Alkaline hydrolysis of poly (ethylene terephthalate) using 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU)

Abstract

Advanced polymer recycling methods can address challenges with mechanical recycling caused by contaminated samples and mixed plastic wastes. In this work, we report alkaline hydrolysis of poly (ethylene terephthalate) (PET) flakes using a super basic reagent, 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) in an aqueous media. The effect of operating conditions including temperature, time, and DBU concentration on the conversion of PET and the yield of terephthalic acid (TPA) was investigated. The relative hydrolysis kinetics were compared for the homogenous reaction of ethyl acetate and heterogenous PET reaction to elucidate the mechanism. While DBU exhibited much higher activity for both systems than NaOH at similar conditions, the increase in rate kinetics was much greater for the PET hydrolysis. This difference in kinetics was attributed to a combination of improved surface wetting of PET by DBU reaction media and the increased activity of the DBU. The hydrolysis of ethyl acetate was studied as a model system to determine the reactant's activity in a homogenous hydrolysis reaction. The effect of surface wetting was studied by conducting contact angle measurements of solutions.