Correlations between the catalyst properties and catalytic activity of Au on ZrO2-CeO2 in the hydrogenation of CO2

To exploit the potential of both ZrO2 and CeO2, the mixed oxides with Ce content up to 5 wt.% were prepared via the simple coprecipitation method, subsequently loaded with Au catalysts, and investigated in the hydrogenation of CO2. The obtained catalysts, namely Au/ZrCex (x = nCe/nZr = 0.0-0.1), exhibit similar Au content (0.7 wt.%), structural and textural properties, however, considerably different acidic/basic properties and great surface oxygen vacancy. The introduction of Ce leads to slightly decreased CO2 conversion, which was found propor-tional to the Ce content. Interestingly, it is evidenced that the methanol selectivity is closely related to the acidic/ basic properties of the catalysts employed. Over the broad range of acid site density (ASD) ranging from 400 to 700 mu mol g-1, the highest methanol selectivity of 27 % was recorded at 250 degrees C and 40 bar over the catalyst exhibiting an ASD of 600 mu mol g-1, which decreased with further increasing ASD. The volcano-shape trend was also discovered for the base site density showing the critical point at 120 mu mol g-1 over the range from 90 to 210 mu mol g-1. These findings suggest that the acidic/basic properties can be tuned, e.g., via thermal treatment, to tailor the product distribution of the CO2 hydrogenation. Above all, the Au catalysts supported on ZrO2-CeO2 mixed oxides exhibit excellent catalytic stability, e.g., a methanol formation rate of 3.32 gCH3OH center dot (gAu center dot h)- 1 is remained over the reaction course of 93 h at 250 degrees C and 40 bar for Au/ZrCe0.025 sample.