Preparation of carbonyl precursors for long-chain oxygenated fuels from cellulose ethanolysis catalyzed by metal oxides

Abstract

Long-chain oxygenated liquid fuels have similar physicochemical properties with diesel fuel, and its oxygen can promote combustion and reduce PM2.5. An approach for the preparation of the precursor from lignocellulose suitable for CC coupling is the key problem to be solved in the production of long-chain oxygenated fuels. In this work, cellulose, as a main component in biomass, was directly alcoholyzed to carbonyl compounds with α-H catalyzed by three typical metal oxides (CaO, MgO and ZnO). The results showed that high temperature was favorable for the conversion of cellulose, but a large number of side products, namely levoglucosan and ethyl-α-D-pyran glucoside, have been detected in liquefied products. These by-products could be transformed into target precursors with α-H over CaO or ZnO with 0.5 mmol at 320 °C in ethanol solvent. Additionally, side reactions of ethanol at elevated temperature could be inhibited with ZnO in water-ethanol co-solvent and the by-products from ethanol dehydration, including 1,1-diethoxyethane, 2-ethoxyethanol, dropped significantly with an increase in carbonyl compounds. Noticeably, compared with pure ethanol, the yield of carbonyl compounds in liquid products increased obviously to 47.4% when the volume ratio of water to ethanol was 3: 10.