CO₂ hydrogenation over copper-based hybrid catalysts for the synthesis of oxygenates

Hybrid catalysts made of Cu-based methanol synthesis catalyst and a zeolite were used for the direct formation of oxygenates (methanol + dimethylether (DME)) from CO₂ hydrogenation, and the catalytic behaviors were studied. The activity of hybrid catalyst with NaZSM-5 was the lowest among hybrid catalysts due to its weakest acidity. To convert methanol into DME, moderate acidity rather than weak acidity was preferable. Among hybrid catalysts with Cu/ZnO/ZrO₂, the hybrid catalyst containing H-Ga-silicate showed the highest yield of oxygenates probably due to weak interaction. The hybrid catalyst with SAPO-34 or HZSM-5, which had a higher acid amount due to solid-solid interaction showed a poor yield oxygenates but a higher yield of hydrocarbons than that with H-Ga silicate. The hybrid catalysts with low fraction of zeolite showed better yield for oxygenation. The modification of reducibility or oxygen coverage due to the interactions between methanol synthesis catalyst and zeolite determined the ability of oxygenate synthesis.