In-Situ FTIR Studies On Cobalt-Rhenium Based Catalysts for Conversion of Syngas to Oxygenates

Syngas is a potential source of ethanol, which can be used as energy carrier or fuel additive. Selecting a suitable catalyst for the conversion of syngas to oxygenates, particularly C2-oxygenates has been well-studied. Rhodium-based catalysts have consistently shown the highest selectivity for C2-oxygenates. However, the high cost of rhodium has led to efforts to develop catalysts based on less costly metals.

Silica-supported cobalt catalysts modified by rhenium and zirconium have been found to be active for the synthesis of C2-oxygenates in the work reported here. The catalyst was synthesized by co-impregnation using Zr-modified-SiO2 support. The catalyst was characterized by TPR, COTPD, ICP-MS, SEM, XRD, in-situ FTIR and BET surface area. In-situ FTIR studies were carried out at elevated pressures. Results at 5 bar show more chemisorbed CO species on the surface compared to that at atmospheric pressure, as expected. More importantly, linearly adsorbed CO at this higher pressure was found to be shifted towards lower wavenumbers compared to that at atmospheric pressure, indicating a stronger adsorption at higher pressures. After heating the sample to high temperature while maintaining the high pressure, to remove the chemisorbed CO, spectra were taken during decreasing pressures. These spectra show appearance of chemisorbed CO species which were linearly attached to the surface. These species probably appeared as a result of trapped gaseous CO at higher pressures, which comes over to the surface when the pressure is reduced.