Sample records for include catalysts polymerization

  1. Ring opening metathesis polymerization catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, R.H.; Johnson, L.K.; Novak, B.M.; Hillmyer, M.; Benedicto, A.; France, M.; Nguyen, S.T. [California Institute of Technology, Pasadena, CA (United States)


    Over the past eight years, a number of new catalysts for the ring opening metathesis polymerization of cyclic olefins have been developed. These catalysts are simple organometallic complexes containing metal carbon multiple bonds that in most cases polymerize olefins by a living process. These catalysts have been used to prepare a family of near monodispersed and structurally homogeneous polymers, a series of telechelic polymers with controlled molecular weight and functionality and triblock polymers with segments with potentially interesting electronic properties. A series of new group VIII catalysts are being developed that allow a wide range of functionality to be incorporated into the polymer side chains. The same catalysts can also be used in the synthesis of fine chemicals.

  2. Hafnium metallocene catalyst for the polymerization of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Ewen, J.A.


    A catalyst is described for the polymerization and copolymerization of olefins comprising a an alumoxane and chiral, stereorigid hafnium metallocene catalyst. It includes a cyclopentadienyl ring and germanium, silicon, phosphorus, nitrogen, boron, and aluminum radicals.

  3. Developments of Chiral Metallocenes as Polymerization Catalysts

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    Takeshi Shiono


    Full Text Available This review article describes developments in chiral metallocenes as polymerization catalysts focusing on C2 symmetric ansa-zirconocene complexes. Selective synthesis of rac-isomers of ansa-zirconocenes are surveyed. Isospecific polymerizations of propylene catalyzed by chiral zirconocenes are summarized. Advanced series of polymerizations by chiral metallocenes such as asymmetric polymerization and polymerization of polar monomers are also introduced.

  4. Polymerization catalyst, production and use

    International Nuclear Information System (INIS)

    Best, S.A.


    A process is described for polymerization of ethylene and alpha-olefins having from 1 to 20 carbon atoms or mixtures of ethylene, alpha-olefins and diolefins. The process comprises polymerizing one or more olefins in the presence of the catalyst system comprising (a) an organoaluminum cocatalyst, and (b) a vanadium containing a catalyst component obtained by treating an inert solid support material in an inert solvent with (i) an organoaluminum compound represented by the formula R/sub m/AIX/sub 3-m/, wherein R represents an alkyl group, cycloalkyl group or aryl group having from 1 to 18 carbon atoms, X represents halogen atoms, and 1≤m≤3, (ii) an acyl halide, and (iii) a vanadium compound. Another process is identified wherein the inert solid support material is an inorganic oxide or mixtures of inorganic oxides. Also a process wherein the inorganic oxide is silica is described

  5. Polymerization catalyst, production and use

    International Nuclear Information System (INIS)

    Best, S.A.


    A process is described for the polymerization of ethylene and alpha-olefins having from 1 to 2 carbon atoms of mixtures of ethylene, alpha-olefins or diolefins. The process comprises polymerizing one or more olefins in the presence of the catalyst system comprising (A) an organo aluminum cocatalyst, and (B) a vanadium-containing catalyst component obtained by sequentially treating an inert solid support material in an inert solvent with (i) a dihydrocarbyl magnesium compound, (ii) optionally an oxygen-containing compound which is an alcohol, ketone or aldehyde, (iii) a vanadium compound, and (iv) a Group IIIa metal halide. The process as above is described wherein the inert solid support material is an inorganic oxide or mixtures of inorganic oxides

  6. Stereospecific olefin polymerization with chiral metallocene catalysts


    Brintzinger, Hans-Herbert; Fischer, David; Mülhaupt, Rolf; Rieger, Bernhard; Waymouth, Robert M.


    Current studies on novel, metallocenebased catalysts for the polymerization of α-olefins have far-reaching implications for the development of new materials as well as for the understanding of basic reaction mechanisms responsible for the growth of a polymer chain at a catalyst center and the control of its stereoregularity. In contrast to heterogeneous Ziegler–Natta catalysts, polymerization by a homogeneous, metallocene-based catalyst occurs principally at a single type of metal center with...

  7. Olefin polymerization over supported chromium oxide catalysts

    NARCIS (Netherlands)

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


    Cr/SiO2 or Phillips-type catalysts are nowadays responsible for a large fraction of all polyethylene (HDPE and LLDPE) worldwide produced. In this review, several key-properties of Cr/SiO2 catalysts will be discussed in relation to their polymerization characteristics. It will be shown how the

  8. Catalyst support structure, catalyst including the structure, reactor including a catalyst, and methods of forming same (United States)

    Van Norman, Staci A.; Aston, Victoria J.; Weimer, Alan W.


    Structures, catalysts, and reactors suitable for use for a variety of applications, including gas-to-liquid and coal-to-liquid processes and methods of forming the structures, catalysts, and reactors are disclosed. The catalyst material can be deposited onto an inner wall of a microtubular reactor and/or onto porous tungsten support structures using atomic layer deposition techniques.

  9. Supported organometallic catalysts for hydrogenation and Olefin Polymerization (United States)

    Marks, Tobin J.; Ahn, Hongsang


    Novel heterogeneous catalysts for the which hydrogenation of olefins and arenes with high conversion rates under ambient conditions and the polymerization of olefins have been developed. The catalysts are synthesized from Ziegler-type precatalysts by supporting them on sulfate-modified zirconia.

  10. Polymerization of ethylene in blocks with catalyst mixture

    International Nuclear Information System (INIS)

    Martins, Roberto S.; Souyza, Giuliana C.; Pereira, Juliano R.T.; Marques, Maria de Fatima V.


    Mixture of two catalysts in one reactor for ethylene/α-olefin copolymerization results in the combination of properties of both catalysts, and thus the synthesis of a novel polymer microstructure characterized by sequences of monomers produced with each catalyst. Adding a reversible transfer agent (CSA) to the binary system enables the production of new block copolymers with enhanced properties. Late transition metal catalysts, such as α-diimine nickel catalyst when activated with MAO show high activity towards olefin polymerization. This paper describes the syntheses of PE with amorphous and crystalline blocks using a binary mixture containing a nickel catalyst with α-diimine ligand which produces highly branched polyethylene (soft PE) and a metallocene (rac-ethylenebis(H 4 -indenyl)ZrCl 2 ) that converts ethylene into polyethylene with high activities and melting temperatures (hard PE). The influence of polymerization temperature and CSA concentration were investigated. The polymeric materials were characterized by density, thermal properties and X-ray diffractometry. (author)

  11. Polymerization of Ethylene Using α-Diimine Nickel Catalyst

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    Hassan Arabi1


    Full Text Available The late transition metal catalysts based on end group of transition metals in the periodic table like Ni, Fe, Co, Pd, Pt were developed rapidly in polyolefin industrial productions. These metals with suitable ligands exhibited specific properties and appropriate activities in the production of polyolefins. These catalysts based on bulky bisimine ligands usually depend on the structures of the ligands and the ortho group position on the aryl ligands show very interesting behaviors in olefin polymerization. When these groups, located in the ortho positions of aryl ligands, become larger, it would have lesser chance in leading to β hydrogen elimination reactions. The ligand 1,4-bis (2,6-diisopropyl phenyl acenaphthene was synthesized by reaction of 2,6- diisopropyl aniline and acenaphthene quinone. The synthesized ligand was then added on nickel (II dibromide salt that produced the 1,4-bis(2,6-diisopropyl phenyl acenaphthene nickel (II dibromide catalyst. The structure of the catalyst was fully characterized by IR, NMR techniques. Ethylene polymerization was performed using the prepared catalyst and the effects of parameters such as, polymerization temperature, cocatalyst, to catalyst molar ratio and monomer pressure, were investigated. One of experimental design methods (Box Behnken was used to minimize the number of tests. The highest activity of catalyst [1420 kgPE/molNih] was obtained at monomer pressure 5 atm, [Al]:[Ni] = 1000 and polymerization temperature of 25°C. Some of the produced polymers were characterized by DSC and 13CNMR. The branched structures with higher methyl branch contents were observed in some polyethylene products.

  12. Sterically shielded diboron-containing metallocene olefin polymerization catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Marks, T.J.; Ja, L.; Yang, X.


    A non-coordinating anion, preferably containing a sterically shielded diboron hydride, if combined with a cyclopenta-dienyl-substituted metallocene cation component, such as a zirconocene metallocene, is a useful olefin polymerization catalyst component. The anion preferably has the formula as shown in the accompanying diagram where R is branched lower alkyl, such as t-butyl.

  13. Sterically shielded diboron-containing metallocene olefin polymerization catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Marks, Tobin J. (Evanston, IL); Ja, Li (Chicago, IL); Yang, Xinmin (Evanston, IL)


    A non-coordinating anion, preferably containing a sterically shielded diboron hydride, if combined with a cyclopenta-dienyl-substituted metallocene cation component, such as a zirconocene metallocene, is a useful olefin polymerization catalyst component. The anion preferably has the formula ##STR1## where R is branched lower alkyl, such as t-butyl.

  14. Metallocene complexes as homogeneous catalysts in olefin polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Alt, H.G. [Universitaet Bayreuth (Germany)


    Ansa metallocene dichloride complexes of titanium, zirconium, and hafnium can be activated by methyl aluminoxane (MAO) to give excellent catalysts for the homogeneous polymerization of ethylene and propylene. The symmetry of the corresponding metallocene dichloride complexes is essential for the stereospecific polymerization of propylene (isotactic, syndiotactic or atactic). The application of fluorenyl groups instead of cyclopentadienyl groups greatly increases the activity of the catalysts. The first ansa bis(fluorenyl) complexes of zirconium and hafnium, (C{sub 13}H{sub 8}-C{sub 2}H{sub 4}-C{sub 13}H{sub 8})MCl{sub 2} (M = Zr, Hf), have been prepared. It was found that after the activation by MAO the zirconium derivative demonstrates a very high activity. Several models are presented in order to discuss the mechanism of the polymerization.

  15. Indium Catalysts for Ring Opening Polymerization: Exploring the Importance of Catalyst Aggregation. (United States)

    Osten, Kimberly M; Mehrkhodavandi, Parisa


    Inexorably, the environmental persistence and damage caused by polyolefins have become major drawbacks to their continued long-term use. Global shifts in thinking from fossil-fuel to renewable biobased resources have urged researchers to focus their attention on substituting fossil-fuel based polymers with renewable and biodegradable alternatives on an industrial scale. The recent development of biodegradable polyesters from ring opening polymerization (ROP) of bioderived cyclic ester monomers has emerged as a promising new avenue toward this goal. Ever increasing numbers of metal-based initiators have been reported in the literature for the controlled ROP of cyclic esters, in particular for the polymerization of lactide to produce poly(lactic acid) (PLA). PLA has several material weaknesses, which hinder its use as a replacement for commodity plastics. Despite many advances in developing highly active and controlled catalysts for lactide polymerization, no single catalyst system has emerged to replace industrially used catalysts and provide access to PLA materials with improved properties. We reported the first example of indium(III) for the ring opening polymerization of lactide. Since then, indium(III) has emerged as a useful Lewis acid in initiators for the controlled polymerization of lactide and other cyclic esters. In particular, we have developed a large family of chiral dinuclear indium complexes bearing tridentate diaminophenolate ligands and tetradentate salen and salan ligands. Complexes within our tridentate ligand family are highly active initiators for the moderately isoselective living and immortal polymerization of rac-lactide, as well as other cyclic esters. We have shown that subtle steric effects influence aggregation in these systems, with polymerization typically proceeding through a dinuclear propagating species. In addition, profound effects on polymerization activities have been observed for central tertiary versus secondary amine donors in

  16. Amphiphilic self-assembled polymeric copper catalyst to parts per million levels: click chemistry. (United States)

    Yamada, Yoichi M A; Sarkar, Shaheen M; Uozumi, Yasuhiro


    Self-assembly of copper sulfate and a poly(imidazole-acrylamide) amphiphile provided a highly active, reusable, globular, solid-phase catalyst for click chemistry. The self-assembled polymeric Cu catalyst was readily prepared from poly(N-isopropylacrylamide-co-N-vinylimidazole) and CuSO(4) via coordinative convolution. The surface of the catalyst was covered with globular particles tens of nanometers in diameter, and those sheetlike composites were layered to build an aggregated structure. Moreover, the imidazole units in the polymeric ligand coordinate to CuSO(4) to give a self-assembled, layered, polymeric copper complex. The insoluble amphiphilic polymeric imidazole Cu catalyst with even 4.5-45 mol ppm drove the Huisgen 1,3-dipolar cycloaddition of a variety of alkynes and organic azides, including the three-component cyclization of a variety of alkynes, organic halides, and sodium azide. The catalytic turnover number and frequency were up to 209000 and 6740 h(-1), respectively. The catalyst was readily reused without loss of catalytic activity to give the corresponding triazoles quantitatively.

  17. Metal content determination in polymerization catalysts by direct methods

    International Nuclear Information System (INIS)

    Bichinho, K.M.; Pires, Gilvan P.; Stedile, F.C.; Santos, J.H.Z. dos


    Metal contents in polymerization catalysts were comparatively determined by Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF) spectroscopy. Catalysts were prepared by grafting metallocene onto bare silica or onto silica chemically modified with methylaluminoxane (MAO). Catalysts were compressed as self-supporting pellets (RBS and XRF), or mounted on adhesive copper tape (XPS). The proximity of the mass of the atomic nuclei did not allow resolution by RBS of the signals corresponding to Zr and Nb, nor Si and Al in catalyst systems such as (nBuCp) 2 ZrCl 2 /Cp 2 NbCl 2 /MAO/SiO 2 . On the other hand, Zr, Nb, Si and Al lines were completely resolved in an XRF spectrum. For supported metallocenes on bare silica, XPS measurement was ca. 40% higher than that obtained by RBS. Silica-supported zirconocene showed good agreement in Zr content determination by XRF and RBS

  18. Sixtieth Anniversary of Ziegler-Natta Catalysts and Stereospecific Polymerization

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    Janović Z.


    Full Text Available This review article highlights the history of the discoveries of organometallic catalysts and stereospecific polymerization of α-olefins, dienes and a number of vinyl monomers by Karl Ziegler and Giulio Natta sixty years ago, their developments and recent progress. As one of the most important achievements in the field of catalysis, macromolecular science and polymer materials, their inventors were awarded the Nobel Prize in Chemistry in 1963 “for their discoveries in the field of chemistry and technology of high polymers”. These discoveries have stimulated an intensive, both basic and applied research all over the world, up to the present times, leading to great development of the polymer industry. The important biographical data and scientific advancements of K. Ziegler and G. Natta are presented as well. Karl Ziegler, a German scientist, Director of Max Planck Institute for Coal Research in Mülheim, besides many scientific achievements, in 1953 discovered a new process for the polymerization of ethylene into linear polyethylene under mild conditions by using titanium chloride and alkyl aluminium catalytic system that was superior to all existing polymerization. Giulio Natta, an Italian scientist, Director of the Department of Industrial Chemistry at Polytechnic, University of Milan, besides many achievements in petrochemical processes, in 1954 obtained for the first time isotactic polypropylene and Montecatini Co. started its production already in 1958. He conducted pioneering studies on the chain microstructure of synthetic organic polymers and postulated the mechanisms of stereospecific polymerizations. Since the discovery of the Zeigler-Natta catalyst, stereospecific polymerization and processes, significant developments have occurred. The breakthrough in polymerization processes such as fluid bed, liquid phase loop reactor and reactor granule technology led to significant development and growth of polyolefin production. In the 1980s

  19. Enantioselective Epoxide Polymerization Using a Bimetallic Cobalt Catalyst

    KAUST Repository

    Thomas, Renee M.


    A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (kfast/kslow) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T m values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides. © 2010 American Chemical Society.

  20. Phenolate constrained geometry polymerization catalyst and method for preparing (United States)

    Marks, T.J.; Chen, Y.X.


    The subject invention involves a method of preparing and the constrained geometry catalyst thereby prepared of the general formula Ar{prime}R4(O)Ar{double_prime}R{prime}{sub 4}M(CH{sub 2}Ph){sub 2} where Ar{prime} is a phenyl or naphthyl group; Ar{double_prime} is a cyclopentadienyl or indenyl group, R and R{prime} are H or alkyl substituents (C{<=}10) and M is Ti, Zr or Hf. The synthetic method involves a simple alkane elimination approach which permits a ``one-pot`` procedure. The catalyst, when combined with a cocatalyst such as Pb{sub 3}C{sup +}B(Ar{sub 3}{sup F}){sub 4}BAr{sub 3}{sup F} or methyl alumoxane where Ar{sup F} is a fluoroaryl group, is an effective catalyst for the polymerization of {alpha}-olefins such as ethylene, propylene and styrene. 1 fig.

  1. Neutral nickel ethylene oligo- and polymerization catalysts: towards computational catalyst prediction and design. (United States)

    Heyndrickx, Wouter; Occhipinti, Giovanni; Jensen, Vidar R


    DFT calculations have been used to elucidate the chain termination mechanisms for neutral nickel ethylene oligo- and polymerization catalysts and to rationalize the kind of oligomers and polymers produced by each catalyst. The catalysts studied are the (κ(2)-O,O)-coordinated (1,1,1,5,5,5-hexafluoro-2,4-acetylacetonato)nickel catalyst I, the (κ(2)-P,O)-coordinated SHOP-type nickel catalyst II, the (κ(2)-N,O)-coordinated anilinotropone and salicylaldiminato nickel catalysts III and IV, respectively, and the (κ(2)-P,N)-coordinated phosphinosulfonamide nickel catalyst V. Numerous termination pathways involving β-H elimination and β-H transfer steps have been investigated, and the most probable routes identified. Despite the complexity and multitude of the possible termination pathways, the information most critical to chain termination is contained in only few transition states. In addition, by consideration of the propagation pathway, we have been able to estimate chain lengths and discriminate between oligo- and polymerization catalysts. In agreement with experiment, we found the Gibbs free energy difference between the overall barrier for the most facile propagation and termination pathways to be close to 0 kcal mol(-1) for the ethylene oligomerization catalysts I and V, whereas values of at least 7 kcal mol(-1) in favor of propagation were determined for the polymerization catalysts III and IV. Because of the shared intermediates between the termination and branching pathways, we have been able to identify the preferred cis/trans regiochemistry of β-H elimination and show that a pronounced difference in σ donation of the two bridgehead atoms of the bidentate ligand can suppress hydride formation and thus branching. The degree of rationalization obtained here from a handful of key intermediates and transition states is promising for the use of computational methods in the screening and prediction of new catalysts of the title class. © 2014 WILEY


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    Full Text Available This article presents results of a study on coating of a polymeric substrate ca-talyst on metallic surface. Stability of coating on metallic surfaces is a proper specification. Sol-gel technology was used to synthesize adhesion promoters of polysilane compounds that act as a mediator. The intermediate layer was coated by synthesized sulfonated polystyrene-divinylbenzene as a catalyst for production of MTBE in catalytic distillation process. Swelling of catalyst and its separation from the metal surface was improved by i increasing the quantity of divinylbenzene in the resin’s production process and ii applying adhesion pro¬moters based on the sol-gel process. The rate of ethyl silicate hydrolysis was intensified by increasing the concentration of utilized acid while the conden¬sation polymerization was enhanced in the presence of OH–. Sol was formed at pH 2, while the pH should be 8 for the formation of gel. By setting the ratio of the initial concentrations of water to ethyl silicate to 8, the gel formation time was minimized.

  3. Olefin polymerization from single site catalysts confined within porous media (United States)

    Kasi, Rajeswari M.

    Single Site Catalysts (SSCs) have been utilized for olefin polymerization. Altering the metal-ligand architecture in the SSCs, polyolefin properties can be enhanced in a rational manner. This influence of the ligands in the SSC on the property of polyolefins prepared can be referred to as the primary ligand influence. Extending this understanding and subsequent control of the metal-ligand framework to the interaction of SSCs within organic and inorganic supports is vital for the synthesis of polyolefins with tailored properties. The motivation behind this thesis was to explore the support influence on the reactivity of the SSC tethered to a support matrix during ethylene homo and copolymerization. In order to address this question of the support influence on the final polyolefin properties, synthetic routes to covalently bind SSCs on different matrices have been explored. Two distinct supported SSCs have been used to prepare branched polyethylenes. Branched polyethylenes can be prepared by either copolymerization (ethylene and alpha-olefin) or oligomerization/copolymerization processes (ethylene and in situ generated alpha-olefin). Synthetic routes to prepare precursor catalysts to Constrained Geometry Catalysts (CGCs) by silyl elimination chemistry have been developed (Chapter 2). Efficient synthetic protocols to assemble CGCs on aminomethylpolysytrene matrices (Chapter 3) and amine-functionalized mesoporous silica (Chapter 4) are also reported. These supported catalysts, with appropriate cocatalysts have been used to prepare ethylene homo and copolymers, the polymer thermal properties and microstructures were analyzed by various analytical techniques. Branched polyethylenes (LLDPE) can be prepared by copolymerization chemistry. It has been observed is that the influence of the support is seen in the production of lower crystalline forms of high density polyethylene (HDPE, 20--50% crystalline), while homogeneous polymerization of analogous soluble CGCs afford HDPE

  4. Chemical oxidative polymerization of m-phenylenediamine and its derivatives using aluminium triflate as a co-catalyst


    Amer, Ismael; Young, Desmond Austin; Vosloo, Hermanus C.M.


    Aromatic diamine monomers, including m-phenylenediamine (mPD), 2-methyl-m-phenylenediamine (2Me-mPD), 4-methyl-m-phenylenediamine (4Me-mPD) and trimethyl-mphenylenediamine (tMe-mPD), were polymerized by chemical oxidation using ammonium persulfate as an oxidant. Aluminium triflate (Al(OTf)3) was also used for the first time as a co-catalyst under various polymerization conditions. The polymerization yield was improved when Al(OTf)3 was introduced to the polymerization reaction ...

  5. Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

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    Kohei Koyanagi


    Full Text Available Supramolecular catalysts have received a great deal of attention because they improve the selectivity and efficiency of reactions. Catalysts with host molecules exhibit specific reaction properties and recognize substrates via host–guest interactions. Here, we examined radical polymerization reactions with a chain transfer agent (CTA that has α-cyclodextrin (α-CD as a host molecule (α-CD-CTA. Prior to the polymerization of N,N-dimethylacrylamide (DMA, we investigated the complex formation of α-CD with DMA. Single X-ray analysis demonstrated that α-CD includes DMA inside its cavity. When DMA was polymerized in the presence of α-CD-CTA using 2,2'-azobis[2-(2-imidazolin-2-ylpropane dihydrochloride (VA-044 as an initiator in an aqueous solution, poly(DMA was obtained in good yield and with narrow molecular weight distribution. In contrast, the polymerization of DMA without α-CD-CTA produced more widely distributed polymers. In the presence of 1,6-hexanediol (C6 diol which works as a competitive molecule by being included in the α-CD cavity, the reaction yield was lower than that without C6 diol.

  6. The Oxidation of Sulfur-Containing Compounds Using Heterogeneous Catalysts of Transition Metal Oxides Deposited on the Polymeric Matrix (United States)

    Dinh Vu, Ngo; Dinh Bui, Nhi; Thi Minh, Thao; Thi Thanh Dam, Huong; Thi Tran, Hang


    We investigate the activity of heterogeneous catalysts of transition metal oxides deposited on the polymeric matrix in the oxidation of sulfur-containing compounds. It is shown that MnO2-10/CuO-10 has the highest catalytic activity. The physicomechanical properties of polymeric heterogeneous catalysts of transition-metal oxides, including the specific surface area, elongation at break and breaking strength, specific electrical resistance, and volume resistivity were studied by using an Inspekt mini 3 kN universal tensile machine in accordance with TCVN 4509:2006 at a temperature of 20 ± 2°C. Results show that heterogeneous polymeric catalysts were stable under severe reaction conditions. Scanning electron microscopy, and energy-dispersive analysis are used to study the surfaces of the catalysts. Microstructural characterization of the catalysts is performed by using x-ray computed tomography. We demonstrate the potential application of polymeric heterogeneous catalysts of transition-metal oxides in industrial wastewater treatment.

  7. Supported Catalysts Useful in Ring-Closing Metathesis, Cross Metathesis, and Ring-Opening Metathesis Polymerization

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    Jakkrit Suriboot


    Full Text Available Ruthenium and molybdenum catalysts are widely used in synthesis of both small molecules and macromolecules. While major developments have led to new increasingly active catalysts that have high functional group compatibility and stereoselectivity, catalyst/product separation, catalyst recycling, and/or catalyst residue/product separation remain an issue in some applications of these catalysts. This review highlights some of the history of efforts to address these problems, first discussing the problem in the context of reactions like ring-closing metathesis and cross metathesis catalysis used in the synthesis of low molecular weight compounds. It then discusses in more detail progress in dealing with these issues in ring opening metathesis polymerization chemistry. Such approaches depend on a biphasic solid/liquid or liquid separation and can use either always biphasic or sometimes biphasic systems and approaches to this problem using insoluble inorganic supports, insoluble crosslinked polymeric organic supports, soluble polymeric supports, ionic liquids and fluorous phases are discussed.

  8. Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts (United States)

    Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol


    A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 -C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 -C.sub.20 hydrocarbyl, SiR".sub.3, NR".sub.2, OR", SR", GeR".sub.3, SnR".sub.3, and C.dbd.C containing groups (R".dbd.C.sub.1 -C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

  9. Electronic effects in Ziegler-Natta polymerization of propylene and ethylene using soluble metallocene catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ik-Mo; Gauthier, W.J.; Ball, J.M.; Iyengar, B.; Collins, S. [Univ. of Waterloo, Ontario (Canada)


    ({eta}{sup 5}-5,6-X{sub 2}C{sub 9}H{sub 5}){sub 2}ZrCl{sub 2} catalysts (4a, X = H; 4b, X = CH{sub 3}; 4d, X = OCH{sub 3}; 4e, X = Cl) were investigated as catalysts for the polymerization of ethylene. In addition, polymerization of propylene and ethylene was studied by using corresponding racemic, ethylene-bridged analogues (5a, X = H; 5b, X = CH{sub 3}; 5d, X = OCH{sub 3}). Both the bridged and non-bridged catalysts were effective as catalysts for both ethylene and propylene polymerization, but the molecular weights were generally lower with the ethylene-bridged catalyst. 19 refs., 3 tabs.

  10. From small molecules to polymeric catalysts in the oscillatory carbonylation reaction: multiple effects of adding HI. (United States)

    Isakova, Anna; Murdoch, Billy J; Novakovic, Katarina


    The oscillatory palladium-catalysed carbonylation reaction opens new horizons for applications in smart materials due to the versatility of its conditions and substrates, as well as the adjustability of amplitude and period of pH oscillations. A variety of viable substrates have been demonstrated, including polymeric alkyne-terminated substrates. However, so far, there have not been any reports of polymer-based palladium catalysts in oscillatory mode. In this paper, we demonstrate pH oscillations in various systems, using commercially available palladium acetate, a triphenylphosphine palladium acetate complex and a polymer-bound palladium catalyst. While palladium acetate was able to generate oscillations under the conditions already established in our previous research on PdI2-catalysed oscillators, the other two catalysts needed the addition of HI to induce oscillations. HI forced an initial pH drop, bringing pH into the range where oscillations generally occur. Addition of HI had a significant effect on all catalysts, modifying the amplitude and period of oscillations, oscillation mode, as well as starting material conversion and product distribution.

  11. Statistical modeling for Toluene Diisocyanate and Polypropylene Glycol Polymerization with Ferric Acetylacetonate as Catalyst

    International Nuclear Information System (INIS)

    Semsarzadeh, M. A.; Salehi, H.


    Polyurethane elastomer was synthesized with propylene glycol and toluene diisocyanate with ferric acetylacetonate catalyst. This polymerization was modeled using the kinetic equations. The number and weight average degrees of polymerization (DP w and DP n ), the number and weight average molecular weights (M w and M n ) and the polydispersity index parameters were found and tested as function of time and conversion and they were finally compared with GPC laboratory and experimental results. The effect of concentration of the catalyst and the addition sequence of starting materials and catalyst on M n , M w , DPI and M z /M n are reported and discussed

  12. A systematic computational study of electronic effects on hydrogen sensitivity of olefin polymerization catalysts (abstract only)

    International Nuclear Information System (INIS)

    Coussens, Betty B; Budzelaar, Peter H M; Friederichs, Nic


    One of the important product parameters of polyolefins is their molecular weight (distribution). A common way to control this parameter is to add molecular hydrogen during the polymerization, which then acts as a chain transfer agent. The factors governing the hydrogen sensitivity of olefin polymerization catalysts are poorly understood and have attracted little attention from computational chemists. To explore the electronic factors determining hydrogen sensitivity we performed density functional calculations on a wide range of simple model systems including some metallocenes and a few basic models of heterogeneous catalysts. As a quantitative measure for hydrogen sensitivity we used the ratio of (i) the rate constant for chain transfer to hydrogen to (ii) the rate constant for ethene insertion, k h /k p (see the scheme below), and as a measure of electrophilicity we used the energy of complexation to the probe molecule ammonia. For isolated species in the gas phase, complexation energies appear to dominate the chemistry. Ethene complexes more strongly than hydrogen and with increasing electrophilicity of the metal centre this difference grows; the hydrogen sensitivity decreases accordingly. Although many factors (like catalyst dormancy and deactivation issues) complicate the comparison with experiment, this result seems to agree both in broad terms with the experimental lower hydrogen sensitivity of heterogeneous catalysts, and more specifically with the increased hydrogen sensitivity of highly alkylated or fused metallocenes. The opposite conclusion reached by Blom (see Blom et al 2002 Macromol. Chem. Phys. 203 381-7) is due to the use of a very different measure of electrophilicity, rather than to different experimental data

  13. Crystal structures and stereospecific propylene polymerizations with chiral hafnium metallocene catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ewen, J.A.; Haspeslagh, L.; Atwood, J.L.; Zhang, H.


    Ligand effects on stereoregulation with homogeneous catalysts have been stimulated considerable interest in Ziegler-Natta propylene polymerizations with metallocene catalysts. The major limitations to development in this area have been that the titanium catalysts are unstable at conventional polymerization temperatures, and that the zirconium analogues only produce low molecular weight oligomers in significant quantities. In this contribution, the authors describe the structures and the polymerization behavior of both rac-ethylenebis(indenyl)hafnium(IV) dichloride (rac-Et(Ind)/sub 2/HfCl/sub 2/) and rac-ethylenebis(4,5,6,7-tetrahydro-1-indenyl)hafnium(IV) dichloride (rac-Et-(IndH/sub 4/)/sub 2/HfCl/sub 2/). The results are compared to those with Ti and Zr analogues. The new Hf catalysts are the first metallocenes to provide high yields of high molecular weight isotactic polypropylene.

  14. Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization. (United States)

    Li, Kuo-Tseng; Wu, Ling-Huey


    Supported olefin polymerization catalysts can prevent reactor-fouling problems and produce uniform polymer particles. Constrained geometry complexes (CGCs) have less sterically hindered active sites than bis-cyclopentadienyl metallocene catalysts. In the literature, micrometer-sized silica particles were used for supporting CGC catalysts, which might have strong mass transfer limitations. This study aims to improve the activity of supported CGC catalysts by using nanometer-sized silica. Ti[(C₅Me₄)SiMe₂(N t Bu)]Cl₂, a "constrained-geometry" titanium catalyst, was supported on MAO-treated silicas (nano-sized and micro-sized) by an impregnation method. Ethylene homo-polymerization and co-polymerization with 1-octene were carried out in a temperature range of 80-120 °C using toluene as the solvent. Catalysts prepared and polymers produced were characterized. For both catalysts and for both reactions, the maximum activities occurred at 100 °C, which is significantly higher than that (60 °C) reported before for supported bis-cyclopentadienyl metallocene catalysts containing zirconium, and is lower than that (≥140 °C) used for unsupported Ti[(C₅Me₄)SiMe₂(N t Bu)]Me₂ catalyst. Activities of nano-sized catalyst were 2.6 and 1.6 times those of micro-sized catalyst for homopolymerization and copolymerization, respectively. The former produced polymers with higher crystallinity and melting point than the latter. In addition, copolymer produced with nanosized catalyst contained more 1-octene than that produced with microsized catalyst.

  15. Polymeric heterogeneous catalysts of transition-metal oxides: surface characterization, physicomechanical properties, and catalytic activity. (United States)

    Nhi, Bui Dinh; Akhmadullin, Renat Maratovich; Akhmadullina, Alfiya Garipovna; Samuilov, Yakov Dmitrievich; Aghajanian, Svetlana Ivanova


    We investigate the physicomechanical properties of polymeric heterogeneous catalysts of transition-metal oxides, specifically, the specific surface area, elongation at break, breaking strength, specific electrical resistance, and volume resistivity. Digital microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive analysis are used to study the surfaces of the catalysts. The experimental results show that polymeric heterogeneous catalysts of transition-metal oxides exhibit high stability and can maintain their catalytic activity under extreme reaction conditions for long-term use. The oxidation mechanism of sulfur-containing compounds in the presence of polymeric heterogeneous catalysts of transition-metal oxides is confirmed. Microstructural characterization of the catalysts is performed by using X-ray computed tomography. The activity of various catalysts in the oxidation of sulfur-containing compounds is determined. We demonstrate the potential application of polymeric heterogeneous catalysts of transition-metal oxides in industrial wastewater treatment. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Logic-Controlled Radical Polymerization with Heat and Light: Multiple-Stimuli Switching of Polymer Chain Growth via a Recyclable, Thermally Responsive Gel Photoredox Catalyst. (United States)

    Chen, Mao; Deng, Shihong; Gu, Yuwei; Lin, Jun; MacLeod, Michelle J; Johnson, Jeremiah A


    Strategies for switching polymerizations between "ON" and "OFF" states offer new possibilities for materials design and fabrication. While switching of controlled radical polymerization has been achieve using light, applied voltage, allosteric effects, chemical reagents, pH, and mechanical force, it is still challenging to introduce multiple external switches using the same catalyst to achieve logic gating of controlled polymerization reactions. Herein, we report an easy-to-synthesize thermally responsive organo-/hydro-gel that features covalently bound 10-phenylphenothiazine (PTH). With this "Gel-PTH", we demonstrate switching of controlled radical polymerization reactions using temperature "LOW"/"HIGH", light "ON"/"OFF", and catalyst presence "IN"/"OUT". Various iniferters/initiators and a wide range of monomers including acrylates, methacrylates, acrylamides, vinyl esters, and vinyl amides were polymerized by RAFT/iniferter and ATRP methods using Gel-PTH and a readily available compact fluorescent light (CFL) source. In all cases, polymer molar masses increased linearly with conversion, and narrow molar mass distributions were obtained. To further highlight the utility of Gel-PTH, we achieved "AND" gating of controlled radical polymerization wherein various combinations of three stimuli were required to induce polymer chain growth. Finally, block copolymer synthesis and catalyst recycling were demonstrated. Logic-controlled polymerization with Gel-PTH offers a straightforward approach to achieve multiplexed external switching of polymer chain growth using a single catalyst without the need for addition of exogenous reagents.

  17. Neodymium Catalyst for the Polymerization of Dienes and Polar Vinyl Monomers. (United States)

    Kularatne, Ruvanthi N; Yang, Annie; Nguyen, Hien Q; McCandless, Gregory T; Stefan, Mihaela C


    Ziegler-Natta catalysts have played a major role in industry for the polymerization of dienes and vinyl monomers. However, due to the deactivation of the catalyst, this system fails to polymerize polar vinyl monomers such as vinyl acetate, methyl methacrylate, and methyl acrylate. Herein, a catalytic system composed of NdCl 3 ⋅3TEP/TIBA is reported, which promotes a quasi-living polymerization of dienes and is also active for the homopolymerization of polar vinyl monomers. Additionally, this catalytic system generates polymyrcene-b-polyisoprene and poly(myrcene)-b-poly(methyl methacrylate) diblock copolymers by sequential monomer addition. To encourage the replacement of petroleum-based polymers by environmentally benign biobased polymers, polymerization of β-myrcene is demonstrated with a catalytic activity of ≈106 kg polymer mol Nd -1 h -1 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Mesoporous Molecular Sieves Based Catalysts for Olefin Metathesis and Metathesis Polymerization (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.

  19. Ring Opening Metathesis Polymerization of Cyclopentene Using a Ruthenium Catalyst Confined by a Branched Polymer Architecture

    KAUST Repository

    Mugemana, Clement


    Multi-arm polystyrene stars functionalized with Grubbs-type catalysts in their cores were synthesized and used for the ring-opening metathesis polymerization (ROMP) of cyclopentene. The spatial confinement of the catalytic sites and the nanoscale phase separation between polystyrene and the growing polypentenamer chains lead to a dramatic inhibition of the ROMP termination and chain transfer steps. Consequently, cyclopentene polymerizations proceeded fast and with a high degree of conversion even in air. The Grubbs second generation catalyst was oxidatively inactivated under the same conditions. In contrast to conventional small-molecule catalysts, the ultimate degree of conversion of cyclopentene monomer and the polydispersity of the product polypentenamer are not affected by the temperature. This indicates that spatial confinement of the catalyst resulted in a significant change in the activation parameters for the alkene metathesis ring-opening.

  20. Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: A mechanistic study

    KAUST Repository

    Ahmed, Syud M.


    The enantioselective polymerization of propylene oxide (PO) using biaryl-linked bimetallic salen Co catalysts was investigated experimentally and theoretically. Five key aspects of this catalytic system were examined: (1) the structural features of the catalyst, (2) the regio- and stereoselectivity of the chain-growth step, (3) the probable oxidation and electronic state of Co during the polymerization, (4) the role of the cocatalyst, and (5) the mechanism of monomer enchainment. Several important insights were revealed. First, density functional theory (DFT) calculations provided detailed structural information regarding the regio- and stereoselective chain-growth step. Specifically, the absolute stereochemistry of the binaphthol linker determines the enantiomer preference in the polymerization, and the interaction between the salen ligand and the growing polymer chain is a fundamental aspect of enantioselectivity. Second, a new bimetallic catalyst with a conformationally flexible biphenol linker was synthesized and found to enantioselectively polymerize PO, though with lower enantioselectivity than the binaphthol linked catalysts. Third, DFT calculations revealed that the active form of the catalyst has two active exo anionic ligands (chloride or carboxylate) and an endo polymer alkoxide which can ring-open an adjacent cobalt-coordinated epoxide. Fourth, calculations showed that initiation is favored by an endo chloride ligand, while propagation is favored by the presence of two exo carboxylate ligands. © 2013 American Chemical Society.

  1. Neutral bimetallic transition metal phenoxyiminato catalysts and related polymerization methods (United States)

    Marks, Tobin J [Evanston, IL; Rodriguez, Brandon A [Evanston, IL; Delferro, Massimiliano [Chicago, IL


    A catalyst composition comprising a neutral bimetallic diphenoxydiiminate complex of group 10 metals or Ni, Pd or Pt is disclosed. The compositions can be used for the preparation of homo- and co-polymers of olefinic monomer compounds.

  2. Synthesis of oxide-supported vanadium catalysts and their activity in ethylene polymerization

    International Nuclear Information System (INIS)

    Czaja, K.; Korach, L.; Bialek, M.


    The activity of oxide supported vanadium-based catalyst system (VOCl 3 /Et 2 AlCl) in low-pressure ethylene polymerization and the properties of the resulting polyethylenes were studied in relation to the type and mode of modification of the oxide support. Alumina and silica and an unconventional silica-type material prepared by sol-gel process were used as supports. Results are compared with those obtained earlier with a catalyst supported on MgCl 2 (THF) 2 . Of the oxides studied, the silica-type sol-gel material dehydrated and subsequently modified with Et 2 AlCl proved to be the best carrier for the vanadium catalyst. The polyethylene prepared by using this catalyst support was found to exhibit good morphology, especially as compared with the polymer prepared over the more active Mg-V-Al catalyst. (author)

  3. A novel polymeric catalyst for the one-pot synthesis of 2,4,5-triaryl ...

    Indian Academy of Sciences (India)

    Abstract. An efficient synthesis of 2,4,5-trisubstituted imidazoles is achieved by three component cyclo- condensation of benzil or benzoin, aldehyde and ammonium acetate by using novel polymeric catalyst. [poly(AMPS-co-AA)] under solvent-free conditions. The key advantages of this process are high yields, shorter.

  4. Rh-mediated carbene polymerization: from multistep catalyst activation to alcohol-mediated chain-transfer

    NARCIS (Netherlands)

    Walters, A.J.C.; Jellema, E.; Finger, M.; Aarnoutse, P.; Smits, J.M.M.; Reek, J.N.H.; de Bruin, B.


    Rh-mediated polymerization of carbenes gives access to new highly substituted and stereoregular polymers. While this reaction is of interest for the synthesis of syndiotactic polymers that are functionalized at every carbon atom of the polymer backbone, the catalyst activation, chain-initiation, and

  5. Neutral nickel oligo- and polymerization catalysts: the importance of alkyl phosphine intermediates in chain termination. (United States)

    Heyndrickx, Wouter; Occhipinti, Giovanni; Minenkov, Yury; Jensen, Vidar R


    An unconventional chain termination reaction has been explored for the SHOP (Shell higher olefin process)-type, anilinotropone, and salicylaldiminato nickel-based oligo- and polymerization catalysts by using density functional theory (DFT). Starting from the tetracoordinate alkyl phosphine complex, the termination reaction was found to involve a rearrangement of the alkyl chain to form a pentacoordinate β-agostic complex, β-hydride elimination, and olefinic chain dissociation and to compete with propagation at sufficiently high phosphine concentration and/or basicity. It provides the first complete and convincing mechanistic rationale for the decreasing chain lengths observed upon increasing phosphine concentration and basicity. The unconventional reaction was found to be a major termination pathway for the SHOP-type catalyst and is very unlikely to lead to branching and olefin isomerization, which is critical for explaining why the SHOP catalyst, in contrast to the anilinotropone and salicylaldiminato catalysts, tends to lead to the oligomerization of ethylene to form linear α-olefins. Based on our results we have proposed a new and extended catalytic cycle for the SHOP-type ethylene oligomerization catalyst. Finally, the importance of the new termination reaction for the SHOP-type catalyst suggests that this reaction may also operate with other ethylene oligomerization nickel catalysts. This prediction was confirmed for a pyrazolonatophosphine catalyst, for which the new termination route was found to be even more facile, which explains the short oligomers produced by this catalyst. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Discovery and Development of Pyridine-bis(imine) and Related Catalysts for Olefin Polymerization and Oligomerization. (United States)

    Small, Brooke L


    For over 40 years following the polyolefin catalyst discoveries of Hogan and Banks (Phillips) and Ziegler (Max Planck Institute), chemists traversed the periodic table searching for new transition metal and lanthanide-based olefin polymerization systems. Remarkably, none of these "hits" employed iron, that is, until three groups independently reported iron catalysts for olefin polymerization in the late 1990's. The history surrounding the discovery of these catalysts was only the beginning of their uniqueness, as the ensuing years have proven these systems remarkable in several regards. Of primary importance are the pyridine-bis(imine) ligands (herein referred to as PDI), which produced iron catalysts that are among the world's most active for ethylene polymerization, demonstrated "staying power" despite over 15 years of ligand improvement efforts, and generated highly active polymerization systems with cobalt, chromium, and vanadium. Although many ligands have been employed in iron-catalyzed polymerization, the PDI family has thus far provided the most information about iron's capabilities and tendencies. For example, iron systems tend to be highly selective for ethylene over higher olefins, making them strong candidates for producing highly crystalline polyethylene, or highly linear α-olefins. Iron PDI polymerizes propylene with 2,1-regiochemistry via a predominantly isotactic, chain end control mechanism. Because the first insertion proceeds via 1,2-regiochemistry, iron (and cobalt) PDI systems can be tailored to make highly linear dimers of α-olefins by "head-to-head" coupling, resulting from a switch in regiochemistry after the first insertion. Finally, PDI ligands, while not being surpassed in activity, have inspired the development of related ligand families and complexes, such as pendant donor diimines (PDD), which are also highly efficient at producing linear α-olefins. This Account will detail a variety of oligomerization and polymerization results

  7. Exploring electronic and steric effects on the insertion and polymerization reactivity of phosphinesulfonato pdii catalysts

    KAUST Repository

    Neuwald, Boris


    Thirteen different symmetric and asymmetric phosphinesulfonato palladium complexes ([{(X1-Cl)-μ-M}n], M=Na, Li, 1= X(P^O)PdMe) were prepared (see Figure 1). The solid-state structures of the corresponding pyridine or lutidine complexes were determined for (MeO)21-py, (iPrO)21-lut, (MeO,Me2)1-lut, (MeO)31-lut, CF31-lut, and Ph1-lut. The reactivities of the catalysts X1, obtained after chloride abstraction with AgBF4, toward methyl acrylate (MA) were quantified through determination of the rate constants for the first and the consecutive MA insertion and the analysis of β-H and other decomposition products through NMR spectroscopy. Differences in the homo- and copolymerization of ethylene and MA regarding catalyst activity and stability over time, polymer molecular weight, and polar co-monomer incorporation were investigated. DFT calculations were performed on the main insertion steps for both monomers to rationalize the effect of the ligand substitution patterns on the polymerization behaviors of the complexes. Full analysis of the data revealed that: 1) electron-deficient catalysts polymerize with higher activity, but fast deactivation is also observed; 2) the double ortho-substituted catalysts (MeO)21 and (MeO)31 allow very high degrees of MA incorporation at low MA concentrations in the copolymerization; and 3) steric shielding leads to a pronounced increase in polymer molecular weight in the copolymerization. The catalyst properties induced by a given P-aryl (alkyl) moiety were combined effectively in catalysts with two different non-chelating aryl moieties, such as cHexO/(MeO)21, which led to copolymers with significantly increased molecular weights compared to the prototypical MeO1. Catalyst control: The influence of steric and electronic effects on the reactivity of phosphinesulfonato PdII catalysts in polymerization and copolymerization is explored through experimental and DFT methods. A comparison of thirteen different X(P O)PdMe catalysts ((P O)= κ2-P

  8. Polymerization of 3-ethynylthiophene with homogeneous and heterogeneous Rh catalysts

    Czech Academy of Sciences Publication Activity Database

    Svoboda, J.; Sedláček, J.; Zedník, J.; Dvořáková, G.; Trhlíková, O.; Rédrová, D.; Balcar, Hynek; Vohlídal, J.


    Roč. 46, č. 8 (2008), s. 2776-2787 ISSN 0887-624X R&D Projects: GA AV ČR KAN100500652; GA ČR GA203/05/2194; GA ČR GD203/03/H140; GA ČR(CZ) GD203/08/H032 Institutional research plan: CEZ:AV0Z40400503 Keywords : catalysis * conjugated polymers * organometallic catalysts * polyacetylenes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.821, year: 2008

  9. Discovery and optimization of new chromium catalysts for ethylene oligomerization and polymerization aided by high-throughput screening. (United States)

    Jones, David J; Gibson, Vernon C; Green, Simon M; Maddox, Peter J; White, Andrew J P; Williams, David J


    High throughput screening (HTS) of a 205 member Schiff base salicylaldimine ligand library derived from salicylaldehydes bearing bulky ortho-substituents, i.e., 9-anthracenyl, 1,4,5,8-tetramethylanthracenyl or triptycenyl, reacted in-situ with (p-tolyl)CrCl2(thf)3, identified two new classes of highly active chromium based systems for the oligomerization and polymerization of ethylene, respectively. The polymerization system comprises bidentate ortho-substituted anthracenyl Schiff bases bearing small primary or secondary alkyl imine substituents. The oligomerization catalysts are based upon tridentate ortho-triptycenyl-substituted Schiff bases with pyridylmethyl or quinolyl substituents. Validation tests confirmed polymerization productivities of up to 3000 g x mmol(-1)h(-1)bar(-1) for the polymerization catalyst systems while the oligomerization catalysts gave productivities up to 10 000 g x mmol(-1)h(-1)bar(-1). Key catalyst precursors have been characterized by X-ray crystallography.

  10. About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

    Directory of Open Access Journals (Sweden)

    Hatice Mutlu


    Full Text Available We report on the catalytic activity of commercially available Ru-indenylidene and “boomerang” complexes C1, C2 and C3 in acyclic diene metathesis (ADMET polymerization of a fully renewable α,ω-diene. A high activity of these catalysts was observed for the synthesis of the desired renewable polyesters with molecular weights of up to 17000 Da, which is considerably higher than molecular weights obtained using the same monomer with previously studied catalysts. Moreover, olefin isomerization side reactions that occur during the ADMET polymerizations were studied in detail. The isomerization reactions were investigated by degradation of the prepared polyesters via transesterification with methanol, yielding diesters. These diesters, representing the repeat units of the polyesters, were then quantified by GC-MS.

  11. SBA-15 Immobilized Ruthenium Carbenes as Catalysts for Ring Closing Metathesis and Ring Opening Metathesis Polymerization

    Czech Academy of Sciences Publication Activity Database

    Bek, David; Žilková, Naděžda; Dědeček, Jiří; Sedláček, J.; Balcar, Hynek


    Roč. 53, 3-4 (2010), s. 200-209 ISSN 1022-5528 R&D Projects: GA AV ČR IAA400400805; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : ring closing metathesis * ring opening metathesis polymerization * hybrid catalysts Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.359, year: 2010

  12. Polymerization of aliphatic alkynes with heterogeneous Mo catalysts supported on mesoporous molecular sieves

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Topka, Pavel; Sedláček, J.; Zedník, J.; Čejka, Jiří


    Roč. 46, č. 7 (2008), s. 2593-2599 ISSN 0887-624X R&D Projects: GA ČR GA203/05/2194; GA AV ČR IAA4040411; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : alkyne polymerization * conjugated polymers * metathesis * Mo heterogeneous catalysts Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.821, year: 2008

  13. Polyethylene/Clay Nanocomposites Produced by In Situ Polymerization with Zirconocene/MAO Catalyst

    Directory of Open Access Journals (Sweden)

    Pimpatima Panupakorn


    Full Text Available Two commercial nanoclays were used here as catalytic fillers for production of polyethylene (PE and linear low-density polyethylene (LLDPE nanocomposites via in situ polymerization with zirconocene/MAO catalyst. It was found that both types of nanoclays designated as clay A and clay B can improve thermal stability to the host polymers as observed from a thermal gravimetric analysis (TGA. The distribution of the clays inside the polymer matrices appeared good due to the in situ polymerization system into which the clays were introduced during the polymer forming reaction. Upon investigating the clays by X-ray diffractometer (XRD and Fourier transform infrared spectroscopy (FTIR, it was observed that the crucial differences between the two clays are the crystallite sizes (A < B and the amounts of amine group (A < B. The higher amount of amine group in clay B was supposed to be a major reason for the lower catalytic activity of the polymerization systems compared to clay A resulting from its deactivating effect on zirconocene catalyst. However, for both clays, increasing their contents in the polymerization systems reduced the catalytic activity due to the higher steric hindrance occurring.

  14. Effect of the amount of catalyst and chain-initiator on the anionic Polymerization of {epsilon}-caprolactam

    Energy Technology Data Exchange (ETDEWEB)

    Chung, D.W.; Oh, Y.T.; Park, Y.T. [Suwon University, Suwon (Korea)


    Monomer casting nylons were synthesized by casting anionic polymerization of {epsilon}-caprolactam. Polymerization rates, molecular weights of the products and the conversions were determined while varying the content of catalysts in the range of 0.2{approx}0.6 mol% and 0.1{approx}1.0 mol% for initiator. The polymerization rates were enhanced as the ration of catalysts to initiator increased. The maximum molecular weight was observed when the ration of catalysts to initiator was 0.8, and as the ratio increased the molecular weight decreased. On the other hand, when the ratio of catalysts to initiator was below 0.8, the conversions and the molecular weights were abruptly diminished due to the termination of growing chain. (author). 11 refs., 3 figs.

  15. Well-defined iron complexes as efficient catalysts for "green" atom-transfer radical polymerization of styrene, methyl methacrylate, and butyl acrylate with low catalyst loadings and catalyst recycling. (United States)

    Nakanishi, So-Ichiro; Kawamura, Mitsunobu; Kai, Hidetomo; Jin, Ren-Hua; Sunada, Yusuke; Nagashima, Hideo


    Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Cationic Ring Opening polymerization of ε-caprolactam by a Montmorillonite Clay Catalyst

    Directory of Open Access Journals (Sweden)

    Djamal Eddine Kherroub


    Full Text Available The ring opening bulk polymerization of ε-caprolactam catalyzed by Maghnite-H+ was reported. Maghnite-H+ is a montmorillonite silicate sheet clay was prepared through a straight forward proton exchange process. The effect of the amount of catalyst, and temperature was studied. Increasing Maghnite-H+ proportion and temperature produced the increase in ε-caprolactam conversion. The kinetics indicated that the polymerization rate is first order with respect to monomer concentration. Mechanism studies showed that monomer inserted into the growing chains with the acyl–oxygen bond scission rather than the break of alkyl–oxygen bond. © 2014 BCREC UNDIP. All rights reservedSubmitted: 3rd October 2013; Revised: 28th February 2014; Accepted: 1st March 2014[How to Cite: Kherroub, D.E., Belbachir, M., Lamouri, S. (2014. Cationic Ring Opening Polymeriza-tion of ε-caprolactam by a Montmorillonite Clay Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (1: 74-79. (doi:10.9767/bcrec.9.1.5555.74-80][Permalink/DOI:

  17. Recent developments in atom transfer radical polymerization (ATRP): methods to reduce metal catalyst concentrations. (United States)

    Lou, Qin; Shipp, Devon A


    Atom transfer radical polymerization (ATRP) was initially developed in the mid-1990s, and with continued refinement and use has led to significant discoveries in new materials. However, metal contamination of the polymer product is an issue that has proven detrimental to widespread industrial application of ATRP. The laboratories of K. Matyjaszewski have made significant progress towards removing this impediment, leading the development of "activators regenerated by electron transfer" ATRP (ARGET ATRP) and electrochemically mediated ATRP (eATRP) technologies. These variants of ATRP allow polymers to be produced with great molecular weight and functionality control but at significantly reduced catalyst concentrations, typically at parts per million levels. This Concept examines these polymerizations in terms of their mechanism and outcomes, and is aimed at giving the reader an overview of recent developments in the field of ATRP. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Polymerization of liquid propylene with a 4th generation Ziegler-Natta catalyst-influence of temperature, hydrogen and monomer concentration and prepolymerization method on polymerization kinetics

    NARCIS (Netherlands)

    Pater, J.T.M.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria


    In a batch-wise operated autoclave reactor, liquid propylene was polymerized using a 4th generation, TiCl4/MgCl2/phthalate ester-AlEt3-R2Si(OMe)2, Ziegler-Natta catalyst system. By using a calorimetric principle it was possible to measure full reaction rate versus time curves for obtaining data on

  19. Study on the effects of temperature, time and policy of pre polymerization on particle morphology in propylene slurry polymerization with heterogeneous ziegler-Natta catalysts

    International Nuclear Information System (INIS)

    Pircheraghi, G.; Pourmahdian, S.; Vatankhah, M.


    The effects of temperature, time and the strategy of pre polymerization were studied on the morphology of polypropylene particles. Propylene polymerization was carried out in slurry phase using fourth generation of Ziegler-Natta Catalyst, cyclohexylmethyl dimethoxysilane as external electron donor, and triethyl aluminum as co-catalyst. Pre polymerizations were carried out based on two strategies: isothermal and non-isothermal conditions. Particle imaging using SEM, bulk density, and particle size distribution was used to analyse the particle morphology. It was found that the variation of initial condition together with the change in the mechanism of particle fracture has a dominant effect on particle morphology. Each combination between the temperature and reaction time causes to have a special effect on the product particle morphology. It has become clear that in isothermal pre polymerization, spherical particles with identical properties were produced. In low temperature experiments particles with porous surface were observed. At increasing temperature, however, the pores disappeared. Non-isothermal pre polymerization produced different morphological types. In all experiments core shell structures were observed that seemed to be related to the structure of catalysts

  20. Immobilized Bis-Indenyl Ligands for Stable and Cost-Effective Metallocene Catalysts of Hydrogenation and Polymerization Reactions (United States)

    Simerly, Thomas Max

    Reactions of catalytic hydrogenations and polymerizations are widely used in industry for manufacture of fine chemicals, pharmaceuticals, and plastics. Homogeneous catalysts for the processes that have low stability and their separation is difficult. Therefore, the development of new highly active and stable catalysts for hydrogenations and polymerizations is a necessity. The objective of this research was the development of a strategy for immobilization of heterogeneous metallocene catalysts. First, a methodology of immobilization of bis-indenyl ligands on the surface of mesoporous silica gel was designed. Four bis-indenyl ligands containing functionalized tethers of various lengths with terminal alkene groups were synthesized. All bis-indenyl ligands were immobilized on the surface of mesoporous functionalized silica gel by two methods: hydrosilylation and thiol-ene coupling of the double bond. After comparing the results, the second strategy was chosen as more efficient. The materials can be used further as intermediates for synthesis of supported metallocene catalysts.

