Selective CO<sub>2</sub> Hydrogenation to Methanol\nby Halogen Deposition over a Cu-Based Catalyst

The hydrogenation\nof carbon dioxide to methanol represents\na promising\npathway for both mitigating greenhouse gas emissions and producing\nvaluable platform molecules. CuO-ZnO-Al<sub>2</sub>O<sub>3</sub> (CZA)\nis the catalyst used for the methanol production from CO<sub>2</sub> due to its high activity under relatively mild conditions. Coproduction\nof CO reduces the methanol selectivity in CO<sub>2</sub> hydrogenation.\nIn this work, the CZA catalyst has been promoted with halogens (Br,\nCl, or I) using halobenzene precursors. The promotion with bromine\nsignificantly improves the methanol selectivity compared to the pristine\ncatalyst. The effect was observed at different amounts of halogen\ndeposited over the catalyst surface. A combination of characterization\ntechniques and kinetic analysis enabled us to explain the effects\nof halogen on the catalytic performance. The presence of varying halogen\namounts in the CZA catalyst enhances methanol selectivity in two ways:\nby suppressing the reverse water–gas shift reaction and by\nhindering methanol decomposition to CO.