Synergistic effects of heteropoly acids and sulfolane on fractionation and utilization of willow

Efficient pretreatment to decrease the recalcitrance of lignocellulosic biomass is considered to be an essential precondition for lignocellulosic valorization. In this study, the heteropoly acids (i.e., phosphotungstic acid, silicotungstic acid and phosphomolybdic acid) assisted sulfolane organosolv pretreatment was developed to reduce the recalcitrance of willow ( Salix matsudana cv. Zhuliu ) for effective saccharify cation and the subsequent lignin valorization. The pretreatment notably increased the accessibility of cellulose with a high glucose yield of 94.77%. The 75.60% of lignin was recovered from the willow with silicotungstic acid assisted sulfolane organosolv pretreatment at 150 °C for 1.5 h. In addition, the recovered lignin had high purity (∼98%), moderate molecular weight (3378–3585 g/mol), low polydispersity (∼2.0) and good antioxidant properties (the RSI value was 1.18). Lignin nanospheres (LNSs) with different morphologies were prepared by separating lignin, which increased the potential application of lignin. Overall, the heteropoly acids assisted sulfolane pretreatment proved to be a promising approach for enzymatic hydrolysis of cellulose and lignin valorization. • Effects of pretreatment process are improved compared with the condition without catalyst. • Glucan digestibility reach to 94.7%. • Lignin reaches a purity of 98.0% and an extraction ratio of 75.6%. • Lignin has better antioxidant activity than commercial antioxidant butylated hydroxytoluene (BHT). • Lignin nanospheres (LNSs) with different morphologies were prepared, which increased the potential application of lignin.