Direct conversion of n-butane to isobutene over Pt-MCM22

The dehydroisomerization of n-butane to isobutylene is a challenging reaction. It has to be carried out > 750 K due to thermodynamic constraints of dehydrogenation. Pt-ZSM5 is a good catalyst for the dehydroisomerization of n-butane, but has high selectivity to by-products at high conversions stemming from oligomerization/cracking of butylenes on the acid sites. MCM22, a microporous material with a layered structure, is a very active and selective catalyst for the skeletal isomerization of butylene. Pt-MCM22 gives good results in the dehydroisomerization of n-butane ≤ 775 K and achieves higher yields of isobutylene than Pt-ZSM5. The formation of cracking products is low. MCM22 can also be utilized as an isomerization catalyst in combination with Pt-ZSM5 to increase the yield of isobutylene in dehydroisomerization. However, a disadvantage of the MCM22 materials is their moderate stability, particularly at higher temperatures. Partial dealumination of the framework occurs during calcination/reduction of Pt-MCM22, leading to enhanced deactivation by coking.