Conversion of cellulose to hydrocarbon fuels by progressive removal of oxygen

Cellulose is converted in a series of cascade reactions to 5-nonanone, a hydrophobic intermediate that can be catalytically upgraded to diesel and jet fuels. [Display omitted] ▶ Cellulose deconstruction has been demonstrated using a strategy that enables the accumulation of levulinic and formic acid to high levels (e.g., 20wt%). ▶ γ-Valerolactone can be produced selectively by hydrogen transfer between formic acid and levulinic acid over a 5wt% Ru/C catalyst in the presence of sulfuric acid. ▶ Extraction of γ-valerolactone has been demonstrated with ethyl acetate, enabling recycle of the sulfuric acid solution and eliminating the need of costly neutralization and disposal steps. ▶ Conversion of γ-valerolactone to 5-nonanone has been demonstrated over a dual catalyst bed consisting of Pd/Nb2O5 and ceria-zirconia. We report a catalytic process to convert cellulose into liquid hydrocarbon fuels (diesel and gasoline), using a cascade strategy to achieve the progressive removal of oxygen from biomass, allowing the control of reactivity and facilitating the separation of products. The process starts with the deconstruction of solid cellulose in an aqueous solution of sulfuric acid yielding an equi-molar mixture of levulinic acid and formic acid. The formic acid in this mixture can then be used (upon decomposition to H2 and CO2) to reduce levulinic acid to γ-valerolactone (GVL) in the sulfuric acid solution over a Ru/C catalyst. The formation of GVL allows strategies for the separation and recycling of the sulfuric acid used in the cellulose deconstruction step. This GVL product, with residual amounts of sulfur, can be upgraded to 5-nonanone with high yields (90%) in a single reactor by using a dual catalyst bed of Pd/Nb2O5 plus ceria-zirconia. The 5-nonanone product is hydrophobic and separates spontaneously from water, yet possesses a functional group that can be used to control the structure and molecular weight of hydrocarbon fuel components formed in downstream catalytic upgrading treatments.