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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. Adsorption of gases on carbon molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, S.N.; Patwardhan, S.R.; Vijayalakshmi, S. (Indian Inst. of Technology, Bombay (India). Dept. of Chemical Engineering); Ganesh, K.S. (Hindustan Petroleum Corp. Ltd., Bombay (India))

    1994-12-01

    Adsorption on carbon molecular sieves (CMS) prepared by coke deposition has become an interesting area of adsorption due to its microporous nature and favorable separation factor on size and shape selectivity basis for many gaseous systems. In the present work CMS was synthesized from coconut shell through three major steps, namely, carbonization, activation, and coke deposition by hydrocarbon cracking. The crushed, washed, and sieved granules of coconut shell (particle size 2--3 mm) were pretreated with sodium silicate solution and oven-dried at 150 C to create the inorganic sites necessary for coke deposition. Carbonization and activation of the dried granules were carried out at 800 C, for 30 min each. The activated char thus produced was subjected to hydrocarbon cracking at 600 C for periods varying from 30 to 180 min. The product samples were characterized in terms of adsorption isotherm, kinetic adsorption curve, surface area, pore volume, pore size distribution, and characteristic energy for adsorption by using O[sub 2], N[sub 2], C[sub 2]H[sub 2], CO[sub 2], C[sub 3]H[sub 6], and CH[sub 4].

  4. Reassessing molecular sieving by kinked carbon nanotubes

    Science.gov (United States)

    Zhang, Zhongqiang; Zhang, Hongwu; Wang, Lei; Ding, Jianning; Wang, Jinbao; Zheng, Yonggang; Ye, Hongfei; Liu, Zhen; Cheng, Guanggui; Ling, Zhiyong

    2011-12-01

    Based on molecular dynamics simulations for the transport of pure nitrogen (N2), oxygen (O2) and their mixture in kinked single-walled carbon nanotubes (SWCNTs), molecular sieving by the kinked model of SWCNTs is presented. The influences of gas pressure, temperature and the component ratio of N2 in the mixture on gas separation are investigated. Considering the tradeoff between the permeability and the purity of O2, the results show that a large gas pressure, 300-500 K of gas temperature and a low component ratio of N2 in the N2-O2 mixture can be advantageous to the efficiency of gas separation. The purity of O2 can be kept higher than 80% when the component ratio of N2 is lower than 3/4, which will be advantageous to the design of multi-level gas separation mechanisms. The findings may provide theoretical references for the design and manufacture of molecular sieving devices in engineering applications.

  5. 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.

  6. 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.

  7. Production of carbon molecular sieves from illinois coals. An assessment

    Science.gov (United States)

    Lizzio, Anthony A.; Rostam-Abadi, Massoud

    1991-01-01

    Chars were produced from an Illinois No. 2 bituminous coal under various pyrolysis and activation conditions and tested for their molecular sieve properties. The amount of N2 compared to the amount of CO2 adsorbed by each char was used as a preliminary indicator of its molecular sieve properties. This relatively simple, but apparently useful test was confirmed by successfully characterizing the well-known molecular sieve properties of a commercial zeolite and molecular sieve carbon. In addition, coal chars having relatively high surface areas (800-1800 m2/g) were produced and tested for their molecular sieving capabilities. These carbon materials, which have high adsorption capacities and relatively narrow pore size distributions, should be ideal candidates for the commercial production of CMS.

  8. Recent Advances on Carbon Molecular Sieve Membranes (CMSMs and Reactors

    Directory of Open Access Journals (Sweden)

    Margot A. Llosa Tanco

    2016-08-01

    Full Text Available Carbon molecular sieve membranes (CMSMs are an important alternative for gas separation because of their ease of manufacture, high selectivity due to molecular sieve separation, and high permeance. The integration of separation by membranes and reaction in only one unit lead to a high degree of process integration/intensification, with associated benefits of increased energy, production efficiencies and reduced reactor or catalyst volume. This review focuses on recent advances in carbon molecular sieve membranes and their applications in membrane reactors.

  9. Recent Advances on Carbon Molecular Sieve Membranes (CMSMs) and Reactors

    OpenAIRE

    Margot A. Llosa Tanco; Pacheco Tanaka, David A.

    2016-01-01

    Carbon molecular sieve membranes (CMSMs) are an important alternative for gas separation because of their ease of manufacture, high selectivity due to molecular sieve separation, and high permeance. The integration of separation by membranes and reaction in only one unit lead to a high degree of process integration/intensification, with associated benefits of increased energy, production efficiencies and reduced reactor or catalyst volume. This review focuses on recent advances in carbon mole...

  10. Synthesis of carbon molecular sieves by activation and coke deposition

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, S.N.; Patwardhan, S.R.; Vijayalakshmi, S.; Gandadhar, B. (Indian Institute of Technology, Bombay (India). Dept. of Chemical Engineering)

    1993-04-01

    Carbon molecular sieves were synthesized from indigenous bituminous coal and coconut shell. After preliminary treatment, these materials were subjected to steam or carbon dioxide activation in the range 500-900[degree]C. In other experiments the raw materials were partly air-oxidized at [approximately] 200[degree]C, mixed with binder and extruded to cylindrical pellets, which were subjected to coke deposition by cracking of methane in the range 750-780[degree]C for 5-14 min. All the products were characterized by analysis of kinetic and equilibrium adsorption data. The molecular sieve performance was judged by the O[sub 2]/N[sub 2] uptake ratio. The best carbon molecular sieves, obtained by methane cracking at 780[degree]C at a flow of 100 ml min[sup -1] had an uptake ratio of 2.667. 11 refs., 7 figs., 5 tabs.

  11. An exceptional kinetic quantum sieving separation effect of hydrogen isotopes on commercially available carbon molecular sieves.

    Science.gov (United States)

    Xing, Yanlong; Cai, Jinjun; Li, Liangjun; Yang, Menglong; Zhao, Xuebo

    2014-08-14

    The quantum sieving effect of H2/D2 at 77 K on commercially available carbon molecular sieves (1.5GN-H and 3KT-172) was studied. An exceptional reverse kinetic quantum effect is observed on 1.5GN-H where D2 diffuses much faster than H2 with a ratio of up to 5.83 at low pressure, and the difference is still very evident even as the pressure increases up to 1 bar. D2 also diffuses faster than H2 on 3KT-172 with a ratio of up to 1.86. However, the reverse kinetic sieving disappears in a polymer-based carbon (PC). The present kinetic quantum sieving effect of H2 and D2 at 77 K on 1.5GN-H is the highest to date.

  12. Functionalized Carbon Molecular Sieve membranes containing Ag-nanoclusters

    NARCIS (Netherlands)

    Barsema, J.N.; Balster, J.; Jordan, V.; Vegt, van der N.F.A.; Wessling, M.

    2003-01-01

    In Carbon Molecular Sieve (CMS) membranes, the separation of O2 and N2 is primarily based on the difference in size between the gas molecules. To enhance the separation properties of these CMS membranes it is necessary to functionalize the carbon matrix with materials that show a high affinity to on

  13. A low cost route to hexagonal mesostructured carbon molecular sieves.

    Science.gov (United States)

    Kim, S S; Pinnavaia, T J

    2001-12-07

    A mesoporous carbon molecular sieve with a hexagonal framework structure (denoted C-MSU-H) has been prepared using a MSU-H silica template that can be assembled from a low cost soluble silicate precursor at near-neutral pH conditions.

  14. Carbon molecular sieve membranes prepared from porous fiber precursor

    NARCIS (Netherlands)

    Barsema, Jonathan N.; Vegt, van der N.F.A.; Koops, G.H.; Wessling, M.

    2002-01-01

    Carbon molecular sieve (CMS) membranes are usually prepared from dense polymeric precursors that already show intrinsic gas separation properties. The rationale behind this approach is that the occurrence of any kind of initial porosity will deteriorate the final CMS performance. We will show that i

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. A heterogeneous model for gas transport in carbon molecular sieves.

    Science.gov (United States)

    Ding, L P; Yuan, Y X; Farooq, S; Bhatia, S K

    2005-01-18

    A dual resistance model with distribution of either barrier or pore diffusional activation energy is proposed in this work for gas transport in carbon molecular sieve (CMS) micropores. This is a novel approach in which the equilibrium is homogeneous, but the kinetics is heterogeneous. The model seems to provide a possible explanation for the concentration dependence of the thermodynamically corrected barrier and pore diffusion coefficients observed in previous studies from this laboratory on gas diffusion in CMS. The energy distribution is assumed to follow the gamma distribution function. It is shown that the energy distribution model can fully capture the behavior described by the empirical model established in earlier studies to account for the concentration dependence of thermodynamically corrected barrier and pore diffusion coefficients. A methodology is proposed for extracting energy distribution parameters, and it is further shown that the extracted energy distribution parameters can effectively predict integral uptake and column breakthrough profiles over a wide range of operating pressures.

  20. Solid-phase reversible trap for [11C]carbon dioxide using carbon molecular sieves.

    Science.gov (United States)

    Mock, B H; Vavrek, M T; Mulholland, G K

    1995-07-01

    A simple, maintenance-free trapping technique which concentrates and purifies no-carrier-added 11CO2 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 11CO2 selectively from gas targets at room temperature. Nitrogen, O2, 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 11CO2 from a 240 cm3 target gas dump and helium flush cycle is > 99%, and the adsorbed 11CO2 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 11C-radiochemicals at this laboratory.

  1. Carbon molecular sieves from bituminous coal by controlled coke deposition

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, S.N.; Patwardhan, S.R.; Gangadhar, B. (Indian Institute of Technology, Bombay (India). Dept. of Chemical Engineering)

    1992-01-01

    Carbon molecular sieves (CMS) and zeolites are widely used as microporous sieving solids for gas and liquid separations. However, due to hydrophobicity, better thermal stability, and neutrality in both acidic and alkaline media, CMSs have definite advantages over zeolites. In the present work, an effort has been made to develop suitable process conditions for synthesizing CMSs from the locally available bituminous coal. The coal was crushed, milled, and agglomerated with sulfate pulp waste liquor (SPWL) or coal-tar pitch (CTP) as the binders, and then carbonized in nitrogen atmosphere at 800{degree}C for about 60 minutes. In order to narrow down the pore mouth sizes, acetylene and benzene were each cracked separately at 800{degree}C to facilitate the deposition of coke on the char. Acetylene and benzene were cracked for 3 to 10 minutes, and 10 to 30 minutes, respectively. Acetylene cracked samples did not show good separation, probably because of over-coking in deeper locations. In contrast benzene cracked samples were found to be highly suitable for CO{sub 2}-CH{sub 4} separation. The best result (i.e. uptake ratio of 39.9) was obtained for feed benzene entrainment in N{sub 2} of 1.27 x 10{sup -4} g/ml, cracking time of 30 minutes, and this ratio was more than 10 times that of non-coked sample. CMS samples produced using SPWL as binder showed poor O{sub 2}/N{sub 2} uptake ratios throughout (1 to 1.5), whereas samples with CTP as binder showed far more encouraging results, the best uptake ratio being 5.5 for benzene-nitrogen feed stream containing 3.508 x 10{sup -4} g/ml benzene and 5 minutes cracking time. This ratio is about 5.5 times more than that of uncoked sample. 4 tabs., 10 figs., 17 refs.

  2. Molecular dynamics simulation of carbon molecular sieve preparation for air separation

    Energy Technology Data Exchange (ETDEWEB)

    Yaghoobpour, Elham; Ahmadpour, Ali; Farhadian, Nafiseh [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shariaty-Niassar, Mojtaba [University of Tehran, Tehran(Iran, Islamic Republic of)

    2015-03-15

    Carbon deposition process on activated carbon (AC) in order to produce carbon molecular sieve (CMS) was simulated using molecular dynamics simulation. The proposed activated carbon for simulation includes micropores with different characteristic diameters and lengths. Three different temperatures of 773 K, 973 K, and 1,273 K were selected to investigate the optimum deposition temperature. Simulation results show that the carbon deposition process at 973 K creates the best adsorbent structure. While at lower temperature some micropore openings are blocked with carbon atoms, at higher temperature the number of deposited carbons on the micropores does not change significantly. Also, carbon deposition process confirms the pseudo-second-order kinetic model with an endothermic behavior. To evaluate the sieving property of adsorbent products, nitrogen and oxygen adsorption on the initial and final adsorbent products are examined. Results show that there is not any considerable difference between the equilibrium adsorption amounts of nitrogen and oxygen on the initial and final adsorbents especially at low pressure (P<10 atm). Although, adsorption kinetics curves of these gases change significantly after the carbon deposition process in comparison with the initial sample. These observations indicate that the final adsorbent has high selectivity towards oxygen compared with the nitrogen, so it can be called a carbon molecular sieve. All simulated results are in good agreement with experiments.

  3. Nanoporous carbon sorbent for molecular-sieve chromatography of lipoprotein complex

    Science.gov (United States)

    Kerimkulova, A. R.; Mansurova, B. B.; Gil'manov, M. K.; Mansurov, Z. A.

    2012-06-01

    The physicochemical characteristics of carbon sorbents are investigated. Electron microscopy data for the sorbent and separated lipoprotein complex are presented. It is found that the obtained carbon sorbent possess high porosity. Nanoporous carbon sorbents for the chromatography of molecular-sieve markers are obtained and tested. The applicability of nanoporous carbon sorbents for separation of lipoprotein complexes (LPC) is investigated.

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

    Energy Technology Data Exchange (ETDEWEB)

    Forsberg, C.W.

    1976-01-01

    Molecular sieves were investigated to separate 1 percent mixtures of krypton in gas streams of a few percent oxygen and 90+ percent carbon dioxide. Such a system will be required to concentrate the krypton gas between radioactive krypton off-gas cleanup systems such as KALC (Krypton Absorption in Liquid Carbon Dioxide) and any krypton gas bottling station. Linde 5A molecular sieves were found capable of selectively removing the CO/sub 2/ from the gas stream while partially separating the oxygen from the krypton; i.e., effecting a three-component gas separation. This use of molecular sieves differs from standard practice in two respects. First, the bulk of the gas (greater than 90 percent) is removed by molecular sieves rather than the normal practice of using molecular sieves to remove trace impurities. Second, in a single bed two separations occur simultaneously, CO/sub 2/ from other gases and krypton from oxygen. The use of molecular sieves for separating krypton and carbon dioxide is superior to alternatives such as CO/sub 2/ freezeout and chemical traps when there are only moderate gas flows and there is a need for very high reliability and ease of maintenance.

  5. Carbon dioxide sorption in a nanoporous octahedral molecular sieve

    Science.gov (United States)

    Williamson, Izaak; Nelson, Eric B.; Li, Lan

    2015-08-01

    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.

  6. A systematic investigation of the preparation and properties of composite carbon molecular sieves containing inorganic oxides

    Science.gov (United States)

    Foley, Henry C.

    1990-01-01

    The objective of this research is to define the methodology for the preparation and characterization of new carbon-based molecular sieves with composite structures. Carbon molecular sieves have found increasing application in the field of separation and purification of gases. These materials are relatively easy to prepare and their surfaces can be modified to some extent. It is expected that by combining inorganic oxides with the carbonaceous structure one can begin to design composite materials with a wider range of possible chemical and physical properties. In this way, the IOM-CMS materials may confer distinct advantages over pure carbon molecular sieves, not just for separation, but also for catalysis. The most recent results in the design and characterization of these IOM-CMS materials are reviewed and summarized. Directions for further research are also presented.

  7. A new beaded carbon molecular sieve sorbent for 222Rn monitoring.

    Science.gov (United States)

    Scarpitta, S C

    1996-05-01

    A new commercially available beaded carbon molecular sieve sorbent, Carboxen-564 (20/45 mesh), was tested and compared to Calgon-PCB (40/80) activated carbon for its adsorptive and desorptive characteristics under controlled conditions of temperature (25 degrees C) and relative humidity (RH). The amount of water vapor adsorbed by the beaded carbon molecular sieve material was typically a factor of 4 lower than the activated carbon, with a concomitant fourfold increase in the 222Rn adsorption coefficient, K(Rn). The maximum K(Rn) value for a thin layer of Carboxen-564, following a 2-d exposure at 40% RH, was 7.2 Bq kg(-1) per Bq m(-3). The K(Rn) or a 1-cm bed, following a 2-d exposure was 5.5 Bq m(-3), a 25% reduction. Under dynamic sampling conditions, where 0.4 g of the beaded carbon molecular sieve was contained in a 6 cm x 0.4 cm diameter tube, the maximum K(Rn) value was 6.5 Bq m(-3) after 2.5 h of sampling at 29% RH when the input flow rate was 4.2 x 10(-3) m3 h-1. Kinetic studies were also conducted under passive sampling conditions. The data show that the 222Rn buildup time-constant for a thin layer of the beaded carbon molecular sieve material was 1.3 h, whereas that of a 1 cm bed was 13 h. The 222Rn desorption time-constants, from gram amounts of the beaded carbon molecular sieve material into air and into a commercially available toluene based liquid scintillation cocktail, were 2 h and 3 h, respectively. Carboxen's high 222Rn adsorbing capacity, rapid kinetics, hydrophobicity and physical properties makes it an attractive alternative to other commercially available activated carbon used in passive and dynamic sampling devices.

  8. Modeling water adsorption in carbon micropores: study of water in carbon molecular sieves.

    Science.gov (United States)

    Rutherford, S W

    2006-01-17

    Measurements of water adsorption equilibrium in a carbon molecular sieve are undertaken in order to gain insight into the nature of water adsorption in carbon micropores. The measurements are taken at low concentrations to emphasize the role of oxygen-containing functional groups in the adsorption of water. Comparisons are made with previously published water adsorption data at higher concentrations to provide a data set spanning a wide range of loading. The assembled data set provides an opportunity for comparison of various theories for prediction of water adsorption in carbon micropores. Shortcomings of current theories are outlined, and an analytical theory that is free of these deficiencies is proposed in this investigation. With the consideration of micropore volume and pore size distribution, the experimental data and proposed isotherm model are consistent with previous studies of Takeda carbon molecular sieves. Also investigated is the uptake kinetics of water, which is characterized by a Fickian diffusion mechanism. The Maxwell-Stefan formulation is applied to characterize the dependence of the diffusional mobility upon loading.

  9. The dependence of the electronic conductivity of carbon molecular sieve electrodes on their charging states.

    Science.gov (United States)

    Pollak, Elad; Genish, Isaschar; Salitra, Gregory; Soffer, Abraham; Klein, Lior; Aurbach, Doron

    2006-04-13

    The dependence of the electronic conductivity of activated carbon electrodes on their potential in electrolyte solutions was examined. Kapton polymer films underwent carbonization (1000 degrees C), followed by a mild oxidation process (CO(2) at 900 degrees C) for various periods of time, to obtain carbons of different pore structures. A specially designed cell was assembled in order to measure the conductivity of carbon electrodes at different potentials in solutions. When the carbon electrodes possessed molecular sieving properties, a remarkable dependence of their conductivity on their charging state was observed. Aqueous electrolyte solutions containing ions of different sizes were used in order to demonstrate this phenomenon. As the average pore size of the activated carbons was larger, their molecular sieving ability was lower, and the dependence of their conductivity on their charging state regained its classical form. This behavior is discussed herein.

  10. 炭分子筛的表征%Characterization of carbon molecular sieve

    Institute of Scientific and Technical Information of China (English)

    车永芳; 张进华; 李小亮; 王婧娟

    2011-01-01

    Carbon molecular sieve is the critical material of the enrichment CBM variable pressure absorption units, whose properties directly determine the function of the variable pressure absorption units. The specific surface area and pore size distribution of carbon molecular sieve is investigated according to analyzing N2 adsorption and desorption isotherms at 77 K. Compare the adsorption ability of carbon molecular sieve for N2, O2, CH4, H2 according to adsorption experiments. Adsorption rates of N2 and CH4 are analyzed, which make it easy for determining the separation ability of different carbon molecular sieve for gas.%炭分子筛是浓缩煤层气变压吸附机组的关键材料,性能的好坏直接影响变压吸附机组的性能.通过在77 K下N2的吸脱附等温线对炭分子筛的比表面积、孔径分布进行测定,通过吸附试验对炭分子筛吸附N2,O2,CO2,CH4,H2的能力及N2和CH4在炭分子筛上的吸附速度进行比较,以确定不同炭分子筛分离气体的能力.

  11. Ag-functionalized carbon molecular-sieve membranes based on polyelectrolyte/polyimide blend precursors

    NARCIS (Netherlands)

    Barsema, Jonathan N.; Vegt, van der Nico F.A.; Koops, Geert Henk; Wessling, Matthias

    2005-01-01

    We prepared dense flat-sheet Ag-functionalized carbon molecular-sieve (CMS) membranes from blends of P84 co-polyimide and a sulfonated poly(ether ether ketone) with a Ag+ counterion (AgSPEEK). These blends offer the possibility of producing new functionalized precursor structures, which were previou

  12. Utility of 5A molecular sieves to measure carbon isotope ratios in lipid biomarkers.

    Science.gov (United States)

    Tolosa, Imma; Ogrinc, Nives

    2007-09-21

    A procedure using 5A zeolite sorption to separate cyclic/branched organic compounds from the linear ones was developed and carbon isotopic fractionation effects were investigated in different families of compounds, e.g. within the hydrocarbon and alcohol compounds. The 5A sieve has a pore size such that only linear components can be incorporated into the pores whereas the cyclic/branched compounds are remaining free in the organic solution. The sorbed compounds were released from the molecular sieve with HF and solvent extracted with hexane. The method enables the isolation of linear saturated classes, such as n-alkanes and n-fatty alcohols from branched/cyclic compounds without isotopic fractionation for compound-specific isotope analysis (CSIA) of delta(13)C. However, alkene hydrocarbons, sterols and some aromatics were completely or partly degraded with the molecular sieve.

  13. Carbon molecular sieves from carbon cloth: Influence of the chemical impregnant on gas separation properties

    Science.gov (United States)

    Rodríguez-Blanco, G.; Giraldo, L.; Moreno-Piraján, J. C.

    2010-06-01

    Carbon materials with molecular sieve properties (CMS) were prepared by pyrolysis of cotton fabrics by chemical activation procedures. To evaluate the changes in the chemical and textural properties, the impregnants AlCl 3, ZnCl 2 and H 3PO 4 were used at 1123 K. The materials were characterized using adsorption of nitrogen and carbon dioxide, TPD, and immersion calorimetry in C 6H 6. Adsorption kinetics of O 2, N 2, CO 2, CH 4, C 3H 8 and C 3H 6 were measured in all the prepared materials to determine their behaviour as molecular sieves. The results confirm that the chemical used as impregnant has a significant effect on the resulting CMS separation properties. All materials exhibit microporosity and low oxygen surface group contents; however, the sample impregnated with zinc chloride, with an immersion enthalpy value of 66.4 J g -1 in benzene, exhibits the best performance in the separation of CH 4-CO 2 and C 3H 8-C 3H 6 at 273 K.

  14. Various conformations of carbon nanocoils prepared by supported Ni-Fe/molecular sieve catalyst.

    Science.gov (United States)

    Yang, Shaoming; Chen, Xiuqin; Takeuchi, K; Motojima, Seiji

    2006-01-01

    The carbon nanocoils with various kinds of conformations were prepared by the catalytic pyrolysis of acetylene using the Ni metal catalyst supported on molecular Sieves which was prepared using Fe-containing kaolin as the raw material. There are four kinds of carbon nanocoils conformations produced by this catalyst. The influences of reaction temperature and gas conditions on the conformations of the nanocoils were investigated and the reasons of forming nano-size coils were discussed by comparison with pure Ni metal catalyst.

  15. 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.

  16. 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.

  17. Diffusion of light gases in 6FDA/BPDA-DAM Carbon Molecular Sieve membranes by Pulsed Field Gradient NMR

    OpenAIRE

    Mueller, Robert; Kanungo, Rohit; Kiyono-Shimobe, Mayumi; Koros, William J.; Vasenkov, Sergey

    2015-01-01

    In this paper, we demonstrate the potential of pulsed field gradient (PFG) NMR spectroscopy to reveal detailed knowledge of self-diffusion of light gases and light gas mixtures in carbon molecular sieve membranes on small length scales. PFG NMR is used to investigate intra-membrane diffusion of carbon dioxide and methane for a broad range of temperatures and mean square displacements in a carbon molecular sieve membrane derived from a 6FDA/BPDA-DAM polyimide film. Diffusion is investigated...

  18. 炭分子筛的研究进展%Progress of Carbon Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    陆安慧; 郑经堂; 王茂章

    2001-01-01

    In this paper,the development of carbon molecular sieves(CMS)both in domestic and abroad has been reviewed,which includes precursors,preparations,and applications of CMS.%本文介绍了国内外炭分子筛的发展现状,包括炭分子筛的前驱体、制备方法以及应用等。

  19. From an equilibrium based MOF adsorbent to a kinetic selective carbon molecular sieve for paraffin/iso-paraffin separation.

    Science.gov (United States)

    Li, Baiyan; Belmabkhout, Youssef; Zhang, Yiming; Bhatt, Prashant M; He, Hongming; Zhang, Daliang; Han, Yu; Eddaoudi, Mohamed; Perman, Jason A; Ma, Shengqian

    2016-11-24

    We unveil a unique kinetic driven separation material for selectively removing linear paraffins from iso-paraffins via a molecular sieving mechanism. Subsequent carbonization and thermal treatment of CD-MOF-2, the cyclodextrin metal-organic framework, afforded a carbon molecular sieve with a uniform and reduced pore size of ca. 5.0 Å, and it exhibited highly selective kinetic separation of n-butane and n-pentane from iso-butane and iso-pentane, respectively.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Biomass-based palm shell activated carbon and palm shell carbon molecular sieve as gas separation adsorbents.

    Science.gov (United States)

    Sethupathi, Sumathi; Bashir, Mohammed Jk; Akbar, Zinatizadeh Ali; Mohamed, Abdul Rahman

    2015-04-01

    Lignocellulosic biomass has been widely recognised as a potential low-cost source for the production of high added value materials and proved to be a good precursor for the production of activated carbons. One of such valuable biomasses used for the production of activated carbons is palm shell. Palm shell (endocarp) is an abundant by-product produced from the palm oil industries throughout tropical countries. Palm shell activated carbon and palm shell carbon molecular sieve has been widely applied in various environmental pollution control technologies, mainly owing to its high adsorption performance, well-developed porosity and low cost, leading to potential applications in gas-phase separation using adsorption processes. This mini-review represents a comprehensive overview of the palm shell activated carbon and palm shell carbon molecular sieve preparation method, physicochemical properties and feasibility of palm shell activated carbon and palm shell carbon molecular sieve in gas separation processes. Some of the limitations are outlined and suggestions for future improvements are pointed out.

  5. 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.

  6. A Virtual Laboratory for the 4 Bed Molecular Sieve of the Carbon Dioxide Removal Assembly

    Science.gov (United States)

    Coker, Robert; Knox, James; O'Connor, Brian

    2016-01-01

    Ongoing work to improve water and carbon dioxide separation systems to be used on crewed space vehicles combines sub-scale systems testing and multi-physics simulations. Thus, as part of NASA's Advanced Exploration Systems (AES) program and the Life Support Systems Project (LSSP), fully predictive COMSOL Multiphysics models of the Four Bed Molecular Sieve (4BMS) of the Carbon Dioxide Removal Assembly (CDRA) on the International Space Station (ISS) have been developed. This Virtual Laboratory is being used to help reduce mass, power, and volume requirements for exploration missions. In this paper we describe current and planned modeling developments in the area of carbon dioxide removal to support future missions as well as the resolution of anomalies observed in the ISS CDRA.

  7. From an equilibrium based MOF adsorbent to a kinetic selective carbon molecular sieve for paraffin/iso-paraffin separation

    KAUST Repository

    Li, Baiyan

    2016-11-04

    We unveil a unique kinetic driven separation material for selectively removing linear paraffins from iso-paraffins via a molecular sieving mechanism. Subsequent carbonization and thermal treatment of CD-MOF-2, the cyclodextrin metal-organic framework, afforded a carbon molecular sieve with a uniform and reduced pore size of ca. 5.0 Å, and it exhibited highly selective kinetic separation of n-butane and n-pentane from iso-butane and iso-pentane, respectively. © The Royal Society of Chemistry.

  8. 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.

  9. Development of Polysulfone (PSF)-Carbon Molecular Sieve (CMS) Mixed Matrix Membrane (MMM) For O2/N2 Gas Separation

    Science.gov (United States)

    Ismail, A. F.; Rahman, W. R.; Aziz, F.

    2009-06-01

    Mixed matrix membranes (MMMs) comprising polysulfone (PSF) Udel® P-1700 and synthesized carbon molecular sieve (CMS) particles (sieve adhesion was achieved in MMMs using the combination of PSF-CMS even at high sieve loading (up to 35 wt%). The formation of `sieve-in-the-cage' morphology in PSF-CMS MMMs has been minimized to a great extend by implementing casting procedure at the operating temperature close to the Tg of polymer matrix. The O2 and N2 permeability for MMMs were increased with increasing CMS loading; while at 20 wt% CMS loading the O2/N2 selectivity attain the highest value which is 5.97 with the O2 permeability of 7.9617 barrers.

  10. Water Vapor Adsorption Capacity of Thermally Fluorinated Carbon Molecular Sieves for CO2 Capture

    Directory of Open Access Journals (Sweden)

    Jin-Young Jung

    2013-01-01

    Full Text Available The surfaces of carbon molecular sieves (CMSs were thermally fluorinated to adsorb water vapor. The fluorination of the CMSs was performed at various temperatures (100, 200, 300, and 400°C to investigate the effects of the fluorine gas (F2 content on the surface properties. Fluorine-related functional groups formed were effectively generated on the surface of the CMSs via thermal fluorination process, and the total pore volume and specific surface area of the pores in the CMSs increased during the thermal fluorination process, especially those with diameters ≤ 8 Å. The water vapor adsorption capacity of the thermally fluorinated CMSs increased compared with the as-received CMSs, which is attributable to the increased specific surface area and to the semicovalent bonds of the C–F groups.

  11. 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.

  12. 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.

  13. Equilibrium and kinetics of water adsorption in carbon molecular sieve: theory and experiment.

    Science.gov (United States)

    Rutherford, S W; Coons, J E

    2004-09-28

    Measurements of water adsorption equilibrium and kinetics in Takeda carbon molecular sieve (CMS) were undertaken in an effort to characterize fundamental mechanisms of adsorption and transport. Adsorption equilibrium revealed a type III isotherm that was characterized by cooperative multimolecular sorption theory. Water adsorption was found to be reversible and did not display hysteresis upon desorption over the conditions studied. Adsorption kinetics measurements revealed that a Fickian diffusion mechanism governed the uptake of water and that the rate of adsorption decreased with increasing relative pressure. Previous investigations have attributed the observed decreasing trend in the rate of adsorption to blocking of micropores. Here, it is proposed that the decrease is attributed to the thermodynamic correction to Fick's law which is formulated on the basis of the chemical potential as the driving force for transport. The thermodynamically corrected formulation accounted for observations of transport of water and other molecules in CMS.

  14. Kinetic isotope effect for H2 and D2 quantum molecular sieving in adsorption/desorption on porous carbon materials.

    Science.gov (United States)

    Zhao, Xuebo; Villar-Rodil, Silvia; Fletcher, Ashleigh J; Thomas, K Mark

    2006-05-25

    Adsorption and desorption of H(2) and D(2) from porous carbon materials, such as activated carbon at 77 K, are usually fully reversible with very rapid adsorption/desorption kinetics. The adsorption and desorption of H(2) and D(2) at 77 K on a carbon molecular sieve (Takeda 3A), where the kinetic selectivity was incorporated by carbon deposition, and a carbon, where the pore structure was modified by thermal annealing to give similar pore structure characteristics to the carbon molecular sieve substrate, were studied. The D(2) adsorption and desorption kinetics were significantly faster (up to x1.9) than the corresponding H(2) kinetics for specific pressure increments/decrements. This represents the first experimental observation of kinetic isotope quantum molecular sieving in porous materials due to the larger zero-point energy for the lighter H(2), resulting in slower adsorption/desorption kinetics compared with the heavier D(2). The results are discussed in terms of the adsorption mechanism.

  15. 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.

  16. 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.

  17. Adsorption equilibrium and thermodynamics of CO2 and CH4 on carbon molecular sieves

    Science.gov (United States)

    Song, Xue; Wang, Li'ao; Ma, Xu; Zeng, Yunmin

    2017-02-01

    Carbon molecular sieves (CMS) are widely used in the separation of dioxide carbon and methane. In this research, three commercial CMS were utilized to analyze the pore structure and chemical properties. The adsorption isotherms of CO2 and CH4 were studied at 298 K, 308 K and 318 K over the pressure range of 0-1 MPa by an Intelligent Gravimetric analysis (IGA-100B, UK). Langmuir model was adopted to fit the experimental data. The working capacity and selectivity were employed to evaluate the adsorbents. The adsorption thermodynamics were discussed. The adsorbed amounts of both CO2 and CH4 are found to be highly related with the BET specific surface area and the volume of micropores, and also are interrelated with the total pore volume and micropore surface area. The standard enthalpy change (ΔHΘ), standard Gibbs free energy (ΔGΘ) and standard entropy change (ΔSΘ) at zero surface loading are negative, manifesting the adsorption process is exothermic and spontaneous, and the system tends to be ordered. With the increasing surface coverage, the absolute values of Gibbs free energy (ΔG) decrease whereas the absolute values of enthalpy change (ΔH) and entropy change(ΔS) increase. This indicates that as the adsorbed amount increases, the degree of the spontaneity reduces, the intermolecular forces among the adsorbate molecules increase, the orderliness of the system improves and the adsorbed amount approaches the maximum adsorbed capacity.

  18. Carbon molecular sieve membranes: a promising alternative for selected industrial applications.

    Science.gov (United States)

    Hägg, May-Britt; Lie, Jon A; Lindbråthen, Arne

    2003-03-01

    Carbon molecular sieve (CMS) membranes (hollow fibers) have been studied for application as possible separation units for selected industrial gas streams. Gas streams at petrochemical plants (polypropene and polyethene) and upgrading of biogas to fuel specifications have been in focus. Gases present in biogas (N(2), CO(2), H(2)O(vap), and CH(4)) and gas streams at polyolefin plants (C(2)H(4), C(3)H(6), and C(3)H(8)) have been measured; both as pure gases and in mixtures. Aging of the CMS-membranes as a function of humidity and pore blocking is discussed; likewise, possible regeneration methods when flux decrease is experienced. Transport mechanisms depending on pore size and molecular properties are also discussed. Excellent separation properties were documented for these applications, but also the need for frequent regeneration of the membrane in order to maintain permeability flux. The mixed gas experiments documented clearly the need for careful pore tailoring in order to optimize selectivity when the membranes were used for alkane-alkene separation.

  19. Enhanced anion electroadsorption into carbon molecular sieve electrodes in acidic media.

    Science.gov (United States)

    Eliad, Linoam; Salitra, Gregory; Pollak, Elad; Soffer, Abraham; Aurbach, Doron

    2005-11-08

    We previously showed that, for neutral electrolytes of small cations and relatively larger anions, it is possible to design certain pore sizes in active carbons that are large enough to electroadsorb cations but too small to allow anion electroadsorption. This situation leads to an electrical double-layer (EDL) capacitance that is significant only at potentials that are negative to the potential of zero charge (PZC); hence, much smaller capacitance is measured at potentials positive to the PZC. It was found that when the electrolyte is a strong acid (e.g., H(2)SO(4), HCl), a considerable capacitance is observed at positive potentials, even when the average pore size is too small to allow the insertion of large anions in neutral electrolyte solutions. This effect disappears when the pore size becomes considerably larger than the size of the ions. In this case, the EDL capacitance at positive potentials for both neutral and acidic solutions is comparable. The following four-step mechanism was found to comply best with the experimental data: (1) By acid catalysis, the protons form carbonium species within the conjugated carbon network. (2) The anions react with the carbonium ions, providing uncharged species in an activated state, which are chemibound as surface groups to the walls of the pores. (3) Because these surface groups are effectively much smaller in size than are the charged ions, they can migrate by chemical bond exchange within the carbon skeleton via constrictions (known to exist in microporous and molecular sieving carbons), which are too narrow to accommodate hydrated charged species. (4) Upon reaching wider spaces, the uncharged species are reionized and solvated by water molecules, which can fill small pores. The justification for the above mechanism is thoroughly discussed and demonstrated by the experimental results.

  20. Extension of the Dubinin-Astakhov equation for evaluating the micropore size distribution of a modified carbon molecular sieve.

    Science.gov (United States)

    Gil, A; Korili, S A; Cherkashinin, G Yu

    2003-06-15

    A new method for the characterization of the pore size distribution of microporous solids is applied on data obtained for activated carbon molecular sieve samples. In this method, based on the Dubinin-Astakhov equation, a simple numerical algorithm is used for the reconstruction of the micropore size distribution from the integral equation that represents the experimental nitrogen adsorption isotherm. The results are compared with the ones obtained on the basis of the well-known Horvath-Kawazoe method. The samples used in this study come from a carbon molecular sieve that has been treated with solutions of concentrated HNO3 at various temperatures and with solutions of H2O2 of various concentrations.

  1. 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%.

  2. The breakthrough curve combination for xenon sampling dynamics in a carbon molecular sieve column.

    Science.gov (United States)

    Shu-jiang, Liu; Zhan-ying, Chen; Yin-zhong, Chang; Shi-lian, Wang; Qi, Li; Yuan-qing, Fan; Huai-mao, Jia; Xin-jun, Zhang; Yun-gang, Zhao

    2015-01-21

    In the research of xenon sampling and xenon measurements, the xenon breakthrough curve plays a significant role in the xenon concentrating dynamics. In order to improve the theoretical comprehension of the xenon concentrating procedure from the atmosphere, the method of the breakthrough curve combination for sampling techniques should be developed and investigated under pulse injection conditions. In this paper, we describe a xenon breakthrough curve in a carbon molecular sieve column, the combination curve method for five conditions is shown and debated in detail; the fitting curves and the prediction equations are derived in theory and verified by the designed experiments. As a consequence, the curves of the derived equations are in good agreement with the fitting curves by tested. The retention times of the xenon in the column are 61.2, 42.2 and 23.5 at the flow rate of 1200, 1600 and 2000 mL min(-1), respectively, but the breakthrough times are 51.4, 38.6 and 35.1 min.

  3. 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

    2016-07-29

    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%.

  4. High performance carbon molecular sieving membranes derived from pyrolysis of metal-organic framework ZIF-108 doped polyimide matrices.

    Science.gov (United States)

    Jiao, Wenmei; Ban, Yujie; Shi, Zixing; Jiang, Xuesong; Li, Yanshuo; Yang, Weishen

    2016-12-11

    Carbon molecular sieve membranes (CMSMs) were fabricated by pyrolysis of MOF-doped polyimide mixed matrix membranes. ZIF-108 (Zn(2-nitroimidazolate)2) was used as a dopant to tailor the micropores of the as-prepared CMSMs into narrow ultramicropores, providing a remarkable combination of permeability and selectivity of membranes in CO2/CH4, O2/N2 and N2/CH4 separation.

  5. Transport and morphological characteristics of polyetherimide-based carbon molecular sieve membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sedigh, M.G.; Xu, L.; Tsotsis, T.T.; Sahimi, M. [Univ. of Southern California, Los Angeles, CA (United States). Dept. of Chemical Engineering

    1999-09-01

    A new class of carbon molecular sieve membranes (CMSMs) has been prepared by carbonization of polyetherimide-coated mesoporous tubular supports. The membranes show higher permeance and better separation factors than other supported CMSMs reported in the literature for the CO{sub 2}/CH{sub 4} and H{sub 2}/CH{sub 4} binary mixtures as well as for the CO{sub 2}H{sub 2}/CH{sub 4} ternary mixture. CO{sub 2}/CH{sub 4} separation factors as high as 145 for the equimolar binary and 155 for the ternary mixture were obtained with a CO{sub 2} permeance about 0.15 (cm{sup 3}/cm{sup 2}{center_dot}psi{center_dot}min). The corresponding H{sub 2}/CH{sub 4} separation factors for the equimolar binary and ternary mixtures were 68 and 50, respectively, with a H{sub 2} permeance of 0.13 (cm{sup 3}/cm{sup 2}{center_dot}psi{center_dot}min). The membrane also shows good stability when tested with CO{sub 2} and Ar single gases, as well as with an equimolar mixture of CO{sub 2}/CH{sub 4}. To study the mechanism of permeation and separation in CMSMs, tests with single gases as well as with binary and ternary mixtures were performed at different temperatures, transmembrane pressure differences, and feed compositions. Elemental analysis, scanning electron microscopy, and gas adsorption were also employed to study the morphology of the resulting membranes. Elemental analysis shows that although the structure consists mostly of carbon, it also still contains oxygen, nitrogen and hydrogen. Scanning electron microscopy of the cross section of the carbonized membrane shows that the carbonized layer lies essentially within the mesoporous {gamma}-alumina layer, a result also verified by N{sub 2} adsorption analysis at 77 K. The experimental data were compared with simulation results with the same mixtures using a nonequilibrium molecular dynamics method.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Diffusion of methane and carbon dioxide in carbon molecular sieve membranes by multinuclear pulsed field gradient NMR.

