Simultaneous dehydrogenation and isomerization of n-butane to isobutene over ZSM-22 and zinc-modified ZSM-5 zeolites

Direct formation of isobutene from n-butane was investigated over a zinc-impregnated potassium-ion-exchanged ZSM-5 dehydrogenation catalyst and an acidic shape-selective ZSM-22 skeletal isomerization catalyst. The experiments were performed in a fixed-bed microreactor system operating at near-atmospheric pressure, High selectivity to n-butene was obtained over the zinc-impregnated potassium-ion-exchanged ZSM-5 dehydrogenation catalysts. The yield of isobutene increased after adding the acidic ZSM-22 skeletal isomerization catalyst, although the selectivity to butene isomers slightly decreased because the skeletal isomerization of n-butene was competing with other acid-catalyzed reactions such as cracking and aromatization.