Activity of bimetallic PdIn/CeO2 catalysts tuned by thermal reduction for improving methanol synthesis via CO2 hydrogenation

Abstract

Synergistic Pd–In₂O₃ catalysts are promising candidates for producing methanol via CO₂ hydrogenation, and the metal phases in them can be tuned by thermal reduction treatment affecting the catalytic activity significantly. This work presents a comprehensive investigation to gain an insight into the effect of thermal reduction temperature on the variation and interaction of Pd and In₂O₃ phases supported on CeO₂ (viz., PdIn/CeO₂) and their correlations with CO₂ hydrogenation toward methanol synthesis. The findings show that Pd/In-rich PdIn alloys and In₂O₃ with relatively strong interaction are key phases (by reducing the PdIn/CeO₂ at 300°C) for promoting methanol formation, leading to a high selectivity to methanol at 78.9% and space–time yield (STY) of 3.6 g_CH3OH g_PdIn⁻¹ h⁻¹. A further increase in reduction temperature (from 300 to 500°C) promoted the formation of homogenized PdIn intermetallic alloys with significantly poor ability for H₂ dissociation and CO₂ activation, and hence poor methanol yield.