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 ∼130 to ∼560 N l h−1 gcat−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 H2 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 °C), whereas the perovskite-based catalysts showed a quick Tin decrease and Tout increase, anyway not exceeding 1200 °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.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (137 K)Download as PowerPoint slideHighlights► Ni/Al2O3 and LaNiO3-based with Ni → Co and Co → Pt substitutions for partial oxidation in SCT reactors. ► Ni/Al2O3 presented very good CH4 conversion (>86%), stable by varying WHSV. ► Ni–La perovskites showed low performances: not active species La2O3, Ni0, NiO and CoO were detected.