Ring-closing depolymerization of polytetrahydrofuran to produce tetrahydrofuran using heteropolyacid as catalyst

This paper mainly explores the degradation of polytetrahydrofuran to prepare tetrahydrofuran. Various catalysts including different Lewis' acids and protonic acids are investigated in the degradation process of polytetrahydrofuran. The results show that heteropolyacids exhibit higher catalytic activity and stability than other catalysts. The optimal conditions for the degradation of polytetrahydrofuran using heteropolyacids (eg. phosphotungstic acid) as catalyst are phosphotungstic acid: polytetrahydrofuran = 1: 10 (mass ratio), 130 °C, 15 min, and the yield of tetrahydrofuran is greater than 95%. Heteropolyacid catalysts, especially phosphotungstic acid, could be separated easily and reused up to 10 times, and the yield of tetrahydrofuran reaches up to 90% when the catalyst phosphotungstic acid is reused 10 times. Meanwhile, the degradation mechanism of polytetrahydrofuran using phosphotungstic acid as catalyst is explored via NMR and FT-IR methods, and the ether bonds (C-O-C) cleavage mechanism is proposed.