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

The performance of Cu/ZnO/Al 2 O 3 (CZA) catalysts promoted by addition of CeO 2 , MnO 2 or ZrO 2 in direct methanol production from unconventional syngas was experimentally investigated. The unconventional syngas used in this study contain 25% H 2 , 25% CO, 20% CH 4 , 20% CO 2 and 10% N 2 , 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 CeO 2 or ZrO 2 to the CZA catalyst improved the methanol yield, albeit with lower selectivity, whereas adding MnO 2 enhanced methanol selectivity but decreased the methanol yield. ZrO 2 ‐promoted catalyst showed the best‐improved activity and stability. The calcined and spent catalysts were characterised using X‐ray diffraction (XRD), N 2 physisorption, N 2 O chemisorption, hydrogen temperature‐programmed reduction (H 2 ‐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 Cu 0 /Cu + ratio. In contrast, catalyst stability was related to the proportion of Cu + among all surface Cu species.