CONVERSION OF LIGHT ALKANES TO AROMATIC-HYDROCARBONS .2. ROLE OF GALLIUM SPECIES IN PROPANE TRANSFORMATION ON GAHZSM5 CATALYSTS

The conversion of propane into benzenic compounds was studied at 530°C on a series of GaHZSM5 catalysts prepared by impregnation of HZSM5 with a solution of gallium nitrate. Gallium species increase the rate of propane conversion and the sensitivity for aromatics. These species have dehydrogenating activity, increasing both propane activation and naphthene aromatization. The conversion of propane into benzenic compounds on GaHZSM5 catalysts can be considered, therefore, as a bifunctional process in which dehydrogenation reactions are catalyzed by the gallium species and oligomerization and oligomer cyclization by the acid sites. The active gallium species seem to be gallium oxide dispersed in the zeolite rather than gallium cations in an exchange position.