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One-Step Synthesis Of ε-Caprolactam From Nitrocyclohexane Catalytic Hydrogenation

Posted on:2010-05-10Degree:MasterType:Thesis
Country:ChinaCandidate:S R TanFull Text:PDF
GTID:2231360302955857Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
ε-Caprolactam is an important organic industrially raw material and widely used to synthesize nylon-6 fibers and resins.Most of current commercial processes forε-caprolactam production employed benzene,phenol or toluene as the starting material. The most widely used technology for caprolactam production employed benzene as the starting material and cyclohexanone oxime is producted from the reaction of cyclohexanone and hydroxylamine,followed by Beckmann rearrangement to obtainε-caprolactam in the presence of fuming sulfuric acid.These methods ofε-caprolactam production involves multi-step reaction and results in the formation of a large amount of ammonium sulfate as by-products and sewage.So the emphasis ofε-caprolactam production and research is to shorten the technique route,lower production cost,reduce energy consumption and environmental pollution by way of green chemistry.One-step synthesis method ofε-caprolactam from nitrocyclohexane shorten technique route,reduce environmental pollution and does not produce ammonium sulfate.It has important theoretical and practical value that nitrocyclohexane is used as the starting material for the production ofε-caprolactam via a one-step catalytic process.In this research,the analytic method was set up.According to the method reaction products were identified by GC-MS.To our delight,ε-caprolactam is directly obtained from such one-step catalytic process.It is found that the reaction results in the formation of a variety of by-products and the main by-products are 2-methyl-2-pentenal and 4-hydroxy-4-methyl-2-pentanone.The quantitative analysis ofε-caprolactam was performed by GC and naphthalene was the internal standard.One-step liquid-phase synthesis ofε-caprolactam from nitrocyclohexane in the composite system of Pd/C(Ni/C,etc.) and 2,4,6-trichloro[1,3,5]triazine(TCT) in N, N-dimethylformamide(DMF) were researched.The results indicate that the conversion of nitrocyclohexane was up to 63.87%and selectivity ofε-caprolactam was up to 15.43%at 80℃and 0.20 MPa for 6 h under the reaction conditions of 1:106 molar ratio of Pd/C with nitrocyclohexane and 1mol/L of nitrocyclohexane concentration in the composite system of Pd/C,TCT in DME The effects of preparation conditions of Ni/C to the synthesis ofε-caprolactam from nitrocyclohexane in the composite system of Ni/C and TCT in DMF were investigated.The results indicated that the Ni/C catalyst calcinated at 550℃for 3 hours and reduced at 600℃gave the best catalytic performance,and 92.35% of conversion and 9.72%of selectivity toε-caprolactam were obtained at 80℃and 0.20 MPa for 6 hours.The catalytic activities of Pd/C,Ni/C,Ni/MgO,Pd/TS and Pd/C+TS were compared.The results show that all of them have catalytic activity on one-step synthesis ofε-caprolactam from nitrocyclohexane.Pd/C and Ni/C give better catalytic performance than Ni/MgO,Pd/TS and Pd/C+TS.Moreover,the effects of Mn-VPO,molybdenum hexacarbony and phosphotungstic acid on one-step synthesis ofε-caprolactam from nitrocyclohexane were briefly researched and the results were not very good.In addition,we try to perform the gas-phase one-step synthesis ofε-caprolactam from nitrocyclohexane over phosphotungstic acid, PbO/SiO2,Pd/TS or Pd/C+TS.The results show that Pd/C plus TS give the best results with 19.27%of yield toε-caprolactam among these catalysts.However,the temperature of gas-phase reaction is very high and the reaction results in the formation of a variety of by-products.In this work we find out appropriate conditions for one-step synthesis ofε-caprolactam from nitrocyclohexane through optimization of reaction conditions and selection of better catalyst.It might have potential applied prospect and prominent theoretical signification.In addition,the possible reaction mechanism of one-step synthesis ofε-caprolactam from nitrocyclohexane was preliminary proposed.
Keywords/Search Tags:nitrocyclohexane, Pd/C, Ni/C, ε-caprolactam, reaction mechanism
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