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Sample records for olefin polymerization catalysts

  1. Stereospecific olefin polymerization catalysts

    DOEpatents

    Bercaw, John E.; Herzog, Timothy A.

    1998-01-01

    A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

  2. Stereospecific olefin polymerization catalysts

    DOEpatents

    Bercaw, J.E.; Herzog, T.A.

    1998-01-13

    A metallocene catalyst system is described for the polymerization of {alpha}-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula shown wherein: R{sup 1}, R{sup 2}, and R{sup 3} are independently selected from the group consisting of hydrogen, C{sub 1} to C{sub 10} alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C{sub 1} to C{sub 10} alkyls as a substituent, C{sub 6} to C{sub 15} aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R{sup 8}){sub 3} where R{sup 8} is selected from the group consisting of C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; R{sup 4} and R{sup 6} are substituents both having van der Waals radii larger than the van der Waals radii of groups R{sup 1} and R{sup 3}; R{sup 5} is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E{sup 1}, E{sup 2} are independently selected from the group consisting of Si(R{sup 9}){sub 2}, Si(R{sup 9}){sub 2}--Si(R{sup 9}){sub 2}, Ge(R{sup 9}){sub 2}, Sn(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}--C(R{sup 9}){sub 2}, where R{sup 9} is C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; and the ligand may have C{sub S} or C{sub 1}-symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from {alpha}-olefin monomers.

  3. Supported organometallic catalysts for hydrogenation and Olefin Polymerization

    DOEpatents

    Marks, Tobin J.; Ahn, Hongsang

    2001-01-01

    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.

  4. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, T.J.; Eisen, M.S.; Giardello, M.A.

    1995-10-03

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C{sub 5}R{prime}{sub 4{minus}x}R*{sub x})A(C{sub 5}R{double_prime}{sub 4{minus}y}R{double_prime}{prime}{sub y})MQ{sub p}, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R{prime}, R{double_prime}, R{double_prime}{prime}, and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3{>=}p{>=}0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form ``cation-like`` species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other {alpha}-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

  5. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, T.J.; Eisen, M.S.; Giardello, M.A.

    1994-07-19

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C[sub 5]R[prime][sub 4[minus]x]R*[sub x])-A-(C[sub 5]R[double prime][sub 4[minus]y]R[prime][double prime][sub y])-M-Q[sub p], where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R[prime], R[double prime], R[prime][double prime], and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3 [<=] p [<=] 0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form cation-like'' species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other [alpha]-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

  6. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1995-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R"'.sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R"', and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  7. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1994-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R'".sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R'", and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  8. Sterically shielded diboron-containing metallocene olefin polymerization catalysts

    DOEpatents

    Marks, Tobin J.; Ja, Li; Yang, Xinmin

    1995-09-05

    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.

  9. Transition metal-free olefin polymerization catalyst

    DOEpatents

    Sen, Ayusman; Wojcinski, II, Louis M.; Liu, Shengsheng

    2001-01-01

    Ethylene and/or propylene are polymerized to form high molecular weight, linear polymers by contacting ethylene and/or propylene monomer, in the presence of an inert reaction medium, with a catalyst system which consists essentially of (1) an aluminum alkyl component, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-octylaluminum and diethylaluminum hydride and (2) a Lewis acid or Lewis acid derivative component, such as B (C.sub.6 F.sub.5).sub.3, [(CH.sub.3).sub.2 N (H) (C.sub.6 H.sub.5)].sup.+ [B (C.sub.6 F.sub.5)4].sup.-, [(C.sub.2 H.sub.5).sub.3 NH].sup.+ [B C.sub.6 F.sub.5).sub.4 ],.sup.-, [C(C.sub.6 F.sub.5).sub.3 ].sup.+ [B(C.sub.6 F.sub.5).sub.4 ].sup.-, (C.sub.2 H.sub.5).sub.2 Al(OCH.sub.3), (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butyl-4-methylphenoxide), (C.sub.2 H.sub.5)Al(2,6 -di-t-butylphenoxide).sub.2, (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butylphonoxide) , 2,6 -di-t-butylphenol.multidot.methylaluminoxane or an alkylaluminoxane, and which may be completely free any transition metal component(s).

  10. Olefin polymerization from single site catalysts confined within porous media

    NASA Astrophysics Data System (ADS)

    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

  11. Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization.

    PubMed

    Li, Hongbo; Marks, Tobin J

    2006-10-17

    A series of bimetallic organo-group 4 "constrained geometry" catalysts and binuclear bisborane and bisborate cocatalysts have been synthesized to probe catalyst center-catalyst center cooperativity effects on olefin enchainment in homogenous olefin polymerization and copolymerization processes. Significant nuclearity effects are found versus mononuclear controls, and the effect can be correlated with metal-metal approach distances and ion pairing effects. Novel polymer structures can be obtained by using such binuclear catalyst/cocatalyst systems.

  12. Development and application of FI catalysts for olefin polymerization: unique catalysis and distinctive polymer formation.

    PubMed

    Makio, Haruyuki; Fujita, Terunori

    2009-10-20

    Catalysts contribute to the efficient production of chemicals and materials in almost all processes in the chemical industry. The polyolefin industry is one prominent example of the importance of catalysts. The discovery of Ziegler-Natta catalysts in the 1950s resulted in the production of high-density polyethylenes (PEs) and isotactic polypropylenes (iPPs). Since then, further catalyst development has led to the production of a new series of polyolefins, including linear low-density PEs, amorphous ethylene/1-butene copolymers, ethylene/propylene/diene elastomers, and syndiotactic PPs (sPPs). Polyolefins are now the most important and the most produced synthetic polymers. This Account describes a family of next-generation olefin polymerization catalysts (FI catalysts) that are currently being used in the commercial production of value-added olefin-based materials. An FI catalyst is a heteroatom-coordinated early transition metal complex that combines a pair of nonsymmetric phenoxy-imine [O(-), N] chelating ligands with a group 4 transition metal. The catalytically active species derived from FI catalysts is highly electrophilic and can assume up to five isomeric structures based on the coordination of the phenoxy-imine ligand. In addition, the accessibility of the ligands of the FI catalysts and their amenability to modification offers an opportunity for the design of diverse catalytic structures. FI catalysts exhibit many unique chemical characteristics: precise control over chain transfers (including highly controlled living ethylene and propylene polymerizations), extremely high selectivity for ethylene, high functional group tolerance, MAO- and borate-free polymerization catalysis, significant morphology polymer formation, controlled multimodal behavior, high incorporation ability for higher alpha-olefins and norbornene, and highly syndiospecific and isospecific polymerizations of both propylene and styrene. These reactions also occur with very high catalyst

  13. High-throughput approaches for the discovery and optimization of new olefin polymerization catalysts.

    PubMed

    Murphy, Vince; Bei, Xiaohong; Boussie, Thomas R; Brümmer, Oliver; Diamond, Gary M; Goh, Christopher; Hall, Keith A; Lapointe, Anne M; Leclerc, Margarete; Longmire, James M; Shoemaker, James A W; Turner, Howard; Weinberg, W Henry

    2002-01-01

    The discovery of new olefin polymerization catalysts is currently a time-intensive trial-and-error process with no guarantee of success. A fully integrated high-throughput screening workflow for the discovery of new catalysts for polyolefin production has been implemented at Symyx Technologies. The workflow includes the design of the metal-ligand libraries using custom-made computer software, automated delivery of metal precursors and ligands into the reactors using a liquid-handling robot, and a rapid primary screen that serves to assess the potential of each metalligand-activator combination as an olefin polymerization catalyst. "Hits" from the primary screen are subjected to secondary screens using a 48-cell parallel polymerization reactor. Individual polymerization reactions are monitored in real time under conditions that provide meaningful information about the performance capabilities of each catalyst. Rapid polymer characterization techniques support the primary and secondary screens. We have discovered many new and interesting catalyst classes using this technology.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

    DOEpatents

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

    2003-04-08

    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 {Cp*MRR'.sub.n }.sup.+ {A}.sup.- 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, and SnR".sub.3 containing groups (R"=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.

  16. Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

    DOEpatents

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

    2003-12-30

    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.

  17. Cyclopentadienyl-Containing Low-Valent Early Transition Metal Olefin Polymerization Catalysts

    DOEpatents

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

    2004-06-08

    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 {Cp*MRR'.sub.n }.sup.+ {A}.sup.- 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"=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.

  18. Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

    DOEpatents

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

    2007-01-09

    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 {Cp*MRR'.sub.n}.sup.+{A}.sup.- 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''=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.

  19. Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

    DOEpatents

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

    2006-10-10

    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 {Cp*MRR'.sub.n}.sup.+{A}.sup.- 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''=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.

  20. Mechanism of activation of a hafnium pyridyl-amide olefin polymerization catalyst: ligand modification by monomer.

    PubMed

    Froese, Robert D J; Hustad, Phillip D; Kuhlman, Roger L; Wenzel, Timothy T

    2007-06-27

    We have investigated the olefin polymerization mechanism of hafnium catalysts supported by a pyridyl-amide ligand with an ortho-metalated naphthyl group. Ethylene-alpha-olefin copolymers from these catalysts have broad molecular weight distributions that can be fit to a bimodal distribution. We propose a unique mechanism to explain this behavior involving monomer modification of the catalyst, which generates multiple catalyst species when multiple monomers are present. More specifically, we present evidence that the hafnium alkyl cation initially undergoes monomer insertion into the Hf-naphthyl bond, which permanently modifies the ligand to generate new highly active olefin polymerization catalysts. Under ethylene/octene copolymerization conditions, a plurality of new catalysts is formed in relative proportion to the respective monomer concentrations. Due to the asymmetry of the metal complex, two "ethylene-inserted" and eight "octene-inserted" isomers are possible, but it is a useful approximation to consider only one of each in the polymerization behavior. Consequently, gel permeation chromatography data for the polymers can be fit to a bimodal distribution having a continuous shift from a predominantly low molecular weight fraction to predominantly higher molecular weight fraction as [octene]/[ethylene] is increased. Theoretical calculations show that such insertions into the Hf-aryl bond have lower barriers than corresponding insertions into the Hf-alkyl bond. The driving forces for this insertion into the Hf-aryl bond include elimination of an eclipsing H-H interaction and formation of a stabilizing Hf-arene interaction. These new "monomer-inserted catalysts" have no beta-agostic interaction, very weak olefin binding, and olefin-insertion transition states which differ on the two sides by more than 4 kcal/mol. Thus, the barrier to site epimerization is very low and high polymerization rates are possible even when the chain wags prior to every insertion

  1. A sterically expanded "constrained geometry catalyst" for highly active olefin polymerization and copolymerization: an unyielding comonomer effect.

    PubMed

    Irwin, Levi J; Reibenspies, Joseph H; Miller, Stephen A

    2004-12-29

    The 14 A octamethyloctahydrodibenzofluorene moiety has been incorporated into a sterically expanded constrained geometry catalyst, Me2Si(eta1-C29H36)(eta1-N-tBu)ZrCl2.OEt2 (1). The solid-state structure suggests that the activated olefin polymerization catalyst is quite spatially accessible, rationalizing its extraordinary reactivity toward alpha-olefins. 1/MAO (MAO = methylaluminoxane) can be more reactive toward alpha-olefins than toward ethylene and exhibit activities that are linearly and continuously proportional to 4-methyl-1-pentene or 1-octene concentration in their copolymerizations with ethylene.

  2. Functional surface groups for single-site heterogeneous α-olefin polymerization catalysts

    NASA Astrophysics Data System (ADS)

    Iiskola, E. I.; Timonen, S.; Pakkanen, T. T.; Härkki, O.; Seppälä, J. V.

    1997-11-01

    A novel heterogeneous α-olefin polymerization catalyst is prepared by the immobilization of CpZrCl 3 on a chemically modified silica support. The surface modification of silica was carried out by utilizing the saturated gas-solid reactions of a silane coupling agent with a hydrocarbon spacer, Cp(CH 2) 3Si(OCH 2CH 3) 3, and a partially dehydroxylated silica. In gas-solid reactions all reactive surface hydroxyl groups were utilized in bonding the silane coupling agent on silica. The immobilization of CpZrCl 3 on the cyclopentadienyl surface formed on the silica was done using liquid-phase reactions. The prepared materials were characterized by FT-IR spectroscopy. The supported catalyst system has a high activity in ethylene polymerization and can be used to produce polyethylene with a narrow molecular weight distribution in the presence of methylaluminoxane. The catalytic activity was doubled when CpZrCl 3 was immobilized on the cyclopentadienyl surface of SiO 2 compared with the activity of CpZrCl 3 in homogeneous catalysis. However, the direct heterogenization of CpZrCl 3 onto unmodified silica produced a catalyst with a very low activity. The effect of surface modification reactions and the surface structure of a support on the catalyst performance is presented and discussed.

  3. Living olefin polymerization processes

    DOEpatents

    Schrock, R.R.; Baumann, R.

    1999-03-30

    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.

  4. Living olefin polymerization processes

    DOEpatents

    Schrock, Richard R.; Baumann, Robert

    1999-01-01

    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.

  5. Living olefin polymerization processes

    DOEpatents

    Schrock, Richard R.; Baumann, Robert

    2003-08-26

    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.

  6. Living olefin polymerization processes

    DOEpatents

    Schrock, Richard R.; Bauman, Robert

    2006-11-14

    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.

  7. Homo-polymerization of alpha-olefins and co-polymerization of higher alpha-olefins with ethylene in the presence of CpTiCl2(OC6H4X-p)/MAO catalysts (X = CH3, Cl).

    PubMed

    Skupinski, W; Nicinski, K; Jamanek, D; Wieczorek, Z

    2005-07-04

    Cyclopentadienyl-titanium complexes containing -OC6H4X ligands (X = Cl,CH3) activated with methylaluminoxane (MAO) were used in the homo-polymerization of ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in co-polymerization of ethylene with the alpha-olefins mentioned. The -X substituents exhibit different electron donor-acceptor properties, which is described by Hammett's factor (sigma). The chlorine atom is electron acceptor, while the methyl group is electron donor. These catalysts allow the preparation of polyethylene in a good yield. Propylene in the presence of the catalysts mentioned dimerizes and oligomerizes to trimers and tetramers at 25 degrees C under normal pressure. If the propylene pressure was increased to 7 atmospheres,CpTiCl2(OC6H4CH3)/MAO catalyst at 25 degrees gave mixtures with different contents of propylene dimers, trimers and tetramers. At 70 degrees C we obtained only propylene trimer. Using the catalysts with a -OC(6)H(4)Cl ligand we obtained atactic polymers with M(w) 182,000 g/mol (at 25 degrees C) and 100,000 g/mol (at 70 degrees C). The superior activity of the CpTiCl2(OC6H4Cl)/MAO catalyst used in polymerization of propylene prompted us to check its activity in polymerization of higher alpha-olefins (1-butene, 1-pentene, 1-hexene)and in co-polymerization of these olefins with ethylene. However, when homo-polymerization was carried out in the presence of this catalyst no polymers were obtained. Gas chromatography analysis revealed the presence of dimers. The activity of the CpTiCl2(OC6H4Cl)/MAO catalyst in the co-polymerization of ethylene with higher alpha-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

  8. Catalyst/cocatalyst nuclearity effects in single-site olefin polymerization. Significantly enhanced 1-octene and isobutene comonomer enchainment in ethylene polymerizations mediated by binuclear catalysts and cocatalysts.

    PubMed

    Li, Hongbo; Li, Liting; Marks, Tobin J; Liable-Sands, Louise; Rheingold, Arnold L

    2003-09-10

    This Communication describes the implementation of a new binuclear homometallic organotitanium "constrained geometry catalyst" (CGC), (mu-CH2CH2-3,3'){ (eta5-indenyl )[1-Me2Si (tBuN)](TiMe2)}2[EBICGC(TiMe2)2; Ti2], together with the bifunctional activators (Ph3C+)2[1,4-(C6F5)3BC6F4B(C6F5)3]2- (B2) and new bisborane 1,4-(C6F5)2BC6F4B(C6F5)2 (BN2) in ethylene + alpha-olefin copolymerization processes. Specifically examined are the comonomers 1-octene and poorly responsive isobutene. Large increases in comonomer enchainment efficiency into the polyethylene microstructure are observed versus the corresponding mononuclear catalyst [1-Me2Si(3-ethylindenyl)(tBuN)]TiMe2 (Ti1) + Ph3C+B(C6F5)4- (B1) or B(C6F5)3 (BN) under identical polymerization conditions. In ethylene + 1-octene copolymerization, 11 times more 1-octene incorporation is observed for Ti2 + B2 vs Ti1 + B1. In ethylene + isobutene copolymerization, 5 times more isobutene incorporation is observed for Ti2 + BN2 vs Ti1 + BN.

  9. Hafnocene-Based Olefin Polymerizations

    NASA Astrophysics Data System (ADS)

    Diesner, T.; Troll, C.; Rieger, B.

    Zirconocenes have been used for a long time in the field of olefin polymerization using MAO as cocatalyst. The equivalent hafnocenes were seldom used due to a lack of productivity while using MAO activation. In the last few years borane and borate activation has come into the focus of research for olefin polymerization. A variety of different hafnocenes were used to investigate the polymerization mechanism and the different cocatalysts.

  10. Organometallic polymerization catalysts

    SciTech Connect

    Waymouth, R.M.

    1993-12-31

    Well-defined transition metal catalysts have resulted in exciting new opportunities in polymer synthesis. The stereochemistry of vinyl polymers can be rationally controlled with choice of the appropriate catalysts. Studies with optically active catalyst precursors have revealed considerable information on the absolute stereochemistry of olefin polymerization and have led to the synthesis of novel chiral polyolefins. The development of homogeneous olefin metathesis catalysts has also led to a variety of well-defined new polymer structures with controlled molecular weight and molecular weight distribution. Recent advances in understanding the mechanisms and stereochemistry of homogeneous transition metal catalyzed polymerization will be discussed. The ability to control polymer structure through catalyst design presents exciting opportunities in the synthesis of {open_quotes}tailor-made{close_quotes} macromolecules.

  11. Theoretical investigation of the stereochemistry of the polymerization of. cap alpha. -olefins and dienes with the participation of Ziegler-Natta catalysts

    SciTech Connect

    Minsker, K.S.; Karpasas, M.M.

    1986-09-01

    The processes involved in the formation of the active polymerization sites in heterogeneous Ziegler-Natta catalysts have been investigated with consideration of the real structure of the components by the atom-atom potential method, the Monte-Carlo method, a modified diatomics-in-molecules method, and the CNDO/2 method with the aid of the available experimental facts. It has been shown that three types of bimetallic active sites (AS), which differ with respect to the spatial configuration of the coordination sphere, viz., AS-1, AS-2, and AS-3, form, depending on the electronic structure of the homogeneous component R /SUB n/ M, the ionic radius of M (M is a metal from groups I-III), and the unit-cell parameters of the heterogeneous component MeX /SUB m/ (Me is a transition metal from groups IV-VIII). Only the AS-1 sites are stereospecific in the polymerization of ..cap alpha..-olefins and 1,3-dienes (isotactic polyolefins and 1,4-trans-polydienes form); the AS-2 sites are nonstereospecific in the polymerization of ..cap alpha..-olefins, but they form stereoregular 1,4-cis-polydienes; the AS-3 sites are nonstereospecific in the polymerization of both ..cap alpha..-olefins and 1,3-dienes. The phenomenon of stereoregularization in the polymerization of ..cap alpha..-olefins and 1,3-dienes is determined by the steric and electrostatic factors.

  12. Influence of supports on gas-phase olefin polymerization over polymer-supported (n-BuCp)2-zirconium chloride/MAO catalysts

    NASA Astrophysics Data System (ADS)

    Hammawa, Hassan

    The influence of support properties on gas-phase olefin polymerization over polymer-supported (n-BuCp)2ZrCl2/MAO catalysts were investigated in a newly fabricated polymerization reactor with enhanced cooling. Inserting Kenics type static mixers into channels used for coolant flow enhanced the cooling efficiency of the new reactor; the coolant channels are drilled along the reactor wall. Good gas-phase temperature control was achieved in polymerization runs with maximum instantaneous rates up to 100 g-PE per hour. Polymerizations were typically run for 1 h at 80°C, 1.4 MPa and, for some runs, gas samples from the reactor were analyzed at 3 min intervals. The polymerization rate profiles are typically acceleration-decay type. Residual aluminum alkyls in the reactor suppressed the initial polymerization rates, but average activities often increased due to broadening of the activity profiles. This effect increased with the amount of aluminum alkyl and decreasing alkyl size as follows: TEA > TIBA > TNOA. Polymer-supported catalysts were prepared by sequentially contacting thermally treated supports with MAO and metallocene solutions followed by vacuum drying the suspensions. Low fragility supports resulted in catalysts that homopolymerized ethylene with low activity due to poor catalyst fragmentation. The product particles consisted of unfragmented catalyst core surrounded by loose polyethylene layer. The average ethylene homopolymerization activity of these catalysts 10--50 g PE/(g cat·h) increased 5--20 times when about 15 mol/m3 1-hexene was initially present in the gas-phase; the catalysts were completely fragmented during the copolymerization. Catalysts made with highly friable supports showed high activity during both ethylene, and ethylene/alpha-olefin polymerizations. 1-Hexene had less significant influence on activity than with the low friability supports under similar polymerization conditions. The presence of 7.5 mol/m3 1-hexene resulted in copolymers of

  13. [Synthetic and mechanistic investigation of olefin polymerization catalyzed by early transition metal compounds

    SciTech Connect

    Bercaw, J.E.

    1993-01-01

    During the second year we continued to prepare and characterize organoyttrium and organoscandium compounds for use as catalysts for polymerizing simple olefins and diolefins. Simple, one-component systems are being pursued, suitable for chain initiation, propagation, and termination studies. This document is divided into: dicarbollide derivatives of scandium as potential catalysts; design, synthesis, and characterization of the first isospecific [alpha] olefin polymerization catalysts; polymerization of [alpha] olefins and 1,5- hexadiene using organoscandium catalysts; and attempted preparations of diastereomeric Nb and Ta olefin/hydride and olefin/alkyl derivatives.

  14. Kinetic resolution of racemic α-olefins with ansa-zirconocene polymerization catalysts: Enantiomorphic site vs. chain end control

    PubMed Central

    Byers, Jeffery A.; Bercaw, John E.

    2006-01-01

    Copolymerization of racemic α-olefins with ethylene and propylene was carried out in the presence of enantiopure C1-symmetric ansa metallocene, {1,2-(SiMe2)2(η5-C5H-3,5-(CHMe2)2)(η5-C5H3)}ZrCl2 to probe the effect of the polymer chain end on enantioselection for the R- or S-α-olefin during the kinetic resolution by polymerization catalysis. Copolymerizations with ethylene revealed that the polymer chain end is an important factor in the enantioselection of the reaction and that for homopolymerization, chain end control generally works cooperatively with enantiomorphic site control. Results from propylene copolymerizations suggested that chain end control arising from a methyl group at the β carbon along the main chain can drastically affect selectivity, but its importance as a stereo-directing element depends on the identity of the olefin. PMID:17032768

  15. STIR: Redox-Switchable Olefin Polymerization Catalysis: Electronically Tunable Ligands for Controlled Polymer Synthesis

    DTIC Science & Technology

    2013-03-28

    REPORT Final Report: STIR: Redox-Switchable Olefin Polymerization Catalysis : Electronically Tunable Ligands for Controlled Polymer Synthesis 14...2211 15. SUBJECT TERMS Catalysis , Redox-Switchable, Polymerization, Polyolefins Brian K. Long University of Tennessee at Knoxville Office of Research...Polymerization Catalysis : Electronically Tunable Ligands for Controlled Polymer Synthesis Report Title ABSTRACT Olefin polymerization catalysts containing

  16. Ethylene polymerization on a SiH4-modified Phillips catalyst: detection of in situ produced α-olefins by operando FT-IR spectroscopy.

    PubMed

    Barzan, Caterina; Groppo, Elena; Quadrelli, Elsje Alessandra; Monteil, Vincent; Bordiga, Silvia

    2012-02-21

    Ethylene polymerization on a model Cr(II)/SiO(2) Phillips catalyst modified with gas phase SiH(4) leads to a waxy product containing a bimodal MW distribution of α-olefins (M(w) < 3000 g mol(-1)) and a highly branched polyethylene, LLDPE (M(w) ≈ 10(5) g mol(-1), T(m) = 123 °C), contrary to the unmodified catalyst which gives a linear and more dense PE, HDPE (M(w) = 86,000 g mol(-1) (PDI = 7), T(m) = 134 °C). Pressure and temperature resolved FT-IR spectroscopy under operando conditions (T = 130-230 K) allows us to detect α-olefins, and in particular 1-hexene and 1-butene (characteristic IR absorption bands at 3581-3574, 1638 and 1598 cm(-1)) as intermediate species before their incorporation in the polymer chains. The polymerization rate is estimated, using time resolved FT-IR spectroscopy, to be 7 times higher on the SiH(4)-modified Phillips catalyst with respect to the unmodified one.

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

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    2000-01-01

    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.

  18. Polymerization catalyst, production and use

    SciTech Connect

    Best, S.A.

    1987-01-06

    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.

  19. Catalytic production of olefin block copolymers via chain shuttling polymerization.

    PubMed

    Arriola, Daniel J; Carnahan, Edmund M; Hustad, Phillip D; Kuhlman, Roger L; Wenzel, Timothy T

    2006-05-05

    We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of alpha-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.

  20. Catalytic Production of Olefin Block Copolymers via Chain Shuttling Polymerization

    NASA Astrophysics Data System (ADS)

    Arriola, Daniel J.; Carnahan, Edmund M.; Hustad, Phillip D.; Kuhlman, Roger L.; Wenzel, Timothy T.

    2006-05-01

    We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of α-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.

  1. Polymerization catalyst, production and use

    SciTech Connect

    Best, S.A.

    1987-04-14

    A process is described for the polymerization of ethylene and alphaolefins having from 1 to 20 carbon atoms or 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 treating an inert support material in an inert solvent with (i) a dihydrocarbyl magnesium compound or a complex or mixture of an organic dihydrocarbyl magnesium compound and an aluminum compound, (ii) optionally an oxygen-containing compound which is an alcohol, ketone or aldehyde, (iii) a Group IIIa metal halide, (iv) at least one vanadium compound, and as the last step a second treatment with a Group IIIa metal halide.

  2. A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst.

    PubMed

    MacAdams, Leonard A; Buffone, Gerald P; Incarvito, Christopher D; Rheingold, Arnold L; Theopold, Klaus H

    2005-02-02

    A structurally characterized cationic chromium(III) alkyl featuring a bulky nacnac ligand catalyzes the polymerization of ethylene as well as the copolymerization of ethylene with alpha-olefins. This well-characterized homogeneous catalyst constitutes a structural as well as functional model of the widely used heterogeneous Phillips olefin polymerization catalyst.

  3. Thermally Stable, Latent Olefin Metathesis Catalysts

    PubMed Central

    Thomas, Renee M.; Fedorov, Alexey; Keitz, Benjamin K.

    2011-01-01

    Highly thermally stable N-aryl,N-alkyl N-heterocyclic carbene (NHC) ruthenium catalysts were designed and synthesized for latent olefin metathesis. These catalysts showed excellent latent behavior toward metathesis reactions, whereby the complexes were inactive at ambient temperature and initiated at elevated temperatures, a challenging property to achieve with second generation catalysts. A sterically hindered N-tert-butyl substituent on the NHC ligand of the ruthenium complex was found to induce latent behavior toward cross-metathesis reactions, and exchange of the chloride ligands for iodide ligands was necessary to attain latent behavior during ring-opening metathesis polymerization (ROMP). Iodide-based catalysts showed no reactivity toward ROMP of norbornene-derived monomers at 25 °C, and upon heating to 85 °C gave complete conversion of monomer to polymer in less than 2 hours. All of the complexes were very stable to air, moisture, and elevated temperatures up to at least 90 °C, and exhibited a long catalyst lifetime in solution at elevated temperatures. PMID:22282652

  4. [Synthetic and mechanistic investigation of olefin polymerization catalyzed by early transition metal compounds]. Progress report, Second year, 1 April 1992--31 March 1992

    SciTech Connect

    Bercaw, J.E.

    1993-08-01

    During the second year we continued to prepare and characterize organoyttrium and organoscandium compounds for use as catalysts for polymerizing simple olefins and diolefins. Simple, one-component systems are being pursued, suitable for chain initiation, propagation, and termination studies. This document is divided into: dicarbollide derivatives of scandium as potential catalysts; design, synthesis, and characterization of the first isospecific {alpha} olefin polymerization catalysts; polymerization of {alpha} olefins and 1,5- hexadiene using organoscandium catalysts; and attempted preparations of diastereomeric Nb and Ta olefin/hydride and olefin/alkyl derivatives.

  5. Polymerization Mechanism of α-Linear Olefin

    NASA Astrophysics Data System (ADS)

    Xing, Wen-guo; Zhang, Chang-qiao; Yu, Ping; Liu, Cheng-bu; Wei, Yun-he

    2010-02-01

    The density functional theory on the level of B3LYP/6-31G was empolyed to study the chain growth mechanism in polymerization process of α-linear olefin in TiCl3/AlEt2Cl catalytic system to synthesize drag reduction agent. Full parameter optimization without symmetry restrictions for reactants, products, the possible transition states, and intermediates was calculated. Vibration frequency was analyzed for all of stagnation points on the potential energy surface at the same theoretical level. The internal reaction coordinate was calculated from the transition states to reactants and products respectively. The results showed as follows: (i) Coordination compounds were formed on the optimum configuration of TiCl3/AlEt2Cl. (ii) The transition states were formed. The energy difference between transition states and the coordination compounds was 40.687 kJ/mol. (iii) Double bond opened and Ti-C(4) bond fractured, and the polymerization was completed. The calculation results also showed that the chain growth mechanism did not essentially change with the increase of carbon atom number of α-linear olefin. From the relationship between polymerization activation energy and carbon atom number of the α-linear olefin, it can be seen that the α-linear olefin monomers with 6-10 carbon atoms had low activation energy and wide range. It was optimum to synthesize drag reduction agent by polymerization.

  6. Bimetallic complexes and polymerization catalysts therefrom

    DOEpatents

    Patton, Jasson T.; Marks, Tobin J.; Li, Liting

    2000-11-28

    Group 3-6 or Lanthanide metal complexes possessing two metal centers, catalysts derived therefrom by combining the same with strong Lewis acids, Bronsted acid salts, salts containing a cationic oxidizing agent or subjected to bulk electrolysis in the presence of compatible, inert non-coordinating anions and the use of such catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers are disclosed.

  7. Polymerization catalyst, production and use

    SciTech Connect

    Best, S.A.; Etherton, B.P.; Kaus, M.J.

    1989-09-12

    This patent describes a polymerization process. It comprises polymerizing ethylene, alpha-olefins of 3 to 20 carbon atoms or mixtures of ethylene and the alpha-olefins in the presence of a catalyst system. The system comprising: an organo aluminum compound of the formula AIR'''/sub eta/X'''/sub 3-eta/ wherein R''' is hydrogen, hydrocarbyl, or substituted hydrocarbyl having from 1 to 20 carbon atoms, X''' is a halogen and eta is a number from 1 to 3, and a transition metal-containing catalyst component. The component comprising the solid reaction product obtained by treating an inert solid support material in an inert solvent with an organonmetallic compound represented by the formula R/sup 1/MgR/sup 2/ wherein R/sup 1/ and R/sup 2/, which may be the same of different,contain 1 to 20 carbon atoms and are selected from alkyl group, aryl group, cycloalkyl group, aralkyl group, alkadienyl group of group; an alcohol; an acyl halide; a titanium halide; Cl/sub 2/, and prereducing the transition metal-containing product with an aluminum alkyl, with the proviso that the first two ingredients can be added to the inert solid simultaneously, as the reaction product of the first two steps or treatment with step two immediately precedes treatment with step one.

  8. Polymerization catalyst, production and use

    SciTech Connect

    Best, S.A.

    1987-01-06

    A process is described for the 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 in the presence of a catalyst system comprising (a) an organo aluminum compound of the formula ALR''/sub n/X''/sub 3-n/ wherein R is hydrogen or a hydrocarbyl group having from 1 to 20 carbon atoms, X is halogen and is a number from 1 to 3, and (b) a transition metal containing catalyst component comprising the solid reaction product obtained by treating an inert solid support material in an inert solvent. This is done sequentially with (A) an organometallic compounds of a Group IIa, IIb or IIIa metal wherein all the metal valencies are satisfied with a hydrocarbon group, (B) an oxygen containing compound selected from ketones, aldehydes, alcohols or mixtures thereof, (C) an acyl halide, (D) at least one transition metal compound of a Group IVb, Vb, VIb or VIII metal, and (E) a group IIIa metal hydrocarbyl dihalide.

  9. Polymerization catalyst, production and use

    SciTech Connect

    Best, S.A.

    1987-01-06

    A process is described for the 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 in the presence of a catalyst system comprising (a) an organo aluminum compound of the formula AIR''/sub n/X''/sub 3-n/ wherein R'' is hydrogen or a hydrocarbyl group having from 1 to 20 carbon atoms, X is halogen and n is a number from 1 to 3, and (B) a transition metal containing catalyst component comprising the solid reaction product obtained by treating an inert solid support material in an inert solvent. This is done sequentially with, optionally (A) Cl/sub 2/, Br/sub 2/, an interhalogen or mixtures thereof, (B) an organometallic compound of a Group IIa, IIb or IIIa metal wherein all the metal valencies are satisfied with a hydrocarbon group, (C) an oxygen containing compound selected from ketones, aldehydes, alcohols or mixtures thereof, (D) an acyl halide, (E) at least one transition metal compound of a Group IVb, VB, VIb or VIII metal, and (F) Cl/sub 2/, Br/sub 2/, an interhalogen or mixtures thereof.

  10. Polymerization catalyst, production and use

    SciTech Connect

    Best, S.A.

    1987-01-06

    A process is described for the 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 in the presence of a catalyst system comprising (a) an organo aluminum compounds of the formula AIR''/sub n/X''/sub 3-n/ wherein R'' is hydrogen or a hydrocarbyl group having from 1 to 20 carbon atoms, X is halogen and n is a number from 1 to 3, and (b) a transition metal containing catalyst component comprising the solid reaction product obtained by treating an inert solid support material in an inert solvent. This is done sequentially with (A) an organometallic compound of a Group IIa, IIb, or IIIa metal wherein all the metal valencies are satisfied with a hydrocarbon group, optionally (B) an oxygen containing compound selected from ketones, aldehydes, alcohols, siloxanes or mixtures thereof, (C) at least one transition metal compound of a Group IVb, Vb, VIb or VIII metal, and (D) a group IIIa metal hydrocarbyl dihalide.

  11. Photochemical preparation of olefin addition catalysts

    NASA Technical Reports Server (NTRS)

    Gray, Harry B. (Inventor); Rembaum, Alan (Inventor); Gupta, Amitava (Inventor)

    1978-01-01

    Novel polymer supported catalysts are prepared by photo-irradiation of low valent transition metal compounds such as Co.sub.2 (CO).sub.8, Rh.sub.4 (CO).sub.12 or Ru.sub.3 (CO).sub.12 in the presence of solid polymers containing amine ligands such as polyvinyl pyridine. Hydroformylation of olefins to aldehydes at ambient conditions has been demonstrated.

  12. Unsupported catalysts in the production of olefins

    SciTech Connect

    Kreuter, W.; Wernicke, H.

    1980-07-01

    A description is given of a process for the production of olefins in two stages wherein, in the first stage, a heavy petroleum fraction is hydrogenated essentially in the liquid phase in the presence of hydrogen and a hydrogenation catalyst and, in the second stage, the thus-hydrogenated fraction is subjected to thermal cracking in the vapor phase in the presence of steam, the improvement which comprises employing as the hydrogenation catalyst a support-free catalyst consisting essentially of at least one of Co-Mo, Ni-Mo, Co-Mo sulfide, Ni-Co-Mo sulfide, Ni-Mo sulfide, Ni-Co sulfide, Co-mo oxide, Ni-Co-Mo oxide, Ni-Mo oxide, Ni-Co oxide, Ni-W sulfide, Ni-W oxide, or organometallic complexes of aforementioned metallic mixtures.

  13. Process and catalyst for carbonylating olefins

    DOEpatents

    Zoeller, J.R.

    1998-06-02

    Disclosed is an improved catalyst system and process for preparing aliphatic carbonyl compounds such as aliphatic carboxylic acids, alkyl esters of aliphatic carboxylic acids and anhydrides of aliphatic carboxylic acids by carbonylating olefins in the presence of a catalyst system comprising (1) a first component selected from at least one Group 6 metal, i.e., chromium, molybdenum, and/or tungsten and (2) a second component selected from at least one of certain halides and tertiary and quaternary compounds of a Group 15 element, i.e., nitrogen, phosphorus and/or arsenic, and (3) as a third component, a polar, aprotic solvent. The process employing the improved catalyst system is carried out under carbonylating conditions of pressure and temperature discussed herein. The process constitutes and improvement over known processes since it can be carried out at moderate carbonylation conditions without the necessity of using an expensive noble metal catalyst, volatile, toxic materials such as nickel tetracarbonyl, formic acid or a formate ester. Further, the addition of a polar, aprotic solvent to the catalyst system significantly increases, or accelerates, the rate at which the carbonylation takes place.

  14. Process and catalyst for carbonylating olefins

    DOEpatents

    Zoeller, Joseph Robert

    1998-06-02

    Disclosed is an improved catalyst system and process for preparing aliphatic carbonyl compounds such as aliphatic carboxylic acids, alkyl esters of aliphatic carboxylic acids and anhydrides of aliphatic carboxylic acids by carbonylating olefins in the presence of a catalyst system comprising (1) a first component selected from at least one Group 6 metal, i.e., chromium, molybdenum, and/or tungsten and (2) a second component selected from at least one of certain halides and tertiary and quaternary compounds of a Group 15 element, i.e., nitrogen, phosphorus and/or arsenic, and (3) as a third component, a polar, aprotic solvent. The process employing the improved catalyst system is carried out under carbonylating conditions of pressure and temperature discussed herein. The process constitutes and improvement over known processes since it can be carried out at moderate carbonylation conditions without the necessity of using an expensive noble metal catalyst, volatile, toxic materials such as nickel tetracarbonyl, formic acid or a formate ester. Further, the addition of a polar, aprotic solvent to the catalyst system significantly increases, or accelerates, the rate at which the carbonylation takes place.

  15. A Ruthenium Catalyst for Olefin Metathesis Featuring an Anti-Bredt N-Heterocyclic Carbene Ligand

    PubMed Central

    Martin, David; Marx, Vanessa M.

    2016-01-01

    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. PMID:27594819

  16. A chameleon catalyst for nonheme iron-promoted olefin oxidation.

    PubMed

    Iyer, Shyam R; Javadi, Maedeh Moshref; Feng, Yan; Hyun, Min Young; Oloo, Williamson N; Kim, Cheal; Que, Lawrence

    2014-11-18

    We report the chameleonic reactivity of two nonheme iron catalysts for olefin oxidation with H2O2 that switch from nearly exclusive cis-dihydroxylation of electron-poor olefins to the exclusive epoxidation of electron-rich olefins upon addition of acetic acid. This switching suggests a common precursor to the nucleophilic oxidant proposed to Fe(III)-η(2)-OOH and electrophilic oxidant proposed to Fe(V)(O)(OAc), and reversible coordination of acetic acid as a switching pathway.

  17. Polymerization catalysts containing electron-withdrawing amide ligands

    DOEpatents

    Watkin, John G.; Click, Damon R.

    2002-01-01

    The present invention describes methods of making a series of amine-containing organic compounds which are used as ligands for group 3-10 and lanthanide metal compounds. The ligands have electron-withdrawing groups bonded to them. The metal compounds, when combined with a cocatalyst, are catalysts for the polymerization of olefins.

  18. Multinuclear group 4 catalysis: olefin polymerization pathways modified by strong metal-metal cooperative effects.

    PubMed

    McInnis, Jennifer P; Delferro, Massimiliano; Marks, Tobin J

    2014-08-19

    Polyolefins are produced today catalytically on a vast scale, and the manufactured polymers find use in everything from artificial limbs and food/medical packaging to automotive and electrical components and lubricants. Although polyolefin monomers are typically cheap (e.g., ethylene, propylene, α-olefins), the resulting polymer properties can be dramatically tuned by the particular polymerization catalyst employed, and reflect a rich interplay of macromolecular chemistry, materials science, and physics. For example, linear low-density polyethylene (LLDPE), produced by copolymerization of ethylene with linear α-olefin comonomers such as 1-butene, 1-hexene, or 1-octene, has small but significant levels of short alkyl branches (C2, C4, C6) along the polyethylene backbone, and is an important technology material due to outstanding rheological and mechanical properties. In 2013, the total world polyolefin production was approximately 211 million metric tons, of which about 11% was LLDPE. Historically, polyolefins were produced using ill-defined but highly active heterogeneous catalysts composed of supported groups 4 or 6 species (usually halides) activated by aluminum alkyls. In 1963, Karl Ziegler and Giulio Natta received the Nobel Prize for these discoveries. Beginning in the late 1980s, a new generation of group 4 molecule-based homogeneous olefin polymerization catalysts emerged from discoveries by Walter Kaminsky, a team led by James Stevens at The Dow Chemical Company, this Laboratory at Northwestern University, and a host of talented groups in Germany, Italy, Japan, the United Kingdom, and the United States. These new "single-site" catalysts and their activating cocatalysts were far better defined and more rationally tunable in terms of structure, mechanism, thermodynamics, and catalyst activity and selectivity than ever before possible. An explosion of research advances led to new catalysts, cocatalysts, deeper mechanistic understanding of both the

  19. Development of group IV molecular catalysts for high temperature ethylene-α-olefin copolymerization reactions.

    PubMed

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

    2015-07-21

    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

  20. Observation of different catalytic activity of various 1-olefins during ethylene/1-olefin copolymerization with homogeneous metallocene catalysts.

    PubMed

    Wannaborworn, Mingkwan; Praserthdam, Piyasan; Jongsomjit, Bunjerd

    2011-01-07

    This research aimed to investigate the copolymerization of ethylene and various 1-olefins. The comonomer lengths were varied from 1-hexene (1-C₆) up to 1-octadecene (1-C₁₈) in order to study the effect of comonomer chain length on the activity and properties of the polymer in the metallocene/MAO catalyst system. The results indicated that two distinct cases can be described for the effect of 1-olefin chain length on the activity. Considering the short chain length comonomers, such as 1-hexene, 1-octene and 1-decene, it is obvious that the polymerization activity decreased when the length of comonomer was higher, which is probably due to increased steric hindrance at the catalytic center hindering the insertion of ethylene monomer to the active sites, hence, the polymerization rate decreased. On the contrary, for the longer chain 1-olefins, namely 1-dodecene, 1-tetradecene and 1-octadecene, an increase in the comonomer chain length resulted in better activity due to the opening of the gap aperture between C(p)(centroid)-M-C(p)-(centroid), which forced the coordination site to open more. This effect facilitated the polymerization of the ethylene monomer at the catalytic sites, and thus, the activity increased. The copolymers obtained were further characterized using thermal analysis, X-ray diffraction spectroscopy and ¹³C-NMR techniques. It could be seen that the melting temperature and comonomer distribution were not affected by the 1-olefin chain length. The polymer crystallinity decreased slightly with increasing comonomer chain length. Moreover, all the synthesized polymers were typical LLDPE having random comonomer distribution.

  1. Dinickel Bisphenoxyiminato Complexes for the Polymerization of Ethylene and α-Olefins

    PubMed Central

    Radlauer, Madalyn; Day, Michael W.; Agapie, Theodor

    2012-01-01

    Dinuclear nickelphenoxyiminato olefin polymerization catalysts based on rigid p-terphenyl frameworks are reported. Permethylation of the central arene of the terphenyl unit and oxygen substitution of the peripheral rings ortho to the aryl-aryl linkages blocks rotation around these linkages allowing atropisomers of the ligand to be isolated. The corresponding syn and anti dinickel complexes (25-s and 25-a) were synthesized and characterized by single crystal X-ray diffraction. These frameworks limit the relative movement of the metal centers restricting the metal-metal distance. Kinetics studies of isomerization of a ligand precursor (7-a) allowed the calculation of the activation parameters for the isomerization process (ΔH‡ = 28.0 ± 0.4 kcal×mol−1 and ΔS‡ = −12.3 ± 0.4 cal×mol−1×K−1). The reported nickel complexes are active for ethylene polymerization [TOF up to 3700 (mol C2H4)×(mol Ni)−1×h−1] and ethylene/α-olefin copolymerization. Only methyl branches are observed in the polymerization of ethylene, while α-olefins are incorporated without apparent chain walking. These catalysts are active in the presence of polar additives and in neat tetrahydrofuran. The syn and anti isomers differ in polymerization activity and polymer degree of branching and molecular weight. For comparison, a series of mononuclear nickel complexes (26, 27-s, 27-a, 28, 30) was prepared and studied. The effects of structure and catalyst nuclearity on reactivity are discussed. PMID:22711966

  2. [UV/Visible spectroscopic study of the beta-diketonate zirconium active species for olefin polymerization].

    PubMed

    Yang, Min; Wang, Lu-Hai; Liu, Pan-Ge; Ren, He-Gang; Liu, Bin-Yuan; Yan, Wei-Dong

    2010-06-01

    The method of UV/Visible absorption spectroscopy for olefin catalytic system was introduced in this paper, whose testing condition was much closer to the polymerization conditions. The actions of olefin polymerization catalyst (dbm)2 ZrCl2 with cocatalyst AlEt2 Cl (or MAO) were investigated by UV/visible absorption spectroscopy at atmosphere temperature. It was shown that the UV/Visible main absorption band of the zirconocenium, which can be related to the ligand to metal charge transfer bands (LMCT), varies greatly upon incremental addition of AlEt2 Cl or MAO. For the low molar ratios of Al/Zr in the catalytic system, there was the substitution of an electron withdrawing chlorine atom by a donating alkyl group. Then a hypsochromic shift of the initial catalyst absorption band, corresponding to the monomethylation of the catalyst, was observed in each catalytic system (dbm)2 ZrCl2/AlEt2 Cl (or (dbm)2 ZrCl2/MAO). On the contrary, further addition of AlEt2 Cl (or MAO) was accompanied by a continuous bathochromic shift of the maximal wavelength, which corresponding to the formation of more dissociated ionic active species. Then, there would be a coordination of monomer to the ionic active species.

  3. Catalyst system for the polymerization of alkenes to polyolefins

    DOEpatents

    Miller, Stephen A.; Bercaw, John E.

    2002-01-01

    The invention provides metallocene catalyst systems for the controlled polymerization of alkenes to a wide variety of polyolefins and olefin coplymers. Catalyst systems are provided that specifically produce isotactic, syndiotactic and steroblock polyolefins. The type of polymer produced can be controlled by varying the catalyst system, specifically by varying the ligand substituents. Such catalyst systems are particularly useful for the polymerization of polypropylene to give elastomeric polypropylenes. The invention also provides novel elastomeric polypropylene polymers characterized by dyad (m) tacticities of about 55% to about 65%, pentad (mmmm) tacticities of about 25% to about 35%, molecular weights (M.sub.w)in the range of about 50,000 to about 2,000,000, and have mmrm+rrmr peak is less than about 5%.

  4. Catalyst system for the polymerization of alkenes to polyolefins

    DOEpatents

    Miller, Stephen A.; Bercaw, John E.

    2004-02-17

    The invention provides metallocene catalyst systems for the controlled polymerization of alkenes to a wide variety of polyolefins and olefin coplymers. Catalyst systems are provided that specifically produce isotactic, syndiotactic and steroblock polyolefins. The type of polymer produced can be controlled by varying the catalyst system, specifically by varying the ligand substituents. Such catalyst systems are particularly useful for the polymerization of polypropylene to give elastomeric polypropylenes. The invention also provides novel elastomeric polypropylene polymers characterized by dyad (m) tacticities of about 55% to about 65%, pentad (mmmm) tacticities of about 25% to about 35%, molecular weights (M.sub.W) in the range of about 50,000 to about 2,000,000, and have mmrm+rrmr peak is less than about 5%.

  5. Effects of vanadium and zinc promotion on the olefin selectivity of iron Fischer-Tropsch catalysts

    SciTech Connect

    Saglam, M.

    1989-02-01

    The aim in most of the studies on Fischer-Tropsch synthesis has been the selective production of olefins, which are the raw materials of petrochemical industry. In this study, the effects of V and Zn addition, separately or together in the form of their oxides, to Fe catalysts obtained through precipitation on the olefin selectivity of the catalysts have been investigated. The experiments have been done in a fixed-bed reactor at different temperatures and pressures with various ratios of H/sub 2//CO. The addition of V separately (catalyst 2) or together with Zn (catalyst 1) has greatly increased the olefin selectivity of Fe catalyst. So the amount of olefin in hydrocarbon fractions has reached over 80%. Besides, the ..cap alpha..-olefin parts in olefin fractions have gone over 90%. But the addition of Zn separately has been less effective on the olefin selectivity of the catalyst.

  6. Integrated process and dual-function catalyst for olefin epoxidation

    DOEpatents

    Zhou, Bing; Rueter, Michael

    2003-01-01

    The invention discloses a dual-functional catalyst composition and an integrated process for production of olefin epoxides including propylene oxide by catalytic reaction of hydrogen peroxide from hydrogen and oxygen with olefin feeds such as propylene. The epoxides and hydrogen peroxide are preferably produced simultaneously in situ. The dual-functional catalyst comprises noble metal crystallites with dimensions on the nanometer scale (on the order of <1 nm to 10 nm), specially dispersed on titanium silicalite substrate particles. The dual functional catalyst catalyzes both the direct reaction of hydrogen and oxygen to generate hydrogen peroxide intermediate on the noble metal catalyst surface and the reaction of the hydrogen peroxide intermediate with the propylene feed to generate propylene oxide product. Combining both these functions in a single catalyst provides a very efficient integrated process operable below the flammability limits of hydrogen and highly selective for the production of hydrogen peroxide to produce olefin oxides such as propylene oxide without formation of undesired co-products.

  7. Enantioselective Iodolactonization of Disubstituted Olefinic Acids Using a Bifunctional Catalyst

    PubMed Central

    Fang, Chao; Paull, Daniel H.; Hethcox, J. Caleb; Shugrue, Christopher R.; Martin, Stephen F.

    2012-01-01

    The enantioselective iodolactonizations of a series of diversely-substituted olefinic carboxylic acids are promoted by a BINOL-derived, bifunctional catalyst. Reactions involving 5-alkyl- and 5-aryl-4(Z)-pentenoic acids and 6-alkyl- and 6-aryl-5(Z)-hexenoic acids provide the corresponding γ- and δ-lactones having stereogenic C–I bonds in excellent yields and >97:3 er. Significantly, this represents the first organocatalyst that promotes both bromo- and iodolactonization with high enantioselectivities. The potential of this catalyst to induce kinetic resolutions of racemic unsaturated acids is also demonstrated. PMID:23199100

  8. Syngas to olefins via dimethyl ether over zeolite catalysts

    SciTech Connect

    Lee, B.G.; Sardesai, A.; Lee, S.

    1998-12-31

    Coal or natural gas-based syngas can be converted to dimethyl ether (DME) in a dual catalytic, single-stage liquid phase process. The process described here converts dimethyl ether to lower olefins, such as ethylene, propylene, and butenes. Thus, a novel process of producing olefins from syngas via dimethyl ether has been introduced. The process feasibility of dimethyl ether conversion has been evaluated and the range of products of this process has also been identified. The effect of operating parameters and catalyst characteristics on product selectivity has been studied. The superior process advantages as well as its competitive economics quite clearly identify this process to be quite promising when conducted on an industrial scale.

  9. A unique palladium catalyst for efficient and selective alkoxycarbonylation of olefins with formates.

    PubMed

    Fleischer, Ivana; Jennerjahn, Reiko; Cozzula, Daniela; Jackstell, Ralf; Franke, Robert; Beller, Matthias

    2013-03-01

    Forget about CO! Carbonylations are among the most important homogeneously catalyzed reactions in the chemical industry, but typically require carbon monoxide. Instead, straightforward and efficient alkoxycarbonylations of olefins can proceed with alkyl formates in the presence of a specific palladium catalyst. Aromatic, terminal aliphatic, and internal olefins are carbonylated to give industrially important linear esters at low catalyst loadings.

  10. Phenolate constrained geometry polymerization catalyst and method for preparing

    DOEpatents

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

    1999-01-05

    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.

  11. Phenolate constrained geometry polymerization catalyst and method for preparing

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    1999-01-01

    The subject invention involves a method of preparing and the constrained geometry catalyst thereby prepared of the general formula Ar'R4(O)Ar"R'.sub.4 M(CH.sub.2 Ph).sub.2 where Ar' is a phenyl or naphthyl group; Ar" is a cyclopentadienyl or indenyl group, R and R' are H or alkyl substituents (C.ltoreq.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.

  12. Biphasic enantioselective olefin epoxidation using Tropos dibenzoazepinium catalysts.

    PubMed

    Vachon, Jérôme; Pérollier, Céline; Monchaud, David; Marsol, Claire; Ditrich, Klaus; Lacour, Jérôme

    2005-07-22

    Several novel chiral iminium TRISPHAT [tris(tetrachlorobenzenediolato)phosphate(V)] salts combining a diphenylazepinium core, chiral exocyclic appendages, and lipophilic counterions have been prepared and tested in biphasic enantioselective olefin epoxidation conditions. Interestingly, the iminium salts derived from commercially available (S)- or (R)-1,2,2-trimethylpropylamine can display efficiency similar to those made from L-acetonamine. Variable-temperature NMR spectroscopy (VT-NMR) and circular dichroism (CD) experiments were performed in search of a correlation between good enantioselectivity in the products and high diastereomeric control of the biphenyl axial chirality of the catalysts.

