Catalysis of Organic..

Griffin, Johnston, Prétôt and van der Schaaf 351consistent with previous reports describing strong product adsorption as the cause forcatalyst deactivation in anisole acetylation over similar catalysts (6,7).Fixed Bed ReactionReaction was also investigated in a fixed bed reactor under trickle flowconditions to investigate whether reaction under flow conditions would affect therate of catalyst deactivation. Conversions and selectivities are shown in Table 5.Rapid deactivation of the catalyst was observed with concomitant progressivedarkening of the catalyst bed indicative of strong adsorption (retention) of materialon the catalyst and resulted in a lower catalyst productivity compared to equivalentreaction in a batch slurry reactor.Table 5. Acylation of thioanisole with iso-butyric anhydride in a trickle bed reactor.Conditions: 60 o C, 42%STA/silica, 4.0g, Liquid WHSV = 33h -1 .Reaction ConversionProduct selectivity / %TOL 2/ min / % o-Ketone p-Ketone 3 Vinyl ester Side prods11 99.9 1.3 92.2 0.3 3.823 94.1 1.2 91.3 0.4 7.134 92.7 1.2 90.5 0.4 7.945 91.0 1.4 91.0 0.6 7.0Average 95.1 1.3 91.2 0.4 7.1Other Acylation ReactionsThe activity of 42%STA/silica catalysts for the acylation of related aromaticreactants with iso-butyric anhydride was investigated. In the presence of anisole andveratrole, 100% anhydride conversion was observed, leading to the expected paraacylationproducts. No reaction was observed in the presence of chlorobenzene andother deactivated aromatic systems.ConclusionsThe results reported in this paper show that supported STA catalysts are efficientcatalysts for the acylation of thioanisole and related activated aromatic molecules inthe presence of iso-butyric anhydride as the acylating agent. The para- substitutedketone isomer is the major acylation product. Optimal catalyst activity is in the rangeof 60 o C to 90 o C. Use of either lower STA concentrations or use of weaker acids egphosphoric acid, decreases the reaction rate and selectivity; this results in greaterhydrolysis of the anhydride. Use of supported STA catalysts is more efficient thanbulk STA since the reaction medium is much cleaner and enables easier removal ofthe catalyst.