Levulinic acid hydrogenolysis on Al2O3-based Ni-Cu bimetallic catalysts

Inexpensive γ-alumina-based nickel-copper bimetallic catalysts were studied for the hydrogenolysis of levulinic acid, a key platform molecule for biomass conversion to biofuels and other valued chemicals, into γ-valerolactone as a first step towards the production of 2-methyltetrahydrofurane. The activities of both monometallic and bimetallic catalysts were tested. Their textural and chemical characteristics were determined by nitrogen physisorption, elemental analysis, temperature-pro-grammed ammonia desorption, and temperature-programmed reduction. The monometallic nickel catalyst showed high activity but the highest by-product production and significant amounts of carbon deposited on the catalyst surface. The copper monometallic catalyst showed the lowest activity but the lowest carbon deposition. The incorporation of the two metals generated a bimetal-lic catalyst that displayed a similar activity to that of the Ni monometallic catalyst and significantly low by-product and carbon contents, indicating the occurrence of important synergetic effects. The influence of the preparation method was also examined by studying impregnated- and sol-gel-derived bimetallic catalysts. A strong dependency on the preparation procedure and calcina-tion temperature was observed. The highest activity per metal atom was achieved using the sol-gel-derived catalyst that was calcined at 450 °C. High reaction rates were achieved;the total levulinic acid conversion was obtained in less than 2 h of reaction time, yielding up to 96%γ-valerolactone, at operating temperature and pressure of 250 °C and 6.5 MPa hydrogen, respec-tively.