China (English)

    胥波; 闫伟东; 孔繁魁; 沈荣; 田现德

    2012-01-01

    In the air separation plant with molecular sieve adsorption and purification process, the work condition of molecular sieve purification system restricts the safe and stable run of the entire air separation system. For the troubles frequently occurring in molecular sieve purification system, such as mechanical trouble of switching over valve, valve action-generated program problem, and program-interlocked control of molecular sieve purification system, the judgment of the trouble causes and treatment measures are detailed.%分子筛吸附净化流程空分设备中,分子筛纯化系统的运行工况制约了整个空分系统的安全稳定运行。针对分子筛纯化系统经常出现的切换阀机械故障、阀门动作导致的程序问题以及分子筛纯化系统程序联锁控制等问题,详细介绍了故障原因判断和处理措施。

  11. 金属改性13x 分子筛在木材阻燃中的抑烟减毒作用%Study on smoke suppression and toxicity reducing by metal-modified 13x molecular sieves in wood flame retardant

    Institute of Scientific and Technical Information of China (English)

    田梁材; 胡云楚; 夏燎原; 陈旬; 王洁; 袁利萍

    2015-01-01

    抑烟、减毒是减少火灾中人员伤亡的重要途径。采用锥形量热法、热分析法和扫描电镜研究了铁和铜改性13x 分子筛和聚磷酸铵复合阻燃木材的燃烧、烟气释放和成炭特性。结果表明:铁、铜改性分子筛与聚磷酸铵复合处理木材的总热释放量(THR)与空白样相比分别降低了36.8%、39.8%,总烟释放量(TSP)降低了69.3%、72.8%,CO 平均产率(YCO)降低了40.2%、44.5%,均具有优异的阻燃、抑烟和减毒效果;热分析和电镜实验表明,APP 的催化脱水作用有利于炭层形成,铁、铜改性分子筛与聚磷酸铵的协同作用使炭层结构紧密。APP 对木材具有高效阻燃作用,但产生大量有毒气体,铁、铜改性分子筛与聚磷酸铵复合阻燃剂在高效阻燃的同时具有少烟低毒的特性。%Smoke suppression and toxicity reducing are the important ways to reduce the fire casualties. By using cone calorimetry, thermal analysis and scanning electron microscopy methods, the burning, smoke release and carbon characteristics of iron and copper-modified 13x molecular sieves with ammonium polyphosphate (APP) flame retardant wood were studied. The results show that total heat release (THR) of iron, copper-modified zeolites-APP composites flame retardant wood were reduced by more 36.8% and 39.8% than the control samples, the total smoke release production (TSP) were reduced by 69.3% and 72.8% than the controls, the average yield of CO (YCO) were reduced by 40.2% and 44.5% than the controls, three indexes all had excellent flame retardant, smoke suppression and toxicity reducing effects. The results of thermal analysis and electron microscopy experiments indicate that the catalytic dehydration of APP helped the carbon layer to form, the synergy of the iron and copper-modified molecular sieves and ammonium polyphosphate make the structure of carbon layer closer. The findings suggested that APP had efficient flame

  12. Cryogenic separation of hydrogen isotopes in single-walled carbon and boron-nitride nanotubes: insight into the mechanism of equilibrium quantum sieving in quasi-one-dimensional pores.

    Science.gov (United States)

    Kowalczyk, Piotr; Gauden, Piotr A; Terzyk, Artur P

    2008-07-17

    Quasi-one-dimensional cylindrical pores of single-walled boron nitride and carbon nanotubes efficiently differentiate adsorbed hydrogen isotopes at 33 K. Extensive path integral Monte Carlo simulations revealed that the mechanisms of quantum sieving for both types of nanotubes are quantitatively similar; however, the stronger and heterogeneous external solid-fluid potential generated from single-walled boron nitride nanotubes enhanced the selectivity of deuterium over hydrogen both at zero coverage and at finite pressures. We showed that this enhancement of the D(2)/H(2) equilibrium selectivity results from larger localization of hydrogen isotopes in the interior space of single-walled boron nitride nanotubes in comparison to that of equivalent single-walled carbon nanotubes. The operating pressures for efficient quantum sieving of hydrogen isotopes are strongly depending on both the type as well as the size of the nanotube. For all investigated nanotubes, we predicted the occurrence of the minima of the D(2)/H(2) equilibrium selectivity at finite pressure. Moreover, we showed that those well-defined minima are gradually shifted upon increasing of the nanotube pore diameter. We related the nonmonotonic shape of the D(2)/H(2) equilibrium selectivity at finite pressures to the variation of the difference between the average kinetic energy computed from single-component adsorption isotherms of H(2) and D(2). In the interior space of both kinds of nanotubes hydrogen isotopes formed solid-like structures (plastic crystals) at 33 K and 10 Pa with densities above the compressed bulk para-hydrogen at 30 K and 30 MPa.

  13. Fracture of Carbon Nanotube - Amorphous Carbon Composites: Molecular Modeling

    Science.gov (United States)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2015-01-01

    Carbon nanotubes (CNTs) are promising candidates for use as reinforcements in next generation structural composite materials because of their extremely high specific stiffness and strength. They cannot, however, be viewed as simple replacements for carbon fibers because there are key differences between these materials in areas such as handling, processing, and matrix design. It is impossible to know for certain that CNT composites will represent a significant advance over carbon fiber composites before these various factors have been optimized, which is an extremely costly and time intensive process. This work attempts to place an upper bound on CNT composite mechanical properties by performing molecular dynamics simulations on idealized model systems with a reactive forcefield that permits modeling of both elastic deformations and fracture. Amorphous carbon (AC) was chosen for the matrix material in this work because of its structural simplicity and physical compatibility with the CNT fillers. It is also much stiffer and stronger than typical engineering polymer matrices. Three different arrangements of CNTs in the simulation cell have been investigated: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. The SWNT and MWNT array systems are clearly idealizations, but the SWNT bundle system is a step closer to real systems in which individual tubes aggregate into large assemblies. The effect of chemical crosslinking on composite properties is modeled by adding bonds between the CNTs and AC. The balance between weakening the CNTs and improving fiber-matrix load transfer is explored by systematically varying the extent of crosslinking. It is, of course, impossible to capture the full range of deformation and fracture processes that occur in real materials with even the largest atomistic molecular dynamics simulations. With this limitation in mind, the simulation results reported here provide a plausible upper limit on

  14. Molecular simulation for novel carbon buckyball materials

    Directory of Open Access Journals (Sweden)

    Hasan R. Obayes

    2015-12-01

    Full Text Available The discovery of buckyballs was unexpected because the researchers were delivering carbon plasmas to reproduce and describe unidentified interstellar matter. Density functional theory was done to study and design the structure of [8]circulene and three new buckyballs with molecular dimensions of less than a nanometer. Cyclic polymerization reactions can be utilized to prepare new buckyballs, and this process also produces molecules of hydrogen. All reactions are spontaneous and exothermic as per the estimations to the values of entropy, Gibbs energy, and enthalpy changes. The results demonstrate that the most symmetric buckyball is the most stable, and the molecular dimensions are less than a nanometer. The new buckyballs are characterized by the high efficiency of their energy gaps, making it potentially useful for solar cell applications.

  15. Adsorção de CO2 em peneiras moleculares micro e mesoporosas

    Directory of Open Access Journals (Sweden)

    Thiago G. Oliveira

    2014-01-01

    Full Text Available Microporous molecular sieves of type Y, Beta, ZSM-5, ZSM-12 and ZSM-35, and mesoporous molecular sieves of type MCM-41 and MCM-48, and these sieves modified with triethanolamine and ethylenediamine were obtained and characterized by XRD, FTIR, TGA and nitrogen adsorption. The adsorption tests were performed by the gravimetric method under a stream of CO2 at ambient temperature and pressure. The adsorbents studied showed maximum adsorption capacity of carbon dioxide in the range of 13.1 to 85.5 mg of CO2 per gram of adsorbent.

  16. The performance of the PCM compounded by lauric acid,PEG and molecular sieve%月桂酸/PEG、分子筛复合相变材料的性能

    Institute of Scientific and Technical Information of China (English)

    郭静; 范竞男; 管福成; 范丹

    2012-01-01

    Orthogonal test method and melting method are used for the preparation of phase change material (PCM) composited of lauric acid, PEG and molecular sieve. The thermal insulation properties, crystal habit and Fourier transformation infrared spectroscope (FTIR) have been studied. The results indicated that a minimum eutectic things can be formed well by lauric acid and PEG4000, the best dosage of the molecular sieve is 30 mg/g, the PCM compounded by lauric acid and PEG4000 has good thermal insulation properties, the soaking time is about 500 s, phase-transition temperature is about 35 ℃ , which is satisfied the requirements of the wearability and building. The self crystallization of lauric acid or PEG4000 and restrain each other result in the decrease in size of the compound PCM's crystal. Some chemical reaction between lauric acid and PEG4000 improve their compatibility.%选用月桂酸与PEG4000为相变材料,分子筛为改性剂,利用正交试验法,采用熔融共混法制备复合的相变体材料,并对其进行保温性能、结晶形态、红外光谱的研究.月桂酸与PEG4000能够形成最低共熔物,分子筛的最佳用量为30 mg/g;LA/PEG4000复合相变体具有良好的保温性能,保温时间在500 s左右,相变温度在35℃左右,满足服用及建筑材料的需求;月桂酸与PEG4000各自结晶,相互抑制,导致复合相变体的晶体尺寸减小;月桂酸与PEG4000之间发生了一定的化学反应,生成的反应物提高了两者之间的相容性.

  17. 微孔-介孔复合分子筛HY-SBA-15的表征及应用%Characterization and catalytic application of HY-SBA-15 composite molecular sieves

    Institute of Scientific and Technical Information of China (English)

    武宝萍; 沈健; 张秋荣

    2012-01-01

    用后合成法制备了微孔-介孔复合分子筛HY-SBA-15(y)(y表示HY与SBA-15的质量比).并用XRD、FT-IR、N2吸脱附及NH3-TPD等技术对HY-SBA-15进行表征.结果表明,HY-SBA-15既具有微孔结构又具有介孔结构,当y=0.10时,微孔与介孔混合晶相显著,且HY-SBA-15 (0.10)复合分子筛具有B酸和L酸,酸性强于HY.用浸渍法将Ni-W活性组分担载在HY-SBA-15 (0.10)载体上,制备加氢脱芳烃催化剂Ni-W/HY-SBA-15 (0.10),选用茂名石化FCC柴油为原料,考察了催化剂的加氢脱芳烃性能.实验结果表明,Ni-W/HY-SBA-15 (0.10)催化剂具有良好的芳烃加氢饱和性能和开环活性.%A series of HY-SBA-15(y) composite molecular sieves (y denotes the weight ratio of HY to SBA-15) were prepared by post-synthesis method and characterized by XRD, FT-IR, N2 sorption, and NH3-TPD. Ni-W/HY-SBA-15(0.10) catalyst was then prepared by impregnating HY-SBA-15 (0.10) with Ni-W solution and used in hydrodearomatization of Maoming FCC diesel oil. The results indicated that HY-SBA-15 has both HY microporous and SBA-15 mesoporous structure and the microporous and mesoporous structures of HY-SBA-15 match remarkably well when the value of y is 0.10. Both Bronsted acid sites and Lewis acid sites are present on the surface of the composite molecular sieve HY-SBA-15(0.10) and its acidity is stronger than that of HY zeolite. When loading Ni and W on it, the Ni-W/HY-SBA-15 (0.10) catalyst exhibits high activity in the hydrodearomatization and opening of aromatic rings.

  18. 介孔分子筛Ti—AIMSU—Y后合成法制备及其催化性能%Post-synthesis and Catalytic Properties of Mesoporous Molecular Sieves Ti-AIMSU-Y

    Institute of Scientific and Technical Information of China (English)

    李惠云; 何其戈; 王云龙; 李娟

    2012-01-01

    Three Ti-A1MSU-Y mesoporous molecular sieves were successfully synthesized by a post-grafting method using the tetrabutyl titanate, bi-cyclopentadienyl titanium dichloride and titanium tetrachloride as the Ti source and the mesoporous molecular sieves as the support. The samples were characterized by FT-IR, XRD, N2 adsorption- desorption techniques, M_AS NMR, UV-Vis and EDS respectively. The catalytic behaviors of samples were measured through oxidation of cyclohexanol. Compared to the A1MSU-Y sieve, the resulting samples Ti-A1MSU-Y remained the original mesoporous structure with a smaller specific BET surface area and volume of pores. The UV-Vis and 27A1 MAS NMR spectra indicated the existence of tetrahedral titanium (IV) and tetrahedral aluminum(IV) in framework sites, and the content of oetahedral aluminium decreases when Ti atoms were grafted onto the inter-surface of A1MSU-Y simultaneously. All Ti-A1MSU-Y catalysts showed significant activity in oxidation of cyclohexanol due to cooperative action of Ti( IV ) and A1 (IV), and Ti(z)-A1MSU-Y with higher Ti/A1 molar ratio is better catalytic activity than Ti (m)-A1MSU-Y and Ti (y)-A1MSU-Y. More importantly, the conversion of cyclohexanol reaches 43.05%and the selectivity of cyclohexanone comes to 100% after 24 h at 80 ℃.%以介孔分子筛AlMSU-Y为载体,钛酸四丁酯、二氯二茂钛、四氯化钛为钛源,采用合成后嫁接法合成了3种Ti-AlMSU-Y介孔分子筛样品.用傅立叶变换红外光谱(FT-IR)、X射线粉末衍射(XRD)、N2吸附-脱附、固体核磁(MASNMR)、紫外一可见漫反射(UV_vis)和能谱(EDS)进行了表征,并以环己醇氧化反应考察了样品的催化性能.实验结果表明,样品Ti-AlMsU-Y仍保持了基体A1MSu—Y介孔孔道结构,钛原子进入分子筛骨架且以骨架四面体钛的形式存在,同时分子筛中非骨架铝的含量相对减少.在环己醇氧化反应中,骨架四面体Ti和骨架四面体A1存

  19. Modeling the hydrodynamics of Phloem sieve plates

    DEFF Research Database (Denmark)

    Jensen, Kaare Hartvig; Mullendore, Daniel Leroy; Holbrook, Noel Michele;

    2012-01-01

    Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play...... are investigated. We find that the sieve plate resistance is correlated to the cell lumen resistance, and that the sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway....

  20. Carbon Chemistry in Dense Molecular Clouds: Theory and Observational Constraints

    OpenAIRE

    Blake, Geoffrey A.

    1990-01-01

    For the most part, gas phase models of the chemistry of dense molecular clouds predict the abundances of simple species rather well. However, for larger molecules and even for small systems rich in carbon these models often fail spectacularly. We present a brief review of the basic assumptions and results of large scale modeling of the carbon chemistry in dense molecular clouds. Particular attention will be paid to the influence of the gas phase C/O ratio in molecular clouds, a...

  1. Influence of Molecular Sieve Supported Metal Oxides on the Desulfurization in Catalytic Cracking of Sulfur-containing Model Compounds and Hydrocarbons%金属担载分子筛对含硫模型化合物和含硫烃的催化裂化脱硫反应的影响

    Institute of Scientific and Technical Information of China (English)

    申宝剑; 李海丽; 李会峰; 鲍晓军; 周小虹

    2003-01-01

    Zn, La, Zr, Sn and Ti loaded molecular sieves were prepared by impregnation method. Conversions of benzothiophene and dibenzothiophene over the metal oxides modified ultra stable zeolite Y(USY), ZSM-5, β and MSU-2 molecular sieve catalysts were investigated by means of micro-activity test (MAT) experiments. The results showed that Zn and La loaded catalysts were better than the other metals, and ZSM-5 with lower SiO2/Al2O3 mole ratio showed better results than those with higher SiO2/Al2O3 as far as desulfurization reaction is considered. A comparison of the desulfurization activities of the La/Zn-USY catalyst with USY catalyst indicated that the bimetal loaded USY catalyst gave good products selectivity when sulfur containing heavy oil was used as the feedstock. The sulfur content in gasoline fraction was decreased by 25%, and there was no loss in the Research Octane Number.

  2. 从分子筛纯化系统的设计及操作谈空分设备节能%Approach to energy-saving for air separation plant from the design and operation of molecular sieve purification system

    Institute of Scientific and Technical Information of China (English)

    张振友

    2012-01-01

    The energy-saving for molecular sieve purification system of air separation plant is analyzed from the process design of molecular sieve purification system, the design and selection of equipment, the engineering design and its operation and maintenance, and%从分子筛纯化系统的流程设计、设备的设计与选型、工程设计及其操作、维护等方面,分析空分设备分子筛纯化系统的节能问题,提出了对节能措施的一些思考和建议。

  3. Molecular exchange of n-hexane in zeolite sieves studied by diffusion-diffusion and T1-diffusion nuclear magnetic resonance exchange spectroscopy

    International Nuclear Information System (INIS)

    Molecular exchange properties and diffusion of n-hexane embedded in a bimodal pore structure with characteristic length scales in the order of nano and micrometres, respectively, formed by packing of zeolite particles, are studied. Two-dimensional (2D) nuclear magnetic resonance (NMR) diffusion correlation experiments together with relaxation-diffusion correlation experiments are performed at low magnetic field using a single-sided NMR scanner. The exchange time covers a range from 10-3 to 10-1 s. The molecular exchange properties are modulated by transport inside the zeolite particles. Different exchange regimes are observed for molecules starting from different positions inside the porous sample. The influence of the spin-lattice relaxation properties of the fluid molecules inside the zeolite particles on the signal intensity is also studied. A Monte Carlo simulation of the exchange process is performed and is used to support the analysis of the experimental data.

  4. A novel carbon fiber based porous carbon monolith

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, T.D.; Klett, J.W.; Weaver, C.E.

    1995-06-01

    A novel porous carbon material based on carbon fibers has been developed. The material, when activated, develops a significant micro- or mesopore volume dependent upon the carbon fiber type utilized (isotropic pitch or polyacrylonitrile). The materials will find applications in the field of fluid separations or as a catalyst support. Here, the manufacture and characterization of our porous carbon monoliths are described. A novel adsorbent carbon composite material has been developed comprising carbon fibers and a binder. The material, called carbon fiber composite molecular sieve (CFCMS), was developed through a joint research program between Oak Ridge National Laboratory (ORNL) and the University of Kentucky, Center for Applied Energy Research (UKCAER).

  5. Preparation of mesoporous-molecular-sieve/polydicyclopentadiene composites%介孔分子筛/聚双环戊二烯复合材料的制备

    Institute of Scientific and Technical Information of China (English)

    陆昶; 黄新辉; 赫玉欣; 张玉清

    2012-01-01

    The mesoporous molecular sieve(SBA-15)/polydicyclopentadiene(PDCPD) composites were prepared by in-situ polymerization with SBA-15 supported catalyst(method 1),SBA-15 modified by coupling agent(method 2),modified SBA-15 supported catalyst(method 3),respectively.The effect of preparing methods on mechanical performances of SBA-15/PDCPD was investigated.The results show that for the SBA-15/PDCPD composites prepared by method 2,although modified SBA-15 can improve the interface interaction between SBA-15 and PDCPD matrix,the polymerization of dicyclopentadiene(DCPD) monomer is difficult to occur in the pores of SBA-15,causing the mechanical performances of composites improve weakly,compared with PDCPD.Method 1 and method 3 applied to prepare SBA-15/PDCPD composites are beneficial to the form of PDCPD molecular chains in the pores of SBA-15.The form of molecular chains in the pores can improve the interface interaction between SBA-15 and PDCPD matrix,enhancing the mechanical performances of composites greatly.Compared with PDCPD,the tensile strength and bending strength of SBA-15/PDCPD prepared by method 1 increase by 24.5% and 24% when the mass ratio of SBA-15/PDCPD is 2∶100,respectively.For the composites prepared by method 3,the quantity of PDCPD molecular chains formed in the pores of SBA-15 is smaller than that of method 1 due to the SBA-15 pores occupied by coupling agent molecule,resulting that the mechanical performances is lower than that of method 1,but higher than that of method 2.%将负载催化剂的SBA-15型介孔分子筛(方法1)、偶联剂表面改性的SBA-15(方法2)、偶联剂表面改性后负载催化剂的SBA-15(方法3),采用原位聚合法分别制备了SBA-15/聚双环戊二烯(PDCPD)复合材料。研究了不同制备方法对SBA-15/PDCPD力学性能的影响。结果表明,对于方法2,虽然偶联剂改性SBA-15可提高与PDCPD界面作用力,但由于分子筛孔道中的双环戊二烯

  6. Effects of the Molecular Sieve 5 A and APP on the Flame Retardance and Smoke Suppression in Wood by Cone Calorimeter%锥形量热法研究APP/5 A分子筛对木材的阻燃抑烟作用

    Institute of Scientific and Technical Information of China (English)

    陈旬; 袁利萍; 胡云楚; 田梁材; 王洁; 夏燎原

    2014-01-01

    采用锥形量热法研究了5A分子筛与聚磷酸铵(APP)在木材燃烧过程中的阻燃作用和烟气吸附调控作用。结果表明:APP单独使用时总热释放量( THR)降低47.56%,但是平均CO产率增加185.71%;5A分子筛单独使用时阻燃效果远远不如APP,THR只降低了16.86%;5A分子筛与APP复合使用THR降低34.23%,总烟释放量(TSP)降低了76.07%,平均CO产率降低了68.33%。5A分子筛能将木材热解产生的以CO为代表的有毒气体催化转化为CO2,从而减少了毒气的产生和释放。5A分子筛与APP联用,在高效阻燃的同时减少烟雾毒气释放,降低了火灾危害。%The effect of molecular sieve 5A and ammonium polyphosphate ( APP) on the flame retardance and smoking-gas absorption in wood during the combustion process was investigated by cone calorimeter. The results showed that when APP was used as sole flame retardant, the total heat release (THR) reduced by 47. 56% while mean yield of CO (mean-COY) increased by 185. 71 %. The application of molecular sieve 5A was found to have an inferior flame retardant efficiency. THR decreased by 16. 86 % through it. However, when 5A molecular sieve and APP was combined and used as flame retardant for wood, THR, total smoke production (TSP) and mean-COY reduced by 34. 23%, 76. 07% and 68. 33%, respectively. CO, a representative toxic, was converted into CO2 by the use of 5A molecular sieve as catalyst. Thus the generation and release of toxic gas reduced. In short, high efficiency of flame retardance and smoke suppression in wood can be achieved when the flame retardants of 5A molecular sieve and APP were coused together. Thus the casualties in the fire were reduced.

  7. Molecular Basis of Microbial One-Carbon Metabolism

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-07-12

    The Gordon Research Conference (GRC) on Molecular Basis of Microbial One-Carbon Metabolism was held at Connecticut College, New London, Connecticut. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  8. N-Ti-MCM-22分子筛的合成及光催化性能研究%STUDY ON SYNTHESIS AND PHOTO-CATALYTIC PROPERTIES OF N-Ti-MCM-22 MOLECULAR SIEVE

    Institute of Scientific and Technical Information of China (English)

    成岳; 苏晓渊; 杨治栋

    2011-01-01

    以叠氮化钠为氮源、硅溶胶为硅源、钛酸四丁酯为钛源、六亚甲基亚胺(HMl)为模板剂,按SiO:0.03TiO:(0-0.01)N:0.03HMI:.0035AIO:0.2NaOH:20HO的摩尔比,采用静态水热晶化法合成了具有MWW层状结构的N-Ti-MCM-22分子筛.研究了所合成的分子筛的光催化性能,考察了催化剂的含氮量、催化剂的投加量、pH值、亚甲基蓝的初始浓度、光催化时间等因素对光催化降解亚甲蓝的影响.结果表明:N-Ti-MCM-22分子筛对亚甲基蓝的光催化降解效果较好,催化剂的投加量为1g/L、亚甲基蓝初始浓度在4mg/L、pH为中性在紫外光下的降解效果较好,脱色率及降解率分别达到了95.9%和97.8%,并采用XRD、TEM和EDS等对分子筛样品进行了表征.%N-Ti-MCM-22 molecular sieve with MWW of layer structure was synthesized using the static hydrothermal crystallization method, sodium azide as nitrogen source, silica sol as silicon source, titanium tetrabutyl as titanate source, hexamethylene imine (HMI) as template agent, in accordance with molar ratio of SiO2 : 0.03TiO2 : (0~ 0.01) N : 0.03HMI : 0.035A12O3 : 0.2NaOH : 20H2O. the photocatalytic properties of synthesis zeolite was studied, the nitrogen-containing catalyst volume, catalyst dosage, pH, initial methylene blue concentration, time and light source of photocatalytic to degradation methylene blue such as the impact factors were investigated. The results showed that N-Ti-MCM-22 molecular sieve photocatalytic degradation of methylene blue is better, catalyst dosage is 1g/L, initial concentration of methylene blue is 4mg/L, pH neutral degradation under ultra-violet light is better, and the degradation rate and decolorization rate is 95.9% and 97.8%, respectively, zeolite samples were characterized with XRD, TEM and EDS.

  9. Progress for Cu-based Small Pore Molecular Sieves as Disel De-NOx Catalysts%铜基小孔分子筛柴油车尾气脱硝催化材料研究进展

    Institute of Scientific and Technical Information of China (English)

    翁端; 王蕾; 吴晓东; 冉锐; 司知蠢

    2013-01-01

    柴油车尾气排放是大气污染物氮氧化物(NOx)的主要来源之一.氨选择性催化还原技术(NH3-SCR)具有高效率、低成本等特征,已成为目前主要的移动源脱硝技术.传统铜基中孔分子筛高温水热稳定较差,而小孔分子筛负载催化材料具有优良的催化活性和水热稳定性,近年受到国内外研究者的广泛关注,成为一种新型NH3-SCR催化材料.综述了铜基小孔分子筛催化材料在柴油车尾气脱硝领域的研究进展.以Cu-SSZ-13和Cu-SAPO-34为例,论述了其突出的低温活性和水热稳定性,总结了Cu含量、Cu物种形态及表面酸性等因素对其催化活性、水热稳定性的影响,归纳其反应活性中心、反应路径等催化机理方面的研究进展.分析表明,该类催化材料是极具发展潜力的NH3-SCR催化材料.其新型催化材料设计、抗中毒机理等还有待进一步深入研究.%NOx is one of the main pollutants in diesel vehicle emissions.Selective catalytic reduction of NOx by ammonia (NH3-SCR) has been extensively studied for the lean NOx control due to its high performance and economic efficiency.Copper based zeolites have been widely used as the De-NOx catalysts and significant research efforts have concentrated on developing different types of zeolites to improve the activity and durability.Recently,SCR catalysts based on small-pore molecular sieves have been reported for NH3-SCR with much improved activities and high thermal durability and have received substantial attention.This review sums up the research progress related with Cu-based small pore molecular sieves,such as Cu-SSZ-13 and Cu-SAPO-34,as diesel De-NOx Catalysts with outstanding low temperature NH3-SCR activity and hydrothermal stability.The nature of the copper species and the surface acidity are the most important factors that affect the NH3-SCR performance.Important results on the active sites and catalytic mechanisms are especially discussed in details

  10. Separation of methane/air by pressure swing adsorption with commercial molecular sieve%分子筛对 CH4/空气混合气的变压吸附分离研究

    Institute of Scientific and Technical Information of China (English)

    刘畅; 张进华; 车永芳; 郭昊乾; 李小亮; 李雪飞

    2015-01-01

    In order to improve adsorption and concentration effects of coalbed methane by pressure swing adsorption (PSA),the upgrading and separation efficiency of methane/air mixture gas was studied by four-tower PSA device based on a kind of commercial molecular sieve.The effects of adsorption time,adsorption pressure,and concentration of raw gas on enrichment and economical efficiency were re-searched.The results showed that the enrichment and separation effects of the molecular sieve was the best when the adsorption time was 180 s while adsorption pressure was 300 kPa.Longer adsorption time or higher adsorption pressure was of no advantage to the reaction.For high,medium and low concentrated coal bed methane,the rate could be improved by more than 20% at one time through controlling the adsorption time and pressure,which could enrich the raw gas to 30.56%,76.33%,89.18%from 10%,35%,65%.The handing capacity for raw gas could increased to 67.77,68.99 and 83.36 m3/(t· h) by 20%,40%,25%.The experiments could provide reference for the industrial application in coal bed methane enrichment.The recovery of methane in product increased to 94.45%,69.68%and 87.22%.%为提高煤层气变压吸附浓缩效果,以一种商品分子筛为对象,研究了该分子筛在小型四塔变压吸附装置上的CH4/空气混合气浓缩分离效果,分析了吸附时间、吸附压力以及原料气浓度对混合气浓缩效果的影响。结果表明,吸附时间过长或吸附压力过高,均不利于获得较好的产品气浓度及回收率。吸附时间180 s,吸附压力300 kPa时,试验商品分子筛对CH4/N2的浓缩分离效果最佳。其中,10%浓度原料气提浓至30.56%,提高约20%,产品气中CH4回收率达到94.45%,对原料气的处理量达到67.77 m3/( t· h);35%浓度原料气提浓至76.33%,提高约40%,产品气中CH4回收率达到69.68%,对原料气的处理量达到68.99 m3/(t· h);65

  11. 介孔分子筛K2O/SBA-15催化酯交换反应研究%Study on transesterification catalyzed by mesoporous molecular sieve K2O/SBA-15

    Institute of Scientific and Technical Information of China (English)

    崔晓燕; 沈健

    2011-01-01

    The solid base catalyst K20/SBA- 15 were prepared with mesoporous molecular sieve SBA - 15 as carrier,and by supporting potassium nitrate and then calcining. The transesterification was studied for the synthesis of n - butyl acrylate from methyl acrylate and n - butanol catalyzed by K2O/SBA - 15. The results showed that when K2O loading was 2% (mass fraction) ,reaction time was 6 h,reaction temperature was 180 ℃, n ( n - butanol ) /n ( methyl acrylate) was 4 and the mass ratio of catalyst to raw material was 0.1, the best conversion of methyl acrylate could reach 64.22%.%以介孔分子筛SBA-15为载体,负载KNO3后经过焙烧,制得K2O/SBA-15固体碱催化剂.对K2O/SBA-15催化丙烯酸甲酯与正丁醇合成丙烯酸正丁酯的酯交换反应进行了研究.结果表明,当K2O负载量为2%,反应时间为6 h,反应温度为180℃,n(正丁醇)/n(丙烯酸甲酯)为4,m(催化剂)/m(原料)为0.1时,丙烯酸甲酯的转化率最大,为64.22%.

  12. Ti-MSU分子筛催化1-丁烯氧化制环氧丁烷的研究%Research on Epoxybutane from 1-Butylene by Ti-MSU Molecular Sieve Catalytic Oxidation

    Institute of Scientific and Technical Information of China (English)

    吴美玲; 周灵杰; 陈玮娜

    2014-01-01

    通过液相浸渍法制备Ti 质量分数为5�5%的Ti-MSU分子筛催化剂,并采用X射线衍射、N2吸附-脱附对催化剂样品进行表征。考察了Ti-MSU催化剂对以过氧化氢异丙苯( CHP)、1-丁烯为原料制备环氧丁烷的反应工艺条件的影响。结果表明,当催化剂床层温度为100℃、反应压力为3�0 MPa、1-丁烯/CHP摩尔比为10∶1、CHP空速为2 h-1时,CHP的转化率达到81�2%,1,2-环氧丁烷( BO)选择性为60�2%,苄醇( DMBA)选择性为87�2%。%5.5%Ti-MSU molecular sieve catalyst was prepared by liquid phase impregnation method. The sam-ple was characterized by X-ray diffraction and N2 adsorption-desorption. With cumene hydroperoxide ( CHP) ,1-bu-tene as raw material,the influence of the process conditions of 5.5%Ti-MSU catalyst on epoxybutane had been in-vestigated. The conversion of CHP was 81.2%,1,2-epoxybutane ( BO) selectivity was 60.2%, benzyl alcohol ( DMBA) selectivity was 87.2%, when the optimum reaction conditions was 100℃ catalyst bed,3.0 MPa reactivity pressure,10∶1 1-butylene/CHP molar ratio and 2h-1 space velocity of CHP.

  13. Research Progress of Immobilization of Lipase on Molecular Sieve Mesoporous Silica SBA-15%介孔材料SBA-15固定化脂肪酶的研究进展

    Institute of Scientific and Technical Information of China (English)

    黄卓楠

    2013-01-01

    Due to the merit of average pore diameter and ordered pore arrangement,more and more attention has been paid to the molecular sieve mesoporous silica SBA-15.The recent research progress of lipase immobilization on SBA-15 mesoporous materials are reviewed in this paper.The factors that influence the immobilization of lipase on mesoporous materials are investigated in detail.At last,the applications and the prospects of the immobilization of lipase on SBA-15 are also presented.%介孔材料由于其孔道分布有序且孔径均匀等优点而在固定化酶催化领域引起人们的广泛关注.本文综述了新型介孔材料SBA-15对脂肪酶固定化的研究进展.总结了SBA-15的孔径大小、形貌及等电点等因素对脂肪酶固定化的影响.归纳了SBA-15上三种不同固定化方法的优缺点,并介绍了SBA-15固定化脂肪酶在手性拆分、酯水解、酯合成及转醇化反应等领域的应用.最后提出SBA-15固定化脂肪酶在发展过程中存在的问题以及今后的发展趋势.

  14. Developing a molecular platform for potential carbon dioxide fixing

    DEFF Research Database (Denmark)

    Mikkelsen, Mette; Jørgensen, Mikkel; Krebs, Frederik C

    2010-01-01

    This paper presents an attempt to develop a new system for fixing carbon dioxide from the atmosphere. The proposed molecular system has been designed to have the capacity to spontaneously bind CO2 from the atmosphere with high affinity. The molecular system is furthermore designed to have...... the ability to liberate CO2 at a later stage in the process, i.e., in a separate compartment. The liberated CO2 presents a carbon neutral way of obtaining pure CO2. The proposed molecular system is based on a small stable organic molecule that potentially have two forms: one without bound CO2 and one...

  15. Molecular sieves analysis by elastic recoil detection

    International Nuclear Information System (INIS)

    The opportunity of water determination in zeolites via hydrogen detection using the elastic recoil detection analysis (ERDA) was investigated. The radiation effect upon the desorption rate of hydrogen in miscellaneous types of zeolites, e.g. Y-Faujasite, ZSM-5, SK, etc. and in a natural clay, e.g. an Algerian bentonite was discussed. Quantitative measurements were carried out in order to determine the amount and distribution shape of hydrogen in each material. Various explanations dealing with hydration and constitution water in such a crystalline framework were proposed. The experimental results are in a good agreement with the corresponding theoretical values

  16. Synthesis and Characterisation of Aluminophosphate Molecular Sieves

    Energy Technology Data Exchange (ETDEWEB)

    Halvorsen, E.N.

    1996-02-01

    Catalysts are very important in petrochemical processes. One of the properties that make crystalline, microporous materials attractive for catalytic purposes is their well-defined structure and ability to act as shape selective catalysts. This doctoral thesis presents the synthesis and characterization of a number of crystalline, microporous aluminophosphates and silicoaluminophosphates. 99 refs., 50 figs., 12 tabs.

