Investigation On Resource Utilization Of PCB-1-Pentene-3-One

PCB-1-pentene-3-one is a key intermediate in the synthesis of the fungicide tebuconazole,which is usually prepared by the aldol condensation of p-chlorobenzaldehyde and pinacolone with basic catalysts in industry,however,p-chlorobenzaldehyde undergoes disproportionation reaction under alkaline conditions to produce by-products p-chlorobenzyl alcohol and p-chlorobenzoic acid,at the same time,p-chlorobenzoic acid reacts with alkali to produce sodium p-chlorobenzoate.Analysis and detection were carried out on the residue of PCB-1-pentene-3-one production kettle,and its main components were p-chlorobenzyl alcohol,sodium p-chlorobenzoate,water and PCB-1-pentene-3-one that was not completely separated.40% of the organic phase is p-chlorobenzyl alcohol,25% is PCB-1-pentene-3-one;10% of the aqueous phase is sodium p-chlorobenzoate.my country,as a major producer of tebuconazole APIs,has an annual output of 100,000 tons.At the same time,a large amount of PCB-1-pentene-3-one residues will be produced,resulting in waste of resources and greater environmental pressure.It is of great significance to deal with kettle residue efficiently and environmentally and further develop its residual value.PCB-1-pentene-3-one kettle residue is a complex mixture.The organic phase and aqueous phase are separated by extraction with 1,2-dichloroethane,and then the sodium p-chlorobenzoate in the aqueous phase is converted into chlorobenzoic acid by sulfuric acid acidification crystallization process to precipitate and separate.The purity reaches 99.4% after ethanol recrystallization.At the same time,the by-product sodium sulfate decahydrate is obtained by evaporation of acidification crystallization mother liquor;For the organic phase,the solvent was recovered by atmospheric distillation,and then p-chlorobenzyl alcohol was separated by rectification.The purity was increased to 97% and the average yield was 90.3%;Finally,PCB-1-penten-3-one was separated from the residue of distillation.PCB-1-penten-3-one was purified by recrystallization in methanol water mixed solvent system.The purity was increased to99% through twice recrystallization.Finally,the total yield of PCB-1-penten-3-one was 85.6%.In order to improve the utilization value of kettle residue,and in view of the shortcomings of a large number of "three wastes" produced in the production process of p-chlorobenzaldehyde in China’s industry,a method for synthesizing p-chlorobenzaldehyde with recovered p-chlorobenzyl alcohol as raw material under the catalytic oxidation of divalent copper salt and hydrogen peroxide was developed,and further studies on the type and amount of catalyst,the amount of oxidant,reaction time,reaction temperature,p H of the reaction system,phase transfer catalyst and co-catalyst for p-chlorobenzaldehyde The influence of the yield of benzaldehyde,the optimal process conditions are: copper acetate monohydrate as catalyst,hydrogen peroxide as oxidant,n（catalyst）: n（substrate）: n（oxidant）= 1: 100: 300,water As a solvent,the reaction temperature was 96℃,and the distillation was carried out for 2 h while the reaction was carried out.Under these conditions,the substrate conversion rate was93.1%,the p-chlorobenzaldehyde selectivity was 97.7%,and the yield was 91.0%.The catalyst and solvent were reused for many times and the product yield could still maintain a high level.In this study,the main components of PCB-1-penten-3-one kettle residue were successfully separated and purified through a variety of separation methods,and p-chlorobenzyl alcohol was transformed into p-chlorobenzaldehyde through a green synthesis process,so as to realize the resource utilization of PCB-1-penten-3-one kettle residue,effectively improve the resource utilization rate,reduce the production cost,and reduce the pressure of environmental protection to a certain extent,which has important industrial application value.