Infrared studies of the adsorption of synthesis gas on zirconium dioxide

The adsorption of CO, CO2, H2, HCOOH, and CH3OH was studied over ZrO2 using FTIR. Bicarbonate, formate, and methoxide species were observed. Bicarbonate was the major species formed from CO2 and was converted into formate in the presence of sufficient hydrogen. Formate was observed following CO adsorption even in the absence of hydrogen. The formate was reduced to methoxide in the presence of hydrogen. The different behavior for CO/H2 and CO2/H2 demonstrated that different mechanisms should be proposed for CO versus CO2 hydrogenation over ZrO2. Formate to methoxide conversion was reversible. Experiments conducted with D2O revealed that surface OH (OD) groups participate in formate formation and in formate to methoxide conversion.