  17. The structure and the properties of the SBA-15-supported vanadium or molybdenum molecular sieves:A DFT prediction%V、Mo修饰SBA-15分子筛结构与催化性质的DFT计算预测

    Institute of Scientific and Technical Information of China (English)

    王中学; 王大喜; 赵震; 陈玉; 刘冰

    2012-01-01

    采用密度泛函方法,计算了介空分子筛SBA-15及V和Mo原子修饰后分子筛的几何参数及红外光谱,与实测值比较,确定了分子筛的合理模型.通过分析模型化合物的前线分子轨道,推测了V和Mo原子修饰前后分子筛表面的酸碱中心及氧化还原性质.最后,由计算得到分子筛表面VO4和MoO5基团的Mayer键级推测,当此类催化剂参与酸碱和氧化还原反应时,基团上的三种化学键(MO-Si、M-OSi和M=O)中,MO-Si键最容易断裂打开,参加化学反应.%A theoretical study on the model clusters of SBA-15 and SBA-15-supported vanadium or molybdenum molecular sieve was carried out. Two model clusters of SBA-15 and two model clusters of SBA-15 supported vanadium or molybdenum molecular sieve were constructed. Their geometries and IR spectra have been calculated. These calculated values suggested that the model clusters employed were reasonable. The frontier molecular orbitals of these model clusters showed that the VO4 and Mo05 groups on the surface of the molecular sieve were the active centers for the acid-base reaction and oxidation-reduction reaction. The Mayer bond orders of the V04 and Mo05 groups were calculated and it was found that the MO-Si bond was easier to break than the MO-Si and M=0 bonds in the process of the chemical reaction.

  18. A chemoreceptor that detects molecular carbon dioxide.

    Science.gov (United States)

    Smith, Ewan St John; Martinez-Velazquez, Luis; Ringstad, Niels

    2013-12-27

    Animals from diverse phyla possess neurons that are activated by the product of aerobic respiration, CO2. It has long been thought that such neurons primarily detect the CO2 metabolites protons and bicarbonate. We have determined the chemical tuning of isolated CO2 chemosensory BAG neurons of the nematode Caenorhabditis elegans. We show that BAG neurons are principally tuned to detect molecular CO2, although they can be activated by acid stimuli. One component of the BAG transduction pathway, the receptor-type guanylate cyclase GCY-9, suffices to confer cellular sensitivity to both molecular CO2 and acid, indicating that it is a bifunctional chemoreceptor. We speculate that in other animals, receptors similarly capable of detecting molecular CO2 might mediate effects of CO2 on neural circuits and behavior.

  19. Effect of H{sub 3}PW{sub 12}O{sub 40} impregnation on Sn-MCM-41 mesoporous molecular sieves and their physico-chemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Nedumaran, D. [Department of Chemistry, Institute of Catalysis and Petroleum Technology, Anna University, Chennai 600025 (India); Department of Chemistry, RMK Engineering College, Chennai (India); Pandurangan, A., E-mail: pandurangan_a@yahoo.com [Department of Chemistry, Institute of Catalysis and Petroleum Technology, Anna University, Chennai 600025 (India)

    2015-01-15

    Graphical abstract: The wide angle XRD shows the well dispersion of HPWA in Sn-MCM-41. It enhances the total acidity of the material. The acidity of the material is correlated with sulfone selectivity. The FT-IR of dibenzothiophene and product shows the formation of sulfone (DBTO{sub 2}). - Highlights: • To enhance the total acidity of Sn-MCM-41 TPA is impregnated. • FT-IR and {sup 31}P MAS NMR confirms the HPWA intact on Sn-MCM-41. • EDAX shows the presence of W and P on Sn-MCM-41. • In ODS formation of sulfone was confirmed by FT-IR and {sup 1}H NMR. • The order of the catalytic activity of the catalysts are 18HSnM > 28HSnM > 8HSnM. - Abstract: Si-Sn-MCM-41 (Si/Sn = 110) mesoporous molecular sieve was synthesized by hydrothermal sol–gel method using cetyltrimethylammonium bromide (CTAB) as surfactant and SnCl{sub 4}·5H{sub 2}O as a metal source. To generate surface acidity of Si-Sn-MCM-41, 12-tungstophosphoric acid (HPWA) is impregnated on it. The acidity of HPWA loading on Sn-MCM-41 was investigated by temperature programmed desorption of NH{sub 3}. The diffused reflectance spectra of ultraviolet radiation, Raman spectra, FT-IR, {sup 29}Si-MAS NMR and {sup 31}P-MAS NMR techniques revealed the intact of α-Keggin anions on Sn-MCM-41. The wide angle XRD results showed that the HPWA is well dispersed on the support. The total acidity was enhanced with increase in loading of H{sub 3}PW{sub 12}O{sub 40}. The catalytic activity was examined in desulfurization of dibenzothiophene in vapor phase system. Among the catalysts 18% HPWA loaded Sn-MCM-41 showed good catalytic activity in desulfurization at 325 °C. The HPWA/Sn-MCM-41 are a suitable solid acid catalyst for converting organic sulfur into insoluble sulfone.

  20. Adsorption competition study between oxygenated compounds and hydrocarbons on molecular sieves; Etude de la competition d`adsorption entre les composes oxygenes et les hydrocarbures sur les tamis moleculaires

    Energy Technology Data Exchange (ETDEWEB)

    Kong Ming, L.

    1996-11-29

    The aim of this study is to determine the competitive behavior of methanol and l -hexene in an n-hexane solvent system using a 13-x and a molecular sieves as the adsorbent. Adsorption was carried out in liquid phase. Parameters such as concentration, flowrate, temperature and column, length were varied in order to assess their effects on the breakthrough curves. In methanol-n-hexane system, it was found that the concentration profiles of the breakthrough curves were not very much influenced by the parameters except for the amount of volume of feed processes. However, changes in the flowrate does not have a significant effect on the concentration profile. A higher flowrate, the profile assumes a more dispersive pattern which of course is expected due to lower contact time if internal diffusion is rate determining. In the case of l -hexane carries out at different temperatures and column lengths there were some differences in concentration profiles. This may be due to experimental difficulties in controlling the flowrate at the start of the experiment rather than inherent adsorption behavior. In the 3-component system, 1 -hexene breakthrough was very much earlier as compared to methanol. Desorption carried out at 383 k and with flowrate of 28{+-}l g/min and for 100 minutes for all cases showed little variation. Re-adsorption under various conditions showed marked reduction in the amount of feed processed. The breakthrough curves were simulated using an Institut Francais du Petrole (IFP) proprietary computer program which is based on selectivity and theoretical plates and which predicts very well for xylene separation. In the 1 -hexene-n-hexane system, the simulator predicted reasonably well in terms of bed volume processed, however, for the methanol-n-hexane system the simulator failed. For the program to be effective, some mathematical treatments needs to be done with respect to the handling of the numerical analysis. To describe the adsorption equilibrium, two

  1. Study on the adsorption behaviours of naphthalene on MCM-41 and SBA-15 mesoporous molecular sieves%萘在介孔分子筛MCM-41与SBA-15上的吸附特性研究

    Institute of Scientific and Technical Information of China (English)

    杨权; 刘应书; 李子宜; 杨雄; 王占营; 姜理俊

    2015-01-01

    In this paper, the adsorption behaviours of naphthalene on two popular mesoporous molecular sieves, SBA-15 and MCM-41 were studied. The adsorption isotherms were obtained, and fitted with isotherm models of Langmuir, Freundlich and D-R. The breakthrough curves of naphthalene at different initial concentrations were measured, and well predicted by the constant-pattern wave model. Results show that the Langmuir model can well describe the adsorption isotherms of naphthalene at low concentration with R2 higher than 99%. The adsorption ability of SBA-15 with a microporous structure is stronger than that of MCM-41 which contains only mesoporous structures. The predictions on breakthrough curves by the constant-pattern model exhibited higher correlation coefficient for SBA-15 than for MCM-41. The overall mass transfer coefficient Ka of naphthalene on SBA-15 is higher than that on MCM-41 , indicating that there is a lower mass transfer resistance and the mass transfer equilibrium can be achieved faster over SBA-15 .%对低浓度气相萘在两种常见介孔分子筛MCM-41和SBA-15上的吸附特性进行研究. 得到了萘在两种吸附剂上的吸附等温线和不同初始浓度下的穿透曲线,并分别与吸附等温线模型( Langmuir、Freundlich、D-R)和恒定浓度波动力学模型进行了拟合. 结果表明, Langmuir模型能很好描述低浓度气相萘的吸附等温线( R2均在99%以上);具有微孔结构的SBA-15对萘的吸附能力要优于仅具备介孔结构的MCM-41. 动力学模型在初始浓度较低时能较好地预测萘在吸附剂上的穿透曲线,且在SBA-15上的相关系数高于MCM-41;萘在2. 76 mol/L时具有较大介孔的SBA-15的总传质系数Ka 更高,表明萘在SBA-15上的总传质阻力更低,更能较快达到传质平衡.

  2. An Improvement to the Number Field Sieve

    OpenAIRE

    Zhang, Qizhi

    2011-01-01

    We improve the "sieve" part of the number field sieve used in factoring integer and computing discrete logarithm. The runtime of our method is shorter than that of existing methods. Under some reasonable assumptions, we prove that it is less than two-thirds of the running time of the algorithm used before asymptotically with probability gr

  3. Molecular Simulation of Carbon Dioxide Adsorbed in a Slit Carbon Pore

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.

  4. Neutral atomic carbon in dense molecular clouds

    Science.gov (United States)

    Zmuidzinas, J.; Betz, A. L.; Boreiko, R. T.; Goldhaber, D. M.

    1988-01-01

    The 370 micron 3P2-3P1 fine-structure line of neutral carbon was detected in seven sources: OMC 1, NGC 2024, S140, W3, DR 21, M17, and W51. Simultaneous analysis of J = 2-1 data and available observations of the J = 1-0 line make it possible to deduce optical depths and excitation temperatures for these lines. These data indicate that both C I lines are likely to be optically thin, and that the ratio of C I to CO column densities in these clouds is typically about 0.1.

  5. MOLECULAR DESCRIPTION OF ELECTROLYTE SOLUTION IN A CARBON AEROGEL ELECTRODE

    Directory of Open Access Journals (Sweden)

    A.Kovalenko

    2003-01-01

    Full Text Available We develop a molecular theory of aqueous electrolyte solution sorbed in a nanoporous carbon aerogel electrode, based on the replica reference interaction site model (replica RISM for realistic molecular quenched-annealed systems. We also briefly review applications of carbon aerogels for supercapacitor and electrochemical separation devices, as well as theoretical and computer modelling of disordered porous materials. The replica RISM integral equation theory yields the microscopic properties of the electrochemical double layer formed at the surface of carbon aerogel nanopores, with due account of chemical specificities of both sorbed electrolyte and carbon aerogel material. The theory allows for spatial disorder of aerogel pores in the range from micro- to macroscopic size scale. We considered ambient aqueous solution of 1 M sodium chloride sorbed in two model nanoporous carbon aerogels with carbon nanoparticles either arranged into branched chains or randomly distributed. The long-range correlations of the carbon aerogel nanostructure substantially affect the properties of the electrochemical double layer formed by the solution sorbed in nanopores.

  6. 固定床双塔并联吸附分离石脑油中正构烷烃%ADSORPTION OF NORMAL PARAFFINS FROM NAPHTHA USING 5A MOLECULAR SIEVES IN A DOUBLE-COLUMN FIXED-BED

    Institute of Scientific and Technical Information of China (English)

    曹昕; 刘纪昌; 沈本贤; 孙辉

    2013-01-01

    In order to make a better use of different components in naphtha to produce ethylene and aromatics based on the strategy of molecular scale management, studies on the adsorption separation of normal paraffins from naphtha using 5A molecular sieve in a double-column fixed-bed were carried out. After 5 adsorption/desorption circles, the adsorption separation process reached dynamic balance. The optimal conditions for the adsorption/desorption process are an operation temperature of 270 ℃, a naphtha feed space velocity of 153. 4 h-1 , a switch time of 30 minutes, an intermediate oil cutting time of 2 minutes and N2 flow rate of 127. 5 h-1. The normal paraffin content in the raffinate oil is less than 3% and the potential aromatic content of the raffinate oil is 10% higher than that of the SGPC naphtha. The normal paraffin content in desorption oil is over 95%. The ethylene yield is improved by 13% - 14% using the desorption oil as stream cracking feed compared to the naphtha feed.%在固定床单柱吸附分离研究的基础上,通过程序控制的5A分子筛固定床双塔并联吸附分离试验装置,对中国石化上海高桥分公司石脑油中正构烷烃吸附/脱附分离过程进行连续操作,考察了多周期运转的吸附分离效果,并对工艺条件进行考察.研究结果表明,吸余油中正构烷烃含量经过5个吸附/脱附周期后趋于稳定,优化的吸附分离操作条件为:石脑油原料体积空速153.4 h-1,吸附/脱附温度270℃,吸附/脱附切换时间30 min,脱附气体体积空速127.5 h-1,中间油切割时间2 min.在该工艺条件下,稳定操作的吸余油中正构烷烃质量分数小于3%,芳烃潜含量比石脑油提高12.31百分点;脱附油中正构烷烃质量分数大于95%,作蒸汽裂解制乙烯原料时,与石脑油相比,乙烯收率提高约14百分点.

  7. Laser ablation of molecular carbon nitride compounds

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, D., E-mail: d.fischer@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Schwinghammer, K. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany); Sondermann, C. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Lau, V.W.; Mannhart, J. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Lotsch, B.V. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Department of Chemistry, University of Munich, LMU, Butenandtstr. 5-13, 81377 Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), 80799 Munich (Germany)

    2015-09-15

    We present a method for the preparation of thin films on sapphire substrates of the carbon nitride precursors dicyandiamide (C{sub 2}N{sub 4}H{sub 4}), melamine (C{sub 3}N{sub 6}H{sub 6}), and melem (C{sub 6}N{sub 10}H{sub 6}), using the femtosecond-pulsed laser deposition technique (femto-PLD) at different temperatures. The depositions were carried out under high vacuum with a femtosecond-pulsed laser. The focused laser beam is scanned on the surface of a rotating target consisting of the pelletized compounds. The resulting polycrystalline, opaque films were characterized by X-ray powder diffraction, infrared, Raman, and X-ray photoelectron spectroscopy, photoluminescence, SEM, and MALDI-TOF mass spectrometry measurements. The crystal structures and optical/spectroscopic results of the obtained rough films largely match those of the bulk materials.

  8. Physisorption of molecular hydrogen on carbon nanotube with vacant defects

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Gang; Shen, Huaze; Wang, Enge; Xu, Limei, E-mail: limei.xu@pku.edu.cn [International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Tangpanitanon, Jirawat [University of Cambridge, Cambridge, Cambridgeshire CB2 1TP (United Kingdom); Wen, Bo [International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871 (China); Beijing Computational Science Research Center, Heqing Street, Haidian District, Beijing 100084 (China); Xue, Jianming [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China)

    2014-05-28

    Physisorption of molecular hydrogen on single-walled carbon nanotubes (SWCNTs) is important for its engineering applications and hydrogen energy storage. Using molecular dynamics simulation, we study the physisorption of molecular hydrogen on a SWCNT with a vacant defect, focusing on the effect of the vacant defect size and external parameters such as temperature and pressure. We find that hydrogen can be physisorbed inside a SWCNT through a vacant defect when the defect size is above a threshold. By controlling the size of the defects, we are able to extract hydrogen molecules from a gas mixture and store them inside the SWCNT. We also find that external parameters, such as low temperature and high pressure, enhance the physisorption of hydrogen molecules inside the SWCNT. In addition, the storage efficiency can be improved by introducing more defects, i.e., reducing the number of carbon atoms on the SWCNT.

  9. 硅/钴摩尔比对MCM-48介孔分子筛结构性能的影响%Effects of Si/Co Molar Ratios on Textural Property of MCM-48 Mesoporous Molecular Sieve

    Institute of Scientific and Technical Information of China (English)

    周旭平; 赵谦; 吴多林; 纪美茹; 姜廷顺

    2011-01-01

    Using tetraethyl orthosilicate (TEOS) as silica source, cetyltrimethyl ammonium bromide (CTAB) as a template and sodium fluoride as a inorganic salt additive, cobalt-incorporated MCM-48 mesoporous materials (Co-MCM-48) were synthesized by the hydrothermal method. Effects of different molar ratios n(Si):n(Co) in synthesis gel on textural property of the MCM-48 mesoporous materials were investigated. The changes in textural properties were evaluated by the X-ray diffraction (XRD), transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible speetrophotometry (UV-Vis), temperature programmed reduction (TPR), and N2 physical adsorption. Results show that when n(Si):n(Co)=25, the as-synthesized Co-MCM-48 still exhibits a cubic mesoporous framework and has a high specific surface area (1 002.9 m2/g). Characterization by the FTIR, UV-Vis and TPR suggests that cobalt is incorporated into framework of the MCM-48. Specific surface area and pore volume of the synthesized Co-MCM-48 sample gradually decrease with the increase of cobalt content in the synthesis gel; pore size gradually increases and mesoporous ordering begins to deteriorate.%以正硅酸乙酯为硅源、十六烷基三甲基溴化铵为模板、氟化钠为添加剂,水热合成钴掺杂的介孔分子筛(cobalt-containing mesoporous molecular sieve,Co-MCM-48),同时研究合成溶胶中不同摩尔比m(Si):n(Co)对MCM-48介孔材料结构性能的影响.通过X射线粉末衍射、N2吸附-脱附、透射电子显微镜、Fourier变换红外光谱(Fourier transform infrared spectroscopy,FTIR)、紫外-可见光谱(ultraviolet-visible spectrpotometry,UV-Vis)、程序升温还原(temperature programmed reduction,TPR)等方法表征分析样品的结构和性能.结果表明:合成溶胶中n(Si):n(Co)=25时,所得Co-MCM-48仍具有立方介孔结构和较高的比表面积(1 002.9m2/g).FTIR谱、UV-Vis谱及TPR测试等证实:Co已经嵌入MCM-48骨架中,随着

  10. Immobilization of α - amylase on MCM -41 mesoporous molecular sieves%α-淀粉酶在MCM-41介孔分子筛上的固定化研究

    Institute of Scientific and Technical Information of China (English)

    王亮亮; 刘雪松; 宋伟明; 邓启刚

    2012-01-01

    采用浸渍法将α-淀粉酶固定在介孔分子筛MCM - 41上.考察了吸附时间、给酶量和pH对α-淀粉酶固定化性能的影响,并对固定化酶的活性、稳定性和载体结构等进行了研究.结果表明,在固定化时间为11h,给酶量为70 mg·g-1,pH =5.9的条件下,固定化酶活性回收率可达48%.与游离酶相比,固定化酶的耐热能力增强,温度达到70℃时,固定化酶相对活性可达到75%,而游离酶只有14%;在pH =3.3 ~8.0的内,固定化酶相对活性为62%~100%,而游离酶的相对活性为5%~100%,固定化酶具有更宽的pH适应性;此外,固定化酶储存稳定性明显增强,并具有一定的可重复操作性,且固定后载体仍然保持了良好的介孔结构.%A kind of α - amylase was immobilized on MCM -41 mesoporous molecular sieves with dipping method. Influence of factors such as adsorption time,initial dosage of enzyme and pH during the immobilization process on the α - amylase immobilization performance as well as the immobilized α - amylase activity, stability,carrier structure were studied. Results showed that when the adsorption time is 11 h,the initial dosage of enzyme is 70 mg · g-1 ,and the pH is kept at 5. 9,recovery of activity of the immobilized enzyme achieves 48%. As compared with the free (non - immobilized) enzyme,the heat resisting capacity of the immobilized enzyme is enhanced. At 70 ℃, relative activity of the immobilized enzyme achieves 75% , while that of free enzyme achieves 14% only. When pH ranges between 3.3 ~ 8. 0, relative activity of the immobilized enzyme achieves 62% - 100% ,while the free enzyme achieves 5% ~ 100%. Obviously,the immobilized enzyme offers broader adaptability for pH. In addition,the storage stability of immobilized α -amylase is obviously improved. The immobilized α - amylase can be used repeatedly for certain times and the carrier after the immobilization still maintains good mesoporous structure.

  11. Sieve tube geometry in relation to phloem flow

    NARCIS (Netherlands)

    Mullendore, D.L.; Windt, C.W.; As, van H.; Knoblauch, M.

    2010-01-01

    Sieve elements are one of the least understood cell types in plants. Translocation velocities and volume flow to supply sinks with photoassimilates greatly depend on the geometry of the microfluidic sieve tube system and especially on the anatomy of sieve plates and sieve plate pores. Several models

  12. Modeling the hydrodynamics of phloem sieve plates

    Directory of Open Access Journals (Sweden)

    Kaare Hartvig Jensen

    2012-07-01

    Full Text Available Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species are investigated. We find that the sieve plate resistance is correlated to the cell lumen resistance, and that the sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway.

  13. The mechanism of selective molecular capture in carbon nanotube networks.

    Science.gov (United States)

    Wan, Yu; Guan, Jun; Yang, Xudong; Zheng, Quanshui; Xu, Zhiping

    2014-07-28

    Recently, air pollution issues have drawn significant attention to the development of efficient air filters, and one of the most promising materials for this purpose is nanofibers. We explore here the mechanism of selective molecular capture of volatile organic compounds in carbon nanotube networks by performing atomistic simulations. The results are discussed with respect to the two key parameters that define the performance of nanofiltration, i.e. the capture efficiency and flow resistance, which demonstrate the advantages of carbon nanotube networks with high surface-to-volume ratio and atomistically smooth surfaces. We also reveal the important roles of interfacial adhesion and diffusion that govern selective gas transport through the network.

  14. Molecular and Metabolic Mechanisms of Carbon Sequestration in Marine Thrombolites

    Science.gov (United States)

    Mobberley, Jennifer

    2013-01-01

    The overall goal of my dissertation project has been to examine the molecular processes underlying carbon sequestration in lithifying microbial ecosystems, known as thrombolitic mats, and assess their feasibility for use in bioregenerative life support systems. The results of my research and education efforts funded by the Graduate Student Researchers Program can be summarized in four peer-reviewed research publication, one educational publication, two papers in preparation, and six research presentations at local and national science meetings (see below for specific details).

  15. Molecular Dynamics Modeling of Carbon Nanotubes and Their Composites

    Science.gov (United States)

    Jensen, Lars R.; Pyrz, Ryszard

    2004-06-01

    The tensile modulus of individual nanotubes and nanotube-polypropylene composites has been determined using molecular dynamics simulations. Simulations of individual single-walled carbon nanotubes showed that their tensile modulus was dependent on the tube structure and the diameter if the diameter was below 1,6 nm. The tensile modulus was determined for an infinite single-walled carbon nanotube embedded in an amorphous polypropylene matrix and for a finite and capped single-walled carbon nanotube embedded in a polypropylene matrix. For the infinite nanotube-polypropylene system the modulus was found to correspond to the one given by the Voigt approximation. For the finite nanotube-polypropylene system the reinforcing effect of the nanotube was not very pronounced. A pull out simulation showed that the length of the nanotube in the simulation was much smaller than the critical length and hence no load transfer between the nanotube and the matrix existed.

  16. Molecular dynamics of a water jet from a carbon nanotube.

    Science.gov (United States)

    Hanasaki, Itsuo; Yonebayashi, Toru; Kawano, Satoyuki

    2009-04-01

    A carbon nanotube (CNT) can be viewed as a molecular nozzle. It has a cylindrical shape of atomistic regularity, and the diameter can be even less than 1 nm. We have conducted molecular-dynamics simulations of water jet from a (6,6) CNT that confines water in a form of single-file molecular chain. The results show that the water forms nanoscale clusters at the outlet and they are released intermittently. The jet breakup is dominated by the thermal fluctuations, which leads to the strong dependence on the temperature. The cluster size n decreases and the release frequency f increases at higher temperatures. The f roughly follows the reaction kinetics by the transition state theory. The speed of a cluster is proportional to the 1/sqrt[n] because of the central limit theorem. These properties make great contrast with the macroscopic liquid jets. PMID:19518333

  17. Growth, modification and integration of carbon nanotubes into molecular electronics

    Science.gov (United States)

    Moscatello, Jason P.

    Molecules are the smallest possible elements for electronic devices, with active elements for such devices typically a few Angstroms in footprint area. Owing to the possibility of producing ultra-high density devices, tremendous effort has been invested in producing electronic junctions by using various types of molecules. The major issues for molecular electronics include (1) developing an effective scheme to connect molecules with the present micro- and nano-technology, (2) increasing the lifetime and stabilities of the devices, and (3) increasing their performance in comparison to the state-of-the-art devices. In this work, we attempt to use carbon nanotubes (CNTs) as the interconnecting nanoelectrodes between molecules and microelectrodes. The ultimate goal is to use two individual CNTs to sandwich molecules in a cross-bar configuration while having these CNTs connected with microelectrodes such that the junction displays the electronic character of the molecule chosen. We have successfully developed an effective scheme to connect molecules with CNTs, which is scalable to arrays of molecular electronic devices. To realize this far reaching goal, the following technical topics have been investigated. (1) Synthesis of multi-walled carbon nanotubes (MWCNTs) by thermal chemical vapor deposition (T-CVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques (Chapter 3). We have evaluated the potential use of tubular and bamboo-like MWCNTs grown by T-CVD and PE-CVD in terms of their structural properties. (2) Horizontal dispersion of MWCNTs with and without surfactants, and the integration of MWCNTs to microelectrodes using deposition by dielectrophoresis (DEP) (Chapter 4). We have systematically studied the use of surfactant molecules to disperse and horizontally align MWCNTs on substrates. In addition, DEP is shown to produce impurityfree placement of MWCNTs, forming connections between microelectrodes. We demonstrate the deposition density is tunable by

  18. Irradiation of carbon nanotubes with carbon projectiles: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Denton, Cristian D. [Departamento de Fisica Aplicada, Universidad de Alicante, 03080 Alicante (Spain); Heredia-Avalos, Santiago; Moreno-Marin, Juan Carlos [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, 03080 Alicante (Spain)

    2013-04-15

    The irradiation of carbon based nanostructures with ions and electrons has been shown to be an appropriate tool to tailor their properties. The defects induced in the nanostructures during irradiation are able to modify their mechanical and electronic properties. Here we simulate the irradiation of carbon nanotubes with carbon ions using a molecular dynamics code. We use the Tersoff potential joined smoothly to the Universal Ziegler-Biersack-Littmark potential at short distances. We study the number of defects produced after irradiation with a single carbon ion finding a saturation with its energy at {proportional_to} 3 keV. We observe, after continuum irradiation with low energy ions, the formation of bumps in the irradiated region. For larger energy ions we find that the diameter of the nanotube shrinks as shown in previous works. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. A new sieve for distinct coordinate counting

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We present a new sieve for the distinct coordinate counting problem.This significantly improves the classical inclusion-exclusion sieve for this problem,in the sense that the number of terms is reduced from 2(k 2) to k!,and reduced further to p(k) in the symmetric case,where p(k) denotes the number of partitions of k.As an illustration of applications,we give an in-depth study of a basic example arising from coding theory and graph theory.

  20. Study on Preparation and Application of Surface Molecularly Imprinted Polymer Based on Mesopocous Molecular Sieve SBA-15%介孔分子筛SBA-15表面印迹聚合物的制备及应用研究

    Institute of Scientific and Technical Information of China (English)

    何宏亮; 顾小丽; 史丽英; 高艳坤; 陈立娜

    2015-01-01

    目的:制备介孔分子筛SBA-15表面印迹聚合物(SBA-15@MIP),并探讨其在微量活性成分测定中的应用。方法:以黄芩素为模板分子、丙烯酰胺为功能单体、四氢呋喃/乙醇(3∶2,V/V)为溶剂、乙二醇二甲基丙烯酸酯为交联剂、偶氮二异丁腈为引发剂,在SBA-15表面进行分子印迹,合成SBA-15@MIP;通过透射电子显微镜和傅里叶红外光谱仪对其进行形态和结构表征;另将SBA-15@MIP作为固相萃取填料,结合高效液相色谱法检测血浆中的黄芩素。结果:合成的SBA-15@MIP仍保留了SBA-15的有序一维孔道结构,成功印迹黄芩素分子;血浆中黄芩素的检测限和定量下限分别为3.5、11.6 ng/ml,其平均回收率为94.4%,RSD为2.9%。结论:成功制得SBA-15@MIP,可用于复杂样品中微量活性成分的测定。%OBJECTIVE:To prepare mesopocous molecular sieve SBA-15 surface molecularly imprinted polymer (SBA-15@MIP),and analyze the application of SBA-15@MIP in the determination of active micro-component. METHODS:Using baica-lein as the template molecule,acrylamide(AM)as the function monomer,tetrahydrofuran/ethanol(3∶2,V/V)as the polymeriza-tion solvent,ethylene glycol dimethacrylate(EGDMA)as the cross-linker,and 2,2-azobisisobutyronitrile(AIBN)as the initiator, SBA-15@MIP was synthesized on the surface of mesopocous molecular sieve SBA-15. The surface morphology and structure of the obtained polymer were characterized by TEM and FT-IR. Finally,the imprinted polymer was used as an adsorbent for solid-phase extraction (SPE) to detect baicalein in plasma samples by HPLC. RESULTS:It revealed that the well-ordered one-dimensional pore structure of SBA-15 was still preserved in the successful synthesized SBA-15@MIP,and baicalein molecule was imprinted suc-cessfully. The limit of detection(LOD)and limit of quantification(LOQ)for baicalein in plasma were 3.5 ng/ml and 11.6 ng/ml, respectively;the average

  1. Molecular dynamics simulations of a lithium/sodium carbonate mixture.

    Science.gov (United States)

    Ottochian, Alistar; Ricca, Chiara; Labat, Frederic; Adamo, Carlo

    2016-03-01

    The diffusion and ionic conductivity of Li x Na1-x CO3 salt mixtures were studied by means of Molecular Dynamics (MD) simulations, using the Janssen and Tissen model (Janssen and Tissen, Mol Simul 5:83-98; 1990). These salts have received particular attention due to their central role in fuel cells technology, and reliable numerical methods that could perform as important interpretative tool of experimental data are thus required but still lacking. The chosen computational model nicely reproduces the main structural behaviour of the pure Li2CO3, Na2CO3 and K2CO3 carbonates, but also of their Li/K and Li/Na mixtures. However, it fails to accurately describe dynamic properties such as activation energies of diffusion and conduction processes, outlining the need to develop more accurate models for the simulation of molten salt carbonates. PMID:26897519

  2. Thermal Transport in Carbon Nanotubes using Molecular Dynamics

    Science.gov (United States)

    Moore, Andrew; Khatun, Mahfuza

    2011-10-01

    We will present results of thermal transport phenomena in Carbon Nanotube (CNT) structures. CNTs have many interesting physical properties, and have the potential for device applications. Specifically, CNTs are robust materials with high thermal conductance and excellent electrical conduction properties. A review of electrical and thermal conduction of the structures will be discussed. The research requires analytical analysis as well as simulation. The major thrust of this study is the usage of the molecular dynamics (MD) simulator, LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). A significant investigation using the LAMMPS code is conducted on the existing Beowulf Computing Cluster at BSU. NanoHUB, an open online resource to the entire nanotechnology community developed by the researchers of Purdue University, is used for further supplementary resources. Results will include the time-dependence of temperature, kinetic energy, potential energy, heat flux correlation, and heat conduction.

  3. On the amount of sieving in factorization methods

    NARCIS (Netherlands)

    Ekkelkamp, Willemina Hendrika

    2010-01-01

    Factorization methods, such as the quadratic sieve and the number field sieve, spend a lot of time on the sieving step, in which the necessary relations are collected for factoring the given number N. Relations are smooth or k-semismooth numbers (numbers with either all prime factors below some

  4. Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

    Science.gov (United States)

    Wannier, P. G.; Sahai, R.

    1987-01-01

    Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

  5. On the molecular origin of supercapacitance in nanoporous carbon electrodes.

    Science.gov (United States)

    Merlet, Céline; Rotenberg, Benjamin; Madden, Paul A; Taberna, Pierre-Louis; Simon, Patrice; Gogotsi, Yury; Salanne, Mathieu

    2012-03-04

    Lightweight, low-cost supercapacitors with the capability of rapidly storing a large amount of electrical energy can contribute to meeting continuous energy demands and effectively levelling the cyclic nature of renewable energy sources. The excellent electrochemical performance of supercapacitors is due to a reversible ion adsorption in porous carbon electrodes. Recently, it was demonstrated that ions from the electrolyte could enter sub nanometre pores, greatly increasing the capacitance. However, the molecular mechanism of this enhancement remains poorly understood. Here we provide the first quantitative picture of the structure of an ionic liquid adsorbed inside realistically modelled microporous carbon electrodes. We show how the separation of the positive and negative ions occurs inside the porous disordered carbons, yielding much higher capacitance values (125 F g(-1)) than with simpler electrode geometries. The proposed mechanism opens the door for the design of materials with improved energy storage capabilities. It also sheds new light on situations where ion adsorption in porous structures or membranes plays a role.

  6. A Molecular Dynamics Study on the Confinement of Carbon Dioxide Molecules in Carbon Nanotubes

    Science.gov (United States)

    Lazor, Meagan; Rende, Deniz; Baysal, Nihat; Ozisik, Rahmi

    2012-02-01

    The influence of atmospheric carbon dioxide (CO2) concentration on global warming is considered as one of the primary environmental issues of the past two decades. The main source of CO2 emission is human activity, such as the use of fossil fuels in transportation and industrial plants. Following the release of Kyoto Protocol in 1997, effective ways of controlling CO2 emissions received much attention. As a result, various materials such as activated carbon, zeolites, and carbon nanotubes (CNTs) were investigated for their CO2 adsorbing properties. CNTs were reported to have CO2 adsorption capability twice that of activated carbon, hence they received the most attention. In the current study, single walled carbon nanotubes (SWNTs) were used as one dimensional nanoporous materials and their CO2 adsorption capacity was analyzed with Molecular Dynamics simulations. Results indicated that SWNTs are excellent CO2 adsorbers and their effectiveness increase at low CO2 concentrations. In addition, we showed that by varying temperature, CO2 can be removed from the SWNTs, providing a simple method to reuse SWNTs.

  7. Stable doping of carbon nanotubes via molecular self assembly

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B.; Chen, Y.; Podzorov, V., E-mail: podzorov@physics.rutgers.edu [Department of Physics and Institute for Advanced Materials and Devices for Nanotechnology, Rutgers University, New Jersey 08854 (United States); Cook, A.; Zakhidov, A. [Department of Physics and NanoTech Institute, University of Texas at Dallas, Richardson, Texas 75083 (United States)

    2014-10-14

    We report a novel method for stable doping of carbon nanotubes (CNT) based on methods of molecular self assembly. A conformal growth of a self-assembled monolayer of fluoroalkyl trichloro-silane (FTS) at CNT surfaces results in a strong increase of the sheet conductivity of CNT electrodes by 60–300%, depending on the CNT chirality and composition. The charge carrier mobility of undoped partially aligned CNT films was independently estimated in a field-effect transistor geometry (~100 cm²V⁻¹s⁻¹). The hole density induced by the FTS monolayer in CNT sheets is estimated to be ~1.8 ×10¹⁴cm⁻². We also show that FTS doping of CNT anodes greatly improves the performance of organic solar cells. This large and stable doping effect, easily achieved in large-area samples, makes this approach very attractive for applications of CNTs in transparent and flexible electronics.

