Hydrogen production via steam reforming of methanol on Cu/ZnO/ Al₂O₃ catalysts: Effects of Al₂O₃ precursors

A series of Cu/ZnO/Al₂O₃ catalysts were prepared by co-precipitation method. This research focuses on investigating the influence of different Al₂O₃ precursors on the catalyst structure through thorough structural characterization techniques. Additionally, the catalytic performance of these catalysts in methanol reforming for hydrogen production was systematically evaluated. The results indicate that the simultaneous co-precipitation of Al³⁺ with Cu²⁺ and Zn²⁺ leads to partial substitution of Cu-Zn in the basic carbonates by Al³⁺. This substitution forms a hydrotalcite-like structure and strengthens Zn-Al interactions. On the contrary, after the co-precipitation of Cu²⁺ and Zn²⁺, introducing the Al₂O₃ precursor has a positive effect on eliminating the adverse effects of Al³⁺ on Cu-Zn substitution in basic carbonates. This process promotes the Cu-ZnO interaction, facilitates the dispersion of CuO species, and enhances the reducibility of catalysts. It also improves the dispersion of Cu on the surface, and ultimately enhanced the catalytic activity. Notably, the catalyst prepared using pseudo-boehmite as the Al₂O₃ precursor exhibited the highest activity. Under the conditions of a H₂O/CH₃OH molar ratio of 1.2 and a reaction temperature of 493 K, methanol conversion reached 94.8%, and the H₂ space-time yield was 97.5 mol/(kg·h). The catalyst activity remained relatively stable after continuous operation for 25 h. Even after being heat-treated at 723 K for 10 h, the activity loss of the catalyst was only 5.37%.