Study on the Separation of M-Xdi Products by Non-Phosgene Pyrolysis System

Abstract

m-Xylylene diisocyanate (m-XDI) is a raw material wildly used in the manufacture of high value-added polyurethane products and others. m-XDI is a heat-sensitive and easily polymerized substance, and obtaining high-purity m-XDI in industry is challenging, difficult and costly. In this paper, a coupling process of crystallization distillation was proposed to meet the challenge. First, an experiment was carried out to produce a simulated liquid close to the actual pyrolysis liquid components by the reaction of XDI and ethanol. Secondly, two key factors, the final crystallization temperature and the concentration of the m-XDI reaction liquid, which have great effect on the crystallization process of the m-XDI reaction liquid, are studied. Combined with m-XDI saturated vapor pressure and m-XDI-TLB VLE data, the process of m-XDI separation by crystallization distillation coupling was simulated (as shown in the Figure 1), and the process was compared with that of m-XDI separation by distillation alone. The purity of 99.1% m-XDI was obtained by the coupled process of crystal distillation.