    Science.gov (United States)

    Mueller, Robert; Kanungo, Rohit; Kiyono-Shimobe, Mayumi; Koros, William J; Vasenkov, Sergey

    2012-07-10

    Carbon molecular sieve (CMS) membranes are promising materials for energy efficient separations of light gases. In this work, we report a detailed microscopic study of carbon dioxide and methane self-diffusion in three CMS membrane derived from 6FDA/BPDA(1:1)-DAM and Matrimid polymers. In addition to diffusion of one-component sorbates, diffusion of a carbon dioxide/methane mixture was investigated. Self-diffusion studies were performed by the multinuclear (i.e., (1)H and (13)C) pulsed field gradient (PFG) NMR technique which combines the advantages of high field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m). Diffusion measurements were carried out at different temperatures and for a broad range of the root-mean-square displacements of gas molecules inside the membranes. The diffusion data obtained from PFG NMR are compared with the corresponding results of membrane permeation measurements reported previously for the same membrane types. The observed differences between the transport diffusivities and self-diffusion coefficients of carbon dioxide and methane are discussed.

  11. Investigations to improve carbon dioxide control with amine and molecular sieve type sorbers

    Science.gov (United States)

    Bertrand, J. F.; Brose, H. F.; Kester, F. L.; Lunde, P. J.

    1972-01-01

    The optimization trends and operating parameters of an integral molecular sieve bed heat exchanger were investigated. The optimum combination of substrate and coating for the HS-B porous polymer was determined based on the CO2 dynamic capacity in the presence of water vapor. Full size HS-B canister performance was evaluated. An Amine CO2 Concentrator utilizing IR-45 sorber material and available Manned Orbiting Laboratory hardware was designed, fabricated and tested for use as an experiment in the NASA 90-day space simulator test of 1970. It supported four men in the simulator for 71 days out of the 90-day test duration.

  12. Synthesis of multi-wall carbon nanotubes by the pyrolysis of ethanol on Fe/MCM-41 mesoporous molecular sieves

    Science.gov (United States)

    Zhao, Qian; Li, Yanhui; Zhou, Xuping; Jiang, Tingshun; Li, Changsheng; Yin, Hengbo

    2010-03-01

    Ordered hexagonal arrangement MCM-41 mesoporous molecular sieves were synthesized by the traditional hydrothermal method, and Fe-loaded MCM-41 mesoporous molecular sieves (Fe/MCM-41) were prepared by the wet impregnation method. Their mesoporous structures were testified by X-ray diffraction (XRD) and the N 2 physical adsorption technique. Carbon nanotubes (CNTs) were synthesized by the chemical vapor deposition (CVD) method via the pyrolysis of ethanol at atmospheric pressure using Fe/MCM-41 as a catalytic template. The effect of different reaction temperatures ranging from 600 to 800 ∘C on the formation of CNTs was investigated. The resulting carbon materials were characterized by various physicochemical techniques such as transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The results show that multi-wall carbon nanotubes (MWCNTs) with an internal diameter of ca. 7.7 nm and an external diameter of ca. 16.9 nm were successfully obtained by the pyrolysis of ethanol at 800 ∘C utilizing Fe/MCM-41 as a catalytic template.

  13. 碳分子筛的制备与应用研究进展%Research Progress in Preparation and Application of Carbon Molecular Sieve

    Institute of Scientific and Technical Information of China (English)

    赵海华; 李广学; 任少阳; 彭飞; 马钊; 董安周; 段艳文

    2015-01-01

    综述了碳分子筛的各种制备方法,如炭化法、气体活化法、碳沉积法等,介绍了碳分子筛在气体分离、除杂脱色、催化等领域的应用,并提出了碳分子筛的研究热点展望。%The preparation method of Carbon Molecular Sieve such as carbonization,gas activation,chemical vapor deposition are reviewed in this paper. Also the application of Carbon Molecular Sieve in gas separation,edulcoration and decoloration, catalysis. Finally outlook the application prospect of the Carbon Molecular Sieve.

  14. Thermal and catalytic degradation of polyethylene wastes in the presence of silica gel, 5A molecular sieve and activated carbon.

    Science.gov (United States)

    González, Yovana Sander; Costa, Carlos; Márquez, M Carmen; Ramos, Pedro

    2011-03-15

    A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700 °C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450 °C and with 5A molecular sieve was 700 °C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000 J/g), similar to the heat of combustion of commercial fuels.

  15. Adsorption equilibrium and transport kinetics for a range of probe gases in Takeda 3A carbon molecular sieve.

    Science.gov (United States)

    Rutherford, S W; Coons, J E

    2005-04-15

    Measurements of adsorption equilibria and transport kinetics for argon, oxygen and nitrogen at 20, 50, and 80 degrees C on commercially derived Takeda carbon molecular sieve (CMS) employed for air separation have been undertaken in an effort to elucidate fundamental mechanisms of transport. Results indicate that micropore diffusion which is modeled by a Fickian diffusion process, governs the transport of oxygen molecules and the pore mouth barrier controls argon and nitrogen transport which is characterized by a linear driving force (LDF) model. For the three temperatures studied, the pressure dependence of the diffusivity and the LDF rate constant appear to be well characterized by a formulation based on the chemical potential as the driving force for transport. Isosteric heat of adsorption at zero loading and activation energy measurements are compared with predictions made from a previously proposed molecular model for characterizing CMS.

  16. 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

  17. Production of carbon molecular sieves from Illinois coal. [Quarterly] technical report, March 1, 1993--May 31, 1993

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-09-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recover processes. The overall objective of this project is to determine whether Illinois Basin coals are suitable feedstocks 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 prepared from Illinois 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 (KOH) 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, e.g., N{sub 2}, O{sub 2}, CO{sub 2}, CH{sub 4}, CO and H{sub 2}, on these chars at 25{degrees}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; both a high adsorption capacity and selectivity were achieved. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II 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.

  18. Niobate-based octahedral molecular sieves

    Science.gov (United States)

    Nenoff, Tina M.; Nyman, May D.

    2003-07-22

    Niobate-based octahedral molecular sieves having significant activity for multivalent cations and a method for synthesizing such sieves are disclosed. The sieves have a net negatively charged octahedral framework, comprising niobium, oxygen, and octahedrally coordinated lower valence transition metals. The framework can be charge balanced by the occluded alkali cation from the synthesis method. The alkali cation can be exchanged for other contaminant metal ions. The ion-exchanged niobate-based octahedral molecular sieve can be backexchanged in acidic solutions to yield a solution concentrated in the contaminant metal. Alternatively, the ion-exchanged niobate-based octahedral molecular sieve can be thermally converted to a durable perovskite phase waste form.

  19. 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.

  20. 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.

  1. Exploring molecular sieve capabilities of activated carbon fibers to reduce the impact of NOM preloading on trichloroethylene adsorption.

    Science.gov (United States)

    Karanfil, Tanju; Dastgheib, Seyed A; Mauldin, Dina

    2006-02-15

    Adsorption of trichloroethylene (TCE) by two activated carbon fibers (ACFs) and two granular activated carbons (GACs) preloaded with hydrophobic and transphilic fractions of natural organic matter (NOM) was examined. ACF10, the most microporous activated carbon used in this study, had over 90% of its pore volume in pores smaller than 10 A. It also had the highest volume in pores 5-8 A, which is the optimum pore size region for TCE adsorption, among the four activated carbons. Adsorption of NOM fractions by ACF10 was, in general, negligible. Therefore, ACF10, functioning as a molecular sieve during preloading, exhibited the least NOM uptake for each fraction, and subsequently the highest TCE adsorption. The other three sorbents had wider pore size distributions, including high volumes in pores larger than 10 A, where NOM molecules can adsorb. As a result, they showed a higher degree of uptake for all NOM fractions, and subsequently lower adsorption capacities for TCE, as compared to ACF10. The results obtained in this study showed that understanding the interplay between the optimum pore size region for the adsorption of target synthetic organic contaminant (SOC) and the pore size region for the adsorption of NOM molecules is important for controlling NOM-SOC competitions. Experiments with different NOM fractions indicated that the degree of NOM loading is important in terms of preloading effects; however the waythatthe carbon pores are filled and loaded by different NOM fractions can be different and may create an additional negative impact on TCE adsorption.

  2. 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.

  3. 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.

  4. 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.

  5. Gas separation performance of carbon molecular sieve membranes based on 6FDA-mPDA/DABA (3:2) polyimide.

    Science.gov (United States)

    Qiu, Wulin; Zhang, Kuang; Li, Fuyue Stephanie; Zhang, Ke; Koros, William J

    2014-04-01

    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 CO2 /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 CO2 /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.

  6. 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.

  7. 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...

  8. A 99 percent purity molecular sieve oxygen generator

    Science.gov (United States)

    Miller, G. W.

    1991-01-01

    Molecular sieve oxygen generating systems (MSOGS) have become the accepted method for the production of breathable oxygen on military aircraft. These systems separate oxygen for aircraft engine bleed air by application of pressure swing adsorption (PSA) technology. Oxygen is concentrated by preferential adsorption in nitrogen in a zeolite molecular sieve. However, the inability of current zeolite molecular sieves to discriminate between oxygen and argon results in an oxygen purity limitations of 93-95 percent (both oxygen and argon concentrate). The goal was to develop a new PSA process capable of exceeding the present oxygen purity limitations. A novel molecular sieve oxygen concentrator was developed which is capable of generating oxygen concentrations of up to 99.7 percent directly from air. The process is comprised of four absorbent beds, two containing a zeolite molecular sieve and two containing a carbon molecular sieve. This new process may find use in aircraft and medical breathing systems, and industrial air separation systems. The commercial potential of the process is currently being evaluated.

  9. A novel processing of carbon nanotubes grown on molecular sieve coated porous ceramics

    Science.gov (United States)

    Mazumder, Sangram; Sarkar, Naboneeta; Park, Jung Gyu; Zhao, Wei; Kim, Sukyoung; Kim, Ik Jin

    2015-08-01

    The present study focuses on the growth of carbon nanotubes (CNTs) on Fe-containing zeolites coated porous ceramics by implementing three different and independent techniques, successively. Direct foaming-derived porous ceramics were subjected to hydrothermal reaction for on-site growth of NaA zeolites within it. The porous ceramics-zeolite composite was subjected to ion-exchange reaction to obtain the catalyst for CNT synthesis. Multi-walled CNTs (MWCNTs) were grown by catalytic chemical vapour deposition (CCVD) process using acetylene as carbon source. Microstructural, thermogravimetric and spectroscopic analyses showed distinctive differences in terms of hollow structural feature, yield and crystallinity of the MWCNTs with different reaction temperatures.

  10. Biogas purification using carbon molecular sieves by pressure swing adsorption%碳分子筛变压吸附提纯沼气的性能

    Institute of Scientific and Technical Information of China (English)

    王骏成; 胡明振; 孙林兵; 刘晓勤

    2015-01-01

    Carbon molecular sieves were selected to separate CH4/CO2 mixture by pressure swing adsorption. Adsorption isotherms of pure CH4,CO2 and N2gases on carbon molecular sieves were measured by the intelligent gravimetric analyzer apparatus(IGA-100,HIDEN)at 25℃,and the gas diffusion rates on the adsorbents were in the order of CO2>N2>CH4. The breakthrough curves were measured by single fixed bed device. Pressures,flow rates and trace nitrogen(2%)were discussed to investigate separation performances,and adsorption mechanisms were also discussed. The results indicated that adsorption capacity of CO2 and CH4 on carbon molecular sieves were 35.9mL/g and 5.4mL/g respectively at pressure of 0.4MPa and flow rate of 200mL/min. The separation coefficient of CO2/CH4 reached 12.6,indicating that pure CH4 could be collected from the fixed bed device,and the carbon molecular sieves could be well regenerated by vacuum desorption. These results suggested that carbon molecular sieves might be suitable for CO2 removal from biogas. The diffusion rate of N2 was faster than that of CH4 on carbon molecular sieves; therefore it is possible to enrich CH4 with high concentration through the fixed bed device.%选择碳分子筛,以 CH4和 CO2为原料气,对变压吸附法提纯沼气中生物甲烷的分离性能进行了研究.采用高精度智能重量分析仪IGA-100测定了25℃下CH4、CO2和N2纯组分气体在碳分子筛上的吸附平衡等温线,计算了3种气体在碳分子筛内的扩散速率CO2>N2>CH4.使用单塔变压吸附装置测量了动态吸附穿透曲线,考察了吸附压力、气体流量和少量氮气等因素对吸附分离的影响,并对吸附机理做了初步探讨.实验结果表明,在吸附压力为0.4MPa、气体流量为200mL/min时,在碳分子筛上CO2穿透吸附量为35.9mL/g,CH4穿透吸附量为5.4mL/g,CO2/CH4分离系数高达 12.6,可直接从吸附塔顶富集纯净的 CH4,而且碳分子筛可以通过抽真空完全再生,是一种理想

  11. 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.

  12. Gas chromatography for in situ analysis of a cometary nucleus. II. Analysis of permanent gases and light hydrocarbons with a carbon molecular sieve porous layer open tubular column.

    Science.gov (United States)

    Szopa, C; Sternberg, R; Coscia, D; Raulin, F; Vidal-Madjar, C

    2000-12-22

    Considering the severe constraints of space instrumentation, a great improvement for the in situ gas chromatographic (GC) determination of permanent and noble gases in a cometary nucleus is the use of a new carbon molecular sieve porous layer open tubular (PLOT) column called Carbobond. No exhaustive data dealing with this column being available, studies were carried out to entirely characterize its analytical performances, especially when used under the operating conditions of the cometary sampling and composition (COSAC) experiment of the European Space Agency (ESA) Rosetta space mission to be launched in 2003 for a rendezvous with comet 46 P/Wirtanen in 2011. The high efficiency and speed of analysis of this column at both atmospheric and vacuum outlet column pressure is demonstrated, and the kinetic mass transfer contribution of this carbon molecular sieve adsorbent is calculated. Besides, differential adsorption enthalpies of several gases and light hydrocarbons were determined from the variation of retention volume with temperature. The data indicate close adsorption behaviors on the Carbobond porous layer adsorbent and on the carbon molecular sieve Carboxen support used to prepare the packed columns. Moreover, taking into account the in situ operating conditions of the experiment, a study of two columns with different porous layer thicknesses allowed one to optimize the separation of the target components and to select the column parameters compatible with the instrument constraints. Comparison with columns of similar selectivity shows that these capillary columns are the first ones able to perform the same work as the packed and micro-packed columns dedicated to the separation of this range of compounds in GC space exploration.

  13. 21 CFR 173.40 - Molecular sieve resins.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Molecular sieve resins. 173.40 Section 173.40 Food... Polymer Substances and Polymer Adjuvants for Food Treatment § 173.40 Molecular sieve resins. Molecular sieve resins may be safely used in the processing of food under the following prescribed conditions:...

  14. 以焦粉为原料制备空分制氮用碳分子筛的研究%Study on the preparation of carbon molecular sieve made with coke fines applied in air-nitrogen

    Institute of Scientific and Technical Information of China (English)

    宋春来

    2009-01-01

    以焦粉为原料,煤焦油、环氧树脂为粘结剂,采取先浸渍再碳化的方法制备空分制氮用的碳分子筛(Carbon molecular sieve,CMS).实验结果表明:当用煤焦油与树脂为粘结剂,粘结剂的含量为20%,碳化温度为700℃,恒温时间为30 min,浸渍时间为30 min时制备的碳分子筛的空分性能最佳,可使空气中的氮气含量达到90%.%The carbon molecular sieve was prepared with coke powder; epoxy resin and coal tar match the compound binder. Taking charring before dipping as method of their pretreatment to prepare the Carbon molecu-lar sieve, the results showed that: When using coal tar and resin as binder, the binder content is 20%, the carbonation temperature is 700 ℃, thermostats time is for 30 min, dipping time is for 30 rnin, carbon molec-ular sieve for the air separation is the best, the nitrogen content in the air can reach to 90 percent.

  15. Carbon molecular sieve membrane from a microporous spirobisindane-based polyimide precursor with enhanced ethylene/ethane mixed-gas selectivity

    KAUST Repository

    Salinas, Octavio

    2017-01-13

    Ethylene is typically produced by steam cracking of various hydrocarbon feedstocks. The gaseous products are then separated in a demethanizer followed by a deethanizer unit and finally sent to a C splitter for the final purification step. Cryogenic distillation of ethylene from ethane is the most energy-intensive unit operation process in the chemical industry. Therefore, the development of more energy-efficient processes for ethylene purification is highly desirable. Membrane-based separation has been proposed as an alternative option for replacement or debottlenecking of C splitters but current polymer membrane materials exhibit insufficient mixed-gas CH/CH selectivity (<7) to be technically and economically attractive. In this work, a highly selective carbon molecular sieve (CMS) membrane derived from a novel spirobisindane-based polyimide of intrinsic microporosity (PIM-6FDA) was developed and characterized. PIM-6FDA showed a single-stage degradation process under an inert nitrogen atmosphere which commenced at ∼480 °C. The CMS formed by pyrolysis at 800 °C had a diffusion/size-sieving-controlled morphology with a mixed-gas (50% CH/50% CH) ethylene/ethane selectivity of 15.6 at 20 bar feed pressure at 35 °C. The mixed-gas ethylene/ethane selectivity is the highest reported value for CMS-type membranes to date.

  16. Influence of carbonization process on the performance of phenolic resin based carbon molecular sieve%炭化工艺对酚醛树脂基碳分子筛性能的影响

    Institute of Scientific and Technical Information of China (English)

    张放; 傅吉全

    2016-01-01

    Using commercial phenolic resin( PF)as the carbon source,F127 triblock polymer as the tem-plate ,the carbon molecular sieve was prepared. The effects of carbonization preparation technology on pore size distribution of carbon molecular sieve were investigated. The as-prepared samples were characterized by N2 adsorption-desorption. The results showed that the carbonization temperature,carbonization time, heating rate had great influence on the pore size distribution of the carbon molecular sieve. Under the preparation condition of carbonization rate 1 ℃·min-1 ,carbonization temperature 800 ℃ and carboniza-tion time 1 h,the pore size distribution of the carbon molecular sieve was the most concentrated,BET surface area,total pore capacity of a single point,and microporous volume of a single point adsorption were 716. 59 m2 ·g-1 ,0. 557 75 cm3 ·g-1 and 0. 301 81 cm3 ·g-1 ,respectively.%以工业酚醛树脂为碳源,三嵌段聚合物F127为模板剂,制备碳分子筛。采用N2吸附-脱附对制备的碳分子筛进行表征,研究炭化制备工艺对碳分子筛孔径分布的影响。结果表明,炭化温度、炭化时间和炭化升温速率对碳分子筛孔径分布影响较大。在炭化升温速率为1℃·min-1、炭化温度800℃和炭化时间1 h 条件下制备的碳分子筛孔径分布最为集中,BET 比表面积716.59 m2·g-1,单点总孔容0.55775 cm3·g-1,单点吸附微孔孔容0.30181 cm3·g-1。

  17. Characterization for carbon molecular sieve used to separate CH4/N2%用于分离 CH4/N2炭分子筛的表征

    Institute of Scientific and Technical Information of China (English)

    车永芳; 张进华; 王岭

    2015-01-01

    基于炭分子筛是浓缩煤层气变压吸附机组的关键材料,其性能的好坏直接影响变压吸附机组的性能,故需对炭分子筛进行快速及准确的评价。介绍了利用微型变压吸附(PSA)对样品炭分子筛进行评价,以研究适用于 PSA 的炭分子筛的评价方法,即炭分子筛的粒度、强度、装填密度和干燥减重等测定指标达标后,再以炭分子筛为吸附剂进行变压吸附实验,以确定炭分子筛分离CH 4/N2的能力。%carbon molecular sieve is the critical material of the enrichment CBM variable pressure absorption units, with its performance directly affect the function of the variable pressure absorption units.Therefore, can be quickly is particularly important for accurate evaluation of carbon molecular sieves.First determine the grit size and strength of the carbon molecular sieve, loading density and dry weight of these basic indicators.These indicators standard after the carbon molecular sieve as adsorbent for pressure swing adsorption experiment, to determine the carbon molecular sieve separation of CH 4 /N2 .

  18. 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.

  19. 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.

  20. 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.

  1. 分子筛CO2去除系统研究%Study on Carbon Dioxide Removal Assembly Using Molecular Sieve Technology

    Institute of Scientific and Technical Information of China (English)

    韩永强; 吴宝治; 杨润泽; 卞强; 李小委

    2013-01-01

    Objective To explore the feasibility of using molecular sieve technology in a carbon dioxide removal assembly in the future space station.Methods The design/operating principle of four beds molecular sieve (4BMS) adsorption-regeneration system developed for space station was systematically analyzed.Under the simulated space station work load conditions,the prototype was tested in a closed demonstration cabin of the environmental control and life support system for consecutive 120 d.Results The CO2 concentration in the sealed cabin was controlled below 0.5% with the metabolism load of 3 persons,the air dew point was always below-33 ℃ and the average power consumption of the system was less than 800 W.Conclusion The prototype 4BMS device can satisfy the CO2 control requirements of the future space station.%目的 探索分子筛CO2去除技术应用于空间站系统的可行性.方法 系统分析了空间站分子筛CO2去除系统(4BMS)原理样机设计和工作原理,在模拟空间站真实负荷的条件下对该原理样机进行了连续120 d密闭舱试验研究.结果 在3人CO2代谢量条件下,该原理样机能有效控制密闭舱内的CO2浓度在0.5%以下,并保证空气露点在-33℃以下,系统功耗不高于800 W.结论 该原理样机满足未来空间站系统对CO2浓度控制的要求.

  2. Spirobisindane-based polyimide as efficient precursor of thermally-rearranged and carbon molecular sieve membranes for enhanced propylene/propane separation

    KAUST Repository

    Swaidan, Ramy Jawdat

    2016-09-02

    High performance thermally-rearranged (TR) and carbon molecular sieve (CMS) membranes made from an intrinsically microporous polymer precursor PIM-6FDA-OH are reported for the separation of propylene from propane. Thermal rearrangement of PIM-6FDA-OH to the corresponding polybenzoxazole (PBO) membrane resulted in a pure-gas C3H6/C3H8 selectivity of 15 and C3H6 permeability of 14 Barrer, positioning it above the polymeric C3H6/C3H8 upper bound. For the first time, the C3H6/C3H8 mixed-gas properties of a TR polymer were investigated and showed a C3H6 permeability of 11 Barrer and C3H6/ C3H8 selectivity of 11, essentially independent of feed pressure up to 5 bar. The CMS membrane made by treatment at 600 C showed further improvement in performance as demonstrated with a pure-gas C3H8/C3H8 selectivity of 33 and a C3H6 permeability of 45 Barrer. The mixed-gas C3H6/C3H8 selectivity dropped from 24 to 17 from 2 to 5 bar feed pressure due to a decrease in C3H6 permeability most likely caused by competitive sorption without any evidence of plasticization. (C) 2016 Elsevier B.V. All rights reserved.

  3. 炭分子筛膜裂解成膜过程研究%Research on Cracking Progress of Preparing Carbon Molecular Sieve Membranes

    Institute of Scientific and Technical Information of China (English)

    任莉; 赵玲艳; 刘策; 张浩; 石小阁

    2012-01-01

    Carbon molecular sieve membrane(CMSM) has been widely used in oil,metallurgy,chemical industry and many other fields as a new separation material.It has been a great breakthrough in the measurement of performance and the improvement of preparation method and it has an excellent performance.To review a mechanism of pyrolysis derived from polymer precursor and the preparation process.To apply the infrared spectroscopy,thermal analysis,XRD,SEM and other analytical tools in the determination process of performance.To offer the signicantly basis data for preparation.%炭分子筛膜(CMSM)作为一种新型的分离膜材料,已被广泛应用于石油、冶金、化工等各个领域,其性能测定、制备方法的改进及应用也得到了很大突破。综述了炭膜的优良性能、CMSM的制备工艺、聚合物前驱体的高温裂解机理。介绍了红外光谱、差热分析、XRD、SEM等表征分析手段在性能测定过程中的应用,为制备过程提供了重要的基础数据。

  4. Research Process of Mercaptan Removal by Activated Carbon and Molecular Sieve%活性炭和分子筛吸附脱硫醇的研究进展

    Institute of Scientific and Technical Information of China (English)

    黄建珍; 许可

    2015-01-01

    The structural characteristics of activated carbon and molecular sieve and the methods of surface modification were intro-duced. What's more, the research progress and the mechanism of mercaptan removal on activated carbon and molecular sieve and the factors that affected the mercaptan removal in domestic and overseas in recent years were reviewed. The results suggested that activated carbon and molecular sieve had obvious effect on mercaptan removal. Finally the improved methods were also proposed in the paper.%介绍了多孔材料活性炭和分子筛的结构特点及表面改性方法,综述了近年来国内外活性炭和分子筛在脱硫醇方面的应用研究进展,归纳了其脱硫醇的机理,论述了影响脱硫醇的因素.研究结果表明,活性炭和分子筛具有显著的脱硫醇效果.最后对目前活性炭和分子筛脱硫醇难以实现大规模应用提出了一些改进的方法,以便更有效地脱除硫醇.

  5. 分子筛脱除碳酸酯中微量水的应用研究%Study on Purification of Microscale Water in Carbonic Ester by Adsorption of 4A Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    王晓梅; 张建荣

    2012-01-01

    To study the adsorption characteristics of 4A molecular sieveswere on microscale water in carbonic ester. To investigate the effects of dosage of 4A molecular sieves, adsorption temperature, adsorption time and reusability of 4A molecular sieves on the purification of water. The results showed that the 4A molecular sieves under high temperature activation treatment has good adsorption effect to water in carbonic ester.%研究了4A分子筛对碳酸酯物质中微量水的脱除及提纯方面的作用,考察了4A分子筛用量、吸附温度、吸附时间等因素的影响,同时对重复再生后分子筛的除水性能进行了研究,结果表明,高温活化处理后的4A分子筛对碳酸酯中的水分具有较好的吸附效果。

  6. 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.

  7. 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.

  8. Study on Adsorption Equilibrium and Diffusion Model of CH4 and N2 on a Carbon Molecular Sieve%CH 4/N 2在炭分子筛上的吸附平衡与扩散模型

    Institute of Scientific and Technical Information of China (English)

    王鹏; 石耀琦; 马正飞; 刘晓勤

    2014-01-01

    使用高精密质量吸附仪(IGA-100,HIDEN)测定了CH4和N2纯组分在炭分子筛上于298、313和328 K温度下的吸附等温线及吸附动力学曲线,研究了CH4和N2在炭分子上的吸附热力学及动力学性质。选择Double Langmuir模型(DL)对吸附等温线数据进行了模拟;选择Fick扩散模型进行了吸附动力学的模拟。结果表明,DL模型可以准确地描述CH4和N2在炭分子筛上的吸附,拟合相关系数都非常接近1,N2在该炭分子筛上的吸附量大于CH4的吸附量;通过Fick扩算模型计算得:24N CH/7.26D D =,N 2在该炭分子筛上的扩散速率大于CH 4,所以该炭分子筛可以实现固定床出口直接富集CH4的目的。%Adsorption isotherms and kinetic curves of pure CH4 and N2 gases absorbing onto a carbon molecular sieve were measured by an intelligent gravimetric analyzer apparatus (IGA-100, HIDEN) at 298, 313 and 328 K, respectively. Thermodynamics and diffusion behaviors of CH4 and N2 on the carbon molecular sieve were also investigated. The Double Langmuir (DL) model and the Fick model were introduced to fit the adsorption isotherm and adsorption kinetic data, respectively. The fitting correction coefficients of the DL model for CH4 and N2 are close to 1 and the adsorption capacity of N2 is higher than that of CH4 on the carbon molecular sieve. The results of the Fick model indicate that the diffusion rate of N2 is much faster than that of CH4 on the carbon molecular sieve. Therefore, it is possible to enrich CH4 through a fixed bed using the carbon molecular sieve studied.

  9. Growth and physico-chemical properties of interconnected carbon nanotubes in FeSBA-15 mesoporous molecular sieves

    Directory of Open Access Journals (Sweden)

    Ulka Suryavanshi

    2016-03-01

    Full Text Available Carbon nanotubes (CNTs with well-defined hollow interiors, and different morphologies have been grown inside the nanochannels of iron substituted SBA-15 (Santa Barbara Amorphous with different iron contents and well-ordered large mesopores by chemical vapour deposition method. This novel method requires only 3 min for the formation of high quality multiwalled CNTs inside the SBA-15. The physico-chemical characteristics of the prepared CNT/Fe-SBA-15 nanocomposite have been analysed with powder X-ray diffraction (XRD, scanning electron microscopy (SEM, Raman spectroscopy and thermogravimetric analysis (TGA. XRD, Raman spectroscopy and TGA results confirm that the formed CNTs in SBA-15 nanochannels are highly pure and graphitic in nature, which can be altered by tuning the Fe content in the support matrix. SEM images show the interconnected network of SBA-15/CNT where CNT bridges the neighbouring SBA-15 nanoparticles. Interestingly, spring like CNTs and multi-terminal junctions such as Y and H junctions were also observed. The morphology of the CNTs inside the nanochannels of the SBA-15 support can also be controlled by the simple adjustment of the iron content in the SBA-15 framework. It has also been found that the content of Fe in the silica framework of SBA-15 plays a significant role in the formation of the CNTs and the amount of deposited CNTs in the nanochannels of SBA-15 increased with increasing the concentration of iron in framework. Among the materials studied, the FeSBA-15 with the nSi/nFe ratio of 2 showed the highest catalytic activity towards the formation of high quality CNTs.

  10. Deposition Temperature Affected to Performance of Carbon Molecular Sieve Applied to CH4/N2 Separation%沉积温度对CH_4/N_2分离用碳分子筛性能的影响

    Institute of Scientific and Technical Information of China (English)

    董卫果

    2012-01-01

    In order to provide technical parameters to prepare the carbon molecular sieve applied to CH4/N2 separation, the paper investigated carbon temperatures of 450, 500, 550, 600 and 650 ~C affected to the performance of the carbon molecular sieve applied to the CH4/N2 separation. The results showed that the adsorption volume and the balanced separation coefficient both would be increased with the carbon deposition temperature increased and then would be decreased in tendency. When the deposition temperature was at 550 ~C, the performance of the carbon molecular sieve would be optimum, the max adsorption volume of CH4 was 1.41 mmol/g and the balanced separation coefficient of CH4/N2 was 4.74. The adsorption/desorption isotherm of nitrogen showed that the carbon molecular sieve sample prepared under the such conditions was micropore mainly.%为给用于分离CH4/N2的碳分子筛制备提供技术参数,考察了碳沉积温度为450、500、550、600、650oС时,其对CH4/N2分离用碳分子筛性能的影响。结果表明:吸附容量和平衡分离系数均随着碳沉积温度的增加呈先增加后减小的趋势,沉积温度为550oС时碳分子筛性能最佳,CH4最大吸附容量达1.41mmol/g,CH4/N2平衡分离系数达4.74。氮气吸附/脱附等温线表明在此条件下制备的碳分子筛样品以微孔为主。

  11. Microscopic Observation of Kinetic Molecular Sieving of Hydrogen Isotopes in a Nanoporous Material

    Science.gov (United States)

    Nguyen, T. X.; Jobic, H.; Bhatia, S. K.

    2010-08-01

    We report quasielastic neutron scattering studies of H2-D2 diffusion in a carbon molecular sieve, demonstrating remarkable quantum effects, with the heavier isotope diffusing faster below 100 K, confirming our recent predictions. Our transition state theory and molecular dynamics calculations show that while it is critical for this effect to have narrow windows of size comparable to the de Broglie wavelength, high flux requires that the energy barrier be reduced through small cages. Such materials will enable novel processes for kinetic molecular sieving of hydrogen isotopes.

  12. 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.

  13. 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.

  14. CH4/O2 Adsorption kinetics on carbon molecular sieve%CH4/O2在炭分子筛上的吸附动力学

    Institute of Scientific and Technical Information of China (English)

    党艳艳

    2013-01-01

    In order to eliminate the safety hidden peril existed in the seam mining on the coal bed methane in the low gassy mine,a deoxidation technique based on the kinetic difference of CH4 and O2 on carbon molecular sieve (CMS) was put forward.The volume method was applied to get kinetic data of pure CH4 and O2 adsorbed on CMS.And a study of the breakthrough curve was carried out on one-bed pressure swing adsorption apparatus.The study results show that the diffusion rate of O2 is larger than CH4 at the initial time of adsorption.It demonstrates from the breakthrough curve that CH4 is first through the fixed bed.Thus CH4 can be enriched directly at the outlet.0.4MPa,the recovery of CH4 is 73.27% when the concentration of CH4 is 92.44%.%为消除低浓度煤层气对煤层开采存在的安全隐患,提出了利用甲烷和氧气在炭分子筛上的动力学差异进行脱氧的工艺.采用容积法测定了纯CH4和O2在炭分子筛颗粒上的吸附动力学数据,并利用单床变压吸附装置测定了混合气体在298.15K,各压力下的穿透曲线.研究结果显示:吸附初期,O2在CMS上的扩散速率明显大于CH4;在混合体系穿透曲线上,O2的穿透时间远大于CH4,炭分子筛固定床表现出对O2的优先吸附选择性,可以实现出口直接富集甲烷的目的.0.4MPa时,当产品气中CH4含量为92.44%时,CH4回收率为73.27%.

  15. Preparation of carbon molecular sieve membranes by KOH activation for gas separation%KOH活化法制备气体分离用炭分子筛膜

    Institute of Scientific and Technical Information of China (English)

    张小勇; 刘锐; 胡浩权; 郑明东

    2012-01-01

    选用KOH为活化剂,利用化学活化法制备炭分子筛膜,考察在热塑性酚醛树脂(PFNR)涂膜液中添加不同质量分数的KOH对炭分子筛膜的影响.结果表明,在炭化过程中,KOH的加入可促进炭分子筛膜孔径的均匀分布,使炭分子筛膜具有发达的孔隙结构.当KOH在PFNR中的添加量从0%增加到4%时,H2的渗透速率由23.68×10-10 mol·m-2·s-1·pa-1提高到28.6×10-10 mol·m-2·s-1·Pa-1;但H2/N2和H2/CH4的分离系数明显下降,分别从471.3下降到147.5、540下降到270.CO2/CH4和O2/N2的分离系数只有轻微下降.%Carbon molecular sieve membranes were prepared by the pyrolysis of a mixture containing phenolic novolac resin and KOH. The effects of KOH on the properties of the membranes were investigated. Results showed that membranes with homogeneous pore size distributions and high gas permeation rates can be obtained by controlling the amount of KOH . Their H2 gas permeability increased from 23.68×10-10to28.6×10-10 mol·m-2·s-1·Pa-1and H2/N2 and H/CH4 selectivity decreased from 471.3 to 147.5 and 540 to 270 respectively, while the CO2/CH4 and O2/N, selectivity changed little with increasing KOH content in the coating solution from 0 to 4 mass% .

  16. 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.

  17. 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)

    McClenny, W A; Colón, M; Oliver, K D

    2001-09-21

    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 sampling experiments both generation and destruction of n-aldehydes by ozone are observed. In field experiments the results of sample analysis for n-aldehydes and benzaldehyde are frequently not proportional to sample volume whereas results for toluene and isoprene, and sometimes for total carbon, are. A simple theory is developed to simulate the net result of three processes: the adsorption of compounds from an air stream onto a solid adsorbent, the generation of compounds by reaction of ozone with materials upstream of or on the adsorbent, and the destruction by ozone of pre-existing compounds and compounds adsorbed from the sample stream. The use of distributed volume pairs is recommended as a way to identify loss of sample integrity during air monitoring experiments.

  18. 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.

  19. Electronic and Magnetic Structure of Octahedral Molecular Sieves

    Science.gov (United States)

    Morey-Oppenheim, Aimee M.

    The major part of this research consists of magnetic and electronic studies of metal doped cryptomelane-type manganese oxide octahedral molecular sieves (KOMS-2). The second part of this study involves the magnetic characterization of cobalt doped MCM-41 before and after use in the synthesis of single walled carbon nanotubes. Manganese oxides have been used widely as bulk materials in catalysis, chemical sensors, and batteries due to the wide range of possible stable oxidation states. The catalytic function of manganese oxides is further tuned by doping the material with numerous transition metals. It is of particular interest the oxidation states of Mn present after doping. New titrations to determine the oxidation state of Mn were investigated. To further examine the structure of KOMS-2, the magnetic contribution of dopant metals was also examined. The KOMS-2 structure having both diamagnetic and paramagnetic metal ions substitutions was studied. MCM-41 with the incorporation of cobalt into the structure was analyzed for its magnetic properties. The material undergoes significant structural change during the synthesis of single walled carbon nanotubes. It was the focus of this portion of the research to do a complete magnetic profile of both the before and after reaction material.

  20. 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.

  1. 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.

  2. Polymeric molecular sieve membranes via in situ cross-linking of non-porous polymer membrane templates

    Science.gov (United States)

    Qiao, Zhen-An; Chai, Song-Hai; Nelson, Kimberly; Bi, Zhonghe; Chen, Jihua; Mahurin, Shannon M.; Zhu, Xiang; Dai, Sheng

    2014-04-01

    High-performance polymeric membranes for gas separation are attractive for molecular-level separations in industrial-scale chemical, energyand environmental processes. Molecular sieving materials are widely regarded as the next-generation membranes to simultaneously achieve high permeability and selectivity. However, most polymeric molecular sieve membranes are based on a few solution-processable polymers such as polymers of intrinsic microporosity. Here we report an in situ cross-linking strategy for the preparation of polymeric molecular sieve membranes with hierarchical and tailorable porosity. These membranes demonstrate exceptional performance as molecular sieves with high gas permeabilities and selectivities for smaller gas molecules, such as carbon dioxide and oxygen, over larger molecules such as nitrogen. Hence, these membranes have potential for large-scale gas separations of commercial and environmental relevance. Moreover, this strategy could provide a possible alternative to ‘classical’ methods for the preparation of porous membranes and, in some cases, the only viable synthetic route towards certain membranes.

  3. Direct electrochemistry and electrocatalytic properties of hemoglobin immobilized on a carbon ionic liquid electrode modified with mesoporous molecular sieve MCM-41.

    Science.gov (United States)

    Li, Yonghong; Zeng, Xiandong; Liu, Xiaoying; Liu, Xinsheng; Wei, Wanzhi; Luo, Shenglian

    2010-08-01

    The direct electron transfer and electrocatalysis of hemoglobin (Hb) entrapped in the MCM-41 modified carbon ionic liquid electrode (CILE) were investigated by using cyclic voltammetry in 0.10 M pH 7.0 phosphate buffer solution (PBS). Due to its uniform pore structure, high surface areas and good biocompatibility, the mesoporous silica sieve MCM-41 provided a suitable matrix for immobilization of biomolecule. The MCM-41 modified CILE showed significant promotion to the direct electron transfer of Hb, which exhibited a pair of well defined and quasi-reversible peaks for heme Fe(III)/Fe(II) with a formal potential of -0.284 V (vs. Ag/AgCl). Additionally, the Hb immobilized on the MCM-41 modified carbon ionic liquid electrode showed excellent electrocatalytic activity toward H(2)O(2). The electrocatalytic current values were linear with increasing concentration of H(2)O(2) in a wide range of 5-310 microM and the corresponding detection limit was calculated to be 5 x 10(-8)M (S/N=3). The surface coverage of Hb immobilized on the MCM-41 modified carbon ionic liquid electrode was about 2.54 x 10(-9) molcm(-2). The Michaelis-Menten constant K(m)(app) of 214 microM indicated that the Hb immobilized on the modified electrode showed high affinity to H(2)O(2). The proposed electrode had high stability and good reproducibility due to the protection effect of MCM-41 and ionic liquid, and it would have wide potential applications in direct electrochemistry, biosensors and biocatalysis.

  4. Analysis and treatment of over-standard carbon dioxide content in the outlet air from molecular sieve adsorber in the larger scale ASU%大型空分设备分子筛出口空气中CO2含量超标分析与处理

    Institute of Scientific and Technical Information of China (English)

    韩磊; 孙瑞

    2015-01-01

    介绍分子筛吸附器出口空气中二氧化碳含量超标,采取优化操作手段,但仍未消除故障,相反,分子筛出口空气中二氧化碳含量继续升高.立即对该套空分进行停机处理,分子筛检修后运行正常.%The phenomena of over-standard carbon dioxide content in the outlet air from molecular sieve adsorber is Introduced. The optimizing operation means were failed to eliminate the fault, however, the carbon dioxide content in the outlet air from molecular sieve adsorber was continue to rise. This ASU was shut down immediately. The molecular sieve adsorber was operating normally after maintenance.

