Furfural is a natural precursor to furan-based chemicals and has the potential to become a major renewable platform chemical for the production of biochemicals and biofuels. However, current industrial furfural production relies on relatively old and inefficient strategies that have hindered its capacity, and low production yields have strongly diminished its competitiveness with petroleum-based alternatives in the global market. This mini-review provides a critical analysis of past and current progress to enhance furfural production from lignocellulosic biomass. First, important chemical and fuel products derived from the catalytic conversion of furfural are outlined. We then discuss the importance of developing integrated production strategies to co-produce furfural with other valuable chemicals. Furfural formation and loss chemistries are explored to understand effective methods to improve furfural yields from pentosans. Finally, selected relevant commercial and academic technologies that promise to improve lignocellulosic furfural production are discussed.

A novel single phase co-solvent system using tetrahydrofuran (THF) promotes hydrolysis of maple wood to sugars, sugar dehydration, and lignin extraction simultaneously and achieves higher overall yields of the fuel precursors furfural, 5-hydroxymethylfurfural (HMF), and levulinic acid (LA) than previously reported from biomass. In a one-pot reaction, we obtained yields of 86% furfural, 21% HMF, and 40% LA in the liquid phase and over 90% extraction of lignin as a solid powder. The co-solvent reaction also produced a glucan-rich residue that is highly digestible by enzymes for biological conversion to ethanol or further thermochemical reaction to additional HMF and levulinic acid. These findings enable an integrated conversion platform in which THF is both a co-solvent and final co-product to enhance production of fuel precursors for catalytic upgrading to renewable liquid hydrocarbons fuels. † Electronic supplementary information (ESI) available. See

5-(Hydroxymethyl)furfural (HMF) and furfural (FF) have been identified as valuable biomass-derived fuel precursors suitable for catalytic hydrodeoxygenation (HDO) to produce high octane fuel additives such dimethyl furan (DMF) and methyl furan (MF), respectively. In order to realize economically viable production of DMF and MF from biomass, catalytic processes with high yields, low catalyst costs, and process simplicity are needed. Here, we demonstrate simultaneous coprocessing of HMF and FF over Cu−Ni/ TiO 2 catalysts, achieving 87.5% yield of DMF from HMF and 88.5% yield of MF from FF in a one pot reaction. The Cu−Ni/TiO 2 catalyst exhibited improved stability and regeneration compared to Cu/TiO 2 and Cu/Al 2 O 3 catalysts for FF HDO, with a ∼7% loss in FF conversion over four sequential recycles, compared to a ∼50% loss in FF conversion for Cu/Al 2 O 3 and a ∼30% loss in conversion for Cu/TiO 2. Characterization of the Cu−Ni/TiO 2 catalyst by X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and H 2 −temperature-programmed reduction and comparison to monometallic Cu and Ni on Al 2 O 3 and TiO 2 and bimetallic Cu−Ni/Al 2 O 3 catalysts suggest that the unique reactivity and stability of Cu−Ni/TiO 2 derives from support-induced metal segregation in which Cu is selectively enriched at the catalyst surface, while Ni is enriched at the TiO 2 interface. These results demonstrate that Cu−Ni/TiO 2 catalysts promise to be a system capable of integrating directly with a combined HMF and FF product stream from biomass processing to realize lower cost production of liquid fuels from biomass.

We introduce a new pretreatment called co-solvent-enhanced lignocellulosic fractionation (CELF) to reduce enzyme costs dramatically for high sugar yields from hemicellulose and cellulose, which is essential for the low-cost conversion of biomass to fuels. CELF employs THF miscible with aqueous dilute acid to obtain up to 95 % theoretical yield of glucose, xylose, and arabinose from corn stover even if coupled with enzymatic hydrolysis at only 2 mgenzyme  gglucan (-1) . The unusually high saccharification with such low enzyme loadings can be attributed to a very high lignin removal, which is supported by compositional analysis, fractal kinetic modeling, and SEM imaging. Subsequently, nearly pure lignin product can be precipitated by the evaporation of volatile THF for recovery and recycling. Simultaneous saccharification and fermentation of CELF-pretreated solids with low enzyme loadings and Saccharomyces cerevisiae produced twice as much ethanol as that from dilute-acid-pretreated solids if both were optimized for corn stover.