  1. Precision synthesis of poly(3-hexylthiophene) from catalyst-transfer Suzuki-Miyaura coupling polymerization. (United States)

    Yokozawa, Tsutomu; Suzuki, Ryosuke; Nojima, Masataka; Ohta, Yoshihiro; Yokoyama, Akihiro


    (t)Bu(3) PPd(Ph)Br (1)-catalyzed Suzuki-Miyaura coupling polymerization of 2-(4-hexyl-5-iodo-2-thienyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2) was investigated. Monomer 2 was polymerized with 1 at 0 °C in the presence of CsF and 18-crown-6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head-to-tail regioregularity. The M(n) values increased up to 11,400 g · mol(-1) in proportion to the feed ratio of 2 to 1. The MALDI-TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst-transfer mechanism. Successive 1-catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well-defined block copolymer of polyfluorene and P3HT. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Modeling intraparticle transports during propylene polymerizations using supported metallocene and dual function metallocene as catalysts: Single particle model

    Directory of Open Access Journals (Sweden)

    Li Hua-Rong


    Full Text Available Two improved multigrain models (MGMs for preparing homopolypropylene and long chain branched polypropylene via propylene polymerization using silica-supported metallocene or dual function metallocene as catalysts are presented in this paper. The presented models are used to predict the intraparticle flow fields involved in the polymerizations. The simulation results show that the flow field distributions involve dare basically identical. The results also show that both the two polymerization processes have an initiation stage and the controlling step for them is reaction-diffusion-reaction with the polymerization proceeding. Furthermore, the simulation results show that the intra particle mass transfer resistance has significant effect on the polymerization but the heat transfer resistance can be ignored.

  3. Half-sandwich group 4 metal siloxy and silsesquioxane complexes : Soluble model systems for silica-grafted olefin polymerization catalysts

    NARCIS (Netherlands)

    Duchateau, R; Cremer, U; Harmsen, RJ; Mohamud, SI; Abbenhuis, HCL; van Santen, RA; Meetsma, A; Thiele, SKH; van Tol, MFH; Kranenburg, M


    The cuboctameric hydroxysilsesquioxane (c-C5H9)(7)Si8O12(OH) (2), obtained after hydrolysis of (c-C5H9)(7)Si8O12Cl (1), and triphenylsilanol have been applied as model supports for silica-grafted olefin polymerization catalysts. The ligands were introduced on group 4 metals by either chloride

  4. A "catalyst switch" Strategy for the sequential metal-free polymerization of epoxides and cyclic Esters/Carbonate

    KAUST Repository

    Zhao, Junpeng


    A "catalyst switch" strategy was used to synthesize well-defined polyether-polyester/polycarbonate block copolymers. Epoxides (ethylene oxide and/or 1,2-butylene oxide) were first polymerized from a monoalcohol in the presence of a strong phosphazene base promoter (t-BuP4). Then an excess of diphenyl phosphate (DPP) was introduced, followed by the addition and polymerization of a cyclic ester (ε-caprolactone or δ-valerolactone) or a cyclic carbonate (trimethylene carbonate), where DPP acted as both the neutralizer of phosphazenium alkoxide (polyether chain end) and the activator of cyclic ester/carbonate. This work has provided a one-pot sequential polymerization method for the metal-free synthesis of block copolymers from monomers which are suited for different types of organic catalysts. © 2014 American Chemical Society.

  5. Effect of Mn doped-titania on the activity of metallocene catalyst by in situ ethylene polymerization

    KAUST Repository

    Abdul Kaleel, S. H.


    Ethylene polymerization was carried out using highly active metallocene catalysts (Cp 2ZrCl 2 and Cp 2TiCl 2) in combination with methylalumoxane. Titanium(IV) oxide containing 1% Mn as dopant was used as nanofillers. The influence of filler concentration, reaction temperature and pressure on the catalytic activity and polymer properties was investigated. There was a fourfold increase in the activity of zirconocene catalyst by addition of doped-titania. The morphology indicates that the doped-titania nanoparticles have a nucleus effect on the polymerization and caused a homogeneous PE shell around them. The optimum condition for polymerization was found to be 30°C. © 2012 The Korean Society of Industrial and Engineering Chemistry.

  6. Isospecific, Chain Shuttling Polymerization of Propylene Oxide Using a Bimetallic Chromium Catalyst: A New Route to Semicrystalline Polyols. (United States)

    Childers, M Ian; Vitek, Andrew K; Morris, Lilliana S; Widger, Peter C B; Ahmed, Syud M; Zimmerman, Paul M; Coates, Geoffrey W


    Hydroxy-telechelic poly(propylene oxide) (PPO) is widely used industrially as a midsegment in polyurethane synthesis. These atactic polymers are produced from racemic propylene oxide using chain shuttling agents and double-metal cyanide catalysts. Unlike atactic PPO, isotactic PPO is semicrystalline with a melting temperature of approximately 67 °C. Currently there is no practical route to hydroxy-telechelic isotactic PPO using racemic propylene oxide as the monomer. In this paper, hydroxy-telechelic isotactic PPO is synthesized from racemic propylene oxide with control of molecular weight using enantioselective and isoselective bimetallic catalysts in conjunction with chain shuttling agents. The discovery of an easily accessible bimetallic chromium catalyst is reported for this transformation. Diol, triol, and polymeric chain shuttling agents are used to give hydroxy-telechelic isotactic PPO of varying functionality and structure. Detailed quantum chemical studies are used to reveal the polymerization mechanism and origin of stereoselectivity.

  7. Activation and deactivation of neutral palladium(II) phosphinesulfonato polymerization catalysts

    KAUST Repository

    Rünzi, Thomas


    13C-Labeled ethylene polymerization (pre)catalysts [κ2-(anisyl)2P,O]Pd(13CH3)(L) (1-13CH3-L) (L = pyridine, dmso) based on di(2-anisyl)phosphine benzenesulfonate were used to assess the degree of incorporation of 13CH3 groups into the formed polyethylenes. Polymerizations of variable reaction time reveal that ca. 60-85% of the 13C-label is found in the polymer after already 1 min polymerization time, which provides evidence that the pre-equilibration between the catalyst precursor 1-13CH3-L and the active species 1-13CH3-(ethylene) is fast with respect to chain growth. The fraction of 1-13CH3-L that initiates chain growth is likely higher than the 60-85% determined from the 13C-labeled polymer chain ends since (a) chain walking results in in-chain incorporation of the 13C-label, (b) irreversible catalyst deactivation by formation of saturated (and partially volatile) alkanes diminishes the amount of 13CH3 groups incorporated into the polymer, and (c) palladium-bound 13CH3 groups, and more general palladium-bound alkyl(polymeryl) chains, partially transfer to phosphorus by reductive elimination. NMR and ESI-MS analyses of thermolysis reactions of 1-13CH3-L provide evidence that a mixture of phosphonium salts (13CH3)xP+(aryl)4-x (2-7) is formed in the absence of ethylene. In addition, isolation and characterization of the mixed bis(chelate) palladium complex [κ2-(anisyl)2P,O]Pd[κ2-(anisyl) (13CH3)P,O] (11) by NMR and X-ray diffraction analyses from these mixtures indicate that oxidative addition of phosphonium salts to palladium(0) species is also operative. The scrambling of palladium-bound carbyls and phosphorus-bound aryls is also relevant under NMR, as well as preparative reactor polymerization conditions exemplified by the X-ray diffraction analysis of [κ2-(anisyl)2P,O] Pd[κ2-(anisyl)(CH2CH3)P,O] (12) and [κ2-(anisyl)2P,O]Pd[κ2-(anisyl) ((CH2)3CH3)P,O] (13) isolated from pressure reactor polymerization experiments. In addition, ESI-MS analyses of reactor

  8. System Identification for Experimental Study for Polymerization Catalyst Reaction in Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Ahmmed Saadi Ibrehem


    Full Text Available In this work, system identification method is used to capture the reactor characteristics of production rate of polyethylene (PE based on published experimental data. The identification method is used to measure the percentage effect on the production rate of PE by measuring the effect of input factors of temperature of reaction, hydrogen concentration, and [Al]/[Ti] molar catalyst ratio. Temperature of reaction has big effects equal 52.4 % on the output of the system and 47.6 % on interaction of the system's parameters compare to other two factors. Also, hydrogen concentration has big effect equal 45.66 % on the output of the system and 14.7 % on interaction of the system's parameters. [Al]/[Ti] molar catalyst ratio has big effect on interaction of the system equal 28.6 and 1.94 % on the output of the system but less than the reaction temperature and hydrogen concentration. All these results depend on experiment results and these results are very important in industrial plants. ©2011 BCREC UNDIP. All rights reserved(Received: 13rd May 2011; Revised: 27th July 2011; Accepted: 22th September 2011[How to Cite: Ahmmed S. Ibrehem. (2011. System Identification for Experimental Study for Polymerization Catalyst Reaction in Fluidized Bed. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (2: 137-146. doi:10.9767/bcrec.6.2.874.137-146][How to Link / DOI: http://dx, || or local: ] | View in 

  9. Highly Stereoselective Heterogeneous Diene Polymerization by Co-MFU-4l: A Single-Site Catalyst Prepared by Cation Exchange. (United States)

    Dubey, Romain J-C; Comito, Robert J; Wu, Zhenwei; Zhang, Guanghui; Rieth, Adam J; Hendon, Christopher H; Miller, Jeffrey T; Dincă, Mircea


    Molecular catalysts offer tremendous advantages for stereoselective polymerization because their activity and selectivity can be optimized and understood mechanistically using the familiar tools of organometallic chemistry. Yet, this exquisite control over selectivity comes at an operational price that is generally not justifiable for the large-scale manufacture of polyfolefins. In this report, we identify Co-MFU-4l, prepared by cation exchange in a metal-organic framework, as a solid catalyst for the polymerization of 1,3-butadiene with high stereoselectivity (>99% 1,4-cis). To our knowledge, this is the highest stereoselectivity achieved with a heterogeneous catalyst for this transformation. The polymer's low polydispersity (PDI ≈ 2) and the catalyst's ready recovery and low leaching indicate that our material is a structurally resilient single-site heterogeneous catalyst. Further characterization of Co-MFU-4l by X-ray absorption spectroscopy provided evidence for discrete, tris-pyrazolylborate-like coordination of Co(II). With this information, we identify a soluble cobalt complex that mimics the structure and reactivity of Co-MFU-4l, thus providing a well-defined platform for studying the catalytic mechanism in the solution phase. This work underscores the capacity for small molecule-like tunability and mechanistic tractability available to transition metal catalysis in metal-organic frameworks.

  10. Formation of Zr3+ compounds in supported organo-zirconium catalysts and their role in ethylene polymerization

    International Nuclear Information System (INIS)

    Maksimov, N.G.; Dudchenko, V.K.; Anufrienko, V.F.; Zakharov, V.A.; Ermakov, Yu.I.


    The EPR method has been used for studying the formation of Zr 3+ in catalysts obtained by treating silica gel with tetrakis-π-allylzirconium. A sharp increase in Zr 3+ number is observed upon treating the catalysts with hydrogen. A change in Zr 3+ spectra has been studied during adsorption of NH 3 , O 2 , NO, and CO. Ethylene adsorption at low temperatures (77-130 K) leads to the formation of ethylene complexes with Zr 3+ ; a temperature rise results in irreversible ethylene binding which corresponds to entering the coordination ethylene into polymerization reaction

  11. Exploration of Cocatalyst Effects on a Bimetallic Cobalt Catalyst System: Enhanced Activity and Enantioselectivity in Epoxide Polymerization

    KAUST Repository

    Widger, Peter C. B.


    Organic ionic compounds were synthesized and investigated as cocatalysts with a bimetallic cobalt complex for enantioselective epoxide polymerization. The identities of both the cation and the anion were systematically varied, and the subsequent reactivity was studied. The nature of the ionic cocatalyst dramatically impacted the rate and enantioselectivity of the catalyst system. The ionic cocatalyst [P(N=P(N(CH2)4)3) 4 +][tBuCO2 -] in combination with a bimetallic cobalt complex produced a catalyst system that exhibited the greatest activity and selectivity for a variety of monosubstituted epoxides. © 2011 American Chemical Society.

  12. Regio- and stereospecific living polymerization and copolymerization of (E)-1,3-pentadiene with 1,3-butadiene by half-sandwich scandium catalysts. (United States)

    Nishii, Kei; Kang, Xiaohui; Nishiura, Masayoshi; Luo, Yi; Hou, Zhaomin


    The living isospecific-cis-1,4-polymerization and block-copolymerization of (E)-1,3-pentadiene with 1,3-butadiene have been achieved for the first time by using cationic half-sandwich scandium catalysts.

  13. Effects of the Linking of Cyclopentadienyl and Ketimide Ligands in Titanium Half-sandwich Olefin Polymerization Catalysts

    Czech Academy of Sciences Publication Activity Database

    Varga, Vojtěch; Večeřa, M.; Gyepes, R.; Pinkas, Jiří; Horáček, Michal; Merna, J.; Lamač, Martin


    Roč. 9, č. 16 (2017), s. 3160-3172 ISSN 1867-3880 R&D Projects: GA ČR(CZ) GA14-08531S; GA ČR(CZ) GA17-13778S Institutional support: RVO:61388955 Keywords : ketimide ligands * olefin polymerization catalysts * cyclopentadienyl Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 4.803, year: 2016

  14. Protected (fluoroaryl)borates as effective counteranions for cationic metallocene polymerization catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Jia, L.; Yang, X.; Ishihara, Atsushi; Marks, T.J. [Northwestern Univ., Evanston, IL (United States)


    The functionalized (fluoroaryl)borate salts Ph{sub 3}C{sup +}B(C{sub 6}F{sub 4}TBS){sub 4}{sup -} and Ph{sub 3}C{sup +}B(C{sub 6}F{sub 4}TBS){sub 4}{sup -} and (TBS - {sup t}BuMe{sub 2}Si; TIPS = {sup i}Pr{sub 3}Si) are prepared in three steps from 1,4-HC{sub 6}F{sub 4}Br. Reaction with zirconocene dimethyls yields crystalline, thermally stable, soluble L{sub 2}ZrCH{sub 3}{sup +}B(C{sub 6}F{sub 4}SiR{sub 3}){sub 4}{sup -} and L{sub 2}{sup -}ZrH{sup +}(C{sub 6}F{sub 4}SiR{sub 3}){sub 4}{sup -} salts (L = {eta}{sup 5}-C{sub 5}H{sub 5}; {eta}{sup 5}-1,2-Me{sub 2}C{sub 5}H{sub 3}; L{sup +} = {eta}{sup 5}-Me{sub 5}C{sub 5}) which function as highly active ethylene polymerization catalysts. 16 refs., 1 tab.

  15. Isospecific propylene polymerization with in situ generated bis(phenoxy-amine)zirconium and hafnium single site catalysts. (United States)

    Makio, Haruyuki; Prasad, Aitha Vishwa; Terao, Hiroshi; Saito, Junji; Fujita, Terunori


    Bis(phenoxy-imine) Zr and Hf complexes were activated with (i)Bu3Al or (i)Bu2AlH in conjunction with Ph3CB(C6F5)4 and tested as catalysts for propylene polymerization with emphasis on the enantioselectivity of the isospecific species and the single site polymerization characteristics. The isoselective species was identified as the in situ generated bis(phenoxy-amine) complex whose isoselectivity was sensitive to subtle changes in ligand structure. By employing specific substituents at certain key positions the isotacticity reached an extremely high level comparable to high-end commercial isotactic polypropylenes (Tm > 160 °C). Single site polymerization characteristics depended upon the efficiency and selectivity of the in situ imine reduction which is sensitive to the substituent on the imine nitrogen and the reaction conditions. By using (i)Bu2AlH as a reducing agent, quantitative imine reduction can be achieved with a stoichiometric amount of the reducing agent. This lower alkylaluminum loading is beneficial for the catalyst and significantly enhances the polymerization activity and the molecular weight of the resultant polymer.

  16. Solid-State Polymerization of Poly(ethylene furanoate Biobased Polyester, I: Effect of Catalyst Type on Molecular Weight Increase

    Directory of Open Access Journals (Sweden)

    Nejib Kasmi


    Full Text Available In this work, we report the synthesis of poly(ethylene furanoate (PEF, catalyzed by three different catalysts, namely, titanium (IV isopropoxide (TIS, tetrabutyltitanate (TBT, and dibutyltin (IV oxide (DBTO, via the two-stage melt polycondensation method. Solid-state polymerization (SSP was conducted at different reaction times (1, 2, 3.5, and 5 h and temperatures 190, 200, and 205 °C, under vacuum. The resultant polymers were analyzed according to their intrinsic viscosity (IV, end groups (–COOH, and thermal properties, via differential scanning calorimetry. DSC results showed that the post polymerization process was favorable to enhance the melting point of the prepared PEF samples. As was expected, the intrinsic viscosity and the average molecular weight of PEF increased with the SSP time and temperature, whereas the number of carboxyl end-groups was decreased. A simple kinetic model was also developed and used to predict the time evolution of polymers IV, as well as the carboxyl and hydroxyl content of PEF during the SSP. From both the experimental measurements and the theoretical simulation results it was proved that the presence of the TIS catalyst resulted in higher transesterification kinetic rate constants and higher reaction rates. The activation energies were not much affected by the presence of different catalysts. Finally, using DBTO as a catalyst, the polyesters produced have higher crystallinity, and as a consequence, higher number of inactive carboxyl and hydroxyl groups.

  17. Polymerization of Lactic Acid by MAGHNITE-H+ a Non-Toxic Montmorillonite Clay Catalyst (United States)

    Harrane, A.; Belaouedj, M. A.; Meghabar, R.; Belbachir, M.


    The development of synthetic biodegradable polymers, such as poly(lactic acid), is particularly important for constructing medical devices, controlled drug release matrix, including scaffolds and sutures, and has attracted growing interest in the biomedical field. Here, we report a novel approach to preparing poly (D, L-lactic acid) (PDLA) as a biodegradable polymer. We investigated in detail the reaction conditions for the simple direct polycondensation of D, L-lactic acid, including the reaction times, temperatures, and catalyst. The molecular weight of synthesized PDLA is dependent on both the reaction temperature, amount of catalyst and time. The optimum reaction condition to obtain PDLA by direct polycondensation using Maghnite-H+[1,2], a proton exchanged Montmorillonite clay, as catalyst was thus determined to be 120 °C, 5% amount of Maghnite-H+ for 28 h with a molecular weight of 7970. The method for PDLA synthesis established here will facilitate production of PDLA of various molecular weights, which may have a potential utility as biomaterials.

  18. Catalyst system comprising a first catalyst system tethered to a supported catalyst (United States)

    Angelici, Robert J.; Gao, Hanrong


    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

  19. Phosphoniums as catalysts for metal-free polymerization: Synthesis of well-defined poly(propylene oxide) (United States)

    Zhang, Jie; Liu, Quan; Ren, Haojun; Zhang, Nanjie; Li, Pengfei; Yang, Kang


    The anionic ring-opening polymerization of propylene oxide (PO) was initiated with glycerol and catalyzed by three new synthetic phosphonium salts, tetrakis (pyrrolidino) phosphonium (Py4P1+), tetrakis (piperidino) phosphonium (Pi4P1+), tetrakis (morpholino) phosphonium (Mo4P1+), and the known tetrakis [cyclohexyl (methyl) amino] phosphonium (Cy4P1+) and tetrakis [tris (dimethylamino) phosphonoamino] phosphazene (P5+). The effects of substituents on the polymerization behavior, especially the molecular weight and its distribution, degree of unsaturation, and the sequential structures of poly (propylene oxide) (PPO) were investigated. The structures of these catalysts and PPOs were characterized by FT-IR, 1H and 13C NMR, and GPC. The results indicate that Cy4P1+, Py4P1+, and Pi4P1+ have lower optimum reaction temperatures at 90, 70, and 70 °C, respectively, and are better than traditional catalysts KOH and double metal cyanide. PPO samples with high molecular weight, narrow polydispersity, and high functionality were accessible when catalyzed with Cy4P1+, Pi4P1+, and P5+ at the optimum temperature. Notably, Pi4P1+ formed unimodal distribution PPO with 9000 g/mol, 2.93 of functionality, and 0.008 mmol/g degree of unsaturation. Majority segments of PPO from five catalysts adopted the stereoregular head-to-tail structure, exhibiting excellent regularity.

  20. A DFT study on the effect of hydrogen in ethylene and propylene polymerization using a Ti-based heterogeneous Ziegler–Natta catalyst

    KAUST Repository

    Bahri-Laleh, Naeimeh


    Hydrogenolysis of a series of model Ziegler-Natta (Z-N) catalysts to form Ti-H bond was studied within DFT. We focused our efforts on Ti species attached to the (110) lateral cut of MgCl 2 which exist as different centres including Ti-C 2H 5, Ti-CH 2CH(CH 3) 2, and Ti-CH(CH 3)CH 2CH 3 in ethylene and propylene polymerization. In the next step, reactivity of Ti-H bond towards ethylene and propylene (1,2- and 2,1-) insertion was investigated. Results showed that insertion of ethylene and propylene into Ti-H bond has less barrier, in comparison with their insertion in Ti-C bond, however, ethylene and propylene 2,1- insertion lead to Ti-C 2H 5 and Ti-CH(CH 3) 2 centres respectively, which were stable due to strong β-agostic interactions. Finally, by considering different possible reactions of active centre, activity depression in ethylene polymerization and activity increase in propylene polymerization were explained in detail. © 2012 Elsevier B.V.

  1. Quantitative Structure-Thermostability Relationship of Late Transition Metal Catalysts in Ethylene Oligo/Polymerization

    Directory of Open Access Journals (Sweden)

    Wenhong Yang


    Full Text Available Quantitative structure–thermostability relationship was carried out for four series of bis(iminopyridine iron (cobalt complexes and α-diimine nickel complexes systems in ethylene oligo/polymerization. Three structural parameters were correlated with thermal stability, including bond order of metal-nitrogen (B, minimum distance (D between central metal and ortho-carbon atoms on the aryl moiety and dihedral angle (α of a central five-membered ring. The variation degree of catalytic activities between optimum and room temperatures (AT was calculated to describe the thermal stability of the complex. By multiple linear regression analysis (MLRA, the thermal stability presents good correlation with three structural parameters with the correlation coefficients (R2 over 0.95. Furthermore, the contributions of each parameter were evaluated. Through this work, it is expected to help the design of a late transition metal complex with thermal stability at the molecular level.

  2. Ionic Liquids as Catalysts for the Radical Acrylate Polymerization Co-initiated by Imine Bases

    International Nuclear Information System (INIS)

    Polenz, I; Spange, S


    The catalysis of the imine base acrylate (IBA) polymerization by Ionic Liquids (ILs) is reported. Addition of IL traces (∼10-50 mM) to an imine base / acrylate mixture leads to both a significant decrease of the activation temperature (40 °C) required for the IBA polymerization process and an increase in the polymerization rate by a factor of 5-40 depending on the IL species. The radical character of the polymerization is proved by copolymerization experiments using methyl methacrylate (MMA) and methacrylonitrile (MAN) and comparison with literature known values of copolymerization parameters r MMA and r MAN of these co-monomers. The influence of the IL on the polymerization kinetics is quantified by the polymerization rate law; the order referring to the IL is 1 indicating its crucial impact on the monomer activation. The IBA activation properties are strongly dependent on the IL interaction strengths with the IBA components verified by the KAMELT-TAFT hydrogen bond donating ability α. The stronger the interaction (higher α) is, the less the IBA polymerization activation. The temperature dependence of four different IL catalysed IBA polymerization is investigated, allows a classification and anomalous non-ARRHENIUS regimes are discussed. Activation energies E A,P span over 20 and 50 kJ·mol −1 , which is between the values of thermal- (∼80 kJ·mol −1 ) and photo-initiation (∼20 kJ·mol −1 )

  3. Poly(N-4-vinylbenzyl-1,4,7-triazacyclononane Copper Complex Grafted Solid Catalyst for Oxidative Polymerization of 2,6-Dimethylphenol

    Directory of Open Access Journals (Sweden)

    Kei Saito


    Full Text Available A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane copper(I complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl-1,4,7-triaza-cyclononane onto polystyrene particles using a radical mediated polymerization method and next by creating the polymer-metal complex of copper-triazacyclononane with these modified particles. Poly(2,6-dimethyl-1,4-phenylene oxide was successfully obtained from the polymerization of 2,6-dimethylphenol using this new metal-organic solid phase catalyst.

  4. Correlation of Polymerization Conditions with Thermal and Mechanical Properties of Polyethylenes Made with Ziegler-Natta Catalysts

    Directory of Open Access Journals (Sweden)

    M. Anwar Parvez


    Full Text Available In this study, the synthesis of polyethylenes has been carried out with titanium-magnesium supported Ziegler-Natta catalysts in laboratory-scale reactors. A correlation of different polymerization conditions with thermal and mechanical properties of polyethylenes has been established. It is seen that there is lowering of molecular weight (Mw, polymer yield, and catalyst activity at high hydrogen pressure and high temperature. The Mw, polymer yield, and catalyst activity are improved with the increase in ethylene pressure. Dynamic mechanical analysis (DMA results show that the increase in temperature and hydrogen pressure decreases storage modulus. The samples with higher Mw showed high activation energy. The melting point decreases with the increase in hydrogen pressure but increases slightly with the increase in ethylene pressure. It is seen that the increase in reaction temperature, ethylene pressure, and hydrogen pressure leads to an increase in crystallinity. The tensile modulus increases with the increase in hydrogen pressure and can be correlated with the crystallinity of polymer. The Mw has a major influence on the flow activation energy and tensile strength. But the other mechanical and thermal properties depend on Mw as well as other parameters.

  5. Stabilizing Single Sites on Solid Supports: Robust Grafted Ti(IV)-Calixarene Olefin Epoxidation Catalysts via Surface Polymerization and Cross-Linking


    Guo, Yijun; Solovyov, Andrew; Grosso-Giordano, Nicolás A.; Hwang, Son-Jong; Katz, Alexander


    This manuscript develops a surface polymerization and cross-linking approach for the stabilization of single-site catalysts on solid surfaces, which is demonstrated here for grafted Ti(IV)-calixarene Lewis acids on silica. Our approach relies on cationic polymerization that is initiated by an adsorbed B(C_6F_5)_3 and uses styrene as the monomer and diisopropenylbenzene as the cross-linking agent. The mildness of this polymerization method is demonstrated by its lack of blocking micropores and...

  6. Nanocomposite catalyst with palladium nanoparticles encapsulated in a polymeric acid: A model for tandem environmental catalysis

    KAUST Repository

    Isimjan, Tayirjan T.


    The synthesis and characterization of a novel hybrid nanocomposite catalyst comprised of palladium nanoparticles embedded in polystyrene sulfonic acid (PSSH) and supported on metal oxides is reported. The catalysts are intended for application in green catalysis, and they are shown to be effective in the hydrolysisreduction sequence of tandem catalytic reactions required for conversion of 2-phenyl-1,3-dioxolane to toluene or of phenol to cyclohexane. The two distinct components in the catalyst, Pd nanoparticles and acidic PSSH, are capable of catalyzing sequential reactions in one pot under mild conditions. This work has demonstrated a powerful approach toward designing highperformance, multifunctional, scalable, and environmentally friendly nanostructured tandem catalysts. © 2013 American Chemical Society.

  7. Hierarchical Porous Interlocked Polymeric Microcapsules: Sulfonic Acid Functionalization as Acid Catalysts


    Wang, Xiaomei; Gu, Jinyan; Tian, Lei; Zhang, Xu


    Owing to their unique structural and surface properties, mesoporous microspheres are widely applied in the catalytic field. Generally, increasing the surface area of the specific active phase of the catalyst is a good method, which can achieve a higher catalytic activity through the fabrication of the corresponding catalytic microspheres with the smaller size and hollow structure. However, one of the major challenges in the use of hollow microspheres (microcapsules) as catalysts is their chem...

  8. Quasi-Living Polymerization of Propene with an Isotactic-Specific Zirconocene Catalyst

    Directory of Open Access Journals (Sweden)

    Kei Nishii


    Full Text Available Propene polymerization with isotactic (iso-specific C2-symmetric rac-Me2Si(2-Me-Benz(e-Ind2ZrCl2 (1 and rac-Me2Si(2-Me-4-Ph-1-Ind2ZrCl2 (2 were conducted under various conditions for achieving iso-specific living polymerization of propene. When Complex 1 was activated with trialkylaluminum-free modified methylaluminoxane (dMMAO at −40 °C, the number-average molecular weight (Mn linearly increased against the polymerization time to reach Mn = 704,000 within 15 min of polymerization, although the molecular weight distributions was broad (Mw/Mn < 3. Thus, it was found that quasi-living polymerization of propene proceeded in the 1-dMMAO system. The living nature of iso-polypropene was confirmed by the block copolymerization, where the Mn value increased from 221,000 to 382,000 after the addition of 1-octene to yield the block copolymer with a melting point of 150 °C.

  9. Kinetic study of a highly active MgCl2-supported Ziegler-Natta catalyst in liquid pool propylene polymerization. II. The influence of alkyl aluminum and alkoxysilane on catalyst activation and deactivation

    NARCIS (Netherlands)

    Shimizu, Fumihiko; Pater, J.T.M.; van Swaaij, Willibrordus Petrus Maria; Weickert, G.


    The influence of alkyl aluminum and alkoxysilane on the kinetics in liquid pool propylene batch polymerization was investigated with a highly active Ziegler-Natta catalyst system that consisted of MgCl2/TiCl4/diester-alkoxysilane/AlR3. In this study, diethyl phthalate and t-BuEtSi(OMe)2 were used as

  10. Surface grafting via photo-induced copper-mediated radical polymerization at extremely low catalyst concentrations

    Czech Academy of Sciences Publication Activity Database

    Laun, J.; Vorobii, Mariia; de los Santos Pereira, Andres; Pop-Georgievski, Ognen; Trouillet, V.; Welle, A.; Barner-Kowollik, C.; Rodriguez-Emmenegger, Cesar; Junkers, T.


    Roč. 36, č. 18 (2015), s. 1681-1686 ISSN 1022-1336 R&D Projects: GA ČR(CZ) GJ15-09368Y; GA MŠk(CZ) ED1.1.00/02.0109 Grant - others:OPPK(XE) CZ.2.16/3.1.00/21545 Program:OPPK Institutional support: RVO:61389013 Keywords : copper-mediated polymerization * photo-induced polymerization * polymer brushes Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.638, year: 2015

  11. Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems (United States)

    Paradies, Jan; Kehr, Gerald; Fröhlich, Roland; Erker, Gerhard


    Bis(1-methylethenyl-cyclopentadienyl)zirconium dichloride (7a) was prepared by a fulvene route. Photolysis at 0°C with Pyrex-filtered UV light resulted in a rapid and complete intramolecular [2+2]cycloaddition reaction to yield the corresponding cyclobutylene-bridged ansa-zirconocene dichloride isomer (8a). This is one of the rare examples of an organic functional group chemistry that leads to carbon–carbon coupling at the framework of an intact sensitive group 4 bent metallocene complex. More sterically hindered open metallocenes that bear bulky isopropyl or tert-butyl substituents at their Cp rings in addition to the active 1-methylethenyl functional group undergo the photochemical ansa-metallocene ring closure reaction equally facile. The metallocene systems used and obtained in this study have served as transition metal components for the generation of active metallocene propene polymerization catalysts. PMID:17032775

  12. One-pot synthesis of linear- and three-arm star-tetrablock quarterpolymers via sequential metal-free ring-opening polymerization using a "catalyst switch" strategy

    KAUST Repository

    Zhao, Junpeng


    A "catalyst switch" strategy has been used to sequentially polymerize four different heterocyclic monomers. In the first step, epoxides (1,2-butylene oxide and ethylene oxide) were successively polymerized from a monohydroxy or trihydroxy initiator in the presence of a strong phosphazene base promoter (t-BuP4). Then, an excess of diphenyl phosphate (DPP) was introduced, followed by addition and polymerization of a cyclic carbonate (trimethylene carbonate) and a cyclic ester (δ-valerolactone or ε-caprolactone). DPP acted as both neutralizer of the phosphazenium alkoxide (polyether chain end) and activator of the cyclic carbonate/ester. Using this method, linear- and star-tetrablock quarterpolymers were prepared in one pot. This work is emphasizing the strength of the previously developed catalyst switch strategy for the facile metal-free synthesis of complex macromolecular architectures. © 2014 Wiley Periodicals, Inc.

  13. New cobalt-mediated radical polymerization (CMRP of methyl methacrylate initiated by two single-component dinuclear β-diketone cobalt (II catalysts.

    Directory of Open Access Journals (Sweden)

    Feng Bao

    Full Text Available Two dinuclear cobalt complexes based on bis-diketonate ligands (ligand 1: 3,3'-(1,3-phenylenebis(1-phenylpropane-1,3-dione; ligand 2: 3,3'-(1,4-phenylenebis(1-phenylpropane-1,3-dione were successfully synthesized. The two neutral catalysts all showed satisfactory activities in the cobalt-mediated radical polymerization (CMRP of methyl methacrylate (MMA with the common initiator of azodiisobutyronitrile (AIBN. The resulting polymerizations have all of the characteristics of a living polymerization and displayed linear semilogarithmic kinetic plots, a linear correlation between the number-average molecular weight and the monomer conversion, and low polydispersities. Mono- or dicomponent low polydispersity polymers could be obtained by using the two dinuclear catalysts under proper reaction conditions. All these improvements facilitate the implementation of the acrylate CMRP and open the door to the scale-up of the syntheses and applications of the multicomponent low polydispersity polymers.

  14. Synthesis and butadiene polymerization behaviors of cationic cobalt-based catalyst

    Directory of Open Access Journals (Sweden)

    Li Liu


    Full Text Available A series of cationic cobalt-based compounds bearing different neutral N-bearing ligands (1,10-phenanthroline, bipyridine, benzimidazole, terpyridine and anionic ligands (trifluoromethanesulfonate, methanesulfonate were synthesized and the simple compound, Co(Phen2Cl2, was also prepared as a reference compound. All the compounds were characterized along with infrared spectra analysis and some of them were further confirmed by single crystal X-ray crystallographic analysis. Upon activation with ethylaluminum sesquichloride, these cationic cobalt(II compounds showed high catalytic activities for butadiene polymerization. The detailed investigations were carried out to disclose the influence of various polymerization conditions, sterical and electronic parameters of the ligands on their performing activities of the compounds.

  15. Multidentate fluorinated alkoxide ligand platforms for oxophilic metal centers: from MOCVD source reagents to polymerization catalysts. (United States)

    Carpentier, Jean-François


    In contrast to simple fluorinated alkoxides, the coordination chemistry of multidentate ligands that incorporate OC(CF(3))(2)CR(2)-type moieties and additional donors (N, O, etc.) has been briefly investigated. In this Perspective, we review some well-defined, unambiguously authenticated main group and transition metal complexes supported by multidentate fluorinated alkoxide ligands and we present aspects of their syntheses, structures, and reactivities. The first part is devoted to the first syntheses of fluorinated alkoxy-imino and fluorinated alkoxy-amino ligand platforms and their application in the preparation of late transition (Ru, Co, Ir, Ni, Pd, Cu) and main group (Sr, Ba, Ga) metal complexes, many of which have been used as chemical vapor deposition (CVD) source reagents. In the second part, heteroleptic complexes based on oxophilic metals (Y, La, Ti, Zr, Hf, Al) and the catalytic performance of these systems in olefin polymerization and ring-opening polymerization (ROP) of cyclic esters are highlighted.

  16. Hierarchical Porous Interlocked Polymeric Microcapsules: Sulfonic Acid Functionalization as Acid Catalysts (United States)

    Wang, Xiaomei; Gu, Jinyan; Tian, Lei; Zhang, Xu


    Owing to their unique structural and surface properties, mesoporous microspheres are widely applied in the catalytic field. Generally, increasing the surface area of the specific active phase of the catalyst is a good method, which can achieve a higher catalytic activity through the fabrication of the corresponding catalytic microspheres with the smaller size and hollow structure. However, one of the major challenges in the use of hollow microspheres (microcapsules) as catalysts is their chemical and structural stability. Herein, the grape-like hypercrosslinked polystyrene hierarchical porous interlocked microcapsule (HPIM-HCL-PS) is fabricated by SiO2 colloidal crystals templates, whose structure is the combination of open mouthed structure, mesoporous nanostructure and interlocked architecture. Numerous microcapsules assembling together and forming the roughly grape-like microcapsule aggregates can enhance the structural stability and recyclability of these microcapsules. After undergoing the sulfonation, the sulfonated HPIM-HCL-PS is served as recyclable acid catalyst for condensation reaction between benzaldehyde and ethylene glycol (TOF = 793 h-1), moreover, exhibits superior activity, selectivity and recyclability.

  17. Characterization of Cr/SiO 2 catalysts and ethylene polymerization by XPS (United States)

    Gaspar, A. B.; Perez, C. A. C.; Dieguez, L. C.


    Cr/SiO 2 catalysts with 1 or 3 wt.% Cr loadings and different chromium precursors were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). A method to determine chromium species in the sample was developed through the decomposition of the Cr 2p XPS spectrum in Cr 6+ and Cr 3+ standard spectra. The results of the binding energy from the Cr 2p region and of the distribution of chromium species allowed to evaluate the dynamic photo-reduction of the surface chromium species during XPS analysis. Photo-reduction of surface Cr 6+ to Cr 3+ species was verified for all samples supported in silica, depending on the precursor and chromium content. Bulk CrO 3 and Cr 2O 3 standards did not reveal variation in the binding energy of Cr 2p 3/2, but a physical mixture of CrO 3 with SiO 2 presented photo-reduction. The behavior of this mixture resembled to the catalysts and suggests the participation of the surface hydroxyls of silica in the photo-reduction process. XPS intensity measurements for assessing dispersion of chromium oxide were used to compare the calcined and reduced catalysts to different chromium precursors. Polyethylene chains were detected by in situ XPS, while oligomerization products were not observed.

  18. Characterization of Cr/SiO2 catalysts and ethylene polymerization by XPS

    International Nuclear Information System (INIS)

    Gaspar, A.B.; Perez, C.A.C.; Dieguez, L.C.


    Cr/SiO 2 catalysts with 1 or 3 wt.% Cr loadings and different chromium precursors were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). A method to determine chromium species in the sample was developed through the decomposition of the Cr 2p XPS spectrum in Cr 6+ and Cr 3+ standard spectra. The results of the binding energy from the Cr 2p region and of the distribution of chromium species allowed to evaluate the dynamic photo-reduction of the surface chromium species during XPS analysis. Photo-reduction of surface Cr 6+ to Cr 3+ species was verified for all samples supported in silica, depending on the precursor and chromium content. Bulk CrO 3 and Cr 2 O 3 standards did not reveal variation in the binding energy of Cr 2p 3/2 , but a physical mixture of CrO 3 with SiO 2 presented photo-reduction. The behavior of this mixture resembled to the catalysts and suggests the participation of the surface hydroxyls of silica in the photo-reduction process. XPS intensity measurements for assessing dispersion of chromium oxide were used to compare the calcined and reduced catalysts to different chromium precursors. Polyethylene chains were detected by in situ XPS, while oligomerization products were not observed

  19. Synthesis of High cis-Polybutadiene in Styrene Solution with Neodymium-Based Catalysts: Towards the Preparation of HIPS and ABS via In Situ Bulk Polymerization

    Directory of Open Access Journals (Sweden)

    Ramón Díaz de León


    Full Text Available In a first step, 1,3-butadiene was selectively polymerized at 60°C in styrene as solvent using NdV3/DIBAH/EASC as the catalyst system. The catalyst system activation process, the addition order of monomers and catalyst components, and the molar ratios [Al]/[Nd] and [Cl]/[Nd] were studied. The catalyst system allowed the selective 1,3-butadiene polymerization, reaching conversions between 57.5 and 88.1% with low polystyrene contents in the order of 6.3 to 15.4%. Molecular weights ranging from 39,000 to 150,000 g/mol were obtained, while cis-1,4 content was found in the interval of 94.4 to 96.4%. On the other hand, the glass transition temperatures of synthesized materials were established in the range of −101.9 to −107.4°C, explained by the presence of polystyrene segments in the polybutadiene chains; in the same sense, the polybutadienes did not show the typical melting endotherm of high cis-polybutadienes. In a second step, the resulting styrene/high cis-1,4 polybutadiene solutions were used to synthesize ABS (adding a fraction of acrylonitrile monomer and HIPS via in situ bulk polymerizations and the results were discussed in terms of morphological development, molecular parameters, dynamical mechanical behavior, and mechanical properties.

  20. Controlled Polymerization of Isoprene with Chromium-Based Metal-Organic Framework Catalysts: Switching from Cyclic to cis-1,4-Selectivity Depending on Activator. (United States)

    Gao, Fei; Zhang, Li; Yu, Chao; Yan, Xinwen; Zhang, Shaowen; Li, Xiaofang


    Chromium-based metal-organic framework (MOF) Cr-MIL-100/101 activated by activator and aluminum trialkyl compound serve as unique, highly efficient heterogeneous single-site catalysts for the controlled polymerization of isoprene, which not only exhibit quasi-living nature in isoprene polymerization but also unprecedentedly switch from cyclic to cis-1,4-selectivity depending on the activator used to yield low molecular weight cyclic PIPs or extremely high molecular weight cis-1,4-PIPs. Such heterogeneous Cr-MOF catalysts can be recycled approximately five times. Based on nitrogen sorption isotherm tests and powder X-ray diffraction, a cationic mechanism is suggested, in which the polymerization takes place inside the open nanochannels of MOF catalysts and the space confinement effect of narrow open nanochannels originated from the coordination of PhNMe 2 from activator [PhNHMe 2 ][B(C 6 F 5 ) 4 ] with the multiple metal centers of MOF catalysts might give a rational explanation for such controlled adjustment on the PIP's structure and properties. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Catalytic oxidation of n-hexane promoted by Ce1−xCuxO2 catalysts prepared by one-step polymeric precursor method

    International Nuclear Information System (INIS)

    Araújo, Vinícius D.; Lima, Maurício M. de; Cantarero, Andrés; Bernardi, Maria I.B.; Bellido, Jorge D.A.; Assaf, Elisabete M.; Balzer, Rosana; Probst, Luiz F.D.; Fajardo, Humberto V.


    Ceria-supported copper catalysts (Ce 1−x Cu x O 2 , with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N 2 -physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce 1−x Cu x O 2 systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce 0.97 Cu 0.03 O 2 and Ce 0.99 Cu 0.01 O 2 , respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO 2 , which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance

  2. Preparation of Carbon Nanotubes/Manganese Dioxide Composite Catalyst with Fewer Oxygen-Containing Groups for Li-O2Batteries Using Polymerized Ionic Liquids as Sacrifice Agent. (United States)

    Ni, Wenpeng; Liu, Shimin; Fei, Yuqing; He, Yude; Ma, Xiangyuan; Lu, Liujin; Deng, Youquan


    Considering the significant influence of oxygen-containing groups on the surface of carbon involved electrodes, a carbon nanotube (CNT)-based MnO 2 composite catalyst was synthesized following a facile method while using polymerized ionic liquids (PIL) as sacrifice agent. Herein, the PIL (polymerized hydrophobic 1-vinyl-3-ethylimidazolium bis ((trifluoromethyl)sulfonyl)imide) wrapped CNTs were prepared. The composite was applied to support MnO 2 by the treatment of KMnO 4 solution, taking advantage of the reaction between PIL and KMnO 4 , which excludes or suppresses the oxidation of CNTs, and the as-synthesized material with fewer oxygen-containing groups acted as a cathode catalyst for Li-O 2 batteries, directly avoiding the application of binders. The catalyst shows enhanced activity compared to that of the samples without PIL, as verified by the lower overpotential during discharging and charging (0.97 V at the current density of 100 mA g -1 ). Meanwhile, the performance parameters such as Coulombic efficiency and rate capability were also improved for the Li-O 2 battery utilizing this catalyst. Further, the formation of confined Li 2 O 2 particles could be responsible for the reduction of charge potential of Li-O 2 batteries due to the synergy effect of the intrinsic catalytic activity of MnO 2 and fewer oxygen functional groups on the catalyst surface.

  3. Polymeric carbon nitride/mesoporous silica composites as catalyst support for Au and Pt nanoparticles. (United States)

    Xiao, Ping; Zhao, Yanxi; Wang, Tao; Zhan, Yingying; Wang, Huihu; Li, Jinlin; Thomas, Arne; Zhu, Junjiang


    Small and homogeneously dispersed Au and Pt nanoparticles (NPs) were prepared on polymeric carbon nitride (CNx )/mesoporous silica (SBA-15) composites, which were synthesized by thermal polycondensation of dicyandiamide-impregnated preformed SBA-15. By changing the condensation temperature, the degree of condensation and the loading of CNx can be controlled to give adjustable particle sizes of the Pt and Au NPs subsequently formed on the composites. In contrast to the pure SBA-15 support, coating of SBA-15 with polymeric CNx resulted in much smaller and better-dispersed metal NPs. Furthermore, under catalytic conditions the CNx coating helps to stabilize the metal NPs. However, metal NPs on CNx /SBA-15 can show very different catalytic behaviors in, for example, the CO oxidation reaction. Whereas the Pt NPs already show full CO conversion at 160 °C, the catalytic activity of Au NPs seems to be inhibited by the CNx support. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Cationic metallocene olefin polymerization catalysts. Thermodynamic and kinetic parameters for ion pair formation, dissociation, and reorganization

    Energy Technology Data Exchange (ETDEWEB)

    Deck, P.A.; Marks, T.J. [Northwestern Univ., Evanston, IL (United States)


    We report here the first detailed calorimetric thermodynamic and NMR spectroscopic kinetic study of a prototypical, structurally well-characterized metallocenium catalyst system, (1,2-Me{sub 2}C{sub 5}H{sub 3}){sub 2}MCH{sub 3}{sup +}CH{sub 3}B(C{sub 6}/F{sub 5}){sub 3}{sup -}(M = Zr, Hf). From the acquired data, it is possible to map out the reaction coordinate(s) for the aforementioned ion pair formation/reorganization processes and to quantify several striking metal and solvent effects thereupon. The present results provide the first quantitative information on the thermodynamics and kinetics of metallocenium ion pair formation, dissociation, and stereomutation. The quantitative data indicate that the stability of the ion pairs with respect to the constituent neutrals is metal-dependent (Zr > Hf) and that processes which loosen the ion pairing and invert the local dissymmetry are also highly metal- and solvent-dependent. These results convey significant implications for catalyst stability, activity, and stereoregulation kinetics of the sterically-sensitive olefin insertion process. 13 refs., 1 fig., 1 tab.

  5. The Role of Co-Activation and Ligand Functionalization in Neutral Methallyl Nickel(II) Catalysts for Ethylene Oligomerization and Polymerization. (United States)

    Ortega, Daniela E; Cortés-Arriagada, Diego; Trofymchuk, Oleksandra S; Yepes, Diana; Gutiérrez-Oliva, Soledad; Rojas, René S; Toro-Labbé, Alejandro


    A detailed quantum chemical study that analyzed the mechanism of ethylene oligomerization and polymerization by means of a family of four neutral methallyl Ni II catalysts is presented. The role of the boron co-activators, BF 3 and B(C 6 F 5 ) 3 , and the position of ligand functionalization (ortho or para position of the N-arylcyano moiety of the catalysts) were investigated to explain the chain length of the obtained polymers. The chain initialization proceeded with higher activation barriers for the ortho-functionalized complexes (≈19 kcal mol -1 ) than the para-substituted isomers (17-18 kcal mol -1 ). Two main pathways were revealed for the chain propagation: The first pathway was favored when using the B(C 6 F 5 ) 3 co-activated catalyst, and it produced long-chain polymers. A second pathway led to the β-hydrogen complexes, which resulted in chain oligomerization; this pathway was preferred when the BF 3 co-activated catalysts were used. Otherwise, the termination of longer chains occurred via a stable hydride intermediate, which was formed with an energy barrier of about 14 kcal mol -1 for the B(C 6 F 5 ) 3 co-activated catalysts. Significant new insights were made into the reaction mechanism, whereby neutral methallyl Ni II catalysts act in oligomerization and polymerization processes. Specifically, the role of co-activation and ligand functionalization, which are key information for the further design of related catalysts, were revealed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The Influence of Mixed Activators on Ethylene Polymerization and Ethylene/1-Hexene Copolymerization with Silica-Supported Ziegler-Natta Catalyst

    Directory of Open Access Journals (Sweden)

    Piyasan Praserthdam


    Full Text Available This article reveals the effects of mixed activators on ethylene polymerization and ethylene/1-hexene copolymerization over MgCl2/SiO2-supported Ziegler-Natta (ZN catalysts. First, the conventional ZN catalyst was prepared with SiO2 addition. Then, the catalyst was tested for ethylene polymerization and ethylene/1-hexene (E/H co-polymerization using different activators. Triethylaluminum (TEA, tri-n-hexyl aluminum (TnHA and diethyl aluminum chloride (DEAC, TEA+DEAC, TEA+TnHA, TnHA+ DEAC, TEA+DEAC+TnHA mixtures, were used as activators in this study. It was found that in the case of ethylene polymerization with a sole activator, TnHA exhibited the highest activity among other activators due to increased size of the alkyl group. Further investigation was focused on the use of mixed activators. The activity can be enhanced by a factor of three when the mixed activators were employed and the activity of ethylene polymerization apparently increased in the order of TEA+ DEAC+TnHA > TEA+DEAC > TEA+TnHA. Both the copolymerization activity and crystallinity of the synthesized copolymers were strongly changed when the activators were changed from TEA to TEA+DEAC+TnHA mixtures or pure TnHA and pure DEAC.  As for ethylene/1-hexene copolymerization the activity apparently increased in the order of TEA+DEAC+TnHA > TEA+TnHA > TEA+DEAC > TnHA+DEAC > TEA > TnHA > DEAC. Considering the properties of the copolymer obtained with the mixed TEA+DEAC+TnHA, its crystallinity decreased due to the presence of TnHA in the mixed activator. The activators thus exerted a strong influence on copolymer structure. An increased molecular weight distribution (MWD was observed, without significant change in polymer morphology.

  7. Cationic metallocene polymerization catalysts based on tetrakis(pentafluorophenyl)borate and its derivatives. Probing the limits of anion `noncoordination` via a synthetic, solution dynamic, structural, and catalytic olefin polymerization study

    Energy Technology Data Exchange (ETDEWEB)

    Jia, L.; Yang, X.; Stern, C.L.; Marks, T.J. [Northwestern Univ., Evanston, IL (United States)


    The silyl-functionalized/protected derivatives of the tetrakis(perfluoroaryl)borate anions, B(C{sub 6}F{sub 4}TBS){sub 4}{sup -} and B(C{sub 6}F{sub 4}TIPS){sub 4}{sup -} (TBS = tert-butyldimethylsilyl and TIPS = triisopropylsilyl) have been synthesized, and a series of stable, highly reactive Zr and Th ion-paired methyl and hydride catalysts have been isolated using these anions. In contrast, the analogous B(C{sub 6}F{sub 5}){sub 4}{sup -}-based zirconocene methyl complexes are not stable at room temperature; however, B(C{sub 6}F{sub 5}){sub 4}{sup -}-based zirconocene hydride complexes can be isolated. The relative coordinative ability of the series of fluoroarylborates with respect to metallocene cations has been evaluated on the basis of spectroscopic and reactivity data. The polymerization activity of the zirconocene catalysts reaches a maximum when B(C{sub 6}F{sub 4}TBS){sub 4}{sup -} and B(C{sub 6}F{sub 4}TIPS){sub 4}{sup -} are counteranions, and the polymerization activity of the Zr constrained geometry catalyst reaches a maximum in aromatic solvents due to arene coordination when B(C{sub 6}F{sub 5}){sub 4}{sup -} is the counteranion. 37 refs., 5 figs., 7 tabs.

  8. Highly active ethylene polymerization and regioselective 1-hexene oligomerization using zirconium and titanium catalysts with tridentate [ONO] ligands. (United States)

    Xu, Tieqi; Liu, Jie; Wu, Guang-Peng; Lu, Xiao-Bing


    A series of tridentate dianionic ligands [4-(t)Bu-6-R-2-(3-R'-5-(t)Bu-2-OC(6)H(2))N=CH C(6)H(2)O](2-) (L) [R = R' = (t)Bu (L1); R = CMe(2)Ph, R' = (t)Bu (L2); R = adamantyl, R' = (t)Bu (L3); R = R' = CMe(2)Ph (L4); R = SiMe(2)(t)Bu, R' = CMe(2)Ph (L5)] were synthesized. Reactions of TiCl(4) with 1 equiv of ligands L1-L5 in toluene afford five-coordinate titanium complexes with general formula LTiCl(2) [L = L1 (1); L2 (2); L3 (3); L4 (4); L5 (5)]. The addition of tetrahydrofuran (THF) to titanium complex 5 readily gives THF-solvated six-coordinate complex 6, which also was obtained by reaction of TiCl(4) with 1 equiv of ligand L5 in THF. Reactions of ZrCl(4) with 1 or 2 equiv of ligands L1-L5 afford six-coordinate zirconium mono(ligand) complexes LZrCl(2)(THF) [L = L2 (7); L4 (8); L5 (9)], and bis(ligand) complexes L(2)Zr [L = L1 (10); L4 (11)]. The molecular structures of complexes 2, 8, and 11 were established by single-crystal X-ray diffraction studies. Upon activation with methylaluminoxane, complexes 1-9 are active for ethylene polymerization. The activities and half-lifes of the catalyst systems based on zirconium complexes are more than 10(6) g of polyethylene (mol Zr)(-1) h(-1) and 6 h, respectively. Complex 9 is more active and long-lived, with a turnover frequency (TOF) of 2.6 × 10(5) (mol C(2)H(4)) (mol Zr)(-1) h(-1), a half-life of >16 h, and a total turnover number (TON) of more than 10(6) (mol C(2)H(4)) (mol Zr)(-1) at 20 °C and 0.5 MPa pressure. Even at 80 °C, complex 9/MAO catalyst system has a long lifetime (t(1/2) > 2 h), as well as high activity that is comparable with that at 20 °C. When activated with methylaluminoxane (MAO), complex 9 also show moderate catalytic activity and more than 99% 2,1-regioselectivity for 1-hexene oligomerization. © 2011 American Chemical Society

  9. UV-induced polymerization of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol diacrylate] hydrophobic catalyst beads in microfluidics

    Directory of Open Access Journals (Sweden)

    Jun Wei


    Full Text Available The catalytic exchange of hydrogen isotopes between hydrogen and water has been known to be a very useful process for the separation of tritium from tritiated water. For the process, a highly active hydrophobic catalyst is needed. This study provides an effective fabrication method of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol diacrylate] [Pt/poly(SDB-TPGDA] hydrophobic catalyst beads with a narrow size distribution. Platinum nanoparticles were prepared by γ-ray-induced reduction in the aqueous phase first, and then uniformly dispersed in SDB-TPGDA comonomer after the hydrophobization of platinum nanoparticles with alkylamine stabilizers. The porous Pt/poly(SDB-TPGDA hydrophobic catalyst beads were synthesized by the UV-initiated polymerization of the mixture droplets prepared in a capillary-based microfluidic system. The size of as-prepared catalyst beads can be controlled in the range of 200–1,000 μm by adjusting the flow rate of dispersed and continuous phases, as well as the viscosity of the continuous phase. Sorbitan monooleate and cyclohexanol were used as coporogens to control the porosities of the catalyst beads.

