Zeolites modification with rare earths

Studies of the acylation of toluene with La-exchanged zeolite Y has shown the dependence of the activity on the rare-earth cation content and the high selectivity to the para isomer. Activities increasing in the order benzoyl < acetyl < propionyl chloride were found for all catalyst modifications. 

We have now investigated further the importance of the modification of the zeolite on its activity in catalysing the acylation reaction. Of particular interest was the application of the rare-earth (RE) exchanged zeolites to acylation reactions using acid chlorides. Previous studies had either tested the RE modified zeolite systems with the carboxylic acid [3,4] or applied only the H-form of the zeolite to the acid chloride system [5-7]. We were interested in the role of the rare-earth cation in enhancing the activity of the catalyst with the acid chloride. 

Aluminosilicate zeolite ([Al]ZSM-5), borosilicate zeolite ([B]ZSM-5), and iron silicate zeolite ([Fe]ZSM-5), doped with transition metal or rare-earth or noble metal were tested as the catalysts. Different modifications of the zeolite do not improve the olefin conversion. Neither isomorphous substitution of Al atom in the zeolite structure by B or Fe, nor doping the zeolite with metals influences notably the conversion of olefin into the acid compared with [Al]ZSM-5 (Table 23). 

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