Promoting Methanol Synthesis and Inhibiting CO<sub>2</sub> Methanation with Bimetallic In–Ru Catalysts
Feiyang Geng, Xun Zhan, Jason C. Hicks
Abstract
In this work, we investigated the promotional effects of In on Ru for the synthesis of methanol via CO2 hydrogenation in the liquid phase. Incorporation of In to Ru results in a methanol selectivity of ∼85% at 240 °C and 3.4 MPa (CO2/H2 = 1/3). Additionally, no methane was observed under the conditions studied (200–240 °C). The combination of In and Ru modulates Ru sites geometrically and electronically. X-ray diffraction and X-ray photoelectron spectroscopy provided evidence of the structural evolution from mixed metal oxides to alloy and intermetallic phases and charge transfer from In to Ru, respectively. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy studies using probe molecules (CO2+H2, CO, formic acid, methanol), as well as CO-temperature-programmed reaction and H2-D2 exchange experiments, were conducted to provide insight into the promotional effect of In. With the incorporation of In, surface formate and methoxy species were stabilized to promote the formation of methanol. Methanation, which is a dominant pathway on monometallic Ru, was inhibited with promoter addition.