Partial oxidation of methane into syngas with oxygen permeating ceramic membrane reactors

Abstract

Partial oxidation of methane (CH4 +1/2O2 ⇌ CO + 2H2) is considered as an alternative reforming reaction to steam reforming for production of syngas. This reaction is a slightly exothermic reaction and produces syngas of H2/CO = 2, which is suitable for the synthesis of hydrocarbon or methanol. In this paper, the catalytic partial oxidation of CH4 with a membrane reactor using oxygen permeating ceramic, in particular, LaGaO3-based oxide, is reported. Supported Ni or Rh catalysts are active and selective for this reaction. On the other hand, a mixed ionic and electronic conducting (MIEC) ceramic membrane is useful for obtaining pure oxygen from air when the gradient in oxygen partial pressure is obtained. As for a MIEC membrane, mixed electronic–oxide ionic conductors of Fe- or Co-based perovskite oxides are widely investigated. However, the improvement in stability in a reducing atmosphere is critically required for the MIEC membrane for the application to the membrane reactor for CH4 partial oxidation. Perovskite oxides of LaGaO3 doped with Sr for a La site and a Fe, Co, or Ni for a Ga site, respectively, are promising as the oxygen-separating membrane for CH4 partial oxidation because of high stability in a reducing atmosphere as well as high permeability of oxygen. The partial oxidation of CH4 with solid oxide fuel cells (SOFCs) is also described. Simultaneous generation of electrical power and syngas is demonstrated by the fabricated fuel cell type reactor using a LaGaO3-based oxide electrolyte.