2,4-甲苯二氨基甲酸酯分解反应性能及机理研究

对不同种类的2,4 甲苯二氨基甲酸酯(TDC)分解制备2,4 甲苯二异氰酸酯（TDI）反应性能及Fe2O3催化反应机理进行了研究。热重和差热扫描结果表明，不同2,4 甲苯二氨基甲酸酯的热分解温度由低到高次序为：2,4 甲苯二氨基甲酸苯酯(TDC(Ph))、2,4 甲苯二氨基甲酸甲酯(TDC(Me))、2,4 甲苯二氨基甲酸丙酯(TDC(Pr))、2,4 甲苯二氨基甲酸丁酯(TDC(Bu))；热分解温度高低反映了热分解反应的难易。而Fe2O3催化分解实验表明，不同2,4 甲苯二氨基甲酸酯催化分解反应由易到难依次为TDC(Ph)、TDC(Bu)、TDC(Pr)、TDC(Me)。可能是催化剂Fe2O3的使用，使得不同2,4 甲苯二氨基甲酸酯催化分解的难易趋势与热分解的不同。借助FTIR表征，推测了Fe2O3催化TDC(Me)分解反应的机理，表明催化剂Fe2O3中的Fe3+与TDC(Me)中的羰基氧发生配位作用是催化分解的关键。

Reaction Performance and Mechanism for Decomposition of 2,4-Toluene Dicarbamate

The decomposition reactions of different toluene 2,4 dicarbamate (TDC) to prepare toluene 2,4 diisocyanate (TDI) and the decomposition mechanism of dimethyl toluene 2,4 dicarbamate catalyzed by Fe2O3 were studied. The thermal decomposition temperature for different TDC increases in the order of diphenyl toluene 2,4 dicarbamate (TDC(Ph)) < dimethyl toluene 2,4 dicarbamate (TDC(Me)) < dipropyl toluene 2,4 dicarbamate (TDC(Pr)) < dibutyl toluene 2,4 dicarbamate (TDC(Bu)), implying the difficulty of decomposition reaction rise. The decomposition experiments of different TDC catalyzed by Fe2O3 were also carried out, and the results show that catalytic decomposition becomes more difficultly from TDC(Ph) via TDC(Bu) and TDC(Pr) to TDC(Me). Combined with the analysis of FTIR, the reaction mechanism for preparing TDI from TDC(Me) catalyzed by Fe2O3 was speculated. The results show that the coordination of Fe3+ in Fe2O3 with carbonyl oxygen in TDC(Me) is the key to catalytic decomposition of TDC.