Selective liquefaction of wheat straw in phenol and its fractionation

For the first time, a method of phenol-selective liquefaction is proposed for the fractionation and multilevel conversion of lignocellulose. Through phenol-selective liquefaction, lignin and hemicellulose are liquefied, with large amounts of cellulose retained in the unliquefied residues. Using a phenol/straw ratio of 3 and a sulfuric acid concentration of 3%, large amounts of hemicellulose (≥85%) and lignin (≥70%) can be liquefied at 100 °C in 30 min, with a high quantity of cellulose (≥80%) retained. Unliquefied residues from selective liquefaction have higher susceptibility for enzymatic attack. Enzymatic hydrolyzation of residues can be as high as 65% in 48 h with 40.7 FPU/g of dry materials, which can then be used to prepare sugar platform intermediates. The liquefied products of wheat straw are then resinified with formaldehyde in the presence of NaOH as a catalyst and synthesized into phenol formaldehyde-type resins reaching up to GB/T 14732-2006 standards. Phenol selective liquefaction, a new technology for the fractionation of lignocellulose, achieves effective fractionation and multilevel conversion of straw components. Hence, it is an important tool to achieve full utilization of biomass and high value-added conversion of lignocellulose.