  13. Ruthenium olefin metathesis catalysts featuring unsymmetrical N-heterocyclic carbenes.

    PubMed

    Paradiso, Veronica; Bertolasi, Valerio; Costabile, Chiara; Grisi, Fabia

    2016-01-14

    New ruthenium Grubbs' and Hoveyda-Grubbs' second generation catalysts bearing N-alkyl/N-isopropylphenyl N-heterocyclic carbene (NHC) ligands with syn or anti backbone configuration were obtained and compared in model olefin metathesis reactions. Different catalytic efficiencies were observed depending on the size of the N-alkyl group (methyl or cyclohexyl) and on the backbone configuration. The presence of an N-cyclohexyl substituent determined the most significant reactivity differences between catalysts with syn or anti phenyl groups on the backbone. In particular, anti catalysts proved highly efficient, especially in the ring-closing metathesis (RCM) of encumbered diolefins, while syn catalysts showed low efficiency in the RCM of less hindered diolefins. This peculiar behavior, rationalized through DFT studies, was found to be related to the high propensity of these catalysts to give nonproductive metathesis events. Enantiopure anti catalysts were also tested in asymmetric metathesis reactions, where moderate enantioselectivities were observed. The steric and electronic properties of unsymmetrical NHCs with the N-cyclohexyl group were then evaluated using the corresponding rhodium complexes. While steric factors proved unimportant for both syn and anti NHCs, a major electron-donating character was found for the unsymmetrical NHC with anti phenyl substituents on the backbone.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  15. Half-sandwich rare-earth-catalyzed olefin polymerization, carbometalation, and hydroarylation.

    PubMed

    Nishiura, Masayoshi; Guo, Fang; Hou, Zhaomin

    2015-08-18

    -site catalysts. This Account is intended to give an overview of our recent studies on organo rare-earth catalysis, in particular the synthesis and application of half-sandwich rare-earth alkyl complexes bearing monocyclopentadienyl ligands for olefin polymerization, carbometalation, and hydroarylation. Treatment of half-sandwich rare-earth dialkyl complexes having the general formula CpMR2 with an equimolar amount of an appropriate borate compound such as [Ph3C][B(C6F5)4] can generate the corresponding cationic monoalkyl species, which serve as excellent single-site catalysts for the polymerization and copolymerization of a wide range of olefin monomers such as ethylene, 1-hexene, styrene, conjugated and nonconjugated dienes, and cyclic olefins. The cationic half-sandwich rare-earth alkyl complexes can also catalyze the regio- and stereoselective alkylative alumination of alkenes and alkynes through insertion of the unsaturated C-C bond into the metal-alkyl bond followed by transmetalation between the resulting new alkyl or alkenyl species and an alkylaluminum compound. Moreover, a combination of deprotonative C-H bond activation of appropriate organic compounds such as anisoles and pyridines by the rare-earth alkyl species and insertion of alkenes into the resulting new metal-carbon bond can lead to catalytic C-H bond alkylation of the organic substrates. Most of these transformations are unique to the rare-earth catalysts with selectivity and functional group tolerance different from those of late-transition-metal catalysts.

  16. Catalyst for converting synthesis gas to light olefins

    DOEpatents

    Rao, V. Udaya S.; Gormley, Robert J.

    1982-01-01

    A catalyst and process for making same useful in the catalytic hydrogenation of carbon monoxide in which a silicalite support substantially free of aluminum is soaked in an aqueous solution of iron and potassium salts wherein the iron and potassium are present in concentrations such that the dried silicalite has iron present in the range of from about 5 to about 25 percent by weight and has potassium present in an amount not less than about 0.2 percent by weight, and thereafter the silicalite is dried and combined with amorphous silica as a binder for pellets, the catalytic pellets are used to convert synthesis gas to C.sub.2 -C.sub.4 olefins.

  17. Molybdenum chloride catalysts for Z-selective olefin metathesis reactions

    NASA Astrophysics Data System (ADS)

    Koh, Ming Joo; Nguyen, Thach T.; Lam, Jonathan K.; Torker, Sebastian; Hyvl, Jakub; Schrock, Richard R.; Hoveyda, Amir H.

    2017-01-01

    The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.

  18. Molybdenum chloride catalysts for Z-selective olefin metathesis reactions.

    PubMed

    Koh, Ming Joo; Nguyen, Thach T; Lam, Jonathan K; Torker, Sebastian; Hyvl, Jakub; Schrock, Richard R; Hoveyda, Amir H

    2017-02-02

    The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.

  19. Ruthenium carbonyl catalyst supported on ceric oxide for preparation of olefins from synthesis gas

    DOEpatents

    Pierantozzi, R.

    1985-04-02

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  20. Ruthenium carbonyl catalyst supported on ceric oxide for preparation of olefins from synthesis gas

    DOEpatents

    Pierantozzi, Ronald

    1985-01-01

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  1. FINAL TECHNICAL REPORT Synthetic, Structural and Mechanistic Investigations of Olefin Polymerization Catalyzed by Early Transition Metal Compounds

    SciTech Connect

    Bercaw, John E.

    2014-05-23

    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.

  2. Neutral bimetallic transition metal phenoxyiminato catalysts and related polymerization methods

    DOEpatents

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

    2012-08-07

    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.

  3. Self-healing polymers---The importance of choosing an adequate healing monomer, and the olefin metathesis polymerization of agricultural oils

    NASA Astrophysics Data System (ADS)

    Mauldin, Timothy C.

    Modern society's immense and ill-fated reliance on petrochemical-based polymeric materials will likely necessitate a shift in polymer production paradigms in the near future. The work presented herein attempts to address this issue via a two-pronged approach. First, efforts to improve the duration of composite materials by incorporation of a self-healing function are discussed, the fruitful application of which can potentially reduce or eliminate the massive carbon footprints associated with the repair/replacement of damaged materials. And second, polymeric materials derived predominately from natural and renewable feedstock---namely vegetable oils---are developed. Early microcapsule-based self-healing materials utilized dicyclopentadiene-filled microcapsules and Grubbs' olefin metathesis catalyst to initiate the healing mechanism. However, the patent-protected catalyst, made from the precious metal ruthenium and sometimes costly ligands, will likely never be inexpensive and therefore limit large-scale applications. Hence, clever approaches to reduce the healing catalyst loading in self-healing polymers are of great interest. To this end, our efforts have revolved around solving the problem of the relatively inefficient use of Grubbs' catalyst during the healing mechanism. Given that the mismatch of the olefin metathesis polymerization and Grubbs' catalyst dissolution (in monomer) kinetics is a known cause of this inefficient use of the catalyst, we attempted to tune the "latency" (i.e. pot life) of the olefin metathesis polymerization to ensure more complete dissolution of catalyst in monomer. In an alternative approach to improving efficient catalyst dissolution, we developed a simple model to predict relative dissolution rates of Grubbs' catalyst in a small library of healing monomers. This model was shown experimentally to be able to aid in the selection of, for example, reactive monomer additives that can yield impressive improvements in catalyst dissolution

  4. A highly effective cobalt catalyst for olefin aziridination with azides: hydrogen bonding guided catalyst design.

    PubMed

    Ruppel, Joshua V; Jones, Jess E; Huff, Chelsea A; Kamble, Rajesh M; Chen, Ying; Zhang, X Peter

    2008-05-15

    [Co(P1)], which was designed on the basis of potential hydrogen-bonding interactions in the metal-nitrene intermediate, is a highly active aziridination catalyst with azides. [Co(P1)] can effectively aziridinate various aromatic olefins with arylsulfonyl azides under mild conditions, forming sulfonylated aziridines in excellent yields. The Co-based system enjoys several attributes associated with the relatively low cost of cobalt and the wide accessibility of arylsulfonyl azides. Furthermore, it generates stable dinitrogen as the only byproduct.

  5. Ruthenium-based olefin metathesis catalysts bearing pH-responsive ligands: External control of catalyst solubility and activity

    NASA Astrophysics Data System (ADS)

    Balof, Shawna Lynn

    2011-12-01

    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

  6. Microporous and mesoporous ZSM-5 catalyst for catalytic cracking of C5 raffinate to light olefins.

    PubMed

    Lee, Joongwon; Hong, Ung Gi; Hwang, Sunhwan; Youn, Min Hye; Song, In Kyu

    2014-11-01

    ZSM5 catalysts (PAM(X)-ZSM5) with micropores and mesopores were prepared using polyacrylamide (PAM) as a soft template at different PAM content (X = 0, 0.12, 0.25, 0.53, 0.64, and 0.78 wt%), and they were applied to the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. The effect of PAM content of PAM(X)-ZSM5 catalysts on the physicochemical properties and catalytic activities was investigated. N2 adsorption-desorption isotherms of PAM(X)-ZSM5 catalysts exhibited a broad hysteresis loop at high relative pressure, indicating the existence of mesopores in the catalysts. It was found that the catalytic performance of PAM(X)-ZSM5 catalysts was closely related to the mesoporosity of the catalysts. Conversion of C5 raffinate and yield for light olefins showed volcano-shaped trends with respect to mesopore/micropore volume ratio of the catalysts. Thus, an optimal PAM content was required to achieve maximum production of light olefins through catalytic cracking of C5 raffinate over microporous and mesoporous PAM(X)-ZSM5 catalysts.

  7. Supported iron nanoparticles as catalysts for sustainable production of lower olefins.

    PubMed

    Torres Galvis, Hirsa M; Bitter, Johannes H; Khare, Chaitanya B; Ruitenbeek, Matthijs; Dugulan, A Iulian; de Jong, Krijn P

    2012-02-17

    Lower olefins are key building blocks for the manufacture of plastics, cosmetics, and drugs. Traditionally, olefins with two to four carbons are produced by steam cracking of crude oil-derived naphtha, but there is a pressing need for alternative feedstocks and processes in view of supply limitations and of environmental issues. Although the Fischer-Tropsch synthesis has long offered a means to convert coal, biomass, and natural gas into hydrocarbon derivatives through the intermediacy of synthesis gas (a mixture of molecular hydrogen and carbon monoxide), selectivity toward lower olefins tends to be low. We report on the conversion of synthesis gas to C(2) through C(4) olefins with selectivity up to 60 weight percent, using catalysts that constitute iron nanoparticles (promoted by sulfur plus sodium) homogeneously dispersed on weakly interactive α-alumina or carbon nanofiber supports.

  8. Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization.

    PubMed

    Li, Kuo-Tseng; Wu, Ling-Huey

    2017-05-05

    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.

  9. Sustainable solid catalyst alkylation of commercial olefins by regeneration with supercritical isobutane

    SciTech Connect

    Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

    2005-12-01

    Supercritical isobutane regeneration of a USY zeolite alkylation catalyst was examined in a continuous, automated reaction / regeneration system. Two feeds were studied; a synthetic isobutane / 2-butene blend, and a commercial refinery isoparaffin / olefin blend. The refinery blend was minimally treated, containing a variety of light olefins, and contaminants, including butadiene, oxygenates and sulfur, which are well known to cause severe catalyst deactivation. Synthetic feed experiments showed that high levels of butene conversion was maintained for more than 200 hours time on stream, and that product quality and catalyst maintenance was relatively stable over the course of the experiment using a 3 hour reaction / 3 hour regeneration cycle. Catalyst activity maintenance was lower when the commercial feed was employed. High levels of alkene conversion were maintained for 78 hours and 192 hours using a 3 hour reaction / 3 hour regeneration cycle and a 2 hour reaction / 2 hour regeneration cycle, respectively.

  10. Olefin Ring Closing Metathesis and Hydrosilylation Reaction in Aqueous Medium by Grubbs Second Generation Ruthenium Catalyst

    EPA Science Inventory

    The Grubbs second generation ruthenium catalyst was shown to catalyze various olefin ring closing metathesis and hydrosilylation reactions in aqueous medium. Reactions proceeded in pure water without any additives or co-solvents, in a short period of time. We found that inhomogen...

  11. Olefin Ring Closing Metathesis and Hydrosilylation Reaction in Aqueous Medium by Grubbs Second Generation Ruthenium Catalyst

    EPA Science Inventory

    The Grubbs second generation ruthenium catalyst was shown to catalyze various olefin ring closing metathesis and hydrosilylation reactions in aqueous medium. Reactions proceeded in pure water without any additives or co-solvents, in a short period of time. We found that inhomogen...

  12. A new efficient iron catalyst for olefin epoxidation with hydrogen peroxide.

    PubMed

    Mikhalyova, Elena A; Makhlynets, Olga V; Palluccio, Taryn D; Filatov, Alexander S; Rybak-Akimova, Elena V

    2012-01-18

    A new aminopyridine ligand derived from bipiperidine (the product of full reduction of bipyridine, bipy) coordinates to iron(II) in a cis-α fashion, yielding a new selective catalyst for olefin epoxidation with H(2)O(2) under limiting substrate conditions.

  13. Catalyst-controlled dioxygenation of olefins: an approach to peroxides, alcohols, and ketones.

    PubMed

    Xia, Xiao-Feng; Zhu, Su-Li; Gu, Zhen; Wang, Haijun; Li, Wei; Liu, Xiang; Liang, Yong-Min

    2015-06-05

    An efficient catalytic approach for the synthesis of substituted peroxides, alcohols, and ketones through a catalyst-controlled highly selective dioxygenation of olefins has been demonstrated. The reported methods are mild and practical, can be switched by the selection of different catalytic systems, and employ peroxide as an oxidant and a reagent at room temperature.

  14. Proximity and cooperativity effects in binuclear d(0) olefin polymerization catalysis. theoretical analysis of structure and reaction mechanism.

    PubMed

    Motta, Alessandro; Fragalà, Ignazio L; Marks, Tobin J

    2009-03-25

    experimentally at closer Zr...Zr proximities in olefin polymerizations mediated by binuclear CGC catalysts.

  15. Chiral Ketone and Iminium Catalysts for Olefin Epoxidation

    NASA Astrophysics Data System (ADS)

    Wong, O. Andrea; Shi, Yian

    Organo-catalyzed asymmetric epoxidation has received much attention in the past 30 years and significant progress has been made for various types of olefins. This review will cover the advancement made in the field of chiral ketone and chiral iminium salt-catalyzed epoxidations.

  16. Hydroformylation of olefinic compounds in the presence of a cobalt catalyst and an organic nitrile promoter

    SciTech Connect

    Virnig, M.J.

    1986-09-16

    A process for preparing a formylated olefinic fatty compound is described comprising reacting an olefinic fatty compound having at least 9 carbon atoms with carbon monoxide and hydrogen in the presence of a catalytic amount of a soluble cobalt salt catalyst and a promoter comprised of an organic nitrile selected from the group consisting of cyano-substituted alkanes having from 2 to 44 carbon atoms and cyano-substituted alkanes having from 4 to 22 carbon atoms containing no substituent other than cyano.

  17. Titanium compounds as catalysts of higher alpha-olefin-based super-high-molecular polymers synthesis

    NASA Astrophysics Data System (ADS)

    Konovalov, K. B.; Kazaryan, M. A.; Manzhay, V. N.; Vetrova, O. V.

    2016-01-01

    The synthesis of polymers of 10 million or more molecular weight is a difficult task even in a chemical lab. Higher α-olefin-based polymer agents of such kind have found a narrow but quite important niche, the reduction of drag in the turbulent flow of hydrocarbon fluids such as oil and oil-products. In its turn, searching for a catalytic system capable to produce molecules of such a high length and to synthesize polymers of a low molecular-mass distribution is part of a global task of obtaining a high-quality product. In this paper we had observed a number of industrial catalysts with respect to their suitability for higher poly-α- olefins synthesis. A number samples representing copolymers of 1-hexene with 1-decene obtained on a previous generation catalyst, a microsphere titanium chloride catalytic agent had been compared to samples synthesized using a titanium-magnesium catalyst both in solution and in a polymer medium.

  18. Diverse stereocontrol effects induced by weakly coordinating anions. Stereospecific olefin polymerization pathways at archetypal C(s)- and C(1)-symmetric metallocenium catalysts using mono- and polynuclear halo-perfluoroarylmetalates as cocatalysts.

    PubMed

    Roberts, John A S; Chen, Ming-Chou; Seyam, Afif M; Li, Liting; Zuccaccia, Cristiano; Stahl, Nicholas G; Marks, Tobin J

    2007-10-24

    Counteranion effects on propylene polymerization rates and stereoselectivities are compared using Cs-symmetric Me2C(Cp)(Flu)ZrMe2 (1; Cp = C5H4,eta5-cyclopentadienyl; Flu = C13H8, eta5-fluorenyl) and C1-symmetric Me2Si(OHF)(CpR*)ZrMe2 (2; OHF = C13H16, eta5-octahydrofluorenyl; CpR* = eta5-3-(-)-menthylcyclopentadienyl) precatalysts activated with the mononuclear and polynuclear perfluoroarylborate, -aluminate, and -gallate cocatalysts/activators B(C6F5)3 (3), B(o-C6F5C6F4)3 (4), Al(C6F5)3 (5), Ph3C+B(C6F5)4- (6) Ph3C+FAl(o-C6F5C6F4)3- (7), Ga(C6F5)3 (8), and recently reported mono- and polymetallic trityl perfluoroarylhalometalates Ph3C+FB(C6F5)3- (9), Ph3C+FB(o-C6F5C6F4)3- (10), (Ph3C+)xFx[Al(C6F5)3]yx- (x = 1, y = 1, 11; x = 1, y = 2, 12; x = 2, y = 3, 13), Ph3C+(C6F5)3AlFAl(o-C6F5C6F4)3- (14), Ph3C+XAl(C6F5)3- (X = Cl, 15; X = Br, 16), and Ph3C+F[Ga(C6F5)3]2- (17). Temperature, propylene concentration, and solvent polarity dependence are surveyed in polymerizations catalyzed by 1 activated with cocatalysts 3-16 and with a 1:2 ratio of Ph3CCl and 5, and with a 1:2 ratio of Ph3CBr and 5, and by 2 activated with 3, 6, 7, 12, and 14. Remarkable stereocontrol with high activities is observed for 1 + 12 and 1 + 14. Polypropylene samples produced using C1-symmetric precatalyst 2 are subjected to microstructural analyses using stochastic models describing the relative contributions of enantiofacial misinsertion and backskip processes. A powerful technique is introduced for calculating interparametric correlation matrices for these nonlinear stochastic models. The collected results significantly extend what is known about ion-pairing effects in the case of Cs-symmetric precatalyst 1 and allow these findings to be applied to the case of C1-symmetric precatalyst 2 as an agent of isospecific propylene polymerization.

  19. Internally coated reaction vessel for use in olefinic polymerization

    SciTech Connect

    Dorsch, J.L.; Smith, J.D.

    1986-04-01

    This patent describes a polymerization reaction vessel having on all the internal surfaces with a coating that consists of the sodium salt of an oligomer(s) having the general structure wherein chi is an integer from 0 to 10. The oligomer(s) is the reaction product of benzaldehyde and resorcinol and wherein the coated surface are characterized by having a critical surface tension of at least 72 dynes/centimeter and a contact angle with water of about zero.

  20. Vanadyl cationic complexes as catalysts in olefin oxidation.

    PubMed

    Nunes, Carla D; Vaz, Pedro D; Félix, Vítor; Veiros, Luis F; Moniz, Tânia; Rangel, Maria; Realista, Sara; Mourato, Ana C; Calhorda, Maria José

    2015-03-21

    Three new mononuclear oxovanadium(IV) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol(-1)V h(-1)) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol(-1)V h(-1)) are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with H2O2. A preference for the internal C=C bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex [VO(acac)(H-BIAN)](+) (1(+)) was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(IV) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a [VO(H-BIAN)(MeOO)](+) complex is the likely active V(IV) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium.

  1. Novel polymerization catalysts and hydride clusters from rare-earth metal dialkyls.

    PubMed

    Nishiura, Masayoshi; Hou, Zhaomin

    2010-04-01

    This Review gives an overview on recent progress in the synthesis and chemistry of rare-earth metal dialkyl complexes bearing monoanionic ancillary ligands, with an emphasis on novel polymerization catalysts. These structurally well-defined and highly reactive compounds are prepared either by alkane elimination reactions between trialkyl rare-earth complexes and acidic neutral ligands, or by the metathetical reactions of rare-earth trihalides with the alkali metal salts of the corresponding ligands. On treatment with an appropriate borate compound, the dialkyl complexes are converted into the corresponding cationic monoalkyl species, which serve as excellent catalysts for the polymerization and copolymerization of a variety of olefins to yield a series of new polymer materials that exhibit novel properties. Alternatively, hydrogenation of the dialkyl rare-earth complexes with H(2) affords a new class of rare-earth polyhydride complexes with unique features in terms of both their structure and reactivity.

  2. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, Robert J.; Gao, Hanrong

    1998-08-04

    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.

  3. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, R.J.; Gao, H.

    1998-08-04

    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, hydrosilication, olefin oxidation, isomerization, hydrocyanidation, 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. 2 figs.

  4. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

    DOEpatents

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

    A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact with a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.

  5. Catalytic deoxydehydration of diols to olefins by using a bulky cyclopentadiene-based trioxorhenium catalyst.

    PubMed

    Raju, Suresh; Jastrzebski, Johann T B H; Lutz, Martin; Klein Gebbink, Robertus J M

    2013-09-01

    A bulky cyclopentadienyl (Cp)-based trioxorhenium compound was developed for the catalytic deoxydehydration of vicinal diols to olefins. The 1,2,4-tri(tert-butyl)cyclopentadienyl trioxorhenium (2) catalyst was synthesised in a two-step synthesis procedure. Dirhenium decacarbonyl was converted into 1,2,4-tri(tert-butyl)cyclopentadienyl tricarbonyl rhenium, followed by a biphasic oxidation with H2 O2 . These two new three-legged compounds with a 'piano-stool' configuration were fully characterised, including their single crystal X-ray structures. Deoxydehydration reaction conditions were optimised by using 2 mol % loading of 2 for the conversion of 1,2-octanediol into 1-octene. Different phosphine-based and other, more conventional, reductants were tested in combination with 2. Under optimised conditions, a variety of vicinal diols (aromatic and aliphatic, internal and terminal) were converted into olefins in good to excellent yields, and with minimal olefin isomerisation. A high turnover number of 1400 per Re was achieved for the deoxydehydration of 1,2-octanediol. Furthermore, the biomass-derived polyols (glycerol and erythritol) were converted into their corresponding olefinic products by 2 as the catalyst.

  6. Unconventional olefin processes

    SciTech Connect

    Hu, Y.C.

    1983-05-01

    The conversion of syngas into olefins is based on the Fischer-Tropsch technology. The FT modified process for olefins includes: upgraded liquids for olefins and aromatics, and catcracking of methanol. Because of the number of catalysts for olefins, data is not yet possible. Economic projections suggest that methanol cracking for olefins will be feasible in 1990. Olefin demand will grow, and C/sub 1/ chemistry research will increase, so that some unconventional olefin processes can be commercialized by then.

  7. Ruthenium indenylidene “1st generation” olefin metathesis catalysts containing triisopropyl phosphite

    PubMed Central

    Guidone, Stefano; Nahra, Fady; Slawin, Alexandra M Z

    2015-01-01

    Summary The reaction of triisopropyl phosphite with phosphine-based indenylidene pre-catalysts affords “1st generation” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L-type ligands. PMID:26425210

  8. The History of Current State of the Art of Propylene Polymerization Catalysts.

    ERIC Educational Resources Information Center

    Goodall, Brian L.

    1986-01-01

    Outlines the development of the modern catalysts for propylene polymerization, considering the historical background; structure of titanium chloride catalysts; first-generation catalysts; cocatalysts; second-generation catalysts; catalysts morphology; and third-generation (supported catalysts). (JN)

  9. The History of Current State of the Art of Propylene Polymerization Catalysts.

    ERIC Educational Resources Information Center

    Goodall, Brian L.

    1986-01-01

    Outlines the development of the modern catalysts for propylene polymerization, considering the historical background; structure of titanium chloride catalysts; first-generation catalysts; cocatalysts; second-generation catalysts; catalysts morphology; and third-generation (supported catalysts). (JN)

  10. The generation of efficient supported (Heterogeneous) olefin metathesis catalysts

    SciTech Connect

    Grubbs, Robert H

    2013-04-05

    Over the past decade, a new family of homogeneous metathesis catalysts has been developed that will tolerate most organic functionalities as well as water and air. These homogeneous catalysts are finding numerous applications in the pharmaceutical industry as well as in the production of functional polymers. In addition the catalysts are being used to convert seed oils into products that can substitute for those that are now made from petroleum products. Seed oils are unsaturated, contain double bonds, and are a ready source of linear hydrocarbon fragments that are specifically functionalized. To increase the number of applications in the area of biomaterial conversion to petrol chemicals, the activity and efficiency of the catalysts need to be as high as possible. The higher the efficiency of the catalysts, the lower the cost of the conversion and a larger number of practical applications become available. Active supported catalysts were prepared and tested in the conversion of seed oils and other important starting materials. The outcome of the work was successful and the technology has been transferred to a commercial operation to develop viable applications of the discovered systems. A biorefinery that converts seed oils is under construction in Indonesia. The catalysts developed in this study will be considered for the next generation of operations.

  11. Nobel Chemistry in the Laboratory: Synthesis of a Ruthenium Catalyst for Ring-Closing Olefin Metathesis--An Experiment for the Advanced Inorganic or Organic Laboratory

    ERIC Educational Resources Information Center

    Greco, George E.

    2007-01-01

    An experiment for the upper-level undergraduate laboratory is described in which students synthesize a ruthenium olefin metathesis catalyst, then use the catalyst to carry out the ring-closing metathesis of diethyl diallylmalonate. The olefin metathesis reaction was the subject of the 2005 Nobel Prize in chemistry. The catalyst chosen for this…

  12. Nobel Chemistry in the Laboratory: Synthesis of a Ruthenium Catalyst for Ring-Closing Olefin Metathesis--An Experiment for the Advanced Inorganic or Organic Laboratory

    ERIC Educational Resources Information Center

    Greco, George E.

    2007-01-01

    An experiment for the upper-level undergraduate laboratory is described in which students synthesize a ruthenium olefin metathesis catalyst, then use the catalyst to carry out the ring-closing metathesis of diethyl diallylmalonate. The olefin metathesis reaction was the subject of the 2005 Nobel Prize in chemistry. The catalyst chosen for this…

  13. LDRD final report on new homogeneous catalysts for direct olefin epoxidation (LDRD 52591).

    SciTech Connect

    Goldberg, Karen; Smythe, Nicole A.; Moore, Joshua T.; Stewart, Constantine A.; Kemp, Richard Alan; Miller, James Edward; Kornienko, Alexander (New Mexico Institute of Mining and Technology); Denney, Melanie C. (University of Washington); Cetto, Kara L.

    2006-02-01

    This report summarizes our findings during the study of a novel homogeneous epoxidation catalyst system that uses molecular oxygen as the oxidant, a ''Holy Grail'' in catalysis. While olefins (alkenes) that do not contain allylic hydrogens can be epoxidized directly using heterogeneous catalysts, most olefins cannot, and so a general, atom-efficient route is desired. While most of the work performed on this LDRD has been on pincer complexes of late transition metals, we also scouted out metal/ligand combinations that were significantly different, and unfortunately, less successful. Most of the work reported here deals with phosphorus-ligated Pd hydrides [(PCP)Pd-H]. We have demonstrated that molecular oxygen gas can insert into the Pd-H bond, giving a structurally characterized Pd-OOH species. This species reacts with oxygen acceptors such as olefins to donate an oxygen atom, although in various levels of selectivity, and to generate a [(PCP)Pd-OH] molecule. We discovered that the active [(PCP)Pd-H] active catalyst can be regenerated by addition of either CO or hydrogen. The demonstration of each step of the catalytic cycle is quite significant. Extensions to the pincer-Pd chemistry by attaching a fluorinated tail to the pincer designed to be used in solvents with higher oxygen solubilities are also presented.

  14. Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts

    PubMed Central

    Binder, Joseph B.; Blank, Jacqueline J.; Raines, Ronald T.

    2008-01-01

    Olefin metathesis in aqueous solvents is sought for applications in green chemistry and with the hydrophilic substrates of chemical biology, such as proteins and polysaccharides. Most demonstrations of metathesis in water, however, utilize exotic complexes. We have examined the performance of conventional catalysts in homogeneous water–organic mixtures, finding that the second-generation Hoveyda–Grubbs catalyst has extraordinary efficiency in aqueous dimethoxyethane and aqueous acetone. High (71–95%) conversions are achieved for ring-closing and cross metathesis of a variety of substrates in these solvent systems. PMID:17949009

  15. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    PubMed Central

    Lafaye, Kevin; Bosset, Cyril; Nicolas, Lionel

    2015-01-01

    Summary Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions. PMID:26664645

  16. Silicoaluminates as “Support Activator” Systems in Olefin Polymerization Processes

    PubMed Central

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

    2010-01-01

    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.

  17. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand-metal interactions.

    PubMed

    Mark, Stefan; Wadepohl, Hubert; Enders, Markus

    2016-01-01

    A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers.

  18. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

    PubMed Central

    Mark, Stefan; Wadepohl, Hubert

    2016-01-01

    Summary A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. PMID:27559387

  19. Origins of initiation rate differences in ruthenium olefin metathesis catalysts containing chelating benzylidenes.

    PubMed

    Engle, Keary M; Lu, Gang; Luo, Shao-Xiong; Henling, Lawrence M; Takase, Michael K; Liu, Peng; Houk, K N; Grubbs, Robert H

    2015-05-06

    A series of second-generation ruthenium olefin metathesis catalysts was investigated using a combination of reaction kinetics, X-ray crystallography, NMR spectroscopy, and DFT calculations in order to determine the relationship between the structure of the chelating o-alkoxybenzylidene and the observed initiation rate. Included in this series were previously reported catalysts containing a variety of benzylidene modifications as well as four new catalysts containing cyclopropoxy, neopentyloxy, 1-adamantyloxy, and 2-adamantyloxy groups. The initiation rates of this series of catalysts were determined using a UV/vis assay. All four new catalysts were observed to be faster-initiating than the corresponding isopropoxy control, and the 2-adamantyloxy catalyst was found to be among the fastest-initiating Hoveyda-type catalysts reported to date. Analysis of the X-ray crystal structures and computed energy-minimized structures of these catalysts revealed no correlation between the Ru-O bond length and Ru-O bond strength. On the other hand, the initiation rate was found to correlate strongly with the computed Ru-O bond strength. This latter finding enables both the rationalization and prediction of catalyst initiation through the calculation of a single thermodynamic parameter in which no assumptions about the mechanism of the initiation step are made.

  20. Development of a ruthenium/phosphite catalyst system for domino hydroformylation-reduction of olefins with carbon dioxide.

    PubMed

    Liu, Qiang; Wu, Lipeng; Fleischer, Ivana; Selent, Detlef; Franke, Robert; Jackstell, Ralf; Beller, Matthias

    2014-06-02

    An efficient domino ruthenium-catalyzed reverse water-gas-shift (RWGS)-hydroformylation-reduction reaction of olefins to alcohols is reported. Key to success is the use of specific bulky phosphite ligands and triruthenium dodecacarbonyl as the catalyst. Compared to the known ruthenium/chloride system, the new catalyst allows for a more efficient hydrohydroxymethylation of terminal and internal olefins with carbon dioxide at lower temperature. Unwanted hydrogenation of the substrate is prevented. Preliminary mechanism investigations uncovered the homogeneous nature of the active catalyst and the influence of the ligand and additive in individual steps of the reaction sequence.

  1. Tandem isomerization-decarboxylation of unsaturated fatty acids to olefins via ruthenium metal-as-ligand catalysts

    USDA-ARS?s Scientific Manuscript database

    A new facile Ru-catalyzed route to bio-olefins3 from unsaturated fatty acids via readily accessible metal-as-ligand type catalyst precursors, [Ru(CO)2RCO2]n and Ru3(CO)12, will be described. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds i...

  2. Theory-assisted development of a robust and Z-selective olefin metathesis catalyst.

    PubMed

    Occhipinti, Giovanni; Koudriavtsev, Vitali; Törnroos, Karl W; Jensen, Vidar R

    2014-08-07

    DFT calculations have predicted a new, highly Z-selective ruthenium-based olefin metathesis catalyst that is considerably more robust than the recently reported (SIMes)(Cl)(RS)RuCH(o-OiPrC6H4) (3a, SIMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene, R = 2,4,6-triphenylbenzene) [J. Am. Chem. Soc., 2013, 135, 3331]. Replacing the chloride of 3a by an isocyanate ligand to give 5a was predicted to increase the stability of the complex considerably, at the same time moderately improving the Z-selectivity. Compound 5a is easily prepared in a two-step synthesis starting from the Hoveyda-Grubbs second-generation catalyst 3. In agreement with the calculations, the isocyanate-substituted 5a appears to be somewhat more Z-selective than the chloride analogue 3a. More importantly, 5a can be used in air, with unpurified and non-degassed substrates and solvents, and in the presence of acids. These are traits that are unprecedented among highly Z-selective olefin metathesis catalysts and also very promising with respect to applications of the new catalyst.

  3. Conversion of syngas to light olefins over silicalite-1 supported iron and cobalt catalysts: Effects of manganese addition

    SciTech Connect

    Das, D.; Ravichandran, G.; Chakrabarty, D.K.

    1996-10-01

    As the demand for light (C2-C4) olefins, an important raw materials for a number of chemical industries, is ever increasing considerable attention is now being paid to the design of suitable catalysts with high selectivity for small chain olefins. Although Fischer-Tropsch synthesis yields a wide spectrum of products from methane to waxes it is possible to restrict the chain growth to a few carbon atoms by containing the active metal panicles inside the small pores of a suitable support like zeolite. The nature of the zeolite support also has a strong influence on the product selectivity due to secondary reactions. This paper discusses the results of syngas conversion to light olefins over iron and cobalt catalysts supported on silicalite-1. Effect of the addition of manganese which is known to improve the selectivity to light olefins is also discussed.

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

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    2001-01-01

    Organo-Lewis acids of the formula BR'R".sub.2 wherein B is boron, R' is fluorinated biphenyl, and R" is a fluorinated phenyl, fluorinated biphenyl, or fluorinated polycyclic fused ring group, and cationic metallocene complexes formed therewith. Such complexes are useful as polymerization catalysts.

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

    DOEpatents

    Marks, Tobin J.; Chen, You-Xian

    2002-01-01

    Organo-Lewis acids of the formula BR'R".sub.2 wherein B is boron, R' is fluorinated biphenyl, and R" is a fluorinated phenyl, fluorinated biphenyl, or fluorinated polycyclic fused ring group, and cationic metallocene complexes formed therewith. Such complexes are useful as polymerization catalysts.

  6. Catalytic pyrolysis of model compounds and waste cooking oil for production of light olefins over La/ZSM-5 catalysts

    NASA Astrophysics Data System (ADS)

    Li, F. W.; Ding, S. L.; Li, L.; Gao, C.; Zhong, Z.; Wang, S. X.; Li, Z. X.

    2016-08-01

    Waste cooking oil (WCO) and its model compounds (oleic acid and methyl laurate) are catalytically pyrolyzed in a fixed-bed reactor over La modified ZSM-5 catalysts (La/ZSM-5) aiming for production of C2-C4 light olefins. The LaO content in catalysts was set at 0, 2, 6, 10 and 14 wt%. The gas and liquid products are analyzed. The La/ZSM-5 catalyst with 6% LaO showed higher selectivity to light olefins when WCO and methyl laurate were pyrolyzed, and olefin content was 26% for WCO and 21% for methyl laurate. The catalyst with 10% LaO showed high selectivity to light olefins (28.5%) when oleic acid was pyrolyzed. The liquid products from WCO and model compounds mainly contain esters and aromatic hydrocarbons. More esters were observed in liquid products from methyl laurate and WCO pyrolysis, indicating that it is more difficult to pyrolyze esters and WCO than oleic acid. The coked catalysts were analyzed by temperature-programmed oxidation. The result shows that graphite is the main component of coke. The conversion of WCO to light olefins potentially provides an alternative and sustainable route for production of the key petrochemicals.

  7. Linker-free, silica-bound olefin-metathesis catalysts: applications in heterogeneous catalysis.

    PubMed

    Cabrera, José; Padilla, Robin; Bru, Miriam; Lindner, Ronald; Kageyama, Takeharu; Wilckens, Kristina; Balof, Shawna L; Schanz, Hans-Jörg; Dehn, Richard; Teles, J Henrique; Deuerlein, Stephan; Müller, Kevin; Rominger, Frank; Limbach, Michael

    2012-11-12

    A set of heterogenized olefin-metathesis catalysts, which consisted of Ru complexes with the H(2)ITap ligand (1,3-bis(2',6'-dimethyl-4'dimethyl aminophenyl)-4,5-dihydroimidazol-2-ylidene) that had been adsorbed onto a silica support, has been prepared. These complexes showed strong binding to the solid support without the need for tethering groups on the complex or functionalized silica. The catalysts were tested in the ring-opening-ring-closing-metathesis (RO-RCM) of cyclooctene (COE) and the self-metathesis of methyl oleate under continuous-flow conditions. The best complexes showed a TON>4000, which surpasses the previously reported materials that were either based on the Grubbs-Hoveyda II complex on silica or on the classical heterogeneous Re(2)O(7)/B(2)O(3) catalyst.

  8. Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.

    PubMed

    Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

    2014-04-01

    Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Zwitterionic Group VIII transition metal initiators supported by olefin ligands

    SciTech Connect

    Bazan, Guillermo C; Chen, Yaofeng

    2011-10-25

    A zwitterionic Group VIII transition metal complex containing the simple and relatively small 3-(arylimino)-but-1-en-2-olato ligand that catalyzes the formation of polypropylene and high molecular weight polyethylene. A novel feature of this catalyst is that the active species is stabilized by a chelated olefin adduct. The present invention also provides methods of polymerizing olefin monomers using zwitterionic catalysts, particularly polypropylene and high molecular weight polyethylene.

  10. Preparation of octahydro- and tetrahydro-[1,10]phenanthroline zirconium and hafnium complexes for olefin polymerization.

    PubMed

    Hwang, Eun Yeong; Park, Geun Ho; Lee, Chun Sun; Kang, Yi Young; Lee, Junseong; Lee, Bun Yeoul

    2015-02-28

    Post-metallocenes were constructed for olefin polymerization using 1,2,3,4,7,8,9,10-octahydro[1,10]phenanthroline and 1,2,3,4-tetrahydro[1,10]phenanthroline derivatives. A series of zirconium complexes - LZrCl2(NHMe2)2 [L = 2,9-H2-C12H12N2 (4), 2,9-Me2-C12H12N2 (5), 2,9-nBu2-C12H12N2 (6), and 2,9-iPr2-C12H12N2 (7)] - and hafnium complexes - LHfCl2(NHMe2)2 [L = 2,9-H2-C12H12N2 (8), 2,9-Me2-C12H12N2 (9), 2,9-nBu2-C12H12N2 (10), and 2,9-iPr2-C12H12N2 (11)] - were synthesized via the reaction of octahydro[1,10]phenanthrolines (2,9-R2-C12H12(NH)2) with (Me2N)2MCl2 (DME). The reaction of 2,9-R2-C12H12(NH)2 with (PhCH2)2ZrCl2 in the presence of a small amount of THF afforded a series of THF adduct analogs, i.e., LZrCl2(THF)2 [L = 2,9-H2-C12H12N2 (12), 2,9-Me2-C12H12N2 (13), 2,9-nBu2-C12H12N2 (14), and 2,9-iPr2-C12H12N2 (15)]. The treatment of 12 and 13 with excess Me3Al resulted in the formation of unexpected complexes, i.e., (η(4)-LAlMe2)ZrCl2(Me) [L = 2,9-H2-C12H12N2 (16) and 2,9-Me2-C12H12N2 (17)], in which the Me2Al unit forms a five-membered ring through binding with the two nitrogen donors and the MeCl2Zr unit slips to an η(4)-binding mode containing the N-C-C-N fragment. The treatment of tetrahydro[1,10]phenanthrolines [2,9-R2-C12NH9(NH)] with M(CH2Ph)4 afforded tribenzyl zirconium complexes LZr(CH2Ph)3 - [L = 2,9-Me2-C12NH9N (18) and 2,9-nBu2-C12NH9N (19)] - and hafnium complexes - LHf(CH2Ph)3 [L = 2,9-Me2-C12NH9N (20), 2,9-nBu2-C12NH9N (21), and 2,9-iPr2-C12NH9N (22)]. The structures of 4, 5, 12, 17, and 22 were elucidated by X-ray crystallography. The newly prepared complexes were screened for ethylene/1-octene copolymerization activity: 12 and 16 were potent catalysts (activities of 74 × 10(6) g mol-Zr h(-1) at ∼120 °C under 30 bar ethylene) for the production of wax-like low-molecular weight polyethylene (Mn: ∼5000), which is widely used in industry.

  11. Additive for lubricants and hydrocarbon fuels comprising reaction products of olefins, sulfur, hydrogen sulfide and polymeric succinimide compounds

    SciTech Connect

    Horodysky, A.G.; Law, D.A.

    1988-11-22

    This patent describes a process for making an additive for lubricants comprising co-reacting: (a) an olefin; (b) sulfur; (c) hydrogen sulfide; and (d) a polymeric succinimide selected from the group consisting of the reaction products of polymeric succinic anhydride with one or more reactants selected from the group consisting of: (a) polyethylene amines selected from the group consisting of diethylene triamines, treithylenetetramine, and tetraethylenepentamine; (b) hydroxyl containing amines, and; (c) polyols in conjunction with (a) or (b) selected from the group consisting of pentaerythritol, and trimethylol propane; at a temperature between about 130/sup 0/C and about 200/sup 0/C and a pressure of about 0 psig to about 900 psig, the reactants being reacted in a molar ratio of olefin, polymeric succinimide, and hydrogen sulfide to sulfur of about 3 to about 0.5, about 0.001, to about 0.4, and about 0.5 to about 0.7, respectively.

  12. Catalytic polymerization of carbon monoxide and olefin, with organo nitro or organo nitrite compound additive

    SciTech Connect

    Drent, E.; Wife, R.L.

    1989-02-21

    In the process of producing linear alternating polymers or carbon monoxide and at least one ethylenically unsaturated hydrocarbon by contacting the carbon monoxide and unsaturated hydrocarbon under polymerization conditions in the presence of a catalyst composition formed from a mixture of a palladium compound, the anion of a non-hydrohalogenic acid having a pKa below about 6 and a bidentate phosphorus ligand, the improvement wherein the mixture from which the catalyst composition is formed additionally contains an organic nitro compound or an organic nitride compound.

  13. Shell Higher Olefins Process.

    ERIC Educational Resources Information Center

    Lutz, E. F.

    1986-01-01

    Shows how olefin isomerization and the exotic olefin metathesis reaction can be harnessed in industrial processes. Indicates that the Shell Higher Olefins Process makes use of organometallic catalysts to manufacture alpha-olefins and internal carbon-11 through carbon-14 alkenes in a flexible fashion that can be adjusted to market needs. (JN)

  14. Shell Higher Olefins Process.

    ERIC Educational Resources Information Center

    Lutz, E. F.

    1986-01-01

    Shows how olefin isomerization and the exotic olefin metathesis reaction can be harnessed in industrial processes. Indicates that the Shell Higher Olefins Process makes use of organometallic catalysts to manufacture alpha-olefins and internal carbon-11 through carbon-14 alkenes in a flexible fashion that can be adjusted to market needs. (JN)

  15. OsO(4) in ionic liquid [Bmim]PF(6): a recyclable and reusable catalyst system for olefin dihydroxylation. remarkable effect of DMAP.

    PubMed

    Yao, Qingwei

    2002-06-27

    [reaction: see text] The combination of the ionic liquid [bmim]PF(6) and DMAP provides a most simple and practical approach to the immobilization of OsO(4) as catalyst for olefin dihydroxylation. Both the catalyst and the ionic liquid can be repeatedly recycled and reused in the dihydroxylation of a variety of olefins with only a very slight drop in catalyst activity.

  16. 9-fluorenemethanol: an internal electron donor to fine tune olefin polymerization activity.

    PubMed

    Gnanakumar, Edwin S; Rao Chokkapu, Eswara; Kunjir, Shrikant; Ajithkumar, T G; Rajamohanan, P R; Chakraborty, Debashis; Gopinath, Chinnakonda S

    2014-06-28

    A new MgCl2 based molecular adduct has been synthesized with 9-fluorenemethanol (9FM) as a novel internal electron donor (IED), along with ethanol (EtOH) (MgCl2·n9FM·xEtOH). The above molecular adduct has been subjected to a variety of structural, spectroscopic and morphological characterization techniques. The results of the solid state (13)C CPMAS NMR technique suggests the coordination of 9FM to MgCl2. Observation of a low angle diffraction peak at 2θ = 5.7° (d = 15.5 Å) underscores the coordination of 9FM along the z-axis, and ethanol in the molecular adduct. Active Ziegler-Natta catalysts were prepared by two different synthesis methods; the conventional method to obtain a high surface area active catalyst, and other one with 9FM as an integral part of the active catalyst in order to study the influence of 9FM as an IED over the active sites. The active catalysts were also characterized thoroughly with different analytical tools. The XRD results show (003) facets of δ-MgCl2 (α-MgCl2) for the conventional (non-conventional) titanated catalyst. Results of the ethylene polymerization activity study reveals that the conventionally prepared highly porous active catalyst shows 1.7-2.5 times higher activity than the non-conventional prepared catalyst; however, the latter shows a low molecular weight distribution and confirms the role of the Lewis base as an IED.

  17. Rhodium fluorapatite catalyst for the synthesis of trisubstituted olefins via cross coupling of Baylis-Hillman adducts and arylboronic acids.

    PubMed

    Kantam, M Lakshmi; Kumar, K B Shiva; Sreedhar, B

    2008-01-04

    Treatment of fluorapatite (prepared by incorporating basic species F(-) in apatite in situ by coprecipitation) with an aqueous solution of RhCl(3) resulted in rhodium-exchanged fluorapatite catalyst (RhFAP), which successfully promoted cross coupling of Baylis-Hillman adducts with arylboronic acids to yield trisubstituted olefins. A variety of arylboronic acids and Baylis-Hillman adducts were converted to the corresponding trisubstituted olefins, demonstrating the versatility of the reaction. The reaction is highly stereoselective. RhFAP was recovered quantitatively by simple filtration and reused with almost consistent activity.

  18. Poly(fluoroalkyl acrylate)-bound ruthenium carbene complex: a fluorous and recyclable catalyst for ring-closing olefin metathesis.

    PubMed

    Yao, Qingwei; Zhang, Yiliang

    2004-01-14

    The synthesis of a fluorous olefin metathesis catalyst derived from the Grubbs second-generation ruthenium carbene complex is described. The air stable fluorous polymer-bound ruthenium carbene complex 1 shows high reactivity in effecting the ring-closing metathesis of a broad spectrum of diene and enyne substrates leading to the formation of di-, tri-, and tetrasubstituted cyclic olefins in minimally fluorous solvent systems (PhCF3/CH2Cl2, 1:9-1:49 v/v). The catalyst can be readily separated from the reaction mixture by fluorous extraction with FC-72 and repeatedly reused. The practical advantage offered by the fluorous catalyst is demonstrated by its sequential use in up to five different metathesis reactions.

  19. Development of a Method for the Preparation of Ruthenium Indenylidene-Ether Olefin Metathesis Catalysts

    PubMed Central

    Jimenez, Leonel R.; Tolentino, Daniel R.; Gallon, Benjamin J.; Schrodi, Yann

    2012-01-01

    The reactions between several derivatives of 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and different ruthenium starting materials [i.e., RuCl2(PPh3)3 and RuCl2(pcymene)(L), where L is tricyclohexylphosphine di-t-butylmethylphosphine, dicyclohexylphenylphosphine, triisobutylphosphine, triisopropylphosphine, or tri-npropylphosphine] are described. Several of these reactions allow for the easy, in-situ and atom-economic preparation of olefin metathesis catalysts. Organic precursor 1-(3,5-dimethoxyphenyl)-1-phenyl-prop-2-yn-1-ol led to the formation of active ruthenium indenylidene-ether complexes, while 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and 1-(3,5-dimethoxyphenyl)-1-methyl-prop-2-yn-1-ol did not. It was also found that a bulky and strong σ-donor phosphine ligand was required to impart good catalytic activity to the new ruthenium complexes. PMID:22580400

  20. Anchored Pd complex in MCM-41 and MCM-48: novel heterogeneous catalysts for hydrocarboxylation of aryl olefins and alcohols.

    PubMed

    Mukhopadhyay, Kausik; Sarkar, Bibhas R; Chaudhari, Raghunath V

    2002-08-21

    We report here, for the first time, synthesis of anchored Pd complexes in mesoporous supports such as MCM-41 and MCM-48 as true heterogeneous catalysts for hydrocarboxylation of aryl olefins and alcohols to give excellent conversion ( approximately 100%) and regioselectivity ( approximately 99%) for 2-arylpropionic acids. The catalysts were characterized by powder-XRD, 31P CP-MAS NMR, FT-IR, TEM, XPS and ICP-AES. Recycle studies with these anchored Pd mesoporous catalysts were performed to confirm true heterogeneity.

  1. Catalyst activator

    DOEpatents

    McAdon, Mark H.; Nickias, Peter N.; Marks, Tobin J.; Schwartz, David J.

    2001-01-01

    A catalyst activator particularly adapted for use in the activation of metal complexes of metals of Group 3-10 for polymerization of ethylenically unsaturated polymerizable monomers, especially olefins, comprising two Group 13 metal or metalloid atoms and a ligand structure including at least one bridging group connecting ligands on the two Group 13 metal or metalloid atoms.

  2. Rationalizing current strategies to protect N-heterocyclic carbene-based ruthenium catalysts active in olefin metathesis from C-H (de)activation.

    PubMed

    Poater, Albert; Bahri-Laleh, Naeimeh; Cavallo, Luigi

    2011-06-21

    Defending second generation Ru-catalysts in olefin metathesis from C-H (de)activation reactions requires precise catalyst design strategies. Computer simulations are used here to rationalize precisely the role of the currently used catalyst structural modifications, and the way these modifications cooperate.

  3. Single Turnover at Molecular Polymerization Catalysts Reveals Spatiotemporally Resolved Reactions.

    PubMed

    Easter, Quinn T; Blum, Suzanne A

    2017-09-11

    Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single-turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Neutral nickel ethylene oligo- and polymerization catalysts: towards computational catalyst prediction and design.

    PubMed

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

    2014-06-23

    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.

  5. Direct catalytic conversion of synthesis gas to lower olefins

    SciTech Connect

    Janardanarao, M. )

    1990-09-01

    Direct conversion of synthesis gas to lower olefins has been considered as a possible solution to meet the growing demand for chemical feedstocks such as ethylene, propylene, and butylenes. This review covers the various catalyst systems and operating conditions that have been used in meeting this objective. Though the product distribution in Fischer--Tropsch synthesis is governed by the existence of an Anderson--Schultz--Flory polymerization model, certain modifications in the catalyst formulations have produced a shift toward lower molecular weight olefins. At the present time, the yields and selectivities of lower olefins are far from optimal, but continued research efforts in this area may lead to the development of stable catalyst systems capable of producing highly desirable distributions of lower olefins.

  6. Rheological properties and lubricity of poly-alpha-olefin oils

    SciTech Connect

    Tsvetkov, O.N.; Kolesova, G.E.; Bogdanov, S.K.; Toporishcheva, R.I.

    1988-01-01

    Oils were obtained by polymerization of alpha-olefins with a complex aluminum chloride catalyst, followed by neutralization of the polymerized product, distillation, and hydrogenation. Materials were tested to determine the kinematic viscosity at above- and below-freezing temperatures and dynamic viscosity at below-freezing temperatures. Poly-alpha-olefin oils were obtained at different levels of average molecular weight by varying the conditions of polymerization and distillation. The antiwear properties of petroleum, PAOO, and alkylbenzene oils having equal viscosities and an addition of zinc dialkyldithiophosphate were compared. The dialkylbenzene oil had strong associative-solvation properties with respect to the additive.

  7. Synthesis of late transition nickel(II) coordination polymer and their catalysis for olefinic polymerization

    NASA Astrophysics Data System (ADS)

    Chenfei, Xu; Zhang, Danfeng

    2017-09-01

    It was illustrated in this paper the successful synthesization of one α-diimine ligand and one new polycondensate ligand. The structure of the ligand was characterized by 1H NMR spectrum, and the structure of the polycondensate ligand was characterized by Thermogravimetric Analysis (TGA) and Element Analysis. Then these two ligands reacted with (DME)NiBr2 for the purpose of preparing α-diimine nickel complex and nickel coordination polymer characterized by Element Analysis and X-ray Photoelectron Spectroscopy (XPS). Then these two catalysts were adopted to facilitate ethylene polymerization and to compare the difference between them. It was found that the activities from nickel coordination polymer/MAO reached 106(g/molNi·h) and the molecule weights were about 105.

  8. Homogeneous and supported catalysts for {alpha}-olefin hydrogenation based on complexes of platinum tetrachloride with aliphatic amines

    SciTech Connect

    Kliger, E.G.; Shuikina, L.P.; Frolov, V.M.

    1995-07-01

    A new efficient catalyst for a-olefin hydrogenation, a reaction of importance to synthetic fuels preparation, that exhibits the catalytic activity without additional treatment with a reducing agent is obtained by the interaction of PtCl{sub 4} with tri-n-octylamine. Molecular hydrogen and ethanol are found to promote the catalytically active complex. On the basis of the IR spectroscopic investigation, a likely structure of the synthesized complex is proposed. A highly active heterogenized platinum-containing catalyst for the hydrogenation of terminal double bonds is prepared by supporting a homogeneous system on {gamma}-Al{sub 2}O{sub 3}.

