Design and demonstration of an experimental membrane reactor set-up for oxidative coupling of methane

In this experimental research, the performance of the oxidative coupling of methane (OCM) reactions in a porous packed bed membrane reactor was investigated. A commercially available porous alpha-alumina membrane was modified to obtain the characteristics needed for a stable and catalytically inert OCM membrane reactor. The silica-sol impregnation-calcination method and a new silicon oxycarbide (SiOC) coating-calcination approach were applied to modify the membrane. The characteristics of the resulted membrane and its typical performance as OCM membrane reactor are reported. Generally, it was observed that the combination of these modification methods positively contributes in lowering the undesired activity of the membrane due to simultaneous achieving a small pore-volume structure and a homogeneous modified membrane surface. Using a flexible experimental set-up, the effects of operating temperature, methane/oxygen ratio, and nitrogen dilution were investigated. The design specifications of this reactor set-up are also reported in details. It was observed that implementing the proposed membrane modification and applying a proper temperature profile significantly improve the oxygen distribution, the selectivity toward the desired products (C-2) and controlling the hot-spot formation. 18.5% C-2-yield and 57% C-2-selectivity were achieved in low diluted gas stream. Moreover, the performance of the membrane reactor in terms of the selectivity, methane conversion and hot-spot formation was compared with the performance of a fluidized bed reactor. This enables one to analyze the mechanisms through which the operating parameters affect the membrane reactor performance and design an efficient membrane reactor accordingly. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.