Effects of promoters (Mg, Zr, Y, Ce) on LDH-derived NiAl nanosheets for low-temperature CO2 methanation

Abstract

Development of highly active Ni-based catalysts for low-temperature CO<inf>2</inf> methanation is challenging. In this work, layered double hydroxides (LDHs) with nanosheet structure are employed as effective catalyst precursors. The X-promoter doped NiAl catalysts derived from LDH precursors (X: Mg, Zr, Y, Ce) were synthesized by one-pot hydrothermal method. The catalytic performance of prepared catalysts was evaluated with CO<inf>2</inf> methanation. Among various promoters, the Ce–NiAl catalyst exhibits the highest methanation activity at low temperature, achieving CO<inf>2</inf> conversion of 90 % at 210 °C and GHSV of 16000 cm³ g⁻¹ h⁻¹, compared to Y–NiAl (85 %), Zr–NiAl (75 %), Mg–NiAl (29 %) and pristine NiAl (25 %). The optimized Ce–NiAl catalyst can perform impressive performance in durability test, maintaining CO<inf>2</inf> conversion of 90 % at 210 °C for 200 h. Characterization confirms that the key improved properties are the increased number of weak basic sites and the enhanced concentration of oxygen vacancies, while Ni sintering is suppressed by the preserved strong metal-support interaction. The in-situ DRIFTS experiments reveal that CO<inf>2</inf> molecules converted into bicarbonates and then formates, followed by the formation of CH<inf>4</inf>. The formate pathway is identified as dominant reaction mechanism over the promoted catalyst. This work demonstrates that one-pot hydrothermal is the effective method for the synthesis of Ce–NiAl LDHs, as highly active catalysts for CO<inf>2</inf> methanation at low temperature.