甲苯二异氰酸酯蒸馏残渣常压水解回收甲苯二胺

Abstract

甲苯二异氰酸酯(TDI)是一种重要的有机化合物，主要由甲苯二胺(TDA)通过光气化反应来制备。对光气化反应产物蒸馏后产生不同分子量且不溶于水的残渣废料，即TDI蒸馏残渣。这些残渣的量相当可观，对环境造成严重危害。目前最常用的残渣处理方法是高温高压水解，同时获得重要工业原料TDA。本文介绍一种简单的TDI残渣处理的新方法。以乙二醇或者三乙四胺或者二者混合物为溶剂，以氢氧化钠为水解促进剂，通过常压水解，无需任何外加高压即可以实现TDI残渣的水解并回收重要工业原料TDA。对影响TDA产率的实验条件，如乙二醇用量、三乙四胺用量、回流时间、氢氧化钠用量以及水解反应时间进行了探讨，优化了水解实验条件。实验结果表明，在优化条件下，TDA的回收率最高可达TDI残渣的54.44%。在实验结果的基础上本文也对TDI残渣的水解机理进行了初步分析。Toluene diisocyanate (TDI) is an important organic compound, usually manufactured from toluene diamine (TDA) as the main raw material through phosgenation. The purification of the phos-genation products by distillation results in high molecular weight and insoluble waste materials in quite a large amount. This residue, often called TDI distillery residue, has been an environment threat and different strategies have been set up for their processing. The most common process currently employed is its hydrolysis under high pressure and high temperature, which also allows recovery of TDA in considerable amount. This paper provides a novel and simple process for the hydrolysis of TDI residue without need for high pressure, and toluene diamine, the important raw material in the production of TDI, was also recovered at the same time. In this process, TDI residue was dispersed in either ethylene glycol, triethylene tetramine or their mixture, along with sodium hydroxide as a catalyst. Heated to the refluxing temperature of the mixture, the hydrolysis was conducted by refluxing at temperature varied from 140˚C to 290˚C under atmosphere pressure. Experimental conditions, including the medium solvent and its amount, reflux time and tempera-ture as well as the amount of alkali solution for the hydrolysis, were studied, and the hydrolysis was optimized with regard to the yield of TDA. Under the optimized conditions, a TDA yield of 54.44% based on the residue mass was achieved. This work therefore presents a reliable and facile process for the hydrolysis of TDI residue. Based on the results, mechanism of the hydrolysis is proposed.