  10. UV-induced polymerization of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol) diacrylate] hydrophobic catalyst beads in microfluidics

    Energy Technology Data Exchange (ETDEWEB)

    Wi, Jun; Li, Xiang; Song, Tong; Song, Zi Fan; Chang, Zhen Qi [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei (China); Meng, Da Qiao [Si Chuan Institute of Materials and Technology, Jiang You (China)


    The catalytic exchange of hydrogen isotopes between hydrogen and water has been known to be a very useful process for the separation of tritium from tritiated water. For the process, a highly active hydrophobic catalyst is needed. This study provides an effective fabrication method of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol) diacrylate] [Pt/poly(SDB-TPGDA)] hydrophobic catalyst beads with a narrow size distribution. Platinum nanoparticles were prepared by γ-ray-induced reduction in the aqueous phase first, and then uniformly dispersed in SDB-TPGDA comonomer after the hydrophobization of platinum nanoparticles with alkylamine stabilizers. The porous Pt/poly(SDB-TPGDA) hydrophobic catalyst beads were synthesized by the UV-initiated polymerization of the mixture droplets prepared in a capillary-based microfluidic system. The size of as-prepared catalyst beads can be controlled in the range of 200-1,000 μm by adjusting the flow rate of dispersed and continuous phases, as well as the viscosity of the continuous phase. Sorbitan monooleate and cyclohexanol were used as coporogens to control the porosities of the catalyst beads.

  11. Tailored cationic palladium(II) compounds as catalysts for highly selective dimerization and polymerization of vinylic monomers: Synthetic and mechanistic aspects

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Z.; Sen, A. (Pennsylvania State Univ., University Park (United States))


    The electrophilic palladium(II)compounds Pd(2,6-di-tert-butylpyridine)[sub 2](CH[sub 3]NO[sub 2])[sub 2](BF[sub 4])[sub 2] (1), Pd(PPh[sub 3])[sub 2](BF[sub 4])[sub 2] (2), and Pd(Ph[sub 2]PCH[sub 2]CH[sub 2]PPh[sub 2])(BF[sub 4])[sub 2] (3) were found to be highly selective catalysts for the acyclic dimerization of vinyl monomers (styrene, ethylene, and propylene) and the linear polymerization of p-divinylbenzene, the reactions proceeding through a carbocationic mechanism. One manifestation of the high selectivity was the ability to catalyze the dimerization of ethylene in the presence of propylene and styrene in the presence of [alpha]-methylstyrene even though the second member of each pair was normally significantly more reactive in reactions involving carbocationic intermediates. The linear polymerization of p-divinylbenzene involved in step-growth mechanism. The synthesis of a telechelic polymer through cross-coupling between the terminal vinyl groups of linear poly(p-divinylbenzene) and the vinyl group of a functionalized styrene derivative was also achieved. The reaction rates for the linear dimerization of styrene and the linear polymerization of p-divinylbenzene were found to be first order in the monomer concentration and fractional order in the catalyst concentration. Mathematical modeling indicated that the fractional order in the catalyst concentration was due to preequilibria involving anion dissociation from the metal center, and actually, the catalytic species in the case of 2 was found to be the dication, Pd(PPh[sub 3])[sub 2][sup 2+]. 17 refs., 6 figs., 4 tabs.

  12. The Electrochemical Performance and Durability of Carbon Supported Pt Catalyst in Contact with Aqueous and Polymeric Proton Conductors

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Skou, Eivind Morten


    Significant differences in catalyst performance and durability are often observed between the use of a liquid electrolyte (e.g. sulfuric acid), and a solid polymer electrolyte (e.g. Nafion®). To understand this phenomenon, we studied the electrochemical behavior of a commercially available carbon...... supported platinum catalyst in four different electrode structures: catalyst powder (CP), catalyst ionomer electrode (CIE), half membrane electrode assembly (HMEA) and full membrane electrode assembly (FMEA) in both ex-situ and in-situ experiments under a simulated start/stop cycle. We found...... that the catalyst performance and stability are very much influenced by the presence of the Nafion ionomers. The proton conducting phase provided by the ionomer and the self-assembled electrode structure render the catalysts a higher utilization and better stability. This is probably due to an enhanced dispersion...

  13. Electrochemical performance and durability of carbon supported Pt catalyst in contact with aqueous and polymeric proton conductors. (United States)

    Andersen, Shuang Ma; Skou, Eivind


    Significant differences in catalyst performance and durability are often observed between the use of a liquid electrolyte (e.g., sulfuric acid), and a solid polymer electrolyte (e.g., Nafion). To understand this phenomenon, we studied the electrochemical behavior of a commercially available carbon supported platinum catalyst in four different electrode structures: catalyst powder (CP), catalyst ionomer electrode (CIE), half membrane electrode assembly (HMEA), and full membrane electrode assembly (FMEA) in both ex situ and in situ experiments under a simulated start/stop cycle. We found that the catalyst performance and stability are very much influenced by the presence of the Nafion ionomers. The proton conducting phase provided by the ionomer and the self-assembled electrode structure render the catalysts a higher utilization and better stability. This is probably due to an enhanced dispersion, an improved proton-catalyst interface, the restriction of catalyst particle aggregation, and the improved stability of the ionomer phase especially after the lamination. Therefore, an innovative electrode HMEA design for ex-situ catalyst characterization is proposed. The electrode structure is identical to the one used in a real fuel cell, where the protons transport takes place solely through solid state proton conducting phase.

  14. Developments in the use of rare earth metal complexes as efficient catalysts for ring-opening polymerization of cyclic esters used in biomedical applications (United States)

    Cota, Iuliana


    Biodegradable polymers represent a class of particularly useful materials for many biomedical and pharmaceutical applications. Among these types of polyesters, poly(ɛ-caprolactone) and polylactides are considered very promising for controlled drug delivery devices. These polymers are mainly produced by ring-opening polymerization of their respective cyclic esters, since this method allows a strict control of the molecular parameters (molecular weight and distribution) of the obtained polymers. The most widely used catalysts for ring-opening polymerization of cyclic esters are tin- and aluminium-based organometallic complexes; however since the contamination of the aliphatic polyesters by potentially toxic metallic residues is particularly of concern for biomedical applications, the possibility of replacing organometallic initiators by novel less toxic or more efficient organometallic complexes has been intensively studied. Thus, in the recent years, the use of highly reactive rare earth initiators/catalysts leading to lower polymer contamination has been developed. The use of rare earth complexes is considered a valuable strategy to decrease the polyester contamination by metallic residues and represents an attractive alternative to traditional organometallic complexes.

  15. Proton-Transfer Polymerization by N-Heterocyclic Carbenes: Monomer and Catalyst Scopes and Mechanism for Converting Dimethacrylates into Unsaturated Polyesters

    KAUST Repository

    Hong, Miao


    This contribution presents a full account of experimental and theoretical/computational investigations into the N-heterocyclic carbene (NHC)-catalyzed proton-transfer polymerization (HTP) that converts common dimethacrylates (DMAs) containing no protic groups into unsaturated polyesters. This new HTP proceeds through the step-growth propagation cycles via enamine intermediates, consisting of the proposed conjugate addition–proton transfer–NHC release fundamental steps. This study examines the monomer and catalyst scopes as well as the fundamental steps involved in the overall HTP mechanism. DMAs having six different types of linkages connecting the two methacrylates have been polymerized into the corresponding unsaturated polyesters. The most intriguing unsaturated polyester of the series is that based on the biomass-derived furfuryl dimethacrylate, which showed a unique self-curing ability Four MeO– and Cl–substituted TPT (1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene) derivatives as methanol insertion products, RxTPT(MeO/H) (R = MeO, Cl; x = 2, 3), and two free carbenes (catalysts), OMe2TPT and OMe3TPT, have been synthesized, while OMe2TPT(MeO/H) and OMe2TPT have also been structurally characterized. The structure/reactivity relationship study revealed that OMe2TPT, being both a strong nucleophile and a good leaving group, exhibits the highest HTP activity and also produced the polyester with the highest Mn, while the Cl–substituted TPT derivatives are least active and efficient. Computational studies have provided mechanistic insights into the tail-to-tail dimerization coupling step as a suitable model for the propagation cycle of the HTP. The extensive energy profile was mapped out and the experimentally observed unicity of the TPT-based catalysts was satisfactorily explained with the thermodynamic formation of key spirocyclic species.

  16. Mechanistic characterization of aerobic alcohol oxidation catalyzed by Pd(OAc)(2)/pyridine including identification of the catalyst resting state and the origin of nonlinear [catalyst] dependence. (United States)

    Steinhoff, Bradley A; Guzei, Ilia A; Stahl, Shannon S


    The Pd(OAc)(2)/pyridine catalyst system is one of the most convenient and versatile catalyst systems for selective aerobic oxidation of organic substrates. This report describes the catalytic mechanism of Pd(OAc)(2)/pyridine-mediated oxidation of benzyl alcohol, which has been studied by gas-uptake kinetic methods and (1)H NMR spectroscopy. The data reveal that turnover-limiting substrate oxidation by palladium(II) proceeds by a four-step pathway involving (1) formation of an adduct between the alcohol substrate and the square-planar palladium(II) complex, (2) proton-coupled ligand substitution to generate a palladium-alkoxide species, (3) reversible dissociation of pyridine from palladium(II) to create a three-coordinate intermediate, and (4) irreversible beta-hydride elimination to produce benzaldehyde. The catalyst resting state, characterized by (1)H NMR spectroscopy, consists of an equilibrium mixture of (py)(2)Pd(OAc)(2), 1, and the alcohol adduct of this complex, 1xRCH(2)OH. These in situ spectroscopic data provide direct support for the mechanism proposed from kinetic studies. The catalyst displays higher turnover frequency at lower catalyst loading, as revealed by a nonlinear dependence of the rate on [catalyst]. This phenomenon arises from a competition between forward and reverse reaction steps that exhibit unimolecular and bimolecular dependences on [catalyst]. Finally, overoxidation of benzyl alcohol to benzoic acid, even at low levels, contributes to catalyst deactivation by formation of a less active palladium benzoate complex.

  17. 2-Methyl-2,4-pentanediol (MPD boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization

    Directory of Open Access Journals (Sweden)

    Julia Kinzel


    Full Text Available Covering hydrophobic regions with stabilization agents to solubilize purified transmembrane proteins is crucial for their application in aqueous media. The small molecule 2-methyl-2,4-pentanediol (MPD was used to stabilize the transmembrane protein Ferric hydroxamate uptake protein component A (FhuA utilized as host for the construction of a rhodium-based biohybrid catalyst. Unlike commonly used detergents such as sodium dodecyl sulfate or polyethylene polyethyleneglycol, MPD does not form micelles in solution. Molecular dynamics simulations revealed the effect and position of stabilizing MPD molecules. The advantage of the amphiphilic MPD over micelle-forming detergents is demonstrated in the polymerization of phenylacetylene, showing a ten-fold increase in yield and increased molecular weights.

  18. 1-Hexene Polymerization Using Ziegler-Natta Catalytic System with Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Maliheh Mazaheriyan


    Full Text Available The effects of process conditions and their interactions on the catalyst activity in 1-hexene polymerization were studied with design of experiments by response surface methodology (RSM using a commercial Ziegler-Natta (ZN catalyst in the form of TiCl4/MgCl2/Di-n-butyl phthalate. The effect of different operational variables on the catalyst activity was examined by performing the primary experiments of 1-hexene polymerization.  Among different operational variables, three variables including monomer concentration, polymerization temperature and cocatalyst/catalyst molar ratio (Al/Ti were considered as the main parameters which affected the catalyst activity in the 1-hexene polymerization. The Box-Behnken model with three main parameters in three level responses for each factor was applied to analyze the parameter relationships. After demonstrating the reproducibility of the experimental results, the statistical analysis of experimental data showed that the monomer concentration and Al/Ti molar ratio affected the catalyst activity significantly. It was found that, at room temperature, by increasing the monomer concentration from 80.0 mmol to 239.9 mmol, the activity of the studied ZN catalyst increased from 75.2 to 265.1 gpoly(1-hexene/gcat. In addition, by changing the Al/Ti ratio from 45.9 to 136.8, the catalyst activity increased from 145.2 to 265.1 gpoly(1-hexene/gcat. The maximum activity of catalyst was obtained at the polymerization temperature around 25°C, and by increasing the temperature the activity of studied catalyst decreased. Based on the RSM, the best polymerization condition was obtained at a polymerization temperature of about 35°C, Al/Ti ratio of 136.8, and monomer concentration of 239.9 mmol, which resulted in maximum productivity of the catalyst.

  19. Hydrogen sulphate-based ionic liquid-assisted electro-polymerization of PEDOT catalyst material for high-efficiency photoelectrochemical solar cells. (United States)

    Carbas, Buket Bezgin; Gulen, Mahir; Tolu, Merve Celik; Sonmezoglu, Savas


    This work reports the facile, one-step electro-polymerization synthesis of poly (3,4-ethylenedioxythiophene) (PEDOT) using a 1-ethyl-3-methylimidazolium hydrogen sulphate (EMIMHSO 4 ) ionic liquid (IL) and, for the first time its utilization as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). Using the IL doped PEDOT as CE, we effectively improve the solar cell efficiency to as high as 8.52%, the highest efficiency reported in 150 mC/cm 2 charge capacity, an improvement of ~52% over the control device using the bare PEDOT CE (5.63%). Besides exhibiting good electrocatalytic stability, the highest efficiency reported for the PEDOT CE-based DSSCs using hydrogen sulphate [HSO 4 ] - anion based ILs is also higher than platinum-(Pt)-based reference cells (7.87%). This outstanding performance is attributed to the enhanced charge mobility, reduced contact resistance, improved catalytic stability, smoother surface and well-adhesion. Our experimental analyses reveal that the [HSO 4 ] - anion group of the IL bonds to the PEDOT, leading to higher electron mobility to balance the charge transport at the cathode, a better adhesion for high quality growth PEDOT CE on the substrates and superior catalytic stability. Consequently, the EMIMHSO 4 -doped PEDOT can successfully act as an excellent alternative green catalyst material, replacing expensive Pt catalysts, to improve performance of DSSCs.

  20. Gas phase polymerization of ethylene with a silica-supported metallocene catalyst: influence of temperature on deactivation.

    NARCIS (Netherlands)

    Roos, P.; Meier, G.B.; Samson, J.J.C.; Samson, Job Jan C.; Weickert, G.; Westerterp, K.R.


    Ethylene was polymerized at 5 bar in a stirred powder bed reactor with silica supported rac-Me2Si[Ind]2ZrCl2/methylaluminoxane (MAO) at temperatures between 40°C and 80°C using NaCl as support bed and triethylaluminium (TEA) as a scavenger for impurities. For this fixed recipe and a given charge of

  1. Catalytic oxidation of n-hexane promoted by Ce{sub 1−x}Cu{sub x}O{sub 2} catalysts prepared by one-step polymeric precursor method

    Energy Technology Data Exchange (ETDEWEB)

    Araújo, Vinícius D., E-mail: [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Lima, Maurício M. de [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Fundación General, Universitat de Valencia, Valencia (Spain); Cantarero, Andrés [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Bernardi, Maria I.B. [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Bellido, Jorge D.A. [CAP-Engenharia Química, Universidade Federal de São João Del-Rei – UFSJ, São João Del-Rei, MG (Brazil); Assaf, Elisabete M. [Instituto de Química, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Balzer, Rosana; Probst, Luiz F.D. [Departamento de Química, Universidade Federal de Santa Catarina – UFSC, 88040-900 Florianópolis, SC (Brazil); Fajardo, Humberto V. [Departamento de Química, Universidade Federal de Ouro Preto – UFOP, 35400-000 Ouro Preto, MG (Brazil)


    Ceria-supported copper catalysts (Ce{sub 1−x}Cu{sub x}O{sub 2}, with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N{sub 2}-physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce{sub 1−x}Cu{sub x}O{sub 2} systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce{sub 0.97}Cu{sub 0.03}O{sub 2} and Ce{sub 0.99}Cu{sub 0.01}O{sub 2}, respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO{sub 2}, which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance.

  2. Chiral and achiral (imino)phenoxy-based cationic group 4 non-metallocene complexes as catalysts for polymerization of renewable α-methylene-γ-butyrolactones. (United States)

    Gowda, Ravikumar R; Chen, Eugene Y-X


    Protonolysis of M(Bn)4 (M = Zr, Ti; Bn = benzyl) with equimolar 2,4-di-tert-butyl-6-[(2,6-diisopropylphenylimino)methyl]phenol [(2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)OH] in toluene at -30 °C to 25 °C cleanly affords the corresponding achiral (imino)phenoxy-tribenzyl complexes, [(2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)O]Zr(Bn)3 (1) and [(2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)O]Ti(Bn)3 (2). A chiral dibenzyl complex 3 incorporating the unsymmetric, tetradentate amino(imino)bis(phenoxy) ligand, [2,4-Br2C6H2(O)(6-CH2(NC5H9))CH2N=CH(2-adamantyl-4-MeC6H2O)]Zr(Bn)2 (3), has also been prepared using the same protonolysis protocol. Abstractive activation of 1 with B(C6F5)3·THF in CD2Cl2 at room temperature (RT) affords clean, quantitative formation of the corresponding zirconium cation [((2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)O)Zr(Bn)2(THF)](+)[BnB(C6F5)3](-) (4). Likewise, benzyl abstraction of 2 with B(C6F5)3·THF in CD2Cl2 at RT generates the cationic titanium complex [((2,6-(i)Pr2C6H3)N=C(3,5-(t)Bu2C6H2)O)Ti(Bn)2(THF)](+)[BnB(C6F5)3](-) (5), accompanied by a small amount of decomposed species as a result of C6F5 transfer. The dibenzyl cations 4 and 5 have been characterized spectroscopically, and their structures have been confirmed by single crystal X-ray diffraction analysis. Characteristics of the coordination polymerization of renewable α-methylene-γ-butyrolactone monomers by the cationic catalysts derived from achiral complexes 1 and 2 as well as chiral complex 3 have been investigated, representing the first study of such polymerization by non-metallocene catalysts.

  3. Catalyst-Free Vapor-Phase Method for Direct Integration of Gas Sensing Nanostructures with Polymeric Transducing Platforms

    Directory of Open Access Journals (Sweden)

    Stella Vallejos


    Full Text Available Tungsten oxide nanoneedles (NNs are grown and integrated directly with polymeric transducing platforms for gas sensors via aerosol-assisted chemical vapor deposition (AACVD method. Material analysis shows the feasibility to grow highly crystalline nanomaterials in the form of NNs with aspect ratios between 80 and 200 and with high concentration of oxygen vacancies at the surface, whereas gas testing demonstrates moderate sensing responses to hydrogen at concentrations between 10 ppm and 50 ppm, which are comparable with results for tungsten oxide NNs grown on silicon transducing platforms. This method is demonstrated to be an attractive route to fabricate next generation of gas sensors devices, provided with flexibility and functionality, with great potential in a cost effective production for large-scale applications.

  4. On the Way to Improve the Environmental Benignity of Chemical Processes: Novel Catalysts for a Polymerization Process

    Directory of Open Access Journals (Sweden)

    Silvana F. Rach


    Full Text Available An example for a process that can, in principle, be improved by the application of a catalyst is the synthesis of poly(2-methyl-propenes (“polyisobutenes”, which are important for numerous industrial applications. Each year several 100,000 t are produced. The production of low-molecular weight polyisobutenes by means of cationic initiation by an excess of Lewis acids is well established. Typically, these initiators require the usage of solvents like chloroform, dichloromethane and ethylene and temperatures far below 0 °C (–100 °C in the case of ethylene as solvent. Solvent stabilized transition metal complexes with weakly coordinating counter anions overcome these drawbacks and thus are not only more efficient, but also more environmentally benign: they can be applied at ambient temperature and in non chlorinated solvents at low concentrations.

  5. Polypropylene Nano composites Obtained by In Situ Polymerization Using Metallocenes Catalyst: Influence of the Nanoparticles on the Final Polymer Morphology

    International Nuclear Information System (INIS)

    Zapata, P.; Quijada, R.


    Polypropylene nano composites containing silica nanospheres based on the sol-gel methods were produced via in situ polymerization using a rac-Et(Ind) 2 ZrCl 2 /methylaluminoxane (MAO) system. Two different routes were used depending on the interaction between the silica nanoparticles with the catalytic system. In route 1 the nanoparticles were added together with the catalytic system (rac-Et(Ind) 2 ZrCl 2 )/(MAO) directly into the reactor, and in route 2 the metallocenes rac-Et(Ind) 2 ZrCl 2 was supported on silica nanospheres pretreated with (MAO). SEM images show that when the nanospheres were added by both routes, they were replicated in the final polymer particle morphology; this phenomenon was more pronounced for PP obtained by route 2. The polypropylene (PP) nano composites obtained by both routes had a slightly higher percent crystallinity and crystallinity temperatures than pure PP. Transmission electron microscopy (TEM) images show that the nanospheres were well dispersed into the polypropylene matrix, particularly in the nano composites obtained by the support system (route 2).

  6. Polypropylene Nanocomposites Obtained by In Situ Polymerization Using Metallocene Catalyst: Influence of the Nanoparticles on the Final Polymer Morphology

    Directory of Open Access Journals (Sweden)

    Paula Zapata


    Full Text Available Polypropylene nanocomposites containing silica nanospheres based on the sol-gel methods were produced via in situ polymerization using a rac-Et(Ind2ZrCl2/methylaluminoxane (MAO system. Two different routes were used depending on the interaction between the silica nanoparticles with the catalytic system. In route 1 the nanoparticles were added together with the catalytic system (rac-Et(Ind2ZrCl2/(MAO directly into the reactor, and in route 2 the metallocene rac-Et(Ind2ZrCl2 was supported on silica nanospheres pretreated with (MAO. SEM images show that when the nanospheres were added by both routes, they were replicated in the final polymer particle morphology; this phenomenon was more pronounced for PP obtained by route 2. The polypropylene (PP nanocomposites obtained by both routes had a slightly higher percent crystallinities and crystallinity temperatures than pure PP. Transmission electron microscopy (TEM images show that the nanospheres were well dispersed into the polypropylene matrix, particularly in the nanocomposites obtained by the support system (route 2.

  7. Polymerization Using Phosphazene Bases

    KAUST Repository

    Zhao, Junpeng


    In the recent rise of metal-free polymerization techniques, organic phosphazene superbases have shown their remarkable strength as promoter/catalyst for the anionic polymerization of various types of monomers. Generally, the complexation of phosphazene base with the counterion (proton or lithium cation) significantly improves the nucleophilicity of the initiator/chain end resulting in highly enhanced polymerization rates, as compared with conventional metalbased initiating systems. In this chapter, the general features of phosphazenepromoted/catalyzed polymerizations and the applications in macromolecular engineering (synthesis of functionalized polymers, block copolymers, and macromolecular architectures) are discussed with challenges and perspectives being pointed out.

  8. The use of pyro-polymeric catalysts and a new cylindrical cell design in oxygen-aluminum generators (United States)

    Kiseleva, E. A.; Zhuk, A. Z.; Kleymenov, B. V.; Oudaltsov, V. G.


    The increase in energy consumption, the economic crisis, the development of certain areas of engineering and energy, as well as the related deterioration of the environmental situation, require the development of new electrochemical current sources with high specific characteristics. In the field of creating air-hydrogen fuel cells, the problems of safety and mobile storage of hydrogen have not been completely solved, stagnation in the development of lithium-ion, lithium-air and lithium-sulfur batteries has been outlined. All this requires searching for new technological solutions, ways to increase the energy and resource characteristics of electrochemical current sources (ECS), reducing their cost [1-2]. The use of metals (aluminum, zinc, magnesium) as an energy carrier is due to their high energy intensity (in combination with the lack of transport, storage and on-board storage problems) of the relatively low cost of metals, their availability, storage safety and the absence of harmful emissions when used. As in the chemical and electrochemical use of metals, safe products (oxides, hydroxides) are formed, which are reduced to metals within the framework of traditional production technologies. Thus, a closed cycle of energy use is organized. The task of this paper is to evaluate the possibility of reducing the cost and increasing the specific power of ECS using oxygen depolarization. The goal is achieved by using non-platinum catalysts and optimizing the design of the current source.

  9. Homo-polymerization of α-Olefins and Co-polymerization of Higher α-Olefins with Ethylene in the Presence of CpTiCl2(OC6H4X-p/MAO Catalysts (X = CH3, Cl

    Directory of Open Access Journals (Sweden)

    Z. Wieczorek


    Full Text Available Cyclopentadienyl-titanium complexes containing –OC6H4X ligands (X = Cl,CH3 activated with methylaluminoxane (MAO were used in the homo-polymerizationof ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in co-polymerization of ethylene with the α-olefins mentioned. The -X substituents exhibitdifferent electron donor-acceptor properties, which is described by Hammett’s factor (σ.The chlorine atom is electron acceptor, while the methyl group is electron donor. Thesecatalysts allow the preparation of polyethylene in a good yield. Propylene in the presenceof the catalysts mentioned dimerizes and oligomerizes to trimers and tetramers at 25oCunder normal pressure. If the propylene pressure was increased to 7 atmospheres,CpTiCl2(OC6H4CH3/MAO catalyst at 25oC gave mixtures with different contents ofpropylene dimers, trimers and tetramers. At 70oC we obtained only propylene trimer.Using the catalysts with a -OC6H4Cl ligand we obtained atactic polymers with Mw182,000 g/mol (at 25oC and 100,000 g/mol (at 70oC. The superior activity of theCpTiCl2(OC6H4Cl/MAO catalyst used in polymerization of propylene prompted us tocheck its activity in polymerization of higher α-olefins (1-butene, 1-pentene, 1-hexeneand in co-polymerization of these olefins with ethylene. However, when homo-polymerization was carried out in the presence of this catalyst no polymers wereobtained. Gas chromatography analysis revealed the presence of dimers. The activity ofthe CpTiCl2(OC6H4Cl/MAO catalyst in the co-polymerization of ethylene with higher α-olefins is limited by the length of the co-monomer carbon chain. Hence, the highest catalyst activities were observed in co-polymerization of ethylene with propylene (here a lower pressure of the reagents and shorter reaction time were applied to obtain catalytic activity similar to that for other co-monomers. For other co-monomers the activity of the catalyst

  10. Enzymes as Green Catalysts for Precision Macromolecular Synthesis. (United States)

    Shoda, Shin-ichiro; Uyama, Hiroshi; Kadokawa, Jun-ichi; Kimura, Shunsaku; Kobayashi, Shiro


    The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.

  11. Uma revisão sobre polimerização de olefinas usando catalisadores Ziegler-Natta heterogêneos A survey on olefins polymerization using heterogeneous Ziegler-Natta catalysts

    Directory of Open Access Journals (Sweden)

    Fabricio Machado


    Full Text Available A produção em larga escala de materiais poliméricos de elevado interesse industrial, provenientes da polimerização estereoespecífica de olefinas, tornou-se possível depois do advento dos catalisadores Ziegler-Natta. Classificados genericamente em seis gerações, esses catalisadores apresentam diferentes desempenhos em relação ao grau de especificidade do polímero, à atividade e ao controle de morfologia da partícula, o que propicia o desenvolvimento de resinas poliolefínicas com características e propriedades muito variadas. O objetivo principal desse trabalho é revisar e discutir algumas das questões fundamentais que estão relacionadas com as reações de polimerização de olefinas realizadas com catalisadores heterogêneos. Dá-se ênfase particular aos fatores determinantes para a condução apropriada dos processos industriais, como, por exemplo, a fragmentação controlada do catalisador, o fenômeno de replicação das características estruturais do catalisador e o controle da morfologia da partícula de polímero, a importância da prepolimerização e os efeitos relacionados à transferência de calor e massa durante a reação. Discutem-se também aspectos relacionados à modelagem dos sistemas de polimerização e às técnicas experimentais usadas para o estudo do fenômeno de fragmentação das partículas de catalisador.Large-scale production of polymer materials of high industrial value through stereospecific polymerization of olefins became possible only after the advent of Ziegler-Natta catalysts. Usually grouped into six different generations, these catalysts present distinct activity and allow for production of polymer materials with distinct degrees of stereospecificity, morphology and end-use properties. The main objective of this work is to review and discuss some of the fundamental issues related to olefins polymerization reactions performed with heterogeneous catalysts. Particular emphasis is given to

  12. Effective half metallocene type titanium complex catalyst for the olefin polymerization; Orefuin jugo ni yukona hafu metarosen gata chitan sakutai shokubai

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, Kotohiro [Nara Institute of Sience and Technology, Nara (Japan)


    From the conventional metallocene complex catalyst, ethylene system copolymer of the wide alpha olefin content can efficiently synthesize titanium complex catalyst of the half metallocene type, when it is used. It became clear that the monomer arrangement differed by the substituent on using ligand, when the non-cross-linking complex catalyst was used, while the monomer arrangement of the copolymer was a statistical random array in the cross-linking cyclopentadienyl - amide (CGC) complex catalyst. (NEDO)

  13. Survey and research on precision polymerization polymeric materials; Seimitsu jugo kobunshi zairyo ni kansuru chosa kenkyu

    Energy Technology Data Exchange (ETDEWEB)



    Survey and research on the precision control of primary structure of polymeric materials and the precision evaluation technology have been conducted to develop advanced polymeric materials. It is proposed that the three basic processes of polymer synthesis, i.e., addition, condensation, and biomimesis, in forming the precision polymerization skeleton are to be covered through a centralized joint research effort with participation of industry, academia, and the government institute and under the leadership of researchers from academic institutions as the team leaders. For the study of technology trends, international conferences held in UK, Germany, and Hawaii are introduced, and domestic meetings, i.e., Annual Polymer Congress and Polymer Conference, are summarized. In addition, Precision Polymerization Forum and International Workshop on Precision Polymerization were held. The basic studies include a quantum-chemical elucidation of the elementary process in polymerization reaction, time-resolved analysis of polymerization process and polymer properties, synthesis of polymers with controlled microstructures by coordination polymerization using metal complexes, synthesis of polymer with controlled microstructures by precision polycondensation, molecular recognition in catalyst-reaction site, and synthesis of imprinting polymers. 246 refs., 117 figs., 14 tabs.

  14. Single-Molecule Visualization of Living Polymerization (United States)


    77 (2011). 11 D. P. Allen , M. M. Van Wingerden & R. H. Grubbs. Well-defined silica-supported olefin metathesis catalysts. Org Lett 11, 1261-1264...magnet position), we can also probe how mechanical tension affects the catalytic kinetics of the polymerization. When the magnets are positioned far...the setup include: two rectangular NdFeB magnets mounted on a rotatable base controlled by a motor via a timing belt , collimated LED illumination

  15. Modelagem do Processo de Fragmentação de Catalisadores Suportados Durante a Pré-polimerização de Olefinas Modeling of Catalyst Fragmentation During Olefin Pre-polymerizations

    Directory of Open Access Journals (Sweden)

    Douglas M. Merquior


    Full Text Available Uma metodologia é proposta para descrever a morfologia das partículas de polímero que são obtidas durante os momentos iniciais da polimerização de olefinas via catálise heterogênea. O método é baseado na análise matemática da capacidade da partícula em liberar a energia mecânica acumulada no seu interior devido à rápida produção de polímero. O balanço entre as quantidades de energia acumulada e liberada é calculado com o auxílio de um modelo dinâmico da reação de pré-polimerização. A combinação da metodologia proposta com o modelo dinâmico permitiu a análise dos mecanismos de fragmentação, indicando a morfologia da partícula de polímero produzida em função do tamanho da partícula e da temperatura do reator.A model-based methodology is proposed for describing the morphology of the polymer particles that are obtained during the very early stages of the olefin polymerization. The method is based on the analysis of the particle capacity to release the amount of energy that is accumulated in its interior during the polymerization, due to the fast polymer production. The balance between the accumulated and released amounts of energy is calculated with the help of a dynamic pre-polymerization reaction model. The combination of the fragmentation criteria and of the polymerization model allows the analysis of the prepolymerization step, indicating the morphology of the final polymer particles as a function of the catalyst particle diameter and reactor temperature.

  16. Phosphazene-promoted anionic polymerization

    KAUST Repository

    Zhao, Junpeng


    In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

  17. NATO Advanced Study Institute on Ring-opening Metathesis Polymerization of Olefins and Polymerization of Alkynes

    CERN Document Server


    The first NATO Advanced Study Institute on Olefin Metathesis and Polymerization Catalysts was held on September 10-22, 1989 in Akcay, Turkey. Based on the fundamental research of RRSchrock, RGrubbs and K.B.Wagener in the field of ring opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) and alkyne polymerization, these areas gained growing interest within the last years. Therefore the second NATO-ASI held on metathesis reactions was on Ring Opening Metathesis Po­ lymerization of Olefins and Polymerization of Alkynes on September 3-16, 1995 in Akcay, Turkey. The course joined inorganic, organic and polymer chemists to exchange their knowledge in this field. This volume contains the main and short lectures held in Akcay. To include ADMET reactions better into the title of this volume we changed it into: Metathesis Polymerization of Olefins and Alkyne Polymerization. This volume is addressed to research scientists, but also to those who start to work in the area of olefin metathesis and al...

  18. Estudo Comparativo de Polimerização de Propileno com Diferentes Catalisadores Metalocênicos Através de um Planejamento de Experimentos Comparative Study of Propylene Polymerization with Different Metallocene Catalysts Using a Statistic Experimental Planning Model

    Directory of Open Access Journals (Sweden)

    Maria de Fátima V. Marques


    Full Text Available Neste trabalho, o desempenho dos catalisadores SiMe2(Ind2ZrCl2, Et(Ind2ZrCl2, SiMe2(Ind2HfCl2 e Et(Ind2HfCl2 na polimerização de propileno usando MAO como cocatalisador empregando-se um Planejamento estatístico de experimentos foi avaliado. As polimerizações foram realizadas em diferentes temperaturas e razões molares alumínio/metal de transição. O efeito destas variáveis na atividade de cada catalisador e nas características do polipropileno obtido foi melhor investigado utilizando-se os modelos propostos para cada variável. Foram observadas influências significativas das condições experimentais principalmente na atividade catalítica, bem como no peso molecular ponderal médio, temperatura de fusão e percentagem de isotaticidade dos polímeros obtidos. A partir dos modelos propostos através do tratamento estatístico realizado pode-se observar que os catalisadores a base de zircônio são os de maior atividade catalítica, enquanto que os hafnocenos produzem polipropileno com peso molecular mais elevado. Os complexos com ponte dimetil-silânica produziram polipropileno com maior peso molecular, estereorregularidade e maior temperatura de fusão do que os similares com ponte etilidênica.In this work, the performance of the catalysts SiMe2(Ind2ZrCl2, Et(Ind2ZrCl2, SiMe2(Ind2HfCl2 e Et(Ind2HfCl2 on propylene polymerization using MAO as cocatalyst and employing a Statistic Experimental Planning Model was evaluated. The polymerizations were carried out at different temperatures and aluminum/transition metal molar ratios. The effect of these variables on the catalyst activity and on the polymer characteristics was investigated using the proposed models for each variable. A significant influence was observed of the experimental conditions on the catalyst activity in particular, but also on the weight-average molecular weight, melting point and isotacticity of the polypropylenes produced; the statistical analysis with the proposed

  19. Ti(C5Me3RSiMe2NBut)Cl2] (R = alkyl or aryl) complexes as catalysts for ethylene polymerization

    Czech Academy of Sciences Publication Activity Database

    Carvalho, M. F. N.; Mach, Karel; Dias, A. R.; Mano, J. F.; Margues, M. M.; Soares, A. M.; Pombeiro, A. J. L.


    Roč. 6, - (2003), s. 331-334 ISSN 1387-7003 R&D Projects: GA AV ČR IBS4040017 Institutional research plan: CEZ:AV0Z4040901 Keywords : catalysis * polymerization * ethylene Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.513, year: 2003

  20. [Rh(cod)Cl]2 Complex Immobilized on Mesoporous Molecular Sieves MCM-41 ů A New Hybrid Catalyst for Polymerization of Phenylacetylene

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Čejka, Jiří; Sedláček, J.; Svoboda, J.; Zedník, J.; Bastl, Zdeněk; Bosáček, Vladimír; Vohlídal, J.


    Roč. 203, 1/2 (2003), s. 287-298 ISSN 1381-1169 R&D Projects: GA ČR GA203/02/0976 Institutional research plan: CEZ:AV0Z4040901 Keywords : hybrid catalyst * MCM-41 * rhodium complexes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.264, year: 2003

  1. Polyolefin nanocomposites in situ polymerization

    International Nuclear Information System (INIS)

    Galland, Griselda Barrera; Fim, Fabiana de C.; Milani, Marceo A.; Silva, Silene P. da; Forest, Tadeu; Radaelli, Gislaine; Basso, Nara R.S.; Quijada, Raul


    Polyethylene and polypropylene nanocomposites using grapheme nanosheets and treated chrysotile have been synthesized by in situ polymerization using metallocene catalysts. The fillers have been submitted to acid, thermal and/ou ultrasound treatments before to introduce them into the polymerization reactor. A complete characterization of the fillers has been done. The nanocomposites have been characterized by SEM, TEM, DRX and AFM. The thermal, mechanic -dynamic, mechanical and electrical properties of the nanocomposites are discussed. (author)

  2. Influência da temperatura e da natureza do catalisador na polimerização do glicerol Influence of temperature and nature of the catalyst on glycerol polymerization

    Directory of Open Access Journals (Sweden)

    Miguel de A. Medeiros


    Full Text Available Neste trabalho, a polimerização do glicerol na presença de catalisador ácido (H2SO4 ou H3PO4 e básico (NaOH, para produzir resinas termofixas foi investigada. Os resultados mostraram que as variáveis como a temperatura de reação, o tipo e a concentração do catalisador são críticas para a obtenção de bons rendimentos e seletividade para materiais poliméricos. Em condições otimizadas, i.e. H2SO4 como catalisador, 140 °C por 24 horas, foi possível obter polímeros com 98% de seletividade. Após polimerização, os materiais obtidos foram submetidos a extrações com diferentes solventes, i.e. água, THF e hexano. Os extratos foram caracterizados por ESI(+-MS e por espectroscopia na região do infravermelho, que permitiram verificar a presença de oligômeros de até seis unidades monoméricas. Para menores tempos de reação, e.g. 4 horas, foi possível obter elevada seletividade (100% para oligômeros, mas com baixa conversão de glicerol (25%. Além disso, verificou-se que os outros catalisadores (H3PO4 e NaOH apresentam baixa atividade para promover a polimerização do glicerol, e.g. rendimento de 25% após 24 horas.In this work, an investigation was made of the glycerol polymerization in the presence of acid (H2SO4 or H3PO4 and base (NaOH catalysts to produce thermosetting resins. The results showed that the reaction temperature and catalyst concentration are critical to obtain good yield and selectivity. Under optimum condition, i.e. H2SO4 catalyst, 140 °C for 24 hours it was possible to obtain polymers with 98% selectivity. After the polymerization the materials were submitted to extractions with different solvents, i.e. water, THF and hexane. The extracts were characterized by ESI(+-MS (Electro-Spray Ionization Mass Spectrometry and by FTIR, showing the presence of short-chain oligomers (up to six units. For shorter reaction times, e.g. 4 hours, it was possible to obtain high selectivity (100% for oligomers, but with low

  3. Request for Symposia Support: Advances in Olefin Polymerization Catalysis (United States)


    included, but were not limited to, heterogeneous catalysis , homogeneous catalysis , advances in catalyst activation, methods for polymer topological...SECURITY CLASSIFICATION OF: This Advances in Olefin Polymerization Catalysis symposium was held at the 247th ACS National Meeting and Exposition...March 19, 2014 in Dallas, Texas and consisted of twelve (12) invited/contributed talks. The hosting ACS division was the Division of Catalysis Science

  4. Preparation, characterization, and activity of α-Ti(HPO4)2 supported metallocene catalysts (United States)

    Shi, Yasai; Yuan, Yuan; Xu, Qinghong; Yi, Jianjun


    A series of heterogeneous catalysts by loading metallocenes on surface of α-Ti(HPO4)2, a kind of solid acid, has been synthesized. Polymerization of alkenes, including ethylene and propylene, based on participation of the heterogeneous catalysts were studied and the results were compared to metallocenes supported on silica gel, α-Zr(HPO4)2 and clay. Higher catalytic activity, larger polymer molecular weight and narrow distribution of polymer molecular weight were obtained. Acidic strength of the support and its influence to metallocenes were studied to discover intrinsic factors in the polymerizations.

  5. Hydroxide catalysts for lignin depolymerization

    Energy Technology Data Exchange (ETDEWEB)

    Beckham, Gregg T; Biddy, Mary J.; Kruger, Jacob S.; Chmely, Stephen C.; Sturgeon, Matthew


    Solid base catalysts and their use for the base-catalyzed depolymerization (BCD) of lignin to compounds such as aromatics are presented herein. Exemplary catalysts include layered double hydroxides (LDHs) as recyclable, heterogeneous catalysts for BCD of lignin.

  6. Hydroxide catalysts for lignin depolymerization

    Energy Technology Data Exchange (ETDEWEB)

    Beckham, Gregg T.; Biddy, Mary J.; Chmely, Stephen C.; Sturgeon, Matthew


    Solid base catalysts and their use for the base-catalyzed depolymerization (BCD) of lignin to compounds such as aromatics are presented herein. Exemplary catalysts include layered double hydroxides (LDHs) as recyclable, heterogeneous catalysts for BCD of lignin.

  7. Polymeric media for tritium fixation. Supplement I

    International Nuclear Information System (INIS)

    Franz, J.A.; Burger, L.L.


    Procedures for the fixation of tritium as TH or THO in two different polymeric media are described. The complete procedure for THO fixation in a polyureylene-polyurethane polumer, including polymer molding procedures and leach tests is presented. The catalytic tritiation of polystyrene under very mild conditions using a rhodium catalyst is also described. Thermal stabilities and cost estimates for the polymers examined under this program are discussed. Organic polymers were found to have attractive features for the fixation and storage of concentrated tritium wastes due to the convenience of fixation procedures and favorable properties of the resulting media

  8. A comparison of stresses in molar teeth restored with inlays and direct restorations, including polymerization shrinkage of composite resin and tooth loading during mastication. (United States)

    Dejak, Beata; Młotkowski, Andrzej


    Polymerization shrinkage of composites is one of the main causes of leakage around dental restorations. Despite the large numbers of studies there is no consensus, what kind of teeth reconstruction--direct or indirect composite restorations are the most beneficial and the most durable. The aim was to compare equivalent stresses and contact adhesive stresses in molar teeth with class II MOD cavities, which were restored with inlays and direct restorations (taking into account polymerization shrinkage of composite resin) during simulated mastication. The study was conducted using the finite elements method with the application of contact elements. Three 3D models of first molars were created: model A was an intact tooth; model B--a tooth with a composite inlay, and model C--a tooth with a direct composite restoration. Polymerization linear shrinkage 0.7% of a direct composite restoration and resin luting cement was simulated (load 1). A computer simulation of mastication was performed (load 2). In these 2 situations, equivalent stresses according to the modified von Mises criterion (mvM) in the materials of mandibular first molar models with different restorations were calculated and compared. Contact stresses in the luting cement-tooth tissue adhesive interface around the restorations were also assessed and analyzed. Equivalent stresses in a tooth with a direct composite restoration (the entire volume of which was affected by polymerization shrinkage) were many times higher than in the tooth restored with a composite inlay (where shrinkage was present only in a thin layer of the luting cement). In dentin and enamel the stress values were 8-14 times higher, and were 13 times higher in the direct restoration than in the inlay. Likewise, contact stresses in the adhesive bond around the direct restoration were 6.5-7.7 times higher compared to an extraorally cured restoration. In the masticatory simulation, shear contact stresses in the adhesive bond around the direct

  9. Polymeric microspheres (United States)

    Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.


    The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

  10. Opioid Addiction: Social Problems Associated and Implications of Both Current and Possible Future Treatments, including Polymeric Therapeutics for Giving Up the Habit of Opioid Consumption

    Directory of Open Access Journals (Sweden)

    M. Cristina Benéitez


    Full Text Available Background. Detoxification programmes seek to implement the most secure and compassionate ways of withdrawing from opiates so that the inevitable withdrawal symptoms and other complications are minimized. Once detoxification has been achieved, the next stage is to enable the patient to overcome his or her drug addiction by ensuring consumption is permanently and completely abandoned, only after which can the subject be regarded as fully recovered. Methods. A systematic search on the common databases of relevant papers published until 2016 inclusive. Results and Conclusion. Our study of the available oral treatments for opioid dependence has revealed that no current treatment can actually claim to be fully effective. These treatments require daily oral administration and, consequently, regular visits to dispensaries, which in most cases results in a lack of patient compliance, which causes fluctuations in drug plasma levels. We then reviewed alternative treatments in the available scientific literature on polymeric sustained release formulations. Research has been done not only on release systems for detoxification but also on release systems for giving up the habit of taking opioids. These efforts have obtained the recent authorization of polymeric systems for use in patients that could help them to reduce their craving for drugs.

  11. The radical trap in atom transfer radical polymerization need not be thermodynamically stable. A study of the MoX(3)(PMe(3))(3) catalysts. (United States)

    Maria, Sébastien; Stoffelbach, François; Mata, José; Daran, Jean-Claude; Richard, Philippe; Poli, Rinaldo


    The molybdenum(III) coordination complexes MoX(3)(PMe(3))(3) (X = Cl, Br, and I) are capable of controlling styrene polymerization under typical atom transfer radical polymerization (ATRP) conditions, in conjunction with 2-bromoethylbenzene (BEB) as an initiator. The process is accelerated by the presence of Al(OPr(i))(3) as a cocatalyst. Electrochemical and synthetic studies aimed at identifying the nature of the spin trap have been carried out. The cyclic voltammogram of MoX(3)(PMe(3))(3) (X = Cl, Br, I) shows partial reversibility (increasing in the order Cl PMe(3))(3) for X = Cl and Br. On the other hand, I(-) is more easily oxidized than the MoI(3)(PMe(3))(3) complex; thus, the putative MoI(4)(PMe(3))(3) complex is redox unstable. Electrochemical studies of MoI(3)(PMe(3))(3) in the presence of X(-) (X = Cl or Br) reveal the occurrence of facile halide-exchange processes, leading to the conclusion that the MoI(3)X(PMe(3))(3) products are also redox unstable. The oxidation of MoX(3)(PMe(3))(3) with (1)/(2)Br(2) yields MoX(3)Br(PMe(3))(3) (X = Cl, Br), whose molecular nature is confirmed by single-crystal X-ray analyses. On the other hand, the oxidation of MoI(3)(PMe(3))(3) by I(2) slowly yields a tetraiodomolybdate(III) salt of iodotrimethylphosphonium, [Me(3)PI][MoI(4)(PMe(3))(3)], as confirmed by an X-ray study. This product has no controlling ability in radical polymerization. The redox instability of MoI(3)X(PMe(3))(3) can be reconciled with its involvement as a radical trapping species in the MoI(3)(PMe(3))(3)-catalyzed ATRP, given the second-order nature of its decomposition rate.

  12. Tunable regioselectivity in 1,3-butadiene polymerization by using 2,6-bis(dimethyl-2-oxazolin-2-yl)pyridine incorporated transition metal (Cr, Fe and Co) catalysts

    KAUST Repository

    Gong, Dirong


    Tridentate complexes Cr(III)Cl3L, [L = 2,6-bis(dimethyl-2-oxazolin-2-yl) pyridine], Fe(III)Cl3L, Fe(II)Cl2L and Co(II)Cl2L have been prepared and fully characterized. The solid structures of Cr(III)Cl3L, Fe(III)Cl3L and Co(II)Cl2L have been revealed by single crystal X-ray diffraction, and the Cr(III)Cl3L and Fe(III)Cl3L complexes both exhibit a distorted octahedral geometry, while the Co(II)Cl2L complex has a trigonal bipyramidal conformation. Four complexes have been examined in regioselective polymerization of butadiene in combination with MAO in toluene at room temperature. The trans-1,4, cis-1,4 enchainment of resultant polybutadiene are controlled by the metal center. Activated by MAO, complex Cr(III)Cl3L produces high level of trans-1,4 selectivity (trans-1,4 up to 93.3%) with moderate polymer yield, complexes Fe(III)Cl3L and Fe(II)Cl2L both show equal cis-1,4 and trans-1,4 with minor 1,2 selectivity (<10%), and Co(II)Cl2L catalyst displays predominated cis-1,4 selectivity, which can be shifted to 1,2 selectivity by adding PPh3 as an additive. Thus, tuning of the cis-1,4, trans-1,4 and 1,2 selectivity in full range via central metal and additive chosen by these 2,6-bis(dimethyl-2-oxazolin-2-yl) pyridine supported catalysts has been achieved. © 2015 Elsevier B.V. All rights reserved.

  13. Organic synthesis with olefin metathesis catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, R.H. [California Institute of Technology, Pasadena, CA (United States)


    Over the past nine years, early transition metal catalysts for the ring opening metathesis polymerization of cyclic olefins have been developed. These catalysts are simple organometallic complexes containing metal carbon multiple bonds that in most cases polymerize olefins by a living process. These catalysts have been used to prepare a family of near monodispersed and structurally homogeneous polymers. A series of group VII ROMP catalysts that allow a wide range of functionality to be incorporated into the polymer side chains have been prepared. The most important member of this family of complexes are the bisphosphinedihalo-ruthenium carbene complexes. These polymerization catalysts can also be used in the synthesis of fine chemicals by ring closing (RCM) and vinyl coupling reactions. The availability of the group VII catalysts allow metathesis to be carried out on highly functionalized substrates such as polypeptides and in unusual environments such as in aqueous emulsions.

  14. Polypropylene/graphite nanocomposites by in situ polymerization

    International Nuclear Information System (INIS)

    Milani, Marceo A.; Galland, Giselda B.; Quijada, Raul


    This work presents the synthesis of nanocomposites of polypropylene/graphite by in situ polymerization using metallocene catalyst and graphene nanosheets. Initially was analyzed which of the metallocene catalysts rac-Et(Ind) 2 ZrCl 2 or rac-Me 2 Si(Ind) 2 ZrCl 2 produces polypropylene with mechanical properties more relevant. Then it were performed the in situ polymerization reactions to obtain the nanocomposites. The polymeric materials were characterized by XRD, DSC, GPC and DMTA. (author)

  15. Facile synthesis of porous graphene-like carbon nitride nanosheets with high surface area and enhanced photocatalytic activity via one-step catalyst-free solution self-polymerization (United States)

    Wu, Shikai; Wen, Shengwu; Xu, Xinmei; Huang, Guozhi; Cui, Yifan; Li, Jinyu; Qu, Ailan


    Porous graphite carbon nitride nanosheets (g-C3N4) are achieved via one-step catalyst-free solution self-polymerization from a single melamine precursor. The resultant porous g-C3N4 nanosheets with the best photodegradation capacity provided the surface area of 669.15 m2/g, which is superior to the surface area of any other porous g-C3N4 reported. Results showed enhanced adsorption and degradation capacity of methyl orange (MO) under UV-visible light irradiation (λ > 350 nm) compared to bulk g-C3N4. The MO oxidation of the porous g-C3N4 nanosheets is driven mostly by the participation of holes, and secondly by rad O2- and rad OH radicals. This approach shed lights on porous g-C3N4 production simply by self-polycondensation of single functional monomer. It also provided a low-cost and eco-friendly method to facilely mass-produce g-C3N4 nanosheets with high surface area for many potential applications.

  16. Organo-Lewis acid as cocatalyst for cationic homogenous metallocene Ziegler-Natta olefin polymerizations

    Energy Technology Data Exchange (ETDEWEB)

    Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Chicago, IL)


    The synthesis of the organo-Lewis acid perfluorobiphenylborane (PBB) and the activation of metallocenes for the formation of a variety of highly active homogeneous Ziegler-Natta metallocene olefin polymerization, copolymerization and ring-opening polymerization catalysts is described.

  17. Oxidation catalyst (United States)

    Ceyer, Sylvia T.; Lahr, David L.


    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  18. Monochloro non-bridged half-metallocene-type zirconium complexes containing phosphine oxide-(thio)phenolate chelating ligands as efficient ethylene polymerization catalysts. (United States)

    Tang, Xiao-Yan; Wang, Yong-Xia; Liu, San-Rong; Liu, Jing-Yu; Li, Yue-Sheng


    A series of novel monochloro half-zirconocene complexes containing phosphine oxide-(thio)phenolate chelating ligands of the type, ClCp'Zr[X-2-R(1)-4-R(2)-6-(Ph(2)P=O)C(6)H(2)](2) (Cp' = C(5)H(5), 2a: X = O, R(1) = Ph, R(2) = H; 2b: X = O, R(1) = F, R(2) = H; 2c: X = O, R(1) = (t)Bu, R(2) = H; 2d: X = O, R(1) = R(2) = (t)Bu; 2e: X = O, R(1) = SiMe(3), R(2) = H; 2f: X = S, R(1) = SiMe(3), R(2) = H; Cp' = C(5)Me(5), 2g: X = O, R(1) = SiMe(3), R(2) = H), have been synthesized in high yields. These complexes were identified by (1)H {(13)C} NMR and elemental analyses. Structures for 2b, 2c and 2f were further confirmed by X-ray crystallography. Structural characterization of these complexes reveals crowded environments around the zirconium. Complexes 2b and 2c adopt six-coordinate, distorted octahedral geometry around the zirconium center, in which the equatorial positions are occupied by three oxygen atoms of two chelating phosphine oxide-bridged phenolate ligands and a chlorine atom. The cyclopentadienyl ring and one oxygen atom of the ligand are coordinated on the axial position. Complex 2f also folds a six-coordinate, distorted octahedral geometry around the Zr center, consisting of a Cp-Zr-O (in P=O) axis [177.16°] and a distorted plane of two sulfur atoms and one oxygen atom of two chelating phosphine oxide-bridged thiophenolate ligands as well as a chlorine atom. When activated by modified methylaluminoxane (MMAO), all the complexes exhibited high activities towards ethylene polymerization at high temperature (75 °C), giving high molecular weight polymers with unimodal molecular weight distribution. The formation of 14-electron, cationic metal alkyl species might come from the Zr-O (in phenol ring) bond cleavage based on the DFT calculations study.

  19. Pentafluorosulfanyl Substituents in Polymerization Catalysis. (United States)

    Kenyon, Philip; Mecking, Stefan


    Highly electron-withdrawing pentafluorosulfanyl groups were probed as substituents in an organometallic catalyst. In Ni(II) salicylaldiminato complexes as an example case, these highly electron-withdrawing substituents allow for polymerization of ethylene to higher molecular weights with reduced branching due to significant reductions in β-hydrogen elimination. Combined with the excellent functional group tolerance of neutral Ni(II) complexes, this suppression of β-hydrogen elimination allows for the direct polymerization of ethylene in water to nanocrystal dispersions of disentangled, ultrahigh-molecular-weight linear polyethylene.

  20. Stereoselectivity in metallocene-catalyzed coordination polymerization of renewable methylene butyrolactones: From stereo-random to stereo-perfect polymers

    KAUST Repository

    Chen, Xia


    Coordination polymerization of renewable α-methylene-γ-(methyl) butyrolactones by chiral C 2-symmetric zirconocene catalysts produces stereo-random, highly stereo-regular, or perfectly stereo-regular polymers, depending on the monomer and catalyst structures. Computational studies yield a fundamental understanding of the stereocontrol mechanism governing these new polymerization reactions mediated by chiral metallocenium catalysts. © 2012 American Chemical Society.

  1. Stereoselectivity in metallocene-catalyzed coordination polymerization of renewable methylene butyrolactones: from stereo-random to stereo-perfect polymers. (United States)

    Chen, Xia; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X


    Coordination polymerization of renewable α-methylene-γ-(methyl)butyrolactones by chiral C(2)-symmetric zirconocene catalysts produces stereo-random, highly stereo-regular, or perfectly stereo-regular polymers, depending on the monomer and catalyst structures. Computational studies yield a fundamental understanding of the stereocontrol mechanism governing these new polymerization reactions mediated by chiral metallocenium catalysts. © 2012 American Chemical Society

  2. Chelating polymeric membranes

    KAUST Repository

    Peinemann, Klaus-Viktor


    The present application offers a solution to the current problems associated with recovery and recycling of precious metals from scrap material, discard articles, and other items comprising one or more precious metals. The solution is premised on a microporous chelating polymeric membrane. Embodiments include, but are not limited to, microporous chelating polymeric membranes, device comprising the membranes, and methods of using and making the same.

