EFFECT OF PRELIMINARY HEAT-TREATMENT ON THE CATALYTIC ACTIVITY AND SELECTIVITY OF H-PENTASILS, GA-PENTASILS AND ZN-PENTASILS IN CONVERSIONSOF C4 HYDROCARBONS

A study has been made of the catalytic properties of H-, Ga- and Zn-pe ntasils calcined in air at 600-1000-degrees-C in conversions of isobut ane and isobutylene. It has been shown that, by varying the treatment temperature t(tr), it is possible to control the catalytic activity of pentasils and the selectivity of formation of aromatization, dehydrog enation and cracking products. The conditions of dehydrogenation of is obutane on Zn-pentasil with a selectivity of >70% have been establishe d. IR spectroscopy of adsorbed pyridine has been used to study the aci dic properties of pentasils, and the high thermal stability of aprotic acid centres formed as a result of modification of the zeolite matrix with zinc or gallium has been found. On the basis of catalytic and sp ectral data, the role of Bronsted and Lewis acid centres in the accele ration of individual stages of conversion of low-molecular weight para ffins and olefins on decationized and modified pentasils is discussed.