B-modified Pd/ZnAl₂O₄ Catalyst for Enhancing CO₂ Hydrogenation to Methanol

Palladium (Pd)-based catalysts are widely used for CO₂ hydrogenation reactions due to the capability to activate H₂, which enhances the overall CO₂ conversion. However, most of the current Pd catalysts reported show high CO₂ conversion only at higher temperature, and the exploration of efficient catalyst enabling low temperature conversion (180–300 °C) is of importance. In this study, a series of Pd-B/ZnAl₂O₄ catalysts were synthesized via in-situ doping, resulting in the Pd crystal transformation induced from crystal to amorphous. The catalytic hydrogenation activity of the amorphous Pd-B catalyst reaches its zenith at a Pd-B mole ratio of 1:2, accompanied by the superior catalysis stability in CO₂ hydrogenation. Various characterization techniques, including XRD, CO-DRIFTS, H₂-TPR, XPS and TEM, were used to investigate the properties of the Pd-B/ZnAl₂O₄ catalyst. The results showed that the Pd-B/ZnAl₂O₄ catalyst exhibited higher dispersion and better CO₂ conversion efficiency compared to unmodified Pd catalyst. Additionally, the methanol space–time yields are nearly doubled when the B decoration is employed. At 280 °C, CO₂ conversion was improved and methanol selectivity remained at ~ 65%. This study provides valuable insights into the design and optimization of Pd-B based catalysts for CO₂ hydrogenation at low temperatures.