New Process for the Acid-Catalyzed Conversion of Cellulosic Biomass (AC3B) into Alkyl Levulinates and Other Esters Using a Unique One-Pot System of Reaction and Product Extraction

A one-pot system used for the chemical/catalytic conversion of cellulosic biomass, and the product extraction was developed. The latter phase was carried out by a distillation technique that combines a temperature-programmed heating with a vacuum level-programmed evacuation (technique of mild vacuum-assisted distillation, MVAD). No environmentally harmful solvent was used: only a high boiling paraffin (n-dodecane) was used to help distil the heavy products. The obtained liquid fractions (light and heavy fractions) could be used, after drying and removal of unused alcohol, for blending into gasoline or diesel/biodiesel. Two different conversion procedures were used: ethanolysis (direct acid-catalyzed conversion in ethanol medium) and a sequential procedure, the latter consisting of the acid hydrolysis followed by the esterification of resulting acids with ethanol''. By using wood residues as raw material, the yields in ethyl levulinate and other by-products-with the only exception of diethyl ether (DEE), were quite similar for both procedures. The incorporation of some H-USY zeolite could significantly decrease the yield of DEE in the ethanolysis procedure. Reported results obtained with some other biomass feed-stocks (particularly, switch grass) showed a good relationship between the product levulinate yield and the cellulose content of the raw material.