  3. Influência do envelhecimento de catalisadores Ziegler-Natta à base de neodímio sobre a polimerização de 1,3-butadieno Influence of ageing of neodymium based Ziegler-Natta catalyst on butadiene polymerization

    Directory of Open Access Journals (Sweden)

    Ivana L. Mello


    Full Text Available Catalisadores envelhecidos em diferentes tempos (0, 5, 15, 40, 80 e 160 dias e diferentes temperaturas (10, 25 e 40 °C foram testados na polimerização 1,4-cis do 1,3-butadieno. Avaliou-se a atividade catalítica bem como as características do polímero obtido (massa molecular e microestrutura. Os resultados encontrados mostraram que a variação nas condições de envelhecimento dos catalisadores não influenciou a microestrutura do polímero. O teor de unidades 1,4-cis permaneceu em torno de 98%, de unidades 1,4-trans em torno de 1,4% e de unidades vinílicas em 0,6%. Entretanto, reações utilizando os catalisadores envelhecidos por 40 dias forneceram polibutadieno com maior massa molecular do que os demais catalisadores. Verificou-se também, uma tendência de maiores conversões das polimerizações com os catalisadores envelhecidos a 25 °C.Catalysts aged for different time periods (0, 5, 15, 40, 80 and 160 days and different temperatures (10, 25 and 40 °C were tested in the cis-1,4 polymerization of 1,3-butadiene. The catalytic activity and polymer characteristics (molecular weight and microstructure were evaluated. The results showed that the catalyst ageing did not affect the polymer microstructure. The cis-1,4 content remained at 98%, trans-1,4 at 1,4% and vinyl units at 0,6%. However, the catalysts aged for 40 days produced polybutadienes with higher molecular weight. Also observed was a tendency to an increased polymerization conversion by the catalysts aged at 25 °C.

  4. Process for impregnating a concrete or cement body with a polymeric material (United States)

    Mattus, Alfred J.; Spence, Roger D.


    A process for impregnating cementitious solids with polymeric materials by blending polymeric materials in a grout, allowing the grout to cure, and contacting the resulting solidified grout containing the polymeric materials with an organic mixture containing a monomer, a cross-linking agent and a catalyst. The mixture dissolves the polymerized particles and forms a channel for distributing the monomer throughout the network formed by the polymeric particles. The organic components are then cured to form a substantially water-impermeable mass.

  5. Post-Polymerization Modifications of Polymeric Monolithic Columns: A Review

    Directory of Open Access Journals (Sweden)

    Sinéad Currivan


    Full Text Available The vast cache of methods used in polymeric monolithic column modification is presented herein, with specific attention to post-polymerization modification reactions. The modification of polymeric monolithic columns is defined and can include the modification of pre-existing surface groups, the addition of polymeric chains or indeed the addition of structures such as nano-particles and nano-structures. The use of these modifications can result in the specific patterning of monoliths, useful in microfluidic device design or in the investigation of modification optimization.

  6. Catalyst Alloys Processing (United States)

    Tan, Xincai


    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  7. Broadening of molecular weight distribution of polymers synthesized by metallocene-based dual-site catalysts

    International Nuclear Information System (INIS)

    Santos, Joao H.Z. dos; Fisch, Adriano G.; Cardozo, Nilo S.M.; Secchi, Argimiro R.


    The main topics related to the use of dual-site catalysts in the production of polymers with broad molecular weight distribution are reviewed. The polymerization using dual-site catalysts is more economical and allows to produce a higher quality product than other processes, such as polymer blend and multistage reactors. However, the formulation of these catalysts is quite complicated since the same catalyst must produce distinct polymer grades. In addition, the release of patents concerning the combination of metallocenes and new technologies for polymerization shows that polymerization processes using dual-site catalysts are of current industrial interest. (author)

  8. Propene bulk polymerization kinetics: Role of prepolymerization and hydrogen

    NARCIS (Netherlands)

    Pater, J.T.M.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria


    An experimental setup for the polymerization of liquid propylene was used to carry out main polymerizations with and without a prepolymerization step. Two types of prepolymerization are introduced: at a constant temperature and at rapidly increasing reactor temperatures. With the present catalyst

  9. Condensation Polymerization

    Indian Academy of Sciences (India)

    building blocks, is essentially the process of polycondensation or step-growth polymerization. Before we leave this LEGO-style discussion, I would leave you with two alternate scenarios; one is to use building blocks bearing two sockets and two balls, as de- picted in the figure, and the other is to use blocks that contain two.

  10. Condensation Polymerization

    Indian Academy of Sciences (India)

    At first, let us begin by treating molecules as LEGO-type building blocks with certain strict rules for linking them; a ball can readily fit with a socket, ... is essentially the process of polycondensation or step-growth polymerization. Before we leave this LEGO-style discussion, I would leave you with two alternate scenarios; one is.

  11. Nanostructured catalyst supports (United States)

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.


    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.


    NARCIS (Netherlands)



    The kinetics of the L-lactide bulk polymerization was studied using tin(II) bis(2-ethylhexanoate) and zinc bis(2,2-dimethyl-3,5-heptanedionato-O,O'). Up to 80% conversion, the rate of polymerization using tin(II) bis(2-ethylhexanoate) is higher than that with the zinc-containing catalyst, while at

  13. Catalyst, method of making, and reactions using the catalyst (United States)

    Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Gao, Yufei [Kennewick, WA


    The present invention includes a catalyst having a layered structure with, (1) a porous support, (2) a buffer layer, (3) an interfacial layer, and optionally (4) a catalyst layer. The invention also provides a process in which a reactant is converted to a product by passing through a reaction chamber containing the catalyst.

  14. A joint experimental/theoretical investigation of the MMA polymerization initiated by yttrium phenoxyamine complexes. (United States)

    Fang, Jian; Tschan, Mathieu J-L; Brulé, E; Robert, Carine; Thomas, Christophe M; Maron, Laurent


    A joint experimental/theoretical study has been carried out on the putative MMA polymerization catalyzed by an yttrium isopropyloxide complex. Despite its high activity in lactone polymerization, this catalyst is found to be unreactive on methyl methacrylate (MMA) polymerization. This surprising result is rationalized using a computational approach at the DFT level. Indeed, the endothermicity of the initiation step explains this lack of reactivity. The theoretical proposal of yttrium amido complexes as catalysts allows overcoming this initiation problem.

  15. Chalcogen catalysts for polymer electrolyte fuel cell (United States)

    Alonso-Vante, Nicolas [Buxerolles, FR; Zelenay, Piotr [Los Alamos, NM; Choi, Jong-Ho [Los Alamos, NM; Wieckowski, Andrzej [Champaign, IL; Cao, Dianxue [Urbana, IL


    A methanol-tolerant cathode catalyst and a membrane electrode assembly for fuel cells that includes such a cathode catalyst. The cathode catalyst includes a support having at least one transition metal in elemental form and a chalcogen disposed on the support. Methods of making the cathode catalyst and membrane electrode assembly are also described.

  16. Luminescent Lanthanide Metal Organic Frameworks for cis-Selective Isoprene Polymerization Catalysis

    Directory of Open Access Journals (Sweden)

    Samantha Russell


    Full Text Available In this study, we are combining two areas of chemistry; solid-state coordination polymers (or Metal-Organic Framework—MOF and polymerization catalysis. MOF compounds combining two sets of different lanthanide elements (Nd3+, Eu3+/Tb3+ were used for that purpose: the use of neodymium was required due to its well-known catalytic properties in dienes polymerization. A second lanthanide, europium or terbium, was included in the MOF structure with the aim to provide luminescent properties. Several lanthanides-based MOF meeting these criteria were prepared according to different approaches, and they were further used as catalysts for the polymerization of isoprene. Stereoregular cis-polyisoprene was received, which in some cases exhibited luminescent properties in the UV-visible range.

  17. Method of distributing liquefaction catalysts in solid carbonaceous material

    Energy Technology Data Exchange (ETDEWEB)

    Weller, S W


    A method of dispersing a liquefaction catalyst within coal or other carbonaceous solids involves providing a suspension in oil of microcapsules containing the catalyst. An aqueous solution of a catalytic metal salt is emulsified in the water-immiscible oil and the resulting minute droplets microencapsulated in polymeric shells by interfacial polycondensation. The catalyst is subsequently blended and dispersed throughout the powdered carbonaceous material to be liquefied. At liquefaction temperatures the polymeric microcapsules are destroyed and the catalyst converted to minute crystallites in intimate contact with the carbonaceous material. 2 tables.

  18. Synthesis of Metallocene Catalyst for Terpolymerization of Ethylene, Propylene and Diene

    Directory of Open Access Journals (Sweden)

    S.M.M. Mortazavi


    Full Text Available The bis(indenyl zirconium dichloride catalyst was synthesized by a modified method at room temperature. Terpolymerization of ethylene, propylene and diene monomers were carried out using this metallocene catalyst under different conditions of different feed ratios of monomers, co-catalyst/catalyst ratios and polymerization temperatures. Methylaluminoxane (MAO was used as a co-catalyst. The highest activity of catalyst was obtained at total pressure 4 bar, co-catalyst/catalyst ratio [Al]/[Zr]=600, polymerization temperature 60°C and E/P=67:33 and momomer feed ratio of 1700 kgEPDM/molZrh. The activity of catalyst showed bell-shaped behaviors versus co-catalyst/catalyst ratio ([Al]/[Zr] and polymerization temperatures. The viscosity-average molecular weight (Mv of terpolymers increased with increasing total pressure at different feed ratios of monomers. However, the viscosity-average molecular weight of terpolymers decreased at higher co-catalyst/catalyst ratios ([Al]/[Zr] and higher polymerization temperatures. The increases in propylene and diene monomers in the feed ratios decreased the catalyst activity and viscosity-average molecular weight of terpolymers. The ratio of maximum average rate of terpolymerization to an average rate of terpolymerization at the end of the polymerization (DI for different terpolymerization conditions was relatively high; an indication of the decay kinetics for this type of metallocene catalyst. Increasing the co-catalyst/catalyst ratio up to [Al]/[Zr] = 500 increased the Et% and ENB% in the final obtained polymers. However, increasing the polymerization temperature, diene and propylene concentrations in the feed ratio decreased the Et% and increased the ENB% contents in the final obtained polymers. Tg of the final terpolymers was between -64 and -52°C. The study on microstructures of some polymer revealed block type of chain microstructures.

  19. Organometallic mediated radical polymerization of vinyl acetate using bis(imino)pyridine vanadium trichloride complexes. (United States)

    Perry, Mitchell R; Allan, Laura E N; Decken, Andreas; Shaver, Michael P


    The synthesis and characterization of one novel proligand and six novel vanadium(III) trichloride complexes is described. The controlled radical polymerization activity towards vinyl acetate of these, and eight other bis(imino)pyridine vanadium trichloride complexes previously reported, is investigated. Those complexes possessing variation at the N-aryl para-position with no steric protection offered by ortho-substituents (4 examples) result in poor control over poly(vinyl acetate) polymerization. Control is improved with increasing steric bulk at the ortho-position of the N-aryl substituent (4 examples) although attempts to increase steric bulk past isopropyl were unsuccessful. Synthesizing bis(imino)pyridine vanadium trichloride complexes with substituted imine backbones restores polymerization control when aliphatic substituents are used (4 examples) but ceases to make any drastic improvements on catalyst lifetime. Modification of the polymerization conditions is also investigated, in an attempt to improve the catalyst lifetime. Expansion of the monomer scope to include other vinyl esters, particularly those derived from renewable resources, shows promising results.

  20. Polymeric reagents

    International Nuclear Information System (INIS)

    Bozkurt, C.


    The system polymer-bound triphenyl phosphine/carbon tetrachloride was used for preparation of 14 C-labelled organic compounds. 7- 14 C-benzyl chloride, 7- 14 C-benzoyl chloride and 7- 14 C-N-butyl benzamide have been prepared in this way. The reaction conditions were optimized using inactive compounds. Using the results of this optimization, radiochemical yields of 90% could be obtained for the first time for the preparation of 14 C-labelled alkyl chlorides and carboxylic acid chlorides from the corresponding alcohols and acids on the carrier. Polymer-bound triphenylphosphine was further studied as a catalyst for Beckmann rearrangement on the example of the rearrangement of cyclohexanoneoxime into epsilon-caprolactam. Yields exceeding 90% could be obtained with polymer-bound triphenylphosphine. However, regeneration of the catalyst could only be achieved by the already known method using trichlorosilane, in part also with methyldichlorosilane. Other reducing agents were unsuccessful in regenerating the catalyst. (G.G.)

  1. Polypropylene obtained through zeolite supported catalysts

    Directory of Open Access Journals (Sweden)

    Queli C. Bastos


    Full Text Available Propylene polymerizations were carried out with f2C(Flu(CpZrCl2 and SiMe2(Ind2ZrCl2 catalysts supported on silica, zeolite sodic mordenite (NaM and acid mordenite (HM. The polymerizations were performed at different temperatures and varying aluminium/zirconium molar ratios ([Al]/[Zr]. The effect of these reaction parameters on the catalyst activity was investigated using a proposed statistical experimental planning. In the case of f2C(Flu(CpZrCl2, SiO2 and NaM were used as support and the catalyst performance evaluated using toluene and pentane as polymerization solvent. The molecular weight, molecular weight distribution, melting point and crystallinity of the polymers were examined. The results indicate very high activities for the syndiospecific heterogeneous system. Also, the polymers obtained had superior Mw and stereoregularity.

  2. Functionalization and Polymerization on the CNT Surfaces

    KAUST Repository

    Albuerne, Julio


    In this review we focus on the current status of using carbon nanotube (CNT) as a filler for polymer nanocomposites. Starting with the historical background of CNT, its distinct properties and the surface functionalization of the nanotube, the three different surface polymerization techniques, namely grafting "from", "to" and "through/in between" were discussed. Wider focus has been given on "grafting from" surface initiated polymerizations, including atom transfer radical polymerization (ATRP), reversible addition fragmentation chain-transfer (RAFT) Polymerization, nitroxide mediated polymerization (NMP), ring opening polymerization (ROP) and other miscellaneous polymerization methods. The grafting "to" and "through / in between" also discussed and compared with grafting from polymerization. The merits and shortcomings of all three grafting methods were discussed and the bottleneck issue in grafting from method has been highlighted. Furthermore the current and potential future industrial applications were deliberated. Finally the toxicity issue of CNTs in the final product has been reviewed with the limited available literature knowledge. © 2013 Bentham Science Publishers.

  3. Ziegler-Natta catalyst for polypropylene and polyethylene nanocomposites preparation

    International Nuclear Information System (INIS)

    Silvino, Alexandre C.; Dias, Marcos L.; Bezerra, Ana Beatriz F.


    Polypropylene and polyethylene nanocomposites are well known for their improved properties when compared with the neat polymers. In this work we report the preparation, characterization and the activity studies of a fourth generation Ziegler-Natta catalyst for the preparation of polyolefin/clay nanocomposites. The catalyst was prepared treating an organo-modified silicate with magnesium and titanium compounds. The content of titanium and that of the magnesium of the catalyst were determined by UV-vis spectroscopy and atomic absorption respectively. The first results show that the catalyst is active for propylene polymerization being suitable for polypropylene/clay nanocomposite preparation. The catalyst activity for ethylene polymerization was also investigated. The X-ray diffraction patterns of the polyethylene samples suggest the clay exfoliation occurs in the in situ polymerization, even with high clay loading (about 9 %) indicating that a nanocomposite was formed. (author)

  4. Development of group IV molecular catalysts for high temperature ethylene-α-olefin copolymerization reactions. (United States)

    Klosin, Jerzy; Fontaine, Philip P; Figueroa, Ruth


    This Account describes our research related to the development of molecular catalysts for solution phase olefin polymerization. Specifically, a series of constrained geometry and nonmetallocene (imino-amido-type) complexes were developed for high temperature olefin polymerization reactions. We have discovered many highly active catalysts that are capable of operating at temperatures above 120 °C and producing copolymers with a useful range of molecular weights (from medium to ultrahigh depending on precatalyst identity and polymerization conditions) and α-olefin incorporation capability. Constrained geometry catalysts (CGCs) exhibit very high activities and are capable of producing a variety of copolymers including ethylene-propylene and ethylene-1-octene copolymers at high reactor temperatures. Importantly, CGCs have much higher reactivity toward α-olefins than classical Ziegler-Natta catalysts, thus allowing for the production of copolymers with any desired level of comonomer. In search of catalysts with improved performance, we discovered 3-amino-substituted indenyl-based CGCs that exhibit the highest activity and produce copolymers with the highest molecular weight within this family of catalysts. Phenanthrenyl-based CGCs were found to be outstanding catalysts for the effective production of high styrene content ethylene-styrene copolymers under industrially relevant conditions. In contrast to CGC ligands, imino-amido-type ligands are bidentate and monoionic, leading to the use of trialkyl group IV precatalysts. The thermal instability of imino-amido complexes was addressed by the development of imino-enamido and amidoquinoline complexes, which are not only thermally very robust, but also produce copolymers with higher molecular weights, and exhibit improved α-olefin incorporation. Imido-amido and imino-enamido catalysts undergo facile chain transfer reactions with metal alkyls, as evidenced by a sharp decrease in polymer molecular weight when the

  5. Metallocene Catalytic Insertion Polymerization of 1-Silene to Polycarbosilanes (United States)

    Tian, Yuelong; Ge, Min; Zhang, Weigang; Lv, Xiaoxu; Yu, Shouquan


    Metallocene of zirconium were used as a catalyst for an insertion polymerization of 1-methylsilene directly into pre-ceramic precursor polyzirconocenecarbosilane (PZCS) during dechlorination of dichlorodimethylesilane by sodium, which exhibits high catalytic effectiveness with the maximum conversion ratio of polycarbosilane up to 91%. The average molecular weights of polymers synthesized are less than 1400, all with very narrow polymolecularities. The mechanism of catalytic polymerization was assumed to be similar to a coordination insertion polymerization of 1-olefins by metallocenes. The obtained PZCS show high ceramic yields with formation of composite ceramics of ZrC-SiC, which are novel polymeric precursors of ultra-high temperature ceramic (UHTC) fiber and composite.


    African Journals Online (AJOL)


    Soon after Ziegler and Natta discovered heterogeneous olefin polymerization catalysts in the mid-1950s, efforts were directed towards devising homogeneous catalysts that would prove amenable for polymerization studies. In 1959, Natta et al. [1] and Breslow et al. [2] reported that the metallocene Cp2TiCl2.

  7. The Use of Electron Donors to Increase Stereospecificity in Ziegler-Natta Propylene Polymerization

    Directory of Open Access Journals (Sweden)

    Farshid Nouri-Ahangarani


    Full Text Available Different chemical components in traditional Ziegler–Natta catalytic system include: (1 titanium and vanadium containing compounds, mostly TiCl4, as an active centre, (2 trialkylaluminium-based Lewis acid compounds, especially triethylaluminium, as precatalyst and alkylating agent, and (3 inorganic compounds, specifically MgCl2 and silica, as catalyst supports. Besides these compounds, shortly after the first discovery of Ziegler-Natta catalysts, electron donors have been considered as the key components for MgCl2-supported Ziegler-Natta catalysts, as they improve the stereospecificity and activity of these types of catalysts. Most electron donor compounds have oxygen atom and only a few contain nitrogen atom in their structure. Starting from benzoate for third-generation Ziegler–Natta catalysts, the discovery of new donors has always updated the performance of Ziegler–Natta catalysts. Since the first discovery of these compounds numerous efforts have been devoted in both industry and academic laboratories, not only to discover new electron donors but also to understand their roles in Ziegler–Natta olefin polymerization and suitable MgCl2-alcohol adducts formation. This article reviews the history of such research and development efforts. The first part of the article describes the historical developments of catalyst, with a special focus on donors of industrial importance, followed by an account given on recent trends in the latest donors developed. The next part of the article covers the historical progress toward mechanistic understanding of how donors improve the performance of Ziegler–Natta catalysts and how they undergo decomposition by interaction with Lewis acidic species such as the AlEt3 and TiCl.

  8. Highly Active Water-Soluble Olefin Metathesis Catalyst


    Hong, Soon Hyeok; Grubbs, Robert H.


    A novel water-soluble ruthenium olefin metathesis catalyst supported by a poly(ethylene glycol) conjugated saturated 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligand is reported. The catalyst displays improved activity in ring-opening metathesis polymerization, ring-closing metathesis, and cross-metathesis reactions in aqueous media.

  9. A clamp-like biohybrid catalyst for DNA oxidation

    NARCIS (Netherlands)

    van Dongen, S.F.M.; Clerx, J.; Norgaard, K.; Bloemberg, T.G.; Cornelissen, Jeroen Johannes Lambertus Maria; Trakselis, M.A.; Nelson, S.W.; Benkovic, S.J.; Rowan, A.E.; Nolte, R.J.M.


    In processive catalysis, a catalyst binds to a substrate and remains bound as it performs several consecutive reactions, as exemplified by DNA polymerases. Processivity is essential in nature and is often mediated by a clamp-like structure that physically tethers the catalyst to its (polymeric)

  10. Oxygen-reducing catalyst layer (United States)

    O'Brien, Dennis P [Maplewood, MN; Schmoeckel, Alison K [Stillwater, MN; Vernstrom, George D [Cottage Grove, MN; Atanasoski, Radoslav [Edina, MN; Wood, Thomas E [Stillwater, MN; Yang, Ruizhi [Halifax, CA; Easton, E Bradley [Halifax, CA; Dahn, Jeffrey R [Hubley, CA; O'Neill, David G [Lake Elmo, MN


    An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

  11. A kinetic and spectroscopic study on the copper catalyzed oxidative coupling polymerization of 2,6-dimethylphenol. X-ray structure of the catalyst precursor tetrakis(N-methylimidazole)bis(nitrato)copper(II)

    NARCIS (Netherlands)

    Baesjou, PJ; Driessen, WL; Challa, G; Reedijk, J


    The complex of copper(II) nitrate with N-methylimidazole (Nmiz) ligand has been studied as a catalyst for the oxidative coupling of 2,6-dimethylphenol by means of kinetic and spectroscopic measurements. The order of the reaction in copper is fractional and depends on the N/Cu ratio and the base/Cu

  12. Mesoporous Molecular Sieves as Supports for Metathesis Catalysts (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. XPS characterization of supported Ziegler-Natta catalysts

    International Nuclear Information System (INIS)

    Kaushik, V.K.; Gupta, V.K.; Naik, D.G.


    Surface analytical technique ESCA (electron spectrometer for chemical analysis) has been used for analysis of catalysts used in propylene polymerization. As a result of this analysis it has been shown that productivity of a catalyst can be correlated to Ti/Mg atomic ratio that indicates dispersion of titanium atoms on magnesium support. A quantitative indicator of productivity, i.e. 'titanium index' has also been evaluated for studied catalysts

  14. Optimal Catalyst and Cocatalyst Precontacting in Industrial Ethylene Copolymerization Processes


    Aigner, Paul; Paulik, Christian; Krallis, Apostolos; Kanellopoulos, Vasileios


    In industrial-scale catalytic olefin copolymerization processes, catalyst and cocatalyst precontacting before being introduced in the polymerization reactor is of profound significance in terms of catalyst kinetics and morphology control. The precontacting process takes place under either well-mixing (e.g., static mixers) or plug-flow (e.g., pipes) conditions. The scope of this work is to study the influence of mixing on catalyst/cocatalyst precontacting for a heterogeneous Ziegler-Natta cata...

  15. Catalysts and method (United States)

    Taylor, Charles E.; Noceti, Richard P.


    An improved catlayst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HC1 and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

  16. Epoxidation catalyst and process (United States)

    Linic, Suljo; Christopher, Phillip


    Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

  17. Copper(0) Mediated Single Electron Transfer Controlled Radical Polymerization toward CF Bonds on Poly(vinylidene fluoride). (United States)

    Tan, Shaobo; Zhang, Yanan; Niu, Zhijing; Zhang, Zhicheng


    The first copper(0) mediated controlled radical polymerization (CRP) of methyl methacrylate (MMA) toward CF bonds onto poly(vinylidene fluoride) (PVDF) is reported with rather high activity. By avoiding the halogen exchange, Cu 0 instead of Cu I complexes utilized as catalyst is responsible for the significantly improved polymerization activity. Using FH decoupled nuclear magnetic resonance technique, the grafting sites onto PVDF are finely located. From this, detailed topologic information including the grafting density, average length of each side chain, along with the overall grafted content of PMMA, is detected by tracking the polymerization as a function of time. This work offers not only a facile CRP strategy based on inactive CF bonds but also a deep insight into the cleavage of F-bearing compounds in organic chemistry. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Newly Developed Techniques on Polycondensation, Ring-Opening Polymerization and Polymer Modification: Focus on Poly(Lactic Acid) (United States)

    Hu, Yunzi; Daoud, Walid A.; Cheuk, Kevin Ka Leung; Lin, Carol Sze Ki


    Polycondensation and ring-opening polymerization are two important polymer synthesis methods. Poly(lactic acid), the most typical biodegradable polymer, has been researched extensively from 1900s. It is of significant importance to have an up-to-date review on the recent improvement in techniques for biodegradable polymers. This review takes poly(lactic acid) as the example to present newly developed polymer synthesis techniques on polycondensation and ring-opening polymerization reported in the recent decade (2005–2015) on the basis of industrial technique modifications and advanced laboratory research. Different polymerization methods, including various solvents, heating programs, reaction apparatus and catalyst systems, are summarized and compared with the current industrial production situation. Newly developed modification techniques for polymer properties improvement are also discussed based on the case of poly(lactic acid). PMID:28773260

  19. Metallocene catalyst containing bulky organic group

    Energy Technology Data Exchange (ETDEWEB)

    Marks, Tobin J. (Evanston, IL); Ja, Li (Chicago, IL); Yang, Xinmin (Evanston, IL)


    An ionic metallocene catalyst for olefin polymerization which comprises: (1) a cyclopentadienyl-type ligand, a Group IVB transition metal, and alkyl, aryl, or hydride substituents, as a cation, and (2) a weakly coordinating anion comprising boron substituted with halogenated, such as tetra fluoro, aryl substituents preferably containing silylalkyl substitution, such as para-silyl t-butyldimethyl.

  20. Metallocene catalyst containing bulky organic group (United States)

    Marks, T.J.; Ja, L.; Yang, X.


    An ionic metallocene catalyst for olefin polymerization which comprises: (1) a cyclopentadienyl-type ligand, a Group IVB transition metal, and alkyl, aryl, or hydride substituents, as a cation, and (2) a weakly coordinating anion comprising boron substituted with halogenated, such as tetrafluoro-aryl substituents preferably containing silylalkyl substitution, such as para-silyl t-butyldimethyl.

  1. Development of GREET Catalyst Module

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhichao [Argonne National Lab. (ANL), Argonne, IL (United States); Benavides, Pahola T. [Argonne National Lab. (ANL), Argonne, IL (United States); Dunn, Jennifer B. [Argonne National Lab. (ANL), Argonne, IL (United States); Cronauer, Donald C. [Argonne National Lab. (ANL), Argonne, IL (United States)


    In this report, we develop energy and material flows for the production of five different catalysts (tar reforming, alcohol synthesis, Zeolite Socony Mobil-5 [ZSM-5], Mo/Co/ γ-Al2O3, and Pt/ γ-Al2O3) and two chemicals (olivine, dimethyl ether of polyethylene glycol [DEPG]). These compounds and catalysts are now included in the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET™) catalyst module.

  2. Catalysts preparing

    International Nuclear Information System (INIS)

    Normatov, I.Sh.; Mirsaidov, U.M.


    One of the base area of zeolites industry using is catalysis. The catalytic properties of zeolites use in the carbonated reactions in the petrochemistry. Last years zeolite catalysts use in oxidative-reduction processes

  3. Lunar CATALYST (United States)

    National Aeronautics and Space Administration — Lunar Cargo Transportation and Landing by Soft Touchdown (Lunar CATALYST) is a NASA initiative to encourage the development of U.S. private-sector robotic lunar...

  4. High temperature structural, polymeric foams from high internal emulsion polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Hoisington, M.A.; Duke, J.R.; Apen, P.G.


    In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

  5. Photo-oxidation catalysts (United States)

    Pitts, J Roland [Lakewood, CO; Liu, Ping [Irvine, CA; Smith, R Davis [Golden, CO


    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  6. Magnetic and dendritic catalysts. (United States)

    Wang, Dong; Deraedt, Christophe; Ruiz, Jaime; Astruc, Didier


    The recovery and reuse of catalysts is a major challenge in the development of sustainable chemical processes. Two methods at the frontier between homogeneous and heterogeneous catalysis have recently emerged for addressing this problem: loading the catalyst onto a dendrimer or onto a magnetic nanoparticle. In this Account, we describe representative examples of these two methods, primarily from our research group, and compare them. We then describe new chemistry that combines the benefits of these two methods of catalysis. Classic dendritic catalysis has involved either attaching the catalyst covalently at the branch termini or within the dendrimer core. We have used chelating pyridyltriazole ligands to insolubilize catalysts at the termini of dendrimers, providing an efficient, recyclable heterogeneous catalysts. With the addition of dendritic unimolecular micelles olefin metathesis reactions catalyzed by commercial Grubbs-type ruthenium-benzylidene complexes in water required unusually low amounts of catalyst. When such dendritic micelles include intradendritic ligands, both the micellar effect and ligand acceleration promote faster catalysis in water. With these types of catalysts, we could carry out azide alkyne cycloaddition ("click") chemistry with only ppm amounts of CuSO4·5H2O and sodium ascorbate under ambient conditions. Alternatively we can attach catalysts to the surface of superparamagnetic iron oxide nanoparticles (SPIONs), essentially magnetite (Fe3O4) or maghemite (γ-Fe2O3), offering the opportunity to recover the catalysts using magnets. Taking advantage of the merits of both of these strategies, we and others have developed a new generation of recyclable catalysts: dendritic magnetically recoverable catalysts. In particular, some of our catalysts with a γ-Fe2O3@SiO2 core and 1,2,3-triazole tethers and loaded with Pd nanoparticles generate strong positive dendritic effects with respect to ligand loading, catalyst loading, catalytic activity and

  7. Optimal Catalyst and Cocatalyst Precontacting in Industrial Ethylene Copolymerization Processes

    Directory of Open Access Journals (Sweden)

    Paul Aigner


    Full Text Available In industrial-scale catalytic olefin copolymerization processes, catalyst and cocatalyst precontacting before being introduced in the polymerization reactor is of profound significance in terms of catalyst kinetics and morphology control. The precontacting process takes place under either well-mixing (e.g., static mixers or plug-flow (e.g., pipes conditions. The scope of this work is to study the influence of mixing on catalyst/cocatalyst precontacting for a heterogeneous Ziegler-Natta catalyst system under different polymerization conditions. Slurry ethylene homopolymerization and ethylene copolymerization experiments with 1-butene are performed in a 0.5 L reactor. In addition, the effect of several key parameters (e.g., precontacting time, and ethylene/hydrogen concentration on catalyst activity is analyzed. Moreover, a comprehensive mass transfer model is employed to provide insight on the mass transfer process and support the experimental findings. The model is capable of assessing the external and internal mass transfer limitations during catalyst/cocatalyst precontacting process. It is shown that catalyst/cocatalyst precontacting is very important for the catalyst activation as well as for the overall catalyst kinetic behavior. The study reveals that there is an optimum precontacting time before and after which the catalyst activity decreases, while this optimum time depends on the precontacting mixing conditions.

  8. Facile Synthesis of Effcient and Selective Ruthenium Olefin Metathesis Catalysts with Sulfonate and Phosphate Ligands


    Teo, Peili; Grubbs, Robert H.


    A series of novel, air-stable ruthenium NHC catalysts with sulfonate and phosphate anions have been prepared easily in one pot at high yields using commercially available precursors. The catalysts were found to be effective for ring-opening metathesis polymerization, ring-closing metathesis, and cross-metathesis. The catalysts showed higher cis-selectivity in olefin cross-metathesis reactions as compared to earlier known ruthenium-based olefin metathesis catalysts, with allylbenzene and cis-1...

  9. Tailoring Synthesis Conditions of Carbon Xerogels towards Their Utilization as Pt-Catalyst Supports for Oxygen Reduction Reaction (ORR

    Directory of Open Access Journals (Sweden)

    María Jesús Lázaro


    Full Text Available Carbon xerogels characterized by different textural, structural and chemical properties were synthesized and used as supports for Pt catalysts for the application in polymer electrolyte fuel cells. Synthesis conditions were varied in order to synthesize carbon xerogels following the sol-gel method. These included the reactants ratio (precursor/formaldehyde, the catalyst concentration (precursor/catalyst ratio and type (basic and acid, the precursor type (resorcinol and pyrogallol and the solvent (aqueous or acetone based. Stoichiometric mixtures of resorcinol and formaldehyde yielded well polymerized gels and highly developed structures. Slow gelation, favored by the presence of acetone as solvent in the sol and low catalyst concentration, resulted in higher polymerization extent with a highly mesoporous or even macroporous texture and more ordered structure, as evidenced by XPS and Raman spectroscopy. Small Pt particles of ca. 3.5 nm were obtained by using carbon xerogels characterized by an ordered surface structure. The specific activity towards the oxygen reduction reaction, i.e., the limiting catalytic process in low temperature fuel cells, is significantly favored by highly ordered carbon xerogels due to a metal-support enhanced interaction. Nevertheless, surface defects favor the distribution of the metallic particles on the surface of carbon, which in the end influences the effectiveness of the catalyst. Accelerated degradation tests were conducted to evaluate catalyst stability under potential cycling conditions. The observed decay of performance was considerably lower for the catalysts based on ordered carbon xerogels stabilizing Pt particles in a higher extent than the other xerogels and the commercial carbon black support.

  10. Highly dispersed metal catalyst (United States)

    Xiao, Xin; West, William L.; Rhodes, William D.


    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  11. Reactive triblock polymers from tandem ring-opening polymerization for nanostructured vinyl thermosets

    Energy Technology Data Exchange (ETDEWEB)

    Amendt, Mark A.; Pitet, Louis M.; Moench, Sarah; Hillmyer, Marc A. (UMM)


    Multiply functional hydroxyl telechelic poly(cyclooctene-s-5-norbornene-2-methylene methacrylate) was synthesized by ring opening metathesis (co)polymerization of cis-cyclooctene and 5-norbornene-2-methylene methacrylate using the second generation Grubbs catalyst in combination with a symmetric chain transfer agent bearing hydroxyl functionality. The resulting hydroxyl-telechelic polymer was used as a macroinitiator for the ring opening transesterification polymerization of d,l-lactide to form reactive poly(lactide)-b-poly(cyclooctene-s-5-norbornene-2-methylene methacrylate)-b-poly(lactide) triblock polymers. Subsequently, the triblocks were crosslinked by free radical copolymerization with several vinyl monomers including styrene, divinylbenzene, methyl methacrylate, and ethyleneglycol dimethacrylate. Certain conditions led to optically transparent thermosets with mesoscale phase separation as evidenced by small angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. Disordered, bicontinuous structures with nanoscopic domains were generated in several cases, rendering the samples attractive for size-selective membrane applications.

  12. Bimetal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ng, K. Y. Simon; Salley, Steve O.; Wang, Huali


    A catalyst comprises a carbide or nitride of a metal and a promoter element. The metal is selected from the group consisting of Mo, W, Co, Fe, Rh or Mn, and the promoter element is selected from the group consisting of Ni, Co, Al, Si, S or P, provided that the metal and the promoter element are different. The catalyst also comprises a mesoporous support having a surface area of at least about 170 m.sup.2 g.sup.-1, wherein the carbide or nitride of the metal and the promoter element is supported by the mesoporous support, and is in a non-sulfided form and in an amorphous form.

  13. Catalyst Architecture

    DEFF Research Database (Denmark)

    Kiib, Hans; Marling, Gitte; Hansen, Peter Mandal


    How can architecture promote the enriching experiences of the tolerant, the democratic, and the learning city - a city worth living in, worth supporting and worth investing in? Catalyst Architecture comprises architectural projects, which, by virtue of their location, context and their combination...... of programs, have a role in mediating positive social and/or cultural development. In this sense, we talk about architecture as a catalyst for: sustainable adaptation of the city’s infrastructure appropriate renovation of dilapidated urban districts strengthening of social cohesiveness in the city development...

  14. AB(2) functional polyesters via ring opening polymerization: synthesis and characterization

    NARCIS (Netherlands)

    Velthoen, I.W.; Dijkstra, Pieter J.; Feijen, Jan


    Aliphatic AB2 functional polyesters were conveniently prepared by the ring opening polymerization of ε-caprolactone and L-lactide in the presence of the AB2 functional initiator 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and Sn(Oct)2 as the catalyst. In L-lactide polymerization, both bis-MPA

  15. Organo-Lewis acid as cocatalyst for cationic homogeneous metallocene Ziegler-Natta olefin polymerizations

    Energy Technology Data Exchange (ETDEWEB)

    Marks, T.J.; Chen, Y.X.


    The synthesis of the organo-Lewis acid perfluorobiphenylborane (PBB) and the activation of metallocenes are disclosed for the formation of a variety of highly active homogeneous Ziegler-Natta metallocene olefin polymerization, copolymerization and ring-opening polymerization catalysts is described.

  16. Living olefin polymerization processes (United States)

    Schrock, Richard R.; Baumann, Robert


    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  17. Living olefin polymerization processes (United States)

    Schrock, Richard R.; Bauman, Robert


    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  18. Catalysts and methods of using the same

    Energy Technology Data Exchange (ETDEWEB)

    Slowing, Igor Ivan; Kandel, Kapil


    The present invention provides a catalyst including a mesoporous silica nanoparticle and a catalytic material comprising iron. In various embodiments, the present invention provides methods of using and making the catalyst. In some examples, the catalyst can be used to hydrotreat fatty acids or to selectively remove fatty acids from feedstocks.

  19. Mass transport models for a single particle in gas phase propylene polymerization

    NARCIS (Netherlands)

    Parasu Veera, U.


    Olefin polymerisation on heterogeneous catalysts is gaining importance due to widening of the polymer properties window. The supported active catalyst on the heterogeneous particle reacts with the monomer and produces polymer. Polymeric flow (PF) model is relatively simple and assume that particle

  20. Coal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kroenig, W.


    Some considerations in the selection of a catalyst for the liquid phase of coal hydrogenation are discussed. Some of the previous history of such selections is mentioned. At one stage of the development, the principal catalyst had been iron sulfate (FeSO/sub 4/.7H/sub 2/O). Later, for reasons of cost and availability of large supplies, selections had turned to mixtures of iron sulfate and one or another of some iron oxide- and aluminum oxide-containing byproducts of aluminum manufacture, namely Bayermasse, Luxamsse, or Lautamasse. Much of the discussion centered on optimal proportions for such mixtures, particularly as related to pH values of resulting coal pastes. Upper Silesian coal was more alkaline than Ruhr coal, and Bayermasse, etc., were quite alkaline. Thus, since the iron sulfate served as a partial neutralizer for the coal as well as a catalyst, it seemed necessary to increase the proportions of iron sulfate in the catalyst mixture when processing coal of greater alkalinity. A further reason for a greater proportion of iron sulfate seemed to be that most of the catalytic activity of the iron came from the ferrous iron of iron sulfate rather than from the ferric iron of the other materials. Ferrous-ferric ratios also seemed to indicate that Luxmasse or Lautamasse might be better catalyst components than Bayermasse but their water content sometimes caused handling problems, so Bayermasse had been more widely used. Formation of deposits in the preheater was more likely due to the Bayermasse than to the iron sulfate; sodium sulfide could help to prevent them.

  1. Hydrogen evolution reaction catalyst (United States)

    Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan


    Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

  2. Controlled free radical polymerization of vinyl acetate with cobalt ...

    Indian Academy of Sciences (India)

    C, the colour-free reaction without solid catalyst impurity was 95% complete within a few hours. The high molecular weight of polyvinyl acetate (PVAc) with its relatively low molecular distribution without unreacted monomer provided a new method in microprocessing of the controlled radical polymerization of vinyl acetate in ...

  3. Controlled radical polymerization of vinyl acetate in presence of ...

    Indian Academy of Sciences (India)

    Mesoporous silica; heterogeneous catalyst; specific sequences; controlled free radical polymerization; ... copolymers. CRP is a common technique for synthesis of (co)polymers with well-defined molecular parameters. (Mw/Mn), reactive end groups, composition and ... bulk copolymerization of vinyl acetate with butyl acrylate.

  4. Schlenk Techniques for Anionic Polymerization

    KAUST Repository

    Ratkanthwar, Kedar


    Anionic polymerization-high vacuum techniques (HVTs) are doubtlessly the most prominent and reliable experimental tools to prepare polymer samples with well-defined and, in many cases, complex macromolecular architectures. Due to the high demands for time and skilled technical personnel, HVTs are currently used in only a few research laboratories worldwide. Instead, most researchers in this filed are attracted to more facile Schlenk techniques. The basic principle of this technique followed in all laboratories is substantially the same, i.e. the use of alternate vacuum and inert gas atmosphere in glass apparatus for the purification/charging of monomer, solvents, additives, and for the manipulation of air-sensitive compounds such as alkyl metal initiators, organometallic or organic catalysts. However, it is executed quite differently in each research group in terms of the structure of Schlenk apparatus (manifolds, connections, purification/storage flasks, reactors, etc.), the use of small supplementary devices (soft tubing, cannulas, stopcocks, etc.) and experimental procedures. The operational methods are partly purpose-oriented while also featured by a high flexibility, which makes it impossible to describe in detail each specific one. In this chapter we will briefly exemplify the application of Schlenk techniques for anionic polymerization by describing the performance of a few experiments from our own work.

  5. Oxidation catalysts on alkaline earth supports (United States)

    Mohajeri, Nahid


    An oxidation catalyst includes a support including particles of an alkaline earth salt, and first particles including a palladium compound on the support. The oxidation catalyst can also include precious metal group (PMG) metal particles in addition to the first particles intermixed together on the support. A gas permeable polymer that provides a continuous phase can completely encapsulate the particles and the support. The oxidation catalyst may be used as a gas sensor, where the first particles are chemochromic particles.

  6. Catalyst Architecture

    DEFF Research Database (Denmark)

    Catalyst Architecture’ takes its point of departure in a broadened understanding of the role of architecture in relation to developmental problems in large cities. Architectural projects frame particular functions and via their form language, they can provide the user with an aesthetic experience....... The broadened understanding of architecture consists in that an architectural project, by virtue of its placement in the context and of its composition of programs, can have a mediating role in a positive or cultural development of the district in question. In this sense, we talk about architecture as catalyst...... cities on the planet have growing pains and social cohesiveness is under pressure from an increased difference between rich and poor, social segregation, ghettoes, immigration of guest workers and refugees, commercial mass tourism etc. In this context, it is important to ask which role architecture...

  7. Alargamento da distribuição de massa molar de polímeros sintetizados com catalisadores metalocênicos dual-site Broadening of molecular weight distribution of polymers synthesized by metallocene-based dual-site catalysts

    Directory of Open Access Journals (Sweden)

    João H. Z. dos Santos


    Full Text Available The main topics related to the use of dual-site catalysts in the production of polymers with broad molecular weight distribution are reviewed. The polymerization using dual-site catalysts is more economical and allows to produce a higher quality product than other processes, such as polymer blend and multistage reactors. However, the formulation of these catalysts is quite complicated since the same catalyst must produce distinct polymer grades. In addition, the release of patents concerning the combination of metallocenes and new technologies for polymerization shows that polymerization processes using dual-site catalysts are of current industrial interest.

  8. Broadening of molecular weight distribution of polymers synthesized by metallocene-based dual-site catalysts; Alargamento da distribuicao de massa molar de polimeros sintetizados com catalisadores metalocenicos dual-site

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Joao H.Z. dos [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica]. E-mail:; Fisch, Adriano G.; Cardozo, Nilo S.M.; Secchi, Argimiro R. [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Engenharia Quimica


    The main topics related to the use of dual-site catalysts in the production of polymers with broad molecular weight distribution are reviewed. The polymerization using dual-site catalysts is more economical and allows to produce a higher quality product than other processes, such as polymer blend and multistage reactors. However, the formulation of these catalysts is quite complicated since the same catalyst must produce distinct polymer grades. In addition, the release of patents concerning the combination of metallocenes and new technologies for polymerization shows that polymerization processes using dual-site catalysts are of current industrial interest. (author)

  9. Polymeric Membrane Reactors


    José M. Sousa; Luís M. Madeira; João C. Santos; Adélio Mendes


    The aim of this chapter is the study of membrane reactors with polymeric membranes, particularly catalytic polymeric membranes. After an introduction where the main advantages and disadvantages of the use of polymeric membranes are summarised, a review of the main areas where they have been applied, integrated in chemical reactors, is presented. This excludes the field of bio-membranes processes, which is analysed in a specific chapter of this book. Particular attention is then given to model...

  10. Mononuclear Nickel(II Complexes with Schiff Base Ligands: Synthesis, Characterization, and Catalytic Activity in Norbornene Polymerization

    Directory of Open Access Journals (Sweden)

    Yi-Mei Xu


    Full Text Available The nickel(II catalyst has manifested higher catalytic activity compared to that of other late transition metal catalysts for norbornene polymerization. Therefore, several structurally similar trans-nickel(II compounds of N,O-chelate bidentate ligands were synthesized and characterized. Both the electronic effect and the steric hindrance influence polymerization. The molecular structures of 2, 4 and 5 were further confirmed by single-crystal X-ray diffraction.

  11. Bi-metallic catalysts, methods of making, and uses thereof

    KAUST Repository

    Basset, Jean-Marie


    Provided herein are bi-metallic catalysts, methods of making, and uses thereof. In some embodiments, the bi-metallic catalyst contains two different metal catalysts that can be used in hydrocarbon metathesis reactions, in some embodiments, the methods of making the bi-metallic catalysts can include two steps utilizing a surface organometallic chemistry approach in which the two different metal catalysts are sequentially grafted onto a support.

  12. Physicochemically functional ultrathin films by interfacial polymerization (United States)

    Lonsdale, Harold K.; Babcock, Walter C.; Friensen, Dwayne T.; Smith, Kelly L.; Johnson, Bruce M.; Wamser, Carl C.


    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclsoed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers.

  13. Heterogeneous Initiators for Sustainable Polymerization Processes (United States)

    Jones, Matthew D.

    One of the main challenges facing the twenty-first century is the need to produce chemicals from renewable resources. The dwindling supplies of fossil fuels coupled with instability in supply mean that technologies that were once deemed too expensive are now becoming more economically viable options. The majority of man-made polymers are derived from crude oil based monomers. However, in recent years a tremendous effort has been channeled into the preparation of polymers from sustainable chemicals. Two classic examples are polylactide (derived from corn starch) and polycarbonates (prepared directly from CO2). This chapter serves as an introduction into these two polymers and reviews the literature associated with heterogeneous catalyst for the polymerizations, concentrating on approaches describing the heterogenization of homogeneous catalysts.

  14. An introduction to catalyst

    International Nuclear Information System (INIS)

    Jeon, Hak Je


    This book explains basic conception of catalyst such as definition, velocity of chemical reaction and velocity of catalyst reaction, absorption with absorption energy and chemical absorption, pore structure with the role of pore and measurement of pore structure, catalyst activity on solid structure, electrical property on catalyst activity, choice and design of catalyst, catalytic reaction with reaction velocity and chemical equilibrium and reaction velocity model, measurement of reaction velocity and material analysis, catalyst for mixed compound, catalyst for solid acid and catalyst for supported metal.

  15. Development of GREET Catalyst Module

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhichao [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division; Dunn, Jennifer B. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division; Cronauer, Donald C. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division


    Catalysts are critical inputs for many pathways that convert biomass into biofuels. Energy consumption and greenhouse gas (GHG) emissions during the production of catalysts and chemical inputs influence the life-cycle energy consumption, and GHG emissions of biofuels and need to be considered in biofuel life-cycle analysis (LCA). In this report, we develop energy and material flows for the production of three different catalysts (tar reforming, alcohol synthesis, Zeolite Socony Mobil-5 [ZSM-5]) and two chemicals (olivine, dimethyl ether of polyethylene glycol [DEPG]). These compounds and catalysts are now included in the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET™) catalyst module. They were selected because they are consumed in existing U.S. Department of Energy (DOE) analyses of biofuel processes. For example, a thermochemical ethanol production pathway (indirect gasification and mixed alcohol synthesis) developed by the National Renewable Energy Laboratory (NREL) uses olivine, DEPG, and tar reforming and alcohol synthesis catalysts (Dutta et al., 2011). ZSM-5 can be used in biofuel production pathways such as catalytic upgrading of sugars into hydrocarbons (Biddy and Jones, 2013). Other uses for these compounds and catalysts are certainly possible. In this report, we document the data sources and methodology we used to develop material and energy flows for the catalysts and compounds in the GREET catalyst module. In Section 2 we focus on compounds used in the model Dutta et al. (2011) developed. In Section 3, we report material and energy flows associated with ZSM-5 production. Finally, in Section 4, we report results.

  16. Step-Growth Polymerization. (United States)

    Stille, J. K.


    Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

  17. Effect of Temperature and Catalyst Concentration on Polyglycerol during Synthesis

    Directory of Open Access Journals (Sweden)

    Carolina Ardila-Suárez


    Full Text Available Morphology, molecular weight, polydispersity, functionality, and thermal properties are important characteristics when using polyglycerol as a building block in the development of materials for industrial applications such as hydrogels, surfactants, asphalts additives, cosmetics, pharmaceutical, biomedical, and drug delivery systems. In this study several experimental techniques are used to understand the effect of process variables during synthesis in the catalyzed etherification of glycerol, a coproduct of biodiesel industry. Biobased polyglycerol is a high-valued product, which is useful as building block material because of its remarkable features, for instance, multiple hydrophilic groups, excellent biocompatibility, and highly flexible aliphatic polyether backbone. A connection between polyglycerol characteristics and process variables during synthesis allows the control of glycerol polymerization through reaction conditions. We show that temperature and catalyst concentration can be tuned with the aim of tailoring fundamental polyglycerol parameters including molecular weight, polydispersity, morphology, and functionality.

  18. Metallocene-catalyzed alkene polymerization and the observation of Zr-allyls (United States)

    Landis, Clark R.; Christianson, Matthew D.


    Single-site polymerization catalysts enable exquisite control over alkene polymerization reactions to produce new materials with unique properties. Knowledge of catalyst speciation and fundamental kinetics are essential for full mechanistic understanding of zirconocene-catalyzed alkene polymerization. Currently the effect of activators on fundamental polymerization steps is not understood. Progress in understanding activator effects requires determination of fundamental kinetics for zirconocene catalysts with noncoordinating anions such as [B(C6F5)4]−. Kinetic NMR studies at low temperature demonstrate a very fast propagation rate for 1-hexene polymerization catalyzed by [(SBI)Zr(CH2SiMe3)][B(C6F5)4] [where SBI is rac-Me2Si(indenyl)2] with complete consumption of 1-hexene before the first NMR spectrum. Surprisingly, the first NMR spectrum reveals, aside from uninitiated catalyst, Zr-allyls as the sole catalyst-containing species. These Zr-allyls, which exist in two diastereomeric forms, have been characterized by physical and chemical methods. The mechanism of Zr-allyl formation was probed with a trapping experiment, leading us to favor a mechanism in which Zr-polymeryl undergoes β-H transfer to metal without dissociation of coordinated alkene followed by σ-bond metathesis to form H2 and Zr-allyl. Zr-allyl species undergo slow reactions with alkene but react rapidly with H2 to form hydrogenation products. PMID:17032772

  19. Applied bioactive polymeric materials

    CERN Document Server

    Carraher, Charles; Foster, Van


    The biological and biomedical applications of polymeric materials have increased greatly in the past few years. This book will detail some, but not all, of these recent developments. There would not be enough space in this book to cover, even lightly, all of the major advances that have occurred. Some earlier books and summaries are available by two of this book's Editors (Gebelein & Carraher) and these should be consul ted for additional information. The books are: "Bioactive Polymeric Systems" (Plenum, 1985); "Polymeric Materials In Medication" (Plenum, 1985); "Biological Acti vi ties of Polymers" (American Chemical Society, 1982). Of these three, "Bioacti ve Polymeric Systems" should be the most useful to a person who is new to this field because it only contains review articles written at an introductory level. The present book primarily consists of recent research results and applications, with only a few review or summary articles. Bioactive polymeric materials have existed from the creation of life...

  20. Palladium - potassium humate coated by Polymetallic catalysts for the process of hydrogenation of nitrocompounds

    Directory of Open Access Journals (Sweden)

    E. Yermoldina


    Full Text Available Results of studies of humic substances in the quality of natural polymeric modifier for the coated palladium catalysts are presented in the paper. Synthesis of new catalysts based on palladium - potassium humate fixed on various inorganic carriers and their catalytic properties have been studied. The catalysts of 0,8% Pd - Potassium’s Humat(1%/B-94 and 0,8% Pd /Shungite 1% КОН are optimal.

  1. Polymer-supported CuPd nanoalloy as a synergistic catalyst for electrocatalytic reduction of carbon dioxide to methane. (United States)

    Zhang, Sheng; Kang, Peng; Bakir, Mohammed; Lapides, Alexander M; Dares, Christopher J; Meyer, Thomas J


    Developing sustainable energy strategies based on CO2 reduction is an increasingly important issue given the world's continued reliance on hydrocarbon fuels and the rise in CO2 concentrations in the atmosphere. An important option is electrochemical or photoelectrochemical CO2 reduction to carbon fuels. We describe here an electrodeposition strategy for preparing highly dispersed, ultrafine metal nanoparticle catalysts on an electroactive polymeric film including nanoalloys of Cu and Pd. Compared with nanoCu catalysts, which are state-of-the-art catalysts for CO2 reduction to hydrocarbons, the bimetallic CuPd nanoalloy catalyst exhibits a greater than twofold enhancement in Faradaic efficiency for CO2 reduction to methane. The origin of the enhancement is suggested to arise from a synergistic reactivity interplay between Pd-H sites and Cu-CO sites during electrochemical CO2 reduction. The polymer substrate also appears to provide a basis for the local concentration of CO2 resulting in the enhancement of catalytic current densities by threefold. The procedure for preparation of the nanoalloy catalyst is straightforward and appears to be generally applicable to the preparation of catalytic electrodes for incorporation into electrolysis devices.

  2. Copolymerization of ethylene and cycloolefin with metallocene catalysts : I. Effect of catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.H.; Jung, H.K.; Kim, W.S.; Min, K.E.; Park, L.S.; Seo, K.H.; Kang, I.K. [Kyungpook National University, Taegu (Korea); Noh, S.K. [Yeoungnam University, Kyungsan (Korea)


    The copolymerization of ethylene (E) and norbornene (N) was examined by using various metallocene catalysts and modified-MAO (MMAO) cocatalyst. For C{sub 2}-symmetry catalysts such as rac-Et(Ind){sub 2}ZrCl{sub 2}, Me{sub 2}Si(Ind){sub 2}ZrCl{sub 2},Me{sub 2}Si(Cp){sub 2}ZrCl{sub 2} and Cs-symmetrical iPr(FluCp)ZrCl{sub 2} as well as CGC and di-bridged zirconocene, the effects of catalyst structure and [N]/[E] feed ratio on catalyst activity, thermal property and [N] content of copolymer (COC) was investigated. For rac-Et(Ind){sub 2}ZrCl{sub 2} catalyst of a constant [N]/[E] feed ratio, the appropriate conditions of [Al]/[Zr] mole ratio, polymerization temperature and cocatalyst structure were found to be 3000, 40 deg. C, MMAO cocatalyst, respectively. As [N]/[E] feed ratio increased. the incorporation of norbornene to copolymer increased while the activity of catalyst decreased except for iPr(FluCp)ZrCl{sub 2}. With consideration of catalyst activity as well as N content, it was found that rac-Et(Ind){sub 2}ZrCl{sub 2}/MMAO system exhibited relatively high activity and controllable T{sub g}. Monomer reactivity ratio was determined by Kelen-Tudos method. (author). 34 refs., 5 tabs., 3 figs.

  3. Synthetic catalysts that separate CO.sub.2 from the atmosphere and gas mixtures (United States)

    Lightstone, Felice C; Wong, Sergio E; Lau, Edmond Y; Satcher, Jr., Joe H; Aines, Roger D


    The creation of a catalyst that can be used for a wide variety of applications including the steps of developing preliminary information regarding the catalyst, using the preliminary information to produce a template of the catalyst, and using the template of the catalyst to produce the catalyst.

