Oxidative coupling of methane was studied with La/MgO catalyst and a distributed oxygen feed through mixed-conducting dense membrane tubes in a shell-and-tube reactor configuration. A SrFeCo0.5O3 membrane was tested, and, a blank 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-combustion material BaCe0.6Sm0.4O3 were only partially successful, giving 7% yield 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 material, BaCe0.8Gd0.2O3, and it was confirmed that this was not a total oxidation catalyst. Yields to C-2 products of up to 16.5% were obtained, higher than those in comparable fixed bed studies. The C-2 yield obtained is the highest reported in the literature for oxidative coupling of methane in dense membrane reactors. The flux of oxygen through both dense membranes increased under reaction conditions, by a factor of four, over the non-reaction flux measured in permeation 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.