  9. Polypyrrole-functionalized ruthenium carbene catalysts as efficient heterogeneous systems for olefin epoxidation.

    PubMed

    Dakkach, Mohamed; Fontrodona, Xavier; Parella, Teodor; Atlamsani, Ahmed; Romero, Isabel; Rodríguez, Montserrat

    2014-07-14

    New Ru complexes containing the bpea-pyr ligand (bpea-pyr stands for N,N-bis(pyridin-2-ylmethyl)-3-(1H-pyrrol-1-yl)propan-1-amine), with the formula [RuCl2(bpea-pyr)(dmso)] (isomeric complexes 2a and 2b) or [Ru(CN-Me)(bpea-pyr)X)](n+) (CN-Me = 3-methyl-1-(pyridin-2-yl)-1H-imidazol-3-ium-2-ide; X = Cl, 3, or X = H2O, 4), have been prepared and fully characterized. Complexes 3 and 4 have been anchored onto an electrode surface through electropolymerization of the attached pyrrole group, yielding stable polypyrrole films. The electrochemical behaviour of 4, which displays a bielectronic Ru(IV/II) redox pair in solution, is dramatically affected by the electropolymerization process leading to the occurrence of two monoelectronic Ru(IV/III) and Ru(III/II) redox pairs in the heterogeneous system. A carbon felt modified electrode containing complex 4 (C-felt/poly-4) has been evaluated as a heterogeneous catalyst in the epoxidation of various olefin substrates using PhI(OAc)2 as an oxidant, displaying TON values of several thousands in all cases and good selectivity for the epoxide product.

  10. Dichlorodioxomolybdenum(VI) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts.

    PubMed

    Oliveira, Tânia S M; Gomes, Ana C; Lopes, André D; Lourenço, João P; Almeida Paz, Filipe A; Pillinger, Martyn; Gonçalves, Isabel S

    2015-08-21

    Treatment of the solvent adduct [MoO2Cl2(THF)2] with either 2 equivalents of N,N-dimethylbenzamide (DMB) or 1 equivalent of N,N'-diethyloxamide (DEO) gave the dioxomolybdenum(vi) complexes [MoO2Cl2(DMB)2] () and [MoO2Cl2(DEO)] (). The molecular structures of and were determined by single-crystal X-ray diffraction. Both complexes present a distorted octahedral geometry and adopt the cis-oxo, trans-Cl, cis-L configuration typical of complexes of the type [MoO2X2(L)n], with either the monodentate DMB or bidentate DEO oxygen-donor ligands occupying the equatorial positions trans to the oxo groups. The complexes were applied as homogeneous catalysts for the epoxidation of olefins, namely cis-cyclooctene (Cy), 1-octene, trans-2-octene, α-pinene and (R)-(+)-limonene, using tert-butylhydroperoxide (TBHP) as oxidant. In the epoxidation of Cy at 55 °C, the desired epoxide was the only product and turnover frequencies in the range of ca. 3150-3200 mol molMo(-1) h(-1) could be reached. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the cosolvent. Complexes and were also applied in liquid-liquid biphasic catalytic epoxidation reactions by using an ionic liquid of the type [C4mim][X] (C4mim = 1-n-butyl-3-methylimidazolium; X = NTf2, BF4 or PF6] as a solvent to immobilise the metal catalysts. Recycling for multiple catalytic runs was achieved without loss of activity.

  11. ( l brace (. eta. sup 5 -C sub 5 Me sub 4 )Me sub 2 Si(. eta. sup 1 -NCMe sub 3 ) r brace (PMe sub 3 )ScH) sub 2 : A unique example of a single-component. alpha. -olefin polymerization catalyst

    SciTech Connect

    Shapiro, P.J.; Bunel, E.; Schaefer, W.P.; Bercaw, J.E. )

    1990-03-01

    The synthesis and structure of the title compound are described. ({l brace}({eta}{sup 5}-C{sub 5}Me{sub 4})Me{sub 2}Si({eta}{sup 1}-NCMe{sub 3}){r brace}Sc(PMe{sub 3})){sub 2}({mu}-H){sub 2} (3) crystallizes with a molecule of toluene per scandium in the monoclinic system, space group C2/c, with a = 21.238 (3) {angstrom}, b = 11.470 (2) {angstrom}, c = 22.253 (3) {angstrom}, {beta} = 113.16 (1){degree}, V = 4984.0 (14) {angstrom}{sup 3}, Z = 8 (four dimers), and d = 1.24 g{center dot}cm{sup {minus}3}. Propene, 1-butene, and 1-pentene are cleanly, albeit slowly, polymerized with >99% head-to-tail coupling to produce linear, atactic polymers with M{sub n} = 3,000-4,000 and PDI's of 1.7-2.1. Chain transfer is relatively slow and appears to occur by {beta}-H elimination. All evidence points to a one-component catalyst system with all scandium centers functioning alike.

  12. Experimental evidence of {alpha}-olefin readsorption in Fischer-Tropsch synthesis on ruthenium-supported ETS-10 titanium silicate catalysts

    SciTech Connect

    Bianchi, C.L.; Ragaini, V.

    1997-05-01

    Fischer-Tropsch synthesis seems to develop the following two consecutive paths: a primary process that involves the formation of {alpha}-olefin products and a secondary process leading to the production of branched isomers and paraffins and requiring the readsorption of primary {alpha}-olefin products. It was already shown by Iglesia et al. that such readsorption steps are of fundamental importance for Ru catalysts and that they occur due to the slow diffusive removal of {alpha}-olefins when the molecular size increases, this resulting in a long intraparticle residence time. In the present paper {alpha}-olefins readsorption was enhanced by changing the metal distribution inside the pores of a titanium silicate (ETS-10), modified by ion exchange with alkali metal ions, used as a support for Ru-based catalysts. 24 refs., 5 figs., 3 tabs.

  13. Palladium-meta-terarylphosphine catalyst for the Mizoroki-Heck reaction of (hetero)aryl bromides and functional olefins.

    PubMed

    Tay, Daniel Weiliang; Jong, Howard; Lim, Yee Hwee; Wu, Wenqin; Chew, Xinying; Robins, Edward G; Johannes, Charles W

    2015-04-17

    The evolutionary meta-terarylphosphine ligand architecture of Cy*Phine was recently shown to be a key feature that imposed outstanding performance in palladium-catalyzed copper-free Sonogashira applications. Herein, the Pd-Cy*Phine combination has similarly proven to be a powerful catalyst system for the Mizoroki-Heck reaction. Using high-throughput screening (HTS) methodology, DMF and NaHCO3 were rapidly identified as the most effective solvent and base pair for the cross-coupling catalysis of challenging and industrially valuable substrates including highly electron-rich heteroaryl bromides and unactivated olefins. Unprotected functional groups were well tolerated using low catalyst loadings, and the simple protocol produced excellent yields (up to 99%) with unprecedented substrate diversity. The Pd-Cy*Phine system broadly outperformed many state-of-the-art commercial alternatives, which demonstrated its potential as a next-generation cross-coupling catalyst.

  14. Ring-opening polymerization by lithium catalysts: an overview.

    PubMed

    Sutar, Alekha Kumar; Maharana, Tungabidya; Dutta, Saikat; Chen, Chi-Tien; Lin, Chu-Chieh

    2010-05-01

    This critical review summarizes recent developments in the preparation and application of lithium catalysts/initiators such as, alkyl lithium, alkoxy lithium and bimetallic lithium compounds for ring-opening polymerization (ROP). The ROP of cyclic esters, cyclic carbonates, cyclo-silazanes, cyclo-silanes, cyclo-siloxanes, cyclo-carboxylate, cyclic phosphirene and quinodimethanes are covered in this review. The present paper emphasizes the polymerization kinetics and the control exhibited by the different types of lithium initiators/catalysts. For the cases where useful properties, such as high molecular weight, narrow PDI, or stereocontrol, have been observed, a more detailed examination of the mechanistic studies of the catalysts/initiators are provided. Furthermore, this review also focuses on the synthesis of block copolymers and graft copolymers by ROP principle. The topics covered in this review regarding lithium compounds toward ROP will be of interest to inorganic, organic and organometallic chemists, material, polymer and catalytic scientists due to its unique mode of activation as compared to transition and inner transition-metals. In addition, use of these compounds in catalysis is steadily growing, because of the complementary reactivity toward ROP as compared to other metals. Finally, some aspects and opportunities which may be of interest in the future are suggested (143 references).

  15. Effect of Feedstock and Catalyst Impurities on the Methanol‐to‐Olefin Reaction over H‐SAPO‐34

    PubMed Central

    Vogt, Charlotte; Ruiz‐Martínez, Javier

    2016-01-01

    Abstract Operando UV/Vis spectroscopy with on‐line mass spectrometry was used to study the effect of different types of impurities on the hydrocarbon pool species and the activity of H‐SAPO‐34 as a methanol‐to‐olefins (MTO) catalyst. Successive reaction cycles with different purity feedstocks were studied, with an intermittent regeneration step. The combined study of two distinct impurity types (i.e., feed and internal impurities) leads to new insights into MTO catalyst activation and deactivation mechanisms. In the presence of low amounts of feed impurities, the induction and active periods of the process are prolonged. Feed impurities are thus beneficial in the formation of the initial hydrocarbon pool, but also aid in the unwanted formation of deactivating coke species by a separate, competing mechanism favoring coke species over olefins. Further, feedstock impurities strongly influence the location of coke deposits, and thus influence the deactivation mechanism, whereas a study of the organic impurities retained after calcination reveals that these species are less relevant for catalyst activity and function as “seeds” for coke formation only. PMID:28163792

  16. Nanoscaled copper metal-organic framework (MOF) based on carboxylate ligands as an efficient heterogeneous catalyst for aerobic epoxidation of olefins and oxidation of benzylic and allylic alcohols.

    PubMed

    Qi, Yue; Luan, Yi; Yu, Jie; Peng, Xiong; Wang, Ge

    2015-01-19

    Aerobic epoxidation of olefins at a mild reaction temperature has been carried out by using nanomorphology of [Cu3(BTC)2] (BTC = 1,3,5-benzenetricarboxylate) as a high-performance catalyst through a simple synthetic strategy. An aromatic carboxylate ligand was employed to furnish a heterogeneous copper catalyst and also serves as the ligand for enhanced catalytic activities in the catalytic reaction. The utilization of a copper metal-organic framework catalyst was further extended to the aerobic oxidation of aromatic alcohols. The shape and size selectivity of the catalyst in olefin epoxidation and alcohol oxidation was investigated. Furthermore, the as-synthesized copper catalyst can be easily recovered and reused several times without leaching of active species or significant loss of activity.

  17. Lithium metal protection enabled by in-situ olefin polymerization for high-performance secondary lithium sulfur batteries

    NASA Astrophysics Data System (ADS)

    An, Yongling; Zhang, Zhen; Fei, Huifang; Xu, Xiaoyan; Xiong, Shenglin; Feng, Jinkui; Ci, Lijie

    2017-09-01

    Lithium metal is considered to be the optimal choice of next-generation anode materials due to its ultrahigh theoretical capacity and the lowest redox potential. However, the growth of dendritic and mossy lithium for rechargeable Li metal batteries lead to the possible short circuiting and subsequently serious safety issues during charge/discharge cycles. For the further practical applications of Li anode, here we report a facile method for fabricating robust interfacial layer via in-situ olefin polymerization. The resulting polymer layer effectively suppresses the formation of Li dendrites and enables the long-term operation of Li metal batteries. Using Li-S cells as a test system, we also demonstrate an improved capacity retention with the protection of tetramethylethylene-polymer. Our results indicate that this method could be a promising strategy to tackle the intrinsic problems of lithium metal anodes and promote the development of Li metal batteries.

  18. Frontiers in olefin polymerization: reinventing the world's most common synthetic polymers.

    PubMed

    Hustad, Phillip D

    2009-08-07

    Synthetic polymers are vital to our society, affecting practically every aspect of modern life. The ubiquitous nature of these materials is a result of years of collaboration between basic and applied researchers across many disciplines, resulting in economic routes to materials that meet customer needs. These considerations are exemplified by recent developments in the synthesis of block copolymers from simple olefins. The practical application of creative chemistry has produced materials with a favorable balance of desirable polymer properties and process economics.

  19. Methanol conversion to light olefins over nanostructured CeAPSO-34 catalyst: Thermodynamic analysis of overall reactions and effect of template type on catalytic properties and performance

    SciTech Connect

    Aghamohammadi, Sogand; Haghighi, Mohammad; Charghand, Mojtaba

    2014-02-01

    Graphical abstract: In this research nanostructured CeAPSO-34 was synthesized to explore the effect of TEAOH and morpholine on its physiochemical properties and MTO performance. Prepared catalysts were characterized with XRD, FESEM, BET, FTIR and NH3-TPD techniques. The results indicated that the nature of the template determines the physiochemical properties of CeAPSO-34 due to different rate of crystal growth. The catalyst obtained by using morpholine showed longer life time as well as sustaining light olefins selectivity at higher values. Furthermore, a comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion. - Highlights: • Introduction of Ce into SAPO-34 framework. • Comparison of CeAPSO-34 synthesized using morpholine and TEAOH. • The nature of the template determines the physiochemical properties of CeAPSO-34. • Morpholine enhances catalyst lifetime in MTO process. • Presenting a complete reaction network for MTO process. - Abstract: TEAOH and morpholine were employed in synthesis of nanostructured CeAPSO-34 molecular sieve and used in methanol to olefins conversion. Prepared samples were characterized by XRD, FESEM, EDX, BET, FTIR and NH{sub 3}-TPD techniques. XRD patterns reflected the higher crystallinity of the catalyst synthesized with morpholine. The FESEM results indicated that the nature of the template determines the morphology of nanostructured CeAPSO-34 due to different rate of crystal growth. There was a meaningful difference in the strength of both strong and weak acid sites for CeAPSO-34 catalysts synthesized with TEAOH and morpholine templates. The catalyst synthesized with morpholine showed higher desorption temperature of both weak and strong acid sites evidenced by NH{sub 3}-TPD characterization. The catalyst obtained using morpholine template had the longer lifetime and sustained desired light olefins at higher values. A comprehensive

  20. Chloride-Bridged Dinuclear Rhodium(III) Complexes Bearing Chiral Diphosphine Ligands: Catalyst Precursors for Asymmetric Hydrogenation of Simple Olefins.

    PubMed

    Kita, Yusuke; Hida, Shoji; Higashihara, Kenya; Jena, Himanshu Sekhar; Higashida, Kosuke; Mashima, Kazushi

    2016-07-11

    Efficient rhodium(III) catalysts were developed for asymmetric hydrogenation of simple olefins. A new series of chloride-bridged dinuclear rhodium(III) complexes 1 were synthesized from the rhodium(I) precursor [RhCl(cod)]2 , chiral diphosphine ligands, and hydrochloric acid. Complexes from the series acted as efficient catalysts for asymmetric hydrogenation of (E)-prop-1-ene-1,2-diyldibenzene and its derivatives without any directing groups, in sharp contrast to widely used rhodium(I) catalytic systems that require a directing group for high enantioselectivity. The catalytic system was applied to asymmetric hydrogenation of allylic alcohols, alkenylboranes, and unsaturated cyclic sulfones. Control experiments support the superiority of dinuclear rhodium(III) complexes 1 over typical rhodium(I) catalytic systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Zero-Valent Amino-Olefin Cobalt Complexes as Catalysts for Oxygen Atom Transfer Reactions from Nitrous Oxide.

    PubMed

    Gianetti, Thomas L; Rodríguez-Lugo, Rafael E; Harmer, Jeffrey R; Trincado, Monica; Vogt, Matthias; Santiso-Quinones, Gustavo; Grützmacher, Hansjörg

    2016-12-05

    The synthesis and characterization of several zero-valent cobalt complexes with a bis(olefin)-amino ligand is presented. Some of these complexes proved to be efficient catalysts for the selective oxidation of secondary and allylic phosphanes, as well as diphosphanes, even with a direct P-P bond. With 5 mol % catalyst loadings the oxidations proceed under mild conditions (25-70 °C, 7-22 h, 2 bar N2 O) and afford good to excellent yields (65-98 %). In this process, the greenhouse gas N2 O is catalytically converted into benign N2 and added-value organophosphorus compounds, some of which are difficult to obtain otherwise. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Structure-property relationships in multilayered polymeric system and olefinic block copolymers

    NASA Astrophysics Data System (ADS)

    Khariwala, Devang

    diffusion. Subsequently, the oxygen permeability was directly related to the composition profile in each layer and changed as the interdiffusion proceeded. This methodology enabled the extraction of the mutual diffusion co-efficient, D, for the Nylon-6/EVOH system. The effect of comonomer content in EVOH on the mutual diffusion coefficient was also studied by comparing the kinetics of interdiffusion of Nylon-6 with two EVOHs containing 24 and 44 mole % ethylene. Chapter 3. Exciting new developments in polyolefin synthesis give rise to olefinic block copolymers with properties typical of thermoplastic elastomers. The block copolymers synthesized by chain shuttling technology consist of crystallizable ethylene-octene blocks with low comonomer content and high melting temperature (hard blocks), alternating with amorphous ethylene-octene blocks with high comonomer content and low glass transition temperature (soft blocks). This study describes the material science of these unique polymers as characterized by thermal analysis, X-ray diffraction, microscopy, and tensile deformation. The crystallizable blocks are long enough to form well-organized lamellar crystals with the orthorhombic unit cell and high melting temperature. The lamellae are organized into space-filling spherulites in all compositions even in copolymers with only 18 wt% hard block. The morphology is consistent with crystallization from a miscible melt. Crystallization of the hard blocks forces segregation of the noncrystallizable soft blocks into the interlamellar regions. Good separation of hard and soft blocks in the solid state is confirmed by distinct and separate beta- and alpha-relaxations in all the block copolymers. Compared to statistical ethylene-octene copolymers, the blocky architecture imparts a substantially higher crystallization temperature, a higher melting temperature and a better organized crystalline morphology, while maintaining a lower glass transition temperature. The differences between

  3. An atom-economic approach to carboxylic acids via Pd-catalyzed direct addition of formic acid to olefins with acetic anhydride as a co-catalyst.

    PubMed

    Wang, Yang; Ren, Wenlong; Shi, Yian

    2015-08-21

    An effective Pd-catalyzed hydrocarboxylation of olefins using formic acid with acetic anhydride as a co-catalyst is described. A variety of carboxylic acids are obtained in good yields with high regioselectivities under mild reaction conditions without the use of toxic CO gas.

  4. Hierarchical structured α-Al2O3 supported S-promoted Fe catalysts for direct conversion of syngas to lower olefins.

    PubMed

    Zhou, Xiangping; Ji, Jian; Wang, Di; Duan, Xuezhi; Qian, Gang; Chen, De; Zhou, Xinggui

    2015-05-25

    Hierarchical structured α-Al2O3 is shown to be able to effectively disperse and immobilize iron species, in comparison with commercial α-Al2O3. After promotion using an appropriate amount of sulfur, iron catalysts exhibit not only enhanced Fischer-Tropsch synthesis activity and selectivity toward lower olefins, but also increased resistance against carbon deposits.

  5. Iron-iron oxide core-shell nanoparticles are active and magnetically recyclable olefin and alkyne hydrogenation catalysts in protic and aqueous media.

    PubMed

    Hudson, Reuben; Rivière, Antoine; Cirtiu, Ciprian M; Luska, Kylie L; Moores, Audrey

    2012-04-04

    We report for the first time the use of iron-iron oxide core-shell nanoparticles for the hydrogenation of olefins and alkynes under mild conditions in ethanol and in an aqueous medium. This catalyst proves robust towards the presence of oxidants, such as oxygen and water, is magnetically recoverable and shows selectivity towards the less activated double bonds.

  6. A simple method for epoxidation of olefins using sodium chlorite as an oxidant without a catalyst.

    PubMed

    Geng, Xue-Li; Wang, Zhi; Li, Xiao-Qiang; Zhang, Chi

    2005-11-11

    [Reaction: see text]. Sodium chlorite has been demonstrated to be capable of epoxidizing a variety of olefins at 55-65 degrees C (oil bath). Chlorine dioxide is believed to be the pivotal epoxidizing agent in the reaction on the basis of the mechanistic studies.

  7. Ligand Exchange-Mediated Activation and Stabilization of a Re-Based Olefin Metathesis Catalyst by Chlorinated Alumina.

    PubMed

    Gallo, Alessandro; Fong, Anthony; Szeto, Kai C; Rieb, Julia; Delevoye, Laurent; Gauvin, Régis M; Taoufik, Mostafa; Peters, Baron; Scott, Susannah L

    2016-10-05

    Extensive chlorination of γ-Al2O3 results in the formation of highly Lewis acidic surface domains depleted in surface hydroxyl groups. Adsorption of methyltrioxorhenium (MTO) onto these chlorinated domains serves to activate it as a low temperature, heterogeneous olefin metathesis catalyst and confers both high activity and high stability. Characterization of the catalyst reveals that the immobilized MTO undergoes partial ligand exchange with the surface, whereby some Re sites acquire a chloride ligand from the modified alumina while donating an oxo ligand to the support. More specifically, Re LIII-edge EXAFS and DFT calculations support facile ligand exchange between MTO and Cl-Al2O3 to generate [CH3ReO2Cl(+)] fragments that interact with a bridging oxygen of the support via a Lewis acid-base interaction. According to IR and solid-state NMR, the methyl group remains intact, and does not evolve spontaneously to a stable methylene tautomer. Nevertheless, the chloride-promoted metathesis catalyst is far more active and productive than MTO/γ-Al2O3, easily achieving a TON of 100 000 for propene metathesis in a flow reactor at 10 °C (compared to TON < 5000 for the nonchlorinated catalyst). Increased activity is a consequence of both a larger fraction of active sites and a higher intrinsic activity for the new sites. Increased stability is tentatively attributed to a stronger interaction between MTO and chlorinated surface regions, as well as extensive depletion of the Brønsted acidic surface hydroxyl population. The reformulated catalyst represents a major advance for Re-based metathesis catalysts, whose widespread use has thus far been severely hampered by their instability.

  8. In situ generated bulky palladium hydride complexes as catalysts for the efficient isomerization of olefins. Selective transformation of terminal alkenes to 2-alkenes.

    PubMed

    Gauthier, Delphine; Lindhardt, Anders T; Olsen, Esben P K; Overgaard, Jacob; Skrydstrup, Troels

    2010-06-16

    Application of an in situ generated bulky palladium(II) hydride catalyst obtained from a 1:1:1 mixture of Pd(dba)(2), P(tBu)(3), and isobutyryl chloride provides an efficient protocol for the isomerization and migration of a variety of olefins. In addition to the isomerization of (Z)- to (E)-olefins, the conjugative migration of allylbenzenes, allyl ethers, and amines was effectively achieved in near-quantitative yields and with excellent functional group tolerance. Catalyst loadings in the range of 0.5-1.0 mol % were typically applied, but even loadings as low as 0.25 mol % could be achieved when the reactions were performed under neat conditions. More interestingly, the investigated catalyst proved to be selective for converting terminal alkenes to 2-alkenes. This one-carbon migration process for monosubstituted olefins provides an alternative catalyst, which bridges the gap between the allylation and propenylation/vinylation protocols. Several substrates, including homoallylic alcohols and amines, were selectively transformed into their corresponding 2-alkenes, and examples using enantiomerically enriched substrates provided products without epimerization at the allylic stereogenic carbon centers. Finally, some mechanistic investigations were undertaken to understand the nature of the active in situ generated Pd-H catalyst. These studies revealed that the catalytic system is highly dependent on the large steric demand of the P(tBu)(3) ligand. The use of an alternative ligand, cataCXium PinCy, also proved effective for generating an active catalyst, and it was demonstrated in some cases to display better selectivity for the one-carbon shifts of terminal olefins. A possible intermediate involved in the preparation of the active catalyst was characterized by its single-crystal X-ray structure, which revealed a monomeric tricoordinated palladium(II) acyl complex, bearing a chloride ligand.

  9. Pd@Pt Core-Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction.

    PubMed

    Datta, Kasibhatta Josena; Datta, Kasibhatta Kumara Ramanatha; Gawande, Manoj B; Ranc, Vaclav; Čépe, Klára; Malgras, Victor; Yamauchi, Yusuke; Varma, Rajender S; Zboril, Radek

    2016-01-26

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2 PdCl4, K2 PtCl6, and Pluronic P123 results in highly branched core-shell nanoparticles (NPs) with a micro-mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core-shell NPs, which differs from the traditional seed-mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion-like Pd@Pt core-shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro-mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Aluminium(III) trifluoromethanesulfonate as an efficient catalyst for the intramolecular hydroalkoxylation of unactivated olefins: experimental and theoretical approaches.

    PubMed

    Coulombel, Lydie; Rajzmann, Michel; Pons, Jean-Marc; Olivero, Sandra; Duñach, Elisabet

    2006-08-16

    The Al(OTf)(3)-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)(3) to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)(3) was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)(3)-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.

  11. Catalyst-controlled C-O versus C-N allylic functionalization of terminal olefins.

    PubMed

    Strambeanu, Iulia I; White, M Christina

    2013-08-14

    The divergent synthesis of syn-1,2-aminoalcohol or syn-1,2-diamine precursors from a common terminal olefin has been accomplished using a combination of palladium(II) catalysis with Lewis acid cocatalysis. Palladium(II)/bis-sulfoxide catalysis with a silver triflate cocatalyst leads for the first time to anti-2-aminooxazolines (C-O) in good to excellent yields. Simple removal of the bis-sulfoxide ligand from this reaction results in a complete switch in reactivity to afford anti-imidazolidinone products (C-N) in good yields and excellent diastereoselectivities. Mechanistic studies suggest the divergent C-O versus C-N reactivity from a common ambident nucleophile arises due to a switch in mechanism from allylic C-H cleavage/functionalization to olefin isomerization/oxidative amination.

  12. Polymerization of olefins through heterogeneous catalysis: 14--The influence of temperature in the solution copolymerization of ethylene

    SciTech Connect

    Jaber, I.A.; Ray, W.H. . Chemical Engineering Dept.)

    1993-10-10

    The influence of temperature variation on the kinetics and the polymer properties in the homo- and copolymerization of ethylene in a solution reactor is discussed. The polymerization is conducted in a semibatch mode at 320 Psig total reactor pressure for 10 min polymerization time. Temperature variations in the range 145-200 C in both homo- and copolymerization of ethylene with 1-octene shows that the highest catalyst yield was obtained at temperature of 165--175 C. At the optimal temperature, a high initial maximum in the rate of ethylene consumption is attained in a few seconds followed by a relatively slow decay when compared with polymerization conducted a higher temperatures. Polymerization at temperatures [>=] 185 C resulted in a lower peak in the consumption rate of ethylene accompanied by a rapid decay with time. In the case of ethylene/1-octene copolymerization, a rather low comonomer incorporation level is obtained at the conditions employed; the 1-octene incorporated was only 0.2--0.7 mol%. Higher M[sub w] values, of about 350,000 at 145 C, are obtained in homopolymerization in comparison to M[sub w] values obtained in copolymerization, of about 195,000 at the same temperature. Over the temperature range of 145--200 C, both M[sub w] and M[sub n] values vary by about 40%.

  13. [Development of novel solid-phase polymeric catalysts for organic syntheses].

    PubMed

    Yamada, Yoichi M A

    2005-10-01

    Highly active and reusable polymeric catalysts were produced by a self-assembly process of non-cross-linked amphiphilic polymeric ligands with inorganic species. Thus a new insoluble tungsten polymeric catalyst PWAA 1 was prepared from H(3)PW(12)O(40) and poly[(N-isopropylacrylamide)-co-(acrylamide with ammonium salt)], which was suitable for the oxidation of alcohols, amines, and sulfides in aqueous hydrogen peroxide. A new insoluble palladium polymeric catalyst PdAS 2 was produced by self-organization of (NH(4))(2)PdCl(4) and poly[(N-isopropylacrylamide)(10)-co-diphenylphosphinostyrene], which is an excellent recyclable catalyst for the Suzuki-Miyaura reaction in water, water-organic solvents, and organic solvents. It is commercially available from Tokyo Kasei Kogyo (TCI). An improved insoluble palladium polymeric catalyst PdAS-V 3 was assembled from (NH(4))(2)PdCl(4) and poly[(N-isopropylacrylamide)(5)-co-diphenylphosphinostyrene], providing a reusable system for the Mizorogi-Heck reaction. A solid-phase titanium asymmetric polymeric catalyst TiSS 4 was made from Ti (O-i-Pr)(4) and poly(styryl-linked binaphtholate-co-styrene) which promotes an enantioselective carbonyl-ene reaction as a recyclable catalyst.

  14. Characterization of bonding between poly(dimethylsiloxane) and cyclic olefin copolymer using corona discharge induced grafting polymerization.

    PubMed

    Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z Hugh

    2012-01-01

    Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated.

  15. Characterization of Bonding Between Poly(dimethylsiloxane) and Cyclic Olefin Coplymer Using Corona Discharge Induced Grafting Polymerization

    PubMed Central

    Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z. Hugh

    2011-01-01

    Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated. PMID:21962541

  16. Co-aromatization of olefin and methane over Ag-Ga/ZSM-5 catalyst at low temperature

    DOE PAGES

    He, Peng; Gatip, Richard; Yung, Matthew; ...

    2017-04-22

    The massive exploitation of shale gas in the past decade has boosted the production of natural gas and reduced its price dramatically. The methane activation and following conversion into more valuable fuels and chemicals have thus become more and more attractive, while the introduction of hydrocarbons to enhance the methane activation at mild conditions represents a promising approach. In the present work, the co-aromatization of methane with propylene has been studied at 400 °C. The presence of methane would increase the toluene to benzene ratio as well as the average carbon number of the formed liquid aromatic products compared tomore » its propylene alone counterpart. Among the gas products, the formations of C3H8, C4H8 and C4H10 also get promoted when methane is present. The incorporation of methane into the product molecules is also directly evidenced by the 1H, 2D and 13C NMR spectroscopy of the liquid products obtained from the reaction between propylene (or styrene) and isotope labelled methane. Hydrogen from methane would contribute a large portion of the hydrogen in the product molecules, while the benzylic and aromatic hydrogen sites are favored compared with those on the alkyl side chains. The activation of methane is also observed in the DRIFT spectra when deuterium enriched methane is engaged as the methane source and evidenced by the escalated exothermic feature when olefin aromatization takes place under methane environment. The excellent catalytic performance of Ag-Ga/ZSM-5 might be because of the better dispersion of Ag and Ga on the ZSM-5 surface and moderate amount of strong Brosted and Lewis surface acid sites. All the observations suggest that methane might be activated nonoxidatively and converted into aromatics if suitable catalyst is charged under the assistance of co-existing olefin. In conclusion, the reported synergetic effect could potentially lead to the more economic utilization of abundant natural gas and petrochemical

  17. Advances in the development of new catalysts for ethylene and α-olefin polymerisation

    NASA Astrophysics Data System (ADS)

    Ivanchev, Sergei S.

    2007-07-01

    The role of catalyst systems in the perfection of polymerisation processes and the improvement of the performance characteristics of polyethylene and other polyolefins is considered. The scope of application of post-metallocene catalysts based on transition metal α-diimine, bis(imino)pyridine and phenoxy imine complexes designed in the last decade is analysed. The structures of complexes depending on the type of ligands are described systematically. The development of research into these catalyst systems is discussed, the optimal structures as regards the activity and selectivity are mentioned, and the mechanism of their action and the prospects for industrial use are demonstrated.

  18. Conversion of Syngas-Derived C2+ Mixed Oxygenates to C3-C5 Olefins over ZnxZryOz Mixed Oxides Catalysts

    SciTech Connect

    Smith, Colin D.; Lebarbier, Vanessa M.; Flake, Matthew D.; Ramasamy, Karthikeyan K.; Kovarik, Libor; Bowden, Mark E.; Onfroy, Thomas; Dagle, Robert A.

    2016-04-01

    In this study we report on a ZnxZryOz mixed oxide type catalyst capable of converting a syngas-derived C2+ mixed oxygenate feedstock to isobutene-rich olefins. Aqueous model feed comprising of ethanol, acetaldehyde, acetic acid, ethyl acetate, methanol, and propanol was used as representative liquid product derived from a Rh-based mixed oxygenate synthesis catalyst. Greater than 50% carbon yield to C3-C5 mixed olefins was demonstrated when operating at 400-450oC and 1 atm. In order to rationalize formation of the products observed feed components were individually evaluated. Major constituents of the feed mixture (ethanol, acetaldehyde, acetic acid, and ethyl acetate) were found to produce isobutene-rich olefins. C-C coupling was also demonstrated for propanol feedstock - a minor constituent of the mixed oxygenate feed - producing branched C6 olefins, revealing scalability to alcohols higher than ethanol following an analogous reaction pathway. Using ethanol and propanol feed mixtures, cross-coupling reactions produced mixtures of C4, C5, and C6 branched olefins. The presence of H2 in the feed was found to facilitate hydrogenation of the ketone intermediates, thus producing straight chain olefins as byproducts. While activity loss from coking is observed complete catalyst regeneration is achieved by employing mild oxidation. For conversion of the mixed oxygenate feed a Zr/Zn ratio of 2.5 and a reaction temperature of 450oC provides the best balance of stability, activity, and selectivity. X-ray diffraction and scanning transmission electron microscopy analysis reveals the presence of primarily cubic phase ZrO2 and a minor amount of the monoclinic phase, with ZnO being highly dispersed in the lattice. The presence of ZnO appears to stabilize the cubic phase resulting in less monoclinic phase as the ZnO concentration increases. Infrared spectroscopy shows the mixed oxide acid sites are characterized as primarily Lewis type acidity. The direct relationship between

  19. Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

    PubMed Central

    Pump, Eva; Pazio, Aleksandra E; Woźniak, Krzysztof; Cavallo, Luigi

    2015-01-01

    Summary Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted compound. The studied complexes are very stable at high temperatures up to 140 °C. The placement of an electron-withdrawing functionality translates into an enhanced activity in RCM. While electronically modified precatalysts, which exist predominantly in the trans-dichloro configuration, gave mostly the RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the reactivity of the complexes. PMID:26425202

  20. Reaction of deuterium with olefins on nickel catalysts: evidence for adsorbed vinylic species

    SciTech Connect

    Mintsa-Eya, V.; Hilaire, L.; Choplin, A.; Touroude, R.; Gault, F.G.

    1983-08-01

    The interaction of deuterium with 1,2-dimethylcyclopentene, 2,3-dimethylcyclopentene, 1-methyl-2-methylenecyclopentane, 1,2-dimethylcyclobutene, 1-methyl-2-methylenecyclobutane, bicyclo(2,2,1)heptene, but-1-ene, and cis-but-2-ene was studied from -85 to 50/sup 0/C on nickel films in a static apparatus and on Ni/pumice in a flow system. Unexpected d/sub 3/ and d/sub 4/ molecules were obtained in the deuteration of bicyclo(2,2,1)heptene. The position of the double bond in the ring of the other cycloolefins was the main factor governing their behavior: in the deuteration of 1,2-dimethylcycloalkenes, the saturated products, especially the trans somers, were much more exchanged and the percentage of trans was lower than when the starting material consisted of the olefins with the double bond in 2,3 or exocyclic positions. The hyperfine distribution, obtained by microwave analysis, of the exchanged d/sub 1/ but-1-ene, revealed that the major part of the deuterium was introduced on C/sub 2/; the cis-trans isomerization was much faster than the double bond migration with the introduction of zero or one deuterium atom while the isomerized but-1-ene showed a multiple exchange up to d/sub 4/; in the isomerized d/sub 1/ but-1-ene, the deuterium atom was distributed on the three carbon atoms C/sub 1/, C/sub 2/, C/sub 3/. Most of these results clearly show that the classical Horiuti-Polanyi mechanism is not the only one taking part in the reactions. The introduction of other intermediaries, sigma-vinylic, sigma-vinylic ..pi..-olefinic, and sigma-vinylic ..pi..-allylic species, provides a coherent explanation for all our findings. It is shown that nickel and iron behave in a very similar way. 5 tables.

  1. Polymeric heterogeneous catalysts of transition-metal oxides: surface characterization, physicomechanical properties, and catalytic activity.

    PubMed

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

    2013-12-16

    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.

  2. New organo-Lewis acids. Tris({beta}-perfluoronaphthyl)borane (PNB) as a highly active cocatalyst for metallocene-mediated Ziegler-Natta {alpha}-olefin polymerization

    SciTech Connect

    Li, L.; Marks, T.J.

    1998-08-31

    Tris({beta}-perfluoronaphthyl)borane (B(C{sub 10}F{sub 7}){sub 3}, PNB) is synthesized from {beta}-perfluoronaphthyllithium and BCl{sub 3} to serve as a new strong organo-Lewis acid cocatalyst. PNB efficiently activates a variety of group 4 dimethyl complexes to form highly active homogeneous Ziegler-Natta olefin polymerization catalysts. Reaction of PNB with rac-Me{sub 2}Si(Ind){sub 2}ZrMe{sub 2} and CGCMMe{sub 2} (M = Zr, Ti; CGC = Me{sub 2}Si({eta}{sup 5}-Me{sub 4}C{sub 5})({sup t}BuN)) (1:1 molar ratio) rapidly produces the base-free cationic complexes rac-Me{sub 2}Si(Ind){sub 2}ZrMe{sup +}MePNB{sup {minus}} (1) and CGCMMe{sup +}MePNB{sup {minus}} (M = Zr, 2; Ti, 3), respectively. The {mu}-methyl dinuclear cationic complex [(CGCTiMe){sub 2}({mu}-Me)]{sup +}MePNB{sup {minus}} (4) is formed when 2:1 CGCTiMe{sub 2}:PNB stoichiometry is employed. In the case of group 4 dimethyl zirconocenes, L{sub 2}ZrMe{sub 2} (L = {eta}{sup 5}-C{sub 5}H{sub 5}, Cp; {eta}{sup 5}-1,2-Me{sub 2}C{sub 5}H{sub 3}, Cp{double_prime}), reaction in a 1:1 metallocene:PNB ratio affords cationic complexes L{sub 2}ZrMe{sup +}MePNB{sup {minus}} (L = Cp, 5; Cp{double_prime}, 6), while the reaction with a 1:2 molar ratio affords dinuclear {mu}-methyl cationic complexes [(L{sub 2}ZrMe){sub 2}({mu}-Me)]{sup +}MePNB{sup {minus}} (L = Cp, 7; Cp{double_prime}, 8). In both reactions, {mu}-F dinuclear cationic complexes [(L{sub 2}ZrMe){sub 2}({mu}F)]{sup +}MePNB{sup {minus}} (L = Cp, 9; Cp{double_prime}, 10) are formed as byproducts. (C{sub 6}F{sub 5}){sub 3}BNCCH{sub 3} and PNBNCCH{sub 3} were synthesized and characterized.

  3. Nanocrystalline SSZ-39 zeolite as an efficient catalyst for the methanol-to-olefin (MTO) process.

    PubMed

    Martín, Nuria; Li, Zhibin; Martínez-Triguero, Joaquín; Yu, Jihong; Moliner, Manuel; Corma, Avelino

    2016-04-26

    The synthesis of nanosized SSZ-39 zeolite has been achieved using a high silica FAU zeolite as the Si and Al source and tetraethylphosphonium (TEP) cations as OSDAs. The obtained SSZ-39 material shows a remarkably high catalyst lifetime compared to conventional SSZ-13 and SSZ-39 materials.

  4. Metallocene catalyst containing bulky organic group

    DOEpatents

    Marks, Tobin J.; Ja, Li; Yang, Xinmin

    1996-03-26

    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.

  5. Metallocene catalyst containing bulky organic group

    DOEpatents

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

    1996-03-26

    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.

  6. Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: a mechanistic study.

    PubMed

    Ahmed, Syud M; Poater, Albert; Childers, M Ian; Widger, Peter C B; LaPointe, Anne M; Lobkovsky, Emil B; Coates, Geoffrey W; Cavallo, Luigi

    2013-12-18

    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.

  7. Ring-expanding olefin metathesis: a route to highly active unsymmetrical macrocyclic oligomeric co-salen catalysts for the hydrolytic kinetic resolution of epoxides.

    PubMed

    Zheng, Xiaolai; Jones, Christopher W; Weck, Marcus

    2007-02-07

    In the presence of the third generation Grubbs catalyst, the ring-expanding olefin metathesis of a monocyclooct-4-en-1-yl functionalized salen ligand and the corresponding Co(II)(salen) complex at low monomer concentrations results in the exclusive formation of macrocyclic oligomeric structures with the salen moieties being attached in an unsymmetrical, flexible, pendent manner. The TOF-MALDI mass spectrometry reveals that the resulting macrocyclic oligomers consist predominantly of dimeric to tetrameric species, with detectable traces of higher homologues up to a decamer. Upon activation under aerobic and acidic conditions, these Co(salen) macrocycles exhibit extremely high reactivities and selectivities in the hydrolytic kinetic resolution (HKR) of a variety of racemic terminal epoxides under neat conditions with very low catalyst loadings. The excellent catalytic properties can be explained in terms of the new catalyst's appealing structural features, namely, the flexible oligomer backbone, the unsymmetrical pendent immobilization motif of the catalytic sites, and the high local concentration of Co(salen) species resulting from the macrocyclic framework. This ring-expanding olefin metathesis is suggested to be a simple way to prepare tethered metal complexes that are endowed with key features--(i) a high local concentration of metal complexes and (ii) a flexible, single point of attachment to the support--that facilitate rapid and efficient catalysis when a bimetallic transition state is required.

  8. Effects of the Functionalization of the Ordered Mesoporous Carbon Support Surface on Iron Catalysts for the Fischer–Tropsch Synthesis of Lower Olefins

    PubMed Central

    Hofmann, Jan P.; van Deelen, Tom W.; Lamme, Wouter S.; Krans, Nynke A.; Hensen, Emiel J. M.

    2017-01-01

    Abstract Ordered mesoporous carbon (CMK‐3) with different surface modifications is applied as a support for Fe‐based catalysts in the Fischer–Tropsch to olefins synthesis (FTO) with and without sodium and sulfur promoters. Different concentrations of functional groups do not affect the size (3–5 nm) of Fe particles in the fresh catalysts but iron (carbide) supported on N‐enriched CMK‐3 and a support with a lower concentration of functional groups show higher catalytic activity under industrially relevant FTO conditions (340 °C, 10 bar, H2/CO=2) compared to a support with an O‐enriched surface. The addition of promoters leads to more noticeable enhancements of the catalytic activity (3–5 times higher) and the selectivity to C2–C4 olefins (≈2 times higher) than surface functionalization of the support. Nitrogen surface functionalization and removal of surface groups before impregnation and calcination, however, further increase the activity of the catalysts in the presence of promoters. The confinement of the Fe nanoparticles in the mesopores of CMK‐3 restricts but does not fully prevent particle growth and, consequently, the decrease of activity under FTO conditions. PMID:28286582

  9. A Well-Defined, Silica-Supported Tungsten Imido Alkylidene OlefinMetathesis Catalyst

    SciTech Connect

    Rhers, Bochra; Salameh, Alain; Baudouin, Anne; Quadrelli, ElsjeA.; Taoufik, Mostafa; Coperet, Christophe; Lefebvre, Frederic; Basset,Jean-Marie; Solans-Monfort, Xavier; Eisenstein, Odile; Lukens, Wayne W.; Lopez, Lordes.P.H.; Sinha, Amritanshu; Schrock, Richard R.

    2006-06-13

    The reaction of [W(=NAr)(=CHtBu)(CH2tBu)2](1; Ar =2,6-iPrC6H3) with a silica partially dehydroxylated at 700oC, SiO2-(700),gives syn-[(_SiO)W(=NAr)(=CHtBu)(CH2tBu)](2) as a major surface species,which was fully characterized by mass balance analysis, IR, NMR, EXAFS,and DFT periodic calculations. Similarly, complex 1 reacts with[(c-C5H9)7Si7O12SiOH]to give [(SiO)W(=NAr)(=CHtBu)(CH2tBu)](2m), whichshows similar spectroscopic properties. Surface complex 2 is a highlyactive propene metathesis catalyst, which can achieve a TON of 16000within 100 h, with only a slow deactivation.

  10. Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

    PubMed Central

    Koy, Maximilian; Altmann, Hagen J; Autenrieth, Benjamin; Frey, Wolfgang

    2015-01-01

    Summary The novel dicationic metathesis catalyst [(RuCl2(H2ITapMe2)(=CH–2-(2-PrO)-C6H4))2+ (OTf−)2] (Ru-2, H2ITapMe2 = 1,3-bis(2’,6’-dimethyl-4’-trimethylammoniumphenyl)-4,5-dihydroimidazol-2-ylidene, OTf− = CF3SO3 −) based on a dicationic N-heterocyclic carbene (NHC) ligand was prepared. The reactivity was tested in ring opening metathesis polymerization (ROMP) under biphasic conditions using a nonpolar organic solvent (toluene) and the ionic liquid (IL) 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM+][BF4 −]. The structure of Ru-2 was confirmed by single crystal X-ray analysis. PMID:26664582

  11. Evidence for an initiation of the methanol-to-olefin process by reactive surface methoxy groups on acidic zeolite catalysts.

    PubMed

    Wang, Wei; Buchholz, Andreas; Seiler, Michael; Hunger, Michael

    2003-12-10

    Recent progress reveals that, in the methanol-to-olefin (MTO) process on acidic zeolites, the conversion of an equilibrium mixture of methanol and DME is dominated by a "hydrocarbon pool" mechanism. However, the initial C-C bond formation, that is, the chemistry during the kinetic "induction period" leading to the reactive hydrocarbon pool, still remains unclear. With the application of a stopped-flow protocol, in the present work, pure surface methoxy groups [SiO(CH(3))Al] were prepared on various acidic zeolite catalysts (H-Y, H-ZSM-5, H-SAPO-34) at temperatures lower than 473 K, and the further reaction of these methoxy species was investigated by in situ (13)C MAS NMR spectroscopy. By using toluene and cyclohexane as probe molecules which are possibly involved in the MTO process, we show the high reactivity of surface methoxy species. Most importantly, the formation of hydrocarbons from pure methoxy species alone is demonstrated for the first time. It was found that (i) surface methoxy species react at room temperature with water to methanol, indicating the occurrence of a chemical equilibrium between these species at low temperatures. In the presence of aromatics and alkanes, (ii) the reactivity of surface methoxy groups allows a methylation of these organic compounds at reaction temperatures of ca. 433 and 493 K, respectively. In the absence of water and other organic species, that is, under flow conditions and on partially methylated catalysts, (iii) a conversion of pure methoxy groups alone to hydrocarbons was observed at temperatures of T >/= 523 K. This finding indicates a possible formation of the first hydrocarbons during the kinetic induction period of the MTO process via the conversion of pure surface methoxy species (case iii). After the first hydrocarbons are formed, or in the presence of a small amount of organic impurities, surface methoxy groups contribute to a further methylation of these organic compounds (case ii), leading to the formation of

  12. Generation effects on the microstructure and product distribution in ethylene polymerization promoted by dendritic nickel catalysts.

    PubMed

    Benito, José M; de Jesús, Ernesto; de la Mata, F Javier; Flores, Juan C; Gómez, Rafael

    2005-11-07

    Carbosilane dendrimers Gn-[(ONNMe2)NiBr2]m, containing up to sixteen terminal pyridylimine nickel complexes, have been studied as catalysts for polymerization of ethylene; the microstructure and the oligomer/polymer distribution are significantly affected by the generation of the dendritic precursor.

  13. A Study of Ziegler–Natta Propylene Polymerization Catalysts by Spectroscopic Methods

    PubMed Central

    Tkachenko, Olga P.; Kucherov, Alexey V.; Kustov, Leonid M.; Virkkunen, Ville; Leinonen, Timo; Denifl, Peter

    2017-01-01

    Ziegler–Natta polymerization catalysts were characterized by a complex of surface- and bulk-sensitive methods (DRIFTS, XPS, ESR, and XAS = XANES + EXAFS). A diffuse-reflectance Fourier-transform IR spectroscopy (DRIFTS) study showed the presence of strong Lewis acid sites in different concentrations and absence of strong basic sites in the polymerization catalysts. X-ray photoelectron spectroscopy (XPS), electron-spin resonance (ESR), and (X-ray absorption near-edge structure (XANES) analysis revealed the presence of Ti4+, Ti3+, Ti2+, and Ti1+ species in the surface layers and in the bulk of catalysts. The samples under study differ drastically in terms of the number of ESR-visible paramagnetic sites. The EXAFS study shows the presence of a Cl atom as a nearest neighbor of the absorbing Ti atom. PMID:28772850

  14. Conversions of lower olefins in the presence of a superhigh-silica zeolite catalyst with added V/sub 2/O/sub 5/

    SciTech Connect

    Minachev, Kh.M.; Kondrat'ev, D.A.; Degachev, A.A.; Borvinskaya, T.B.; Bondarenko, T.N.; Nefedov, B.K.; Alekseeva, T.V.

    1982-02-20

    The addition of V/sub 2/O/sub 5/ is known to increase the selectivity of formation of p-xylene (PX) from 1-octene in the presence of the Na form of superhigh-silica zeolite (SHSZ). The preferential formation of PX from ethylene, propene, and 1-hexene in the presence of SHSZ of the ZSM type with added Sb/sub 2/O/sub 3/, MgO, and B/sub 2/O/sub 3/ has been reported in patents. Continuing our study of the catalytic properties of SHSZ, we have examined the effects of adding V/sub 2/O/sub 5/ on the conversions of C/sub 3/-C/sub 4/ olefins. For purposes of comparison, experiments using ethylene with the original and modified catalysts were carried out, since the reactions of ethylene over catalysts of this type have been thoroughly studied.

  15. Axially coordinated chiral salen Mn(III) anchored onto azole onium modified ZnPS-PVPA as effective catalysts for asymmetric epoxidation of unfunctionalized olefins.

    PubMed

    Huang, Jing; Fu, Xiangkai; Wang, Gang; Miao, Qiang; Wang, Guomin

    2012-09-21

    A series of chiral salen Mn(III) immobilized onto azole onium modified zinc poly(styrene-phenylvinyl phosphonate)-phosphate (ZnPS-PVPA) were prepared. The catalysts were characterized by FT-IR, diffusion reflection UV-vis, AAS, N(2) volumetric adsorption, SEM, TEM, XPS, XRD, TG and elemental analysis. The results showed that the chiral salen Mn(III) complex was successfully immobilized onto ZnPS-PVPA. These prepared catalysts were evaluated in the asymmetric epoxidation of unfunctionalized olefins with m-CPBA and NaIO(4) as oxidants and demonstrated higher catalytic activities than those of the corresponding homogeneous chiral salen Mn(III) catalyst under the same conditions. Moreover, these heterogeneous catalysts were stable and could be recycled nine times without significant loss of activity. Furthermore, this novel type of catalyst could also be validly used in large-scale reactions with superior catalytic disposition being maintained at the same level, which indicated the potential for applications in industry.

  16. A fast-initiating ionically tagged ruthenium complex: a robust supported pre-catalyst for batch-process and continuous-flow olefin metathesis.

    PubMed

    Borré, Etienne; Rouen, Mathieu; Laurent, Isabelle; Magrez, Magaly; Caijo, Fréderic; Crévisy, Christophe; Solodenko, Wladimir; Toupet, Loic; Frankfurter, René; Vogt, Carla; Kirschning, Andreas; Mauduit, Marc

    2012-12-14

    In this study, a new pyridinium-tagged Ru complex was designed and anchored onto sulfonated silica, thereby forming a robust and highly active supported olefin-metathesis pre-catalyst for applications under batch and continuous-flow conditions. The involvement of an oxazine-benzylidene ligand allowed the reactivity of the formed Ru pre-catalyst to be efficiently controlled through both steric and electronic activation. The oxazine scaffold facilitated the introduction of the pyridinium tag, thereby affording the corresponding cationic pre-catalyst in good yield. Excellent activities in ring-closing (RCM), cross (CM), and enyne metathesis were observed with only 0.5 mol % loading of the pre-catalyst. When this powerful pre-catalyst was immobilized onto a silica-based cationic-exchange resin, a versatile catalytically active material for batch reactions was generated that also served as fixed-bed material for flow reactors. This system could be reused at 1 mol % loading to afford metathesis products in high purity with very low ruthenium contamination under batch conditions (below 5 ppm). Scavenging procedures for both batch and flow processes were conducted, which led to a lowering of the ruthenium content to as little as one tenth of the original values. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. ansa-Rare-earth-metal catalysts for rapid and stereoselective polymerization of renewable methylene methylbutyrolactones.

