Gold catalysts polymers

Direct Oxidation of Propylene to Propylene Oxide. Comparison of ethylene (qv) and propylene gas-phase oxidation on supported silver and silver—gold catalysts shows propylene oxide formation to be 17 times slower than ethylene oxide (qv) formation and the CO2 formation in the propylene system to be six times faster, accounting for the lower selectivity to propylene oxide than for ethylene oxide. Increasing gold content in the catalyst results in increasing acrolein selectivity (198). In propylene oxidation a polymer forms on the catalyst surface that is oxidized to CO2 (199—201). Studies of propylene oxide oxidation to CO2 on a silver catalyst showed a rate oscillation, presumably owing to polymerization on the catalyst surface upon subsequent oxidation (202). 

In the book, the section on homogeneous catalysis covers soft Pt(II) Lewis acid catalysts, methyltrioxorhenium, polyoxometallates, oxaziridinium salts, and N-hydroxyphthalimide. The section on heterogeneous catalysis describes supported silver and gold catalysts, as well as heterogenized Ti catalysts, and polymer-supported metal complexes. The section on phase-transfer catalysis describes several new approaches to the utilization of polyoxometallates. The section on biomimetic catalysis covers nonheme Fe catalysts and a theoretical description of the mechanism on porphyrins. 

Y. Xia, Z. Shi and Y. Lu, Gold microspheres with hierarchical structure/ conducting polymer composite film preparation, characterization and application as catalyst. Polymer 51, 1328-1335 (2010). 

Keywords gold clusters, gold catalysts, porous cooidination polymers, A(-alkylation... 

Gold catalysts can be used in a solventless liquid-phase system to oxidize cyclohexane to cyclo-hexanol and cyclohexanone using oxygen. Almost all the cyclohexane produced (4.4 million tonnes per annum, and expected to grow at ca. 3%) is converted to cyclohexanol and cyclohexanone, the intermediates in the production of caprolactam and adipic acid, used in the manufacture of nylon-6 and nylon-66 polymers, respectively. The present commercial process for cyclohexane oxidation is carried out at around 423 K and 1-2 MPa over a catalyst such as cobalt naphthenate with approximately 4% conversion and 70-85% selectivity to cyclohexanol and cyclohexanone [66,67,93]. 

Polymer-immobilised catalysts containing gold particles smaller than 10 nm have been prepared by impregnating Merck Ion Exchanger IV with HAuCU, and have been used to synthesise ureas and carbamates by reaction of amines with carbon monoxide and oxygen 16 so for example the oxycarbonylation of aniline proceeded at 448 K and 5 MPa pressure (C0 02 = 2 l) in 1-3 h to give yields of up to 99% of phenylmethyl-carbamate (Scheme 13.3). 

A gold-palladium catalyst which includes potassium acetate is very well established for the production of vinyl acetate monomer (VAM) from ethene, acetic acid and oxygen in selectivities as high as 96% (see Section 8.4). VAM is an important intermediate used in the production of polyvinyl acetate, polyvinyl butyral and a variety of other polymers, and the gold-catalysed process followed many years of industrially focused research and patent activity in a number of large industrial companies 39-43... 

Thiols also provide good binding points toward a metal surface such as gold for the synthesis of polymer brushes, etc. A protected initiator (FI-24) gave thiol-functionalized PMMA with Ni-2 as a catalyst.334 The thiophene-capped PMMA from FI-25 can be employed as a macromonomer for electrochemical copolymerization with pyrrole,335 as with those from FI-20 (see above). 

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