PLATINUM PROMOTING EFFECTS IN PT GA ZEOLITE CATALYSTS OF LOWER ALKANEAROMATIZATION .2. THE CATALYTIC PROPERTIES IN N-BUTANE AROMATIZATION,FORMATION OF THE CATALYTICALLY ACTIVE-SITES AND REACTION-MECHANISM/

Catalytic properties of a series of Ga- and Pt-Ga-containing zeolites of ZSM-5 structure in n-butane aromatization have been studied in wide range of reaction conditions. The profound Pt promotion has been well established on the basis of product selectivities analysis at differe nt temperatures and contact times but equal conversions. The Pt and Ga synergy was also found to increase significantly selectivity to aroma tics at the account of rapid dehydrogenation and suppressing such side reactions as hydrogenolysis and hydrogenation (Pt), cracking and isom erization (Ga). Both far distance effects (hydrogen spillover) and int imate contact between Pt particles and reduced Ga (1) ions seem to be responsible for the enhancement of aromatization activity and stabilit y of Pt-Ga zeolite catalysts. Active sites involve Pt, Ga1+ and proton ic zeolite centers which formation and structure were considered in de tail. Finally, aromatization process scheme was proposed to find out m ost important steps controlled by Pt and Ga active sites.