Effect of aluminum proportion on the Cu/ZnO/Al₂O₃ methanol-synthesis catalyst

The objective of this work is to investigate the effect of Al contents on the performance of methanol-synthesis catalysts. A series of catalyst samples with various Al contents were prepared with fractional precipitation method, and characterized with methods including XRD, TG-MS, XRF, N₂ physisorption and H₂-TPR. Results show that Al addition affected the subcarbonate structure in precursors, which promoted the formation of high temperature carbonates, and thus has an effect on the catalyst performance. With Al addition, the BET surface area of the calcined catalysts, catalyst activity and thermostability increased to different degrees. When the molar ratio of Al³⁺ in catalyst increased to 30%, the CO conversions before and after heat treatment were 76% and 67%, respectively, at the conditions of 230 ℃, 4 MPa and syngas composition of 13%CO, 1.2%CO₂, 80%H₂ and 5.8%Ar. The catalyst sample with 0.3 of Al³⁺/(Cu²⁺+Zn²⁺+Al³⁺) molar ratio remains good catalyst performance.