  5. Preparation of coal-based carbon molecular sieve and its application effects in CH4/N2 separation%煤基碳分子筛的制备及CH4/N2分离性能研究

    Institute of Scientific and Technical Information of China (English)

    张进华; 车永芳; 李兰廷; 梁大明; 段超; 何正刚

    2011-01-01

    以煤为原料,通过气相碳沉积法制备了CH4/N2变压吸附分离用碳分子筛,研究了苯沉积量对碳分子筛吸附性能的影响.用液氮吸附(77 K)、扫描电镜对碳分子筛孔结构及表面形貌进行了表征,结果表明:制备的碳分子筛(CMS-1)平衡分离系数大于5,比表面积SBET=251.5 m2/g,微孔孔容Vm=0.1178 mL/g,孔径主要分布在0.35~2 nm,能满足CH4/N2变压吸附分离要求.%Take coal as raw material to produce carbon molecular sieves with the method of vapor carbon deposition,which is used to concentrate methane from CH4/N2 mixtures. The effect of benzene deposition amount on the adsorption properties was studied. The pore structure of carbon molecular sieves was characterized by liquid nitrogen adsorption method (77 K). Environmental scanning electron microscopy (ESEM) was used to observe the surface morphology. The experimental results show that equilibrium separation factor of CMS-1 is greater than five, CMS-1 can meet the CH4/N2 PSA separation requirement, its BET specific surface area is 251.5 m2/g, the micro pore volume is 0.1178 cm3/g and its pore diameter size distributes mostly from 0.35 nm to 2.00 nm.

  6. Dynamic quantum molecular sieving separation of D2 from H2-D2 mixture with nanoporous materials.

    Science.gov (United States)

    Niimura, Subaru; Fujimori, Toshihiko; Minami, Daiki; Hattori, Yoshiyuki; Abrams, Lloyd; Corbin, Dave; Hata, Kenji; Kaneko, Katsumi

    2012-11-14

    Quantum molecular sieving separability of D(2) from an H(2)-D(2) mixture was measured at 77 K for activated carbon fiber, carbon molecular sieve, zeolite and single wall carbon nanotube using a flow method. The amount of adsorbed D(2) was evidently larger than H(2) for all samples. The maximum adsorption ratio difference between D(2) and H(2) was 40% for zeolite (MS13X), yielding a selectivity for D(2) with respect to H(2) of 3.05.

  7. 聚醚酰亚胺基炭分子筛膜的形成及其气体分离性能研究%Research on formation and gas separation performance of polyetherimide based carbon molecular sieve membranes

    Institute of Scientific and Technical Information of China (English)

    闫健娜; 高会元; 张彦改; 任莉

    2012-01-01

    以商用聚醚酰亚胺(PEI)作为前驱体,采用经过ZrO2-Al2O3复合溶胶修饰的陶瓷氧化铝为支撑体,浸渍涂膜制备聚合物膜,在空气中预氧化处理后,经500~800℃不同的炭化温度下制备出气体分离炭分子筛膜。为了考察炭化温度对炭膜结构和气体分离性能的影响,采用热重分析(TG)、拉曼光谱(Raman)、X射线衍射(XRD)、扫描电镜(SEM)和气体渗透等测试手段,对热解过程聚合物膜热稳定性、炭微晶结构及石墨化进程、微观形貌和气体分离性能进行了系统研究。结果表明,不同的炭化温度对所形成炭膜表现出不同物理和化学结构、炭结构和孔结构,最终影响炭分子筛膜的气体渗透性和分离选择性。%A-type carbon molecular sieve gas separation membranes were synthesized at different pyrolysis temperatures of 500-800℃ by dip-coating a commercial polyetherimide(PEI) precursor on a porous ZrO2-Al2O3 composite sol-modified alumina support and further treated by pre-oxidation in air.To investigate the influence of carbonization temperature on the carbon membrane structure and gas separation performance,thermal gravimetric analysis(TG),Raman spectroscopy(Raman),X-ray diffraction(XRD),scanning electron microscopy(SEM) and gas permeability tests were employed to systematically study thermal stability of polymer film during the pyrolysis,carbon microcrystalline structure and graphitization evolution,surface morphology studies and gas separation properties.The results indicated that the carbon membranes derived from different carbonization temperatures possessed the different physical and chemical structure,carbon structures and pore structure,which affected the permeability and selectivity of the carbon molecular sieve gas separation membranes.

  8. 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.

  9. 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.

  10. 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.

  11. Nickel phosphate molecular sieve as electrochemical capacitors material

    Science.gov (United States)

    Yang, Jing-He; Tan, Juan; Ma, Ding

    2014-08-01

    The nickel phosphate molecular sieve VSB-5 as an electrode material for supercapacitors is investigated by cyclic voltammetry (CV) and chronopotentiometry in alkaline media. The VSB-5 shows high specific capacitance and excellent cycling stability. The specific capacitance of VSB-5 is 2740 F g-1 at a current density of 3 A g-1 and there is no significant reduction in Coulombic efficiency after 3000 cycles at 30 A g-1. In comparison with mesoporous nickel phosphate NiPO, porous nickel hydroxide and mesoporous nickel oxide, this remarkable electrochemical performance of VSB-5 will make nickel phosphate material a promising new electrode material for high performance supercapacitors.

  12. 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

  13. 甲烷沉积法对甲烷/氮气分离炭分子筛性能的研究%Effect of CH4 Sedimentary Conditions on Performance of Carbon Molecular Sieve in Methane/Nitrogen Separation Process

    Institute of Scientific and Technical Information of China (English)

    张香兰; 周玮; 张英; 张祥; 张雷杰; 石好亮

    2011-01-01

    Carbon molecular sieve with high methane/nitrogen separation performance is the premise for low. Concentration coalbed methane separation by swing pressure adsorption. Coconut shell carbonized materials was used as raw material in this paper. The raw material was activated to prepare carbon precursor, and then deposited by CH4 to prepare carbon molecular sieve (CMS). The effects of deposition time, deposition temperature, CH4 concentration and velocity in CH4/N2 mixture on the separation performance of CMS in methane/nitrogen separation process using pressure swing adsorption (PSA) were studied. N2 adsorption method was used to analyze the specific surface area and pore size distribution of carbon precursor. The results show that carbon precursor prepared under carbonization time 40 min, activation temperature 850 ℃, activation time 120 min, and steam flowing 1.71 g/min has higher micropores than that under other preparation conditions. The concentration of separated methane and nitrogen increases with the increase of the deposition temperature significantly, deposition time, sedimentary agent concentration and sedimentary dosage have little influence on the concentration of separated methane and nitrogen. The optimal sedimentary conditions are: deposition temperature 850 ℃, CH4 concentration 20. 6% , CH4 gas mixture flow rate 1 200 mL/min, deposition time 120 min.%高性能甲烷/氮气分离用炭分子筛是保证低浓度煤层气变压吸附分离的前提.以椰壳炭化料为原料在一定条件下活化制备了炭前驱体,以甲烷为沉积剂通过气相炭沉积调孔制备炭分子筛,考察沉积时间、沉积温度、沉积剂浓度和沉积剂量对变压吸附分离甲烷/氮气效果的影响,采用N2吸附法分析了炭前驱体的比表面积和孔径分布.结果表明:炭化时间40 min,活化温度850℃,活化时间120 min,水蒸气流量1.71 g/min时得到的炭前驱体微孔发达.以甲烷作为沉积剂时,甲烷/氮气的分离

  14. 分子筛运行末期出现微量二氧化碳的原因分析及处理措施%Causes Analysis and Measures to Deal with Trace Quantities of Carbon Dioxide in the Last Phase of Molecular Sieve Operation

    Institute of Scientific and Technical Information of China (English)

    张旭燕; 王玉峰

    2011-01-01

    分子筛运行末期出现微量二氧化碳对空分装置的安全运行带来严重的影响,从能够引起分子筛运行末期出现微量二氧化碳的原因入手分析,找出解决该问题的处理措施,为装置的安全运行提供了保障。%There is serious influnce on the safe operation of air separation plant caused by trace quantities of carbon dioxide in the last phase of molecular sieve operation.The writer try to start with the causes analysis of trace quantities of carbon dioxide in the last phase of molecular sieve operation to figure out measures to deal with the problem and it will ensure the safty of air separation plant operation.

  15. HMS介孔分子筛催化剂上苯酚氧化羰基化合成碳酸二苯酯%Oxidative Carbonylation of Phenol to Diphenyl Carbonate over Mesoporous HMS Molecular Sieve Supported Catalyst

    Institute of Scientific and Technical Information of China (English)

    程庆彦; 李超毅; 王延吉; 赵新强

    2011-01-01

    HMS mesoporous molecular sieves was synthesized with octadecylamine as the template and a novel HMS supported Pd ( Salen) complex catalyst was prepared by microwave-assisted solvothermal impregnation. The complex and the catalyst were characterized by means of FTIR, 1H NMR, XRD and N2 adsorption-desorption. The complex structure was confirmed and the characterization results showed that the Pd(Salen) complex was supported on HMS molecular sieves. The catalytic performance of the supported schiff base complex catalyst Pd( Salen)/HMS in oxidative carbonylation of phenol to diphenyl carbonate ( DPC) was investigated. The effects of reaction temperature, reaction pressure and reaction time on the DPC yield in the oxidative carbonylation were studied. The DPC yield was 18. 8% under the appropriate reaction conditions of reaction temperature 373 K, pressure 4.0 Mpa(n(CO) : n(O2) 7 : 1 )and reaction time 8 h.%以正十八胺为模板剂合成了介孔HMS分子筛,采用微波辅助分步浸渍溶剂热法在HMS分子筛上合成了结构新颖的Pd(Salen)配合物催化剂;采用FTIR和1H NMR等手段确定了Pd( Salen)配合物的结构,XRD和N2吸附-脱附表征结果显示Pd( Salen)固载于HMS分子筛上.将该负载型Pd(Salen)/HMS催化剂用于苯酚氧化羰基化合成碳酸二苯酯的反应中,该催化剂对此反应具有较好的催化性能,考察了反应温度、反应压力、反应时间等条件对碳酸二苯酯收率的影响,并对工艺条件进行了优化.实验结果表明,当反应温度为373 K、反应压力为4.0 MPa(n(CO)∶n(O2) =7∶1)、反应时间为8h时,碳酸二苯酯收率可达18.8%.

  16. 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.

  17. D sub 2 DT gas purification by cryosorption on 5 A molecular sieve

    Energy Technology Data Exchange (ETDEWEB)

    Blet, V.; Labrune, D.; Guidon, H.; Hircq, B. (CEA, 91 - Bruyeres le Chatel (France)); Moll, G. (USSI INGENIERIE, 92 - Bagneux (France))

    1991-12-01

    Purification of deuterium and deuterium-tritium gas has been performed by cryosorption of impurities on 5 A molecular sieve as absorbent. This process is efficient for most of the impurities (nitrogen, methane, oxygen, carbon oxides, argon, water) except helium. In closed loop operations, their residual levels can be better than 10 vpm during at least 5 h if the trap temperature is sufficiently low (<93 K). At low temperature, cryosorption of D{sub 2} and DT gas is significant. Nevertheless, their recovery can be easily achieved by heating up the adsorbent. (orig.).

  18. D{sub 2} and DT gas purification by cryosorption on 5 Angstrom molecular sieve

    Energy Technology Data Exchange (ETDEWEB)

    Blet, V.; Labrune, D.; Guidon, H.; Hircq, B. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France); Moll, G. [Societe de Construction d`une Usine de Separation Isotopique (USSI), 92 - Le Plessis-Robinson (France)

    1991-12-31

    Purification of deuterium and deuterium-tritium gas has been performed by cryosorption of impurities on 5 A molecular sieve as adsorbent. This process is efficient for most of the impurities (nitrogen, methane, oxygen, carbon oxides, argon, water) except helium. In closed loop operations, their residual levels can be better than 10 vpm during at least 5 hours if the trap temperature is sufficiently low (< 93 K). At low temperature, cryosorption of D{sub 2} and DT gas is significant. Nevertheless, their recovery can be easily achieved by heating up the adsorbent.

  19. 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.

  20. Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization

    Science.gov (United States)

    Shi, Chun-Wei; Wu, Wen-Yuan; Li, Shuai; Bian, Xue; Zhao, Shan-Lin; Pei, Ming-Yuan

    2016-03-01

    Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves.

  1. Preparation and study of controllable particle size of nickel-doped carbon molecular sieves%金属镍掺杂可控粒径碳分子筛的制备研究

    Institute of Scientific and Technical Information of China (English)

    刘瑾; 邓盾; 赵芬娜; 林庆文

    2011-01-01

    Nickel-doped carbon molecular sieves (CMS) with controlled particle size have been prepared by the method of inverse suspension polymerization to synthesize poly(furfuryl alcohol) with nickel nitrate as carbon precursor,utilizing template porous nanosilica, through a mild carbonization and post-treatment process. The preparation mechanism and micro-structure of CMS have been characterized through XRD,SEM, N2 adsorption,FT-IR and TGA. The results show that the different carbonization conditions have a definite effect on the particle size and distribution of CMS, additionally, when the carbonization temperature from 650℃ up to 700℃, the mesopore volume and the total pore volume raised to 0. 40 and 0. 67cm3/g,respectively. The micropore volume has expanded twice with the carbonization heating rate increased. The XRD and AAS analysis proved that nickel have been doped into CMS by ratio of 2.24wt% successfully.%采用反相悬浮聚合,以纳米SiO2为模板制备出含Ni2+的聚糠醇微粒,将其作为碳前驱体,经炭化和后处理成功制得Ni掺杂粒径可控碳分子筛(CMS).利用XRD、N2吸附、FT-IR和TGA对其制备机理和微结构进行了表征.结果表明,不同炭化条件对CMS粒径大小及分布有一定的影响;炭化温度由650℃升至700℃,介孔体积和总孔容量分别升至0.40和0.67cm3/g,升温速率提高微孔孔容量增加2倍;XRD和AAS分析显示有2.24%(质量分数)镍掺杂到CMS中.

  2. 甘蔗渣炭分子筛的制备、结构及其吸附性能%Synthesis, structure and adsorption properties of bagasse-based carbon molecular sieves

    Institute of Scientific and Technical Information of China (English)

    郭海蓉; 王国梅; 麻少莹; 李斌

    2012-01-01

    Bagasse-based carbon molecular sieves ( BCMS) were synthesized by a two-stage carbonization method, using bagasse as the raw material, and phenol-formaldehyde resin and carboxymethyl cellulose as the binders. The BCMS were characterized by N2 adsorption, X-ray powder diffraction differential thermal analysis, scanning and transmission electron microscopy and adsorptive de-coloring tests. Results showed that the BCMS had mainly micropores with the size centered at 0.72 run, a micropore volume of 0.11 cmVg and a Brunauer-Emmett-Teller surface area of 269 mVg. XRD showed that apart from the broad peaks at 20 values of 23° and 44°, ascribed to amorphous carbon, there are peaks ascribed to a monoclinic single crystal belonging to C2/c (15) space group, with size of 57.7 nm and cell parameters of a = 2.0437 nm,6 = 0. 3497nm,c= 1. 0345 nm, a = 90.000°, 0=106.439°, 7 = 90.000°. The BCMS had developed pores with a hierarchical structure, which afforded them a high adsorption capacity of 1.296 g/g for coloring substances in a clear sugarcane liquor.%以甘蔗渣为碳质原料、酚醛树脂与少量羧甲基纤维素混合物为黏合剂,通过二次炭化法制备甘蔗渣炭分子筛(Bagasse carbon molecular sieves,BCMS),并采用N2吸附-脱附、X射线衍射(XRD)、差热分析(DTA)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)以及吸附实验对其进行结构分析与性质表征.结果表明,BCMS以微孔为主,孔径大小主要集中在0.72nm,微孔体积为0.11cm3/g,比表面积为269 m2/g;部分BCMS以晶体形式存在,具有五元环排列的微孔结构,晶粒尺寸为57.7 nm,属单斜晶系,空间群为C2/c(15),晶胞参数为a=2.0437nm,b=0.3497nm,c=1.0345nm,α=90.000°,β=106.439°,γ=90.000°;BCMS孔结构发达,具有特殊的“孔中孔”结构,对蔗汁中有色物质具有较强的吸附能力,其饱和吸附量为1.296 g/g(色素/BCMS).

  3. Analysis and Control of Excessive Carbon Dioxide at the Exit of Molecular Sieve Purification Apparatus%分子筛纯化器出口二氧化碳含量超标分析与控制

    Institute of Scientific and Technical Information of China (English)

    姬明明

    2014-01-01

    Excessive carbon dioxide in the molecular sieve purification system of air separation plant seriously affects the long-term safe and stable operation of the equipment, as gradually deposition of frozen water and carbon dioxide to the expander, low temperature heat exchanger, rectifying tower, valves and piping can cause blocking inside the cold box affecting normal operation or even push the acetylene and hydrocarbons inside the cold box to exces-sive levels causing explosion and other accidents. In practice, seriously and accurately analyz-ing and learning lessons from experiences of such accidents while drawing up prevention and control measures is an effective way to avoid similar accidents happening again.%空分装置分子筛纯化系统二氧化碳含量超标,对设备长周期安全稳定运行影响极大,被冻结的水分和二氧化碳逐渐沉积到膨胀机、低温换热器、精馏塔、阀门、管道等。轻则造成冷箱内设备堵塞,影响装置正常运行;重则使冷箱内乙炔、碳氢化合物含量超标引起爆炸等安全事故。在实际操作中,注意总结事故经验教训,认真准确分析并制定预防控制方法,是避免类似事故再次发生的有效途径。

  4. Study on the pyrolysis of cellulose for bio-oil with mesoporous molecular sieve catalysts.

    Science.gov (United States)

    Yu, Feng-wen; Ji, Deng-xiang; Nie, Yong; Luo, Yao; Huang, Cheng-jie; Ji, Jian-bing

    2012-09-01

    Mesoporous materials possess a hexagonal array of uniform mesopores, high surface areas, and moderate acidity. They are one of the important catalysts in the field of catalytic pyrolysis. In this paper, mesoporous materials of Al-MCM-41, La-Al-MCM-41, and Ce-Al-MCM-41 were synthesized, characterized, and tested as catalysts in the cellulose catalytic pyrolysis process using a fixed bed pyrolysis reactor. The results showed that mesoporous materials exhibited a strong influence on the pyrolytic behavior of cellulose. The presence of these mesoporous molecular sieve catalysts could vary the yield of products, which was that they could decrease the yield of liquid and char and increase the yield of gas product, and could promote high-carbon chain compounds to break into low-carbon chain compounds. Mesoporous molecular sieve catalysts were benefit to the reaction of dehydrogenation and deoxidation and the breakdown of carbon chain. Further, La-Al-MCM-41 and Ce-Al-MCM-41 catalysts can produce more toluene and 2-methoxy-phenol, as compared to the non-catalytic runs.

  5. The Application of Molecular Sieve in Catalysis%分子筛的催化应用

    Institute of Scientific and Technical Information of China (English)

    罗五魁; 陈峰; 叶楠

    2012-01-01

    In this paper,the authors expounded research situation of molecular sieve in catalysis field in recent years.Finally,the authors emphatically introduced application of catalysis of molecular in conversion reaction of low carbon olefin,dehydrocyclization of alkane,aromatization of hydrocarbon,isomerization of hydrocarbon,reaction of oxidation reduction and methyl alcohol transformation to low carbon olefin.%综述了近年来分子筛在催化领域的研究情况,着重介绍了其在低碳烯烃转化反应、烷烃的脱氢环化、烃类的芳构化、烃类的异构化、氧化还原反应及甲醇转化为低碳烯烃等方面的催化应用。

  6. Recovery of silica from electronic waste for the synthesis of cubic MCM-48 and its application in preparing ordered mesoporous carbon molecular sieves using a green approach

    Science.gov (United States)

    Liou, Tzong-Horng

    2012-07-01

    The electronics industry is one of the world's fastest growing manufacturing industries. However, e-waste has become a serious pollution problem. This study reports the recovery of e-waste for preparing valuable MCM-48 and ordered mesoporous carbon for the first time. Specifically, this study adopts an alkali-extracted method to obtain sodium silicate precursors from electronic packaging resin ash. The influence of synthesis variables such as gelation pH, neutral/cationic surfactant ratio, hydrothermal treatment temperature, and calcination temperature on the mesophase of MCM-48 materials is investigated. Experimental results confirm that well-ordered cubic MCM-48 materials were synthesized in strongly acidic and strongly basic media. The resulting mesoporous silica had a high surface area of 1,317 m2/g, mean pore size of about 3.0 nm, and a high purity of 99.87 wt%. Ordered mesoporous carbon with high surface area (1,715 m2/g) and uniform pore size of CMK-1 type was successfully prepared by impregnating MCM-48 template using the resin waste. The carbon structure was sensitive to the sulfuric acid concentration and carbonization temperature. Converting e-waste into MCM-48 materials not only eliminates the disposal problem of e-waste, but also transforms industrial waste into a useful nanomaterial.

  7. 煤层气浓缩用碳分子筛的研制及性能研究%Preparation and separation performances of carbon molecular sieve for coal-bed methane purification

    Institute of Scientific and Technical Information of China (English)

    李兰廷

    2016-01-01

    为评价分析碳分子筛(Carbon Molecular Sieves,CMS)产品性能,以酚醛树脂废料为主要原料,通过添加助剂,采用炭化/气相沉积一体化工艺,制备了专用于煤层气提浓的BM碳分子筛(记为BMCMS).采用CO2吸附法、加压热重法及四塔变压吸附法对BMCMS及商业碳分子筛(记为JCCMS)的孔隙结构、CH4和N,的吸附容量、速度以及对煤层气的实际分离性能等进行研究.结果表明,BMCMS碳分子筛的孔隙以0.85 nm以下微孔为主,主要分布在0.4~0.65 nm,其比例占整个孔隙的66%以上,高于JCCMS的65%;碳分子筛的孔隙直径为N2分子的1.1~1.8倍时,该类孔隙适宜吸附N2,而对CH4的吸附具有阻碍作用;当用于PSA浓缩抽采煤层气时,可将煤层气中CH4浓度提高25.6%,实际运行指标优于JCCMS.

  8. 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.

  9. Catalytic Transformation of Bio-oil to Olefins with Molecular Sieve Catalysts

    Science.gov (United States)

    Huang, Wei-wei; Gong, Fei-yan; Zhai, Qi; Li, Quan-xin

    2012-08-01

    Catalytic conversion of bio-oil into light olefins was performed by a series of molecular sieve catalysts, including HZSM-5, MCM-41, SAPO-34 and Y-zeolite. Based on the light olefins yield and its carbon selectivity, the production of light olefins decreased in the following order: HZSM-5>SAPO-34>MCM-41> Y-zeolite. The highest olefins yield from bio-oil using HZSM-5 catalyst reached 0.22 kg/kgbio-oil with carbon selectivity of 50.7% and a nearly complete bio-oil conversion. The reaction conditions and catalyst characterization were investigated in detail to reveal the relationship between the catalyst structure and the production of olefins. The comparison between the pyrolysis and catalytic pyrolysis of bio-oil was also performed.

  10. 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

  11. 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

  12. Self-Assembly and Dynamics of Organic 2D Molecular Sieves: Ab Initio and Molecular Dynamics Studies

    Science.gov (United States)

    St. John, Alexander; Wexler, Carlos

    2015-03-01

    Spontaneous molecular self-assembly is a promising route for bottom-up manufacturing of two-dimensional (2D) nanostructures with specific topologies on atomically flat surfaces. Of particular interest is the possibility of selective lock-and-key interaction of guest molecules inside cavities formed by complex self-assembled host structures. Our host structure is a monolayer consisting of interdigitated 1,3,5-tristyrylbenzene substituted by alkoxy peripheral chains containing n = 6, 8, 10, 12, or 14 carbon atoms (TSB3,5-C n) deposited on a highly ordered pyrolytic graphite (HOPG) surface. Using ab initio methods from quantum chemistry and molecular dynamics simulations, we construct and analyze the structure and functionality of the TSB3,5-C n monolayer as a molecular sieve. Supported by ACS-PRF 52696-ND5.

  13. n-alkane profiles of engine lubricating oil and particulate matter by molecular sieve extraction.

    Science.gov (United States)

    Caravaggio, Gianni A; Charland, Jean-Pierre; Macdonald, Penny; Graham, Lisa

    2007-05-15

    As part of the Canadian Atmospheric Fine Particle Research Program to obtain reliable primary source emission profiles, a molecular sieve method was developed to reliably determine n-alkanes in lubricating oils, vehicle emissions, and mobile source dominated ambient particulate matter (PM). This work was also initiated to better calculate carbon preference index values (CPI: the ratio of the sums of odd over even n-alkanes), a parameter for estimating anthropogenic versus biogenic contributions in PM. n-Alkanes in lubricating oil and mobile source dominated PM are difficult to identify and quantify by gas chromatography due to the presence of similar components that cannot be fully resolved. This results in a hump, the unresolved complex mixture (UCM) that leads to incorrect n-alkane concentrations and CPI values. The sieve method yielded better chromatography, unambiguous identification of n-alkanes and allowed examination of differences between n-alkane profiles in light (LDV) and heavy duty vehicle (HDV) lubricating oils that would have been otherwise difficult. These profile differences made it possible to relate the LDV profile to that of the PM samples collected during a tunnel study in August 2001 near Vancouver (British Columbia, Canada). The n-alkane PM data revealed that longer sampling times result in a negative artifact, i.e., the desorption of the more volatile n-alkanes from the filters. Furthermore, the sieve procedure yielded n-alkane data that allowed calculation of accurate CPI values for lubricating oils and PM samples. Finally, this method may prove helpful in estimating the respective diesel and gasoline contributions to ambient PM.

  14. CH4/N2混合气在炭分子筛上的变压吸附分离%Separation of methane/nitrogen mixture by pressure swing adsorption on carbon molecular sieve

    Institute of Scientific and Technical Information of China (English)

    席芳; 林文胜; 顾安忠

    2011-01-01

    The breakthrough curves of CH4/N2 mixture on a carbon molecular sieve (CMS) fixed adsorption bed were measured. The separation ability of this CMS was studied. The influence of fed gas velocity and adsorption pressure on separation was determined,as well as the influence on CH4 recovery. The results show that N2 is with preferentially ad-sorption and there is nearly no N2 at the exit of the fixed bed at the initial time of adsorption. With a proper adsorption time, the CH4 concentration in the product can be up to 96%. The feed gas velocity has a greater influence on separa-tion than that of pressure, and it is adverse to the separation when the velocity is too large. The CH4 recovery decreases as the velocity or pressure increases.%测量了CH4/N2混合气在一种炭分子筛固定床上的穿透曲线;研究了该炭分子筛对CH4的提浓效果,以及原料气流速和吸附压力对分离效果及CH4回收率的影响.结果表明:在吸附初期,该炭分子筛选择性吸附N2,吸附床出口基本检测不到N2,合理地控制吸附时间可使吸附床出口气中CH4浓度达到96%以上;原料气流速对分离效果的影响大于压力的影响,且流速太大不利于CH4/N2混合气的分离;随着流速和压力的增加,CH4的回收率减小.

  15. A study of piperidinium structure-directing agents in the synthesis of silica molecular sieves under fluoride-based conditions.

    Science.gov (United States)

    Zones, Stacey I; Burton, Allen W; Lee, Greg S; Olmstead, Marilyn M

    2007-07-25

    This study is a continuation of our efforts to understand the interplay in the self-assembly chemistry for formation of molecular sieves from guest organocations and inorganic silicon oxide. In this particular study we focus on the competitive interplay of the organocations and the synthesis cofactor fluoride anion. The anions play a key role in structure determination, as a function of net solution concentration. They compete with the role for the space-filling organocation in determining which molecular sieve host structure will be specified. In this study we look at this competition in the synthesis for a series of 33 different organocations derived from the piperidine ring system. Derivatives were prepared which both fixed substituents on the carbon and nitrogen centers on the ring. Results were discussed in terms of product selectivity from synthesis as a function of solution concentration for the reactants. A total of 17 different host topologies were found in this series, and a correlation was seen for (a) open-framework lattices (low framework densities) under the most concentrated reaction conditions and then (b) high framework density products once the conditions were more dilute. Some surprising synthesis differences are seen in comparing the performance of these structure directing agents (SDAs) in fluoride media vs hydroxide media (the more conventional environment for zeolite/molecular sieve syntheses involving silicate chemistry). Finally molecular modeling was used to understand some of the trends in product selectivity for closely related guest (SDA) candidates.

  16. 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.

  17. 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

  18. 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; XIE Xin; HE YuFeng; WANG YunPu; HE NaiPu; ZHANG ZhengLin; SONG PengFei; LIU WenJun

    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.

  19. 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)

  20. Synthesis and Characterization of the TAPO-5 Molecular Sieve

    Directory of Open Access Journals (Sweden)

    Sarah P.O. Rios

    2002-09-01

    Full Text Available Aluminophosphate sieves with AFI structure substituted by Ti (denominated TAPO-5 have been synthesized hydrothermally. These materials were characterized by X-ray diffraction (XRD, chemical analysis (ICP, scanning electronic microscopy (SEM, ultraviolet diffuse reflectance spectroscopy (DRS-UV and thermogravimetric analysis (TGA. XRD results showed the materials have good TAPO-5 crystallinity, although DRS-UV spectra indicated anatase phase as contamination. TGA analysis showed mass loss in the range of high temperatures, which can be attributed to protonated template decomposition. This indicates the existence of structural charge as a consequence of Ti incorporation into AFI structure

  1. 空分设备分子筛纯化系统出口空气中二氧化碳含量超标分析与处理%Analysis and treatment of exceedance of carbon dioxide content in outlet air of molecular sieve purification system of

    Institute of Scientific and Technical Information of China (English)

    张振友

    2011-01-01

    分子筛纯化系统出口空气中二氧化碳含量超标是影响空分设备稳定运行的主要因素之一。文章从分子筛纯化系统加工气体质量,设计制造,安装操作以及分子筛本身性能4方面,综合分析了导致二氧化碳含量超标的根本原因和处理措施。%The exceedance of carbon dioxide content in outlet air of molecular sieve purification system in one of main factors impairing the stable run of air separation plant. Here, the essential causes for the said exceedance of carbon dioxide content are compreh

  2. [Preparation and evaluation of novel mesoporous molecular sieve of baicalin surface molecularly imprinted polymers].

    Science.gov (United States)

    Gu, Xia-li; He, Hong-liang; Shi, Li-ying; Gao, Yan-kun; Chen, Li-na

    2015-05-01

    Taking mesoporous molecular sieve MCM-41 as a substrate, baicalin (BA) as template, acrylamide (AM) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent, ethanol as solvent, under thermal polymerization initiator of azobis isobutyronitrilo (AIBN) , a kind of selective recognition of baicalin surface molecularly imprinted polymer was synthesized. The surface morphologies and characteristics of the MIPs were characterized by infrared spectroscopy (IR) and transmission electron microscope (TEM). The adsorption properties of polymer microsphere for the template were tested by the dynamic adsorption equilibrium experiments and static adsorption equilibrium experiments. The experiment showed that the imprinting process was successfully and the well-ordered one-dimensional pore structure of MCM-41 was still preserved. Furthermore, molecularly imprinted polymers had higher selective ability for BA, then provided a new method for the efficient separation and enrichment of baicalin active ingredients from medicinal plants Scutellaria baicalensis.

  3. Sieving hydrogen based on its high compressibility

    Science.gov (United States)

    Chen, Hangyan; Sun, Deyan; Gong, Xingao; Liu, Zhifeng

    2011-03-01

    Based on carbon nanotube intramolecular junction and a C60, a molecular sieve for hydrogen is presented. The small interspace between C60 and junction provides a size changeable channel for the permselectivity of hydrogen while blocking Ne and Ar. The sieving mechanism is due to the high compressibility of hydrogen.

  4. 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.

  5. Structure–property tuning in hydrothermally stable sol–gel-processed hybrid organosilica molecular sieving membranes

    NARCIS (Netherlands)

    Elshof, ten J.E.; Dral, A.P.

    2016-01-01

    Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol–gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes w

  6. 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.

  7. 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…

  8. 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

  9. Effect of soil sieving on respiration induced by low-molecular-weight substrates

    Science.gov (United States)

    Datta, Rahul; Vranová, Valerie; Pavelka, Marian; Rejšek, Klement; Formánek, Pavel

    2014-03-01

    The mesh size of sieves has a significant impact upon soil disturbance, affecting pore structure, fungal hyphae, proportion of fungi to bacteria, and organic matter fractions. The effects are dependent upon soil type and plant coverage. Sieving through a 2 mm mesh increases mineralization of exogenously supplied carbohydrates and phenolics compared to a 5 mm mesh and the effect is significant (p<0.05), especially in organic horizons, due to increased microbial metabolism and alteration of other soil properties. Finer mesh size particularly increases arabinose, mannose, galactose, ferulic and pthalic acid metabolism, whereas maltose mineralization is less affected. Sieving through a 5 mm mesh size is suggested for all type of experiments where enhanced mineralization of low-molecular-weight organic compounds needs to be minimalized.

  10. Preparation and Electrochemical Performance of Carbon Materials by Using NaY Molecular Sieves as the Template%凹凸棒NaY分子筛模板炭材料的制备及其电化学性能研究

    Institute of Scientific and Technical Information of China (English)

    李贵贤; 袁琦罡; 宏飞; 张峰博

    2014-01-01

    以凹凸棒为原料,采用水热原位晶化法合成了NaY分子筛,然后采用模板法以制备得到的纳米级NaY分子筛为模板,麦芽糖为碳源,制备得到一种微孔模板炭材料。采用XRD、FESEM、N2吸附/脱附等手段对NaY分子筛和微孔模板炭材料的物理性能进行表征。测试结果表明,NaY分子筛的粒径小于100 nm,比表面积为487 m2/g;模板炭材料的比表面积为789.2 m2/g、总孔容为0.62 m3/g,平均孔径为1.5 nm。随后,采用恒电流充放电测试、循环伏安测试对模板炭材料的电化学性能进行测试。恒电流充放电测试表明,当电流密度为600 mA/g时,材料的比电容可达163.3 F/g,循环伏安测试中材料表现出了良好的循环伏安曲线的矩形特征,较好的说明了材料具有良好的倍率性能。%Using attapulgite as raw materials, nano-scale NaY molecular sieves were synthesized by in-situ crystallization method. Then porous carbon materials were synthesized by using the NaY molecular sieves as hard template and maltose as carbon precursor. XRD, FESEM, N2 adsorption/desorption tests were conducted to investigate physical properties of NaY molecular sieves and porous carbon materials. The results show that the size of NaY molecular sieves is less than 100nm and BET area is 487 m2/g; specific surface area and pore volume of the porous carbon materials reach up to 789.2 m2/g, 0.62 cm3/g, respectively. The constant current charge/discharge tests and cyclic voltammetry tests were employed to investigate the electrochemical performance of the prepared porous carbon material. When the current density is 600 mA/g, the maximum specific capacitance of the material is 163.3 F/g. The cyclic voltammetry curves maintain a typical quasi-rectangular feature when the scan rate increases from 5 mV/s to 100 mV/s, which proves that the material has well rate performance.

  11. 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.

  12. 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.

  13. Cycloaddition of carbon dioxide with epoxide catalyzed by SBA-15 molecular sieves loaded with graphitic carbon nitride%SBA -15分子筛负载氮化碳催化二氧化碳与环氧化合物环加成反应

    Institute of Scientific and Technical Information of China (English)

    柳士鑫; 闫洪伟

    2015-01-01

    The catalytic activation of carbon dioxide is the key for its utilization as C1 resource. In order to develop efficient catalysts for the activation of carbon dioxide,dicyandiamide was loaded on the mesochannels of SBA-15 molecular sieve by impregnation method,and then after calcination,SBA-15 loaded graphitic carbon nitride(g-C3 N4 )catalysts were obtained. The catalysts were characterized by transmission electron microscopy,X-ray diffraction,N2 adsorption and X-ray photoelectron spectroscopy. The results showed that the mesoporous structure of SBA-15 molecular sieve had not changed significantly after loading g-C3 N4 . g-C3 N4 nanophases were dispersed in the channels of SBA-15 molecular sieve. g-C3 N4 / SBA-15 catalyst was employed for the catalytic synthesis of cyclic carbonate from cycloaddition of carbon dioxide with epoxide. The effects of catalyst composition and the reaction conditions on catalytic performance were investigated. The results showed that g-C3N4 / SBA-15 catalyst could effectively catalyze the cycloaddition of carbon dioxide with epoxide. Under the condition of reaction temperature 140 ℃,reaction pressure 3.5 MPa, reaction time 4 h,ZnBr2 amount 1. 0mol% ,dicyandiamide mass fraction 20% and g-C3 N4 / SBA-15 as the catalyst,cyclic carbonate yield reached 91. 6% . g-C3 N4 / SBA-15 catalyst had the advantages of simple preparation process,cheap raw materials and excellent catalytic performance.%二氧化碳的催化活化是其作为 C1资源利用的关键。为了开发高效二氧化碳活化催化剂,将二聚氰胺通过浸渍法负载到介孔分子筛 SBA -15孔道中,高温焙烧后,得到 SBA -15负载的石墨相氮化碳 g - C3 N4催化剂。采用透射电镜、X 射线衍射、N2吸附和 X 射线光电子能谱对催化剂进行表征。结果表明,负载 g - C3 N4后,SBA -15分子筛的介孔结构未发生明显变化,g - C3 N4以纳米态分布于 SBA -15分子筛的孔道中。将 g - C3 N4/ SBA -15催化剂用

  14. 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.

  15. Synthesis of highly selective zeolite topology molecular sieve for adsorption of benzene gas

    Science.gov (United States)

    Wei, Lin; Chen, Yunlin; Zhang, Baoping; Zu, Zhinan

    2013-02-01

    Shangdong fly ash (SFA), Fangshan fly ash (FFA) and Heilongjiang fly ash (HFA) were selected as the raw materials to be used for synthesis of highly selective zeolite topology molecular sieve. Twice foaming method was studied in terms of synthetic zeolite. The experimental products were characterized by means of X-ray fluorescence (XRF), scanning electron microscope (SEM), X-ray diffraction (XRD), and automated surface area & pore size analyser. The results indicated that 10 M NaOH was chosen as modification experiment condition to process SFA. Crystallization temperature and time were 140 °C and 8 h, respectively. Zeolite topology molecular sieve was prepared with Si/Al molar ratio of 7.9, and its adsorption ratio of benzene gas was up to 66.51%.

  16. 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.  ……

  17. 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.

  18. 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.

  19. 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.

  20. Preparation, Characterization, and Application of Magnetic Fe-SBA-15 Mesoporous Silica Molecular Sieves

    OpenAIRE

    Huang, Huayu; Ji, Yongsheng; Qiao, Zhenfeng; Zhao, Chuande; He, Jianguo; Zhang, Haixia

    2010-01-01

    Magnetic Fe-SBA-15 mesoporous silica molecular sieves were prepared, characterized, and used for magnetic separation. Wet impregnation, drying, and calcination steps led to iron inclusion within the mesopores. Iron oxide was reduced to the metal form with hydrogen, and the magnetic Fe-SBA-15 was obtained. Fourier-transform infrared spectroscopy confirmed the preparation process from the oxide to metal forms. The structure of magnetic materials was confirmed by Mössbauer spectra. Powder X-ray ...

  1. Separation of ethanol-water mixtures using 3A molecular sieve

    Energy Technology Data Exchange (ETDEWEB)

    Carton, A.; Gonzalez, G.; Iniguez de la Torre, A.; Cabezas, J.L.

    1987-01-01

    An experimental study of 3A molecular sieve behavior, in order to obtain anhydrous ethanol, was developed. The adsorption of water in vapor phase was performed in an essentially isothermal fixed bed. 99.9 wt% ethanol was recovered operating with azeotropic distillation and different flow rates. A simple model in terms of a driving force and linear equilibrium was tested. Runs in liquid phase were also carried out, obtaining lower treatment-capacities than when working in vapor phase.

  2. A ’Smart’ Molecular Sieve Oxygen Concentrator with Continuous Cycle Time Adjustment.

    Science.gov (United States)

    1996-04-01

    A ’smart’ molecular sieve oxygen concentrator (MSOC) is controlled by a set of computer algorithms . The ’smart’ system automatically adjusts...determine if concentrator performance could be controlled by computer algorithms which continuously adjust concentrator cycle time. A two-bed... Computer algorithms or decision process were developed which allowed the software to control concentrator cycle time. Step changes in product flow from 5

  3. Molecular sieve sampling of CO{sub 2} from decomposition of soil organic matter for AMS radiocarbon measurements

    Energy Technology Data Exchange (ETDEWEB)

    Haemaelaeinen, K. [Dating Laboratory, Finnish Museum of Natural History, P.O. Box 64, University of Helsinki, FIN 00014 (Finland); Fritze, H. [Finnish Forest Research Institute (METLA), Vantaa (Finland); Jungner, H. [Dating Laboratory, Finnish Museum of Natural History, P.O. Box 64, University of Helsinki, FIN 00014 (Finland); Karhu, K. [Finnish Environment Institute (SYKE), Helsinki (Finland); Oinonen, M., E-mail: markku.j.oinonen@helsinki.f [Dating Laboratory, Finnish Museum of Natural History, P.O. Box 64, University of Helsinki, FIN 00014 (Finland); Sonninen, E. [Dating Laboratory, Finnish Museum of Natural History, P.O. Box 64, University of Helsinki, FIN 00014 (Finland); Spetz, P.; Tuomi, M.; Vanhala, P.; Liski, J. [Finnish Environment Institute (SYKE), Helsinki (Finland)

    2010-04-15

    A molecular sieve based procedure has been established for sampling CO{sub 2} of decomposing soil organic matter for AMS radiocarbon measurements. The sampling and desorption lines are capable to produce well measurable (>1 mg) AMS targets.

