Catalysis Today, Vol.171, No.1, 84-96, 2011
Catalytic partial oxidation of CH4 with nickel-lanthanum-based catalysts
The aim of this work, concerning with the partial oxidation of methane to syngas in a self-sustained short contact time reactor using pure oxygen as oxidant, was the development of perovskite-based nickel-lanthanum (LaNiO3 with Ni partially substituted by Co and Pt) catalysts and the comparison of their performance with that of 5% nickel on alumina catalyst. The prepared catalytic materials were arranged in a fixed bed and the activity tests were carried out by increasing the WHSV from similar to 130 to similar to 560 N l h(-1) g(cat)(-1). Perovskite-based catalysts were characterized by performances lower than that of 5% Ni/Al2O3. The very low perovskites catalytic performance towards the partial oxidation of methane was mainly due to the high reducibility of their structures into La2O3, metallic Ni, and Ni oxides; moreover, La and Ni species further reacted with the CPO reaction products CO2 and H2O leading thus to the formation of the poorly active species La(OH)(3), La2NiO4 and La2O2CO3. On the contrary, 5% Ni/Al2O3 catalyst showed a very satisfactory CH4 conversion always above 85%, remaining stable by varying WHSV. The same trend was noticed for H-2 and CO selectivity, both around 90%. Furthermore, as concerns the bed temperature by increasing WHSV, 5% Ni/Al2O3 catalyst presented quite stable Tin and Tout (the latter around 1200-1250 degrees C), whereas the perovskite-based catalysts showed a quick Tin decrease and Tout increase, anyway not exceeding 1200 degrees C. The good performance and high thermal stability of 5% Ni/Al2O3 catalyst was probably related to the arrangement of the nickel particles, which resulted somehow thermally protected as partially embedded in the alumina carrier. (C) 2011 Elsevier B. V. All rights reserved.