Methanol carbonylation with metal/zeolite catalysts

Fuller, G.P., 2002. Methanol carbonylation with metal/zeolite catalysts. PhD, Nottingham Trent University.

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The industrial production of acetic acid currently uses a homogeneous methanol carbonylation process that requires the presence of a halide promoter. The commercially viable formation of further products, e.g. ethanol, via this route is restricted by the halide impurities in the intermediate acetic acid. Considering the growing importance of methanol, as a feedstock from natural gas, over that of the established petrochemical resources, there is an incentive for the development of a halide free acetic acid process. Heterogeneous catalysts, especially protonated zeolites incorporating copper, have previously been reported to produce acetic acid by methanol carbonylation, in the absence of a halide promoter, and these form the basis of this work. The carbonylation of methanol, has been carried out here in a fixed bed reactor under conditions typically of 350°C, 8 bar gauge and a CO : methanol ratio of 8.8 : 1. The two main aims of the work have been to determine (i) the role of copper and (ii) the effect of the zeolite’s pore structure. Mordenite zeolites of different silica/alumina ratios were studied both in their proton and copper forms. Copper was introduced using several techniques, including ionexchange, impregnation and solid state exchange. It was found that copper significantly promoted the proton form only when it was introduced by ion-exchange. Examples o f zeolites with different framework structures, e.g. ZSM-5, theta, and beta, were similarly studied in both their proton and copper forms. It was confirmed that the unique pore structure of mordenite, large pores containing narrow side pockets, was the most productive for methanol carbonylation. On comparing the reactivity of the different catalysts tested, this work concludes that the carbonylation of methanol occurs at Bronsted acid sites and is therefore in direct competition with hydrocarbon formation. Furthermore, if the Bronsted acid sites are isolated from each other, e.g. in the narrow channels of H/theta, then the carbonylation reaction is promoted. Conversely, high concentrations of methanol activated in the channel intersections of H/ZSM-5 or H/beta cause the preferential formation of hydrocarbons.

Item Type: Thesis
Creators: Fuller, G.P.
Date: 2002
ISBN: 9781369312645
Divisions: Schools > School of Science and Technology
Record created by: Jill Tomkinson
Date Added: 24 Aug 2020 13:10
Last Modified: 31 May 2021 15:17

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