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

    Science.gov (United States)

    Moritz, Michał; Geszke-Moritz, Małgorzata

    2015-03-01

    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 (Qmax) 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 (Qmax 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.

  5. 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).

  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. 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.

  8. 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

  9. 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.

  10. Molecular Sieve Steam Heater Leak Accident and Processing%分子筛蒸汽加热器泄露事故及处理

    Institute of Scientific and Technical Information of China (English)

    陈庆山

    2015-01-01

    Air separation plant molecular sieve column system for steam heater tube material causes leakage problem, steam runs into the dirty side of nitrogen, makes exceed carbon in the analysis of molecular sieve export while the molecular sieve regenerate, causes heat exchanger inside cold box“ice block” unsustainable system load, and affects the normal operation of air separation and after system. The accident treatment process, cause analysis, specific methods and steps of accident prevention were introduced.%空分装置分子筛系统因蒸汽加热器列管材质问题导致泄露,蒸汽进入污氮气侧使分子筛再生时无法达到指标,分子筛出口二氧化碳分析超标,造成冷箱内换热器“冰堵”系统负荷无法维持,影响了空分及后系统的正常运行,详细介绍了事故处理过程,原因分析,事故预防的具体方法和步骤。

  11. CH4/CO2混合组分在13X分子筛上的吸附平衡及分离性能%Adsorption Equilibrium and Separation of Methane and Carbon Dioxide Mixtures on 13X Molecular Sieve

    Institute of Scientific and Technical Information of China (English)

    陆江园; 刘伟; 孙林兵; 刘晓勤

    2013-01-01

      采用高精度智能重量分析仪IGA-100对13X分子筛进行CH4、CO2的吸附分离实验。于298、310、326 K温度下,分别测定了CH4、CO2纯组分及混合组分的吸附等温线。纯组分吸附等温线用DL(Double-Langmuir)模型拟合,并通过DL-IAST(Ideal Adsorbed Solution Theory,IAST)模型与实验测定值进行比较。利用该模型计算出不同温度下混合气中各组分的吸附量,得到了CO2的吸附选择性。结果表明,DL-IAST模型可以准确地描述CH4、CO2在13X分子筛上的吸附行为。在298 K时,随着压力的增加,CO2的吸附选择性增加,最后稳定在80左右;当温度一定时,CO2吸附选择性随着混合物中CO2浓度增加而减小。%Pure gas and binary gas mixture adsorption isotherms of methane and carbon dioxide on 13X molecular sieve were measured by using the high-precision intelligent gravimetric analyzer at temperature of 298, 310 and 326 K, respectively. Double-Langmuir model was used to study the pure gas adsorption;the DL model and the ideal adsorbed solution theory (IAST) were combined to predict the binary gas mixture adsorption isotherms and using the model, the adsorption amount of the single component of gas mixture and the selectivity of CO2 were calculated. It shows that the combined method (DL-IAST) can be applied to describe the adsorption of CH4 and CO2 binary mixtures on 13X molecular sieve perfectly. The selectivity of CO2 increases with increasing pressure and finally reaches 80 at 298 K;when the temperature is constant, the selectivity of CO2 decreases with increasing the CO2 concentration.

  12. Structural and thermotropic peculiarities of hydrogen-bonded liquid crystals confined in mesoporous molecular sieves

    Science.gov (United States)

    Gnatyuk, I.; Gavrilko, T.; Yaroshchuk, O.; Holovina, N.; Shcherban, N.; Baran, J.; Drozd, M.

    2016-12-01

    The phase behaviour and structural organization of hydrogen-bonded liquid crystals were investigated under confinement to mesoporous molecular sieves. As such liquid crystalline compounds, 4-hexylbenzoic and 4-butylcyclohexanecarboxylic acids with different head group structure and alkyl chain length where selected and filled in the AlMCM-41 sieves. With FTIR spectroscopy it was found that some part of incorporated acid molecules, presumably located in the inner space of the AlMCM-41 pores, is in undissociated form of open dimers or chain associates and thus shows spectroscopic features characteristic to the bulk-like species. The other FTIR spectra components indicate strong interaction of the incorporated monomeric molecules with the pore surface. Two specific mechanisms are shown to be involved in molecular interactions at the interface: (1) deprotonation of monomeric acid molecules on the pore surface with formation of COO- carboxylate ions and (2) bonding of these ions to the pore surface by a coordinated bond R-COO-…Al+ with Lewis acid sites. Differential scanning calorimetry revealed that these near-surface processes lead to complete suppression of mesomorphic properties of the studied acids under confinement to nanopores.

  13. Zeolite molecular sieves have dramatic acid-base effects on enzymes in nonaqueous media.

    Science.gov (United States)

    Fontes, Nuno; Partridge, Johann; Halling, Peter J; Barreiros, Susana

    2002-02-05

    Zeolite molecular sieves very commonly are used as in situ drying agents in reaction mixtures of enzymes in nonaqueous media. They often affect enzyme behavior, and this has been interpreted in terms of altered hydration. Here, we show that zeolites can also have dramatic acid-base effects on enzymes in low water media, resulting from their cation-exchange ability. Initial rates of transesterification catalyzed by cross-linked crystals of subtilisin were compared in supercritical ethane, hexane, and acetonitrile with water activity fixed by pre-equilibration. Addition of zeolite NaA (4 A powder) still caused remarkable rate enhancements (up to 20-fold), despite the separate control of hydration. In the presence of excess of an alternative solid-state acid-base buffer, however, zeolite addition had no effect. The more commonly used Merck molecular sieves (type 3 A beads) had similar but somewhat smaller effects. All zeolites have ion-exchange ability and can exchange H+ for cations such as Na+ and K+. These exchanges will tend to affect the protonation state of acidic groups in the protein and, hence, enzymatic activity. Zeolites pre-equilibrated in aqueous suspensions of varying pH-pNa gave very different enzyme activities. Their differing basicities were demonstrated directly by equilibration with an indicator dissolved in toluene. The potential of zeolites as acid-base buffers for low-water media is discussed, and their ability to overcome pH memory is demonstrated.

  14. Synthesis of a new meso/microporous composite molecular sieve of MCM-41/mordenite

    Institute of Scientific and Technical Information of China (English)

    WANG Shan; DOU Tao; LI Yuping; ZHANG Ying; YAN Zichun; LI Xiaofeng

    2005-01-01

    An MCM-41/mordenite composite with twofold porous structure and stepwise-distributed acidity was prepared for the first time by using zeolite mordenite as the silica-alumina source. The composite molecular sieve has been investigated and compared with a mechanical mixture of mordenite and MCM-41 for their structure, acidity and catalytic activity by means of XRD, N2 adsorption and desorption, HRTEM, DTG, NH3-TPD and catalytic reaction. The characterization results show that the structure and property of the composite molecular sieve are quite different from those of the mechanical mixture, which might be ascribed to the incorporation of secondary building units characteristic of zeolite mordenite into the mesoporous walls of the composite which gives rise to the thicker mesoporous walls, the higher hydrothermal stability and more strong acid sites. Furthermore, the new strategy could be used as a new general method for the preparation of catalysts for the reaction system with multifold large molecules, and the results were well confirmed by the dealkylation of C10+ aromatic hydrocarbon.

  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. Specific Carbon Isotopic Analysis of n-Alkanes in Soils by Gas Chromatography-Isotope Ratio Mass Spectrometry with 5A Molecular Sieve Adsorption and Mixed Solvent Elution%5A分子筛吸附混合溶剂洗脱-气相色谱-同位素质谱分析土壤中正构烷烃单体碳同位素

    Institute of Scientific and Technical Information of China (English)

    张逐月; 刘美美; 谢曼曼; 王道聪; 凌媛; 尚文郁; 刘舒波; 岑况; 孙青

    2012-01-01

    利用5A分子筛吸附,环己烷-正戊烷混合溶剂洗脱分离富集正构烷烃,用气相色谱法测定正构烷烃含量,气相色谱-气体同位素质谱( GC -C- IRMS)测定土壤样品中正构烷烃单体碳同位素.实验优化了5A分子筛用量和洗脱剂的比例,需要络合的正构烷烃的量与分子筛加入量呈线性关系,络合xmg的正构烷烃,需加入2.75xg分子筛,络合环己烷-正戊烷最佳比例为9∶91.探讨了络合过程中5A分子筛对不同链长正构烷烃的络合规律,短链正构烷烃被5A分子筛优先吸附,长链正构烷烃的络合相对滞后.正构烷烃的络合洗脱回收率为44% ~ 72%,精密度(RSD,n=6)为4%~8%;正构烷烃单体碳同位素分析精度为0.04‰~0.38‰( 1σ).采用5A分子筛净化混合溶剂洗脱方法,分析加油站附近的实际土壤样品,未分峰基本消除,获得良好的净化效果,满足正构烷烃单体碳同位素分析的要求.%n-alkanes were concentrated after separating by a 5A molecular sieve and extracted by a mixture solvent of cyclohexane and n-pentane. In this study, the amount of 5A molecular sieve and the ratios of cyclohexane and n-pentane were optimized as 2.76 g and 9 : 91, respectively. It was discovered that short carbon chain n-alkanes were readily absorbed by a.5A molecular sieve, compared to the long carbon chain n-alkanes. The complexation efficiency is higher for long carbon chain n-alkanes than that of short carbon chain n-alkanes with enough 5A molecular material at higher temperature. In this study, n-alkanes contents were determined by Gas Chromatography ( CC) and compound specific carbon isotope ratios of individual n-alkanes in soil were measured by Gas Chromatography-lsotope Ratio Mass Spectrometry ( GC-IRMS). The recoveries of n-alkanes ranged from44% to 72%c with a precision of 4% - 8%. The accuracies of compound specific carbon isotopes of n-alkanes ranged from 0.04%e to 0. 38%e (1σ). The 5A molecular sieve

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

    Energy Technology Data Exchange (ETDEWEB)

    Asthalter, T [Institut fuer Physikalische Chemie, Universitat Stuttgart, D-70569 Stuttgart (Germany); Sergueev, I [European Synchrotron Radiation Facility, F-38043 Grenoble (France); Buerck, U van; Wagner, F E [Experimentalphysik E13, Technische Universitaet Muenchen, D-85747 Garching (Germany); Haerter, P [Anorganische Chemie, Technische Universitaet Muenchen, D-85747 Garching (Germany); Kornatowski, J [Max-Planck-Institut fuer Kohlenforschung, D-45470 Muelheim (Germany); Klingelhoefer, S; Behrens, P, E-mail: t.asthalter@ipc.uni-stuttgart.d [Anorganische Chemie, Leibniz-Universitaet Hannover, D-30167 Hannover (Germany)

    2010-03-01

    A detailed study on the slow dynamics of ferrocene in the unidimensional channels of the molecular sieves SSZ-24 and AlPO{sub 4}-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.

  19. SYNTHESIS OF MULTI-WALL CARBON NANOTUBES USING Fe-LOADED MESOPOROUS MOLECULAR SIEVE AS CATALYTIC TEMPLATE%采用负载铁的介孔分子筛催化模板剂合成多壁碳纳米管

    Institute of Scientific and Technical Information of China (English)

    姜廷顺; 李梅; 李艳慧; 李萌; 殷恒波

    2009-01-01

    用水热法合成纯硅介孔分子筛(mesoporous molecular sieves,MCM-41.用浸渍法将MCM-41负载不同量铁制得负载铁的介孔分子筛(Fe-loading mesoporous molecular sieve,Fe/MCM-41).以Fe/MCM-41作为催化剂催化热解乙醇制备碳纳米管.用N2物理吸附、Raman光谱、透射电镜和高分辨透射电镜等手段对样品进行了表征.结果表明:制备出了多壁碳纳米管,并且随着催化剂中Fe负载量的增加,所生成碳纳米管的管径增加.

  20. Porous carbon nanotubes: Molecular absorption, transport, and separation

    Science.gov (United States)

    Yzeiri, Irena; Patra, Niladri; Král, Petr

    2014-03-01

    We use classical molecular dynamics simulations to study nanofluidic properties of porous carbon nanotubes. We show that saturated water vapor condenses on the porous nanotubes, can be absorbed by them and transported in their interior. When these nanotubes are charged and placed in ionic solutions, they can selectively absorb ions in their interior and transport them. Porous carbon nanotubes can also be used as selective molecular sieves, as illustrated on a room temperature separation of benzene and ethanol.

  1. Vacuum sorption pumping at cryogenic temperatures of argon and oxygen on molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Perona, J.J.; Gibson, M.R.; Byers, C.H.

    1988-01-01

    Cryosorption pumping is a method of excavating enclosed volumes by adsorbing gas on a deep bed of solid sorbent (typically a zeolite) at cryogenic temperatures. Modeling the dynamic behavior of these systems for air pumping requires information on two major constituents of air, oxygen and argon, which had not been previously studied, as well as data on a nonadsorbing specie, helium. Deep beds of Davison 4A molecular sieves were subjected to a metered flow of pure gas and the pressure history of the experiment was monitored, using computer data acquisition techniques. Particle size variations is the major variable in determining the mechanism of the process. The data acquired in the current study compare favorably with previous experiments. Previously developed models for the dynamic sorption behavior of deep beds under vacuum for two extreme conditions, micropore and micropore control were tested in this study. The sorption behavior of argon clearly fit into the category of macropore controlled sorption, indicating that these species are adsorbed primarily on the surface of the zeolite crystals, much like the theoretical and experimental results for N/sub 2/ cryosorption on the same sieves of Crabb. On the other hand oxygen sorption is most likely micropore controlled, and may be molded by the method of Praznick. 11 refs., 7 figs., 1 tab.

  2. A portable molecular-sieve-based CO{sub 2} sampling system for radiocarbon measurements

    Energy Technology Data Exchange (ETDEWEB)

    Palonen, V., E-mail: vesa.palonen@helsinki.fi [Department of Physics, University of Helsinki, P.O. Box 43, Helsinki FI-00014 (Finland)

    2015-12-15

    We have developed a field-capable sampling system for the collection of CO{sub 2} samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO{sub 2} concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO{sub 2} selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO{sub 2} from chambers prior to the CO{sub 2} build-up phase and sampling. In addition, both the CO{sub 2} and H{sub 2}O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO{sub 2} and the determination of CO{sub 2} flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Investigation of Fe-SAPO-5 Molecular Sieve for Purification of Carbon Dioxide%Fe-SAPO-5分子筛纯化二氧化碳的研究

    Institute of Scientific and Technical Information of China (English)

    佟天宇

    2015-01-01

    SAPO-5 molecular was synthesized by hydrothermal method, andthenthe Fe-SAPO-5 sorbent was prepared by impregnation method. The sample was characterized by means of XRD and IR techniques. The Fe-SAPO-5 sorbent was usedtopurifycarbondioxide.Effectofdifferent load, temperature and space velocityon properties of prepared sorbent was investigated.The results show thatwhenthe experimentaltemperature is25℃,the pressure is1 MPa andspace velocityis80 mL/minand FeOXcontentis 9 %(wt), thepurityof CO2can reach to 99.99%.%采用水热合成法制备了 SAPO-5分子筛,并通过浸渍法制备了一系列的 Fe-SAPO-5吸附剂,并通过XRD和IR手段对其进行表征。以Fe-SAPO-5作为吸附剂进行二氧化碳气体的提纯精制研究,并研究了不同负载量、温度及空速对其性能的影响。实验结果表明,在反应温度为25℃,压力1.0 MPa,空速为80mL/min的条件下,9%(wt )FeOx/SAPO-5吸附效果最佳,产品纯度可达99.99%。

  13. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Carran, Richard S.; Ghosh, Arun, E-mail: Arun.Ghosh@agresearch.co.nz; Dyer, Jolon M.

    2013-12-15

    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{sup +} and Ca{sup 2+} 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. 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.

  16. 不同ZSM-5分子筛对增产低碳烯烃的性能对比及改性研究%Performance comparison of and modification research on ZSM-5 molecular sieves for improving output of low-carbon olefins

    Institute of Scientific and Technical Information of China (English)

    樊江涛; 柳召永; 王智峰; 廖翼涛; 高雄厚

    2013-01-01

    低硅择形分子筛在增产液化气和丙烯方面优于高硅择形分子筛,但加入低硅择形分子筛助剂后汽油收率降低幅度较大.改性后ZSM-5分子筛制备的催化剂与未改性ZSM-5分子筛制备的催化剂相比,液化气和丙烯产率均有明显提高,重油产率明显降低,转化率升高,总液收基本不变,汽油中烯烃含量有所降低,芳烃含量提高.%The performance of shape-selective molecular sieve catalyst with low silicon content such as improving output of liquefied petroleum gas and propylene were better than that of shape-selective catalysts with high silicon content,but the yield of gasoline decreased significantly if the additive with low silicon content was added.Compared with the catalyst prepared by using the original ZSM-5 molecular sieve,the properties of the catalyst prepared with modified ZSM-5 molecular sieve were enhanced,and the yield of liquefied petroleum gas and propylene and the conversion were obviously increased,and heavy oil yield was reduced remarkably;the content of aromatic compounds in gasoline was increased and the content of olefin was slightly decreased,while the total liquid yield was kept unchanged.

  17. 利用SBA-15介孔内纳米碳合成含介孔的ZSM-5分子筛%Synthesis of ZSM-5 Molecular Sieves Containing Mesopore Using Nanocarbon in SBA-15 Mesopores

    Institute of Scientific and Technical Information of China (English)

    李工; 邓中林; 周书喜; 佟惠娟; 刘天华

    2009-01-01

    The mesopores of SBA-15 molecular sieve were filled by sucrose and the fillings were carbonized. SBA-15 molecular sieves containing nanocarbon carbon were impregnated by the slution of aluminum source and TPABr under the condition of alkalinity and weak acidity repectively, the framework of SBA-15 molecular sieve was changed into the crystal construction of ZSM-5 molecular sieve and lastly the ZSM-5 molecular sieves containing me-sopore were gained after removing the carbon. The samples were characterized by XRD, N_2 adsorption-desorption, ~(27)Al MAS NMR, NH_3-TPD, TEM and SEM methods. We researched the effect of synthesis condition on structure of samples, such as crystallizing time and so on. Results showed that ZSM-5 molecular sieve synthesised under the condition of alkalinity contained a small amount mesopores with pore diameter about 3. 2nm ~4. 2nm and its acid strength was slightly lower than that of ZSM-5 molecular, the sample synthesized unde the condition of weak acidity contained more pores with pore diameter about 1.4~1. 6nm and its acid strength was obvious lower than that of ZSM-5 molecular.%SBA-15介孔分子筛内填充蔗糖并炭化后, 分别在碱性和弱酸性条件下, 用含铝源及TPABr的溶液浸渍,将SBA-15分子筛孔壁的无定形结构转化成ZSM-5分子筛的晶体结构, 除碳后得到含介孔的ZSM-5分子筛. 用X射线衍射、 N_2吸附-脱附、 ~(27)Al MAS NMR、 NH_3-TPD、 TEM、 SEM等对样品进行了表征, 考察了晶化时间等参数对样品的影响. 结果表明, 碱性条件下合成的ZSM-5分子筛晶体中含有少量孔径约3.2~4.2 nm的介孔孔道, 其酸强度接近与常规ZSM-5分子筛的酸强度;弱酸性条件下合成的ZSM-5分子筛晶体中含有大量孔径约1.4~1.6 nm的孔道, 其酸强度明显低于常规ZSM-5分子筛的酸强度.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. Comparison of Kinetic Study of CTMA+ Removal of Molecular Sieve Ti-MCM-41 Synthesized with Natural and Commercial Silica

    OpenAIRE

    Fontes,Maria do Socorro Braga; Melo,Dulce Maria de Araújo; Costa,Cintia de Castro; Braga,Renata Martins; Melo,Marcus Antonio de Freitas; Alves,José Antônio Barros Leal Reis

    2015-01-01

    This work aimed to determine and compare the apparent activation energy, involved in thermal decomposition of CTMA+ from the pores of Ti-MCM-41 synthesized by two different source of silica in order to evaluate their influence in the template removal. The molecular sieves Ti-MCM-41 were synthesized using rice husk ash (RHA), as alternative low cost source of silica, and commercial silica gel, obtaining two mesoporous material by hydrothermal synthesis of gel molar composition of: 1.0 CTMABr: ...

  3. [Synergetic effects of silicon carbide and molecular sieve loaded catalyst on microwave assisted catalytic oxidation of toluene].

    Science.gov (United States)

    Wang, Xiao-Hui; Bo, Long-Li; Liu, Hai-Nan; Zhang, Hao; Sun, Jian-Yu; Yang, Li; Cai, Li-Dong

    2013-06-01

    Molecular sieve loaded catalyst was prepared by impregnation method, microwave-absorbing material silicon carbide and the catalyst were investigated for catalytic oxidation of toluene by microwave irradiation. Research work examined effects of silicon carbide and molecular sieve loading Cu-V catalyst's mixture ratio as well as mixed approach changes on degradation of toluene, and characteristics of catalyst were measured through scanning electron microscope, specific surface area test and X-ray diffraction analysis. The result showed that the fixed bed reactor had advantages of both thermal storage property and low-temperature catalytic oxidation when 20% silicon carbide was filled at the bottom of the reactor, and this could effectively improve the utilization of microwave energy as well as catalytic oxidation efficiency of toluene. Under microwave power of 75 W and 47 W, complete-combustion temperatures of molecular sieve loaded Cu-V catalyst and Cu-V-Ce catalyst to toluene were 325 degrees C and 160 degrees C, respectively. Characteristics of the catalysts showed that mixture of rare-earth element Ce increased the dispersion of active components in the surface of catalyst, micropore structure of catalyst effectively guaranteed high adsorption capacity for toluene, while amorphous phase of Cu and V oxides increased the activity of catalyst greatly.

  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. 神府丝炭制备分离CH4/N2的炭分子筛工艺及其性能研究%Preparation of formed carbon molecular sieve from fusain of Shenfu coal for separation of CH4/N2 and its performance

    Institute of Scientific and Technical Information of China (English)

    王德超; 杨志远; 刘娇萍; 廖宏斌; 杨根源

    2016-01-01

    以神府煤丝炭(SFF)为原料,采用炭化-KOH活化-苯气相碳沉积方法制备用于变压吸附分离CH4/N2所用的成型炭分子筛(FCMS),活化过程的最优条件为:碱炭质量比=3∶1,活化温度为700℃,活化时间为90 min;碳沉积过程最优条件为:碳沉积温度为800℃,碳沉积时间为5 min,苯流率为3 mL/min,在此条件下,FCMS的碘吸附值和比表面积分别为985.23 mg/g和1 195.52 m2/g,微孔孔容占63.18%.利用FCMS进行了CH4和N2吸附量测试和Langrnuir吸附模型的拟合,得出CH4为强吸附组分,CH4/N2在FCMS上的分离系数为2.50.单塔穿透实验表明,CH4在FCMS上的穿透时间延迟了171 s,证实了FCMS吸附甲烷的能力增强.%Using fusain of Shenfu coal as raw material,the formed carbon molecular sieve (FCMS) for the separation of CH4 and N2 is prepared by carbonization-KOH chemical activation-benzene vapor carbon deposition technology.The optimal activation conditions are:3 of mass ratio of potassium hydroxide and fusain,700 ℃ of activation temperature and 90 minutes of activation time.The optimal conditions of carbon deposition process are 800 ℃ of deposition temperature,5 minutes of deposition time and 3 mL/min of benzene flow rate.Under optimal experimental condition,the iodine sorption value and SBEr are 985.23 mg/g and 1 195.52 m2/g,respectively.The micropore volumes is 63.18%.CH4 and N2 adsorption capacity are performed on FCMS and the adsorption data is fitted by Langmuir model.The results indicate that CH4 is the strong adsorbed component and the separation factor is 2.50.Breakthrough experiment results show that the breakthrough time of CH4 is delayed by 171 s.It surggests that the adsorption capacity of CH4 on FCMS is strengthened.

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

    Science.gov (United States)

    Zhang, Xiaoxing; Li, Xin; Luo, Chenchen; Dong, Xingchen; Zhou, Lei

    2015-11-11

    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.

  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. 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.

  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. Luminescence of Nanosized Supramolecular Material of Mesoporous Molecular Sieve and Samarium (Ⅲ) Complex

    Institute of Scientific and Technical Information of China (English)

    YIN Wei; ZHANG Mai-sheng

    2003-01-01

    The solutions of rare earth complexes Sm(Phen)2(TTA)(Bipy)(NO3)3 and Sm(L)x(TTA)4-x(NO3)3[L=Phen(1,10-phenanthroline) or Bipy(2,2′-bipyridine), x=4, 3, 2, 1, 0; TTA is 2-thenoyltrifluoacetone] in EtOH(1×10-3 mol/L) were prepared. The coefficients of antenna effect are 31.5, 18.2 and 5.6 for Phen, Bipy and TTA, respectively, when the electron configuration of the excited state of the samarium atom in the complexes is 4D1/2. The fluorescent intensity and the lifetime of the supramolecular encapsulation products of (CH3)3Si-MCM-41 and Sm3+ complexes are stronger and longer than those of the encapsulation products of MCM-41 and Sm3+ complexes respectively. The results show that the host with lipophilic channels is more favourable to the fluorescence of the rare earth complexes than the hydrophilic mesoporous molecular sieve. The fluorescent intensity of (CH3)3Si-MCM-41-Sm(Phen)3(TTA)(NO3)3 is the strongest amongthe encapsulation series of Sm3+ complexes, which is assumed to result from the greatly reduction of SiO-H vibration relaxation in host (CH3)3Si-MCM-41 and the presence of the discrete strong luminescent centres of the guest molecules associated with the nanosized material′s structure. The luminescent decay halftime of the supramolecular materials is much shorter than that of the powder of the samarium complexes. The result shows that the ligand transferring energy from the triplet state to the singlet state of Sm3+(T1→S, intersystem crossing) becomes higher. The fluorescent experimental results indicate that the interaction between the host and the guest influences the luminescent properties of the nanostructured supramolecular materials.

  11. Influence of the rare earth content (La) on the performance and coke selective of USY molecular sieve%稀土含量(La)对USY分子筛性能及其焦炭选择性的影响

    Institute of Scientific and Technical Information of China (English)

    唐莉; 朱学梅; 孙雪芹; 高雄厚; 刘丛华; 张亮

    2012-01-01

    采用XRD、固定床微反装置、快速精密定炭仪研究了用高温水蒸气法及稀土LaCl3改性NaY分子筛后分子筛的稳定性、活性及其焦炭选择性.结果表明,随着USY分子筛La含量的增加,其晶胞常数增大,活性增加,结晶度减小,老化后的533峰保留率降低,结晶度的降低并不是真正意义上的分子筛减少,而是稀土干扰导致的.综合比较稀土含量和晶胞的作用,可知晶胞大小可能是影响稳定性的最主要因素,而后才是稀土的影响.La含量增加,积炭含量增加,其焦炭选择性变差.%The techniques such as XRD, MAT, the rapid precision instrument for carbon were used to investigate the stability, activity and selectivity coke of the NaY molecular sieve modified with high temperature steam method and rare earth. The results showed that with the increase of the content of La,the crystal cell constant and activity of molecular sieve are all increased; the crystallinity and the 533 peak after aging of molecular sieve are all decreased. The crystallinity of molecular sieve decreased, which does not means molecular sieve decreased, but it' s rare earth interference. Comprehensive comparison the influence of rare earth content with crystal cell on the stability of molecular sieve, it can be seen that the crystal cell size may be the most important factor,and then it's the rare earth. With the increased of La content, the carbon content increased, and the coke selective becomes poor.

  12. 径向流分子筛使用末期CO2含量超标的处理%Treatment of Excessive CO2 Content at the Final Phase of Radial Flow Molecular Sieve Usage

    Institute of Scientific and Technical Information of China (English)

    长孙峰; 高永春

    2015-01-01

    Excessive carbon dioxide content in the air from the outlet of radial flow molecular sieve absorber at the end of adsorption affects the safe operation of air separation plant. The causes of the trouble were analyzed from the aspects of technical design, molecular sieve operation parameters and equipment factors and countermeasures were taken, which has solved the problem.%径向流分子筛在使用过程末期CO2含量超高,影响空分安全运行。从工艺设计、分子筛运行参数和设备等方面分析了原因,并采取措施解决了问题。

  13. 多级纳米孔分子筛在非均相催化中的应用现状及发展前景%Application status and development prospects of hierarchically nanoporous molecular sieves in heterogeneous catalysis

    Institute of Scientific and Technical Information of China (English)

    亢玉红; 李健; 马向荣; 马亚军

    2016-01-01

    传统分子筛因其单一的微孔孔道,在工业应用中表现为扩散阻力差、催化易失活,尤其在涉及大分子的反应过程中催化活性较差是阻碍其工业应用的现实难题,通过优化制备路线得到的多级纳米孔分子筛催化材料可有效解决传统分子筛存在的上述应用缺陷。多级纳米孔分子筛相比传统分子筛因其特殊的孔道结构和物化性能,在非均相催化方面具有丰富的催化活性位点、较短的扩散路径、较高的传递效率和较长的催化寿命,特别在涉及非均相催化反应的现代化学工业中展现出重要的潜在应用价值。综述多级纳米孔分子筛在烃类异构化反应、加氢裂化反应、烷基化与酰基化反应、烯烃氧化反应以及甲醇制烃类等反应中的诸多优势及潜在应用。%Compared to the conventional molecular sieves with single microporous channels,the main pur-pose of the development of synthetic routes for hierarchically nanoporous molecular sieves is to improve the catalytic performances of conventional molecular sieves by resolving some problems such as low molec-ular diffusion efficiency,quick catalytic deactivation and weak activity to bulky molecules. Hierarchically nanoporous molecular sieves with special texture and physicochemical properties possess rich catalytic active sites,short diffusion path,high transfer efficiency,and long catalytic life in heterogeneous catalysis aspect. Hierarchically nanoporous molecular sieves have important and potential application in modern chemical industry involving heterogeneous catalytic reactions. In this paper,the advantages and potential applications of hierarchically nanoporous molecular sieves in hydrocarbon isomerization reaction,hydro-cracking reaction,alkylation and acylation reaction,hydrocarbon oxidation reaction and methanol to hydro-carbon reaction were reviewed.

  14. 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

  15. Phase behavior and molecular mobility of n-octylcyanobiphenyl confined to molecular sieves: dependence on the pore size.

    Science.gov (United States)

    Frunza, Ligia; Frunza, Stefan; Kosslick, Hendrik; Schönhals, Andreas

    2008-11-01

    The molecular dynamics of 4-n-octyl-4'-cyanobiphenyl (8CB) confined inside the pores of a series of AlMCM-41 samples with the same structure, constant composition (SiAl=14.7) but different pore sizes (diameter between 2.3 and 4.6 nm) was investigated by broadband dielectric spectroscopy (10(-2)-10(9) Hz) in a large temperature interval. Two relaxation processes are observed: one has a bulklike behavior and is assigned to the 8CB in the pore center. The relaxation time of the second relaxation process is essentially slower than that of the former one and this process is related to the dynamics of molecules in a surface layer with a paranematic order. Both relaxation processes are specifically influenced by the interaction of the molecules with the surface and by the confinement. Above the clearing temperature the temperature dependence of the relaxation rate of the bulklike process obeys the Vogel-Fulcher-Tammann (VFT) law. The Vogel temperature increases with decreasing pore size. This is explained by increasing influence of paranematic potential of the surface layer with decreasing pore size. The temperature dependence of the relaxation rate of the surface layer follows also the VFT formula and the Vogel temperature decreases with decreasing pore size. This temperature dependence is controlled by both the interaction of the 8CB molecules with the surface via hydrogen bonding and by spatial confinement effects. To discriminate between both effects the data for the surface layer of 8CB confined to the molecular sieves are compared with results concerning 8CB adsorbed as a quasimonolayer on the surface of silica spheres of aerosil. On this basis a confinement parameter is defined and discussed.

  16. Diffusion energy profiles in silica mesoporous molecular sieves modelled with the fragment molecular orbital method

    Science.gov (United States)

    Roskop, Luke; Fedorov, Dmitri G.; Gordon, Mark S.

    2013-07-01

    The fragment molecular orbital (FMO) method is used to model truncated portions of mesoporous silica nanoparticle (MSN) pores. The application of the FMO/RHF (restricted Hartree-Fock) method to MCM-41 type MSNs is discussed and an error analysis is given. The FMO/RHF method is shown to reliably approximate the RHF energy (error ∼0.2 kcal/mol), dipole moment (error ∼0.2 debye) and energy gradient (root mean square [RMS] error ∼0.2 × 10-3 a.u./bohr). Several FMO fragmentation schemes are employed to provide guidance for future applications to MSN models. An MSN pore model is functionalised with (phenyl)propyl substituents and the diffusion barrier for benzene passing through the pore is computed by the FMO/RHF-D method with the Grimme dispersion correction (RHF-D). For the reaction coordinates examined here, the maximum FMO/RHF-D interaction energies range from -0.3 to -5.8 kcal/mol.

  17. 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.

  18. Time-Dependent CO[subscript 2] Sorption Hysteresis in a One-Dimensional Microporous Octahedral Molecular Sieve

    Energy Technology Data Exchange (ETDEWEB)

    Espinal, Laura; Wong-Ng, Winnie; Kaduk, James A.; Allen, Andrew J.; Snyder, Chad R.; Chiu, Chun; Siderius, Daniel W.; Li, Lan; Cockayne, Eric; Espinal, Anais E.; Suib, Steven L. (IIT); (NIST); (Connecticut)

    2014-09-24

    The development of sorbents for next-generation CO{sub 2} mitigation technologies will require better understanding of CO{sub 2}/sorbent interactions. Among the sorbents under consideration are shape-selective microporous molecular sieves with hierarchical pore morphologies of reduced dimensionality. We have characterized the non-equilibrium CO{sub 2} sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO{sub 2} sorption hysteresis increases when the gas/sorbent system is allowed to equilibrate for longer times at each pressure step. Density functional theory calculations indicate a 'gate-keeping' role of the cation in the tunnel, only allowing CO{sub 2} molecules to enter fully into the tunnel via a highly unstable transient state when CO{sub 2} loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO{sub 2} is responsible for the observed hysteretic behavior.

  19. 小晶粒SAPO-34分子筛研究进展%Research advances in small crystal SAPO-34 molecular sieves

    Institute of Scientific and Technical Information of China (English)

    朱伟平; 李飞; 薛云鹏; 郭磊

    2014-01-01

    SAPO-34分子筛被用作甲醇反应制低碳烯烃(乙烯、丙烯)(MTO)工艺的催化剂。然而,传统的SAPO-34分子筛催化剂容易失活,单程寿命较短。研究表明,降低SAPO-34分子筛粒径,可以有效地提高催化剂比表面积,减弱扩散的限制,增加催化剂的活性中心和抗积炭能力、加速反应热去除以及延长催化剂单程寿命。本文介绍了小晶粒SAPO-34分子筛具有的特性和制备小晶粒SAPO-34分子筛技术的研究进展,并提出研究开发建议。%SAPO-34 molecular sieves were used as the catalyst of the methanol to olefins (MTO) process, however, the conventional SAPO-34 catalysts were easy to loss activity and had a short single cycle life. It was found that reducing the crystalline size of SAPO-34 could improve the specific surface area, weaken the diffusion limit, increase the active sites, enhance the anti-carbon deposition ability, accelerate removing the heat of reaction and prolong the single cycle life. The characteristics and research advances of the small crystal SAPO-34 molecular sieves were presented, and some suggestions were given for developing these catalysts.

  20. 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。

  1. 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.

  2. 煤矸石制备4A分子筛的研究%Preparation of molecular sieve using coal gangue

    Institute of Scientific and Technical Information of China (English)

    杨建利; 杜美利; 于春侠; 石超

    2013-01-01

    煤矸石是采煤过程中产出的固体废弃物,随着煤炭生产的不断扩大与日俱增.大量煤矸石堆积侵占农田、耕地,造成严重的环境污染,如何高效利用成为急需解决的问题.煤矸石的化学组成以SiO2和Al2O3为主,这些组分正是合成分子筛的主要原料.以煤矸石制备分子筛不但解决了分子筛合成的高成本问题,而且又能提高煤矸石制品的附加值,同时对煤矸石资源化,精细化高效利用提供新的有效途径,达到变废为宝的效果,实现了环保低碳的要求.我国不同矿区煤矸石化学组成成分差异很大,本研究在分析陕西澄合矿区煤矸石化学组分的基础上,改变不同的工艺条件通过添加导向剂和柠檬酸助剂水热法制备4A分子筛,经XRD和SEM表征,成功合成了粒径约为1 ~2 μm性能优良的4A分子筛.%Coal gangue is a kind of solidwastes during procedure of coal extration. With the constant expansion of the coal production, output of coal gangue is growing. Most of the coal gangue accumulate in farmland land and cause severe environmental pollution. How to use coal gangue has become a hotspot. Chemical constitution of coal gangue is mainly in SiO2 and A12O3, these constituents just are main raw material to prepare molecular sieve. Using coal gangue to prepare molecular sieve not only solving high-cost problem, improving added value, reaching the goal in using gangue to recycly and fine efficient u-sing, so as to provide new effective way to achieve the effect of reuse, and realize environmental protection in low carbon requirements. The composition of coal gangue is different greatly in our country. The study mainly focused on chemical analysis of chenghe mining area coal, using different reagents and reaction conditions to prepare high-quality molecular sieve, by X-ray diffraction (XRD) and scanning e-lectron microscope ( SEM) characterization, molecular sieve is prepared by using citric acid and guide agent

  3. 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

  4. 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.

  5. 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.

  6. A novel molecular sieve supporting material for enhancing activity and stability of Ag3PO4 photocatalyst

    Science.gov (United States)

    Wu, Qiang; Wang, Peifu; Niu, Futao; Huang, Cunping; Li, Yang; Yao, Weifeng

    2016-08-01

    A small-pore silicon-substituted silicon aluminum phosphate (SAPO-34) molecular sieve, for the first time, is reported to significantly increase both the activity and life span of Ag3PO4 photocatalyst for visible-light degradation of methylene blue (MB) and rhodamine B (RhB). Results show that 60 wt.% Ag3PO4/SAPO-34 exhibits the highest photocatalytic degradation efficiencies for both MB (91.0% degradation within 2.0 min) and RhB (91.0% degradation within 7.0 min). In comparison, pure Ag3PO4 powder photocatalyst requires 8.0 min and 12.0 min for decomposing 91.0% of MB and RhB, respectively. During MB degradation the rate constant for 60 wt.% Ag3PO4/SAPO-34 increases 317.2% in comparison with the rate constant of pure Ag3PO4. This activity is also much higher than literature reported composite or supported Ag3PO4 photocatalysts. In three photocatalytic runs for the degradation of RhB, the rate constant for 60 wt.% Ag3PO4/SAPO-34 reduces from 0.33 to 0.18 min-1 (45.5% efficiency loss). In contrast, the rate constant of pure Ag3PO4 catalyst decreases from 0.2 to 0.07 min-1 (80.0% efficiency loss). All experimental results have shown that small pores and zero light absorption loss of SAPO-34 molecular sieves minimize Ag3PO4 loading, enhance photocatalytic activity and prolong the lifespan of Ag3PO4 photocatalyst.

  7. 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.

  8. 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

  9. 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.

  10. 新型分子筛CeAPO-5的合成及表征%Synthesis and Characterization of Cerium Aluminophosphate Molecular Sieve ( CeAPO-5 )

    Institute of Scientific and Technical Information of China (English)

    张岩; 高平强

    2011-01-01

    采用水热合成法,以拟薄水铝石,正磷酸,碳酸铈,水为原料,三乙胺为模板剂合成了新型CeAPO-5分子筛.利用XRD、FT-IR、SEM和BET等手段对它的晶体结构、表面形貌做了系统的表征.结果表明CeAPO-5分子筛具有AlPO4-5分子筛的晶体结构.Ce(III)的引入并没有改变分子筛的骨架结构.但会增加新型分子筛CeAPO-5分子筛的比表面积.%Cerium (Ⅲ) aluminophosphate molecular sieve has been synthesized starting from pseudo-boehmite, phosphoric acid, cerium carbonate, and water, in the presence of a triethylamine organic template. Based on the synthesized material, many of characterization were carried out by XRD, IT-IR, SEM, BET methods. It shows that the material has a tetrahedral framework of [ APO4 ] and [ PO4]. The obtained structure was similar to that of AIPO4-5. The incorporation of Ce (Ⅲ) ions into the framework did not change the AIPO4-5 structure, but did,however, increase the surface area.

