Rare earth-first-row transition metal perovskites as catalysts for the autothermal reforming of hydrocarbon fuels to generate hydrogen

Perovskite oxides (ABO(3)) containing rare earth elements on the A-site and first-row transition metal elements on the B-site were studied as catalysts for autothermal reforming of liquid hydrocarbon fuels to produce hydrogen for fuel cell systems. Experiments were conducted in a fixed bed microreactor at temperatures of 600-800 degrees C and gas-hourly space velocities (GHSV) ranging from 4600 to 28,000 h(-1) using 2,2,4-trimethylpentane (isooctane) as a surrogate fuel. We have found that the two binary oxides, LaNiO3 and LaCoO3, produced high yields of H-2, but were not structurally stable. These perovskites decomposed to La2O3 and Ni/NiO or Co/CoO under the reducing conditions present in the reformer. Three other binary oxides, LaCrO3, LaFeO3, and LaMnO3, were structurally stable but significantly less active than LaNiO3 and LaCoO3. The partial substitution of chromium, iron, aluminum, gallium, or manganese on the B-site of LaNiO3 to yield LaBxNi1-xO3 was shown to improve the structural stability without a significant decrease in the H2 yield. The effects of substituting rare earth elements for La and the substitution of alkaline earth elements on the A-site (La(1-y)A(y)B(x)Ni(1-x)O(3)) on catalyst performance and stability were also investigated. Finally, La0.8Sr0.2M0.9Ni0.1O3 catalysts (where M = Cr, Mn, or Fe) were tested with a benchmark fuel mixture containing from 0 to 50 ppmw sulfur. These tests showed that using chromium as a stabilizing element in LaNiO3 imparts the most sulfur tolerance. (c) 2007 Elsevier B.V. All rights reserved.