Aviation biofuel range cycloalkane from renewables: Liquid-phase catalytic conversion of menthol on niobia-supported catalysts

Renewable terpene biomass has attracting interest for producing high energy density fuel, particularly cycloalkane in the range of jet fuels. In this contribution, catalytic conversion of menthol to p-menthane was systematically investigated. Noble metals (Pt, Pd and Ru) supported on a Lewis-BrOnsted acidic oxide (Nb2O5) were explored, considering the effects of reaction temperature and the balance between acid and metal sites. Catalysts kinetics were quite distinct, and Pd-based catalyst rendered the most active one. Yields of p-menthane of around 90% were determined over Pt and Pd catalysts, while it was only similar to 70% on Ru/Nb2O5, on which the formation of p-menthene was also observed. These results evidenced that the reaction proceeds as a cascade reaction at which acid-catalyzed menthol dehydration and metal-catalyzed cycloalkene hydrogenation lead to the aimed cycloalkane. Reaction temperature and the balance between acid and metal sites were shown to be the key aspects affecting catalyst performance.