  8. Molecular Dynamics Simulation of Water Confined in Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    WANG Yan; YUAN Hong-Jun

    2007-01-01

    Molecular dynamics simulations are performed for water conGned in carbon nanotubes with various diameters (11.0-13.8 A). The simulations under an isobaric pressure (one atmosphere) by lowering temperatures from 300K to 190 K are carried out. Water molecules within variously sized tubes tend to transform from disorder to order with different configurations (four-water-molecule ring, six-water-molecule ring and seven-water-molecule ring) at phase transition temperatures, which may be lowered by the increasing tube radius. It is also found that the configurations of water in (10, 10) tube are not unique (seven-molecule ring and seven-molecule ring plus water chain).

  9. Characterization and catalysis performance of mesoporous molecular sieve Al- MCM- 41 with different Si/Al ratio%不同硅铝比Al-MCM-41介孔分子筛的表征及催化合成氯乙酸正辛酯

    Institute of Scientific and Technical Information of China (English)

    宋伟明; 董晓娟; 邓启刚; 赵云鹏

    2011-01-01

    以十六烷基三甲基溴化铵( CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,乙二胺为碱性介质,当n(TEOS)∶n( NaAl02)∶n(CTAB)∶n(H2NCH2CH2NH2)∶n(H2O)=1∶x∶0.12∶ 3.5∶130,其中x=0.1,0.033,0.02,0.01,0.006 7时,水热法合成了Al - MCM - 41介孔分子筛.通过XRD,N2吸附-脱附,NH3 - TPD和TEM等手段对不同硅铝比(n(Si)/n(Al))的Al - MCM -41介孔分子筛进行了表征.结果表明,当n(Si)/n( Al)由150减小至30时,Al - MCM -41介孔分子筛仍具有典型的六方介孔结构特征,但当n( Si)/n(Al)=10时,样品结构有序性下降.Al - MCM - 41介孔分子筛酸量随着n( Si)/n( Al)减小而增大.将Al - MCM - 41介孔分子筛用于催化合成氯乙酸正辛酯,相同反应条件下,n( Si) /n( Al) =30的Al - MCM - 41介孔分子筛为催化剂时酯化率最高,由此表明,Al - MCM - 41介孔分子筛作为催化剂,反应酯化率不仅取决于样品酸量,也与其晶体结构相关.当Al - MCM - 41介孔分子筛用量为氯乙酸质量的3%,反应温度为120~140℃,n(氯乙酸)∶n(正辛醇)=1∶1.2时,酯化率可达94.34%.%Mesoporous molecular sieve MCM -41 containing Si and Al with Si/Al molar ratio equal to 10,30, 50,100 and 150 were synthesized under hydrothermal conditions using cetyltrimethylammonium bromide (CTAB) as template and tetraethylorthosilicate (TEOS) as silica source and ethylenediamine as alkaline medium. The optimum molar ratio was n(TEOS): n{ NaA102) : n( CTAB) : n( H2NCH2CH2NH2): n( H20) = 1: x: 0. 12: 3. 5: 130, where x = 0. 1,0. 033 ,0. 02,0. 01 and 0. 006 7 respectively. The structure and physical and chemical surface properties of the samples were characterized by XRD, N2 adsorption - desorption, NH3 -TPD,TEM,et al. The results indicated that when Si/Al molar ratio of the samples drops from 150 to 30,the mesoporous molecular sieve MCM - 41 keeps its characteristics of typical hexagonal mesoporous structure. However,as the Si/Al molar ratio declines further to 10, the ordered

  10. Molecular dynamics analysis on impact behavior of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Seifoori, Sajjad, E-mail: sajjad.seifoori@vru.ac.ir

    2015-01-30

    Graphical abstract: - Highlights: • We present an analytical solution of impact based on two degree of freedom model. • The accuracy is verified by Molecular dynamics simulations. • The effects of the small-size effects on the dynamic deflections are investigated. • The relative motion is also accounted that is due to local indentation. - Abstract: Dynamic analysis of impact of a nanoparticle on carbon nanotubes is investigated based on two degree of freedom model. The accuracy and stability of the present methods are verified by molecular dynamics (MD) simulations. The effect of different types of boundary condition on the maximum dynamic deflections is studied for zigzag and armchair SWCNTs with various aspect ratios (length/diameter). Besides, the influences of velocity of impactor on the dynamic deflections are studied. It is shown that the dynamic behavior on the armchair and zigzag single-walled carbon nanotubes are almost similar. Finally, by making use of the above MD simulation and theoretical results some insight has been obtained about the dynamic characteristics of the impact problems of nanobeam structures. Nonlocal Timoshenko beam models TBT2 should be employed for an accurate prediction of the dynamic deflection rather than nonlocal Euler–Bernoulli beam models EBT2 which ignores the effects of transverse shear deformation and rotary inertia that is especially significant for short beams. The results from nonlocal EBT2 and TBT2 models demonstrated good agreement with MD simulation. The EBT2 and TBT2 models also account for the relative motion between the nanoparticle and the nanobeam that is due to local indentation as can be seen in MD simulation.

  11. Molecular dynamics analysis on impact behavior of carbon nanotubes

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • We present an analytical solution of impact based on two degree of freedom model. • The accuracy is verified by Molecular dynamics simulations. • The effects of the small-size effects on the dynamic deflections are investigated. • The relative motion is also accounted that is due to local indentation. - Abstract: Dynamic analysis of impact of a nanoparticle on carbon nanotubes is investigated based on two degree of freedom model. The accuracy and stability of the present methods are verified by molecular dynamics (MD) simulations. The effect of different types of boundary condition on the maximum dynamic deflections is studied for zigzag and armchair SWCNTs with various aspect ratios (length/diameter). Besides, the influences of velocity of impactor on the dynamic deflections are studied. It is shown that the dynamic behavior on the armchair and zigzag single-walled carbon nanotubes are almost similar. Finally, by making use of the above MD simulation and theoretical results some insight has been obtained about the dynamic characteristics of the impact problems of nanobeam structures. Nonlocal Timoshenko beam models TBT2 should be employed for an accurate prediction of the dynamic deflection rather than nonlocal Euler–Bernoulli beam models EBT2 which ignores the effects of transverse shear deformation and rotary inertia that is especially significant for short beams. The results from nonlocal EBT2 and TBT2 models demonstrated good agreement with MD simulation. The EBT2 and TBT2 models also account for the relative motion between the nanoparticle and the nanobeam that is due to local indentation as can be seen in MD simulation

  12. Carbon Nanomaterials and DNA: from Molecular Recognition to Applications.

    Science.gov (United States)

    Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

    2016-03-15

    DNA is polymorphic. Increasing evidence has indicated that many biologically important processes are related to DNA's conformational transition and assembly states. In particular, noncanonical DNA structures, such as the right-handed A-form, the left-handed Z-form, the triplex, the G-quadruplex, the i-motif, and so forth, have been specific targets for the diagnosis and therapy of human diseases. Meanwhile, they have been widely used in the construction of smart DNA nanomaterials and nanoarchitectures. As rising stars in materials science, the family of carbon nanomaterials (CNMs), including two-dimensional graphene, one-dimensional carbon nanotubes (CNTs), and zero-dimensional graphene or carbon quantum dots (GQDs or CQDs), interact with DNA and are able to regulate the conformational transitions of DNA. The interaction of DNA with CNMs not only opens new opportunities for specific molecular recognition, but it also expands the promising applications of CNMs from materials science to biotechnology and biomedicine. In this Account, we focus on our contributions to the field of interactions between CNMs and DNA in which we have explored their promising applications in nanodevices, sensing, materials synthesis, and biomedicine. For one-dimensional CNTs, two-dimensional graphene, and zero-dimensional GQDs and CQDs, the basic principles, binding modes, and applications of the interactions between CNMs and DNA are reviewed. We aim to give prominence to the important status of CNMs in the field of molecular recognition for DNA. First, we summarized our discovery of the interactions between single-walled carbon nanotubes (SWNTs) with duplex, triplex, and human telomeric i-motif DNA and their interesting applications. For example, SWNTs are the first chemical agents that can selectively stabilize human telomeric i-motif DNA and induce its formation under physiological conditions. On the basis of this principle, two types of nanodevices were designed. One was used for

  13. Laser ablation molecular isotopic spectrometry of carbon isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Bol' shakov, Alexander A. [Applied Spectra, Inc., Fremont, CA (United States); Jain, Jinesh [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Russo, Richard E. [Applied Spectra, Inc., Fremont, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); McIntyre, Dustin [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Mao, Xianglei [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-08-28

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented:empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5–476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrumyielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies

  14. Carbon nanodots as molecular scaffolds for development of antimicrobial agents.

    Science.gov (United States)

    Ngu-Schwemlein, Maria; Chin, Suk Fun; Hileman, Ryan; Drozdowski, Chris; Upchurch, Clint; Hargrove, April

    2016-04-01

    We report the potential of carbon nanodots (CNDs) as a molecular scaffold for enhancing the antimicrobial activities of small dendritic poly(amidoamines) (PAMAM). Carbon nanodots prepared from sago starch are readily functionalized with PAMAM by using N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Electron microscopy images of these polyaminated CNDs show that they are approximately 30-60nm in diameter. Infrared and fluorescence spectroscopy analyses of the water-soluble material established the presence of the polyamidoaminated moiety and the intrinsic fluorescence of the nanodots. The polyaminated nanodots (CND-PAM1 and CND-PAM2) exhibit in vitro antimicrobial properties, not only to non-multidrug resistant bacteria but also to the corresponding Gram-negative multidrug bacteria. Their minimum inhibitory concentration (MIC) ranges from 8 to 64μg/mL, which is much lower than that of PAMAM G1 or the non-active PAMAM G0 and CNDs. Additionally, they show synergistic effect in combination with tetracycline or colistin. These preliminary results imply that CNDs can serve as a promising scaffold for facilitating the rational design of antimicrobial materials for combating the ever-increasing threat of antibiotic resistance. Moreover, their fluorescence could be pertinent to unraveling their mode of action for imaging or diagnostic applications. PMID:26923697

  15. Laser ablation molecular isotopic spectrometry of carbon isotopes

    Science.gov (United States)

    Bol‧shakov, Alexander A.; Mao, Xianglei; Jain, Jinesh; McIntyre, Dustin L.; Russo, Richard E.

    2015-11-01

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented: empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5-476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrum yielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies.

  16. The Number Field Sieve for Discrete Logarithms

    OpenAIRE

    Haarberg, Henrik Røst

    2016-01-01

    We present two general number field sieve algorithms solving the discrete logarithm problem in finite fields. The first algorithm presented deals with discrete logarithms in prime fields, while the second considers prime power fields. We prove, using the standard heuristic, that these algorithms will run in sub-exponential time. We also give an overview of different index calculus algorithms solving the discrete logarithm problem efficiently for different possible relations between th...

  17. Eigenvalues in the large sieve inequality

    OpenAIRE

    Ramaré, Olivier

    2007-01-01

    We provide some evidence that the eigenvalues of the hermitian form $\\sum_{a/q}|\\sum_{n\\le N}\\varphi_ne(na/q)|^2$ tend to have a limit distribution when $N$ and $Q$ go simultaneously to infinity in such a way that $N/Q^2$ tends to a constant. We also present some background material, as well as a large sieve equality, when $N\\Log^7 N = o(Q)$, that follows from our results.

  18. Molecular-dynamic studies of carbon-water-carbon composite nanotubes.

    Science.gov (United States)

    Zou, Jian; Ji, Baohua; Feng, Xi-Qiao; Gao, Huajian

    2006-11-01

    We recently reported the discovery via molecular-dynamic simulations that single-walled carbon nanotubes (SWCNTs) with different diameters, lengths, and chiralities can coaxially self-assemble into multi-walled carbon nanotubes (MWCNTs) in water via the spontaneous insertion of smaller tubes into larger ones. Here, we extend that study to investigate the various water structures formed between two selected SWCNTs after such coaxial assembly. Depending on the tube geometry, typical water structures, besides the bulk phase, include a one-dimensional (1D) ordered water chain inside the smaller tube, a uniform or nonuniform water shell between the two tubes, and a "boundary layer" of water near the exterior wall of the larger tube. It was found that a concentric water shell consisting of up to three layers of water molecules can form between the two SWCNTs, which leads to a class of carbon-water-carbon composite nanotubes. Analysis of the potential energy of the SWCNT-water system indicated that the composite nanotubes are stabilized by both the tube-tube and tube-water van der Waals interactions. Geometrically confined between the two SWCNTs, water mono- and bilayers are found to be stable, highly condensed, and ordered, although the average number of hydrogen bonds per water molecule is reduced. In contrast, a water trilayer between the two CNTs can be easily disrupted by thermal fluctuations.

  19. Molecular and carbon isotopic compositions of gas inclusions of deep carbonate rocks in the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shixin; WANG Xianbin; MENG Zifang; LI Yuan; Paul Farrimond; LI Liwu; DUAN Yi

    2004-01-01

    Gaseous components of gas inclusions in deep carbonate rocks (>5700 m) from the Tacan 1 well were analyzed by online mass spectrometry by means of either the stepwise heating technique or vacuum electromagnetism crushing. The carbon isotopic compositions of gases released by vacuum electromagnetism crushing were also measured. Although the molecular compositions of gas inclusions show differences between the two methods, the overall characteristics are that gas inclusions mainly contain CO2, whilst hydrocarbon gases, such as CH4, C2H6 and C3H8, are less abundant. The content of CO is higher in the stepwise heating experiment than that in the method of vacuum electromagnetism crushing, and there are only minor amounts of N2, H2 and O2 in gas inclusions. Methane δ13C values of gas inclusions in Lower Ordovician and Upper Cambrian rocks (from 5713.7 to 6422 m; -52‰-63‰) are similar to those of bacterial methane, but their chemical compositions do not exhibit the dry character in comparison with biogenic gases. These characteristics of deep gas inclusions may be related to the migration fractionation. Some deep natural gases with light carbon isotopic characteristics in the Tazhong Uplift may have a similar origin. The δ13C1 values of gas inclusions in Lower Cambrian rocks (7117-7124 m) are heavier (-39‰), consistent with highly mature natural gases. Carbon isotopic compositions of CO2 in the gas inclusions of deep carbonate rocks are similar (from -4‰ to -13‰) to those of deep natural gases, indicating predominantly an inorganic origin.

  20. 2D IMAGE BASED SIEVING FOR PARTICLE AGGREGATE GRADATION

    Institute of Scientific and Technical Information of China (English)

    Chen Ken; John Zaniewski; Zhao Pan; Yang Ren'er

    2008-01-01

    Acquiring the size gradation for particle aggregates is a common practice in the granule related industry, and mechanical sieving or screening has been the normal method. Among many drawbacks of this conventional means, the major ones are time-consuming, labor-intensive, and being unable to provide real-time feedback for process control. In this letter, an optical sieving approach is introduced. The two-dimensional images are used to develop methods for inferring particle volume and sieving behavior for gradation purposes. And a combination of deterministic and probabilistic methods is described to predict the sieving behaviors of the particles and to construct the gradation curves for the aggregate sample. Comparison of the optical sieving with standard mechanical sieving shows good correlation.

  1. Cyclic sieving and rational Catalan theory

    OpenAIRE

    Bodnar, Michelle; Rhoades, Brendon

    2015-01-01

    Let $a < b$ be coprime positive integers. Armstrong, Rhoades, and Williams defined a set $\\mathsf{NC}(a,b)$ of `rational noncrossing partitions', which form a subset of the ordinary noncrossing partitions of $\\{1, 2, \\dots, b-1\\}$. Confirming a conjecture of Armstrong et. al., we prove that $\\mathsf{NC}(a,b)$ is closed under rotation and prove an instance of the cyclic sieving phenomenon for this rotational action. We also define a rational generalization of the $\\mathfrak{S}_a$-noncrossing p...

  2. Coulombic dragging of molecular assemblies on nanotubes

    Science.gov (United States)

    Kral, Petr; Sint, Kyaw; Wang, Boyang

    2009-03-01

    We show by molecular dynamics simulations that polar molecules, ions and their assemblies could be Coulombically dragged on the surfaces of single-wall carbon and boron-nitride nanotubes by ionic solutions or individual ions moving inside the nanotubes [1,2]. We also briefly discuss highly selective ionic sieves based on graphene monolayers with nanopores [3]. These phenomena could be applied in molecular delivery, separation and desalination.[3pt] [1] Boyang Wang and Petr Kral, JACS 128, 15984 (2006). [0pt] [2] Boyang Wang and Petr Kral, Phys. Rev. Lett. 101, 046103 (2008). [0pt] [3] Kyaw Sint, Boyang Wang and Petr Kral, JACS, ASAP (2008).

  3. Dielectric constants of binary mixtures of propylene carbonate with dimethyl carbonate and ethylene carbonate from molecular dynamics simulation: comparison between non-polarizable and polarizable force fields

    Science.gov (United States)

    Lee, Sanghun; Park, Sung Soo

    2013-01-01

    Using non-polarizable and polarizable molecular dynamics simulations, binary mixtures of propylene carbonate + dimethyl carbonate and propylene carbonate + ethylene carbonate with various compositions were investigated. The polarizable model produces more reasonable estimation of dielectric constants than the non-polarizable model; however, combining the electronic continuum model with the non-polarizable MD improves the comparison between the two models. Fair agreement was found between the results from these simulations and available experimental data. In addition, for a better understanding of the mixing behaviour, the excess dielectric constants over the entire composition were calculated. By comparison of the two mixtures in various mole fractions, distinctive mixing behaviours of propylene carbonate + dimethyl carbonate (poorly symmetric mixture) and propylene carbonate + ethylene carbonate (highly symmetric mixture) were observed.

  4. Resolution enhancement of photon sieve based on apodization

    Science.gov (United States)

    Cheng, Guanxiao; Xing, Tingwen; Liao, Zhijie; Yang, Yong; Ma, Jianling

    2008-03-01

    Photon sieve is a novel diffractive optical element modulating either amplitude or phase which consists of a great number of pinholes distributed appropriately over the Fresnel zones for the focusing and imaging of light. Photon sieve has the advantages of the diameter of pinholes beyond the limitation of the corresponding Fresnel zone width and the minimum background in the focal plane. Furthermore, photon sieve can be fabricated on a single surface without any supporting struts required unlike the Fresnel zone plate. Photon sieve can be used as EUV telescope for solar orbiter, space-based surveillance telescope operating at visible light, or other imaging components. Photon sieve can also be used as one of the promising lithographic tools for nanoscale science and engineering to obtain the lower cost, higher flexibility and better resolution. The approaches to enhancing imaging resolution of photon sieve are presented in detail. According to Fresnel-Kirchhoff diffraction theory, the diffractive field of photon sieve is described by means of the discrete fast Fourier transform algorithm. The related contents include the calculation of point spread function, the suppression of side lobes, the imaging bandwidth, the physical limit of resolution, and the diffraction efficiency. Imaging properties of photon sieve are analyzed on the basis of precise test.

  5. Computational sieving applied to some classical number-theoretic problems

    NARCIS (Netherlands)

    Riele, H.J.J. te

    1998-01-01

    Many problems in computational number theory require the application of some sieve. Efficient implementation of these sieves on modern computers has extended our knowledge of these problems considerably. This is illustrated by three classical problems: the Goldbach conjecture, factoring large number

  6. Computational sieving applied to some classical number-theoretic problems

    OpenAIRE

    Riele, te, H.

    1999-01-01

    Many problems in computational number theory require the application of some sieve. Efficient implementation of these sieves on modern computers has extended our knowledge of these problems considerably. This is illustrated by three classical problems: the Goldbach conjecture, factoring large numbers, and computing the summatory function of the M'{obius function.

  7. Molecular dynamics simulation on mechanical property of carbon nanotube torsional deformation

    Institute of Scientific and Technical Information of China (English)

    Chen Ming-Jun; Liang Ying-Chun; Li Hong-Zhu; Li Dan

    2006-01-01

    In this paper torsional deformation of the carbon nanotubes is simulated by molecular dynamics method. The Brenner potential is used to set up the simulation system. Simulation results show that the carbon nanotubes can bear larger torsional deformation, for the armchair type (10,10) single wall carbon nanotubes, with a yielding phenomenon taking place when the torsional angle is up to 63°(1.1rad). The influence of carbon nanotube helicity in torsional deformation is very small. The shear modulus of single wall carbon nanotubes should be several hundred GPa, not 1 GPa as others reports.

  8. Using Pyrolysis Molecular Beam Mass Spectrometry to Characterize Soil Organic Carbon in Native Prairie Soils

    Science.gov (United States)

    The objective of this study was to characterize soil organic carbon (SOC) with pyrolysis molecular beam mass spectrometry (py-MBMS) and then to determine correlations between the mass spectra and associated soil characterization data. Both soil carbon chemistry and the organic forms in which SOC is...

  9. Computational Nanotechnology of Molecular Materials, Electronics, and Actuators with Carbon Nanotubes and Fullerenes

    Science.gov (United States)

    Srivastava, Deepak; Menon, Madhu; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

    2001-01-01

    The role of computational nanotechnology in developing next generation of multifunctional materials, molecular scale electronic and computing devices, sensors, actuators, and machines is described through a brief review of enabling computational techniques and few recent examples derived from computer simulations of carbon nanotube based molecular nanotechnology.

  10. Effect of Ethanol/water Volume Ratio on Pore Structure for Cu-HMS Mesoporous Molecular Sieve and Catalytic Performance for PdCl2/Cu-HMS%醇水体积比对Cu-HMS介孔分子筛结构及PdCl2/Cu-HMS催化性能的影响

    Institute of Scientific and Technical Information of China (English)

    张萍波; 周燕; 范明明; 蒋平平

    2013-01-01

    Five copper-containing hexagonal mesoporous molecular sieves (Cu-HMS) with different particle sizes and specific surface areas were synthesized by adjusting ethanol/water volume ratio of the synthetic system.The effects of ethanol/water volume ratio on the structure and surface morphology were characterized by means of infrared resonance (IR) spectroscopy,X-ray powder diffraction (XRD),scanning electron microscopy(SEM) and N2 adsorption-desorption.The selectivity of all the PdC12/CuHMS catalysts reached 100% by oxidative carbonylation of ethanol in the gas-phase reaction.When ethanol/water volume ratio was about 1.O,the specific surface areas of Cu-HMS reached 1520.36 m2/g,and space time yield of DEC was 110.3g/(L·h).%通过改变EtOH/H2O体积比,制备了5个不同粒径和比表面积的Cu-HMS分子筛.采用红外、XRD、SEM和BET进行表征,研究不同乙醇/水体积比对Cu-HMS结构和表面形貌的影响.不同粒径的Cu-HMS与活性组分PdCl2结合制成氧化羰基合成碳酸二乙酯(DEC)的催化剂,选择性均达到100%.EtOH/H2O体积比为1.0的Cu-HMS分子筛的比表面积可达1520.36 m2/g,DEC的时空收率达到110.3g/(L·h).

  11. Molecular simulation of carbon dioxide adsorption for carbon capture and storage

    Science.gov (United States)

    Tenney, Craig M.

    Capture of CO2 from fossil fuel power plants and sequestration in unmineable coal seams are achievable methods for reducing atmospheric emissions of this greenhouse gas. To aid the development of effective CO2 capture and sequestration technologies, a series of molecular simulation studies were conducted to study the adsorption of CO2 and related species onto heterogeneous, solid adsorbents. To investigate the influence of surface heterogeneity upon adsorption behavior in activated carbons and coal, isotherms were generated via grand canonical Monte Carlo (GCMC) simulation for CO2 adsorption in slit-shaped pores with several variations of chemical and structural heterogeneity. Adsorption generally increased with increasing oxygen content and the presence of holes or furrows, which acted as preferred binding sites. To investigate the potential use of the flexible metal organic framework (MOF) Cu(BF4)2(bpy)2 (bpy=bipyridine) for CO2 capture, pure- and mixed-gas adsorption was simulated at conditions representative of power plant process streams. This MOF was chosen because it displays a novel behavior in which the crystal structure reversibly transitions from an empty, zero porosity state to a saturated, expanded state at the "gate pressure". Estimates of CO2 capacity above the gate pressure from GCMC simulations using a rigid MOF model showed good agreement with experiment. The CO2 adsorption capacity and estimated heats of adsorption are comparable to common physi-adsorbents under similar conditions. Mixed-gas simulations predicted CO2/N2 and CO2/H 2selectivities higher than typical microporous materials. To more closely investigate this gating effect, hybrid Monte-Carlo/molecular-dynamics (MCMD) was used to simulate adsorption using a flexible MOF model. Simulation cell volumes remained relatively constant at low gas pressures before increasing at higher pressure. Mixed-gas simulations predicted CO2/N 2 selectivities comparable to other microporous adsorbents. To

  12. Source Molecular Effect on Amorphous Carbon Film Deposition

    OpenAIRE

    Kawazoe, Hiroki; Inayoshi, Takanori; Shinohara, Masanori; Matsuda, Yoshinobu; Fujiyama, Hiroshi; Nitta, Yuki; Nakatani, Tatsuyuki

    2009-01-01

    We investigated deposition process of amorphous carbon films using acetylene and methane as a source molecule, by using infrared spectroscopy in multiple internal reflection geometry (MIR-IRAS). We found that deposited film structures were different due to source molecules.

  13. On the amount of sieving in factorization methods

    OpenAIRE

    Ekkelkamp, Willemina Hendrika

    2010-01-01

    Factorization methods, such as the quadratic sieve and the number field sieve, spend a lot of time on the sieving step, in which the necessary relations are collected for factoring the given number N. Relations are smooth or k-semismooth numbers (numbers with either all prime factors below some bound or all with the exception of at most k prime factors that do not exceed a second bound) or pairs of these type of numbers. In this thesis, we predict the amount of k-semismooth numbers needed to ...

  14. Chemical analysis and molecular models for calcium-oxygen-carbon interactions in black carbon found in fertile Amazonian anthrosoils.

    Science.gov (United States)

    Archanjo, Braulio S; Araujo, Joyce R; Silva, Alexander M; Capaz, Rodrigo B; Falcão, Newton P S; Jorio, Ado; Achete, Carlos A

    2014-07-01

    Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change. PMID:24892495

  15. Single-Wall Carbon Nanotube Growth from Graphite Layers-a Tight Binding Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    Yuntuan FANG; Min ZHU; Yongshun WANG

    2003-01-01

    The growth of single-wall carbon nanotube from graphite layers is studied by tight binding molecular dynamics simulation. Given temperature of 2500 K or 3500 K and an interval of 0.25 nm for the two layers of graphite, a single-wall carbon nanotube with a zigzag shell will be produced. On the other conditions the carbon nanotube cannot grow or grows with too many defects. All carbon nanotube ends have pentagons which play an important role during the tube ends closing.

  16. Molecular switches in carbon-rich organometallic compounds: Theoretical aspects

    Science.gov (United States)

    Costuas, Karine

    2015-01-01

    Organometallic complexes associated with an appropriate choice of ancillary ligands reveal to have a wide range of physical properties leading to promising applications when incorporated in nano-size devices. The challenge is to design innovative multifunctional compounds based on redox active carbon-rich organometallics associated with spin carriers and/or photochromic units. A multidisciplinary approach in this area has proved to be efficient in a series a systems combining carbon-rich bridging ligands and redox metallic moieties. In this domain, the role of theoretical investigations based on quantum mechanics tools have a crucial role in rationalizing and in helping designing systems possessing target properties.

  17. Sampling and monitoring of carbon-14 in gaseous effluents from nuclear facilities

    International Nuclear Information System (INIS)

    This study reviews the possibilities from sampling and monitoring C-14 in gaseous effluents from nuclear facilities. After oxidation of various forms of carbon-14 in the off-gas into CO2 three main processes for trapping are used either separately or in combination. These are sorption, freezing and chemical processes. Absorption in alkaline solutions or solids or molecular sieve adsorption are the most frequently used methods. The main counting methods used are gas proportional counting and liquid scintillation counting

  18. Centrifugal Sieve for Size-Segregation/ Beneficiation of Regolith Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Utilizing centrifugal force as the primary body-force, combined with both shearing flow and vibratory motion the proposed centrifugal-sieve separators can provide...

  19. On the range of validity of the autoregressive sieve bootstrap

    CERN Document Server

    Kreiss, Jens-Peter; Politis, Dimitris N; 10.1214/11-AOS900

    2012-01-01

    We explore the limits of the autoregressive (AR) sieve bootstrap, and show that its applicability extends well beyond the realm of linear time series as has been previously thought. In particular, for appropriate statistics, the AR-sieve bootstrap is valid for stationary processes possessing a general Wold-type autoregressive representation with respect to a white noise; in essence, this includes all stationary, purely nondeterministic processes, whose spectral density is everywhere positive. Our main theorem provides a simple and effective tool in assessing whether the AR-sieve bootstrap is asymptotically valid in any given situation. In effect, the large-sample distribution of the statistic in question must only depend on the first and second order moments of the process; prominent examples include the sample mean and the spectral density. As a counterexample, we show how the AR-sieve bootstrap is not always valid for the sample autocovariance even when the underlying process is linear.

  20. Mesh Algorithms for PDE with Sieve I: Mesh Distribution

    CERN Document Server

    Knepley, Matthew G

    2009-01-01

    We have developed a new programming framework, called Sieve, to support parallel numerical PDE algorithms operating over distributed meshes. We have also developed a reference implementation of Sieve in C++ as a library of generic algorithms operating on distributed containers conforming to the Sieve interface. Sieve makes instances of the incidence relation, or \\emph{arrows}, the conceptual first-class objects represented in the containers. Further, generic algorithms acting on this arrow container are systematically used to provide natural geometric operations on the topology and also, through duality, on the data. Finally, coverings and duality are used to encode not only individual meshes, but all types of hierarchies underlying PDE data structures, including multigrid and mesh partitions. In order to demonstrate the usefulness of the framework, we show how the mesh partition data can be represented and manipulated using the same fundamental mechanisms used to represent meshes. We present the complete des...

  1. Ionized carbon in side-illuminated molecular clouds

    International Nuclear Information System (INIS)

    The C II fine-structure line has been observed in five sources for which the ionization front/molecular cloud interface is viewed approximately edge-on. The LSR velocity of the C II emission is generally in good agreement with that observed for molecular species such as CO. However, the observed linewidths of 3-14 km/s are typically wider than those of molecular lines and often show rapid spatial variations in the observed regions. The C II brightness temperature are typically equal to or slightly higher than the dust temperature at all locations observed. In the optically thin approximation, C II excitation temperatures are 100 K or more and column densities are 10 to the 18th/sq cm for all sources except M17, which has a more intense and complicated line profile with a larger spatial extent than any other source observed. 58 refs

  2. Post-sieve element transport of photoassimilates in sink regions.

    Science.gov (United States)

    Patrick, J W; Offler, C E

    1996-08-01

    Photoassimilate transport from the sieve elements to the recipient sink cells, principally in the form of sucrose, provides a link between sink metabolism and compartmentation with phloem import. Phloem unloading has focused attention on photoassimilate transport across the sieve element boundary. However, post-sieve element transport can be of equal or greater significance. Three cellular pathways of sieve element unloading and post-sieve element transport are identified. These are apoplastic, symplastic and symplastic interrupted by an apoplastic step. The symplastic path is considered to be the common path, while the remaining pathways serve specialized functions. In particular, the apoplastic step isolates the sieve element transport function from the effects of solute concentration or osmotic changes in the sink cells. Switching between apo- and symplastic routes within a given sink has been found to be linked with such changes. Plasmodesmatal transport undoubtedly involves a diffusive component, but whether bulk flow contributes to the symplastic flux of photoassimilate from the sieve elements to the recipient sink cells is yet to be established unequivocally. Efflux across the plasma membranes of the sieve element-companion cell (se-cc) complexes and other vascular cells occurs by passive diffusion. Along the axial route, retrieval from the phloem apoplast is mediated by sucrose/proton symport. However, this mechanism is absent in terminal sinks. Non-vascular efflux from the maternal tissues of developing seed is passive in cereals and energy-coupled in certain grain legumes. Accumulation of sugars from the apoplast of all sinks with an apoplastic step universally occurs by a plasma membrane-bound sugar/proton symport mechanism. Regulation of symplastic transport could be mediated by a combination of sink metabolism and compartmentation coupled with changes in the transport properties of the interconnecting plasmodesmata. PMID:21245245

  3. On the range of validity of the autoregressive sieve bootstrap

    OpenAIRE

    Kreiss, Jens-Peter; Paparoditis, Efstathios; Politis, Dimitris N.

    2012-01-01

    We explore the limits of the autoregressive (AR) sieve bootstrap, and show that its applicability extends well beyond the realm of linear time series as has been previously thought. In particular, for appropriate statistics, the AR-sieve bootstrap is valid for stationary processes possessing a general Wold-type autoregressive representation with respect to a white noise; in essence, this includes all stationary, purely nondeterministic processes, whose spectral density is everywhere positive....

  4. Sieve likelihood ratio inference on general parameter space

    Institute of Scientific and Technical Information of China (English)

    SHI; Jian; SHEN; Xiaotong

    2005-01-01

    In this paper,a theory on sieve likelihood ratio inference on general parameter spaces(including infinite dimensional) is studied.Under fairly general regularity conditions,the sieve log-likelihood ratio statistic is proved to be asymptotically x2 distributed,which can be viewed as a generalization of the well-known Wilks' theorem.As an example,a emiparametric partial linear model is investigated.

  5. Molecular simulation of polycyclic aromatic hydrocarbon sorption to black carbon

    NARCIS (Netherlands)

    J.J.H. Haftka; J.R. Parsons; H.A.J. Govers

    2009-01-01

    Strong sorption of hydrophobic organic contaminants to soot or black carbon (BC) is an important environmental process limiting the bioremediation potential of contaminated soils and sediments. Reliable methods to predict BC sorption coefficients for organic contaminants are therefore required. A co

  6. A molecular organic carbon isotope record of Miocene climate changes

    NARCIS (Netherlands)

    Schoell, M.; Schouten, S.; Sinninghe Damsté, J.S.; Leeuw, J.W. de; Summons, R.E.

    1994-01-01

    The difference in carbon-13 (13C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in 18O (δ18O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters

  7. Reactions of carbon atoms in pulsed molecular beams

    Energy Technology Data Exchange (ETDEWEB)

    Reisler, H. [Univ. of Southern California, Los Angeles (United States)

    1993-12-01

    This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

  8. Surface reactions of molecular and atomic oxygen with carbon phosphide films.

    Science.gov (United States)

    Gorham, Justin; Torres, Jessica; Wolfe, Glenn; d'Agostino, Alfred; Fairbrother, D Howard

    2005-11-01

    The surface reactions of atomic and molecular oxygen with carbon phosphide films have been studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Carbon phosphide films were produced by ion implantation of trimethylphosphine into polyethylene. Atmospheric oxidation of carbon phosphide films was dominated by phosphorus oxidation and generated a carbon-containing phosphate surface film. This oxidized surface layer acted as an effective diffusion barrier, limiting the depth of phosphorus oxidation within the carbon phosphide film to phosphorus atoms as well as the degree of phosphorus oxidation. For more prolonged AO exposures, a highly oxidized phosphate surface layer formed that appeared to be inert toward further AO-mediated erosion. By utilizing phosphorus-containing hydrocarbon thin films, the phosphorus oxides produced during exposure to AO were found to desorb at temperatures >500 K under vacuum conditions. Results from this study suggest that carbon phosphide films can be used as AO-resistant surface coatings on polymers.

