CATALYTIC CONVERSION OF PROPANE TO AROMATICS - EFFECTS OF ADDING GA AND OR PT TO HZSM-5/

ZSM-5 catalysts without (H) and with added metals (Ga, PtGa, Pt) have been studied for propane conversion and aromatization at 530 degrees C , with the contact time varied by three orders of magnitude. From init ial rate and selectivity determinations, the role of the modifying met als has been ascertained. On metal-free HZSM-5 propane yields equimola r methane and ethylene as well as propylene. Adding metals increases t he rate of propylene formation, as a result of their dehydrogenation a ctivity, which acts additively rather than synergistically. The intrin sic dehydrogenation activity, observed at low conversion and time on s tream, increases in the order Ga < PtGa < Pt. At higher conversion and /or longer time on stream, the reverse order is found for the formatio n of aromatics. It is shown that Pt but not Ga undergoes rapid coke de activation under aromatization conditions. (C) 1994 Academic Press, In c.