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

摘要

The operation of a packed-bed memgrane reactor (PBMR) was analyzed in comparison to a conventional fixed-bved reactor (FBR) for the oxidation of ethane over a VO_x/gamma-Al_2O_3 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 uing 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 thecombination of catalytically active membranes and catalyst particles.This provides a large catalytically active surface area and allows to suppress possible wall reactioins with the alumina membrane yielding only OC_x.No soot formation was observed during the experiments.The presented results show that,if the reaction kinetics is known,membrane reactors can be o9ptimized for various objectives.