    PubMed

    Hu, Yangjian; Miyake, Garret M; Wang, Baoli; Cui, Dongmei; Chen, Eugene Y-X

    2012-03-12

    Two ansa-half-sandwich rare-earth-metal (REM) dialkyl complexes supported by an ethylene-bridged fluorenyl (Flu)-N-heterocyclic carbene (NHC) ligand, [M{C(2)H(4)(η(5)-Flu-κ(1)-NHC)}(CH(2)SiMe(3))(2)] (M=Y, 1; Lu, 2), and a chiral ansa-sandwich samarocene incorporating a C(2) ligand, [Sm(η(5)-C(12)H(8))(2)(thf)(2)] (3), have been investigated for the coordination-addition polymerization of renewable methylene butyrolactones, α-methylene-γ-butyrolactone (MBL) and γ-methyl-α-methylene-γ-butyrolactone ((γ)MMBL). Both ansa-half-sandwich complexes 1 and 2 exhibit exceptional activity for the polymerization of (γ)MMBL at room temperature in dimethylformamide (DMF); with a 0.25 mol% catalyst loading, quantitative monomer conversion can be achieved under 1 min, giving a high turn-over frequency (TOF) of 24,000 h(-1). This TOF value represents a rate enhancement, by a factor of 8, 22, or 2400, over the polymerizations by unbridged samarocene [Sm(Cp*)(2)(thf)(2)] (Cp*=η(5) -pentamethylcyclopentadienyl), by bridged ansa-samarocene 3 with C(2) ligation, or by the corresponding REM trialkyls without the ansa-Flu-NHC ligation, respectively. Complexes 1 and 2 are also highly active for the polymerization of β-methyl-α-methylene-γ-butyrolactone ((β)MMBL), realizing the first example of the metal-mediated coordination polymerization of this monomer and its copolymerization with (γ)MMBL. More remarkably, the resulting P(β)MMBL homopolymer is highly stereoregular (91% mm) and exhibits a high T(g) of 290 °C. In sharp contrast, catalysts 1 and 2 have poor activity and efficiency in the polymerization of the parent MBL or the acyclic analog methyl methacrylate. Polymerization and kinetic studies using the most active catalyst (1) of the series have uncovered characteristics of its (γ)MMBL polymerization and yielded a unimolecular propagation mechanism. A surprising chain-initiation pathway for the polymerization in DMF by 1 has been revealed, and catalytic

  18. Coordination polymerization of renewable butyrolactone-based vinyl monomers by lanthanide and early metal catalysts.

    PubMed

    Miyake, Garret M; Newton, Stacie E; Mariott, Wesley R; Chen, Eugene Y-X

    2010-08-07

    This contribution reports the first study of coordination-addition polymerization of renewable butyrolactone-based vinyl monomers, MBL (alpha-methylene-gamma-butyrolactone) and MMBL (gamma-methyl-alpha-methylene-gamma-butyrolactone), using neutral lanthanocene(II), non-lanthanocene(III), and cationic group 4 metallocene catalysts. The samarocene(II) catalyst, Cp*(2)Sm(THF)(2), promotes a rapid, efficient, and controlled polymerization of MBL and MMBL in DMF at ambient temperature, exhibiting a high TOF of 3000 h(-1), typically near quantitative initiator efficiency, and the ability to control the polymer MW. The resulting atactic PMBL and PMMBL have high T(g)'s of 194 degrees C and 227 degrees C, respectively; when compared to atactic PMMA having comparable MW, the T(g) and onset decomposition temperatures of the PMMBL produced are substantially higher (by approximately 120 degrees C and 40 degrees C, respectively). Owing to the living/controlled characteristics of this polymerization, well-defined random and block copolymers of MBL with MMA and MMBL can be readily synthesized. Results of the kinetic and polymerization studies indicate that the true active species is the trivalent samarocene centers attached to the single growing polymer chain, derived presumably from a redox-then-radical-coupling process. In comparison, the polymerizations by non-lanthanocene(III) silylamides, Ln[N(SiMe(3))(2)](3) (Ln = La, Nd, Sm, Er), and by cationic group 4 metallocene and half-metallocene catalysts incorporating C(2) and C(s) symmetric ligands are much slower and less effective. Catalytic polymerization of MBL by Cp*(2)Sm(THF)(2) has also been realized in the presence of an enolizable organo acid as a suitable chain transfer agent.

  19. Transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates: Catalysts for asymmetric olefin hydroamination and acceptorless alcohol decarbonylation

    SciTech Connect

    Manna, Kuntal

    2012-12-17

    The research presented and discussed in this dissertation involves the synthesis of transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates, and their application in catalytic enantioselective olefin hydroamination and acceptorless alcohol decarbonylation. Neutral oxazolinylboranes are excellent synthetic intermediates for preparing new borate ligands and also developing organometallic complexes. Achiral and optically active bis(oxazolinyl)phenylboranes are synthesized by reaction of 2-lithio-2-oxazolide and 0.50 equiv of dichlorophenylborane. These bis(oxazolinyl)phenylboranes are oligomeric species in solid state resulting from the coordination of an oxazoline to the boron center of another borane monomer. The treatment of chiral bis(oxazolinyl)phenylboranes with sodium cyclopentadienide provide optically active cyclopentadienyl-bis(oxazolinyl)borates H[PhB(C5H5)(OxR)2] [OxR = Ox4S-iPr,Me2, Ox4R-iPr,Me2, Ox4S-tBu]. These optically active proligands react with an equivalent of M(NMe2)4 (M = Ti, Zr, Hf) to afford corresponding cyclopentadienyl-bis(oxazolinyl)borato group 4 complexes {PhB(C5H4)(OxR)2}M(NMe2)2 in high yields. These group 4 compounds catalyze cyclization of aminoalkenes at room temperature or below, providing pyrrolidine, piperidine, and azepane with enantiomeric excesses up to 99%. Our mechanistic investigations suggest a non-insertive mechanism involving concerted C-N/C-H bond formation in the turnover limiting step of the catalytic cycle. Among cyclopentadienyl-bis(oxazolinyl)borato group 4 catalysts, the zirconium complex {PhB(C5H4)(Ox4S-iPr,Me2)2}Zr(NMe2)2 ({S-2}Zr(NMe2)2) displays highest activity and enantioselectivity. Interestingly, S-2

  20. Bifunctional Organic Polymeric Catalysts with a Tunable Acid-Base Distance and Framework Flexibility

    PubMed Central

    Chen, Huanhui; Wang, Yanan; Wang, Qunlong; Li, Junhui; Yang, Shiqi; Zhu, Zhirong

    2014-01-01

    Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage. PMID:25267260

  1. Bifunctional Organic Polymeric Catalysts with a Tunable Acid-Base Distance and Framework Flexibility

    NASA Astrophysics Data System (ADS)

    Chen, Huanhui; Wang, Yanan; Wang, Qunlong; Li, Junhui; Yang, Shiqi; Zhu, Zhirong

    2014-09-01

    Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage.

  2. Preparation of single-site catalyst inside the functionalized nanopore of silica and its ethylene polymerization.

    PubMed

    Lee, Sang Yun; Ko, Young Soo

    2013-06-01

    Amorphous silica have been functionalized with organo-silane, and (n-BuCp)2ZrCI2 and methylaluminoxane (MAO) were subsequently immobilized on the functionalized silica for the further evaluation as a catalyst of ethylene polymerization. Four organo-silanes such as 3-aminopropyltrimethoxysilane (1NS), N-[(3-trimethoxysilyl)propyl]ethylenediamine (2NS), N1-[3-(trimethoxysilyl)propyl]diethylenetriamine (3NS), and 4-(triethoxysilyl)butyronitrile (1NCy), were employed for this study. The Zr content and polymerization activity of the supported catalysts were strongly dependent on the kind and structure of organo-silane. 2NS showed the highest Zr content with higher activity, indicating the more Zr could be captured due to a stronger interaction between (n-BuCp)2ZrCl2 and amine group.

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

    PubMed Central

    Koyanagi, Kohei; Takashima, Yoshinori; Nakamura, Takashi; Yamaguchi, Hiroyasu

    2016-01-01

    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-yl)propane 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. PMID:28144318

  4. Organotitanium(IV) compounds as catalysts for the polymerization of isocyanates: The polymerization of isocyanates with functionalized side chains

    SciTech Connect

    Patten, T.E.; Novak, B.M. Lawrence Berkeley Lab., CA )

    1993-02-01

    Catalysts of the form CpTiCl[sub 2]X, where X = [minus]OCH[sub 2]CF[sub 3], [minus]N(CH[sub 3])[sub 2], or [minus]CH[sub 3] (2a, 2b, 2c; Cp = [eta][sup 5]-cyclopentadienyl), CP*TiCl[sub 2]OCH[sub 2]CF[sub 3](3; Cp* = [eta][sup 5]-pentamethylcyclopentadienyl), and Cp[sub 2]TiClOCH[sub 2]-CF[sub 3](4) were used to polymerize a variety of isocyanates. Titanium-alkoxide, -amide, and -alkyl bonds were all found to be active in initiating the insertion of isocyanate monomer. An advantageous consequence of the lesser Lewis acidity of 2a-c relative to TiCl[sub 3]OCH[sub 2]CF[sub 3](1) is that the polymerization of highly functionalized monomers is possible using 2a-c and not 1. 2-Isocyanotoethyl methacrylate (2IEM) was polymerized, using 2b, through the isocyanato group to a linear polymer; the resulting properties of this material were found to be quite different from what was reported by Graham et al. 2IEM trimer was synthesized and subsequently cross-linked using a free-radical initiator, and it was found that the properties of this material matched those of the earlier report. The Diels-Alder adduct of 2IEM with cyclopentadiene, 2-((2-isocyanatoethoxy)carbonyl)-2-methylbicyclo[2.2.1]hept-5-ene (2IECMBH) was prepared and also polymerized using 2b. The use of cyclopentadienyltitanium trichloride derivatives also provides a general route through which a wide variety of end groups may be incorporated onto the end of the polyisocyanate chain.

  5. Functionalized SBA-15 supported nickel (II)–oxime–imine catalysts for liquid phase oxidation of olefins under solvent-free conditions

    SciTech Connect

    Paul, Luna; Banerjee, Biplab; Bhaumik, Asim; Ali, Mahammad

    2016-05-15

    A new oxime–imine functionalized highly ordered mesoporous SBA-15 (SBA-15-NH{sub 2}-DAMO) has been synthesized via post-synthesis functionalization of SBA-15 with 3-aminopropyl-triethoxysilane followed by the Schiff base condensation with diacetylmonooxime, which was further reacted with Ni(ClO{sub 4}){sub 2} to yield the functionalized nickel catalyst SBA-15-NH{sub 2}-DAMO-Ni. All the synthesized materials were thoroughly characterized using different characterization techniques. It was found that SBA-15-NH{sub 2}-DAMO-Ni catalyzes the one-pot oxidation of olefins like styrene, cyclohexene, cyclooctene, 1-hexene and 1-octene to the corresponding benzaldehyde, cyclohexene-1-ol and cyclooctene-oxide, respectively under solvent-free conditions by using tert-butylhydroperoxide as oxidant. - Graphical abstract: A new well characterized oxime–imine functionalized highly ordered mesoporous SBA-15-NH{sub 2}-DAMO-Ni complex catalyzes the one-pot oxidation of olefins under solvent free mild conditions.

  6. Functionalized SBA-15 supported nickel (II)-oxime-imine catalysts for liquid phase oxidation of olefins under solvent-free conditions

    NASA Astrophysics Data System (ADS)

    Paul, Luna; Banerjee, Biplab; Bhaumik, Asim; Ali, Mahammad

    2016-05-01

    A new oxime-imine functionalized highly ordered mesoporous SBA-15 (SBA-15-NH2-DAMO) has been synthesized via post-synthesis functionalization of SBA-15 with 3-aminopropyl-triethoxysilane followed by the Schiff base condensation with diacetylmonooxime, which was further reacted with Ni(ClO4)2 to yield the functionalized nickel catalyst SBA-15-NH2-DAMO-Ni. All the synthesized materials were thoroughly characterized using different characterization techniques. It was found that SBA-15-NH2-DAMO-Ni catalyzes the one-pot oxidation of olefins like styrene, cyclohexene, cyclooctene, 1-hexene and 1-octene to the corresponding benzaldehyde, cyclohexene-1-ol and cyclooctene-oxide, respectively under solvent-free conditions by using tert-butylhydroperoxide as oxidant.

  7. Activation of Surface ReO x Sites on Al 2 O 3 Catalysts for Olefin Metathesis

    SciTech Connect

    Lwin, Soe; Li, Yuanyuan; Frenkel, Anatoly I.; Wachs, Israel E.

    2015-11-06

    The nature of activated surface ReOx sites and surface reaction intermediates for supported ReOx/Al2O3 catalysts during propylene self-metathesis were systematically investigated for the first time using in situ spectroscopy (Raman, UV–vis, XAS (XANES/EXAFS) and IR). In situ Raman spectroscopy reveals that olefins selectively interact with the surface dioxo ReO4 sites anchored at acidic alumina hydroxyls. In situ UV–vis indicates that surface Re5+ and some Re6+ sites form, and in situ XAS indicates a reduction in the number of Re=O bond character in the propylene self-metathesis reaction environment, especially as the temperature is increased. The appearance of oxygenated products during propylene activation supports the conclusion that catalyst activation involves removal of oxygen from the surface rhenia sites (pseudo-Wittig mechanism). Isotopic CD3CD=CD2 → CH3CH=CH2 switch experiments demonstrate the presence of surface Re=CD2 and Re=CDCD3 reaction intermediates, with the surface Re=CD2 species being the most abundant reaction intermediate. In situ IR spectroscopy indicates the presence of significant surface propylene π complexes on alumina and rhenia sites of the catalyst, which complicates analysis of surface reaction intermediates during propylene self-metathesis.

  8. Organo-modified ZnAl layered double hydroxide as new catalyst support for the ethylene polymerization.

    PubMed

    He, Fu-An; Zhang, Li-Ming

    2007-11-15

    Organo-modified ZnAl layered double hydroxide was used for the first time to support a nickel a-diimine catalyst for the ethylene polymerization, and its effects on the catalytic activity, the morphology, thermal stability, and dynamic viscoelastic properties of the resultant polyethylene material were investigated. Different from the homogeneous nickel a-diimine catalyst, the supported catalyst system was found to have a long-lasting polymerization activity. Moreover, the resultant polyethylene material showed good particle morphology, improved thermal stability, as well as enhanced storage modulus and complex viscosity.

  9. Production of diesel fuel from light olefins

    SciTech Connect

    Tabak, S.A.; Krambeck, F.J.

    1986-03-01

    Mobile Research and Development Corporation has developed a catalytic process for converting light olefinic compounds to high quality gasoline and distillate. The process has been named Mobil Olefin to Gasoline and Distillate (MOGD) Process. Based on the Mobile zeolite catalyst ZSM-5, light olefins can be shape selectively oligomerized to higher molecular weight iso-olefins. In the gasoline boiling range, these olefins have a high octane number and for the diesel fuel range product a high cetane number and low pour point following hydrogenation. Through normally designed to process propylene or butylene, MOGD is applicable to a wide range of feed streams ranging from ethylene to 400/sup 0/F endpoint olefinic naphtha. The process has been tested using commercially-produced catalyst in refinery scale equipment.

  10. Synthetic and Mechanistic Investigations of Polymerization Catalyzed for Early Transition Metal Compounds

    SciTech Connect

    John E. Bercaw

    2001-03-18

    The objectives of the research program are (1) to discover new types of chemical transformations between hydrocarbons and transition-metal compounds, (2) to investigate their mechanisms; and (3) to explore the possibilities of coupling these transformations with others to catalyze chemical reactions for the preparation of fuels, commodity chemicals and polymeric materials. A current focus is the catalytic polymerization of alpha-olefins. New and superior polymers with different microstructures and potentially very useful kinetic resolutions of abundant, racemic alpha-olefins could be realized, if sufficient control over the polymerization process could be achieved. Well defined, yttrocene catalysts have been synthesized, some with known absolute configurations, and their reactions with an isotopically chiral 1-pentene monomer have been examined. These experiments have revealed the absolute olefin facial preferences for 1-pentene addition to Y-H and Y-pentyl bonds. A new class of zirconocene catalysts having doubly-linked cyclopentadienyl ligands has been developed, which allow the preparation of polypropylenes varying from isotactic to syndiotactic. These catalysts are highly reactive, permitting the polymerization of normally unreactive monomers such as 3-substituted alpha olefins. Chiral versions effect polymerization of such racemic monomers with useful kinetic resolutions.

  11. Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst.

    PubMed

    Yeow, Jonathan; Xu, Jiangtao; Boyer, Cyrille

    2016-06-08

    Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (λ = 460 nm, 0.7 mW/cm(2)), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

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

    PubMed

    Lou, Qin; Shipp, Devon A

    2012-10-08

    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.

  13. An S(N)Ar approach to sterically hindered ortho-alkoxybenzaldehydes for the synthesis of olefin metathesis catalysts.

    PubMed

    Engle, Keary M; Luo, Shao-Xiong; Grubbs, Robert H

    2015-04-17

    A three-step procedure has been developed for preparing ortho-alkoxybenzaldehydes from ortho-fluorobenzaldehydes that tolerates the use of sterically hindered sodium alkoxide nucleophiles. The protocol is modular and operationally convenient. The ortho-alkoxybenzaldehyde products can be converted in one additional step to ortho-alkoxystyrenes by a Wittig reaction. These styrenes are precursors to the chelating benzylidene moiety in a proposed series of novel ruthenium complexes for use in olefin metathesis. Chelation with three representative styrenes has been demonstrated.

  14. 'Catalysts' for polyacrylamide gel polymerization and detection of proteins by silver staining.

    PubMed

    Hochstrasser, D F; Merril, C R

    1988-01-01

    The crosslinker diacrylyl-piperazine produces polyacrylamide gels which display improved electrophoretic separation of proteins and better physical strength. It also produces gels with improved detection of proteins by ammoniacal silver staining by reducing the background. This reduced background provided us with an opportunity to investigate residual background staining caused by the catalytic reagents utilized in the polymerization of acrylamide gels. The commonly used catalyst system, tetramethyl-ethylenediamine and ammonium persulfate was shown to be responsible for the yellow staining background found after a prolonged development time with silver staining. An alternate catalyst system has been designed to decrease further the formation of this background staining. Dimethyl-piperazine or tetramethylethylenediamine, potassium or ammonium persulfate, and sodium thiosulfate are shown to provide for gels which have excellent mechanical and staining characteristics. These catalytic systems produce little background staining despite prolonged development time with the ammoniacal silver stain, and they reduce background staining with the dichromate silver stain.

  15. Synthesis of silicon carbide nanorods by catalyst-assisted pyrolysis of polymeric precursor

    NASA Astrophysics Data System (ADS)

    Yang, Weiyou; Miao, Hezhuo; Xie, Zhipeng; Zhang, Ligong; An, Linan

    2004-01-01

    In this Letter, we report the synthesis of β-SiC nanorods by the pyrolysis of a polysilazane polymeric precursor in the presence of 3 wt% FeCl 2 as a catalyst. The precursor is completely converted to the nanorods after heat-treated at 1700 °C for 2 h, accompanied by ˜50% weight loss. Electron microscopy study reveals that the nanorods preferentially grow along [1 1 1] direction; and the diameters of the nanorods range from 80 to 200 nm and lengths are ˜4 μm. A solid-liquid-solid growth mechanism is proposed.

  16. Employing high-resolution materials characterization to understand the effects of Pd nanoparticle structure on their activity as catalysts for olefin hydrogenation.

    PubMed

    Knecht, Marc R; Pacardo, Dennis B

    2010-06-01

    Recent developments in nanotechnology have led to the production of new materials with a wide array of applications, particularly in catalysis. Because of their small size, nanoparticles have a maximized surface-to-volume ratio, thus making them attractive targets for use as catalytic structures; however, the number of analytical techniques available to fully characterize materials on such a size scale is quite limited. As a result, a complete understanding of the entire nanoparticle structure remains unclear, especially when considering the active structural motif from which the specific activity arises. Metallic Pd materials have been widely studied due to their immense potential as catalysts for reactions such as olefin hydrogenation and C-C bond synthesis. These materials require surface passivants to act as ligands and stabilize the nanoparticles against aggregation and bulk formation. These ligands have the added value to function as gates that selectively allow reagents to reach the active surface of the Pd nanoparticles for chemical turnover. This accounts for the observed selectivities of the catalysts with the corresponding changes in the turnover frequency values. Here we present a broad overview of recent advances in the use of Pd nanoparticles for the industrially important hydrogenation reaction with a focus on characterizing and understanding the base structural effects that give rise to the catalytic activity.

  17. The Oxidation of Sulfur-Containing Compounds Using Heterogeneous Catalysts of Transition Metal Oxides Deposited on the Polymeric Matrix

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  18. Olefins can limit desulfurization of reformer feedstock

    SciTech Connect

    Ali, S.A.; Anabtawi, J.A.

    1995-07-03

    Pilot plant studies have shown that the presence of even very small amounts of olefins may limit the desulfurization of reformer feedstocks to trace levels. Engineers at the Research Institute of King Fahd University of Petroleum and Minerals observed under typical industrial conditions the recombination reaction of olefins with hydrogen sulfide to form mercaptans. The results indicate that the advantage of using highly active (third generation) CoMo hydrotreating catalysts can be masked by these reactions if the olefins are not saturated. The trend in naphtha reforming is to use high-rhenium, bimetallic catalysts that display less resistance to sulfur than do balanced Pt-Re catalysts. Due consideration, therefore, should be given to these undesirable recombination reactions while designing hydrotreaters and selecting hydrodesulfurization (HDS) and reforming catalysts. The paper discusses catalysts and feedstock tests, catalyst activity, temperature effects, space velocity, feedstock effect, catalyst performance, and recommendations.

  19. Olefin metathesis in air

    PubMed Central

    Piola, Lorenzo; Nahra, Fady

    2015-01-01

    Summary Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance. PMID:26664625

  20. Formaldehyde Polymerization on (WO3)3/TiO2(110) Model Catalyst

    SciTech Connect

    Kim, Jooho; Kay, Bruce D.; Dohnalek, Zdenek

    2010-10-14

    Polymerization of formaldehyde, H2CO, was studied under ultrahigh vacuum conditions on a model catalyst consisting of monodispersed (WO3)3 clusters anchored on TiO2(110. Formaldehyde oligomers, (H2CO)n, desorbing from the polymer that formed on the catalyst surface are detected between 250 and 325 K in temperature programmed desorption experiments. At least two monolayers (ML) of H2CO are required on the surface to observe (H2CO)n desorption and the amount saturates for H2CO coverages in excess of ~30 ML. The presence of H2CO multilayers is required for the polymerization to take place indicating that it had to occur below 100 K. The saturation amount increases with increasing coverage of (WO3)3 clusters with the highest amount of ~13 ML observed on 1.2 (WO3)3/nm2 . No (H2CO)n desorption was observed on the bare TiO2(110) surface.

  1. Alkylation of isobutane with light olefins: Yields of alkylates for different olefins

    SciTech Connect

    Albright, L.F.; Kranz, K.E.; Masters, K.R.

    1993-12-01

    For alkylation of isobutane with C{sub 3}-C{sub 5} olefins using sulfuric acid as the catalyst, the yields of alkylates with different olefins are compared as the operating conditions are changed. The results of recent pilot plant experiments with propylene, C{sub 4} olefins, and C{sub 5} olefins permit such comparisons. The yields expressed as weight of alkylate produced per 100 wt of olefin consumed varied from about 201:100 to 220:100. Weight ratios of the isobutane consumed per olefin consumed vary from about 101:100 to 120:100. differences of yield values are explained by the changes in the overall chemistry. The procedure employed to calculate yields with good accuracy is based on the analysis of the alkylate and the amount of conjunct polymers produced. Based on literature data, yields are also reported for alkylations using HF as the catalyst.

  2. Olefin hydration

    SciTech Connect

    Butt, M.H.D.; Waller, F.J.

    1993-08-03

    An improved process for the hydration of olefins to alcohols is described wherein the improvement comprises contacting said olefins with the catalytic composition comprising a perfluorinated ion-exchange polymer containing sulfonic acid groups supported on an inert carrier wherein said carrier comprises calcined shot coke with a mean pore diameter of about 1,000 Angstroms in the presence of water at a temperature of from about 180 C to about 250 C.

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

    PubMed

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

    2011-06-01

    (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.

  4. Stereoretentive Olefin Metathesis: An Avenue to Kinetic Selectivity.

    PubMed

    Montgomery, T Patrick; Ahmed, Tonia S; Grubbs, Robert H

    2017-09-04

    Olefin metathesis is an incredibly valuable transformation that has gained widespread use in both academic and industrial settings. Lately, stereoretentive olefin metathesis has garnered much attention as a method for the selective generation of both E- and Z-olefins. Early studies employing ill-defined catalysts showed evidence for retention of the stereochemistry of the starting olefins at low conversion. However, thermodynamic ratios E/Z were reached as the reaction proceeded to equilibrium. Recent studies in olefin metathesis have focused on the synthesis of catalysts that can overcome the inherent thermodynamic preference of an olefin, providing synthetically useful quantities of a kinetically favored olefin isomer. These reports have led to the development of stereoretentive catalysts that not only generate Z-olefins selectively, but also kinetically produce E-olefins, a previously unmet challenge in olefin metathesis. Advancements in stereoretentive olefin metathesis using tungsten, ruthenium, and molybdenum catalysts are presented. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Marked counteranion effects on single-site olefin polymerization processes. Correlations of ion pair structure and dynamics with polymerization activity, chain transfer, and syndioselectivity.

    PubMed

    Chen, Ming-Chou; Roberts, John A S; Marks, Tobin J

    2004-04-14

    Counteranion effects on the rate and stereochemistry of syndiotactic propylene enchainment by the archetypal C(s)-symmetric precatalyst [Me(2)C(Cp)(Flu)]ZrMe(2) (1; Cp = C(5)H(4); Flu = C(13)H(8), fluorenyl) are probed using the cocatalysts MAO (2), B(C(6)F(5))(3) (3)(,) B(2-C(6)F(5)C(6)F(4))(3) (4)(,) Ph(3)C(+)B(C(6)F(5))(4)(-) (5), and Ph(3)C(+)FAl(2-C(6)F(5)C(6)F(4))(3)(-) (6), offering greatly different structural and ion pairing characteristics. Reaction of 1 with 3 affords [Me(2)C(Cp)(Flu)]ZrMe(+) MeB(C(6)F(5))(3)(-) (7). In the case of 4, this reaction leads to formation the micro-methyl dinuclear diastereomers [([Me(2)C(Cp)(Flu)]ZrMe)(2)(micro-Me)](+) MeB(2-C(6)F(5)C(6)F(4))(3)(-) (8). A similar reaction with 6 results in diastereomeric [Me(2)C(Cp)(Flu)]ZrMe(+) FAl(2-C(6)F(5)C(6)F(4))(3)(-) (10) ion pairs. The molecular structures of 7 and 10 have been determined by single-crystal X-ray diffraction. Reorganization pathways available to these species have been examined using EXSY and dynamic NMR, revealing that the cation-MeB(C(6)F(5))(3)(-) interaction is considerably weaker/more mobile than in the FAl(2-C(6)F(5)C(6)F(4))(3)(-)-derived analogue. Polymerizations mediated by 1 in toluene over the temperature range of -10 degrees to +60 degrees C and at 1.0-5.0 atm propylene pressure (at 60 degrees C) reveal that activity, product syndiotacticity, m and mm stereodefect generation, and chain transfer processes are highly sensitive to the nature of the ion pairing. Thus, the complexes activated with 4 and 5, having the weakest ion pairing, yield the highest estimated propagation rates, while with 6, having the strongest pairing, yields the lowest. The strongly coordinating, immobile FAl(2-C(6)F(5)C(6)F(4))(3)(-) anion produces the highest/least temperature-dependent product syndiotacticity, lowest/least temperature-dependent m stereodefect abundance, and highest product molecular weight. These polypropylene microstructural parameters, and also M(w), are least

  6. Presenting a new kinetic model for methanol to light olefins reactions over a hierarchical SAPO-34 catalyst using the Langmuir-Hinshelwood-Hougen-Watson mechanism.

    PubMed

    Azarhoosh, Mohammad Javad; Halladj, Rouein; Askari, Sima

    2017-10-25

    In this study, a new kinetic model for methanol to light olefins (MTO) reactions over a hierarchical SAPO-34 catalyst using the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was presented and the kinetic parameters was obtained using a genetic algorithm (GA) and genetic programming (GP). Several kinetic models for the MTO reactions have been presented. However, due to the complexity of the reactions, most reactions are considered lumped and elementary, which cannot be deemed a completely accurate kinetic model of the process. Therefore, in this study, the LHHW mechanism is presented as kinetic models of MTO reactions. Because of the non-linearity of the kinetic models and existence of many local optimal points, evolutionary algorithms (GA and GP) are used in this study to estimate the kinetic parameters in the rate equations. Via the simultaneous connection of the code related to modelling the reactor and the GA and GP codes in the MATLAB R2013a software, optimization of the kinetic models parameters was performed such that the least difference between the results from the kinetic models and experiential results was obtained and the best kinetic parameters of MTO process reactions were achieved. A comparison of the results from the model with experiential results showed that the present model possesses good accuracy.

  7. Presenting a new kinetic model for methanol to light olefins reactions over a hierarchical SAPO-34 catalyst using the Langmuir–Hinshelwood–Hougen–Watson mechanism

    NASA Astrophysics Data System (ADS)

    Javad Azarhoosh, Mohammad; Halladj, Rouein; Askari, Sima

    2017-10-01

    In this study, a new kinetic model for methanol to light olefins (MTO) reactions over a hierarchical SAPO-34 catalyst using the Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism was presented and the kinetic parameters was obtained using a genetic algorithm (GA) and genetic programming (GP). Several kinetic models for the MTO reactions have been presented. However, due to the complexity of the reactions, most reactions are considered lumped and elementary, which cannot be deemed a completely accurate kinetic model of the process. Therefore, in this study, the LHHW mechanism is presented as kinetic models of MTO reactions. Because of the non-linearity of the kinetic models and existence of many local optimal points, evolutionary algorithms (GA and GP) are used in this study to estimate the kinetic parameters in the rate equations. Via the simultaneous connection of the code related to modelling the reactor and the GA and GP codes in the MATLAB R2013a software, optimization of the kinetic models parameters was performed such that the least difference between the results from the kinetic models and experiential results was obtained and the best kinetic parameters of MTO process reactions were achieved. A comparison of the results from the model with experiential results showed that the present model possesses good accuracy.

  8. Copolymerization of Propylene and Polar Monomers Using Pd/IzQO Catalysts.

    PubMed

    Nakano, Ryo; Nozaki, Kyoko

    2015-09-02

    Palladium catalysts bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands polymerize α-olefins while incorporating polar monomers. The steric environment provided by N-heterocyclic-carbene (NHC) enables regioselective insertion of α-olefins and polar monomers, yielding polypropylene, propylene/allyl carboxylate copolymers, and propylene/methyl acrylate copolymer. Known polymerization catalysts bearing NHC-based ligands decompose rapidly, whereas the present catalyst is durable because of structural confinement, wherein the NHC-plane is coplanar to the metal square plane. The present catalyst system enables facile access to a new class of functionalized polyolefins and helps conceive a new fundamental principle for designing NHC-based ligands.

  9. The Physical Structure and Mechanical Properties of Ethylene/alpha-Olefin Copolymers Produced via Constrained Geometry Single-Site Catalyst

    NASA Astrophysics Data System (ADS)

    Sehanobish, Kalyan

    1996-03-01

    The tensile deformation behavior of homogeneous ethylene/alpha-olefin copolymers with narrow molecular weight distribution was studied as a function of comonomer content. At low comonomer content, the polymers behaved as typical semicrystalline thermoplastics; at high comonomer content, deformation was elastomeric. Polymers were classified into four different categories based on their melting behavior and morphology. True stress-strain temperature diagrams with clearly identified morphological states were constructed to fingerprint the materials. A First stage model based on network structure of thermodynamic junction points provide a satisfactory description of this structure. A relationship between the concentration of tie chains between the junction points and the strain hardening behavior has been obtained incorporating the conventional chain statistics. This unique and controllable polymer structure has created a window for the polymer physicists to develop a true predictive structure-property model. Ability to develop resins with controlled molecular architecture is also allowing industries to rapidly design polymers to meet processability and performance requirements for a wide variety of applications.

  10. Synergistic effect of ultrasonication and phase transfer catalysts in radical polymerization of methyl methacrylate - A kinetic study.

    PubMed

    Prabha, J; Susan Jemima, W; Jayaprada, M; Umapathy, M J

    2017-03-01

    Methyl methacrylate (MMA) has been polymerized to poly methyl methacrylate (PMMA) by employing three different phase transfer catalysts (PTC) such as 1,4-bis(dimethylhexyl)ethylenediammoniumbromide (DMHEDAB), 1,4bis(dimethylheptyl)ethylenediammoniumbromide (DMH1EDAB) and 1,4-bis(dimethyloctyl)ethylenediammonium bromide (DMOEDAB) under the influence of ultrasound radiation. The radical polymerization was performed under unstirred condition at a temperature of 60±1°C in an oxygen free atmosphere employing water soluble K2S2O8 as initiator. Various parameters such as role of [Monomer], [Initiator], [PTC], solvent and temperature were investigated on rate of polymerization (Rp) and the synergic efficacy of ultrasound wave variation and phase transfer catalysts were also assessed. It was found that the rate of polymerization (Rp) increased drastically for all the three catalyst under the influence of ultrasound and the order of efficiency was found to be [Formula: see text] This increase may be due to the number of carbon chain attached to the polar group which facilitate and accelerate the rate of polymerization.

  11. Synthesis of Conjugated Diblock Copolymers: Two Mechanistically Distinct, Sequential Living Polymerizations using a Single Catalyst

    SciTech Connect

    Wu, Zong-Quan; Radcliffe, Jonathan D.; Ono, Robert J.; Chen, Zheng; Li, Zicheng; Bielawski, Christopher W.

    2012-01-01

    Block copolymers comprised of poly(3-hexylthiophene) and three different poly(isocyanide)s were synthesized in a single pot via the sequential addition of 2-bromo-3-hexyl-5-chloromagnesiothiophene followed by 2-(2-methoxyethoxy)ethyl 4-isocyanobenzoate, tert-butyl 4-isocyanobenzoate, or 1-isocyanohexadecane to a solution of 1,3-bis(diphenylphosphino)propane dichloronickel. Similarly, block copolymers of poly(1-dodecylpyrrole) along with poly(2,5-bis(hexyloxy)phenylene) and a poly(arylisocyanide) were also prepared using an analogous methodology. The respective mechanistically distinct polymerizations proceeded in a controlled fashion, were mediated by a common catalyst, and afforded well-defined block copolymers with tunable molecular weights and compositions. Selected block copolymers exhibited higher-order structures in solution and microphase separation characteristics in the solid state.

  12. Chitosan-g-hematin: enzyme-mimicking polymeric catalyst for adhesive hydrogels.

    PubMed

    Ryu, Ji Hyun; Lee, Yuhan; Do, Min Jae; Jo, Sung Duk; Kim, Jee Seon; Kim, Byung-Soo; Im, Gun-Il; Park, Tae Gwan; Lee, Haeshin

    2014-01-01

    Phenol derivative-containing adhesive hydrogels has been widely recognized as having potential for biomedical applications, but their conventional production methods, utilizing a moderate/strong base, alkaline buffers, the addition of oxidizing agents or the use of enzymes, require alternative approaches to improve their biocompatibility. In this study, we report a polymeric, enzyme-mimetic biocatalyst, hematin-grafted chitosan (chitosan-g-hem), which results in effective gelation without the use of alkaline buffers or enzymes. Furthermore, gelation occurs under mild physiological conditions. Chitosan-g-hem biocatalyst (0.01%, w/v) has excellent catalytic properties, forming chitosan-catechol hydrogels rapidly (within 5 min). In vivo adhesive force measurement demonstrated that the hydrogel formed by the chitosan-g-hem activity showed an increase in adhesion force (33.6 ± 5.9 kPa) compared with the same hydrogel formed by pH-induced catechol oxidation (20.6 ± 5.5 kPa) in mouse subcutaneous tissue. Using the chitosan-g-hem biocatalyst, other catechol-functionalized polymers (hyaluronic acid-catechol and poly(vinyl alcohol)-catechol) also formed hydrogels, indicating that chitosan-g-hem can be used as a general polymeric catalyst for preparing catechol-containing hydrogels. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  13. Selective conversion of bio-oil to light olefins: controlling catalytic cracking for maximum olefins.

    PubMed

    Gong, Feiyan; Yang, Zhi; Hong, Chenggui; Huang, Weiwei; Ning, Shen; Zhang, Zhaoxia; Xu, Yong; Li, Quanxin

    2011-10-01

    Light olefins are the basic building blocks for the petrochemical industry. In this work, selective production of light olefins from catalytic cracking of bio-oil was performed by using the La/HZSM-5 catalyst. With a nearly complete conversion of bio-oil, the maximum yield reached 0.28±0.02 kg olefins/(kg bio-oil), which was close to that from methanol. Addition of La into zeolite efficiently changed the total acid amount of HZSM-5, especially the acid distribution among the strong, medium and weak acid sites. A moderate increase of the number of the medium acid sites effectively enhanced the olefins selectivity and improved the catalyst stability. The comparison between the catalytic cracking and pyrolysis of bio-oil was studied. The mechanism of the conversion of bio-oil to light olefins was also discussed.

  14. Oligomerization of Biomass-Derived Light Olefins to Liquid Fuel: Effect of Alkali Treatment of HZSM-5 Catalyst

    DOE PAGES

    Wang, Xiaoxing; Hu, Xiaoyan; Song, Chunshan; ...

    2017-09-27

    As a part of a new approach to convert biomass to liquid fuels, we investigated the effects of alkali treatment on the property and performance of HZSM-5 for oligomerization of biomass-derived ethylene under atmospheric pressure. The characterization results showed that alkali treatment led to the increase in the total and mesopore volumes, but decrease in the surface area and micropore volume. Furthermore, when NaOH concentration was low (< 0.5 M), the ZSM-5 structure was largely preserved with the increase in the mesopores and acidity, while higher NaOH concentration can severely destroy the zeolite structure, resulting in a significant reduction inmore » the micropores and acidity. The ethylene oligomerization results showed that not only the ethylene conversion and the liquid yield increased, but also the catalyst stability was improved after proper NaOH treatment. Finally, we discussed the relationship between the structure and performance« less

  15. Highly Stereoselective Heterogeneous Diene Polymerization by Co-MFU-4l: A Single-Site Catalyst Prepared by Cation Exchange.

    PubMed

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

    2017-09-13

    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.

  16. Self-assembled complexes of non-cross-linked amphiphilic polymeric ligands with inorganic species: highly active and reusable solid-phase polymeric catalysts.

    PubMed

    Yamada, Yoichi M A

    2005-07-01

    I present herein the development of highly active and reusable polymeric catalysts produced by self-assembly process of non-cross-linked amphiphilic polymeric ligands with inorganic species. Thus, PWAA 1 prepared from H3PW12O40 and poly[(N-isopropylacrylamide)-co-(acrylamide with ammonium salt)] is suitable for oxidation of alcohols, amines, and sulfides in aqueous hydrogen peroxide. PdAS 2 produced by self-organization of (NH4)2PdCl4 and poly[(N-isopropylacrylamide)10-co-diphenylphosphinostyrene] is an excellent recyclable catalyst for Suzuki-Miyaura reaction in water, water-organic solvent, and organic solvent. It is commercially available from Tokyo Kasei Kogyo (TCI). PdAS-V 3 assembled from (NH4)2PdCl4 and poly[(N-isopropylacrylamide)5-co-diphenylphosphinostyrene] provides recycling system of itself for Mizorogi-Heck reaction. TiSS 4 made from Ti(O-i-Pr)4 and poly(styryl-linked binaphtholate-co-styrene) promotes an enantioselective carbonyl-ene reaction as a recyclable catalyst.

  17. Metathesis process for preparing an alpha, omega-functionalized olefin

    DOEpatents

    Burdett, Kenneth A.; Mokhtarzadeh, Morteza; Timmers, Francis J.

    2010-10-12

    A cross-metathesis process for preparing an .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha.,.omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first zone.

  18. Make olefins from syn gas

    SciTech Connect

    Rao, V.U.S.; Gormley, R.J.

    1980-11-01

    The medium pore zeolite ZSM-5 can be made within a wide range of values of the ratio SiO/sub 2//Al/sub 2/O/sub 3/. The crystal structures of ZSM-5 and Silicalite appear to be very similar. However, Silicalite has essentially no Al. Hence it appears that Silicalite is the limiting form of ZSM-5 when the Al concentration is vanishingly small. A comparison of the properties of ZSM-5 and Silicalite is shown. Silicalite provides an interesting contrast to ZSM-5 owing to the lack of acidity in the former. In comparing products from catalysts based on ZSM-5 and Silicalite, one can discern reactions which result from the acid function in ZSM-5. Our studies on bifunctional catalysts based on ZSM-5 and Silicalite were performed on zeolites or molecular sieves impregnated with Fe and/or Co. The aim was to convert synthesis gas (CO + H/sub 2/), which can be derived from the gasification of coal, to olefins or gasoline. In the case of the ZSM-based catalyst containing Fe, the transition metal catalyzes the hydrogenation of CO, and the acid function of the zeolite catalyzes the conversion of the oxygenates and olefins in the product to aromatics, resulting in a high octane gasoline product. Recent work from our laboratory has clearly shown that if Silicalite is used instead of ZSM-5 as the support, the production of aromatics is almost completely suppressed, and the product stream is rich in olefins. In the present article, molecular sieve based catalysts that can proide olefins are discussed, and some aspects of gasoline production using zeolite based catalysts as well as the control of shift activity are also being considered. 4 tables.

  19. Electrochemical driven water oxidation by molecular catalysts in situ polymerized on the surface of graphite carbon electrode.

    PubMed

    Wang, Lei; Fan, Ke; Daniel, Quentin; Duan, Lele; Li, Fusheng; Philippe, Bertrand; Rensmo, Håkan; Chen, Hong; Sun, Junliang; Sun, Licheng

    2015-05-07

    A simple strategy to immobilize highly efficient ruthenium based molecular water-oxidation catalysts on the basal-plane pyrolytic graphite electrode (BPG) by polymerization has been demonstrated. The electrode 1@BPG has obtained a high initial turnover frequency (TOF) of 10.47 s(-1) at ∼700 mV overpotential, and a high turnover number (TON) up to 31600 in 1 h electrolysis.

  20. Characterization of a model Ziegler-Natta catalyst for ethylene polymerization

    NASA Astrophysics Data System (ADS)

    Schmidt, J.; Risse, T.; Hamann, H.; Freund, H.-J.

    2002-06-01

    Based on the work of the Somorjai group [Magni and Somorjai, Catal. Lett. 35, 205 (1995)] we have prepared a thin well ordered MgCl2(001) film by MgCl2 evaporation from a Knudsen cell. This film does not absorb TiCl4 at room temperature if it is not activated by increasing the defect density via electron or ion bombardment. The nature of some of the defects created is characterized by in situ ESR measurements and Auger spectroscopy. Paramagnetic surface defects are altered by the bonding of TiCl4 to the surface as observed by ESR spectroscopy. Ti3+ centers are detected if particularly severely defected MgCl2 layers are prepared. Reactivity studies show however, that these species are not correlated with polymerization activity. Interaction with aluminum alkyl leads to the formation of the active catalyst and we observe for the first time directly ethyl radicals formed from trimethyl-aluminum in an abstraction process which may be formulated as TiCl4/surface+AlMe3→Me-TiCl3/surface+AlMe2Cl, Me-TiCl3/surface→TiCl3/surface+Meṡ, and Meṡ+Me3Al→C2H5ṡ+AlH(Me)2. The presence of the aluminum alkyl is observed via in situ IRAS in the same apparatus.

  1. Phenyl Benzo[b]phenothiazine as a Visible Light Photoredox Catalyst for Metal-Free Atom Transfer Radical Polymerization.

    PubMed

    Dadashi-Silab, Sajjad; Pan, Xiangcheng; Matyjaszewski, Krzysztof

    2016-12-23

    This paper reports use of phenyl benzo[b]phenothiazine (Ph-benzoPTZ) as a visible light-induced metal-free atom transfer radical polymerization (ATRP) photoredox catalyst. Well-controlled polymerizations of various methacrylate monomers were conducted under a 392 nm visible light LED using Ph-benzoPTZ to activate different alkyl halides. The use of the photocatalyst enabled temporal control over the growth of polymer chains during intermittent on/off periods. The polymerization was initiated and progressed only under stimulation by light and completely stopped in the absence of light. Block copolymers were synthesized to demonstrate high retention of chain end fidelity in the polymers and livingness of the process.

  2. A mineral support and biotic catalyst are essential in the formation of highly polymeric soil humic substances

    NASA Astrophysics Data System (ADS)

    Zavarzina, A. G.

    2006-12-01

    The hypothesis was proposed that highly polymeric humic substances in the mineral horizons of soils in a temperate humid climate originate from polymerization of water-soluble structural precursors directly on mineral surfaces under the catalytic effect of immobilized phenoloxidases (heterophasic biocatalysis). This hypothesis was confirmed by a laboratory experiment using a mixture of monomeric phenols and nitrogenous compounds as structural precursors, fungal laccase as a biotic catalyst, and a hydroxyaluminum-kaolinite complex as a mineral support. Enzymic oxidation of phenolic precursors on the mineral surface was substantially more rapid than abiotic oxidation and led to synthesis of a highly polymeric fraction with a molecular weight over 75 kDa. These products were not produced on the mineral with an absence of laccase (abiotic catalysis) or in solution without the mineral matrix (homogeneous catalysis).

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

    PubMed

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

    2013-07-07

    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.

  4. Conversion of olefins to liquid motor fuels

    DOEpatents

    Rabo, Jule A.; Coughlin, Peter K.

    1988-01-01

    Linear and/or branched claim C.sub.2 to C.sub.12 olefins are converted to hydrocarbon mixtures suitable for use as liquid motor fuels by contact with a catalyst capable of ensuring the production of desirable products with only a relatively minor amount of heavy products boiling beyond the diesel oil range. The catalyst having desirable stability during continuous production operations, comprises a steam stabilized zeolite Y catalyst of hydrophobic character, desirably in aluminum-extracted form. The olefins such as propylene, may be diluted with inerts, such as paraffins or with water, the latter serving to moderate the acidity of the catalyst, or to further moderate the activity of the aluminum-extracted catalyst, so as to increase the effective life of the catalyst.

  5. Olefins from methanol by modified zeolites

    SciTech Connect

    Inui, T.; Takegami, Y.

    1982-11-01

    Compares the effects of modified catalysts (ZSM-34 and ZSM-5 class zeolites) on methanol conversion to olefins (MTO) with regard to olefin selectivity and cost. Presents tables with prices of olefins in the US and Japan; comparison of methanol-cracking with naphtha cracking; methanol conversion data for Type-1, Type-II and reference catalysts; hydrocarbon distribution from MTO processes; and speculative economics for MTO processes of Concept-1 and 2. Diagrams the proposed MTO process scheme. Scanning electron micrographs of the zeolite catalysts are shown. Graphs indicate the change of ethylene prices in the US since 1978 and forecast ethylene prices in several countries. Concludes that the prices of ethylene for both MTO processes examined compare favorably with products of conventional processes.

  6. Cobalt carbonyl catalyzed olefin hydroformylation in supercritical carbon dioxide

    SciTech Connect

    Rathke, J.W.; Klingler, R.J.

    1992-12-31

    A method of olefin hydroformylation is provided wherein an olefin reacts with a carbonyl catalyst and with reaction gases such as hydrogen and carbon monoxide in the presence of a supercritical reaction solvent, such as carbon dioxide. The invention provides higher yields of n-isomer product without the gas-liquid mixing rate limitation seen in conventional Oxo processes using liquid media.

  7. Cobalt carbonyl catalyzed olefin hydroformylation in supercritical carbon dioxide

    DOEpatents

    Rathke, Jerome W.; Klingler, Robert J.

    1993-01-01

    A method of olefin hydroformylation is provided wherein an olefin reacts with a carbonyl catalyst and with reaction gases such as hydrogen and carbon monoxide in the presence of a supercritical reaction solvent, such as carbon dioxide. The invention provides higher yields of n-isomer product without the gas-liquid mixing rate limitation seen in conventional Oxo processes using liquid media.

  8. Cobalt carbonyl catalyzed olefin hydroformylation in supercritical carbon dioxide

    DOEpatents

    Rathke, J.W.; Klingler, R.J.

    1993-03-30

    A method of olefin hydroformylation is provided wherein an olefin reacts with a carbonyl catalyst and with reaction gases such as hydrogen and carbon monoxide in the presence of a supercritical reaction solvent, such as carbon dioxide. The invention provides higher yields of n-isomer product without the gas-liquid mixing rate limitation seen in conventional Oxo processes using liquid media.

  9. Synthesis and characterization of novel antibacterial polymers and clay delivery systems and polymeric phase transfer catalysts

    NASA Astrophysics Data System (ADS)

    Dizman, Bekir

    The research presented in this dissertation involves the syntheses of both novel antibacterial polymers and nanocomposites and polymeric phase transfer catalysts. The first section describes the synthesis, characterization, and antibacterial activities of new acrylate/methacrylate and acrylamide/methacrylamide polymers containing pendant quaternary ammonium compounds and norfloxacin. The first part of this section focuses on the syntheses and antibacterial activities of new water-soluble bis-quaternary ammonium methacrylate monomers and polymers (Chapter II). The monomers and polymers showed antibacterial activities against Staphylococcus aureus and Escherichia coli and the activity increased as the alkyl chain length in ammonium groups increased from 4 to 6 carbons. The results are very encouraging since polymers with quaternary ammonium compounds containing short alkyl chains are generally not active against bacteria. The second part of the first section involves the syntheses and antibacterial activities of various new monomers and polymers with amine and mono-quaternary ammonium groups on the side chain (Chapter III). The monomers were either the derivatives of 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) or based on acrylamide and methacrylamide derivatives. All monomers were homopolymerized and copolymerized with 2-hydroxyethylmethacrylate (HEMA). Amine monomers, their homopolymers and copolymers did not show any antibacterial activity against S. aureus and E. coli while the quaternized AHM-3-(aminomethyl) pyridine monomer, its homopolymer and copolymer with HEMA showed antibacterial activities against both bacteria. It was also found that the antibacterial activity of the quaternized methacrylamide-3-(aminomethyl) pyridine monomers and polymers increased as the alkyl chain length in ammonium groups increased. (Abstract shortened by UMI.)

  10. Sensitivity of catalyst/base ratio on curing of resin luting agents: polymerization exotherm analysis.

    PubMed

    Griggs, J A; Shen, C; Anusavice, K J

    1994-09-01

    Currently, the proposed test of the International Standardization Organization (ISO) for measuring working and setting times of resin luting agents is based on measurement of times to reach specified stages on the polymerization exotherm. The objective of this study was to use this test to investigate the influence of variations in the mass ratios of catalyst paste to base paste on the working and setting times of three dual-cured dental resin luting agents. The materials used were Dicor Light Activated Cement (Dentsply International Inc.), Palfique Inlay Resin Cement (Tokuyama Soda Co.), and Vivadent Dual Cement (Vivadent). Fifteen specimens of each material were tested for working time by spatulating mass ratios from 0.7 to 1.3 for 30s at 23 degrees C and recording the time from beginning of spatulation to the time at which a temperature increase occurs. Ten specimens of each material were tested for setting time by spatulating in a similar manner at 37 degrees C and recording the time at which the temperature reaches a maximum value. The data were fitted to the relation, In t = In A + Bm, where t is the time in seconds, m is the mass ratio, and A and B are regression coefficients. The results suggest that working and setting times of the specimens were independent of variations in mass ratio. A comparison among the materials was made by using a multiple linear regression with the relation, In t = In C + Dm + E gamma + Fm gamma, where gamma is a dummy variable to help distinguish between materials, and C, D, E, and F are regression coefficients. The results suggest that differences in materials influence the working time but not the setting time. These results infer that variations in mass ratio (+/- 20%) often observed in the clinical setting should not have a significant influence on the working and setting times of resin luting agents.

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

    PubMed

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

    2017-02-15

    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.

  12. Controlled Ring-Opening Metathesis Polymerization by Molybdenum and Tungsten Alkylidene Complexes

    DTIC Science & Technology

    1988-07-29

    weights and low polydispersities (as low as 1.03) consistent with a living catalyst system employing 50, 100, 200, and 400 eq of monomer. The reactions are...secondary metathesis of polymer chains Bulky alkoxide ligands Wittig-like reaction Ring-opening metathesis polymerization (ROMP) Feast monomer Cyclic...olefins Retro Diels-Alder reaction Norbornene (NBE) Low temperature column chromatography Endo-,endo-5,6-dicarbomethoxynorbornene Discrete, soluble

  13. Quaternized polymeric microgels as metal free catalyst for H2 production from the methanolysis of sodium borohydride

    NASA Astrophysics Data System (ADS)

    Sahiner, Nurettin; Sengel, Sultan Butun

    2016-12-01

    Polymeric microgels derived from tris(2-amino ethyl)amine (TAEA) and glycerol diglycidyl ether as p(TAEA-co-GDE) via microemulsion polymerization techniques are protonated by 0.5 M HCl treatment as p(TAEA-co-GDE)-HCl). These microgels are then exposed to anion exchange reactions with differ ionic liquid forming salts, such as potassium thiocyanate (PTC), sodium dicyanamide (SDCA), ammonium hexafluorophosphate (AHFP), and sodium tetrafluoroborate (STFB) in aqueous medium for the preparation of p(TAEA-co-GDE) based ionic liquid colloidal microgels. These anions exchanged p(TAEA-co-GDE) ionic liquid colloids (ILCs) are directly used as catalyst for hydrogen (H2) generation from the methanol solution of sodium borohydride (NaBH4). Various parameters affecting the H2 production rate such as the catalyst types, NaBH4 amount, and the temperature are investigated. It is found that the methanolysis of NaBH4 catalyzed by p(TAEA-co-GDE)-HCl obeys the first order reaction kinetic. The activation energy, enthalpy and entropy of the protonated p(TAEA-co-GDE) microgels are calculated and found as the 30.37 kJ mol-1, 27.96 kJ mol-1, and -148.08 J mol-1 K-1, respectively. Furthermore, the hydrogen generation rate of 3018 mL min-1 g-1 catalyzed by p(TAEA-co-GDE)-HCl catalyst is attained.

  14. Synthesis, structural elucidation, and catalytic properties in olefin epoxidation of the polymeric hybrid material [Mo3O9(2-[3(5)-pyrazolyl]pyridine)]n.

