Research On Process Of N-phosphono -methyliminodiacetic Acid Catalytic Oxidation To Synthesize Glyphosate Over Modified Granular Activated Carbon

The Glyphosate (PMG) is a widely used herbicide which is rapid growth in market demand and has been the first in the world’s pesticide sales. The PMG Synthesis by N-phosphonomethyliminodiacetic acid (PMIDA) oxidation over active carbon and oxygen as oxidation is the final step but the key step, which is a cascade reaction and the PMG will be oxidized continuously. Therefore, the reactor type and operation process have effect on the yield of PMG. The technology is confined to intermittent reaction process due to the low activity of activated carbon, and the solubility is small of PMG which causes water evaporation largely energy consumption of PMG in crystallization process so that hindered the process of industrial application prospect. This research attempts to explore the optimization of reaction process through dynamics analysis by using granular activated carbon modified which is highly active as catalyst and reduce the energy consumption of the process by using the evaporation sedimentation patent technology which generates of new secondary cleaning of the steam. The specific tasks of study are as follows:1. Research for kinetics of chemical reaction:Experience were carried out with oxygen as the oxidizing agent and the granular active carbon as the catalyst in a 100 mL external recycle differentia] reactor, with reaction temperature ranging from 313.15 K to 343.15 K and the pressure of 0.1 MPa. Based on the data collected in the reaction, the macro kinetic model of the reactions of two steps was developed by the nonlinear least square method and the result turns out that the reaction is 1-1 level cascade reaction. Then the pre-exponential factors and the apparent activation energies of two oxidation steps were calculated on the variation of reaction rate coefficients with different temperatures. The activation energy for the oxidation of PMIDA was 29.64 kJ/mol, and the activation energy for the oxidation of PMG was 20.97 kJ/mol. The pre-exponential factors for the oxidation of PMIDA were 585.99 mol-0.7m-2s-1, and the pre-exponentiaJ factors for the oxidation of PMG were 1.89 mol-0.5m-2s-1. The macro kinetic model of the reaction series including two steps was all set up completely in this way. At last, the result agreed well with the experimental data to verify the macro kinetic model. The mean relative error of PMIDA concentrations was 5.55%, and the mean relative error of PMG concentrations was 8.43% which were all could meet the needs of engineering production.2. The simulation study of reaction process:The reaction of PMIDA catalytic oxidation is a typical gas-liquid-solid three phase reaction. This research intended to adopt packed bed reactor to reduce the back mixing in the process. Aspen Plus was used to study different reaction conditions which influenced catalytic oxygenation. By optimizing for the whole process, the length of plug flow reactor, the pressure and the mass flow rate of oxygen were set to 6.11 m,0.30 MPa and 2 kg/h. Under the conditions, PMIDA conversion rate was 97.87%, the maximum yield of PMG was 89.75%. To save energy, the excess oxygen after reaction could be used again through circulation and circulation recovery was 96.3%.3. Simulated optimizing designing of separating product system:The solution of PMG is very small and the product of PMIDA oxidization in the continuous process contains majority of water above 90% which will cause quite a lot of energy consumption. The evaporation and precipitation reactor is used to carry out the reformation of mother liquor concentration process in producing PMG, and the steam produced should be used in recycle to reduce energy consumption. In the process of Aspen Plus, to study the influence which different reaction conditions on the results of catalytic oxygenation. Steam used again released the heat energy about 66.46 kw to provide heat for the heater. The energy consumption in other simulation unit is totally 87.75 kw, and the heat of evaporation is 75.74%. This technology can greatly reduce the energy consumption and improve the economic benefit, provide the certain reference value for practical production.