Direct conversion of CO2 into methanol over promoted indium oxide-based catalysts

Supported indium oxide catalysts are investigated for the CO2 hydrogenation to methanol at a total pressure of 40 bar (528–573 K) using a laboratory flow reactor. Surface reducibility, optical spectral characteristics, and catalytic rates and selectivity were correlated to catalyst composition. Promoted catalysts, especially Yttrium or Lanthanum-promoted indium oxide, require higher temperatures (H2-TPR) for surface reduction and display higher CO2 desorption temperatures (CO2-TPD). The promoted samples also have ˜20% higher methanol selectivity compared to the non-promoted catalyst, while having similar methanol formation rates (0.330–0.420 gMeOH gcat.−1 h−1 at 573 K). From 528 K to 558 K, methanol selectivity was over 80%, over all the promoted catalysts, and nearly 100% selectivity was observed at the low temperature range (˜528 K) investigated. The reaction kinetics of Y-promoted catalyst and the results of CO co-feeding experiments suggest that formate pathway is the likely reaction mechanism for methanol formation.