| Summary: | The work contained in this thesis covers the sulfonylation reaction between toluene and one of methanesulfonic anhydride and methanesulfonyl chloride. The desired products of these reactions are the three isomers (onho. meta and para) of methyl tolyl sulfone and the by-products are methanesulfonic acid, when methanesulfonic anhydride was used as the sulfonylating agent, and hydrogen chloride when methanesulfonyI chloride was the sulfonylating agent. When this reaction was carried out using the traditional Friedel-Crafts catalyst, AlCl) the thermodynamic isomer ratio of 60 % ortlw, 30 % para and 10 % meta was obtained. The aim of this work was to increase the selectivity of the sulfonylation reactions to the para isomer as this was required by the industrial partner (Zeneca) for use in further reactions. The two sulfonylation reactions were carried out over a range of catalysts including Alell , a silica-alumina, a montmorillonite clay and several zeolite catalysts. The main catalyst studied was zeolite Beta as in an empirical test of a range of catalsyts it had given the greatest percentage of para isomer, with a selectivity of 60 per cent obtained under certain conditions. Reaction times, temperatures and stoichiometry were amongst the variables investigated for their role in the reaction. It was found that the reaction had an initial induction period whichever solid-acid catalyst was used, and also that the reaction stopped by twenty four hours, presumably due to catalyst coking. Yields of methyl tolyl sulfone of up to fifty per cent with a selectivity of sixty per cent for the para isomer were obtained using zeolite Beta with some catalysts giving higher yields but correspondingly lower para selectivities. The catalysts were studied using a variety of analytical techniques. The analysis of the catalysts, particularly for a series of well-characterised zeolite Y’s, was compared to the catalysis results and several interesting trends were observed. The Sil Al ratio of catalysts did not have a consistent effect on the yield or selectivity, however the amount of extra› framework aluminium was shown to have a near-linear relationship to the yield. The disproportionate yield in the sulfonylation reaction for zeolite Beta was linked to the ability of zeolite Beta, much investigated recently, to have very mobile aluminiums either in the framework or dislodging from the framework. These act as Lewis acid sites.
|
|---|
