| N-acetyl-L-cysteine is an acetylated amino acid with antioxidant and mucolytic properties,which is widely used in the field of medicine.In addition,it is also applied to various industries such as agriculture and cosmetics,with a broad market and economic value.However,the direct preparation of N-acetyl-L-cysteine from Lcysteine in China is still relatively traditional,which has problems of organic solvent pollution,complex process and easy racemization.Therefore,we developed a green electrochemical process for the direct preparation of N-acetyl-L-cysteine from Lcystine.In this paper,a series of engineering problems have been studied around the industrial application of the preparation process:(1)The improvement of mass transfer.Fluent software was used to simulate the fluid flow in the existing electrolyser,and the problems of short-circuited flow and stagnation zone were found.The structure of the electrolyser was redesigned to improve the mass transfer.The simulation results of the newly designed electrolyser showed that the streamline in the optimized electrolyser was more zigzag.The short-circuited caused by laminar flow and the retention of electrolyte in the corner were solved.The structure of the electrochemical reactor which is more conducive to mass transfer was obtained.(2)The selection of electrode materials.The electrochemical yield,current efficiency and potential distribution of silver electrode,carbon electrode and lead electrode were studied,which confirmed that lead electrode was suitable for industrial production of N-acetyl-L-cysteine.Although carbon electrodes and silver electrodes also met the requirements for electrochemical yield,the uneven distribution of the potential in carbon electrodes was likely to cause serious partial hydrogen evolution,while the current efficiency of silver was slightly lower and the material cost was high.(3)The completion of industrialization test.The process route and parameters for the preparation of N-acetyl-L-cysteine from L-cystine were determined by laboratory experiments.The feasibility of the scale-up process was examined by the kilogram scale experiment,and the shortcomings in the traditional desalting method were solved by introducing electrodialyser.Finally,the industrialization test is carried out to adjust the process and an evaluation of economic and technical was given. |
