Oxidative dehydrogenation of ethane over a Pt-coated monolith versus Pt-loaded pellets: Surface area and thermal effects

The catalytic performance of Pt-coated gamma-Al2O3 pellets is compared to the performance of a Pt-coated alpha-Al2O3 monolith in the oxidative dehydrogenation of ethane to ethylene at short contact times. The use of the high surface area gamma-Al2O3 support has a detrimental impact upon the production of the desired reactive intermediate, C2H4. The porous nature of the high surface area pellet support reduces the selectivity to intermediate products (C2H4) in favor of complete combustion. The axial and radial temperature profiles of the monolith and packed bed were examined to better understand the difference in catalytic performance of the two catalyst configurations. The radial temperature profile for the Pt-coated gamma-Al2O3 pellets shows hot spot formation along the center-line of the catalyst bed which leads to lower C2H4 selectivity and can lead to thermal runaway. However, the radial temperature profile of the Pt-coated alpha-Al2O3 monolith is fairly flat across the monolith with a slight temperature drop between the edge of the catalyst and the reactor wall. This more uniform catalyst temperature leads to a higher production of C2H4. (C) 1998 Academic Press.