Catalytic partial oxidation of CH 4 with nickel–lanthanum-based catalysts

Abstract

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 (LaNiO 3 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 ∼130 to ∼560 N l h −1 g cat −1. Perovskite-based catalysts were characterized by performances lower than that of 5% Ni/Al 2O 3. The very low perovskites catalytic performance towards the partial oxidation of methane was mainly due to the high reducibility of their structures into La 2O 3, metallic Ni, and Ni oxides; moreover, La and Ni species further reacted with the CPO reaction products CO 2 and H 2O leading thus to the formation of the poorly active species La(OH) 3, La 2NiO 4 and La 2O 2CO 3. On the contrary, 5% Ni/Al 2O 3 catalyst showed a very satisfactory CH 4 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/Al 2O 3 catalyst presented quite stable T in and T out (the latter around 1200–1250 °C), whereas the perovskite-based catalysts showed a quick T in decrease and T out increase, anyway not exceeding 1200 °C. The good performance and high thermal stability of 5% Ni/Al 2O 3 catalyst was probably related to the arrangement of the nickel particles, which resulted somehow thermally protected as partially embedded in the alumina carrier.