Liquefaction of Peanut Shells with Cation Exchange Resin and Sulfuric Acid as Dual Catalyst for the Subsequent Synthesis of Rigid Polyurethane Foam

The conversion of lignocellulosic biomass from renewable raw materials to high value-added fine chemicals expanded their application in biodegradable polymers materials synthesis, such as polyurethanes and phenolic resin, etc. In this work, the strong-acid cation exchange resin and sulfuric acid as the dual catalyst offered an effective way to catalyze the liquefaction reaction of the peanut shells. The properties of liquefied products were characterized by means of hydroxyl value, viscosity and solubility tests, while the properties of peanut shells and liquefaction residue were analyzed by means of ATR-FTIR, TG and SEM techniques. The results indicated that the liquefied products could be completely dissolved in deionized water, methanol and polyethylene glycol, respectively, and they could be a preferable substitution of petrochemical polyols as soft segments to synthesize the rigid polyurethane foams. Moreover, the cellulose and hemicellulose in the peanut shells were easily decomposed into smaller molecules via the breakage of the C–O bond besides five-membered and hexatomic ring, while the lignin could be degraded via the breakage of the C–O chemical bonds of β-O-4, 4-O-5 and dibenzodioxocin units. The fabricated rigid polyurethane (RPU) foam, containing higher percentage of open pores with uniform size, can be potentially utilized for flower mud and sound-absorbing materials.