Development of highly selective In2O3/ZrO2 catalyst for hydrogenation of CO2 to methanol: An insight into the catalyst preparation method

Abstract

This study explored the potential of In2O3/ZrO2 catalyst for direct CO2 hydrogenation to methanol. Despite the excellent properties proven by density functional theory (DFT) studies, the experimental works on this catalyst are still very limited. In this study, In2O3/ZrO2 catalysts were synthesized via wetness impregnation (In2O3/ZrO2(WI)), citric acid-based sol-gel method (In2O3/ZrO2(SG)) and deposition-precipitation assisted by urea hydrolysis (In2O3/ZrO2(UH)). Results indicated the impressive effect of preparation method on the catalytic activity where In2O3/ZrO2(SG) presented superior catalytic performance, followed by In2O3/ZrO2(UH) and In2O3/ZrO2(WI), with the CO2 conversion of 16.23%, methanol selectivity of 94.39% and STY of 0.95 gmethanol/gcat·h. To unravel the structure-function relationship, several characterization techniques including XRD, HR-TEM, SEM-EDX, H2-TPR, CO2-TPD, N2 adsorption-desorption isotherm and XPS were implemented to analyze the developed catalysts. The analyses indicated that the excellent performance of In2O3/ZrO2 (SG) was due to its smaller crystallite size, strong metal-support interaction, high reducibility and high concentration of basic sites and oxygen vacancies on the catalyst surface. Time-on-stream stability test showed that In2O3/ZrO2 (SG) catalyst could sustain its high activity and selectivity within 100 h, signifying the high potential of this catalyst for direct hydrogenation of CO2 to methanol with minimum side reactions and deactivation.