Comparison of catalytic combustion of carbon monoxide and formaldehyde over Au/ZrO2 catalysts

Catalytic combustion reactions of carbon monoxide and formaldehyde are compared over Au/ZrO2 catalysts with varied Au loadings (0.25–4 wt%) and calcination temperatures (110–450 °C). The combustion of CO shows a distinct induction period over most catalysts while the reaction of HCHO proceeds steadily over every catalyst. Catalysts with varied calcination temperatures exhibit the same activity order in both reactions. The catalyst calcined at 200 °C appears to show the highest activity for either of the two reactions, suggesting that the amount of metallic Au and size of Au particles are crucial for both reactions. The mass specific activity (MSA) of Au in those catalysts calcined at 200 °C decreases with increasing Au loading for CO combustion but is almost independent of the Au loadings for HCHO combustion. Moisture (2000 ppm H2O) addition to the gaseous feed of the CO combustion reaction eliminates the induction period, and the MSA of Au turns to be nearly constant and independent of the Au loadings. Possible reasons for the similarities/dissimilarities in gold catalysis for the combustion reactions of CO and HCHO are discussed.