Amphiphilic catalyst for decomposition of unsaturated polyester resins to valuable chemicals with 100% atom utilization efficiency

Abstract

Plastic waste is increasingly aggravating environmental pollution problems. Unsaturated polyester resin is one kind of thermoset resins. Its three-dimensional network endows it good mechanical and chemical properties, but made its degradation and recovery challenging. Here we report a novel and efficient reaction system consisting of amphiphilic p-toluenesulfonic acid/acetic acid aqueous solution for decomposition of unsaturated polyester resin by acyl exchange reaction. Amphiphilic p-toluenesulfonic acid facilitated the entrance of itself and solvent into the resin and consequently promoted catalytic cleavage of ester bonds in unsaturated polyester resin. Water, as a co-catalyst, stabilized the key reaction intermediate species, which reduced largely the overall reaction activation energy and thus accelerated the degradation of the resins. Unsaturated polyester resin was completely degraded and converted to the valuable chemicals at 180 °C, which can be then recycled by a new separation process. The degradation products were mainly ethylene glycol diacetate, phthalic acid, and copolymer products of styrene and maleic anhydride, with the mass ratio of 43.18%, 24.81% and 44.16% to raw unsaturated polyester resin waste, respectively. The atoms of unsaturated polyester resin were completely incorporated into the high-value degradation products with zero production of waste. Hence, this work provides a green, economical, practical strategy to degrade waste unsaturated polyester resin and recycle high-value chemicals with an 100% atom utilization efficiency.