    PubMed

    Amarante, Tatiana R; Neves, Patrícia; Gomes, Ana C; Nolasco, Mariela M; Ribeiro-Claro, Paulo; Coelho, Ana C; Valente, Anabela A; Paz, Filipe A Almeida; Smeets, Stef; McCusker, Lynne B; Pillinger, Martyn; Gonçalves, Isabel S

    2014-03-03

    The reaction of [MoO2Cl2(pzpy)] (1) (pzpy = 2-[3(5)-pyrazolyl]pyridine) with water in an open reflux system (16 h), in a microwave synthesis system (120 °C, 2 h), or in a Teflon-lined stainless steel digestion bomb (100 °C, 19 h) gave the molybdenum oxide/pyrazolylpyridine polymeric hybrid material [Mo3O9(pzpy)]n (2) as a microcrystalline powder in yields of 72–79%. Compound 2 can also be obtained by the hydrothermal reaction of MoO3, pzpy, and H2O at 160 °C for 3 d. Secondary products isolated from the reaction solutions included the salt (pzpyH)2(MoCl4) (3) (pzpyH = 2-[3(5)-pyrazolyl]pyridinium), containing a very rare example of the tetrahedral MoCl4(2–) anion, and the tetranuclear compound [Mo4O12(pzpy)4] (4). Reaction of 2 with excess tert-butylhydroperoxide (TBHP) led to the isolation of the oxodiperoxo complex [MoO(O2)2(pzpy)] (5). Single-crystal X-ray structures of 3 and 5 are described. Fourier transform (FT)-IR and FT Raman spectra for 1, 4, and 5 were assigned based on density functional theory calculations. The structure of 2 was determined from synchrotron powder X-ray diffraction data in combination with other physicochemical information. In 2, a hybrid organic–inorganic one-dimensional (1D) polymer, ∞(1)[Mo3O9(pzpy)], is formed by the connection of two very distinct components: a double ladder-type inorganic core reminiscent of the crystal structure of MoO3 and 1D chains of corner-sharing distorted {MoO4N2} octahedra. Compound 2 exhibits moderate activity and high selectivity when used as a (pre)catalyst for the epoxidation of cis-cyclooctene with TBHP. Under the reaction conditions used, 2 is poorly soluble and is gradually converted into 5, which is at least partly responsible for the catalytic reaction.

  15. Synthesis and Understanding of Novel Catalysts

    SciTech Connect

    Stair, Peter C.

    2013-07-09

    The research took advantage of our capabilities to perform in-situ and operando Raman spectroscopy on complex systems along with our developing expertise in the synthesis of uniform, supported metal oxide materials to investigate relationships between the catalytically active oxide composition, atomic structure, and support and the corresponding chemical and catalytic properties. The project was organized into two efforts: 1) Synthesis of novel catalyst materials by atomic layer deposition (ALD). 2) Spectroscopic and chemical investigations of coke formation and catalyst deactivation. ALD synthesis was combined with conventional physical characterization, Raman spectroscopy, and probe molecule chemisorption to study the effect of supported metal oxide composition and atomic structure on acid-base and catalytic properties. Operando Raman spectroscopy studies of olefin polymerization leading to coke formation and catalyst deactivation clarified the mechanism of coke formation by acid catalysts.

  16. Synthesis of interlocked molecules by olefin metathesis

    NASA Astrophysics Data System (ADS)

    Clark, Paul Gregory

    A large body of work in the Grubbs group has focused on the development of functional-group tolerant ruthenium alkylidene catalysts that perform a number of olefin metathesis reactions. These catalysts have seen application in a wide range of fields, including classic total synthesis as well as polymer and materials chemistry. One particular family of compounds, interlocked molecules, has benefitted greatly from these advances in catalyst stability and activity. This thesis describes several elusive and challenging interlocked architectures whose syntheses have been realized through the utilization of different types of ruthenium-catalyzed olefin metathesis reactions. Ring-closing olefin metathesis has enabled the synthesis of a [c2]daisy-chain dimer with the ammonium binding site near the cap of the dimer. A deprotonated DCD possessing such a structural attribute will more forcefully seek to restore coordinating interactions upon reprotonation, enhancing its utility as a synthetic molecular actuator. Dimer functionalization facilitated incorporation into linear polymers, with a 48% size increase of an unbound, extended analogue of the polymer demonstrating slippage of the dimer units. Ongoing work is directed at further materials studies, in particular, exploring the synthesis of macroscopic networks containing the DCD units and analyzing the correlation between molecular-scale extension-contraction manipulations and resulting macro-scale changes. A "clipping" approach to a polycatenated cyclic polymer, a structure that resembles a molecular "charm bracelet", has been described. The use of ring-opening metathesis polymerization of a carbamate monomer in the presence of a chain transfer agent allowed for the synthesis of a linear polymer that was subsequently functionalized and cyclized to the corresponding cyclic analogue. This cyclic polymer was characterized through a variety of techniques, and subjected to further functionalization reactions, affording a cyclic

  17. Ring-Opening Polymerization of L-Lactide to Cyclic Poly(Lactide) by Zeolitic Imidazole Framework-8 Catalyst.

    PubMed

    Luo, Zhixiong; Chaemchuen, Somboon; Zhou, Kui; Verpoort, Francis

    2017-09-18

    The catalytic activity of ZIF-8 in the ring-opening polymerization of L-lactide without solvents or co-catalysts is presented for the first time. Two different synthetic strategies have been applied for synthesizing ZIF-8, either under solvothermal condition or by spray-drying procedure. Their catalytic activities are found to be correlating with the presence of open active sites in ZIF-8 structure. The structural defects which afford active acid and basic sites are supposed to cooperatively catalyze the reaction. ZIF-8 assembled by spray-drying technique, displays a superior catalytic activity at temperature of 160 °C, leading to the formation of high molecular weight cyclic polylactide. The ZIF-8 catalysts could be recycled and reused without any significant loss of catalytic activity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Methods for suppressing isomerization of olefin metathesis products

    DOEpatents

    Firth, Bruce E.; Kirk, Sharon E.; Gavaskar, Vasudeo S.

    2015-09-22

    A method for suppressing isomerization of an olefin metathesis product produced in a metathesis reaction includes adding an isomerization suppression agent to a mixture that includes the olefin metathesis product and residual metathesis catalyst from the metathesis reaction under conditions that are sufficient to passivate at least a portion of the residual metathesis catalyst. The isomerization suppression agent is phosphorous acid, a phosphorous acid ester, phosphinic acid, a phosphinic acid ester or combinations thereof. Methods of refining natural oils are described.

  19. Methods for suppressing isomerization of olefin metathesis products

    DOEpatents

    Firth, Bruce E.; Kirk, Sharon E.

    2015-10-27

    A method for suppressing isomerization of an olefin metathesis product produced in a metathesis reaction includes adding an isomerization suppression agent that includes nitric acid to a mixture that includes the olefin metathesis product and residual metathesis catalyst from the metathesis reaction under conditions that are sufficient to passivate at least a portion of the residual metathesis catalyst. Methods of refining a natural oil are described.

  20. Surface-Initiated Titanium-Mediated Coordination Polymerization from Catalyst-Functionalized Single and Multiwalled Carbon Nanotubes

    SciTech Connect

    Priftis, Dimitrios; Petzetakis, Nikolaos; Sakellariou, Georgios; Pitsikalis, Marinos; Baskaran, Durairaj; Mays, Jimmy; Hadjichristidis, Nikos

    2009-01-01

    Single (SWNTs) and multiwalled (MWNTs) carbon nanotubes were functionalized with a titanium alkoxide catalyst through a Diels-Alder cycloaddition reaction. The catalyst-functionalized carbon nanotubes (CNTs) were used for the surface initiated titanium-mediated coordination polymerizations of L-lactide (L-LA), -caprolactone (-CL) and n-hexyl isocyanate (HIC) employing the grafting from technique. 1H NMR, IR and Raman spectra showed that the precursor catalyst was successfully synthesized and covalently attached on the CNTs surface. Thermogravimetric analysis (TGA) revealed that the grafted poly(L-lactide) (PLLA) content could be controlled with time. The final polymer-grafted CNTs were readily dissolved in organic solvents as compared to the insoluble pristine and catalyst-functionalized CNTs. The presence of thick layers of polymers around the CNTs was observed through transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) proved that the glass transition (Tg) and melting (Tm) temperatures of the PLLA are affected by the presence of the CNTs, while PLLA R-helix conformation remains intact, as revealed by the circular dichroism (CD) spectra.

  1. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2013-07-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  2. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann [Agoura Hills, CA

    2011-11-29

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  3. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2015-09-22

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  4. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2016-02-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  5. Solvent-free cyclization of linear dienes using olefin metathesis and the Thorpe-Ingold effect

    SciTech Connect

    Forbees, M.D.E.; Myers, T.L.; Maynard, H.D.; Schulz, G.R. ); Patton, J.T.; Smith, D.W. Jr.; Wagener, K.B. )

    1992-12-30

    The olefin metathesis reaction is of great synthetic utility in polymer chemistry. The recent development of ring-opening (ROMP) and acyclic diene (ADMET) metathesis polymerization reactions has opened new avenues for the synthesis of novel polymeric materials. Recently the authors used ADMET to synthesize several photochemically active poly(keto olefins) using the catalyst Mo(CHCMe[sub 2]Ph)(NAr)(OCMe(CF[sub 3])[sub 2])[sub 2] (Ar = 2,6-diisopropylphenyl) (1) developed by Schrock and co-workers in 1990. In the course of that work, they discovered that neat samples of highly substituted dienes will cyclize quantitatively via metathesis to give difunctional five- and seven-membered rings instead of the expected linear polymer. Examples of substituted diene cyclizations by metathesis even in the presence of a solvent are rare. Their systematic exploitation in organic synthesis has therefore been limited to two recent studies by Fu and Grubbs, who cyclized several substituted diene ethers, amines, and amides to unsaturated oxygen and nitrogen heterocycles. Cyclization of unsubstituted dienes in various solvents has been reported, but complete conversion occurred in only a few cases. Formation of cyclic alkene oligomers from back-biting during the ROMP reaction is also known. The reactions reported here are unusual in that they are intermolecular between catalyst and substrate, yet can give 100% yield of product solely from the monomer in the absence of solvent. 13 refs.

  6. Metallocene Catalytic Insertion Polymerization of 1-Silene to Polycarbosilanes

    PubMed Central

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

    2015-01-01

    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. PMID:26541636

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

    NASA Astrophysics Data System (ADS)

    Polenz, I.; Spange, S.

    2014-08-01

    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 rMMA and rMAN 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 EA,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).

  8. Iron(III) complexes of 2-(1H-benzo[d]imidazol-2-yl)phenol and acetate or nitrate as catalysts for epoxidation of olefins with hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Dutta, Amit Kumar; Samanta, Suvendu; Dutta, Supriya; Lucas, C. Robert; Dawe, Louise N.; Biswas, Papu; Adhikary, Bibhutosh

    2016-07-01

    Cheap and environmentally friendly Fe(III) catalysts [Fe(L)2(CH3COO)] (1) and [Fe(L)2(NO3)]·2CH3OH (2) where HL = 2-(1H-benzo[d]imidazol-2-yl)phenol for epoxidation of olefins have been developed. The catalysts have been characterized by elemental analyses, IR, UV-Vis spectroscopy and by X-ray crystallography. The X-ray structures reveal mononuclear compounds having a bidentate acetate or nitrate in 1 and 2, respectively. Catalytic epoxidations of styrene and cyclohexene have been carried out homogeneously by using 30% aqueous hydrogen peroxide in acetonitrile in the presence of catalytic amounts of 1 or 2. Yields of the respective epoxides were fair (1) to good (2) and selectivities were good in all cases although 2 produced two to three times the yield, depending on the substrate, than 1 and higher selectivity as well. A hypothesis for these differences in catalytic efficacy between 1 and 2 that is consistent with mechanistic details of related enzymatic and biomimetic model systems is proposed. Herein we report [Fe(L)2(NO3)]·2CH3OH (2) as the first structurally characterized non-heme iron epoxidation catalyst with a bidentate nitrate ligand.

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

    PubMed

    Saito, Kei; Miyamoto, Koji; Nanayakkara, Sepa; Ihara, Hirotaka; Hearn, Milton T W

    2016-01-26

    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.

  10. Rare-earth-catalyzed C-H bond addition of pyridines to olefins.

    PubMed

    Guan, Bing-Tao; Hou, Zhaomin

    2011-11-16

    An efficient and general protocol for the ortho-alkylation of pyridines via C-H addition to olefins has been developed, using cationic half-sandwich rare-earth catalysts, which provides an atom-economical method for the synthesis of alkylated pyridine derivatives. A wide range of pyridine and olefin substrates including α-olefins, styrenes, and conjugated dienes are compatible with the catalysts.

  11. Dizinc Lactide Polymerization Catalysts: Hyperactivity by Control of Ligand Conformation and Metallic Cooperativity

    PubMed Central

    Thevenon, Arnaud; Romain, Charles; Bennington, Michael S.; White, Andrew J. P.; Davidson, Hannah J.

    2016-01-01

    Abstract Understanding how to moderate and improve catalytic activity is critical to improving degradable polymer production. Here, di‐ and monozinc catalysts, coordinated by bis(imino)diphenylamido ligands, show remarkable activities and allow determination of the factors controlling performance. In most cases, the dizinc catalysts significantly out‐perform the monozinc analogs. Further, for the best dizinc catalyst, the ligand conformation controls activity: the catalyst with “folded” ligand conformation shows turnover frequency (TOF) values up to 60 000 h−1 (0.1 mol % loading, 298 K, [LA]=1 m), whilst that with a “planar” conformation is much slower, under similar conditions (TOF=30 h−1). Dizinc catalysts also perform very well under immortal conditions, showing improved control, and are able to tolerate loadings as low as 0.002 mol % whilst conserving high activity (TOF=12 500 h−1). PMID:27295339

  12. Simultaneous Chain-Growth and Step-Growth Polymerization of Methoxystyrenes by Rare-Earth Catalysts.

    PubMed

    Shi, Xiaochao; Nishiura, Masayoshi; Hou, Zhaomin

    2016-11-14

    The simultaneous chain-growth and step-growth polymerization of a monomer is of great interest and importance because it can produce unique macromolecules which are difficult to prepare by other means. However, such a transformation is usually difficult to achieve in one polymerization system because chain-growth polymerization and step-growth polymerization proceed by different reaction mechanisms. Reported here is the simultaneous chain-growth and step-growth polymerization of para- and meta-methoxystyrenes catalyzed by half-sandwich rare-earth alkyl complexes, and the step-growth polymerization proceeds by the C-H polyaddition of anisyl units to vinyl groups. This unprecedented transformation affords a new family of macromolecules containing unique alternating anisole-ethylene sequences. In contrast to para- and meta-methoxystyrenes, ortho-methoxystyrene exclusively undergo syndiospecific, living chain-growth polymerization by continuous C=C bond insertion to give perfect syndiotactic poly(ortho-methoxystyrene) with high molecular weight and narrow polydispersity (rrrr >99 %, Mn up to 280 kg mol(-1) , Mw /Mn <1.10).

  13. 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.

    PubMed

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

    2014-05-05

    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.

  14. Degradable Polycaprolactone and Polylactide Homopolymer and Block Copolymer Brushes Prepared by Surface-Initiated Polymerization with Triazabicyclodecene and Zirconium Catalysts.

    PubMed

    Grubbs, Joe B; Arnold, Rachelle M; Roy, Anandi; Brooks, Karson; Bilbrey, Jenna A; Gao, Jing; Locklin, Jason

    2015-09-22

    Surface-initiated ring-opening polymerization (SI-ROP) of polycaprolactone (PCL) and polylactide (PLA) polymer brushes with controlled degradation rates were prepared on oxide substrates. PCL brushes were polymerized from hydroxyl-terminated monolayers utilizing triazabicyclodecene (TBD) as the polymerization catalyst. A consistent brush thickness of 40 nm could be achieved with a reproducible unique crystalline morphology. The organocatalyzed PCL brushes were chain extended using lactide in the presence of zirconium n-butoxide to successfully grow PCL/PLA block copolymer (PCL-b-PLA) brushes with a final thickness of 55 nm. The degradation properties of "grafted from" PCL brush and the PCL-b-PLA brush were compared to "grafted to" PCL brushes, and we observed that the brush density plays a major role in degradation kinetics. Solutions of methanol/water at pH 14 were used to better solvate the brushes and increase the kinetics of degradation. This framework enables a control of degradation that allows for the precise removal of these coatings.

  15. Effect of process conditions on olefin selectivity during conventional and supercritical Fischer-Tropsch synthesis

    SciTech Connect

    Bukur, D.B.; Lang, X.; Akgerman, A.; Feng, Z.

    1997-07-01

    A precipitated iron catalyst (100 Fe/5 Cu/4.2 K/25 SiO{sub 2} on mass basis) was tested in a fixed-bed reactor under a variety of process conditions during conventional Fischer-Tropsch synthesis (FTS) and supercritical Fischer-Tropsch synthesis (SFTS). In both modes of operation it was found that: total olefin content decreases whereas 2-olefin content increases with either increase in conversion or H{sub 2}/CO molar feed ratio. Total olefin and 2-olefin selectivities were essentially independent of reaction temperature. The effect of conversion was more pronounced during conventional FTS. Comparison of olefin selectivities in the two modes of operation reveals that total olefin content is greater while the 2-olefin content is smaller during SFTS. Also, both the decrease in total olefin content and the increase in 2-olefin content with increase in carbon number (i.e., molecular weight of hydrocarbon products) was significantly less pronounced during SFTS in comparison to the conventional FTS. The obtained results suggest that 1-olefins, and to a smaller extent n-paraffins, are the primary products of FTS. Secondary reactions (isomerization, hydrogenation, and readsorption) of high molecular weight {alpha}-olefins occur to a smaller extent during SFTS, due to higher diffusivities and desorption rates of {alpha}-olefins in the supercritical propane than in the liquid-filled catalyst pores (conventional FTS).

  16. Catalysts comprising magnesium and a transition metal

    SciTech Connect

    Bujadoux, K.

    1984-10-09

    A catalyst comprising the product obtained by bringing into contact a compound of magnesium comprising at least one species selected from the group consisting of magnesium monohalides (MgX), halo-magnesium hydrides (HMgX) and magnesium hydride (MgH/sub 2/), X being a halogen and the said species MgX or HMgX being obtained by thermal decomposition of a powdery organo-magnesium halide R/sub 1/MgX wherein R/sub 1/ is an organic radical; and at least one halide of a transistion metal selected from the group consisting of titanium and vanadium, the valency of said metal in said halide being lower than or equal to 3, the quantities being such that the atomic ratio of magnesium to said transistion metal is between 1 and 25, and a catalyst system including the catalyst that is suitable for use in the polymerization of olefins and particularly ethylene.

  17. Iron-catalyzed aminohydroxylation of olefins.

    PubMed

    Williamson, Kevin S; Yoon, Tehshik P

    2010-04-07

    We have discovered that N-sulfonyl oxaziridines react with a broad range of olefins in the presence of iron salts to afford 1,3-oxazolidines. This process provides access to 1,2-aminoalcohols with the opposite sense of regioselectivity produced from the copper-catalyzed oxyamination previously reported by our laboratories. Thus, either regioisomeric form of 1,2-aminoalcohols can easily be obtained from the reaction of oxaziridines with olefins, and the sense of regioselectivity can be controlled by the appropriate choice of inexpensive, nontoxic, first-row transition-metal catalyst.

  18. Olefin metathesis in nano-sized systems

    PubMed Central

    Diallo, Abdou K; Gatard, Sylvain; Liang, Liyuan; Ornelas, Cátia; Martinez, Victor; Méry, Denise; Ruiz, Jaime

    2011-01-01

    Summary The interplay between olefin metathesis and dendrimers and other nano systems is addressed in this mini review mostly based on the authors’ own contributions over the last decade. Two subjects are presented and discussed: (i) The catalysis of olefin metathesis by dendritic nano-catalysts via either covalent attachment (ROMP) or, more usefully, dendrimer encapsulation – ring closing metathesis (RCM), cross metathesis (CM), enyne metathesis reactions (EYM) – for reactions in water without a co-solvent and (ii) construction and functionalization of dendrimers by CM reactions. PMID:21286399

  19. Design of an etch-resistant cyclic olefin photoresist

    NASA Astrophysics Data System (ADS)

    Allen, Robert D.; Opitz, Juliann; Wallow, Thomas I.; Di Pietro, Richard A.; Hofer, Donald C.; Jayaraman, Saikumar; Hullihan, Karen A.; Rhodes, Larry F.; Goodall, Brian L.; Shick, Robert A.

    1998-06-01

    In the quest for a high performance 193 nm photoresist with robust plasma etching resistance equivalent to or better than the DUV resists of today, we have focused on the use of cyclic olefin polymers. In this paper, we will discuss monomer synthesis, polymerization approaches, polymer properties and early lithographic results of 193 nm photoresists formulated from cyclic olefin polymeric materials made from a metal-catalyzed addition polymerization process. The goal of this work is to produce a 193 nm photoresist with excellent imaging performance and etch resistance exceeding DUV resists, and in fact approaching novolak-based photoresists.

  20. Catalytic living ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

    Nagarkar, Amit A.; Kilbinger, Andreas F. M.

    2015-09-01

    In living ring-opening metathesis polymerization (ROMP), a transition-metal-carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well-defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst.

  1. Halloysite nanotube supported Ag nanoparticles heteroarchitectures as catalysts for polymerization of alkylsilanes to superhydrophobic silanol/siloxane composite microspheres.

    PubMed

    Li, Cuiping; Li, Xueyuan; Duan, Xuelan; Li, Guangjie; Wang, Jiaqiang

    2014-12-15

    Halloysite nanotube supported Ag nanoparticles heteroarchitectures have been prepared through a very simple electroless plating method. Robust Ag nanocrystals can be reproducibly fabricated by soaking halloysite nanotubes in ethanolic solutions of AgNO3 and butylamine. By simply adjusting the molar ratio of AgNO3 and butylamine, Ag nanoparticles with tunable size and quantity on halloysite nanotube are achieved. It reveals that the Ag nanoparticles are well-dispersed on the surface of halloysite nanotubes. The halloysite nanotube supported Ag nanoparticles heteroarchitectures can serve as active catalysts for the polymerization of an alkylsilane C18H37SiH3 with water to form silanol/siloxane composite microspheres and exhibit interesting superhydrophobicity ascribed to the micro/nanobinary structure.

  2. New Cobalt-Mediated Radical Polymerization (CMRP) of Methyl Methacrylate Initiated by Two Single-Component Dinuclear β-Diketone Cobalt (II) Catalysts

    PubMed Central

    Bao, Feng; Feng, Lingling; Gao, Jie; Tan, Zhifang; Xing, Bin; Ma, Rui; Yan, Chunjie

    2010-01-01

    Two dinuclear cobalt complexes based on bis-diketonate ligands (ligand 1: 3,3′-(1,3-phenylene)bis(1-phenylpropane-1,3-dione); ligand 2: 3,3′-(1,4-phenylene)bis(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. PMID:21049027

  3. Structural features of macrocyclic cobalt complexes - catalysts of chain transfer to a monomer in radical polymerization

    SciTech Connect

    Gridnev, A.A.; Lampeka, Ya.D.; Smirnov, B.R.; Yatsimirskii, K.B.

    1987-11-01

    Data are given on the catalytic activity of a series of cobalt coordination compounds with macrocyclic and acyclic ligsnds of different structures in radical polymerization reactions of methacrylic monomers. The influence of various factors (especially the structure of the ligand) on the manifestation of catalytic properties of the compounds studied is discussed.

  4. Replacing tin in lactide polymerization: design of highly active germanium-based catalysts.

    PubMed

    Guo, Jia; Haquette, Pierre; Martin, Juliette; Salim, Karine; Thomas, Christophe M

    2013-12-16

    Most germane: Hexacoordinate germanium(IV) species exhibit unprecedented activities, yet controlled behavior, as initiators for the ring-opening polymerization of rac-lactide to form polylactide polymers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Improved light olefin yield from methyl bromide coupling over modified SAPO-34 molecular sieves.

    PubMed

    Zhang, Aihua; Sun, Shouli; Komon, Zachary J A; Osterwalder, Neil; Gadewar, Sagar; Stoimenov, Peter; Auerbach, Daniel J; Stucky, Galen D; McFarland, Eric W

    2011-02-21

    As an alternative to the partial oxidation of methane to synthesis gas followed by methanol synthesis and the subsequent generation of olefins, we have studied the production of light olefins (ethylene and propylene) from the reaction of methyl bromide over various modified microporous silico-aluminophosphate molecular-sieve catalysts with an emphasis on SAPO-34. Some comparisons of methyl halides and methanol as reaction intermediates in their conversion to olefins are presented. Increasing the ratio of Si/Al and incorporation of Co into the catalyst framework improved the methyl bromide yield of light olefins over that obtained using standard SAPO-34.

  6. Enhanced Olefin Cross Metathesis Reactions: The Copper Iodide Effect

    PubMed Central

    Voigtritter, Karl; Ghorai, Subir

    2011-01-01

    Copper iodide has been shown to be an effective co-catalyst for the olefin cross metathesis reaction. In particular, it has both a catalyst stabilizing effect due to iodide ion, as well as copper(I)-based phosphine-scavenging properties that apply to use of the Grubbs-2 catalyst. A variety of Michael acceptors and olefinic partners can be cross-coupled under mild conditions in refluxing diethyl ether that avoid chlorinated solvents. This effect has also been applied to chemistry in water at room temperature using the new surfactant TPGS-750-M. PMID:21528868

  7. Cis-Selective Ring-Opening Metathesis Polymerization with Ruthenium Catalysts

    PubMed Central

    Keitz, Benjamin K.; Fedorov, Alexey; Grubbs, Robert H.

    2012-01-01

    Using a C-H activated, ruthenium-based metathesis catalyst, the cis selective ROMP of several monocyclic alkenes, as well as norbornene and oxanorbornene-type monomers is reported. The cis content of the isolated polymers depended heavily on monomer structure and temperature. By lowering the temperature, cis content as high as 96% could be obtained. PMID:22239675

  8. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

    PubMed Central

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J

    2015-01-01

    Summary Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  9. Catalytic oligomerization of ethylene to higher linear alpha-olefins promoted by the cationic group 4 [(eta 5-Cp-(CMe2-bridge)-Ph)MII(ethylene)2]+ (M = Ti, Zr, Hf) active catalysts: a density functional investigation of the influence of the metal on the catalytic activity and selectivity.

    PubMed

    Tobisch, Sven; Ziegler, Tom

    2004-07-28

    A detailed theoretical analysis is presented of the catalytic abilities of heavier group 4 (M = Zr, Hf) metals for linear ethylene oligomerization with the cationic [(eta(5)-C(5)H(4)-(CMe(2)-bridge)-C(6)H(5))M(IV)(CH(3))(2)](+) complex as precatalyst, employing a gradient-corrected DFT method. The parent Ti system has been reported as a highly selective catalyst for ethylene trimerization. The mechanism involving metallacycle intermediates, originally proposed by Briggs and Jolly, has been supported by the present study to be operative for the investigated class of group 4 catalysts. Metallacycle growth through bimolecular ethylene uptake and subsequent insertion is likely to occur at uniform rates for larger cycles that are furthermore comparable for Ti, Zr, and Hf catalysts. Ethylene insertion into the two smallest five- and seven-membered cycles is found to become accelerated for Zr and Hf catalysts, which is due to geometrical factors. In contrast, electronic effects act to raise the barrier for metallacycle decomposition, affording alpha-olefins upon descending group 4. This process is furthermore predicted to be kinetically more difficult for larger metallacycles. The oligomer distribution of the Zr-mediated reaction is likely to comprise predominantly 1-hexene together with 1-octene, while 1-butene and alpha-olefins of chain lengths C(10)-C(18) should occur only in negligible portions. A similar composition of alpha-olefins having C(6)-C(18) chain lengths is indicated for the Hf catalysts, but with long-chain oligomers and polymers as the prevalent fraction. Between the group 4 catalysts of the investigated type, the Zr system appears as the most promising candidate having catalytic potential for production of 1-octene, although not selectively. The influence of temperature to modulate the oligomer product composition has been evaluated.

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

    PubMed Central

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

    2017-01-01

    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. PMID:28300062

  11. Polymerization of Lactic Acid by MAGHNITE-H+ a Non-Toxic Montmorillonite Clay Catalyst

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    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.

  13. Neutral, single-component nickel (II) polyolefin catalysts that tolerate heteroatoms

    PubMed

    Younkin; Connor; Henderson; Friedrich; Grubbs; Bansleben

    2000-01-21

    More than half of the 170 million metric tons of polymers produced each year are polyolefins. Current technology uses highly active cationic catalysts, which suffer from an inability to tolerate heteroatoms such as oxygen, nitrogen, and sulfur. These systems require scrupulously clean starting materials and activating cocatalysts. A family of catalysts has been developed whose members are tolerant of both heteroatoms and less pure starting materials. These heteroatom-tolerant neutral late transition metal complexes are in fact highly active systems that produce high-molecular-weight polyethylene, polymerize functionalized olefins, and require no cocatalyst.

  14. Real‐time Analysis of a Working Triethylaluminium‐Modified Cr/Ti/SiO2 Ethylene Polymerization Catalyst with In Situ Infrared Spectroscopy

    PubMed Central

    Cicmil, Dimitrije; Meeuwissen, Jurjen; Vantomme, Aurélien

    2016-01-01

    Abstract A diffuse reflectance infrared Fourier‐transform (DRIFT) study has been conducted at 373 K and 1 bar on an industrial Cr/Ti/SiO2 Phillips‐type catalyst modified with, and without, triethylaluminium (TEAl) as co‐catalyst. The reaction rate of the polymerization of ethylene, as monitored by the increase in the methylene stretching band of the growing polyethylene (PE), has been investigated as a function of the titanium content. After an initial period of mixed kinetics, with the reaction rate significantly higher for the TEAl‐modified catalysts compared with the non‐modified catalysts, the polymerization proceeded as a pseudo‐zero‐order reaction with a reaction rate that increased as a function of titanium loading. Furthermore, it was found that the higher Ti loading caused the appearance of more acidic hydroxyl groups and modified the Cr sites by making them more Lewis acidic, ultimately shortening the induction time and increasing the initial polymerization rate. PMID:27840661

  15. Process feasibility of DME to olefin conversion

    SciTech Connect

    Tartamella, T.L.; Fullerton, K.L.; Lee, S.; Kulik, C.J.

    1994-12-31

    The production of hydrocarbons via a synthetic route has been extensively studied by Mobil through its methanol based Methanol-to-Gasoline (MTG) process. An alternative approach using dimethyl ether (DME) has been developed by the University of Akron -- UA/EPRI DME-to-Hydrocarbons Process. The process feasibility of the production of hydrocarbons from DME has been illustrated in a bench scale, fluidized bed reactor using ZSM-5 type catalyst. In an effort to satisfy the growing demand for olefins as an intermediate chemical feedstocks a mechanistic/kinetic study was developed. The synthesis of olefins has been studied in packed bed micro-reactor using ZSM-5 catalyst. Experimental work has given details of reaction kinetics and mechanism in the conversion of DME to olefins. DME concentration weight hourly space velocity (WHSV), as well as reactor temperature and pressure were investigated in the study. This work was used as a precursor to the production of olefins/hydrocarbons from DME in a fluidized bed reactor. Product gas analysis was performed using an external GC standard method.

  16. Light olefins from coal derived syngas

    SciTech Connect

    Sardesai, A.; Tartamella, T.; Lee, S.

    1996-12-31

    Synthesis of methanol from coal-derived synthesis gas is a well established technology, and methanol has been used as a feedstock for the synthesis of gasoline range hydrocarbons and olefins commercially. However, an efficient hydrocarbon synthesis process, based on a single-stage dimethyl ether synthesis from syngas, has been developed at the University of Akron. This UA/EPRI`s DTH (Dimethyl Ether to Hydrocarbons) process has significant advantages over its counterpart methanol conversion process in the areas of heat duties, hydrocarbon selectivities, product yield, and reactor size. Lower olefins are the intermediate products in the conversion of dimethyl ether to aromatic hydrocarbons. C{sub 2}-C{sub 4} olefins can be selectively produced by varying the operating parameters of the process, viz., temperature, pressure, DME concentration in the feed, space time, acidity of the catalyst, etc. The present work focuses on the effect of key process variables on the dimethyl ether conversion to lower olefins in a fixed bed microreactor system over ZSM-5 type zeolite catalyst. Experimental results with respect to gaseous hydrocarbon product yields and selectivities have been examined in this study.

  17. Method of polymerizing exo-methylene cyclic organic compounds using homogeneous ring-opening catalysts

    DOEpatents

    Marks, Tobin J.; Yang, Xinmin; Jia, Li

    1994-01-01

    The regiospecific (1,2-Me.sub.2 C.sub.5 H.sub.3).sub.2 ZrMe.sup.+ MeB(C.sub.6 F.sub.5).sub.3.sup.- mediated ring-opening polymerization of methylenecyclobutane and its copolymerization with ethylene to polyolefins of microstructure--{CH.sub.2 CH.sub.2 CH.sub.2 C(CH.sub.2)]--.sub.n and {--[CH.sub.2 CHR]--.sub.x [CH.sub.2 CH.sub.2 CH.sub.2 C(CH.sub.2)]--.sub.y }.sub.n' respectively, is disclosed.

  18. Antimicrobial activities of silver used as a polymerization catalyst for a wound-healing matrix

    PubMed Central

    Babu, Ranjith; Zhang, Jianying; Beckman, Eric J.; Virji, Mohammed; Pasculle, William A.; Wells, Alan

    2007-01-01

    Wound healing is a complex and orchestrated process that re-establishes the barrier and other functions of the skin. While wound healing proceeds apace in healthy individual, bacterial overgrowth and infection disrupts this process with significant morbidity and mortality. As such, any artificial matrix to promote wound healing must also control infecting microbes. We had earlier developed a two-part space-conforming gel backbone based on polyethyleneglycol (PEG) or lactose, which used ionic silver as the catalyst for gelation. As silver is widely used as an in vitro antimicrobial, use of silver as a catalyst for gelation provided the opportunity to assess its function as an anti-microbial agent in the gels. We found that these gels show bacteriostatic and bactericidal activity for a range of Gram-negative and Gram-positive organisms, including aerobic as well as anaerobic bacteria. This activity lasted for days, as silver leached out of the formed gels over a day in the manner of second-order decay. Importantly the gels did not limit either cell growth or viability, though cell migration was affected. Adding collagen I fragments to the gels corrected this effect on cell migration. We also found that the PEG gel did not interfere with hemostasis. These observations provide the basis for use of the gel backbones for incorporation of anesthetic agents and factors that promote wound repair. In conclusion, silver ions can serve dual functions of catalyzing gelation and providing anti-microbial properties to a biocompatible polymer. PMID:16635526

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

    PubMed

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

    2017-07-26

    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, BF3 and B(C6 F5 )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(C6 F5 )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 BF3 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(C6 F5 )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.

  20. Photocatalytic Hydrogen Production using Polymeric Carbon Nitride with a Hydrogenase and a Bioinspired Synthetic Ni Catalyst**

    PubMed Central

    Caputo, Christine A; Gross, Manuela A; Lau, Vincent W; Cavazza, Christine; Lotsch, Bettina V; Reisner, Erwin

    2014-01-01

    Solar-light-driven H2 production in water with a [NiFeSe]-hydrogenase (H2ase) and a bioinspired synthetic nickel catalyst (NiP) in combination with a heptazine carbon nitride polymer, melon (CNx), is reported. The semibiological and purely synthetic systems show catalytic activity during solar light irradiation with turnover numbers (TONs) of more than 50 000 mol H2 (mol H2ase)−1 and approximately 155 mol H2 (mol NiP)−1 in redox-mediator-free aqueous solution at pH 6 and 4.5, respectively. Both systems maintained a reduced photoactivity under UV-free solar light irradiation (λ>420 nm). PMID:26300567

  1. Photocatalytic Hydrogen Production using Polymeric Carbon Nitride with a Hydrogenase and a Bioinspired Synthetic Ni Catalyst**

    PubMed Central

    Caputo, Christine A; Gross, Manuela A; Lau, Vincent W; Cavazza, Christine; Lotsch, Bettina V; Reisner, Erwin

    2014-01-01

    Solar-light-driven H2 production in water with a [NiFeSe]-hydrogenase (H2ase) and a bioinspired synthetic nickel catalyst (NiP) in combination with a heptazine carbon nitride polymer, melon (CNx), is reported. The semibiological and purely synthetic systems show catalytic activity during solar light irradiation with turnover numbers (TONs) of more than 50 000 mol H2 (mol H2ase)−1 and approximately 155 mol H2 (mol NiP)−1 in redox-mediator-free aqueous solution at pH 6 and 4.5, respectively. Both systems maintained a reduced photoactivity under UV-free solar light irradiation (λ>420 nm). PMID:25205168

  2. Mechanistic Investigation of Catalyst-Transfer Suzuki-Miyaura Condensation Polymerization of Thiophene-Pyridine Biaryl Monomers with the Aid of Model Reactions.

    PubMed

    Tokita, Yu; Katoh, Masaru; Ohta, Yoshihiro; Yokozawa, Tsutomu

    2016-11-21

    We have investigated the requirements for efficient Pd-catalyzed Suzuki-Miyaura catalyst-transfer condensation polymerization (Pd-CTCP) reactions of 2-alkoxypropyl-6-(5-bromothiophen-2-yl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (12) as a donor-acceptor (D-A) biaryl monomer. As model reactions, we first carried out the Suzuki-Miyaura coupling reaction of X-Py-Th-X' (Th=thiophene, Py=pyridine, X, X'=Br or I) 1 with phenylboronic acid ester 2 by using tBu3 PPd(0) as the catalyst. Monosubstitution with a phenyl group at Th-I mainly took place in the reaction of Br-Py-Th-I (1 b) with 2, whereas disubstitution selectively occurred in the reaction of I-Py-Th-Br (1 c) with 2, indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the Mn of the obtained polymer, as well as the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra, indicated that Suzuki-Miyaura coupling polymerization of 12 with (o-tolyl)tBu3 PPdBr initiator 13 proceeded in a step-growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki-Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step-growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th-Pd-Py complex formed by transmetalation of polymer Th-Br with (Pin)B-Py-Th-Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal-arene η(2) -coordination for D and A monomers may be needed for CTCP reactions of biaryl D-A monomers. © 2016 Wiley-VCH Verlag

  3. Redox-Neutral Rh(III)-Catalyzed Olefination of Carboxamides with Trifluoromethyl Allylic Carbonate.

    PubMed

    Park, Jihye; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Lee, Seok-Yong; Lee, Jong Suk; Kwak, Jong Hwan; Um, Sung Hee; Kim, In Su

    2016-11-18

    The rhodium(III)-catalyzed olefination of various carboxamides with α-CF3-substituted allylic carbonate is described. This reaction provides direct access to linear CF3-allyl frameworks with complete trans-selectivity. In particular, a rhodium catalyst provided Heck-type γ-CF3-allylation products via the β-O-elimination of rhodacycle intermediate and subsequent olefin migration process.

  4. Iron(III)-Catalyzed Ring-Closing Carbonyl-Olefin Metathesis.

    PubMed

    Saá, Carlos

    2016-09-05

    Recent developments in catalytic carbonyl-olefin metathesis are summarized in this Highlight. Schindler and co-workers have reported that the environmentally benign FeCl3 catalyst promotes ring-closing carbonyl-olefin metathesis (RCCOM) in high yield under very mild conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Olefin Insertion into a Pd-F Bond: Catalyst Reactivation Following β-F Elimination in Ethylene/Vinyl Fluoride Copolymerization.

    PubMed

    Wada, Shinji; Jordan, Richard F

    2017-02-06

    The discrete (phosphinoarenesulfonate)Pd fluoride complex (PO(Bp,OMe) )PdF(lutidine), where PO(Bp,OMe) =(2-MeOC6 H4 )(2-{2,6-(MeO)2 C6 H3 }C6 H4 )(2-SO3 -5-MeC6 H3 )P, inserts vinyl fluoride (VF) to form (PO(Bp,OMe) )PdCH2 CHF2 (lutidine) and inserts multiple ethylene (E) units to generate polyethylene that contains -CH2 F chain ends. These results provide strong evidence that the -CHF2 and -CH2 F chain ends in E/VF copolymer generated by (phosphinoarenesulfonate)PdR catalysts form by β-F elimination of Pd(β-F-alkyl) species, VF or E insertion of the resulting (PO)PdF species, and subsequent chain growth. These results also imply that β-F elimination is not an important catalyst deactivation reaction in this system.

  6. Polymerization of perfluorobutadiene

    NASA Technical Reports Server (NTRS)

    Newman, J.; Toy, M. S.

    1970-01-01

    Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

  7. Ultrasound assisted free radical polymerization of glycidyl methacrylate by a new disite phase-transfer catalyst system: A kinetic study.

    PubMed

    Sankar, Kavitha; Rajendran, Venugopal

    2012-11-01

    The kinetics of multi-site phase-transfer catalyzed free radical polymerisation of glycidyl methacrylate (GMA) using potassium peroxy disulphate (PDS) as water soluble initiator and newly synthesized 1,4-dihexadecylpyrazine-1,4-diium dibromide as multi-site phase-transfer catalyst (MPTC) has been investigated in ethyl acetate/water two phase system at constant temperature 65±1°C under nitrogen atmosphere and ultrasound irradiation conditions. The rate of polymerization increases with an increase in concentrations of GMA, PDS and MPTC. The order with respect to monomer, initiator and MPTC were found to be 1.0, 0.5 and 1.0, respectively. The comparative study reveals that the Rp of GMA determined in the presence of PTC combined with ultrasound has shown more enhancements in the activity than PTC alone. Based on the observed results a suitable mechanism has been proposed to account for the experimental observations and its significance was discussed. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Probing the Mechanism of the Double C—H (De)Activation Route of a Ru-Based Olefin Metathesis Catalyst

    NASA Astrophysics Data System (ADS)

    Poater, Albert; Cavallo, Luigi

    A theoretical study of a double C—H activation mechanism that deactivates a family of second generation Ru-based catalysts is presented. DFT calculations are used to rationalize the complex mechanistic pathway from the starting precatalyst to the experimentally characterized decomposition products. In particular, we show that all the intermediates proposed by Grubbs and coworkers are indeed possible intermediates in the deactivation pathway, although the sequence of steps is somewhat different

  9. Catalytic Intramolecular Ketone Alkylation with Olefins by Dual Activation.

    PubMed

    Lim, Hee Nam; Dong, Guangbin

    2015-12-07

    Two complementary methods for catalytic intramolecular ketone alkylation reactions with unactivated olefins, resulting in Conia-ene-type reactions, are reported. The transformations are enabled by dual activation of both the ketone and the olefin and are atom-economical as stoichiometric oxidants or reductants are not required. Assisted by Kool's aniline catalyst, the reaction conditions can be both pH- and redox-neutral. A broad range of functional groups are thus tolerated. Whereas the rhodium catalysts are effective for the formation of five-membered rings, a ruthenium-based system that affords the six-membered ring products was also developed.

  10. Highly Z-Selective Metathesis Homocoupling of Terminal Olefins

    PubMed Central

    Jiang, Annie J.; Zhao, Yu; Schrock, Richard R.; Hoveyda, Amir H.

    2009-01-01

    Mo and W MonoAryloxide-Pyrrolide (MAP) olefin metathesis catalysts can couple terminal olefins to give as high as >98% Z-products in moderate to high yields with as little as 0.2% catalyst. Results are reported for 1-hexene, 1-octene, allylbenzene, allyltrimethylsilane, methyl-10-undecenoate, methyl-9-decenoate, allylB(pinacolate), allylOBenzyl, allylNHTosyl, and allylNHPh. It is proposed that high Z-selectivity is achieved because a large aryloxide only allows metallacyclobutanes to form that contain adjacent cis substituents and because isomerization of Z-product to E-product can be slow in that same steric environment. PMID:19919135

  11. Further work on sodium montmorillonite as catalyst for the polymerization of activated amino acids

    NASA Technical Reports Server (NTRS)

    Eirich, F. R.; Paecht-Horowitz, M.

    1986-01-01

    When the polycondensation of amino acid acylates was catalyzed with Na-montmorillonite, the polypeptides were consistently found to exhibit a distribution of discrete molecular weights, for as yet undiscovered reasons. One possible explanation was connected to the stepwise mode of monomer addition. New experiments have eliminated this possibility, so that there is the general assumption that this discreteness is the result of a preference of shorter oligomers to add to others of the same length, a feature that could be attributed to some structure of the platelet aggregates of the montmorillonite. The production of optical stereoisomers is anticipated when D,L-amino acids are polymerized on montmorillonite. Having used an optically active surface, the essence of the results lies not only in the occurrence of optically active oligomers and polymers, but also in the fact that the latter exhibit the same molecular weight characteristics as the D,L-polymers. Preparatory to work contemplated on a parallel synthesis of amino acid and nucleotide oligomers, studies were continued on the co-adsorption of amino acids, nucleotides, and amino acid-nucleotides on montmorillonite.

  12. Iron(III)-catalysed carbonyl-olefin metathesis

    NASA Astrophysics Data System (ADS)

    Ludwig, Jacob R.; Zimmerman, Paul M.; Gianino, Joseph B.; Schindler, Corinna S.

    2016-05-01

    The olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon-carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments in the synthesis of molecules relevant to the petroleum, materials, agricultural and pharmaceutical industries. These reactions are characterized by their use of discrete metal alkylidene catalysts that operate via a well-established mechanism. While the corresponding carbonyl-olefin metathesis reaction can also be used to construct carbon-carbon bonds, currently available methods are scarce and severely hampered by either harsh reaction conditions or the required use of stoichiometric transition metals as reagents. To date, no general protocol for catalytic carbonyl-olefin metathesis has been reported. Here we demonstrate a catalytic carbonyl-olefin ring-closing metathesis reaction that uses iron, an Earth-abundant and environmentally benign transition metal, as a catalyst. This transformation accommodates a variety of substrates and is distinguished by its operational simplicity, mild reaction conditions, high functional-group tolerance, and amenability to gram-scale synthesis. We anticipate that these characteristics, coupled with the efficiency of this reaction, will allow for further advances in areas that have historically been enhanced by olefin metathesis.

  13. Preparation of olefins from synthesis gas using ruthenium supported on ceric oxide

    DOEpatents

    Pierantozzi, R.

    1985-04-09

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  14. Preparation of olefins from synthesis gas using ruthenium supported on ceric oxide

    DOEpatents

    Pierantozzi, Ronald

    1985-01-01

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  15. MICROWAVE-EXPEDITED OLEFIN EPOXIDATION OVER HYDROTALCITES USING HYDROGEN PEROXIDE AND ACETONITRILE

    EPA Science Inventory

    An efficient microwave-assisted expoxidation of olefins is described over hydrotalcite catalysts in the presence of hydrogen peroxide and acetonitrile. This general and selective protocol is extremely fast and is applicable to a wide variety of subtrates.

  16. Effect of EtOH/MgCl(2) molar ratios on the catalytic properties of MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalyst for ethylene polymerization.

    PubMed

    Patthamasang, Supanan; Jongsomjit, Bunjerd; Praserthdam, Piyasan

    2011-09-29

    MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalysts for ethylene polymerization were prepared by impregnation of MgCl(2) on SiO(2) in heptane and further treatment with TiCl(4). MgCl(2)·nEtOH adduct solutions were prepared with various EtOH/MgCl(2) molar ratios for preparation of the MgCl(2)-supported and MgCl(2)-SiO(2)-supported catalysts in order to investigate the effect on polymerization performance of both catalyst systems. The catalytic activities for ethylene polymerization decreased markedly with increased molar ratios of [EtOH]/[MgCl(2)] for the MgCl(2)-supported catalysts, while for the bi-supported catalysts, the activities only decreased slightly. The MgCl(2)-SiO(2)-supported catalyst had relatively constant activity, independent of the [EtOH]/[MgCl(2)] ratio. The lower [EtOH]/[MgCl(2)] in MgCl(2)-supported catalyst exhibited better catalytic activity. However, for the MgCl(2)-SiO(2)-supported catalyst, MgCl(2) can agglomerate on the SiO(2) surface at low [EtOH]/[MgCl(2)] thus not being not suitable for TiCl(4) loading. It was found that the optimized [EtOH]/[MgCl(2)] value for preparation of bi-supported catalysts having high activity and good spherical morphology with little agglomerated MgCl(2) was 7. Morphological studies indicated that MgCl(2)-SiO(2)-supported catalysts have good morphology with spherical shapes that retain the morphology of SiO(2). The BET measurement revealed that pore size is the key parameter dictating polymerization activity. The TGA profiles of the bi-supported catalyst also confirmed that it was more stable than the mono-supported catalyst, especially in the ethanol removal region.

  17. At the frontier between heterogeneous and homogeneous catalysis: hydrogenation of olefins and alkynes with soluble iron nanoparticles.

    PubMed

    Rangheard, Claudine; de Julián Fernández, César; Phua, Pim-Huat; Hoorn, Johan; Lefort, Laurent; de Vries, Johannes G

    2010-09-28

    The use of non-supported Fe nanoparticles in the hydrogenation of unsaturated C-C bonds is a green catalytic concept at the frontier between homogeneous and heterogeneous catalysis. Iron nanoparticles can be obtained by reducing Fe salts with strong reductants in various solvents. FeCl(3) reduced by 3 equivalents of EtMgCl forms an active catalyst for the hydrogenation of a range of olefins and alkynes. Olefin hydrogenation is relatively fast at 5 bar using 5 mol% of catalyst. The catalyst is also active for terminal olefins and 1,1' and 1,2-cis disubstituted olefins while trans-olefins react much slower. 1-Octyne is hydrogenated to mixtures of 1-octene and octane. Kinetic studies led us to propose a mechanism for this latter transformation where octane is obtained by two different pathways. Characterization of the nanoparticles via TEM, magnetic measurements and poisoning experiments were undertaken to understand the true nature of our catalyst.

  18. A fully integrated high-throughput screening methodology for the discovery of new polyolefin catalysts: discovery of a new class of high temperature single-site group (IV) copolymerization catalysts.

    PubMed

    Boussie, Thomas R; Diamond, Gary M; Goh, Christopher; Hall, Keith A; LaPointe, Anne M; Leclerc, Margarete; Lund, Cheryl; Murphy, Vince; Shoemaker, James A W; Tracht, Ursula; Turner, Howard; Zhang, Jessica; Uno, Tetsuo; Rosen, Robert K; Stevens, James C

    2003-04-09

    For the first time, new catalysts for olefin polymerization have been discovered through the application of fully integrated high-throughput primary and secondary screening techniques supported by rapid polymer characterization methods. Microscale 1-octene primary screening polymerization experiments combining arrays of ligands with reactive metal complexes M(CH(2)Ph)(4) (M = Zr, Hf) and multiple activation conditions represent a new high-throughput technique for discovering novel group (IV) polymerization catalysts. The primary screening methods described here have been validated using a commercially relevant polyolefin catalyst, and implemented rapidly to discover the new amide-ether based hafnium catalyst [eta(2)-(N,O)[bond](2-MeO[bond]C(6)H(4))(2,4,6-Me(3)C(6)H(2))N]Hf(CH(2)Ph)(3) (1), which is capable of polymerizing 1-octene to high conversion. The molecular structure of 1 has been determined by X-ray diffraction. Larger scale secondary screening experiments performed on a focused 96-member amine-ether library demonstrated the versatile high temperature ethylene-1-octene copolymerization capabilities of this catalyst class, and led to significant performance improvements over the initial primary screening discovery. Conventional one gallon batch reactor copolymerizations performed using selected amide-ether hafnium compounds confirmed the performance features of this new catalyst class, serving to fully validate the experimental results from the high-throughput approaches described herein.

  19. Chiral Cu(salen)-Based Metal-Organic Framework for Heterogeneously Catalyzed Aziridination and Amination of Olefins.

    PubMed

    Liu, Yan; Li, Zijian; Yuan, Guozan; Xia, Qingchun; Yuan, Chen; Cui, Yong

    2016-12-19

    A homochiral 3D porous metal-organic framework was assembled from a chiral dicarboxylic acid-functionalized Cu(salen)-based catalyst and could serve as an efficient heterogeneous catalyst for aziridination and allylic amination of olefins. Besides easy separation and reuse of the catalyst, the chiral framework confinement could impart substrate size selectivity, enhance catalyst activity, and induce product enantioselectivity.

  20. Hydrogenation of the Exocyclic Olefinic Bond at C-16/C-17 Position of ent-Kaurane Diterpene Glycosides of Stevia rebaudiana Using Various Catalysts

    PubMed Central

    Chaturvedula, Venkata Sai Prakash; Prakash, Indra

    2013-01-01

    Catalytic hydrogenation of the exocyclic double bond present between C16 and C17 carbons of the four ent-kaurane diterpene glycosides namely rebaudioside A, rebaudioside B, rebaudioside C, and rebaudioside D isolated from Stevia rebaudiana has been carried out using Pt/C, Pd(OH)2, Rh/C, Raney Ni, PtO2, and 5% Pd/BaCO3 to their corresponding dihydro derivatives with 17α and 17β methyl group isomers. Reactions were performed using the above-mentioned catalysts with the solvents methanol, water, and ethanol/water (8:2) under various conditions. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data, including a comparison with reported spectral data. PMID:23896597

  1. Hydrogenation of the exocyclic olefinic bond at C-16/C-17 position of ent-kaurane diterpene glycosides of Stevia rebaudiana using various catalysts.

    PubMed

    Chaturvedula, Venkata Sai Prakash; Prakash, Indra

    2013-07-26

    Catalytic hydrogenation of the exocyclic double bond present between C16 and C17 carbons of the four ent-kaurane diterpene glycosides namely rebaudioside A, rebaudioside B, rebaudioside C, and rebaudioside D isolated from Stevia rebaudiana has been carried out using Pt/C, Pd(OH)2, Rh/C, Raney Ni, PtO2, and 5% Pd/BaCO3 to their corresponding dihydro derivatives with 17α and 17β methyl group isomers. Reactions were performed using the above-mentioned catalysts with the solvents methanol, water, and ethanol/water (8:2) under various conditions. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data, including a comparison with reported spectral data.