  9. Molecular Dynamics Simulation of Formaldehyde Adsorption and Diffusion in Single-Wall Carbon Nanotube

    Institute of Scientific and Technical Information of China (English)

    Pin Lv; Zhenan Tang; Jun Yu; Yanbing Xue

    2006-01-01

    For gas sensor application, adsorption and diffusion of formaldehyde gas in single-wall carbon nanotube were investigated by using molecular dynamics simulation. The conformations of formaldehyde molecule adsorbed in carbon nanotube were optimized according to principle of minimum energy. The axis of conformatiot is parallel to the axis of carbon nanotube and about 0.3 nm~0.4 nm away from carbon nanotube wall. The conformation, which is different from that of the formaldehyde molecule in the gas-phase, rotates around carbon nanotube axis. The adsorption energy and diffusivity of formaldehyde molecule in single-wall carbon nanotube is of-56.2 kJ/mol and of 0.2× 10-4 cm2/s, respectively.

  10. Molecular dynamics of bimolecular reactions : the equilibrium constant of dimerisation of carbon dioxide : rebinding molecular dynamics of nitric oxide to the V68F myoglobin mutant

    OpenAIRE

    Tsintsarska, Stefka

    2007-01-01

    1.1 Carbon dioxide 1.1.1 Significance Theoretical and experimental investigations of weakly bound molecular complexes are of fundamental importance for understanding of molecular interactions responsible for properties of condensed phases. The carbon dioxide clusters provide a simple model for such studies. Carbon dioxide has been a subject of many papers in recent years. Some deal with its role in the biosphere, mainly the greenhouse effect. The greenhouse effect is the ris...

  11. Direct Observation of Molecular Oxygen Production from Carbon Dioxide

    CERN Document Server

    Larimian, Seyedreza; Mai, Sebastian; Marquetand, Philipp; González, Leticia; Baltuška, Andrius; Kitzler, Markus; Xie, Xinhua

    2016-01-01

    Oxygen ($O_2$) is one of the most important elements required to sustain life. The concentration of $O_2$ on Earth has been accumulated over millions of years and has a direct connection with that of $CO_2$. Further, $CO_2$ plays an important role in many other planetary atmospheres. Therefore, molecular reactions involving $CO_2$ are critical for studying the atmospheres of such planets. Existing studies on the dissociation of $CO_2$ are exclusively focused on the C--O bond breakage. Here we report first experiments on the direct observation of molecular Oxygen formation from $CO_2$ in strong laser fields with a reaction microscope. Our accompanying simulations suggest that $CO_2$ molecules may undergo bending motion during and after strong-field ionization which supports the molecular Oxygen formation process. The observation of the molecular Oxygen formation from $CO_2$ may trigger further experimental and theoretical studies on such processes with laser pulses, and provide hints in studies of the $O_2$ an...

  12. MCM-41 ordered mesoporous molecular sieves synthesis and characterization

    Directory of Open Access Journals (Sweden)

    Rogério A.A. Melo

    1999-07-01

    Full Text Available The aim of this work was to study the hydrothermal synthesis of Si and SiAlMCM-41 performed under both autogenic pressure and refluxing conditions. XRD data showed that the MCM-41 phase may be formed by both processes and that the synthesized material in the presence of Al and/or under reflux presents the hexagonally arrangement of less ordered mesopores. However, as verified by XRD and physisorption data, the order was improved with higher synthesis times. 29Si and 1H - 29Si C/P MAS NMR spectra showed that a great part of the Si atoms exists as silanol groups which originate resonance peaks at -110, -100 and -91 ppm. The presence of Al atoms may generate Si(3Si, Al and Si(2Si, 2Al environments which might be contributing to resonance peaks at -100 and -91 ppm. The 27Al MAS NMR spectrum of the as synthesized AlSiMCM-41 showed a resonance peak of tetrahedral framework aluminum close to 53 ppm and two others, one close to 14 ppm attributed to Al(H2O6+3 species and the other a weak signal close to 32 ppm attributed to pentacoordinated Al. 27Al MAS NMR spectra of the calcined sample showed a peak at 0 ppm corresponding to an hexacoordinated extra-framework aluminum formed during calcination.

  13. Preparation of Zeolite Molecular Sieve by Using Hydrogel Method

    International Nuclear Information System (INIS)

    Zeolite A was synthesized from hydrogel solution which prepared from silica and alumina precursors under hydrothermal condition at atmospheric pressure. Before preparing of hydrogel solution, the amount of raw materials which used in resulting hydrogel with appropriate mole ratio was calculated by material balance. In this study,totally ten experiments were carried out for zeolite A formation. The important parameters for these experiments were the kinds of precursors,their concentration (starting material composition), synthesis time and temperature. All product samples from these experiments were characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and analyzed by gravimetric method. The results show that the favourable sample for this research work which can be prepared with a molar composition of SiO2: Al2O3: 2Na2O: 70H2O by agitation at room temperature for 30 minutes, ageing at room temperature and crystallization at 95Ccentre dot centre dot for 24hrs. The percent yield of favourable result is 70%.

  14. Synthesis and Characterization of Mesoporous Europium (Ⅲ) Silicate Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    Yin Wei

    2005-01-01

    The luminescent nanosized Eu-MCM (1:10) was synthesized by means of sol-gel-assisted self-assembly under basic conditions at room temperature. The results of 29Si-MAS NMR show that the peaks are Q4, Q3, Q2 [(SiO)4-mSi-(OH)m (m=0, 1, 2), at -δ111, -δ103, -δ90], and q3, q2, q1, q0 [(SiO)4-nSi-(O-Eu)n (n=1, 2, 3, 4 ), at -δ83, -δ72, -δ55, -δ47]. The result proves Eu3+ doped Si-O framework. The HRTEM image shows that the regular uniform nanoparticles with a diameter of 15 nm possess large pore with Φ8 nm, which is consistent with the result of N2 adsorption. The patterns of selected-area electron diffraction, XRD, and pore-size distribution plot of Eu-MCM (1:10) show that the sample of Eu-MCM (1:10) possesses the both of crystal and amorphous phases. The FT IR results indicate that the peaks near 970 cm-1 are assigned to the deformation vibration of silanol group. The as-product was calcined at 800 ℃ and the mesoporous material possesses enormous specific areas and large pores, which shows that the mesoporous material is ultrastable.

  15. Advanced Nanostructured Molecular Sieves for Energy Efficient Industrial Separations

    Energy Technology Data Exchange (ETDEWEB)

    Kunhao Li, Michael Beaver

    2012-01-18

    Due to the very small relative volatility difference between propane and propylene, current propane/propylene separation by distillation requires very tall distillation towers (150-250 theoretical plates) and large reflux ratios (up to 15), which is considered to be the most energy consuming large-scale separation process. Adsorptive separation processes are widely considered to be more energy-efficient alternatives to distillation. However, slow diffusion kinetics/mass transport rate through the adsorbent bed often limits the performance of such processes, so further improvements are possible if intra-particle mass transfer rates can be improved. Rive Technology, Inc. is developing and commercializing its proprietary mesoporous zeolite technology for catalysis and separation. With well-controlled intracrystalline mesoporosity, diffusion kinetics through such mesoporous zeolite based catalysts is much improved relative to conventional zeolites, leading to significantly better product selectivity. This 'proof-of-principle' project (DE-EE0003470) is intended to demonstrate that Rive mesoporous zeolite technology can be extended and applied in adsorptive propane/propylene separation and lead to significant energy saving compared to the current distillation process. In this project, the mesoporous zeolite Y synthesis technology was successfully extended to X and A zeolites that are more relevant to adsorbent applications. Mesoporosity was introduced to zeolite X and A for the first time while maintaining adequate adsorption capacity. Zeolite adsorbents were tested for liquid phase separation performance using a pulse flow test unit and the test results show that the separation selectivity of the mesoporous zeolite adsorbent is much closer to optimal for a Simulated Moving Bed (SMB) separation process and the enhanced mesoporosity lead to >100% increase of overall mass transport rate for propane and propylene. These improvements will significantly improve the performance of an adsorptive separation unit for propane/propylene separation compared with traditional zeolite adsorbents. The enhanced transport will allow for more efficient utilization of a given adsorbent inventory by reducing process cycle time, allowing a faster production rate with a fixed amount of adsorbent or smaller adsorbent inventory at a fixed production rate. Smaller adsorbent inventory would also lead to significant savings in the capital cost due to smaller footprint of the equipment. Energy consumption calculation, based on the pulse test results for rived NaX zeolite adsorbent, of a hypothetical moderate-scale SMB propane/propylene separation plant that processes 6000 BPSD refinery grade propylene (70% propylene) will consume about 60-80% less energy (both re-boiler and condenser duties) compared to a C3 splitter that process the same amount of feed. This energy saving also translates to a reduction of 30,000-35,000 tons of CO2 emission per year at this moderate processing rate. The enhancement of mass transport achievable by introduction of controlled mesoporosity to the zeolite also opens the door for the technology to be applied to several other adsorption separation processes such as the separation of xylene isomers by SMB, small- and large scale production of O2/N2 from air by pressure swing adsorption, the separation of CO2 from natural gas at natural gas wellheads, and the purification of ultra-high purity H2 from the off gas produced by steam-methane-reforming.

  16. Estimation of mechanical properties of single wall carbon nanotubes using molecular mechanics approach

    Indian Academy of Sciences (India)

    P Subba Rao; Sunil Anandatheertha; G Narayana Naik; G Gopalakrishnan

    2015-06-01

    Molecular mechanics based finite element analysis is adopted in the current work to evaluate the mechanical properties of Zigzag, Armchair and Chiral Single wall Carbon Nanotubes (SWCNT) of different diameters and chiralities. Three different types of atomic bonds, that is Carbon–Carbon covalent bond and two types of Carbon–Carbon van der Waals bonds are considered in the carbon nanotube system. The stiffness values of these bonds are calculated using the molecular potentials, namely Morse potential function and Lennard-Jones interaction potential function respectively and these stiffness’s are assigned to spring elements in the finite element model of the CNT. The geometry of CNT is built using a macro that is developed for the finite element analysis software. The finite element model of the CNT is constructed, appropriate boundary conditions are applied and the behavior of mechanical properties of CNT is studied.

  17. A molecular organic carbon isotope record of miocene climate changes.

    Science.gov (United States)

    Schoell, M; Schouten, S; Damsté, J S; de Leeuw, J W; Summons, R E

    1994-02-25

    The difference in carbon-13 ((13)C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in (18)O (delta(18)O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (delta(13)C = 25.4 +/- 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C(35) hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing (13)C concentrations in Middle and Late Miocene samples (delta(13)C = -29.5 to -31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone. PMID:17831625

  18. DNA Based Carbon Nanotube Porphyrin Nanohybrids Molecular Recognization and Regeneration

    OpenAIRE

    Riccitelli, Molly M; Zhang, Hanyu; Choi, Jong Hyun

    2013-01-01

    In the search to improve solar cells, scientists are exploring new materials that will provide better current transfer. One material that has emerged as a strong contender is the single walled carbon nanotube (SWNT). Current DNA-SWNT based films combined with chromophores have poor operational lifetimes compared to commercial solar cells. Once exposed to light the chromophore begins to degrade, eventually rendering the solar cell unusable. To solve this problem, we used a method involving mul...

  19. Molecular, radioactive and stable carbon isotope characterization of estuarine particulate organic matter

    OpenAIRE

    Megens, L.; van der Plicht, J.; De Leeuw, JW; Leeuw, Jan W. de; Mook, W.G.

    1998-01-01

    Organic matter in sediments and suspended matter is a complex mixture of constituents with different histories, sources and stabilities. To study these components in a suspended matter sample from the Ems-Dollard Estuary, we used combined molecular analysis with pyrolysis/gas chromatography/mass spectrometry and stable and radioactive carbon isotope analyses of the bulk and separated chemical fractions. Carbohydrates and proteins, ca. 50% of the total organic carbon (TOC), are much younger th...

  20. Synthesis of Heteroaromatic Compounds by Oxidative Aromatization Using an Activated Carbon/Molecular Oxygen System

    Directory of Open Access Journals (Sweden)

    Masahiko Hayashi

    2009-08-01

    Full Text Available A variety of heteroaromatic compounds, such as substituted pyridines, pyrazoles, indoles, 2-substituted imidazoles, 2-substituted imidazoles, 2-arylbenzazoles and pyrimidin-2(1H-ones are synthesized by oxidative aromatization using the activated carbon and molecular oxygen system. Mechanistic study focused on the role of activated carbon in the synthesis of 2-arylbenzazoles is also discussed. In the final section, we will disclose the efficient synthesis of substituted 9,10-anthracenes via oxidative aromatization.

  1. Electronic transport properties of a molecular switch with carbon nanotube electrodes: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P., E-mail: ss_zhaop@ujn.edu.c [School of Science, University of Jinan, Jinan 250022 (China); School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Wang, P.J.; Zhang, Z. [School of Science, University of Jinan, Jinan 250022 (China); Liu, D.S. [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Department of Physics, Jining University, Qufu 273155 (China)

    2010-01-01

    We have studied the electronic transport properties of a new kind of optical molecular switch with two single-walled carbon nanotube (SWCNT) electrodes using first-principles transport calculations. It is shown that the enol form shows an overall higher conductance than the keto form at low-bias voltage, which is independent of the SWCNTs' chirality. Meantime, it is possible to tune the conductance of the molecular switch by changing the chirality of the SWCNTs.

  2. Molecular dynamics simulations of the morphology transformations in unzipped carbon nanotubes

    Science.gov (United States)

    Xu, Jiafang; Zhang, Yingnan; Wang, Tao; Zheng, Xin; Li, Wen; Dong, Zihan; Wang, Wensen

    2016-08-01

    Tuning the assembly of carbon nanomaterials to obtain a kaleidoscope of carbon nanostructures is very important and challenging for the development of nanotechnology. Using molecular dynamics simulations method, we studied the morphology transformations of unzipped CNTs with different unzipping patterns. By modulating the unzipping patterns, the CNTs could self-assemble forming graphene nanoribbons and carbon nanoscrolls. From the energy analyzation, we find that the van der Waals interactions are responsible for the assembly of the unzipped CNTs. This unusual self-assembling method for CNTs could provide clues for further studies on the design of novel nanostructures.

  3. Wetting of Liquid Iron in Carbon Nanotubes and on Graphene Sheets: A Molecular Dynamics Study

    Institute of Scientific and Technical Information of China (English)

    GAO Yu-Feng; YANG Yang; SUN De-Yan

    2011-01-01

    Using molecular dynamics simulations, we study the wetting of liquid iron in a carbon nanotube and on a graphene sheet. It is found that the contact angle of a droplet in a carbon nanotube increases linearly with the increase of wall curvature but is independent of the length of the filled liquid. The contact angle for a droplet on a graphene sheet decreases with the increasing droplet size. The line tension of a droplet on a graphene sheet is also obtained.Detailed studies show that liquid iron near the carbon walls exhibits the ordering tendencies in both the normal and tangential directions.

  4. Molecular and morphological characterization of hydrochar produced by microwave-assisted hydrothermal carbonization of cellulose

    Directory of Open Access Journals (Sweden)

    Marcela Guiotoku

    2012-05-01

    Full Text Available The objective of this work was to characterize the morphology and molecular composition of the hydrochar produced by microwave-assisted hydrothermal carbonization of cellulose. The produced hydrochar consists mainly of aggregate microspheres with about 2.0 µm in diameter, with aliphatic and aromatic structures and the presence of carbonyl functional groups. The aromatic groups are formed mainly by benzofuran-like structures, being chemically different from common cellulose char. Microwave-assisted hydrothermal carbonization yields a functionalized carbon-rich material similar to that produced by the conventional hydrothermal process.

  5. A molecular organic carbon isotope record of Miocene climate changes

    OpenAIRE

    Schoell, M.; Schouten, S.; Sinninghe Damsté, J.S.; J. W. de Leeuw; Summons, R. E.

    1994-01-01

    The difference in carbon-13 (13C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in 18O (δ18O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (δ13C = 25.4 ± 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfu...

  6. Molecular Carbon Chains and Rings in TMC-1

    OpenAIRE

    Cernicharo, José; Fosse, David; Gerin, M.; Cox, Pierre

    2000-01-01

    We present mapping results in several rotational transitions of HC3N, C6H, both cyclic and linear C3H2 and C3H, towards the cyanopolyyne peak of the filamentary dense cloud TMC-1 using the IRAM 30m and MPIfR 100m telescopes. The spatial distribution of the cumulene carbon chain propadienylidene H2C3 (hereafter l-C3H2) is found to deviate significantly from the distributions of the cyclic isomer c-C3H2, HC3N, and C6H which in turn look very similar. The cyclic over linear abundance ratio of C3...

  7. Parametric Study of ReaxFF Simulation Parameters for Molecular Dynamics Modeling of Reactive Carbon Gases.

    Science.gov (United States)

    Jensen, Benjamin D; Bandyopadhyay, Ananyo; Wise, Kristopher E; Odegard, Gregory M

    2012-09-11

    The development of innovative carbon-based materials can be greatly facilitated by molecular modeling techniques. Although the Reax Force Field (ReaxFF) can be used to simulate the chemical behavior of carbon-based systems, the simulation settings required for accurate predictions have not been fully explored. Using the ReaxFF, molecular dynamics (MD) simulations are used to simulate the chemical behavior of pure carbon and hydrocarbon reactive gases that are involved in the formation of carbon structures such as graphite, buckyballs, amorphous carbon, and carbon nanotubes. It is determined that the maximum simulation time step that can be used in MD simulations with the ReaxFF is dependent on the simulated temperature and selected parameter set, as are the predicted reaction rates. It is also determined that different carbon-based reactive gases react at different rates, and that the predicted equilibrium structures are generally the same for the different ReaxFF parameter sets, except in the case of the predicted formation of large graphitic structures with the Chenoweth parameter set under specific conditions.

  8. Recent advances in molecular electronics based on carbon nanotubes.

    Science.gov (United States)

    Bourgoin, Jean-Philippe; Campidelli, Stéphane; Chenevier, Pascale; Derycke, Vincent; Filoramo, Arianna; Goffman, Marcelo F

    2010-01-01

    Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field.

  9. Mechanisms of oxygen reduction reactions for carbon alloy catalysts via first principles molecular dynamics

    International Nuclear Information System (INIS)

    Carbon alloy catalysts (CACs) are one of promising candidates for platinum-substitute cathode catalysts for polymer electrolyte fuel cells. We have investigated possible mechanisms of oxygen reduction reactions (ORRs) for CACs via first-principles-based molecular dynamics simulations. In this contribution, we review possible ORRs at likely catalytic sites of CACs suggested from our simulations. (author)

  10. Evaluation and selection of sensing materials for carbon dioxide (CO 2) sensor by molecular modeling

    NARCIS (Netherlands)

    Chen, X.P.; Wong, C.K.Y.; Yuan, C.A.; Zhang, G.Q.

    2011-01-01

    We report a molecular modeling study to evaluate and select conducting polymers (CPs) as the sensing materials of carbon dioxide (CO2) sensor. The interaction between polymer and gas and the adsorption of the gas molecules in the polymer matrix are investigated. Polymers considered for this work inc

  11. Evaluation and selection of sensing materials for carbon dioxide (CO2) sensor by molecular modeling

    NARCIS (Netherlands)

    Chen, X.P.; Wong, C.K.Y.; Yuan, C.A.; Zhang, G.Q.

    2011-01-01

    We report a molecular modeling study to evaluate and select conducting polymers (CPs) as the sensing materials of carbon dioxide (CO2) sensor. The interaction between polymer and gas and the adsorption of the gas molecules in the polymer matrix are investigated. Polymers considered for this work inc

  12. Collisions of fast, highly stripped carbon, niobium, and lead ions with molecular hydrogen

    International Nuclear Information System (INIS)

    The range of experimental confirmation of our scaling rule for electron loss from a hydrogen atom in collision with a heavy, highly stripped ion has been considerably broadened by new measurements on carbon-, niobium-, and lead-ion projectiles in molecular hydrogen

  13. Molecular and biochemical characterization of carbonic anhydrases of Paracoccidioides

    Science.gov (United States)

    Tomazett, Mariana Vieira; Zanoelo, Fabiana Fonseca; Bailão, Elisa Flávia Cardoso; Bailão, Alexandre Melo; Borges, Clayton Luiz; Soares, Célia Maria de Almeida

    2016-01-01

    Abstract Carbonic anhydrases (CA) belong to the family of zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide to bicarbonate. In the present work, we characterized the cDNAs of four Paracoccidioides CAs (CA1, CA2, CA3, and CA4). In the presence of CO2, there was not a significant increase in fungal ca1, ca2 and ca4 gene expression. The ca1 transcript was induced during the mycelium-to-yeast transition, while ca2 and ca4 gene expression was much higher in yeast cells, when compared to mycelium and mycelium-to-yeast transition. The ca1 transcript was induced in yeast cells recovered directly from liver and spleen of infected mice, while transcripts for ca2 and ca4 were down-regulated. Recombinant CA1 (rCA1) and CA4 (rCA4), with 33 kDa and 32 kDa respectively, were obtained from bacteria. The enzymes rCA1 (β-class) and rCA4 (α-class) were characterized regarding pH, temperature, ions and amino acids addition influence. Both enzymes were stable at pHs 7.5-8.5 and temperatures of 30-35 °C. The enzymes were dramatically inhibited by Hg+2 and activated by Zn+2, while only rCA4 was stimulated by Fe2+. Among the amino acids tested (all in L configuration), arginine, lysine, tryptophan and histidine enhanced residual activity of rCA1 and rCA4. PMID:27560991

  14. Mesh Algorithms for PDE with Sieve I: Mesh Distribution

    Directory of Open Access Journals (Sweden)

    Matthew G. Knepley

    2009-01-01

    Full Text Available We have developed a new programming framework, called Sieve, to support parallel numerical partial differential equation(s (PDE algorithms operating over distributed meshes. We have also developed a reference implementation of Sieve in C++ as a library of generic algorithms operating on distributed containers conforming to the Sieve interface. Sieve makes instances of the incidence relation, or arrows, the conceptual first-class objects represented in the containers. Further, generic algorithms acting on this arrow container are systematically used to provide natural geometric operations on the topology and also, through duality, on the data. Finally, coverings and duality are used to encode not only individual meshes, but all types of hierarchies underlying PDE data structures, including multigrid and mesh partitions. In order to demonstrate the usefulness of the framework, we show how the mesh partition data can be represented and manipulated using the same fundamental mechanisms used to represent meshes. We present the complete description of an algorithm to encode a mesh partition and then distribute a mesh, which is independent of the mesh dimension, element shape, or embedding. Moreover, data associated with the mesh can be similarly distributed with exactly the same algorithm. The use of a high level of abstraction within the Sieve leads to several benefits in terms of code reuse, simplicity, and extensibility. We discuss these benefits and compare our approach to other existing mesh libraries.

  15. Ab initio Molecular Dynamics Study on Small Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    叶林晖; 刘邦贵; 王鼎盛

    2001-01-01

    Ab initio molecular dynamics simulations are performed on small single wall nanotubes. By structural relaxation,the equilibrium C-C bond lengths and bond angles are determined. Our result shows that for both zigzag and armchair nanotubes there are two nonequivalent bond lengths. One bond stretches from that of the graphene sheet, while the other shrinks. Small variations on bond angles are also shown. Energy bands are calculated for the optimized structures. It is found that the intrinsic curvature of the very small nanotube greatly modifies the energy band which can no longer be well described in the tight-binding zone-folding picture. In our calculation very small nanotubes are metallic. The energy per atom fits quite well with the relation of E(R) = E0 + f/R2 even for the extreme small radius. The implications of the results on the properties of small nanotubes are discussed.

  16. Belowground Carbon Cycling Processes at the Molecular Scale: An EMSL Science Theme Advisory Panel Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Hess, Nancy J.; Brown, Gordon E.; Plata, Charity

    2014-02-21

    As part of the Belowground Carbon Cycling Processes at the Molecular Scale workshop, an EMSL Science Theme Advisory Panel meeting held in February 2013, attendees discussed critical biogeochemical processes that regulate carbon cycling in soil. The meeting attendees determined that as a national scientific user facility, EMSL can provide the tools and expertise needed to elucidate the molecular foundation that underlies mechanistic descriptions of biogeochemical processes that control carbon allocation and fluxes at the terrestrial/atmospheric interface in landscape and regional climate models. Consequently, the workshop's goal was to identify the science gaps that hinder either development of mechanistic description of critical processes or their accurate representation in climate models. In part, this report offers recommendations for future EMSL activities in this research area. The workshop was co-chaired by Dr. Nancy Hess (EMSL) and Dr. Gordon Brown (Stanford University).

  17. Molecular Dynamics Study of Carbon Nanotubes/Polyamide Reverse Osmosis Membranes: Polymerization, Structure, and Hydration.

    Science.gov (United States)

    Araki, Takumi; Cruz-Silva, Rodolfo; Tejima, Syogo; Takeuchi, Kenji; Hayashi, Takuya; Inukai, Shigeki; Noguchi, Toru; Tanioka, Akihiko; Kawaguchi, Takeyuki; Terrones, Mauricio; Endo, Morinobu

    2015-11-11

    Carbon nanotubes/polyamide (PA) nanocomposite thin films have become very attractive as reverse osmosis (RO) membranes. In this work, we used molecular dynamics to simulate the influence of single walled carbon nanotubes (SWCNTs) in the polyamide molecular structure as a model case of a carbon nanotubes/polyamide nanocomposite RO membrane. It was found that the addition of SWCNTs decreases the pore size of the composite membrane and increases the Na and Cl ion rejection. Analysis of the radial distribution function of water confined in the pores of the membranes shows that SWCNT+PA nanocomposite membranes also exhibit smaller clusters of water molecules within the membrane, thus suggesting a dense membrane structure (SWCNT+PA composite membranes were 3.9% denser than bare PA). The results provide new insights into the fabrication of novel membranes reinforced with tubular structures for enhanced desalination performance. PMID:26505521

  18. Molecular and stable carbon isotopic compositions of hopanoids in seep carbonates from the South China Sea continental slope

    Science.gov (United States)

    Guan, Hongxiang; Sun, Yongge; Mao, Shengyi; Zhu, Xiaowei; Wu, Nengyou

    2014-10-01

    The lipid biomarkers of hopanoids in cold seep carbonates from the South China Sea continental slope were investigated by gas chromatography-mass spectrometer (GC-MS) and gas chromatography-isotope ratio-mass spectrometer (GC-ir-MS). The distribution of hopanes/hopenes shows a preference for the ‘biological’ 17β(H), 21β(H)-over the ‘geological’ 17α(H), 21β(H)-configuration. This interpretation is in agreement with the strong odd-even preference of long-chain n-alkanes in those samples, suggesting that the ββ hopanes may be the early diagenetic products of biohopanoids and the αβ, βα configurations of hopanes were mainly derived from allochthonous sources contributing to the organic matter of the carbonates. In terms of hopanoid acids, the C30 to C33 17β(H), 21β(H)-hopanoid acids were detected with C32 17β(H), 21β(H)-hopanoid acid being the most abundant. However, there is a significant difference in stable carbon isotopic compostions of the C32 17β(H), 21β(H)-hopanoic acid among samples (-30.7‰ to -69.8‰). The δ13C values match well with the carbon isotopic compositions of SRB-derived iso-/anteiso-C15:0 fatty acids in the samples, which strongly depend on the carbon utilization types by microbe. The most abundant compound of hopanols detected in the samples, C30-17β(H), 21β(H)-hopanol, may be a good indicator of diagenetic product of type I methanotrophs. The molecular and carbon isotopic compositions of hopanoids demonstrate clearly that there is a combination contribution of both SRB and type I or type X methanotrophs to the source organism in the seep carbonates from the South China Sea continental slope.

  19. Molecular Carbon Chains and Rings in TMC-1

    CERN Document Server

    Fosse, D; Gerin, M; Cox, P; Fosse, David; Cernicharo, Jose; Gerin, Maryvonne; Cox, Pierre

    2000-01-01

    We present mapping results in several rotational transitions of HC3N, C6H, both cyclic and linear C3H2 and C3H, towards the cyanopolyyne peak of the filamentary dense cloud TMC-1 using the IRAM 30m and MPIfR 100m telescopes. The spatial distribution of the cumulene carbon chain propadienylidene H2C3 (hereafter l-C3H2) is found to deviate significantly from the distributions of the cyclic isomer c-C3H2, HC3N, and C6H which in turn look very similar. The cyclic over linear abundance ratio of C3H2 increases by a factor of 3 across the filament, with a value of 28 at the cyanopolyyne peak. This abundance ratio is an order of magnitude larger than the range (3 to 5) we observed in the diffuse interstellar medium. The cyclic over linear abundance ratio of C3H also varies by ~2.5 in TMC-1, reaching a maximum value (13) close to the cyanopolyyne peak. These behaviors might be related to competitive processes between ion-neutral and neutral-neutral reactions for cyclic and linear species.

  20. Hexile Sieve Analysis of Prime and Composite Integers

    CERN Document Server

    Creft, Roger

    2012-01-01

    Here we demonstrate a sieve for analysing primes and their composites, using equivalence classes based on the modulo 6 return value as applied to the Natural numbers. Five features of this 'Hexile' sieve are reviewed. The first aspect, is that it narrows the search for primes to one-third of the Natural numbers. The second feature is that we can obtain from the equivalence class formulae, a property of its diophantine equations to distinguish between primes and composites resulting from multiplication of these primes. Thirdly we can from these diophantine formulations ascribe a non-random occurence to not only the composites in the two equivalence classes but by default and as a consequence : non-randomness of occurence to the resident primes. Fourthly we develop a theoretical basis for sieving primes. Of final mention is that the diophantine equations allows another route to a prime counting function using combinatorics or numerical analysis.

  1. Study on the numerical simulation of batch sieving process

    Institute of Scientific and Technical Information of China (English)

    JIAO Hong-guang; MA Jiao; ZHAO Yue-min; CHEN Lun-jian

    2006-01-01

    Screening was widely used in many sectors of industry. However, it is rather incomplete to the cognition of the sieving process for us due to the daedal separation process involving interactions of thousands of particulates. To address this problem, two dimensional numerical simulation of batch sieving process was performed by adopting advanced discrete element method (DEM), which is one of the highly nonlinear digitized dynamic simulative methods and can be used to reveal the quantitative change from particle dimension level. DEM simulation results show that the jam phenomena of sieve-plate apertures of the "blinding particles" in the screen feed can be demonstrated vividly and results also reveal that the velocity of particle moving on the screen plate will vary along with the screen length. This conclusion will be helpful to the design and operation of screen.

  2. Molecular simulation studies of CO2 adsorption by carbon model compounds for carbon capture and sequestration applications.

    Science.gov (United States)

    Liu, Yangyang; Wilcox, Jennifer

    2013-01-01

    Effects of oxygen-containing surface functionalities on the adsorption of mixtures including CO(2)/CH(4), CO(2)/N(2), and CO(2)/H(2)O have been investigated in the current work. Together with Bader charge analysis, electronic structure calculations have provided the initial framework comprising both the geometry and corresponding charge information required to carry out statistical-based molecular simulations. The adsorption isotherms and selectivity of CO(2) from CO(2)/N(2), CO(2)/CH(4), and CO(2)/H(2)O gas mixtures were determined by grand canonical Monte Carlo simulations at temperature/pressure conditions relevant to carbon capture and sequestration applications. The interactions between the surfaces with induced polarity and nonpolar/polar molecules have been investigated. It has been observed that, due to the induced polarity of the surface functionalization, the selectivity of CO(2) over CH(4) increases from approximately 2 to higher than 5, and the selectivity of CO(2) over N(2) increases from approximately 5 to 20, especially in the low-pressure regime. However, water vapor will always preferentially adsorb over CO(2) in carbon-based systems containing oxygen functionalized surfaces at conditions relevant to carbon capture application. Molecular simulation results indicate that the surface chemistry in micropores is tunable thereby influencing the selectivity for enhanced uptake of CO(2).

  3. How surface fire in Siberian Scots pine forests affects soil organic carbon in the forest floor: Stocks, molecular structure, and conversion to black carbon (charcoal)

    OpenAIRE

    Czimczik, Claudia I; Preston, Caroline M; Schmidt, Michael W I; Schulze, Ernst-Detlef

    2003-01-01

    [1] In boreal forests, fire is a frequent disturbance and converts soil organic carbon (OC) to more degradation-resistant aromatic carbon, i.e., black carbon (BC) which might act as a long-term atmospheric-carbon sink. Little is known on the effects of fires on boreal soil OC stocks and molecular composition. We studied how a surface fire affected the composition of the forest floor of Siberian Scots pine forests by comparing the bulk elemental composition, molecular structure (13C-MAS NMR), ...

  4. Electron microscopy investigation of interface between carbon fiber and ultra high molecular weight polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Stepashkin, A.A.; Chukov, D.I., E-mail: dil_chukov@yahoo.com; Gorshenkov, M.V.; Tcherdyntsev, V.V.; Kaloshkin, S.D.

    2014-02-15

    Highlights: • Effect of the carbon fibers surface treatments on the adhesive interactions in UHMWPE composites was studied. • Air oxidation of carbon filler ensures most significant increase in adhesion interaction in UHMWPE based composites. • Nanosized UHMWPE fibers with 20–40 nm in diameter and with 6–10 μm in length, was observed on the surface of carbon fibers. -- Abstract: Scanning electron microscopy was used to investigate the surface of initial and modified high-strength and high-modulus carbon fibers as well as interfaces in the ultra high molecular weight polyethylene, filled with above-mentioned fibers. Effect of the fibers surface modifying method on the adhesive interactions in composites was studied. It was observed that interaction of matrix with a modified surface of fibers results in a formation of bonds with strength higher than the yield strength of the polymer. It results in a formation of long nanosized polymer wires at tensile fracture of composites.

  5. Self-healing in defective carbon nanotubes: a molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Chenli; Shen Huishen [Department of Engineering Mechanics, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2007-09-26

    The self-healing phenomenon of defective single-walled carbon nanotubes (SWCNTs) is observed at the atomic level from a molecular dynamics (MD) simulation test. The ideal network of carbon nanotubes is unable to avoid damage under destabilizing loads at high temperature, leading to unforeseen patterns in bond breakages and vacancy defects on the wall. We observe that (10, 10) and (17, 0) carbon nanotubes containing such vacancies are energetically unstable. In the situation of unloading or increasing temperature, the local structures around the vacancies reconstruct through dangling bond saturation, forming non-hexagonal rings, 5-7-7-5 defects or an ideal graphite network. We find that a defective carbon nanotube with large vacancies is re-mendable, and the Stone-Wales (SW) construction is energetically preferred in self-healing processes.

  6. Trends in nanoscale mechanics mechanics of carbon nanotubes, graphene, nanocomposites and molecular dynamics

    CERN Document Server

    2014-01-01

    This book contains a collection of the state-of-the-art reviews written by the leading researchers in the areas of nanoscale mechanics, molecular dynamics, nanoscale modeling of nanocomposites and mechanics of carbon nanotubes. No other book has reviews of the recent discoveries such as a nanoscale analog of the Pauli’s principle, i.e., effect of the spatial exclusion of electrons or the SEE effect, a new Registry Matrix Analysis for the nanoscale interfacial sliding and new data on the effective viscosity of interfacial electrons in nanoscale stiction at the interfaces. This volume is also an exceptional resource on the well tested nanoscale modeling of carbon nanotubes and nanocomposites, new nanoscale effects, unique evaluations of the effective thickness of carbon nanotubes under different loads, new data on which size of carbon nanotubes is safer and many other topics. Extensive bibliography concerning all these topics is included along with the lucid short reviews. Numerous illustrations are provided...

