High-pressure CO, H2, CO2 and Ethylene Pulses Applied in the Hydrogenation of CO to Higher Alcohols over a Bulk Co-Cu Catalyst

The reaction pathways of higher alcohol synthesis over a bulk Co-Cu catalyst (Co : Cu=2 : 1) were investigated by applying high-pressure pulse experiments as a surface-sensitive operando method at 280 degrees C and 60 bar. Using high-pressure CO and H-2 pulses in a syngas flow with a H-2:CO ratio of 1, it was shown that the surface of the working 2CoCu catalyst is saturated with adsorbed CO, but not with adsorbed atomic hydrogen, because only the H-2 pulses increased the yields of all alcohols and alkanes. The reverse water gas shift reaction (WGSR) was investigated by pulsing CO2. The CO2 pulses poisoned the formation of methanol, ethanol, and 1-propanol, and the absence of significant CO and H2O responses indicates that the WGSR is not efficiently catalyzed by the applied 2CoCu catalyst excluding the presence of exposed Cu-0 sites. A series of ethylene pulses showed that when a threshold mole fraction of ethylene of about 1 vol % is surpassed, 2CoCu is an active catalyst for the hydroformylation of ethylene to 1-propanol pointing to the presence of highly coordinatively unsaturated Co sites