Effect of preparation method on Indium-based materials, and their activity for CO2 hydrogenation to methanol

Methanol synthesis through CO2 hydrogenation reaction seems to be a promising approach to mitigate the excess of CO2 anthropogenic emissions in the atmosphere and substitute the traditional syngas-based CH3OH synthesis process. In2O3 has recently attracted growing interest as a highly selective and stable catalyst for this reaction, and zirconia has been reported as a potential support to significantly improve In2O3 catalytic activity. In this work, the effect of the preparation methods on the material and catalytic properties of both pure In2O3 and mixed In2O3-ZrO2 were investigated. Three main methods were employed, namely the solution combustion, urea hydrolysis, and coprecipitation using three different precipitating agents (ammonia solution, sodium carbonate, and sodium oxalate). Additionally, the role of Pd was also studied with a series of In2O3-ZrO2-Pd samples prepared by the urea hydrolysis method. The preparation method and the composition strongly influenced the physicochemical properties of the materials and their catalytic performances. In general, the ZrO2 introduction significantly improved the performance of the pure In2O3. Pd played a role as a promoter although the effect was not significantly pronounced in the tested samples due to a substantially narrow range of the Pd loadings. Indeed, among the In2O3-ZrO2-Pd samples, the max yield of methanol at 300 °C was obtained with the sample IZP-0.50, having a medium loading among the three tested catalysts. The absolute max yield of methanol production was achieved with the catalyst prepared with the coprecipitation using sodium carbonate at 300 °C which was comparable with those reported in the literature: this catalyst had a STY of 107.54 mmol gIn^(-1) h^(-1).