Methanol and C2 oxygenate synthesis over cesium doped Cu/ZnO and Cu/ZnO/Al2O3 catalysts: A study of selectivity and 13C incorporation patterns

Cesium formate significantly promotes methanol and C2 oxygenate (methyl formate MF and ethanol EtOH) synthesis over the CuZnO catalyst. 13C NMR analysis of the product obtained from 13CH3OH and 12COH2 shows that MF is formed by direct carbonylation of methanol and EtOH is formed by coupling of oxygenated C1 intermediates originating from methanol. The C1 coupling mechanism overrides various CO insertion paths to ethanol over the present Cs/Cu/ZnO catalyst. The kinetic significance of C1 aldehydic species such as adsorbed formyl and formaldehyde is supported by experimental evidence and theoretical calculations.