| Acetaldoxime is an important raw material for the preparation of methomyl and thiodicarb.Besides that,it is also an important organic reagent and deoxidizer.At present,it is mainly prepared by Raching process in industry.However,the reaction process is complex,which consumes large amounts of raw materials.Moreover,the side reactions may cause many serious environmental pollutions.Oxime exchange method is a new process for the preparation of acetaldoxime with excellent reaction selectivity and less side reactions.With the gradual maturity of the ammoxime preparation techniques,the production capacity of ketoxime is rising while the price is further reduced.It provides sufficient and relative cheap raw material supplied for the preparation of acetaldehyde oxime by oxime exchange method.Therefore,speeding up the process research may help the industrial application realized quickly.However,the research of this process is inadequate.There are some problems such as the unnecessarily oxidation of acetaldehyde oxime during reaction process.And it is difficult to obtain acetaldehyde oxime with high purity due to the existence of many groups of azeotropes in the reaction solution.Firstly,the process conditions of preparing acetaldoxime by oxime exchange method were studied using butanone oxime and acetaldehyde as raw materials.The effects of catalyst type,catalyst dosage,material ratio,reaction temperature and time were investigated to explore the reaction rules of the process.On this basis,the oxidation of acetaldoxime,the volatilization of butanone oxime and acetaldehyde were effectively avoided under 0.2 Mpa N2 atmosphere.And the product quality was further improved.The selectivity percentage of acetaldoxime was 96.12%,and the conversion rate of butanone oxime was 98.77%.This work focuses on the separation and purification of reaction liquid.The basic processes of vacuum distillation and extractive vacuum distillation were stimulated by Aspen Plus.And the simulation process is further optimized by sensitivity analysis.After the comparison and analysis of the two processes,it was determined that the vacuum distillation is better for the separation and purification.On this basis,the experimental verification of the vacuum distillation process is carried out according to the simulation conditions,and the appropriate adjustment and optimization are made.The best process conditions and results are as follows:Feeding mass flow rate Ff=200 g/h,feeding temperature Tf=25℃.1)Column 1 pressure P=0.1 MPa,number of plates N=20,feed position Nf=9,top temperature TD=22℃,reflux ratio R=2,the purity of acetaldehyde was 98.62%and the yield was 95.56%.2)Column 2 pressure P=-0.08 MPa,number of plates N=25,feed position Nf=10,top temperature TD=32.5℃,reflux ratio R=2,the purity of butanone was 88.94%and the yield was 92.88%.3)Column 3 pressure P=-0.09MPa,number of plates N=30,feed positions Nf=20,top temperature TD=48.7℃,reflux ratio R=5.4)Column 4 pressure P=0.1 MPa,number of plates N=20,feed position Nf=11,top temperature TD=115℃,reflux ratio R=3,the purity of acetaldoxime was 95.33%and the yield was 94.31%.It provides a guidance for further studies on the separation and purification process of acetaldoxime prepared by oxime exchange method.Finally,butanone oxime was prepared by the method of ammoximation using recovered butanone.And the process of continuous reaction was studied.In the experiment,butanone,ammonia water and hydrogen peroxide were used as raw materials.The self-made fixed bed reactor（the catalyst bed was 20 cm in length,1.5 mm in inner diameter.Ti-Mor was catalyst and the weight was 1.5g,and the import and export were respectively sealed with specific membranes）was used to realize the continuity of the process of preparing butanone oxime by ammoximation.The reaction rules and effects of reaction conditions such as reaction temperature,space time,material ratio of hydrogen peroxide to butanone,material ratio of ammonia to butanone on the reaction were investigated to obtain the optimal reaction conditions.The conversion of butanone and selectivity of butanone oxime are over 99.6%and 99.8%,respectively.In addition,the sealed membrane can effectively filter the catalyst and realize the reuse of the catalyst. |
