Catalytic combustion of methane in simulated PSA offgas over Mn-substituted La-Sr-hexaaluminate (LaxSr1-xMnAl11O19)

Mn-substituted La, Sr-hexaaluminate was studied as a catalyst for the catalytic combustion of pressure swing adsorption (PSA) offgas from a hydrogen station based on steam reforming of petroleum gas. The catalytic activity and thermal stability were tested under simulated PSA offgas condition and the catalysts were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), CO2-temperature programmed desorption (TPD) and N-2 physisorption for BET. All the LaxSr1-xMnAl11O19 catalysts prepared by co-precipitation method contained hexaaluminate structure as the major phase after 5 h calcination at 1200 degrees C. Partial substitution of La for Sr in SrMnAl11O19 increased the specific surface area and consequently the catalytic activity for oxidation of methane. The CO2 in the simulated PSA offgas was found to suppress the catalytic activity in methane oxidation if the catalyst had appreciable surface basicity. The most active catalyst, La0.6Sr0.4MnAl11O19, retained its lattice structure and chemical composition even after 40-h thermal aging at 1000 degrees C under PSA offgas composition. (C) 2010 Elsevier B.V. All rights reserved.