Study On Preparation And Reaction Kinetics Of Glyphosate By Catalytic Oxidation Method Using Activated Carbon As Catalyst

N-phosphonomethyl glycine（PMG）, which derives from the amino acid, is a kind of the important herbicide. Because of its high effective, low to xicity and little harmful effects on the environment, Glyphosate has been became the most popular herbicide. In this paper, in view of the process that utilizing activated carbon as the oxcatalyst oxidizes the aqueous solutions of PMIDA to obtain glyphosate, The oxidative decarboxylation reaction has many disadvantages such as low product yield and purity, glyphosate wastewater cannot utilization, We have done a lot of improvement, mainly work as follows:First, we optimized the process of oxidative decarboxylation of PMIDA to PMG, and studied the influent factors, including the reaction time, reaction temperature, reaction pressure, gas flow, stir speed on the effect of the yield, selectivity and conversion rate of PMG. The optimal process conditions are as follows: reaction time was 120 min, reaction temperature was 65℃, reaction pressure was 0.8Mpa, gas flow was 130 ml/min, stir speed was 800 rpm, on this condition, the yield of glyphosate can reach 93%, the selectivity of glyphosate can reach 95%。In addition, on the based of the optimal process conditions, a novel preparation process is proposed that the glyphosate can be obtained by recycled liquid. By the adsorption experiment of activated carbon for formaldehyde, we found that the activated carbon can be a relatively good solution for the adsorption of formaldehyde, and can reduce the concentration of formaldehyde to 1%. Then we synthetize glyphosate by recycled liquid whose concentration of formaldehyde was reduce to 1%, the experiment result is good.Finally, in a 0.5L autoclave, we stuied the macro kinetics of methylation side reaction with glyphosate and as the reactant, activated carbon as the catalyst. According to the principle of the methylation side reaction, mechanism of methylation side reaction was proposed, and the intrinsic kinetics model was established as following:-dC_A/dt=K_AC_tC²_HCHOC_AThrough the experiment, we found that the rate of methylation side reaction is proportional to the concentration of catalyst and the reaction order of formaldehyde is tow,the correctness of the instrinsic kinetics model is verified by experimental data, the kinetic parameters were obtained by fitting the experimental data: the reaction activation energy was 4.3688×104,the pre-exponential factor was 4.7852×1010,so we obtain the reaction kinetics equation:-r_A=4.785210¹⁰C₁C²_HCHOe^{-4.3688×104l（RT）}C_A...