Methanol synthesis from CO and CO2 Hydrogenations over supported palladium catalysts

The hydrogenation of CO and CO2 was carried out over palladium catalysts supported on various metal oxides. A significant support effect of Ga2O3 on the methanol synthesis activity from CO2 hydrogenation was observed. On the other hand, a Pd/ZrO2 catalyst showed high methanol synthesis activity from CO hydrogenation. Furthermore, the hydrogenation reaction over Pd/Ga2O3 and Pd/ZrO2 catalysts was investigated by in situ infrared spectroscopy in order to understand the active sites and the reaction mechanism. On the Pd/Ga2O3 catalyst, surface formate and methoxy species were observed during CO and CO2 hydrogenation. In contrast, the reaction pathway was clearly different between CO and CO2 hydrogenation over the Pd/ZrO2 catalyst. That is, surface formaldehyde and methoxy species were observed as intermediates during CO hydrogenation, while surface formate and methoxy species were detected during CO2 hydrogenation. It was thus found that the reaction mechanisms of methanol synthesis from CO and CO2 hydrogenation were strongly dependent on the types of supports over the Pd catalysts.