  7. Adsorption of benzene, cyclohexane and hexane on ordered mesoporous carbon.

    Science.gov (United States)

    Wang, Gang; Dou, Baojuan; Zhang, Zhongshen; Wang, Junhui; Liu, Haier; Hao, Zhengping

    2015-04-01

    Ordered mesoporous carbon (OMC) with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound (VOC) disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal. PMID:25872710

  8. Three-dimensional array foci of generalized Fibonacci photon sieves

    CERN Document Server

    Zhang, Junyong; Zhu, Jianqiang; Lin, Zunqi

    2015-01-01

    We present a new kind of photon sieves on the basis of the generalized Fibonacci sequences. The required numbers and locations of axial foci can be designed by generalized Fibonacci photon sieves (GFiPS). Furthermore, the three-dimensional array foci can be controllable and adjustable by the optical path difference scaling factor (OPDSF) when the amplitude modulation is replaced with the phase modulation. Multi-focal technologies can be applied to nano-imaging, THZ, laser communications, direct laser writing, optical tweezers or atom trapping, etc.

  9. The effect of molecular mobility on electronic transport in carbon nanotube-polymer composites and networks

    International Nuclear Information System (INIS)

    A multiscale modeling approach to the prediction of electrical conductivity in carbon nanotube (CNT)–polymer composite materials is developed, which takes into account thermally activated molecular mobility of the matrix and the CNTs. On molecular level, a tight-binding density functional theory and non-equilibrium Green's function method are used to calculate the static electron transmission function in the contact between two metallic carbon nanotubes that corresponds to electron transport at 0 K. For higher temperatures, the statistical distribution of effective contact resistances is considered that originates from thermal fluctuations of intermolecular distances caused by molecular mobility of carbon nanotube and the polymer matrix. Based on this distribution and using effective medium theory, the temperature dependence of macroscopic electrical resistivity for CNT-polymer composites and CNT mats is calculated. The predicted data indicate that the electrical conductivity of the CNT-polymer composites increases linearly with temperature above 50 K, which is in a quantitative agreement with the experiments. Our model predicts a slight nonlinearity in temperature dependence of electric conductivity at low temperatures for percolated composites with small CNT loading. The model also explains the effect of glass transition and other molecular relaxation processes in the polymer matrix on the composite electrical conductivity. The developed multiscale approach integrates the atomistic charge transport mechanisms in percolated CNT-polymer composites with the macroscopic response and thus enables direct comparison of the prediction with the measurements of macroscopic material properties

  10. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    Science.gov (United States)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  11. Ancient low-molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw.

    Science.gov (United States)

    Drake, Travis W; Wickland, Kimberly P; Spencer, Robert G M; McKnight, Diane M; Striegl, Robert G

    2015-11-10

    Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high-temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low-molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters. PMID:26504243

  12. Black Carbon in Estuarine (Coastal) High-molecular-weight Dissolved Organic Matter

    Science.gov (United States)

    Mannino, Antonio; Harvey, H. Rodger

    2003-01-01

    Dissolved organic matter (DOM) in the ocean constitutes one of the largest pools of organic carbon in the biosphere, yet much of its composition is uncharacterized. Observations of black carbon (BC) particles (by-products of fossil fuel combustion and biomass burning) in the atmosphere, ice, rivers, soils and marine sediments suggest that this material is ubiquitous, yet the contribution of BC to the ocean s DOM pool remains unknown. Analysis of high-molecular-weight DOM isolated from surface waters of two estuaries in the northwest Atlantic Ocean finds that BC is a significant component of DOM, suggesting that river-estuary systems are important exporters of BC to the ocean through DOM. We show that BC comprises 4-7% of the dissolved organic carbon (DOC) at coastal ocean sites, which supports the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition. Flux calculations suggest that BC could be as important as vascular plant-derived lignin in terms of carbon inputs to the ocean. Production of BC sequesters fossil fuel- and biomass-derived carbon into a refractory carbon pool. Hence, BC may represent a significant sink for carbon to the ocean.

  13. 3D molecular line formation in dwarf carbon-enhanced metal-poor stars

    CERN Document Server

    Behara, N T; Bonifacio, P; Sbordone, L; Hernandez, J I Gonzalez; Caffau, E

    2009-01-01

    We present a detailed analysis of the carbon and nitrogen abundances of two dwarf carbon-enhanced metal-poor (CEMP) stars: SDSS J1349-0229 and SDSS J0912+0216. We also report the oxygen abundance of SDSS J1349-0229. These stars are metal-poor, with [Fe/H] < -2.5, and were selected from our ongoing survey of extremely metal-poor dwarf candidates from the Sloan Digital SkySurvey (SDSS). The carbon, nitrogen and oxygen abundances rely on molecular lines which form in the outer layers of the stellar atmosphere. It is known that convection in metal-poor stars induces very low temperatures which are not predicted by `classical' 1D stellar atmospheres. To obtain the correct temperature structure, one needs full 3D hydrodynamical models. Using CO5BOLD 3D hydrodynamical model atmospheres and the Linfor3D line formation code, molecular lines of CH, NH, OH and C2 were computed, and 3D carbon, nitrogen and oxygen abundances were determined. The resulting carbon abundances were compared to abundances derived using atom...

  14. Molecular Line Observations of a Carbon-Chain-Rich Core L492

    CERN Document Server

    Hirota, T; Hirota, Tomoya; Yamamoto, Satoshi

    2006-01-01

    We report on molecular abundances and distributions in a starless dense core L492. We have found that the abundances of carbon-chain molecules such as CCS, C$_{3}$S, HC$_{3}$N, HC$_{5}$N, and HC$_{7}$N are comparable to those in chemically young dark cloud cores called "carbon-chain--producing regions", such as L1495B, L1521B, L1521E, and TMC-1. This is the first dark cloud core with extremely rich in carbon-chain-molecules that is found outside the Taurus region. In addition, the deuterium fractionation ratios of DNC/HNC and DCO$^{+}$/HCO$^{+}$ are also comparable to those in carbon-chain--producing regions, being significantly lower than those in the evolved prestellar cores such as L1498 and L1544. On the other hand, the abundances of NH$_{3}$ and N$_{2}$H$^{+}$ are systematically higher than those in carbon-chain--producing regions. Our mapping observations reveal that the central hole of molecular distributions, which were reported for CCS and C$^{34}$S in evolved prestellar cores is not significant in L...

  15. A molecular mechanics approach for analyzing tensile nonlinear deformation behavior of single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    Yu Wang; Daining Fang; Ai Kah Soh; Bin Liu

    2007-01-01

    In this paper, by capturing the atomic informa-tion and reflecting the behaviour governed by the nonlin-ear potential function, an analytical molecular mechanics approach is proposed. A constitutive relation for single-walled carbon nanotubes (SWCNT's) is established to describe the nonlinear stress-strain curve of SWCNT's and to predict both the elastic properties and breaking strain of SWCNT's during tensile deformation. An analysis based on the virtual internal bond (VIB) model proposed by P. Zhang et al. is also presented for comparison. The results indicate that the proposed molecular mechanics approach is indeed an acceptable analytical method for analyzing the mechanical behavior of SWCNT's.

  16. 两种吸附剂对SF6分解特征组分吸附的实验与分析%A Comparative Experimental Study on the Interaction of SF6 Feature Decomposition Products With Alumina and Molecular Sieve kdhF-03

    Institute of Scientific and Technical Information of China (English)

    唐炬; 曾福平; 梁鑫; 裘吟君; 袁静帆; 张晓星

    2013-01-01

    研究吸附剂对在局部放电下SF6分解组分的影响是探究利用分解组分诊断 SF6电气设备内部早期绝缘缺陷的重要内容。为此,在建立的特定吸附实验研究平台上,选用SF6电气设备中最常用的活性氧化铝和kdhF-03型分子筛吸附剂,对局部放电(partial discharge,PD)下产生的4种SF6稳定分解特征组分(CF4、CO2、SO2F2和SOF2)进行吸收特性研究,利用气相色谱仪和质谱联用仪定时检测气室内气体残余量,结合吸附量和等温吸附线对吸附机制和作用过程进行了深入分析。结果表明:两种吸附剂几乎不吸附 CF4,对CO2略有吸附,但对SO2F2和SOF2有较强的吸附能力,吸附量由多到少依次为SOF2>SO2F2>CO2>CF4。因此,在利用特征组分含量及变化规律辨识 SF6气体绝缘设备的绝缘缺陷时,必须考虑吸附剂的影响。实验也发现选用SOF2+SO2整体作为辨识 SF6设备内部绝缘缺陷的一种特征组分更有效。%As the decomposition products of SF6 could be affected by the absorbent, it is important to study this kind of influence before we use the decomposition products of SF6 to diagnose faults in SF6 electrical equipment. Two kinds of absorbents were widely used in power apparatus, namely activated alumina and molecular sieve kdhF-03, were chosen as the samples. The absorption characteristics of this two absorbents on the four stable decomposition products of SF6, namely CF4, CO2, SO2F2 and SOF2, were investigated based on our adsorption experiment platform. The concentration of the decomposition products was detected by a gas chromatograph and a gas chromatograph-mass spectrometer. And then the adsorption mechanism and reaction process of the two absorbent were analyzed based on the adsorption capacity and adsorption isotherms. The results show that the two kinds of adsorbents hardly adsorb CF4, and slightly adsorb CO2, but have strong adsorption ability on SO2F2 and SOF2. The

  17. A possible formation mechanism of double-walled and multi-walled carbon nanotube: a molecular dynamics study

    Science.gov (United States)

    Han, Dianrong; Luo, Chenglin; Dai, Yafei; Zhu, Xingfeng

    2016-09-01

    Molecular dynamics simulations based on an empirical potential were performed to study the interaction of graphene nanoribbons and the single-walled carbon nanotubes. The results indicated that a piece of graphene nanoribbon can form a tube structure inside or outside single-walled carbon nanotubes spontaneously under certain condition. Based on this kind of spontaneous phenomenon, we proposed a new possible formation mechanism of double walled carbon nanotube and multi-walled carbon nanotube, and suggested the possibility of controlling the structure of double-walled carbon nanotube and/or multi-walled carbon nanotube.

  18. Anisotropy of the water-carbon interaction: molecular simulations of water in low-diameter carbon nanotubes.

    Science.gov (United States)

    Pérez-Hernández, Guillermo; Schmidt, Burkhard

    2013-04-14

    Effective Lennard-Jones models for the water-carbon interaction are derived from existing high-level ab initio calculations of water adsorbed on graphene models. The resulting potential energy well (εCO + 2εCH ≈ 1 kJ mol(-1)) is deeper than most of the previously used values in the literature on water in carbon nanotubes (CNTs). Moreover, a substantial anisotropy of the water-carbon interaction (εCO ≈ 2εCH) is obtained, which is neglected in most of the literature. We systematically investigate the effect of this anisotropy on structure and dynamics of TIP5P water confined in narrow, single-walled CNTs by means of molecular dynamics simulations for T = 300 K. While for isotropic models water usually forms one-dimensional, ordered chains inside (6,6) CNTs, we find frequent chain ruptures in simulations with medium to strongly anisotropic potentials. Here, the water molecules tend to form denser clusters displaying a liquid-like behaviour, allowing for self-diffusion along the CNT axis, in contrast to all previous simulations employing spherical (εCH = 0) interaction models. For (7,7) CNTs we observe structures close to trigonal, helical ice nanotubes which exhibit a non-monotonous dependence on the anisotropy of the water-carbon interaction. Both for vanishing and for large values of εCH we find increased fluctuations leading to a more liquid-like behaviour, with enhanced axial diffusion. In contrast, structure and dynamics of water inside (8,8) CNTs are found to be almost independent of the anisotropy of the underlying potential, which is attributed to the higher stability of the non-helical fivefold water prisms. We predict this situation to also prevail for larger CNTs, as the influence of the water-water interaction dominates over that of the water-carbon interaction.

  19. Complex and distributional weights for sieved ultraspherical polynomials

    Directory of Open Access Journals (Sweden)

    Jairo A. Charris

    1996-01-01

    Full Text Available Contour integral and distributional orthogonality of sieved ultraspherical polynomials are established for values of the parameters outside the natural range of orthogonality by positive measures on the real line. A general representation theorem for moment functionals is included.

  20. Factoring integers with large prime variations of the quadratic sieve

    NARCIS (Netherlands)

    Boender, H.; Riele, H.J.J. te

    1995-01-01

    We present the results of many factorization runs with the single and double large prime variations (PMPQS, and PPMPQS, respectively) of the quadratic sieve factorization method on SGI workstations, and on a Cray C90 vectorcomputer. Experiments with 71--, 87--, and 99--digit numbers show that for ou

  1. Ultra-broadband achromatic imaging with diffractive photon sieves

    Science.gov (United States)

    Zhao, Xiaonan; Hu, Jingpei; Lin, Yu; Xu, Feng; Zhu, Xiaojun; Pu, Donglin; Chen, Linsen; Wang, Chinhua

    2016-06-01

    Diffractive optical elements suffer from large chromatic aberration due to the strong wavelength-dependent nature in diffraction phenomena, and therefore, diffractive elements can work only at a single designed wavelength, which significantly limits the applications of diffractive elements in imaging. Here, we report on a demonstration of a wavefront coded broadband achromatic imaging with diffractive photon sieves. The broadband diffraction imaging is implemented with a wavefront coded pinhole pattern that generates equal focusing power for a wide range of operating wavelength in a single thin-film element without complicated auxiliary optical system. Experimental validation was performed using an UV-lithography fabricated wavefront coded photon sieves. Results show that the working bandwidth of the wavefront coded photon sieves reaches 28 nm compared with 0.32 nm of the conventional one. Further demonstration of the achromatic imaging with a bandwidth of 300 nm is also performed with a wavefront coded photon sieves integrated with a refractive element.

  2. The effect of empirical potential functions on modeling of amorphous carbon using molecular dynamics method

    International Nuclear Information System (INIS)

    Empirical potentials have a strong effect on the hybridization and structure of amorphous carbon and are of great importance in molecular dynamics (MD) simulations. In this work, amorphous carbon at densities ranging from 2.0 to 3.2 g/cm3 was modeled by a liquid quenching method using Tersoff, 2nd REBO, and ReaxFF empirical potentials. The hybridization, structure and radial distribution function G(r) of carbon atoms were analyzed as a function of the three potentials mentioned above. The ReaxFF potential is capable to model the change of the structure of amorphous carbon and MD results are in a good agreement with experimental results and density function theory (DFT) at low density of 2.6 g/cm3 and below. The 2nd REBO potential can be used when amorphous carbon has a very low density of 2.4 g/cm3 and below. Considering the computational efficiency, the Tersoff potential is recommended to model amorphous carbon at a high density of 2.6 g/cm3 and above. In addition, the influence of the quenching time on the hybridization content obtained with the three potentials is discussed.

  3. Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

    Science.gov (United States)

    Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

    1988-01-01

    Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

  4. The effect of empirical potential functions on modeling of amorphous carbon using molecular dynamics method

    Energy Technology Data Exchange (ETDEWEB)

    Li, Longqiu, E-mail: longqiuli@gmail.com [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001 (China); Xu, Ming; Song, Wenping [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001 (China); Ovcharenko, Andrey [Western Digital Corporation, San Jose, CA (United States); Zhang, Guangyu; Jia, Ding [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001 (China)

    2013-12-01

    Empirical potentials have a strong effect on the hybridization and structure of amorphous carbon and are of great importance in molecular dynamics (MD) simulations. In this work, amorphous carbon at densities ranging from 2.0 to 3.2 g/cm{sup 3} was modeled by a liquid quenching method using Tersoff, 2nd REBO, and ReaxFF empirical potentials. The hybridization, structure and radial distribution function G(r) of carbon atoms were analyzed as a function of the three potentials mentioned above. The ReaxFF potential is capable to model the change of the structure of amorphous carbon and MD results are in a good agreement with experimental results and density function theory (DFT) at low density of 2.6 g/cm{sup 3} and below. The 2nd REBO potential can be used when amorphous carbon has a very low density of 2.4 g/cm{sup 3} and below. Considering the computational efficiency, the Tersoff potential is recommended to model amorphous carbon at a high density of 2.6 g/cm{sup 3} and above. In addition, the influence of the quenching time on the hybridization content obtained with the three potentials is discussed.

  5. Improved wear performance of ultra high molecular weight polyethylene coated with hydrogenated diamond like carbon

    OpenAIRE

    Puértolas, J. A.; Martínez-Nogués, V.; Martínez-Morlanes, M. J.; Mariscal, M. D.; Medel, F. J.; López-Santos, Carmen; Yubero, Francisco

    2010-01-01

    Hydrogenated diamond like carbon (DLCH) thin films were deposited on medical grade ultra high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition. The DLCH coating thicknesses ranged from 250 to 700. nm. The substrates were disks made of UHMWPEs typically used for soft components in artificial joints, namely virgin GUR 1050 and highly crosslinked (gamma irradiated in air to 100. kGy) UHMWPEs. Mechanical and tribological properties under bovine s...

  6. Ancient low–molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw

    OpenAIRE

    Drake, Travis W.; Wickland, Kimberly P.; Spencer, Robert G.M.; McKnight, Diane M.; Striegl, Robert G.

    2015-01-01

    To our knowledge, this study is the first to directly link rapid microbial consumption of ancient permafrost-derived dissolved organic carbon (DOC) to CO2 production using a novel bioreactor. Rapid mineralization of the freshly thawed DOC was attributed to microbial decomposition of low–molecular-weight organic acids, which were completely consumed during the experiments. Our results indicate that substantial biodegradation of permafrost DOC occurs immediately after thaw and before downstream...

  7. Molecular Dynamics Simulation Study of Carbon-Nanotube Oscillator in Graphene Nanoribbon Trench

    OpenAIRE

    Lee, Eunae; Kang, Jeong Won; Kim, Ki-Sub; Kwon, Oh-Kuen

    2016-01-01

    Graphene/carbon-nanotube (CNT) hybrid material can be useful in energy storage and nanoelectronic technologies. Here we address the CNT-oscillator encapsulated in a graphene-nanoribbon (GNR) trench as a novel design, and investigate its properties via classical molecular dynamics simulations. Since the energy barrier was very low while the CNT was encapsulated in the GNR trench, the CNT absorbed on the GNR surface could easily be encapsulated in the GNR trench. MD simulations showed that the ...

  8. Molecular Simulation of Hydrogen Adsorption Density in Single-Walled Carbon Nanotubes and Multilayer Adsorption Mechanism

    Institute of Scientific and Technical Information of China (English)

    Lianquan GUO; Changxiang MA; Shuai WANG; He MA; Xin LI

    2005-01-01

    The adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) was studied by molecular dynamics (MD)sim.lation. It was found that the hydrogen molecules distribute regularly inside and outside of the tube. Density distribution was computed for H2 molecule. Theoretical analysis of the result showed the multilayer adsorption mechanism of SWCNTs. The storage of H2 in SWCNTs is computed, which provides essential theoretical reference for further study of hydrogen adsorption in SWCNTs.

  9. Molecular Dynamical Simulation of Water/Ice Phase Transitions within Carbon Nanotubes under Various Pressures

    Institute of Scientific and Technical Information of China (English)

    YIN Bing; DONG Shun-Le

    2009-01-01

    A molecular dynamics simulation is performed for water confined within carbon nanotubes with diameters 11.00 (A) and 12.38 (A).Under pressures from 0.1 MPa to 500MPa the simulations are carried out by cooling from 300K to 240 K.Water molecules tend to transform from disordered to ordered with different configurations (square,pentagonal,hexagonal and hexagonal plus a chain).It is concluded that denser structures may appear under high pressures.

  10. Molecular dynamics simulations of defect production in graphene by carbon irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Asencio, J.; Caturla, M.J., E-mail: mj.caturla@ua.es

    2015-06-01

    We present molecular dynamics simulations with empirical potentials to study the type of defects produced when irradiating graphene with low energy carbon ions (100 eV and 200 eV) and different dose rates. Simulations show the formation of very stable structures such as dimers, single chains of carbons and double chains of carbons. These structures are similar to those described in the literature, observed experimentally when irradiating graphene. For high doses or dose rates, the formation of nanopores is observed, similar to previous results by other authors for higher energies of the implanted ions. These simulations show how tunning the different parameters of irradiation conditions can be used to selectively create defects in graphene.

  11. Gas solubility of carbon dioxide and of oxygen in cyclohexanol by experiment and molecular simulation

    International Nuclear Information System (INIS)

    Highlights: ► Gas solubility measurements of carbon dioxide in liquid cyclohexanol are reported. ► Gas solubility measurements of oxygen in liquid cyclohexanol are reported. ► Henry’s law constant data is determined from the present experimental results. ► Very good agreement between experiment and molecular simulation is achieved. ► Ambiguity for the Henry’s law constant of oxygen in cyclohexanol is resolved. - Abstract: Henry’s law constant data of carbon dioxide and of oxygen in liquid cyclohexanol are determined at temperatures between (303 and 392) K by means of a precise experimental high-pressure view-cell technique with a synthetic method. Furthermore, molecular simulations are carried out with a molecular mixture model, based on the modified Lorentz–Berthelot combination rule that contains one binary interaction parameter which is adjusted to one experimental Henry’s law constant for each binary mixture. The molecular model yields good results for the Henry’s law constant over the entire temperature range.

  12. Molecular scale buckling mechanics in individual aligned single-wall carbon nanotubes on elastomeric substrates.

    Science.gov (United States)

    Khang, Dahl-Young; Xiao, Jianliang; Kocabas, Coskun; MacLaren, Scott; Banks, Tony; Jiang, Hanqing; Huang, Yonggang Y; Rogers, John A

    2008-01-01

    We have studied the scaling of controlled nonlinear buckling processes in materials with dimensions in the molecular range (i.e., approximately 1 nm) through experimental and theoretical studies of buckling in individual single-wall carbon nanotubes on substrates of poly(dimethylsiloxane). The results show not only the ability to create and manipulate patterns of buckling at these molecular scales, but also, that analytical continuum mechanics theory can explain, quantitatively, all measurable aspects of this system. Inverse calculation applied to measurements of diameter-dependent buckling wavelengths yields accurate values of the Young's moduli of individual SWNTs. As an example of the value of this system beyond its use in this type of molecular scale metrology, we implement parallel arrays of buckled SWNTs as a class of mechanically stretchable conductor.

  13. Carbon Electrode-Molecule Junctions: A Reliable Platform for Molecular Electronics.

    Science.gov (United States)

    Jia, Chuancheng; Ma, Bangjun; Xin, Na; Guo, Xuefeng

    2015-09-15

    The development of reliable approaches to integrate individual or a small collection of molecules into electrical nanocircuits, often termed "molecular electronics", is currently a research focus because it can not only overcome the increasing difficulties and fundamental limitations of miniaturization of current silicon-based electronic devices, but can also enable us to probe and understand the intrinsic properties of materials at the atomic- and/or molecular-length scale. This development might also lead to direct observation of novel effects and fundamental discovery of physical phenomena that are not accessible by traditional materials or approaches. Therefore, researchers from a variety of backgrounds have been devoting great effort to this objective, which has started to move beyond simple descriptions of charge transport and branch out in different directions, reflecting the interdisciplinarity. This Account exemplifies our ongoing interest and great effort in developing efficient lithographic methodologies capable of creating molecular electronic devices through the combination of top-down micro/nanofabrication with bottom-up molecular assembly. These devices use nanogapped carbon nanomaterials (such as single-walled carbon nanotubes (SWCNTs) and graphene), with a particular focus on graphene, as point contacts formed by electron beam lithography and precise oxygen plasma etching. Through robust amide linkages, functional molecular bridges terminated with diamine moieties are covalently wired into the carboxylic acid-functionalized nanogaps to form stable carbon electrode-molecule junctions with desired functionalities. At the macroscopic level, to improve the contact interface between electrodes and organic semiconductors and lower Schottky barriers, we used SWCNTs and graphene as efficient electrodes to explore the intrinsic properties of organic thin films, and then build functional high-performance organic nanotransistors with ultrahigh responsivities

  14. In silico carbon molecular beam epitaxial growth of graphene on the h-BN substrate: carbon source effect on van der Waals epitaxy

    Science.gov (United States)

    Lee, Jonghoon; Varshney, Vikas; Park, Jeongho; Farmer, Barry L.; Roy, Ajit K.

    2016-05-01

    Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon molecular beam epitaxy (CMBE) techniques using solid carbon sublimation have reported relatively poor quality of the graphene. In this article, the CMBE growth of graphene on the h-BN substrate is numerically studied in order to identify the effect of the carbon source on the quality of the graphene film. The carbon molecular beam generated by the sublimation of solid carbon source materials such as graphite and glassy carbon is mostly composed of atomic carbon, carbon dimers and carbon trimers. Therefore, the graphene film growth becomes a complex process involving various deposition characteristics of a multitude of carbon entities. Based on the study of surface adsorption and film growth characteristics of these three major carbon entities comprising graphite vapour, we report that carbon trimers convey strong traits of vdW epitaxy prone to high quality graphene growth, while atomic carbon deposition is a surface-reaction limited process accompanied by strong chemisorption. The vdW epitaxial behaviour of carbon trimers is found to be substantial enough to nucleate and develop into graphene like planar films within a nanosecond of high flux growth simulation, while reactive atomic carbons tend to impair the structural integrity of the crystalline h-BN substrate upon deposition to form an amorphous interface between the substrate and the growing carbon film. The content of reactive atomic carbons in the molecular beam is suspected to be the primary cause of low quality graphene reported in the literature. A possible optimization of the molecular beam composition towards the synthesis of better quality graphene films is suggested.Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon

  15. Molecular investigations into a globally important carbon pool: Permafrost-protected carbon in Alaskan soils

    Science.gov (United States)

    Waldrop, M.P.; Wickland, K.P.; White, Rickie; Berhe, A.A.; Harden, J.W.; Romanovsky, V.E.

    2010-01-01

    The fate of carbon (C) contained within permafrost in boreal forest environments is an important consideration for the current and future carbon cycle as soils warm in northern latitudes. Currently, little is known about the microbiology or chemistry of permafrost soils that may affect its decomposition once soils thaw. We tested the hypothesis that low microbial abundances and activities in permafrost soils limit decomposition rates compared with active layer soils. We examined active layer and permafrost soils near Fairbanks, AK, the Yukon River, and the Arctic Circle. Soils were incubated in the lab under aerobic and anaerobic conditions. Gas fluxes at -5 and 5 ??C were measured to calculate temperature response quotients (Q10). The Q10 was lower in permafrost soils (average 2.7) compared with active layer soils (average 7.5). Soil nutrients, leachable dissolved organic C (DOC) quality and quantity, and nuclear magnetic resonance spectroscopy of the soils revealed that the organic matter within permafrost soils is as labile, or even more so, than surface soils. Microbial abundances (fungi, bacteria, and subgroups: methanogens and Basidiomycetes) and exoenzyme activities involved in decomposition were lower in permafrost soils compared with active layer soils, which, together with the chemical data, supports the reduced Q10 values. CH4 fluxes were correlated with methanogen abundance and the highest CH4 production came from active layer soils. These results suggest that permafrost soils have high inherent decomposability, but low microbial abundances and activities reduce the temperature sensitivity of C fluxes. Despite these inherent limitations, however, respiration per unit soil C was higher in permafrost soils compared with active layer soils, suggesting that decomposition and heterotrophic respiration may contribute to a positive feedback to warming of this eco region. Published 2010. This article is a US Government work and is in the public domain in the

  16. Ab initio study of transport properties of an all-carbon molecular switch based on C20 molecule

    Institute of Scientific and Technical Information of China (English)

    OUYANG Fang-ping; XU Hui

    2007-01-01

    Choosing closed-ended armchair (5, 5) singlewall carbon nanotubes (CCNTs) as electrodes, we have investigated the electron transport properties across a carbon molecular junction consisting of a C20 molecule sandwiched between two semi-infinite carbon nanotubes. It is shown that the Landauer conductance of this carbon hybrid system can be tuned within several orders of magnitude not only by varying the tube-C20 distance, but more importantly by changing the orientation of the C20 molecule and rotating the C20 molecule or one of the tubes around the symmetry axis of the system at fixed distances. This fact could make this all-carbon molecular system a possible candidate for a nanoelectronic switching device. Moreover, our study also reveals that molecular configuration selection and structural relaxation would play an important role in the design of such devices.

  17. Molecular simulation of the diffusion of uranyl carbonate species in aqueous solution

    Science.gov (United States)

    Kerisit, Sebastien; Liu, Chongxuan

    2010-09-01

    Potential-based molecular dynamics simulations of aqueous uranyl carbonate species (M xUO 2(CO 3) y2+2x-2y with M = Mg, Ca, or Sr) were carried out to gain molecular-level insight into the hydration properties of these species. The simulation results were used to estimate the self-diffusion coefficients of these uranyl carbonate species, which often dominate uranyl speciation in groundwater systems. The diffusion coefficients obtained for the monoatomic alkaline-earth cations and polyatomic ions (uranyl, carbonate, and uranyl tri-carbonate) were compared with those calculated from the Stokes-Einstein (SE) equation and its variant formulation by Impey et al. (1983). Our results show that the equation of Impey et al. (1983), originally formulated for monovalent monoatomic ions, can be extended to divalent monoatomic ions, with some success in reproducing the absolute values and the overall trend determined from the molecular dynamics simulations, but not to polyatomic ions, for which the hydration shell is not spherically symmetrical. Despite the quantitative failure of both SE formulations, a plot of the diffusion coefficients of the uranyl carbonate complexes as a function of the inverse of the equivalent spherical radius showed that a general linear dependence is observed for these complexes as expected from the SE equation. The nature of the alkaline-earth cation in the uranyl carbonate complexes was not found to have a significant effect on the ion's diffusion coefficient, which suggests that the use of a single diffusion coefficient for different alkaline-earth uranyl carbonate complexes in microscopic diffusion models is appropriate. The potential model reproduced well published quantum mechanical and experimental data of UO(CO)32x-4 and of the individual constituent ions, and therefore is expected to offer reliable predictions of the structure of magnesium and strontium uranyl carbonate aqueous species, for which there is no structural data available to date

  18. Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations

    International Nuclear Information System (INIS)

    In this dissertation, we will present a systematic study of structures of fullerenes ranging from C20 to C100 by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks

  19. Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, B.

    1993-08-01

    In this dissertation, we will present a systematic study of structures of fullerenes ranging from C{sub 20} to C{sub 100} by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks.

  20. Process of Energetic Carbon Atom Deposition on Si (001) Substrate by Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    于威; 滕晓云; 李晓苇; 傅广生

    2002-01-01

    The process of energetic C atom deposition on Si (001)-(2×1) is studied by the molecular dynamics method using the semi-empirical many-bond Tersoff potential. It is found that the incident energy of the carbon atom has an important effect on the collision process and its diffusion process on the substrate. Most of the incident energy of the carbon atom is transferred to the substrate atoms within the initial two vibration periods of substrate atoms and its value increases with the incident energy. The spreading distance and penetration depth of the incident atom increasing with the incident energy are also identified. The simulated results imply that an important effect of energy of incident carbon on the film growth at Iow substrate temperature provides activation energy for silicon carbide formation through the vibration enhancement of local substrate atoms. In addition, suppressing carbon atom inhomogeneous collection and dispensing with the silicon diffusion process may be effectively promoted by the spreading and penetration of the energetic carbon atom in the silicon substrate.

  1. Molecular Ultrasound Imaging of Early Vascular Response in Prostate Tumors Irradiated with Carbon Ions

    Directory of Open Access Journals (Sweden)

    Moritz Palmowski

    2009-09-01

    Full Text Available Individualized treatments with combination of radiotherapy and targeted drugs require knowledge about the behavior of molecular targets after irradiation. Angiogenic marker expression has been studied after conventional radiotherapy, but little is known about marker response to charged particles. For the very first time, we used molecular ultrasound imaging to intraindividually track changes in angiogenic marker expression after carbon ion irradiation in experimental tumors. Expression of intercellular adhesion molecule-1 (ICAM-1 and of αvβ3-integrin in subcutaneous AT-1 prostate cancers in rats treated with carbon ions (16 Gy was studied using molecular ultrasound and immunohistochemistry. For this purpose, cyanoacrylate microbubbles were synthesized and linked to specific ligands. The accumulation of targeted microbubbles in tumors was quantified before and 36 hours after irradiation. In addition, tumor vascularization was analyzed using volumetric Doppler ultrasound. In tumors, the accumulation of targeted microbubbles was significantly higher than in nonspecific ones and could be inhibited competitively. Before irradiation, no difference in binding of αvβ3-integrin-specific or ICAM-1-specific microbubbles was observed in treated and untreated animals. After irradiation, however, treated animals showed a significantly higher binding of αvβ3-integrin-specific microbubbles and an enhanced binding of ICAM-1-specific microbubbles than untreated controls. In both groups, a decrease in vascularization occurred during tumor growth, but no significant difference was observed between irradiated and nonirradiated tumors. In conclusion, carbon ion irradiation upregulates ICAM-1 and αvβ3-integrin expression in tumor neovasculature. Molecular ultrasound can indicate the regulation of these markers and thus may help to identify the optimal drugs and time points in individualized therapy regimens.

  2. STUDIES ON MOLECULAR WEIGHT DISTRIBUTION OF CARBON FIBER POLYMER PRECURSORS SYNTHESIZED USING MIXED SOLVENTS

    Institute of Scientific and Technical Information of China (English)

    G.Santhana Krishnan; A.Burkanudeen; N.Murali; Hemant Phadnis

    2012-01-01

    The molecular weight distributions were estimated for carbon fiber polymer precursors such as poly(acrylonitrileco-itaconic acid) synthesized by semi batch solution polymerization in mixed solvents media with the azonitrile compounds as initiator under the different ratios of solvent and non solvent from 0.75 to 2.5 in weight.The copolymer was characterized by using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) analyses.The molecular weight distributions were evaluated by Mv/Mn ratios estimated from viscosity and osmotic measurements,and Mw/Mn estimated from size exclusion chromatography.The molecular weight distributions of these polymers as determined from Mv/Mn and Mw/Mn are 2.9 to 3.2 and 2.0 to 2.5 respectively.The molecular distributions were close to a narrow distribution of 2.0 when the solvent/non-solvent ratio was varied between 1.4 and 2.0.Intrinsic viscosity [η] as a function of molecular weight of poly(acrylonitrile-co-itaconic acid) was evaluated by means of low angle laser light scattering with size exclusion chromatography (SEC-LALLS) and viscometry with SEC (SEC-VISCO).The relationship between [η] and Mw for poly(acrylonitrile-co-itaconic acid) in DMF at 50℃ was [η] =1.1 × 10-5 Mw0.79,where [η] is obtained in dL/g.

  3. Organic Geochemistry of the Hamersley Province: Relationships Among Organic Carbon Isotopes, Molecular Fossils, and Lithology

    Science.gov (United States)

    Eigenbrode, Jennifer L.

