Glycine Synthesis Of Glyphosate Reaction Mechanism And Process Optimization

This thesis has studied the mechanism of the synthesis of glyphosate from glycine,clarified the factors which influence the formations of several intermediates, product, by-products, found the main factor of increasing the yield of glyphosate, and then optimized the process of the synthesis of glyphosate which called "glycine method".Generally the "glycine method" was known as four steps reactions together with several side-reactions, which was completed as one-pot reaction involves more than 20 reactants and intermediates. The one-pot reaction was complicated and the mechanism of each step was unclear, so that the side-reactions were very difficult to control and the yield was not stable. Furthermore, "glycine method" was restricted by its high-energy-cost, high-material-consumption, low production of Solid glyphosate, large quantity of "three wastes".In this thesis, we employed ¹³C-NMR,³¹P-NMR, and ¹H-NMR technique to monitor the reaction process, and found that the molar ratio of the reactant, temperature, time and pH were the main factors which influenced the reaction selectivity; and the formations of by-products such as hydroxymethyl phosphonic acid,phosphite,polaris and N-(methylation)glyphosate decreased the yield of glyphosate. The generation mechanism and condition of these outgrowths were discussed in details, a method to restain the side-reaction was proposed in this thesis.Based on the study of the mechanism and the investigation of the condition of restrain the side-reactions, the process of the "glycine method" was optimized systemically, such as the temperature and time of condensation and acidolysis,the batch charging,the molar ratio of reactants; the acidolysis in low temperature without alcohol and the reuse of mother liquor were proposed; the consumption of dimethylphosphite, methanol, hydrochloride, soda and steam were reduced effectively; and the generation of chloromethane and dimethoxymethane were controlled largely, only one time of triethylamine recyvling received the same effect of several times recycling before. The efficiency of desolventizing, acidolysis and concentration were optimized and the production of single tank was increased. At the same time, the consumption of materials, cost of energy and three wastes were reduced greatly, the yield and quality of glyphosate were stabilized. All of these were helpful for automatic control in industry produce glyphosate in large quantitie.In summary, this thesis has an important theoretical clarification for glyphosate's mechanism, valuable contributions for process optimizing, and useful reference for industry application.