INSITU FOURIER-TRANSFORM INFRARED INVESTIGATION OF THE INTERACTION OF CO-CO2-H2 WITH CU CATALYSTS AT LOW-TEMPERATURES AND HIGH-PRESSURES

The adsorption and reaction of a CO-CO2-H-2 mixture on supported Cu catalysts has been investigated by in situ Fourier-transform infrared spectroscopy using a high-pressure cell. The results show that methanol can be synthesized at low temperatures under conditions where none of the expected reaction intermediates (formate, methoxy) are observed. When the pressure is lowered, a Cu methoxy species was observed, but Cu formate was never detected. The consequences of these observations with regard to the mechanism of methanol synthesis on Cu catalysts is considered. The fact that none of the expected reaction intermediates are observed under conditions where methanol is synthesized has important consequences in relation to the use of chemical scavenging techniques for the study of reaction mechanisms, and this point is discussed briefly.