  4. Biomass processing over gold catalysts

    CERN Document Server

    Simakova, Olga A; Murzin, Dmitry Yu


    The book describes the valorization of biomass-derived compounds over gold catalysts. Since biomass is a rich renewable feedstock for diverse platform molecules, including those currently derived from petroleum, the interest in various transformation routes has become intense. Catalytic conversion of biomass is one of the main approaches to improving the economic viability of biorefineries.  In addition, Gold catalysts were found to have outstanding activity and selectivity in many key reactions. This book collects information about transformations of the most promising and important compounds derived from cellulose, hemicelluloses, and woody biomass extractives. Since gold catalysts possess high stability under oxidative conditions, selective oxidation reactions were discussed more thoroughly than other critical reactions such as partial hydrogenation, acetalization, and isomerization. The influence of reaction conditions, the role of the catalyst, and the advantages and disadvantages of using gold are pre...

  5. Dynamics of Catalyst Nanoparticles

    DEFF Research Database (Denmark)

    Hansen, Thomas Willum; Cavalca, Filippo; Wagner, Jakob Birkedal

    Transmission electron microscopy (TEM) is extensively used in catalysis research. Recent developments in aberration correction allows imaging surface structures with unprecedented resolution. Using these correctors in conjunction with environmental TEM (ETEM), where imaging of materials can be done...... under gas exposure, dynamic phenomena such as sintering and growth can be observed with sub-Ångstrøm resolution. Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals...... and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. In order to initiate a systematic study of the dynamics and sintering of nanoparticles, various catalytic systems have been...

  6. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells (United States)


    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  7. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells. (United States)

    Mansor, Noramalina; Jorge, A Belen; Corà, Furio; Gibbs, Christopher; Jervis, Rhodri; McMillan, Paul F; Wang, Xiaochen; Brett, Daniel J L


    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li + Cl - ), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li + Cl - catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA.

  8. Tailoring iron complexes for ethylene oligomerization and/or polymerization. (United States)

    Zhang, Wenjuan; Sun, Wen-Hua; Redshaw, Carl


    Recent progress in the use of iron-based complex pre-catalysts for ethylene reactivity is reviewed, illustrating the current state-of-the-art and the potential usefulness of such systems for delivering solely ethylene oligomerization or polymerization products. The problems associated with the industrial use of late transition metal complex pre-catalysts are generally regarded as catalyst deactivation and the formation of more products of lower molecular weight at elevated temperature. These problems have been addressed for iron-based complex pre-catalysts via the fine tuning of substituents of existing ligands and/or the design of new ligand sets. Results revealed that modified bis(imino)pyridyliron dichlorides were capable of operating at elevated temperatures, and were capable of delivering highly linear polyethylene. Other new models of iron complexes have achieved high activity for ethylene oligomerization and/or polymerization. Particularly successful has been the use of the 2-iminophenanthrolyliron pre-catalyst, which have now been utilized in a 500 tonne pilot plant.

  9. Electroactivity in Polymeric Materials

    CERN Document Server


    Electroactivity in Polymeric Materials provides an in-depth view of the theory of electroactivity and explores exactly how and why various electroactive phenomena occur. The book explains the theory behind electroactive bending (including ion-polymer-metal-composites –IPMCs), dielectric elastomers, electroactive contraction, and electroactive contraction-expansion cycles.  The book also balances theory with applications – how electroactivity can be used – drawing inspiration from the manmade mechanical world and the natural world around us.  This book captures: A complete introduction to electroactive materials including examples and recent developments The theory and applications of numerous topics like electroactive bending of dielectric elastomers and electroactive contraction and expansion New topics, such as biomimetic applications and energy harvesting This is a must-read within the electroactive community, particularly for professionals and graduate students who are interested in the ...

  10. Sulfur tolerant zeolite supported platinum catalysts for aromatics hydrogenation (United States)


    An experimental study of sulfur tolerant zeolite platinum catalysts for aormatics hydrogenation. Platinum catalysts supported on Y-zeolite have been prepared and characterized in various ways, including the hydrogenation of toluene in a high pressure...

  11. Polymeric coordination compounds

    Indian Academy of Sciences (India)


    Ce(dipic)3Sr(dipicH2)(OH2)3·5H2O (4) (dipicH2 – dipicolinic acid) exhibits 1-D polymeric chain structure, built up of alternating nine coordinate Ce and eight coordinate. Sr polyhedra. The analogous Ce–Ba compound (5) exhibits a polymeric chain built up of nine coordinate Ba units only, arranged in a hexagonal lattice.

  12. Surface Initiated Polymerizations via e-ATRP in Pure Water

    Directory of Open Access Journals (Sweden)

    Seyed Schwan Hosseiny


    Full Text Available Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very controlled growth of the polymer chains leading towards a steady increase in film thickness. Electrochemical quartz crystal microbalance displayed a highly regular increase in surface confined mass only after the addition of the pre-copper catalyst which is reduced in situ and transformed into the catalyst. Even after isolation and washing of the modified electrode surface, reinitiation was achieved with retention of the controlled electrochemical ATRP reaction. This reinitiation after isolation proves the livingness of the polymerization. This approach has interesting potential for smart thin film materials and offers also the possibility of post-modification via additional electrochemical induced reactions.

  13. Silicoaluminates as “Support Activator” Systems in Olefin Polymerization Processes (United States)

    Tabernero, Vanessa; Camejo, Claudimar; Terreros, Pilar; Alba, María Dolores; Cuenca, Tomás


    In this work we report the polymerization behaviour of natural clays (montmorillonites, MMT) as activating supports. These materials have been modified by treatment with different aluminium compounds in order to obtain enriched aluminium clays and to modify the global Brönsted/Lewis acidity. As a consequence, the intrinsic structural properties of the starting materials have been changed. These changes were studied and these new materials used for ethylene polymerization using a zirconocene complex as catalyst. All the systems were shown to be active in ethylene polymerization. The catalyst activity and the dependence on acid strength and textural properties have been also studied. The behaviour of an artificial silica (SBA 15) modified with an aluminium compound to obtain a silicoaluminate has been studied, but no ethylene polymerization activity has been found yet.

  14. Nanostructured catalysts for organic transformations. (United States)

    Chng, Leng Leng; Erathodiyil, Nandanan; Ying, Jackie Y


    The development of green, sustainable and economical chemical processes is one of the major challenges in chemistry. Besides the traditional need for efficient and selective catalytic reactions that will transform raw materials into valuable chemicals, pharmaceuticals and fuels, green chemistry also strives for waste reduction, atomic efficiency and high rates of catalyst recovery. Nanostructured materials are attractive candidates as heterogeneous catalysts for various organic transformations, especially because they meet the goals of green chemistry. Researchers have made significant advances in the synthesis of well-defined nanostructured materials in recent years. Among these are novel approaches that have permitted the rational design and synthesis of highly active and selective nanostructured catalysts by controlling the structure and composition of the active nanoparticles (NPs) and by manipulating the interaction between the catalytically active NP species and their support. The ease of isolation and separation of the heterogeneous catalysts from the desired organic product and the recovery and reuse of these NPs further enhance their attractiveness as green and sustainable catalysts. This Account reviews recent advances in the use of nanostructured materials for catalytic organic transformations. We present a broad overview of nanostructured catalysts used in different types of organic transformations including chemoselective oxidations and reductions, asymmetric hydrogenations, coupling reactions, C-H activations, oxidative aminations, domino and tandem reactions, and more. We focus on recent research efforts towards the development of the following nanostructured materials: (i) nanostructured catalysts with controlled morphologies, (ii) magnetic nanocomposites, (iii) semiconductor-metal nanocomposites, and (iv) hybrid nanostructured catalysts. Selected examples showcase principles of nanoparticle design such as the enhancement of reactivity, selectivity


    Novel and diversified macromolecular structures, which include polymers with designed topologies (top), compostions (middle), and functionalities (bottom), can be prepared by atom transfer radical polymerization processes. These polymers can be synthesized from a large variety of...

  16. Method of performing sugar dehydration and catalyst treatment (United States)

    Hu, Jianli [Kennewick, WA; Holladay, Johnathan E [Kennewick, WA; Zhang, Xinjie [Burlington, MA; Wang, Yong [Richland, WA


    The invention includes a method of treating a solid acid catalyst. After exposing the catalyst to a mixture containing a sugar alcohol, the catalyst is washed with an organic solvent and is then exposed to a second reaction mixture. The invention includes a process for production of anhydrosugar alcohol. A solid acid catalyst is provided to convert sugar alcohol in a first sample to an anhydrosugar alcohol. The catalyst is then washed with an organic solvent and is subsequently utilized to expose a second sample. The invention includes a method for selective production of an anhydrosugar. A solid acid catalyst is provided within a reactor and anhydrosugar alcohol is formed by flowing a starting sugar alcohol into the reactor. The acid catalyst is then exposed to an organic solvent which allows a greater amount of additional anhydrosugar to be produced than would occur without exposing the acid catalyst to the organic solvent.

  17. Efeito de doadores de elétrons na polimerização de butadieno com catalisadores à base de neodímio Effect of electron donors on the polymerization of butadiene with Ziegler-Natta catalysts based on neodymium

    Directory of Open Access Journals (Sweden)

    Tereza C. J. Rocha


    Full Text Available Foi estudado um processo de polimerização de butadieno, em escala de laboratório, para a obtenção de polibutadieno com alto teor de unidades repetitivas 1,4-cis. Foi utilizado um sistema catalítico do tipo Ziegler-Natta ternário, constituído por versatato de neodímio (catalisador, hidreto de diisobutilalumínio (cocatalisador e cloreto de tert-butila (agente de cloração. O solvente utilizado foi uma mistura de hexano e ciclo-hexano (80/20 v/v. Foi estudado sistematicamente o efeito da presença de dois doadores de elétrons, tetra-hidrofurano (THF e tetrametiletilenodiamina (TMEDA. Os doadores de elétrons foram adicionados ao meio da polimerização e/ou à solução do preparo do catalisador. A proporção dos compostos doadores de elétrons variou entre 20 e 200 ppm para o THF e entre 0 e 15 ppm para o TMEDA. Observou-se o efeito dos doadores de elétrons sobre a estereosseletividade e a atividade do sistema catalítico, a massa molar e a distribuição de massa molar do polibutadieno obtido. Os polímeros foram caracterizados por espectroscopia na região do infravermelho, cromatografia por exclusão de tamanho e calorimetria diferencial de varredura. Foram obtidos polímeros com teores de unidades 1,4-cis variando entre 99,2% e 93%. A massa molar ponderal média, , variou de 2,2 a 7,0 x 10(5. A temperatura de transição vítrea dos polímeros se manteve em torno de -110 ºC.A laboratory scale process for producing polybutadiene with high content of cis-1,4 repeating units was studied. A Ziegler-Natta catalytic system constituted of neodymium versatate (catalyst, diisobutylaluminium hydride (cocatalyst and tert-butyl chloride (chlorinating agent was used. The solvent employed was a mixture of hexane and cyclohexane (80/20 v/v. The effect of two electron donors, tetrahydrofuran (THF and tetramethylethylenediamine (TMEDA, was studied. The electron donors were added to the polymerization medium and/or to the solvent employed in the



    Edita Jasiukaitytė-Grojzdek,; Matjaž Kunaver,; Ida Poljanšek


    Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst at different temperatures. At the highest treatment temperature (150 °C) liquefaction of wood pulp cellulose was achieved and was dependant on cellulose polymerization degree (DP). Furthermore, the rate of amorphous cellulose weight loss was found to increase with cellulose degree of polymerization, while the rate of crystalline cellulose weight loss was reciprocal to the size of the crystallites. ...

  19. Influência do agente de cloração do catalisador à base de veodímio e da razão molar Cl: Nd na polimerização do butadieno Influence of the chlorinating agent of neodymium based catalysts and Cl: Nd molar ratio on butadiene polymerization

    Directory of Open Access Journals (Sweden)

    Cintia N. Ferreira


    Full Text Available Neste trabalho foi utilizado um sistema catalítico composto por hidreto de diisobutilalumínio (DIBAH, versatato de neodímio (NdV e um agente de cloração para avaliar a influência da fonte de cloro e da razão molar Cl:Nd nas características da reação de polimerização (conversão e constante de velocidade de propagação e do polibutadieno (massa molecular e microestrutura. Os agentes de cloração estudados foram cloreto de t-butila (t-BuCl, sesquicloreto de etilalumínio (EASC e cloreto de dietilalumínio (DEAC. As razões molares Cl:Nd utilizadas foram: 1:1, 3:1 e 5:1 para o t-BuCl; 0,5:1, 1:1 e 3:1 para o EASC e 1:1, 1,5:1, 3:1 e 5:1 para o DEAC. Foi observada a existência, para cada agente de cloração, de um valor ótimo de razão molar Cl:Nd para o qual a conversão foi máxima. O DEAC apresentou uma maior conversão em relação aos outros agentes de cloração; em contrapartida, o t-BuCl produziu polibutadienos com maior teor de unidades 1,4-cis e maior massa molecular (n e wIn this work catalyst systems consisting of diisobutylaluminium hydride (DIBAH, neodymium versatate (NdV and a chlorinating agent were employed to study the influence of the chloride source and Cl:Nd molar ratio on 1,3-butadiene polymerization and polybutadiene's characteristics (molecular weight and microstructure. The chloride sources studied were t-butyl chloride, ethylaluminium sesquichloride (EASC and diethylaluminium chloride (DEAC. The Cl:Nd molar ratios used were 1:1, 3:1 e 5:1 for t-butyl chloride; 0.5:1, 1:1 and 3:1 for EASC and 1:1, 1.5:1, 3:1 and 5:1 for DEAC. A maximum value of Cl:Nd molar ratio exists. Moreover, DEAC showed to be more reactive than EASC and t-BuCl but t-BuCl produced higher molecular weight and cis-1,4 units contents.

  20. Supported catalyst systems and method of making biodiesel products using such catalysts (United States)

    Kim, Manhoe; Yan, Shuli; Salley, Steven O.; Ng, K. Y. Simon


    A heterogeneous catalyst system, a method of preparing the catalyst system and a method of forming a biodiesel product via transesterification reactions using the catalyst system is disclosed. The catalyst system according to one aspect of the present disclosure represents a class of supported mixed metal oxides that include at least calcium oxide and another metal oxide deposited on a lanthanum oxide or cerium oxide support. Preferably, the catalysts include CaO--CeO.sub.2ZLa.sub.2O.sub.3 or CaO--La.sub.2O.sub.3/CeO.sub.2. Optionally, the catalyst may further include additional metal oxides, such as CaO--La.sub.2O.sub.3--GdOxZLa.sub.2O.sub.3.

  1. Conductive cotton prepared by polyaniline in situ polymerization using laccase. (United States)

    Zhang, Ya; Dong, Aixue; Wang, Qiang; Fan, Xuerong; Cavaco-Paulo, Artur; Zhang, Ying


    The high-redox-potential catalyst laccase, isolated from Aspergillus, was first used as a biocatalyst in the oxidative polymerization of water-soluble conductive polyaniline, and then conductive cotton was prepared by in situ polymerization under the same conditions. The polymerization of aniline was performed in a water dispersion of sodium dodecylbenzenesulfonate (SDBS) micellar solution with atmospheric oxygen serving as the oxidizing agent. This method is ecologically clean and permits a greater degree of control over the kinetics of the reaction. The conditions for polyaniline synthesis were optimized. Characterizations of the conducting polyaniline and cotton were carried out using Fourier transform infrared spectroscopy, UV-vis spectroscopy, cyclic voltammetry, the fabric induction electrostatic tester, and the far-field EMC shielding effectiveness test fixture.

  2. Recent advances on polymeric membranes for membrane reactors

    KAUST Repository

    Buonomenna, M. G.


    Membrane reactors are generally applied in high temperature reactions (>400 °C). In the field of fine chemical synthesis, however, much milder conditions are generally applicable and polymeric membranes were applied without their damage. The successful use of membranes in membrane reactors is primary the result of two developments concerning: (i) membrane materials and (ii) membrane structures. The selection of a suited material and preparation technique depends on the application the membrane is to be used in. In this chapter a review of up to date literature about polymers and configuration catalyst/ membranes used in some recent polymeric membrane reactors is given. The new emerging concept of polymeric microcapsules as catalytic microreactors has been proposed. © 2012 Bentham Science Publishers. All rights reserved.

  3. Polyethylene-waste tire dust composites via in situ polymerization

    International Nuclear Information System (INIS)

    Reyes A, Y. K.; Narro C, R. I.; Ramos A, M. E.; Neira V, M. G.; Diaz E, J.; Enriquez M, F.; Valencia L, L. A.; Saade C, H.; Diaz de L, R.


    Polyethylene/waste tire dust (WTD) composites were obtained by an in situ polymerization technique. The surface of the WTD was modified with deposition of polyethylene by using plasma polymerization. Ethylene polymerization was carried out using bis(cyclopentadienyl) titanium dichloride (Cp 2 TiCl 2 ) as homogeneous metallocenes catalyst, while diethylaluminum chloride (DEAC), ethyl aluminum sesquichloride (EASC) and methyl alumino xane (Mao) were used as co-catalysts at two different [Al]/[Ti] molar ratio. The main characteristics of the obtained polyethylenes were determined by size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that by using EASC and Mao the highest catalytic activities were presented at a [Al]/[Ti] molar ratio of 9.17 and 18.33 respectively. Even though it was possible to obtain polyethylene using WTD (modified or unmodified) the catalytic activity was lower than in the case in which no WTD was added in ethylene polymerization. Scanning transmission electronic microscopy images evidenced that the original morphology of the polyethylenes was not modified by the presence of WTD. (Author)

  4. Polyethylene-waste tire dust composites via in situ polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Reyes A, Y. K.; Narro C, R. I.; Ramos A, M. E. [Universidad Autonoma de Coahuila, Facultad de Ciencias Quimicas, Blvd. Venustiano Carranza s/n, 25280 Saltillo, Coahuila (Mexico); Neira V, M. G.; Diaz E, J.; Enriquez M, F.; Valencia L, L. A.; Saade C, H.; Diaz de L, R., E-mail: [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna Hermosillo No. 40, Col. San Jose de los Cerritos, 25293 Saltillo, Coahuila (Mexico)


    Polyethylene/waste tire dust (WTD) composites were obtained by an in situ polymerization technique. The surface of the WTD was modified with deposition of polyethylene by using plasma polymerization. Ethylene polymerization was carried out using bis(cyclopentadienyl) titanium dichloride (Cp{sub 2}TiCl{sub 2}) as homogeneous metallocenes catalyst, while diethylaluminum chloride (DEAC), ethyl aluminum sesquichloride (EASC) and methyl alumino xane (Mao) were used as co-catalysts at two different [Al]/[Ti] molar ratio. The main characteristics of the obtained polyethylenes were determined by size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that by using EASC and Mao the highest catalytic activities were presented at a [Al]/[Ti] molar ratio of 9.17 and 18.33 respectively. Even though it was possible to obtain polyethylene using WTD (modified or unmodified) the catalytic activity was lower than in the case in which no WTD was added in ethylene polymerization. Scanning transmission electronic microscopy images evidenced that the original morphology of the polyethylenes was not modified by the presence of WTD. (Author)

  5. Catalysts and methods for ring opening metathesis polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Schrock, Richard Royce; Autenrieth, Benjamin


    The present invention, among other things, provides highly syndiotactic poly(dicyclopentadiene) and/or hydrogenated poly(dicyclopentadiene), compositions thereof, and compounds and methods for preparing the same. In some embodiments, a provided compound is a compound of formula I, II or III. In some embodiments, a provided method comprises providing a compound of formula I, II or III.

  6. Catalysts and methods for ring opening metathesis polymerization (United States)

    Schrock, Richard Royce; Autenrieth, Benjamin


    The present invention, among other things, provides highly syndiotactic poly(dicyclopentadiene) and/or hydrogenated poly(dicyclopentadiene), compositions thereof, and compounds and methods for preparing the same. In some embodiments, a provided compound is a compound of formula I, II or III. In some embodiments, a provided method comprises providing a compound of formula I, II or III.

  7. Determination of polymerization particle morphology using synchrotron computed microtomography

    International Nuclear Information System (INIS)

    Jones, K.W.; Spanne, P.; Lindquist, W.B.; Conner, W.C.; Ferrero, M.


    Polymerization of monomers over heterogeneous catalysts results in the fragmentation of the catalysts and subsequent transport in the polymer particles that are produced. Characterization of the process using nondestructive synchrotron computed microtomography techniques makes possible measurement of the distribution of the catalyst fragments in an individual particle and, in addition, gives an estimate of the particle porosity and surface area. The present experiment was carried out using the x-ray microscopy facility at the Brookhaven National Synchrotron Light Source (NSLS) X26 beam line. The tomographic sections were analyzed using autocorrelation techniques to determine porosity and surface area values. The results are compared to values obtained using conventional methods. This procedure makes possible the extraction of quantitative information about porosity and specific area from the tomograms. 9 refs., 7 figs., 1 tab

  8. Plasma polymerization by Softplasma

    DEFF Research Database (Denmark)

    Jiang, J.; Wu, Zhenning; Benter, Maike


    In the late 19th century, the first depositions - known today as plasma polymers, were reported. In the last century, more and more research has been put into plasma polymers. Many different deposition systems have been developed. [1, 2] Shi F. F. broadly classified them into internal electrode......, external electrode, and electrodeless microwave or high frequency reactors. [3] Softplasma™ is an internal electrode plasma setup powered by low frequenc~ gower supply. It was developed in late 90s for surface treatment of silicone rubber. [ ]- 5] It is a low pressure, low electron density, 3D homogenous...... plasma. In this study, we are presenting the surface modification"pf polymers by plasma polymerization using Softplasma™. Softplasma™ can be used for two major types of polymerization: polymerization of vinyl monomers, where plasma acts as initiator; chemical vapour deposition, where plasma acts...

  9. Tris(trimethylsilyl)silane as a co-initiator for dental adhesive: Photo-polymerization kinetics and dynamic mechanical property. (United States)

    Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette


    The purpose of this study was to evaluate the polymerization behavior of a model dentin adhesive with tris(trimethylsilyl)silane (TTMSS) as a co-initiator, and to investigate the polymerization kinetics and mechanical properties of copolymers in dry and wet conditions. A co-monomer mixture based on HEMA/BisGMA (45/55, w/w) was used as a model dentin adhesive. The photoinitiator system included camphorquinone (CQ) as the photosensitizer and the co-initiator was ethyl-4-(dimethylamino) benzoate (EDMAB) or TTMSS. Iodonium salt, diphenyliodonium hexafluorophosphate (DPIHP) serving as a catalyst, was selectively added into the adhesive formulations. The control and the experimental formulations were characterized with regard to the degree of conversion (DC) and dynamic mechanical properties under dry and wet conditions. In two-component photoinitiator system (CQ/TTMSS), with an increase of TTMSS concentration, the polymerization rate and DC of CC double bond increased, and showed a dependence on the irradiation time and curing light intensity. The copolymers that contained the three-component photoinitiator system (CQ/TTMSS/DPIHP) showed similar dynamic mechanical properties, under both dry and wet conditions, to the EDMAB-containing system. The DC of formulations using TTMSS as co-initiator showed a strong dependence on irradiation time. With the addition of TTMSS, the maximum polymerization rate can be adjusted and the network structure became more homogenous. The results indicated that the TTMSS could be used as a substitute for amine-type co-initiator in visible-light induced free radical polymerization of methacrylate-based dentin adhesives. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Silicatein Filaments and Subunits from a Marine Sponge Direct the Polymerization of Silica and Silicones in vitro (United States)

    Cha, Jennifer N.; Shimizu, Katsuhiko; Zhou, Yan; Christiansen, Sean C.; Chmelka, Bradley F.; Stucky, Galen D.; Morse, Daniel E.


    Nanoscale control of the polymerization of silicon and oxygen determines the structures and properties of a wide range of siloxane-based materials, including glasses, ceramics, mesoporous molecular sieves and catalysts, elastomers, resins, insulators, optical coatings, and photoluminescent polymers. In contrast to anthropogenic and geological syntheses of these materials that require extremes of temperature, pressure, or pH, living systems produce a remarkable diversity of nanostructured silicates at ambient temperatures and pressures and at near-neutral pH. We show here that the protein filaments and their constituent subunits comprising the axial cores of silica spicules in a marine sponge chemically and spatially direct the polymerization of silica and silicone polymer networks from the corresponding alkoxide substrates in vitro, under conditions in which such syntheses otherwise require either an acid or base catalyst. Homology of the principal protein to the well known enzyme cathepsin L points to a possible reaction mechanism that is supported by recent site-directed mutagenesis experiments. The catalytic activity of the "silicatein" (silica protein) molecule suggests new routes to the synthesis of silicon-based materials.

  11. Screening of Catalysts for Hydrodeoxygenation of Phenol as Model Compound for Bio-oil

    DEFF Research Database (Denmark)

    Mortensen, Peter Mølgaard; Grunwaldt, Jan-Dierk; Jensen, Peter Arendt


    Four groups of catalysts have been tested for hydrodeoxygenation (HDO) of phenol as a model compound of bio-oil, including: oxide catalysts, methanol synthesis catalysts, reduced noble metal catalysts, and reduced non-noble metal catalysts. In total 23 different catalysts were tested at 100 bar H2...... and 275 °C in a batch reactor. The experiments showed that none of the tested oxides and methanol synthesis catalysts had any significant activity for phenol HDO at the given conditions, which were linked to their inability to hydrogenate the phenol. HDO of phenol over reduced metal catalysts could...

  12. Complex Macromolecular Architectures by Living Cationic Polymerization

    KAUST Repository

    Alghamdi, Reem D.


    Poly (vinyl ether)-based graft polymers have been synthesized by the combination of living cationic polymerization of vinyl ethers with other living or controlled/ living polymerization techniques (anionic and ATRP). The process involves the synthesis of well-defined homopolymers (PnBVE) and co/terpolymers [PnBVE-b-PCEVE-b-PSiDEGVE (ABC type) and PSiDEGVE-b-PnBVE-b-PSiDEGVE (CAC type)] by sequential living cationic polymerization of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiDEGVE), using mono-functional {[n-butoxyethyl acetate (nBEA)], [1-(2-chloroethoxy) ethyl acetate (CEEA)], [1-(2-(2-(t-butyldimethylsilyloxy)ethoxy) ethoxy) ethyl acetate (SiDEGEA)]} or di-functional [1,4-cyclohexanedimethanol di(1-ethyl acetate) (cHMDEA), (VEMOA)] initiators. The living cationic polymerizations of those monomers were conducted in hexane at -20 0C using Et3Al2Cl3 (catalyst) in the presence of 1 M AcOEt base.[1] The PCEVE segments of the synthesized block terpolymers were then used to react with living macroanions (PS-DPE-Li; poly styrene diphenyl ethylene lithium) to afford graft polymers. The quantitative desilylation of PSiDEGVE segments by n-Bu4N+F- in THF at 0 °C led to graft co- and terpolymers in which the polyalcohol is the outer block. These co-/terpolymers were subsequently subjected to “grafting-from” reactions by atom transfer radical polymerization (ATRP) of styrene to afford more complex macromolecular architectures. The base assisted living cationic polymerization of vinyl ethers were also used to synthesize well-defined α-hydroxyl polyvinylether (PnBVE-OH). The resulting polymers were then modified into an ATRP macro-initiator for the synthesis of well-defined block copolymers (PnBVE-b-PS). Bifunctional PnBVE with terminal malonate groups was also synthesized and used as a precursor for more complex architectures such as H-shaped block copolymer by “grafting-from” or

  13. Catalytic Membranes Embedding Selective Catalysts: Preparation and Applications (United States)

    Drioli, Enrico; Fontananova, Enrica

    The embedding of a catalyst in membranes is today recognized as a promising strategy to develop highly efficient and eco-friendly heterogeneous catalytic chemical processes. When a catalyst is heterogenized within or on the surface of a membrane, the membrane composition (characteristics of the membrane material: hydrophobic or hydrophilic, presence of chemical groups with specific functionality, etc.) and the membrane structure (dense or porous, symmetric or asymmetric), can positively influence the catalyst performance, not only by the selective sorption and diffusion of reagents and/or products, but also influencing the catalyst activity by electronic and conformational effect. These effects are similar to those occurring in biological membranes. In this chapter, after a preliminary presentation of the basic principles of membrane reactors and polymer membranes, the preparation, characterization and applications of polymeric catalytic membranes, will be discussed.

  14. Catalysts for improved fuel processing

    Energy Technology Data Exchange (ETDEWEB)

    Borup, R.L.; Inbody, M.A. [and others


    This report covers our technical progress on fuel processing catalyst characterization for the specific purpose of hydrogen production for proton-exchange-membrane (PEM) fuel cells. These development efforts support DOE activities in the development of compact, transient capable reformers for on-board hydrogen generation starting from candidate fuels. The long-term objective includes increased durability and lifetime, in addition to smaller volume, improved performance, and other specifications required meeting fuel processor goals. The technical barriers of compact fuel processor size, transient capability, and compact, efficient thermal management all are functions of catalyst performance. Significantly, work at LANL now tests large-scale fuel processors for performance and durability, as influenced by fuels and fuel constituents, and complements that testing with micro-scale catalyst evaluation which is accomplished under well controlled conditions.

  15. Effect of different ligands on the controlled polymerization of monodisperse polystyrene nanospheres by atom transfer radical polymerization in an aqueous emulsion

    Directory of Open Access Journals (Sweden)

    E. J. Tang


    Full Text Available Polystyrene nanospheres have been synthesized by atom transfer radical polymerization (ATRP to control the molecular weight distribution in the aqueous system. The crucial factor in such a system is the ligand that adjusts the solubility of the catalyst in different phases to control the concentration of both the activator and the deactivator in reaction phase. The effect of different ligands including ethylenediamine, 1,10-phenanthroline (phen and 4,4-dinonyl-2, 2-bipyridyl (dNbpy on the catalytic solubility in the organic and aqueous phase has been investigated. The molecular weight distribution of polymer obtained in this way was analyzed by gel permeation chromatography (GPC. It showed that the obtained polymer particles presented a broad molecular weight distribution (polydispersity index 1.78 with ethylenediamine as the ligand, but the polymerization rate was high and conversion reached 96.8%. The molecular weight distribution of polystyrene was narrowest with dNbpy as ligand, but the conversion was lowest and only achieved to 69%. Possible reasons were the influence of the structure of three different ligands on the control of ATRP reaction. SEM and GPC indicated that the polystyrene nanospheres presented regular sphere with a diameter of about 120 nm and uniform molecular weight distribution, which possessed a significant potentials in drug carrier field.

  16. A new type of self-supported, polymeric Ru-carbene complex for homogeneous catalysis and heterogeneous recovery: synthesis and catalytic activities for ring-closing metathesis. (United States)

    Chen, Shu-Wei; Kim, Ju Hyun; Shin, Hyunik; Lee, Sang-Gi


    A novel 2nd generation Grubbs-type catalyst tethering an isopropoxystyrene has been synthesized and automatically polymerized in solution to form a self-supported polymeric Ru-carbene complex, which catalyzed ring-closing metathesis homogeneously, but was recovered heterogeneously.

  17. Inflation of a Polymeric Menbrane

    DEFF Research Database (Denmark)

    Kristensen, Susanne B.; Larsen, Johannes R.; Hassager, Ole


    We consider an axisymmetric polymeric membrane inflated by a uniform pressure difference acting across the membrane.......We consider an axisymmetric polymeric membrane inflated by a uniform pressure difference acting across the membrane....

  18. Continuous controlled radical polymerization of methyl acrylate in a copper tubular reactor. (United States)

    Chan, Nicky; Cunningham, Michael F; Hutchinson, Robin A


    The use of copper tubing as both the reactor and as a catalyst source is demonstrated for continuous controlled radical polymerization of methyl acrylate at ambient temperature and at low solvent content of 30%. The high surface area provided by the copper walls mediates the reaction via the single electron transfer-living radical polymerization (SET-LRP) mechanism. The polymerizations proceeded quickly, reaching 67% conversion at a residence time of 16 min. Ligand concentration could also be reduced without a sharp drop in polymerization rate, demonstrating the potential for decreased raw material and post-process purification costs. Chain extension experiments conducted using synthesized polymer showed high livingness. The combination of living polymer produced at high polymerization rates at ambient temperature and low volatile organic solvent content demonstrate the potential of a copper reactor for scale up of SET-LRP. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Enhancement of alkylation catalysts for improved supercritical fluid regeneration (United States)

    Ginosar, Daniel M.; Petkovic, Lucia M.


    A method of modifying an alkylation catalyst to reduce the formation of condensed hydrocarbon species thereon. The method comprises providing an alkylation catalyst comprising a plurality of active sites. The plurality of active sites on the alkylation catalyst may include a plurality of weakly acidic active sites, intermediate acidity active sites, and strongly acidic active sites. A base is adsorbed to a portion of the plurality of active sites, such as the strongly acidic active sites, selectively poisoning the strongly acidic active sites. A method of modifying the alkylation catalyst by providing an alkylation catalyst comprising a pore size distribution that sterically constrains formation of the condensed hydrocarbon species on the alkylation catalyst or by synthesizing the alkylation catalyst to comprise a decreased number of strongly acidic active sites is also disclosed, as is a method of improving a regeneration efficiency of the alkylation catalyst.

  20. Methyltrioxorhenium as catalyst for olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, W.A. (Technische Univ. Muenchen, Garching (Germany). Anorganisch-Chemisches Inst.); Wagner, W. (Consortium fuer Elektrochemische Industrie GmbH, Muenchen (Germany)); Flessner, U.N.; Volkhardt, U.; Komber, H. (Institut fuer Technologie der Polymere, Dresden (Germany))


    No cocatalysts are needed as additives when methyltrioxorhenium (MTO) supported on acidic carriers is employed to catalyze the metathesis of functionalized olefins. A typical system is MTO/Al{sub 2}O{sub 3}-SiO{sub 2}, which is active, for instance, in the metathesis of allyl halides, allylsilanes, unsaturated carboxylates, and nitriles. MTO in combination with R{sub n}AlCl{sub 3-n} is a homogeneous catalyst in ring-opening polymerizations (R = CH{sub 3}, C{sub 2}H{sub 5}; n = 1,2). (orig.).

  1. Cooperative catalysis designing efficient catalysts for synthesis

    CERN Document Server

    Peters, René


    Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Br?nsted base catalysis to e.g. metal-assisted organocatalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating acti

  2. Polymeric coordination compounds

    Indian Academy of Sciences (India)


    Metal coordination polymers with one- and two-dimensional structures are of current interest due to their possible relevance to material science 1. In continuation of our previous studies 2,3, several new polymeric compounds are reported here. Among the complexes of silver with aminomethyl pyridine (amp) ...

  3. Polymerized and functionalized triglycerides (United States)

    Plant oils are useful sustainable raw materials for the development of new chemical products. As part of our research emphasis in sustainability and green polymer chemistry, we have explored a new method for polymerizing epoxidized triglycerides with the use of fluorosulfonic acid. Depending on the ...

  4. Design of heterogeneous catalysts

    DEFF Research Database (Denmark)

    Frey, Anne Mette

    The title of my PhD thesis is “Design of Heterogeneous Catalysts”. Three reactions have been investigated: the methanation reaction, the Fischer-Tropsch reaction, and the NH3-based selective catalytic reduction (SCR) of NO. The experimental work performed in connection with the methanation reaction...... hydrogenation. For both systems a maximum in catalytic activity was found for some of the bimetallic catalysts being superior to the monometallic catalysts. This resulted in volcano curves for all investigated systems. In the Fischer-Tropsch reaction promotion of cobalt catalysts with manganese was studied...... well, and the best catalyst prepared had a C5+ yield almost a factor of two higher than a standard air calcined Co catalyst. In the NH3-SCR reaction it is desirable to develop an active and stable catalyst for NOx removal in automotive applications, since the traditionally used vanadium-based catalyst...

  5. Enhanced gasification of wood in the presence of mixed catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Weber, S. L.; Mudge, L. K.; Sealock, Jr., L. J.; Robertus, R. J.; Mitchell, D. E.

    Experimental results obtained in laboratory investigations of steam gasification of wood in the presence of mixed catalysts are presented. These studies are designed to test the technical feasibility of producing specific gaseous products from wood by enhancing its reactivity and product specificity through the use of combined catalysts. The desired products include substitute natural gas, hydrocarbon synthesis gas and ammonia synthesis gas. The gasification reactions are controlled through the use of specific catalyst combinations and operating parameters. A primary alkali carbonate gasification catalyst impregnated into the wood combined with specific commercially available secondary catalysts produced the desired products. A yield of 50 vol % methane was obtained with a randomly mixed combination of a commercial nickel methanation catalyst and silica-alumina cracking catalyst at a weight ratio of 3:1 respectively. Steam gasification of wood in the presence of a commercial Si-Al cracking catalyst produced the desired hydrocarbon synthesis gas. Hydrogen-to-carbon monoxide ratios needed for Fischer-Tropsch synthesis of hydrocarbons were obtained with this catalyst system. A hydrogen-to-nitrogen ratio of 3:1 for ammonia synthesis gas was achieved with steam-air gasification of wood in the presence of catalysts. The most effective secondary catalyst system employed to produce the ammonia synthesis gas included two commercially prepared catalysts formulated to promote the water-gas shift reaction.

  6. In situ synthesis of nanoclay filled polyethylene using polymer supported metallocene catalyst system

    Directory of Open Access Journals (Sweden)

    Z. V. P Murthy


    Full Text Available In situ ethylene polymerizations were performed using bis(cyclopentadienetitanium dichloride supported on polyethersulfone as catalyst. The bis(cyclopentadienetitanium dichloride supported on polyethersulfone catalyst activity estimated by ethylene polymerization was 360 kgPE/molTi/h. During polymerization the fillers used were montmorillionite nanoclays having surface modifications with 35-45 wt% dimethyl dialkyl(14-18amine (FA and 25-30 wt% trimethyl stearyl ammonium (FB. These fillers were pretreated with methylaluminoxine (MAO; cocatalyst for better dispersion onto the polymer matrix. The formation of polyethylene within the whole matrix was confirmed by FTIR studies. It was found that the nature of nanofiller did not have any remarkable effect on the melting characteristics of the polymer. TGA study indicates that nanoclay FB filled polyethylene has higher thermal stability than nanoclay FA filled polyethylene. The melting temperature of the obtained polyethylenes was 142 ºC, which corresponds to that synthesized by the polyether sulfone supported catalyst.

  7. Polymerization of N-(fluoro phenyl) maleimides. [. gamma. radiation

    Energy Technology Data Exchange (ETDEWEB)

    Barrales-Rienda, J.M.; Ramos, J.G.; Chaves, M.S.


    Poly(N-aryl maleimide)s of characteristic structures have been synthesized and some of their physical properties studied. The polymerization of N-(fluoro phenyl) maleimides by free-radical initiation in bulk or in solution and by anionic catalyst have been studied to compare the characteristics of polymerization by ..gamma..-ray irradiation with that by free-radical initiation. The polymers were characterized by elemental analysis, intrinsic viscosity, spectroscopy (IR and NMR), programmed thermogravimetric analysis, and x-ray diffraction. Spectra of polymers prepared by radiation and anionic polymerization were nearly identical with those of polymers prepared by free-radical polymerization initiated by azobisisobutyronitrile in bulk or in solution and by the self-initiated thermal polymerization. A variety of reaction conditions were tried, but all attempts to change the molecular structure of the polymers were unsuccessful. Rates of thermal degradation for poly(N-(fluoro phenyl) maleimide)s have been analyzed by using a multiple-heating-rate procedure. Overall activation energy, order of reaction, and frequency factor have been evaluated. 6 figures, 8 tables.

  8. Dipeptide catalysed prebiotic polymerization of RNA

    DEFF Research Database (Denmark)

    Wieczorek, Rafal; Luisi, Pier Luigi; Monnard, Pierre-Alain


    toward more peptide synthesis. In the present work we describe a prebiotically plausible system in which the SerHis dipeptide acts as catalyst for the formation of RNA oligomers from imidazole derivatives of mononucleotides. The thermodynamic shift towards condensation was achieved using water......-concentrated in the remaining liquid microinclusions, thus creating an environment with low water activity in which condensation reactions can occur. Successful oligomerization of RNA monomers catalysed by the SerHis dipeptide was observed in a broad range of pH, and with all four natural nucleobases. The isomeric dipeptide...... HisSer did not exhibit any catalytic properties thus indicating that the specific, spatial arrangement of amino acid residues in the SerHis structure is responsible for its catalytic activity. Establishing novel synthetic pathways to RNA polymerization is important, as to date no convincing prebiotic...

  9. Polymeric molecular sieve membranes for gas separation

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng; Qiao, Zhenan; Chai, Songhai


    A porous polymer membrane useful in gas separation, the porous polymer membrane comprising a polymeric structure having crosslinked aromatic groups and a hierarchical porosity in which micropores having a pore size less than 2 nm are present at least in an outer layer of the porous polymer membrane, and macropores having a pore size of over 50 nm are present at least in an inner layer of the porous polymer membrane. Also described are methods for producing the porous polymer membrane in which a non-porous polymer membrane containing aromatic rings is subjected to a Friedel-Crafts crosslinking reaction in which a crosslinking molecule crosslinks the aromatic rings in the presence of a Friedel-Crafts catalyst and organic solvent under sufficiently elevated temperature, as well as methods for using the porous polymer membranes for gas or liquid separation, filtration, or purification.

  10. Recent Developments in the Synthesis of Biomacromolecules and their Conjugates by Single Electron Transfer-Living Radical Polymerization. (United States)

    Lligadas, Gerard; Grama, Silvia; Percec, Virgil


    Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile tool for the synthesis of vinyl polymers with well-defined topology and chain end functionality. The crucial step in SET-LRP is the disproportionation of the Cu(I)X generated by activation with Cu(0) wire, powder, or nascent Cu(0) generated in situ into nascent, extremely reactive Cu(0) atoms and nanoparticles and Cu(II)X 2 . Nascent Cu(0) activates the initiator and dormant chains via a homogeneous or heterogeneous outer-sphere single-electron transfer mechanism (SET-LRP). SET-LRP provides an ultrafast polymerization of a plethora of monomers (e.g., (meth)-acrylates, (meth)-acrylamides, styrene, and vinyl chloride) including hydrophobic and water insoluble to hydrophilic and water soluble. Some advantageous features of SET-LRP are (i) the use of Cu(0) wire or powder as readily available catalysts under mild reaction conditions, (ii) their excellent control over molecular weight evolution and distribution as well as polymer chain ends, (iii) their high functional group tolerance allowing the polymerization of commercial-grade monomers, and (iv) the limited purification required for the resulting polymers. In this Perspective, we highlight the recent advancements of SET-LRP in the synthesis of biomacromolecules and of their conjugates.

  11. Ruthenium-based olefin metathesis catalysts bearing pH-responsive ligands: External control of catalyst solubility and activity (United States)

    Balof, Shawna Lynn


    Sixteen novel, Ru-based olefin metathesis catalysts bearing pH responsive ligands were synthesized. The pH-responsive groups employed with these catalysts included dimethylamino (NMe2) modified NHC ligands as well as N-donor dimethylaminopyridine (DMAP) and 3-(o-pyridyl)propylidene ligands. These pH-responsive ligands provided the means by which the solubility and/or activity profiles of the catalysts produced could be controlled via acid addition. The main goal of this dissertation was to design catalyst systems capable of performing ring opening metathesis (ROMP) and ring closing metathesis (RCM) reactions in both organic and aqueous media. In an effort to quickly gain access to new catalyst structures, a template synthesis for functionalized NHC ligand precursors was designed, in addition to other strategies, to obtain ligand precursors with ancillary NMe2 groups. Kinetic studies for the catalysts produced from these precursors showed external control of catalyst solubility was afforded via protonation of the NMe2 groups of their NHC ligands. Additionally, this protonation afforded external control of catalyst propagation rates for several catalysts. This is the first known independent external control for the propagation rates of ROMP catalysts. The incorporation of pH-responsive N-donor ligands into catalyst structures also provided the means for the external control of metathesis activity, as the protonation of these ligands resulted in an increased initiation rate based on their fast and irreversible dissociation from the metal center. The enhanced external control makes these catalysts applicable to a wide range of applications, some of which have been explored by us and/or through collaboration. Three of the catalysts designed showed remarkable metathesis activity in aqueous media. These catalysts displayed comparable RCM activity in aqueous media to a class of water-soluble catalysts reported by Grubbs et al., considered to be the most active catalyst for

  12. Prepolymerization and morphology. Study on the factors determining powder morphology in propylene polymerization.

    NARCIS (Netherlands)

    Pater, J.T.M.


    Due to the developments in catalysis and the use of improved and dedicated catalysts in modern polymerization processes, the variety of different grades of polyolefins produced (and with that the variety of possible applications) has increased rapidly over the past decades. Combined with the low

  13. A polymeric-semiconductor-metal-complex hybrid photocatalyst for visible-light CO(2) reduction. (United States)

    Maeda, Kazuhiko; Sekizawa, Keita; Ishitani, Osamu


    A polymeric carbon nitride semiconductor is demonstrated to photocatalyse CO2 reduction to formic acid under visible light (λ > 400 nm) with a high turnover number (>200 for 20 hours) and selectivity (>80%), when coupled with a molecular ruthenium complex as a catalyst.

  14. Gas phase polymerization of propylene. Reaction kinetics and molecular weight distribution

    NARCIS (Netherlands)

    Meier, G.B.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria


    Gas-phase polymerizations have been executed at different temperatures, pressures, and hydrogen concentrations using Me2Si[Ind]2ZrCl2 / methylaluminoxane / SiO2(Pennsylvania Quarts) as a catalyst. The reaction rate curves have been described by a kinetic model, which takes into account the initially

  15. Acrylamide Homopolymers and Acrylamide-N-Isopropylacrylamide Block Copolymers by Atomic Transfer Radical Polymerization in Water

    NARCIS (Netherlands)

    Wever, D. A. Z.; Raffa, P.; Picchioni, F.; Broekhuis, A. A.


    Atomic transfer radical polymerization (ATRP) of acrylamide has been accomplished in aqueous media at room temperature. By using methyl 2-chloropropionate (MeClPr) as the initiator and tris[2-(dimethylamino)ethyl]-amine (Me6TREN)/copper halogenide (CuX) as the catalyst system, different linear

  16. Mechanical alloying of a hydrogenation catalyst used for the remediation of contaminated compounds (United States)

    Quinn, Jacqueline W. (Inventor); Clausen, Christian A. (Inventor); Geiger, Cherie L. (Inventor); Aitken, Brian S. (Inventor)


    A hydrogenation catalyst including a base material coated with a catalytic metal is made using mechanical milling techniques. The hydrogenation catalysts are used as an excellent catalyst for the dehalogenation of contaminated compounds and the remediation of other industrial compounds. Preferably, the hydrogenation catalyst is a bimetallic particle including zero-valent metal particles coated with a catalytic material. The mechanical milling technique is simpler and cheaper than previously used methods for producing hydrogenation catalysts.

  17. Palladium catalyst system comprising zwitterion and/or acid-functionalized ionic liquid

    DEFF Research Database (Denmark)


    The present invention concerns a catalyst system in particular a catalyst system comprising Palladium (Pd), a zwitterion and/or an acid-functionalized ionic liquid, and one or more phosphine ligands, wherein the Pd catalyst can be provided by a complex precursor, such as Pd(CH3COO)2, PdCI2, Pd(CH3......COCHCOCH3), Pd (CF3COO)2, Pd(PPh3)4 or Pd2(dibenzylideneacetone)3. Such catalyst systems can be used for e.g. alkoxycarbonylation reactions, carboxylation reactions, and/or in a co-polymerization reaction, e.g. in the production of methyl propionate and/or propanoic acid, optionally in processes forming...... methyl methacrylate and/or methacrylic acid. Catalyst systems according to the invention are suitable for reactions forming separable product and catalyst phases and supported ionic liquid phase SILP applications....

  18. Palladium catalyst system comprising zwitterion and/or acid-​functionalized ionic liquid

    DEFF Research Database (Denmark)


    The present invention concerns a catalyst system in particular a catalyst system comprising Palladium (Pd), a zwitterion and/or an acid-functionalized ionic liquid, and one or more phosphine ligands, wherein the Pd catalyst can be provided by a complex precursor, such as Pd(CH3COO)2, PdCI2, Pd(CH3......COCHCOCH3), Pd (CF3COO)2, Pd(PPh3)4 or Pd2(dibenzylideneacetone)3. Such catalyst systems can be used for e.g. alkoxycarbonylation reactions, carboxylation reactions, and/or in a co-polymerization reaction, e.g. in the production of methyl propionate and/or propanoic acid, optionally in processes forming...... methyl methacrylate and/or methacrylic acid. Catalyst systems according to the invention are suitable for reactions forming separable product and catalyst phases and supported ionic liquid phase SILP applications....

  19. Radiation-induced heterophase polymerizations

    International Nuclear Information System (INIS)

    Carenza, M.; Palma, G.


    Investigations were carried out on the morphology of particles produced in the early stages of radiation-induced heterophase polymerization of acrylonitrile in quiescent conditions over a wide temperature range both in bulk and with addition of a solvent or a comonomer. The data were compared with the corresponding data obtained in the polymerization of vinyl chloride, producing an amorphous polymer, taking into account also the kinetic behaviours of the two polymerization systems. The particle morphologies in the two systems were quite similar at low polymerization temperatures but there were considerable differences when higher temperatures were involved. This change was interpreted on the basis of differences in compatability between the liquid phase and the polymer particle phase for the two systems. In order to account for the two different kinetic behaviours, a two-phase polymerization model was formulated and also a polymerization model in which the surface of the polymer particles was the locus of polymerization. (author)

  20. Highly tunable porous organic polymer (POP) supports for metallocene-based ethylene polymerization (United States)

    Wang, Xiong; Li, Zhenyou; Han, Xiaoyu; Han, Zhengang; Bai, Yongxiao


    Porous organic Polymers (POPs) can not only exhibit high specific surface area and pore volume, but also tunable pore size distribution. Herein, copolymers of 2-hydroxyethylmethylacrylate (HEMA) and divinylbenzene (DVB) with specific pore structure were synthesized via a dispersion polymerization strategy, and then immobilized metallocene catalysts with well-defined pore structure were obtained on the produced POP supports. The nitrogen sorption and Gel permeation chromatography (GPC) results demonstrate that the pore structure of the immobilized metallocene catalyst is highly dependent on the pore structure of the POPs, and the pore structure of metallocene catalysts or the POPs has a significant influence on the molecular chain growth of the produced polyethylene. By tuning the distribution of the active species scattered in the micro- and the narrow meso-pore range (roughly ≤4 nm), the chain growth of the polyolefin can be tailored effectively during the polymerization process, although differential scanning calorimetry (DSC) and temperature rising elution fractionation (TREF) results show that the chemical composition distributions (CCDs) of produced PE from the POPs-supported metallocene catalysts are not determined by polymerization activity or molecule chain length, but mainly by the active site species scattered in the supported catalysts. Scanning electron micrograph (SEM) shows that the produced polyethylene has highly porous fabric which consists of nanofiber and spherical beads of micron dimension.

  1. Cross-linking of polymeric materials

    International Nuclear Information System (INIS)

    Bloom, L.I.; Du Plessis, T.A.; Meij, G.O.


    The invention provides a method of producing a cured polymeric artifact from a polymeric thermoplastic starting material, the material of the artifact having reduced thermoplasticity relative to the starting material and exhibiting an enhanced degree of cross-linking relative to the starting material. The method includes subjecting a polymeric thermoplastic starting material, which is capable of being cross-linked by irradiation, to sufficient irradiation partially to cross-linked the starting material to produce a thermoplastic partially cross-linked intermediate material. The thermoplasticity of the intermediate material is then reduced by heating it to raise its melting point. The invention also provides a method of making a partially cross-linked feedstocks and a master batch for use in making such artifacts

  2. Development of radioisotope labeled polymeric carriers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Jin; Jeong, Jea Min; Hwang, Hyun Jeong [Ewha Womans University, Seoul (Korea)


    This research was performed with the aim of developing polymeric radioisotope or drug carriers for obtaining efficient diagnostic therapeutic efficacy. As polymers, polyethylene oxides, polylactides, polycaprolactone were chosen to prepare the devices including micelle system, microemulsion, nanospheres. In addition, anticancer drug loaded polylactide microparticulates were fabricated as a regional chemotherapeutics for the treatment of cancer. Technetium or radioactive iodine was labeled to the polymeric carriers via ligands such as DTPA and HPP, respectively. Labeling efficiency was above 90% and stable enough up to 24 hours. Moreover, injected polymer carriers demonstrated higher blood maintenance and bone uptake than Tin colloid, a control. These results suggested that radioisotope carrying polymeric particulate are promising tools for diagnosing blood vessels or bones. Besides, anticancer drug loaded particulates demonstrated appropriate maintenance of therapeutic concentration and localization. Therefore it was proposed that this therapeutic system may be potential as a cancer therapy modality. 20 refs., 24 figs.,5 tabs. (Author)

  3. Methods of making textured catalysts (United States)

    Werpy, Todd [West Richland, WA; Frye, Jr., John G.; Wang, Yong [Richland, WA; Zacher, Alan H [Kennewick, WA


    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  4. Synthesis and chemistry of fluorinated alpha-Iminocarboxamide Nickel and Zirconium catalysts

    International Nuclear Information System (INIS)

    Alsaygh, A.A.


    Synthesis and investigations of Nickel-based olefin oligomerization and polymerization catalysts, fluorinated alpha-Iminocarboxamide u3-Penzyl (II) Ni Complexes is reported. The synthesis of the above mentioned catalysts by the direct reaction of the potassium salt of the ligand, Ni(COD)2 (bis(1, 5-cyclooctadiene)-nickel and Benzyl halide in THF and starting temperature of -35C led to the formation of the two isomers: The [N-O] and the [N-N]. Moreover, the complexes di alpha-fluorinated Iminocarboxamide Zr-dimmer has been synthesized, investigated and tested for ethylene polymerization. (author)

  5. Alloy catalyst material

    DEFF Research Database (Denmark)


    The present invention relates to a novel alloy catalyst material for use in the synthesis of hydrogen peroxide from oxygen and hydrogen, or from oxygen and water. The present invention also relates to a cathode and an electrochemical cell comprising the novel catalyst material, and the process use...... of the novel catalyst material for synthesising hydrogen peroxide from oxygen and hydrogen, or from oxygen and water....

  6. Thermally bisignate supramolecular polymerization (United States)

    Venkata Rao, Kotagiri; Miyajima, Daigo; Nihonyanagi, Atsuko; Aida, Takuzo


    One of the enticing characteristics of supramolecular polymers is their thermodynamic reversibility, which is attractive, in particular, for stimuli-responsive applications. These polymers usually disassemble upon heating, but here we report a supramolecular polymerization that occurs upon heating as well as cooling. This behaviour arises from the use of a metalloporphyrin-based tailored monomer bearing eight amide-containing side chains, which assembles into a highly thermostable one-dimensional polymer through π-stacking and multivalent hydrogen-bonding interactions, and a scavenger, 1-hexanol, in a dodecane-based solvent. At around 50 °C, the scavenger locks the monomer into a non-polymerizable form through competing hydrogen bonding. On cooling, the scavenger preferentially self-aggregates, unlocking the monomer for polymerization. Heating also results in unlocking the monomer for polymerization, by disrupting the dipole and hydrogen-bonding interactions with the scavenger. Analogous to 'upper and lower critical solution temperature phenomena' for covalently bonded polymers, such a thermally bisignate feature may lead to supramolecular polymers with tailored complex thermoresponsive properties.


    Joris, G.G.


    It has been fuund that the presence of chlorine as an impurity adversely affects the performance of finely divided platinum catalysts such as are used in the isotopic exchange process for the production of beavy water. This chlorine impurity may be removed from these catalysts by treating the catalyst at an elevated temperature with dry hydrogen and then with wet hydrogen, having a hydrogen-water vapor volume of about 8: 1. This alternate treatment by dry hydrogen and wet hydrogen is continued until the chlorine is largely removed from the catalyst.

  8. Photolithographic Olefin Metathesis Polymerization


    Weitekamp, Raymond A.; Atwater, Harry A.; Grubbs, Robert H.


    Patterning functional materials is a central challenge across many fields of science. The ability to lithographically fabricate micro- and nanostructures has been one of the most impactful technological breakthroughs of the last century. In part due to the complexity of the chemical processes in photoresists, there is a limited variety of materials that can currently be patterned by photolithography. We report a negative tone photoresist using a photoactivated olefin metathesis catalyst, whic...

