Synergetic effects of hydrogenation and acidic sites in phosphorus-modified nickel catalysts for the selective conversion of furfural to cyclopentanone

Abstract

Cyclopentanone (CPO) is a value-added chemical that can be produced from furfural via hydrogenation coupled with an acid-catalysis step. Developing an effective bi-functional catalyst remains a challenge to be overcome. In this study, phosphorus was introduced to Ni/Al₂O₃ to modify the distribution of acidic sites and to tailor the activity of the metal sites for hydrogenation, with the aim of developing an active and cost-effective transition-metal-based catalyst for the conversion of furfural to CPO. The results showed that phosphorus species could react with both alumina and metallic nickel, forming an AlPO₄ phase and nickel phosphide species. The formation of the AlPO₄ phase reduced the specific area of the catalyst and increased the abundance of acidic sites. The formation of nickel phosphide species (Ni₂P, Ni₃P, and Ni₁₂P₅) tailored the selectivity of the hydrogenation sites. Furfural was only hydrogenated to furfuryl alcohol (FA), while further hydrogenation to tetrahydrofurfuryl alcohol (TFA) was inhibited. The introduced acidic sites further catalyzed the conversion of the formed FA to CPO. The balanced distribution of the hydrogenation sites and the acidic sites, as well as their tailored activity for hydrogenation and acid-catalyzed reactions, was crucial for the selective conversion of furfural to CPO.