    2012-01-01

    Molecular fossils are particularly valuable ancient biosignatures that can provide key insight about microbial sources and ecology in early Earth studies. In particular, hopanes carrying 2-methyl or 3-methyl substituents are proposed to be derived from cyanobacteria and oxygen-respiring methanotrophs, respectively, based on both their modem occurrences and their Proterozoic and Phanerozoic sedimentary distributions. Steranes are likely from ancestral eukaryotes. The distribution of methylhopanes, steranes, and other biomarkers in 2.72-2.56 billion-year-old rocks from the Hamersley Province, Western Australia show relationships to lithology, facies, and isotopes of macromolecular carbon, and other biomarkers. These observations support biomarker syngenicity and thermal maturity. Moreover, ecological signatures are revealed, including a surprising relationship between isotopic values for bulk macromolecular carbon and the biomarker for methanotrophs. The record suggests that cyanobacteria were likely key organisms of shallow-water microbial ecosystems providing molecular oxygen, fixed carbon, and possibly fixed nitrogen, and methanotrophs were not alone in recycling methane and other C-13-depleted substrates.

  4. Rectifying Properties of a Nitrogen/Boron-Doped Capped-Carbon-Nanotube-Based Molecular Junction

    Institute of Scientific and Technical Information of China (English)

    ZHAO Peng; LIU De-Sheng; ZHANG Ying; WANG Pei-Ji; ZHANG Zhong

    2011-01-01

    @@ Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbonnanotube-based molecular junction.Obvious rectifying behavior is observed and it is strongly dependent on the doping site.The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer.Moreover, the rectifying performance can be further improved by adjusting the distance between the Cso nanotube caps.%Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbon-nanotube-based molecular junction. Obvious rectifying behavior is observed and it is strongly dependent on the doping site. The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer. Moreover, the rectifying performance can be further improved by adjusting the distance between the C60 nanotube caps.

  5. Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

    CERN Document Server

    Glover, Simon C O

    2015-01-01

    Carbon monoxide (CO) is widely used as a tracer of molecular hydrogen (H2) in metal-rich galaxies, but is known to become ineffective in low metallicity dwarf galaxies. Atomic carbon has been suggested as a superior tracer of H2 in these metal-poor systems, but its suitability remains unproven. To help us to assess how well atomic carbon traces H2 at low metallicity, we have performed a series of numerical simulations of turbulent molecular clouds that cover a wide range of different metallicities. Our simulations demonstrate that in star-forming clouds, the conversion factor between [CI] emission and H2 mass, $X_{\\rm CI}$, scales approximately as $X_{\\rm CI} \\propto Z^{-1}$. We recover a similar scaling for the CO-to-H2 conversion factor, $X_{\\rm CO}$, but find that at this point in the evolution of the clouds, $X_{\\rm CO}$ is consistently smaller than $X_{\\rm CI}$, by a factor of a few or more. We have also examined how $X_{\\rm CI}$ and $X_{\\rm CO}$ evolve with time. We find that $X_{\\rm CI}$ does not vary ...

  6. Simulating Molecular Interactions of Carbon Nanoparticles with a Double-Stranded DNA Fragment

    Directory of Open Access Journals (Sweden)

    Zhuang Wang

    2015-01-01

    Full Text Available Molecular interactions between carbon nanoparticles (CNPs and a double-stranded deoxyribonucleic acid (dsDNA fragment were investigated using molecular dynamics (MD simulations. Six types of CNPs including fullerenes (C60 and C70, (8,0 single-walled carbon nanotube (SWNT, (8,0 double-walled carbon nanotube (DWNT, graphene quantum dot (GQD, and graphene oxide quantum dot (GOQD were studied. Analysis of the best geometry indicates that the dsDNA fragment can bind to CNPs through pi-stacking and T-shape. Moreover, C60, DWNT, and GOQD bind to the dsDNA molecules at the minor groove of the nucleotide, and C70, SWNT, and GQD bind to the dsDNA molecules at the hydrophobic ends. Estimated interaction energy implies that van der Waals force may mainly contribute to the mechanisms for the dsDNA-C60, dsDNA-C70, and dsDNA-SWNT interactions and electrostatic force may contribute considerably to the dsDNA-DWNT, dsDNA-GQD, and dsDNA-GOQD interactions. On the basis of the results from large-scale MD simulations, it was found that the presence of the dsDNA enhances the dispersion of C60, C70, and SWNT in water and has a slight impact on DWNT, GQD, and GOQD.

  7. Dynamic molecular structure of plant biomass-derived black carbon (biochar)

    Energy Technology Data Exchange (ETDEWEB)

    Keiluweit, M.; Nico, P.S.; Johnson, M.G.; Kleber, M.

    2009-11-15

    Char black carbon (BC), the solid residue of incomplete combustion, is continuously being added to soils and sediments due to natural vegetation fires, anthropogenic pollution, and new strategies for carbon sequestration ('biochar'). Here we present a molecular-level assessment of the physical organization and chemical complexity of biomass-derived chars and, specifically, that of aromatic carbon in char structures. BET-N{sub 2} surface area, X-ray diffraction (XRD), synchrotron-based Near-edge X-ray Absorption Fine Structure (NEXAFS), and Fourier transform infrared (FT-IR) spectroscopy are used to show how two plant materials (wood and grass) undergo analogous, but quantitatively different physical-chemical transitions as charring temperature increases from 100 to 700 C. These changes suggest the existence of four distinct categories of char consisting of a unique mixture of chemical phases and physical states: (i) in transition chars the crystalline character of the precursor materials is preserved, (ii) in amorphous chars the heat-altered molecules and incipient aromatic polycondensates are randomly mixed, (iii) composite chars consist of poorly ordered graphene stacks embedded in amorphous phases, and (iv) turbostratic chars are dominated by disordered graphitic crystallites. The molecular variations among the different char categories translate into differences in their ability to persist in the environment and function as environmental sorbents.

  8. Carbon doping of GaN with CBr4 in radio-frequency plasma-assisted molecular beam epitaxy

    OpenAIRE

    Green, D S; Mishra, U. K.; Speck, J.S.

    2004-01-01

    Carbon tetrabromide (CBr4) was studied as an intentional dopant during rf plasma molecular beam epitaxy of GaN. Secondary ion mass spectroscopy was used to quantify incorporation behavior. Carbon was found to readily incorporate under Ga-rich and N-rich growth conditions with no detectable bromine incorporation. The carbon incorporation [C] was found to be linearly related to the incident CBr4 flux. Reflection high-energy electron diffraction, atomic force microscopy and x-ray diffraction wer...

  9. Multi-walled carbon nanotube reinforced ultra-high molecular weight polyethylene composites

    Science.gov (United States)

    Ruan, Shilun

    This thesis is concerned with the development of high performance ultrahigh molecular polyethylene (UHMWPE) fibers reinforced using multiwalled carbon nanotubes (MWCNTs). A novel process has been developed, whereby, MWCNT/UHMWPE nanocomposite fibers with Young's modulus up to 137 GPa and tensile strength of ˜4.2 GPa has been produced. This fiber possesses the best specific mechanical properties amongst all current commercial high performance fibers. Systematic investigations were carried out to elucidate the mechanisms of reinforcement. Firstly, systematical experimental studies were carried out to investigate the CNT reinforcing effect on nanocomposite fibers prepared with different PE molecular orientations. The overall effect can be classified into three regions. At low molecular orientation levels, the CNTs act to toughen and strengthen the nanocomposites. At the intermediate molecular orientations, the CNTs have negligible effects on the mechanical properties of the nanocomposites. At very high molecular orientations, the CNTs act to mainly stiffen and strengthen the nanocomposite. Secondly, systematic investigations were carried out to investigate the structure evolution as well as the load transfer between the embedded CNTs and that of the matrix PE. Thermal and morphological studies demonstrate that CNTs act as effective nucleation sites for PE crystal growth. The load transfer mechanisms in both the low and high molecular orientation fibers are similar. Major differences were related to CNT alignment effects. The highly oriented fibers show CNT alignment effect in the initial elastic regime, whereas the CNTs in the fibers of low molecular orientations show no appreciable alignment in the elastic regime. Finally, based on the experimental observations, a mechanistic model has been proposed to elucidate the reinforcement mechanisms. This model proposes that there exists an absorption layer surrounding CNTs. (Abstract shortened by UMI.)

  10. A Chemical Template for Synthesis of Molecular Sheets of Calcium Carbonate

    Science.gov (United States)

    Rianasari, Ina; Benyettou, Farah; Sharma, Sudhir Kumar; Blanton, Thomas; Kirmizialtin, Serdal; Jagannathan, Ramesh

    2016-05-01

    Inspired by the discovery of graphene and its unique properties, we focused our research to develop a scheme to create nacre like lamellar structures of molecular sheets of CaCO3 interleaved with an organic material, namely carbon. We developed a facile, chemical template technique, using a formulation of poly(acrylic) acid (PAA) and calcium acetate to create lamellar stacks of single crystal sheets of CaCO3, with a nominal thickness of 17 Å, the same as a unit-cell dimension for calcite (c–axis = 17.062 Å), interleaved with amorphous carbon with a nominal thickness of 8 Å. The strong binding affinity between carboxylate anions and calcium cations in the formulation was used as a molecular template to guide CaCO3 crystallization. Computational modeling of the FTIR spectra showed good agreement with experimental data and confirmed that calcium ions are bridged between polymer chains, resulting in a net-like polymer structure. The process readily lends itself to explore the feasibility of creating molecular sheets of other important inorganic materials and potentially find applications in many fields such as super capacitors and “low k di-electric” systems.

  11. A Chemical Template for Synthesis of Molecular Sheets of Calcium Carbonate.

    Science.gov (United States)

    Rianasari, Ina; Benyettou, Farah; Sharma, Sudhir Kumar; Blanton, Thomas; Kirmizialtin, Serdal; Jagannathan, Ramesh

    2016-01-01

    Inspired by the discovery of graphene and its unique properties, we focused our research to develop a scheme to create nacre like lamellar structures of molecular sheets of CaCO3 interleaved with an organic material, namely carbon. We developed a facile, chemical template technique, using a formulation of poly(acrylic) acid (PAA) and calcium acetate to create lamellar stacks of single crystal sheets of CaCO3, with a nominal thickness of 17 Å, the same as a unit-cell dimension for calcite (c-axis = 17.062 Å), interleaved with amorphous carbon with a nominal thickness of 8 Å. The strong binding affinity between carboxylate anions and calcium cations in the formulation was used as a molecular template to guide CaCO3 crystallization. Computational modeling of the FTIR spectra showed good agreement with experimental data and confirmed that calcium ions are bridged between polymer chains, resulting in a net-like polymer structure. The process readily lends itself to explore the feasibility of creating molecular sheets of other important inorganic materials and potentially find applications in many fields such as super capacitors and "low k di-electric" systems. PMID:27145699

  12. Size-reduction and sorting behavior in sieve hammer mills

    Science.gov (United States)

    Schallnus, Harald

    Experiments were performed in a continuously operating sieve hammer mill to determine the duration of presence of the material to be ground in the size reduction machine. The test stand, analysis techniques, evaluation methods, and selection and production of samples are described. It is shown that the duration of presence of the material in the grinding space of the mill is approximately comparable to that in an ideal mixer. The type of sieve casing has an essential effect on the duration of presence. A combined model for the description of the size reduction and sorting behavior which allows the determination of the process coefficients (size reduction speed, sorting speed, mass transition coefficient) and their dependence on the different parameters, was developed.

  13. A parallel line sieve for the GNFS Algorithm

    Directory of Open Access Journals (Sweden)

    Sameh Daoud

    2014-08-01

    Full Text Available RSA is one of the most important public key cryptosystems for information security. The security of RSA depends on Integer factorization problem, it relies on the difficulty of factoring large integers. Much research has gone into problem of factoring a large number. Due to advances in factoring algorithms and advances in computing hardware the size of the number that can be factorized increases exponentially year by year. The General Number Field Sieve algorithm (GNFS is currently the best known method for factoring large numbers over than 110 digits. In this paper, a parallel GNFS implementation on a BA-cluster is presented. This study begins with a discussion of the serial algorithm in general and covers the five steps of the algorithm. Moreover, this approach discusses the parallel algorithm for the sieving step. The experimental results have shown that the algorithm has achieved a good speedup and can be used for factoring a large integers.

  14. Focusing properties of phase-only generalized Fibonacci photon sieves

    Science.gov (United States)

    Ke, Jie; Zhang, Junyong

    2016-06-01

    We propose a new algorithm to extend the standard Fibonacci photon sieve to the phase-only generalized Fibonacci photon sieve (GFiPS) and find that the focusing properties of the phase-only GFiPS are only relevant to the characteristic roots of the recursion relation of the generalized Fibonacci sequences. By switching the transparent and opaque zones on the basis of the generalized Fibonacci sequences, we not only realize adjustable bifocal lengths, but also give their corresponding analytic expressions. Besides, we investigate a special phase-only GFiPS, a spiral-phase GFiPS, which can present twin vortices along the axial coordinate. Compared with the single focusing system, bifocal system can be exploited to enhance the processing speed, and offer a broad range of applications, such as direct laser writing, optical tweezers or atom trapping and paralleled fluorescence microscope.

  15. A parallel line sieve for the GNFS Algorithm

    OpenAIRE

    Sameh Daoud; Ibrahim Gad

    2014-01-01

    RSA is one of the most important public key cryptosystems for information security. The security of RSA depends on Integer factorization problem, it relies on the difficulty of factoring large integers. Much research has gone into problem of factoring a large number. Due to advances in factoring algorithms and advances in computing hardware the size of the number that can be factorized increases exponentially year by year. The General Number Field Sieve algorithm (GNFS) is currently the best ...

  16. 3D Oxidized Graphene Frameworks for Efficient Nano Sieving

    Science.gov (United States)

    Pawar, Pranav Bhagwan; Saxena, Sumit; Badhe, Dhanashree Kamlesh; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-01-01

    The small size of Na+ and Cl− ions provides a bottleneck in desalination and is a challenge in providing alternatives for continuously depleting fresh water resources. Graphene by virtue of its structural properties has the potential to address this issue. Studies have indicated that use of monolayer graphene can be used to filter micro volumes of saline solution. Unfortunately it is extremely difficult, resource intensive and almost impractical with current technology to fabricate operational devices using mono-layered graphene. Nevertheless, graphene based devices still hold the key to solve this problem due to its nano-sieving ability. Here we report synthesis of oxidized graphene frameworks and demonstrate a functional device to desalinate and purify seawater from contaminants including Na+ and Cl− ions, dyes and other microbial pollutants. Micro-channels in these frameworks help in immobilizing larger suspended solids including bacteria, while nano-sieving through graphene enables the removal of dissolved ions (e.g. Cl−). Nano-sieving incorporated with larger frameworks has been used in filtering Na+ and Cl− ions in functional devices. PMID:26892277

  17. 3D Oxidized Graphene Frameworks for Efficient Nano Sieving.

    Science.gov (United States)

    Pawar, Pranav Bhagwan; Saxena, Sumit; Badhe, Dhanashree Kamlesh; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-01-01

    The small size of Na(+) and Cl(-) ions provides a bottleneck in desalination and is a challenge in providing alternatives for continuously depleting fresh water resources. Graphene by virtue of its structural properties has the potential to address this issue. Studies have indicated that use of monolayer graphene can be used to filter micro volumes of saline solution. Unfortunately it is extremely difficult, resource intensive and almost impractical with current technology to fabricate operational devices using mono-layered graphene. Nevertheless, graphene based devices still hold the key to solve this problem due to its nano-sieving ability. Here we report synthesis of oxidized graphene frameworks and demonstrate a functional device to desalinate and purify seawater from contaminants including Na(+) and Cl(-) ions, dyes and other microbial pollutants. Micro-channels in these frameworks help in immobilizing larger suspended solids including bacteria, while nano-sieving through graphene enables the removal of dissolved ions (e.g. Cl(-)). Nano-sieving incorporated with larger frameworks has been used in filtering Na(+) and Cl(-) ions in functional devices. PMID:26892277

  18. One-pot synthesis of molecular bottle-brush functionalized single-walled carbon nanotubes with superior dispersibility in water.

    Science.gov (United States)

    Deng, Yong; Hu, Qin; Yuan, Qiulin; Wu, Yan; Ling, Ying; Tang, Haoyu

    2014-01-01

    Molecular bottle-brush functionalized single-walled carbon nanotubes (SWCNTs) with superior dispersibility in water are prepared by a one-pot synthetic methodology. Elongating the main-chain and side-chain length of molecular bottle-brushes can further increase SWCNT dispersibility. They show significant enhancement of SWCNT dispersibility up to four times higher than those of linear molecular functionalized SWCNTs. PMID:24307218

  19. Compressive characteristics of single walled carbon nanotube with water interactions investigated by using molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.H., E-mail: chwong@ntu.edu.sg; Vijayaraghavan, V.

    2014-01-24

    The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.

  20. Structural modeling of dahlia-type single-walled carbon nanohorn aggregates by molecular dynamics.

    Science.gov (United States)

    Hawelek, L; Brodka, A; Dore, John C; Hannon, Alex C; Iijima, S; Yudasaka, M; Ohba, T; Kaneko, K; Burian, A

    2013-09-19

    The structure of dahlia-type single-walled carbon nanohorn aggregates has been modeled by classical molecular dynamics simulations, and the validity of the model has been verified by neutron diffraction. Computer-generated models consisted of an outer part formed from single-walled carbon nanohorns with diameters of 20-50 Å and a length of 400 Å and an inner turbostratic graphite-like core with a diameter of 130 Å. The diffracted intensity and the pair correlation function computed for such a constructed model are in good agreement with the neutron diffraction experimental data. The proposed turbostratic inner core explains the occurrence of the additional (002) and (004) graphitic peaks in the diffraction pattern of the studied sample and provides information about the interior structure of the dahlia-type aggregates. PMID:23978218

  1. Controlled route to the fabrication of carbon and boron nitride nanoscrolls: A molecular dynamics investigation

    Science.gov (United States)

    Perim, Eric; Paupitz, Ricardo; Galvão, Douglas S.

    2013-02-01

    Carbon nanoscrolls (graphene layers rolled up into papyrus-like tubular structures) are nanostructures with unique and interesting characteristics that could be exploited to build several new nanodevices. However, an efficient and controlled synthesis of these structures was not achieved yet, making its large scale production a challenge to materials scientists. Also, the formation process and detailed mechanisms that occur during its synthesis are not completely known. In this work, using fully atomistic molecular dynamics simulations, we discuss a possible route to nanoscrolls made from graphene layers deposited over silicon oxide substrates containing chambers/pits. The scrolling mechanism is triggered by carbon nanotubes deposited on the layers. The process is completely general and can be used to produce scrolls from other lamellar materials, like boron nitride, for instance.

  2. (Questions)n on phloem biology. 2. Mass flow, molecular hopping, distribution patterns and macromolecular signalling.

    Science.gov (United States)

    van Bel, Aart J E; Furch, Alexandra C U; Hafke, Jens B; Knoblauch, Michael; Patrick, John W

    2011-10-01

    This review speculates on correlations between mass flow in sieve tubes and the distribution of photoassimilates and macromolecular signals. Since micro- (low-molecular compounds) and macromolecules are withdrawn from, and released into, the sieve-tube sap at various rates, distribution patterns of these compounds do not strictly obey mass-flow predictions. Due to serial release and retrieval transport steps executed by sieve tube plasma membranes, micromolecules are proposed to "hop" between sieve element/companion cell complexes and phloem parenchyma cells under source-limiting conditions (apoplasmic hopping). Under sink-limiting conditions, micromolecules escape from sieve tubes via pore-plasmodesma units and are temporarily stored. It is speculated that macromolecules "hop" between sieve elements and companion cells using plasmodesmal trafficking mechanisms (symplasmic hopping). We explore how differential tagging may influence distribution patterns of macromolecules and how their bidirectional movement could arise. Effects of exudation techniques on the macromolecular composition of sieve-tube sap are discussed. PMID:21889037

  3. Liquid flow-induced energy harvesting in carbon nanotubes: a molecular dynamics study.

    Science.gov (United States)

    Xu, Baoxing; Chen, Xi

    2013-01-28

    Energy harvesting by the flow of a hydrochloric acid-water solution through a carbon nanotube (CNT) is explored using atomistic simulations. Through ion configurations near the CNT wall, the ion drifting velocity is obtained, and the induced voltage along the axial direction is obtained as a function of key material and system parameters, including the applied flow rate, ambient temperature, solution concentration and nanotube diameter. The molecular mechanism of ion hopping and motion is elucidated and related to the variation of material and system parameters. PMID:23223386

  4. Adsorption of Molecular Gases on Silver/Carbon Nanotube Composites at Low Temperatures and Low Pressures

    Directory of Open Access Journals (Sweden)

    M. Barberio

    2014-01-01

    Full Text Available We present an experimental study adsorption of molecular gases (N2, H2, O2, CH4, C2H4, and C2H6 on multiwalled carbon nanotubes (MWCNTs and MWCNT doped with Ag at low temperatures (35 K and pressures (10−6 Torr using the temperature programmed desorption technique. Our results show that the desorption kinetics is of the first order; furthermore comparative measurements indicate that Ag/MWCNTs have an adsorption capacity higher than that of a pure sample suggesting that these composites are good candidates as gas cryosorbers for applications in cryopumps or sensor of latest generation.

  5. The thinnest molecular separation sheet by graphene gates of single-walled carbon nanohorns.

    Science.gov (United States)

    Ohba, Tomonori

    2014-11-25

    Graphene is possibly the thinnest membrane that could be used as a molecular separation gate. Several techniques including absorption, cryogenic distillation, adsorption, and membrane separation have been adopted for constructing separation systems. Molecular separation using graphene as the membrane has been studied because large area synthesis of graphene is possible by chemical vapor deposition. Control of the gate sizes is necessary to achieve high separation performances in graphene membranes. The separation of molecules and ions using graphene and graphene oxide layers could be achieved by the intrinsic defects and defect donation of graphene. However, the controllability of the graphene gates is still under debate because gate size control at the picometer level is inevitable for the fabrication of the thinnest graphene membranes. In this paper, the controlled gate size in the graphene sheets in single-walled carbon nanohorns (NHs) is studied and the molecular separation ability of the graphene sheets is assessed by molecular probing with CO2, O2, N2, CH4, and SF6. Graphene sheets in NHs with different sized gates of 310, 370, and >500 pm were prepared and assessed by molecular probing. The 310 pm-gates in the graphene sheets could separate the molecules tested, whereas weak separation properties were observed for 370 pm-gates. The amount of CO2 that penetrated the 310 pm-gates was more than 35 times larger than that of CH4. These results were supported by molecular dynamics simulations of the penetration of molecules through 300, 400, and 700 pm-gates in graphene sheets. Therefore, a gas separation membrane using a 340-pm-thick graphene sheet has high potential. These findings provide unambiguous evidence of the importance of graphene gates on the picometer level. Control of the gates is the primary challenge for high-performance separation membranes made of graphene. PMID:25347389

  6. Molecular imprinted polypyrrole modified glassy carbon electrode for the determination of tobramycin

    International Nuclear Information System (INIS)

    Graphical abstract: Atomic force microscopic images of (A) bare GCE and (B) TOB imprinted PPy/GCE surface. - Highlights: • Glassy carbon electrode based on molecularly imprinted polypyrrole was prepared. • The developed surfaces were characterized by AFM, FTIR, EIS and CV. • The developed nanosensor was applied to egg and milk samples. - Abstract: Over the past two decades, molecular imprinted polymers have attracted a broad interest from scientists in sensor development. In the preparation of molecular imprinted polymers the desired molecule (template) induces the creation of specific recognition sites in the polymer. In this study, the glassy carbon electrode (GCE) based on molecularly imprinted polypyrrole (PPy) was fabricated for the determination of tobramycin (TOB). The developed electrode was prepared by incorporation of a template molecule (TOB) during the electropolymerization of pyrrole on GCE in aqueous solution using cyclic voltammetry (CV) method. The performance of the imprinted and non-imprinted electrodes was evaluated by square wave voltammetry (SWV). The effect of pH, monomer and template concentrations, electropolymerization cycles on the performance of the imprinted and non-imprinted electrodes was investigated and optimized. The non-modified and TOB-imprinted surfaces were characterized by using atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and CV. The linearity range of TOB was 5.0 × 10−10–1.0 × 10−8 M with the detection limit of 1.4 × 10−10 M. The developed nanosensor was applied successfully for the determination of TOB in egg and milk

  7. Molecular dynamics insight to phase transition in n-alkanes with carbon nanofillers

    Directory of Open Access Journals (Sweden)

    Monisha Rastogi

    2015-05-01

    Full Text Available The present work aims to investigate the phase transition, dispersion and diffusion behavior of nanocomposites of carbon nanotube (CNT and straight chain alkanes. These materials are potential candidates for organic phase change materials(PCMs and have attracted flurry of research recently. Accurate experimental evaluation of the mass, thermal and transport properties of such composites is both difficult as well as economically taxing. Additionally it is crucial to understand the factors that results in modification or enhancement of their characteristic at atomic or molecular level. Classical molecular dynamics approach has been extended to elucidate the same. Bulk atomistic models have been generated and subjected to rigorous multistage equilibration. To reaffirm the approach, both canonical and constant-temperature, constant- pressure ensembles were employed to simulate the models under consideration. Explicit determination of kinetic, potential, non-bond and total energy assisted in understanding the enhanced thermal and transport property of the nanocomposites from molecular point of view. Crucial parameters including mean square displacement and simulated self diffusion coefficient precisely define the balance of the thermodynamic and hydrodynamic interactions. Radial distribution function also reflected the density variation, strength and mobility of the nanocomposites. It is expected that CNT functionalization could improve the dispersion within n-alkane matrix. This would further ameliorate the mass and thermal properties of the composite. Additionally, the determined density was in good agreement with experimental data. Thus, molecular dynamics can be utilized as a high throughput technique for theoretical investigation of nanocomposites PCMs.

  8. Tamices moleculares que combinan micro y meso porosidad: una revisión

    Directory of Open Access Journals (Sweden)

    Carmen M. López*

    2009-12-01

    Full Text Available Molecular sieves combining micro and mesoporosity: a review. A review of molecular sieves combining micro and mesoporosity is presented. A summary of different routes employed for the preparation of these solids, is showed by citing recent works reported in this subject. In order to evaluate the catalytic potential of these new solids, several catalytic studies are presented.

  9. Dispersion of carbon nanotubes using mixed surfactants: experimental and molecular dynamics simulation studies.

    Science.gov (United States)

    Sohrabi, B; Poorgholami-Bejarpasi, N; Nayeri, N

    2014-03-20

    The ability of cationic-rich and anionic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) for dispersing of carbon nanotubes (CNTs) in aqueous media has been studied through both the experimental and molecular dynamics simulation methods. Compared to the pure CTAB and SDS, these mixtures are more effective with the lower concentrations and more individual CNTs, reflecting a synergistic effect in these mixtures. The synergistic effects observed in mixed surfactant systems are mainly due to the electrostatic attractions between surfactant heads. In addition, the surface charge related to the colloidal stability of mixed surfactant-covered nanotubes has been characterized by means of ζ-potential measurements. The results indicate that the hydrophobic interactions between surfactant tails also give rise to the higher adsorption of surfactant molecules. Furthermore, molecular dynamics (MD) simulations have been performed to provide insight about the structure of surfactant aggregates onto nanotubes and to attempt an explanation of the experimental results. The MD simulation results indicate that the random and disordered adsorption of mixed surfactants onto carbon nanotubes may be preferred for a low surfactant concentration. Our research may provide experimental and theoretical bases for using mixed surfactants to disperse CNTs, which can open an avenue for new applications of mixed surfactants. PMID:24555914

  10. Electronic Transport Properties of an Anthraquinone-Based Molecular Switch with Carbon Nanotube Electrodes

    Institute of Scientific and Technical Information of China (English)

    ZHAO Peng; LIU De-Sheng

    2012-01-01

    Based on the nonequilibrium Green's function method and density functional theory calculations,we theoretically investigate the electronic transport properties of an anthraquinone-based molecular switch with carbon nanotube electrodes.The molecules that comprise the switch can convert between reduced hydroquinone (HQ) and oxidized anthraquinne (AQ) states via redox reactions.Our results show that the on-off ratio is increased one order of magnitude when compared to the case of gold electrodes.Moreover,an obvious negative differential resistance behavior at much low bias (0.07 V) is observed in the HQ form.%Based on the nonequilihrium Green's function method and density functional theory calculations, we theoretically investigate the electronic transport properties of an anthraquinone-based molecular switch with carbon nanotube electrodes. The molecules that comprise the switch can convert between reduced hydroquinone (HQ) and oxidized anthraquinne (AQ) states via redox reactions. Our results show that the on-off ratio is increased one order of magnitude when compared to the case of gold electrodes. Moreover, an obvious negative differential resistance behavior at much low bias (0.07 V) is observed in the HQ form.

  11. Molecular dynamics study of mechanical properties of carbon nanotube reinforced aluminum composites

    Science.gov (United States)

    Srivastava, Ashish Kumar; Mokhalingam, A.; Singh, Akhileshwar; Kumar, Dinesh

    2016-05-01

    Atomistic simulations were conducted to estimate the effect of the carbon nanotube (CNT) reinforcement on the mechanical behavior of CNT-reinforced aluminum (Al) nanocomposite. The periodic system of CNT-Al nanocomposite was built and simulated using molecular dynamics (MD) software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). The mechanical properties of the nanocomposite were investigated by the application of uniaxial load on one end of the representative volume element (RVE) and fixing the other end. The interactions between the atoms of Al were modeled using embedded atom method (EAM) potentials, whereas Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential was used for the interactions among carbon atoms and these pair potentials are coupled with the Lennard-Jones (LJ) potential. The results show that the incorporation of CNT into the Al matrix can increase the Young's modulus of the nanocomposite substantially. In the present case, i.e. for approximately 9 with % reinforcement of CNT can increase the axial Young's modulus of the Al matrix up to 77 % as compared to pure Al.

  12. Molecular Dynamics Modeling of Carbon Nanotube Composite Fracture Using ReaxFF

    Science.gov (United States)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2016-01-01

    Carbon nanotube (CNT) fiber reinforced composites with specific tensile strengths and moduli approaching those of aerospace grade carbon fiber composites have recently been reported. This achievement was enabled by the emerging availability of high N/tex yarns in kilometer-scale quantities. While the production of this yarn is an impressive advance, its strength is still much lower than that of the individual CNTs comprising the yarn. Closing this gap requires understanding load transfer between CNTs at the nanometer dimensional scale. This work uses reactive molecular dynamics simulations to gain an understanding at the nanometer scale of the key factors that determine CNT nanocomposite mechanical performance, and to place more realistic upper bounds on the target properties. While molecular dynamics simulations using conventional force fields can predict elastic properties, the ReaxFF reactive forcefield can also model fracture behavior because of its ability to accurately describe bond breaking and formation during a simulation. The upper and lower bounds of CNT composite properties are investigated by comparing systems composed of CNTs continuously connected across the periodic boundary with systems composed of finite length CNTs. These lengths, effectively infinite for the continuous tubes and an aspect ratio of 13 for the finite length case, result from practical limitations on the number of atoms that can be included in a simulation. Experimentally measured aspect ratios are typically on the order of 100,000, so the calculated results should represent upper and lower limits on experimental mechanical properties. Finally, the effect of various degrees of covalent crosslinking between the CNTs and amorphous carbon matrix is considered to identify the amount of CNT-matrix covalent bonding that maximizes overall composite properties.

  13. Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

    CERN Document Server

    Verkhovtsev, Alexey V; Solov'yov, Andrey V

    2014-01-01

    The stability of a single-walled carbon nanotube placed on top of a catalytic nickel nanoparticle is investigated by means of molecular dynamics simulations. As a case study, we consider the $(12,0)$ nanotube consisting of 720 carbon atoms and the icosahedral Ni$_{309}$ cluster. An explicit set of constant-temperature simulations is performed in order to cover a broad temperature range from 400 to 1200 K, at which a successful growth of carbon nanotubes has been achieved experimentally by means of chemical vapor deposition. The stability of the system depending on parameters of the involved interatomic interactions is analyzed. It is demonstrated that different scenarios of the nanotube dynamics atop the nanoparticle are possible depending on the parameters of the Ni-C potential. When the interaction is weak the nanotube is stable and resembles its highly symmetric structure, while an increase of the interaction energy leads to the abrupt collapse of the nanotube in the initial stage of simulation. In order t...

  14. Molecular dynamics simulation of the deposition process of hydrogenated diamond-like carbon (DLC) films

    Institute of Scientific and Technical Information of China (English)

    ZHANG YuJun; DONG GuangNeng; MAO JunHong; XIE YouBai

    2008-01-01

    The deposition process of hydrogenated diamond-like carbon (DLC) film greatly affects its frictional properties. In this study, CH3 radicals are selected as source species to deposit hydrogenated DLC films for molecular dynamics simulation. The growth and structural properties of hydrogenated DLC films are investigated and elucidated in detail. By comparison and statistical analysis, the authors find that the ratio of carbon to hydrogen in the films generally shows a monotonously increasing trend with the increase of impact energy. Carbon atoms are more reactive during deposition and more liable to bond with substrate atoms than hydrogen atoms. In addition, there exists a peak value of the number of hydrogen atoms deposited in hydrogenated DLC films. The trends of the variation are opposite on the two sides of this peak point, and itbecomes stable when impact energy is greater than 80 eV. The average relative density also indicates a rising trend along with the increment of impact energy, while it does not reach the saturation value until impact energy comes to 50 eV. The hydrogen content in source species is a key factor to determine the hydrogen content in hydrogenated DLC films. When the hydrogen content in source species is high, the hydrogen content in hydrogenated DLC films is accordingly high.

  15. Nanoscale soldering of axially positioned single-walled carbon nanotubes: a molecular dynamics simulation study.

    Science.gov (United States)

    Cui, Jianlei; Yang, Lijun; Zhou, Liang; Wang, Yang

    2014-02-12

    The miniaturization of electronics devices into the nanometer scale is indispensable for next-generation semi-conductor technology. Carbon nanotubes (CNTs) are considered to be the promising candidates for future interconnection wires. To study the carbon nanotubes interconnection during nanosoldering, the melting process of nanosolder and nanosoldering process between single-walled carbon nanotubes are simulated with molecular dynamics method. As the simulation results, the melting point of 2 nm silver solder is about 605 K because of high surface energy, which is below the melting temperature of Ag bulk material. In the nanosoldering process simulations, Ag atoms may be dragged into the nanotubes to form different connection configuration, which has no apparent relationship with chirality of SWNTs. The length of core filling nanowires structure has the relationship with the diameter, and it does not become longer with the increasing diameter of SWNT. Subsequently, the dominant mechanism of was analyzed. In addition, as the heating temperature and time, respectively, increases, more Ag atoms can enter the SWNTs with longer length of Ag nanowires. And because of the strong metal bonds, less Ag atoms can remain with the tight atomic structures in the gap between SWNT and SWNT. The preferred interconnection configurations can be achieved between SWNT and SWNT in this paper.

  16. Purification, molecular cloning, and expression of 2-hydroxyphytanoyl- CoA lyase, a peroxisomal thiamine pyrophosphate-dependent enzyme that catalyzes the carbon-carbon bond cleavage during à-oxidation of 3- methyl-branched fatty acids

    CERN Document Server

    Foulon, V; Croes, K; Waelkens, E

    1999-01-01

    Purification, molecular cloning, and expression of 2-hydroxyphytanoyl- CoA lyase, a peroxisomal thiamine pyrophosphate-dependent enzyme that catalyzes the carbon-carbon bond cleavage during à-oxidation of 3- methyl-branched fatty acids

  17. Hydrophilic solutes in modified carbon dioxide extraction-prediction of the extractability using molecular dynamic simulation.

