Alkylation on synthetic zeolites: II. Selectivity of p-xylene formation

Abstract

The influence of the calcination temperature and the degree of cation exchange of NH 4-Y, and the addition of hydrogen chloride to Mn-Y zeolite, in relation to the selectivity of p-xylene formation, was studied for the alkylation reaction of toluene with methanol. It was found that within a certain range of calcination temperature ( i.e., 400–550 °C), p-xylene can be obtained selectively. A proportional relation between the catalytic activity and the selectivity of p-xylene with the degree of cation exchange was also observed. The addition of hydrogen chloride to Mn-Y zeolite has shown a promoting effect in p-xylene selectivity. These behaviors of the treated catalysts can be related to Brönsted acidity. It has also been shown that the alkylation reaction was dominant, while the isomerization reaction of the produced xylene (under the conditions employed) was depressed. It has been established that the p-xylene selectivity is a function of Brönsted acidity.