Oxidative coupling of methane using oxygen-permeable dense membrane reactors

Oxidative coupling of methane was studied with La/MgO catalyst and a distri buted oxygen feed through mixed-conducting dense membrane tubes in a shell- and-tube reactor configuration. A SrFeCo0.5O3 membrane was tested, and, a b lank run confirmed that it acted as a total oxidation catalyst, with no C-2 products. Attempts to coat the inside of the membrane tube with a non-comb ustion material BaCe0.6Sm0.4O3 were only partially successful, giving 7% yi eld to C-2 products. The oxygen flux through the coated tube was reduced to 30% of its original value. A membrane tube was fabricated from a non-combustion oxygen-permeating mate rial, BaCe0.8Gd0.2O3, and it was confirmed that this was not a total oxidat ion catalyst. Yields to C-2 products of up to 16.5% were obtained, higher t han those in comparable fixed bed studies. The C-2 yield obtained is the hi ghest reported in the literature for oxidative coupling of methane in dense membrane reactors. The flux of oxygen through both dense membranes increased under reaction co nditions, by a factor of four, over the non-reaction flux measured in perme ation experiments. Changes in surface morphology were observed for the side of the membrane in contact with the reducing atmosphere. Similar phenomena have been observed in previous studies. (C) 2000 Elsevier Science B.V. All rights reserved.