尿素羰化法绿色合成间苯二亚甲基二氨基甲酸酯

Green synthesis of m-xylylene dicarbamate using urea as carbonylation reagent

间苯二亚甲基二氨基甲酸酯(XDC)是非光气绿色合成特种异氰酸酯间苯二亚甲基二异氰酸酯(XDI)的关键中间体。本工作以TiO_(2)作为催化剂,以尿素、间苯二甲胺(XDA)和乙醇为原料绿色高效合成XDC。通过气质联用,分析了XDC合成的主副反应,推测了主反应路径,并优化了反应工艺条件。结果表明,以TiO_(2)作为催化剂时,催化剂用量为0.2 g,即约为15wt%XDA,乙醇用量为0.2 mol,n(urea):n(XDA)=3:1,反应温度为205℃,反应时间为6 h时,XDA转化率为100%,XDC收率可达82.4%。本研究提供了XDC绿色高效的合成方法。

M-xylylene diisocyanate(XDI) is an important special isocyanate that draws more and more attention in recent years. The introduction of the –CH_(2)– group between the benzene ring and isocyanate group, which makes it resistant to yellowing, can be applied in the fields of high value-added polyurethanes, such as high-grade coatings, medical polyurethane, high-grade optical polyurethane, and so on. M-xylylene dicarbamate(XDC) is the key intermediate for the synthesis of XDI via the nonphosgene thermal decomposition route. In this work, a novel methodology for the synthesis of XDC via carbonylation of m-xylylenediamine(XDA) using urea as carbonylation reagent over TiO_(2) catalyst was proposed. The standard XDC sample was first synthesized by the reverse reaction between XDI and ethanol, and then, the qualitative analysis of the standard XDC sample was characterized by FT-IR and 1 H-NMR to confirm its structure. The standard curve of XDC was then successfully established in liquid chromatography with a correlation coefficient of more than 0.999. The qualitative analysis of the target product was carried out by GC-MS, and the reaction path was primarily speculated. Furthermore, the effects of different catalysts, reaction temperature, reaction time, the molar ratio of raw materials, and catalyst dosage on the yield of XDC were studied. The results showed that using Ti O_(2) as the catalyst, under the optimized conditions, the reaction temperature of 205 ℃, the reaction time of 6 h, n(urea):n(XDA) of 3:1, the amount of catalyst was 15 wt% XDA, the conversion of XDA was 100%, and the yield of XDC could reach to as high as 82.4%. Therefore, this process not only provides a feasible route for green, effective, and economic production of XDC, but also provides a theoretical basis for the non-phosgene synthesis of special isocyanate XDI.