  11. Preparation and application of zirconium sulfate supported on SAPO-34 molecular sieve as solid acid catalyst for esterification

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Dongyan, E-mail: xdy0156@sina.com; Ma, Hong; Cheng, Fei

    2014-05-01

    Graphical abstract: - Highlights: • SAPO-34 supported zirconium sulfate solid acid catalyst was prepared. • Esterification of acetic acid with ethanol can be catalyzed by ZS/SAPO-34. • The hydration of ZS is vital to the acidic property and catalytic performance. • The ZS/SAPO-34 catalyst treated at 200 °C shows good reusability. - Abstract: Zirconium sulfate (ZS) was supported on SAPO-34 molecular sieve by using an incipient wetness impregnation method with zirconium sulfate as the precursor. The as-prepared catalysts were used as solid acid catalyst for esterification reaction of acetic acid with ethanol. The influence of calcination temperature on the acidic property, catalytic activity, and reusability of ZS/SAPO-34 catalysts were mainly investigated. FT-IR, SEM, EDS and TG analysis have been carried out to demonstrate the characteristics of ZS/SAPO-34 catalysts. It was found that the 30 wt%ZS/SAPO-34 catalysts display the property of superacid irrespective of calcination temperature. The ZS/SAPO-34 catalyst treated at 200 °C can enhance the interaction between the supported ZS and SAPO-34 and keep the catalyst remaining substantially active after several reaction cycles. However, further increasing calcination temperature will cause the transfer of ZS from hydrate to anhydrous phase, and thus the decrease of activity.

  12. 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.

  13. Effects of octahedral molecular sieve on treatment performance, microbial metabolism, and microbial community in expanded granular sludge bed reactor.

    Science.gov (United States)

    Pan, Fei; Xu, Aihua; Xia, Dongsheng; Yu, Yang; Chen, Guo; Meyer, Melissa; Zhao, Dongye; Huang, Ching-Hua; Wu, Qihang; Fu, Jie

    2015-12-15

    This study evaluated the effects of synthesized octahedral molecular sieve (OMS-2) nanoparticles on the anaerobic microbial community in a model digester, expanded granular sludge bed (EGSB) reactor. The addition of OMS-2 (0.025 g/L) in the EGSB reactors resulted in an enhanced operational performance, i.e., COD removal and biogas production increased by 4% and 11% respectively, and effluent volatile fatty acid (VFA) decreased by 11% relative to the control group. The Biolog EcoPlate™ test was employed to investigate microbial metabolism in the EGSB reactors. Results showed that OMS-2 not only increased the microbial metabolic level but also significantly changed the community level physiological profiling of the microorganisms. The Illumina MiSeq high-throughput sequencing of 16S rRNA gene indicated OMS-2 enhanced the microbial diversity and altered the community structure. The largest bacterial genus Lactococcus, a lactic acid bacterium, reduced from 29.3% to 20.4% by abundance in the presence of 0.25 g/L OMS-2, which may be conducive to decreasing the VFA production and increasing the microbial diversity. OMS-2 also increased the quantities of acetogenic bacteria and Archaea, and promoted the acetogenesis and methanogenesis. The X-ray photoelectron spectroscopy illustrated that Mn(IV)/Mn(III) with high redox potential in OMS-2 were reduced to Mn(II) in the EGSB reactors; this in turn affected the microbial community.

  14. Cr-MCM-41 Molecular Sieves Crystallized at Room Temperature for Reaction of Ethane with CO2

    Institute of Scientific and Technical Information of China (English)

    Yanan Li; Xin He; Shujie Wu; Ke Zhang; Guangdong Zhou; Jie Liu; Kaiji Zhen; Tonghao Wu; Tiexin Cheng

    2005-01-01

    A series of Cr-containing MCM-41 molecular sieves crystallized at room temperature with a hexagonal and well-ordered structure were synthesized. XRD, FT-IR and DRS UV-Vis techniques were used to characterize the samples. The results indicate incorporation of Cr into the MCM-41 framework,and dispersion of some Cr2O3 on the surface or/and in the bulk of the MCM-41. Test of catalytic properties of the series of samples for the topic reaction was carried out using a continuous-flow fixed-bed quartz reactor. Factors influencing the catalytic performance for this title reaction, such as Cr/Si ratio in MCM-41 and reaction temperature were investigated. The experimental results indicate that over the 5%CrMCM-41 a 43.27% conversion of ethane and a 86.70% selectivity for ethylene were achieved in the ethane dehydrogenation with CO2 to ethylene at 973 K. It is suggested that both Cr6+ and Cr3+ are the catalytic activity center.

  15. 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.

  16. 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

  17. 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.

  18. 制氧机分子筛吸附器运行异常的分析与处理%The Analysis and Treatment of Abnormal Operation of Oxygenerator Molecular Sieve Adsorber

    Institute of Scientific and Technical Information of China (English)

    徐鹏

    2016-01-01

    分子筛纯化系统作为空气分离过程中清除杂质的一个重要环节,其工作状况的稳定是保证制氧机安全、长期、稳定运行的关键因素之一。阐述了分子筛吸附器二氧化碳含量异常波动的现象、原因分析以及处理,并为处理类似故障提供相关的操作经验。%As an important link in air separation process, the stable operation of molecular sieve purification system is one of the key factors of ensuring the safe, long-term and stable operation of oxygenerator, stabilize its working conditions is to ensure safety of oxygen, one of the key factors in long-term, stable operation. It describes thephenomenon, cause analysis and treatment of abnormal fluctuations of carbon dioxide content in molecular sieve adsorber, and provides relevant experience to deal with similar failures.

  19. 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.

  20. Glycidol-modified gels for molecular-sieve chromatography. Surface hydrophilization and pore size reduction.

    Science.gov (United States)

    Eriksson, K O

    1987-11-01

    Divinyl sulfone-crosslinked agarose gels were made hydrophilic by coupling glycidol to the agarose chains. The concentration of glycidol in the reaction mixture determines the pore size of the gels (the glycidol molecules probably form polymers, the degree of polymerization increasing with the glycidol concentration). Gels prepared with moderate glycidol concentrations are still porous enough to be used for separation of proteins and peptides. Gels with a high degree of glycidol polymerization are suited for desalting of low-molecular-weight compounds, for instance peptides.

  1. 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

  2. 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.

  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. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Salas, P. [Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, Apartado Postal 1-1010, Queretaro 76000 (Mexico)], E-mail: psalas@fata.unam.mx; Wang, J.A. [Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Instituto Politecnico Nacional, Av. Politecnico S/N, Col. Zacatenco, 07738 Mexico D.F. (Mexico); Armendariz, H.; Angeles-Chavez, C. [Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Chen, L.F. [Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Instituto Politecnico Nacional, Av. Politecnico S/N, Col. Zacatenco, 07738 Mexico D.F. (Mexico)

    2009-03-15

    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 {sup 29}Si MAS-NMR techniques. FTIR spectra show that the intensity of the band around 890 cm{sup -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 Q{sup 3}/Q{sup 4} value obtained from {sup 29}Si 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 Zr{sup 4+} 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.

  6. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, L.F. [Departamento de Ciencias Basicas, Universidad Autonoma Metropolitana-A, Av. San Pablo 180, Col. Reynosa-Tamaulipas, 02200 Mexico D.F. (Mexico)]. E-mail: chenlf2001@yahoo.com; Zhou, X.L. [Petroleum Processing Research Center, East China University of Science and Technology, 200237 Shanghai (China); Norena, L.E. [Departamento de Ciencias Basicas, Universidad Autonoma Metropolitana-A, Av. San Pablo 180, Col. Reynosa-Tamaulipas, 02200 Mexico D.F. (Mexico)]. E-mail: lnf@correo.azc.uam.mx; Wang, J.A. [Laboratorio de Catalisis y Materiales, SEPI-ESIQIE, Instituto Politecnico Nacional, Av. Politecnico S/N, Col. Zacatenco, 07738 Mexico D.F. (Mexico); Navarrete, J. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Salas, P. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Montoya, A. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Del Angel, P. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico); Llanos, M.E. [Grupo de Molecular Ingenieria, Instituto Mexicano del Petroleo, Eje Lazaro Cardenas 152, 07730 Mexico D.F. (Mexico)

    2006-12-30

    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 m{sup 2}/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 m{sup 2}/g and an uniform pore diameter distribution. Fourier transform infrared (FT-IR) characterization and {sup 29}Si 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.

  8. The effects of manganese oxide octahedral molecular sieve chitosan microspheres on sludge bacterial community structures during sewage biological treatment

    Science.gov (United States)

    Pan, Fei; Liu, Wen; Yu, Yang; Yin, Xianze; Wang, Qingrong; Zheng, Ziyan; Wu, Min; Zhao, Dongye; Zhang, Qiu; Lei, Xiaoman; Xia, Dongsheng

    2016-11-01

    This study examines the effects of manganese oxide octahedral molecular sieve chitosan microspheres (Fe3O4@OMS-2@CTS) on anaerobic and aerobic microbial communities during sewage biological treatment. The addition of Fe3O4@OMS-2@CTS (0.25 g/L) resulted in enhanced levels of operational performance for decolourization dye X-3B. However, degradation dye X-3B inhibition in the presence of Fe3O4@OMS-2@CTS was recorded as greater than or equal to 1.00 g/L. Illumina MiSeq high throughput sequencing of the 16 S rRNA gene showed that 108 genera were observed during the anaerobic process, while only 71 genera were observed during the aerobic process. The largest genera (Aequorivita) decreased from 21.14% to 12.65% and the Pseudomonas genera increased from 10.57% to 12.96% according to the abundance in the presence of 0.25 g/L Fe3O4@OMS-2@CTS during the anaerobic process. The largest Gemmatimonas genera decreased from 21.46% to 11.68% and the Isosphaerae genera increased from 5.8% to 11.98% according to the abundance in the presence of 0.25 g/L Fe3O4@OMS-2@CTS during the aerobic process. Moreover, the X-ray photoelectron spectroscopy results show that the valence states of Mn and Fe in Fe3O4@OMS-2@CTS changed during sewage biological treatment.

  9. Mesoporous molecular sieve catalysts

    DEFF Research Database (Denmark)

    Højholt, Karen Thrane

    be used as solid acid catalysts but can also be used as a size-selective matrix. It was shown that it is possible to encapsulate 1-2 nm sized gold nanoparticles by silicalite-1 or ZSM-5 zeolite crystals thereby forming a sintering-stable and substrate size-selective oxidation catalyst. After carrying out...... calcination experiments, both in situ and ex situ indicated that the gold nanoparticles embedded in the crystals were highly stable towards sintering. The catalytic tests proved that the embedded gold nanoparticles were active in selective aldehyde oxidation and were only accessible through the micropores...

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

    Institute of Scientific and Technical Information of China (English)

    刘鹏; 沈健

    2015-01-01

    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。%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.

  11. Study on the Application of Molecular Sieve in Wastewater Treatment%分子筛在污水处理中的应用研究

    Institute of Scientific and Technical Information of China (English)

    罗五魁; 茹晶晶; 叶楠; 黄晓辉

    2016-01-01

    水体的污染会严重危害人类的身体健康,污水的处理已是人类面临的重大问题。分子筛对污水中污染物具有较好的吸附能力,且分子筛能再生多次使用,不会产生二次污染,在污水处理中有广泛的应用。本文概述了生活污水、农业污水及工业污水的来源;阐述了今年来分子筛在处理污水中的重金属离子、污水中的氨氮、有机污染物及其他污染物的应用情况;并分析了分子筛在污水处理过程中的应用前景。%Water pollution will seriously endanger human health, wastewater treatment is the major problem facing humanity. Molecular sieve has better adsorption capacity of pollutants in wastewater and the molecular sieve can be regenerated for several times, and does not cause secondary pollution, is widely used in the wastewater treatment. The sources of domestic wastewater, agricultural wastewater and industrial wastewater were summarized. The molecular sieve for the adsorption of pollutants of heavy metal ions, ammonia nitrogen, organic pollutants and other pollutants in the wastewater treatment was discussed, the development and preview were pointed out.

  12. Synthesis and modification of mesoporous silica and the preparation of molecular sieve thin films via pulsed laser deposition

    Science.gov (United States)

    Coutinho, Decio Heringer

    2001-07-01

    describes the evaluation of the HISIV(TM) 1000 molecular sieve for TBC adsorption. The TBC equilibrium capacity was determined from a cyclohexane/TBC liquid mixture and was comparable to alumina adsorbents. Practicum One. A fluorescent diagnostic system was developed to image the inhomogeneous mixture formed as two miscible fluids mix. This diagnostic for the mixing fraction uses a commercially available CCD color camera, a polarity sensitive fluorescent probe (DCM), and the planar laser induced fluorescence (PLIF) imaging technique to track the mixing of two miscible fluids of different polarity (ethanol and decane). The DCM fluorescence spectrum shifts to the red with increasing polarity, and the CCD camera's red, green, and blue color channels serve as spectral filters for the probe's fluorescence.

  13. 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

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

    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.

  15. 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.

  16. Synthesis and applications of SSZ-13 zeolite molecular sieves%SSZ-13沸石分子筛的合成及应用

    Institute of Scientific and Technical Information of China (English)

    袁龙; 王亚松; 王闯

    2016-01-01

    Progresses in the synthesis,namely hydrothermal synthesis,interzeolite conversion and solid grinding,and applications of SSZ-13 zeolite molecular sieves were reviewed. Modified SSZ-13 zeolite molecular sieves were also concisely introduced,such as metal-modifi ed SSZ-13 and hierarchical SSZ-13. It was pointed out that a high-effi cient synthesis route for the industrialization of the synthesis should be exploited,which involved adding inexpensive and high performance organic templates or without using any organic template. The applications of the SSZ-13 zeolite molecular sieves in methanol to olefi n,selective catalytic reduction,and gas adsorption and separation were summarized. The problems about the easy coking in catalytic reactions and the fast inactivation at high temperature should be solved,and the adsorption and separation properties of the SSZ-13 zeolite molecular sieves should be improved.%综述了水热法、转晶法、固相研磨法等SSZ-13沸石分子筛的合成方法,介绍了SSZ-13沸石分子筛引入金属杂原子、调变孔尺寸等改性方法。指出开发价格低廉、性能优越的模板剂或不使用有机模板剂的高效合成路线,是实现工业化生产的发展方向。概述了SSZ-13沸石分子筛在甲醇制烯烃、选择性催化还原和气体吸附/分离等应用的研究进展。在催化反应中的积碳和高温失活等问题亟待解决,气体吸附/分离性能还有提高的空间。

  17. 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

  18. SAPO-34分子筛催化剂制备及发展现状%Preparation and development status of SAPO-34 molecular sieve catalysts for methanol to olefins

    Institute of Scientific and Technical Information of China (English)

    张媛; 张伟; 刘志玲; 张菊; 裴婷

    2016-01-01

    乙烯和丙烯作为重要的化工原料,在经济发展中的需求量越来越大。在石油资源越来越匮乏的今天,甲醇制烯烃作为一种可以代替常规石油路线生产低碳烯烃的新工艺受到广泛关注。SAPO-34分子筛因为高甲醇转化率和优良烯烃选择性成为当前甲醇制烯烃工艺催化剂的研究重点。合成SAPO-34分子筛的影响因素有模板剂、合成原料和反应条件等。通过调节分子筛粒径尺寸、酸性、金属改性可以实现分子筛的性能优化。介绍了SAPO-34分子筛催化剂常用的制备方法和一些分子筛催化剂改进的专利。使用一定时间后催化剂由于积炭而失活,再生工艺目前主要采用烧焦再生。2011年,神华煤制烯烃示范工程进入工业化运行,近年陆续有多套甲醇制烯烃装置投产和在建,煤制烯烃正在改变中国聚烯烃市场格局。%Ethylene and propylene are important chemical materials. The demand for them grows very fast in the economic developments. The technologies of Methanol-to-Olefins( MTO)as a new production tech-nology of low carbon olefins instead of conventional oil routes was gained widely attention. SAPO-34 molecular sieves were studied intensively because of its high methanol conversion and good selectivity to olefins. The influence factors of SAPO-34 molecular sieves synthesis such as the templates,raw materials and reaction conditions were discussed. The performance of molecular sieves was optimized by adjusting the particle size of molecular sieves,acidity and metal modification. Additionally,the normal preparation methods of SAPO-34 molecular catalysts for MTO and some patents about their performance optimization were introduced. The regeneration process of the deactivation catalysts for carbon deposit was mainly cal-cination. In 2011,MTO project of Shenhua Group was industrialized. In recent years,many MTO projects went into operation and are under construction

  19. 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.

  20. Carbon Nanotubes: Molecular Electronic Components

    Science.gov (United States)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1997-01-01

    The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.

  1. 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)

  2. Sieving of H2 and D2 Through End-to-End Nanotubes

    Science.gov (United States)

    Devagnik, Dasgupta; Debra, J. Searles; Lamberto, Rondoni; Stefano, Bernardi

    2014-10-01

    We study the quantum molecular sieving of H2 and D2 through two nanotubes placed end-to-end. An analytic treatment, assuming that the particles have classical motion along the axis of the nanotube and are confined in a potential well in the radial direction, is considered. Using this idealistic model, and under certain conditions, it is found that this device can act as a complete sieve, allowing chemically pure deuterium to be isolated from an isotope mixture. We also consider a more realistic model of two carbon nanotubes and carry out molecular dynamics simulations using a Feynman—Hibbs potential to model the quantum effects on the dynamics of H2 and D2. Sieving is also observed in this case, but is caused by a different process.

  3. 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.

  4. Confinement of Ionic Liquids in Nanocages: Tailoring the Molecular Sieving Properties of ZIF-8 for Membrane-Based CO2 Capture.

    Science.gov (United States)

    Ban, Yujie; Li, Zhengjie; Li, Yanshuo; Peng, Yuan; Jin, Hua; Jiao, Wenmei; Guo, Ang; Wang, Po; Yang, Qingyuan; Zhong, Chongli; Yang, Weishen

    2015-12-14

    Fine-tuning of effective pore size of microporous materials is necessary to achieve precise molecular sieving properties. Herein, we demonstrate that room temperature ionic liquids can be used as cavity occupants for modification of the microenvironment of MOF nanocages. Targeting CO2 capture applications, we tailored the effective cage size of ZIF-8 to be between CO2 and N2 by confining an imidazolium-based ionic liquid [bmim][Tf2 N] into ZIF-8's SOD cages by in-situ ionothermal synthesis. Mixed matrix membranes derived from ionic liquid-modified ZIF-8 exhibited remarkable combinations of permeability and selectivity that transcend the upper bound of polymer membranes for CO2 /N2 and CO2 /CH4 separation. We observed an unusual response of the membranes to varying pressure, that is, an increase in the CO2 /CH4 separation factor with pressure, which is highly desirable for practical applications in natural gas upgrading.

  5. Carbon Nanotube Based Molecular Electronics

    Science.gov (United States)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1998-01-01

    Carbon nanotubes and the nanotube heterojunctions have recently emerged as excellent candidates for nanoscale molecular electronic device components. Experimental measurements on the conductivity, rectifying behavior and conductivity-chirality correlation have also been made. While quasi-one dimensional simple heterojunctions between nanotubes with different electronic behavior can be generated by introduction of a pair of heptagon-pentagon defects in an otherwise all hexagon graphene sheet. Other complex 3- and 4-point junctions may require other mechanisms. Structural stability as well as local electronic density of states of various nanotube junctions are investigated using a generalized tight-binding molecular dynamics (GDBMD) scheme that incorporates non-orthogonality of the orbitals. The junctions investigated include straight and small angle heterojunctions of various chiralities and diameters; as well as more complex 'T' and 'Y' junctions which do not always obey the usual pentagon-heptagon pair rule. The study of local density of states (LDOS) reveal many interesting features, most prominent among them being the defect-induced states in the gap. The proposed three and four pointjunctions are one of the smallest possible tunnel junctions made entirely of carbon atoms. Furthermore the electronic behavior of the nanotube based device components can be taylored by doping with group III-V elements such as B and N, and BN nanotubes as a wide band gap semiconductor has also been realized in experiments. Structural properties of heteroatomic nanotubes comprising C, B and N will be discussed.

  6. 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.

  7. Metal-organic-framework-based tandem molecular sieves as a dual platform for selective microextraction and high-resolution gas chromatographic separation of n-alkanes in complex matrixes.

    Science.gov (United States)

    Chang, Na; Gu, Zhi-Yuan; Wang, He-Fang; Yan, Xiu-Ping

    2011-09-15

    Metal-organic frameworks (MOFs) were employed to design tandem molecular sieves as a dual platform for selective solid-phase microextraction (SPME) and high-resolution gas chromatographic (GC) separation of target analytes in complex matrixes. An elegant combination of a ZIF-8-coated fiber for SPME with a ZIF-8-coated capillary for GC allows selective extraction and separation of n-alkanes from complex matrixes such as petroleum-based fuel and biological fluids. The proposed tandem ZIF-8 molecular sieves not only offered good enhancement factors from 235 (hexane) to 1212 (nonane), but also exhibited wide linearity with 3 orders of magnitude for the tested linear alkanes. The limits of detection for the linear alkanes ranged from 0.46 ng L(-1) (nonane) to 1.06 ng L(-1)(hexane). The relative standard deviations of retention time, peak area, peak height, and half peak width for five replicate determinations of the tested n-alkanes at 30 ng L(-1) were 0.02-0.26%, 1.9-8.6%, 1.4-6.0%, and 1.3-7.2%, respectively. The developed tandem ZIF-8 molecular sieves were further used for the determination of linear alkanes in petroleum-based fuel and human serum. The large diversity in structure and pore size allows various combinations of MOFs for designing an MOF-based tandem molecular sieve platform to achieve different selectivities in extraction and chromatographic separation and to solve headache problems in complex real sample analysis.

  8. Study of physical chemical properties of nanostructured carbon sorbent for cleanup of biomolecules

    OpenAIRE

    Almagul Kerimkulova; M. Koldasbekova; Аmіr Kenzhehan; Moldir Kerimkulova; Zulkhair Mansurov; Murat Gilmanov

    2012-01-01

    The technology of nanostructured carbon sorbent. Optimized the conditions of carbonization of plant material and studied the basic structural and physicochemical properties of the sorbent. Studied the molecular-sieve and adsorption characteristics of the sorbent.

  9. Study of physical chemical properties of nanostructured carbon sorbent for cleanup of biomolecules

    Directory of Open Access Journals (Sweden)

    Almagul Kerimkulova

    2012-03-01

    Full Text Available The technology of nanostructured carbon sorbent. Optimized the conditions of carbonization of plant material and studied the basic structural and physicochemical properties of the sorbent. Studied the molecular-sieve and adsorption characteristics of the sorbent.

  10. Carbon membranes precursor, preparation, and funtionalization

    NARCIS (Netherlands)

    Barsema, Jonathan Nathaniel

    2004-01-01

    In this thesis we study the preparation of Carbon Molecular Sieve (CMS) membranes for the separation of gases. The gases are separated based on their size difference and affinity for the membrane material.

  11. Sieve in expansion

    CERN Document Server

    Kowalski, Emmanuel

    2010-01-01

    This is a survey report for the Bourbaki Seminar (Exp. no. 1028, November 2010) concerning sieve and expanders, in particular the recent works of Bourgain, Gamburd and Sarnak introducing "sieve in orbits", and the related developments concerning expansion properties of Cayley graphs of finite linear groups.

  12. All-carbon molecular tunnel junctions.

    Science.gov (United States)

    Yan, Haijun; Bergren, Adam Johan; McCreery, Richard L

    2011-11-30

    This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon molecular electronic junctions were fabricated by orienting a layer of organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd of current density at 0.5 V carbon devices exhibit current density-voltage (J-V) behavior similar to those with metallic Cu top contacts. However, the all-carbon devices display enhanced stability to bias extremes and greatly improved thermal stability. Completed carbon/nitroazobenzene(NAB)/carbon junctions can sustain temperatures up to 300 °C in vacuum for 30 min and can be scanned at ±1 V for at least 1.2 × 10(9) cycles in air at 100 °C without a significant change in J-V characteristics. Furthermore, these all-carbon devices can withstand much higher voltages and current densities than can Cu-containing junctions, which fail upon oxidation and/or electromigration of the copper. The advantages of carbon contacts stem mainly from the strong covalent bonding in the disordered carbon materials, which resists electromigration or penetration into the molecular layer, and provides enhanced stability. These results highlight the significance of nonmetallic contacts for molecular electronics and the potential for integration of all-carbon molecular junctions with conventional microelectronics.

  13. 不同模板剂合成的 SAPO -34分子筛催化丁烯裂解%Catalytic cracking of 1-butene over SAPO-34 molecular sieves synthesized by different templates

    Institute of Scientific and Technical Information of China (English)

    胡云峰; 胡影; 陈焕

    2015-01-01

    Currently,the demand for propene is rising because of downstream products. It is important to improve the production capacity of propene. SAPO-34 with eight-membered ring channel can effectively improve the selectivity to low carbon olefin,especially the selectivity to propene. In this paper,SAPO-34 molecular sieves were synthesized by using diethylamine(DEA),tetraethylammonium hydroxide(TEAOH) and DEA + TEAOH as the templates,and characterized by XRD,NH3-TPD and SEM. The influence of the templates on the catalytic properties of SAPO-34 molecular sieves for 1-butene catalytic cracking was investigated in a fixed bed reactor. The results indicated that templates had the important influence on particle size,acid strength,acid amounts and catalytic properties. The sample prepared with TEAOH as the template had the least acid amount and the weakest acid strength. The sample synthesized with DEA template possessed the most acid amount and the strongest acid strength. The double templates exhibited additive effect. In 1-butene catalytic cracking reaction,the less the amount of acid sites and the weaker the acidity of SAPO-34 molecular sieve,the higher the selectivity to propene. The highest yield of propene was 33. 61% .%受下游产品的影响,丙烯需求量逐年上升,提高丙烯生产能力显得尤为重要。SAPO -34分子筛具有八元环孔道结构,在丁烯裂解中可有效提高低碳烯烃选择性,尤其是丙烯选择性。以二乙胺、四乙基氢氧化铵和二乙胺+四乙基氢氧化铵为模板剂合成 SAPO -34分子筛,采用 XRD、NH3- TPD 和 SEM 等进行表征,并在固定床反应器上考察模板剂对分子筛催化性能的影响。结果表明,模板剂种类对制备的 SAPO -34分子筛的晶粒大小、酸强度、酸量以及催化性能有重要影响。以四乙基氢氧化铵为模板剂合成的分子筛酸量最少,酸性最弱;以二乙胺为模板剂合成的分子筛酸量最大且

  14. The Effect of Operating Conditions on Drying Characteristics and Quality of Ginger (Zingiber Officinale Roscoe) Using Combination of Solar Energy-Molecular Sieve Drying System

    Science.gov (United States)

    Hasibuan, R.; Zamzami, M. A.

    2017-03-01

    Ginger (Zingiber officinale Roscoe) is an agricultural product that can be used as beverages and snacks, and especially for traditional medicines. One of the important stages in the processing of ginger is drying. The drying process intended to reduce the water content of 85-90% to 8-10%, making it safe from the influence of fungi or insecticide. During the drying takes place, the main ingredient contained in ginger is homologous ketone phenolic known as gingerol are chemically unstable at high temperatures, for the drying technology is an important factor in maintaining the active ingredient (gingerol) which is in ginger. The combination of solar energy and molecular sieve dryer that are used in the research is capable of operating 24 hours. The purpose of this research is to study the effect of operating conditions (in this case the air velocity) toward the drying characteristics and the quality of dried ginger using the combination of solar energy and molecular sieve dryer. Drying system consist of three main parts which is: desiccator, solar collector, and the drying chamber. To record data changes in the mass of the sample, a load cell mounted in the drying chamber, and then connected to the automated data recording system using a USB data cable. All data of temperature and RH inside the dryer box and the change of samples mass recorded during the drying process takes place and the result is stored in the form of Microsoft Excel. The results obtained, shows that the air velocity is influencing the moisture content and ginger drying rate, where the moisture content equilibrium of ginger for the air velocity of 1.3 m/s was obtained on drying time of 360 minutes and moisture content of 2.8%, at 1.0 m/s was obtained on drying time of 300 minutes and moisture content of 1.4%, at 0, 8 m/s was obtained at 420 minutes drying time and the moisture content is 2.0%. The drying characteristics shows that there are two drying periods, which is: the increasing drying rate

  15. SFC在分子筛纯化系统切换控制中的应用%Application of SFC in switching-over control of molecular sieve purification system

    Institute of Scientific and Technical Information of China (English)

    付定君; 伍晓娟; 徐平林

    2011-01-01

    针对分子筛纯化系统切换控制的特点,结合横河CETUMCS3000控制系统中的顺序控制功能,介绍了SFC在分子筛纯化系统切换控制中的应用,以及一些组态经验和维护措施。%Application of SFC in switching-over control of molecular sieve purification system is briefed on basis of the features of switching-over control of molecular sieve purification system in combination with function of sequence control of Henghe CETUM CS3000 control system and experiences on configuration and maintenance measures are described.

  16. A magnetic route to measure the average oxidation state of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS).

    Science.gov (United States)

    Shen, Xiong-Fei; Ding, Yun-Shuang; Liu, Jia; Han, Zhao-Hui; Budnick, Joseph I; Hines, William A; Suib, Steven L

    2005-05-04

    A magnetic route has been applied for measurement of the average oxidation state (AOS) of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS). The method gives AOS measurement results in good agreement with titration methods. A maximum analysis deviation error of +/-7% is obtained from 10 sample measurements. The magnetic method is able to (1) confirm the presence of mixed-valent manganese and (2) evaluate AOS and the spin states of d electrons of both single oxidation state and mixed-valent state Mn in manganese oxides. In addition, the magnetic method may be extended to (1) determine AOS of Mn in manganese oxide OMS with dopant "diamagnetic" ions, such as reducible V5+ (3d0) ions, which is inappropriate for the titration method due to interference of redox reactions between these dopant ions and titration reagents, such as KMnO4, (2) evaluate the dopant "paramagnetic" ions that are present as clusters or in the OMS framework, and (3) determine AOS of other mixed-valent/single oxidation state ion systems, such as Mo3+(3d3)-Mo4+(3d2) systems and Fe3+ in FeCl3.

  17. 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)

  18. 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.

  19. Route to Renewable PET: Reaction Pathways and Energetics of Diels–Alder and Dehydrative Aromatization Reactions Between Ethylene and Biomass-Derived Furans Catalyzed by Lewis Acid Molecular Sieves

    OpenAIRE

    2015-01-01

    Silica molecular sieves that have the zeolite beta topology and contain framework Lewis acid centers (e.g., Zr-β, Sn-β) are useful catalysts in the Diels–Alder and dehydrative aromatization reactions between ethylene and various renewable furans for the production of biobased terephthalic acid precursors. Here, the main side products in the synthesis of methyl 4-(methoxymethyl)benzene carboxylate that are obtained by reacting ethylene with methyl 5-(methoxymethyl)-furan-2-carboxylate are iden...

  20. 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

  1. MCM-41介孔分子筛中负载酞菁配合物的研究%Study of Metal-phthalocyanine Encapsulated in Mesoporous Molecular Sieves MCM-41

    Institute of Scientific and Technical Information of China (English)

    崔子祥; 薛永强; 李萍

    2012-01-01

    Zn-phthalocyanine complex(Ⅱ), which periphery has substituents was synthesized, and encapsulated in mesoporous molecular sieves MCM-41. The prepared samples was characterized by FT-1R, UV-vis-Nir, XRD, FESEM, TEM and N2 adsorption-desorption instrument. The research shows that the prepared phthalocyanine copper zinc can be encapsulated in mesoporous molecular sieves MCM-41 in the form of monomer and dipolymer. The prepared phthalocyanine zinc with high concentration encapsulated in MCM-41 is in favour of preparing mesoporous molecular sieves samples with higher crystallinity and pore canal order.%合成了Zn-酞菁化合物,通过水热法将酞菁化合物负载在MCM-41介孔分子筛中.利用FT-IR、UV-vis-Nir、XRD、FESEM、TEM及N2吸附-脱附仪对酞菁负载后的样品进行了表征.研究结果表明:较高浓度Zn-酞菁能够负载到介孔分子筛中,并且随着酞菁配合物浓度的增加,介孔分子筛孔道的有序性及结晶度都提高.

  2. Cu-酞菁配合物在MCM-41中的装载研究%The Study of Encapsulation of Metal-phthalocyanine in Mesoporous Molecular Sieves MCM-41

    Institute of Scientific and Technical Information of China (English)

    崔子祥; 薛永强; 杜锡光; 李萍

    2011-01-01

    The2(3), 9(10), 16(17), 23 (24)-tetra-(N, N-bisethylamineethoxyl) Cu(Ⅱ)-phthalocyanine complexes with flexible peripheral substituents were synthesized and encapsulated in mesoporous molecular sieves MCM-41. The prepared samples were characterized by UV-vis-Nir, FT-IR, XRD, TEM, FESEM and N2 adsorption-desoption isotherms. Results show that the prepared phothalocyanine copper ( Ⅱ ) was encapsulated in mesoporous molecular sieves MCM-41 in the form of monomer and dimer. The phothalocyanine copper ( II ) encapsulated in MCM-41 with high concentration was in favour of preparing mesoporous molecular sieves samples with higher crystallinity and pore channel order.%合成了具有柔性取代基的2(3),9(10),16(17),23(24)-四-(N,N-二-乙胺基乙氧基)Cu-酞菁配合物,并且装载到MCM-41中.利用UV-Vis-Nir,FT-IR,XRD,TEM,FESEM及N2吸附-脱附等温线对制备的样品进行了表征.研究表明:制备的Cu-酞菁配合物能够装载到MCM-41中;较高浓度的Cu-酞菁配合物在MCM-41中的装载,有利于制备结晶度及孔道有序性较高的介孔分子筛样品.

  3. 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.

  4. 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.

  5. 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

  6. Preparation and Hydrothermal Stability of Hydrophobic HMS Molecular Sieve%疏水性 HMS 分子筛的制备及水热稳定性

    Institute of Scientific and Technical Information of China (English)

    王广建; 韩亚飞; 褚衍佩; 冯庆吉; 王芳

    2015-01-01

    以三甲基氯硅烷和六甲基二硅氮烷为硅烷化试剂,分别采用气相和液相硅烷化法对 HMS 分子筛进行表面改性制备疏水性 HMS 分子筛。考察了改性方法、硅烷试剂与分子筛摩尔比、反应温度和时间对硅烷化效果的影响,研究了改性前后HMS 的骨架特征、微观结构和疏水性、水热稳定性。结果表明:气相硅烷化法较液相法优势明显,硅烷化程度和效率均较高;在双硅烷化试剂、反应温度90℃、硅烷试剂与分子筛摩尔之比0.8、反应时间8 h 等条件下,改性前后 HMS 的静态水吸附量分别为45.46%和1.38%,疏水性得到明显提高。HMS 经硅烷化改性后保持介孔骨架结构和蠕虫状孔道,同时水热稳定性得到有效改善,800℃水蒸气处理6 h 后介孔结构仍然存在。%The hydrophobic HMS molecular sieve was prepared with trimethylchlorosilane and hexamethyldisilazane as silane agents by a vapor silylation method and a liquid silylation method. The effects of modification modes, reaction temperature and time, molar ratio of silane agents to HMS on the silylation were investigated. The framework character, microstructures and hydrophobic property, hydrothermal stability of HMS before and after modification were also analyzed. The results indicate that the gas phase method has some advantages such as its high efficiency and degree of silanization. The static water adsorption capacity of HMS before and after silanization are 45.38% and 1.38%, respectively, and the hydrophobic of HMS is enhanced under the optimal conditions (i.e., use of mixed silane agents, reaction temperature of 90 , reaction time of 8 h, and molar ratio of silane agents to HMS of 0.8). The℃hydrophobic HMS maintains the mesoporous structure and typical vermicular channel of HMS molecular sieve. Also, the hydrothermal stability of HMS is improved efficiently after modification, and the mesoporous structure is retained even after

  7. New perspectives in the Fischer-Tropsch synthesis using cobalt supported on mesoporous molecular sieves; Novas perspectivas na sintese de Fischer-Tropsch usando cobalto suportado em peneiras moleculares mesoporosas

    Energy Technology Data Exchange (ETDEWEB)

    Souza, M.J.B.; Silva, A.O.S. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Dept. de Engenharia Quimica; Fernandes Junior, V.J.; Araujo, A.S. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Dept. de Quimica

    2004-07-01

    The conversion of synthesis gas to liquid products via Fischer-Tropsch synthesis (FTS) is an important process in the generation of clean fuels of sulfur and nitrogen compounds. Catalysts based on iron are very used in the conventional process due its cheap manufacture price. Recently the use of cobalt as promoter gave good results. MCM-41 mesoporous materials were discovered by Mobil scientists in the nineties and ever since they have great successes as support and catalyst in several processes of the oil industry as catalytic cracking, reformer and hydrotreating. In this work are presented new alternatives for FTS with the use of cobalt supported on molecular sieves of the type MCM-41. A comparative study with the usual catalysts based on silica was accomplished with different levels of cobalt. (author)

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

    Science.gov (United States)

    Sang, Yu; Jiao, Qingze; Li, Hansheng; Wu, Qin; Zhao, Yun; Sun, Kening

    2014-12-01

    A series of HZSM-5/MCM-41 composite molecular sieves (HZM-Ns ( x)) were prepared by employing nano-ZSM-5 zeolites with the SiO2/Al2O3 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, N2 adsorption-desorption measurement, and NH3 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 SiO2/Al2O3 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 SiO2/Al2O3 ratio.

  9. 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.

  10. 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).

  11. 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

  12. 不同铝源对 SBA -15分子筛改性影响%Effects of different aluminum sources on the modification of SBA-15 molecular sieve

    Institute of Scientific and Technical Information of China (English)

    王浩; 王继锋; 樊宏飞; 孙晓艳

    2014-01-01

    为比较不同铝源对 SBA -15分子筛改性的影响,以正硅酸乙酯为硅源,分别用异丙醇铝、氯化铝和硝酸铝对 SBA -15分子筛进行改性,运用 XRD、N2等温吸附-脱附、SEM、TEM 和气相色谱对样品进行表征。将3种不同铝源改性 SBA -15分子筛与 USY 分子筛复合制备加氢裂化催化剂,在固定床微型反应装置进行加氢裂化性能评价,结果表明,异丙醇铝在酸性条件下水解生成的 Al(OH)-4更容易进入 SiO2骨架中,生成的产物异丙醇不影响铝离子的掺杂,由于异丙醇铝与正硅酸乙酯的水解速率一致,改性后所得材料孔分布更均一,规整性更高。将异丙醇铝对 SBA -15分子筛改性后,与 USY 制备的复合分子筛催化剂用于正十二烷加氢裂化反应,选择性和转化率优于氯化铝和硝酸铝改性的分子筛。%In order to investigate the influence of different aluminum sources on the modification of SBA-15 molecular sieve,modified AlSBA-15 molecular sieves were prepared using tetraethyl orthosilicate as silica source,isopropanol aluminum,aluminum chloride and aluminum nitrate as aluminum sources. The as-prepared samples were characterized by means of XRD,TEM,SEM,N2 adsorption-desorption and gas chromatography. The composite molecular sieves catalysts AlSBA-15/ USY were prepared by using USY zeolite and AlSBA-15 samples,The hydrocracking performance of as-prepared catalysts were evaluated in a fixed bed microreactor. The results showed that under acidic condition,isopropanol aluminum hydrolyzed and formed Al(OH)-4 , which easily entered the framework of SiO2;hydrolysate isopropanol did not affected the doping of Al(OH)-4 . Because hydrolysis rates of isopropanol aluminum and tetraethyl orthosilicate were consistent, the as-prepared samples after modification possessed more uniform pore size distribution and higher regu-larity. The composite molecular sieve catalyst prepared by USY zeolite and Al

  13. Uniaxial tension of drying sieves

    Directory of Open Access Journals (Sweden)

    Bojić Nada V.

    2013-01-01

    Full Text Available Although the literature contains numerous studies that have been developed to describe the nonlinear behavior of drying sieves' operation, there are no papers in this which report deeper investigation of the drying sieve behavior when exposed to tension and thermo stabilization. The aim of this paper is to provide insight into the elastoplastic behavior of the thermo stabilized and not stabilized sieves subjected to the tensile force. Within this work both theoretical and experimental investigations were performed. The sieves were joined by using a spiral. In separate experiments tests of wire base and weft of the weave mesh were performed, both for thermo stabilized and not thermo stabilized sieves, sieves joining and the sieve thermo stabilization itself. It was established that the thermo stabilization of sieves provides for stability of sieves' dimensions and that open thermo stabilized drying sieve exhibits better mechanical properties and exploitation characteristics then the sieves joining. [Projekat Ministarstva nauke Republike Srbije, br. ON174004: Micromechanics criteria of damage and fracture and br. TR 32036: Development of software for solving the coupled multi-physical problems

  14. Synthesis of Zeolite Nanomolecular Sieves of Different Si/Al Ratios

    OpenAIRE

    Pankaj Sharma; Moon Hee Han; Churl-Hee Cho

    2015-01-01

    Nanosized zeolite molecular sieves of different Si/Al ratios have been prepared using microwave hydrothermal reactor (MHR) for their greater application in separation and catalytic science. The as-synthesized molecular sieves belong to four different type zeolite families: MFI (infinite and high silica), FAU (moderate silica), LTA (low silica and high alumina), and AFI (alumina rich and silica-free). The phase purity of molecular sieves has been assessed by X-ray diffraction (XRD) analysis an...

