Organocatalytic upgrading of biorefining building blocks and subsequent transformation to liquid fuels

摘要

Owing to their unique ability to dissolve lignocellulosic biomass and related carbohydrates under relatively mild conditions, plus several other concurrent advantages (e.g., as designable and recyclable solvents with low volatility and toxicity), ionic liquids (ILs) such as 1-alkyl(R)-3-methyl(M)imidazolium(IM) chloride salts, [RMIM]Cl, have attracted rapidly growing interest, particularly in the pursuit of renewable energy and sustainable chemicals from plant biomass. For instance, ILs enabled homogenous hydrolysis of cellulose to sugars in high to quantitative conversion, with or without additional catalyst, and catalyzed conversion of glucose or cellulose into the biomass platform chemical 5-hydroxymethylfurfural (HMF), a key and versatile biorefining building block for value-added chemicals and liquid fuels. Upgrading of HMF can be achieved by acid-catalyzed etherification, metal-catalyzed transformations such as hydrogenation/hydrogenolysis to 2,5-dimethylfuran, a liquid fuel with a 40% higher energy density than ethanol, and aldol condensation with enolizable organic compounds followed by dehydration/hydrogenation into C9 to C_(15) liquid alkanes (fuels), thus upgrading it into the kerosene/jet fuel range (C_(12) to C_(15)). Direct coupling of two HMF molecules would make a C_(12) biofuel intermediate, but HMF or furfural cannot undergo aldol self-condensation because they possess no α-H.