Study On Beckmann Rearrangement Of Long Carbon Chain Ketone Oxime And Hydrolysis Of Rearrangement Products

In organic chemistry,Beckmann rearrangement is defined as the nucleophilic reaction of an aldehyde oxime or ketoxime undergoing intramolecular rearrangement under the action of an acidic catalyst to form an N-substituted amide;Hydrolysis is defined as the reaction of one compound with water,which is decomposed into two or more new compounds.Rearrangement and hydrolysis are important chemical processes and are widely used in the preparation of pharmaceutical synthesis and chemical intermediates,especially the synthesis of amides.Polymers containing amide bonds（-CO-NH-）in molecular chains are called polyamide（PA）,which is commonly called nylon（nylon）.Aliphatic polyamides are widely used in automobiles,electrical appliances,medicine,textiles and other fields because of the regularly alternating arrangement of polar amide bonds in the molecular chain,which can make the molecular chain form hydrogen bonds and have strong intermolecular force,which make these materials have good wear resistance,impact resistance,corrosion resistance and other unique properties.In polyamide molecular chains,nylon with more than 10 carbon atoms is called long carbon chain nylon.Long carbon chain nylon has better dimensional stability and low temperature toughness than ordinary nylon.It is a high performance material developed in China.PA11 and PA1212 are the main types of long carbon chain nylon.At present,the production of PA11 adopts the pyrolysis process of methyl ricinoleate,which is monopolized by Akma Company of France and imported nearly 10,000 tons annually in China.PA6 is currently the largest production of conventional nylon.In the production of its monomer-caprolactam,the rearrangement of cyclohexanone oxime mainly adopts the liquid Beckmann rearrangement process.Although the liquid rearrangement process is different in the world,fuming sulfuric acid is used as catalyst.The process has mature technology,high conversion and yield,but there are many problems,such as large amount of catalyst,serious equipment corrosion,by-product of a large number of low-value ammonium sulfate,and so on.In this research group,the preparation process of PA11 monomer is different from that of French akma company.The methyl 12-hydroxystearate is prepared from castor oil,and then the PA11 monomer-11-aminoundecanoic acid and PA1212 monomer-dodecanedioic acid are prepared through oxidation,oximization,rearrangement and hydrolysis.Rearrangement is a key step affecting the yield of the monomer.The rearrangement of raw materials and products has not been reported.The main task of this experiment is to determine the technical route of rearrangement and hydrolysis according to the nature of raw materials through exploratory research.The main task of this experiment is to determine the technical route of rearrangement and hydrolysis according to the nature of raw materials through exploratory research.On this basis,the influencing factors of the process were investigated,and the optimum process conditions were determined in order to provide the basis for industrial production.The specific work is as follows:（1）Methyl 12-oxime stearate was synthesized from methyl 12-hydroxy stearate,a derivative of castor oil,by oxidation and oximation,and used as raw material for rearrangement study.（2）The solvent liquid phase rearrangement process was determined.methyl 12-oxime stearate,the main component of the rearranged raw materials,was rearranged to form long chain amides by Beckmann rearrangement.The system was diluted with toluene as solvent,using cyanuric chloride as catalyst and anhydrous zinc chloride as co-catalyst.The catalyst was dissolved in some solvents and batched into the reaction system.The rearrangement reaction temperature was controlled by diluting the system and adding catalyst in batches to prevent flying temperature.The rearrangement route has the advantages of mild reaction conditions,high conversion,low cost and easy availability of catalysts,low consumption and recyclability,and it is a green rearrangement process.（3）The rearranged product was purified to obtain pure long-chain amide,and its structure was identified by FT-IR.The method for determining the content of main and by-products by GC analysis was determined.（4）The effects of key factors such as catalyst,amount of promoter,reaction temperature,reaction time and moisture content on the yield of rearrangement reaction were investigated,and the optimum process conditions were determined.The results showed that when the amount of cyanuric chloride was 1.5%,Zn Cl₂ was 0.6%,reaction temperature was100-110℃,reaction time was 60 min,moisture content was≤0.08%,the conversion of methyl 12-oxime stearate was 100%,and the selectivity of long chain amide was over 95%.The main by-product of the rearrangement reaction is methyl 12-carbonyl stearate.The mechanism of the catalytic rearrangement reaction of cyanuric chloride is briefly analyzed.（5）The treatment of rearranged wastewater was studied.After the rearrangement reaction is completed,the water is heated to add the cyanuric chloride to cyanuric acid and dissolved in water to separate the organic phase;the solubility of the cyanuric acid is determined,and the amount of the rearrangement washing water is determined.The separated wastewater was adjusted to about p H=7.93 to form Zn（OH）₂ precipitate and flocculate to remove trace organic matter.The filtrate was cooled and crystallized to recover cyanuric acid,and its content was determined by HPLC to be 93.2%.（6）The hydrolysis process of amide with KOH as catalyst was determined,and the rearranged products were hydrolyzed to form four products such as 11-aminoundecanoic acid and dodecanedioic acid,etc.The effects of KOH dosage,reaction temperature,reaction time and other key factors on the hydrolysis reaction were investigated,and the optimum hydrolysis conditions were determined.The results showed that when the molar ratio of KOH to raw material was 3.1,the reaction temperature was 165℃and the reaction time was 6 h,the hydrolysis effect was the best,and the conversion of amide was over 96%.