Sol-gel synthesis and application of NiO, NiTiO3 and Ni5TiO4(BO3)2 on open-cell TiO2 foams for CO2 methanation

Abstract

Bottleneck of fixed-bed reactors for methanation in a Power-to-Methane (PtM) context is a reliable thermal-management due to the exothermic nature of the reaction under dynamic operation. Novel titania (TiO2) open-cell foam supports with promising heat, mass, and momentum transfer properties and Ni-based catalytic coatings are presented on a technical scale. The coating with promising catalyst candidates NiO, NiTiO3 and Ni5TiO4(BO3)2 is conducted by a scalable sol–gel synthesis. Ni5TiO4(BO3)2 is known as a promising tar removal catalyst, but shows no activity for the methanation reaction. Despite a low BET-surface area, high-loaded (57 wt% Ni) mixed-oxide NiO/NiTiO3 (∼57% NiO/∼43% NiTiO3) shows promising results. Adjusted activation with respect to high-temperature strong metal support interactions (SMSI) leads to a methane-yield close to equilibrium at 400 °C (CO2 conversion: 75%, CH4 selectivity: 99%). The catalyst is stable under realistic methanation conditions for at least 120 h of operation and outperforms an industrial catalyst (20 wt% Ni-Al2O3) above 400 °C. This study reveals the underestimated potential that lies in transition metal-supported foam catalysts for direct methanation and is fundamental for further research regarding temperature control for dynamic PtM processes.