  9. Tribology of polymeric nanocomposites friction and wear of bulk materials and coatings

    CERN Document Server

    Friedrich, Klaus


    Tribology of Polymeric Nanocomposites provides a comprehensive description of polymeric nanocomposites, both as bulk materials and as thin surface coatings, and provides rare, focused coverage of their tribological behavior and potential use in tribological applications. Providing engineers and designers with the preparation techniques, friction and wear mechanisms, property information and evaluation methodology needed to select the right polymeric nanocomposites for the job, this unique book also includes valuable real-world examples of polymeric nanocomposites in a

  10. Radiation chemistry of polymeric system

    International Nuclear Information System (INIS)

    Machi, Sueo; Ishigaki, Isao


    Among wide application of radiation in the field of polymer chemistry, practices of polymerization, graft polymerization, bridging, etc. are introduced hereinafter. As for the radiation sources of radiation polymerization, in addition to the 60 Co-γ ray with long permeation distance which has been usually applied, electron beam accelerators with high energy, large current and high reliability have come to be produced, and the liquid phase polymerization by electron beam has attracted attention industrially. Concerning polymerizing reactions, explanations were given to electron beam polymerization under high dose rate, the polymerization in supercooling state or under high pressure, and emulsifying polymerization. As for radiation bridging, radiation is applied for the bridging of hydrogel, acceleration of bridging and improvement of radiation resistance. It is also utilized for reforming membranes by graft polymerization, and synthesis of polymers for medical use. Application of fixed enzymes in the medical field has been investigated by fixing various enzymes by low temperature γ-ray polymerization with glassy monomers such as HEMA. (Kobatake, H.)

  11. Towards the computational design of solid catalysts

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Bligaard, Thomas; Rossmeisl, Jan


    Over the past decade the theoretical description of surface reactions has undergone a radical development. Advances in density functional theory mean it is now possible to describe catalytic reactions at surfaces with the detail and accuracy required for computational results to compare favourably...... with experiments. Theoretical methods can be used to describe surface chemical reactions in detail and to understand variations in catalytic activity from one catalyst to another. Here, we review the first steps towards using computational methods to design new catalysts. Examples include screening for catalysts...

  12. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.


    Mansor, N.; Jorge, A. B.; Corà, F.; Gibbs, C.; Jervis, R.; McMillan, P. F.; Wang, X.; Brett, D. J.


    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li(+)Cl(-)), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion...

  13. Development of a hydrophobic catalyst for recombining radiolytically generated H2 and O2 in nuclear reactors

    International Nuclear Information System (INIS)

    Belapurkar, A.D.; Gupta, N.M.


    A catalyst is developed for efficient recombination of H 2 and O 2 in presence of water vapor and without requirement of an external heat source. The catalyst, comprising of finely dispersed platinum on a large area polymeric support, is hydrophobic in nature and is therefore resistant to water poisoning. The exothermicity of H 2 -O 2 reaction results in the rise of catalyst temperature and hence in its high and sustained catalytic activity. In order to prevent its over-heating, the catalyst sheet is sandwiched between the two metallic plates which also help in maintaining the catalyst panel at an isothermal temperature. The performance of this catalyst, evaluated both on bench and pilot plant scale, is found to be long lasting. Due to the flexible nature of this catalyst material, different convenient reactor designs may be envisaged for use in nuclear reactors for recombining radiolytically generated H 2 and O 2 . (author)

  14. Dates in the development of catalysts

    Energy Technology Data Exchange (ETDEWEB)



    A chronological listing is presented of the dates on which various I. G. Farbenindustrie catalysts were first used. In most cases the entries gave compositions and some hints at the methods of preparation of the catalysts as well as the code numbers for the catalysts. The listing started in December, 1924, and extended throught August, 1941. Some of the more important catalysts were the following: 5058, tungsten disulfide (WS/sub 2/), produced from the thio salt by dry decomposition (1930); 6434, a diluted mixture of hydrogen fluoride-treated ''Terrana'' and 10% WS/sub 2/ (1935); 6719, a prehydrogenation catalyst of 75 parts ferrous sulfide (FeS), 22 parts WS/sub 2/, and 3 parts nickel monosulfide (NiS) (1937); 7019, an aromatization catalyst of 100 parts primry coal, 15 parts chromic oxide (Cr/sub 2/O/sub 3/), and 5 parts vanadium sesquioxide (V/sub 2/O/sub 3/) (1938); 7360, a DHD catalyst of activated alumina (Al/sub 2/O/sub 3/) and 55 g/l molybdenum trioxide (MoO/sub 3/) (1939); 7846, a prehydrogenated catalyst, a sulfonated mixture of activated alumina, 100 g/l MoO/sub 3/, and 30 g/l nickel sesquioxide (Ni/sub 2/O/sub 3/) (1940); and 8376 W, a prehydrogenation catalyst, a sulfonated mixture of activated alumina, 250 g/l tungsten trioxide (WO/sub 3/), and 50 g/l Ni/sub 2/O/sub 3/ (1941). Other caalysts given included numbers 1724, 2365, 2473, 2500, 3510, 3884, 5053, 5676, 6525, and 6561. Compounds used other than those mentioned above included molybdenum disulfide (MoS/sub 2/), zinc sulfide (ZnS), zinc oxide (ZnO), and magnesium oxide (MgO).

  15. Concluding remarks: progress toward the design of solid catalysts. (United States)

    Gates, Bruce C


    The 2016 Faraday Discussion on the topic "Designing New Heterogeneous Catalysts" brought together a group of scientists and engineers to address forefront topics in catalysis and the challenge of catalyst design-which is daunting because of the intrinsic non-uniformity of the surfaces of catalytic materials. "Catalyst design" has taken on a pragmatic meaning which implies the discovery of new and better catalysts on the basis of fundamental understanding of the catalyst structure and performance. The presentations and discussion at the meeting illustrate the rapid progress in this understanding linked with improvements in spectroscopy, microscopy, theory, and catalyst performance testing. The following text includes a statement of recurrent themes in the discussion and examples of forefront science that evidences progress toward catalyst design.

  16. The Design of Reactions, Catalysts and Materials with Aromatic Ions (United States)

    Bandar, Jeffrey Scott

    This thesis details the use of aromatic ions, especially aminocyclopropenium ions, as empowering design elements in the development of new chemical reactions, organic catalysts and polymeric materials. A particular focus is placed throughout on understanding the relationship between the structure of aromatic ions and their performance in these novel applications. Additionally, the benefits that aromatic ions provide in these contexts are highlighted. The first chapter briefly summarizes the Lambert Group's prior efforts toward exploiting the unique reactivity profiles of aromatic ions in the context of new reaction design. Also provided in the first chapter is a comprehensive literature review of aminocyclopropenium ions, upon which the majority of advances described in this thesis are based. To set the stage for the first application of aminocyclopropenium ions, Chapter 2 provides an account of existing highly Bronsted basic functional groups, including guanidines, proazaphosphatranes and iminophosphoranes. The provided review on the synthesis and use in asymmetric catalysis of these bases indicates that there is a high need for conceptually new Bronsted basic functional groups. To address this need, the development of chiral 2,3-bis(dialkylamino)cyclopropenimines as a new platform for asymmetric Bronsted base catalysis is described in Chapter 3. This new class of Bronsted base is readily synthesized on scale, operates efficiently under practical conditions, and greatly outperforms closely related guanidine-based catalysts. Structure-activity relationship studies, mechanistic experiments and computational transition state modeling are all discussed in the context of asymmetric glycinate imine Michael reactions in order to arrive at a working model for cyclopropenimine chemistry. Cumulatively, this chapter provides a "user's guide" to understanding and developing further applications of 2,3-bis(dialkylamino)cyclopropenimines. The use of our optimal chiral 2,3-bis

  17. Magnetic catalyst bodies

    NARCIS (Netherlands)

    Teunissen, Wendy; Bol, A.A.; Geus, John W.


    After a discussion about the importance of the size of the catalyst bodies with reactions in the liquid-phase with a suspended catalyst, the possibilities of magnetic separation are dealt with. Deficiencies of the usual ferromagnetic particles are the reactivity and the clustering of the

  18. Catalyst for Ammonia Oxidation

    DEFF Research Database (Denmark)


    The present invention relates to a bimetallic catalyst for ammonia oxidation, a method for producing a bimetallic catalyst for ammonia oxidation and a method for tuning the catalytic activity of a transition metal. By depositing an overlayer of less catalytic active metal onto a more catalytic...

  19. Catalyst for hydrocarbon conversion

    International Nuclear Information System (INIS)

    Duhaut, P.; Miquel, J.


    A description is given for a catalyst and process for hydrocarbon conversions, e.g., reforming. The catalyst contains an alumina carrier, platinum, iridium, at least one metal selected from uranium, vanadium, and gallium, and optionally halogen in the form of metal halide of one of the aforesaid components. (U.S.)

  20. Hydroliquefaction of coal with supported catalysts: 1980 status review

    Energy Technology Data Exchange (ETDEWEB)

    Polinski, Leon M.; Stiegel, Gary J.; Tischer, Richard E.


    The objectives of the program have been to determine catalyst deactivation kinetic models and catalyst deactivation modes for supported Co-Mo and Ni-Mo catalysts used primarily in coal liquefaction via the H-COAL process. Emphasis has been on developing methods to increase catalyst usage by determining how to decrease catalyst replacement rates in the process and how to decrease catalyst poisoning. An important conclusion reached via model analysis and verified by experiment is that larger diameter (1/16 in.) catalysts resist poisoning deactivation much more than smaller (1/32 in.) catalysts over extended periods (60 to 110 hours) of time. If this trend can be verified, it gives a powerful tool for reducing catalyst replacement rate in the H-COAL ebullated bed system by factors of 2 or more. A second conclusion is that poisoning of catalysts occurs by several possible mechanisms or modes. Indirect or direct evidence of all these modes can be presented, though the relative importance of each mechanism has not been established. The modes include (a) poisoning by coking - with gradual increase in C/H ratio (more refractory coke) with time, (b) poisoning by metallization (selective/non-selective adsorption of inorganics such as Ti and Fe on the catalyst), (c) sintering - increase in larger pores/decrease in surface area, and (d) parallel poisoning by irreversible nitrogen compound adsorption.

  1. Single-layer transition metal sulfide catalysts (United States)

    Thoma, Steven G [Albuquerque, NM


    Transition Metal Sulfides (TMS), such as molybdenum disulfide (MoS.sub.2), are the petroleum industry's "workhorse" catalysts for upgrading heavy petroleum feedstocks and removing sulfur, nitrogen and other pollutants from fuels. We have developed an improved synthesis technique to produce SLTMS catalysts, such as molybdenum disulfide, with potentially greater activity and specificity than those currently available. Applications for this technology include heavy feed upgrading, in-situ catalysis, bio-fuel conversion and coal liquefaction.

  2. Selective Degradation of Organic Pollutants Using an Efficient Metal-Free Catalyst Derived from Carbonized Polypyrrole via Peroxymonosulfate Activation. (United States)

    Hu, Peidong; Su, Hanrui; Chen, Zhenyu; Yu, Chunyang; Li, Qilin; Zhou, Baoxue; Alvarez, Pedro J J; Long, Mingce


    Metal-free carbonaceous materials, including nitrogen-doped graphene and carbon nanotubes, are emerging as alternative catalysts for peroxymonosulfate (PMS) activation to avoid drawbacks of conventional transition metal-containing catalysts, such as the leaching of toxic metal ions. However, these novel carbocatalysts face relatively high cost and complex syntheses, and their activation mechanisms have not been well-understood. Herein, we developed a novel nitrogen-doped carbonaceous nanosphere catalyst by carbonization of polypyrrole, which was prepared through a scalable chemical oxidative polymerization. The defective degree of carbon substrate and amount of nitrogen dopants (i.e., graphitic nitrogen) were modulated by the calcination temperature. The product carbonized at 800 °C (CPPy-F-8) exhibited the best catalytic performance for PMS activation, with 97% phenol degradation efficiency in 120 min. The catalytic system was efficient over a wide pH range (2-9), and the reaction of phenol degradation had a relatively low activation energy (18.4 ± 2.7 kJ mol -1 ). The nitrogen-doped carbocatalyst activated PMS through a nonradical pathway. A two-step catalytic mechanism was extrapolated: the catalyst transfers electrons to PMS through active nitrogen species and becomes a metastable state of the catalyst (State I); next, organic substrates are oxidized and degraded by serving as electron donors to reduce State I. The catalytic process was selective toward degradation of various aromatic compounds with different substituents, probably depending on the oxidation state of State I and the ionization potential (IP) of the organics; that is, only those organics with an IP value lower than ca. 9.0 eV can be oxidized in the CPPy-F-8/PMS system.

  3. Packaging based on polymeric materials

    Directory of Open Access Journals (Sweden)

    Jovanović Slobodan M.


    Full Text Available In the past two years the consumption of common in the developed countries world wide (high tonnage polymers for packaging has approached a value of 50 wt.%. In the same period more than 50% of the packaging units on the world market were made of polymeric materials despite the fact that polymeric materials present 17 wt.% of all packaging materials. The basic properties of polymeric materials and their environmental and economical advantages, providing them such a position among packaging materials, are presented in this article. Recycling methods, as well as the development trends of polymeric packaging materials are also presented.

  4. Synthesis of magnetic polymeric microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Gervald, A Yu; Gritskova, Inessa A; Prokopov, Nikolai I [M.V. Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow (Russian Federation)


    The key types of magnetic polymeric microspheres are considered. Methods of synthesis of different types of magnetic nanoparticles and of preparation of stable magnetic fluids on their basis are outlined. The overview of the methods for the manufacture of magnetic polymeric microspheres is presented. The effect of the synthesis conditions on the characteristics of magnetic polymeric microspheres such as the diameter and the particle size distribution and the content of magnetic material is discussed by particular examples. The application fields of magnetic polymeric microspheres are briefly surveyed.

  5. Synthesis of magnetic polymeric microspheres

    International Nuclear Information System (INIS)

    Gervald, A Yu; Gritskova, Inessa A; Prokopov, Nikolai I


    The key types of magnetic polymeric microspheres are considered. Methods of synthesis of different types of magnetic nanoparticles and of preparation of stable magnetic fluids on their basis are outlined. The overview of the methods for the manufacture of magnetic polymeric microspheres is presented. The effect of the synthesis conditions on the characteristics of magnetic polymeric microspheres such as the diameter and the particle size distribution and the content of magnetic material is discussed by particular examples. The application fields of magnetic polymeric microspheres are briefly surveyed.

  6. An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

    Directory of Open Access Journals (Sweden)

    Zaiku Xie


    Full Text Available Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT, etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts.

  7. Boron-containing catalysts for dry reforming of methane to synthesis gas

    KAUST Repository

    Takanabe, Kazuhiro


    The present invention uses a cobalt catalyst for carbon dioxide reforming of lower alkanes to synthesis gas having a cobalt catalyst on an oxide support where the supported cobalt catalyst has been modified with a boron precursor. The boron-treated cobalt catalyst systems as described herein show significant increases in the conversion of CH4 and CO2 during the dry reforming of methane (DRM) reaction as compared to traditional catalysts. Described herein are supported catalysts and methods of using the catalysts for the dry reforming of methane to synthesis gas, with the supported catalysts in the present invention include a boron-treated cobalt catalyst disposed on an oxide support. Also described herein are processes for preparing the supported catalysts.

  8. Surface coordination polymerization of ethylene by hydrozirconation-immobilized metallocene. (United States)

    Zheng, Jun; Wang, Yanhui; Ye, Lin; Lin, Yichao; Tang, Tao; Zhang, Jidong


    Hydrozirconation on vinyl-terminated substrates (silicon wafer and nanosilica sphere) is employed as an efficient way for immobilization of zirconocene catalyst through Zr-C bonds, which is applied in surface coordination ethylene polymerization producing surface-tethered polyethylene (PE). The formation of Zr-C σ bond induced by hydrozirconation provides an initiator precursor for growing a layer of PE covalently linked onto substrates. The results from SEM, AFM, and TEM show that the surface polymerization is controlled by hydrozirconation. Surface pattern or core-shell structure with crystalline PE coating can be formed, when silicon wafer is selectively functionalized with vinyl-groups or vinyl-modified nanosilica is applied. It is believed that hydrozirconation for the synthesis of zirconocene initiator can be a versatile route to prepare polyolefin hybrid materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Performance of (CoPC)n catalyst in active lithium-thionyl chloride cells (United States)

    Shah, Pinakin M.


    An experimental study was conducted with anode limited D size cells to characterize the performance of an active lithium-thionyl chloride (Li/SOCl2) system using the polymeric cobalt phthalocyanine, (CoPC)n, catalyst in carbon cathodes. The author describes the results of this experiment with respect to initial voltage delays, operating voltages, and capacities. The effectiveness of the preconditioning methods evolved to alleviate passivation effects on storage are also discussed. The results clearly demonstrated the superior high rate capability of cells with the catalyst. The catalyst did not adversely impact the performance of cells after active storage for up to 6 months, while retaining its beneficial influences.

  10. Catalysts, methods of making catalysts, and methods of use

    KAUST Repository

    Renard, Laetitia


    Embodiments of the present disclosure provide for catalysts, methods of making catalysts, methods of using catalysts, and the like. In an embodiment, the method of making the catalysts can be performed in a single step with a metal nanoparticle precursor and a metal oxide precursor, where a separate stabilizing agent is not needed.

  11. Polymer-Supported Cinchona Alkaloid-Derived Ammonium Salts as Recoverable Phase-Transfer Catalysts for the Asymmetric Synthesis of α-Amino Acids

    Directory of Open Access Journals (Sweden)

    Carmen Nájera


    Full Text Available Alkaloids such as cinchonidine, quinine and N-methylephedrine have been N-alkylated using polymeric benzyl halides or co-polymerized and then N-alkylated, thus affording a series of polymer-supported chiral ammonium salts which have been employed as phase-transfer catalysts in the asymmetric benzylation of an N-(diphenylmethyleneglycine ester. These new polymeric catalysts can be easily recovered by simple filtration after the reaction and reused. The best ee’s were achieved when Merrifield resin-anchored cinchonidinium ammonium salts were employed.

  12. Polymerization of Polar Monomers from a Theoretical Perspective

    KAUST Repository

    Alghamdi, Miasser


    Density functional theory calculations have been used to investigate catalytic mechanism of polymer formation containing polar groups, from the synthesis of the monomer to the synthesis of the macromolecule. In the spirit of a sustainable and green chemistry, we initially focused attention on the coupling of CO2 as economically convenient and recyclable C1 source with C2H4 to form acrylate and/or butirro-lactone, two important polar monomers. In this process formation of a mettallolactone via oxidative coupling of CO2 and C2H4 is an important intermediate. Given this background, we explored in detail (chapter-3) several Ni based catalysts for CO2 coupling with C2H4 to form acrylate. In this thesis we report on the competitive reaction mechanisms (inner vs outer sphere) for the oxidative coupling of CO2 and ethylene for a set of 11 Ni-based complexes containing bisphosphine ligands. In another effort, considering incorporation of a C=C bond into a metal-oxygen-Functional-Group moiety is a challenging step in several polymerization reactions, we explored the details of this reaction (chapter4) using two different catalysts that are capable to perform this reaction in the synthesis of heterocycles. Specifically, the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-Bis-diphenylphosphino-propane), and the [Pd]/BPh3 intramolecular alkoxyfunctionalizations. Rest of the thesis we worked on understanding the details of the polymerization of polar monomers using organocatalysts based on N-heterocyclic carbenes (NHC) or N-heterocyclic olefins (NHO). In particular (chapter-5) we studied the polymerization of N-methyl N-carboxy- anhydrides, towards cyclic poly(N-substituted glycine)s, promoted by NHC catalysts. In good agreement with the experimental findings, we demonstrated that NHC promoted ring opening polymerization of N-Me N-Carboxyanhydrides may proceed via two different catalytic pathways. In a similar effort we studied polymerization of

  13. Polymerization of Ethylene Catalyzed by Vanadium(III Complexes

    Directory of Open Access Journals (Sweden)

    Hamdi Ali Elagab


    Full Text Available Thirty five  complexes of 1,2- bis(benzimidazole, benzothiazole and benzoxazolebenzene,  1,2-bis(benzimidazole, benzothiazole and benzoxazole-4-methyl-benzene, 1,2-bis  (benzimidazole, benzothiazole and benzoxazole4-bromobenzene, 1, 2-bis(benzimidazole, benzothiazole and benzoxazole 4- chlorobenzene,  and 2, 6-bis(benzimidazole, benzothiazole and benzoxazole pyridine compounds with V (III metal centers were synthesized, characterized, activated with methylalumoxane (MAO and then tested for catalytic ethylene polymerization. The catalysts generally show moderate to good activities compared to the benchmark catalyst Cp2ZrCl2. The activities of the various catalysts were found to be function of the hetero atoms in the ligand frameworks and also strongly influenced by the bridging unit of the ligand. The highest activity was obtained with 36 / MAO (442 kg PE / mol cat. h. The produced polyethylenes showed high molecular weights (up to 2.7 × 106 g/mol and broad molecular weight distributions (PD = 1.4 - 16.6. Thermal analysis of polyethylenes produced with vanadium complexes revealed that the catalyst systems were capable to produce high density polyethylenes with melting temperatures > 135 °C and crystallization temperatures range from 117-120 °C with high degree of crystallinity. DOI: 

  14. Hollow Nano- and Microstructures as Catalysts. (United States)

    Prieto, Gonzalo; Tüysüz, Harun; Duyckaerts, Nicolas; Knossalla, Johannes; Wang, Guang-Hui; Schüth, Ferdi


    Catalysis is at the core of almost every established and emerging chemical process and also plays a central role in the quest for novel technologies for the sustainable production and conversion of energy. Particularly since the early 2000s, a great surge of interest exists in the design and application of micro- and nanometer-sized materials with hollow interiors as solid catalysts. This review provides an updated and critical survey of the ever-expanding material architectures and applications of hollow structures in all branches of catalysis, including bio-, electro-, and photocatalysis. First, the main synthesis strategies toward hollow materials are succinctly summarized, with emphasis on the (regioselective) incorporation of various types of catalytic functionalities within their different subunits. The principles underlying the scientific and technological interest in hollow materials as solid catalysts, or catalyst carriers, are then comprehensively reviewed. Aspects covered include the stabilization of catalysts by encapsulation, the introduction of molecular sieving or stimuli-responsive "auxiliary" functionalities, as well as the single-particle, spatial compartmentalization of various catalytic functions to create multifunctional (bio)catalysts. Examples are also given on the applications which hollow structures find in the emerging fields of electro- and photocatalysis, particularly in the context of the sustainable production of chemical energy carriers. Finally, a critical perspective is provided on the plausible evolution lines for this thriving scientific field, as well as the main practical challenges relevant to the reproducible and scalable synthesis and utilization of hollow micro- and nanostructures as solid catalysts.

  15. Catalyst in Basic Oleochemicals

    Directory of Open Access Journals (Sweden)

    Eva Suyenty


    Full Text Available Currently Indonesia is the world largest palm oil producer with production volume reaching 16 million tones per annum. The high crude oil and ethylene prices in the last 3 – 4 years contribute to the healthy demand growth for basic oleochemicals: fatty acids and fatty alcohols. Oleochemicals are starting to replace crude oil derived products in various applications. As widely practiced in petrochemical industry, catalyst plays a very important role in the production of basic oleochemicals. Catalytic reactions are abound in the production of oleochemicals: Nickel based catalysts are used in the hydrogenation of unsaturated fatty acids; sodium methylate catalyst in the transesterification of triglycerides; sulfonic based polystyrene resin catalyst in esterification of fatty acids; and copper chromite/copper zinc catalyst in the high pressure hydrogenation of methyl esters or fatty acids to produce fatty alcohols. To maintain long catalyst life, it is crucial to ensure the absence of catalyst poisons and inhibitors in the feed. The preparation methods of nickel and copper chromite catalysts are as follows: precipitation, filtration, drying, and calcinations. Sodium methylate is derived from direct reaction of sodium metal and methanol under inert gas. The sulfonic based polystyrene resin is derived from sulfonation of polystyrene crosslinked with di-vinyl-benzene. © 2007 BCREC UNDIP. All rights reserved.[Presented at Symposium and Congress of MKICS 2007, 18-19 April 2007, Semarang, Indonesia][How to Cite: E. Suyenty, H. Sentosa, M. Agustine, S. Anwar, A. Lie, E. Sutanto. (2007. Catalyst in Basic Oleochemicals. Bulletin of Chemical Reaction Engineering and Catalysis, 2 (2-3: 22-31.  doi:10.9767/bcrec.2.2-3.6.22-31][How to Link/DOI: || or local:

  16. Recent Progress on Transition Metal Catalyst Separation and Recycling in ATRP. (United States)

    Ding, Mingqiang; Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin


    Atom transfer radical polymerization (ATRP) is a versatile and robust tool to synthesize a wide spectrum of monomers with various designable structures. However, it usually needs large amounts of transition metal as the catalyst to mediate the equilibrium between the dormant and propagating species. Unfortunately, the catalyst residue may contaminate or color the resultant polymers, which limits its application, especially in biomedical and electronic materials. How to efficiently and economically remove or reduce the catalyst residue from its products is a challenging and encouraging task. Herein, recent advances in catalyst separation and recycling are highlighted with a focus on (1) highly active ppm level transition metal or metal free catalyzed ATRP; (2) post-purification method; (3) various soluble, insoluble, immobilized/soluble, and reversible supported catalyst systems; and (4) liquid-liquid biphasic catalyzed systems, especially thermo-regulated catalysis systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Study of spent hydrorefining catalysts

    International Nuclear Information System (INIS)

    Gellerman, M.M.; Aliev, R.R.; Sidel'kovskaya, V.G.


    Aluminonickelmolybdenum catalysts for diesel fuel hydrorefining have been studied by DTA, XSPS, and diffuse reflection spectroscopy. Chemical and phase states of molybdenum compounds in samples of fresh catalyst, regenerated one after one year operation, and clogged with coke catalyst after five year operation, are determined. Chemical reactions and crystal-phase transformations of the molybdenum compounds during catalyst deactivation and regeneration are discussed

  18. Catalysts for Environmental Remediation

    DEFF Research Database (Denmark)

    Abrams, B. L.; Vesborg, Peter Christian Kjærgaard


    on titania (V2O5-WO3/TiO2) as the example catalyst. The main photocatalysts examined for mineralization of organic compounds were TiO2 and MoS2. It is important to obtain insight into the catalyst structure-to-activity relationship in order to understand and locate the active site(s). In this chapter......The properties of catalysts used in environmental remediation are described here through specific examples in heterogeneous catalysis and photocatalysis. In the area of heterogeneous catalysis, selective catalytic reduction (SCR) of NOx was used as an example reaction with vanadia and tungsta...

  19. Method for reactivating solid catalysts used in alkylation reactions (United States)

    Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.


    A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

  20. Transition metal complexes supported on metal-organic frameworks for heterogeneous catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Omar K.; Hupp, Joseph T.; Delferro, Massimiliano; Klet, Rachel C.


    A robust mesoporous metal-organic framework comprising a hafnium-based metal-organic framework and a single-site zirconium-benzyl species is provided. The hafnium, zirconium-benzyl metal-organic framework is useful as a catalyst for the polymerization of an alkene.

  1. The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability

    NARCIS (Netherlands)

    Shamiri, A.; Chakrabarti, M.H.; Jahan, S.; Hussain, M.A.; Kaminsky, W.; Aravind, P.V.; Yehye, W.A.


    50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New

  2. Inhibition of Microbial Growth by Fatty Amine Catalysts from Polyurethane Foam Test Tube Plugs (United States)

    Bach, John A.; Wnuk, Richard J.; Martin, Delano G.


    When polyurethane foam test tube plugs are autoclaved, they release volatile fatty amines that inhibit the growth of some microorganisms. The chemical structures of these amines were determined by the use of a gas chromatographmass spectrometer. They are catalysts used to produce the foam. The problem of contaminating growth media with toxic substances released from polymeric materials is discussed. PMID:1096816

  3. End Functionalization by Ring Opening Polymerization: Influence of Reaction Conditions on the Synthesis of End Functionalized Poly(lactic Acid)


    Icart, Luis P.; Fernandes, Edson; Agüero, Lissette; Cuesta, Maelia Z.; Silva, Dionisio Z.; Rodríguez-Fernández, Daniel E.; Souza Jr., Fernando G.; Lima, Luis Maurício T. R.; Dias, Marcos L.


    In this paper, chemical functionalization of poly(lactic acid) (PLA) was carried out by using of salicyl aldehyde (SAl) and salicylic acid (SAc) as co-initiators of ring opening polymerization (ROP). Two factorial designs (22) were performed to evaluate the effects of the lactide/catalyst and co-initiator/catalyst molar ratios on the content of aldehyde or carboxylic acid end groups, thermal properties and molecular weight (Mw) of PLA. Tin(II) 2-ethylhexanoate was used as a catalyst. The co-i...

  4. Intrinsic embedded sensors for polymeric mechatronics: flexure and force sensing. (United States)

    Jentoft, Leif P; Dollar, Aaron M; Wagner, Christopher R; Howe, Robert D


    While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm), three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor.

  5. Intrinsic Embedded Sensors for Polymeric Mechatronics: Flexure and Force Sensing

    Directory of Open Access Journals (Sweden)

    Leif P. Jentoft


    Full Text Available While polymeric fabrication processes, including recent advances in additive manufacturing, have revolutionized manufacturing, little work has been done on effective sensing elements compatible with and embedded within polymeric structures. In this paper, we describe the development and evaluation of two important sensing modalities for embedding in polymeric mechatronic and robotic mechanisms: multi-axis flexure joint angle sensing utilizing IR phototransistors, and a small (12 mm, three-axis force sensing via embedded silicon strain gages with similar performance characteristics as an equally sized metal element based sensor.

  6. Comparison of Ethylene/1-Hexene Copolymers Microstructures Synthesized by Homogeneous and Heterogeneous Metallocene Catalysts

    Directory of Open Access Journals (Sweden)

    Saeid Ahmadjo


    Full Text Available The substituted (bis-2-PhIndZrCl2 and non-substituted (bis-IndZrCl2 indenylbased metallocene catalysts were synthesized and used in homogenous and heterogeneous forms for copolymerization of ethylene and 1-hexene. The MCM-41 nano silica was used as support in heterogenization of the catalysts. The substituted (bis-2-PhIndZrCl2 metallocene catalyst in homogenous and heterogeneous forms showed lower activities in comparison to non-substituted (bis-IndZrCl2 metallocene catalyst. The microstructures of the obtained copolymers were investigated by techniques such as DSC, CNMR and TRRF. The kinetic study showed that the decay index (DI was decreased for both homogeneous catalysts due to unstable kinetic behaviors. However, the decay index contents approached one, using heterogeneous forms of catalyst which was an indication of stable kinetic behaviors. The kinetic results also displayed negative effect on the catalysts activities both in the homogeneous and heterogeneous forms by addition of comonomer on the polymerization. The triad distributions of obtained polymer by NMR technique exhibited the higher ratio of EEH, EHE, EEE triads than the other triads. The comonomer incorporationacceptability of substituted metallocene catalyst (bis-2-PhIndZrCl2 was higher than non-substituted catalyst (bis-IndZrCl2 as its comonomer acceptability increased from 1.3% to 5.4% by substitution mechanism. Microstructures of copolymers obtained by supported metallocene catalyst showed more non-uniform comonomer distribution in comparison with unsupported catalyst. The lamella thickness distributions for polymer obtained by supported substituted metallocene catalyst (bis-2-PhIndZrCl2 were in the ranges (3-8 . However, for supported metallocene non-substituted catalysts (bis-IndZrCl2 the lamella thickness were in the ranges (3-16 .

  7. Polymerization with freezing

    International Nuclear Information System (INIS)

    Ben-Naim, E; Krapivsky, P L


    Irreversible aggregation processes involving reactive and frozen clusters are investigated using the rate equation approach. In aggregation events, two clusters join irreversibly to form a larger cluster; additionally, reactive clusters may spontaneously freeze. Frozen clusters do not participate in merger events. Generally, freezing controls the nature of the aggregation process, as demonstrated by the final distribution of frozen clusters. The cluster mass distribution has a power-law tail, F k ∼k -γ , when the freezing process is sufficiently slow. Different exponents, γ = 1 and 3, are found for the constant and the product aggregation rates, respectively. For the latter case, the standard polymerization model, either no gels, or a single gel, or even multiple gels, may be produced

  8. Collaborative Research: Polymeric Multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Shenqiang [Temple Univ., Philadelphia, PA (United States). College of Engineering


    The goal of this project is to investigate room temperature magnetism and magnetoelectric coupling of polymeric multiferroics. A new family of molecular charge-transfer crystals has been emerged as a fascinating opportunity for the development of all-organic electrics and spintronics due to its weak hyperfine interaction and low spin-orbit coupling; nevertheless, direct observations of room temperature magnetic spin ordering have yet to be accomplished in organic charge-transfer solids. Furthermore, room temperature magnetoelectric coupling effect hitherto known multiferroics, is anticipated in organic donor-acceptor complexes because of magnetic field effects on charge-transfer dipoles, yet this is also unexplored. The PI seeks to fundamental understanding of the control of organic crystals to demonstrate and explore room temperature multiferroicity. The experimental results have been verified through the theoretical modeling.

  9. Catalyst for microelectromechanical systems microreactors (United States)

    Morse, Jeffrey D [Martinez, CA; Sopchak, David A [Livermore, CA; Upadhye, Ravindra S [Pleasanton, CA; Reynolds, John G [San Ramon, CA; Satcher, Joseph H [Patterson, CA; Gash, Alex E [Brentwood, CA


    A microreactor comprising a silicon wafer, a multiplicity of microchannels in the silicon wafer, and a catalyst coating the microchannels. In one embodiment the catalyst coating the microchannels comprises a nanostructured material. In another embodiment the catalyst coating the microchannels comprises an aerogel. In another embodiment the catalyst coating the microchannels comprises a solgel. In another embodiment the catalyst coating the microchannels comprises carbon nanotubes.

  10. Peptide-templated noble metal catalysts: syntheses and applications. (United States)

    Wang, Wei; Anderson, Caleb F; Wang, Zongyuan; Wu, Wei; Cui, Honggang; Liu, Chang-Jun


    Noble metal catalysts have been widely used in many applications because of their high activity and selectivity. However, a controllable preparation of noble metal catalysts still remains as a significant challenge. To overcome this challenge, peptide templates can play a critical role in the controllable syntheses of catalysts owing to their flexible binding with specific metallic surfaces and self-assembly characteristics. By employing peptide templates, the size, shape, facet, structure, and composition of obtained catalysts can all be specifically controlled under the mild synthesis conditions. In addition, catalysts with spherical, nanofiber, and nanofilm structures can all be produced by associating with the self-assembly characteristics of peptide templates. Furthermore, the peptide-templated noble metal catalysts also reveal significantly enhanced catalytic behaviours compared with conventional catalysts because the electron conductivity, metal dispersion, and reactive site exposure can all be improved. In this review, we summarize the research progresses in the syntheses of peptide-templated noble metal catalysts. The applications of the peptide-templated catalysts in organic reactions, photocatalysis, and electrocatalysis are discussed, and the relationship between structure and activity of these catalysts are addressed. Future opportunities, including new catalytic materials designed by using biological principles, are indicated to achieve selective, eco-friendly, and energy neutral synthesis approaches.

  11. Kinetics and Mechanism of Bulk Polymerization of Vinyl Chloride in a Polymerization Reactor

    Directory of Open Access Journals (Sweden)

    A. S. Ibrahim


    Full Text Available Polyvinyl chloride (PVC is the third most commonly produced polymer and is important because of its mechanical characteristics. The most common method of PVC manufacturing is the process of suspension. Although, there are several benefits associated with suspension, this study will focus on the bulk polymerization of vinyl chloride; highlight the physical and chemical properties of PVC, which can be changed through an estimation of the optimum ratio that exists between the hydrophilic and hydrophobic parts of the polymer’s surface, and propose a new mathematical model which will be helpful for the conversion of PVC into a useful form. The result will be the proposal of a new dynamic mathematical model for the three-phase structure model. All particles have been taken into account in the proposed model, which helped contribute to the reaction in gel, solid, and liquid phases, emphasizing the use of mercury (Hg as a catalyst. The proposed mathematical model considers the heat and mass transfer between the liquid, gel, and solid phases with chemical reactions that occur between the liquid and solid phases, and between the gel and solid phases. The effect of the catalyst and volumetric flow rates of vinyl chloride monomer (VCM on the system have been evaluated through the proposed mathematical model. Furthermore, the study’s experimental data have been compared with the findings of the suggested model in the context of concentration and temperature reaction. Obtained results show good agreement between the proposed mathematical model and the actual plant data.

  12. Apolipoprotein E: Essential Catalyst of the Alzheimer Amyloid Cascade

    Directory of Open Access Journals (Sweden)

    Huntington Potter


    Full Text Available The amyloid cascade hypothesis remains a robust model of AD neurodegeneration. However, amyloid deposits contain proteins besides Aβ, such as apolipoprotein E (apoE. Inheritance of the apoE4 allele is the strongest genetic risk factor for late-onset AD. However, there is no consensus on how different apoE isotypes contribute to AD pathogenesis. It has been hypothesized that apoE and apoE4 in particular is an amyloid catalyst or “pathological chaperone”. Alternatively it has been posited that apoE regulates Aβ clearance, with apoE4 been worse at this function compared to apoE3. These views seem fundamentally opposed. The former would indicate that removing apoE will reduce AD pathology, while the latter suggests increasing brain ApoE levels may be beneficial. Here we consider the scientific basis of these different models of apoE function and suggest that these seemingly opposing views can be reconciled. The optimal therapeutic target may be to inhibit the interaction of apoE with Aβ rather than altering apoE levels. Such an approach will not have detrimental effects on the many beneficial roles apoE plays in neurobiology. Furthermore, other Aβ binding proteins, including ACT and apo J can inhibit or promote Aβ oligomerization/polymerization depending on conditions and might be manipulated to effect AD treatment.

  13. The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability

    Directory of Open Access Journals (Sweden)

    Ahmad Shamiri


    Full Text Available 50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New metallocene/methylaluminoxane (MAO catalysts open the possibility to synthesize polymers with highly defined microstructure, tacticity, and steroregularity, as well as long-chain branched, or blocky copolymers with excellent properties. This improvement in polymerization is possible due to the single active sites available on the metallocene catalysts in contrast to their traditional counterparts. Moreover, these catalysts, half titanocenes/MAO, zirconocenes, and other single site catalysts can control various important parameters, such as co-monomer distribution, molecular weight, molecular weight distribution, molecular architecture, stereo-specificity, degree of linearity, and branching of the polymer. However, in most cases research in this area has reduced academia as olefin polymerization has seen significant advancements in the industries. Therefore, this paper aims to further motivate interest in polyolefin research in academia by highlighting promising and open areas for the future.

  14. The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability (United States)

    Shamiri, Ahmad; Chakrabarti, Mohammed H.; Jahan, Shah; Hussain, Mohd Azlan; Kaminsky, Walter; Aravind, Purushothaman V.; Yehye, Wageeh A.


    50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New metallocene/methylaluminoxane (MAO) catalysts open the possibility to synthesize polymers with highly defined microstructure, tacticity, and steroregularity, as well as long-chain branched, or blocky copolymers with excellent properties. This improvement in polymerization is possible due to the single active sites available on the metallocene catalysts in contrast to their traditional counterparts. Moreover, these catalysts, half titanocenes/MAO, zirconocenes, and other single site catalysts can control various important parameters, such as co-monomer distribution, molecular weight, molecular weight distribution, molecular architecture, stereo-specificity, degree of linearity, and branching of the polymer. However, in most cases research in this area has reduced academia as olefin polymerization has seen significant advancements in the industries. Therefore, this paper aims to further motivate interest in polyolefin research in academia by highlighting promising and open areas for the future. PMID:28788120

  15. Polypropylene reinvented: Costs of using metallocene catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Brockmeier, N.F.


    This study develops scoping estimates of the required capital investment and manufacturing costs to make a zirconocene catalyst/cocatalyst system [(F{sub 6}-acen)Zr(CH{sub 2}CMe{sub 3})(NMe{sub 2}Ph)][B(C{sub 6}F{sub 5}){sub 4}] immobilized on a silica support. Costs for this fluorine-based system are compared with estimates for two other metallocene catalysts using methylaluminoxane (MAO)-based cocatalysts. Including wt of support and cocatalyst, each of the production facilities for making the 3 zirconocene catalyst systems is sized at 364--484 tonnes/year. Cost to make the F-based catalyst system is estimated to be $10780/kg, assuming 20% return on capital invested. Costs for the two MAO-based catalyst system fall in the range of $10950--12160/kg, assuming same return. Within the {plus_minus}50% accuracy of these estimates, these differences are not significant. Given a catalyst productivity of 250 kg resin/gram zirconocene, the cost contribution in the finished ethylene-propylene copolymer resin is 4.4 cents/kg, excluding selling, administrative, research costs.

  16. Latent olefin metathesis catalysts


    Monsaert, Stijn; Lozano Vila, Ana; Drozdzak, Renata; Van Der Voort, Pascal; Verpoort, Francis


    Olefin metathesis is a versatile synthetic tool for the redistribution of alkylidene fragments at carbon-carbon double bonds. This field, and more specifically the development of task-specific, latent catalysts, attracts emerging industrial and academic interest. This tutorial review aims to provide the reader with a concise overview of early breakthroughs and recent key developments in the endeavor to develop latent olefin metathesis catalysts, and to illustrate their use by prominent exampl...

  17. Plasmatron-catalyst system (United States)

    Bromberg, Leslie; Cohn, Daniel R.; Rabinovich, Alexander; Alexeev, Nikolai


    A plasmatron-catalyst system. The system generates hydrogen-rich gas and comprises a plasmatron and at least one catalyst for receiving an output from the plasmatron to produce hydrogen-rich gas. In a preferred embodiment, the plasmatron receives as an input air, fuel and water/steam for use in the reforming process. The system increases the hydrogen yield and decreases the amount of carbon monoxide.

  18. Iron-Mediated Homogeneous ICAR ATRP of Methyl Methacrylate under ppm Level Organometallic Catalyst Iron(III Acetylacetonate

    Directory of Open Access Journals (Sweden)

    Jian Wu


    Full Text Available Atom Transfer Radical Polymerization (ATRP is an important polymerization process in polymer synthesis. However, a typical ATRP system has some drawbacks. For example, it needs a large amount of transition metal catalyst, and it is difficult or expensive to remove the metal catalyst residue in products. In order to reduce the amount of catalyst and considering good biocompatibility and low toxicity of the iron catalyst, in this work, we developed a homogeneous polymerization system of initiators for continuous activator regeneration ATRP (ICAR ATRP with just a ppm level of iron catalyst. Herein, we used oil-soluble iron (III acetylacetonate (Fe(acac3 as the organometallic catalyst, 1,1′-azobis (cyclohexanecarbonitrile (ACHN with longer half-life period as the thermal initiator, ethyl 2-bromophenylacetate (EBPA as the initiator, triphenylphosphine (PPh3 as the ligand, toluene as the solvent and methyl methacrylate (MMA as the model monomer. The factors related with the polymerization system, such as concentration of Fe(acac3 and ACHN and polymerization kinetics, were investigated in detail at 90 °C. It was found that a polymer with an acceptable molecular weight distribution (Mw/Mn = 1.43 at 45.9% of monomer conversion could be obtained even with 1 ppm of Fe(acac3, making it needless to remove the residual metal in the resultant polymers, which makes such an ICAR ATRP process much more industrially attractive. The “living” features of this polymerization system were further confirmed by chain-extension experiment.

  19. Synthesis of polypropylene/graphite nanocomposites by means of in situ polymerization

    International Nuclear Information System (INIS)

    Montagna, Larissa S.; Basso, Nara R.S.


    The nanotechnology presents a large field for research and development of new polymeric materials based in nanocomposites. This work is related to the synthesis of nanocomposites of polypropylene with graphite as filler. The sheets of graphite in nanometer dimensions were made by means of the chemical exfoliation and thermal treatment. The synthesis of the nanocomposites was carried through by means of the in situ polymerization using a metallocene catalyst and with different amounts of inorganic load (0,5; 1 and 2%). The synthesized nanocomposites were characterized by scanning electron microscopy (SEM) and X-Ray diffraction (XRD). (author)

  20. Polymeric micelles for drug targeting. (United States)

    Mahmud, Abdullah; Xiong, Xiao-Bing; Aliabadi, Hamidreza Montazeri; Lavasanifar, Afsaneh


    Polymeric micelles are nano-delivery systems formed through self-assembly of amphiphilic block copolymers in an aqueous environment. The nanoscopic dimension, stealth properties induced by the hydrophilic polymeric brush on the micellar surface, capacity for stabilized encapsulation of hydrophobic drugs offered by the hydrophobic and rigid micellar core, and finally a possibility for the chemical manipulation of the core/shell structure have made polymeric micelles one of the most promising carriers for drug targeting. To date, three generations of polymeric micellar delivery systems, i.e. polymeric micelles for passive, active and multifunctional drug targeting, have arisen from research efforts, with each subsequent generation displaying greater specificity for the diseased tissue and/or targeting efficiency. The present manuscript aims to review the research efforts made for the development of each generation and provide an assessment on the overall success of polymeric micellar delivery system in drug targeting. The emphasis is placed on the design and development of ligand modified, stimuli responsive and multifunctional polymeric micelles for drug targeting.

  1. Poly(dendrimers) with phosphorescent iridium(III) complex-based side chains prepared via ring-opening metathesis polymerization

    NARCIS (Netherlands)

    Lai, W.-Y.; Balfour, M.N.; Levell, J.W.; Bansal, A.K.; Burn, P.L.; Lo, S.-C.; Samuel, I.D.W.


    Phosphorescent poly(dendrimers) with a norbornene-derived backbone have been synthesized using ring-opening metathesis polymerization with the Grubbs III catalyst. The dendrimers are comprised of a heteroleptic iridium(III) complex core with two 2-phenylpyridyl ligands and a phenyltriazolyl ligand,

  2. Soy-based polymeric surfactants prepared in carbon dioxide media and influence of structure on their surface properties (United States)

    Soybean oil (SO) and epoxidized soybean oil (ESO) were polymerized in the CO2 media (supercritical and sub-supercritical) by BF3•OEt2 catalyst. The resulting polymers (PSO and PESO) were hydrolyzed into polysoaps (HPSO) and (HPESO) with Na+, K+, or TEA+ (triethanolamine, ammonium salt) counter ions....

  3. Method for hydrogen production and metal winning, and a catalyst/cocatalyst composition useful therefor (United States)

    Dhooge, Patrick M.


    A catalyst/cocatalyst/organics composition of matter is useful in electrolytically producing hydrogen or electrowinning metals. Use of the catalyst/cocatalyst/organics composition causes the anode potential and the energy required for the reaction to decrease. An electrolyte, including the catalyst/cocatalyst composition, and a reaction medium composition further including organic material are also described.

  4. Continuous wasteless ecologically safe technology of propylenecarbonate production in presence of phthalocyanine catalysts (United States)

    Afanasiev, Vladimir Vasilievich [Moscow, RU; Zefirov, Nikolai Serafimovich [Moscow, RU; Zalepugin, Dmitry Yurievich [Moscow, RU; Polyakov, Victor Stanislavovich [Moscow, RU; Tilkunova, Nataliya Alexandrovna [Moscow, RU; Tomilova, Larisa Godvigovna [Moscow, RU


    A continuous method of producing propylenecarbonate includes carboxylation of propylene oxide with carbon dioxide in presence of phthalocyanine catalyst on an inert carrier, using as the phthalocyanine catalyst at least one catalyst selected from the group consisting of not-substituted, methyl, ethyl, butyl, and tret butyl-substituted phthalocyanines of metals, including those containing counterions, and using as the carrier a hydrophobic carrier.

  5. Phosphasalen indium complexes showing high rates and isoselectivities in rac-lactide polymerizations

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Dominic; White, Andrew J.P. [Department of Chemistry, Imperial College London (United Kingdom); Forsyth, Craig M. [School of Chemistry, Monash University, Clayton, VIC (Australia); Bown, Mark [CSIRO Manufacturing, Bayview Avenue, Clayton, VIC (Australia); Williams, Charlotte K. [Department of Chemistry, Oxford University (United Kingdom)


    Polylactide (PLA) is the leading bioderived polymer produced commercially by the metal-catalyzed ring-opening polymerization of lactide. Control over tacticity to produce stereoblock PLA, from rac-lactide improves thermal properties but is an outstanding challenge. Here, phosphasalen indium catalysts feature high rates (30±3 m{sup -1} min{sup -1}, THF, 298 K), high control, low loadings (0.2 mol %), and isoselectivity (P{sub i}=0.92, THF, 258 K). Furthermore, the phosphasalen indium catalysts do not require any chiral additives. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Hyper-cross-linked, hybrid membranes via interfacial polymerization


    Raaijmakers, Michiel


    Hyper-cross-linked, hybrid membranes consist of covalent networks of alternating organic and inorganic, or biological groups. This thesis reports on the preparation of such hybrid networks via interfacial polymerization. The structure-property relationships of the hybrid networks depend strongly on the type, size and flexibility of the constituents. The collection of polymers that can be synthesized via interfacial polymerization includes polyamides, polyurethanes, polyureas, polyanilines, po...

  7. The innovation catalysts. (United States)

    Martin, Roger L


    A few years ago the software development company Intuit realized that it needed a new approach to galvanizing customers. The company's Net Promoter Score was faltering, and customer recommendations of new products were especially disappointing. Intuit decided to hold a two-day, off-site meeting for the company's top 300 managers with a focus on the role of design in innovation. One of the days was dedicated to a program called Design for Delight. The centerpiece of the day was a PowerPoint presentation by Intuit founder Scott Cook, who realized midway through that he was no Steve Jobs: The managers listened dutifully, but there was little energy in the room. By contrast, a subsequent exercise in which the participants worked through a design challenge by creating prototypes, getting feedback, iterating, and refining, had them mesmerized. The eventual result was the creation of a team of nine design-thinking coaches--"innovation catalysts"--from across Intuit who were made available to help any work group create prototypes, run experiments, and learn from customers. The process includes a "painstorm" (to determine the customer's greatest pain point), a "soljam" (to generate and then winnow possible solutions), and a "code-jam" (to write code "good enough" to take to customers within two weeks). Design for Delight has enabled employees throughout Intuit to move from satisfying customers to delighting them.

  8. Activation of molecular catalysts using semiconductor quantum dots (United States)

    Meyer, Thomas J [Chapel Hill, NC; Sykora, Milan [Los Alamos, NM; Klimov, Victor I [Los Alamos, NM


    Photocatalytic materials based on coupling of semiconductor nanocrystalline quantum dots (NQD) and molecular catalysts. These materials have capability to drive or catalyze non-spontaneous chemical reactions in the presence of visible radiation, ultraviolet radiation, or both. The NQD functions in these materials as a light absorber and charge generator. Following light absorption, the NQD activates a molecular catalyst adsorbed on the surface of the NQD via transfer of one or more charges (either electrons or electron-holes) from the NQD to the molecular catalyst. The activated molecular catalyst can then drive a chemical reaction. A photoelectrolytic device that includes such photocatalytic materials is also described.

  9. Combined catalysts for the combustion of fuel in gas turbines (United States)

    Anoshkina, Elvira V.; Laster, Walter R.


    A catalytic oxidation module for a catalytic combustor of a gas turbine engine is provided. The catalytic oxidation module comprises a plurality of spaced apart catalytic elements for receiving a fuel-air mixture over a surface of the catalytic elements. The plurality of catalytic elements includes at least one primary catalytic element comprising a monometallic catalyst and secondary catalytic elements adjacent the primary catalytic element comprising a multi-component catalyst. Ignition of the monometallic catalyst of the primary catalytic element is effective to rapidly increase a temperature within the catalytic oxidation module to a degree sufficient to ignite the multi-component catalyst.

  10. Organometallic Polymeric Conductors (United States)

    Youngs, Wiley J.


    For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for

  11. Methods of producing epoxides from alkenes using a two-component catalyst system (United States)

    Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian


    Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

  12. Strategic Formulation of Graphene Oxide Sheets for Flexible Monoliths and Robust Polymeric Coatings Embedded with Durable Bioinspired Wettability †. (United States)

    Das, Avijit; Deka, Jumi; Rather, Adil M; Bhunia, Bibhas K; Saikia, Partha Pratim; Mandal, Biman B; Raidongia, Kalyan; Manna, Uttam


    Artificial bioinspired superhydrophobicity, which is generally developed through appropriate optimization of chemistry and hierarchical topography, is being recognized for its immense prospective applications related to environment and healthcare. Nevertheless, the weak interfacial interactions that are associated with the fabrication of such special interfaces often provide delicate biomimicked wettability, and the embedded antifouling property collapses on exposure to harsh and complex aqueous phases and also after regular physical deformations, including bending, creasing, etc. Eventually, such materials with potential antifouling property became less relevant for practical applications. Here, a facile, catalyst-free, and robust 1,4-conjugate addition reaction has been strategically exploited for appropriate covalent integration of modified graphene oxide to developing polymeric materials with (1) tunable mechanical properties and (2) durable antifouling property, which are capable of performing both in air and under oil. Furthermore, this approach provided a facile basis for (3) engineering a superhydrophobic monolith into arbitrary free-standing shapes and (4) decorating various flexible (metal, synthetic plastic, etc.) and rigid (glass, wood, etc.) substrates with thick and durable three-dimensional superhydrophobic coatings. The synthesized superhydrophobic monoliths and polymeric coatings with controlled mechanical properties are appropriate to withstand different physical insults, including twisting, creasing, and even physical erosion of the material, without compromising the embedded antiwetting property. The materials are also equally resistant to various harsh chemical environments, and the embedded antifouling property remained unperturbed even after continuous exposure to extremes of pH (pH 1 and pH 11), artificial sea water for a minimum of 30 days. These flexible and formable free-standing monoliths and stable polymeric coatings that are extremely

  13. Characteristics of honeycomb catalysts to recover tritiated hydrogen and methane

    International Nuclear Information System (INIS)

    Tatsuhiko, Uda; Masahiro, Tanaka; Kenzo, Munakata


    Applicability of honeycomb catalysts to the tritium recovery system was examined considering tritium release accidents in the fusion plant where large volumes of air would be processed by the air cleanup system. Catalytic oxidation of isotopic hydrogen isotopes including tritium is a conventional method for the removal of tritium from air in the working space. However, the high throughput of air causes pressure drop in catalyst beds, which results in high load to the process gas pumping system. The honeycomb catalyst has an advantage in terms of pressure drop, which is estimated to be far less than that in conventional particle-packed catalyst beds. Our previous studies revealed that honeycomb catalysts made of cordierite and Al-Cr-Fe metal alloy substances have preferable oxidizing performance. It was found that the platinum-deposited cordierite catalyst shows the higher oxidation rate for hydrogen gas, and the palladium-deposited metal honeycomb catalyst shows the higher oxidation rate for methane gas. In this study, the properties of honeycomb catalysts were more systematically studied by changing experimental parameters such as noble metal content, mesh density and so forth to obtain design data base for high performance honeycomb catalysts. With regard to catalysts, the amount of noble metal deposited on the honeycomb substrates were varied from 1 g/L to 4 g/L and the mesh density of the honeycombs were changed from 260 to 400 CPSI as well. For operating conditions, the flow rate of the process gases was varied from 0.016 to 0.12 m 3 /hr, and the concentration of water vapor was changed from 0 to 1.4 %. Results of experimental study suggest that honeycomb catalysts are useful for the treatment of gases with high volumetric velocity in a fusion plant because of their low pressure drop in the catalyst reactor. The platinum catalysts were found to be suitable for oxidation of hydrogen gas, while the palladium catalysts exhibit better performance for oxidation of

  14. Durability of Polymeric Encapsulation Materials for a PMMA/glass Concentrator Photovoltaic System

    Energy Technology Data Exchange (ETDEWEB)

    Miller, David C.; Kempe, Michael D.; Muller, Matthew T; Gray, Matthew H.; Araki, Kenji; Kurtz, Sarah R.


