Ethane aromatization on Ga-Pt/HZSM-5 zeolites prepared by solid-state modification

The results of a comparative study of the catalytic properties of gallium and platinum pentasil (ZSM-5) zeolites, prepared according to the solid-state modification and impregnation techniques, in the ethane aromatization reaction are reported. It has been found that the procedure for the preparation of bimetallic catalysts has no substantial effect on their activity and selectivity for aromatic hydrocarbons. The formation of the active sites of the catalysts obtained by solid-state modification was investigated with the use of X-ray diffraction and X-ray photoelectron spectroscopy, and it has been supposed that Ga-Pt clusters similar to the species revealed earlier in bimetallic pentasil catalysts prepared by impregnation are produced as a result of topochemical reactions involving hydrogen. Based on the catalytic and physicochemical data, a reaction scheme for the ethane aromatization on Ga-Pt/HZSM-5 is proposed, which suggests the involvement of bimetallic clusters in a key step, the dehydrogenation of ethane followed by the formation of ethylene oligomers and their dehydrocyclization.