  2. [Cu(H2btec)(bipy)]infinity: a novel metal organic framework (MOF) as heterogeneous catalyst for the oxidation of olefins.

    PubMed

    Brown, Kareen; Zolezzi, Santiago; Aguirre, Pedro; Venegas-Yazigi, Diego; Paredes-García, Verónica; Baggio, Ricardo; Novak, Miguel A; Spodine, Evgenia

    2009-02-28

    A new extended metal-organic framework [Cu(H2btec)(bipy)]infinity. (1) (H4btec= 1,2,4,5-benzenetetracarboxylic acid; bipy = 2,2'-bipyridine) has been hydrothermally synthesized. Violet crystals are formed in a monoclinic system with a space group C2/c; a = 10.1810(18) A, b = 14.4360(18) A, c = 12.894(3) A, beta = 112.94(3) degrees. In the title compound 1 each Cu(II) centre has a distorted square planar environment, completed by two N atoms from one bipy ligand and two O atoms belonging to two dihydrogen benzene-1,2,4,5-tetracarboxylate anions (H2btec2-). The {Cu(bipy)}2+ moieties are bridged by H2btec2- anions to form an infinite one-dimensional coordination polymer with a zig-zag chain structure along the c axis. A double-chain structure is formed by hydrogen bonds between adjacent zig-zag chains. There are also pi-pi stacking interactions between the bipy ligands, with an average distance of 3.62 A resulting in a two-dimensional network structure. Compound 1 was tested as a catalyst for the oxidation of cyclohexene and styrene, with tert-butyl hydroperoxide (TBHP) as oxidant. The catalytic activity (24 h and 75 degrees C) found for [Cu(H2btec)(bipy)]infinity shows a high value for the conversion of cyclohexene (64.5%), and a lower one for styrene (23.7%). High turnover frequency (TOF) values for the epoxide products were observed, indicating that the catalyst synthesized in this work, not only has a high activity and selectivity for epoxidation reactions but is also very efficient.

  3. Carbon-Carbon Bond Formation in a Weak Ligand Field: Leveraging Open Shell First Row Transition Metal Catalysts.

    PubMed

    Chirik, Paul James

    2017-01-12

    Unique features of Earth abundant transition metal catalysts are reviewed in the context of catalytic carbon-carbon bond forming reactions. Aryl-substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open shell iron and cobalt alkyl complexes have been synthesized that serve as single component olefin polymerization catalysts. Reduced bis(imino)pyridine iron- and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Electronic structure studies support open shell intermediates, a deviation from traditional strong field organometallic compounds that promote catalytic C-C bond formation.

  4. Stoichiometric and catalytic homologation of olefins on the Fischer-Tropsch catalysts Fe/SiO/sub 2/, Ru/SiO/sub 2/, Os/SiO/sup 2/, and Rh/SiO/sub 2/. Mechanistic implication in the mode of C-C bond formation

    SciTech Connect

    Leconte, M.; Theolier, A.; Rojas, D.; Basset, J.M.

    1984-02-22

    The formation of C/sub 4/ olefinic hydrocarbons both in CO + H/sub 2/ and C/sub 3/H/sub 6/ + H/sub 2/ reactions has been studied to test the assumption that the same mechanism is involved in the C-C bond formation in syn gas conversion and olefin hydrogenation. The yields of linear and branched olefins were measured at various contact times, and initial selectivities were obtained by extrapolation to zero conversion. The catalyst systems studied for the reactions were Fe, Ru, Rh, and Os supported by SiO/sub 2/. The results indicated that the same mechanism was involved in the C-C bond formation starting from CO + H/sub 2/, CH/sub 2/N/sub 2/ + H/sub 2/, or C/sub n/ H/sub 2n/ + H/sub 2/, and the mode of the C-C bond formation was shown to involve the addition of a C/sub 1/ fragment to a C/sub n/ fragment.

  5. Facile synthesis of Co(II) and Cu(II) complexes of 2-hydroxybenzophenone: An efficient catalyst for oxidation of olefins and DFT study

    NASA Astrophysics Data System (ADS)

    Lashanizadegan, Maryam; Alavijeh, Roya Karimi; Anafcheh, Maryam

    2017-10-01

    Two diketone complexes of Cu(II) and Co(II) were easily synthesized in reaction of M(CH3COO)2 with 2-Hydroxybenzophenone (bpoH). The complexes of M(bpo)2 were characterized by UV-vis, IR spectroscopy, and elemental analysis. The complexes are active catalysts for the oxidation of styrene using TBHP as an oxidant. Under the optimized reaction conditions, 100% conversion of styrene with 63.5% selectivity for Benzaldehyde and 36.5% for Styrene oxide were obtained by Cu(bpo)2. Also, the effect of imidazole was investigated. Results confirmed that the addition of imidazole accelerates the oxidation of styrene. Our DFT results confirmed the necessity of diffuse functions in the basis set and including an accurate treatment of the dispersion energy for obtaining the most stable structure in these systems. Therefore, the geometry optimization and the vibrational frequencies were calculated at the M06-2X/6-311++G(d,p) level. The scaled theoretical frequencies and the structural parameters are in excellent agreement with the experimental data. The natural charge analysis indicated that an electron is transferred from Cu(bpo)2 back to the TBHP to break the Osbnd O bond and formation of tert-butoxyl radicals. Coordination of imidazole in the axial position of the Cu(bpo)2 significantly assists in moving back of electron and increases the activity of the complex in oxidation.

  6. Bio-olefins from unsaturated fatty acids via tandem catalysis

    USDA-ARS?s Scientific Manuscript database

    A new catalytic route to bio-olefins from unsaturated fatty acids will be described. At the heart of the process, the catalyst apparently functions in a tandem mode by both dynamically isomerizing the positions of double bonds in an aliphatic chain and, subsequently, decarboxylating specific isomers...

  7. Single-Molecule Visualization of Living Polymerization

    DTIC Science & Technology

    2014-02-18

    siloxane bond†. Langmuir 24, 1343-1349 (2007). 4 M. Scholl, S. Ding, C. W. Lee & R. H. Grubbs. Synthesis and activity of a new generation of ruthenium ...Vougioukalakis & G. R. H. Ruthenium -based heterocyclic carbene-coordinated olefin metathesis catalysts. Chem Rev 110 (2010). 6 T. Lionnet, J. F. Allemand...2012). 10 X. Bantreil & S. P. Nolan. Synthesis of n-heterocyclic carbene ligands and derived ruthenium olefin metathesis catalysts. Nat Protoc 6, 69

  8. Supported neodymium catalysts for isoprene and rac-β-butyrolactone polymerization: modulation of reactivity by controlled grafting.

    PubMed

    Terrier, Michael; Brulé, Emilie; Vitorino, Marta J; Ajellal, Noureddine; Robert, Carine; Gauvin, Régis M; Thomas, Christophe M

    2011-01-17

    A series of hybrid materials, bearing neodymium silylamide initiating groups, have been shown to mediate isoprene polymerization when combined with alkyl aluminum activators [methylaluminoxane, AlEt(2)Cl, Al(iBu)(3)]. The surface species nature and relative distribution were correlated with isoprene polymerization activity and selectivity. This approach to stereocontrol modulation has been extended to racemic β-butyrolactone isoselective ring opening polymerization.

  9. Electrochemical performance and durability of carbon supported Pt catalyst in contact with aqueous and polymeric proton conductors.

    PubMed

    Andersen, Shuang Ma; Skou, Eivind

    2014-10-08

    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.

  10. Recovery of olefin monomers

    SciTech Connect

    Golden, Timothy Christoph; Weist, Jr., Edward Landis; Johnson, Charles Henry

    2004-03-16

    In a process for the production of a polyolefin, an olefin monomer is polymerised said polyolefin and residual monomer is recovered. A gas stream comprising the monomer and nitrogen is subjected to a PSA process in which said monomer is adsorbed on a periodically regenerated silica gel or alumina adsorbent to recover a purified gas stream containing said olefin and a nitrogen rich stream containing no less than 99% nitrogen and containing no less than 50% of the nitrogen content of the gas feed to the PSA process.

  11. Selective olefin recovery

    SciTech Connect

    1996-07-01

    This report presents the results of the outstanding studies on olefin product purities, pyridine recovery, and absorber offgas utilization. Other reports issued since the May 2 technical review meeting in Grangemouth evaluated the impact of the new VLE data on the solution stripping operation and the olefin loadings in the lean and rich solutions. This report completes the bulk of Stone & Webster`s engineering development of the absorber/stripper process for Phase I. The final feasibility study report (to be issued in August) will present an updated design and economics.

  12. Retrofitting olefin cracking plants

    SciTech Connect

    Sumner, C.; Fernandez-Baujin, J.M.

    1983-12-01

    This article discusses the retrofitting of liquid crackers which produce olefins so that gaseous feedstocks can be used. Naphtha and gas oil are the predominant design feedstocks for producing olefins. The price of gaseous feedstocks such as ethane, propane and butane have become economically more attractive than liquid feedstocks. Existing liquid crackers will be able to produce ethylene at 85% or higher capacity when cracking propane and butane feedstock with only minor changes. Topics considered include revamping for vacuum gas oil (VGO) feedstocks and revamping for liquefied petroleum gas (LPG) feedstocks.

  13. The beneficial use of ultrasound in synthesis of nanostructured Ce-doped SAPO-34 used in methanol conversion to light olefins.

    PubMed

    Charghand, Mojtaba; Haghighi, Mohammad; Aghamohammadi, Sogand

    2014-09-01

    Methanol to olefins process is an interesting route for synthesis of light olefins over nanostructured catalysts. The present research deals with catalyst development by sonochemical method for methanol to olefins reaction with the aim of reaching the most efficient catalyst. The CeSAPO-34 catalyst was prepared via ultrasound assisted hydrothermal method and characterized by XRD, FESEM, PSD, EDX, BET and FTIR techniques. The characteristics and performance of this sample were compared to the catalyst prepared by conventional hydrothermal method. XRD patterns reflected the higher crystallinity of the catalyst synthesized by ultrasound application. In comparison, particles with smaller sizes obtained by applying ultrasonic irradiation. The catalyst obtained using ultrasound had the longer lifetime and sustained desired light olefins at higher values.

  14. New tetradentate N,N,N,N-chelating α-diimine ligands and their corresponding zinc and nickel complexes: synthesis, characterisation and testing as olefin polymerisation catalysts.

    PubMed

    Li, Lidong; Gomes, Clara S B; Gomes, Pedro T; Duarte, M Teresa; Fan, Zhiqiang

    2011-04-07

    A series of zinc complexes of the general formula {[ZnCl(ArN=C(An)-C(An)=NAr)](+)}(2)[Zn(2)Cl(6)](2-) (where Ar = 2-(1-benzyl-1H-1,2,3-triazol-4-yl)phenyl 2a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)phenyl 2b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)phenyl 2c; An = acenaphthene backbone) were prepared by the condensation of acenaphthenequinone with the corresponding o-triazolyl-substituted anilines (2-(1-benzyl-1H-1,2,3-triazol-4-yl)aniline 1a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)aniline 1b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline 1c) which were formed by the copper(I)-catalyzed Huisgen[3+2] dipolar cycloaddition between 2-ethynylaniline and the corresponding azides in high yields, using anhydrous ZnCl(2) as the metal template, in boiling glacial acetic acid. Zinc complexes of the type [ZnCl(ArN=C(An)-C(An)=NAr)](+)[ZnCl(3)(NCCH(3))](-) (4a-c) were synthesized by crystallisation of the corresponding complexes 2a-c in acetonitrile, at -20 °C. After removal of zinc dichloride from complexes 2a-c by the addition of potassium oxalate, in dichloromethane, the tetradentate N,N,N,N-chelating α-diimine ligands of the type ArN=C(An)-C(An)=NAr (5a-c) were obtained. The new ligand precursors and zinc complexes were characterised by elemental analysis, (1)H and (13)C{(1)H} NMR spectroscopy, two-dimensional NMR spectroscopy, and X-ray diffraction. Reaction of the ligand precursors 5a-c with [NiBr(2)(DME)], in dichloromethane, gave nickel complexes of the type [NiBr(2)(ArN=C(An)-C(An)=NAr)] (6a-c). The results of single crystal X-ray diffraction characterisation and magnetic susceptibility measurements demonstrated that nickel complexes 6a-c possess octahedral geometries around the nickel atoms with variable configurations, the Br atoms of which can be ionized when dissolved in methanol. In preliminary catalytic tests, complexes 6a-c revealed to be active as catalysts for the polymerisation of norbornene and styrene, when activated by cocatalyst MAO. The characterisation

  15. Practical carbon–carbon bond formation from olefins through nickel-catalyzed reductive olefin hydrocarbonation

    PubMed Central

    Lu, Xi; Xiao, Bin; Zhang, Zhenqi; Gong, Tianjun; Su, Wei; Yi, Jun; Fu, Yao; Liu, Lei

    2016-01-01

    New carbon–carbon bond formation reactions expand our horizon of retrosynthetic analysis for the synthesis of complex organic molecules. Although many methods are now available for the formation of C(sp2)–C(sp3) and C(sp3)–C(sp3) bonds via transition metal-catalyzed cross-coupling of alkyl organometallic reagents, direct use of readily available olefins in a formal fashion of hydrocarbonation to make C(sp2)–C(sp3) and C(sp3)–C(sp3) bonds remains to be developed. Here we report the discovery of a general process for the intermolecular reductive coupling of unactivated olefins with alkyl or aryl electrophiles under the promotion of a simple nickel catalyst system. This new reaction presents a conceptually unique and practical strategy for the construction of C(sp2)–C(sp3) and C(sp3)–C(sp3) bonds without using any organometallic reagent. The reductive olefin hydrocarbonation also exhibits excellent compatibility with varieties of synthetically important functional groups and therefore, provides a straightforward approach for modification of complex organic molecules containing olefin groups. PMID:27033405

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

    PubMed Central

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

    2014-01-01

    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

  17. Developments in the use of rare earth metal complexes as efficient catalysts for ring-opening polymerization of cyclic esters used in biomedical applications

    NASA Astrophysics Data System (ADS)

    Cota, Iuliana

    2017-04-01

    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.

  18. Fluidized bed pyrolysis to gases containing olefins

    SciTech Connect

    Kuester, J.L.

    1980-01-01

    Recent gasification data are presented for a system designed to produce liquid hydrocarbon fuel from various biomass feedstocks. The factors under investigation were feedstock type, fluidizing gas type, residence time, temperature and catalyst usage. The response was gas phase composition. A fluidized bed system was utilized with a separate regenerator-combustor. An olefin content as high as 39 mole % was achieved. Hydrogen/carbon monoxide ratios were easily manipulated via steam addition over a broad range with an autocatalytic effect apparent for most feedstocks.

  19. On the fraction of CrII sites involved in the C2H4 polymerization on the Cr/SiO2 Phillips catalyst: a quantification by FTIR spectroscopy.

    PubMed

    Groppo, E; Lamberti, C; Cesano, F; Zecchina, A

    2006-06-07

    An estimation of the fraction of Cr(II) sites involved in the C(2)H(4) polymerization on a Cr(II)/SiO(2) Phillips catalyst has been obtained by means of in situ alternated CO adsorption and C(2)H(4) polymerization FTIR experiments: about 28% of the total surface sites react fast with C(2)H(4), while a lower fraction, which depends upon the temperature reaction conditions, is more slowly involved, in agreement with XANES results.

  20. EXPOXIDATION OF OLEFINS AND α,β-UNSATURATED KEYTONES OVER SONOCHEMICALLY PREPARED HYDROXYAPATITES USING HYDROGEN PEROXIDE

    EPA Science Inventory

    An effective and environmentally friendly protocol for the epoxidation of olefins and α,β-unsaturated ketones in the presence of hydroxyapatite as catalyst using hydrogen peroxide is described. The catalyst is active and reusable for the selective epoxidation of a variety...

  1. EXPOXIDATION OF OLEFINS AND α,β-UNSATURATED KEYTONES OVER SONOCHEMICALLY PREPARED HYDROXYAPATITES USING HYDROGEN PEROXIDE

    EPA Science Inventory

    An effective and environmentally friendly protocol for the epoxidation of olefins and α,β-unsaturated ketones in the presence of hydroxyapatite as catalyst using hydrogen peroxide is described. The catalyst is active and reusable for the selective epoxidation of a variety...

  2. Chain length dependence of {alpha}-olefin readsorption in Fischer-Tropsch synthesis

    SciTech Connect

    Kuipers, E.W.; Vinkenburg, I.H.; Oosterbeek, H.

    1995-03-01

    The total product concentration and the paraffin/olefin ratio have been measured up to C{sub 14} for Fischer-Tropsch synthesis on polycrystalline Co foils. The influences due to surface area, a wax coating, the H{sub 2}/CO ratio and flow velocity on concentration and selectivity have been determined. The paraffin/olefin ratio increases exponentially with chain length which is attributed to a chain-length-dependent olefin readsorption mechanism. The probability of readsorption depends on the heat of physisorption of the olefins on the catalyst as well as on their heat of dissolution in and their diffusivity through the product wax. All three factors predict an increase of the paraffin/olefin ratio with carbon number. Physisorption and dissolution are shown to cause a much stronger chain-length dependence than diffusion and will usually dominate. 36 refs., 9 figs.

  3. Development of optically transparent cyclic olefin photoresist binder resins

    NASA Astrophysics Data System (ADS)

    Rhodes, Larry F.; Chang, Chun; Burns, Cheryl; Barnes, Dennis A.; Bennett, Brian; Seger, Larry; Wu, Xiaoming; Sobek, Andy; Mishak, Mike; Peterson, Craig; Langsdorf, Leah; Hada, Hideo; Shimizu, Hiroaki; Sasaki, Kazuhito

    2005-05-01

    Of all candidate 193 nm photoresist binder resins, transition metal catalyzed vinyl addition cyclic olefin (i.e., norbornene) polymers (PCO) hold the promise of high transparency and excellent etch resistance. In order to access lower molecular weight polymers, which are typically used in photoresists, α-olefin chain transfer agents (CTAs) are used in synthesizing vinyl addition poly(norbornenes). For example, HFANB (α,α-bis(trifluoromethyl)bicyclo [2.2.1]hept-5-ene-2-ethanol) homopolymers (p(HFANB)) with molecular weights (Mn) less than 5000 have been synthesized using such chain transfer agents. However, the optical density (OD) at 193 nm of these materials was found to rise as their molecular weights decreased consistent with a polymer end group effect. Extensive NMR and MS analysis of these polymers revealed that olefinic end groups derived from the chain transfer agent were responsible for the deleterious rise in OD. Chemical modification of these end groups by epoxidation, hydrogenation, hydrosilation, etc. lowers the OD of the polymer by removing the olefinic chromophore, however, it does require a second synthetic step. Thus a new class of non-olefinic chain transfer agents has been developed at Promerus that allow for excellent control of vinyl addition cyclic olefin polymer molecular weight and low optical density without the need of a post-polymerization chemical modification. Low molecular weight homopolymers of HFANB have been synthesized using these chain transfer agents that exhibit ODs <= 0.07 absorbance units per micron. This molecular weight control technology has been applied to both positive tone and negative tone vinyl addition cyclic olefin binder resins. Lithographic and etch performance of positive tone photoresists based on these binder resins will be presented.

  4. Enantioselective Olefin Metathesis with Cyclometalated Ruthenium Complexes

    PubMed Central

    2015-01-01

    The success of enantioselective olefin metathesis relies on the design of enantioenriched alkylidene complexes capable of transferring stereochemical information from the catalyst structure to the reactants. Cyclometalation of the NHC ligand has proven to be a successful strategy to incorporate stereogenic atoms into the catalyst structure. Enantioenriched complexes incorporating this design element catalyze highly Z- and enantioselective asymmetric ring opening/cross metathesis (AROCM) of norbornenes and cyclobutenes, and the difference in ring strain between these two substrates leads to different propagating species in the catalytic cycle. Asymmetric ring closing metathesis (ARCM) of a challenging class of prochiral trienes has also been achieved. The extent of reversibility and effect of reaction setup was also explored. Finally, promising levels of enantioselectivity in an unprecedented Z-selective asymmetric cross metathesis (ACM) of a prochiral 1,4-diene was demonstrated. PMID:25137310

  5. Selective conversion of syngas to light olefins.

    PubMed

    Jiao, Feng; Li, Jinjing; Pan, Xiulian; Xiao, Jianping; Li, Haobo; Ma, Hao; Wei, Mingming; Pan, Yang; Zhou, Zhongyue; Li, Mingrun; Miao, Shu; Li, Jian; Zhu, Yifeng; Xiao, Dong; He, Ting; Yang, Junhao; Qi, Fei; Fu, Qiang; Bao, Xinhe

    2016-03-04

    Although considerable progress has been made in direct synthesis gas (syngas) conversion to light olefins (C2(=)-C4(=)) via Fischer-Tropsch synthesis (FTS), the wide product distribution remains a challenge, with a theoretical limit of only 58% for C2-C4 hydrocarbons. We present a process that reaches C2(=)-C4(=) selectivity as high as 80% and C2-C4 94% at carbon monoxide (CO) conversion of 17%. This is enabled by a bifunctional catalyst affording two types of active sites with complementary properties. The partially reduced oxide surface (ZnCrO(x)) activates CO and H2, and C-C coupling is subsequently manipulated within the confined acidic pores of zeolites. No obvious deactivation is observed within 110 hours. Furthermore, this composite catalyst and the process may allow use of coal- and biomass-derived syngas with a low H2/CO ratio.

  6. Metal-catalyzed reductive coupling of olefin-derived nucleophiles: Reinventing carbonyl addition.

    PubMed

    Nguyen, Khoa D; Park, Boyoung Y; Luong, Tom; Sato, Hiroki; Garza, Victoria J; Krische, Michael J

    2016-10-21

    α-Olefins are the most abundant petrochemical feedstock beyond alkanes, yet their use in commodity chemical manufacture is largely focused on polymerization and hydroformylation. The development of byproduct-free catalytic C-C bond-forming reactions that convert olefins to value-added products remains an important objective. Here, we review catalytic intermolecular reductive couplings of unactivated and activated olefin-derived nucleophiles with carbonyl partners. These processes represent an alternative to the longstanding use of stoichiometric organometallic reagents in carbonyl addition. Copyright © 2016, American Association for the Advancement of Science.

  7. Group IV complexes containing the benzotriazole phenoxide ligand as catalysts for the ring-opening polymerization of lactides, epoxides and as precatalysts for the polymerization of ethylene.

    PubMed

    Pappuru, Sreenath; Chokkapu, Eswara Rao; Chakraborty, Debashis; Ramkumar, Venkatachalam

    2013-12-14

    A series of Ti(IV), Zr(IV) and Hf(IV) benzotriazole phenoxide (BTP) complexes were synthesized and characterized by various spectroscopic techniques, elemental analysis and X-ray crystallography. The monosubstituted Zr(IV) BTP complexes [(μ-L)Zr(O(i)Pr)3]2 1-3 [L = (C1)BTP-H (1), (TCl)BTP-H (2), (pent)BTP-H (3)] and tetrasubstituted Zr(IV), Hf(IV) complexes ZrL4 4-6 [L = (C1)BTP-H (4), (TCl)BTP-H (5), (pent)BTP-H (6)] and HfL4 7-9 [L = (C1)BTP-H (7), (TCl)BTP-H (8), (pent)BTP-H (9)] were prepared by the reaction of Zr(O(i)Pr)4·((i)PrOH) and Hf(O(t)Bu)4 in toluene with the respective ligands in different stoichiometric proportions. The reaction between BTP and TiCl4 and ZrCl4 and HfCl4 in a 2 : 1 stoichiometric reaction resulted in the formation of disubstituted group IV chloride complexes L2MCl2 10-12 [L = (C1)BTP-H, M = Ti, Zr and Hf]. The molecular structures of complexes 1, 4, 7, 10, 11, and 12 were determined by single-crystal X-ray studies. The X-ray structure of 1 reveals a dimeric Zr(IV) complex containing a Zr2O2 core bridged through the oxygen atoms of the phenoxide groups. Each Zr atom is distorted from an octahedral symmetry. These complexes were found to be active towards the ring-opening polymerization (ROP) of L-lactide (L-LA) and rac-lactide (rac-LA). Complex 1 produced highly heterotactic poly(lactic acid) (PLA) from rac-LA under melt conditions with narrow molecular weight distributions (MWDs) and well controlled number average molecular weights (M(n)). Additionally, epoxide polymerizations using rac-cyclohexene oxide (CHO), rac-propylene oxide (PO), and rac-styrene oxide (SO) were also carried out with these complexes. The yield and molecular weight of the polymer was found to increase with the extension of reaction time. Compounds 1-12 were activated by methylaluminoxane (MAO) and show good activity for ethylene polymerization and produced high molecular weight polyethylene.

  8. Domino hydroformylation/aldol condensation/hydrogenation catalysis: highly selective synthesis of ketones from olefins.

    PubMed

    Fang, Xianjie; Jackstell, Ralf; Börner, Armin; Beller, Matthias

    2014-11-24

    A general and highly chemo- and regioselective synthesis of ketones from olefins by domino hydroformylation/aldol condensation/hydrogenation reaction has been developed. A variety of olefins are efficiently converted into various ketones in good to excellent yields and regioselectivities in the presence of a specific rhodium phosphine/base-acid catalyst system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Imino phenoxide complexes of niobium and tantalum as catalysts for the polymerization of lactides, ε-caprolactone and ethylene.

    PubMed

    Saha, Tanmoy Kumar; Mandal, Mrinmay; Thunga, Madhubabu; Chakraborty, Debashis; Ramkumar, Venkatachalam

    2013-07-28

    Imino phenoxide complexes of Nb and Ta show precise control towards the solvent free ring-opening polymerization of lactides (LA) and ε-caprolactone (CL). There is a close proximity between the observed number average molecular weight (M(n)) and theoretical molecular weight and the molecular weight distributions (MWDs) were found to be narrow. Analysis of low molecular weight oligomers of LA synthesized from these compounds revealed that the ligand is incorporated as one of the end terminal groups in the polymer chain. In addition, these complexes were realized to be precatalysts for the polymerization of ethylene.

  10. Synthesis of block copolymers consists on vinylidene chloride and α- Methylstyrene by cationic polymerization using an acid exchanged motmorillonite clay as heterogeneous catalyst (Algerian MMT)

    NASA Astrophysics Data System (ADS)

    Ayat, Moulkheir; Belbachir, Mohamed; Rahmouni, Abdelkader

    2017-07-01

    The aim of this study was to develop the efficient and versatile method for the synthesis of block copolymers consists by cationic polymerization vinylidene chloride (VDC) and alpha-methylstyrene (alpha-MS) in the presence of a natural Algerian montmorillonite clay modified by 0.05-0.35 M H2SO4 (Algerian MMT-H+). It was found that H2SO4 concentration allows controlling the chemical composition, the porous structure of the acid-activated clays and their catalytic performance. The maximal yield of polymer is observed in the presence of Algerian MMT modified by 0.25 M H2SO4. Effects of VDC/MS molar ration, catalyst concentration, reaction time, reaction temperature and polarity medium on yield and molecular weight of polymer were revealed in the presence of the most active sample.

  11. 2-Methyl-2,4-pentanediol (MPD) boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization

    PubMed Central

    Kinzel, Julia; Sauer, Daniel F; Bocola, Marco; Arlt, Marcus; Mirzaei Garakani, Tayebeh; Thiel, Andreas; Beckerle, Klaus; Polen, Tino; Okuda, Jun

    2017-01-01

    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. PMID:28845193

  12. 2-Methyl-2,4-pentanediol (MPD) boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization.

    PubMed

    Kinzel, Julia; Sauer, Daniel F; Bocola, Marco; Arlt, Marcus; Mirzaei Garakani, Tayebeh; Thiel, Andreas; Beckerle, Klaus; Polen, Tino; Okuda, Jun; Schwaneberg, Ulrich

    2017-01-01

    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.

  13. Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation.

    PubMed

    Herzberger, Jana; Niederer, Kerstin; Pohlit, Hannah; Seiwert, Jan; Worm, Matthias; Wurm, Frederik R; Frey, Holger

    2016-02-24

    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.

  14. Final Report: Experimental and Theoretical Studies of Surface Oxametallacycles - Connections to Heterogeneous Olefin Epoxidation

    SciTech Connect

    Mark A. Barteau

    2009-09-15

    This project has aimed at the rational design of catalysts for direct epoxidation of olefins. This chemistry remains one of the most challenging problems in heterogeneous catalysis. Although the epoxidation of ethylene by silver catalysts to form ethylene oxide (EO) has been practiced for decades, little progress has been made in expanding this technology to other products and processes. We have made significant advances through the combination of surface science experiments, Density Functional Theory (DFT) calculations, and catalytic reactor experiments, toward understanding the mechanism of this reaction on silver catalysts, and to the rational improvement of selectivity. The key has been our demonstration of surface oxametallacycle intermediates as the species that control reaction selectivity. This discovery permits the influence of catalyst promoters on selectivity to be probed, and new catalyst formulations to be developed. It also guides the development of new chemistry with potential for direct epoxidation of more complex olefins. During the award period we have focused on 1. the formation and reaction selectivity of complex olefin epoxides on silver surfaces, and 2. the influence of co-adsorbed oxygen atoms on the reactions of surface oxametallacycles on silver, and 3. the computational prediction, synthesis, characterization and experimental evaluation of bimetallic catalysts for ethylene epoxidation. The significance of these research thrusts is as follows. Selective epoxidation of olefins more complex than ethylene requires suppression of not only side reactions available to the olefin such as C-H bond breaking, but it requires formation and selective ring closure of the corresponding oxametallacycle intermediates. The work carried out under this grant has significantly advanced the field of catalyst design from first principles. The combination of computational tools, surface science, and catalytic reactor experiments in a single laboratory has few

  15. Olefin recovery via chemical absorption

    SciTech Connect

    Barchas, R.

    1998-06-01

    The recovery of fight olefins in petrochemical plants has generally been accomplished through cryogenic distillation, a process which is very capital and energy intensive. In an effort to simplify the recovery process and reduce its cost, BP Chemicals has developed a chemical absorption technology based on an aqueous silver nitrate solution. Stone & Webster is now marketing, licensing, and engineering the technology. The process is commercially ready for recovering olefins from olefin derivative plant vent gases, such as vents from polyethylene, polypropylene, ethylene oxide, and synthetic ethanol units. The process can also be used to debottleneck C{sub 2} or C{sub 3} splinters, or to improve olefin product purity. This paper presents the olefin recovery imp technology, discusses its applications, and presents economics for the recovery of ethylene and propylene.

  16. In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst

    NASA Astrophysics Data System (ADS)

    Baek, Heeyoel; Minakawa, Maki; Yamada, Yoichi M. A.; Han, Jin Wook; Uozumi, Yasuhiro

    2016-05-01

    A porous phenolsulphonic acid—formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity.

  17. In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst

    PubMed Central

    Baek, Heeyoel; Minakawa, Maki; Yamada, Yoichi M. A.; Han, Jin Wook; Uozumi, Yasuhiro

    2016-01-01

    A porous phenolsulphonic acid—formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity. PMID:27189631

  18. Reduce olefin plant fouling

    SciTech Connect

    Martin, J.F. )

    1988-11-01

    Process-side fouling reduces the overall operating efficiency of an olefin plant. The fouling is commonly caused by the formation of organic polymers which also can contain small amounts of inorganic constituents. The fouling is measured reduced if a properly selected antifoulant is used. Specific equipment and areas of the plant affected by process fouling are listed. The fouling tendency in each area is related to the pyrolysis furnace charge and unit operating conditions. To a lesser extent, the design of the plant will dictate which process equipment will experience fouling.

  19. Metal-free oxidative olefination of primary amines with benzylic C-H bonds through direct deamination and C-H bond activation.

    PubMed

    Gong, Liang; Xing, Li-Juan; Xu, Tong; Zhu, Xue-Ping; Zhou, Wen; Kang, Ning; Wang, Bin

    2014-09-14

    An oxidative olefination reaction between aliphatic primary amines and benzylic sp(3) C-H bonds has been achieved using N-bromosuccinimide as catalyst and tert-butyl hydroperoxide as oxidant. The olefination proceeds under mild metal-free conditions through direct deamination and benzylic C-H bond activation, and provides easy access to biologically active 2-styrylquinolines with (E)-configuration.

  20. Enantioselective, desymmetrizing, bromolactonization reactions of symmetric olefinic dicarboxylic acids.

    PubMed

    Murai, Kenichi; Nakajima, Junki; Nakamura, Akira; Hyogo, Norimichi; Fujioka, Hiromichi

    2014-12-01

    The results of studies leading to the development of enantioselective desymmetrizing, bromolactonization reactions of symmetric olefinic dicarboxylic acids, which are promoted by a C3 -symmetric trisimidazoline catalyst, are described. These processes generated carboxylic-acid-containing bromolactones in moderately high enantiomeric excesses. The results of optimization studies showed that reactions in a mixed solvent system of toluene and acetone proceeded with the highest levels of enantioselectivity. NMR studies probing the interactions between the catalyst and dicarboxylic acid substrates, as well as the effect of acetone on the stereochemistry of the process, are also described. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Sunflower-based Feedstocks in Nonfood Applications: Perspectives from Olefin Metathesis

    PubMed Central

    Marvey, Bassie B.

    2008-01-01

    Sunflower (Helianthus annuus L.) oil remains under-utilised albeit one of the major seed oils produced world-wide. Moreover, the high oleic sunflower varieties make the oil attractive for applications requiring high temperature processes and those targeting the C=C double bond functionality. Herein an overview of the recent developments in olefin metathesis of sunflower-based feedstocks is presented. The improved performance of olefin metathesis catalysts leading to high turnover numbers, high selectivity and catalyst recyclability, opens new opportunities for tailoring sunflower-based feedstocks into products required for possible new niche market applications. Promising results in biofuel, biopolymers, fragrances and fine chemicals applications have been reported. PMID:19325810

  2. Stereoselective synthesis of macrocyclic peptides via a dual olefin metathesis and ethenolysis approach.

    PubMed

    Mangold, Shane L; Grubbs, Robert H

    2015-08-01

    Macrocyclic compounds occupy an important chemical space between small molecules and biologics and are prevalent in many natural products and pharmaceuticals. The growing interest in macrocycles has been fueled, in part, by the design of novel synthetic methods to these compounds. One appealing strategy is ring-closing metathesis (RCM) that seeks to construct macrocycles from acyclic diene precursors using defined transition-metal alkylidene catalysts. Despite its broad utility, RCM generally gives rise to a mixture of E- and Z-olefin isomers that can hinder efforts for the large-scale production and isolation of such complex molecules. To address this issue, we aimed to develop methods that can selectively enrich macrocycles in E- or Z-olefin isomers using an RCM/ethenolysis strategy. The utility of this methodology was demonstrated in the stereoselective formation of macrocyclic peptides, a class of compounds that have gained prominence as therapeutics in drug discovery. Herein, we report an assessment of various factors that promote catalyst-directed RCM and ethenolysis on a variety of peptide substrates by varying the olefin type, peptide sequence, and placement of the olefin in macrocycle formation. These methods allow for control over olefin geometry in peptides, facilitating their isolation and characterization. The studies outlined in this report seek to expand the scope of stereoselective olefin metathesis in general RCM.

  3. Stereoselective synthesis of macrocyclic peptides via a dual olefin metathesis and ethenolysis approach

    PubMed Central

    Mangold, Shane L.

    2015-01-01

    Macrocyclic compounds occupy an important chemical space between small molecules and biologics and are prevalent in many natural products and pharmaceuticals. The growing interest in macrocycles has been fueled, in part, by the design of novel synthetic methods to these compounds. One appealing strategy is ring-closing metathesis (RCM) that seeks to construct macrocycles from acyclic diene precursors using defined transition-metal alkylidene catalysts. Despite its broad utility, RCM generally gives rise to a mixture of E- and Z-olefin isomers that can hinder efforts for the large-scale production and isolation of such complex molecules. To address this issue, we aimed to develop methods that can selectively enrich macrocycles in E- or Z-olefin isomers using an RCM/ethenolysis strategy. The utility of this methodology was demonstrated in the stereoselective formation of macrocyclic peptides, a class of compounds that have gained prominence as therapeutics in drug discovery. Herein, we report an assessment of various factors that promote catalyst-directed RCM and ethenolysis on a variety of peptide substrates by varying the olefin type, peptide sequence, and placement of the olefin in macrocycle formation. These methods allow for control over olefin geometry in peptides, facilitating their isolation and characterization. The studies outlined in this report seek to expand the scope of stereoselective olefin metathesis in general RCM. PMID:26509000

  4. Designing polyethylenes of complex chain architectures via Pd-diimine-catalyzed "living" ethylene polymerization.

    PubMed

    Ye, Zhibin; Xu, Lixin; Dong, Zhongmin; Xiang, Peng

    2013-07-18

    Polymer chain architecture is a critically important chain parameter governing intrinsically the properties and applications of polymers. The rapid developments in "living"/controlled polymerization techniques, particularly the controlled radical polymerization techniques, in the past two decades have enabled the precision synthesis of novel polymers having a great variety of complex yet well-defined chain architectures from various monomer stocks. For polyolefins synthesized via catalytic coordination polymerization, the design of complex chain architectures, however, has only started recently because of the relatively limited advancements in the catalytic "living" olefin polymerization technique. In this regard, the versatile Pd-diimine catalysts have provided some unprecedented opportunities, due to their outstanding features, in rendering successfully a novel class of polyethylenes of various new complex chain architectures through the "living" ethylene polymerization protocol. The complex chain architectures designed to date have included hyperbranched, hybrid hyperbranched-linear, block, gradient and block-gradient, star, telechelic, graft and comb, and surface-tethered polymer brushes. This Feature Article attempts to summarize the recent developments achieved in the area, with an emphasis on the synthetic strategies for the architectural design. These developments demonstrate the great potential for further advancements of this new exciting research area.

  5. Phosphine- and hydrogen-free: highly regioselective ruthenium-catalyzed hydroaminomethylation of olefins.

    PubMed

    Gülak, Samet; Wu, Lipeng; Liu, Qiang; Franke, Robert; Jackstell, Ralf; Beller, Matthias

    2014-07-07

    A highly regioselective ruthenium-catalyzed hydroaminomethylation of olefins is reported. Using easily available trirutheniumdodecacarbonyl an efficient sequence consisting of a water-gas shift reaction, hydroformylation of olefins, with subsequent imine or enamine formation and final reduction is realized. This novel procedure is highly practical (ligand-free, one pot) and economic (low catalyst loading and inexpensive metal). Bulk industrial as well as functionalized olefins react with various amines to give the corresponding tertiary amines generally in high yields (up to 92 %), excellent regioselectivities (n/iso>99:1), and full chemoselectivity in favor of terminal olefins. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Homogeneous dihydroxylation of olefins catalyzed by OsO(4)(2-) immobilized on a dendritic backbone with a tertiary nitrogen at its core position.

    PubMed

    Fujita, Ken-Ichi; Inoue, Kensuke; Tsuchimoto, Teruhisa; Yasuda, Hiroyuki

    2012-01-01

    OsO(4)(2-) immobilized on a poly(benzyl ether) dendrimer with a tertiary nitrogen at its core position efficiently catalyzed the homogeneous dihydroxylation of olefins with a low level of osmium leaching. The dendritic osmium catalyst could be applied to the wide range of olefins. Furthermore, the dendritic osmium catalyst was recovered by reprecipitation and then reused up to five times.

  7. Preparation of AIE-active fluorescent polymeric nanoparticles through a catalyst-free thiol-yne click reaction for bioimaging applications.

    PubMed

    Cao, Qian-Yong; Jiang, Ruming; Liu, Meiying; Wan, Qing; Xu, Dazhuang; Tian, Jianwen; Huang, Hongye; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-11-01

    Fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) characteristics have attracted much attention for biomedical applications due to their remarkable AIE feature, high water dispersity and desirable biocompatibility. The development of facile and effective strategies for fabrication of these AIE-active FPNs therefore should be of great importance for their biomedical applications. In this work, we reported that a catalyst-free thiol-yne click reaction can be utilized for fabrication of AIE-active FPNs in short reaction time and even without protection of inert gas. The results indicated that the obtained AIE-active amphiphilic copolymers (PEGMA-PhE) can readily self-assemble into luminescent nanoparticles (PEGMA-PhE FPNs) with high water dispersity, uniform size and morphology, red fluorescence. Cell viability examination and cell uptake behavior of PEGMA-PhE FPNs confirmed that these AIE-active FPNs possess low toxicity towards cells and can be easily internalized by cells through non-specific route. Therefore the remarkable properties of PEGMA-PhE FPNs such as high water dispersity, AIE-active fluorescence and nanoscale size as well as excellent biocompatibility make them promising for biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Low severity coal liquefaction promoted by cyclic olefins

    SciTech Connect

    Curtis, C.W.

    1992-07-27

    Low severity coal liquefaction allows for solubilization of coal with reduced gas make. These lower severity conditions may result in some selective bond rupture. Promotion of coal solubilization through hydrogen transfer using highly active and effective hydrogen donors is the objective of this study. The highly effective donors being tested are cyclic olefins. Representative cyclic olefins are isotetralin, which is 1,4,5,8-tetrahydronaphthalene, and 1,4,5,8,9,10-hexahydroanthracene. These compounds are hydroaromatics without aromatic rings and have been shown to be highly effective donors. The objective of the work performed in this study during this quarter was to evaluate reaction parameters for low severity liquefaction reactions using the cyclic olefin, hexahydroanthracene, and the aromatic, anthracene. These model compounds were reacted under a variety of conditions to evaluate their reactivity without coal. The reactions were performed under both thermal and catalytic conditions. Finely divided catalysts from different molybdenum precursors were used to determine their activity in promoting hydrogenation and hydrogen transfer at low severity conditions. The catalysts used were Molyvan L, sulfurized oxymolybdenum dithiocarbamate, molybdenum naphthenate, and Molyvan 822, organo molybdenum dithiocarbamate.

  9. The Ziegler—Natta olefin insertion reaction for cationic metals

    NASA Astrophysics Data System (ADS)

    Jensen, Vidar R.; Siegban, Per E. M.

    1993-09-01

    The catalytic Ziegler—Natta polymerization reaction has been studied for a set of metal cations, in order to identify the role of the positive charge on this process. Geometry optimizations have been performed for the reactant metal—methyl systems, the π-coordinated olefin systems, the transition states for the olefin insertion and finally for the product metal—propyl systems. All valence electrons are correlated. The cations selected for this study are the transition metals Zr + and Ti +, the non-transition metals Be +, Mg +, Al + and finally also Si +. The transition metal cations are found to have very low barriers for the insertion, but the lowest barrier is actually found for Be +. The results are discussed in terms of the ionization energies and the accessibility to valence p and d orbitals. Comparisons are made to previous theoretical work on cationic model systems.

  10. Conversion of methanol to gasoline extended project: methanol to olefins modification and operation of the demonstration plant milestone report

    SciTech Connect

    Johnson, D.; Soto, J.; Avidan, A.; Gierlich, H.; Thiagaraja, N.

    1986-04-01

    This milestone report documents operation of the fluid-bed Methanol-to Olefins (MTO process in a 100 BPD demonstration plant. The MTO process converts methanol to light olefins over Mobil's shape selective zeolite catalyst. High octane gasoline is a coproduct. The olefin mixture produced is especially well suited for production of premium diesel or jet fuel via Mobil's Olefins to Gasoline and Distillate (MOGD) Process. The scope of this project, however, covered only the MTO process. Specific conclusions which can be drawn from the 100 BPD demonstration plant operation and the 4 BPD pilot plant pretests, are: Total olefins yield in both units were within 1 to 2 wt% when compared at similar conditions; methanol breakthrough occurred at a lower propane/propene ratio, indicating better conversion efficiency, in the 100 BPT unit; stable steady-state operation with continuous regeneration and fresh catalyst makeup was successfully demonstrated in the 100 BPD plant; lower pressure increased total olefins yield at constant methanol conversion. Pressure could not be reduced below about 2.2 bar in the 100 BPD demonstration plant, due to bottlenecks in the gas compressor and in heat removal; and higher reactor temperatures increased total olefins yield at constant methanol conversion. however, higher reactor temperatures also increased light paraffins yield.

  11. Cobalt Fischer-Tropsch catalysts having improved selectivity

    DOEpatents

    Miller, James G.; Rabo, Jule A.

    1989-01-01

    The promoter(s) Mn oxide or Mn oxide and Zr oxide are added to a cobalt Fischer-Tropsch catalyst combined with the molecular sieve TC-103 or TC-123 such that the resultant catalyst demonstrates improved product selectivity, stability and catalyst life. The improved selectivity is evidenced by lower methane production, higher C5+ yield and increased olefin production.

  12. Low severity coal liquefaction promoted by cyclic olefins. Quarterly report, July--September, 1994

    SciTech Connect

    Curtis, C.W.

    1994-12-31

    Previous research indicates that the cyclic olefin, 1,4,5,8,9,10-hexahydroanthracene (HHA), is one of the most effective hydrogen donors tested under low severity conditions. A mild acidic pretreatment of the coal prior to liquefaction has proven to be significant in increasing conversion of low rank coals under low severity conditions as well. Coal conversion can also be improved by employing hydrotreating catalysts. In this study, reactions with coal mild acidic pretreatment were performed with cyclic olefins with and without catalysts. These reactions provided the data to prove whether catalysts are effective under low severity conditions. Evaluating the effect of these three factors (mild acidic pretreatment, hydrogen donation by cyclic olefins, and the use of slurry phase catalysts) on the reactivity of low severity coal liquefaction was the basis of this study. By examining the results, it is clear that the combination of all of the most favorable factors produced coal conversions of more than 50%. The effectiveness of HHA was tested by performing reactions without a cyclic olefin which produced substantially lower coal conversion, thus proving how effective hydrogen donation by cyclic olefins is in low severity coal liquefaction. The mild acidic pretreatment demonstrated its effectiveness on increasing the conversion low rank coals. By promoting higher conversion for the lignite than for the subbituminous coal, suggested that the lower the rank is, the better mild acidic pretreatment works. The catalyst MoNaph proved its effectiveness in low severity coal liquefaction, too, although the reactions with the other slurry phase catalysts NiOct was not effective. Also, synergy among the mild acid pretreatment, HHA and MoNaph occurred yielding high coal conversions for both coals.

  13. Zirconium and hafnium complexes of the thio(bisphenolato) ligand: synthesis, structural characterization and testing as 1-hexene polymerization catalysts.

    PubMed

    Janas, Zofia; Godbole, Dorota; Nerkowski, Tomasz; Szczegot, Krzysztof

    2009-11-07

    Thio(bisphenolato) complexes of the type [M2(mu-tbop-kappa3O,S,O)2Cl4] [M = Zr 1, Hf 2 and tbop = 2,2-thiobis{4-(1,1,3,3-tetramethyl-butyl)phenolate}] were prepared by HCl elimination from tbopH2 and MCl4. Substitution of the chlorides in 1 and 2 by 2,6-diisopropylphenolato groups (dipp) generates new compounds [M2(mu-tbop-kappa3O,S,O)2(dipp)4] (M = Zr 3, Hf 4). The structures of 1-4 were confirmed by NMR spectroscopy; complexes 3 and 4 were further investigated by X-ray crystallography. These studies showed 1-4 to be dimers either in the solid state or in solution and to have metal centers adopting distorted octahedral geometry. However treatment of MCl4 with [Al2(mu-OEt)2(tbop-kappa3O,S,O)2] or [Al2(mu-tbop-kappa3O,S,O)2Me2] gave heterotrinuclear complexes [M(tbop-kappa3O,S,O)2Cl2(mu-AlX2)2] (M = Zr, X = Cl 5, X = Me 7 and M = Hf, X = Cl 6, X = Me 8) for which the single-crystal X-ray diffraction analysis showed zirconium and hafnium centers to have eight-coordinate dodecahedral geometry. Complexes 1-6 after activation with aluminium alkyls and supporting on MgCl2 showed a lack of activity in the ethene polymerization process and moderate activity towards 1-hexene producing high molecular weight atactic poly(1-hexenes).

  14. Production of light olefins by catalytic conversion of lignocellulosic biomass with HZSM-5 zeolite impregnated with 6wt.% lanthanum.

    PubMed

    Huang, Weiwei; Gong, Feiyan; Fan, Minghui; Zhai, Qi; Hong, Chenggui; Li, Quanxin

    2012-10-01

    Catalytic conversion of rice husk, sawdust, sugarcane bagasse, cellulose, hemicellulose and lignin into olefins was performed with HZSM-5 containing 6 wt.% lanthanum. The olefins yields for different feedstocks decreased in the order: cellulose>hemicellulose>sugarcane bagasse>rice husk>sawdust>lignin. Biomass containing higher content of cellulose or hemicellulose produced more olefins than feedstocks with higher content of lignin. Among the biomass types, sugarcane bagasse provided the highest olefin yield of 0.12 kg olefins/(kg dry biomass) and carbon yield of 21.2C-mol%. Temperature, residence time and the catalyst/feed ratio influenced olefin yield and selectivity. While the HZSM-5 zeolite was catalytically active, the incorporation of lanthanum at 2.9, and 6.0 wt.% increased the production of olefins from rice husk by 15.6% and 26.5%, respectively. The conversion of biomass to light olefins potentially provides an alternative and sustainable route for production of the key petrochemicals.

  15. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    EPA Science Inventory

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  16. The Production and Recovery of C2-C4 Olefins from Syngas.

    ERIC Educational Resources Information Center

    Murchison, C. B.; And Others

    1986-01-01

    Discusses reacting coal-derived hydrogen and carbon monoxide (syngas) at relatively high selectivity to ethylene, propylene, and butenes over novel catalysts. In addition, data are given which illustrate a unique ethylene removal step which is compatible with operating the olefin synthesis at low conversion. (JN)

  17. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    EPA Science Inventory

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  18. Single-Pass Catalytic Conversion of Syngas into Olefins via Methanol.

    PubMed

    Olsbye, Unni

    2016-06-20

    All together now: Combination in a single reactor of the catalysts for converting syngas into methanol and methanol into olefins was recently reported by Cheng et al. This approach considerably simplifies the catalytic conversion of natural gas. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Catalytic properties of iron-based mixed oxides in the oxidation of methanol and olefins

    NASA Astrophysics Data System (ADS)

    Trifirò, F.; Carbucicchio, M.; Villa, P. L.

    1998-12-01

    The selective oxidation of alcohols and olefins is carried out commercially on complex systems based on Fe and Mo or Sb mixed oxides. The role of active phases and of the dopant in the catalysts has been elucidated using several characterization techniques and catalytic data.

  20. The Production and Recovery of C2-C4 Olefins from Syngas.

    ERIC Educational Resources Information Center

    Murchison, C. B.; And Others

    1986-01-01

    Discusses reacting coal-derived hydrogen and carbon monoxide (syngas) at relatively high selectivity to ethylene, propylene, and butenes over novel catalysts. In addition, data are given which illustrate a unique ethylene removal step which is compatible with operating the olefin synthesis at low conversion. (JN)

  1. Liquefaction with microencapsulated catalysts

    DOEpatents

    Weller, Sol W.

    1985-01-01

    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. STERIC EFFECTS IN ALPHA-OLEFIN REACTIVITY

    DTIC Science & Technology

    successfully applied to alpha - olefins to correlate reaction rates with steric effects and to explain, in part, the difficulty of obtaining desirable polymers from these olefins ....Addition reactions to the double bond of a series of sterically-hindered alpha - olefins have been carried out. The kinetics of these reaction were...measured and the rates of reaction correlated with the steric effects present in the olefin . A theory known as "Newman’s rule of six" has been

  3. 21 CFR 177.1520 - Olefin polymers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Olefin polymers. 177.1520 Section 177.1520 Food and... CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1520 Olefin polymers. The olefin polymers listed in paragraph...

  4. Synthesis, magnetic behaviour, and X-ray structures of dinuclear copper complexes with multiple bridges. Efficient and selective catalysts for polymerization of 2,6-dimethylphenol.

    PubMed

    Murugavel, Ramaswamy; Pothiraja, Ramasamy; Gogoi, Nayanmoni; Clérac, Rodolphe; Lecren, Lollita; Butcher, Ray J; Nethaji, Munirathinam

    2007-06-21

    The use of a potentially tridentate mono-anionic bridging ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol (bdmpp-H), in assembling new dimeric copper complexes with interesting magnetic properties has been investigated. The reaction of copper hydroxide or copper acetate with phenyl phosphinic acid or diphenyl phosphinic acid in the presence of bdmpp-H produces the dinuclear complexes [Cu(bdmpp)(ppi)]2 (1) and [Cu(bdmpp)(dppi-H)]2(dppi)2 (2) (ppi-H = phenylphosphinic acid: dppi-H = diphenylphosphinic acid), respectively. The products have been characterized with the help of analytical, thermal, and spectroscopic (IR, UV-vis, and EPR) techniques. Single crystal X-ray diffraction studies of 1 and 2 reveal that the two bdmpp ligands hold together the dimeric copper unit in each complex through mu-O alkoxide and the pyrazolyl nitrogen ligating centers. Two phenyl phosphinate ligands additionally bridge the dicopper core in 1 to result in octahedral coordination geometry around each metal ion. The diphenyl phosphinic acid acts as a terminal ligand in 2, and thus completes a square pyramidal geometry around each copper ion. Both complexes show a very short Cu...Cu separation (3.001 and 3.065 angstroms for 1 and 2, respectively). The investigation of the magnetic properties reveals the efficiency of the double alkoxide bridge between the two paramagnetic copper ions to mediate strong antiferromagnetic interactions [J/k(B) = -620(5) K (-431(4) cm(-1)) and -685(5) K (-476(4) cm(-1)) for 1 and 2, respectively]. Compounds 1 and 2, along with a few other copper phosphate complexes, were tested as catalysts for the oxidative polymerization of 2,6-dimethylphenol; 1 and 2 were found to be efficient catalysts with an increased selectivity for the formation of the polyphenylene ether. However a related mononuclear octahedral copper complex [Cu(imz)4(dtbp)2] (dtbp-H = di-tert-butylphosphate) was found to be more efficient.

