Research On Oxide Process Of Pmida In The Jet Loop Reactor

The oxidation reaction of N-Phosphonomethyl iminodiacetic acid(PMIDA) is a typical gas-liquid-solid three phase reaction, and the mass transfer between gas and liquid has a significant impact on reaction rate. Compared with traditional batch reactor, jet loop reactor has many advantages such as faster thermal mass transfer, fully reactant mixing, easily continuous and upsizing, and it is an ideal reactor for oxide process of PMIDA. Because of a large number of solid-liquid mixture is required to be separated in a short time in batch reactor, and it is difficult to guarantee the yield, so it is significant to study the continuous oxidation process.A set of continuous oxidation pilot experiment system of PMIDA which is composed of jet loop reactor and ceramic membrane filtration device is designed and related experiment is studied in this paper.1. The intermittent oxidation reaction of PMIDA is tested in a 300L jet loop reactor with PMIDA and oxygen as the oxidant, activated carbon as the catalyst, and the reaction time, the circulation flow rate, reaction temperature are analyzed in this paper. The studies show that:with the growth of reaction time, the yield of glyphosate is increasing at first then reducing, and there is a best reaction time, when the temperature is 80 ℃, the best reaction time is about 50 minutes, the maximum yield is about 0.93; with the increase of circulation flow, the best reaction time to reach the optimum yield is shortened with little effect on the yield of glyphosate; In the range of experimental conditions, the reaction time to reach the optimum yield will be reduced with the increase of reaction temperature, but the yield of glyphosate will be reduced; by comparing the calculated value which is offered by intrinsic kinetics equation of PMIDA oxidation and the value offered by the poilt jet loop reactor, we can see that there is a big gap of reaction rate between them, the mainly reason is that the transfer resistance is large in the early stage of the reaction in the pilot device, so there is a greater impact on the apparent reaction rate.2. In order to simulate the separation of activated carbon catalyst and materials, a cold-flow model test is proceed with the help of a set which is composed of jet loop reactor and ceramic membrane filtration device. The stability of ceramic membrane filtration components and the impact of filter pressure and membrane module circulation flow on filtration flux are discussed in this paper. The studies show that:because of the cross-flow method is adopted by ceramic membrane module in this continuous reaction system, the separation effect of activated carbon filter solid-liquid is good, the stability in the longer term filtering can be ensured, and continuous oxidation reaction and solid-liquid separation can be realized, too. Filtration flux are greatly affected by the filtration pressure proportionally, when the filtrating pressure is low, the greater the filtrating pressure, the larger the filtration flux will be; on the contrary, when the filtrating pressure is high, the increasing trend of filtration flux is gradually with the increase of filtrating pressure. In addition to this, the filtration flux increases with the growth of circulation flow rate.3. In order to simulate the oxide process of PMIDA, a mathematical model is established in the jet loop reactor. The result shows that the optimal space time of continuous reaction is about 39 minutes with concentration of PMIDA 7.7%, reaction temperature 80 ℃, concentration of catalyst 45%, reaction pressure 0.3MPa and the yield of glyphosate is 0.95.