    The durability of polymeric encapsulation materials was examined using outdoor exposure at the nominal geometric concentration of 500 suns. The results for 36 months cumulative field deployment are presented for materials including: poly(ethylene-co-vinyl acetate), (EVA); polyvinyl butyral (PVB); ionomer; polyethylene/ polyoctene copolymer (PO); thermoplastic polyurethane (TPU); poly(dimethylsiloxane) (PDMS); poly(diphenyl dimethyl siloxane) (PDPDMS); and poly(phenyl-methyl siloxane) (PPMS). Measurements of the field conditions including ambient temperature and ultraviolet (UV) dose were recorded at the test site during the experiment. Measurements for the experiment included optical transmittance (with subsequent analysis of solar-weighted transmittance, UV cut-off wavelength, and yellowness index), mass, visual photography, photoelastic imaging, and fluorescence spectroscopy. While the results to date for EVA are presented and discussed, examination here focuses more on the siloxane materials. A specimen recently observed to fail by thermal decomposition is discussed in terms of the implementation of the experiment as well as its fluorescence signature, which was observed to become more pronounced with age. Modulated thermogravimetry (allowing determination of the activation energy of thermal decomposition) was performed on a subset of the siloxanes to quantify the propensity for decomposition at elevated temperatures. Supplemental, Pt-catalyst- and primer-solutions as well as peroxide-cured PDMS specimens were examined to assess the source of the luminescence. The results of the study including the change in optical transmittance, observed failure modes, and subsequent analyses of the failure modes are described in the conclusions.

  15. Kinetics of silica polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Weres, O.; Yee, A.; Tsao, L.


    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  16. γ-Diimine palladium(II based complexes mediated polymerization of methyl methacrylate

    Directory of Open Access Journals (Sweden)

    Mahmoud Sunjuk


    Full Text Available The synthesis of new palladium(II complexes of the type [Pd(A–NC–ph–CN–ACl2] (4a–e (A = cyclohexyl (a, 2-isoprpropyl (b, pyrenyl (c, naphthyl (d, and 2,6-diisopropyl (e is described. The isolated γ-diimine ligands and their corresponding palladium(II complexes were characterized by their physical properties, elemental analysis, 1H NMR-, 13C NMR, and infrared spectroscopy. The palladium(II complexes (4a–e were employed successfully as catalysts for atom transfer radical polymerization (ATRP of methyl methacrylate (MMA in the presence of ethyl-2-bromoisobutyrate (EBIB as initiator at 90 °C. Polymerization with these catalyst systems afforded polymers with low molecular weight distribution (Mw/Mn and syndio-rich atactic poly (MMA with relatively higher [rr] diads.

  17. Catalyst component interactions in nickel/alumina catalyst

    Directory of Open Access Journals (Sweden)

    Kiš Erne E.


    Full Text Available The influence of nickel loading (5; 10; 20 wt% Ni, temperature of heat treatment (400; 700; 1100°C and way of catalyst preparation on the catalyst component interactions (CCI in the impregnated, mechanical powder mixed and co-precipitated catalyst was investigated. For sample characterization, low temperature nitrogen adsorption (LTNA and X-ray diffraction (XRD were applied. Significant differences were revealed, concerning CCI in dependence of nickel loading, temperature of heat treatment and way of catalyst preparation. The obtained results show that the support metal oxide interactions (SMI in impregnated and co-precipitated catalysts are more intensive than in the mechanical powder mixed catalyst. The degree and intensity of CCI is expressed by the ratio of real and theoretical surface area of the catalyst. This ratio can be used for a quantitative estimation of CCI and it is generally applicable to all types of heterogeneous catalysts.

  18. Metal-free phenanthrenequinone cyclotrimer as an effective heterogeneous catalyst. (United States)

    Zhang, Jian; Wang, Xuan; Su, Qi; Zhi, Linjie; Thomas, Arne; Feng, Xinliang; Su, Dang Sheng; Schlögl, Robert; Müllen, Klaus


    A phenanthrenequinone macrocyclic trimer was synthesized and used as a heterogeneous catalyst for oxidative dehydrogenation of ethylbenzene. This model molecule under comparable kinetic conditions is up to 47 times more active than extended solid catalysts including nanocarbons, metal phosphates, and oxides, confirming the hypothesis that diketone-like groups can serve as active sites.

  19. Oxidative dehydrogenation of propane over niobia supported vanadium oxide catalysts

    NARCIS (Netherlands)

    Watling, T.C.; Watling, T.C.; Deo, G.; Seshan, Kulathuiyer; Wachs, I.E.; Lercher, J.A.


    Oxidative dehydrogenation (ODH) of propane is examined over a series of catalysts, which include Nb2O5 supported monolayer V2O5 catalysts, bulk vanadia-niobia with different vanadium oxide loadings and prepared by four different methods, V2O5and Nb2O5. The intrinsic activity (TOF) of the samples

  20. Supported organoiridium catalysts for alkane dehydrogenation (United States)

    Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo


    Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

  1. Organo-Lewis acids as cocatalysts in cationic metallocene polymerization catalysis. Unusual characteristics of sterically encumbered tris(perfluorobiphenyl)borane

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.X.; Stern, C.L.; Yang, S.; Marks, T.J. [Northwestern Univ., Evanston, IL (United States)


    Organo-Lewis acids such as methylalumoxane (MAO) and B(C{sub 6}F{sub 5} ){sub 3} (I) play pivotal roles as alkide/hydride abstractors/ cocatalysts in generating highly active, cationic olefin polymerization catalysts (II; L,L` = anionic ancillary ligands; X{sup -} = weakly coordinating anion). We communicate here the unusual cocatalytic characteristics of the new, sterically encumbered fluoroarylborane, tris(2,2`,2``-perfluorobiphenyl)-borane (PBB, III). Characteristics include substantially different abstractive and ion pair structure/reactivity relationships vis-a-vis I. PPB was synthesized as colorless microcrystals in 76% yield from C{sub 6}F{sub 5}Br. Reaction with group 4 and Th methyls proceeds cleanly to yield cationic complexes, which were characterized by standard {sup 1}H/{sup 13}C/{sup 19}F NMR spectroscopic and analytical techniques. The results illustrate the substantial and surprising differences in cationic complex ion pair structure and reactivity that can be brought about by modifications in fluoroarylborane catalyst architecture. 10 refs., 1 fig., 1 tab.

  2. Oxide Nanocrystal Model Catalysts. (United States)

    Huang, Weixin


    Model catalysts with uniform and well-defined surface structures have been extensively employed to explore structure-property relationships of powder catalysts. Traditional oxide model catalysts are based on oxide single crystals and single crystal thin films, and the surface chemistry and catalysis are studied under ultrahigh-vacuum conditions. However, the acquired fundamental understandings often suffer from the "materials gap" and "pressure gap" when they are extended to the real world of powder catalysts working at atmospheric or higher pressures. Recent advances in colloidal synthesis have realized controlled synthesis of catalytic oxide nanocrystals with uniform and well-defined morphologies. These oxide nanocrystals consist of a novel type of oxide model catalyst whose surface chemistry and catalysis can be studied under the same conditions as working oxide catalysts. In this Account, the emerging concept of oxide nanocrystal model catalysts is demonstrated using our investigations of surface chemistry and catalysis of uniform and well-defined cuprous oxide nanocrystals and ceria nanocrystals. Cu2O cubes enclosed with the {100} crystal planes, Cu2O octahedra enclosed with the {111} crystal planes, and Cu2O rhombic dodecahedra enclosed with the {110} crystal planes exhibit distinct morphology-dependent surface reactivities and catalytic properties that can be well correlated with the surface compositions and structures of exposed crystal planes. Among these types of Cu2O nanocrystals, the octahedra are most reactive and catalytically active due to the presence of coordination-unsaturated (1-fold-coordinated) Cu on the exposed {111} crystal planes. The crystal-plane-controlled surface restructuring and catalytic activity of Cu2O nanocrystals were observed in CO oxidation with excess oxygen. In the propylene oxidation reaction with O2, 1-fold-coordinated Cu on Cu2O(111), 3-fold-coordinated O on Cu2O(110), and 2-fold-coordinated O on Cu2O(100) were identified

  3. Chain-growth cycloaddition polymerization via a catalytic alkyne [2 + 2 + 2] cyclotrimerization reaction and its application to one-shot spontaneous block copolymerization. (United States)

    Sugiyama, Yu-ki; Kato, Rei; Sakurada, Tetsuya; Okamoto, Sentaro


    A cobalt-catalyzed alkyne [2 + 2 + 2] cycloaddition reaction has been applied to polymerizations yielding linear polymers via selective cross-cyclotrimerization of yne-diyne monomers, which occurs in a chain-growth manner. Additionally, through control of the alkyne reactivity of the two monomers, this method was efficiently applied to the spontaneous block copolymerization of their mixture. Here we present the proposed mechanism of the catalyst transfer process of this cycloaddition polymerization.

  4. Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation. (United States)

    Herzberger, Jana; Niederer, Kerstin; Pohlit, Hannah; Seiwert, Jan; Worm, Matthias; Wurm, Frederik R; Frey, Holger


    The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

  5. Fuel cell catalyst degradation

    DEFF Research Database (Denmark)

    Arenz, Matthias; Zana, Alessandro


    Fuel cells are an important piece in our quest for a sustainable energy supply. Although there are several different types of fuel cells, the by far most popular is the proton exchange membrane fuel cell (PEMFC). Among its many favorable properties are a short start up time and a high power density...... increasing focus. Activity of the catalyst is important, but stability is essential. In the presented perspective paper, we review recent efforts to investigate fuel cell catalysts ex-situ in electrochemical half-cell measurements. Due to the amount of different studies, this review has no intention to give...

  6. Olefin metathesis catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S.G.; Banks, R.L.


    A process is described for preparing a disproportionation catalyst comprising admixing a catalytically effective amount of a calcined and activated catalyst consisting essentially of at least one metal oxide selected from molybdenum oxide and tungsten oxide and a support containing a major proportion of silica or alumina with a promoting amount of a methylating agent selected from the group consisting of dimethyl sulfate, dimethylsulfoxide, trimethyloxonium tetrafluorborate, methyl iodide, and methyl bromide, and subjecting same to inert atmospheric conditions for the methylating agent to promote the activity of the calcined molybdenum and tungsten oxides for the disproportionation of olefins.

  7. Ziegler-Natta catalysts for the preparation of polypropylene clay nanocomposites from magnesium ethoxide;Catalisadores Ziegler-Natta para preparacao de nanocompositos de polipropileno/argila partindo-se de etoxido de magnesio

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Maria de Fatima V.; Silva, Micheli G. da; Ferreira, Ana Luiza R., E-mail: fmarques@ima.ufrj.b [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Inst. de Macromoleculas Profa. Eloisa Mano; Ramis, Luciana B. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)


    In the present work, the process for the preparation of Ziegler-Natta catalysts based on MgCl{sub 2}/TiCl{sub 4} was evaluated on the synthesis of isotactic polypropylene. The catalysts were produced by the chemical activation process aiming the morphology control, in order to obtain catalyst particles with spherical form. The synthesis of the catalytic support was accomplished from magnesium ethoxide at different preparation conditions. Commercial clays were also added in the preparation of ZN catalysts, which were employed in propylene polymerization. The purpose was to synthesizing polypropylene nanocomposites by in situ polymerization technique. The results indicated that the developed methods of catalyst preparation were effective, since they have shown high activities and they produced PP with high melting temperatures. It was possible to verify by XRD that the catalytic components were inserted in the clays galleries and the polymers obtained by means of those catalysts are possibly exfoliated nanocomposites. (author)

  8. Polymerization of 5-alkyl δ-lactones catalyzed by diphenyl phosphate and their sequential organocatalytic polymerization with monosubstituted epoxides

    KAUST Repository

    Zhao, Junpeng


    Organocatalytic ring-opening polymerization (ROP) reactions of three renewable 5-alkyl δ-lactones, namely δ-hexalactone (HL), δ-nonalactone (NL) and δ-decalactone (DL), using diphenyl phosphate (DPP) were investigated. Room temperature, together with a relatively high monomer concentration (≥3 M), was demonstrated to be suitable for achieving a living ROP behavior, a high conversion of the lactone, a controlled molecular weight and a low dispersity of the polyester. HL, containing a 5-methyl substituent, showed a much higher reactivity (polymerization rate) and a slightly higher equilibrium conversion than the compounds with longer alkyl substituents (NL and DL). The effectiveness of DPP-catalyzed ROP of 5-alkyl δ-lactones facilitated the one-pot performance following the t-BuP4-promoted ROP of monosubstituted epoxides. It has been shown in an earlier study that substituted polyethers acted as "slow initiators" for non-substituted lactones. However, efficient initiations were observed in the present study as substituted lactones were polymerized from the substituted polyethers. Therefore, this reinforces the previously developed "catalyst switch" strategy, making it a more versatile tool for the synthesis of well-defined polyether-polyester block copolymers from a large variety of epoxide and lactone monomers. © The Royal Society of Chemistry 2015.

  9. Lewis pair polymerization by classical and frustrated Lewis pairs: Acid, base and monomer scope and polymerization mechanism

    KAUST Repository

    Zhang, Yuetao


    Classical and frustrated Lewis pairs (LPs) of the strong Lewis acid (LA) Al(C 6F 5) 3 with several Lewis base (LB) classes have been found to exhibit exceptional activity in the Lewis pair polymerization (LPP) of conjugated polar alkenes such as methyl methacrylate (MMA) as well as renewable α-methylene-γ-butyrolactone (MBL) and γ-methyl- α-methylene-γ-butyrolactone (γ-MMBL), leading to high molecular weight polymers, often with narrow molecular weight distributions. This study has investigated a large number of LPs, consisting of 11 LAs as well as 10 achiral and 4 chiral LBs, for LPP of 12 monomers of several different types. Although some more common LAs can also be utilized for LPP, Al(C 6F 5) 3-based LPs are far more active and effective than other LA-based LPs. On the other hand, several classes of LBs, when paired with Al(C 6F 5) 3, can render highly active and effective LPP of MMA and γ-MMBL; such LBs include phosphines (e.g., P tBu 3), chiral chelating diphosphines, N-heterocyclic carbenes (NHCs), and phosphazene superbases (e.g., P 4- tBu). The P 4- tBu/Al(C 6F 5) 3 pair exhibits the highest activity of the LP series, with a remarkably high turn-over frequency of 9.6 × 10 4 h -1 (0.125 mol% catalyst, 100% MMA conversion in 30 s, M n = 2.12 × 10 5 g mol -1, PDI = 1.34). The polymers produced by LPs at RT are typically atactic (P γMMBL with ∼47% mr) or syndio-rich (PMMA with ∼70-75% rr), but highly syndiotactic PMMA with rr ∼91% can be produced by chiral or achiral LPs at -78 °C. Mechanistic studies have identified and structurally characterized zwitterionic phosphonium and imidazolium enolaluminates as the active species of the current LPP system, which are formed by the reaction of the monomer·Al(C 6F 5) 3 adduct with P tBu 3 and NHC bases, respectively. Kinetic studies have revealed that the MMA polymerization by the tBu 3P/ Al(C 6F 5) 3 pair is zero-order in monomer concentration after an initial induction period, and the polymerization

  10. CATALYSTS NHI Thermochemical Systems FY 2009 Year-End Report

    Energy Technology Data Exchange (ETDEWEB)

    Daniel M. Ginosar


    Fiscal Year 2009 work in the Catalysts project focused on advanced catalysts for the decomposition of sulfuric acid, a reaction common to both the Sulfur-Iodine (S-I) cycle and the Hybrid Sulfur cycle. Prior years’ effort in this project has found that although platinum supported on titanium oxide will be an acceptable catalyst for sulfuric acid decomposition in the integrated laboratory scale (ILS) project, the material has short comings, including significant cost and high deactivation rates due to sintering and platinum evaporation. For pilot and larger scale systems, the catalyst stability needs to be improved significantly. In Fiscal Year 2008 it was found that at atmospheric pressure, deactivation rates of a 1 wt% platinum catalyst could be reduced by 300% by adding either 0.3 wt% iridium (Ir) or 0.3 wt% ruthenium (Ru) to the catalyst. In Fiscal Year 2009, work focused on examining the platinum group metal catalysts activity and stability at elevated pressures. In addition, simple and complex metal oxides are known to catalyze the sulfuric acid decomposition reaction. These metal oxides could offer activities comparable to platinum but at significantly reduced cost. Thus a second focus for Fiscal Year 2009 was to explore metal oxide catalysts for the sulfuric acid decomposition reaction. In Fiscal Year 2007 several commercial activated carbons had been identified for the HI decomposition reaction; a reaction specific to the S-I cycle. Those materials should be acceptable for the pilot scale project. The activated carbon catalysts have some disadvantages including low activity at the lower range of reactor operating temperature (350 to 400°C) and a propensity to generate carbon monoxide in the presence of water that could contaminate the hydrogen product, but due to limited funding, this area had low priority in Fiscal Year 2009. Fiscal Year 2009 catalyst work included five tasks: development, and testing of stabilized platinum based H2SO4 catalysts

  11. Sequence-regulated copolymers via tandem catalysis of living radical polymerization and in situ transesterification. (United States)

    Nakatani, Kazuhiro; Ogura, Yusuke; Koda, Yuta; Terashima, Takaya; Sawamoto, Mitsuo


    Sequence regulation of monomers is undoubtedly a challenging issue as an ultimate goal in polymer science. To efficiently produce sequence-controlled copolymers, we herein developed the versatile tandem catalysis, which concurrently and/or sequentially involved ruthenium-catalyzed living radical polymerization and in situ transesterification of methacrylates (monomers: RMA) with metal alkoxides (catalysts) and alcohols (ROH). Typically, gradient copolymers were directly obtained from the synchronization of the two reactions: the instantaneous monomer composition in feed gradually changed via the transesterification of R(1)MA into R(2)MA in the presence of R(2)OH during living polymerization to give R(1)MA/R(2)MA gradient copolymers. The gradient sequence of monomers along a chain was catalytically controlled by the reaction conditions such as temperature, concentration and/or species of catalysts, alcohols, and monomers. The sequence regulation of multimonomer units was also successfully achieved in one-pot by monomer-selective transesterification in concurrent tandem catalysis and iterative tandem catalysis, providing random-gradient copolymers and gradient-block counterparts, respectively. In contrast, sequential tandem catalysis via the variable initiation of either polymerization or in situ transesterification led to random or block copolymers. Due to the versatile adaptability of common and commercially available reagents (monomers, alcohols, catalysts), this tandem catalysis is one of the most efficient, convenient, and powerful tools to design tailor-made sequence-regulated copolymers. © 2012 American Chemical Society

  12. Transition metal catalyzed polymerization of butadiene in supercritical CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Borkowsky, S. [Los Alamos National Lab., NM (United States)]|[Stanford Univ., CA (United States); Tumas, W. [Los Alamos National Lab., NM (United States); Waymouth, R.M. [Stanford Univ., CA (United States)


    A class of Ni(II) catalysts has been shown to stereoselectively catalyze the 1,4-polymerization of butadiene. The authors have been investigating the use of supercritical CO{sub 2} as an environmentally benign replacement solvent for conventional hydrocarbon and halocarbon solvents for a variety of chemical transformations. Above 31 C, CO{sub 2} enters a supercritical phase, where its physical properties are both liquid-like and gas-like. Importantly, the solvent properties such as dielectric constant for supercritical fluids can be varied by changing the pressure of the fluid. In this report, the authors present results of an investigation of the polymerization of 1,3-butadiene using [({pi}-allyl) Ni(CF{sub 3}CO{sub 2})]{sub 2} in supercritical CO{sub 2}. They conducted 1,3-butadiene polymerizations in CO{sub 2} to determine whether or not they could systematically and predictably adjust the regiochemistry/stereochemistry of the polybutadiene product by varying the solution properties at different pressures. They also mention experiments with CO catalysts that are known to give 1,2-syndiotactic polybutadiene, and with a Pd catalyst system that is known to copolymerize olefin with CO to give perfectly alternating copolymers.

  13. Monocomponent disproportionation catalyst

    International Nuclear Information System (INIS)

    Zemtsov, L.M.; Davydov, B.Eh.; Karpacheva, G.P.; Khoroshilova, V.V.; Samedova, T.G.


    Dechlorination of transition metal salts and formation of arene complexes are shown to take place as a result of ultraviolet irradiation of benzene solutions of WCl 6 or MoCl 5 . These compounds catalyse the disproportionation reaction (metathesis) of olefine, polydienes, as well as ring-opening polymerization of cyclopentene

  14. Optimization of fuel cell membrane electrode assemblies for transition metal ion-chelating ordered mesoporous carbon cathode catalysts

    Directory of Open Access Journals (Sweden)

    Johanna K. Dombrovskis


    Full Text Available Transition metal ion-chelating ordered mesoporous carbon (TM-OMC materials were recently shown to be efficient polymer electrolyte membrane fuel cell (PEMFC catalysts. The structure and properties of these catalysts are largely different from conventional catalyst materials, thus rendering membrane electrode assembly (MEA preparation parameters developed for conventional catalysts not useful for applications of TM-OMC catalysts. This necessitates development of a methodology to incorporate TM-OMC catalysts in the MEA. Here, an efficient method for MEA preparation using TM-OMC catalyst materials for PEMFC is developed including effects of catalyst/ionomer loading and catalyst/ionomer-mixing and application procedures. An optimized protocol for MEA preparation using TM-OMC catalysts is described.

  15. Deactivation-resistant catalyst for selective catalyst reduction of NOx

    DEFF Research Database (Denmark)


    The present invention relates to a catalyst for selective catalytic reduction of NOx in alkali metal containing flue gas using ammonia as reductant, the catalyst comprising a surface with catalytically active sites, wherein the surface is at least partly coated with a coating comprising at least...... one metal oxide. In another aspect the present invention relates to the use of said catalyst and to a method of producing said catalyst. In addition, the present invention relates to a method of treating an catalyst for conferring thereon an improved resistance to alkali poisoning....

  16. Romp as a versatile method for the obtention of differentiated polymeric materials

    Directory of Open Access Journals (Sweden)

    Valdemiro P. Carvalho Jr.


    Full Text Available Ring Opening Metathesis Polymerization (ROMP of cyclic olefins is a powerful transition metal-catalyzed reaction for syntheses of polymers and copolymers. The key feature of this reaction is the [2+2]-cycloaddition mechanism, with retention of the olefinic unsaturation in the polymer chain and occurrence of living polymerization. With the development of metal-carbene type catalysts for this process, many addressed polymeric materials have been successfully prepared to be employed in several fields of the science and technology. This review summarizes recent examples of syntheses of polymers with amphiphilic features such as block, graft, brush or star copolymers; as well syntheses of biomaterials, dendronized architectures, photoactive polymers, cross-linked or self-healing materials, and polymers from renewed supplies.

  17. Investigations of the Ligand Electronic Effects on α-Diimine Nickel(II Catalyzed Ethylene Polymerization

    Directory of Open Access Journals (Sweden)

    Lihua Guo


    Full Text Available The synthesis and characterization of a series of dibenzhydryl-based α-diimine Ni(II complexes bearing a range of electron-donating or -withdrawing groups are described. Polymerization with ethylene is investigated in detail, involving the activator effect, influence of polymerization conditions on catalyst activity, thermal stability, polymer molecular weight and melting point. All of these Ni(II complexes show great activity (up to 6 × 106 g of PE (mol of Ni−1·h−1, exceptional thermal stability (stable at up to 100 °C and generate polyethylene with very high molecular weight (Mn up to 1.6 × 106 and very narrow molecular weight distribution. In the dibromo Ni(II system, the electronic perturbations exhibit little variation on the ethylene polymerization. In the Ni(acac system, dramatic ligand electronic effects are observed in terms of catalytic activity and polyethylene molecular weight.

  18. Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst (United States)

    Zelenay, Piotr; Wu, Gang


    A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

  19. The polymerizations of alkylsilane and bis-(γ-triethoxysilylpropyl)-tetrasulfide catalyzed by copper nanoparticles and the effects of transition metal ions on the polymerizations of alkylsilane catalyzed by silver nanoparticles

    International Nuclear Information System (INIS)

    Yan Jiangmei; Zi Guoli; Yang Feng; Mi Yangli; Yang Xikun; Wang Wei; Zou Qinpeng; Wang Jiaqiang


    Poly(vinylpyrrolidone) (PVP)-capped copper nanoparticles synthesized by solvent-based polyol reduction were found to be effective catalysts for the polymerization of octadecylsilane and bis-(γ-triethoxysilylpropyl)-tetrasulfide. Comparing with PVP-capped silver nanoparticles, copper nanoparticles exhibited different catalytic activity, and the polymerization products also showed different morphologies. The effects of transition metal ions on the polymerization of octadecylsilane catalyzed by PVP-capped silver nanoparticles were also investigated. It was found that transition of metal ions not only had strong effects on the morphologies of the products of polymerizations, but also resulted in the disappearance of silver oxide. The products were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD).

  20. Analysis for organic residues from aids to polymerization used to make plastics intended for food contact. (United States)

    Fordham, P J; Gramshaw, J W; Castle, L


    Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (1H-NMR) and GC-MS. NMR detected the presence of cyanoisopropyl radical residues in the plastic at 470-3400 mg/kg whereas GC-MS detected TMSN at only 65-540 mg/kg in the samples. It is concluded that the bulk of cyanoisopropyl residues detected by NMR were either polymer-bound or were the products of side-reactions of the initiator radical. The migration of TMSN itself into the food simulants 3% aqueous acetic acid, 15% aqueous ethanol, and olive oil, at 40 degrees C for 10 days, was measured using GC-MS. Migration was very low with straw) and plastics intended for food contact and their potential for migration to foods is correspondingly low.

  1. Catalysts for biobased fuels. New catalyst formulations for vehicles fuelled by biobased motor fuels

    Energy Technology Data Exchange (ETDEWEB)

    Pettersson, L.J.; Wahlberg, A.M.; Jaeraas, S.G. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Technology


    The long-term objective for the project is to develop tailor-made exhaust gas catalysts for heavy-duty vehicles fuelled by biobased motor fuels operating in urban traffic. In this report an experimental study of catalytic oxidation of ethanol in a laboratory flow reactor is presented. The miniature catalyst samples consisted of monolithic cordierite substrates onto which various combinations of washcoat material and active material were applied. Oxides of Cu and Cu-Mn, as well as different combinations of precious metals were evaluated as active material supported on various washcoat materials. The experimental conditions were chosen in order to simulate the exhaust from a diesel engine fuelled by neat ethanol. Catalyst characterization included measurements of BET surface area and pore size distribution as well as temperature programmed reduction (TPR) analysis. When comparing the TPR profiles with the light-off curves from the ethanol oxidation experiments, we have found an indication of a correlation between activity and reducibility of the catalyst. There also seems to be a correlation between TPR profile and pore size distribution for titania-supported catalysts. When combining two precious metals as active material, a positive synergistic effect has been observed. The light-off temperature (T{sub 50}) is considerably lower for some of these combinations than for the corresponding monometallic catalysts. The base metal oxide catalysts tested were more selective for oxidation of ethanol to carbon dioxide and water than the precious metal catalysts. The results also indicate that the oxidation of nitric oxide to the more hazardous nitrogen dioxide can be suppressed by using a suitable combination of active material and washcoat material 45 refs, 97 figs, 4 tabs

  2. Olefin metathesis and catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S. G.; Banks, R. L.


    Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one methylating agent under conditions suitable for the methylating agent compounds to promote the activity of tungsten and molybdenum oxides for the disproportionation reaction.

  3. Sabatier Catalyst Poisoning Investigation (United States)

    Nallette, Tim; Perry, Jay; Abney, Morgan; Knox, Jim; Goldblatt, Loel


    The Carbon Dioxide Reduction Assembly (CRA) on the International Space Station (ISS) has been operational since 2010. The CRA uses a Sabatier reactor to produce water and methane by reaction of the metabolic CO2 scrubbed from the cabin air and the hydrogen byproduct from the water electrolysis system used for metabolic oxygen generation. Incorporating the CRA into the overall air revitalization system has facilitated life support system loop closure on the ISS reducing resupply logistics and thereby enhancing longer term missions. The CRA utilizes CO2 which has been adsorbed in a 5A molecular sieve within the Carbon Dioxide Removal Assembly, CDRA. There is a potential of compounds with molecular dimensions similar to, or less than CO2 to also be adsorbed. In this fashion trace contaminants may be concentrated within the CDRA and subsequently desorbed with the CO2 to the CRA. Currently, there is no provision to remove contaminants prior to entering the Sabatier catalyst bed. The risk associated with this is potential catalyst degradation due to trace organic contaminants in the CRA carbon dioxide feed acting as catalyst poisons. To better understand this risk, United Technologies Aerospace System (UTAS) has teamed with MSFC to investigate the impact of various trace contaminants on the CRA catalyst performance at relative ISS cabin air concentrations and at about 200/400 times of ISS concentrations, representative of the potential concentrating effect of the CDRA molecular sieve. This paper summarizes our initial assessment results.


    DEFF Research Database (Denmark)


    of alkali metal and/or alkali-earth compounds which process comprises using a catalyst combined of (i) a formed porous superacidic support, said superacidic support having an Hammett acidity stronger than Ho=-12, and (ii) a metal oxide catalytic component deposited on said superacidic support selected from...

  5. Deactivation and Regeneration of Ni/ZA Catalyst in Hydrocracking of Polypropylene

    Directory of Open Access Journals (Sweden)

    Imam Khabib


    Full Text Available The phenomena of catalyst deactivation and the effects of regeneration method on the characteristics and activity of Ni/ZA catalyst after being used in a continuous cracking reaction of polypropylene have been studied. Ni/ZA catalyst was prepared using sonochemical method with total metal intake of 4%. Characteristics and activity of fresh, spent, and regenerated catalyst were evaluated to get a better understanding about the catalyst deactivation. Characteristics which have been observed include catalyst acidity, porosity, crystallinity, and surface morphology. Catalytic activity test of Ni/ZA catalyst on polypropylene cracking reaction at temperature of 500 °C with H2 flow rate of 20 mL/min and catalyst:feed ratio of 1:2 (w/w showed the decrease of some catalyst characteristics such as specific surface area, total pore volume, and acidity due to coke fouling over a five-times continuous experiment. Regeneration of catalyst with oxidation-reduction method has been able to increase the activity and acidity of catalyst up to 7.47% and 38.54%, respectively, compared to those of spent catalyst, while the catalyst surface area and total pore volume decreased up to 32.83% and 26.92%, respectively.

  6. Multiscale simulation of heterophase polymerization : application to the synthesis of multicomponent colloidal polymer particles


    Hernandez Garcia, Hugo Fernando


    Heterophase polymerization is a technique widely used for the synthesis of high performance polymeric materials with applications including paints, inks, adhesives, synthetic rubber, biomedical applications and many others. Due to the heterogeneous nature of the process, many different relevant length and time scales can be identified. Each of these scales has a direct influence on the kinetics of polymerization and on the physicochemical and performance properties of the final product. There...

  7. Noble metal ionic catalysts. (United States)

    Hegde, M S; Madras, Giridhar; Patil, K C


    Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NO(x), and unburned hydrocarbons-need to be fully converted to CO(2), N(2), and H(2)O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al(2)O(3) or SiO(2) promoted by CeO(2). However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce(1-x)M(x)O(2-delta) and Ce(1-x-y)Ti(y)M(x)O(2-delta) (M = Pt, Pd, Rh; x = 0.01-0.02, delta approximately x, y = 0.15-0.25) oxides in fluorite structure. In these oxide catalysts, Pt(2+), Pd(2+), or Rh(3+) ions are substituted only to the extent of 1-2% of Ce(4+) ion. Lower-valent noble metal ion substitution in CeO(2) creates oxygen vacancies. Reducing molecules (CO, H(2), NH(3)) are adsorbed onto electron-deficient noble metal ions, while oxidizing (O(2), NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NO(x) reduction (with >80% N(2) selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO(2) or Ce(1-x)Ti(x)O(2) were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the

  8. Method of making metal-polymer composite catalysts (United States)

    Zelena, Piotr [Los Alamos, NM; Bashyam, Rajesh [Los Alamos, NM


    A metal-polymer-carbon composite catalyst for use as a cathode electrocatalyst in fuel cells. The catalyst includes a heteroatomic polymer; a transition metal linked to the heteroatomic polymer by one of nitrogen, sulfur, and phosphorus, and a recast ionomer dispersed throughout the heteroatomic polymer-carbon composite. The method includes forming a heteroatomic polymer-carbon composite and loading the transition metal onto the composite. The invention also provides a method of making a membrane electrode assembly for a fuel cell that includes the metal-polymer-carbon composite catalyst.

  9. Computational fluid dynamic modeling of fluidized-bed polymerization reactors

    Energy Technology Data Exchange (ETDEWEB)

    Rokkam, Ram [Iowa State Univ., Ames, IA (United States)


    Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.

  10. Synthesis and Characterization of Novel Polymethylene-Based 3-Miktoarm Star Copolymers by Combining Polyhomologation with Other Living Polymerizations

    KAUST Repository

    Altaher, Maryam


    Polyethylene (PE) is produced in a huge scale globally and has plenty of desirable properties. It is used in coating, packaging, and artificial joint replacements. The growing need for high performance polyethylene led to the development of new catalysts, monomers and polymerizations. The synthesis of polymethylene (equivalent to polyethylene) by living polyhomologation opened the way to well-defined polymethylenes-based polymeric materials with controlled structure, molecular weight and narrow polydispersity. Such model polymers are substantial to study the structure-properties relationships. This research presents a new strategy based on the in situ formation of B-thexyl-silaboracyclic serving as initiating sites for the polyhomologation of dimethylsulfoxonium methylide. Combination with metal-free ring-opening polymerization (ROP) of ɛ-caprolactone (CL) and atom transfer radical polymerization (ATRP) of styrene led to three polymethylene-based 3-miktoarm stars copolymers PCL(PM-OH)2, Br-PCL(PM-OH)2 and PS(PM-OH)2.

  11. Sexual selection studies: A NESCent catalyst meeting

    NARCIS (Netherlands)

    Roughgarden, J.; Adkins-Regan, E.; Akcay, E.; Hinde, C.A.; Hoquet, T.; O'Connor, C.; Prokop, Z.M.; Prum, R.O.; Shafir, S.; Snow, S.S.; Taylor, D.; Cleve, Van J.; Weisberg, M.


    A catalyst meeting on sexual selection studies was held in July 2013 at the facilities of the National Evolutionary Synthesis Center (NESCent) in Durham, NC. This article by a subcommittee of the participants foregrounds some of the topics discussed at the meeting. Topics mentioned here include the

  12. Heterogeneously catalyzed coal hydroliquefaction: screening of catalysts and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Legarreta, J.; Arias, P.L.; Marco, I. de; Chomon, M.J.; Caballero, B.; Cambra, J.F.; Guemez, B.; Fierro, J.L.G. (Universidad del Pais Vasco, Bilbao (Spain). Escuel de Ingenieros de Bilbao)


    This project is centred upon the study of the activities of different catalysts in one-step coal liquefaction processes. A series of alumina supported catalysts was prepared by multistep impregnation, including a conventional CoMo/Al[sub 2]O[sub 3] and other preparations containing Zn as a second promoter, and the alumina was acidified with different fluorine contents. These catalysts were extensive physicochemically characterized and their hydrodesulphurization (HDS) and hydrogenation (HYD) activities were tested using a model compound (thiophene). The results obtained indicate that partial substitution of Co by Zn does not affect the HDS and HYD activities and that fluorination diminishes these activities because of textural changes of the carrier. The prepared catalysts were tested in coal liquefaction and their activities were compared to those of cheap iron containing dispersion catalysts such as red mud, Fe[sub 2]O[sub 3] aerosol, and Cottrell and pyrite ashes (by-products of the sulphur acid industry). Prior to the study and comparison of the catalyst activities and exploration of the influence of various operating conditions (temperature, tetralin/coal ratio, type of solvent and operating pressure) on catalytic and non-catalytic coal liquefaction was performed. The coal used in most of the experiments was a Spanish subbituminous A coal. Additionally, a comparison of all the catalysts was carried out with a standard high volatile bituminous coal. Supported catalysts present higher activities than iron-based catalysts. Among these catalysts, red mud proved to be the most active. Catalytic experiments using anthracene oil as solvent and CoZnMo/fluorinated alumina catalysts present maximum yields indicating that Zn as second promoter and carrier acidification to be beneficial in coal liquefaction with solvents similar to those used in real plants. 41 refs., 9 figs., 13 tabs.

  13. Influence of Gold on Ce-Zr-Co Fluorite-Type Mixed Oxide Catalysts for Ethanol Steam Reforming

    Directory of Open Access Journals (Sweden)

    Véronique Pitchon


    Full Text Available The effect of gold presence on carbon monoxide oxidation and ethanol steam reforming catalytic behavior of two Ce-Zr-Co mixed oxides catalysts with a constant Co charge and different Ce/Zr ratios was investigated. The Ce-Zr-Co mixed oxides were obtained by the pseudo sol-gel like method, based on metallic propionates polymerization and thermal decomposition, whereas the gold-supported Ce-Zr-Co mixed oxides catalysts were prepared using the direct anionic exchange. The catalysts were characterized using XRD, TPR, and EDXS-TEM. The presence of Au in doped Ce-Zr-Co oxide catalyst decreases the temperature necessary to reduce the cobalt and the cerium loaded in the catalyst and favors a different reaction pathway, improving the acetaldehyde route by ethanol dehydrogenation, instead of the ethylene route by ethanol dehydration or methane re-adsorption, thus increasing the catalytic activity and selectivity into hydrogen.

  14. Studies in reactive extrusion processing of biodegradable polymeric materials (United States)

    Balakrishnan, Sunder

    Various reaction chemistries such as Polymerization, Polymer cross-linking and Reactive grafting were investigated in twin-screw extruders. Poly (1,4-dioxan-2-one) (PPDX) was manufactured in melt by the continuous polymerization of 1,4-dioxan-2-one (PDX) monomer in a twin-screw extruder using Aluminum tri-sec butoxide (ATSB) initiator. Good and accurate control over molecular weight was obtained by controlling the ratio of monomer to initiator. A screw configuration consisting of only conveying elements was used for the polymerization. The polymerization reaction was characterized by a monomer-polymer dynamic equilibrium, above the melting temperature of the polymer, limiting the equilibrium conversion to 78-percent. Near complete (˜100-percent) conversion was obtained on co-polymerizing PDX monomer with a few mol-percent (around 8-percent) Caprolactone (CL) monomer in a twin-screw extruder using ATSB initiator. The co-polymers exhibited improved thermal stability with reduction in glass transition temperature. The extruder was modeled as an Axial Dispersed Plug Flow Reactor for the polymerization of CL monomer using Residence Time Distribution (RTD) Analysis. The model provided a good fit to the experimental RTD and conversion data. Aliphatic and aliphatic-aromatic co-polyesters, namely Polycaprolactone (PCL) and Poly butylenes (adipate-co-terephthalate) (Ecoflex) were cross-linked in a twin-screw extruder using radical initiator to form micro-gel reinforced biodegradable polyesters. Cross-linked Ecoflex was further extrusion blended with talc to form blends suitable to be blown into films. A screw configuration consisting of conveying and kneading elements was found to be effective in dispersion of the talc particles (5--10 microns) in the polyester matrix. While the rates of crystallization increased for the talc filled polyester blends, overall crystallinity reduced. Mechanical, tear and puncture properties of films made using the talc filled polyester blends

  15. Hoveyda-Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves-The influence of pore size on the catalyst activity

    Czech Academy of Sciences Publication Activity Database

    Shinde, Tushar; Žilková, Naděžda; Hanková, V.; Balcar, Hynek


    Roč. 179, č. 1 (2012), s. 123-129 ISSN 0920-5861 R&D Projects: GA AV ČR IAA400400805; GA AV ČR KAN100400701; GA ČR GD203/08/H032 Institutional research plan: CEZ:AV0Z40400503 Keywords : olefin metathesis * ring opening metathesis polymerization * Hoveyda-Grubbs catalyst Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.980, year: 2012

  16. Preferential polymerization and adsorption of L-optical isomers of amino acids relative to D-optical isomers on kaolinite templates. (United States)

    Jackson, T. A.


    Experiments on the polymerization of the L- and D-optical isomers of aspartic acid and serine using kaolinite as a catalyst showed that the L-optical isomers were polymerized at a much higher rate than the D-optical isomers; racemic (DL-) mixtures were polymerized at an intermediate rate. The peptides formed from the L-monomers were preferentially adsorbed by the clay. In the absence of kaolinite, no significant or consistent difference in the behavior of the L- and D-optical isomers was observed. In experiments on the adsorption of L- and D-phenylalanine by kaolinite, the L-optical isomer was preferentially adsorbed.

  17. On-demand photoinitiated polymerization (United States)

    Boydston, Andrew J; Grubbs, Robert H; Daeffler, Chris; Momcilovic, Nebojsa


    Compositions and methods for adjustable lenses are provided. In some embodiments, the lenses contain a lens matrix material, a masking compound, and a prepolymer. The lens matrix material provides structure to the lens. The masking compound is capable of blocking polymerization or crosslinking of the prepolymer, until photoisomerization of the compound is triggered, and the compound is converted from a first isomer to a second isomer having a different absorption profile. The prepolymer is a composition that can undergo a polymerization or crosslinking reaction upon photoinitiation to alter one or more of the properties of the lenses.

  18. New Trends in Gold Catalysts

    Directory of Open Access Journals (Sweden)

    Leonarda F. Liotta


    Full Text Available Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as ~200 K when in a nanocrystalline state, as discovered by Haruta in the late 1980s [1]. Since then, extensive activity in both applied and fundamental research on gold has been initiated. The importance of the catalysis by gold represents one of the fasted growing fields in science and is proven by the promising applications in several fields, such as green chemistry and environmental catalysis, in the synthesis of single-walled carbon nanotubes, as modifiers of Ni catalysts for methane steam and dry reforming reactions and in biological and electrochemistry applications. The range of reactions catalyzed by gold, as well as the suitability of different supports and the influence of the preparation conditions have been widely explored and optimized in applied research [2]. Gold catalysts appeared to be very different from the other noble metal-based catalysts, due to their marked dependence on the preparation method, which is crucial for the genesis of the catalytic activity. Several methods, including deposition-precipitation, chemical vapor deposition and cation adsorption, have been applied for the preparation of gold catalysts over reducible oxides, like TiO2. Among these methods, deposition-precipitation has been the most frequently employed method for Au loading, and it involves the use of tetrachloroauric (III acid as a precursor. On the other hand, the number of articles dealing with Au-loaded acidic supports is smaller than that on basic supports, possibly because the deposition of [AuCl4]− or [AuOHxCl4−x]− species on acidic supports is difficult, due to their very low point of zero charge. Despite this challenge, several groups have reported the use of acidic zeolites as supports for gold. Zeolites

  19. Ruthenium Olefin Metathesis Catalysts Bearing an N-Fluorophenyl-N-Mesityl-Substituted Unsymmetrical N-Heterocyclic Carbene


    Vougioukalakis, Georgios C.; Grubbs, Robert H.


    Two new ruthenium-based olefin metathesis catalysts, each bearing an unsymmetrical N-heterocyclic carbene ligand, have been synthesized and fully characterized. Their catalytic performance has been evaluated in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization reactions.

  20. Polymeric AIE-based nanoprobes for biomedical applications: recent advances and perspectives (United States)

    Zhang, Xiaoyong; Wang, Ke; Liu, Meiying; Zhang, Xiqi; Tao, Lei; Chen, Yiwang; Wei, Yen


    The development of polymeric luminescent nanomaterials for biomedical applications has recently attracted a large amount of attention due to the remarkable advantages of these materials compared with small organic dyes and fluorescent inorganic nanomaterials. Among these polymeric luminescent nanomaterials, polymeric luminescent nanomaterials based on dyes with aggregation-induced emission (AIE) properties should be of great research interest due to their unique AIE properties, the designability of polymers and their multifunctional potential. In this review, the recent advances in the design and biomedical applications of polymeric luminescent nanomaterials based on AIE dyes is summarized. Various design strategies for incorporation of these AIE dyes into polymeric systems are included. The potential biomedical applications such as biological imaging, and use in biological sensors and theranostic systems of these polymeric AIE-based nanomaterials have also been highlighted. We trust this review will attract significant interest from scientists from different research fields in chemistry, materials, biology and interdisciplinary areas.

  1. Characteristics of Polyaniline Cobalt Supported Catalysts for Epoxidation Reactions (United States)

    Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Mirosław


    A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II) : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established. PMID:24701183

  2. Apparatus and Process for Controlled Nanomanufacturing Using Catalyst Retaining Structures (United States)

    Nguyen, Cattien (Inventor)


    An apparatus and method for the controlled fabrication of nanostructures using catalyst retaining structures is disclosed. The apparatus includes one or more modified force microscopes having a nanotube attached to the tip portion of the microscopes. An electric current is passed from the nanotube to a catalyst layer of a substrate, thereby causing a localized chemical reaction to occur in a resist layer adjacent the catalyst layer. The region of the resist layer where the chemical reaction occurred is etched, thereby exposing a catalyst particle or particles in the catalyst layer surrounded by a wall of unetched resist material. Subsequent chemical vapor deposition causes growth of a nanostructure to occur upward through the wall of unetched resist material having controlled characteristics of height and diameter and, for parallel systems, number density.

  3. Characteristics of Polyaniline Cobalt Supported Catalysts for Epoxidation Reactions

    Directory of Open Access Journals (Sweden)

    Grzegorz Kowalski


    Full Text Available A study of polyaniline (PANI doping with various cobalt compounds, that is, cobalt(II chloride, cobalt(II acetate, and cobalt(II salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established.

  4. The effect of the central donor in bis(benzimidazole)-based cobalt catalysts for the selective cis-1,4-polymerisation of butadiene. (United States)

    Cariou, Renan; Chirinos, Juan J; Gibson, Vernon C; Jacobsen, Grant; Tomov, Atanas K; Britovsek, George J P; White, Andrew J P


    A series of bis(benzimidazole)-based cobalt(II) dichloride complexes containing a range of different central donors has been synthesized and characterized. The nature of the central donor affects the binding of the ligand to the cobalt centre and determines the coordination geometry of the metal complexes. All complexes have been shown to catalyse the polymerization of butadiene, in combination with MAO as the co-catalyst, to give cis-1,4-polybutadiene with high selectivity. The nature of the central donor has a marked influence on the polymerization activity of the catalysts, but does not affect the polymer microstructure. The addition of PPh(3) generally increases the polymerization activity of these cobalt catalysts and results in predominantly (60-70%) 1,2-vinyl-polybutadiene.

  5. Scalable synthesis of palladium nanoparticle catalysts by atomic layer deposition

    International Nuclear Information System (INIS)

    Liang Xinhua; Lyon, Lauren B.; Jiang Yingbing; Weimer, Alan W.


    Atomic layer deposition (ALD) was used to produce Pd/Al 2 O 3 catalysts using sequential exposures of Pd(II) hexafluoroacetylacetonate and formalin at 200 °C in a fluidized bed reactor. The ALD-prepared Pd/alumina catalysts were characterized by various methods including hydrogen chemisorption, XPS, and TEM, and compared with a commercially available 1 wt% Pd/alumina catalyst, which was also characterized. The content of Pd on alumina support and the size of Pd nanoparticles can be controlled by the number of ALD-coating cycles and the dose time of the Pd precursor. One layer of organic component from the Pd precursor remained on the Pd particle surface. The ALD 0.9 wt% Pd/alumina had greater active metal surface area and percent metal dispersion than the commercial 1 wt% Pd/alumina catalyst. The ALD and commercial catalysts were subjected to catalytic testing to determine their relative activities for glucose oxidation to gluconic acid in aqueous solution. The ALD 0.9 wt% Pd/alumina catalyst had comparable activity as compared to the commercial 1 wt% Pd catalyst. No noticeable amount of Pd leaching was observed for the ALD-prepared catalysts during the vigorously stirred reaction.

  6. Genotoxic evaluation of polymeric nanoparticles

    Directory of Open Access Journals (Sweden)

    Tamara Iglesias Alonso


    Full Text Available An important strategy for optimizing the therapeutic efficacy of many conventional drugs is the development of polymeric nanoparticles (NPs, as it may expand their activities, reduce their toxicity, increase their bioactivity and improve biodistribution. The main objective of this study was to evaluate the genotoxicity of 8 different poly (anhydride NPs designed for the oral administration of therapeutic compounds by using the comet assay in combination with the enzyme formamidopypiridine DNA-glycosylase (FPG. Furthermore, the mitogen capacity of the NPs was evaluated by the proliferation assay. All NPs were tested at four concentrations (0, 0.5, 1 and 2 mg/mL in Caco-2 cells after 3 hours of treatment while selected NPs were also tested after 24 h. The comet assay was performed immediately after the treatment and cell proliferation was assessed by counting the treated cells after their incubation at 37 °C for 48h. Cells treated with 1 µM of the photosensitizer Ro 19-8022 plus 5 min of light, as well as cells treated with 100 µM H2O2 were included as positive controls in all the experiments. All NPs studied did not result in any increase in the frequency of strand breaks or alkali-labile sites in Caco-2 cells but they induced a slight concentration-dependent increase in net FPG sensitive sites (oxidized and/or alkylated bases. Furthermore, treated cells did not show changes in levels of proliferation in comparison with the negative control.

  7. A simple synthesis method of sulfur-free Fe-N-C catalyst witih high ORR activity

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Zhongfen [Los Alamos National Laboratory; Johnston, Christina M [Los Alamos National Laboratory; Zelenay, Piotr [Los Alamos National Laboratory


    To try to deconvolute which factors affect the activity and durability of metal-nitrogen-carbon (M-N-C) type non-precious catalysts for oxygen reduction reaction (ORR), M-N-C catalysts based on ion chloride, polyaniline (PANI) and Ketjen Black carbon support were synthesized using different synthetic conditions. The catalysts were characterized electrochemically and tested as cathodes for Hydrogen fuel cells. PANI is usually chemically oxidative polymerized using ammonium persulfate (APS) as oxidant. To eliminate sulfur in the synthesized catalysts, a simple synthesis method using ion chloride as oxidant for aniline polymerization was developed. Two different aniline polymerization conditions led to very different product morphologies. Synthesized at low initial proton concentration, the final product was composed of dense micrometer sized particles. A decomposable salt was found to be able to prohibit PANI cross linking during the drying and annealing process and thus led to porous product. The porous catalyst has much higher ORR activity than the dense product due to more accessible active sites. Synthesized at high proton concentration, the catalyst appeared to be porous. The decomposable salt treatment did not make too much improvement in the porous structure and electrochemical activity. However, fuel cell testing using air as cathode feeder indicates that the salt treatment improves mass transfer in the cathode layer. Catalyst synthesized using this simple method has performance comparable to our state-of-the art catalyst synthesized in a much more complicated procedure. The factor that sulfur sources are completely eliminated in the synthesis suggests that sulfur is not necessary for the ORR catalysis activity.

  8. synthesis of microporous polymers by frontal polymerization

    Indian Academy of Sciences (India)


    EGDM) copolymers of varying compositions were synthesized by free-radically triggered thermal frontal polymerization (FP) as well as by suspension polymerization (SP) using azobisisobutyronitrile [AIBN] as initiator. The two sets of copolymers.

  9. New catalysts for clean environment

    Energy Technology Data Exchange (ETDEWEB)

    Maijanen, A.; Hase, A. [eds.] [VTT Chemical Technology, Espoo (Finland)


    VTT launched a Research Programme on Chemical Reaction Mechanisms (CREAM) in 1993. The three-year programme (1993-1995) has focused on reaction mechanisms relevant to process industries and aimed at developing novel catalysts and biocatalysts for forest, food, and specialty chemicals industries as well as for energy production. The preliminary results of this programme have already been presented in the first symposium organized in Espoo in September 1994. To conclude the programme the second symposium is organized in Otaniemi, Espoo on January 29 - 30, 1996. Papers by 19 speakers and 17 poster presentations of the 1996 Symposium are included in this book. The Symposium consists of four sessions: Biotechnology for Natural Fibers Processing, New Biocatalysts, Catalysts for Clean Energy, and New Opportunities for Chemical Industry. The CREAM programme has tried to foresee solutions for the problems challenged by the public concern on environmental aspects, especially dealing with industrial processes and novel use of raw materials and energy. The programme has followed the basic routes that can lead to natural and simple solutions to develop processes in the fields of forest, food fine chemicals, and energy industry. This symposium presents the results of the programme to learn and further discuss together with the international experts that have been invited as keynote speakers. (author)

  10. Electrocatalytic Activity and Stability of M-Fe Catalysts Synthesized by Polymer Complex Method for PEFC Cathode

    KAUST Repository

    Ou, Yiwei


    The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

  11. Synthesis of a molecularly defined single-active site heterogeneous catalyst for selective oxidation of N-heterocycles. (United States)

    Zhang, Yujing; Pang, Shaofeng; Wei, Zhihong; Jiao, Haijun; Dai, Xingchao; Wang, Hongli; Shi, Feng


    Generally, a homogeneous catalyst exhibits good activity and defined active sites but it is difficult to recycle. Meanwhile, a heterogeneous catalyst can easily be reused but its active site is difficult to reveal. It is interesting to bridge the gap between homogeneous and heterogeneous catalysis via controllable construction of a heterogeneous catalyst containing defined active sites. Here, we report that a molecularly defined, single-active site heterogeneous catalyst has been designed and prepared via the oxidative polymerization of maleimide derivatives. These polymaleimide derivatives can be active catalysts for the selective oxidation of heterocyclic compounds to quinoline and indole via the recycling of -C=O and -C-OH groups, which was confirmed by tracing the reaction with GC-MS using maleimide as the catalyst and by FT-IR analysis with polymaleimide as the catalyst. These results might promote the development of heterogeneous catalysts with molecularly defined single active sites exhibiting a comparable activity to homogeneous catalysts.

  12. Fluoropolymer materials and architectures prepared by controlled radical polymerizations

    DEFF Research Database (Denmark)

    Hansen, Natanya Majbritt Louie; Jankova Atanasova, Katja; Hvilsted, Søren


    This review initially summarizes the mechanisms, merits and limitations of the three controlled radical polymerizations: nitroxide mediated polymerization (NMP), atom transfer radical polymerization (ATRP) or metal catalyzed living radical polymerization, and reversible addition–fragmentation chain...

  13. Reactivity of Aryl Halides for Reductive Dehalogenation in (Seawater Using Polymer-Supported Terpyridine Palladium Catalyst

    Directory of Open Access Journals (Sweden)

    Toshimasa Suzuka


    Full Text Available A polymer-supported terpyridine palladium complex was prepared. The complex was found to promote hydrodechlorination of aryl chlorides with potassium formate in seawater. Generally, reductive cleavage of aryl chlorides using transition metal catalysts is more difficult than that of aryl bromides and iodides (reactivity: I > Br > Cl; however, the results obtained did not follow the general trend. Therefore, we investigated the reaction inhibition agents and found a method to remove these inhibitors. The polymeric catalysts showed high catalytic activity and high reusability for transfer reduction in seawater.

  14. A Ruthenium Catalyst for Olefin Metathesis Featuring an Anti-Bredt N-Heterocyclic Carbene Ligand. (United States)

    Martin, David; Marx, Vanessa M; Grubbs, Robert H; Bertrand, Guy


    A ruthenium complex bearing an "anti-Bredt" N-heterocyclic carbene was synthesized, characterized and evaluated as a catalyst for olefin metathesis. Good conversions were observed at room temperature for the formation of di- and tri-substituted olefins by ring-closing metathesis. It also allowed for the ring-opening metathesis polymerization of cyclooctadiene, as well as for the cross-metathesis of cis -1,4-diacetoxy-2-butene with allyl-benzene, with enhanced Z / E kinetic selectivity over classical NHC-based catalysts.

  15. Ruthenium Olefin Metathesis Catalysts Bearing Carbohydrate-Based N-Heterocyclic Carbenes (United States)

    Keitz, Benjamin K.; Grubbs, Robert H.


    Ru-based olefin metathesis catalysts containing carbohydrate-derived NHCs from glucose and galactose were synthesized and characterized by NMR spectroscopy. 2D-NMR spectroscopy revealed the presence of Ru-C (benzylidene) rotamers at RT and the rate of rotation was measured using magnetization transfer and VT-NMR spectroscopy. The catalysts were found to be effective at ring-opening metathesis polymerization (ROMP), ring closing metathesis (RCM), cross metathesis (CM), and asymmetric ring opening cross metathesis (AROCM) and showed surprising selectivity in both CM and AROCM. PMID:21603126

  16. Mesoporous molecular sieve catalysts

    DEFF Research Database (Denmark)

    Højholt, Karen Thrane

    This thesis deals with a very specific class of molecular sieves known as zeolites. Zeolites are a class of crystalline aluminosilicates characterised by pores or cavities of molecular dimensions as part of their crystal structure. In this work zeolites were modified for the use and understanding...... of different catalytic applications. Primarily the zeolites were modified regarding the porosity and the introduction of metals to the framework. The obtained materials were used as solid acid catalysts, as an inert matrix for stabilising metal nanoparticles and as an anchoring material for molecular metal....... Furthermore, preliminary work was done using mesoporous ZSM-5 zeolites as support material for anchoring molecular CoMo6 species for the application as potential bi-functional catalyst in simultaneous hydrodesulfurisation (HDS) and hydrocracking. HDS activity tests revealed that the anchoring improved...

