Abstract
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.
Highlights
Polyurethanes (PUs), as an extensive variety of polymers, are widely applied in foams, elastomers, coatings, adhesives and sealants
In this study, the concentrated sulfuric acid and strong-acid cation exchange resin (SCER) were employed as a dual catalyst to enhance the liquefaction process of peanut shells
When the SCER was solely utilized as the catalyst during the liquefaction process, the pores of SCER could be blocked by peanut shell powder, resulting in a low liquefaction yield
Summary
Polyurethanes (PUs), as an extensive variety of polymers, are widely applied in foams, elastomers, coatings, adhesives and sealants. Rigid polyurethane (RPU) foams widely serve in the heat and cold preservation field including household refrigerators, industrial pipelines and building layers, depending on their particular incorporation of preferable thermal isolation and mechanical properties [1]. The synthesis of PUs is determined through the reaction of isocyanates with polyols to from urethane (–NH–(C=O)–O–) linkages. Polymers 2019, 11, 993 supplied from petroleum-derived feedstocks [2]. According to the total amount of global polymer consumption in 2011, 5% arises from polyurethane raw materials—isocyanates and polyols [3]. Due to the fast consumption of petroleum feedstocks, it is urgent to explore alternative biomass resources which can be further translated into basic chemical raw materials. As renewable and globally available resources, biomass possesses ignorable sulfur and other pernicious elements, and can be identified as a carbon-neutral resource without the net increment of the CO2 concentration in the atmosphere [4]
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