Low-pressure methanol synthesis from CO2over metal-promoted Ni-Ga intermetallic catalysts

Abstract

Ni-Ga and M-Ni-Ga (M=Au, Co, Cu) catalysts were evaluated for methanol synthesis from CO2 at 10 bar and 200-270 °C. The following trend in turnover frequency (TOF) for CO2 hydrogenation was observed: AuNiGa > CuNiGa > NiGa > CoNiGa, where TOF increased with decreasing catalyst affinity for CO. The presence of a third metal was found to influence both the formation of the Ni-Ga intermetallic phase as well as the number of available sites for CO chemisorption. Phase formation, catalyst composition and stability were evaluated using therm ogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning transmission electron microscopy and energy dispersive X-ray spectroscopy (STEM-EDX). Au-Ni-Ga, which showed a nearly 4-fold improvement in TOF at 263 °C and 10 bar compared to Ni-Ga, consisted of Ni3Ga particles decorated with Au, as evidenced by post catalysis characterization.