论文标题:尿素法合成甲苯-2，4-二氨基甲酸酯反应研究
Study on Synthesis of Toluene-2,4-Dicarbamates via Urea Route
论文作者
论文导师 赵新强,论文学位 硕士,论文专业 化学工艺
论文单位 河北工业大学,点击次数 323,论文页数 68页File Size29090K
2007-05-01论文网 http://www.lw23.com/lunwen_449182/
urea; toluene-2,4-diisocyanate; toluene-2,4-dicarbamates; thermodynamic analysis; reaction mechanism
尿素法合成甲苯二异氰酸酯(TDI)是一条清洁而经济的工艺路线。以尿素为原料合成甲苯-2，4-二氨基甲酸酯是尿素法合成TDI的重要步骤。对该反应进行实验研究具有重要的理论意义和应用价值。 首先对尿素法合成甲苯-2，4-二氨基甲酸甲酯(TDC(Me))反应体系进行了热力学分析，发现该反应为吸热反应，在298K下_rG~o为-61.7 kJ·mol~(-1)，预期有较高的平衡转化率。其次，运用液质联用技术对TDC(Me)合成反应进行了定性分析，确定了副产物并推测主要副反应是原料2，4-二氨基甲苯(TDA)和中间产物3-氨基-4-甲基苯基脲(TU)的甲基化反应；以质谱分析结果和热力学分析结论推测出可能的反应路径。同样，运用液质联用技术对甲苯-2，4-二氨基甲酸丙酯TDC(Pr)合成反应进行了定性分析，确定了副产物并推测其主要副反应是中间产物3-氨基-4甲基苯氨基甲酸丙酯(TMC)与TU和甲苯-2，4-二脲(TBU)之间的缩合反应。最后，考察了反应条件对合成TDC(Me)，TDC(Et)和TDC(Pr)三个反应的影响。TDC(Me)合成反应适宜的反应条件为：反应温度180℃，反应时间为16h，n(TDA)：n(Me)=1：88，n(TDA)：n(Urea)=1：2.5。在此条件下，TDA转化率为93.6％，TDC(Me)产率13.4％，选择性14.3％。甲苯-2，4-二氨基甲酸乙酯(TDC(Et))合成反应适宜的反应条件为：反应时间4h，反应温度180℃，n(TDA)：n(Urea)=1：2.5，n(TDA)：n(Et)=1：100。在此条件下，TDA转化率为78.7％，TDC(Et)产率43.2％，选择性55.0％。TDC(Pr)合成反应适宜的反应条件与TDC(Et)合成反应体系的反应条件相近：反应温度170℃，反应时间4h，n(TDA)：n(Urea)=1：3，n(TDA)：n(Pr)=1：84。在此条件下，TDA转化率为95.3％，TDC(Pr)产率66.1％，选择性69.4％
The synthesis of toluene diisocyanate (TDI) starting from urea is a clean and economicroute. The preparation of toluene dicarbamates using urea as a starting material is an importantstep in the manufacture of TDI via urea route. Hence the study on this reaction has a greattheoretical significance and application value. Firstly, thermodynamic analysis of the reaction system for synthesizing dimethyl toluene-2,4-dicarbamate (TDC(Me)) via urea route was studied. The result showed that the mainreaction was endothermic and its _rG~o was -61.7 kJ.mol~(-1)at 298K, which suggested that highequilibrium conversion could be expected. Secondly, LC-MS was used in qualitative analysis ofthe constitutes in the reaction system for synthesing TDC(Me). The main side-reactions weremethylation reactions of 2,4-toluene diamine (TDA) and 3-amino-4-methylphenyl urea (TU).The possible reaction pathway was presumed based on LC-MS result and the thermodynamicanalysis conclusion. Additionally LC-MS was also used in qualitative analysis of the reactionsystem for the synthesis of dipropyl toluene-2,4-dicarbamate (TDC(Pr)). The main side-reactions were condensation reactions between 3-amino-4-methyl N-propylphenylcarbamate(TMC) with TU or toluene 2,4-bisurea (TBU). Lastly, the effects of reaction conditions onTDC(Me), TDC(Et) and TDC(Pr) synthesis reaction were investigated. The optimal conditionsfor the synthesis of TDC(Me) were as follows: reaction temperature 180℃, reaction time 16h,n(TDA):n(Me)=1:88, n(TDA):n(Urea)=1:2.5. Under these conditions, TDA conversion was93.6%, and TDC(Me) yield and selectivity were 13.4% and 14.3%, respectively. The optimalconditions for the synthesis of TDC(Et) were: reaction temperature 180℃, reaction time 4h,n(TDA):n(Et)=1:100, n(TDA):n(Urea)=1:2.5. Under these conditions, TDA conversion was78.7%, and TDC(Et) yield and selectivity were separately 43.2% and 55.0%. The optimalconditions for TDC(Pr) synthesis were similar as those for TDC(Et) synthesis: reactiontemperature 170℃, reaction time 4h, n(TDA):n(Pr)=1:84, n(TDA):n(Urea)=1:3.0. Underthese conditions TDA conversion was 95.3%, and TDC(Pr) yield and selectivity were 66.1%and 69.4%, respectively.
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