The Study Of Glycine-dimethyl Phosphite Synthesis Of Glyphosate

N-phosphonomethylglycine(PMG) is one of broad-spectrum herbicides with good bioactivity such as low toxicity, high efficiency and other characteristics, which destroys the ruderal after in bud and derives from the amino acid. Acoording to the actuality and problem of glycine and glphosate industry, the topic proposed to use chloroacetic acid,paraformaldehyde and dimethyl phosphite as the main raw materials, after synthesis, condensation and hydrolysis directly synthesis high-purity glyphosate through one-pot method. This process simplified the synthesis process of chloracetic acidâ†'glycineâ†'glyphosate to achieve the integration of the two production chain and reduce production costs and effectively improve the conversion rate of chloroacetic acid and eliminate the synthesis of glycine on the environmental pollution. In this paper, our arm is to further examine chloroacetate one-pot preparation of glyphosate technology by studying and analysising the synthesis of glyphosate through glycine - dimethyl phosphate.Several factors were experimental analyzed, such as the ratio of the reactants, adding order, water content, cooling method of esterification liquid and hydrolysis process of dropping sequence, dropping time of the esterification, reaction temperature, atmospheric and vacuum distillation time and so on. The optimum process conditions are as follows:(1) The molar ratio of reactants:paraformaldehyde: glycine: triethylamine: anhydrous methanol: dimethyl phosphite: hydrochloric acid = 1.95: 1: 0.85: 7.0: 1.26: 3.(2) In the depolymerization and addition stages, adding order: first add anhydrous methanol, triethylamine and paraformaldehyde then plus glycine.(3) Reduce the water content in the reaction system as much as possible, especially in the eaterification stage.(4) In the hydrolysis process of acidification stage, esterification liquid should be cooled down to be room temperature slowly before dropping into hydrochloric acid solution. To make sure dropping time last 40min least, the dropping speed should be controlled. The reaction temperature was within 8~25℃.(5) In the hydrolysis process of desolventizing Stage, controlling the atmospheric distillation time around 3.5h;In the hydrolysis process of removal of hydrochloric acid, controlling the vacuum distillation time around 1h; the hydrolysis temperature in the range of 115~120℃.At the preferred reaction conditions above, the solid purity of glyphosate can be more than 90%; the tatal yield can reach 81.87%. Add water to the crystal Liquid of hydrolysis, thereafter adjust the pH value of the crystal liquid about 1.5 by using 30% NaOH solution, which makes the minimum solubility of glyphosate in the crystal solution and can improve the solid yield of glyphosate.In the optimized process conditions above, we also preliminarily discussed the impact of triethylamine hydrochloride which is generated in the preparation of glycine through chloroacetic acid on the total yield of glyphosate. Results show that: (1) Triethylamine hydrochloride is extremely adverse to the generation of glyphosate. When the amount of triethylamine hydrochloride was 0.1 mol, the total yield of glyphosate reduced to 32.59%. Therefore we should minimize or eliminate the impact of triethylamine hydrochloride on the experiment in the process of preparing glyphosate with one pot method. (2) Frozen the esterification liquid 0.5h which contains 0.1mol triethylamine hydrochloride acid,and then filtered to remove triethylamine hydrochloride, the total yield of PMG can be increased to 67.06%.