  17. Photo catalyst; Ko shokubai

    Energy Technology Data Exchange (ETDEWEB)



    While titanium oxide is excited by the light, electrons of titanium oxide are taken away by the light energy to form positive holes. Water will be decomposed into hydrogen ion and hydroxy radical (OH) by these positive holes. This hydroxy radical is a strong reactive substance called active oxygen, it decomposes organisms. Besides this photo- catalyst function, the titanium oxide can also make surface of a substance superhydrophilic. The super hydrophilicity results in not forming water drops on the glass surface but spreading all over the surface to prevent a covering of fog on the glass surface. The published patents concerning the photo catalysts were 593 from Jan. 1998 to Jan. 1999. The applicant order is the first TOTO 143, the second Daikin Industry 19, the third Toshiba Raitech, Nitto Denko, Hitachi 17 respectively. (NEDO)

  18. High-Activity Dealloyed Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kongkanand, Anusorn [General Motors LLC, Pontiac, MI (United States)


    Reduction of costly Pt usage in proton exchange membrane fuel cell electrodes is one of the major challenges towards development and commercialization of fuel cell vehicles. Although few have met the initial-kinetic activity requirements in a realistic fuel cell device, no catalyst material has ever met the demanding fuel cell durability targets set by DOE. In this project, a team of 4 universities and 2 companies came together to investigate a concept that appeared promising in preliminary non-fuel cell tests then to further develop the catalyst to a mature level ready for vehicle implementation. The team consists of academia with technical leadership in their respective areas, a catalyst supplier, and a fuel cell system integrator.The tightly collaborative project enabled development of a highly active and durable catalyst with performance that significantly exceeds that of previous catalysts and meets the DOE targets for the first time (Figure 1A). The catalyst was then further evaluated in full-active-area stack in a realistic vehicle operating condition (Figure 1B). This is the first public demonstration that one can realize the performance benefit and Pt cost reduction over a conventional pure Pt catalyst in a long-term realistic PEMFC system. Furthermore, systematic analyses of a range of catalysts with different performance after fuel cell testing allowed for correlation between catalyst microstructure and its electrocatalytic activity and durability. This will in turn aid future catalyst development.

  19. Capillary thinning of polymeric filaments

    DEFF Research Database (Denmark)

    Kolte, Mette Irene; Szabo, Peter; Hassager, Ole


    The capillary thinning of a polymeric filament is analysed experimentally as well as by means of numerical simulation. The experimental procedure is as follows. Initially a liquid sample is kept between two cylindrical plates. Then the bottom plate is lowered under gravity to yield a given strain...

  20. Actin Polymerization and ATP Hydrolysis (United States)

    Korn, Edward D.; Carlier, Marie-France; Pantaloni, Dominique


    F-actin is the major component of muscle thin filaments and, more generally, of the microfilaments of the dynamic, multifunctional cytoskeletal systems of nonmuscle eukaryotic cells. Polymeric F-actin is formed by reversible noncovalent self-association of monomeric G-actin. To understand the dynamics of microfilament systems in cells, the dynamics of polymerization of pure actin must be understood. The following model has emerged from recent work. During the polymerization process, adenosine 5'-triphosphate (ATP) that is bound to G-actin is hydrolyzed to adenosine 5'-diphosphate (ADP) that is bound to F-actin. The hydrolysis reaction occurs on the F-actin subsequent to the polymerization reaction in two steps: cleavage of ATP followed by the slower release of inorganic phosphate (Pi). As a result, at high rates of filament growth a transient cap of ATP-actin subunits exists at the ends of elongating filaments, and at steady state a stabilizing cap of ADP \\cdot Pi-actin subunits exists at the barbed ends of filaments. Cleavage of ATP results in a highly stable filament with bound ADP \\cdot Pi, and release of Pi destabilizes the filament. Thus these two steps of the hydrolytic reaction provide potential mechanisms for regulating the monomer-polymer transition.

  1. Biodegradable polymeric prodrugs of naltrexone

    NARCIS (Netherlands)

    Bennet, D.B.; Li, X.; Adams, N.W.; Kim, S.W.; Hoes, C.J.T.; Hoes, C.J.T.; Feijen, Jan


    The development of a biodegradable polymeric drug delivery system for the narcotic antagonist naltrexone may improve patient compliance in the treatment of opiate addiction. Random copolymers consisting of the ¿-amino acids N5-(3-hydroxypropyl--glutamine and -leucine were synthesized with equimolar

  2. Deactivation of Oxidation Catalysts (United States)


    been observed to decrease CO oxidation even at 500TC ( Farrauto and Wedding, 1973, p. 254) by a sulfate formation mechanism, it is likely that the...sulfated CoO, in the study of Farrauto and Wedding (1973) and that no deactivation was observed in the previously discussed study by Pope et al...This is attributed to the adsorption of HO on the catalyst surface which competes with the adsorption of ethanol. Farrauto and Wedding (1973) studied

  3. Olefin metathesis and catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Kukes, S. G.; Banks, R. L.


    Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory material containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one treating agent selected from chlorinated silicon compounds, thionyl chloride, and sulfuryl chloride under conditions suitable for the treating agent to promote the activity of tungsten and molybdenum oxides for the disporoportionation reaction.

  4. Catalyst in Basic Oleochemicals


    Eva Suyenty; Herlina Sentosa; Mariani Agustine; Sandy Anwar; Abun Lie; Erwin Sutanto


    Currently Indonesia is the world largest palm oil producer with production volume reaching 16 million tones per annum. The high crude oil and ethylene prices in the last 3 – 4 years contribute to the healthy demand growth for basic oleochemicals: fatty acids and fatty alcohols. Oleochemicals are starting to replace crude oil derived products in various applications. As widely practiced in petrochemical industry, catalyst plays a very important role in the production of basic oleochemic...

  5. Acetone production using silicon nanoparticles and catalyst compositions

    KAUST Repository

    Chaieb, Sahraoui


    Embodiments of the present disclosure provide for a catalytic reaction to produce acetone, a catalyst that include a mixture of silicon particles (e.g., about 1 to 20 nm in diameter) and a solvent, and the like.

  6. Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

    Directory of Open Access Journals (Sweden)

    N. Barhoumi


    Full Text Available A reactive rotational molding (RRM process was developed to obtain a PA6 by activated anionic ring-opening polymerization of epsilon-caprolactam (APA6. Sodium caprolactamate (C10 and caprolactam magnesium bromide (C1 were employed as catalysts, and difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20 was used as an activator. The kinetics of the anionic polymerization of !-caprolactam into polyamide 6 was monitored through dynamic rheology and differential scanning calorimetry measurements. The effect of the processing parameters, such as the polymerization temperature, different catalyst/activator combinations and concentrations, on the kinetics of polymerization is discussed. A temperature of 150°C was demonstrated to be the most appropriate. It was also found that crystallization may occur during PA6 polymerization and that the combination C1/C20 was well suited as it permitted a suitable induction time. Isoviscosity curves were drawn in order to determine the available processing window for RRM. The properties of the obtained APA6 were compared with those of a conventionally rotomolded PA6. Results pointed at lower cycle times and increased tensile properties at weak deformation.

  7. Development of Polymeric Coatings for Antifouling Applications (United States)

    Toumayan, Edward Philip

    Fouling, or the deposition of unwanted material onto a surface, is a serious problem that can impair the function of submerged structures, such as marine-going vessels and underwater equipment. Water filtration membranes are particularly susceptible to fouling due to their microstructure and high water pressure operating conditions. For this reason, there has been considerable interest in developing fouling-resistant, or "antifouling" coatings for membranes, specifically coatings that mitigate fouling propensity while maintain high water flux. Polymer coatings have garnered significant interest in antifouling literature, due to their synthetic versatility and variety, and their promising resistance to a wide range of foulants. However, antifouling research has yet to establish a consistent framework for polymer coating synthesis and fouling evaluation, making it difficult or impossible to compare previously established methodologies. To this end, this work establishes a standardized methodology for synthesizing and evaluating polymer antifouling coatings. Specifically, antifouling coatings are synthesized using a grafting-from polymerization and fouling propensity is evaluated by quartz crystal microbalance with dissipation (QCM-D). Using this framework, a number of different surface functionalization strategies are compared, including grafting-to and grafting-from polymerization. A number of different surface functionalization strategies, including grafting-to and grafting-from, were investigated and the fouling performance of these films was evaluated. Primarily, sulfobetaine methacrylate, and poly(ethylene oxide) methacrylate monomers were investigated, among others. Grafting-to, while advantageous from a characterization standpoint, was ultimately limited to low grafting densities, which did not afford a significant improvement in fouling resistance. However, the higher grafting densities achievable by grafting-from did indicate improved fouling resistance. A

  8. Preparations of spherical polymeric particles from Tanzanian ...

    African Journals Online (AJOL)

    Spherical Polymeric Particles (SPP) have been prepared from Tanzanian Cashew Nut Shell Liquid (CNSL) by suspension polymerization technique involving either step-growth or chain- growth polymerization mechanisms. The sizes of the SPP, which ranged from 0.1 to 2.0 mm were strongly influenced by the amounts of ...

  9. Catalyst component interactions in nickel/alumina catalyst


    Kiš Erne E.; Lazić Matilda M.; Bošković Goran C.


    The influence of nickel loading (5; 10; 20 wt% Ni), temperature of heat treatment (400; 700; 1100°C) and way of catalyst preparation on the catalyst component interactions (CCI) in the impregnated, mechanical powder mixed and co-precipitated catalyst was investigated. For sample characterization, low temperature nitrogen adsorption (LTNA) and X-ray diffraction (XRD) were applied. Significant differences were revealed, concerning CCI in dependence of nickel loading, temperature of heat treatme...

  10. Tacticities study of high poly-α-olefins, from poly-1-hexene to poly-1-octadecene, obtained with metallocenes catalysts

    International Nuclear Information System (INIS)

    Silva, Luciano F. da; Galland, Griselda B.


    High poly-α-olefins such as poly-1-hexene, poly-1-octene, poly-1-decene, poly-1-dodecene, poly-1-tetradecene, poly-1-hexadecene and poly-1-octadecene were obtained with the homogeneous iso specific catalyst rac-Et[Ind]ZrCl 2 /MAO and with the homogeneous syndiospecific catalyst Me 2 C[Cp(9-Flu)]ZrCl 2 /MAO at the polymerization temperatures of 0 deg C, 30 deg C and 60 deg C. The polymers were analyzed by 13 C NMR to study the influence of the α - olefins sizes, the catalysts type and the polymerization temperatures in their tacticities. The stereospecific control of both catalytic systems decreased with the increase of the reaction temperature and with the α-olefin size. (author)

  11. Glycine Polymerization on Oxide Minerals (United States)

    Kitadai, Norio; Oonishi, Hiroyuki; Umemoto, Koichiro; Usui, Tomohiro; Fukushi, Keisuke; Nakashima, Satoru


    It has long been suggested that mineral surfaces played an important role in peptide bond formation on the primitive Earth. However, it remains unclear which mineral species was key to the prebiotic processes. This is because great discrepancies exist among the reported catalytic efficiencies of minerals for amino acid polymerizations, owing to mutually different experimental conditions. This study examined polymerization of glycine (Gly) on nine oxide minerals (amorphous silica, quartz, α-alumina and γ-alumina, anatase, rutile, hematite, magnetite, and forsterite) using identical preparation, heating, and analytical procedures. Results showed that a rutile surface is the most effective site for Gly polymerization in terms of both amounts and lengths of Gly polymers synthesized. The catalytic efficiency decreased as rutile > anatase > γ-alumina > forsterite > α- alumina > magnetite > hematite > quartz > amorphous silica. Based on reported molecular-level information for adsorption of Gly on these minerals, polymerization activation was inferred to have arisen from deprotonation of the NH3 + group of adsorbed Gly to the nucleophilic NH2 group, and from withdrawal of electron density from the carboxyl carbon to the surface metal ions. The orientation of adsorbed Gly on minerals is also a factor influencing the Gly reactivity. The examination of Gly-mineral interactions under identical experimental conditions has enabled the direct comparison of various minerals' catalytic efficiencies and has made discussion of polymerization mechanisms and their relative influences possible Further systematic investigations using the approach reported herein (which are expected to be fruitful) combined with future microscopic surface analyses will elucidate the role of minerals in the process of abiotic peptide bond formation.

  12. Improving the Energy Efficiency of Direct Formate Fuel Cells with a Pd/C-CeO2 Anode Catalyst and Anion Exchange Ionomer in the Catalyst Layer

    Directory of Open Access Journals (Sweden)

    Hamish Andrew Miller


    Full Text Available This article describes the development of a high power density Direct Formate Fuel Cell (DFFC fed with potassium formate (KCOOH. The membrane electrode assembly (MEA contains no platinum metal. The cathode catalyst is FeCo/C combined with a commercial anion exchange membrane (AEM. To enhance the power output and energy efficiency we have employed a nanostructured Pd/C-CeO2 anode catalyst. The activity for the formate oxidation reaction (FOR is enhanced when compared to a Pd/C catalyst with the same Pd loading. Fuel cell tests at 60 °C show a peak power density of almost 250 mW cm−2. The discharge energy (14 kJ, faradic efficiency (89% and energy efficiency (46% were determined for a single fuel charge (30 mL of 4 M KCOOH and 4 M KOH. Energy analysis demonstrates that removal of the expensive KOH electrolyte is essential for the future development of these devices. To compensate we apply for the first time a polymeric ionomer in the catalyst layer of the anode electrode. A homopolymer is synthesized by the radical polymerization of vinyl benzene chloride followed by amination with 1,4-diazabicyclo[2.2.2]octane (DABCO. The energy delivered, energy efficiency and fuel consumption efficiency of DFFCs fed with 4 M KCOOH are doubled with the use of the ionomer.

  13. Emulsion Polymerization of Tung Oil-Based Latexes with Asolectin as a Biorenewable Surfactant

    Directory of Open Access Journals (Sweden)

    Ashley Johns


    Full Text Available Bio-based vesicles, with potential application in drug delivery and/or catalyst encapsulation, have been prepared by the free radical emulsion co-polymerization of tung oil, divinylbenzene (DVB, n-butyl methacrylate (BMA, and asolectin in a xylene/water mixture. The free radical polymerization was initiated by di-tert-butyl peroxide (DTBP at 100 °C in a convection oven. Molecular weights of approximately 11,000 Da were measured by Matrix-assisted Laser Desorption/Ionization-Time of Flight (Maldi-TOF for tung oil-asolectin copolymers, verifying that significant polymerization occurs under the cure conditions employed. The cure of the co-monomer mixture employed in this work was monitored by Dielectric Analysis (DEA, while changes in the Raman spectrum of all co-monomers before and after the cure, along with differential scanning calorimetry (DSC analysis, have been used to verify the need of a post-cure step and completion of the polymerization reaction. Scanning Transmission Electron Microscopy (STEM images of the emulsion after polymerization indicate that vesicles were formed, and vesicle size distribution of samples prepared with different amounts of tung oil were determined using a Zetasizer.

  14. Metal nanoparticles/ionic liquid/cellulose: polymeric membrane for hydrogenation reactions

    Directory of Open Access Journals (Sweden)

    Marcos Alexandre Gelesky


    Full Text Available Rhodium and platinum nanoparticles were supported in polymeric membranes with 10, 20 and 40 µm thickness. The polymeric membranes were prepared combining cellulose acetate and the ionic liquid (IL 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonylimide (BMI.(NTf2. The presence of metal nanoparticles induced an increase in the polymeric membrane surface areas. The increase of the IL content resulted in an improvement of elasticity and decrease in tenacity and toughness, whereas the stress at break was not affected. The presence of IL probably causes an increase in the separation between the cellulose molecules that result in a higher flexibility and processability of the polymeric membrane. The CA/IL/M(0 combinations exhibit an excellent synergistic effect that enhances the activity and durability of the catalyst for the hydrogenation of cyclohexene. The CA/IL/M(0 polymeric membrane displays higher catalytic activity (up to 7.353 h-1 for the 20 mm of CA/IL/Pt(0 and stability than the nanoparticles dispersed only in the IL.

  15. Grafting study of polysulfone polymeric membranes by gamma ray irradiation

    International Nuclear Information System (INIS)

    Furtado Filho, Acacio A.M.; Gomes, Ailton de S.


    Radiation-induced grafting of styrene poli sulfone films were investigated by simultaneous method in solution using gamma-ray from a radio nuclide 60 Co source. The gamma-ray energy of high intensity induced breaking of chemical bonds leading to free radical formation. The radical start a conventional polymerization sequence comparable with that obtained with a chemical catalyst acting as initiator. The effects of grafting conditions such as irradiation total dose, dose rate and addition of cross linking agent, were studied by means of morphology analysis, thermal degradation and crystallinity. After the grafting reaction, the membranes were submitted to an exhaustive extraction with solvent to remove the polystyrene homopolymer formed. The degree of grafting (DOG) was analyzed by percentage of weight increase. As a result, the reaction always follows the same pattern: DOG increases rapidly initially whilst propagation is the main reaction, then more slowly as termination becomes more frequent. (author)

  16. Dispersion enhanced metal/zeolite catalysts (United States)

    Sachtler, Wolfgang M. H.; Tzou, Ming-Shin; Jiang, Hui-Jong


    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  17. Comonomer-induced stereo-selectivity enhancement in a c2 -symmetric metallocene-catalyzed propylene polymerization. (United States)

    Ma, Lin; Dong, Jin-Yong


    Propylene polymerization is carried out with a C 2 -symmetric metallocene catalyst of rac-Et(Ind)2 ZrCl2 /MAO at 40 °C in the presence of a cyclo-triene of trans,trans,cis-1,5,9-cyclododecatriene ((E,E,Z)-CDT). Comonomer incorporations are rather low (7% in [mmmm]). (E,E,Z)-CDT is speculated to coordinate to the metal center forming comonomer-complexed active sites in charge of the entire polymerization reaction with decreased activity however increased propylene -enantiomorphic selectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Supported Molten Metal Catalysis. A New Class of Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ravindra Datta; Ajeet Singh; Manuela Serban; Istvan Halasz


    We describe a new class of heterogeneous catalysts called supported molten metal catalysis (SMMC), in which molten metal catalysts are dispersed as nanodroplets on the surface of porous supports, allowing much larger active surface area than is possible in conventional contacting techniques for catalytic metals that are molten under reaction conditions, thus greatly enhancing their activity and potential utility. Specific examples of different types of reactions are provided to demonstrate the broad applicability of the technique in designing active, selective, and stable new catalysts. It is shown that dispersing the molten metal on a support in the suggested manner can enhance the rate of a reaction by three to four orders of magnitude as a result of the concomitant increase in the active surface area. New reaction examples include {gamma}-Al{sub 2}O{sub 3} supported molten Te (melting point 450 C) and Ga (MP 30 C) catalysts for bifunctional methylcyclohexane dehydrogenation. These catalysts provide activity similar to conventional Pt-based catalysts for this with better resistance to coking. In addition, results are described for a controlled pore glass supported molten In (MP 157 C) catalyst for the selective catalytic reduction of NO with ethanol in the presence of water, demonstrating activities superior to conventional catalysts for this reaction. A discussion is also provided on the characterization of the active surface area and dispersion of these novel supported catalysts. It is clear based on the results described that the development of new active and selective supported molten metal catalysts for practical applications is entirely plausible.

  19. Mechanistic Studies of Hafnium-Pyridyl Amido-Catalyzed 1-Octene Polymerization and Chain Transfer Using Quench-Labeling Methods. (United States)

    Cueny, Eric S; Johnson, Heather C; Anding, Bernie J; Landis, Clark R


    Chromophore quench-labeling applied to 1-octene polymerization as catalyzed by hafnium-pyridyl amido precursors enables quantification of the amount of active catalyst and observation of the molecular weight distribution (MWD) of Hf-bound polymers via UV-GPC analysis. Comparison of the UV-detected MWD with the MWD of the "bulk" (all polymers, from RI-GPC analysis) provides important mechanistic information. The time evolution of the dual-detection GPC data, concentration of active catalyst, and monomer consumption suggests optimal activation conditions for the Hf pre-catalyst in the presence of the activator [Ph 3 C][B(C 6 F 5 ) 4 ]. The chromophore quench-labeling agents do not react with the chain-transfer agent ZnEt 2 under the reaction conditions. Thus, Hf-bound polymeryls are selectively labeled in the presence of zinc-polymeryls. Quench-labeling studies in the presence of ZnEt 2 reveal that ZnEt 2 does not influence the rate of propagation at the Hf center, and chain transfer of Hf-bound polymers to ZnEt 2 is fast and quasi-irreversible. The quench-label techniques represent a means to study commercial polymerization catalysts that operate with high efficiency at low catalyst concentrations without the need for specialized equipment.

  20. FINAL TECHNICAL REPORT Synthetic, Structural and Mechanistic Investigations of Olefin Polymerization Catalyzed by Early Transition Metal Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Bercaw, John E. [California Institute of Technology


    The goal of this project is to develop new catalysts and provide understanding of ligand effects on catalyst composition in order to guide development of superior catalyst systems for polymerization of olefins. Our group is designing and synthesizing new “LX2”,“pincer” type ligands and complexing early transition metals to afford precatalysts. In a collaboration with Hans Brintzinger from the University of Konstanz, we are also examining the structures of the components of catalyst systems obtained from reaction of zirconocene dichlorides with aluminum alkyls and aluminum hydrides. Such systems are currently used commercially to produce polyolefins, but the nature of the active and dormant species as well as the mechanisms of their interconversions are not understood. New information on catalyst design and performance may lead to new types of polymers and/or new chemical transformations between hydrocarbons and transition metal centers, ultimately contributing to the development of catalytic reactions for the production of fuels, commodity and polymeric materials.

  1. Non-PGM cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Colon-Mercado, H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Elvington, M. [Savannah River Consulting, Aiken, SC (United States); Ganesan, P. [Savannah River Consulting, Aiken, SC (United States)


    A unique approach has been developed to probe the non-PGM catalyst active site for the Oxygen Reduction Reaction (ORR) for PEMFCs. Iron based functionalities have been engineered into a variety of catalysts to evaluate their impact on activity for the ORR. A series of high surface area catalysts were synthesized and the impact of the chemical structure on the electrochemical and electrocatalytic properties was investigated. Elemental and surface analyses of the prepared catalysts reveal the incorporation of iron in a targeted and controlled manner. A high surface area framework catalyst was prepared that shows exceptional activity, comparable to state-of-the-art materials. The results of this research project provided critical seed data for the newly awarded ElectroCat project, which focuses on rationally designed framework catalysts for the oxygen reduction reaction.

  2. Hyperfine interactions in metallic catalysts

    International Nuclear Information System (INIS)

    Saitovitch, Henrique; Silva, Paulo R.J.; Passos, Fabio B.


    Heterogeneous catalysts are of fundamental importance in several modern chemical processes. The characterization of catalysts is an issue of very present interest as it can provide a better understanding of the fundamental aspects of the catalytic phenomena, thus helping in the development of more efficient catalysts. In order to extend and improve the characterization of catalysts, new and less conventional methods are being applied, such as nuclear spectroscopies. In this paper we focus on the application of angular correlation, with can be used to resolve different local environments of probe atoms in solids and can be applied, as shown here, in the characterization of heterogeneous catalysts. A brief theoretical introduction is given and experimental results related to catalytic systems of alumina and niobia-supported Pt-In and Pd-In catalysts are presented. (author)

  3. Catalyst systems and uses thereof (United States)

    Ozkan, Umit S [Worthington, OH; Holmgreen, Erik M [Columbus, OH; Yung, Matthew M [Columbus, OH


    A method of carbon monoxide (CO) removal comprises providing an oxidation catalyst comprising cobalt supported on an inorganic oxide. The method further comprises feeding a gaseous stream comprising CO, and oxygen (O.sub.2) to the catalyst system, and removing CO from the gaseous stream by oxidizing the CO to carbon dioxide (CO.sub.2) in the presence of the oxidation catalyst at a temperature between about 20 to about C.

  4. Ring-Opening Metathesis Activity of Ruthenium-Based Olefin Metathesis Catalyst Coordinated with 1,3-Bis(2,6-Diisopropylphenyl)-4,5-Dihydroimidazoline (United States)

    Karabulut, Solmaz; Verpoort, Francis

    A 1,3-bis-(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene substituted ruthenium (Ru)-based complex (4) has been prepared starting from (PCy3)2(Cl)2Ru=CHPh (2). The catalytic performance of catalyst (4) is checked on ring-opening metathesis polymerization (ROMP) of the low strain monomer, cycloocta-1,5-diene (COD), and also compared with catalyst (2) and (3).

  5. One-pot synthesis of well-defined polyether/polyester block copolymers and terpolymers by a highly efficient catalyst switch approach

    KAUST Repository

    Alamri, Haleema


    A highly efficient methodology, based on a novel catalyst switch approach with rapid crossover characteristics, was developed for the one-pot synthesis of block co/terpolymers of cyclic ethers and esters. This new approach, which takes advantage of one of the best catalysts for epoxide (t-BuP4) and cyclic ester (t-BuP2) polymerization, opens new horizons toward the synthesis of cyclic ether/ester complex macromolecular architectures. © The Royal Society of Chemistry 2016.

  6. Grape and wine polymeric polyphenols: Their importance in enology. (United States)

    Li, Lingxi; Sun, Baoshan


    Phenolic compounds are important constituents of red wine, contributing to its sensory properties and antioxidant activity. Owing to the diversity and structural complexity, study of these compounds was mainly limited, during the last three decades, on their low-molecular-mass compounds or simple phenolic compounds. Only in recent years, much attention has been paid to highly polymerized polyphenols in grape and red wines. The reason for this is largely due to the development of analytical techniques, especially those of HPLC-ESI-MS, permitting the structural characterization of highly polymerized polyphenols. Furthermore, the knowledge on the biological properties of polymeric polyphenols of red wine is very limited. Grape polyphenols mainly consist of proanthocyanidins (oligomers and polymers) and anthocyanins, and low amount of other phenolics. Red wine polyphenols include both grape polyphenols and new phenolic products formed from them during winemaking process. This leads to a great diversity of new polyphenols and makes wine polyphenol composition more complex. The present paper summarizes the advances in the research of polymeric polyphenols in grape and red wine and their important role in Enology. Scientific results indicate that polymeric polyphenols, as the major polyphenols in grape and red wine, play a major role in red wine sensory properties, color stability and antioxidant activities.

  7. Reuse of Hydrotreating Spent Catalyst

    International Nuclear Information System (INIS)

    Habib, A.M.; Menoufy, M.F.; Amhed, S.H.


    All hydro treating catalysts used in petroleum refining processes gradually lose activity through coking, poisoning by metal, sulfur or halides or lose surface area from sintering at high process temperatures. Waste hydrotreating catalyst, which have been used in re-refining of waste lube oil at Alexandria Petroleum Company (after 5 years lifetime) compared with the same fresh catalyst were used in the present work. Studies are conducted on partial extraction of the active metals of spent catalyst (Mo and Ni) using three leaching solvents,4% oxidized oxalic acid, 10% aqueous sodium hydroxide and 10% citric acid. The leaching experiments are conducting on the de coked extrude [un crushed] spent catalyst samples. These steps are carried out in order to rejuvenate the spent catalyst to be reused in other reactions. The results indicated that 4% oxidized oxalic acid leaching solution gave total metal removal 45.6 for de coked catalyst samples while NaOH gave 35% and citric acid gave 31.9 % The oxidized leaching agent was the most efficient leaching solvent to facilitate the metal removal, and the rejuvenated catalyst was characterized by the unchanged crystalline phase The rejuvenated catalyst was applied for hydrodesulfurization (HDS) of vacuum gas oil as a feedstock, under different hydrogen pressure 20-80 bar in order to compare its HDS activity

  8. Mixed Alcohol Synthesis Catalyst Screening

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Mark A.; White, James F.; Stevens, Don J.


    National Renewable Energy Laboratory (NREL) and Pacific Northwest National Laboratory (PNNL) are conducting research to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). PNNL is tasked with obtaining commercially available or preparing promising mixed-alcohol catalysts and screening them in a laboratory-scale reactor system. Commercially available catalysts and the most promising experimental catalysts are provided to NREL for testing using a slipstream from a pilot-scale biomass gasifier. From the standpoint of producing C2+ alcohols as the major product, it appears that the rhodium catalyst is the best choice in terms of both selectivity and space-time yield (STY). However, unless the rhodium catalyst can be improved to provide minimally acceptable STYs for commercial operation, mixed alcohol synthesis will involve significant production of other liquid coproducts. The modified Fischer-Tropsch catalyst shows the most promise for providing both an acceptable selectivity to C2+ alcohols and total liquid STY. However, further optimization of the Fischer-Tropsch catalysts to improve selectivity to higher alcohols is highly desired. Selection of a preferred catalyst will likely entail a decision on the preferred coproduct slate. No other catalysts tested appear amenable to the significant improvements needed for acceptable STYs.

  9. Supported Dendrimer-Encapsulated Metal Clusters: Toward Heterogenizing Homogeneous Catalysts. (United States)

    Ye, Rong; Zhukhovitskiy, Aleksandr V; Deraedt, Christophe V; Toste, F Dean; Somorjai, Gabor A


    Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles-some without homogeneous analogues-for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence, and structural uniformity, dendrimers have proven to be versatile scaffolds for the synthesis and stabilization of small nanoclusters. Then these dendrimer-encapsulated metal clusters (DEMCs) are adsorbed onto mesoporous silica. Through this method, we have achieved selective transformations that had been challenging to accomplish in a heterogeneous setting, e.g., π-bond activation and aldol reactions. Extensive investigation into the catalytic systems under reaction conditions allowed us to correlate the structural features (e.g., oxidation states) of the catalysts and their activity. Moreover, we have

  10. Selective Oxidations using Nanostructured Heterogeneous Catalysts

    DEFF Research Database (Denmark)

    Mielby, Jerrik Jørgen

    The aim of this thesis is to investigate and develop new efficient methods to oxidise alcohols and amines using heterogeneous catalysts and either O2 or H2O2 as oxidants. From an economic and environmental point of view, these oxidants are ideal, because they are cheap and readily available and b...... stability, catalytic activity and selectivity for the gas-phase oxidation of bioethanol to acetaldehyde, which may become a favourable and green alternative to the ethylene route.......The aim of this thesis is to investigate and develop new efficient methods to oxidise alcohols and amines using heterogeneous catalysts and either O2 or H2O2 as oxidants. From an economic and environmental point of view, these oxidants are ideal, because they are cheap and readily available......, the chapter focuses on the use of supported metal catalysts for the selective oxidation of alcohols, which are currently dominated by the platinum group metals. Chapter 2 deals with the most important methods to characterise heterogeneous catalysts, including X-ray powder diffraction, physisorption analysis...

  11. A lipase-responsive vehicle using amphipathic polymer synthesized with the lipase as catalyst. (United States)

    Ge, Jun; Lu, Diannan; Yang, Cheng; Liu, Zheng


    We describe an enzyme-responsive polymeric vehicle, which is of great interest in controlled drug delivery, biosensing, and other related areas. The polymer synthesized using lipase as catalyst in DMSO has a favorable molecular structure that is quickly hydrolyzed by lipase in aqueous phase, and allows a fast release of encapsulated molecules. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


    NARCIS (Netherlands)

    Sie, S.T.


    Abstract of WO 9521691 (A1) Described is a reactor (1) at least partially filled with catalyst granules (11), which is intended for catalytically reacting at least one gas and at least one liquid with each other. According to the invention the catalyst granules (11) are collected in agglomerates

  13. Isospecific polymerization of 1-hexene by C1-symmetric half-metallocene dimethyl complexes of group 4 metals with bidentate N-substituted iminomethylpyrrolyl ligands. (United States)

    Yasumoto, Takahiro; Yamamoto, Keishi; Tsurugi, Hayato; Mashima, Kazushi


    Non-bridged half-metallocene dimethyl complexes of group 4 metals 2a-4a with an N-4-methoxyphenyl(iminomethyl)pyrrolyl ligand 1a were synthesized and characterized by NMR spectroscopy and X-ray analysis. Upon activation with [Ph3C][B(C6F5)4], these complexes became active catalysts for the polymerization of 1-hexene. A series of hafnium complexes with various N-substituents on the imine group of ligands 1b-1g were also prepared and applied as catalysts for 1-hexene polymerization. The activation parameters for the exchange process between the two methyl groups bound to the metal for Cp*MMe2(R-pyr) complexes were estimated by NMR shape analysis at various temperatures. The findings indicated that the transition state of the ligand flipping process might be associated with the isoselectivity of the polymerization reaction.


    Directory of Open Access Journals (Sweden)



    Full Text Available Here, of great interest to us is a quantitative study of the scattering properties from ramified polymeric systems of arbitrary topology. We consider three types of systems, namely ramified polymers in solution, ramified polymer blends, or ternary mixtures made of two ramified polymers of different chemical nature immersed in a good solvent. To achieve the goal of the study, use is made of the Random Phase Approximation. First we determine the exact expression of the form factor of an ideal ramified polymer of any topology, from which we extract the exact expression of its gyration radius. Using the classical Zimm's formulae and the exact form factor, we determine all scattering properties of these three types of ramified polymeric systems. The main conclusion is that ramification of the chains induces drastic changes of the scattering properties.

  15. Understanding the Performance of Automotive Catalysts via Spatial Resolution of Reactions inside Honeycomb Monoliths

    Energy Technology Data Exchange (ETDEWEB)

    Partridge Jr, William P. [ORNL; Choi, Jae-Soon [ORNL


    By directly resolving spatial and temporal species distributions within operating honeycomb monolith catalysts, spatially resolved capillary inlet mass spectrometry (SpaciMS) provides a uniquely enabling perspective for advancing automotive catalysis. Specifically, the ability to follow the spatiotemporal evolution of reactions throughout the catalyst is a significant advantage over inlet-and-effluent-limited analysis. Intracatalyst resolution elucidates numerous catalyst details including the network and sequence of reactions, clarifying reaction pathways; the relative rates of different reactions and impacts of operating conditions and catalyst state; and reaction dynamics and intermediate species that exist only within the catalyst. These details provide a better understanding of how the catalyst functions and have basic and practical benefits; e.g., catalyst system design; strategies for on-road catalyst state assessment, control, and on-board diagnostics; and creating robust and accurate predictive catalyst models. Moreover, such spatiotemporally distributed data provide for critical model assessment, and identification of improvement opportunities that might not be apparent from effluent assessment; i.e., while an incorrectly formulated model may provide correct effluent predictions, one that can accurately predict the spatiotemporal evolution of reactions along the catalyst channels will be more robust, accurate, and reliable. In such ways, intracatalyst diagnostics comprehensively enable improved design and development tools, and faster and lower-cost development of more efficient and durable automotive catalyst systems. Beyond these direct contributions, SpaciMS has spawned and been applied to enable other analytical techniques for resolving transient distributed intracatalyst performance. This chapter focuses on SpaciMS applications and associated catalyst insights and improvements, with specific sections related to lean NOx traps, selective catalytic

  16. Novel Reforming Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa D; Haller, Gary L


    Aqueous phase reforming is useful for processing oxygenated hydrocarbons to hydrogen and other more useful products. Current processing is hampered by the fact that oxide based catalysts are not stable under high temperature hydrothermal conditions. Silica in the form of structured MCM-41 is thermally a more stable support for Co and Ni than conventional high surface area amorphous silica but hydrothermal stability is not demonstrated. Carbon nanotube supports, in contrast, are highly stable under hydrothermal reaction conditions. In this project we show that carbon nanotubes are stable high activity/selectivity supports for the conversion of ethylene glycol to hydrogen.

  17. A Catalyst for Change

    DEFF Research Database (Denmark)

    Lønsmann, Dorte


    into in a process that hinges on new members functioning as tools for management to bring about the desired change. The article shows that while the newcomer is used as a catalyst for increased use of English and for the creation of a 'global mindset,' she is at the same time socialized into the existing Danish...... for changing language practices toward more English, with the ultimate aim of creating a 'global mindset' in the organization. Language socialization in a transient multilingual setting is shown to focus on and assign positive value to new linguistic norms that experienced members are socialized...

  18. Sleeving nanocelluloses by admicellar polymerization. (United States)

    Trovatti, Eliane; Ferreira, Adriane de Medeiros; Carvalho, Antonio José Felix; Ribeiro, Sidney José Lima; Gandini, Alessandro


    This investigation reports the first application of admicellar polymerization to cellulose nanofibers in the form of bacterial cellulose, microfibrillated cellulose, and cellulose nanowhiskers using styrene and ethyl acrylate. The success of this physical sleeving was assessed by SEM, FTIR, and contact angle measurements, providing an original and simple approach to the modification of cellulose nanofibers in their pristine aqueous environment. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Polymeric Microspheres for Medical Applications

    Directory of Open Access Journals (Sweden)

    Ketie Saralidze


    Full Text Available Synthetic polymeric microspheres find application in a wide range of medical applications. Among other applications, microspheres are being used as bulking agents, embolic- or drug-delivery particles. The exact composition of the spheres varies with the application and therefore a large array of materials has been used to produce microspheres. In this review, the relation between microsphere synthesis and application is discussed for a number of microspheres that are used for different treatment strategies.

  20. Microwave-assisted ADMET polymerization


    Rojas Jiménez, Giovanni


    Microwave-assisted ADMET polymerization is reported on a series of α,ω-diene monomers, both polar and non-polar. Investigations indicate that of the multiple microwave modes possible, constant power is the most advantageous, providing polymers up to M‾w=31,000g/mol. Molecular weight values are nearly triple in comparison with conventional oil bath heating. Polymers are characterized by NMR, GPC, TGA, and DSC. Microwave irradiation provides a highly controllable and energy efficient ADMET poly...

  1. In-situ characterization of heterogeneous catalysts

    CERN Document Server

    Rodriguez, Jose A; Chupas, Peter J


    Helps researchers develop new catalysts for sustainable fuel and chemical production Reviewing the latest developments in the field, this book explores the in-situ characterization of heterogeneous catalysts, enabling readers to take full advantage of the sophisticated techniques used to study heterogeneous catalysts and reaction mechanisms. In using these techniques, readers can learn to improve the selectivity and the performance of catalysts and how to prepare catalysts as efficiently as possible, with minimum waste. In-situ Characterization of Heterogeneous Catalysts feat

  2. Application, Deactivation, and Regeneration of Heterogeneous Catalysts in Bio-Oil Upgrading

    Directory of Open Access Journals (Sweden)

    Shouyun Cheng


    Full Text Available The massive consumption of fossil fuels and associated environmental issues are leading to an increased interest in alternative resources such as biofuels. The renewable biofuels can be upgraded from bio-oils that are derived from biomass pyrolysis. Catalytic cracking and hydrodeoxygenation (HDO are two of the most promising bio-oil upgrading processes for biofuel production. Heterogeneous catalysts are essential for upgrading bio-oil into hydrocarbon biofuel. Although advances have been achieved, the deactivation and regeneration of catalysts still remains a challenge. This review focuses on the current progress and challenges of heterogeneous catalyst application, deactivation, and regeneration. The technologies of catalysts deactivation, reduction, and regeneration for improving catalyst activity and stability are discussed. Some suggestions for future research including catalyst mechanism, catalyst development, process integration, and biomass modification for the production of hydrocarbon biofuels are provided.

  3. Catalytic olefin polymerization with early transition metal compounds

    NARCIS (Netherlands)

    Eshuis, Johan Jan Willem


    The catalysis of organic reactions by soluble metal complexes has become a major tool in synthesis, both in the laboratory and in the chemical industry. Processes catalyzed by transition metal complexes include carbonylation, olefin polymerization, olefin addition, olefin oxidation and alkane and

  4. Radiation-Induced Polymerization Monitored with Fluorogenic Molecular Probes

    NARCIS (Netherlands)

    Frahn, M.S.


    Each year over one billion pounds of acrylic-based polymeric products are produced world wide. Such products include windows in aircraft, lenses in eyeglasses and CD players, coatings on parquet flooring and various architectural structures such as skylights and domes. Often these products are made

  5. Non-equilibrium supramolecular polymerization. (United States)

    Sorrenti, Alessandro; Leira-Iglesias, Jorge; Markvoort, Albert J; de Greef, Tom F A; Hermans, Thomas M


    Supramolecular polymerization has been traditionally focused on the thermodynamic equilibrium state, where one-dimensional assemblies reside at the global minimum of the Gibbs free energy. The pathway and rate to reach the equilibrium state are irrelevant, and the resulting assemblies remain unchanged over time. In the past decade, the focus has shifted to kinetically trapped (non-dissipative non-equilibrium) structures that heavily depend on the method of preparation (i.e., pathway complexity), and where the assembly rates are of key importance. Kinetic models have greatly improved our understanding of competing pathways, and shown how to steer supramolecular polymerization in the desired direction (i.e., pathway selection). The most recent innovation in the field relies on energy or mass input that is dissipated to keep the system away from the thermodynamic equilibrium (or from other non-dissipative states). This tutorial review aims to provide the reader with a set of tools to identify different types of self-assembled states that have been explored so far. In particular, we aim to clarify the often unclear use of the term "non-equilibrium self-assembly" by subdividing systems into dissipative, and non-dissipative non-equilibrium states. Examples are given for each of the states, with a focus on non-dissipative non-equilibrium states found in one-dimensional supramolecular polymerization.

  6. Catalysts for the selective oxidation of hydrogen sulfide to sulfur (United States)

    Srinivas, Girish; Bai, Chuansheng


    This invention provides catalysts for the oxidation of hydrogen sulfide. In particular, the invention provides catalysts for the partial oxidation of hydrogen sulfide to elemental sulfur and water. The catalytically active component of the catalyst comprises a mixture of metal oxides containing titanium oxide and one or more metal oxides which can be selected from the group of metal oxides or mixtures of metal oxides of transition metals or lanthanide metals. Preferred metal oxides for combination with TiO.sub.2 in the catalysts of this invention include oxides of V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Tc, Ru, Rh, Hf, Ta, W, Au, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Catalysts which comprise a homogeneous mixture of titanium oxide and niobium (Nb) oxide are also provided. A preferred method for preparing the precursor homogenous mixture of metal hydroxides is by coprecipitation of titanium hydroxide with one or more other selected metal hydroxides. Catalysts of this invention have improved activity and/or selectivity for elemental sulfur production. Further improvements of activity and/or selectivity can be obtained by introducing relatively low amounts (up to about 5 mol %)of a promoter metal oxide (preferably of metals other than titanium and that of the selected second metal oxide) into the homogeneous metal/titanium oxide catalysts of this invention.

  7. Impregnation alternatives for Fe-based coal liquefaction catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.K.; Armstong, B.T.; Givens, E.N. [Univ. of Kentucky, Lexington, KY (United States)


    Because of the cost effective and environmentally compatible nature of Fe, attention has been directed towards improving the utilization of this metal in direct coal liquefaction. Among the several factors thought to affect catalyst activity, much of this work has focused on dispersion. Weller and Pelipetz reported the importance of catalyst dispersion, based on experiments with a wide variety of catalysts in solvent-free liquefaction studies. And in the presence of solvent, other studies have demonstrated the advantages of adding the precursor by impregnation over its addition in the form of particulates. In general, a high surface/volume ratio, along with intimate contact between the active catalyst and coal, are thought to be the controlling factors. Dispersion, as normally inferred from changes in catalyst activity, may be affected by the mode of addition, the presence of solvent, and the initial composition of the precursor (e.g., soluble organometallics); and for coal-impregnated catalyst precursors, the choice of impregnation solvent and impregnation conditions. A variety of innovative strategies have been developed to introduce catalyst precursors to the liquefaction reaction while seeking to maintain particle size and distribution. These have included the use of emulsions and colloids, direct addition of ultra-fine particles to the slurry`s addition of oil soluble organometallics and carbonyls, ion exchange and impregnating the coal. This paper describes the results of liquefaction experiments carried out with the impregnation of subbituminous coal with iron.

  8. Core-shell and asymmetric polystyrene-gold composite particles via one-step Pickering emulsion polymerization. (United States)

    Zhang, Mingmeng; Ngo, Thao H; Rabiah, Noelle I; Otanicar, Todd P; Phelan, Patrick E; Swaminathan, Raja; Dai, Lenore L


    Core-shell structured polystyrene-gold composite particles are synthesized from one-step Pickering emulsion polymerization. The surface coverage of the core-shell composite particles is improved with increasing gold nanoparticle (AuNP) hydrophobicity and concentration. At high surface coverage, the AuNPs exhibit an ordered hexagonal pattern, likely due to electrostatic repulsion during the emulsion polymerization process. In addition to core-shell structured polystyrene-gold composite particles, an intriguing observation is that at low AuNP concentrations, asymmetric polystyrene-gold nanocomposite particles are simultaneously formed, where a single gold nanoparticle is attached onto each polystyrene particle. It is found that these asymmetric particles are formed via a "seeded-growth" mechanism. The core-shell and asymmetric polystyrene-gold composite particles prove to be efficient catalysts as they successfully catalyze the Rhodamine B reduction reaction with stable performance and show high recyclability as catalysts.

  9. Multicomponent polymeric materials

    CERN Document Server

    Thomas, Sabu; Saha, Prosenjit


    The book offers an in-depth review of the materials design and manufacturing processes employed in the development of multi-component or multiphase polymer material systems. This field has seen rapid growth in both academic and industrial research, as multiphase materials are increasingly replacing traditional single-component materials in commercial applications. Many obstacles can be overcome by processing and using multiphase materials in automobile, construction, aerospace, food processing, and other chemical industry applications. The comprehensive description of the processing, characterization, and application of multiphase materials presented in this book offers a world of new ideas and potential technological advantages for academics, researchers, students, and industrial manufacturers from diverse fields including rubber engineering, polymer chemistry, materials processing and chemical science. From the commercial point of view it will be of great value to those involved in processing, optimizing an...

  10. Robust Cross-Linked Stereocomplexes and C60 Inclusion Complexes of Vinyl-Functionalized Stereoregular Polymers Derived from Chemo/Stereoselective Coordination Polymerization. (United States)

    Vidal, Fernando; Falivene, Laura; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X


    The successful synthesis of highly syndiotactic polar vinyl polymers bearing the reactive pendant vinyl group on each repeat unit, which is enabled by perfectly chemoselective and highly syndiospecific coordination polymerization of divinyl polar monomers developed through this work, has allowed the construction of robust cross-linked supramolecular stereocomplexes and C60 inclusion complexes. The metal-mediated coordination polymerization of three representative polar divinyl monomers, including vinyl methacrylate (VMA), allyl methacrylate (AMA), and N,N-diallyl acrylamide (DAA) by Cs-ligated zirconocenium ester enolate catalysts under ambient conditions exhibits complete chemoselectivity and high stereoselectivity, thus producing the corresponding vinyl-functionalized polymers with high (92% rr) to quantitative (>99% rr) syndiotacticity. A combined experimental (synthetic, kinetic, and mechanistic) and theoretical (DFT) investigation has yielded a unimetallic, enantiomorphic-site-controlled propagation mechanism. Postfunctionalization of the obtained syndiotactic vinyl-functionalized polymers via the thiol-ene click and photocuring reactions readily produced the corresponding thiolated polymers and flexible cross-linked thin-film materials, respectively. Complexation of such syndiotactic vinyl-functionalized polymers with isotactic poly(methyl methacrylate) and fullerene C60 generates supramolecular crystalline helical stereocomplexes and inclusion complexes, respectively. Cross-linking of such complexes affords robust cross-linked stereocomplexes that are solvent-resistant and also exhibit considerably enhanced thermal and mechanical properties compared with the un-cross-linked stereocomplexes.

  11. Robust Crosslinked Stereocomplexes and C60 Inclusion Complexes of Vinyl-Functionalized Stereoregular Polymers Derived from Chemo/Stereoselective Coordination Polymerization

    KAUST Repository

    Vidal, Fernando


    The successful synthesis of highly syndiotactic polar vinyl polymers bearing the reactive pendant vinyl group on each repeat unit, which is enabled by perfectly chemoselective and highly syndiospecific coordination polymerization of divinyl polar monomers developed through this work, has allowed the construction of robust crosslinked supramolecular stereocomplexes and C60 inclusion complexes. The metal-mediated coordination polymerization of three representative polar divinyl monomers, including vinyl methacrylate (VMA), allyl methacrylate (AMA), and N,N-diallyl acrylamide (DAA) by Cs-ligated zirconocenium ester enolate catalysts under ambient conditions exhibits complete chemoselectivity and high stereoselectivity, thus producing the corresponding vinyl-functionalized polymers with high (92% rr) to quantitative (>99% rr) syndiotacticity. A combined experimental (synthetic, kinetic, and mechanistic) and theoretical (DFT) investigation has yielded a unimetallic, enantiomorphic-site controlled propagation mechanism. Post-functionalization of the obtained syndiotactic vinyl-functionalized polymers via the thiol-ene click and photocuring reactions readily produced the corresponding thiolated polymers and flexible crosslinked thin film materials, respectively. Complexation of such syndiotactic vinyl-functionalized polymers with isotactic poly(methyl methacrylate) and fullerene C60 generates supramolecular crystalline helical stereocomplexes and inclusion complexes, respectively. Crosslinking of such complexes afforded robust crosslinked stereocomplexes that are solvent resistant and also exhibit considerably enhanced thermal and mechanical properties as compared to the uncrosslinked stereocompexes.

  12. The structural basis of serpin polymerization studied by hydrogen/deuterium exchange and mass spectrometry. (United States)

    Tsutsui, Yuko; Kuri, Barbara; Sengupta, Tanusree; Wintrode, Patrick L


    The serpinopathies are a group of inherited disorders that share as their molecular basis the misfolding and polymerization of serpins, an important class of protease inhibitors. Depending on the identity of the serpin, conditions arising from polymerization include emphysema, thrombosis, and dementia. The structure of serpin polymers is thus of considerable medical interest. Wild-type alpha(1)-antitrypsin will form polymers upon incubation at moderate temperatures and has been widely used as a model system for studying serpin polymerization. Using hydrogen/deuterium exchange and mass spectrometry, we have obtained molecular level structural information on the alpha(1)-antitrypsin polymer. We found that the flexible reactive center loop becomes strongly protected upon polymerization. We also found significant increases in protection in the center of beta-sheet A and in helix F. These results support a model in which linkage between serpins is achieved through insertion of the reactive center loop of one serpin into beta-sheet A of another. We have also examined the heat-induced conformational changes preceding polymerization. We found that polymerization is preceded by significant destabilization of beta-sheet C. On the basis of our results, we propose a mechanism for polymerization in which beta-strand 1C is displaced from the rest of beta-sheet C through a binary serpin/serpin interaction. Displacement of strand 1C triggers further conformational changes, including the opening of beta-sheet A, and allows for subsequent polymerization.

  13. Strong liquid-crystalline polymeric compositions (United States)

    Dowell, F.


    Strong liquid-crystalline polymeric (LCP) compositions of matter are described. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment. 27 figures.

  14. Catalysts for Efficient Production of Carbon Nanotubes (United States)

    Sun, Ted X.; Dong, Yi


    Several metal alloys have shown promise as improved catalysts for catalytic thermal decomposition of hydrocarbon gases to produce carbon nanotubes (CNTs). Heretofore almost every experiment on the production of carbon nanotubes by this method has involved the use of iron, nickel, or cobalt as the catalyst. However, the catalytic-conversion efficiencies of these metals have been observed to be limited. The identification of better catalysts is part of a continuing program to develop means of mass production of high-quality carbon nanotubes at costs lower than those achieved thus far (as much as $100/g for purified multi-wall CNTs or $1,000/g for single-wall CNTs in year 2002). The main effort thus far in this program has been the design and implementation of a process tailored specifically for high-throughput screening of alloys for catalyzing the growth of CNTs. The process includes an integral combination of (1) formulation of libraries of catalysts, (2) synthesis of CNTs from decomposition of ethylene on powders of the alloys in a pyrolytic chemical-vapor-decomposition reactor, and (3) scanning- electron-microscope screening of the CNTs thus synthesized to evaluate the catalytic efficiencies of the alloys. Information gained in this process is put into a database and analyzed to identify promising alloy compositions, which are to be subjected to further evaluation in a subsequent round of testing. Some of these alloys have been found to catalyze the formation of carbon nano tubes from ethylene at temperatures as low as 350 to 400 C. In contrast, the temperatures typically required for prior catalysts range from 550 to 750 C.

  15. Catalysts for low temperature oxidation (United States)

    Toops, Todd J.; Parks, III, James E.; Bauer, John C.


    The invention provides a composite catalyst containing a first component and a second component. The first component contains nanosized gold particles. The second component contains nanosized platinum group metals. The composite catalyst is useful for catalyzing the oxidation of carbon monoxide, hydrocarbons, oxides of nitrogen, and other pollutants at low temperatures.

  16. Direct methanol feed fuel cell with reduced catalyst loading (United States)

    Kindler, Andrew (Inventor)


    Improvements to direct feed methanol fuel cells include new protocols for component formation. Catalyst-water repellent material is applied in formation of electrodes and sintered before application of ionomer. A membrane used in formation of an electrode assembly is specially pre-treated to improve bonding between catalyst and membrane. The improved electrode and the pre-treated membrane are assembled into a membrane electrode assembly.

  17. Allenyl esters as quenching agents for ruthenium olefin metathesis catalysts. (United States)

    Roy, Animesh; Silvestri, Maximilian A; Hall, Robert A; Lepore, Salvatore D


    In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification.

  18. Influence of temperature on the results of prehydrogenation (saturation) with concentrated and diluted catalysts. The preparation of such catalysts

    Energy Technology Data Exchange (ETDEWEB)


    In July 1941 systematic tests had been made with the alumina--molybdenum--nickel catalyst 7846. The results of those tests were summarized in this report. A test with catalyst 5058 was underway at this time and a test with alumina--tungsten--nickel catalyst 7846 W250-8376 was planned. In prehydrogenation of bituminous coal middle oils with catalyst 7846, usually done at 434/sup 0/C, the temperature was varied and it was observed that: at 300/sup 0/C, the catalyst began to show hydrogenation effects and to reduce phenols and nitrogen compounds; at 442/sup 0/C maximum hydrogenation effect was obtained; practically no splitting of C-C bonds took place below 434/sup 0/C; and below 434/sup 0/C the catalyst worked fully reversibly with respect to temperature change. The preparation of catalyst 6434 was discussed. Adsorption of hydrogen by tungsten sulfide was also a topic of this report, and it included the preparation of WS/sub 2/. Studies of the adsorption at about 25/sup 0/C showed adsorption increased appreciably up to 48 hours. The final value was fairly constant down to pressures under 100 mm and equaled about 1 ccH/sub 2//gWS/sub 2/. At pressures below 100 mm the quantity adsorbed dropped rapidly and equalled only .45 ccH/sub 2//gWS/sub 2/ at 13 mm Hg.

  19. Supported molten-metal catalysts (United States)

    Datta, Ravindra; Singh, Ajeet; Halasz, Istvan; Serban, Manuela


    An entirely new class of catalysts called supported molten-metal catalysts, SMMC, which can replace some of the existing precious metal catalysts used in the production of fuels, commodity chemicals, and fine chemicals, as well as in combating pollution. SMMC are based on supporting ultra-thin films or micro-droplets of the relatively low-melting (metals and semimetals from groups 1, 12, 13, 14, 15 and 16, of the periodic table, or their alloys and intermetallic compounds, on porous refractory supports, much like supported microcrystallites of the traditional solid metal catalysts. It thus provides orders of magnitude higher surface area than is obtainable in conventional reactors containing molten metals in pool form and also avoids corrosion. These have so far been the chief stumbling blocks in the application of molten metal catalysts.

  20. Polymerization of Phenylacetylene-Based Monodendrons with Alkoxy Peripheral Groups and Oxygen/Nitrogen Permeation Behavior of Their Membranes

    Directory of Open Access Journals (Sweden)

    Takashi Kaneko


    Full Text Available Monodendron monomers with alkoxy peripheral groups were synthesized, and the focal point of monodendrons, terminal acetylene, was polymerized with rhodium catalyst to yield corresponding polydendrons with a high molecular weight. The polydendrons were soluble in common organic solvents and readily formed membranes. Oxygen permselectivity was improved in the polydendrons with a space-persistent dendritic crowd. It was found that the well-defined dendritic and rod-like structure of the polydendrons was useful for permselective membrane.