abstract
Minor additions of alumina into perovskite-type SrFe0.7Al0.3O3-delta, a composition close to the solid solution formation limits in SrFe1-xAlxO3-delta system, result in decreasing thermal expansion and increasing oxygen permeability. The improved sinterability of SrFe0.7Al0.3O3-based composite with 3 wt.% Al2O3 addition enables to fabricate high-quality tubular membranes for the methane conversion reactors. No essential degradation in the performance of SrFe0.7Al0.3O3-delta membranes under air/CH4 or air/H-2-H2O gradients at 973-1223 K was observed during 200-700h. The stable operation under high oxygen chemical potential gradients is possible due to surface-limited oxygen transport, indicated by the dependencies of oxygen permeability on the membrane thickness. Applying porous layers of the same composition, synthesized via cellulose-precursor technique, onto the permeate-side surface leads to substantially higher oxygen fluxes. For a model reactor with the surface-modified SrFe0.7Al0.3O3-delta membrane and commercial Ni/Al2O3 catalyst, the CH4 conversion rate achieved 90-97% at 1073-1123 K, when the CO selectivity was almost 100%. (c) 2005 Elsevier B.V. All rights reserved.
keywords
PARTIAL OXIDATION; REDUCING ATMOSPHERE; METHANE; PEROVSKITE; SYNGAS; CONDUCTIVITY; REACTORS; SURFACE; EXPANSION; TRANSPORT
subject category
Engineering; Polymer Science
authors
Kharton, VV; Shaula, AL; Snijkers, FMM; Cooymans, JFC; Luyten, JJ; Yaremchenko, AA; Valente, AA; Tsipis, EV; Frade, JR; Marques, FMB; Rocha, J
our authors
Aleksey Yaremchenko
Principal Researcher
Anabela Tavares Aguiar Valente
Principal Researcher
Anabela Tavares Aguiar Valente
Principal Researcher
Fernando Manuel Bico Marques
Full professor
João Rocha
Full Professor
Jorge Ribeiro Frade
Retired Professor