Study On Re-use And Treatment To Residue Durning The Methyl Carbamate Production

The technologies synthesize Methyl Carbamate (MC) which has great economic value with urea and methanol has been successfully achieved in industrial production. However, in the production process, there are little residues left after the MC has been isolated from the reaction system by the vacuum distillation. If these residues were not recycled, for one thing, a large waste of resources would be wasted, for another thing, environmental pollution would be caused seriously. In order to solve these probnd advanced treat the waste residues which based on the problems above. After reviewing a large number of literatures, it can be concluded that, the main ingredients of residues are urea, MC and biuret. After repeated study, the method Of dimethylamino-benzaldehyde colorimetric is used to determinate the content of urea and MC. The principle is that MC and urea all can react with the dimethylamino benzaldehyde-Ehrlich reaction and generate lemon yellow material (dimethylamine benzene methylene amino methyl formate and N-dimethylamine benzene methylene urea). The concentrations and absorbances of these two substances are consistent with Beer's Law. So spectrophotometry can be used to measure the concentration of MC and urea. The method of copper complex salt photometry is used to determinate the content of biuret. The principle is that in alkaline solution without interference of ammonia and other insoluble matter, biuret can react with the double salt of copper tartrate and generate purple biuret of copper complexes. The concentration and absorbance of this complex is consistent with Beer's Law. So spectrophotometry can be used to measure the concentration of biuret. The maximum absorption wavelength, medium acidity, the amount of chromogenic material, reaction time of the two methods had been optimized. The precision and accuracy of the two methods, linear range and detection limit of calibration curve have been measured. The results are satisfactory. The respectively percentages of urea, MC and biuret are 40.09%, 20.10% and9.16% which are determinated by the two methods. The optimum conditions synthesizing methyl carbamate (MC) with residues and methanol are: the reaction temperature is 174℃, the feed ratio of methanol and residues is 6:1(the ratio of quality), the reaction time is 3.5h, and the Self-styled pressure is 1.9MPa.In the closed system and the optimum reaction conditions, the crude MC yield is 86.39%, the use efficiency of the residuces is 69.58%. Atmospheric distillation is used to isolated methanol from the reaction system. Isolated methanol can be used again and the results were very good. Vacuum distillation is used to isolate crude MC from the reaction system. The purity of crude MC is 96.32%. The purity of MC product is 99.25% after purification.