Research On Reaction Engineering Of N-Phosphonomethvliminodiacetic Acid Oxidation

Glyphosate (PMG) is a widely used herbicide with a broad spectrum of activity which is very effective and has little harmful effects on the environment. The key step of glyphosate preparation is N-phosphonomethyliminodiacetic acid (PMIDA) catalytic oxidation with active carbon as catalyst. Although PMIDA catalytic oxidation has been implemented in industrial scale production, there’re few studies published on the reac-tion kinetics, especially on the reaction order of dissolved oxygen, which has become the key point of developing and optimizing the process.In this thesis, a series of experiments were carred out to determine the reaction rates with temperatures ranging from50to80℃, pressures from0.1to0.4MPa and the mass ratios of catalyst and initial PMIDA from0.1to1.0. The apparent kinetic equa-tions of different temperatures were first deduced from the measured results of PMIDA and PMG concentrations under different conditions. And the power law indexes of dissolved oxygen concentration in the macro kinetic equations were determined on the base of the dissolubility of oxygen under the above conditions. Then apparent activa-tion energies and pre-exponential factors were calculated on the variation of reaction rate coefficients with temperature. By this way, a macro kinetic model of the reaction series was set up completely. The macro kinetic model was verified by experimental results and the mean relative error of PMIDA and PMG concentrations was5.8%and6.7%respectively. The model is able to meet the needs of engineering applications.Oscillatory flow reactor (OFR) is a novel chemical process equipment for its unique advantages in transfer intensification including efficient transport of mass and energy, and good fluid mixing. The industrial application field of OFR has expanded to polymerization reaction, flocculation, suspension separation, crystallization and so on. Considering the advantages, OFR is a good choice for PMIDA catalytic oxidation as it is a typical multi-phase reaction. In this thesis, the serial multi-tank model with sec-ondary flow and inter-cell back-mixing (SMTSIB) and the above macro kinetics model were used to numerically simulate PMIDA catalytic oxidation and the effects of oscil- lation frequency, amplitude and the number of cells were studied. The simulation re-sults were validated by experiments and the mean relative error of PMIDA and PMG concentrations was9.11%and7.81%respectively, which confirmed the reliability of the simulation results.