Deactivation behaviour of intermetallic Ga‐Ni catalyst in CO2 hydrogenation to methanol

Abstract The chemical conversion of greenhouse gas CO 2 to environmentally benign compounds, especially alternative fuels like methanol, is an inevitable solution to the global warming problem. The intermetallic catalysts exhibit superior catalytic activity compared to the monometallic ones but suffer from loss of activity during the reaction. Herein, we report the influence of the preparation method on the deactivation behaviour of Ga 3 Ni 5 catalyst in CO 2 hydrogenation to methanol. The Ga 3 Ni 5 catalyst was prepared through three different methods. The spent catalysts from the reactor were characterized by X‐ray diffraction, transmission electron microscopy‐energy dispersive X‐ray spectroscopy (TEM‐EDX), Brunaue‐Emmett‐Teller (BET), H 2 ‐pulse chemisorption, and Fourier‐transform infrared spectroscopy (FTIR) technique to evaluate the cause and nature of deactivation. After 250 hr of CO 2 hydrogenation, all catalysts had lost about 50% of their initial activity due to the erosion of active sites. The nanoparticle dispersion was found to increase in the order Ga 3 Ni 5 ‐CE< Ga 3 Ni 5 ‐IWI < Ga 3 Ni 5 ‐CP. The activity of catalysts during methanol synthesis (at 473 K, 20 bar) initially depicted a similar trend. However, the selectivity to methanol remained comparatively high for the catalysts prepared by the co‐precipitation method. The loss of activity in Ga 3 Ni 5 catalysts was mainly attributed to the metal sintering and a lesser extent, by coke deposition. The kinetics of deactivation was studied based on the normalized dispersion, and the deactivation rate constant was estimated using the power‐law kinetic rate model. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.