  15. The synthesis and structure characterization of microporous vinyl-functionalized SAPO-11 molecular sieve%乙烯基功能化微孔SAPO-11分子筛的合成与结构表征

    Institute of Scientific and Technical Information of China (English)

    余安安; 周丹; 庞涛; 鲁新环; 夏清华

    2012-01-01

    Vinyl-functionalized SAPO-11 molecular sieve was synthesized by using vinyltriethoxy silane as organic silicon source. The initial reagents were constituted with a mixture of 1.0 Al2O3 : 1.0 P2O5 : 0.75 WD-20 : 2.0 DPA : 30 H2O : 30 C2H5OH. In the H2O/C2H3OH system and weak acid environment, vinyl-functionalized SAPO-11 molecular sieve had been synthesized at 200 ℃ for 72 h. Various techniques, including XRD, TEM, FT-IR, TGA and XRF proved that vinyl groups had been successfully introduced into the frameworks of inorganic SAPO-11 molecular sieve.%以乙烯基三乙氧基硅烷为唯一硅源,探讨各种反应条件对合成乙烯基功能化SAPO-11分子筛的影响.初始反应物摩尔比为Al2O3∶P2O5∶WD-20∶DPA∶H2O∶C2H5OH=1.0∶1.0∶0.75∶2.0∶30∶30,在弱酸性环境的水/醇水解体系下,200℃晶化72 h后可成功地合成出乙烯基功能化SAPO- 11分子筛.产物经XRD、TEM、FT-IR、TGA、XRF等表征分析,乙烯基基团已被成功引入到无机SAPO-11的骨架中.

  16. 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.

  17. Isopropylation of Naphthalene over AlMCM-48 Mesoporous Molecular Sieves%AlMCM-48介孔分子筛对萘异丙基化反应的活性

    Institute of Scientific and Technical Information of China (English)

    王树国; 李英; 巩雁军; 吴东; 孙予罕; 钟炳

    2001-01-01

    The isopropylation of naphthalene with isopropanol over AlMCM-48 mesoporous molecular sieves was studied. AlMCM-48 showed high activity and shape selectivity to the isopropylation of naphthalene. Grafting aluminum on MCM-48 improved its acidity. It was found that with the increasing of Al content, the performance of AlMCM-48 catalysts for naphthalene conversion was enhanced. High naphthalene conversion of 89.5 % was achieved over AlMCM-48 with Si/Al=5.3 under the reaction conditions:n(isopropanol) /n(naphthalene)=2, temperature T=250 ℃ , time t=4 h.

  18. 以哌啶为模板剂的MCM-22分子筛合成%Synthesis of MCM-22 Molecular Sieve Using Piperidine as an Organic Template

    Institute of Scientific and Technical Information of China (English)

    张斌; 王振东; 孙洪敏; 杨为民; 吴鹏

    2013-01-01

    为合成不同硅铝比的MCM-22分子筛,对分子筛配料中的硅铝比、碱度、模板剂和晶化助剂用量等进行了考察,并用X射线衍射、扫描电镜、电感耦合等离子体发射光谱、X射线光电子能谱仪及氮气吸脱附等手段对样品进行了表征.结果表明,以哌啶(PI)为模板剂、硼酸(BA)为晶化助剂,在n(OH-)/n(SiO2)为0.03~0.20、n(PI)/n(SiO2)大于0.03及n(BA)/n(SiO2)大于0.05的条件下,可得到硅铝比为25~500的MCM-22分子筛.与以六亚甲基亚胺为模板剂相比,以哌啶为模板剂制得的MCM-22分子筛具有更小的晶粒尺寸和更大的比表面积.%For synthesizing MCM-22 molecular sieves with different silica-alumina ratio, the effects of ingredient SiO2 to A12O3 ratio, alkali concentration, and the amount of organic template and crystallization-supporting agent, on the molecular sieves were studied systematically. The obtained MCM-22 samples were characterized by X-ray diffraction, scanning electron microscopy, inductively coupled plasma-atomic emission spectrometry, X-ray photoelectron spectroscopy and N2 adsorption-desorption. The results show that, MCM-22 molecular sieves with silica-alumina ratio of 25-500 could be successfully synthesized under this condition: using piperidine (PI) as the organic template and boric acid (BA) as the crystallization-supporting agent, n(OH-)/n(SiO2) of 0.03-0.20, n(PI)/n(SiO2) > 0.03 and n(BA)/n(SiO2) > 0.05. Moreover, the obtained molecular sieves using PI as the template have a smaller particle size and a larger specific surface area than those using hexamethyleneimine as the template.

  19. Applications of Ordered Mesoporous Molecular Sieve SBA-15/MCM-41 in Electrochemical Catalysis%有序介孔分子筛SBA-15/MCM-41在电催化方面的应用

    Institute of Scientific and Technical Information of China (English)

    李洋; 邸婧; 郑华均

    2014-01-01

    The classification and development of mesoporous material were introduced in this paper. The applications of mesoporous molecular sieve SBA-15/MCM-41 in electrochemical catalysis were summa-rized in view of the present problems of electricity catalysis.%介绍了有序介孔材料的分类与发展,针对目前电催化领域存在的问题,综述了介孔分子筛SBA-15/MCM-41材料在电催化方面的应用。

  20. 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.

  1. 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.

  2. Research progress on catalytic oxidation by Schiff base complexes supported on mesoporous molecular sieve%介孔分子筛固载希夫碱金属配合物催化氧化研究进展

    Institute of Scientific and Technical Information of China (English)

    董阳阳; 白金泉; 王乔乔

    2013-01-01

    Schiff base complexes immobilized on mesoporous molecular sieve with high activity can be easily prepared and repeatedly used. It is considered to be a heterogeneous catalyst with great application potential. This article reviews the recent progress in oxidation catalyzed by Schiff base complexes supported on mesoporous molecular sieve, including catalytic oxidation of olefin, alkane, alcohol, sulfur ether.%介孔分子筛固载希夫碱金属配合物具有易于制备,反应活性高,可重复使用等优点,被认为是一种极具应用潜力的多相催化剂.近年来介孔分子筛固载希夫碱金属配合物在催化氧化方面研究较多.综述了近几年介孔分子筛固载希夫碱金属配合物在催化氧化方面的研究进展,主要包括催化氧化烯烃、烷烃、醇以及硫醚.

  3. 高酸性ZrMCM-41分子筛的合成和表征%Synthesis and characterization of highly acidic ZrMCM-41 molecular sieves

    Institute of Scientific and Technical Information of China (English)

    赵慧霞; 王绪绪

    2001-01-01

    Zirconium containing MCM-41 molecular sieves with high surfacearea, good crystallinity and Si / Zr ratio from 20 - ∞ were synthesized in a near neutral condition by using a sodium silicate as silicon source and a zirconyl nitrite as zirconium source. The introduction of zirconium into the molecular sieve resulted in a linear increasing of B and L acidic sites of the solid. At least one third of zirconium is on the surface or near the surface in the form of [(≡Si-O)3Zr=O]-. The surface zirconyl species as centers of negative charge compensated by sodium ions presents a property of ion exchange.%以硅酸钠为硅源、以硝酸氧锆为锆源,在接近中性的条件下合成出了Si/Zr比20~∞的,具有高比表面和良好晶体性的含锆MCM-41分子筛.锆的引入使分子筛的B酸和L酸线性增加.至少有大约三分之一的锆原子以[(≡Si-O)3Zr=O]-的形式处在表面或接近表面,在合成样品中它由钠离子补偿,经氢离子交换转变成酸性中心.

  4. Synthesis of 4A molecular sieves from gangue with high iron and silica contents by iron removal and alkali melting activation%高铁高砂煤矸石除铁及碱融活化合成4A分子筛

    Institute of Scientific and Technical Information of China (English)

    孔德顺; 吴红; 毕迎鑫

    2011-01-01

    高铁高砂的劣质煤矸石经酸浸除铁和纯碱碱融活化处理后,除铁率达到96.8%,高岭石及石英砂被完全活化,煤矸石生成了可溶于碱液的中间产物霞石(NaAlSiO4)及活性偏高岭石,将其再进行水热晶化得到了4A分子筛.用XRF、XRD、SEM等对原矿、预处理产物和产品进行了检测.结果表明:产品为较纯净的4A分子筛,粒径小于2 μm,干基产品的钙离子交换量为295.5 mg CaCO3/g.%Poor quality gangue with high iron and silica contents was treated to remove iron impurity by acid leaching and activated by sodium carbonate melting , the iron removal ratio was up to 96.8%. Kaolinite and silica were activated completely,and gangue turned into intermediate product nepheline (NaAlSiO4 ) and active metakaolinite,4A molecular sieve s were obtained by hydrothermal crystallization. Green ore, pretreated material, and products were characterized by XRF, XRD and SEM etc.. Results showed that the products were pure 4A molecular sieve with particle size less than 2 μm and the Ca2+ ion exchange capacity of dry product was 295.5 mg CaCO3/g.

  5. Influence of various alcohol on the hydrothermal synthesis of SAPO-56 molecular sieve%醇对水热合成SAPO-56分子筛的影响

    Institute of Scientific and Technical Information of China (English)

    宋孟璐; 董贺新; 韩丽; 陈宜俍; 詹予忠

    2015-01-01

    A series of SAPO-56 molecular sieve were synthesized by hydrothermal method with methanol, ethanol,n-propanol,n-butyl alcohol,iso-propanol and ethylene glycol partly substituting water,respective-ly. The effects of alcohols and their amounts on the product purity and morphology were investigated. The results showed that methanol strongly influenced the synthesis of SAPO-56 molecular sieves,SAPO-20 mo-lecular sieves were obtained when methanol exceeds 12 . 5%. When using n-propanol substituting 12 . 5%water,a mixture containing considerable SAPO-17 was formed. Further increasing n-propanol resulted in mixtures of SAPO-17,SAPO-41 and SAPO-20. When using ethanol,iso-propanol,n-butyl alcohol and gly-col ethylene substituting 12. 5% water,almost pure SAPO-56 molecular sieves could still be synthesized. With the increasing of alcohol substitution in the synthesis system,SAPO-17,SAPO-41 and SAPO-20 mix-tures were produced. The addition of alcohols also notably influenced the morphology of SAPO-56 molecu-lar sieves,and the products may transform from usual hexagonal plate into thicker cutter top hexagonal bi-pyramid or hexagonal bipyramid.%分别以甲醇、乙醇、丙醇、丁醇、异丙醇和乙二醇替代部分水,采用静态水热法合成SAPO-56分子筛,考察了不同醇及醇替代量对产物纯度和形貌的影响。结果表明,甲醇强烈影响 SAPO-56分子筛的合成,甲醇替代水12.5%以上产物为SAPO-20分子筛。丙醇替代水12.5%即有相当量的SAPO-17杂晶生成,进一步增加丙醇逐步生成SAPO-17、SAPO-41和SAPO-20等杂晶。乙醇、异丙醇、正丁醇、乙二醇替代水12.5%仍可合成较纯净的SAPO-56分子筛。随着反应体系中醇替代量的增加,同样逐步生成SAPO-17、SAPO-41和SAPO-20等杂晶。添加醇对SAPO-56分子筛的形貌也有很大影响,通常产物会由六方片状变成较厚的切顶六方双锥或六方双锥。

  6. 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) .

  7. Generalized Fibonacci photon sieves.

    Science.gov (United States)

    Ke, Jie; Zhang, Junyong

    2015-08-20

    We successfully extend the standard Fibonacci zone plates with two on-axis foci to the generalized Fibonacci photon sieves (GFiPS) with multiple on-axis foci. We also propose the direct and inverse design methods based on the characteristic roots of the recursion relation of the generalized Fibonacci sequences. By switching the transparent and opaque zones, according to the generalized Fibonacci sequences, we not only realize adjustable multifocal distances but also fulfill the adjustable compression ratio of focal spots in different directions.

  8. STRUCTURE DETERMINATION OF SRM-2 MOLECULAR SIEVE FROM POWDER X-RAY DIFFRACTION DATA%基于X射线粉末衍射的SRM-2分子筛晶体结构解析

    Institute of Scientific and Technical Information of China (English)

    张丽伟; 周涵; 代振宇; 李黎声

    2012-01-01

    Based on high resolution experimental X-ray powder diffraction spectra of SRM-2 molecular sieve,the patterns of its polycrystalline structure were indexed,analyzed and simulated by molecular structure analysis software,which provided important information on its crystal structure,such as space group,and crystal lattice parameters. From the known crystal structure parameters, an approximate structure was first assembled and refined with Rietveld method subsequently. Results show that in SRM-2 molecular sieve, a cage is consisted of 48 framework atoms (twelve 4-membered rings, eight 6-membered rings and six 8-membered rings) and a cages are connected by double 8-membered rings with pore diameter of 0. 419 nm. The crystal structure of SRM-2 molecular sieve belongs to cubic crystal system, 123 space groups. Its unit cell parameters are a = 6 = c=l. 511 1 nm,∠α=∠β =∠γ = 90. 00°.%对SRM-2分子筛粉末进行X射线扫描,获得较高分辨率的衍射数据.用分子模拟软件Materials Studio对谱图进行指标化计算,确定晶体所属晶系和空间群.用分子模拟软件中的结构构建和优化工具,构建SRM 2分子筛的初始结构模型,用Rietveld全谱图拟合方法精修晶体结构.结果表明,SRM-2分子筛是由48个骨架原子(12个四元环,8个六元环或6个八元环)构成的α笼通过双八元环连接而成,孔口直径为0.419 nm;SRM-2分子筛晶体属于立方晶系,I23空间群,晶胞参数为:a=b=c=1.511 1 nm,∠α=∠β=∠γ=90.00°.

  9. Molecular Selectivity of Brown Carbon Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey; Roach, Patrick J.; Eckert, Peter A.; Gilles, Mary K.; Wang, Bingbing; Lee, Hyun Ji; Hu, Qichi

    2014-10-21

    Complementary methods of high-resolution mass spectrometry and micro-spectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene (LSOA) and a-pinene (PSOA). Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas were detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl- imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the a-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

  10. 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

  11. 微波消解/AAS法测定分子筛中的镍含量%Determination of nickel in molecular sieve catalyst by microwave digestion-atomic absorption spectrometry

    Institute of Scientific and Technical Information of China (English)

    陈震; 贾隽涵; 王宸宸; 王永娟; 易玉峰; 丁福臣

    2016-01-01

    分子筛催化剂以及含有金属钨的催化剂在一般的微波消解体系下难以被消解。探索了以浓HCl、浓HCl+H2 O2、浓HNO3+H2 O2、王水、浓H2 SO4+H2 O2、浓H2 SO4+浓HNO3、浓H3 PO4为消解体系,消解含金属钨的分子筛催化剂。找到了一种能在短时间内既能消解分子筛催化剂又可以消解含金属钨的浓H3 PO4消解体系。并通过原子吸收光谱法和分光光度法对催化剂中的镍含量进行了测量。该方法样品用量少、省时、省酸、操作简单、环境污染小。%Molecular sieve catalysts and catalysts containing tungsten are difficult to be dissolved by mi -crowave in routine acidic digestion system .Acidic digestion system of concentrated hydrochloric acid ,con-centrated hydrochloric acid and hydrogen peroxide mixture ,concentrated nitric acid and hydrogen perox-ide mixture,nitrohydrochloric acid,concentrated sulphuric acid and hydrogen peroxide mixture ,concen-trated sulphuric acid and concentrated nitric acid mixture ,concentrated phosphoric acid were used to dis-solve molecular sieve catalysts containing tungsten by microwave .Concentrated phosphoric acid was found to be the suitable digestion system to dissolve the molecular sieve catalyst containing tungsten in a short period of time .The nickel content in the catalyst was measured by atomic absorption spectrometry and spectrophotometry.The method has the advantage of less sample needed ,high-speed,less acid needed, simplicity of operation and little of environmental pollution .

  12. Catalytic ozonation of chlorobenzoic acid over cobalt oxide supported on MCM-41 mesoporous molecular sieves%钴负载MCM-41分子筛催化臭氧氧化水中氯代苯甲酸

    Institute of Scientific and Technical Information of China (English)

    曾俊喻; 邴吉帅; 蓝冰燕; 廖高祖; 张秋云; 李旭凯; 李来胜

    2012-01-01

    通过水热法合成介孔分子筛MCM-41,采用等体积浸渍法制备了Co负载MCM-41分子筛催化剂(Co/MCM-41).小角X-射线粉末衍射(XRD)、紫外-可见漫反射光谱(UV-vis DRS)、N2吸附-脱附等温线及透射电镜(TEM)等对催化剂的成分、结构的表征结果显示,Co/MCM-41保持了纯硅MCM-41有序的介孔结构,钴元素以钴氧化物形式存在,比表面达到772 m.2g-1.将Co/MCM-41分子筛用于催化臭氧氧化水中对氯苯甲酸(p-CBA)的研究,结果表明,在优化条件下(2%负载量和25℃反应温度),催化剂的加入显著改善了TOC去除率,达到84.6%,是单独臭氧氧化的1.6倍.%MCM-41 mesoporous molecular sieve was synthesized by a hydrothermal method and Co/MCM-41 was prepared by an incipient wetness impregnation method.The materials were characterized by a low angle X-ray powder diffraction(XRD),UV-Vis diffuse reflection spectroscopy(UV-DRS),N2 adsorption-desorption and transmission electron microscopy(TEM).The results showed that the material retained a highly ordered mesopore structure of pure silica MCM-41 and had a surface area of 772 m2·g-1,Cobalt ions mainly exist as cobalt oxide clusters distributed on the surface of molecular sieve.In this study,Co/MCM-41 mesoporous molecular sieve was used for catalytic ozonation of p-CBA.The results showed that under the optimal condition(2% cobalt load and 25 ℃),the mineralization of p-CBA increased to 84.6% in the presence of catalyst,which is 1.6 times that of ozone alone at the reaction time of 60 min.

  13. Molecular selectivity of brown carbon chromophores.

    Science.gov (United States)

    Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A; Roach, Patrick; Eckert, Peter; Gilles, Mary K; Wang, Bingbing; Lee, Hyun Ji Julie; Hu, Qichi

    2014-10-21

    Complementary methods of high-resolution mass spectrometry and microspectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene SOA (LSOA) and α-pinene SOA (PSOA). The LSOA compounds readily formed adducts with Na(+) under electrospray ionization conditions, with only a small fraction of compounds detected in the protonated form. In contrast, a significant fraction of PSOA compounds appeared in the protonated form because of their increased molecular rigidity. Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas was detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl-imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the α-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

  14. 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

  15. 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.

  16. Synthesis of aluminophosphate molecular sieves in quaternary ammonium salts and pentaerythritol eutectic mixture%季铵盐-季戊四醇低共熔混合物中合成磷酸铝分子筛

    Institute of Scientific and Technical Information of China (English)

    裴仁彦; 田志坚; 于海斌; 张耀日; 霍志萍

    2013-01-01

    Aluminophosphate molecular sieves were synthesized in eutectic mixtures consisted of quaternary ammonium salts and pentaerythritol.The as-synthesized products were characterized by X-ray diffraction,scanning electron microscopy,thermal gravimetric analysis and NMR spectroscopy.The results showed that A1PO4-16 and A1PO4-5 molecular sieves were synthesized in the eutectic mixture of tetraethylammonium chloride and choline chloride,while a cristobalite dense phase was formed in the eutectic mixture of tetrapropylammonium bromide and tetrabutylammonium bromide.The structuredirecting abilities of the quaternary ammonium cation was subject to its charge density.The smaller the charge density of the quanternary ammonium was,the weaker structure-directing ability it had.%在4种季铵盐和季戊四醇的低共融混合物中合成了磷酸铝分子筛,并通过X射线衍射、扫描电子显微镜、热重分析以及核磁共振技术进行表征.结果表明,在氯化胆碱和四乙基氯化铵的低共熔混合物中分别合成了ALPO4-16和AlPO4-5分子筛,而在四丙基溴化铵和四丁基溴化铵低共熔混合物中仅得到方石英致密相.表明在实验条件下,季铵盐阳离子的电荷密度影响结构导向能 力,电荷密度越小,结构导向能力越弱.

  17. 磷酸铝分子筛中骨架扭曲度与杂原子取代的关系%Relationship Between Framework Distortion and Heteroatom-substitution in Aluminophosphate Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    李双宝; 窦志宇; 何兴权; 崔丽莉; 张誉腾

    2013-01-01

    Aluminophosphate molecular sieve frameworks AFI, AEL, ATO, SBS, SBE, SBT, JRY and MA-PO-CJ69 were optimized by means of computer simulation methods. The standard deviations of Al—O, O—O, Al—P, and P—P distances in A1O4 and A1P4 tetrahedra, as well as their continuous shape measure ( CShM ) values were calculated. Calculation results show that the introduction of heteroatoms is necessary for the formation of molecular sieve frameworks with high distortions. In addition, Heteroatoms occupy the most distorted tetrahedra sites. On the contrary, zeolite frameworks with low distortions can be synthesized without the addition of heteroatoms. These results agreed well with the experimental results.%采用计算机模拟方法对AFI,AEL,ATO,SBS,SBE,SBT,JRY和MAPO-CJ69等磷酸铝分子筛的骨架进行了几何优化,通过计算这些骨架结构中A1O4和AlP4四面体的A1-O,O-O,Al-P和p-p各键长的标准偏差及AlO4和AlP4四面体的连续形状度量(CShM),得到了这些分子筛骨架中四面体的扭曲度.通过对比发现,具有较大扭曲度的骨架在实验中往往需要引入杂原子以稳定整个结构,且杂原子优先进入骨架中扭曲度大的位置;而扭曲度较小的骨架结构无需引入杂原子就能够合成出来.

  18. 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。

  19. Escape of water molecular from Carbon Nanotubes

    Science.gov (United States)

    Li, Jiaxi; Li, Wenfeng; Zhang, Jianwei

    2014-03-01

    Understanding and controlling the transport of water molecules through nanopores have attracted great interest due to potential applications for designing novel nanofluidic devices, machines and sensors. In this work, we theoretically investigate the effects of an external nonuniform electric field on the escape of water molecules through single-walled carbon nanotubes (SWNTs) by using of molecular dynamics (MD) simulations. When polar water molecules are placed in the gradient electric field, the electric force is experienced that can drive the water molecules. Molecular dynamics simulations show that the escape probability of water obeys the Boltzmann distribution. Our results show that energy barrier delta E is independent of temperature which indicates that it is a single-barrier system. From the MD results statistics, the key parameters could be determined such that the relationship between energy barrier delta E and diameter of SWNTs and nozzle distance of the charge r would be revealed that could deepen our current theoretical understanding on transport of water molecular inside SWNTs with the nonuniform electric field.

  20. 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.

  1. 脉冲放电等离子体协同Mn/TiO2-分子筛、Fe/TiO2-分子筛、Cu/TiO2-分子筛催化剂降解甲醛%Research of pulse discharge plasma combined with Mn/TiO2-molecular、Fe/TiO2-molecular、Cu/TiO2-molecular sieve catalysts decomposition of formaldehyde

    Institute of Scientific and Technical Information of China (English)

    董冰岩; 施志勇; 何俊文; 王晖; 周海金; 张鹏; 聂亚林

    2015-01-01

    In order to further improve formaldehyde removal efficiency,increase carbon dioxide selectivity,and decrease the generation concentration of ozone in pulse discharge plasma,a method of discharge plasma combined with catalysts was adopted in this research. Molecular sieve was used as carrier,then three catalysts were prepared,i.e. Mn/TiO2-molecular sieve,Fe/TiO2-molecular sieve and Cu/TiO2-molecular sieve catalysts,which were characterized by XRD,SEM,EDS and FT-IR. Decomposition of formaldehyde in pulse discharge plasma combined with three catalysts was studied. Effects of plasma combined with different catalysts on formaldehyde removal efficiency,carbon dioxide selectivity and generation concentration of ozone were compared. The results showed that catalysts have synergistic effects on pulse discharge plasma. It could improve formaldehyde removal efficiency,increase carbon dioxide selectivity,and decrease generation concentration of ozone efficiently. Mn/TiO2-molecular sieve catalyst has the best synergistic effect with the impulse voltage of 20kV,the frequency of 40Hz and the gas flow rate of 0.5L/min,i.e. its formaldehyde removal efficiency achieved 94.4% and carbon dioxide selectivity achieved 42.2%. Characterization results showed that Mn/TiO2-molecular sieve catalyst uniform dispersion of active ingredients is as well as the existence of anatase TiO2,and microcrystalline state MnOx increased the oxidation of formaldehyde decomposition. Meanwhile,the mechanism of degrading formaldehyde in discharge plasma combined with Mn/TiO2-molecular sieve catalyst was also discussed.%为进一步提高脉冲放电等离子降解甲醛的效率,增加CO2选择性,降低O3产生量,研究采用放电等离子体和催化剂协同技术.实验以分子筛为载体,分别制备了Mn/TiO2-分子筛、Fe/TiO2-分子筛和Cu/TiO2-分子筛3种催化剂,并利用 XRD、SEM、EDS、FT-IR 方法对催化剂进行表征分析.进行了脉冲放电等离子体协同 3 种催化剂降

  2. Ionothermal synthesis of zeolitic molecular sieves:Properties,progress and prospect%离子热合成沸石分子筛:技术特性、研究进展与应用前景

    Institute of Scientific and Technical Information of China (English)

    田志坚; 刘浩

    2015-01-01

    离子热法是一种以离子液体或低共熔物为反应介质、在低挥发性的离子态反应环境中合成沸石分子筛的方法。离子热合成可在接近常压下进行,因此不但能够克服常规液相合成体系高压带来的操作困难,而且为分子筛合成机理研究提供了便利,同时便于与微波等电磁技术耦合。本文总结了离子热法在沸石分子筛材料合成及机理研究方面取得的进展。通过调变反应介质种类、反应物组成、晶化条件以及添加氟或有机胺等可以得到不同组成、结构的沸石分子筛产物以及AlPO、SAPO分子筛膜;在离子热合成过程中,离子液体和低共熔物的阳离子、有机胺或铵盐、金属阳离子等能够独立或协同起到结构导向作用。预期离子热法可为分子筛器件的放大生产提供一条灵活、方便的途径。%Ionothermal synthesis is a method that uses either ionic liquid (IL) or deep eutectic solvent (DES) as reaction medium to synthesize zeolitic molecular sieves. The reaction environment of ionothermal synthesis is ionic and extremely low volatile. This is due to the inherent characteristics of IL/DES,as well as their isolation-deactivation effect on molecular reactants via hydrogen bonds. Compared with hydro/solvothermal routes,the most significant property of ionothermal synthesis is that it can take place at ambient pressure with few safety risks. This property brings convenience to in situ studies,and benefits the application of microwave heating to the synthesis of molecular sieves. Moreover,great flexibility is shown in ionothermal synthesis. By alternating reaction medium, reactant composition and crystallization condition,zeolitic products with various compositions and structures can be ionothermally synthesized. In the past decade,fruitful results have been obtained with respect to both the synthesis of zeolitic materials and the study of formation mechanisms of molecular sieves

  3. NEW DEVELOPMENTS IN CARBON MOLECULAR SIEVE MEMBRANE%炭分子筛膜研究的新进展

    Institute of Scientific and Technical Information of China (English)

    晏丽红; 胡浩权

    2002-01-01

    炭分子筛膜是一种用于气体分离的高效、节能的新型材料,具有好的气体分离选择性,高的热和化学稳定性,近年来得到国内外广泛的重视和发展.本文从制备炭分子筛膜的原料、制备工艺及其在气体分离应用等方面综述了国内外近年来炭分子筛膜的研究进展,并指出了目前存在的问题.

  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. 利用沸石分子筛提高航空汽油辛烷值方法研究%Improvement of aviation gasoline octane number via adsorption by zeolite molecular sieve

    Institute of Scientific and Technical Information of China (English)

    陈凯; 向海; 柳华; 孙婷; 徐成刚

    2014-01-01

    The key factor to impede the development of the unleaded aviation gasoline was the low octane number of the aviation gasoline itself. The feasibility of separation of 2,2,4-methylpentane and 2-methylheptane by using β-zeolite molecular sieve was thoroughly studied. The experimental results showed that at the same temperature and pressure, the adsorption capacity of 2-methylheptane was higher than that of 2,2,4-trimethylpentane, and the saturated adsorption capacity of the single component decreased with the increase of adsorption temperature and increased with the increase of pressure. The isotherm adsorption experiments of 2,2,4-methylpentane and 2-methylheptane binary mixture confirmed that they could be separated via adsorption by β-zeolite molecular sieve, which was attributed to the structure characteristics of the molecular sieve and the size difference of the isomer molecules. During the isotherm adsorption experiments of the binary mixture, from a certain time the concentration of 2,2,4-trimethylpentane at outlet was much higher than that at inlet due to the desorption of 2,2,4-trimethylpentane in the adsorption bed.%航空汽油基础油辛烷值较低是制约航空汽油无铅化发展的主要因素。本研究对利用β-沸石分子筛分离2,2,4-三甲基戊烷与2-甲基庚烷混合物的可行性进行了考察。结果表明,在相同温度及压力下,β-沸石分子筛对2-甲基庚烷的吸附能力远优于2,2,4-三甲基戊烷,且组分的饱和吸附量随温度的升高而减少,随压力的增加而增加。双组分吸附试验证明了利用β-沸石分子筛完全能够实现2,2,4-三甲基戊烷与2-甲基庚烷的分离,这主要归因于分子筛本身的结构特征及同分异构体分子大小的差异。双组分吸附试验中,2,2,4-三甲基戊烷出口体积分数在某一时刻以后高于入口体积分数,这主要是因为吸附床内部发生了脱附现象。

  6. 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.

  7. 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.

  8. Synthesis of Highly Selective Zeolite Topology Molecular Sieve Using Third Foaming Method%三次致孔法制备类沸石分子筛的研究

    Institute of Scientific and Technical Information of China (English)

    魏琳; 陈云琳; 张宝平; 祖志楠

    2012-01-01

    本研究以山东粉煤灰(FA_1)、房山粉煤灰(FA_2)及黑龙江粉煤灰(FA_3)为原料,采用三次致孔法水热晶化合成类沸石分子筛,并研究了三次致孔法处理粉煤灰的晶型转化和颗粒团聚变化.并采用X射线衍射(XRD)、扫描电子显微镜(SEM)和X荧光法(XRF)进行检测.结果表明,以20% HCl、液固比(L/S)为10的活化条件处理FA_1,得到物相单一且表面结构稳定的晶体;10 mol/L NaOH的改性条件下,进一步得到结晶良好的团聚体;晶化条件:硅铝物质的量比(Si/Al)为7.9,晶化温度为140℃,晶化时间为8h,制备出对苯蒸气吸附率为63.72%的类沸石分子筛.%Shangdong fly ash ( FA-1) , Fangshan fly ash (FA-2) and Heilongjiang fly ash (FA-3) were selected as the raw materials to be used for synthesis of highly selective zeolite topology molecular sieve. The crystal transformation and particles reunion were studied in terms of synthetic zeolite by third foaming method. The experimental products were characterized by means of X-ray fluorescence (XRF), scanning electron microscope ( SEM) , and X-ray diffraction ( XRD). The result indicated that the condition of modification experiment is FA_1 processed by 10 mol/L NaOH, crystallization temperature and time are 140 ℃ and 8 h, respectively. With Si/Al of 7.9, zeolite topology molecular sieve is prepared,and the adsorption ratio is 63.72% for benzene gas.

  9. Development in crystallization mechanism and crystallization kinetics of SAPO-34 molecular sieves%SAPO-34分子筛晶化机理及晶化动力学研究

    Institute of Scientific and Technical Information of China (English)

    邢爱华; 冯琦瑶; 张新锋; 姜继东

    2016-01-01

    对SAPO-34分子筛晶化过程中预相形成、诱导期内晶核生成、晶体生长和晶化过程的研究进行综述。SAPO-34分子筛晶化过程首先形成不稳定的层状预相结构,进而发展为具有有序排列晶格骨架的晶核。结晶热力学控制晶相结构,晶化动力学控制晶体成核和生长速率。影响晶化动力学的关键因素是温度和浓度,成核速率和晶体生长速率互相竞争控制晶粒大小。晶化过程的Si取代机理和Si分布影响分子筛酸性。晶化动力学研究结果表明,温度升高,结晶速率增加,成核时间缩短。%The pre-phase formation,the crystal nuclei generation in the induction period,crystal growth and the termination of crystallization during the crystallization process of SAPO-34 molecular sieves were summarized. A firstly formed layered prephase evolved into orderly lattice frame of crystal nucleus. Crys-talline thermodynamics controled phase structure and crystallization kinetics controled the rates of the crystal nucleation and crystal growth. The key influential factors of the crystallization kinetics were the crystallization temperature and concentration;the competition of the nucleation rate and crystal growth rate determined the crystal size. The Si substitution mechanism and Si distribution during the crystallization process had influence on the acidity of the molecular sieve. The research results of crystallization kinetics showed that the crystallization rate increased and the nucleation time was shortened with the increase of the crystallization temperatures.

  10. Carbogenic molecular sieves for reaction and separation by design: A novel approach to shape selective super base, super acid and catalytic membranes. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Foley, Henry C.

    2002-03-18

    This report details the findings of three years of research plus one year of a no-cost extension. Primary results are the work with supported nanoporous carbon membranes for separation and reaction as well as with cesium-nanoporous carbon catalysts. The work resulted in 17 plus 2 papers (2 are in progress) and partial or full support for five Ph.D. students. Two patents were filed based on this research.

  11. 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....

  12. 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.

  13. 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。

  14. Study on molecular sieve catalyst on catalytic properties of phenol and isopropanol alkylation%分子筛催化剂对苯酚异丙醇烷基化反应催化性能的研究

    Institute of Scientific and Technical Information of China (English)

    张丽; 赵娜; 王莹莹

    2013-01-01

    Alkylation of phenol with isopropanol was carried out on three different kinds of molecular sieve catalysts, MCM-56, ZSM-22 and Beta zeolite. X-ray diffraction and NH3-TPD were used to characterize the three zeolite.The remit showd that the weak acid sites of the catalysts favor o-isopropyl phenol and the strong acad sites favor p-isopropyl phenol.%本文研究了用MCM-56、ZSM-22、Beta分子筛作催化剂催化苯酚异丙醇烷基化反应的催化性能.用X射线衍射、氨程序升温脱附两种表征方法对3种分子筛进行了表征.实验表明:当分子筛具有弱酸性位时易于邻异丙基苯酚的生成,具有强酸性位时易于对异丙基苯酚的生成.

  15. 陶瓷纤维基硅胶/分子筛复合吸附剂的实验研究%Experimental Research on Silical Gel/Molecular Sieve Composite Adsorbents With Ceramic Fiber Matrix

    Institute of Scientific and Technical Information of China (English)

    蒋赣; 方玉堂; 丁静

    2011-01-01

    采用浸渍法在基材上原位反应生成硅胶,以硅溶胶作为分子筛的分散剂、黏合剂制备出陶瓷纤维基硅胶/分子筛复合吸附剂,采用静态法测定了吸附剂纸片和块体的吸附量,并利用静态吸附床结构来模拟转轮的工作状态,结果表明:在不同湿度条件下,复合吸附剂具有较高的静态和动态吸附量。%Silica gel/molecular sieve composite adsorbents(CA)were prepared by impregnation reaction on the ceramic fiber sheet which silica sol was used as dispersant and adhesive.The static adsorption performance of CA sheet and monolithic was tested,and their dynamic adsorption performance was also measured by using adsorbent bed to simulate the dehumidifying process of rotary-type dehumidifier.The results of experiments showed that CA had excellent dehumidifying ability under different humidity condition.

  16. Graphitic carbon grown on fluorides by molecular beam epitaxy.

    Science.gov (United States)

    Jerng, Sahng-Kyoon; Lee, Jae Hong; Kim, Yong Seung; Chun, Seung-Hyun

    2013-01-03

    We study the growth mechanism of carbon molecules supplied by molecular beam epitaxy on fluoride substrates (MgF2, CaF2, and BaF2). All the carbon layers form graphitic carbon with different crystallinities depending on the cation. Especially, the growth on MgF2 results in the formation of nanocrystalline graphite (NCG). Such dependence on the cation is a new observation and calls for further systematic studies with other series of substrates. At the same growth temperature, the NCG on MgF2 has larger clusters than those on oxides. This is contrary to the general expectation because the bond strength of the carbon-fluorine bond is larger than that of the carbon-oxygen bond. Our results show that the growth of graphitic carbon does not simply depend on the chemical bonding between the carbon and the anion in the substrate.

  17. 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

  18. 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.

  19. 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

  20. The Progress of the Free Radical Polymerizations in the Channelof Mesoporous Molecular Sieve%介孔材料孔道内进行的自由基聚合反应研究进展

    Institute of Scientific and Technical Information of China (English)

    张发爱; 宋程; 余彩莉

    2011-01-01

    介孔材料具有孔道大小均匀、排列有序、高比表面积、孔径连续可调的特性,主要应用在催化、吸附、分离、传感器以及光、电、磁等许多领域.近年来,研究人员利用其空旷的孔道作为聚合"微反应器",在其内部进行了许多类型的聚合反应.综述了近二十年来在介孔材料孔道内烯类单体进行的自由基聚合反应,包括常规的自由基聚合反应和活性聚合反应,讨论了所得聚合物和介孔材料/聚合物复合材料的性能,认为对其聚合反应机理和应用值得进一步研究.%Mesoporous molecular sieves (MMS) have been used in many fields such as catalysis,absorption, separation and sensor along with optical, electrical and magnetic science, due to their uniform and order channel, large specific surface area and adjustable pore size. Recently, a lot of polymerizations were carried out in the channel of MMS, taking the advantage of their empty channels as the microreactor. The latest 20 years progress of the free radical polymerizations in the channel of MMS,including the regular free radical polymerization and active free radical polymerization were reviewed.The properties of the polymer and polymer/MMS composite were discussed.The polymerization mechanism and application need further investigated.

  1. Synthesis of Cu-HMS Molecular Sieve and Aromatic Hydrocarbon Oxidation Using Cu-HMS%Cu-HMS分子筛的合成及对芳烃氧化反应的催化

    Institute of Scientific and Technical Information of China (English)

    张美英; 王乐夫; 季山; 黄仲涛; 罗维

    2004-01-01

    采用中性模板法于室温下合成了含铜的分子筛Cu-HMS,并以该分子筛为多相催化剂,对温和条件下异丙苯的氧化进行了研究.结果表明,以硝酸铜为铜源的Cu-HMS-3催化剂具有很高的催化活性,异丙苯转化率和过氧化氢异丙苯选择性都很高,分别达39.6%和98.5%.催化剂可以回收使用.另外,以Cu-HMS-3为催化剂对甲苯和乙苯的氧化进行了研究,发现在本实验条件下,甲苯未发生反应,3种芳烃的活性顺序为甲苯乙苯<异丙苯.%A copper-containing molecular sieve Cu-HMS was synthesized using the neutral templating pathway at room temperature. Then the product was used as heterogeneous catalyst for the oxidation of cumene under mild conditions. The results show that Cu-HMS-3 with copper nitrate as copper source has excellent catalytic activity, high cumene conversion and cumene hydroperoxide selectivity, that is, 39.6% and 98.5%. The catalyst can be recycled. Furthermore, the oxidations of toluene and ethylbenzene were investigated with Cu-HMS-3 as catalyst. It is found that there is no oxidation reaction observed for toluene. The activities of the three aromatic hydrocarbons follow the order of tolueneethylbenzene

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

    Institute of Scientific and Technical Information of China (English)

    吴美玲; 周灵杰; 陈玮娜

    2014-01-01

    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.%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%。

  3. 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%.

  4. 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.

