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1、湘潭大学 硕士学位论文 尿素与苯胺合成N，N-二苯基脲的清洁生产工艺研究 姓名：游志敏 申请学位级别：硕士 专业：环境工程 指导教师：戴友芝;李会泉 20080519 尿素与苯胺合成 N, N-二苯基脲的清洁生产工艺研究 I 摘 要 N, N-二苯基脲是一种重要的有机中间体， 主要用于制备磺胺类药物和异氰酸酯 等化学品。其传统合成方法以剧毒光气为直接或间接原料，易造成重大环境污染和 生态危害，必将被淘汰。作为光气法替代工艺而开发的工业尿素法，以尿素和苯胺 为原料，水为溶剂，盐酸为催化剂，N, N-二苯基脲产率只有 40左右，废物产量 大，排放大量苯胺废水和氯化氢废气，后处理困难，环境效益低。由
2、于尿素价格低 廉，又是重要的 CO2资源化工业产品，因此，尿素法生产 N, N-二苯基脲具有较高 的经济和环保开发潜能。然而，如何达到原料最大化利用、废物最小化或零排放， 还有一些值得环保工作者深入研究的问题。 本文以尿素和苯胺为原料，研究了在非水溶剂、非盐酸催化体系中合成 N,N- 二苯基脲的工艺；在此基础上，进一步研究了无溶剂非催化合成 N, N-二苯基脲的 清洁工艺及其强化方法，并对反应机理进行了探讨。主要研究内容和结果如下： （1） 比较研究了在不同溶剂体系中和不同催化剂作用下尿素与苯胺合成 N, N-二苯基脲的产率，发现二甲苯为溶剂具有副反应少、产率较高的特点，乙酸锌和 对甲苯磺酸乙
3、酸铅复合催化剂具有最好的催化活性。最佳工艺条件为：n(苯胺) : n(尿素) : n(二甲苯)= 3: 1: 2，乙酸锌和对甲苯磺酸乙酸铅催化，144 反应 1.5 h， N, N-二苯基脲产率分别为 94.0和 92.9。 （2） 研究了无溶剂非催化条件下，以尿素与苯胺合成 N, N-二苯基脲的清洁工 艺，考察了物料比、温度、时间、搅拌速率等因素对产率的影响。产物的红外、核 磁共振、质谱、紫外等分析结果表明，反应得到的产物是 N, N-二苯基脲。当苯胺 与尿素摩尔比为 5: 1 时，180 ，反应 1.5 h，N, N-二苯基脲产率达到 92.1。 （3） 在无溶剂非催化合成 N, N-二苯
4、基脲的过程中，强化加热、通氮移氨和减 压移氨可以有效提高 N, N-二苯基脲的产率；同时，通过减压蒸发，可简单、有效 的实现产物分离，还可进一步提高产率；反应介质苯胺循环利用，可提高较低温度 条件下 N, N-二苯基脲的产率和原料的利用率。当苯胺与尿素摩尔比为 5: 1 时，180 ，反应 1.5 h，减压蒸发分离产物，N, N-二苯基脲产率可达 99.1。 （4） 研究了无溶剂非催化条件下，尿素与苯胺合成 N, N-二苯基脲的反应机 理。液相色谱分析和验证实验结果表明，异氰酸和苯基脲是主要的反应中间体。反 应历程为：尿素先受热分解，生成氨气和异氰酸；异氰酸与苯胺反应生成苯基脲； 苯基脲进一步
5、与苯胺发生亲核取代反应，生成 N, N-二苯基脲。 （5） 提出了尿素与苯胺反应合成 N, N-二苯基脲的清洁生产工艺，该工艺不加 任何催化剂和溶剂，N, N-二苯基脲的产率高，副产的氨气用于尿素工业生产，整个 生产过程不排放有毒有害废物，实现了污染的源头控制和资源的高效利用。 关键词：关键词：尿素；苯胺；N, N-二苯基脲；清洁工艺；过程强化 湘潭大学硕士学位论文 II Abstract N, N-diphenylurea is an important organic intermediate, which mainly used for the synthesis of sulfa dr
6、ugs, isocyanate and other chemicals. The traditional method for the preparation of N, N-diphenylurea utilizes phosgene as a raw material directly or indirectly, which is toxic, corrosive, expensive, and restricted to employ. The industrial synthesis of N, N-diphenylurea from urea and aniline uses wa
7、ter as solvent and hydrochloric acid as catalyst, giving only 40% yield of N, N-diphenylurea, and dischargeing aniline waste water and hydrogen chloride waste gas, which are both difficult to be handled. As urea is a cheap material and an important industrial chemical synthesized from CO2, there is
8、high economic and environmental potential in N, N-diphenylurea synthesis from urea. But how to maximize the utilizing efficiency of raw materials and minimize the quantity of waste need further study. In this dissertation, a process of N, N-diphenylurea catalytic synthesis from urea and aniline in o
9、rganic solvents, using neither water nor hydrochloric acid, was investigated. Based on this , a clean process of N, N-diphenylurea synthesis from urea and aniline without any catalysts and solvents was developed, the reaction mechanism was also mentioned and proved. The main contents studied and res
10、ults obtained shows as follow: (1) The synthesis of N, N-diphenylurea from urea and aniline catalyzed by various catalysts in a variety of solvents was investigated. It is found that xylene is the optimal solvent, zinc acetate and p-toluenesulfonic acid - lead acetate catalysts are the optimal catal
11、ysts. The yield of N, N-diphenylurea reached 94.0% and 92.9% under the optimum reaction condition of temperature 144 , aniline/urea/xylene ratio 3:1:2 (molar ratio), reaction time 1.5 h, catalyzed by zinc acetate and p-toluenesulfonic acid - lead acetate, respectively. (2) The clean process of N, N-
12、diphenylurea synthesis from urea and aniline without any solvents and catalysts was investigated, the various reaction conditions on the yield of N, N-diphenylurea were also studied. The results of FT-IR, MS, NMR and UV analysis showed that the product of the developed process was N, N-diphenylurea
13、with high purity, the yield of N, N-diphenylurea reached 92.1% under the optimum reaction condition of temperature 180 , aniline/urea ratio 5:1 (molar ratio), reaction time 1.5 h. (3) Investigation showed that the yield of N, N-diphenylurea could be further improved by fast reaction and ammonia remo
14、val through inputing N2 into reaction liquids or reducing pressure of reaction system. The coupling of reaction and separation can be 尿素与苯胺合成 N, N-二苯基脲的清洁生产工艺研究 III easily achieved by vacuum filtration, resulting in the promotion of product yield. The yield of N, N-diphenylurea and material utilizin
15、g ratio could be increased by recycle of the reactants (aniline), under the lower temperature. The yield of N, N-diphenylurea reached 99.1% under the optimum reaction condition of temperature 180 , aniline/urea ratio 5:1 (molar ratio), reaction time 1.5 h, product separating by vacuum evaporation. (
16、4) The reaction mechanism was discussed by means of HPLC analysis and proving experiment, it has been ascertained that isocyanic acid and phenylurea are the major intermediates in the reaction. Based on the analysis of experimental resultes, the reaction might carry through the following pathway: phenylurea is obtained with aniline reacting with isocyanic acid from urea pyrolysis, and then reacts with aniline to produce N, N-diphenylurea. (