    Science.gov (United States)

    Günther, Martina; Maus, Martin; Wagner, Karl Gerhard; Schmidt, Peter Christian

    2005-06-01

    Super- and subcritical carbon dioxide (CO2) extractions of crude drugs were simulated by molecular modelling to predict the extractability of different hydrophilic plant constituents under various extraction conditions. The CO2 extraction fluids were simulated either with pure CO2 or with solvent modified CO2 at different pressures and temperatures. Molecular modelling resulted in three different solubility parameters: the total solubility parameter delta and the partial solubility parameters delta(d) for the van der Waals and delta(EL) for the polar forces. Thus, delta(EL) enabled the estimation of the polarity of the extraction fluids and the solute molecules. If the value of delta(EL) of the extraction fluid reached the value of the solute molecule in the crude drug, i.e. minimum extraction value, the compound was soluble at the distinct extraction conditions. For a further increase in yield of the hydrophilic solutes, the polarity of the extraction fluid had to be increased, too. That means delta(EL) of the fluid exceeded the minimum extraction value. All simulations were verified by CO2 extractions of the secondary roots of Harpagophytum procumbens (harpagoside, stachyose) and the seeds of Aesculus hippocastanum (aescin). CO2 extractions of the flowers of Matricaria recutita ((-)-alpha-bisabolol) were obtained from literature data. These four constituents with different properties, like molecular size and the allocation of polar functional groups were extracted, analysed, simulated and the extract content was correlated with the extraction fluid used, respectively. PMID:15911229

  18. A Molecular Surface Functionalization Approach to Tuning Nanoparticle Electrocatalysts for Carbon Dioxide Reduction.

    Science.gov (United States)

    Cao, Zhi; Kim, Dohyung; Hong, Dachao; Yu, Yi; Xu, Jun; Lin, Song; Wen, Xiaodong; Nichols, Eva M; Jeong, Keunhong; Reimer, Jeffrey A; Yang, Peidong; Chang, Christopher J

    2016-07-01

    Conversion of the greenhouse gas carbon dioxide (CO2) to value-added products is an important challenge for sustainable energy research, and nanomaterials offer a broad class of heterogeneous catalysts for such transformations. Here we report a molecular surface functionalization approach to tuning gold nanoparticle (Au NP) electrocatalysts for reduction of CO2 to CO. The N-heterocyclic (NHC) carbene-functionalized Au NP catalyst exhibits improved faradaic efficiency (FE = 83%) for reduction of CO2 to CO in water at neutral pH at an overpotential of 0.46 V with a 7.6-fold increase in current density compared to that of the parent Au NP (FE = 53%). Tafel plots of the NHC carbene-functionalized Au NP (72 mV/decade) vs parent Au NP (138 mV/decade) systems further show that the molecular ligand influences mechanistic pathways for CO2 reduction. The results establish molecular surface functionalization as a complementary approach to size, shape, composition, and defect control for nanoparticle catalyst design. PMID:27322487

  19. Atomic carbon as a tracer of molecular gas in high-redshift galaxies: perspectives for ALMA

    CERN Document Server

    Tomassetti, Matteo; Romano-Diaz, Emilio; Ludlow, Aaron D; Papadopoulos, Padelis P

    2014-01-01

    We use a high-resolution simulation that tracks the non-equilibrium abundance of molecular hydrogen, H2, within a massive high-redshift galaxy to produce mock ALMA maps of the fine-structure lines of atomic carbon CI 1-0 and CI 2-1. Inspired by recent observational and theoretical work, we assume that CI is thoroughly mixed in giant molecular clouds and demonstrate that its emission is an excellent proxy for H2. The entire H2 mass of a galaxy at redshift z<4 can be detected using a compact interferometric configuration with a large synthesized beam (that does not resolve the target galaxy) in less than 1 hour of integration time. Low-resolution imaging of the CI lines (in which the target galaxy is resolved into 3-4 beams) will detect nearly 50-60 per cent of the molecular hydrogen in less than 12 hours. In this case, the data cube also provides valuable information regarding the dynamical state of the galaxy. We conclude that ALMA observations of the CI 1-0 and 2-1 emission will widely extend the interval...

  20. Biofuel Manufacturing from Woody Biomass: Effects of Sieve Size Used in Biomass Size Reduction

    OpenAIRE

    Meng Zhang; Xiaoxu Song; Deines, T. W.; Pei, Z. J.; Donghai Wang

    2012-01-01

    Size reduction is the first step for manufacturing biofuels from woody biomass. It is usually performed using milling machines and the particle size is controlled by the size of the sieve installed on a milling machine. There are reported studies about the effects of sieve size on energy consumption in milling of woody biomass. These studies show that energy consumption increased dramatically as sieve size became smaller. However, in these studies, the sugar yield (proportional to biofuel yie...

  1. Molecular simulation study of temperature effect on ionic hydration in carbon nanotubes.

    Science.gov (United States)

    Shao, Qing; Huang, Liangliang; Zhou, Jian; Lu, Linghong; Zhang, Luzheng; Lu, Xiaohua; Jiang, Shaoyi; Gubbins, Keith E; Shen, Wenfeng

    2008-04-14

    Molecular dynamics simulations have been performed to investigate the hydration of Li(+), Na(+), K(+), F(-), and Cl(-) inside the carbon nanotubes at temperatures ranging from 298 to 683 K. The structural characteristics of the coordination shells of ions are studied, including the ion-oxygen radial distribution functions, the coordination numbers, and the orientation distributions of the water molecules. Simulation results show that the first coordination shells of the five ions still exist in the nanoscale confinement. Nevertheless, the first coordination shell structures of cations change more significantly than those of anions because of the preferential orientation of the water molecules induced by the carbon nanotube. The first coordination shells of cations are considerably less ordered in the nanotube than in the bulk solution, whereas the change of the first coordination shell structures of the anions is minor. Furthermore, the confinement induces the anomalous behavior of the coordination shells of the ions with temperature. The first coordination shell of K(+) are found to be more ordered as the temperature increases only in the carbon nanotube with the effective diameter of 1.0 nm, implying the enhancement of the ionic hydration with temperature. This is contrary to that in the bulk solution. The coordination shells of the other four ions do not have such behavior in the carbon nanotube with the effective diameter ranging from 0.73 to 1.00 nm. The easier distortion of the coordination shell of K(+) and the match of the shell size and the nanotube size may play roles in this phenomenon. The exchange of water molecules in the first coordination shells of the ions with the solution and the ion diffusion along the axial direction of the nanotube are also investigated. The mobility of the ions and the stability of the coordination shells are greatly affected by the temperature in the nanotube as in the bulk solutions. These results help to understand the

  2. Separation of DNA Fragments with a Broad Range of Molecular Weight by Capillary Electrophoresis with Sieving Matrix of Poly (ethylene oxide)%聚环氧乙烷无胶筛分毛细管电泳分离宽分子量范围DNA片段

    Institute of Scientific and Technical Information of China (English)

    李玉荣; 陈长宝; 周杰

    2011-01-01

    在无胶筛分毛细管电泳中,以聚环氧乙烷为筛分介质,用硅烷化处理的毛细管柱(31.2 cm×75 μm i.d.,有效长度21.0 cm)分离DL5000 DNA Marker(DNA长度为100~5000 bp),考察了筛分介质浓度、缓冲液pH值、分离电压和溴化乙锭浓度对分离双链DNA片段的影响,优化得到分离100~5000 bp DNA片段的最佳条件.毛细管电泳的最佳条件为PEO浓度5 mg/mL,缓冲液pH值8.0,电压-12.0 kV及溴化乙锭浓度3.0 μg/mL.在此条件下,可对山梨醇脱氢酶基因(SDH)和乙烯受体基因(ETR1)的聚合酶链式反应(PCR)扩增产物同时进行检测,分离和鉴定效果良好.%DL5000 DNA marker fragments( 100-5000 bp) were separated by non-gel sieve capillary electrophoresis on a silanized fused silica capillary column(31.2 cm ×75 μm i.d. with effective length 21.0 cm)using poly( ethylene oxide) as sieve matrix. The influences of poly( ethylene oxide) concentration, pH value of running buffer, separation voltage and ethidium bromide concentration on the separation efficiency of different lengths of double-strand DNA fragments were investigated. The optimum conditions for separation of 100-5000 bp DNA fragments were established as 5 mg/mL poly ( ethylene oxide), pH = 8.0, 3.0 μg/mL ethidium bromide and voltage of - 12.0 kV. Under these conditions, the multiplex polymerase chain reaction (PCR) magnified products from the sorbitol dehydrogenase gene (SDH) and the ethylene receptor gene (ETR1) were simultaneously detected, and good identification and resolution were obtained.

  3. A differential delay equation arising from the sieve of Eratosthenes

    Science.gov (United States)

    Cheer, A. Y.; Goldston, D. A.

    1990-07-01

    The differential delay equation defined by ω (u) = 1/u for 1 ≤ u ≤ 2 and (uω (u))' = ω (u - 1) for u ≥ 2 was introduced by Buchstab in connection with an asymptotic formula for the number of uncanceled terms in the sieve of Eratosthenes. Maier has recently used this result to show there is unexpected irregularity in the distribution of primes in short intervals. The function ω (u) is studied in this paper using numerical and analytical techniques. The results are applied to give some numerical constants in Maier's theorem.

  4. Importance of sieve size in deep-sea macrobenthic studies

    Digital Repository Service at National Institute of Oceanography (India)

    Pavithran, S.; Ingole, B.S.; Nanajkar, M.; Goltekar, R.C.

    subjected to Shapiro-Wilks test to check for normality (Statistica 5.5 1999). Mann-Whitney U tests and student’s t-tests were used to test for significant differences between parameters. Non-parametric Kruskal Wallis ANOVA was used as a global... 17 Table 1: Mann-Whitney U and Students t-tests of macrofaunal density, biomass, number of species, and three diversity indices for sieves of two different mesh sizes. Mann-Whitney U test U p n Macrofaunal...

  5. Factorization of RSA-140 using the number field sieve

    OpenAIRE

    Cavallar, S.H.; Dodson, B.; Lenstra, A.K.; Leyland, P. C.; Lioen, W.M.; Montgomery, P. L.; Murphy, B.; Riele, te, H.; Zimmermann, P

    1999-01-01

    On February 2, 1999, we completed the factorization of the 140--digit number RSA--140 with the help of the Number Field Sieve factoring method (NFS). This is a new general factoring record. The previous record was established on April 10, 1996 by the factorization of the 130--digit number RSA--130, also with the help of NFS. The amount of computing time spent on RSA--140 was roughly twice that needed for RSA--130, about half of what could be expected from a straightforward extrapolation of th...

  6. Electroanalysis of myoglobin based on electropolymerized molecularly imprinted polymer poly-o-phenylenediamine and carbon nanotubes/screen printed electrode.

    Science.gov (United States)

    Shumyantseva, V V; Bulko, T V; Sigolaeva, L V; Kuzikov, A V; Archakov, A I

    2016-05-01

    Electroanalysis of myoglobin as a marker of acute myocardial infarction by means of screenprinted electrodes modified with multiwalled carbon nanotubes and polymeric artificial antibodies is developed. Plastic antibodies to myoglobin (molecularly imprinted polymers, MIPs) based on o-phenylenediamine were produced by electropolymerization. Molecular imprinting technology in biosensor analysis was used as alternative to natural receptors (namely, antibodies) and demonstrated high sensitivity (1.5 × 10(-2) A/nmol of myoglobin) and selectivity.

  7. Temperature effects on polymer-carbon composite sensors: evaluating the role of polymer molecular weight and carbon loading

    Science.gov (United States)

    Homer, M. L.; Lim, J. R.; Manatt, K.; Kisor, A.; Lara, L.; Jewell, A. D.; Yen, S. -P. S.; Shevade, A. V.; Ryan, M. A.

    2003-01-01

    We report the effect of environmental condtions coupled with varying polymer properties and carbon loadings on the performance of polymer-carbon black composite film, used as sensing medium in the JPL Electronic Nose.

  8. Medical sieve: a cognitive assistant for radiologists and cardiologists

    Science.gov (United States)

    Syeda-Mahmood, T.; Walach, E.; Beymer, D.; Gilboa-Solomon, F.; Moradi, M.; Kisilev, P.; Kakrania, D.; Compas, C.; Wang, H.; Negahdar, R.; Cao, Y.; Baldwin, T.; Guo, Y.; Gur, Y.; Rajan, D.; Zlotnick, A.; Rabinovici-Cohen, S.; Ben-Ari, R.; Guy, Amit; Prasanna, P.; Morey, J.; Boyko, O.; Hashoul, S.

    2016-03-01

    Radiologists and cardiologists today have to view large amounts of imaging data relatively quickly leading to eye fatigue. Further, they have only limited access to clinical information relying mostly on their visual interpretation of imaging studies for their diagnostic decisions. In this paper, we present Medical Sieve, an automated cognitive assistant for radiologists and cardiologists designed to help in their clinical decision-making. The sieve is a clinical informatics system that collects clinical, textual and imaging data of patients from electronic health records systems. It then analyzes multimodal content to detect anomalies if any, and summarizes the patient record collecting all relevant information pertinent to a chief complaint. The results of anomaly detection are then fed into a reasoning engine which uses evidence from both patient-independent clinical knowledge and large-scale patient-driven similar patient statistics to arrive at potential differential diagnosis to help in clinical decision making. In compactly summarizing all relevant information to the clinician per chief complaint, the system still retains links to the raw data for detailed review providing holistic summaries of patient conditions. Results of clinical studies in the domains of cardiology and breast radiology have already shown the promise of the system in differential diagnosis and imaging studies summarization.

  9. Molecular Insights into Carbon Nanotube Supercapacitors: Capacitance Independent of Voltage and Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Guang [Vanderbilt Univ., Nashville, TN (United States). Dept. of Chemical and Biomolecular Engineering; Li, Song [Vanderbilt Univ., Nashville, TN (United States). Dept. of Chemical and Biomolecular Engineering; Atchison, Jennifer S. [Leibniz Inst. for New Materials (INM), Saarbrücken (Germany); Presser, Volker [Leibniz Inst. for New Materials (INM), Saarbrücken (Germany); Cummings, Peter T. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Chemical and Biomolecular Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science

    2013-04-12

    Molecular dynamics (MD) simulations of supercapacitors with single-walled carbon nanotube (SWCNT) electrodes in room-temperature ionic liquids were performed to investigate the influences of the applied electrical potential, the radius/curvature of SWCNTs, and temperature on their capacitive behavior. It is found that (1) SWCNTs-based supercapacitors exhibit a near-flat capacitance–potential curve, (2) the capacitance increases as the tube radius decreases, and (3) the capacitance depends little on the temperature. We report the first MD study showing the influence of the electrode curvature on the capacitance–potential curve and negligible dependence of temperature on capacitance of tubular electrode. The latter is in good agreement with recent experimental findings and is attributed to the similarity of the electrical double layer (EDL) microstructure with temperature varying from 260 to 400 K. The electrode curvature effect is explained by the dominance of charge overscreening and increased ion density per unit area of electrode surface.

  10. Calculation of the paramagnetism of large carbon nanotubes, using a parameter-independent molecular orbital model

    Science.gov (United States)

    Collado, J. R. Alvarez

    A previous self-consistent field molecular orbital method, able to describe systems having a large number of unpaired electrons, n, is reviewed and improved. This method is applied to the study of paramagnetism in large (1,000-16,000 atoms) zigzag carbon nanotubes, represented by their n values. The computational scheme is based on the Hückel neglect differential overlap approach. It is shown that dependence of n on the semiempirical parameters is very small, and so they can be removed from the calculation. Enhancement of the paramagnetism (increase of n), by use of a strong external magnetic field, is also studied. Finally, the dependence of the Fermi one-electron potential energies and the spin atomic densities on both the parameters and the shape of the nanotubes is analyzed.0

  11. Synthesis and analytical applications of molecularly imprinted polymers on the surface of carbon nanotubes: a review

    International Nuclear Information System (INIS)

    This review (with 142 references) summarize the state of the art in molecularly imprinting technology as applied to the surface of carbon nanotubes (CNTs) which result in so-called CNTs-MIPs. These nanomaterials offer a remedy to the flaws of traditional MIPs, such as poor site accessibility for templates, slow mass transfer and template leakage. They also are flexible in that different materials can be integrated with CNTs. Given the advantages of using CNT-MIPs, this technology has experienced rapid expansion, not the least because CNT-MIPs can be produced at low cost and by a variety of synthetic approaches. We summarize methods of, and recent advances in the synthesis of CNT-MIPs, and then highlight some representative applications. We also comment on their potential future developments and research directions. (author)

  12. Molecular dynamics investigation of carbon nanotube junctions in non-aqueous solutions

    KAUST Repository

    Gkionis, Konstantinos

    2014-07-23

    The properties of liquids in a confined environment are known to differ from those in the bulk. Extending this knowledge to geometries defined by two metallic layers in contact with the ends of a carbon nanotube is important for describing a large class of nanodevices that operate in non-aqueous environments. Here we report a series of classical molecular dynamics simulations for gold-electrode junctions in acetone, cyclohexane and N,N-dimethylformamide solutions and analyze the structure and the dynamics of the solvents in different regions of the nanojunction. The presence of the nanotube has little effect on the ordering of the solvents along its axis, while in the transversal direction deviations are observed. Importantly, the orientational dynamics of the solvents at the electrode-nanotube interface differ dramatically from that found when only the electrodes are present.

  13. Molecular Dynamics for Elastic and Plastic Deformation of a Single-Walled Carbon Nanotube Under Nanoindentation

    Institute of Scientific and Technical Information of China (English)

    FANG Te-Hua; JIAN Sheng-Rui; CHUU Der-San

    2004-01-01

    @@ Mechanical characteristics of a suspended (10, 10) single-walled carbon nanotube (SWCNT) during atomic force microscopy (AFM) nanoindentation are investigated at different temperatures by molecular dynamics simulations.The results indicate that the Young modulus of the (10, 10) SWCNT under temperatures of 300-600K is 1.2-1.3 TPa. As the temperature increases, the Young modulus of the SWCNT increases, but the axial strain of the SWCNT decreases. The strain-induced spontaneous formation of the Stone-Wales defects and the rippled behaviour under inhomogeneous stress are studied. The rippled behaviour of the SWCNT is enhanced with the increasing axial strain. The adhesive phenomenon between the probe and the nanotube and the elastic recovery of the nanotube during the retraction are also investigated.

  14. Mechanical Properties of Carbon Nanofiber Reinforced Polymer Composites-Molecular Dynamics Approach

    Science.gov (United States)

    Sharma, Sumit; Chandra, Rakesh; Kumar, Pramod; Kumar, Navin

    2016-06-01

    Molecular dynamics simulation has been used to study the effect of carbon nanofiber (CNF) volume fraction ( V f) and aspect ratio ( l/d) on mechanical properties of CNF-reinforced polypropylene (PP) composites. Materials Studio 5.5 has been used as a tool for finding the modulus and damping in composites. CNF composition in PP was varied by volume from 0% to 16%. The aspect ratio of CNF was varied from l/d = 5 to l/d = 100. Results show that, with only 2% addition by volume of CNF in PP, E 11 increases 748%. Increase in E 22 is much less in comparison to the increase in E 11. With the increase in the CNF aspect ratio ( l/d) up to l/d = 60, the longitudinal loss factor ( η 11) decreases rapidly. The results of this study have been compared with those available in the literature.

  15. Molecular Dynamics Study of Double-Walled Carbon Nanotubes for Nano-Mechanical Manipulation

    Science.gov (United States)

    Kimoto, Yoshihisa; Mori, Hideki; Mikami, Tomohito; Akita, Seiji; Nakayama, Yoshikazu; Higashi, Kenji; Hirai, Yoshihiko

    2005-04-01

    Double-walled carbon nanotubes (DWNTs) are expected to be useful as elements in nano-mechanical systems such as nanobearings and nanosliders. A molecular dynamics simulation is carried out to estimate the relative motion between the inner and outer tubes. The force required to pull the inner tube out of the outer tube is evaluated quantitatively by pulling the inner tube under a constant velocity for DWNTs with various inter-tube spacings and chiralities. When the inner tube is pulled under smaller constant force, the inner tube vibrates inside the outer tube without being pulled out, and an energetics is applied to explain the critical force and vibrational amplitude. The constant force induces not only vibration along the tube axis but also rotation around the tube axis, which indicates the possibility of creating a slider crank mechanism using a DWNT.

  16. Molecular dynamics simulation of the test of single-walled carbon nanotubes under tensile loading

    Institute of Scientific and Technical Information of China (English)

    FU ChenXin; CHEN YunFei; JIAO JiWei

    2007-01-01

    Molecular dynamics (MD) simulations were performed to do the test of single-walled carbon nanotubes (SWCNT) under tensile loading with the use of Brenner potential to describe the interactions of atoms in SWCNTs. The Young's modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT's deformation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure behavior.

  17. Molecular dynamics simulation of the test of single-walled carbon nanotubes under tensile loading

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Molecular dynamics (MD) simulations were performed to do the test of sin-gle-walled carbon nanotubes (SWCNT) under tensile loading with the use of Bren-ner potential to describe the interactions of atoms in SWCNTs. The Young’s modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT’s de-formation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure be-havior.

  18. Molecular simulation of carbon dioxide, brine, and clay mineral interactions and determination of contact angles.

    Science.gov (United States)

    Tenney, Craig M; Cygan, Randall T

    2014-01-01

    Capture and subsequent geologic storage of CO2 in deep brine reservoirs plays a significant role in plans to reduce atmospheric carbon emission and resulting global climate change. The interaction of CO2 and brine species with mineral surfaces controls the ultimate fate of injected CO2 at the nanoscale via geochemistry, at the pore-scale via capillary trapping, and at the field-scale via relative permeability. We used large-scale molecular dynamics simulations to study the behavior of supercritical CO2 and aqueous fluids on both the hydrophilic and hydrophobic basal surfaces of kaolinite, a common clay mineral. In the presence of a bulk aqueous phase, supercritical CO2 forms a nonwetting droplet above the hydrophilic surface of kaolinite. This CO2 droplet is separated from the mineral surface by distinct layers of water, which prevent the CO2 droplet from interacting directly with the mineral surface. Conversely, both CO2 and H2O molecules interact directly with the hydrophobic surface of kaolinite. In the presence of bulk supercritical CO2, nonwetting aqueous droplets interact with the hydrophobic surface of kaolinite via a mixture of adsorbed CO2 and H2O molecules. Because nucleation and precipitation of minerals should depend strongly on the local distribution of CO2, H2O, and ion species, these nanoscale surface interactions are expected to influence long-term mineralization of injected carbon dioxide. PMID:24410258

  19. Molecular simulation of carbon dioxide, brine, and clay mineral interactions and determination of contact angles.

    Science.gov (United States)

    Tenney, Craig M; Cygan, Randall T

    2014-01-01

    Capture and subsequent geologic storage of CO2 in deep brine reservoirs plays a significant role in plans to reduce atmospheric carbon emission and resulting global climate change. The interaction of CO2 and brine species with mineral surfaces controls the ultimate fate of injected CO2 at the nanoscale via geochemistry, at the pore-scale via capillary trapping, and at the field-scale via relative permeability. We used large-scale molecular dynamics simulations to study the behavior of supercritical CO2 and aqueous fluids on both the hydrophilic and hydrophobic basal surfaces of kaolinite, a common clay mineral. In the presence of a bulk aqueous phase, supercritical CO2 forms a nonwetting droplet above the hydrophilic surface of kaolinite. This CO2 droplet is separated from the mineral surface by distinct layers of water, which prevent the CO2 droplet from interacting directly with the mineral surface. Conversely, both CO2 and H2O molecules interact directly with the hydrophobic surface of kaolinite. In the presence of bulk supercritical CO2, nonwetting aqueous droplets interact with the hydrophobic surface of kaolinite via a mixture of adsorbed CO2 and H2O molecules. Because nucleation and precipitation of minerals should depend strongly on the local distribution of CO2, H2O, and ion species, these nanoscale surface interactions are expected to influence long-term mineralization of injected carbon dioxide.

  20. The effective modulus of super carbon nanotubes predicted by molecular structure mechanics.

    Science.gov (United States)

    Li, Ying; Qiu, Xinming; Yang, Fan; Wang, Xi-Shu; Yin, Yajun

    2008-06-01

    A super carbon nanotube (ST) is a kind of hierarchical structure constructed from carbon nanotubes (named as CNT arm tubes). With the detailed construction of a Y-junction considered, the effective mechanical properties of ST structures are studied by the molecular structure mechanics (MSM) method. The Young's modulus and shear modulus of STs are found to depend mainly on the aspect ratio of CNT arm tubes instead of the chirality of the ST. A scale law is adopted to express the relation between the effective modulus (Young's modulus or shear modulus) and the aspect ratio of the CNT arm tubes. The Poisson's ratio of the ST is affected by both the aspect ratio of the CNT arm tubes and the chirality of the ST. The deformation of the ST comes from both the bending and the stretching of the CNT arm tubes. The Y-junction acts as an reinforcement phase to make the bending and stretching couple together and induce large linearity in ST structures. PMID:21825768

  1. Molecular dynamics simulation of the formation of sp3 hybridized bonds in hydrogenated diamondlike carbon deposition processes.

    Science.gov (United States)

    Murakami, Yasuo; Horiguchi, Seishi; Hamaguchi, Satoshi

    2010-04-01

    The formation process of sp3 hybridized carbon networks (i.e., diamondlike structures) in hydrogenated diamondlike carbon (DLC) films has been studied with the use of molecular-dynamics simulations. The processes simulated in this study are injections of hydrocarbon (CH3 and CH) beams into amorphous carbon (a-C) substrates. It has been shown that diamondlike sp3 structures are formed predominantly at a subsurface level when the beam energy is relatively high, as in the "subplantation" process for hydrogen-free DLC deposition. However, for hydrogenated DLC deposition, the presence of abundant hydrogen at subsurface levels, together with thermal spikes caused by energetic ion injections, substantially enhances the formation of carbon-to-carbon sp3 bonds. Therefore, the sp3 bond formation process for hydrogenated DLC films essentially differs from that for hydrogen-free DLC films.

  2. Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

    KAUST Repository

    Kadoura, Ahmad Salim

    2016-05-26

    Molecular dynamics simulations were carried out to study the structural and transport properties of carbon dioxide, methane, and their mixture at 298.15 K in Na-montmorillonite clay in the presence of water. The simulations show that, the self-diffusion coefficients of pure CO2 and CH4 molecules in the interlayers of Na-montmorillonite decrease as their loading increases, possibly because of steric hindrance. The diffusion of CO2 in the interlayers of Na-montmorillonite, at constant loading of CO2, is not significantly affected by CH4 for the investigated CO2/CH4 mixture compositions. We attribute this to the preferential adsorption of CO2 over CH4 in Na-montmorillonite. While the presence of adsorbed CO2 molecules, at constant loading of CH4, very significantly reduces the self-diffusion coefficients of CH4, and relatively larger decrease in those diffusion coefficients are obtained at higher loadings. The preferential adsorption of CO2 molecules to the clay surface screens those possible attractive surface sites for CH4. The competition between screening and steric effects leads to a very slight decrease in the diffusion coefficients of CH4 molecules at low CO2 loadings. The steric hindrance effect, however, becomes much more significant at higher CO2 loadings and the diffusion coefficients of methane molecules significantly decrease. Our simulations also indicate that, similar effects of water on both carbon dioxide and methane, increase with increasing water concentration, at constant loadings of CO2 and CH4 in the interlayers of Na-montmorillonite. Our results could be useful, because of the significance of shale gas exploitation and carbon dioxide storage.

  3. Molecular carbon isotope variations in core samples taken at the Permian-Triassic boundary layers in southern China

    Science.gov (United States)

    Wang, Ruiliang; Zhang, Shuichang; Brassell, Simon; Wang, Jiaxue; Lu, Zhengyuan; Ming, Qingzhong; Wang, Xiaomei; Bian, Lizeng

    2012-07-01

    Stable carbon isotope composition (δ13C) of carbonate sediments and the molecular (biomarker) characteristics of a continuous Permian-Triassic (PT) layer in southern China were studied to obtain geochemical signals of global change at the Permian-Triassic boundary (PTB). Carbonate carbon isotope values shifted toward positive before the end of the Permian period and then shifted negative above the PTB into the Triassic period. Molecular carbon isotope values of biomarkers followed the same trend at and below the PTB and remained negative in the Triassic layer. These biomarkers were acyclic isoprenoids, ranging from C15 to C40, steranes (C27 dominates) and terpenoids that were all significantly more abundant in samples from the Permian layer than those from the Triassic layer. The Triassic layer was distinguished by the dominance of higher molecular weight (waxy) n-alkanes. Stable carbon isotope values of individual components, including n-alkanes and acyclic isoprenoids such as phytane, isop-C25, and squalane, are depleted in δ13C by up to 8-10‰ in the Triassic samples as compared to the Permian. Measured molecular and isotopic variations of organic matter in the PT layers support the generally accepted view of Permian oceanic stagnation followed by a massive upwelling of toxic deep waters at the PTB. A series of large-scale (global) outgassing events may be associated with the carbon isotope shift we measured. This is also consistent with the lithological evidence we observed of white thin-clay layers in this region. Our findings, in context with a generally accepted stagnant Permian ocean, followed by massive upwelling of toxic deep waters might be the major causes of the largest global mass extinction event that occurred at the Permian-Triassic boundary.

  4. Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products.

    Science.gov (United States)

    Chevrot, Guillaume; Sollier, Arnaud; Pineau, Nicolas

    2012-02-28

    We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 μs). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations. PMID:22380052

  5. Ameliorative effects of pomegranate on carbon tetrachloride hepatotoxicity in rats: A molecular and histopathological study.

    Science.gov (United States)

    Ibrahim, Zein Shaban; Nassan, Mohamed Abdo; Soliman, Mohamed Mohamed

    2016-04-01

    The present study aimed to investigate the molecular mechanism underlying the hepatoprotective effects of pomegranate (POM) against oxidative stress in a rat model of carbon tetrachloride (CCl4)-induced liver damage. Injection of rats with CCl4 resulted in hepatic inflammation and lipid accumulation via the upregulation of interleukin (IL)‑6 and sterol regulatory element‑binding protein 1c (SREBP‑1c) mRNA expression. CCl4 induced downregulation of the anti‑inflammatory factors alpha 2‑macroglobulin (α‑2M) and IL‑10 in comparison with the POM treated group. In addition, CCl4 induced downregulation of superoxide dismutase (SOD), glutathione S‑transferase (GST) and catalase (CAT) expression. Conversely, prior administration of POM counteracted the deleterious alterations induced by CCl4. POM downregulated CCl4-induced IL‑6 upregulation, normalized the increase in SREBP‑1c expression, and prevented CCl4‑induced α‑2M downregulation. POM counteracted CCL4‑induced alterations via immunosuppressive, anti‑inflammatory and regenerative effects by upregulating transforming growth factor‑β1, HSP70 and IL-10 mRNA expression. In addition, POM increased reactive oxygen species scavenging activity by augmenting the antioxidant defense mechanism against CCl4 hepatotoxicity, as demonstrated by detecting SOD, CAT and GST expression. These results confirm that, at the molecular level, POM exerts hepatoprotective effects against CCl4‑induced oxidative stress and liver tissue damage. PMID:26936425

  6. An energy dispersive x-ray scattering and molecular dynamics study of liquid dimethyl carbonate

    Science.gov (United States)

    Gontrani, Lorenzo; Russina, Olga; Marincola, Flaminia Cesare; Caminiti, Ruggero

    2009-12-01

    In this work, we report on the first x-ray diffraction study on liquid dimethyl carbonate. Diffraction spectra were collected with an energy-dispersive instrument, whose wide Q-range allows the structure determination of weakly ordered systems (such as liquids). The structural correlation in this liquid ranges up to about 20 Å. The observed patterns are interpreted with a structural model derived from classical molecular dynamics simulations. The simulations were run using OPLS force field, only slightly modified to restrain bond distances to the experimental values. The model structure function and radial distribution functions, averaged among the productive trajectory frames, are in very good agreement with the corresponding experimental ones. Molecular dynamics results show that the deviations from C2v cis-cis structure, predicted by ab initio calculations and observed by electron diffraction in the gas phase, are small. By analyzing the intra- and intermolecular pair distribution functions, it was possible to assign the peaks of the experimental radial distribution function to specific structural correlations, and to compute the different average intermolecular coordination numbers. The intermolecular methyl-carbonyl oxygen distance is thoroughly discussed to assess the presence of weak C-H⋯ṡO hydrogen bonds.

  7. Investigation of the influence factors of polyethylene molecule encapsulated into carbon nanotubes by molecular dynamics simulation

    International Nuclear Information System (INIS)

    In this work, the influence factors, namely chirality, temperature, radius and surface chemical modification, of the interaction energy for polyethylene (PE) molecule encapsulated into single-walled carbon nanotubes (SWNTs) had been investigated by molecular mechanics (MM) and molecular dynamics (MD) simulation. The results showed that all these factors would influence the interaction energy between PE and SWNTs. The interaction energy between PE molecule and the armchair SWNTs is largest among eight kinds of chiral SWNTs. The interaction energy decreases with the increase of temperature or the SWNT radius. The methyl, phenyl, hydroxyl, carboxyl, -F, and amino groups, have been introduced onto the surface of the SWNTs by the simulation software and the influence of SWNT chemical modification has also been investigated. The interaction energy between PE and chemically modified SWNTs is larger than that between PE and pristine SWNTs, and increases with increasing the concentration of the modified groups monotonously. In addition, the group electronegativity and van der Waals force will affect the interaction energy between PE and chemically modified SWNTs greatly, which can be attributed to the electronic structures of the chemically modified groups. This study can provide some useful suggestions for the composite material design and drug transport.

  8. Molecular Quantum Spintronics: Supramolecular Spin Valves Based on Single-Molecule Magnets and Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Wolfgang Wernsdorfer

    2011-10-01

    Full Text Available We built new hybrid devices consisting of chemical vapor deposition (CVD grown carbon nanotube (CNT transistors, decorated with TbPc2 (Pc = phthalocyanine rare-earth based single-molecule magnets (SMMs. The drafting was achieved by tailoring supramolecular π-π interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (TB ~ 1 K of isolated TbPc2 SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined. Our results introduce a new design for operable molecular spintronic devices using the quantum effects of individual SMMs.