  5. Alkylation of Phenol with Isopropanol on HMCM- 56 Molecular Sieves%HMCM-56分子筛催化苯酚与异丙醇烷基化反应的研究

    Institute of Scientific and Technical Information of China (English)

    段卫东; 商永臣; 肖瑞杰; 李杨; 赵娜; 赵欣

    2011-01-01

    Alkylation of phenol with isopropanol was camed out in HMCM -56 molecular sieves catalyst. The effects of various reaction parameters such as reaction temperature, reactant ratio ( molar ratio of isopropanoll to phenol), catalyst loading and space velocity on catalyst performance were discussed. Employing analytical and spectroscopic techniques XRD showed a HMCM -56 structure with highly ordered crystalline structure. Optimal reaction conditions : T = 220 ℃ ,WHSV = 3.0 h^-1 , catalyst loading = 0.3 g, nIPA/nphenol=0.8, phenol conversion rate of 75% ,the total of selectivity O -isopropyl phenol and isopropyl phenol was 65% .%研究HMCM-56分子筛上苯酚与异丙醇烷基化反应,探讨了反应条件包括温度,原料配比,催化剂的装填量,空速对催化剂催化性能的影响.通过X射线衍射、研究催化剂的酸性及晶相.得到最佳反应条件:T=220℃,WHSV=3.0h^-1,Catalyst Loading=0.3g,n(IPA)/n(Phenol)=0.8,苯酚的转化率可达75%,邻异丙基苯酚和对异丙基苯酚的总选择性为65%.

  6. 甘油脱水制丙烯醛分子筛型催化剂的研究%Research of Molecular Sieve Catalysts in Glycerol Dehydration to Acrolein

    Institute of Scientific and Technical Information of China (English)

    朱烨楠; 马田林; 丁建飞

    2015-01-01

    随着世界石油资源的日益紧张,可作替代能源的生物柴油广受青睐。伴随着其产量不断增大,大量的副产物甘油导致了市场过剩。开发和利用甘油是近期的研究热点,甘油脱水制取丙烯醛是提高生物柴油经济性的一条有效途径。本文结合近年来国内外甘油脱水制丙烯醛的研究进展,重点阐述了分子筛型催化剂在甘油脱水制丙烯醛领域的研究情况。此外,还讨论了目前存在的问题,指出了今后甘油脱水制丙烯醛的研究方向和展望。%With growing tensions of the world's oil resources, biodiesel as popular alternative energy has drawn much attention from the public. With the increasing production of biodiesel, a large volume of byproduct glycerol has led to a drastic surplus in chemical markets. Development and utilization of glycerol is a hot spot in recent study. De-hydration of glycerol to acrolein is an effective way to improve the utilization rate of biodiesel production. Combining with the recent progress in glycerol dehydration to acrolein, this paper lay emphasis on molecular sieve based cata-lysts. What’ s more, the current main problems of the reaction of glycerol dehydration are proposed and the research work in glycerol dehydration to acrolein in the future is proposed. In addition, the application prospect of the research is also forecasted.

  7. Experimental Study on Synthesis Molecular Sieve Ashes of Circulating Fluidized Bed%利用循环流化床飞灰合成分子筛实验研究

    Institute of Scientific and Technical Information of China (English)

    姚刚; 卿山; 马林转; 岳争超; 何屏; 李瑛

    2009-01-01

    Experimental study showed when n (SiO2) /n (Al2O3)≈3.3, Na2O/SiO2 was 1.2~1.5, H2O/Na2O was 40~70, the gel temperature was 60 -70 ℃, time continued 2h, reaction temperature was 90 -95 ℃, the crystallization time continued 4 -6 h, the fly ash of circulating fluidized bed boiler could synthesize the molecular sieve of higher crystallinity. It had better characteristic peak of P zeolite by the characterization of XRD, good stability by TGA. The relative degree of crystallization was 53%.%利用循环流化床锅炉粉煤灰在n(SiO2)/n(Al2O3)≈3.3、Na2O/SiO2为1.2~L 5、H2O/Na2O为40~70、凝胶温度和时间分别为60-70℃、时间2 h、晶化反应温度在90-95℃,晶化时间为4-6 h的条件下可以合成出较高结晶度的分子筛,通过XRD表征发现,产品具有良好的P型分子筛特征峰,其相对结晶度为53%.热重分析可知其具有好的稳定性.

  8. 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.

  9. Interaction of collagen with carbon nanotube: a molecular dynamics investigation.

    Science.gov (United States)

    Gopalakrishnan, R; Subramanian, V

    2011-02-01

    In variety of biological applications carbon nano materials interact with different biological macromolecules, such as proteins, carbohydrates and nucleic acids. In this study carbon nanotube (CNT) has been used as the model for carbon nanomaterials. Since, collagen is a large protein; model collagen like peptide (CPs) has been used to understand the interaction between CNT and collagen. Molecular dynamics (MD) simulation showed that the hydrophobic-hydrophobic interaction of the CNT-CPs play a crucial role in attracting the CPs towards the CNT. No structural aberrations occured in collagen upon interaction with CNT and hence CNT can be employed in the tissue engineering applications.

  10. 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.

  11. 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.

  12. Electronic and molecular structure of carbon grains

    Science.gov (United States)

    Almloef, Jan; Luethi, Hans-Peter

    1990-01-01

    Clusters of carbon atoms have been studied with large-scale ab initio calculations. Planar, single-sheet graphite fragments with 6 to 54 atoms were investigated, as well as the spherical C(sub 60) Buckminsterfullerene molecule. Polycyclic aromatic hydrocarbons (PAHs) have also been considered. Thermodynamic differences between diamond- and graphite-like grains have been studied in particular. Saturation of the peripheral bonds with hydrogen is found to provide a smooth and uniform convergence of the properties with increasing cluster size. For the graphite-like clusters the convergence to bulk values is much slower than for the three-dimensional complexes.

  13. Carbon chemistry in dense molecular clouds: Theory and observational constraints

    Science.gov (United States)

    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. Researchers present a brief review of the basic assumptions and results of large scale modeling of the carbon chemistry in dense molecular clouds. Particular attention is to the influence of the gas phase C/O ratio in molecular clouds, and the likely role grains play in maintaining this ratio as clouds evolve from initially diffuse objects to denser cores with associated stellar and planetary formation. Recent spectral line surveys at centimeter and millimeter wavelengths along with selected observations in the submillimeter have now produced an accurate inventory of the gas phase carbon budget in several different types of molecular clouds, though gaps in our knowledge clearly remain. The constraints these observations place on theoretical models of interstellar chemistry can be used to gain insights into why the models fail, and show also which neglected processes must be included in more complete analyses. Looking toward the future, larger molecules are especially difficult to study both experimentally and theoretically in such dense, cold regions, and some new methods are therefore outlined which may ultimately push the detectability of small carbon chains and rings to much heavier species.

  14. Multicomponent ballistic transport in narrow single wall carbon nanotubes: Analytic model and molecular dynamics simulations

    Science.gov (United States)

    Mutat, T.; Adler, J.; Sheintuch, M.

    2011-01-01

    The transport of gas mixtures through molecular-sieve membranes such as narrow nanotubes has many potential applications, but there remain open questions and a paucity of quantitative predictions. Our model, based on extensive molecular dynamics simulations, proposes that ballistic motion, hindered by counter diffusion, is the dominant mechanism. Our simulations of transport of mixtures of molecules between control volumes at both ends of nanotubes give quantitative support to the model's predictions. The combination of simulation and model enable extrapolation to longer tubes and pore networks.

  15. 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.

  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. 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.

  18. Synthesis of biodiesei catalyzed by CaO supported on molecular sieve prepared by microwave%分子筛微波辐射负载CaO催化合成生物柴油

    Institute of Scientific and Technical Information of China (English)

    周玉杰; 张建安; 武海棠; 刘宏娟; 程可可; 戴玲妹; 刘德华; 刘建

    2009-01-01

    研究微波辐射法制备固体碱催化剂CaO/NaY在合成生物柴油中的应用.结果表明,该催化剂在醇油摩尔比9:1,催化剂质量分数3%,反应温度65℃,反应时间3 h等条件下,以精制大豆油为原料制备的生物柴油得率可达95%;而以酸值(以KOH计)为4mg/g和含水质量分数为1.5%的油脂为原料,生物柴油得率可分别达到92.4%和84.8%.催化剂结构表征表明:微波辐射改善了CaO在载体NaY上的分散,其总碱量(H-≥27)达到3.798mmol/g,是一种固体超强碱.%With molecular sieve NaY as carrier, supported solid base CaO/NaY was prepared by microwave irradiation, and the transesterification of soybean oil and methanol to produce biodiesel was investigated with the catalyst. The results show that the yield of biodiesel can be about 95% under the conditions when molar ratio of methanol to soybean oil is 9 : 1, catalyst mass fraction is 3%, reaction temperature is 65℃ and reaction time is 3 h. The CaO/NaY catalyst is more tolerant to free fatty acids and water, and the yield is 92.4% and 84.8% respectively when acid value (as KOH) is 4 mg/g and water mass fraction is 1.5%. Moreover, X-ray diffraction (XRD) analysis shows that CaO is well dispersed in NaY after microwave irradiation, and CaO/NaY is a kind of solid super base with total basicity of 3.798 mmol/g(H-≥27).

  19. Research on Synthesis of Al-SBA-15 Mesoporous Molecular Sieves in Phosphoric Acid Medium%磷酸介质体系中合成Al-SBA-15介孔分子筛的研究

    Institute of Scientific and Technical Information of China (English)

    赵红建; 马富

    2012-01-01

    以正硅酸乙酯为硅源,非离子表面活性剂P123为模板剂,异丙醇铝为铝源,在磷酸介质中合成出了Al-SBA-15介孔分子筛.采用XRD、TEM、SEM、N2 -BET、TG-DTA等表征手段,考察了所得材料的物化性能.分析了初始溶液中硅铝比对介观结构的影响.所得材料在XRD谱图中(100)、(110)和(200)处出现较强衍射峰,氮气吸-脱附曲线为典型的Ⅳ型且有H1滞后环,结合TEM分析表明产物具有二维六方排列的介孔结构(空间群为p6mm),SEM结果表明相对纯硅SBA-15,Al-SBA-15介孔分子筛长程有序性没有受到限制.%Using tetraethyl orthosilicate as silica source,non-ionic surfactant P123 as template and aluminum isopropoxide as aluminum source,Al-SBA-15 mesoporous molecular sieves were obtained in the presence of phosphoric acid.By means of XRD,TEM,SEM,N2-BET,TG-DTA techniques,the properties of the samples were characterized.The effect of the molar ratio of Si/Al in the starting reactant solution on the mesoporous structure was investigated.The materials exhibited strong reflection peaks at (100),(110) and (200) reflection lines.N2 adsorption-desorption isotherms were typical Ⅳ type with a H1 hysteresis loop.XRD and TEM results showed that the samples possessed 2D hexagonal symmetry (p6mm) mesostructure.SEM images revealed that Al-SBA-15 hold the long range ordering mesoporous structure compared with pure silica SBA-15.

  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. SYNTHESIS OF METHYL 1-NAPHTHYLACETATELAURATE CATALYZED BY SULFONATED MOLECULAR SIEVE IN FIXED BED%磺化分子筛固定床合成1-萘乙酸甲酯的研究

    Institute of Scientific and Technical Information of China (English)

    杨玉峰

    2012-01-01

    实验以甲醇与1—萘乙酸先预酯化,再将预酯化液在262-磺化分子筛固定床反应器中高温酯化工艺合成1-萘乙酸甲酯.考察了高温酯化反应的影响因素.最佳高温酯化条件为:预酯化液的酸值(KOH)为60mg/g,甲醇与1-萘乙酸的质量比为0.5,反应温度为95℃,反应物流量为0.9 mL/min,总酯化率达99.0%以上.催化剂循环使用11次,表现出优良的催化活性和稳定性.与传统工艺相比无需中和、水洗、萃取等步骤便可得到高纯度的产品.%Esterification of 1-naphthylacetic acid with methanol was carried out first. Then such fore-esterification liquid was used as raw materials for the synthesis of methyl 1-naphthylacetate by high temperature esterification catalyzed by 262-sulfonated molecular sieve in fixed bed reactor. Factors affecting the high temperature esterification were investigated. The optimum conditions were found as follows; mass ratio of methyl alcohol to 1-naphthylacetic acid 0. 5,flow rate of reactant 0. 9 mL/min, reaction temperature 95 ℃ , reaction time 1 h. Under the optimum conditions, the esterification yield could reach above 99%. The catalysts were reused for 11 times with 99% of the esterification yield, demonstrating the high catalytic performance and stability of the catalysts. Compared with the traditional process, this method produces high purity methyl 1-naphthylacetate without the tedious steps like neutralization, washing, extraction and so on.

  2. Molecular Dynamics Simulations of Carbon Nanotubes in Water

    Science.gov (United States)

    Walther, J. H.; Jaffe, R.; Halicioglu, T.; Koumoutsakos, P.

    2000-01-01

    We study the hydrophobic/hydrophilic behavior of carbon nanotubes using molecular dynamics simulations. The energetics of the carbon-water interface are mainly dispersive but in the present study augmented with a carbon quadrupole term acting on the charge sites of the water. The simulations indicate that this contribution is negligible in terms of modifying the structural properties of water at the interface. Simulations of two carbon nanotubes in water display a wetting and drying of the interface between the nanotubes depending on their initial spacing. Thus, initial tube spacings of 7 and 8 A resulted in a drying of the interface whereas spacing of > 9 A remain wet during the course of the simulation. Finally, we present a novel particle-particle-particle-mesh algorithm for long range potentials which allows for general (curvilinear) meshes and "black-box" fast solvers by adopting an influence matrix technique.

  3. Carbonization in polyacrylonitrile (PAN) based carbon fibers studied by ReaxFF molecular dynamics simulations.

    Science.gov (United States)

    Saha, Biswajit; Schatz, George C

    2012-04-19

    The carbonization mechanism in polyacrylonitrile (PAN) based carbon nanofibers is studied using ReaxFF molecular dynamics simulations. Simulations are performed at two carbonization temperatures, 2500 and 2800 K, and also at two densities, 1.6 and 2.1 g/cm(3), that are relevant to the experimental carbonization conditions. The results are analyzed by examining the evolution of species with time, including carbon-only ring structures and gaseous species. Formation mechanisms are proposed for species like N(2), H(2), NH(3), and HCN and five-, six-, and seven-membered carbon-only rings, along with polycyclic structures. Interestingly, the formation of five-membered rings follows N(2) formation and usually occurs as a precursor to six-membered rings. Elimination mechanisms for the gaseous molecules are found that are in agreement with previously proposed mechanisms; however, alternative mechanisms are also proposed.

  4. 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.

  5. Molecular Dynamics Simulations of Laser Powered Carbon Nanotube Gears

    Science.gov (United States)

    Srivastava, Deepak; Globus, Al; Han, Jie; Chancellor, Marisa K. (Technical Monitor)

    1997-01-01

    Dynamics of laser powered carbon nanotube gears is investigated by molecular dynamics simulations with Brenner's hydrocarbon potential. We find that when the frequency of the laser electric field is much less than the intrinsic frequency of the carbon nanotube, the tube exhibits an oscillatory pendulam behavior. However, a unidirectional rotation of the gear with oscillating frequency is observed under conditions of resonance between the laser field and intrinsic gear frequencies. The operating conditions for stable rotations of the nanotube gears, powered by laser electric fields are explored, in these simulations.

  6. 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 abi...... with bound CO2. One class of molecules that undergo a reaction compatible with our purposal is the merocyanine dyes that exhibit photochromic properties. Based on this structural class of molecules, a system for the potential fixing of CO2 has been developed....

  7. 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).

  8. Fullerenes, carbon nanotubes, and graphene for molecular electronics.

    Science.gov (United States)

    Pinzón, Julio R; Villalta-Cerdas, Adrián; Echegoyen, Luis

    2012-01-01

    With the constant growing complexity of electronic devices, the top-down approach used with silicon based technology is facing both technological and physical challenges. Carbon based nanomaterials are good candidates to be used in the construction of electronic circuitry using a bottom-up approach, because they have semiconductor properties and dimensions within the required physical limit to establish electrical connections. The unique electronic properties of fullerenes for example, have allowed the construction of molecular rectifiers and transistors that can operate with more than two logical states. Carbon nanotubes have shown their potential to be used in the construction of molecular wires and FET transistors that can operate in the THz frequency range. On the other hand, graphene is not only the most promising material for replacing ITO in the construction of transparent electrodes but it has also shown quantum Hall effect and conductance properties that depend on the edges or chemical doping. The purpose of this review is to present recent developments on the utilization carbon nanomaterials in molecular electronics.

  9. Modeling the hydrodynamics of Phloem sieve plates

    DEFF Research Database (Denmark)

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

    2012-01-01

    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....

  10. 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

  11. Organotemplate-Free Hydrothermal Synthesis of Isomorphously Co-Substituted Mordenite Molecular Sieve%无有机模板剂水热合成Co同晶取代的丝光沸石分子筛

    Institute of Scientific and Technical Information of China (English)

    王琦; 吴雅静; 王军; 林晓

    2012-01-01

    An organotemplate-free hydrothermal route was investigated for synthesizing isomorphously Co-substituted mordenite molecular sieve using only the inorganic raw materials such as sodium silicate,aluminum sulfate,cobalt nitrate,and sodium hydroxide.Textural properties and Co ion states for the obtained solid products were characterized by powder X-ray diffraction (XRD),scanning electron microscope (SEM),inductively coupled plasma (ICP),nitrogen adsorption,ultraviolet-visible (UV-Vis)spectra,and thermogravimetric (TG) analysis.The results showed that Co ions were incorporated into the framework structure of the mordenite without the presence of extra-framework Co species.Typical synthesis conditions were n(Co)/n(SiO2)=0.01-0.04,n(SiO2)/n(Al2O3)=20-50,n(H2O)/n(SiO2)=40,n(Na2O)/n(SiO2)=0.4,crystallization temperature 170 °C,and crystallization time 3-7 d.The structure-directing function of Na+ ions in the absence of an organic template was discussed.Products obtained by the present allinorganic systems possess open micropores and do not require traditional high-temperature calcination.Thus,we demonstrate a low cost,low energy consumption,and environmentally benign synthesis of Co-mordenite.%在硅酸钠、硫酸铝、硝酸钴和氢氧化钠的全无机体系条件下,采用无有机模板剂水热法合成了Co同晶取代的丝光沸石分子筛.通过粉末X射线衍射(XRD)、扫描电子显微镜(SEM)、电感耦合等离子体(ICP)光谱、氮气吸附、紫外-可见(UV-Vis)光谱、热重(TG)分析等手段对所得固体产物的织构性质以及钴在分子筛中的存在状态进行了表征.结果表明,该方法成功地将Co离子引入到丝光沸石分子筛的骨架结构中,未发现骨架外Co物种.典型的合成条件为n(Co)/n(SiO2) =0.01-0.04,n(SiO2)/n(AI2O3)=20-50,n(H2O)/n(SiO2) =40,n(Na2O)/n(SiO2)=0.4,晶化温度170°C,晶化时间3-7 d.讨论了Na+离子在无有机模板剂合成中的结构导向作用.全无机体系合成得到的产

  12. Capability of molecular sieve-supported FeSO4 catalyst for selective catalytic reduction of Nox%NaY分子筛担载FeSO4催化剂用于氨气还原NOx的性能

    Institute of Scientific and Technical Information of China (English)

    任雯; 赵博; 禚玉群; 陈昌和

    2011-01-01

    This paper focuses on the NO reduction by ammonia via FeSO4 catalyst supported by molecular sieve in a fixed bed reactor at 400℃ . The experimental results indicate that the catalyst has immediate catalytic effect on NO reduction. Due to its improved physical structure, the catalyst improves the NO reduction rate by 20% compared with pure FeSO4.The effects of preparation conditions on catalytic activity, including the mix ratio, impregnation agent and impregnation time etc. , are investigated. Mossbauer spectroscopy is used for the study. It is found that Fe2+ is oxidized to Fe3+ during the preparation and most FeSO4 is transferred to Fe(OH)SO4 and Fe2O(SO4)2. Fe(OH)SO4 is better than the other speices in NO reduction and the ratio of different species is related to the water and oxygen content in atmosphere. The results of in-situ FTIR indicate that Fe is the reaction centre. NH3 is absorbed on the catalyst and reacts with NO, which can be explained by Eley-Rideal mechanism. Compared with other commercial catalysts, FeSO4 demonstrates great industrial potentials because of its low cost and excellent catalytic effect at high space velocity.%研究了分子筛担载FeSO4催化剂在SCR脱硝反应中的催化性能和反应机理.实验结果表明,在同等工况下分子筛担载FeSOt后的催化剂具有更好的物理结构,与纯FeSO4相比脱硝率可提高将近20%.经Mossbauer谱分析,催化剂制备过程中Fe2+转化为Fe3+,其具体存在形式为Fe(OH)SO4与Fe2O(SO4)2,前者催化脱硝效果优于后者.原位红外分析结果表明,吸附在分子筛担载催化剂表面的氨与气相中的NO反应,Fe离子是吸附及发生催化氧化还原反应的活性中心.与钒、钛系SCR催化剂相比,所制备的催化剂不但具有廉价、高效的优点,而且能适应更高的反应空速,具有良好的工业应用前景.

  13. 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

  14. C25沸石分子筛催化合成2-乙酰噻吩连续反应%Continuous synthesis of 2-acetyl thiophene with C25 zeolite molecular sieve

    Institute of Scientific and Technical Information of China (English)

    酆月飞; 曾爱武

    2014-01-01

    With C25 zeolite molecular sieve as catalyst,thiophene and acetic anhydride as raw materials,continuous synthesis of 2-acetyl thiophene was conducted in a trickle bed reactor. The effects of reaction temperature,molar ratio of raw materials,feed flow rate on the Friedel-Crafts acylation reaction were investigated via orthogonal experiment. The optimum reaction condition was:reaction temperature 70℃,molar ratio of thiophene and acetic anhydride 1∶2,feed flow rate 0.05mL/min. Considering the influence of acetic acid on the reaction,the best molar ratio of thiophene,acetic anhydride and acetic acid was 1∶2∶1. Under those conditions,output of 2-acetyl thiophene was 15.10g per unit mass of catalyst,catalyst service life was 4215 min and initial conversion of thiophene could reach 99.98%. The catalyst was characterized with 13C NMR MAS,27Al NMR MAS,and TGA analysis. Bronsted acid sites played an important role in catalysis and the main deactivation type was coking deactivation by compounds with high boiling point.%在滴流床反应器中,以C25沸石分子筛为催化剂,噻吩和乙酸酐为原料对噻吩酰化合成2-乙酰噻吩进行了连续反应实验研究。通过正交试验研究了反应温度、原料配比、进料流量对噻吩 Friedel-Crafts 酰基化反应的影响,确定了最佳反应条件:反应温度70℃,噻吩与乙酸酐摩尔配比1∶2,进料流量0.05mL/min。考察了副产物乙酸对反应的影响,确定了噻吩、乙酸酐和乙酸的最佳摩尔比为1∶2∶1,在最佳反应条件下,单位质量催化剂的2-乙酰噻吩产量为15.10g,催化剂寿命是4215min,噻吩初始转化率高达99.98%。采用固体13C、27Al 核磁共振技术、热重分析对催化剂进行表征,结果表明,催化剂主要催化活性在 B 酸位,失活类型为高沸点物质的积炭失活。

  15. 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.)

  16. Sifting Limits for the \\Lambda^2\\Lambda^- Sieve

    CERN Document Server

    Franze, Craig

    2010-01-01

    Sifting limits for the $\\Lambda^{2}\\Lambda^{-}$ sieve, Selberg's lower bound sieve, are computed for integral dimensions $1<\\kappa\\le10$. The evidence strongly suggests that for all $\\kappa\\ge3$ the $\\Lambda^{2}\\Lambda^{-}$ sieve is superior to the competing combinatorial sieves of Diamond, Halberstam, and Richert. A method initiated by Grupp and Richert for computing sieve functions for integral $\\kappa$ is also outlined.

  17. 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.

  18. 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

  19. Magnetic Susceptibility of Molecular Carbon: Nanotubes and Fullerite

    Science.gov (United States)

    Ramirez, A. P.; Haddon, R. C.; Zhou, O.; Fleming, R. M.; Zhang, J.; McClure, S. M.; Smalley, R. E.

    1994-07-01

    Elemental carbon can be synthesized in a variety of geometrical forms, from three-dimensional extended structures (diamond) to finite molecules (C60 fullerite). Results are presented here on the magnetic susceptibility of the least well-understood members of this family, nanotubes and C60 fullerite. (i) Nanotubes represent the cylindrical form of carbon, intermediate between graphite and fullerite. They are found to have significantly larger orientation-averaged susceptibility, on a per carbon basis, than any other form of elemental carbon. This susceptibility implies an average band structure among nanotubes similar to that of graphite. (ii) High-resolution magnetic susceptibility data on C60 fullerite near the molecular orientational-ordering transition at 259 K show a sharp jump corresponding to 2.5 centimeter-gram-second parts per million per mole of C60. This jump directly demonstrates the effect of an intermolecular cooperative transition on an intramolecular electronic property, where the susceptibility jump may be ascribed to a change in the shape of the molecule due to lattice forces.

  20. Modeling Carbon and Hydrocarbon Molecular Structures in EZTB

    Science.gov (United States)

    Lee, Seungwon; vonAllmen, Paul

    2007-01-01

    A software module that models the electronic and mechanical aspects of hydrocarbon molecules and carbon molecular structures on the basis of first principles has been written for incorporation into, and execution within, the Easy (Modular) Tight-Binding (EZTB) software infrastructure, which is summarized briefly in the immediately preceding article. Of particular interest, this module can model carbon crystals and nanotubes characterized by various coordinates and containing defects, without need to adjust parameters of the physical model. The module has been used to study the changes in electronic properties of carbon nanotubes, caused by bending of the nanotubes, for potential utility as the basis of a nonvolatile, electriccharge- free memory devices. For example, in one application of the module, it was found that an initially 50-nmlong carbon, (10,10)-chirality nanotube, which is a metallic conductor when straight, becomes a semiconductor with an energy gap of .3 meV when bent to a lateral displacement of 4 nm at the middle.

  1. 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.

  2. Molecular profiling of permafrost soil organic carbon composition and degradation

    Science.gov (United States)

    Gu, B.; Mann, B.

    2014-12-01

    Microbial degradation of soil organic matter (SOM) is a key process for terrestrial carbon (C) cycling, though the dynamics of these transformations remain unclear at the molecular level. This study reports the application of ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to profile molecular components of Arctic SOM collected from the surface water and the mineral horizon of a low-centered polygon soil at Barrow Environmental Observatory (BEO), Barrow, Alaska. Soil samples were subjected to anaerobic warming experiments for a period of 40 days, and the SOM was extracted before and after the incubation to determine the components of organic C that were degraded over the course of the study. A CHO index based on molecular composition data was utilized to codify SOM components according to their observed degradation potential. Carbohydrate- and lignin-like compounds in the water-soluble fraction (WSF) demonstrated a high degradation potential, while structures with similar stoichiometries in the base-soluble fraction (BSF) were not readily degraded. The WSF of SOM also shifted to a wider range of measured molecular masses including an increased prevalence of larger compounds, while the size distribution of compounds in the BSF changed little over the same period. Additionally, the molecular profiling data indicated an apparently ordered incorporation of organic nitrogen in the BSF immobilized as primary and secondary amines, possibly as components of N-heterocycles, which may provide insight into nitrogen immobilization or mobilization processes in SOM. Our study represents an important step forward for studying Arctic SOM with improved understanding of the molecular properties of soil organic C and the ability to represent SOM in climate models that will predict the impact of climate change on soil C and nutrient cycling.

  3. 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.

  4. Molecular mechanics methods for individual carbon nanotubes and nanotube assemblies

    Science.gov (United States)

    Eberhardt, Oliver; Wallmersperger, Thomas

    2015-04-01

    Since many years, carbon nanotubes (CNTs) have been considered for a wide range of applications due to their outstanding mechanical properties. CNTs are tubular structures, showing a graphene like hexagonal lattice. Our interest in the calculation of the mechanical properties is motivated by several applications which demand the knowledge of the material behavior. One application in which the knowledge of the material behavior is vital is the CNT based fiber. Due to the excellent stiffness and strength of the individual CNTs, these fibers are expected to be a promising successor for state of the art carbon fibers. However, the mechanical properties of the fibers fall back behind the properties of individual CNTs. It is assumed that this gap in the properties is a result of the van-der-Waals interactions of the individual CNTs within the fiber. In order to understand the mechanical behavior of the fibers we apply a molecular mechanics approach. The mechanical properties of the individual CNTs are investigated by using a modified structural molecular mechanics approach. This is done by calculating the properties of a truss-beam element framework representing the CNT with the help of a chemical force field. Furthermore, we also investigate the interactions of CNTs arranged in basic CNT assemblies, mimicking the ones in a simple CNT fiber. We consider the van-der-Waals interactions in the structure and calculate the potential surface of the CNT assemblies.

  5. Molecular dynamics analysis on buckling of defective carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kulathunga, D D T K; Ang, K K [Department of Civil Engineering, National University of Singapore (Singapore); Reddy, J N, E-mail: cveangkk@nus.edu.s [Department of Mechanical Engineering, Texas A and M University, College Station, TX 77843-3123 (United States)

    2010-09-01

    Owing to their remarkable mechanical properties, carbon nanotubes have been employed in many diverse areas of applications. However, similar to any of the many man-made materials used today, carbon nanotubes (CNTs) are also susceptible to various kinds of defects. Understanding the effect of defects on the mechanical properties and behavior of CNTs is essential in the design of nanotube-based devices and composites. It has been found in various past studies that these defects can considerably affect the tensile strength and fracture of CNTs. Comprehensive studies on the effect of defects on the buckling and vibration of nanotubes is however lacking in the literature. In this paper, the effects of various configurations of atomic vacancy defects, on axial buckling of single-walled carbon nanotubes (SWCNTs), in different thermal environments, is investigated using molecular dynamics simulations (MDS), based on a COMPASS force field. Our findings revealed that even a single missing atom can cause a significant reduction in the critical buckling strain and load of SWCNTs. In general, increasing the number of missing atoms, asymmetry of vacancy configurations and asymmetric distribution of vacancy clusters seemed to lead to higher deterioration in buckling properties. Further, SWCNTs with a single vacancy cluster, compared to SWCNTs with two or more vacancy clusters having the same number of missing atoms, appeared to cause higher deterioration of buckling properties. However, exceptions from the above mentioned trends could be expected due to chemical instabilities of defects. Temperature appeared to have less effect on defective CNTs compared to pristine CNTs.

  6. 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.

  7. Carbon nanotubes as nanodelivery systems an insight through molecular dynamics simulations

    CERN Document Server

    Lim, Melvin Choon Giap

    2013-01-01

    This book showcases the application of carbon nanotubes as nanodelivery systems for copper atoms, using molecular dynamics simulations as a means of investigation. The nanodelivery system of the carbon nanotube presents the possible usage of the carbon structure in many areas in the future. This book is comprehensive and informative, and serves as a guide for any reader who wishes to perform a molecular dynamics simulation of his own and to conduct an analytical study of a molecular system.

  8. 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.

  9. Cyclic sieving, promotion, and representation theory

    CERN Document Server

    Rhoades, Brendon

    2010-01-01

    We prove a collection of conjectures of D. White \\cite{WComm}, as well as some related conjectures of Abuzzahab-Korson-Li-Meyer \\cite{AKLM} and of Reiner and White \\cite{ReinerComm}, \\cite{WComm}, regarding the cyclic sieving phenomenon of Reiner, Stanton, and White \\cite{RSWCSP} as it applies to jeu-de-taquin promotion on rectangular tableaux. To do this, we use Kazhdan-Lusztig theory and a characterization of the dual canonical basis of $\\mathbb{C}[x_{11}, ..., x_{nn}]$ due to Skandera \\cite{SkanNNDCB}. Afterwards, we extend our results to analyzing the fixed points of a dihedral action on rectangular tableaux generated by promotion and evacuation, suggesting a possible sieving phenomenon for dihedral groups. Finally, we give applications of this theory to cyclic sieving phenomena involving reduced words for the long elements of hyperoctohedral groups and noncrossing partitions.

  10. Molecular dynamics simulations of carbon nanotube-based gears

    Science.gov (United States)

    Han, Jie; Globus, Al; Jaffe, Richard; Deardorff, Glenn

    1997-09-01

    We use a molecular dynamics simulation to investigate the properties and design space of molecular gears fashioned from carbon nanotubes with teeth added via a benzyne reaction known to occur with 0957-4484/8/3/001/img1. Brenner's reactive hydrocarbon potential is used to model interatomic forces within each molecular gear. A Lennard - Jones 6 - 12 potential or the Buckingham 0957-4484/8/3/001/img2 potential plus electrostatic interaction terms are used for intermolecular interactions between gears. A number of gear and gear/shaft configurations are simulated on parallel computers. One gear is powered by forcing the atoms near the end of the nanotube to rotate, and a second gear is allowed to rotate by keeping the atoms near the end of its nanotube constrained to a cylinder. The meshing aromatic gear teeth transfer angular momentum from the powered gear to the driven gear. Results suggest that these gears can operate at up to 50 - 100 GHz in a vacuum at room temperature. The failure mode involves tooth slip, not bond breaking, so failed gears can be returned to operation by lowering the temperature and/or rotation rate.

  11. Molecular Dynamics Simulation of Carbon Nanotube Based Gears

    Science.gov (United States)

    Han, Jie; Globus, Al; Jaffe, Richard; Deardorff, Glenn; Chancellor, Marisa K. (Technical Monitor)

    1996-01-01

    We used molecular dynamics to investigate the properties and design space of molecular gears fashioned from carbon nanotubes with teeth added via a benzyne reaction known to occur with C60. A modified, parallelized version of Brenner's potential was used to model interatomic forces within each molecule. A Leonard-Jones 6-12 potential was used for forces between molecules. One gear was powered by forcing the atoms near the end of the buckytube to rotate, and a second gear was allowed.to rotate by keeping the atoms near the end of its buckytube on a cylinder. The meshing aromatic gear teeth transfer angular momentum from the powered gear to the driven gear. A number of gear and gear/shaft configurations were simulated. Cases in vacuum and with an inert atmosphere were examined. In an extension to molecular dynamics technology, some simulations used a thermostat on the atmosphere while the hydrocarbon gear's temperature was allowed to fluctuate. This models cooling the gears with an atmosphere. Results suggest that these gears can operate at up to 50-100 gigahertz in a vacuum or inert atmosphere at room temperature. The failure mode involves tooth slip, not bond breaking, so failed gears can be returned to operation by lowering temperature and/or rotation rate. Videos and atomic trajectory files in xyz format are presented.

  12. Synthesis of Zeolite Nanomolecular Sieves of Different Si/Al Ratios

    Directory of Open Access Journals (Sweden)

    Pankaj Sharma

    2015-01-01

    Full Text Available Nanosized zeolite molecular sieves of different Si/Al ratios have been prepared using microwave hydrothermal reactor (MHR for their greater application in separation and catalytic science. The as-synthesized molecular sieves belong to four different type zeolite families: MFI (infinite and high silica, FAU (moderate silica, LTA (low silica and high alumina, and AFI (alumina rich and silica-free. The phase purity of molecular sieves has been assessed by X-ray diffraction (XRD analysis and morphological evaluation done by electron microscopy. Broad XRD peaks reveal that each zeolite molecular sieve sample is composed of nanocrystallites. Scanning electron microscopic images feature the notion that the incorporation of aluminum to MFI zeolite synthesis results in morphological change. The crystals of pure silica MFI zeolite (silicalite-1 have hexagon lump/disk-like shape, whereas MFI zeolite particles with Si/Al molar ratios 250 and 100 have distorted hexagonal lump/disk and pseudo spherical shapes, respectively. Furthermore, phase pure zeolite nanocrystals of octahedron (FAU, cubic (LTA, and rod (AFI shape have been synthesized. The average sizes of MFI, FAU, LTA, and AFI zeolite crystals are 250, 150, 50, and 3000 nm, respectively. Although the length of AFI zeolite rods is in micron scale, the thickness and width are of a few nanometers.

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

    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

    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 recovery was 94.4%(RSD=2.9%). CONCLUSIONS:SBA-15@MIP is prepared successfully,and can be applied for the determination of active micro-component.%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

  14. 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.

  15. Process for attaching molecular wires and devices to carbon nanotubes and compositions thereof

    Science.gov (United States)

    Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

    2008-01-01

    The present invention is directed towards processes for covalently attaching molecular wires and molecular electronic devices to carbon nanotubes and compositions thereof. Such processes utilize diazonium chemistry to bring about this marriage of wire-like nanotubes with molecular wires and molecular electronic devices.

  16. 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.

  17. 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).

  18. 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.

  19. 碳分子筛的制法、性质和用途%The Preparation Method, Behaviour and Application of Carbon Molecular Sieve

    Institute of Scientific and Technical Information of China (English)

    胡逢恺

    2001-01-01

    本文综述了碳分子筛的制法、性质和用途,论述了碳分子筛的研究进展,指出碳分子筛的优越性在于它具有潜在新用途,加强这方面的研究是化学、化工工作者探讨的领域之一.

  20. MUSTANG-MR structural sieving server: applications in protein structural analysis and crystallography.

    Directory of Open Access Journals (Sweden)

    Arun S Konagurthu

    Full Text Available BACKGROUND: A central tenet of structural biology is that related proteins of common function share structural similarity. This has key practical consequences for the derivation and analysis of protein structures, and is exploited by the process of "molecular sieving" whereby a common core is progressively distilled from a comparison of two or more protein structures. This paper reports a novel web server for "sieving" of protein structures, based on the multiple structural alignment program MUSTANG. METHODOLOGY/PRINCIPAL FINDINGS: "Sieved" models are generated from MUSTANG-generated multiple alignment and superpositions by iteratively filtering out noisy residue-residue correspondences, until the resultant correspondences in the models are optimally "superposable" under a threshold of RMSD. This residue-level sieving is also accompanied by iterative elimination of the poorly fitting structures from the input ensemble. Therefore, by varying the thresholds of RMSD and the cardinality of the ensemble, multiple sieved models are generated for a given multiple alignment and superposition from MUSTANG. To aid the identification of structurally conserved regions of functional importance in an ensemble of protein structures, Lesk-Hubbard graphs are generated, plotting the number of residue correspondences in a superposition as a function of its corresponding RMSD. The conserved "core" (or typically active site shows a linear trend, which becomes exponential as divergent parts of the structure are included into the superposition. CONCLUSIONS: The application addresses two fundamental problems in structural biology: first, the identification of common substructures among structurally related proteins--an important problem in characterization and prediction of function; second, generation of sieved models with demonstrated uses in protein crystallographic structure determination using the technique of Molecular Replacement.

  1. 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

  2. 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.

  3. 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.

  4. Heme oxygenase-1/carbon monoxide: from metabolism to molecular therapy.

    Science.gov (United States)

    Ryter, Stefan W; Choi, Augustine M K

    2009-09-01

    Heme oxygenase-1 (HO-1), a ubiquitous inducible stress-response protein, serves a major metabolic function in heme turnover. HO activity cleaves heme to form biliverdin-IXalpha, carbon monoxide (CO), and iron. Genetic experiments have revealed a central role for HO-1 in tissue homeostasis, protection against oxidative stress, and in the pathogenesis of disease. Four decades of research have witnessed not only progress in elucidating the molecular mechanisms underlying the regulation and function of this illustrious enzyme, but also have opened remarkable translational applications for HO-1 and its reaction products. CO, once regarded as a metabolic waste, can act as an endogenous mediator of cellular signaling and vascular function. Exogenous application of CO by inhalation or pharmacologic delivery can confer cytoprotection in preclinical models of lung/vascular injury and disease, based on anti-apoptotic, anti-inflammatory, and anti-proliferative properties. The bile pigments, biliverdin and bilirubin, end products of heme degradation, have also shown potential as therapeutics in vascular disease based on anti-inflammatory and anti-proliferative activities. Further translational and clinical trials research will unveil whether the HO-1 system or any of its reaction products can be successfully applied as molecular medicine in human disease.

  5. Hydrocarbon Synthesis from Carbon Dioxide and Hydrogen: A Two-Step Process

    Science.gov (United States)

    2013-08-14

    with an immersion cooler (SP Scientific) in a water bath, and the product gas stream was first dried over a bed of 3 Å molecular sieves prior to GC...Commonwealth realm Crown government in the course of their duties. Article Hydrocarbon Synthesis from Carbon Dioxide and Hydrogen: A Two-Step Process...AUG 2013 2. REPORT TYPE 3. DATES COVERED 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Hydrocarbon Synthesis from Carbon Dioxide and Hydrogen: A

  6. Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Peng; Aiona, Paige K.; Li, Ying; Shiraiwa, Manabu; Laskin, Julia; Nizkorodov, Sergey A.; Laskin, Alexander

    2016-11-01

    Emissions from biomass burning are a significant source of brown carbon (BrC) in the atmosphere. In this study, we investigate the molecular composition of freshly-emitted biomass burning organic aerosol (BBOA) samples collected during test burns of selected biomass fuels: sawgrass, peat, ponderosa pine, and black spruce. We characterize individual BrC chromophores present in these samples using high performance liquid chromatography coupled to a photodiode array detector and a high-resolution mass spectrometer. We demonstrate that both the overall BrC absorption and the chemical composition of light-absorbing compounds depend significantly on the type of biomass fuels and burning conditions. Common BrC chromophores in the selected BBOA samples include nitro-aromatics, polycyclic aromatic hydrocarbon derivatives, and polyphenols spanning a wide range of molecular weights, structures, and light absorption properties. A number of biofuel-specific BrC chromophores are observed, indicating that some of them may be used as potential markers of BrC originating from different biomass burning sources. On average, ~50% of the light absorption above 300 nm can be attributed to a limited number of strong BrC chromophores, which may serve as representative light-absorbing species for studying atmospheric processing of BrC aerosol. The absorption coefficients of BBOA are affected by solar photolysis. Specifically, under typical atmospheric conditions, the 300 nm absorbance decays with a half-life of 16 hours. A “molecular corridors” analysis of the BBOA volatility distribution suggests that many BrC compounds in the fresh BBOA have low volatility (<1 g m-1) and will be retained in the particle phase under atmospherically relevant conditions.

