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With the continuous development of society and a serious energy crisis, renewable energy has become highly important. As platform compounds that can produce large amounts of chemical products, 5‐hydroxymethyl furfural (5‐HMF) and levulinic acid (LA) have attracted the attention of many researchers. Production of 5‐HMF and LA with lignocellulose is currently one of the most promising research directions in biomass energy. Conventionally, production of 5‐HMF and LA with lignocellulose is typically performed in aqueous solutions containing dilute mineral acids as catalysts. Recently, advances have been reported in the use of heterogeneous catalysts for conversion of lignocellulose into 5‐HMF and LA in different solvents to eliminate the use of mineral acids. In this paper, the merits, demerits, and requirements for commercialization are outlined for 5‐HMF and LA production from lignocellulose in aqueous solution, and different solvents are reviewed. Special attention is focused on the use of green chemicals (such as γ‐valerolactone) and ionic liquids as solvents due to their clean and recoverable characteristics. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

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In this study, formic acid was selected as the catalyst to pretreat corn stover which is also a good substrate for biohydrogen and biogas production. The pretreatment effect and the acidogenic characteristic of hydrolysates were also evaluated. Using corn stover (8.00 g) mixed with 72.00 g of formic acid (2.5%) at temperature 190 °C for reaction time 10 min, 17.36 ± 0.80 g/L glucose, 18.13 ± 0.83 g/L xylose, 5.45 ± 0.25 g/L arabinose, 3.88 ± 0.17 g/L acetic acid, and 1.96 ± 0.07 g/L furfural were obtained in the hydrolysate. The kinetic parameters of the Saeman model were determined to predict the percentage of xylan remaining in the substrate and the xylose in the liquid. Two kinds of specific hydrolysates (the highest yield of total sugar and highest yield of furfural) in the following acidogenic fermentation experiments were examined. The results indicated that both of the hydrolysates were shown to be butyric acid type fermentation and got the highest VFAs concentration of 6.3 ± 0.48 g/L. Diluted formic acid had good catalytic effects on the hydrolysis of corn stover. The hydrolysates obtained from the pretreatment process could be used as good substrates for acidogenic fermentation process.

Low pollution, slight corrosion, and low cost are the main challenges in the conversion of biomass to biogas. In this work, based on the whole process optimization of biomass conversion, an effective method using an ultra-low concentration of FeCl 2 was proposed to simultaneously promote the biochemical reaction and improve the pretreatment effect. The concentration of FeCl 2 in the pretreatment was determined according to the requirements of the minimum amount which led to the optimal performance of the anaerobic system and had economical importance. The effects of FeCl 2 in the pretreatment and anaerobic fermentation were evaluated by comparing with that of distilled water in the production of hydrolysis products and organic acids. The optimal condition was obtained at 180 • C and 10 min with 1 × 10 −5 mol/L FeCl 2 pretreatment. At that condition, hemicellulose achieved a high conversion of 97.6%, and the released xylose reached nearly 95%. At least 77.5% of the organic matter in the solution can be utilized for subsequent fermentation. FeCl 2 pretreatment also accelerated the anaerobic acidification fermentation process and promoted organic acid yields. The work provided a meaningful and economical choice for the conversion technology of biomass to biogas.