  5. Transport-enhanced. alpha. -olefin readsorption pathways in Ru-catalyzed hydrocarbon synthesis

    SciTech Connect

    Iglesia, E.; Reyes, S.C.; Madon, R.J. )

    1991-05-01

    Residence time and cofeed studies show that olefins and paraffins are primary products in Ru-catalyzed hydrocarbon synthesis. Olefins readsorb and initiate surface chains that are indistinguishable from those formed directly from CO/H{sub 2} and that continue to grow and ultimately desorb as high molecular weight hydrocarbons. Transport-enchanced {alpha}-olefin readsorption leads to an increase in chain growth probability ({alpha}) and in paraffin content with increasing pore and bed residence time. Deviations from conventional (Flory) polymerization kinetics and the increasing paraffinic content of higher hydrocarbons are quantitatively described by transport effects on the residence time of intermediate olefins, without requiring the presence of several types of chain growth sites. The transport-reaction model combines a description of diffusive and convective transport with a mechanistic kinetic model of olefin readsorption and of CO hydrogenation and chain growth. It quantitatively describes carbon number, site density, pellet size, and space velocity effects on hydrocarbon synthesis rate and product distribution. The model is consistant with the experimentally observed maximum C{sub 5+} selectivities at intermediate values of site density and pellet size. These intermediate values permit extensive readsorption of {alpha}-olefins without significant CO arrival transport limitations.

  6. A Bicyclo[4.2.0]octene-Derived Monomer Provides Completely Linear Alternating Copolymers via Alternating Ring-Opening Metathesis Polymerization (AROMP).

    PubMed

    Tan, Li; Parker, Kathlyn A; Sampson, Nicole S

    2014-10-14

    Strained bicyclic carbomethoxy olefins were utilized as substrates in alternating ring-opening metathesis polymerization and found to provide low-dispersity polymers with novel backbones. The polymerization of methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate with cyclohexene in the presence of the fast-initiating Grubbs catalyst (H2IMes)(3-Br-Pyr)2Cl2Ru=CHPh leads to a completely linear as well as alternating copolymer, as demonstrated by NMR spectroscopy, isotopic labeling, and gel permeation chromatography. In contrast, intramolecular chain-transfer reactions were observed with [5.2.0] and [3.2.0] bicyclic carbomethoxy olefins, although to a lesser extent than with the previously reported monocyclic cyclobutenecarboxylic ester monomers [Song A.; Parker K. A.; Sampson N. S.J. Am. Chem. Soc.2009, 131, 3444]. Inclusion of cyclohexyl rings fused to the copolymer backbone minimizes intramolecular chain-transfer reactions and provides a framework for creating alternating functionality in a one-step polymerization.

  7. Chelate bis(imino)pyridine cobalt complexes: synthesis, reduction, and evidence for the generation of ethene polymerization catalysts by Li+ cation activation.

    PubMed

    Kleigrewe, Nina; Steffen, Winfried; Blömker, Tobias; Kehr, Gerald; Fröhlich, Roland; Wibbeling, Birgit; Erker, Gerhard; Wasilke, Julia-Christina; Wu, Guang; Bazan, Guillermo C

    2005-10-12

    Treatment of the bis(iminobenzyl)pyridine chelate Schiff-base ligand 8 (ligPh) with FeCl2 or CoCl2 yielded the corresponding (ligPh)MCl2 complexes 9 (Fe) and 10 (Co). The reaction of 10 with methyllithium or "butadiene-magnesium" resulted in reduction to give the corresponding (ligPh)Co(I)Cl product 11. Similarly, the bis(aryliminoethyl)pyridine ligand (ligMe) was reacted with CoCl2 to yield (ligMe)CoCl2 (12). Reduction to (ligMe)CoCl (13) was effected by treatment with "butadiene-magnesium". Complex 13 reacted with Li[B(C6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (ligMe)CoCH3 (17) with Li[B(C6F5)4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33 g(PE) mmol(cat)(-1) h(-1) bar(-1) at room temperature) upon treatment with a stoichiometric amount of Li[B(C6F5)4]. A third ligand (lig(OMe)) was synthesized featuring methoxy groups in the ligand backbone (22). Coordination to FeCl2 and CoCl2 yielded the desired compounds 23 and 24. Reaction with MeLi gave (ligOMe)CoMe (25/26). Treatment of 25/26 with excess B(C6F5)3 gave the eta6-arene cation complex 27, where one Co-N linkage was cleaved. Activation of 25/26 with Li[B(C6F5)4] again gave a catalytically active species.

  8. Cobalt carbide nanoprisms for direct production of lower olefins from syngas.

    PubMed

    Zhong, Liangshu; Yu, Fei; An, Yunlei; Zhao, Yonghui; Sun, Yuhan; Li, Zhengjia; Lin, Tiejun; Lin, Yanjun; Qi, Xingzhen; Dai, Yuanyuan; Gu, Lin; Hu, Jinsong; Jin, Shifeng; Shen, Qun; Wang, Hui

    2016-10-06

    Lower olefins-generally referring to ethylene, propylene and butylene-are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The 'Fischer-Tropsch to olefins' (FTO) process has long offered a way of producing lower olefins directly from syngas-a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.

  9. Conversion of 2,3-butanediol to 2-butanol, olefins and fuels

    DOEpatents

    Lilga, Michael A.; Lee, Guo-Shuh; Lee, Suh-Jane

    2016-12-13

    Embodiments of an integrated method for step-wise conversion of 2,3-butanediol to 2-butanol, and optionally to hydrocarbons, are disclosed. The method includes providing an acidic catalyst, exposing a composition comprising aqueous 2,3-butanediol to the acidic catalyst to produce an intermediate composition comprising methyl ethyl ketone, providing a hydrogenation catalyst that is spatially separated from the acidic catalyst, and subsequently exposing the intermediate composition to the hydrogenation catalyst to produce a composition comprising 2-butanol. The method may further include subsequently exposing the composition comprising 2-butanol to a deoxygenation catalyst, and deoxygenating the 2-butanol to form hydrocarbons. In some embodiments, the hydrocarbons comprise olefins, such as butenes, and the method may further include subsequently exposing the hydrocarbons to a hydrogenation catalyst to form saturated hydrocarbons.

  10. Refining of plant oils to chemicals by olefin metathesis.

    PubMed

    Chikkali, Samir; Mecking, Stefan

    2012-06-11

    Plant oils are attractive substrates for the chemical industry. Their scope for the production of chemicals can be expanded by sophisticated catalytic conversions. Olefin metathesis is an example, which also illustrates generic issues of "biorefining" to chemicals. Utilization on a large scale requires high catalyst activities, which influences the choice of the metathesis reaction. The mixture of different fatty acids composing a technical-grade plant oil substrate gives rise to a range of products. This decisively determines possible process schemes, and potentially provides novel chemicals and intermediates not employed to date.

  11. Primary amine synthesis from syngas, olefins and ammonia

    SciTech Connect

    Knifton, J.F.; Lin, J.J.

    1996-10-01

    The selective preparation of aliphatic primary amines from an olefin, synthesis gas (CO/H{sub 2}) and ammonia has been developed involving the use of homogeneous catalysts comprising cobalt octacarbonyl, phosphine ligand, and an ether or acetamide solvent system. 1-Hexene oxoamination typically yields a mix of C{sub 7} plus C{sub 14} primary amine in 57% selectivity. Process parameter studies involving changes in [NH{sub 3}], [Co], P/Co molar ratios, H{sub 2}/CO ratios, etc. provide some insight into the mechanism of this multistep synthesis and the practical limits (ca. 65%) to primary amine selectivity and yield.

  12. Synthesis of polytetrafluoroethylene based olefinic copolymer by gamma radiation grafting

    NASA Astrophysics Data System (ADS)

    Ferreto, H. F. R.; Lima, L. F. C. P.; Parra, D. F.; Zaia, V.; Lugão, A. B.

    2007-12-01

    High speed extrusion of linear low density polyethylene (LLDPE) is limited by processes shortcoming known as 'melt fracture' and 'sharkskin', which are surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and with poor surface properties. The fluoropolymer processing additives are used to eliminate the surface defect by coating the die wall and inducing slip at the coated fluoropolymer surface/LLDPE interface. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer grafted with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by grafting an olefinic monomer the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to allow recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. The olefinic monomer used was 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). The obtained copolymer (0.2-2.0 wt%) was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the developed process rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect 'melt fracture'.

  13. Aromatizing olefin metathesis by ligand isolation inside a metal-organic framework.

    PubMed

    Vermeulen, Nicolaas A; Karagiaridi, Olga; Sarjeant, Amy A; Stern, Charlotte L; Hupp, Joseph T; Farha, Omar K; Stoddart, J Fraser

    2013-10-09

    The aromatizing ring-closing metathesis has been shown to take place inside an extended porous framework. Employing a combination of solvent-assisted linker exchange and postsynthesis modification using olefin metathesis, the noninterpenetrated SALEM-14 was formed and converted catalytically into PAH-MOF-1 with polycyclic aromatic hydrocarbon (PAH) pillars. The metal-organic framework in SALEM-14 prevents "intermolecular" olefin metathesis from occurring between the pillars in the presence of the first generation Hoveyda-Grubbs catalyst, while favoring the production of a PAH, which can be released from the framework under acidic conditions in dimethylsulfoxide.

  14. Carbalumination of higher alpha-olefins catalyzed by titanium and zirconium complexes

    SciTech Connect

    Dzhemilev, U.M.; Ibragimov, A.G.; Tolstikov, G.A.; Vostrikova, O.S.

    1985-07-20

    The authors report on efforts to find catalysts capable of activating trialkylaluminums for the carbalumination of alpha-olefins in order to develop a highly selective and efficient method for the one-step preparation of higher alkylaluminums which are otherwise difficult to prepare. Experimentation produced a regioselective method for the carbometallation of higher alpha-olefins using Et/sub 3/Al and Et/sub 2/AlCl in the presence of titanium and zirconium complexes, which permits the preparation of higher trialkylakuminums and dialkylaluminum halides in high yield under mild conditions in one step.

  15. Mechanistic insights into the rhenium-catalyzed alcohol-to-olefin dehydration reaction.

    PubMed

    Korstanje, Ties J; Jastrzebski, Johann T B H; Klein Gebbink, Robertus J M

    2013-09-23

    Rhenium-based complexes are powerful catalysts for the dehydration of various alcohols to the corresponding olefins. Here, we report on both experimental and theoretical (DFT) studies into the mechanism of the rhenium-catalyzed dehydration of alcohols to olefins in general, and the methyltrioxorhenium-catalyzed dehydration of 1-phenylethanol to styrene in particular. The experimental and theoretical studies are in good agreement, both showing the involvement of several proton transfers, and of a carbenium ion intermediate in the catalytic cycle. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Synthesis of hierarchical SAPO-34 nanocrystals with improved catalytic performance for methanol to olefins

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Zhao, Pengbo; Ma, Jinghong; Li, Ruifeng

    2016-11-01

    SAPO-34 molecular sieve was hydrothermally synthesized by using organosilane phenylaminopropyl-trimethoxysilane (PHAPTMS) as a part of silicon source and tetraethylammonium hydroxide as microporous template at 160 °C. The XRD, SEM and N2 adsorption/desorption characterizations revealed the hierarchical SAPO-34 is a nanocrystal assembly of 50 nm particles prepared in the system. The catalyst showed improved stability and unusual selectivity of propylene and butylene in methanol to olefins reaction by introducing the mesoporous structure and changing the surface acid sites distribution. The yield of light olefins in hydrocarbons was up to 86%, the selectivity of C3= and C4= reached more than 40% and 10%.

  17. Substantially isotactic, linear, alternating copolymers of carbon monoxide and an olefin

    DOEpatents

    Sen, A.; Jiang, Z.

    1996-05-28

    The compound, [Pd(Me-DUPHOS)(MeCN){sub 2}](BF{sub 4}){sub 2}, [Me-DUPHOS: 1,2-bis(2,5-dimethylphospholano)benzene] is an effective catalyst for the highly enantioselective, alternating copolymerization of olefins, such as aliphatic {alpha}-olefins, with carbon monoxide to form optically active, isotactic polymers which can serve as excellent starting materials for the synthesis of other classes of chiral polymers. For example, the complete reduction of a propylene-carbon monoxide copolymer resulted in the formation of a novel, optically active poly(1,4-alcohol). Also, the previously described catalyst is a catalyst for the novel alternating isomerization cooligomerization of 2-butene with carbon monoxide to form optically active, isotactic poly(1,5-ketone).

  18. Substantially isotactic, linear, alternating copolymers of carbon monoxide and an olefin

    DOEpatents

    Sen, Ayusman; Jiang, Zhaozhong

    1996-01-01

    The compound, [Pd(Me-DUPHOS)(MeCN).sub.2 ](BF.sub.4).sub.2, [Me-DUPHOS: 1,2-bis(2,5-dimethylphospholano)benzene] is an effective catalyst for the highly enantioselective, alternating copolymerization of olefins, such as aliphatic .alpha.-olefins, with carbon monoxide to form optically active, isotactic polymers which can serve as excellent starting materials for the synthesis of other classes of chiral polymers. For example, the complete reduction of a propylene-carbon monoxide copolymer resulted in the formation of a novel, optically active poly(1,4-alcohol). Also, the previously described catalyst is a catalyst for the novel alternating isomerization cooligomerization of 2-butene with carbon monoxide to form optically active, isotactic poly(1,5-ketone)

  19. Heavy-atom kinetic isotope effects, cocatalysts, and the propagation transition state for polymerization of 1-hexene using the rac-(C(2)H(4)(1-indenyl)(2))ZrMe(2) catalyst precursor.

    PubMed

    Landis, Clark R; Rosaaen, Kimberly A; Uddin, Jamal

    2002-10-16

    Using 13C NMR techniques, the 12C/13C kinetic isotope effects (KIEs) for the polymerization of 1-hexene catalyzed by rac-(C2H4(1-indenyl)2)ZrMe2 in the presence of four different cocatalysts (tris(pentfluorophenyl)borane, tris(pentafluorophenyl)alane, anilinium tetrakis(pentafluorophenyl)borate, and methylalumoxane) have been determined. All cocatalysts yield similar KIEs within experimental uncertainty, with values of 1.009(1) and 1.017(2) at C1 and C2, respectively. Ab initio DFT computational modeling of the polymerization KIE indicates that alkene binding to the catalyst must be reversible, with the majority of the KIE developing in the subsequent migratory insertion reaction.

  20. Z-Selective Olefin Metathesis on Peptides: Investigation of Side-Chain Influence, Preorganization, and Guidelines in Substrate Selection

    PubMed Central

    2015-01-01

    Olefin metathesis has emerged as a promising strategy for modulating the stability and activity of biologically relevant compounds; however, the ability to control olefin geometry in the product remains a challenge. Recent advances in the design of cyclometalated ruthenium catalysts has led to new strategies for achieving such control with high fidelity and Z selectivity, but the scope and limitations of these catalysts on substrates bearing multiple functionalities, including peptides, remained unexplored. Herein, we report an assessment of various factors that contribute to both productive and nonproductive Z-selective metathesis on peptides. The influence of sterics, side-chain identity, and preorganization through peptide secondary structure are explored by homodimerization, cross metathesis, and ring-closing metathesis. Our results indicate that the amino acid side chain and identity of the olefin profoundly influence the activity of cyclometalated ruthenium catalysts in Z-selective metathesis. The criteria set forth for achieving high conversion and Z selectivity are highlighted by cross metathesis and ring-closing metathesis on diverse peptide substrates. The principles outlined in this report are important not only for expanding the scope of Z-selective olefin metathesis to peptides but also for applying stereoselective olefin metathesis in general synthetic endeavors. PMID:25102124

  1. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Li, S.-M.

    2008-04-01

    Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA); however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ether formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ) were estimated for a fast initial uptake governed by the mass accommodation coefficient (α) and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7-1×10-4. These processes may potentially lead to a considerable amount of SOA from the various biogenic hydrocarbons under acidic conditions, which can be highly significant for freshly nucleated aerosols, particularly given the large array of atmospheric olefins.

  2. Reversible and irreversible processing of biogenic olefins on acidic aerosols

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Li, S.-M.

    2007-08-01

    Recent evidence has suggested that heterogeneous chemistry of oxygenated hydrocarbons, primarily carbonyls, plays a role in the formation of secondary organic aerosol (SOA); however, evidence is emerging that direct uptake of alkenes on acidic aerosols does occur and can contribute to SOA formation. In the present study, significant uptake of monoterpenes, oxygenated monoterpenes and sesquiterpenes to acidic sulfate aerosols is found under various conditions in a reaction chamber. Proton transfer mass spectrometry is used to quantify the organic gases, while an aerosol mass spectrometer is used to quantify the organic mass uptake and obtain structural information for heterogeneous products. Aerosol mass spectra are consistent with several mechanisms including acid catalyzed olefin hydration, cationic polymerization and organic ester formation, while measurable decreases in the sulfate mass on a per particle basis suggest that the formation of organosulfate compounds is also likely. A portion of the heterogeneous reactions appears to be reversible, consistent with reversible olefin hydration reactions. A slow increase in the organic mass after a fast initial uptake is attributed to irreversible reactions, consistent with polymerization and organosulfate formation. Uptake coefficients (γ) were estimated for a fast initial uptake governed by the mass accommodation coefficient (α) and ranged from 1×10-6-2.5×10-2. Uptake coefficients for a subsequent slower reactive uptake ranged from 1×10-7-1×10-4. These processes are estimated to potentially produce greater than 2.5 μg m-3 of SOA from the various biogenic hydrocarbons under atmospheric conditions, which can be highly significant given the large array of atmospheric olefins.

  3. Polymerization of Functionalized Norbornenes Employing Mo(CH-t-Bu)(NAr) (O-t-Bu)2 as the Initiator

    DTIC Science & Technology

    1990-12-05

    polymerized in THF straightforwardly. Proton NMR spectra of polv-8 shows it to contain 60 % trans olefinic linkages. TGA analysis reveals a Tg at 108 *C...4. TGA analysis of poiy-6. Figure 5. GPC trace of poly-I/5. Figure 6. 125 MHz 13C NMR (CDCl3 ) spectra in the olefinic region of (a) poly-5; (b) poly

  4. Iron particle size effects for direct production of lower olefins from synthesis gas.

    PubMed

    Torres Galvis, Hirsa M; Bitter, Johannes H; Davidian, Thomas; Ruitenbeek, Matthijs; Dugulan, A Iulian; de Jong, Krijn P

    2012-10-03

    The Fischer-Tropsch synthesis of lower olefins (FTO) is an alternative process for the production of key chemical building blocks from non-petroleum-based sources such as natural gas, coal, or biomass. The influence of the iron carbide particle size of promoted and unpromoted carbon nanofiber supported catalysts on the conversion of synthesis gas has been investigated at 340-350 °C, H(2)/CO = 1, and pressures of 1 and 20 bar. The surface-specific activity (apparent TOF) based on the initial activity of unpromoted catalysts at 1 bar increased 6-8-fold when the average iron carbide size decreased from 7 to 2 nm, while methane and lower olefins selectivity were not affected. The same decrease in particle size for catalysts promoted by Na plus S resulted at 20 bar in a 2-fold increase of the apparent TOF based on initial activity which was mainly caused by a higher yield of methane for the smallest particles. Presumably, methane formation takes place at highly active low coordination sites residing at corners and edges, which are more abundant on small iron carbide particles. Lower olefins are produced at promoted (stepped) terrace sites that are available and active, quite independent of size. These results demonstrate that the iron carbide particle size plays a crucial role in the design of active and selective FTO catalysts.

  5. Microwave-Assisted Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Nicks, François; Borguet, Yannick; Sauvage, Xavier; Bicchielli, Dario; Delfosse, Sébastien; Delaude, Lionel; Demonceau, Albert

    Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers have been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared to conventional heating methods. The present contribution aims at illustrating the advantages of this technology in olefin metathesis and, when data are available, at comparing microwave-heated and conventionally heated experiments

  6. Mechanism of promotion of iron Fischer-Tropsch catalysts: Quarterly report for period ending March 31, 1986

    SciTech Connect

    1986-01-01

    The Fischer-Tropsch reaction is a complex combination of many reactions. Among those that have been demonstrated to occur on the catalyst surface are CO dissociation, build-up of carbon chains by a polymerization process, desorption of products such as olefins and oxygen-containing compounds, water formation and its subsequent shift reaction to form CO/sub 2/, olefin hydrogenation, isomerization and reincorporation in the synthesis and, probably, other reactions yet to be identified and studied. The tracer technique, involving the feeding of /sup 14/C-labled compounds to the synthesis, is being used here in an effort to learn how catalyst additives and supports influence these reactions and determine the final product distribution. /sup 14/C labeled ethanol, when added to a CO/H/sub 2/ feed, undergoes dehydrogenation to establish essentially an equilibrium ethanol-acetaldehyde mixture. However, under the reaction conditions used, ethyl acetate and 1,1-diethoxyethane (actual) are significant products; the /sup 14/C label permits use to identify these products as being derived from ethanol. In addition, it appears that aldol condensation of acetaldehyde occurs to a minor extent. 28 refs., 17 figs., 1 tab.

  7. Carboxy-directed asymmetric hydrogenation of α-alkyl-α-aryl terminal olefins: highly enantioselective and chemoselective access to a chiral benzylmethyl center.

    PubMed

    Yang, Shuang; Zhu, Shou-Fei; Guo, Na; Song, Song; Zhou, Qi-Lin

    2014-04-07

    A carboxy-directed asymmetric hydrogenation of α-alkyl-α-aryl terminal olefins was developed by using a chiral spiro iridium catalyst, providing a highly efficient approach to the compounds with a chiral benzylmethyl center. The carboxy-directed hydrogenation prohibited the isomerization of the terminal olefins, and realized the chemoselective hydrogenation of various dienes. The concise enantioselective syntheses of (S)-curcudiol and (S)-curcumene were achieved by using this catalytic asymmetric hydrogenation as a key step.

  8. Building Indenylidene-Ruthenium Catalysts for Metathesis Transformations

    NASA Astrophysics Data System (ADS)

    Clavier, Hervé; Nolan, Steven P.

    Ruthenium-mediated olefin metathesis has emerged as an indispensable tool in organic synthesis for the formation carbon-carbon double bonds, attested by the large number of applications for natural product synthesis. Among the numerous catalysts developed to mediate olefin metathesis transformations, ruthenium-indenylidene complexes are robust and powerful pre-catalysts. The discovery of this catalyst category was slightly muddled due to a first mis-assignment of the compound structure. This report provides an overview of the synthetic routes for the construction of the indenylidene pattern in ruthenium complexes. The parameters relating to the indenylidene moiety construction will be discussed as well as the mechanism of this formation

  9. Cobalt Fischer-Tropsch catalysts having improved selectivity

    DOEpatents

    Miller, James G.; Rabo, Jule A.

    1989-01-01

    A cobalt Fischer-Tropsch catalyst having an improved steam treated, acid extracted LZ-210 support is taught. The new catalyst system demonstrates improved product selectivity at Fischer-Tropsch reaction conditions evidenced by lower methane production, higher C.sub.5.sup.+ yield and increased olefin production.

  10. Hydrous metal oxide catalysts for oxidation of hydrocarbons

    SciTech Connect

    Miller, J.E.; Dosch, R.G.; McLaughlin, L.I.

    1993-07-01

    This report describes work performed at Sandia under a CRADA with Shell Development of Houston, Texas aimed at developing hydrous metal oxide (HMO) catalysts for oxidation of hydrocarbons. Autoxidation as well as selective oxidation of 1-octene was studied in the presence of HMO catalysts based on known oxidation catalysts. The desired reactions were the conversion of olefin to epoxides, alcohols, and ketones, HMOs seem to inhibit autoxidation reactions, perhaps by reacting with peroxides or radicals. Attempts to use HMOs and metal loaded HMOs as epoxidation catalysts were unsuccessful, although their utility for this reaction was not entirely ruled out. Likewise, alcohol formation from olefins in the presence of HMO catalysts was not achieved. However, this work led to the discovery that acidified HMOs can lead to carbocation reactions of hydrocarbons such as cracking. An HMO catalyst containing Rh and Cu that promotes the reaction of {alpha}-olefins with oxygen to form methyl ketones was identified. Although the activity of the catalyst is relatively low and isomerization reactions of the olefin simultaneously occur, results indicate that these problems may be addressed by eliminating mass transfer limitations. Other suggestions for improving the catalyst are also made. 57 refs.

  11. Chloromethane to olefins over H-SAPO-34: Probing the hydrocarbon pool mechanism

    SciTech Connect

    Fickel, Dustin W.; Sabnis, Kaiwalya D.; Li, Luanyi; Kulkarni, Neeta; Winter, Lea R.; Yan, Binhang; Chen, Jingguang G.

    2016-09-09

    In this paper, by means of in situ FTIR and ex situ13C NMR studies, the initial periods of the chloromethane-to-olefins (CTO) reaction over SAPO-34 were probed in order to investigate the activation period of the reaction and to elucidate the formation of the catalyst active site. A methylated benzene species has been observed to form during the initial activation period of the reaction, and a direct positive correlation was constructed between the formation of this species and the catalytic activity. The data thus indicate that these methylated benzene species contribute to the formation of active sites within SAPO-34 for the CTO reaction. This is the first known report identifying a direct semi-quantitative correlation between the catalyst activity and growth of a methylated benzene active species, during the activation period of the chloromethane to olefins reaction. Finally, the findings here in correspond well to those reported for the methanol to olefins reaction, suggesting that a similar ‘hydrocarbon pool’ mechanism may be responsible for the formation of light olefins in CTO chemistry as well.

  12. Chloromethane to olefins over H-SAPO-34: Probing the hydrocarbon pool mechanism

    SciTech Connect

    Fickel, Dustin W.; Sabnis, Kaiwalya D.; Li, Luanyi; Kulkarni, Neeta; Winter, Lea R.; Yan, Binhang; Chen, Jingguang G.

    2016-09-09

    In this paper, by means of in situ FTIR and ex situ13C NMR studies, the initial periods of the chloromethane-to-olefins (CTO) reaction over SAPO-34 were probed in order to investigate the activation period of the reaction and to elucidate the formation of the catalyst active site. A methylated benzene species has been observed to form during the initial activation period of the reaction, and a direct positive correlation was constructed between the formation of this species and the catalytic activity. The data thus indicate that these methylated benzene species contribute to the formation of active sites within SAPO-34 for the CTO reaction. This is the first known report identifying a direct semi-quantitative correlation between the catalyst activity and growth of a methylated benzene active species, during the activation period of the chloromethane to olefins reaction. Finally, the findings here in correspond well to those reported for the methanol to olefins reaction, suggesting that a similar ‘hydrocarbon pool’ mechanism may be responsible for the formation of light olefins in CTO chemistry as well.

  13. Chloromethane to olefins over H-SAPO-34: Probing the hydrocarbon pool mechanism

    DOE PAGES

    Fickel, Dustin W.; Sabnis, Kaiwalya D.; Li, Luanyi; ...

    2016-09-09

    In this paper, by means of in situ FTIR and ex situ13C NMR studies, the initial periods of the chloromethane-to-olefins (CTO) reaction over SAPO-34 were probed in order to investigate the activation period of the reaction and to elucidate the formation of the catalyst active site. A methylated benzene species has been observed to form during the initial activation period of the reaction, and a direct positive correlation was constructed between the formation of this species and the catalytic activity. The data thus indicate that these methylated benzene species contribute to the formation of active sites within SAPO-34 for themore » CTO reaction. This is the first known report identifying a direct semi-quantitative correlation between the catalyst activity and growth of a methylated benzene active species, during the activation period of the chloromethane to olefins reaction. Finally, the findings here in correspond well to those reported for the methanol to olefins reaction, suggesting that a similar ‘hydrocarbon pool’ mechanism may be responsible for the formation of light olefins in CTO chemistry as well.« less

  14. Dual template synthesis of a highly mesoporous SSZ-13 zeolite with improved stability in the methanol-to-olefins reaction.

    PubMed

    Wu, Leilei; Degirmenci, Volkan; Magusin, Pieter C M M; Szyja, Bartłomiej M; Hensen, Emiel J M

    2012-10-04

    The dual template synthesis of zeolite SSZ-13 by use of trimethyl-adamantanammonium hydroxide and a diquaternary-ammonium mesoporogen induces considerable mesoporosity without impeding zeolite microporosity. The strongly improved accessibility of Brønsted sites in mesoporous SSZ-13 increases its stability during application as an acid catalyst in the methanol-to-olefins reaction.

  15. ULTRASOUND-ASSISTED EPOXIDATION OF OLEFINS AND A,B-UNSATURATED KETONES OVER HYDROTALCITES USING HYDROGEN PEROXIDE

    EPA Science Inventory

    An efficient ultrasound-assisted epoxidation of olefins and a,B-unsaturated ketones over hydrotacite catalysts in the presence of hydrogen peroxide and acetonitrile is described. This general and selective protocol is relatively fast and is applicable to a wide variety of substra...

  16. Enantioselective Cyclopropanation of a Wide Variety of Olefins Catalyzed by Ru(II)-Pheox Complexes.

    PubMed

    Chanthamath, Soda; Iwasa, Seiji

    2016-10-18

    The transition-metal-catalyzed asymmetric cyclopropanation of olefins with diazoacetates has become one of the most important methods for the synthesis of optically active cyclopropane derivatives, which are key pharmaceutical building blocks and present in a large number of natural products. To date, significant progress has been made in this area of research, and efficient stereocontrolled synthetic approaches to cyclopropane derivatives have been developed using rhodium, ruthenium, copper, and cobalt catalysts. However, the vast majority of these strategies are limited to electron-rich olefins, such as styrene derivatives, due to the electrophilicity of the metal-carbene intermediates generated from the reaction of the metal with the diazo compound. Recently, the D2-symmetric Co(II)-phophyrin complexes developed by Zhang et al. were shown to be the most efficient catalysts for the asymmetric cyclopropanation of electron-deficient olefins. This catalytic system is mechanistically distinct from the previous rhodium and copper catalytic systems, proceeding via radical intermediates. However, the asymmetric cyclopropanation of vinyl carbamates, allenes, and α,β-unsaturated carbonyl compounds has rarely been reported. Therefore, the development of new powerful catalysts for the asymmetric cyclopropanation of a wide range of olefinic substrates is the next challenge in this field. In this Account, we summarize our recent studies on the Ru(II)-Pheox-catalyzed asymmetric cyclopropanation of various olefins, including vinyl carbamates, allenes, and α,β-unsaturated carbonyl compounds. We demonstrate that the developed catalytic system effectively promotes the asymmetric cyclopropanation of a wide variety of olefins to produce the desired cyclopropane products in high yields with excellent stereocontrol. The use of succinimidyl-, ketone-, and ester-functionalized diazoacetates as carbene sources was found to be crucial for the high stereoselectivity of the

  17. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    PubMed Central

    Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Summary Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition. PMID:26664629

  18. Calcium-based Lewis acid catalysts.

    PubMed

    Begouin, Jeanne-Marie; Niggemann, Meike

    2013-06-17

    Recently, Lewis acidic calcium salts bearing weakly coordinating anions such as Ca(NTf₂)₂, Ca(OTf)₂, CaF₂ and Ca[OCH(CF₃)₂]₂ have been discovered as catalysts for the transformation of alcohols, olefins and carbonyl compounds. High stability towards air and moisture, selectivity and high reactivity under mild reaction conditions render these catalysts a sustainable and mild alternative to transition metals, rare-earth metals or strong Brønsted acids.

  19. Sustainable polymerizations in recoverable microemulsions.

    PubMed

    Chen, Zhenzhen; Yan, Feng; Qiu, Lihua; Lu, Jianmei; Zhou, Yinxia; Chen, Jiaxin; Tang, Yishan; Texter, John

    2010-03-16

    Free radical and atom-transfer radical polymerizations were conducted in monomer/ionic liquid microemulsions. After the polymerization and isolation of the resultant polymers, the mixture of the catalyst and ionic liquids (surfactant and continuous phase) can be recovered and reused, thereby dramatically improving the environmental sustainability of such chemical processing. The addition of monomer to recovered ionic liquid mixtures regenerates transparent, stable microemulsions that are ready for the next polymerization cycle upon addition of initiator. The method combines the advantages of IL recycling and microemulsion polymerization and minimizes environmental disposable effects from surfactants and heavy metal ions.

  20. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, T.J.; Ijadi-Maghsooodi, S; Yi Pang.

    1993-10-19

    A polymeric material is described which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6].

  1. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

    1992-05-19

    A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

  2. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

    1993-10-19

    A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

  3. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

    1992-05-19

    A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6]/hv.

  4. Engineering a dirhodium artificial metalloenzyme for selective olefin cyclopropanation

    PubMed Central

    Srivastava, Poonam; Yang, Hao; Ellis-Guardiola, Ken; Lewis, Jared C.

    2015-01-01

    Artificial metalloenzymes (ArMs) formed by incorporating synthetic metal catalysts into protein scaffolds have the potential to impart to chemical reactions selectivity that would be difficult to achieve using metal catalysts alone. In this work, we covalently link an alkyne-substituted dirhodium catalyst to a prolyl oligopeptidase containing a genetically encoded L-4-azidophenylalanine residue to create an ArM that catalyses olefin cyclopropanation. Scaffold mutagenesis is then used to improve the enantioselectivity of this reaction, and cyclopropanation of a range of styrenes and donor–acceptor carbene precursors were accepted. The ArM reduces the formation of byproducts, including those resulting from the reaction of dirhodium–carbene intermediates with water. This shows that an ArM can improve the substrate specificity of a catalyst and, for the first time, the water tolerance of a metal-catalysed reaction. Given the diversity of reactions catalysed by dirhodium complexes, we anticipate that dirhodium ArMs will provide many unique opportunities for selective catalysis. PMID:26206238

  5. Request for Symposia Support: Advances in Olefin Polymerization Catalysis

    DTIC Science & Technology

    2014-11-24

    Philippe.Sautet@ens-lyon.fr, Etienne Grau3, Anne Lesage4, Sebastien Norsic3, Christophe Coperet2, Vincent Monteil3. (1) Ecole Normale Superieure de...Catalyse Polymères et Procédés, University of Lyon, Lyon, France, (4) CNRS, Ecole Normale Supérieure de Lyon, Centre de RMN à Très Hauts Champs

  6. High-throughput evaluation of olefin copolymer composition by means of attenuated total reflection Fourier tranform infrared spectroscopy.

    PubMed

    Tuchbreiter, A; Marquardt, J; Zimmermann, J; Walter, P; Mülhaupt, R; Kappler, B; Faller, D; Roths, T; Honerkamp, J

    2001-01-01

    As a consequence of developing fully automated reactors for organic and organometallic synthesis and polymerizations combined with rapid on-line analysis, databases, and data mining, the analysis of polymers with respect to composition and properties has been speeded up. High-throughput evaluation of olefin copolymers requires fast measurements and high accuracy without tedious sample preparation such as pressing KBr pellets. This has been achieved by using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR spectroscopy) in conjunction with multivariate calibration in order to determine the composition of olefin copolymers such as ethene/propene, ethene/1-hexene and ethene/1-octene copolymers.

  7. Cobalt carbide nanoprisms for direct production of lower olefins from syngas

    NASA Astrophysics Data System (ADS)

    Zhong, Liangshu; Yu, Fei; An, Yunlei; Zhao, Yonghui; Sun, Yuhan; Li, Zhengjia; Lin, Tiejun; Lin, Yanjun; Qi, Xingzhen; Dai, Yuanyuan; Gu, Lin; Hu, Jinsong; Jin, Shifeng; Shen, Qun; Wang, Hui

    2016-10-01

    Lower olefins—generally referring to ethylene, propylene and butylene—are basic carbon-based building blocks that are widely used in the chemical industry, and are traditionally produced through thermal or catalytic cracking of a range of hydrocarbon feedstocks, such as naphtha, gas oil, condensates and light alkanes. With the rapid depletion of the limited petroleum reserves that serve as the source of these hydrocarbons, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The ‘Fischer-Tropsch to olefins’ (FTO) process has long offered a way of producing lower olefins directly from syngas—a mixture of hydrogen and carbon monoxide that is readily derived from coal, biomass and natural gas. But the hydrocarbons obtained with the FTO process typically follow the so-called Anderson-Schulz-Flory distribution, which is characterized by a maximum C2-C4 hydrocarbon fraction of about 56.7 per cent and an undesired methane fraction of about 29.2 per cent (refs 1, 10, 11, 12). Here we show that, under mild reaction conditions, cobalt carbide quadrangular nanoprisms catalyse the FTO conversion of syngas with high selectivity for the production of lower olefins (constituting around 60.8 per cent of the carbon products), while generating little methane (about 5.0 per cent), with the ratio of desired unsaturated hydrocarbons to less valuable saturated hydrocarbons amongst the C2-C4 products being as high as 30. Detailed catalyst characterization during the initial reaction stage and theoretical calculations indicate that preferentially exposed {101} and {020} facets play a pivotal role during syngas conversion, in that they favour olefin production and inhibit methane formation, and thereby render cobalt carbide nanoprisms a promising new catalyst system for directly converting syngas into lower olefins.

  8. Catalysts and process for liquid hydrocarbon fuel production

    DOEpatents

    White, Mark G.; Ranaweera, Samantha A.; Henry, William P.

    2016-08-02

    The present invention provides a novel process and system in which a mixture of carbon monoxide and hydrogen synthesis gas, or syngas, is converted into hydrocarbon mixtures composed of high quality distillates, gasoline components, and lower molecular weight gaseous olefins in one reactor or step. The invention utilizes a novel supported bimetallic ion complex catalyst for conversion, and provides methods of preparing such novel catalysts and use of the novel catalysts in the process and system of the invention.

  9. Enhanced catalyst for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1986-01-01

    The conversion of synthesis gas to liquid molar fuels by means of a cobalt Fischer-Tropsch catalyst composition is enhanced by the addition of molybdenum, tungsten or a combination thereof as an additional component of said composition. The presence of the additive component increases the olefinic content of the hydrocarbon products produced. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  10. Enantioselective Hydroaminomethylation of Olefins Enabled by Rh/Brønsted Acid Relay Catalysis.

    PubMed

    Meng, Jing; Li, Xing-Han; Han, Zhi-Yong

    2017-03-03

    Herein, by employing a rhodium catalyst with a commercial ligand and a phosphoric acid catalyst, highly chemo-, regio-, and enantioselective hydroaminomethylation of olefins is realized through a relay catalytic hydroformylation/dynamic kinetic reductive amination process. The method features mild conditions (1 bar of syngas, room temperature in most cases), high yields (up to 99%), and high enantioselectivities (up to >99.5:0.5 er). Besides styrenes, acrylamides also provided the products with high yields and enantioselectivities. Aliphatic alkenes and vinyl esters are also applicable for the current method, albeit lower yields and enantioselectivities were obtained.

  11. Z-Selective Olefin Synthesis via Iron-Catalyzed Reductive Coupling of Alkyl Halides with Terminal Arylalkynes

    PubMed Central

    2015-01-01

    Selective catalytic synthesis of Z-olefins has been challenging. Here we describe a method to produce 1,2-disubstituted olefins in high Z selectivity via reductive cross-coupling of alkyl halides with terminal arylalkynes. The method employs inexpensive and nontoxic catalyst (iron(II) bromide) and reductant (zinc). The substrate scope encompasses primary, secondary, and tertiary alkyl halides, and the reaction tolerates a large number of functional groups. The utility of the method is demonstrated in the synthesis of several pharmaceutically relevant molecules. Mechanistic study suggests that the reaction proceeds through an iron-catalyzed anti-selective carbozincation pathway. PMID:25831473

  12. Nickel-Catalyzed Insertion of Alkynes and Electron-Deficient Olefins into Unactivated sp(3) C-H Bonds.

    PubMed

    Maity, Soham; Agasti, Soumitra; Earsad, Arif Mahammad; Hazra, Avijit; Maiti, Debabrata

    2015-08-03

    Insertion of unsaturated systems such as alkynes and olefins into unactivated sp(3) C-H bonds remains an unexplored problem. We herein address this issue by successfully incorporating a wide variety of functionalized alkynes and electron-deficient olefins into the unactivated sp(3) C-H bond of pivalic acid derivatives with excellent syn- and linear- selectivity. A strongly chelating 8-aminoquinoline directing group proved beneficial for these insertion reactions, while an air-stable and inexpensive Ni(II) salt has been employed as the active catalyst.

  13. Isolation of Pure Disubstituted E Olefins through Mo-Catalyzed Z-Selective Ethenolysis of Stereoisomeric Mixtures

    PubMed Central

    Marinescu, Smaranda C.; Levine, Daniel S.; Zhao, Yu; Schrock, Richard R.; Hoveyda, Amir H.

    2011-01-01

    MonoAryloxide-Pyrrolide (MAP) complexes of molybdenum are employed for the selective ethenolysis of 1,2-disubstituted Z olefins in the presence of the corresponding E olefins. Reactions are performed in the presence of 0.02−3.0 mol % catalyst at 22 °C under 20 atm of ethylene. We demonstrate that the Z isomer of an easily accessible E:Z mixture can be destroyed through ethenolysis and the E alkene thereby isolated readily in high yield and exceptional stereoisomeric purity. PMID:21718001

  14. Morphology of Novel Semicrystalline Ethylene-α-Olefin Block Copolymers

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Register, Richard; Landes, Brian

    2009-03-01

    In semicrystalline block copolymers, the solid-state structure can be set either by block incompatibility or by crystallization of one or more blocks. Depending on the block interaction strength, a wide array of solid-state morphologies may be observed, ranging from spherulitic to confined crystallization within preexisting microphase-separated domains. Dow Chemical has recently developed a novel chain shuttling polymerization process to produce olefin block copolymers with alternating amorphous and semicrystalline chain segments, where each block exhibits the most-probable distribution. We examined the melt and solid-state morphologies of these novel olefin block copolymers, having a high octene content in the amorphous block, using two- dimensional synchrotron small-angle and wide-angle x-ray scattering on specimens oriented by channel die compression. Multiblock and diblock copolymers with near-symmetric compositions showed well-ordered lamellar structures at room temperature with long periods exceeding 100 nm, with little dependence on thermal history, indicating the presence of a mesophase-separated melt which templates crystallization.

  15. Catalytic conversion of biomass-derived feedstocks into olefins and aromatics with ZSM-5: the hydrogen to carbon effective ratio

    SciTech Connect

    Zhang, Huiyan; Cheng, Yu-Ting; Vispute, Tushar P.; Xiao, Rui; Huber, George W.

    2011-01-01

    Catalytic conversion of ten biomass-derived feedstocks, i.e.glucose, sorbitol, glycerol, tetrahydrofuran, methanol and different hydrogenated bio-oil fractions, with different hydrogen to carbon effective (H/C{sub eff}) ratios was conducted in a gas-phase flow fixed-bed reactor with a ZSM-5 catalyst. The aromatic + olefin yield increases and the coke yield decreases with increasing H/C{sub eff} ratio of the feed. There is an inflection point at a H/C{sub eff} ratio = 1.2, where the aromatic + olefin yield does not increase as rapidly as it does prior to this point. The ratio of olefins to aromatics also increases with increasing H/C{sub eff} ratio. CO and CO₂ yields go through a maximum with increasing H/C{sub eff} ratio. The deactivation rate of the catalyst decreases significantly with increasing H/C{sub eff} ratio. Coke was formed from both homogeneous and heterogeneous reactions. Thermogravimetric analysis (TGA) for the ten feedstocks showed that the formation of coke from homogeneous reactions decreases with increasing H/C{sub eff} ratio. Feedstocks with a H/C{sub eff} ratio less than 0.15 produce large amounts of undesired coke (more than 12 wt%) from homogeneous decomposition reactions. This paper shows that the conversion of biomass-derived feedstocks into aromatics and olefins using zeolite catalysts can be explained by the H/C{sub eff} ratio of the feed.

  16. Understanding the desensitizing mechanism of olefin in explosives: shear slide of mixed HMX-olefin systems.

    PubMed

    Zhang, Chaoyang; Cao, Xia; Xiang, Bin

    2012-04-01

    We simulated the shear slide behavior of typical mixed HMX-olefin systems and the effect of thickness of olefin layers (4-22 Å) on the behavior at a molecular level by considering two cases: bulk shear and interfacial shear. The results show that: (1) the addition of olefin into HMX can reduce greatly the shear sliding barriers relative to the pure HMX in the two cases, suggesting that the desensitizing mechanism of olefin is controlled dominantly by its good lubricating property; (2) the change of interaction energy in both systoles of shear slide is strongly dominated by van der Waals interaction; and (3) the thickness of olefin layers in the mixed explosives can influence its desensitizing efficiency. That is, the excessive thinness of olefin layers in the mixed explosive systems, for example, several angstroms, can lead to very high sliding barriers.

  17. REVERSIBILITY OF RADICAL-OLEFIN REACTIONS.

    DTIC Science & Technology

    ALKENES, *STYRENES, *POLYVINYL CHLORIDE, CHEMICAL EQUILIBRIUM, POLYMERIZATION, POLYMERIZATION, FREE RADICALS , MOLECULAR ISOMERISM, TRACER STUDIES, CHEMICAL REACTIONS, DECOMPOSITION, SYNTHESIS(CHEMISTRY).

  18. Homobimetallic Ruthenium-N-Heterocyclic Carbene Complexes For Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Sauvage, Xavier; Demonceau, Albert; Delaude, Lionel

    In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene (NHC) ligands are reviewed. Emphasis is placed on the last category of bimetallic compounds. Three representatives of this new type of molecular scaffold were investigated. Thus, [(p-cymene)Ru(m-Cl)3RuCl (h2-C2H4)(L)] complexes with L = PCy3 (15a), IMes (16a), or IMesCl2 (16b) were prepared. They served as catalyst precursors for cross-metathesis (CM) of various styrene derivatives. These experiments revealed the outstanding aptitude of complex 16a (and to a lesser extent of 16b) to catalyze olefin metathesis reactions. Contrary to monometallic Ru-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addition of a diazo compound nor visible light illumination to initiate the ring-opening metathesis of norbornene or cyclooctene. When diethyl 2,2-diallylmalonate and N,N-diallyltosylamide were exposed to 16a,b, a mixture of cycloisomerization and ring-closing metathesis (RCM) products was obtained in a nonselective way. Addition of phenylacetylene enhanced the metathetical activity while completely repressing the cycloisomerization process.

  19. Chemistry of Furan Conversion into Aromatics and Olefins over HZSM-5: A Model Biomass Conversion Reaction

    SciTech Connect

    Cheng, Yu-Ting; Huber, George W.

    2011-06-03

    The conversion of furan (a model of cellulosic biomass) over HZSM-5 was investigated in a thermogravimetric analysis–mass spectrometry system, in situ Fourier transform infrared analysis, and in a continuous-flow fixed-bed reactor. Furan adsorbed as oligomers at room temperature with a 1.73 of adsorbed furan/Al ratio. These oligomers were polycyclic aromatic compounds that were converted to CO, CO₂, aromatics, and olefins at temperatures from 400 to 600 °C. Aromatics (e.g., benzene, toluene, and naphthalene), oligomer isomers (e.g., benzofuran, 2,2-methylenebisfuran, and benzodioxane), and heavy oxygenates (C₁₂{sub +} oligomers) were identified as intermediates formed inside HZSM-5 at different reaction temperatures. During furan conversion, graphite-type coke formed on the catalyst surface, which caused the aromatics and olefins formation to deactivate within the first 30 min of time on-stream. We have measured the effects of space velocity and temperature for furan conversion to help us understand the chemistry of biomass conversion inside zeolite catalysts. The major products for furan conversion included CO, CO₂, allene, C₂–C₆ olefins, benzene, toluene, styrene, benzofuran, indene, and naphthalene. The aromatics (benzene and toluene) and olefins (ethylene and propylene) selectivity decreased with increasing space velocity. Unsaturated hydrocarbons such as allene, cyclopentadiene, and aromatics selectivity increased with increasing space velocity. The product distribution was selective to olefins and CO at high temperatures (650 °C) but was selective to aromatics (benzene and toluene) at intermediate temperatures (450–600 °C). At low temperatures (450 °C), benzofuran and coke contributed 60% of the carbon selectivity. Several different reactions were occurring for furan conversion over zeolites. Some important reactions that we have identified in this study include Diels–Alder condensation (e.g., two furans form benzofuran and water

  20. Catalytic Olefin Hydroamidation Enabled by Proton-Coupled Electron Transfer

    PubMed Central

    2015-01-01

    Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-atom, electron, and proton transfer events with a thiophenol cocatalyst furnish the product and regenerate the active forms of the photocatalyst and base. Mechanistic studies indicate that the amide substrate can be selectively homolyzed via PCET in the presence of the thiophenol, despite a large difference in bond dissociation free energies between these functional groups. PMID:26439818

  1. Metal containing polymeric functional microspheres

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

    1979-01-01

    Polymeric functional microspheres containing metal or metal compounds are formed by addition polymerization of a covalently bondable olefinic monomer such as hydroxyethylmethacrylate in the presence of finely divided metal or metal oxide particles, such as iron, gold, platinum or magnetite, which are embedded in the resulting microspheres. The microspheres can be covalently bonded to chemotherapeutic agents, antibodies, or other proteins providing a means for labeling or separating labeled cells. Labeled cells or microspheres can be concentrated at a specific body location such as in the vicinity of a malignant tumor by applying a magnetic field to the location and then introducing the magnetically attractable microspheres or cells into the circulatory system of the subject. Labeled cells can be separated from a cell mixture by applying a predetermined magnetic field to a tube in which the mixture is flowing. After collection of the labeled cells, the magnetic field is discontinued and the labeled sub-cell population recovered.

  2. Ru-Based Z-Selective Metathesis Catalysts with Modified Cyclometalated Carbene Ligands†

    PubMed Central

    Bronner, Sarah M.; Herbert, Myles B.; Patel, Paresma R.; Marx, Vanessa M.; Grubbs, Robert H.

    2014-01-01

    A series of cyclometalated Z-selective ruthenium olefin metathesis catalysts with alterations to the N-heterocyclic carbene (NHC) ligand were prepared. X-Ray crystal structures of several new catalysts were obtained, elucidating the structural features of this class of cyclometalated complexes. The metathesis activity of each stable complex was evaluated, and one catalyst, bearing geminal dimethyl backbone substitution, was found to be comparable to our best Z-selective metathesis catalyst to date. PMID:25346842

  3. Low severity coal liquefaction promoted by cyclic olefins. Quarterly report, April--June 1992

    SciTech Connect

    Curtis, C.W.

    1992-07-27

    Low severity coal liquefaction allows for solubilization of coal with reduced gas make. These lower severity conditions may result in some selective bond rupture. Promotion of coal solubilization through hydrogen transfer using highly active and effective hydrogen donors is the objective of this study. The highly effective donors being tested are cyclic olefins. Representative cyclic olefins are isotetralin, which is 1,4,5,8-tetrahydronaphthalene, and 1,4,5,8,9,10-hexahydroanthracene. These compounds are hydroaromatics without aromatic rings and have been shown to be highly effective donors. The objective of the work performed in this study during this quarter was to evaluate reaction parameters for low severity liquefaction reactions using the cyclic olefin, hexahydroanthracene, and the aromatic, anthracene. These model compounds were reacted under a variety of conditions to evaluate their reactivity without coal. The reactions were performed under both thermal and catalytic conditions. Finely divided catalysts from different molybdenum precursors were used to determine their activity in promoting hydrogenation and hydrogen transfer at low severity conditions. The catalysts used were Molyvan L, sulfurized oxymolybdenum dithiocarbamate, molybdenum naphthenate, and Molyvan 822, organo molybdenum dithiocarbamate.

  4. Synthesis of Poly(3-alkylthiophene)–Poly(arylisocyanide) Diblock Copolymers. Two Mechanistically Distinct, Sequential Living Polymerizations Using a Single Catalyst

    SciTech Connect

    Wu, Zong-Quan; Ono, Robert J.; Chen, Zheng; Bielawski, Christopher W.

    2010-09-21

    Block copolymers of poly(3-hexylthiophene) and a poly(arylisocyanide) were synthesized in a single pot via the addition of 2-bromo-3-hexyl-5-chloromagnesiothiophene followed by n-decyl 4-isocyanobenzoate to a solution of Ni(1,3-bis(diphenylphosphino)propane)Cl 2. The respective mechanistically distinct polymerizations proceeded in a controlled fashion and afforded well-defined block copolymers with tunable molecular weights and compositions. The block copolymers exhibited microphase separation characteristics in the solid state.

