The effect of the catalytic layer design on oxidative dehydrogenation of propane over monoliths at short contact times

Abstract

Main factors determining performance of straight channel corundum monolith supported catalysts in the autothermal reaction of propane oxidative dehydrogenation at short contact times are verified. It was made possible by using a unique design of the catalytic reactor which allows an independent tuning of the gas preheat temperature and the catalyst temperature. It is also equipped with a cooled sampler to cut any homogeneous reactions after the catalyst layer. The effects of the front and back thermal shields, feed rate, relative contact time and the void space between the catalytic monoliths or after them are elucidated. The performance of the monolithic catalyst is compared with that crushed and packed into a granulated layer. A substantial impact of the homogeneous gas-phase reactions on the propane conversion and product selectivities is demonstrated. In turn, their share depends upon the longitudinal temperature gradient within the monolithic layer as determined by the heat generation in the inlet part due to propane combustion by oxygen, its transfer along the monolith layer and consumption in the rear part of the monolith in the absence of oxygen through endothermic reactions of dehydrogenation, cracking and steam reforming. In the autothermal mode of the propane oxidative dehydrogenation at short contact times on monolithic catalysts, the effect of those factors is as important as that of the catalyst and feed chemical composition.