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Abstract: Reactor modules consisting of four gas-tight microtubular membranes made of the mixed oxygen ion and electron conducting perovskite, La0.6Sr0.4Co0.2Fe0.8O3−δ have been tested for oxygen permeation and hydrogen production by membrane-based steam reforming, i.e., simultaneous syngas production coupled with water splitting. The membranes were subjected to two known axial temperature profiles in the temperature of 900°C. The microtubes showed good stability under reaction conditions, operating over a total operation period of ca 400h of oxygen permeation followed by ca 400h of steam reforming. An induction period of approximately 30h was observed before steam reforming commenced. Both the methane and water side outlet gas compositions were measured which allowed for accurate material balance; this indicated that the hydrogen production occurred due to oxygen flux across the membrane and not just surface reaction. Post operation analysis of the microtubes revealed the presence of a strontium enriched dense layer on the water exposed membrane surface and of crystallites enriched with cobalt and sulfur on the methane feed side surface. [Copyright &y& Elsevier]