Operation modes of packed-bed membrane reactors in the catalytic oxidation of hydrocarbons

The operation of a packed-bed membrane reactor (PBMR) was analyzed in comparison to a conventional fixed-bed reactor (FBR) for the oxidation of ethane over a VOx/gamma-Al2O3 catalyst (1.4% V) as a model reaction. In most of the cases conversions were higher in the PBMR compared to the FBR. Based on the different concentration and contact time profiles, three operation modes for the PBMR were identified, selective oxidation mode with low oxygen to hydrocarbon ratios, CO favoring mode and deep oxidation mode using large oxygen excess. All modes offer advantages compared to the FBR operated under similar conditions because they increase selectivity of the desired product. In selective oxidation mode in the PBMR a maximum ethylene yield of 33% was obtained compared to 22% in the FBR. For selective oxidation mode, it should be recommended the combination of catalytically active membranes and catalyst particles. This provides a large catalytically active surface area and allows to suppress possible wall reactions with the alumina membrane yielding only CO,. No soot formation was observed during the experiments. The presented results show that, if the reaction kinetics is known, membrane reactors can be optimized for various objectives. (C) 2003 Elsevier B.V. All rights reserved.