Recovery of the polymers formed during thermal cracking of N-substituted dicarbamates over Fe–Ni/Al2O3

Abstract

The thermal cracking behavior of diethyl hexamethylenedicarbamate (EHDC) was investigated in this work. The polymers formed under different conditions were analyzed by IR and TG, indicating that the polymers were mixtures of EHDC, polyureas, imines and others. The polymers could be converted to EHDC by a simple alcoholysis reaction for the first time over Fe–Ni/Al₂O₃ catalysts. Under the optimized reaction conditions, the yield of EHDC could reach up to 52% with 99% selectivity over 8% Fe–3% Ni/Al₂O₃ catalysts. The catalysts were extensively characterized by BET, XPS, XRD, SEM, TEM, H₂-TPR and NH₃-TPD, showing that the interaction effect between Fe species and Ni species may be attributed to high catalytic performance of the catalyst. Meanwhile, the loss of active components resulted in decreased catalytic activity.