  9. Molecular quantum spintronics: supramolecular spin valves based on single-molecule magnets and carbon nanotubes.

    Science.gov (United States)

    Urdampilleta, Matias; Nguyen, Ngoc-Viet; Cleuziou, Jean-Pierre; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang

    2011-01-01

    We built new hybrid devices consisting of chemical vapor deposition (CVD) grown carbon nanotube (CNT) transistors, decorated with TbPc(2) (Pc = phthalocyanine) rare-earth based single-molecule magnets (SMMs). The drafting was achieved by tailoring supramolecular π-π interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (T(B) ~ 1 K) of isolated TbPc(2) SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined. Our results introduce a new design for operable molecular spintronic devices using the quantum effects of individual SMMs. PMID:22072910

  10. Carbon paste electrode modified with duplex molecularly imprinted polymer hybrid film for metronidazole detection.

    Science.gov (United States)

    Xiao, Ni; Deng, Jian; Cheng, Jianlin; Ju, Saiqin; Zhao, Haiqing; Xie, Jin; Qian, Duo; He, Jun

    2016-07-15

    A novel electrochemical sensor based on duplex molecularly imprinted polymer (DMIP) hybrid film modified carbon paste electrode (CPE) has been developed for highly sensitive and selective determination of metronidazole (MNZ). A conductive poly(anilinomethyltriethoxysilane) film is firstly electrodeposited on the surface of a CPE, and then a molecularly imprinted polysiloxane (MIPS) membrane is covalently covered on the film via sol-gel process. The as-constructed DMIP hybrid film, combining the advantages of MIPS and conducting MIP, can make feasible the direct and efficient signal transformation between the target analyte and the transducer, as well as enhance the imprinting recognition capability, mass transfer efficiency and the detection sensitivity. Under optimized conditions, the reduction peak currents of MNZ are linear to MNZ concentrations in the range from 4.0×10(-7) to 2.0×10(-4) molL(-1) with a detection limit of 9.1×10(-8)molL(-1). The RSD values vary from 2.9% to 4.7% for intra-day and from 3.4% to 4.2% for inter-day precision. The DMIP-based sensor has been successfully applied for the determination of MNZ in biological and pharmaceutical samples. The accuracy and reliability of the method is further confirmed by high performance liquid chromatography. PMID:26921552

  11. Co-adsorption of N2 in the presence of CH4 within carbon nanospaces: evidence from molecular simulations.

    Science.gov (United States)

    Kumar, K Vasanth; Rodríguez-Reinoso, Francisco

    2013-01-25

    Molecular simulations were performed to study the separation of CH(4) and N(2) from mixtures of composition x(CH(4))/x(N(2)) = 5/95 and x(CH(4))/x(N(2)) = 10/90 at 50 bar and 298 K on prototype carbon materials with different pore structures. The studied carbon structures include a slit and a tubular pore, that represent the simplest form of activated carbon and carbon nanotubes, respectively, in addition to a realistic porous carbon model with disordered pore structure and a recently introduced carbon foam model, which has a three-dimensional pore structure. The results indicate that, depending on the pressure and composition, the pore structure influences both the CH(4)/N(2) selectivity and the adsorption behaviour of the fluid molecules. The selectivity was decided by the interactions between CH(4) and N(2) molecules within the pore structure, in addition to the solid-fluid interactions. The simulation results indicate that, at least for the case of activated carbons (slit and random pores), it would not be appropriate to predict the binary adsorption behaviour of methane and nitrogen by means of pure component information. Regardless of the pore structure, the simulation results indicate that carbon materials show a CH(4)/N(2) (thermodynamic) selectivity of only 2-3 up to 2 bar at 298 K, and above this pressure, at equilibrium, none of the carbon materials is adequate for the efficient separation of this mixture.

  12. Investigating Molecular Inheritance of Carbon in Star-forming Regions along a Galactic Gradient

    KAUST Repository

    Smith, Rachel L.

    2015-04-01

    Observations of CO isotopologues taken at high spectral resolution toward young stellar objects (YSOs) are valuable tools for investigating protoplanetary chemical reservoirs, and enable robust comparisons between YSOs and solar system material (meteorites and the Sun). Investigating a range of YSO environments also helps parameterize variations in the distribution and evolution of carbon-based molecules, furthering an understanding of prebiotic chemistry. We have begun a wide survey of massive YSOs using Keck-NIRSPEC at high spectral resolution (R=25,000). Fundamental and first-overtone near-IR CO rovibrational absorption spectra have thus far been obtained toward 14 massive, luminous YSOs at Galactocentric radii (RGC) ranging from ~4.5 to 9.7 kpc. From these data we can obtain precise [12CO]/[13CO] gas-phase abundance ratios along a Galactic gradient, and [12CO]/[13CO]Gas can be further evaluated against published [12CO2]/[13CO2]Ice and [12CO]/[13CO]Ice because all observations are in absorption, a robust study of molecular inheritance is possible by virtue of comparing 12C/13C along the same lines-of-sight. Initial results for cold CO gas at RGC ~ 6.1 kpc and 9.4 kpc reveal [12C16O]/[13C16O] of 59+/‑8 and 74+/‑3, respectively, roughly following an expected 12C/13C Galactic gradient. Thus far, we find [12CO]/[13CO] in the cold CO gas to be lower than [12CO2]/[13CO2]Ice, suggesting that CO2 may not originate from CO reservoirs as often assumed. While very high-resolution observations of CO gas toward low-mass YSOs observed with VLT-CRIRES show significant heterogeneity in [12CO]/[13CO] at RGC ~ 8 kpc, this dispersion is not found for the massive YSOs. Both the low-mass and massive YSOs have higher [12CO]/[13CO] in warm vs. cold gas, and both show signatures suggesting possible interplay between CO ice and gas reservoirs. Overall, our results indicate that carbon isotopic evolution in massive YSO environments may follow different paths compared to low-mass YSOs

  13. Molecular Dynamics Studies on Application of Carbon Nanotubes and Graphene Sheets as Nanoresonator Sensors

    Science.gov (United States)

    Arash, Behrouz

    The main objective of the research is to study the potential application of carbon nanotubes and graphene sheets as nano-resonator sensors in the detection of atoms/molecules with vibration and wave propagation analyses. It is also aimed to develop and examine new methods in the design of nano-resonator sensors for differentiating distinct gas atoms and different macromolecules, such as DNA molecules. The hypothesis in the detection techniques is that atoms or molecules attached on the surface of the nano-resonator sensors would induce a recognizable shift in the resonant frequency of or wave velocity in the sensors. With this regard, a sensitivity index based on the shift in resonant frequency of the sensors in the vibration analysis and/or a shift in wave velocity in the sensors in the wave propagation analysis is defined and examined. In order to achieve the objective, the vibration characteristics of carbon nanotubes and graphenes are studied using molecular dynamics simulations to first propose nano-resonator sensors, which are able to differentiate distinct gas atoms with high enough resolutions even at low concentration. It is also indicated that the nano-resonator sensors are effective devices to identify different genes even with the same number of nucleobases in the structure of single-strand DNA macromolecules. The effect of various parameters such as size and restrained boundary conditions of the sensors, the position of attached atoms/molecules being detected, and environment temperature on the sensitivity of the sensors is investigated in detail. Following the studies on vibration-based sensors, the wave propagation analysis in carbon nanotubes and graphene sheets is first investigated by using molecular dynamics simulations to design nano-resonator sensors. Moreover, a nonlocal finite element model is presented and calibrated for the first time to model propagation of mechanical waves in graphene sensors attached with atoms through a verification

  14. Transport properties of carbon dioxide and methane from molecular dynamics simulations.

    Science.gov (United States)

    Aimoli, C G; Maginn, E J; Abreu, C R A

    2014-10-01

    Transport properties of carbon dioxide and methane are predicted for temperatures between (273.15 and 573.15) K and pressures up to 800 MPa by molecular dynamics simulations. Viscosities and thermal conductivities were obtained through the Green-Kubo formalism, whereas the Einstein relation was used to provide self-diffusion coefficient estimates. The differences in property predictions due to the force field nature and parametrization were investigated by the comparison of seven different CO2 models (two single-site models, three rigid three-site models, and two fully flexible three-site models) and three different CH4 models (two single-site models and one fully flexible five-site model). The simulation results show good agreement with experimental data, except for thermal conductivities at low densities. The molecular structure and force field parameters play an important role in the accuracy of the simulations, which is within the experimental deviations reported for viscosities and self-diffusion coefficients considering the most accurate CO2 and CH4 models studied. On the other hand, the molecular flexibility does not seem to improve accuracy, since the explicit account of vibrational and bending degrees of freedom in the CO2 flexible models leads to slightly less accurate results. Nonetheless, the use of a correctional term to account for vibrational modes in rigid models generally improves estimations of thermal conductivity values. At extreme densities, the caging effect observed with single-site representations of the molecules restrains mobility and leads to an unphysical overestimation of viscosities and, conversely, to the underestimation of self-diffusion coefficients. This result may help to better understand the limits of applicability of such force fields concerning structural and transport properties of dense systems. PMID:25296778

  15. Carbon sources in the Beaufort Sea revealed by molecular lipid biomarkers and compound specific isotope analysis

    Directory of Open Access Journals (Sweden)

    I. Tolosa

    2012-10-01

    Full Text Available Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids and compound specific isotope analysis of suspended particulate organic matter (SPM and surface sediments of the Mackenzie Shelf and slope (Southeast Beaufort Sea, Arctic Ocean, were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the sedimentary organic matter (OM.

    Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and < 1%, respectively. In marine SPM from the Mackenzie slope, the major contributions were fresh and detrital algal components (> 80% with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75% whereas those from the slope contained the highest proportion of fossil (40% and C3 terrestrial plant material (10%. Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the

  16. Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation

    DEFF Research Database (Denmark)

    Froelich, Daniel R.; Mullendore, Daniel L.; Jensen, Kåre Hartvig;

    2011-01-01

    Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led...

  17. Bio-methanation Of Fine Sieved Fraction Sequestered From Raw Municipal Sewage

    NARCIS (Netherlands)

    Ghasimi, D.S.M.

    2016-01-01

    Fine sieves can be implemented as compact alternatives to primary clarification. Fine sieved fraction (FSF) is a heterogeneous substrate that mainly consists of fibers originating from toilet paper and thus contains a high cellulosic fraction. Conducted researchers during my PhD: • Investigating

  18. Paleo-Reconstruction of Carbon Cycling in Large-River Delta-Front Estuaries: Use of Molecular Biomarkers

    Science.gov (United States)

    Bianchi, T. S.

    2014-12-01

    The burial of organic carbon (OC) in river deltas and continental margins worldwide account for approximately 90% of the carbon burial in the ocean. In particular, sediments in large-river delta-front estuaries have been shown to be repositories and integrators of land-use change across expansive watersheds that drain the continents to the ocean. Thus, separating natural and human-driven changes in the transport of terrestrial organic carbon (TOC) to ocean is important in understanding the effects of climate change on TOC fluxes. Molecular biomarkers of TOC (e.g., lignin phenols, fatty acids, sterols) in LDE sediments have been used extensively to reconstruct of carbon cycling changes that are reflective of land-use change in the watersheds. However, due to the highly variable hydrologic regimes across continents, continental margins (e.g., active versus passive), and coastal dynamics in LDEs, the fate and transport of these molecular biomarkers varies considerably. Here I will discuss some of the key molecular biomarkers that have been used to date in such historical reconstruction exercises in LDEs (e.g., Mississippi/Atchafalaya, Yangtze, Yellow, Ganges-Brahmaputra, Colville Rivers), and explore how margin-type, residence time of transport, redox, and molecular stability, to name a few, impact the utility of using different biomarkers in paleo-reconstruction studies.

  19. Integration of carbon nanotubes with semiconductor technology: fabrication of hybrid devices by III–V molecular beam epitaxy

    DEFF Research Database (Denmark)

    Stobbe, Søren; Lindelof, P. E.; Nygård, J.

    2006-01-01

    on incorporation of singlewall nanotubes in III–V semiconductor heterostructures grown by molecular beam epitaxy (MBE). We demonstrate that singlewall carbon nanotubes can be overgrown using MBE; electrical contacts to the nanotubes are obtained by GaMnAs grown at 250 °C. The resulting devices can exhibit field...

  20. Synthesis of Mesoporous Carbons from Date Pits for the Adsorption of Large Molecular Weight Micropollutants in Wastewater

    KAUST Repository

    Al Jeffrey, Ahmed

    2013-07-01

    Efficient reuse of waste water requires removal of micro-pollutants from waste water streams by affordable and sustainable methods. Activated carbon is considered a powerful adsorbent due to its high surface area and low cost of treatment, compared to other expensive methods such as membrane filtration. Producing activated carbon with larger mesoporosity (>2nm) is of particular interest in industry in the removal of larger molecular sized pollutants. This study reports the synthesis of mesoporous activated carbons from a nonsoluble biomass precursor (date-pits) along with chemical activation using ZnCl2. Thus, produced activated carbon showed high surface area and large mesopore volume up to 1571 m2/g and 2.00 cm3/g respectively. In addition, the pore size of the product was as high as 9.30 nm. As a method of verification, HRTEM (Highresolution transmission electron microscopy) was used to directly authenticate the pore size of the synthesized activated carbons. Tannic acid and atrazine were used as model waste water pollutants and the adsorption capability of the produced activated carbon for these pollutants were evaluated and compared to a commercial mesoporous carbon: G60 from Norit. The results showed that the sorption capacity of produced activated carbon for tannic acid was 2 times that of G60 while the sorption capacity of produced activated carbon for atrazine was lower than that of G60. The activated carbon was also evaluated for adsorption of real secondary effluent municipal wastewater and the results suggest that the produced activated carbon was able to sorb a greater amount of biopolymers than G60. These results demonstrate that the thus-produced activated carbon may be a promising sorbent for waste water treatment.

  1. Biomarker and molecular isotope approaches to deconvolve the terrestrial carbon isotope record: modern and Eocene calibrations

    Science.gov (United States)

    Diefendorf, A. F.; Freeman, K. H.; Wing, S.; Currano, E. D.

    2010-12-01

    generally 2-3‰ enriched relative to angiosperm leaves, we project that the far more abundant angiosperm lipids will be about 4-6 ‰ depleted relative to small amounts of conifer n-alkanes in natural samples. In addition, we report carbon isotope values of the terpenoids from the MVA (triterpenoids) and MEP (diterpenoids) synthesis pathways for our plant sample set. Bulk leaf tissue-to-lipid fractionation factors for terpenoids are similar and generally small, -0.4 and -0.6‰, for MVA and MEP products, respectively. Estimates of precipitation from fossil leaves at the Fifteenmile site allow us to predict leaf fractionation values for different plant types (bulk) and for triterpenoid and diterpenoid compound classes. Our fractionation factors, when applied to an estimate for the δ13C value of late Eocene CO2, agree well with bulk and molecular data. An understanding of molecular production biases greatly improves our ability to reconstruct both paleovegetation and δ13C of atmospheric CO2.

  2. An early nodulin-like protein accumulates in the sieve element plasma membrane of Arabidopsis

    DEFF Research Database (Denmark)

    Khan, Junaid A.; Wang, Qi; Sjölund, Richard D.;

    2007-01-01

    Membrane proteins within the sieve element-companion cell complex have essential roles in the physiological functioning of the phloem. The monoclonal antibody line RS6, selected from hybridomas raised against sieve elements isolated from California shield leaf (Streptanthus tortuosus; Brassicaceae......) tissue cultures, recognizes an antigen in the Arabidopsis (Arabidopsis thaliana) ecotype Columbia that is associated specifically with the plasma membrane of sieve elements, but not companion cells, and accumulates at the earliest stages of sieve element differentiation. The identity of the RS6 antigen...... floral and vegetative tissues, the sieve element-specific ENOD is expressed only within the phloem. Members of the ENOD subfamily of the cupredoxin superfamily do not appear to bind copper and have unknown functions. Phenotypic analysis of homozygous T-DNA insertion mutants for the gene At3g20570 shows...

  3. Grain size analysis of sediments from the northern Andaman Sea: Comparison of laser diffraction and sieve-pipette techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Rao, P.S.

    A comparison has been made of sand, silt, and clay percentage of 118 samples from the Ayeyarwady continental shelf, northern Andaman Sea, measured by the sieve-laser diffraction technique and by classical sieve-pipette methods. Clay and silt...

  4. Molecular simulation of multi-component adsorption processes related to carbon capture in a high surface area, disordered activated carbon

    OpenAIRE

    Di Biase, Emanuela; Sarkisov, Lev

    2015-01-01

    We employ a previously developed model of a high surface area activated carbon, based on a random packing of small fragments of a carbon sheet, functionalized with hydroxyl surface groups, to explore adsorption of water and multicomponent mixtures under conditions representing typical carbon capture processes. Adsorption of water is initialized and proceeds through the growth of clusters around the surface groups, in a process predominantly governed by hydrogen bond interactions. In contrast,...

  5. Nanoporous carbons as promising novel methane adsorbents for natural gas technology

    Institute of Scientific and Technical Information of China (English)

    Ali Morad Rashidi; Roghaye Lotfi; Amideddin Nouralishahi; Mohammad Ali Khodagholi; Masoud Zare; Faeghe Eslamipour

    2011-01-01

    Nanoporous carbons were synthesized using furfuryl alcohol and sucrose as precursors and MCM-41 and mordenite as nanoporous templates.The produced nanoporous carbons were used as adsorbent for methane storage.The average pore diameter of the samples varied from 3.9 nm to 5.9 nm and the BET surface area varied from 320 m2/g to 824 m2/g.The volumetric adsorption experiments revealed that MCM-41 and sucrose had better performance compared with mordenite and furfuryl alcohol,correspondingly.Also,the effect of precursor to template ratio on the structure of nanoporous carbons and their adsorption capacities was investigated.The nanoporous carbon produced from MCM-41 mesoporous molecular sieve partially filled by sucrose shows the best methane adsorption capacity among the tested samples.

  6. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization

    Science.gov (United States)

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-01

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~ 6 s.

  7. Molecular dynamics study of the behavior of nitromethanes enclosed inside carbon nanotube containers.

    Science.gov (United States)

    Bae, Se Won; Cho, Soo Gyeong

    2016-07-01

    We utilized molecular dynamics (MD) to investigate the behavior of nitromethane molecules (NMs) enclosed inside carbon nanotube (CNT) containers sealed with buckybowl caps. Two different sizes of CNT containers, i.e., (10,10) and (20,20), were employed to contain the energetic NMs. After loading the NMs into these containers, MD simulations were carried out at different loading densities. The loading density was changed from 0.4 to 2.0 g/cc. At low loading densities, NMs preferentially resided near the surface of the CNT wall (orienting themselves in the cylindrical direction) and near the buckybowl caps (orienting themselves in the principal-axis direction). This behavior suggests the buckybowl caps and the CNT wall have attractive interactions with the NMs. The distribution of the NMs inside the containers did not change upon increasing the temperature from ambient to 100 °C. However, the positional preference of the NMs found at ambient temperature to 100 °C was not the same as that observed at 1000 °C due to the increased thermal motions of the NMs. The size of the CNT container had a significant effect on the fluidity of the NMs. From 25 to 100 °C, the NMs inside the (10,10) CNT container were only mobile at low loading densities. On the other hand, in the (20,20) CNT container, the NMs showed good mobility up to a loading density of 1.6 g/cc. Graphical Abstract Attractive interactions between the nitromethanes and the buckybowl caps as well as the carbon nanotube wall. PMID:27262575

  8. Molecular dynamics study of the behavior of nitromethanes enclosed inside carbon nanotube containers.

    Science.gov (United States)

    Bae, Se Won; Cho, Soo Gyeong

    2016-07-01

    We utilized molecular dynamics (MD) to investigate the behavior of nitromethane molecules (NMs) enclosed inside carbon nanotube (CNT) containers sealed with buckybowl caps. Two different sizes of CNT containers, i.e., (10,10) and (20,20), were employed to contain the energetic NMs. After loading the NMs into these containers, MD simulations were carried out at different loading densities. The loading density was changed from 0.4 to 2.0 g/cc. At low loading densities, NMs preferentially resided near the surface of the CNT wall (orienting themselves in the cylindrical direction) and near the buckybowl caps (orienting themselves in the principal-axis direction). This behavior suggests the buckybowl caps and the CNT wall have attractive interactions with the NMs. The distribution of the NMs inside the containers did not change upon increasing the temperature from ambient to 100 °C. However, the positional preference of the NMs found at ambient temperature to 100 °C was not the same as that observed at 1000 °C due to the increased thermal motions of the NMs. The size of the CNT container had a significant effect on the fluidity of the NMs. From 25 to 100 °C, the NMs inside the (10,10) CNT container were only mobile at low loading densities. On the other hand, in the (20,20) CNT container, the NMs showed good mobility up to a loading density of 1.6 g/cc. Graphical Abstract Attractive interactions between the nitromethanes and the buckybowl caps as well as the carbon nanotube wall.

  9. Molecular dynamics simulations of proton-ordered water confined in low-diameter carbon nanotubes.

    Science.gov (United States)

    Li, Shujuan; Schmidt, Burkhard

    2015-03-21

    The present work deals with molecular dynamics simulations of water confined in single-walled carbon nanotubes (CNTs), with emphasis on the proton-ordering of water and its polarization. First, the water occupancy of open-ended armchair and zigzag CNTs immersed in water under ambient NPT conditions is calculated for various water models, and for varying Lennard-Jones parameters of the water-carbon interaction. As a function of the CNT diameter, the water density displays several oscillations before converging to the bulk value. Based on these results, the water structures encapsulated in 10 nm long armchair CNTs (n,n) with 5 ≤ n ≤ 10, are investigated under NVT conditions. Inside the smallest nanotubes (n = 5, 6) highly ferroelectric (FE), quasi-one-dimensional water chains are found while inside the other CNTs water molecules assemble into single-walled ice nanotubes (INTs). There are several, near-degenerate minimum energy INT structures: single helical structures were found for 7 ≤ n ≤ 10, in all cases in FE arrangement. In addition, a double helical INT structure was found for n = 8 with an even higher polarization. Prism-like structures were found only for 8 ≤ n ≤ 10 with various FE, ferrielectric (FI), and antiferroelectric (AF, n = 9, 10) proton ordering. The coexistence of the nearly iso-energetic FE, FI, and AF INT structures separated by high barriers renders the molecular dynamics highly metastable, typically with nanosecond timescales at room temperature. Hence, the replica exchange simulation method is used to obtain populations of different INT states at finite temperatures. Many of the FE INT structures confined in low-diameter CNTs are still prevalent at room temperature. Both helix-helix and helix-prism structural transitions are detected which can be either continuous (around 470 K for n = 8) or discontinuous (at 218 K for n = 9). Also melting-like transitions are found in which the INT structures are disrupted leading to a loss of FE

  10. Graphene coated with controllable N-doped carbon layer by molecular layer deposition as electrode materials for supercapacitors

    Science.gov (United States)

    Chen, Yao; Gao, Zhe; Zhang, Bin; Zhao, Shichao; Qin, Yong

    2016-05-01

    In this work, graphene is coated with nitrogen-doped carbon layer, which is produced by a carbonization process of aromatic polyimide (PI) films deposited on the surfaces of graphene by molecular layer deposition (MLD). The utilization of MLD not only allows uniform coating of PI layers on the surfaces of pristine graphene without any surface treatment, but also enables homogenous dispersion of doped nitrogen atoms in the carbonized products. The as-prepared N-doped carbon layer coated graphene (NC-G) exhibited remarkable capacitance performance as electrode materials for supercapacitor, showing a high specific capacitance of 290.2 F g-1 at current density of 1 A g-1 in 6 M KOH aqueous electrolyte, meanwhile maintaining good rate performance and stable cycle capability. The NC-G synthesized by this way represents an alternative promising candidate as electrode material for supercapacitors.

  11. Carbon Dioxide - rock interaction: from molecular observations to theorised interactions in fluid-rock systems

    Science.gov (United States)

    Calcara, Massimo; Borgia, Andrea

    2013-04-01

    Current global warming theories have produced some benefits: among them, detailed studies on CO2 and its properties, possible applications and perspectives. Starting from its use as a "green solvent" (for instance in decaffeination process), to enhance system in oil recovery, to capture and storage enough amount of CO2 in geological horizon. So, a great debate is centred around this molecule. One More useful research in natural horizon studies is its theorised use in Enhanced Geothermal Systems with CO2 as the only working fluid. In any case, the CO2 characteristics should be deeply understood, before injecting a molecule prone to change easily its aggregation state at relatively shallow depth. CO2 Rock interaction becomes therefore a focal point in approaching research sectors linked in some manner to natural or induced presence of carbon dioxide in geological horizons. Possible chemical interactions between fluids and solids have always been a central topic in defining evolution of the system as a whole in terms of dissolutions, reactions, secondary mineral formation and, in case of whichever plant, scaling. Questions arise in case of presence of CO2 with host rocks. Chemical and molecular properties are strategic. CO2 Rock interactions are based on eventual solubility capability of pure liquid and supercritical CO2 seeking and eventually quantifying its polar and/or ionic solvent capabilities. Single molecule at STP condition is linear, with central carbon atom and oxygen atoms at opposite site on a straight line with a planar angle. It has a quadrupolar moment due to the electronegativity difference between carbon and oxygen. As soon as CO2 forms bond with water, it deforms even at atmospheric pressure, assuming an induced dipole moment with a value around 0.02 Debye. Hydrated CO2 forms a hydrophilic bond; it deforms with an angle of 178 degrees. Pure CO2 forms self aggregates. In the simplest case a dimer, with two molecules of CO2 exerting mutual attraction

  12. Molecular dynamics simulation on the initial stage of 1 eV carbon deposition on silicon

    International Nuclear Information System (INIS)

    The deposition process of 1 eV carbon on silicon has been investigated by molecular dynamics (MD) simulations up to a fluence of 5.3   ×   1014 atoms cm−2 which corresponds more or less to monolayer coverage. At such low impact energies, atoms are expected to stay on the sample surface, which is also observed up to a fluence of 2   ×   1014 atoms cm−2. For higher fluence, carbon atoms start mixing into the silicon substrate. This process seems to get initiated by the increasing strain caused by the carbon atoms deposited on the silicon surface, and which leads to some gradual distortions. The latter are important for the migration of carbon atoms into the silicon lattice. During the whole process the top part of the silicon sample gets amorphized and the coordination of the carbon atoms increases from 1 or 2 to mostly 4-fold coordinated carbon atoms. The process can be considered as the starting point of silicon carbide formation and allows to explain how nm thick films can be formed from 1 eV deposition energies. The low carbon concentration of about 7% in the modified layer is, however, too low to observe a transition towards the latter. (paper)

  13. Clean Donor Oxidation Enhances the H2 Evolution Activity of a Carbon Quantum Dot-Molecular Catalyst Photosystem.

    Science.gov (United States)

    Martindale, Benjamin C M; Joliat, Evelyne; Bachmann, Cyril; Alberto, Roger; Reisner, Erwin

    2016-08-01

    Carbon quantum dots (CQDs) are new-generation light absorbers for photocatalytic H2 evolution in aqueous solution, but the performance of CQD-molecular catalyst systems is currently limited by the decomposition of the molecular component. Clean oxidation of the electron donor by donor recycling prevents the formation of destructive radical species and non-innocent oxidation products. This approach allowed a CQD-molecular nickel bis(diphosphine) photocatalyst system to reach a benchmark lifetime of more than 5 days and a record turnover number of 1094±61 molH2  (molNi )(-1) for a defined synthetic molecular nickel catalyst in purely aqueous solution under AM1.5G solar irradiation. PMID:27355200

  14. Effect of sodium polyacrylate molecular weight on the crystallogenesis of calcium carbonate

    Science.gov (United States)

    Jada, A.; Ait Akbour, R.; Jacquemet, C.; Suau, J. M.; Guerret, O.

    2007-08-01

    Aqueous solutions of sodium polyacrylates (NaPA) series having molecular weights ( Mw) ranging from 2540 to 9890 g mol -1 are used as precipitation media to control the size and shape of calcium carbonate (CaCO 3) particles. The retarding effect of polyacrylates on CaCO 3 nucleation is evidenced by the increase of the induction time, τ, of the precipitated CaCO 3, from τ=55 s in the absence of additives, to τ values in the range 100-2500 s in the presence of NaPA samples. The data also show the coexistence of two polymorphs, calcite and vaterite, for CaCO 3 particles as prepared in the presence of NaPA samples. The vaterite fraction, fv, varies in all instances with the polymer concentration, Cpoly (g. L -1), and reaches its maximum value, fv,max at optimal ratio, R (mol. g -1), of Ca ion to polymer (NaPA), R=[Ca]/([NaPA]=Cpoly). No simple general trend is found to explain the influence of the molecular weight ( Mw) of NaPA on the induction time, τ, and on the vaterite fraction, fv, since these two parameters are found to vary with Cpoly and Mw. However, under certain experimental conditions, an optimum polymer molecular weight ( Mw=5530 g mol -1) of the NaPA series, gives the highest values of fv,max and τ. Such optimum indicates the influence of Mw of NaPA on CaCO 3 nucleation and growth, and it is related to the surface density and the rate of adsorption of the polymer onto the growing crystal. The CaCO 3 particle size is reduced from about 20 μm, as obtained in the control experiment, to sizes varying in the range 2-8 μm in the presence NaPA samples. Polymers having low Mw values ( Mw<5000 g mol -1) are found to be more efficient in reducing the CaCO 3 particle size.

  15. Ultrasonically Improved Sieving of Food Materials for Manufacturing of Direct Expanded Extrudates

    Directory of Open Access Journals (Sweden)

    Mladen Brnčić

    2009-12-01

    To obtain the best fraction of corn fl our for extrusion processing (200 – 450 μm, sieving was conducted in shaker “Analysette 3” with sieving times of 5, 10 and 15 minutes. For each of these three measurements an agglomerate creation was spotted, followed by the major remain of the sample at the mesh of 450 μm. Sieving was repeated with aid of ultrasound (250 W, using power generator and by ultrasonic ring with transducer (“UIS 250 L” mounted on the sieves. Sieving was conducted again with sieving times of 5, 10 and 15 minutes, and variable amplitude of works of 25, 50 and 75% for ultrasound. Within each of these nine measurements a partial or complete agglomerate breakdown was achieved, and an optimal fraction for extrusion processing was acquired. For the desirable particle size fraction in range of 200 – 450 μm for extrusion, under the conditions of 10 and 15 minutes of sieving time with amplitude work of 75%, the most of the sample remained within desirable range (83,79% and 83.4%.

  16. Electron emission and molecular fragmentation during hydrogen and deuterium ion impact on carbon surfaces

    Science.gov (United States)

    Qayyum, A.; Schustereder, W.; Mair, C.; Scheier, P.; Märk, T. D.; Cernusca, S.; Winter, HP.; Aumayr, F.

    2003-03-01

    Molecular fragmentation and electron emission during hydrogen ion impact on graphite surfaces has been investigated in the eV to keV impact energy region typical for fusion edge plasma conditions. As a target surface graphite tiles for the Tokamak experiment Tore Supra in CEA-Cadarache/France and highly oriented pyrolytic graphite (HOPG) have been used. For both surfaces studied, the experimentally observed threshold for electron emission is at about 50 eV/amu impact energy. Electron emission from the high conductivity side of the carbon tile is 15-20% less as compared to its low conductivity side, whereas results for HOPG are generally between these two cases. Deuterium and hydrogen ions are almost equally effective in liberating electrons from graphite when comparing results for the same impact velocity. Surface-induced dissociation of deuterium ions D 3+ upon impact on Tore Supra graphite tiles, in the collision energy range of 20-100 eV, produced only atomic fragment ions D +. The other possible fragment ion D 2+ could not be observed.

  17. Molecular dynamics study of the catalyst particle size dependence on carbon nanotube growth

    Science.gov (United States)

    Ding, Feng; Rosén, Arne; Bolton, Kim

    2004-08-01

    The molecular dynamics method, based on an empirical potential energy surface, was used to study the effect of catalyst particle size on the growth mechanism and structure of single-walled carbon nanotubes (SWNTs). The temperature for nanotube nucleation (800-1100 K), which occurs on the surface of the cluster, is similar to that used in catalyst chemical vapor deposition experiments, and the growth mechanism, which is described within the vapor-liquid-solid model, is the same for all cluster sizes studied here (iron clusters containing between 10 and 200 atoms were simulated). Large catalyst particles, which contain at least 20 iron atoms, nucleate SWNTs that have a far better tubular structure than SWNTs nucleated from smaller clusters. In addition, the SWNTs that grow from the larger clusters have diameters that are similar to the cluster diameter, whereas the smaller clusters, which have diameters less than 0.5 nm, nucleate nanotubes that are ≈0.6-0.7 nm in diameter. This is in agreement with the experimental observations that SWNT diameters are similar to the catalyst particle diameter, and that the narrowest free-standing SWNT is 0.6-0.7 nm.

  18. Electron emission and molecular fragmentation during hydrogen and deuterium ion impact on carbon surfaces

    International Nuclear Information System (INIS)

    Molecular fragmentation and electron emission during hydrogen ion impact on graphite surfaces has been investigated in the eV to keV impact energy region typical for fusion edge plasma conditions. As a target surface graphite tiles for the Tokamak experiment Tore Supra in CEA-Cadarache/France and highly oriented pyrolytic graphite (HOPG) have been used. For both surfaces studied, the experimentally observed threshold for electron emission is at about 50 eV/amu impact energy. Electron emission from the high conductivity side of the carbon tile is 15-20% less as compared to its low conductivity side, whereas results for HOPG are generally between these two cases. Deuterium and hydrogen ions are almost equally effective in liberating electrons from graphite when comparing results for the same impact velocity. Surface-induced dissociation of deuterium ions D3+ upon impact on Tore Supra graphite tiles, in the collision energy range of 20-100 eV, produced only atomic fragment ions D+. The other possible fragment ion D2+ could not be observed

  19. Molecularly imprinted polymer based electrochemical detection of L-cysteine at carbon paste electrode.

    Science.gov (United States)

    Aswini, K K; Vinu Mohan, A M; Biju, V M

    2014-04-01

    A methacrylic acid (MAA) based molecularly imprinted polymer (MIP) modified carbon paste electrode (CPE) was developed for electrochemical detection of L-cysteine (Cys). Characterisation of MIP was done with FTIR and the modified electrode with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). CV, DPV and impedance analysis demonstrated that the modified electrode is responsive towards the target molecule. The optimum percentage composition of MIP for MIP/CPE and the effect of pH towards the electrode response for Cys were studied. The detection of Cys in the range of 2×10(-8) to 18×10(-8)M at MIP/CPE was monitored by DPV with a limit of detection of 9.6nM and R(2) of 0.9974. Also, various physiological interferents such as ascorbic acid, L-tryptophan, D-glucose, D-cysteine and L-cysteine were found to have little effect on DPV response at MIP/CPE. The utility of the electrode was proved by the effective detection of Cys from tap water and human blood plasma samples with reproducible results.

  20. Press-Printed Conductive Carbon Black Nanoparticle Films for Molecular Detection at the Microscale.

    Science.gov (United States)

    Della Pelle, Flavio; Vázquez, Luis; Del Carlo, Michele; Sergi, Manuel; Compagnone, Dario; Escarpa, Alberto

    2016-08-26

    Carbon black nanoparticle (CBNP) press-transferred film-based transducers for the molecular detection at the microscale level were proposed for the first time. Current-sensing atomic force microscopy (CS-AFM) revealed that the CBNP films were effectively press-transferred, retaining their good conductivity. A significant correlation between the morphology and the resistance was observed. The highest resistance was localized at the top of the press-transferred film protrusions, whereas low values are usually obtained at the deep crevices or grooves. The amount of press-transferred CBNPs is the key parameter to obtain films with improved conductivity, which is in good agreement with the electrochemical response. In addition, the conductivity of such optimum films was not only Ohmic; in fact, tunneling/hopping contributions were observed, as assessed by CS-AFM. The CBNP films acted as exclusive electrochemical transducers as evidenced by using two classes of molecules, that is, neurotransmitters and environmental organic contaminants. These results revealed the potential of these CBNP press-transferred films for providing new options in microfluidics and other related micro- and nanochemistry applications.