  5. Magnetic and dendritic catalysts.

    PubMed

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

    2015-07-21

    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

  6. Transition-metal-catalyzed carbonylation reactions of olefins and alkynes: a personal account.

    PubMed

    Wu, Xiao-Feng; Fang, Xianjie; Wu, Lipeng; Jackstell, Ralf; Neumann, Helfried; Beller, Matthias

    2014-04-15

    Carbon monoxide was discovered and identified in the 18th century. Since the first applications in industry 80 years ago, academic and industrial laboratories have broadly explored CO's use in chemical reactions. Today organic chemists routinely employ CO in organic chemistry to synthesize all kinds of carbonyl compounds. Despite all these achievements and a century of carbonylation catalysis, many important research questions and challenges remain. Notably, apart from academic developments, industry applies carbonylation reactions with CO on bulk scale. In fact, today the largest applications of homogeneous catalysis (regarding scale) are carbonylation reactions, especially hydroformylations. In addition, the vast majority of acetic acid is produced via carbonylation of methanol (Monsanto or Cativa process). The carbonylation of olefins/alkynes with nucleophiles, such as alcohols and amines, represent another important type of such reactions. In this Account, we discuss our work on various carbonylations of unsaturated compounds and related reactions. Rhodium-catalyzed isomerization and hydroformylation reactions of internal olefins provide straightforward access to higher value aldehydes. Catalytic hydroaminomethylations offer an ideal way to synthesize substituted amines and even heterocycles directly. More recently, our group has also developed so-called alternative metal catalysts based on iridium, ruthenium, and iron. What about the future of carbonylation reactions? CO is already one of the most versatile C1 building blocks for organic synthesis and is widely used in industry. However, because of CO's high toxicity and gaseous nature, organic chemists are often reluctant to apply carbonylations more frequently. In addition, new regulations have recently made the transportation of carbon monoxide more difficult. Hence, researchers will need to develop and more frequently use practical and benign CO-generating reagents. Apart from formates, alcohols, and metal

  7. Polymeric microspheres

    DOEpatents

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

    2004-04-13

    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.

  8. Ruthenium—Arene Complexes Derived from NHC•CO2 and NHC•CS2 Zwitterionic Adducts and Their Use in Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Delaude, Lionel; Demonceau, Albert

    A range of imidazol(in)ium-2-carboxylates and -dithiocarboxylates bearing alkyl or aryl groups on their nitrogen atoms were prepared by reacting the corresponding N-heterocyclic carbenes (NHCs) with either carbon dioxide or carbon disulfide. All the zwitterionic products were characterized by various analytical techniques, including thermogravimetric analysis (TGA). Their ability to act as NHC ligand precursors for in situ catalytic applications was investigated in the ruthenium-promoted ring-opening metathesis polymerization (ROMP) of cyclo-octene. Upon exposure to the [RuCl2(p-cymene)]2 dimer, the NHC CO2 adducts readily dissociated to generate [RuCl2(p-cymene)(NHC)] complexes that were highly active catalyst precursors for olefin metathesis. Conversely, the NHC CS2 betaines retained their zwitterionic nature and led to new cationic complexes of the [RuCl(p-cymene)(NHC CS2)]+PF6 - type that were devoid of any significant catalytic activity in the reaction under consideration

  9. Catalysis Science Initiative: Catalyst Design by Discovery Informatics

    SciTech Connect

    Delgass, William Nicholas; Abu-Omar, Mahdi; Caruthers, James; Ribeiro, Fabio; Thomson, Kendall; Schneider, William

    2016-07-08

    atoms in the interfacial region. Some of the first theoretical descriptions of this important chemistry and potential new source of control of catalyst properties are be in preparation for submission. On the homogeneous catalysis side, we have used single site olefin polymerization as the testbed. This system is important because changes in a single ligand bonded to the catalytically active metal site can alter the rates of individual steps in the polymerization sequence and thereby change the properties of the resulting polymer, potentially improving its value in a hundred million pound per year industry. We have made a major advance in understanding such systems by developing a population balance kinetic model that allows us to predict the molecular weight distribution (MWD) of the product. That, in turn, allows use of MWD data to fit kinetic parameters. By combining monomer loss data, MWD, measurement of the number of working active sites, and polymer end group analysis, we have a rich data set that is highly discriminating of kinetic mechanism. Thus, we have a robust tool for producing high quality, detailed kinetic parameters, which we have used to refine mechanisms presented in the literature and discover relationships between steric and electronic properties of group IV catalysts and individual rate constants in a number of systems. Our recent work on six-coordinate Zr, Ti, and Hf amine bis(phenolate) systems, we have shown that: • The sterics (bulkiness) of the ligands specifically affect the chain termination reaction • The electron density on the metal controls misinsertion (flipped orientation) of the olefin into the growing polymer • Steric effects related to the size of the ortho ligand on the catalyst have been shown to strongly affect its the degree of dormancy, i.e. tendency to stop reacting • Changes in the size of the amine pendent group on the catalyst can have such a strong effect on chain termination as to change the catalyst from one that

  10. Low severity coal liquefaction promoted by cyclic olefins. Quarterly report, January--March 1993

    SciTech Connect

    Curtis, C.W.

    1993-07-01

    The combination of some of these methods could further improve low severity conversion. It seems logical that a combination of a proven pretreatment technique with a good dissolution catalyst or a good hydrogen donor would increase reactivity. The importance of surface chemistry with yield and nature of reactions shown in early research indicates the physical importance of pretreatment. Swelling of the coal with an organic solvent improves the contact. This good contact is also important to slowing retrogressive reactions. The best conversions come when the initial products of liquefaction are preserved. In addition to the physical importance of pretreatment, there is a chemical advantage. Shams saw not only the effect of minimization of organic oxygen coupling reactions, but with his process there also seemed to be a demineralization. The minerals removed the catalysts for retrogressive reactions. The chemistry of liquefaction is still not well understood. Stansberry`s attempt to determine whether catalysts liberate species or just further decomposition was largely inconclusive. There was improvement in conversion so the catalysts seemingly assisted in bond breakage. These good catalytic effects were also seen in the work involving coprocessing. The most compelling factor in each of these procedures, is the ability of the coal to receive the hydrogen that it needs to be liquefied. Bedell and Curtis (1991) found that cyclic olefins gave their hydrogen up much more readily than did hydroaromatics. The coal conversion was a significantly improved. The combination of retrogressive reaction suppression and good hydrogen donability should provide for good coal conversion. It was this reasoning that influenced the decision to investigate a combination of the HCl/methanol pretreatment and the usage of cyclic olefins as hydrogen donors. The increased reactivity of the pretreated coal should enhance the effect of the hydrogen donability of the cyclic olefins.

  11. Functionalized olefin cross-coupling to construct carbon–carbon bonds

    PubMed Central

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-01-01

    Carbon–carbon (C–C) bonds form the backbone of many important molecules, including polymers, dyes, and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavor heavily relies on the ability to form C–C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a fundamentally new chemical transformation that allows for the facile construction of highly substituted and uniquely functionalized C–C bonds. Using a simple iron catalyst, an inexpensive silane, and a benign solvent under an ambient atmosphere, heteroatom-substituted olefins are easily merged with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than sixty examples are presented with a wide array of substrates, demonstrating the unique chemoselectivity and mildness of this simple reaction. PMID:25519131

  12. Functionalized olefin cross-coupling to construct carbon-carbon bonds

    NASA Astrophysics Data System (ADS)

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-12-01

    Carbon-carbon (C-C) bonds form the backbone of many important molecules, including polymers, dyes and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavour relies heavily on the ability to form C-C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a chemical transformation that allows the facile construction of highly substituted and uniquely functionalized C-C bonds. Using a simple iron catalyst, an inexpensive silane and a benign solvent under ambient atmosphere, heteroatom-substituted olefins are easily reacted with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than 60 examples are presented with a wide array of substrates, demonstrating the chemoselectivity and mildness of this simple reaction.

  13. Catalyst Activity Comparison of Alcohols over Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Wang, Yong

    2013-01-01

    Alcohol transformation to transportation fuel range hydrocarbon on HZSM-5 (SiO2 / Al2O3 = 30) catalyst was studied at 360oC and 300psig. Product distributions and catalyst life were compared using methanol, ethanol, 1-propanol or 1-butanol as a feed. The catalyst life for 1-propanol and 1-butanol was more than double compared to that for methanol and ethanol. For all the alcohols studied, the product distributions (classified to paraffin, olefin, napthene, aromatic and naphthalene compounds) varied with time on stream (TOS). At 24 hours TOS, liquid product from 1-propanol and 1-butanol transformation primarily contains higher olefin compounds. The alcohol transformation process to higher hydrocarbon involves a complex set of reaction pathways such as dehydration, oligomerization, dehydrocyclization, and hydrogenation. Compared to ethylene generated from methanol and ethanol, oligomerization of propylene and butylene has a lower activation energy and can readily take place on weaker acidic sites. On the other hand, dehydrocyclization of propylene and butylene to form the cyclic compounds requires the sits with stronger acid strength. Combination of the above mentioned reasons are the primary reasons for olefin rich product generated in the later stage of the time on stream and for the extended catalyst life time for 1 propanol and 1 butanol compared to methanol and ethanol conversion over HZSM-5.

  14. Theoretical insights into the mechanism of olefin elimination in the methanol-to-olefin process over HZSM-5, HMOR, HBEA, and HMCM-22 zeolites.

    PubMed

    Wang, Sen; Chen, Yanyan; Wei, Zhihong; Qin, Zhangfeng; Chen, Jialing; Ma, Hong; Dong, Mei; Li, Junfen; Fan, Weibin; Wang, Jianguo

    2014-10-02

    The mechanism of olefin elimination in the process of methanol-to-olefins (MTO) over a series of zeolites like HZSM-5, HMOR, HBEA, and HMCM-22 was investigated by DFT-D calculations, which is a crucial step that controls the MTO product distribution. The results demonstrate that the manners of olefin elimination are related to the pore structure of zeolite catalyst and the interaction between proton transfer reagent (water or methanol) and zeolite acidic framework. The indirect spiro mechanism is preferable to the direct mechanism over HMOR, HBEA, and HMCM-22 zeolites with large pores, as suggested by the energy barrier of rate-determining step and the potential energy surface (PES), but is unfavorable over HZSM-5 with medium-sized pores due to the steric hindrance of spiro intermediates. Over various zeolites, water and methanol perform differently in proton transfer to form the spiro intermediates; over HMOR and HBEA with strong acidity, water is superior to methanol in promoting propene elimination, whereas over HMCM-22 with relatively weaker acidity, methanol is more favorable as a proton transfer reagent.

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

    PubMed

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

    2005-04-27

    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 < Br < I) for the one-electron oxidation wave. Addition of X(-) changes the voltammogram, indicating the formation of MoX(4)(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.

  16. Simple, Chemoselective, Catalytic Olefin Isomerization

    PubMed Central

    2015-01-01

    Catalytic amounts of Co(SaltBu,tBu)Cl and organosilane irreversibly isomerize terminal alkenes by one position. The same catalysts effect cycloisomerization of dienes and retrocycloisomerization of strained rings. Strong Lewis bases like amines and imidazoles, and labile functionalities like epoxides, are tolerated. PMID:25398144

  17. Cyclic alkyl amino carbene (CAAC) ruthenium complexes as remarkably active catalysts for ethenolysis

    SciTech Connect

    Marx, Vanessa M.; Sullivan, Alexandra H.; Melaimi, Mohand; Virgil, Scott C.; Keitz, Benjamin K.; Weinberger, David S.; Bertrand, Guy; Grubbs, Robert H.

    2014-12-17

    In this paper, an expanded family of ruthenium-based metathesis catalysts bearing cyclic alkyl amino carbene (CAAC) ligands was prepared. These catalysts exhibited exceptional activity in the ethenolysis of the seed-oil derivative methyl oleate. In many cases, catalyst turnover numbers (TONs) of more than 100,000 were achieved, at a catalyst loading of only 3 ppm. Remarkably, the most active catalyst system was able to achieve a TON of 340 000, at a catalyst loading of only 1 ppm. Finally, this is the first time a series of metathesis catalysts has exhibited such high performance in cross-metathesis reactions employing ethylene gas, with activities sufficient to render ethenolysis applicable to the industrial-scale production of linear α-olefins (LAOs) and other terminal-olefin products.

  18. Cyclic alkyl amino carbene (CAAC) ruthenium complexes as remarkably active catalysts for ethenolysis

    DOE PAGES

    Marx, Vanessa M.; Sullivan, Alexandra H.; Melaimi, Mohand; ...

    2014-12-17

    In this paper, an expanded family of ruthenium-based metathesis catalysts bearing cyclic alkyl amino carbene (CAAC) ligands was prepared. These catalysts exhibited exceptional activity in the ethenolysis of the seed-oil derivative methyl oleate. In many cases, catalyst turnover numbers (TONs) of more than 100,000 were achieved, at a catalyst loading of only 3 ppm. Remarkably, the most active catalyst system was able to achieve a TON of 340 000, at a catalyst loading of only 1 ppm. Finally, this is the first time a series of metathesis catalysts has exhibited such high performance in cross-metathesis reactions employing ethylene gas, withmore » activities sufficient to render ethenolysis applicable to the industrial-scale production of linear α-olefins (LAOs) and other terminal-olefin products.« less

  19. Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust

    SciTech Connect

    Carlson, Torren R.; Cheng, Yu-Ting; Jae, Jungho; Huber, George W.

    2011-10-26

    Catalytic fast pyrolysis of pine wood sawdust and furan (a model biomass compound) with ZSM-5 based catalysts was studied with three different reactors: a bench scale bubbling fluidized bed reactor, a fixed bed reactor and a semi-batch pyroprobe reactor. The highest aromatic yield from sawdust of 14% carbon in the fluidized bed reactor was obtained at low biomass weight hourly space velocities (less than 0.5 h-1) and high temperature (600 °C). Olefins (primarily ethylene and propylene) were also produced with a carbon yield of 5.4% carbon. The biomass weight hourly space velocity and the reactor temperature can be used to control both aromatic yield and selectivity. At low biomass WHSV the more valuable monocyclic aromatics are produced and the formation of less valuable polycyclic aromatics is inhibited. Lowering the reaction temperature also results in more valuable monocyclic aromatics. The olefins produced during the reaction can be recycled to the reactor to produce additional aromatics. Propylene is more reactive than ethylene. Co-feeding propylene to the reactor results in a higher aromatic yield in both continuous reactors and higher conversion of the intermediate furan in the fixed bed reactor. When olefins are recycled aromatic yields from wood of 20% carbon can be obtained. After ten reaction–regeneration cycles there were metal impurities deposited on the catalyst, however, the acid sites on the zeolite are not affected. Of the three reactors tested the batch pyroprobe reactor yielded the most aromatics, however, the aromatic product is largely naphthalene. The continuous reactors produce less naphthalene and the sum of aromatics plus olefin products is higher than the pyroprobe reactor.

  20. Highly Robust Palladium(II) α-Diimine Catalysts for Slow-Chain-Walking Polymerization of Ethylene and Copolymerization with Methyl Acrylate.

    PubMed

    Dai, Shengyu; Sui, Xuelin; Chen, Changle

    2015-08-17

    A series of sterically demanding α-diimine ligands bearing electron-donating and electron-withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, including high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow-chain-walking activity of these Pd complexes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Application of PEG-400 as a green biodegradable polymeric medium for the catalyst-free synthesis of spiro-dihydropyridines and their use as acetyl and butyrylcholinesterase inhibitors.

    PubMed

    Maryamabadi, Ammar; Hasaninejad, Alireza; Nowrouzi, Najmeh; Mohebbi, Gholamhossein; Asghari, Behvar

    2016-03-15

    A simple, efficient and green approach for the synthesis of spiro-dihydropyridines derivatives by one-pot multi-component reaction of isatin or acenaphthoquinone derivatives (1 equiv) with malononitrile (1 equiv) and N,N'-substituted-2-nitroethene-1,1-diamines (1 equiv) in PEG-400 under catalyst-free conditions is described. This method provides several advantages such as environmental friendliness, short reaction time, and simple workup procedure for the synthesis of biologically important compounds. The ability of synthesized compounds in inhibition of acetyl and butyrylcholinesterase were investigated both in vitro and in silico. All compounds showed moderate to high level activity against both acetyl and butyrylcholinesterase. There was a good correlation between in vitro and in silico studies.

  2. 40 CFR 721.10672 - Sodium olefin sulfonate derivative (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Sodium olefin sulfonate derivative... Specific Chemical Substances § 721.10672 Sodium olefin sulfonate derivative (generic). (a) Chemical... as sodium olefin sulfonate derivative (PMNs P-09-447 and P-09-448) are subject to reporting...

  3. Microreactor for efficient catalyst evaluation

    NASA Astrophysics Data System (ADS)

    Besser, Ronald S.; Ouyang, Sean; Surangalikar, Harshal; Prevot, Michelle

    2001-09-01

    This paper describes ongoing work in the development of microreactor-based systems for applications in the chemical process industry. The microreactors discussed here are formed from silicon using robust micromachining processes to produce devices with micrometer-scale fluidic structures including passageways for the introduction and removal of gases, and a reaction zone with a thin-film catalyst. We describe experiments done to characterize these reactors for use as development tools for industrial catalytic processes in terms of catalyst screening, acquisition of rate laws, and determination of optimal process conditions. The system studied here, the reaction of a cyclic olefin (cyclohexene) with hydrogen in the presence of platinum catalyst, is a model for industrially important catalytic hydrogenation and dehydrogenation reactions.

  4. Z-Selective Olefin Metathesis Reactions Promoted by Tungsten Oxo Alkylidene Complexes

    PubMed Central

    Peryshkov, Dmitry V.; Schrock, Richard R.; Takase, Michael K.; Müller, Peter; Hoveyda, Amir H.

    2011-01-01

    Addition of LiOHMT (OHMT = O-2,6-dimesitylphenoxide) to W(O)(CH-t-Bu)(PMe2Ph)2Cl2 led to WO(CH-t-Bu)Cl(OHMT)(PMe2Ph) (4). Subsequent addition of Li(2,5-Me2C4H2N) to 4 yielded yellow W(O)(CH-t-Bu)(OHMT)(Me2Pyr)(PMe2Ph) (5). Compound 5 is a highly effective catalyst for the Z-selective coupling of selected terminal olefins (at 0.2% loading) to give product in >75% yield with >99% Z configuration. Addition of two equivalents of B(C6F5)3 to 5 led to catalyst activated at the oxo ligand by B(C6F5)3. 5.B(C6F5)3 is a highly active catalyst that produces thermodynamic products (~20% Z). PMID:22107254

  5. A Practical Solution to Stereodefined Tetrasubstituted Olefins.

    PubMed

    Dai, Jianxin; Wang, Minyan; Chai, Guobi; Fu, Chunling; Ma, Shengming

    2016-03-02

    Olefins, compounds with a carbon-carbon double bond, are of fundamental importance, and stereodefined construction of tetrasubstituted carbon-carbon double bond is a significant challenge. Here we show a unique and practical method for the preparation of stereodefined, fully substituted olefins via conjugate addition of organozinc reagents to readily available 2,3-allenals. Through mechanistic studies, it is confirmed that the geometry of the newly formed double bond is controlled by unique regiospecific oxygen-protonation of the enolate intermediates, generating 1,3-alkadienols. Such alkadienols would undergo a concerted 1,5-H-transfer reaction via a six-membered transition state to ensure the configuration of the carbon-carbon double bond in the final products. Using the readily available organozinc reagents and 2,3-allenals provides a very rapid access to a wide range of tetrasubstituted olefins with defined stereochemistry, bearing an extremely versatile aldehyde functionality.

  6. Polymerization of monomer-based ferrofluids.

    PubMed

    Bian, Pei; McCarthy, Thomas J

    2010-05-04

    Ferrofluids based on oleate-stabilized nanoparticulate magnetite in cyclic olefin carrier solvents were prepared. Puddles of fluids containing 20-70 wt % magnetite in 1,5-cyclooctadiene or dicyclopentadiene can be moved or positioned on surfaces or in vessels with moderate magnetic fields (inexpensive NdFeB magnets). The surfaces of puddles with concentrations >40 wt % distort in response to magnetic fields applied perpendicular to the puddle surface and exhibit pointed liquid asperities. The liquid surface topography (asperity height and number per unit area) can be controlled by the strength of the applied field. The cyclic olefin carriers can be polymerized by ring-opening metathesis, solidifying the ferrofluid samples in the shape of the magnetically distorted monomeric solvent suspensions.

  7. Catalysts and process for liquid hydrocarbon fuel production

    DOEpatents

    White, Mark G; Liu, Shetian

    2014-12-09

    The present invention provides a novel process and system in which a mixture of carbon monoxide and hydrogen synthesis gas, or syngas, is converted into hydrocarbon mixtures composed of high quality gasoline components, aromatic compounds, and lower molecular weight gaseous olefins in one reactor or step. The invention utilizes a novel molybdenum-zeolite catalyst in high pressure hydrogen for conversion, as well as a novel rhenium-zeolite catalyst in place of the molybdenum-zeolite catalyst, and provides for use of the novel catalysts in the process and system of the invention.

  8. (Z)-Selective Takai olefination of salicylaldehydes

    PubMed Central

    Galloway, Warren R J D; Sore, Hannah F; Goodman, Jonathan M

    2017-01-01

    The Takai olefination (or Takai reaction) is a method for the conversion of aldehydes to vinyl iodides, and has seen widespread implementation in organic synthesis. The reaction is usually noted for its high (E)-selectivity; however, herein we report the highly (Z)-selective Takai olefination of salicylaldehyde derivatives. Systematic screening of related substrates led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations. PMID:28326141

  9. Conductive Polymeric Ionic Liquid/Fe3O4 Nanocomposite as an Efficient Catalyst for the Voltammetric Determination of Amlodipine Besylate.

    PubMed

    Fathirad, Fariba; Mostafavi, Ali; Afzali, Daryoush

    2017-03-01

    A novel conductive polymeric ionic liquid (IL)-Fe3O4 nanocomposite (represented as PIL-Fe3O4) based on inorganic-organic hybrid material was synthesized using two different methods. Nuclear magnetic resonance, Fourier transform infrared, X-ray diffraction, and field emission scanning electron microscopy characterized the structures of IL, Fe3O4 nanoparticles, and PIL-Fe3O4. The electrochemical sensors based on PIL-Fe3O4-modified glassy carbon electrode were fabricated, and each of these nanocomposites was examined for the ability to determine amlodipine besylate (AMD). The electrochemical study of the modified electrodes, as well as its efficiency for the electro-oxidation of AMD, was described in 0.1 M phosphate-buffered solution (pH 7.0) using voltammetric methods. The results exhibit a linear dynamic range from 1 to 500 nM and a detection limit of 0.36 nM. Finally, the modified electrode was used for the determination of AMD in pharmaceutical and biological samples.

  10. Nonproductive events in ring-closing metathesis using ruthenium catalysts.

    PubMed

    Stewart, Ian C; Keitz, Benjamin K; Kuhn, Kevin M; Thomas, Renee M; Grubbs, Robert H

    2010-06-30

    The relative TONs of productive and nonproductive metathesis reactions of diethyl diallylmalonate are compared for eight different ruthenium-based catalysts. Nonproductive cross metathesis is proposed to involve a chain-carrying ruthenium methylidene. A second more-challenging substrate (dimethyl allylmethylallylmalonate) that forms a trisubstituted olefin product is used to further delineate the effect of catalyst structure on the relative efficiencies of these processes. A steric model is proposed to explain the observed trends.

  11. ARTICLE Molecular Dynamic Simulation on the Absorbing Process of Isolating and Coating of α-olefin Drag Reducing Polymer

    NASA Astrophysics Data System (ADS)

    Li, Bing; Sheng, Xiang; Xing, Wen-guo; Dong, Gui-lin; Liu, Yong-jun; Zhang, Chang-qiao; Chen, Xiang-jun; Zhou, Ning-ning; Qin, Zhan-bo

    2010-12-01

    The absorbing process in isolating and coating process of α-olefin drag reducing polymer was studied by molecular dynamic simulation method, on basis of coating theory of α-olefin drag reducing polymer particles with polyurethane as coating material. The distributions of sodium laurate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate on the surface of α-olefin drag reducing polymer particles were almost the same, but the bending degrees of them were obviously different. The bending degree of SLA molecules was greater than those of the other two surfactant molecules. Simulation results of absorbing and accumulating structure showed that, though hydrophobic properties of surfactant molecules were almost the same, water density around long chain sulfonate sodium was bigger than that around alkyl sulfate sodium. This property goes against useful absorbing and accumulating on the surface of α-olefin drag reducing polymer particles; simulation results of interactions of different surfactant and multiple hydroxyl compounds on surface of particles showed that, interactions of different surfactant and one kind of multiple hydroxyl compound were similar to those of one kind of surfactant and different multiple hydroxyl compounds. These two contrast types of interactions also exhibited the differences of absorbing distribution and closing degrees to surface of particles. The sequence of closing degrees was derived from simulation; control step of addition polymerization interaction in coating process was absorbing mass transfer process, so the more closed to surface of particle the multiple hydroxyl compounds were, the easier interactions with isocyanate were. Simulation results represented the compatibility relationship between surfactant and multiple hydroxyl compounds. The isolating and coating processes of α-olefin drag reducing polymer were further understood on molecule and atom level through above simulation research, and based on the simulation, a

  12. Coke formation and carbon atom economy of methanol-to-olefins reaction.

    PubMed

    Wei, Yingxu; Yuan, Cuiyu; Li, Jinzhe; Xu, Shutao; Zhou, You; Chen, Jingrun; Wang, Quanyi; Xu, Lei; Qi, Yue; Zhang, Qing; Liu, Zhongmin

    2012-05-01

    The methanol-to-olefins (MTO) process is becoming the most important non-petrochemical route for the production of light olefins from coal or natural gas. Maximizing the generation of the target products, ethene and propene, and minimizing the production of byproducts and coke, are major considerations in the efficient utilization of the carbon resource of methanol. In the present work, the heterogeneous catalytic conversion of methanol was evaluated by performing simultaneous measurements of the volatile products generated in the gas phase and the confined coke deposition in the catalyst phase. Real-time and complete reaction profiles were plotted to allow the comparison of carbon atom economy of methanol conversion over the catalyst SAPO-34 at varied reaction temperatures. The difference in carbon atom economy was closely related with the coke formation in the SAPO-34 catalyst. The confined coke compounds were determined. A new type of confined organics was found, and these accounted for the quick deactivation and low carbon atom economy under low-reaction-temperature conditions. Based on the carbon atom economy evaluation and coke species determination, optimized operating conditions for the MTO process are suggested; these conditions guarantee high conversion efficiency of methanol.

  13. Rare earth metal bis(amide) complexes bearing amidinate ancillary ligands: synthesis, characterization, and performance as catalyst precursors for cis-1,4 selective polymerization of isoprene.

    PubMed

    Luo, Yunjie; Fan, Shimin; Yang, Jianping; Fang, Jianghua; Xu, Ping

    2011-03-28

    A family of rare earth metal bis(amide) complexes bearing monoanionic amidinate [RC(N-2,6-Me(2)C(6)H(3))(2)](-) (R = cyclohexyl (Cy), phenyl (Ph)) as ancillary ligands were synthesized and characterized. One-pot salt metathesis reaction of anhydrous LnCl(3) with one equivalent of amidinate lithium [RC(N-2,6-Me(2)C(6)H(3))(2)]Li, following the introduction of two equivalents of NaN(SiMe(3))(2) in THF at room temperature afforded the neutral and unsolvated mono(amidinate) rare earth metal bis(amide) complexes [RC(N-2,6-Me(2)C(6)H(3))(2)]Y[N(SiMe(3))(2)](2) (R = Cy (1); R = Ph (2)), and the "ate" mono(amidinate) rare earth metal bis(amide) complex [CyC(N-2,6-Me(2)C(6)H(3))(2)]Lu[N(SiMe(3))(2)](2)(μ-Cl)Li(THF)(3) (3) in 61-72% isolated yields. These complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray single crystal diffraction. Single crystal structural determination revealed that the central metal in complexes 1 and 2 adopts a distorted tetrahedral geometry, and in complex 3 forms a distorted trigonal bipyramidal geometry. In the presence of AlMe(3), and in combination with one equimolar amount of [Ph(3)C][B(C(6)F(5))(4)], complexes 1 and 2 showed high activity towards isoprene polymerization to give high molecular weight polyisoprene (M(n) > 10(4)) with good cis-1,4 selectivity (>90%).

  14. Organo-Lewis acids as cocatalysts in cationic metallocene polymerization catalysis. Unusual characteristics of sterically encumbered tris(perfluorobiphenyl)borane

    SciTech Connect

    Chen, Y.X.; Stern, C.L.; Yang, S.; Marks, T.J.

    1996-12-11

    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.

  15. Triblock Terpolymers by Simultaneous Tandem Block Polymerization (STBP).

    PubMed

    Freudensprung, Ines; Klapper, Markus; Müllen, Klaus

    2016-02-01

    A route of synthesizing triblock terpolymers in a one-pot, "one-step" polymerization approach is presented. The combination of two distinct polymerization techniques through orthogonal catalyst/initiator functionalities attached to a polymeric linker furnishes novel pathways to ABC-terpolymers. Both polymerizations have to be compatible regarding mechanisms, chosen monomers, and solvents. Here, an α,ω-heterobifunctional poly(ethylene glycol) serves as poly-meric catalyst/initiator to obtain triblock terpolymers of poly(norbornene)-b-poly(ethylene glycol)-b-poly(L-lactic acid) PNB-PEG-PLLA via simultaneous ring opening metathesis poly-merization and ring opening polymerization in a fast one-pot polymerization. Structural characterization of the polymers is provided via (1)H-, DOSY-, and (1)H,(1)H-COSY-NMR, while solution and thin film self-assembly are investigated by dynamic light scattering and atomic force microscopy.

  16. Catalytical Photocyclization of Arylamines with a-Olefins in the Synthesis of 2-Alkylquinoline

    ERIC Educational Resources Information Center

    Makhmutov, Aynur; Usmanov, Salavat; Mustafin, Ahat

    2016-01-01

    The article deals with the results of investigation of the process of catalytical photocyclization of aniline and aniline hydrochloride with a-olefins (hexene-1, heptene-1 and octene-1). The following compounds of d- and f-metals are tested as probable catalysts: CuSO4•5H2O, EuCl3•6H2O, PrCl3•6H2O, TbCl3•6H2O, La2O3, MnO2, NiSO4•6H2O, NiCl2•6H2O,…

  17. A serine-substituted P450 catalyzes highly efficient carbene transfer to olefins in vivo.

    PubMed

    Coelho, Pedro S; Wang, Z Jane; Ener, Maraia E; Baril, Stefanie A; Kannan, Arvind; Arnold, Frances H; Brustad, Eric M

    2013-08-01

    Whole-cell catalysts for non-natural chemical reactions will open new routes to sustainable production of chemicals. We designed a cytochrome 'P411' with unique serine-heme ligation that catalyzes efficient and selective olefin cyclopropanation in intact Escherichia coli cells. The mutation C400S in cytochrome P450(BM3) gives a signature ferrous CO Soret peak at 411 nm, abolishes monooxygenation activity, raises the resting-state Fe(III)-to-Fe(II) reduction potential and substantially improves NAD(P)H-driven activity.

  18. A Serine-Substituted P450 Catalyzes Highly Efficient Carbene Transfer to Olefins In Vivo

    PubMed Central

    Coelho, Pedro S.; Wang, Z. Jane; Ener, Maraia E.; Baril, Stefanie A.; Kannan, Arvind A.; Arnold, Frances H.; Brustad, Eric M.

    2013-01-01

    Genetically encoded catalysts for non-natural chemical reactions will open new routes to sustainable production of chemicals. We designed a unique serine-heme ligated cytochrome “P411” that catalyzes efficient and selective carbene transfers from diazoesters to olefins in intact Escherichia coli cells. The mutation C400S in cytochrome P450BM3 gives a signature ferrous-CO Soret peak at 411 nm, abolishes monooxygenation activity, raises the resting state FeIII/II reduction potential, and significantly improves NAD(P)H-driven cyclopropanation activity. PMID:23792734

  19. Synthesis and characterization of new magnetically recoverable molybdenum nanocatalyst for epoxidation of olefins

    NASA Astrophysics Data System (ADS)

    Masteri-Farahani, M.; Kashef, Z.

    2012-04-01

    New heterogeneous molybdenum catalyst was prepared through covalent attachment of a Schiff base ligand on the surface of silica coated magnetite nanoparticles via aminopropyl spacer and subsequent complexation with MoO2(acac)2. The prepared nanocatalyst was characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopies and vibrating sample magnetometry. Catalytic epoxidation of some olefins and allylic alcohols by prepared nanocatalyst using tert-butyl hydroperoxide and cumene hydroperoxide as oxidants was achieved with good activities and selectivities.

  20. Synthesis of pterostilbene by Julie Olefination

    USDA-ARS?s Scientific Manuscript database

    A simple, stereoselective route for the synthesis of the biologically active compounds trans-pterostilbene and tetramethoxy stilbene from the readily available starting materials 3,5-dimethoxy benzyl alcohol and 4-hydroxy benzaldehyde was developed using Julia olefination as a key reaction....

  1. Olefin Recovery from Chemical Industry Waste Streams

    SciTech Connect

    A.R. Da Costa; R. Daniels; A. Jariwala; Z. He; A. Morisato; I. Pinnau; J.G. Wijmans

    2003-11-21

    The objective of this project was to develop a membrane process to separate olefins from paraffins in waste gas streams as an alternative to flaring or distillation. Flaring these streams wastes their chemical feedstock value; distillation is energy and capital cost intensive, particularly for small waste streams.

  2. Bromination of olefins with HBr and DMSO.

    PubMed

    Karki, Megha; Magolan, Jakob

    2015-04-03

    A simple and inexpensive methodology is reported for the conversion of alkenes to 1,2-dibromo alkanes via oxidative bromination using HBr paired with dimethyl sulfoxide, which serves as the oxidant as well as cosolvent. The substrate scope includes 21 olefins brominated in good to excellent yields. Three of six styrene derivatives yielded bromohydrins under the reaction conditions.

  3. Synthesis and Characterization of Organo-Rare-Earth Metal Monoalkyl Complexes Supported by Carbon σ-Bonded Indolyl Ligands: High Specific Isoprene 1,4-Cis Polymerization Catalysts.

    PubMed

    Guo, Liping; Zhu, Xiancui; Zhang, Guangchao; Wei, Yun; Ning, Lixin; Zhou, Shuangliu; Feng, Zhijun; Wang, Shaowu; Mu, Xiaolong; Chen, Jun; Jiang, Yuzhe

    2015-06-15

    A series of N-protected 3-imino-functionalized indolyl ligands 1-R-3-(R'N═CH)C8H5N [R = Bn, R' = 2,6-(i)Pr2C6H3 (HL(1)); R = CH3, R' = 2,6-(i)Pr2C6H3 (HL(2)); R = Bn, R' = (t)Bu (HL(3))] and 1-CH3-2-(2,6-(i)Pr2C6H3N═CH)C8H5N (HL(4)) was prepared via reactions of N-protected indolyl aldehydes with corresponding amines. The C-H σ-bond metathesis followed by alkane elimination reactions between RE(CH2SiMe3)3(thf)2 and HL(1)-HL(3) afforded the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes. Reactions of RE(CH2SiMe3)3(thf)2 with 2 equiv of HL(1) or HL(2) gave the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes L(1)2RECH2SiMe3 (RE = Y(1), Er(2), Dy(3)) and L(2)2RECH2SiMe3 (RE = Y(5), Er(6), Dy(7), Yb(8)), while reaction of Yb(CH2SiMe3)3(thf)2 with 2 equiv of HL(1) afforded the ytterbium dialkyl complex L(1)Yb(CH2SiMe3)2(thf)2 (4). Reactions of RE(CH2SiMe3)3(thf)2 with HL(3) gave the tris(heteroaryl) rare-earth metal complexes L(3)3RE (RE = Y(9), Er(10)). In the presence of cocatalysts, the rare-earth metal monoalkyl complexes initiated isoprene polymerization with a high activity (90% conversion of 1000 equiv of isoprene in 25 min) producing polymers with high regio- and stereoselectivity (1,4-cis polymers up to 99%).

  4. Wood-derived olefins by steam cracking of hydrodeoxygenated tall oils.

    PubMed

    Pyl, Steven P; Dijkmans, Thomas; Antonykutty, Jinto M; Reyniers, Marie-Françoise; Harlin, Ali; Van Geem, Kevin M; Marin, Guy B

    2012-12-01

    Tall oil fractions obtained from Norwegian spruce pulping were hydrodeoxygenated (HDO) at pilot scale using a commercial NiMo hydrotreating catalyst. Comprehensive two dimensional gas chromatography (GC×GC) showed that HDO of both tall oil fatty acids (TOFA) and distilled tall oil (DTO) produced highly paraffinic hydrocarbon liquids. The hydrotreated fractions also contained fatty acid methyl esters and norabietane and norabietatriene isomers. Steam cracking of HDO-TOFA in a pilot plant revealed that high light olefin yields can be obtained, with 35.4 wt.% of ethene and 18.2 wt.% of propene at a coil outlet pressure (COP) of 1.7 bara, a dilution of 0.45 kg(steam)/kg(HDO-TOFA) and a coil outlet temperature (COT) of 820 °C. A pilot plant coking experiment indicated that cracking of HDO-TOFA at a COT of 850 °C results in limited fouling in the reactor. Co-cracking of HDO tall oil fractions with a typical fossil-based naphtha showed improved selectivity to desired light olefins, further demonstrating the potential of large scale olefin production from hydrotreated tall oil fractions in conventional crackers.

  5. Pyrazolylcyclotriphosphazene containing pendant polymers: synthesis, characterization, and phosphate ester hydrolysis using a Cu(II)-metalated cross-linked polymeric catalyst.

    PubMed

    Chandrasekhar, Vadapalli; Athimoolam, Arunachalampillai; Srivatsan, S G; Sundaram, P Shanmuga; Verma, Sandeep; Steiner, Alexander; Zacchini, Stefano; Butcher, Raymond

    2002-10-07

    A multi-pyrazolyl cyclotriphosphazene containing polymerizable group N(3)P(3)(3,5-Me(2)Pz)(5)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2)) (2) has been prepared from the corresponding chloro derivative N(3)P(3)Cl(5)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2)) (1). The X-ray structures of 1 and 2 have been determined. Compound 2 undergoes ready metalation with CuCl(2) to afford N(3)P(3)(3,5-Me(2)Pz)(5)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2)).CuCl(2) (3). Model compound N(3)P(3)(3,5-Me(2)Pz)(5)(O-C(6)H(4)-p-CHO).CuCl(2) (6) has been prepared and characterized by spectroscopy and X-ray crystallography. In this compound, the coordination around copper is distorted trigonal bipyramidal, and the cyclotriphosphazene coordinates in a non-gem N(3) mode. Compound 2 has been copolymerized with divinylbenzene to afford cross-linked multisite coordinating polymer CPPL which is readily metalated with CuCl(2) to afford copper-containing polymer CPPL-Cu. The coordination environment around copper in CPPL-Cu has been evaluated by obtaining its EPR, optical, and IR spectra and comparing them with those of model compounds 3 and 6. The utility of CPPL-Cu as a heterogeneous catalyst has been demonstrated in the phosphate ester hydrolysis involving three model phosphate esters: p-nitrophenyl phosphate (pNPP), bis(p-nitrophenyl) phosphate (bNPP), and 2-(hydroxypropyl)-p-nitrophenyl phosphate (hNPP). In all of these reactions, a significant rate enhancement of ester hydrolysis is observed. Detailed kinetic analyses to evaluate Michaelis-Menten parameters have also been carried out along with experiments to elucidate the effect of pH, solvent, and temperature on the rate of hydrolysis. Recycling experiments on the hydrolysis of pNPP with CPPL-Cu shows that it can be recycled several times over without affecting the rates.

  6. Enhanced catalyst and process for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1986-01-01

    The conversion of synthesis gas to liquid molar fuels by means of a cobalt Fischer-Tropsch catalyst composition is enhanced by the addition of molybdenum, tungsten or a combination thereof as an additional component of said composition. The presence of the additive component increases the olefinic content of the hydrocarbon products produced. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  7. Oxidation catalyst

    DOEpatents

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    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.

  8. A theoretically-guided optimization of a new family of modular P,S-ligands for iridium-catalyzed hydrogenation of minimally functionalized olefins.

    PubMed

    Margalef, Jèssica; Caldentey, Xisco; Karlsson, Erik A; Coll, Mercè; Mazuela, Javier; Pàmies, Oscar; Diéguez, Montserrat; Pericàs, Miquel A

    2014-09-15

    A library of modular iridium complexes derived from thioether-phosphite/phosphinite ligands has been evaluated in the asymmetric iridium-catalyzed hydrogenation of minimally functionalized olefins. The modular ligand design has been shown to be crucial in finding highly selective catalysts for each substrate. A DFT study of the transition state responsible for the enantiocontrol in the Ir-catalyzed hydrogenation is also described and used for further optimization of the crucial stereodefining moieties. Excellent enantioselectivities (enantiomeric excess (ee) values up to 99 %) have been obtained for a range of substrates, including E- and Z-trisubstituted and disubstituted olefins, α,β-unsaturated enones, tri- and disubstituted alkenylboronic esters, and olefins with trifluoromethyl substituents. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Application of the entropy theory of glass formation to poly(α-olefins)

    NASA Astrophysics Data System (ADS)

    Stukalin, Evgeny B.; Douglas, Jack F.; Freed, Karl F.

    2009-09-01

    The entropy theory of glass formation, which has previously been developed to describe general classes of polymeric glass-forming liquids, is extended here to model the thermodynamic and dynamic properties of poly(α-olefins). By combining this thermodynamic theory with the Adam-Gibbs model (which relates the configurational entropy to the rate of structural relaxation), we provide systematic computations for all four characteristic temperatures (TA, Tc, Tg, T0), governing the position and breadth of the glass transition, and the fragility parameters (D,m) describing the strength of the temperature dependence of the structural relaxation time, where TA is the temperature below which the relaxation is non-Arrhenius, Tc is the crossover or empirical mode-coupling temperature, Tg is the glass transition temperature, and T0 is the temperature at which the extrapolated relaxation time diverges. These temperatures and fragility parameters are evaluated as a function of molar mass, pressure, and the length n of the α-olefin side chains. The nearest neighbor interaction energy and local chain rigidities are found to strongly influence the four characteristic temperatures and the low temperature fragility. We also observe an "internal plasticization" of the poly(α-olefins) wherein the fragility decreases as the number n of "flexible" side group units increases. Our computations provide solid support for a pressure counterpart of the Vogel-Fulcher-Tammann relation. The entropy theory of glass formation predicts systematic changes in fragility with chain stiffness, cohesive energy, polymerization index, and side chain length, and qualitative trends in these parameters are discussed.

  10. Synthesis gas and olefins from the catalytic autothermal reforming of volatile and non-volatile liquids

    NASA Astrophysics Data System (ADS)

    Dreyer, Bradon Justin

    2007-12-01

    The research presented in this thesis develops an understanding of a clean energy process technology, catalytic partial oxidation (CPO). CPO is a process in which a carbon containing fuel, such as a hydrocarbon, is passed over a noble metal catalyst (e.g. rhodium and platinum) to efficiently generate synthesis gas (H2 and CO) and olefins (e.g. ethylene and propylene) in millisecond contact times. Chapter 1 introduces CPO and compares this technology with conventional methods for synthesis gas and olefin production. CPO has several advantages over the traditional synthesis gas and olefin production methods. One advantage includes autothermal operation, requiring no external heat input from furnaces or heat exchangers. Autothermal operation allows these reactors to be built compactly. The short contact-times associated with CPO further enable for high throughput in relatively small reactor systems, and more compact reactors typically translate to faster response times if transient operation is required. Nobel metal based CPO catalysts are also resistant to deactivation, resulting in less catalyst replacement, regeneration, and maintenance, and an increase in operating efficiency. An overview of the many applications of the chemicals produced from CPO is also presented in Chapter 1. The chemicals produced are crucial in generating valuable chemical intermediates that are eventually incorporated in consumer products, medical devices, building structures, and fertilizers. Additionally, H2 can be used as a source of energy in mobile fuel applications. Fuel cells convert H2 and O2 into electricity and water at higher efficiencies than thermal engine generators. Due to the difficulties in H2 storage, these more efficient energy generators are dependent on hydrogen obtained from synthesis gas production in compact, portable fuel reformers, such as CPO reactors. Furthermore, H2 and CO can be used in reducing environmentally harmful emissions. Particularly, the implementation

  11. The effect of aliphatic olefins on the stability of diesel fuel

    SciTech Connect

    Adiwar; Batts, B.D.

    1995-04-01

    The effect of aliphatic olefins on the storage stability of a number of distillates was observed and characterized, mainly by determining the amounts of total insolubles formed during accelerated ageing. It was observed that the aliphatic olefins, in light cycle oil (LCO), a product of catalytic cracking, accelerated the degradation process in accordance with general expectations and in straight run diesel (SRD) and hydrotreated diesel (HTD), aliphatic olefins were shown to have no effect on stability. However, contrary to expectations, the aliphatic olefins inhibited the degradation process of light waxy gas oil (LWGO). The effect of aliphatic isomers on the degradation of LCO is in the order of terminal olefins < internal olefins < branched chain olefins. The effect of aliphatic olefinic isomers on LWGO is, on the other hand, in the order of terminal olefin > internal olefins > branched chain olefins. Three possible mechanisms to explain the effect of aliphatic olefins on the LCO and LWGO samples are proposed.

  12. Two-stage production of olefins utilizing a faujasite structure zeolite in hydrogenation stage

    SciTech Connect

    Kreuter, W.; Mansmann, M.; Watson, A.; Weber, H.; Wernicke, H.J.

    1980-02-12

    A process is disclosed for the production of olefins in two stages. In the first stage, heavy petroleum fractions are hydrogenated in the presence of hydrogen and a hydrogenation catalyst and, in the second stage, the thus-hydrogenated fractions are subjected to thermal cracking the presence of steam. The improvement comprises employing as the hydrogenation catalyst a zeolite of the faujasite structure combined with elements from groups VIB, VIIB and VIII of the periodic table of the elements, wherein the alkali component of the zeolite is exchanged at least partially for ammonium, hydronium, alkaline earth and/or rare earth ions, and the elements are present in a metallic, ionic, oxidic and/or sulfidic form.

  13. Heteropolytungstate nanoparticles: Microemulsion-mediated preparation and investigation of their catalytic activity in the epoxidation of olefins

    SciTech Connect

    Masteri-Farahani, M. Ghorbani, M.

    2016-04-15

    Highlights: • Keggin type Q{sub 3}PW{sub 12}O{sub 40} nanoparticles were synthesized by using microemulsion system. • The nanoparticles have uniform size of about 25 nm and spherical morphologies. • The prepared nanoparticles act as reusable catalyst in the epoxidation of olefins with H{sub 2}O{sub 2}. - Abstract: Keggin type Q{sub 3}PW{sub 12}O{sub 40} nanoparticles (Q = cetyltrimethylammonium cation) were synthesized in water-in-oil (w/o) microemulsion consisted of water/cetyltrimethylammonium bromide/n-butanol/isooctane. Reaction of Na{sub 2}WO{sub 4}, Na{sub 2}HPO{sub 4} and hydrochloric acid within water containing nanoreactors of reverse micelles resulted in the preparation of Q{sub 3}PW{sub 12}O{sub 40} nanoparticles. The resultant nanoparticles were analyzed by physicochemical methods such as FT-IR spectroscopy, X-ray diffraction, energy-dispersive X-ray analysis, thermogravimetric analyses (TGA-DTA), scanning and transmission electron microscopy and atomic force microscopy which show nearly uniform spherical nanoparticles with size of about 15 nm. Finally, catalytic activity of the Q{sub 3}PW{sub 12}O{sub 40} nanoparticles was examined in the epoxidation of olefins with H{sub 2}O{sub 2}. The prepared nanoparticles acted as recoverable and reusable catalyst in the epoxidation of olefins with H{sub 2}O{sub 2}.

  14. Binary and Ternary Catalytic Systems for Olefin Metathesis Based on MoCl5/SiO2

    NASA Astrophysics Data System (ADS)

    Bykov, Victor I.; Belyaev, Boris A.; Butenko, Tamara A.; Finkelshtein, Eugene Sh.

    Kinetics of α-olefin metathesis in the presence of binary (MoCl5/ SiO2-Me4Sn) and ternary catalytic systems (MoCl5/SiO2-Me4Sn-ECl4, E = Si or Ge) was studied. Specifically, kinetics and reactivity of 1-decene, 1-octene, and 1-hexene in the metathesis reaction at 27°C and 50°C in the presence of MoCl5/ SiO2-SnMe4 were examined and evaluated in detail. It was shown that experimental data comply well with the simple kinetic equation for the rate of formation of symmetrical olefins with allowance for the reverse reaction and catalyst deactivation: r = left( {k_1 \\cdot c_α - k_{ - 1} \\cdot c_s } right) \\cdot e^{ - k_d \\cdot tilde n_{tot} } . The coefficients for this equation were determined, and it was shown that these α-olefins had practically the same reactivity. It was found that reactivation in the course of metathesis took place due to the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5-6% of the amount of Mo) and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The role of individual components of the catalytic systems was revealed.

  15. Methanol and ethanol conversion into hydrocarbons over H-ZSM-5 catalyst

    NASA Astrophysics Data System (ADS)

    Hamieh, S.; Canaff, C.; Tayeb, K. Ben; Tarighi, M.; Maury, S.; Vezin, H.; Pouilloux, Y.; Pinard, L.

    2015-07-01

    Ethanol and methanol are converted using H-ZSM-5 zeolite at 623 K and 3.0 MPa into identical hydrocarbons (paraffins, olefins and aromatics) and moreover with identical selectivities. The distribution of olefins as paraffins follows the Flory distribution with a growth probability of 0.53. Regardless of the alcohol, the catalyst lifetime and selectivity into hydrocarbons C3+ are high in spite of an important coke content. The coke that poisons the Brønsted acid sites without blocking their access is composed in part of radical polyalkylaromatics. The addition of hydroquinone, an inhibitor of radicals, to the feed, provokes an immediate catalyst deactivation.

  16. Polymerization process

    SciTech Connect

    Kostelnik, R.J.

    1987-03-03

    An improved process is described for preparing a hydrocarbon fluid friction reducing composition comprising mixing two or more alpha-monoolefins having 2 to about 30 carbon atoms in a diluent or an organic solvent and copolymerizing the alpha-monoolefins in the presence of a catalyst. The catalyst is comprised of a reducible or reduced titanium halide and an organo metal catalyst activator consisting of, per each 100 total moles of activator, about 1 to 20 moles of at least one trialkylaluminium compound, each alkyl group of which has 1 to 10 carbon atoms and about 99 to 80 moles of at least one dialkylaluminium halide compound, each alkyl group of which has 1 to about 10 carbon atoms. The mole ratio of activator to catalyst in the reaction mixture is in the range of about 0.001:1 to 50:1.

  17. Application of a silver-olefin coordination polymer as a catalytic curing agent for self-healing epoxy polymers

    NASA Astrophysics Data System (ADS)

    Everitt, D. T.; Coope, T. S.; Trask, R. S.; Wass, D. F.; Bond, I. P.

    2015-05-01

    A silver-olefin based coordination polymer was prepared in a simple, one step process to act as an initiator to facilitate the ring-opening polymerization of epoxides. Thermal analysis found the complex to be capable of curing a range of commercially available epoxy resins used in the manufacture of conventional composite materials. Curing of the oligomeric diglycidyl ether bisphenol A resin, Epon 828, in combination with a non-toxic solvent, ethyl phenylacetate, was studied by differential scanning calorimetry. The mechanical characterization of the resultant cured polymers was conducted by single lap shear tests. Tapered double cantilever beam (TDCB) test specimens containing 2.5 pph of silver-olefin initiator, both with and without embedded microcapsules, were analyzed for their healing performance. Healing efficiency values were found to be strongly dependent on the applied healing temperature. A mean recovery of 74% fracture load was found in TDCB samples after being healed at 70 °C for 48 h.

  18. Decomposition Pathways of Z-Selective Ruthenium Metathesis Catalysts

    PubMed Central

    Herbert, Myles B.; Lan, Yu; Keitz, Benjamin K.; Liu, Peng; Endo, Koji; Day, Michael W.; Houk, K. N.; Grubbs, Robert H.

    2012-01-01

    The decomposition of a Z-selective ruthenium metathesis catalyst and structurally similar analogs has been investigated utilizing X-ray crystallography and density functional theory. Isolated X-ray crystal structures suggest that recently reported C-H activated catalysts undergo decomposition via insertion of the alkylidene moiety into the chelating ruthenium-carbon bond followed by hydride elimination, which is supported by theoretical calculations. The resulting ruthenium hydride intermediates have been implicated in previously observed olefin migration, and thus lead to unwanted byproducts in cross metathesis reactions. Preventing these decomposition modes will be essential in the design of more active and selective Z-selective catalysts. PMID:22500642

  19. Catalysts Encapsulated in Molecular Machines.

    PubMed

    Pan, Tiezheng; Liu, Junqiu

    2016-06-17

    Smart catalysts offer the control of chemical processes and sequences of transformations, and catalysts with unique catalytic behavior can afford chiral products or promote successive polymerization. To meet advanced demands, the key to constructing smart catalysts is to incorporate traditional catalytic functional groups with trigger-induced factors. Molecular machines with dynamic properties and particular topological structures have typical stimulus-responsive features. In recent years, scientists have made efforts to utilize molecular machines (molecular switches, rotaxanes, motors, etc.) as scaffolds to develop smart catalysts. This Minireview focuses on the achievements of developing catalysts encapsulated in molecular machines and their remarkable specialties. This strategy is believed to provide more potential applications in switchable reactions, asymmetric synthesis, and processive catalysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Rhodium catalyzed oxidative coupling of salicylaldehydes with diazabicyclic olefins: a one pot strategy involving aldehyde C-H cleavage and π-allyl chemistry towards the synthesis of fused ring chromanones.

    PubMed

    Jijy, E; Prakash, Praveen; Shimi, M; Pihko, Petri M; Joseph, Nayana; Radhakrishnan, K V

    2013-08-25

    An efficient one pot strategy for the synthesis of cyclopentene fused chromanone derivatives through the direct oxidative coupling of salicylaldehydes with bicyclic olefins in the presence of a rhodium-copper catalyst system is described. This is the first report on the ring opening-ring closing of bicyclic hydrazines via metal catalyzed oxidative coupling reaction.