Enhancing the catalytic performance of Cu/ZnO/Al2O3 catalyst in methanol synthesis from biomass‐derived syngas with CeO2, MnO2 and ZrO2 as promoters

Abstract

The performance of Cu/ZnO/Al2O3 (CZA) catalysts promoted by addition of CeO2, MnO2 or ZrO2 in direct methanol production from unconventional syngas was experimentally investigated. The unconventional syngas used in this study contain 25% H2, 25% CO, 20% CH4, 20% CO2 and 10% N2, representing biomass‐derived syngas cultivated from an industrial wood chips pyrolysis plant. The catalysts were synthesised using co‐precipitation technique and tested for methanol synthesis in a fixed‐bed reactor. The activity test of the catalysts showed that the addition of CeO2 or ZrO2 to the CZA catalyst improved the methanol yield, albeit with lower selectivity, whereas adding MnO2 enhanced methanol selectivity but decreased the methanol yield. ZrO2‐promoted catalyst showed the best‐improved activity and stability. The calcined and spent catalysts were characterised using X‐ray diffraction (XRD), N2 physisorption, N2O chemisorption, hydrogen temperature‐programmed reduction (H2‐TPR) and X‐ray photoelectron spectroscopy (XPS). The characterisation results indicate that the catalytic activity is dependent on Cu dispersion, Cu‐active surface area, the catalyst reducibility, Brunauer–Emmett–Teller (BET) surface area and the Cu0/Cu+ ratio. In contrast, catalyst stability was related to the proportion of Cu+ among all surface Cu species.