Analysis And Optimization Of The Synthesis Of Pendimethalin With Continuous Nitrification By Uniform Design Method

With the increasing attention of the state to food safety and environmental protection,the market demand for low toxic herbicide,i.e.pendimethalin is increasing,the continuous production technology of pendimethalin has been paid more and more attention.Therefore,analysis and optimization of this technology is important practical significance to further improve production capacity.The factors that influence results of synthetic reaction of pendimethalin were explored with single-factor experiments,and the characteristics of synthesis of pendimethalin by continuous nitration process were studied.Two reactors in series were selected for continuous nitrification and continuous nitrification device of laboratory scale is set up,then the experimental data can be obtained and the optimization results can be verified.In order to analyze the pendimethalin and the main by-products in the synthetic product,The standard sample of pendimethalin and its nitrosamine compound was obtained by column chromatography on the basis of the synthetic products of the laboratory.The content of pendimethalin and Nnitroso-pendimethalin in products was analyzed by HPLC,and the detection conditions are optimized.Due to the complex molecular structure of pendimethalin is difficult to establish a mechanism model,the continuous nitrification process of the product was analyzed and optimized by uniform design.Because of the less data points in uniform design,it is difficult to establish quadratic response surface models directly through multiple regression analysis,To solve this problem,in this paper,a modeling method based on reaction mechanism analysis and lasso regression is proposed.The main achievements of this paper are as follows:(1)The standard samples of pendimethalin and N-nitroso-pendimethalin wereobtained,The 1H-NMR confirmed the molecular structure of the standard sample is consistent with the literature results.(2)Combination reaction mechanism analysis and lasso regression method,the second-order polynomial model between the content of pendimethalin and Nnitroso-pendimethalin and the important influencing factors during continuous nitrification was established.(3)The optimal process parameters for the nitration process are nitric acid content being 50%,reactor 1 temperature being 55?,reactor 2 temperature being 40? and mole ratio between nitric acid and aniline salt being 2.75,and the content of pendimethalin in the product is 79.23%.