KINETIC MODELING OF ETHENE AND PROPENE AROMATIZATION OVER HZSM-5 AND GAHZSM-5

A kinetic model for ethene and propene aromatization over HZSM-5 and G aHZSM-5 is developed. This model describes olefin oligomerization and cracking on zeolite catalytic sites (ZCS), diene formation via hydroge n transfer on ZCS and via dehydrogenation on gallium species, diene cy clization on ZCS, and formation of cyclic diolefins and aromatics via hydrogen transfer on ZCS and via dehydrogenation on gallium species. T he rate constants of various reaction steps are compared, and the cont ribution of gallium in formation of dienes and aromatics is estimated. It is shown that aromatics formation accelerates olefin conversion du e to the olefin consumption, on one hand, and inhibits olefin conversi on due to the partial blocking of the zeolite catalytic sites, on the other hand. Because of this, both the increase and the decrease in ole fin conversion over GaHZSM-5 can be observed (in comparison with HZSM- 5), depending on the feed olefin and on the reaction conditions.