Preparation And Performance Evaluation Of Catalyst For Producing N-Phosphonomethyl Glycine By Air (Oxygen) Catalytic Oxidation

Glyphosate (N-phosphonomethyl glycine) is a kind of non-selective herbicide, whose advantages are high effective, broad-spectrum, low toxicity for the human and animals and little harmful effects on the environment. Air(oxygen) catalytic oxidation to synthesis glyphpsate belong to green chemistry and characterized with low cost, high yield, good quality and little pollution. The key of catalytic oxidation method is highly efficient catalyst.In this paper, catalysts were prepared by water vapor activation and the most suitable one was selected by the catalytic oxidation reaction. The selectivity of glyphosate was improved by optimizing the process conditions. As a result, we obtained the optimal conditions:1(4.72wt%solid content): m(PMIDA):m(catalyst)=5:1, temperature was65℃, pressure was0.6MPa, time was90min, flow rate of oxygen was60ml/min and stirring speed was800rpm;2(8.2wt%-35wt%solid content):m(PMIDA):m(catalyst)=5:1, temperature was70℃, pressure was0.5MPa, time was65min, flow rate of oxygen was60ml/min and stirring speed was800rpm. Under the above conditions, the selectivity of glyphosate reached above97%.The performance of prepared catalyst were compared with factory catalyst. The results show that the initial reaction rate was4times faster,5%higher selectivity and less formaldehyde. The scale-up experiment show that prepared good catalyst can be applied to industrial production and almost not influenced by scale-up experiment.The catalyst was modified by surface oxidation, surface reduction and transition metal. In which roasting2h at800℃with ammonia achieved best result:the formaldehyde content in glyphosate droped from above150g/kg to127.15g/kg, however the selectivity of glyphosate is not affected. Then transition metal Mn、Co、Ni、Zn and Fe oxides and ions were loaded to the catalysts. In a conclution the efficiency of loading0.32wt%Mnwas best:the formaldehyde content droped to115.32g/kg, however the selectivity of glyphosate remained invariant.From the characterization of catalysts, we can see that suitable graphitization was helpful and a certain amount of pore and micro hole in the catalysts can enhance the performance. BET specific surface area of the prepared good catalyst was747.978m2/g, pore volume was0.449cm3/g and average pore diameter was3.808nm.