Oxidative dehydrogenation of light paraffins in novel short contact time reactors. Experimental and theoretical investigation

A previous study on the selective oxidation of propane over a commercial Pt/Al2O3 catalyst is herein extended to the oxidative dehydrogenation (ODH) of ethane. ODH tests were performed in an annular reactor, wherein catalytic experiments could be performed at varying temperatures on a wider operating field than that characteristic of autothermal reactors; besides, gas-phase experiments were performed for comparison. Together with the results of a theoretical analysis on homogeneous ethane oxidative pyrolysis, the bulk of data indicated that the high-temperature production of ethylene observed in the presence of the catalyst could be well explained by the single contribution of gas-phase radical reactions. The catalyst was proved to be active, instead, in the non-selective oxidation of paraffins to CO,. Further tests in an insulated millisecond contact time reactor demonstrated that the catalytic combustion reactions could be exploited to ignite the gas-phase reactions; comparison with the simulations of a purely homogeneous adiabatic reactor showed that at the highest temperatures the observed ethylene yields were close to the maximum obtainable values. (C) 2001 Elsevier Science Ltd. All rights reserved.