Liquefaction of cornstalk residue using 5-sulfosalicylic acid as the catalyst for the production of flexible polyurethane foams

Due to the huge demand for as well as the limited reserves of fossil resources, renewable biomass that can be converted into chemicals has become a global research focus. In this paper, cornstalk residue was liquefied using a mixture of polyethylene glycol with a molecular weight of 400 g/mol (PEG400) and ethylene carbonate (EC) as the liquefaction reagent and 5-sulfosalicylic acid (SSA) as the catalyst. The liquefaction product of the cornstalk residue (CRL) was used to replace petroleum polyols to prepare flexible polyurethane foams. The results showed that the optimum liquefaction conditions were as follows: PEG400/EC was 7.5:2.5 (w/w), the ratio of liquid/solid was 5:1 (w/w), the liquefaction temperature was 160 C, the mass of SSA was 4 g, and the liquefaction time was 60 min. The hydroxyl number and residue content of the CRL at optimal conditions were 315.7 mg KOH/g and 4.5%, respectively. The compressive strength and apparent density of the polyurethane foam, which was prepared by 90 wt% CRL, 10 wt% commercial polyether GE-220, and methylene diphenyl diisocyanate, were 205.6 kPa and 0.075 g/cm3, respectively.