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Dimethyl carbonate instead of phosgene synthesis of isocyanate, is a clean, gentle and non-phosgene process route with industrialization prospects. It consists of aromatic (n) carbamate synthesis and further decomposition of the reaction composition, the (n) aromatic carbamate liquid phase catalytic decomposition reaction process is studied. First of all, on the toluene Dicarbamate (TDC) thermal decomposition of the preparation of toluene diisocyanate (TDI) were studied to examine the influence of temperature, pressure, catalyst concentration, and the heat carrier and the catalyst is reused for the TDC the liquid phase decomposition performance. When the solvent and heat carrier for different components, the optimum reaction conditions: temperature of 260 ° C and a pressure of 6.7kPa TDI yield up to 91.3%. Catalyst reuse preferably, the heat carrier after repeated use TDI yield will decline slowly. When the solvent and heat carrier for the same component, the optimum reaction conditions were: isooctyl phthalate (DOP) as solvent, the reaction temperature of 260 ° C, the reaction pressure 5.4kPa, condensing a head temperature of 165 ° C, TDI's The highest yield was 99%; Dioctyl phthalate better reuse of zinc powder. Secondly, 1,6 - hexamethylene carbamate (HDC) prepared by thermal decomposition of 1,6 - hexamethylene diisocyanate (HDI) were studied. Examine eight kinds of catalysts and three inert high boiling point and heat carrier the HDC thermal decomposition reaction performance, determine the zinc powder is suitable catalyst, naphthenic oil is suitable for heat carrier. The reaction conditions were optimized, the HDI a yield of up to 80.3%. Taking into account the temperature control, heat carrier with stability and other factors to determine the appropriate reaction conditions: reaction temperature of 260 ° C, pressure of 8.0kPa conditions HDI yield of 71.3%. Repeatability study on the catalyst and the heat carrier, the reuse of the catalyst is preferably heat carrier in repeated use HDI yield decreased. Finally, the determination of a 8.0kPa TDI-DOP binary vapor-liquid equilibrium data. Distillation process of separating a mixture of TDI and DOP with ASPEN engineering software simulation, to produce 5,000 tons of TDI, for example, the optimum number of theoretical plates 7, the best feed plate 4 board, the best a reflux ratio of 1.2, the rectifying section of the tower diameter of 0.93m, stripping section tower diameter 1.63m, the the condenser power of -1.2 × 10 5kcal / h the the evaporator power for 5.9 × 10 5kcal / h. Operate in this condition, you can guarantee the quality of products to meet the requirements.
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