  7. 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.

  8. Activated Carbon Composites for Air Separation

    Energy Technology Data Exchange (ETDEWEB)

    Contescu, Cristian I [ORNL; Baker, Frederick S [ORNL; Tsouris, Costas [ORNL; McFarlane, Joanna [ORNL

    2008-03-01

    In continuation of the development of composite materials for air separation based on molecular sieving properties and magnetic fields effects, several molecular sieve materials were tested in a flow system, and the effects of temperature, flow conditions, and magnetic fields were investigated. New carbon materials adsorbents, with and without pre-loaded super-paramagnetic nanoparticles of Fe3O4 were synthesized; all materials were packed in chromatographic type columns which were placed between the poles of a high intensity, water-cooled, magnet (1.5 Tesla). In order to verify the existence of magnetodesorption effect, separation tests were conducted by injecting controlled volumes of air in a flow of inert gas, while the magnetic field was switched on and off. Gas composition downstream the column was analyzed by gas chromatography and by mass spectrometry. Under the conditions employed, the tests confirmed that N2 - O2 separation occurred at various degrees, depending on material's intrinsic properties, temperature and flow rate. The effect of magnetic fields, reported previously for static conditions, was not confirmed in the flow system. The best separation was obtained for zeolite 13X at sub-ambient temperatures. Future directions for the project include evaluation of a combined system, comprising carbon and zeolite molecular sieves, and testing the effect of stronger magnetic fields produced by cryogenic magnets.

  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 equilibria and condensation sequences in carbon rich gases

    Science.gov (United States)

    Sharp, C. M.; Wasserburg, G. J.

    1993-01-01

    Chemical equilibria in stellar atmospheres have been investigated by many authors. Lattimer, Schramm, and Grossman presented calculations in both O rich and C rich environments and predicted possible presolar condensates. A recent paper by Cherchneff and Barker considered a C rich composition with PAH's included in the calculations. However, the condensation sequences of C bearing species have not been investigated in detail. In a carbon rich gas surrounding an AGB star, it is often assumed that graphite (or diamond) condenses out before TiC and SiC. However, Lattimer et al. found some conditions under which TiC condenses before graphite. We have performed molecular equilibrium calculations to establish the stability fields of C(s), TiC(s), and SiC(s) and other high temperature phases under conditions of different pressures and C/O. The preserved presolar interstellar dust grains so far discovered in meteorites are graphite, diamond, SiC, TiC, and possibly Al2O3.

  11. Formation of carbon nanoscrolls from graphene sheet: A molecular dynamics study

    Science.gov (United States)

    Zhang, Danhui; Yang, Houbo

    2016-12-01

    In recent year, carbon nanoscrolls have attracted intensive attention both in theory and experiments for their unique and excellent fundamental properties and the wide range of potential applications. In this paper, the fabrication of carbon nanoscrolls using graphene and carbon nanotubes has been studied by molecular dynamics (MD) method. The formation mechanism of carbon nanoscrolls has been presented convincing explanations. Furthermore, the position and number of carbon nanotubes also influence the formation of carbon nanoscrolls. Our theoretical results will provide researchers a powerful guide and helpful assistance in designing better targeted programs in experiments.

  12. Self-assembly of single-walled carbon nanotubes into multiwalled carbon nanotubes in water: molecular dynamics simulations.

    Science.gov (United States)

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

    2006-03-01

    We report discoveries from a series of molecular dynamics simulations that single-walled carbon nanotubes, with different diameters, lengths, and chiralities, can coaxially self-assemble into multiwalled carbon nanotubes in water via spontaneous insertion of smaller tubes into larger ones. The assembly process is tube-size-dependent, and the driving force is primarily the intertube van der Waals interactions. The simulations also suggest that a multiwalled carbon nanotube may be separated into single-walled carbon nanotubes under appropriate solvent conditions. This study suggests possible bottom-up self-assembly routes for the fabrication of novel nanodevices and systems.

  13. Conditions of Using Mesoporous Molecular Sieves Al-MCM-41 as Catalyst to Synthesize Isoprene Ene Acid Ethyl Ester as Pesticide%利用中孔分子筛Al-MCM-41催化合成农药异戊烯酸乙酯的条件

    Institute of Scientific and Technical Information of China (English)

    唐晓红; 吴崇珍; 梁丽珍; 李成未; 李保军

    2012-01-01

    [方法]利用中孔分子筛A1-MCM-41作催化剂,直接用反应物乙醇作带水剂,以乙醇和异戊烯酸为原料,采用分批补充乙醇的工艺方法合成农药异戊烯酸乙酯.考察了催化剂用量、反应物物质的量比、反应温度和反应时间对反应转化率和选择性的影响.[结果]该反应最佳的合成条件:异戊烯酸和乙醇的物质的量比为1∶8,催化剂的量为异戊烯酸质量的1.8%,反应时间为6h,反应在剧烈回流温度下进行.在此条件下,异戊烯酸转化率可达89.9%,产品纯度大于99.7%.[结论]中孔分子筛Al-MCM-41可作为合成异戊烯酸乙酯高效而环保的固体酸催化剂.%[Methods] The isoprene ene acid ethyl ester was synthesized from isoprene ene acid and ethanol by using mesoporous molecular sieves AI-MCM-41 as catalyst and directly using reactant ethanol as dehydrant. The process methods of replenishing ethanol in batches was used. The factors such as catalyst amount, reactant ratio, reaction temperature and reaction time which affect the conversion and selectivity were investigated. [Results] The experimental result showed that the optimum conditions are as follows: the mole ratio of isoprene ene acid to ethanol is 1:8: the amount of catalyst is 1.8% to isoprene ene acid: the reaction time is 6 h at reflux temperature. The conversion is 89.9% and the purity of the product is above 99.7% under the optimum conditions. [Conclusions] The mesoporous molecular sieves AI-MCM-41 can be used as efficient and environmental solid acid catalyst on the catalytic synthesis of isoprene ene acid ethyl ester.

  14. 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).

  15. 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.

  16. 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.

  17. Nuclear magnetic resonance and molecular modeling study of exocyclic carbon-carbon double bond polarization in benzylidene barbiturates

    Science.gov (United States)

    Figueroa-Villar, J. Daniel; Vieira, Andreia A.

    2013-02-01

    Benzylidene barbiturates are important materials for the synthesis of heterocyclic compounds with potential for the development of new drugs. The reactivity of benzylidene barbiturates is mainly controlled by their exocyclic carbon-carbon double bond. In this work, the exocyclic double bond polarization was estimated experimentally by NMR and correlated with the Hammett σ values of the aromatic ring substituents and the molecular modeling calculated atomic charge difference. It is demonstrated that carbon chemical shift differences and NBO charge differences can be used to predict their reactivity.

  18. Dehydrogenative [2 + 2 + 1] Heteroannulation Using a Methyl Group as a One-Carbon Unit: Access to Pyrazolo[3,4-c]quinolines.

    Science.gov (United States)

    Deng, Guo-Bo; Li, Hai-Bing; Yang, Xu-Heng; Song, Ren-Jie; Hu, Ming; Li, Jin-Heng

    2016-05-06

    A practical and straightforward access to pyrazolo[3,4-c]quinolines by molecular sieve mediated dehydrogenative [2 + 2 + 1] heteroannulation of N-(o-alkenylaryl)imines with aryldiazonium salts is described using a sp(3)-hybrid carbon atom as a one-carbon unit. The reaction enables the formation of three new chemical bonds, a C-C bond and two C-N bonds, in a single reaction and features simple operation and excellent functional group tolerance.

  19. Adsorption of aromatic compounds by carbonaceous adsorbents: a comparative study on granular activated carbon, activated carbon fiber, and carbon nanotubes.

    Science.gov (United States)

    Zhang, Shujuan; Shao, Ting; Kose, H Selcen; Karanfil, Tanju

    2010-08-15

    Adsorption of three aromatic organic compounds (AOCs) by four types of carbonaceous adsorbents [a granular activated carbon (HD4000), an activated carbon fiber (ACF10), two single-walled carbon nanotubes (SWNT, SWNT-HT), and a multiwalled carbon nanotube (MWNT)] with different structural characteristics but similar surface polarities was examined in aqueous solutions. Isotherm results demonstrated the importance of molecular sieving and micropore effects in the adsorption of AOCs by carbonaceous porous adsorbents. In the absence of the molecular sieving effect, a linear relationship was found between the adsorption capacities of AOCs and the surface areas of adsorbents, independent of the type of adsorbent. On the other hand, the pore volume occupancies of the adsorbents followed the order of ACF10 > HD4000 > SWNT > MWNT, indicating that the availability of adsorption site was related to the pore size distributions of the adsorbents. ACF10 and HD4000 with higher microporous volumes exhibited higher adsorption affinities to low molecular weight AOCs than SWNT and MWNT with higher mesopore and macropore volumes. Due to their larger pore sizes, SWNTs and MWNTs are expected to be more efficient in adsorption of large size molecules. Removal of surface oxygen-containing functional groups from the SWNT enhanced adsorption of AOCs.

  20. 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.

  1. 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

  2. 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.

  3. Carbon Nanomembranes

    Science.gov (United States)

    Angelova, Polina; Gölzhäuser, Armin

    2017-03-01

    This chapter describes the formation and properties of one nanometer thick carbon nanomembranes (CNMs), made by electron induced cross-linking of aromatic self-assembled monolayers (SAMs). The cross-linked SAMs are robust enough to be released from the surface and placed on solid support or over holes as free-standing membranes. Annealing at 1000K transforms CNMs into graphene accompanied by a change of mechanical stiffness and electrical resistance. The developed fabrication approach is scalable and provides molecular level control over thickness and homogeneity of the produced CNMs. The mechanisms of electron-induced cross-linking process are discussed in details. A variety of polyaromatic thiols: oligophenyls as well as small and extended condensed polycyclic hydrocarbons have been successfully employed, demonstrating that the structural and functional properties of the resulting nanomembranes are strongly determined by the structure of molecular monolayers. The mechanical properties of CNMs (Young's modulus, tensile strength and prestress) are characterized by bulge testing. The interpretation of the bulge test data relates the Young's modulus to the properties of single molecules and to the structure of the pristine SAMs. The gas transport through the CNM is measured onto polydimethylsiloxane (PDMS) - thin film composite membrane. The established relationship of permeance and molecular size determines the molecular sieving mechanism of permeation through this ultrathin sheet.

  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. The Fate of Molecular Markers in Soils and Their Implications for Soil Carbon Cycling

    Science.gov (United States)

    Wiesenberg, G. L.

    2014-12-01

    During the past decades molecular markers were discovered to be of diagnostic character for tracing the origin and fate of organic matter in soils. Molecular proxies themselves and their combination with compound-specific isotope analyses became powerful tools to distinguish between various biogenic and anthropogenic sources of organic matter and to trace carbon turnover at a molecular level. In the meantime various field and laboratory experiments provided deeper insight into soil organic matter dynamics at a molecular scale. We learnt from these experiments that carbon turnover at a molecular scale occurs in a similar time frame like for bulk soil organic matter and that selective preservation is not an issue for most coumpounds in active soils, but e.g. in fossil soils. Nevertheless, e.g. plant wax-derived alkanes and root-derived suberin markers point to a slower turnover of specific compounds. Recently, molecular markers enabled deciphering root-derived processes that occur in the rhizosphere of living and dead roots within the soil or even in the deep subsoil (up to several meters below the soil surface). Thus, the proposed carbon sequestration by roots in subsoils is not necessarily relevant in the long-term on a decadal or centennial scale. Although molecular markers were not determined to be valuable tools to sequester carbon in the soil, they strongly help elucidating processes relevant for cycling of bulk organic matter from the soil surface towards the deep subsoil.

  6. 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.

  7. Effect of molecular weight on the electrophoretic deposition of carbon black nanoparticles in moderately viscous systems.

    Science.gov (United States)

    Modi, Satyam; Panwar, Artee; Mead, Joey L; Barry, Carol M F

    2013-08-06

    Electrophoretic deposition from viscous media has the potential to produce in-mold assembly of nanoparticles onto three-dimensional parts in high-rate, polymer melt-based processes like injection molding. The effects of the media's molecular weight on deposition behavior were investigated using a model system of carbon black and polystyrene in tetrahydrofuran. Increases in molecular weight reduced the electrophoretic deposition of the carbon black particles due to increases in suspension viscosity and preferential adsorption of the longer polystyrene chains on the carbon black particles. At low deposition times (≤5 s), only carbon black deposited onto the electrodes, but the deposition decreased with increasing molecular weight and the resultant increases in suspension viscosity. For longer deposition times, polystyrene codeposited with the carbon black, with the amount of polystyrene increasing with molecular weight and decreasing with greater charge on the polystyrene molecules. This deposition behavior suggests that use of lower molecular polymers and control of electrical properties will permit electrophoretic deposition of nanoparticles from polymer melts for high-rate, one-step fabrication of nano-optical devices, biochemical sensors, and nanoelectronics.

  8. Molecular Modeling and Adsorption Properties of Ordered Silica-Templated CMK Mesoporous Carbons.

    Science.gov (United States)

    Jain, Surendra Kumar; Pellenq, Roland J-M; Gubbins, Keith E; Peng, Xuan

    2017-03-07

    Realistic molecular models of silica-templated CMK-1, CMK-3, and CMK-5 carbon materials have been developed by using carbon rods and carbon pipes that were obtained by adsorbing carbon in a model MCM-41 pore. The interactions between the carbon atoms with the silica matrix were described using the PN-Traz potential, and the interaction between the carbon atoms was calculated by the reactive empirical bond order (REBO) potential. Carbon rods and pipes with different thicknesses were obtained by changing the silica-carbon interaction strength, the temperature, and the chemical potential of carbon vapor adsorption. These equilibrium structures were further used to obtain the atomic models of CMK-1, CMK-3, and CMK-5 materials using the same symmetry as found in TEM pictures. These models are further refined and made more realistic by adding interconnections between the carbon rods and carbon pipes. We calculated the geometric pore size distribution of the different models of CMK-5 and found that the presence of interconnections results in some new features in the pore size distribution. Argon adsorption properties were investigated using GCMC simulations to characterize these materials at 77 K. We found that the presence of interconnection results greatly improves the agreement with available experimental data by shifting the capillary condensation to lower pressures. Adding interconnections also induces smoother adsorption/condensation isotherms, and desorption/evaporation curves show a sharp jump. These features reflex the complexity of the nanovoids in CMKs in terms of their pore morphology and topology.

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

    Energy Technology Data Exchange (ETDEWEB)

    Costuas, Karine, E-mail: kcostuas@univ-rennes1.fr [Sciences chimiques de Rennes, UMR 6226 CNRS - Université de Rennes 1, Avenue du Général Leclerc F-35042 Rennes (France)

    2015-01-22

    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.

  10. 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.

  11. Very-high-strength (60-GPa) carbon nanotube fiber design based on molecular dynamics simulations

    Science.gov (United States)

    Cornwell, Charles F.; Welch, Charles R.

    2011-05-01

    The mechanical properties of carbon nanotubes such as low density, high stiffness, and exceptional strength make them ideal candidates for reinforcement material in a wide range of high-performance composites. Molecular dynamics simulations are used to predict the tensile response of fibers composed of aligned carbon nanotubes with intermolecular bonds of interstitial carbon atoms. The effects of bond density and carbon nanotube length distribution on fiber strength and stiffness are investigated. The interstitial carbon bonds significantly increase load transfer between the carbon nanotubes over that obtained with van der Waals forces. The simulation results indicate that fibers with tensile strengths to 60 GPa could be produced by employing interstitial cross-link atoms. The elastic modulus of the fibers is also increased by the bonds.

  12. 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.

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

    NARCIS (Netherlands)

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

    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

  14. 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.

  15. The synthesis of Co-doped SAPO-5 molecular sieve and its performance in the oxidation of cyclohexane with molecular oxygen%Co掺杂SAPO-5分子筛制备及其催化氧气氧化环己烷反应性能

    Institute of Scientific and Technical Information of China (English)

    校准; 詹望成; 郭耘; 郭杨龙; 龚学庆; 卢冠忠

    2016-01-01

    的稳定性.本文以传统均相Co盐催化剂的多相化为出发点,制备了Co掺杂SAPO-5与分子筛催化剂(Co-SAPO-5),考察了Co掺杂量对催化剂结构、表面性质以及氧气选择性氧化环己烷反应性能的影响.结果表明,一部分Co进入分子筛骨架,同时有少量Co以氧化钴形式高度分散在SAPO-5表面. Co掺杂对SAOP-5催化剂比表面积没有显著影响,但可使其孔体积减小.相反, Co掺杂可以提高SAOP-5分子筛表面B酸性位数量和总酸量.活性测试结果表明,环己烷转化率随着Co-SAPO-5催化剂中Co含量的增加而增加,但KA油选择性在转化率高于6.3%时急剧下降.还考察了反应温度、反应时间、初始氧气压力和催化剂用量对Co-SAPO-5分子筛催化剂性能的影响,得到了最优反应条件.以Co-SAPO-5-0.2(Co/Si摩尔比为0.2)分子筛为催化剂时, KA油总收率最高可达7.8%.另外, Co-SAPO-5催化剂在环己烷氧化反应中显示出很好的稳定性, Co-SAPO-5-0.2催化剂套用6次后活性几乎没有变化.%Silicoaluminophosphate (SAPO) molecular sieves doped with cobalt (Co‐SAPO‐5) were synthesized hydrothermally with different concentrations of Co. Each sample was characterized by X‐ray dif‐fraction, N2 adsorption‐desorption, scanning electron microscopy, ultraviolet‐visible spectroscopy, temperature‐programmed desorption of NH3 (NH3‐TPD), and infrared spectrascopy of adsorbed pyridine (Py‐IR). The results showed that Co was highly dispersed in the Co‐SAPO‐5 samples. In addition, a part of the Co content had been incorporated into the SAPO‐5 framework, while the remainder existed on the surface as extra‐framework Co. The surface areas of the Co‐SAOP‐5 sam‐ples were similar to the SAPO‐5 sample. However, the pore volumes of the Co‐SAOP‐5 samples were lower than that of the SAOP‐5 sample. As the concentration of Co increased, the pore volume gradu‐ally decreased

  16. Synthesis, Characterization and Catalytic Activity of Cu-Zn-Al-MCM-41 Mesoporous Molecular Sieves%Cu-Zn-Al-MCM-41介孔分子筛的合成、表征及催化性能研究

    Institute of Scientific and Technical Information of China (English)

    杨蓓玉; 顾剑江; 赵峰; 姚娟; 菅盘铭

    2013-01-01

    The catalysts of different copper content Cu-Zn-Al-MCM-41 mesoporous molecular sieves were synthesized by hydrothermal method with cetyltrimethylammonium bromide (CTAB) as template, sodium silicate as silicon source and copper nitrate, zinc sulfate, aluminium nitrate as metal source. The catalysts were characterized by XRD, TEM, FT-IR, UV-vis and BET, respectively, and their catalytic abilities were investigated by CO hydrogenation. The results show that the Cu-Zn-Al-MCM-41 mesoporous molecular sieves have uniform hexagonal mesoporous structure and uniform pore distribution with average pore diameter of about 2.5 nm. The metal ions are incorporated into the framework of MCM-41. With the increase of copper content the pore diameter of MCM-41 is increased while the surface area is decreased. The catalysts have hydrogenation and dehydration bifunctional catalytic ability. The hydrogenation of CO over the catalysts can yield 2-butanol with 2-propanol as the solvent and during the hydrogenation the catalytic activity of the catalyst is good. The conversion of CO is increased with increasing copper content of the catalyst. The conversion of CO is 89%under the condition of using the catalyst with nSi:nCu:nZn:nAl=40:4:1:1, reaction temperature=493 K and reaction time=4 h.%采用水热合成法,以十六烷基三甲基溴化铵(CTAB)为模板剂,硅酸钠为硅源,硝酸铜、硫酸锌、硝酸铝为金属源,合成了不同铜含量的Cu-Zn-Al-MCM-41介孔分子筛。利用XRD、TEM、FT-IR、UV-vis和BET技术手段对合成样品进行表征,并考察其对CO加氢反应的催化性能。结果表明,合成的Cu-Zn-Al-MCM-41介孔分子筛具有典型的六方介孔结构,孔径均一,平均直径在2.5 nm左右,且金属离子进入分子筛骨架结构中。随着铜含量的增加,孔径增大而比表面积降低。该催化剂具有加氢脱水双功能催化作用,在异丙醇存在下,对CO加氢反应生成仲

  17. Ionized carbon in side-illuminated molecular clouds

    Science.gov (United States)

    Boreiko, R. T.; Betz, A. L.; Zmuidzinas, J.

    1990-01-01

    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.

  18. Carbon Nanotube Based Molecular Electronics and Motors: A View from Classical and Quantum Dynamics Simulations

    Science.gov (United States)

    Srivastava, Deepak; Saini, Subhash (Technical Monitor)

    1998-01-01

    The tubular forms of fullerenes popularly known as carbon nanotubes are experimentally produced as single-, multiwall, and rope configurations. The nanotubes and nanoropes have shown to exhibit unusual mechanical and electronic properties. The single wall nanotubes exhibit both semiconducting and metallic behavior. In short undefected lengths they are the known strongest fibers which are unbreakable even when bent in half. Grown in ropes their tensile strength is approximately 100 times greater than steel at only one sixth the weight. Employing large scale classical and quantum molecular dynamics simulations we will explore the use of carbon nanotubes and carbon nanotube junctions in 2-, 3-, and 4-point molecular electronic device components, dynamic strength characterization for compressive, bending and torsional strains, and chemical functionalization for possible use in a nanoscale molecular motor. The above is an unclassified material produced for non-competitive basic research in the nanotechnology area.

  19. 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.

  20. N-doped carbon networks: alternative materials tracing new routes for activating molecular hydrogen.

    Science.gov (United States)

    Cortese, Remedios; Ferrante, Francesco; Roggan, Stefan; Duca, Dario

    2015-02-23

    The fragmentation of molecular hydrogen on N-doped carbon networks was investigated by using molecular (polyaromatic macrocycles) as well as truncated and periodic (carbon nanotubes) models. The computational study was focused on the ergonicity analysis of the reaction and on the properties of the transition states involved when constellations of three or four pyridinic nitrogen atom defects are present in the carbon network. Calculations show that whenever N-defects are embedded in species characterized by large conjugated π-systems, either in polyaromatic macrocycles or carbon nanotubes, the corresponding H2 bond cleavage is largely exergonic. The fragmentation Gibbs free energy is affected by the final arrangement of the hydrogen atoms on the defect and by the extension of the π-electron cloud, but it is not influenced by the curvature of the system.

  1. Preparation of ZnO/Co-MCM-41 Molecular Sieves and Their Catalytic Performance for Isoamyl Alcohol Oxidation%Co掺杂ZnO/MCM-41分子筛的制备及对异戊醇的催化氧化性能

    Institute of Scientific and Technical Information of China (English)

    高虎飞; 赵彬侠; 刘卫娟; 刘林学; 叶维; 高晗; 章毅; 张小里

    2013-01-01

    以Co掺杂的介孔分子筛MCM-41为载体,采用等体积浸渍法制备了系列5% ZnO/xCo-MCM-41催化剂,并用于催化分子氧氧化异戊醇合成异戊醛的反应.通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、紫外-可见漫反射光谱(UV-Vis DRS)、扫描电子显微镜(SEM)、氨气程序升温脱附(NH3-TPD)、氢气程序升温还原(H2-TPR)和氮气吸附-脱附等手段对样品进行表征,并考察了Co掺杂量对分子筛结构和催化性能的影响.结果表明,随着Co掺杂量的增大,样品的比表面积和孔体积均减小,而其平均孔径呈先增大后减小的趋势.当Co掺杂量为0.05时,5% ZnO/O.05Co-MCM-41仍保持了MCM-41高度有序的六方介孔结构,具有高比表面积(989 m2/g)、较大孔径(2.88 nm)和孔体积(0.88 cm3/g),引入的Co主要以孤立态钴离子[Single-site Co(Ⅱ)]形式存在于MCM-41骨架,MCM-41骨架中的Co可以有效提高ZnO微粒的分散度,适度降低5% ZnO/MCM-41的表面酸性,并大幅度提高5%ZnO/MCM-41的氧化还原性.与5% ZnO/MCM-41相比,5% ZnO/O.05Co-MCM-41可使异戊醛的选择性提高28.3%.%Co-doped MCM-41 supported catalysts 5%ZnO/xCo-MCM-41 were prepared by impregnation method,and applied in the synthesis of isovaleric aldehyde from isoamyl alcohol with dioxygen.The samples were characterized via X-ray diffraction (XRD),fourier transform-infrared spectroscopy (FTIR),ultravioletvisible diffuse reflectance spectroscopy (UV-Vis DRS),scanning electron microscopy (SEM),NH3 temperature programmed desorption (NH3-TPD),H2 temperature programmed reduction(H2-TPR) and N2 adsorptiondesorption.The effects of Co-doping amount on the structure and catalytic performance of molecular sieves were investigated.The results showed that the specific area and pore volume of samples decreased gradually with the increase of Co-doping amount,while median pore diameter first increased and then decreased.5%ZnO/Co-MCM-41 molecular sieves still remained

  2. Dust around AFGL 2688, molecular shielding, and the production of carbon chain molecules

    Science.gov (United States)

    Jura, M.; Kroto, H.

    1990-01-01

    The molecular, IR, and optical maps of the evolved carbon star AFGL 2688 (the 'Egg' Nebula) are all consistent with a model of a bipolar outflow of approximately 0.0001 solar masses/yr that stopped as this object evolved beyond the asymptotic giant branch about 200 years ago. In order to explain the extended HC7N emission around this star, it is proposed that carbon grains are collisionally fragmented as they supersonically steam through the circumstellar envelope.

  3. 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.

  4. 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...

  5. Molecular carbon isotopic evidence for the origin of geothermal hydrocarbons

    Science.gov (United States)

    Des Marais, D. J.; Donchin, J. H.; Nehring, N. L.; Truesdell, A. H.

    1981-01-01

    Isotopic measurements of individual geothermal hydrocarbons that are, as a group, of higher molecular weight than methane are reported. It is believed in light of this data that the principal source of hydrocarbons in four geothermal areas in western North America is the thermal decomposition of sedimentary or groundwater organic matter.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Intelligent Prediction of Sieving Efficiency in Vibrating Screens

    Directory of Open Access Journals (Sweden)

    Bin Zhang

    2016-01-01

    Full Text Available In order to effectively predict the sieving efficiency of a vibrating screen, experiments to investigate the sieving efficiency were carried out. Relation between sieving efficiency and other working parameters in a vibrating screen such as mesh aperture size, screen length, inclination angle, vibration amplitude, and vibration frequency was analyzed. Based on the experiments, least square support vector machine (LS-SVM was established to predict the sieving efficiency, and adaptive genetic algorithm and cross-validation algorithm were used to optimize the parameters in LS-SVM. By the examination of testing points, the prediction performance of least square support vector machine is better than that of the existing formula and neural network, and its average relative error is only 4.2%.

  11. 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...

  12. 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...

  13. 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

  14. 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

  15. Structural and chemical evolution of single-wall carbon nanotubes under atomic and molecular deuterium interaction

    NARCIS (Netherlands)

    Lisowski, W.; Keim, E.G.; Berg, van den A.H.J.; Smithers, M.A.

    2005-01-01

    The interaction of atomic (D) and molecular (D2) deuterium, as present in a (D + D2) gas mixture, with single-wall carbon nanotubes (SWNTs) has been studied by means of a combination of scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The SWNT samp

  16. Modeling of the Electro-Mechanical Response of Carbon Nanotubes: Molecular Dynamics and Transport Calculations

    Science.gov (United States)

    Svizhenko, Alexel; Anantram, M. P.; Maiti, Amitesh

    2003-01-01

    This paper presents viewgraphs on the modeling of the electromechanical response of carbon nanotubes, utilizing molecular dynamics and transport calculations. The topics include: 1) Simulations of the experiment; 2) Effect of diameter, length and temperature; and 3) Study of sp3 coordination-"The Table experiment".

  17. Carbon Monoxide Depletion in Orion B Molecular Cloud Cores

    CERN Document Server

    Savva, D; Phillips, R R; Gibb, A G

    2003-01-01

    We have observed several cloud cores in the Orion B (L1630) molecular cloud in the 2-1 transitions of C18O, C17O and 13C18O. We use these data to show that a model where the cores consist of very optically thick C18O clumps cannot explain their relative intensities. There is strong evidence that the C18O is not very optically thick. The CO emission is compared to previous observations of dust continuum emission to deduce apparent molecular abundances. The abundance values depend somewhat on the temperature but relative to `normal abundance' values, the CO appears to be depleted by about a factor of 10 at the core positions. CO condensation on dust grains provides a natural explanation for the apparent depletion both through gas-phase depletion of CO, and through a possible increase in dust emissivity in the cores. The high brightness of HCO+ relative to CO is then naturally accounted for by time-dependent interstellar chemistry starting from `evolved' initial conditions. Theoretical work has shown that conden...

  18. Sieve likelihood ratio inference on general parameter space

    Institute of Scientific and Technical Information of China (English)

    SHEN Xiaotong; SHI Jian

    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.

  19. Molecular and biochemical characterization of carbonic anhydrases of Paracoccidioides

    Directory of Open Access Journals (Sweden)

    Mariana Vieira Tomazett

    Full Text Available 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.

  20. 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).

  1. 气体透过碳膜的非平衡动力学模拟研究%Non-equilibrium Molecular Dynamics Simulation on Pure Gas Permeability Through Carbon Membranes

    Institute of Scientific and Technical Information of China (English)

    王淑梅; 于养信; 高光华

    2006-01-01

    The permeation of various pure gas (H2, He, Ne, CH4 and Ar) through carbon membranes is investigated using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit pore is employed instead of the one-dimensional pore. Compared with the experiments, simulation results show that the improvement of pore model is very necessary. The effects of membrane thickness, pore width and temperature on gas permeance and ideal separation factor are also discussed. Results show that gas permeates through membrane according to Knudsen diffusion in large pore, while Knudsen diffusion is accompanied by molecular sieving in small pore. Moreover, methane is easily adsorbed on the membrane surface due to strong attractive interactions of membrane and shows higher permeance than that of Knudsen flow. In addition, it is noted that when membrane thickness is thin enough the permeance of gas does not decrease with the increase of membrane thickness due to the strong adsorption until membrane resistance becomes dominant.

  2. 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.

  3. 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.

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

    Science.gov (United States)

    Liu, Yangyang; Wilcox, Jennifer

    2013-01-02

    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).

  5. 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.

  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. 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.

  8. 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.

  9. 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.

  10. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huan [Department of Nuclear Science & Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing (China); Tang, Xiaobin, E-mail: tangxiaobin@nuaa.edu.cn [Department of Nuclear Science & Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing (China); Jiangsu Key Laboratory of Nuclear Energy Equipment Materials Engineering, Nanjing (China); Chen, Feida; Huang, Hai; Liu, Jian [Department of Nuclear Science & Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing (China); Chen, Da [Department of Nuclear Science & Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing (China); Jiangsu Key Laboratory of Nuclear Energy Equipment Materials Engineering, Nanjing (China)

    2016-07-01

    Highlights: • Various incident sites of CNTs are classified into three types for the first time. • Different ion energies and fluences are considered to study the radiation damage. • CNTs have ability to heal the radiation-induced damage at higher temperature. • Stability of a large-diameter tube excels in a slim one under the same conditions. - Abstract: 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. 全自动固相萃取分子筛脱水气质联用法测定水中有机磷农药残留%Using Automated Solid Phase Extraction and Molecular Sieve Dehydration Coupled with Gas Chromatography/Mass Spectrometry

    Institute of Scientific and Technical Information of China (English)

    秦明友

    2015-01-01

    院建立了气相色谱质谱联用法测定水中有机磷农药残留的方法,样品用全自动固相萃取分子筛脱水进行预处理,对固相萃取盘的类型进行了比选,试验了萃取盘的穿透性,优化了萃取条件,用丙酮和甲基叔丁基醚(MTBE)作萃取剂,用DVB萃取盘进行萃取。方法相关系数(r2)为0.9930~0.9991,检出限为0.000006~0.000018 mg/L,方法用于饮用水、工业废水和生污水中有机磷农药的测定,对高、中、低浓度的样品进行加标回收测定(n=6),精密度为2.7%~16.7%,平均加标回收率为71.7%~101.2%。方法具有良好精密度、准确度和灵敏度,前处理方法简单快速,环境友好。%Automated solid phase extraction and molecular sieve dehydration coupled with gas chromatog-raphy/mass spectrometry (GC/MS) was used to determine the residues of organophosphorous pesticides in water samples.The extraction disk penetrating was tested and the extraction condition was optimized. Using acetone and methyl tert-butyl ether (MTBE)as the eluen and DVB disk as the extraction disk, the pro-posed method has been successfully applied for the determination of organophosphorous pesticides residues in drinking water, industrial wastewater and raw sewage with satisfactory results for its sensitivity, precision and repeatability. The average recoveries were between 71.7%-101.2% with RSD of 2.7%-16.7%(n=6). The limits of detection was between 0.000006~0.000018 mg/L.

  12. A cytosolic carbonic anhydrase molecular switch occurs in the gills of metamorphic sea lamprey

    Science.gov (United States)

    Ferreira-Martins, D.; McCormick, Stephen; Campos, A.; Lopes-Marques, M.; Osorio, H.; Coimbra, J.; Castro, L.F.C.; Wilson, Jonthan M

    2016-01-01

    Carbonic anhydrase plays a key role in CO2 transport, acid-base and ion regulation and metabolic processes in vertebrates. While several carbonic anhydrase isoforms have been identified in numerous vertebrate species, basal lineages such as the cyclostomes have remained largely unexamined. Here we investigate the repertoire of cytoplasmic carbonic anhydrases in the sea lamprey (Petromyzon marinus), that has a complex life history marked by a dramatic metamorphosis from a benthic filter-feeding ammocoete larvae into a parasitic juvenile which migrates from freshwater to seawater. We have identified a novel carbonic anhydrase gene (ca19) beyond the single carbonic anhydrase gene (ca18) that was known previously. Phylogenetic analysis and synteny studies suggest that both carbonic anhydrase genes form one or two independent gene lineages and are most likely duplicates retained uniquely in cyclostomes. Quantitative PCR of ca19 and ca18 and protein expression in gill across metamorphosis show that the ca19 levels are highest in ammocoetes and decrease during metamorphosis while ca18 shows the opposite pattern with the highest levels in post-metamorphic juveniles. We propose that a unique molecular switch occurs during lamprey metamorphosis resulting in distinct gill carbonic anhydrases reflecting the contrasting life modes and habitats of these life-history stages.

  13. 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.

    2015-01-01

    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.

  14. 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.

  15. Leaf carbon assimilation and molecular phylogeny in Cattleya species (Orchidaceae).

    Science.gov (United States)

    Andrade-Souza, V; Almeida, A-A F; Corrêa, R X; Costa, M A; Mielke, M S; Gomes, F P

    2009-08-11

    We examined leaf CO(2) assimilation and how it varied among species within the orchid genus Cattleya. Measurements of CO(2) assimilation and maximum quantum yield of PS II (Fv/Fm) were made for mature leaves of nine species using a portable system for photosynthesis measurement and a portable fluorometer. Leaf area was measured with an area meter, and the specific leaf mass was determined. DNA of nine Cattleya species and two species of Hadrolaelia was extracted using the CTAB protocol. Each sample was amplified and sequenced using primers for the trnL gene. The phylogenetic analyses, using neighbor-joining and maximum parsimony methods, retrieved a group that included Cattleya and Hadrolaelia species, in which the unifoliate species were separated from the bifoliates. The topologies of the two cladograms showed some similarities. However, C. guttata (bifoliate) was placed in the unifoliate clade in the neighbor-joining tree, while C. warneri (unifoliate) was not placed in this clade in the maximum parsimony tree. Most Cattleya species keep the leaf stomata closed from 6 am to 4 pm. We suggest that C. elongata, C. tigrina and C. tenuis have C(3)-crassulacean acid metabolism since they open their stomata around 12 am. The Fv/Fm values remained relatively constant during the measurements of CO(2) assimilation. The same was observed for the specific leaf mass values, although great variations were found in the leaf area values. When the species were grouped using molecular data in the neighbor-joining analysis, no relation was observed with CO(2) assimilation.

  16. Phase equilibria in carbon dioxide expanded solvents: Experiments and molecular simulations.

    Science.gov (United States)

    Houndonougbo, Yao; Jin, Hong; Rajagopalan, Bhuma; Wong, Kean; Kuczera, Krzysztof; Subramaniam, Bala; Laird, Brian

    2006-07-06

    We present complementary molecular simulations and experimental results of phase equilibria for carbon dioxide expanded acetonitrile, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. The volume expansion measurements were done using a high-pressure Jerguson view cell. Molecular simulations were performed using the Gibbs ensemble Monte Carlo method. Calculations in the canonical ensemble (NVT) were performed to determine the coexistence curve of the pure solvent systems. Binary mixtures were simulated in the isobaric-isothermal distribution (NPT). Predictions of vapor-liquid equilibria of the pure components agree well with experimental data. The simulations accurately reproduced experimental data on saturated liquid and vapor densities for carbon dioxide, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. In all carbon dioxide expanded liquids (CXL's) studied, the molecular simulation results for the volume expansion of these binary mixtures were found to be as good as, and in many cases superior to, predictions based on the Peng-Robinson equation of state, demonstrating the utility of molecular simulation in the prediction of CXL phase equilibria.

  17. The effect of molecular mobility on electronic transport in carbon nanotube-polymer composites and networks

    Energy Technology Data Exchange (ETDEWEB)

    Shenogin, Sergei, E-mail: sergei.shenogin.ctr.ru@us.af.mil [Air Force Research Laboratory, Materials and Manufacturing Directorate, 2941 Hobson Way, Wright-Patterson Air Force Base, Ohio 45433 (United States); University of Dayton Research Institute, 300 College Park, Dayton, Ohio 45469 (United States); Lee, Jonghoon [Air Force Research Laboratory, Materials and Manufacturing Directorate, 2941 Hobson Way, Wright-Patterson Air Force Base, Ohio 45433 (United States); UTC, Inc., 1270 N Fairfield Rd, Dayton, Ohio 45432 (United States); Voevodin, Andrey A.; Roy, Ajit K. [Air Force Research Laboratory, Materials and Manufacturing Directorate, 2941 Hobson Way, Wright-Patterson Air Force Base, Ohio 45433 (United States)

    2014-12-21

    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.

  18. 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...

  19. Investigations on the antiretroviral activity of carbon nanotubes using computational molecular approach.

    Science.gov (United States)

    Krishnaraj, R Navanietha; Chandran, Saravanan; Pal, Parimal; Berchmans, Sheela

    2014-01-01

    Carbon nanotubes are the interesting class of materials with wide range of applications. They have excellent physical, chemical and electrical properties. Numerous reports were made on the antiviral activities of carbon nanotubes. However the mechanism of antiviral action is still in infancy. Herein we report, our recent novel findings on the molecular interactions of carbon nanotubes with the three key target proteins of HIV using computational chemistry approach. Armchair, chiral and zigzag CNTs were modeled and used as ligands for the interaction studies. The structure of the key proteins involved in HIV mediated infection namely HIV- Vpr, Nef and Gag proteins were collected from the PDB database. The docking studies were performed to quantify the interaction of the CNT with the three different disease targets. Results showed that the carbon nanotubes had high binding affinity to these proteins which confirms the antagonistic molecular interaction of carbon nanotubes to the disease targets. The modeled armchair carbon nanotubes had the binding affinities of -12.4 Kcal/mole, -20 Kcal/mole and -11.7 Kcal/mole with the Vpr, Nef and Gag proteins of HIV. Chiral CNTs also had the maximum affinity of -16.4 Kcal/mole to Nef. The binding affinity of chiral CNTs to Vpr and Gag was found to be -10.9 Kcal/mole and -10.3 Kcal/mole respectively. The zigzag CNTs had the binding affinity of -11.1 Kcal/mole with Vpr, -18.3 Kcal/mole with Nef and -10.9 with Gag respectively. The strong molecular interactions suggest the efficacy of CNTs for targeting the HIV mediated retroviral infections.

  20. 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.