Oxidative dehydrogenation of propane over monoliths at short contact times

A specially designed tubular microreactor with independent control of feed preheat as well as catalyst temperature and allowing to rapidly quench reac tion products was used to test performance of supported Pt-based monolithic catalysts in the reaction of propane oxidative dehydrogenation at short co ntact times. To minimize the impact of undesired homogeneous reactions capa ble of decreasing propylene selectivity, proprietary straight-channel thin- wall high cell density corundum micromonoliths were chosen as supports. Cat alytic properties of supported platinum were modified by using promoters kn own as dehydrogenation catalysts (tin, zinc aluminate spinel, transition me tal pyrophosphates) as well as by tuning reaction mixture composition (prop ane/oxygen ratio, water and hydrogen content). In the operation temperature range up to 900 degrees C with contact times similar to 0.03-0.1 s, ethyle ne/propylene selectivities were found to strongly depend upon the chemical composition of the active component and type of feed. The results thus obta ined demonstrate that for Pt-based catalysts, propylene yield can be substa ntially improved by suppressing secondary reactions of deep oxidation and c racking. (C) 2000 Elsevier Science B.V. All rights reserved.