Catalysis of Organic..

Griffin, Johnston, Prétôt and van der Schaaf 34739. Supported Heteropoly AcidCatalysts for Friedel-Crafts AcylationKenneth G. Griffin 1 , Peter Johnston 1 , Roger Prétôt 2and Paul A. van der Schaaf 21 Johnson Matthey plc, Catalyst Development, Royston, SG8 5HE, UK2 Ciba Specialty Chemicals Inc., CH-4002 Basel, SwitzerlandAbstractjohnsp@matthey.comThe liquid phase Friedel-Crafts acylation of thioanisole with iso-butyric anhydride toproduce 4-methyl thiobutyrophenone has been studied using supported silicotungsticacid catalysts. Reaction is rapid, giving the para-acylation product in high yield.Reactions have been performed in both batch slurry and trickle bed reactors. In bothreactors catalyst deactivation due to strong adsorption of product was observed.IntroductionThe Friedel-Crafts acylation of aromatic compounds is an important synthesis routeto aromatic ketones in the production of fine and specialty chemicals. Industriallythis is performed by reaction of an aromatic compound with a carboxylic acid orderivative e.g. acid anhydride in the presence of an acid catalyst. Commonly, eitherLewis acids e.g. AlCl 3 , strong mineral acids or solid acids e.g. zeolites, clays areused as catalysts; however, in many cases this gives rise to substantial waste andcorrosion difficulties. High reaction temperatures are often required which may leadto diminished product yields as a result of byproduct formation. Several studiesdetail the use of zeolites for this reaction (1).In this paper we report the use of supported heteropoly acid (silicotungstic acid)and supported phosphoric acid catalysts for the acylation of industrially relevantaromatic feedstocks with acid anhydrides in the synthesis of aromatic ketones. Inparticular, we describe the acylation of thioanisole 1 with iso-butyric anhydride 2 toform 4-methyl thiobutyrophenone 3. The acylation of thioanisole with aceticanhydride has been reported in which a series of zeolites were used as catalysts.Zeolite H-beta was reported to have the highest activity of the zeolites studied (41mol % conversion, 150 o C) (2).