Enhanced 1,2-propanediol production from glycerol using bimetallic Ni–Cu catalysts on different supports

Abstract

The activity of Ni–Cu bimetallic catalysts on various commercial supports (SiO₂–Al₂O₃ and SiO₂) and synthesized pristine supports (AlO(OH), Al-TUD-1 and meso-TiO₂) in glycerol dehydration-hydrogenation for the formation of 1,2-propanediol (1,2-PD) was investigated. The catalytic performance of bimetallic Ni–Cu on various supports was evaluated, with the Ni–Cu/AlO(OH) catalyst exhibiting a superior activity, achieving 79.5% selectivity for 1,2-propanediol at 90.2% glycerol conversion. The results were promising, revealing that the bimetallic 25 wt% Ni–10 wt% Cu catalyst incorporated Lewis acidity, significantly enhancing the selectivity for 1,2-propanediol in the glycerol dehydration-hydrogenation process. This high performance could be attributed to the well-dispersed Ni and Cu nanoparticles on AlO(OH), the mesoporous structure of AlO(OH) with a large pore structure, and the presence of sufficient acid sites on the catalyst. Acid site analysis revealed that metal loading generally reduced Lewis acidity, while Brønsted acidity showed a slight increase, suggesting a shift in the catalytic mechanism influenced by metal-support interactions. Comparative analysis exhibited that synthesized supports like meso-TiO₂ and Al-TUD-1 offered high Lewis acid sites due to their mesoporous frameworks. However, AlO(OH) stood out due to its unique surface hydroxyl groups and moderate acidity, promoting metal–support interactions and catalyst stability. The findings suggest the importance of support selection in the design of bimetallic catalysts for maximizing glycerol conversion and 1,2-PD production.