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Study On One-Step Synthesis Of ε-Caprolactam From Nitrosation Of Cyclohexane

Posted on:2009-08-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:K Y YouFull Text:PDF
GTID:1101360245490809Subject: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 for caprolactam production employed benzene, phenol or toluene 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. The conventional methods of preparation ofε-caprolactam must undergo multi-step conversion of elementary material; the atom economical utilization is also not desirable and results in the formation of a large amount of ammonium sulfate as by-products. So the emphasis of caprolactam production and research is to shorten the technique route and reduce environmental pollution by way of green chemistry. From both synthetic and industrial points of view, it is very attractive that cyclohexane is used as the starting material for the production ofε-caprolactam via a one-step catalytic process. In this work, we try to explore a novel route for one-step synthesis ofε-caprolactam from cyclohexane and nitrosyl sulfuric acid catalyzed by a proper catalyst in the presence of fuming sulfuric acid. The optimization of the reaction conditions and the filtration of better catalyst to one-step synthesis ofε-caprolactam have been accomplished successfully. Moreover, the final products of nitrosation reaction were identified by GC-MS and LC-MS, and the possible reaction mechanism of nitrosation of cyclohexane was proposed in this work.The nitrosation reaction between cyclohexane and nitrosyl sulfuric acid over the catalysts such as carboxylic acids, activated carbon and the transition metal salt et al to obtainε-caprolactam in the presence of fuming sulfuric acid had been researched in this work. It can be found that MnAc2 gave the best results with 10.9% of conversion and 52.4% of selectivity toε-caprolactam among present catalysts under the optimized conditions. A series of non-reductive M-VPO and M-AlVPO composite catalysts, reductive M-VPO and M-AlVPO composite catalysts and the reductive-supported M/VPO and M/AlVPO composite catalysts are designed and prepared. The catalytic performances of various VPO composite catalysts were examined under the optimized conditions. The results show that the Mn-Al-VPO composite catalyst gives the best results with 11.7% of conversion and 34.7% of selectivity toε-caprolactam among present non-reductive VPO composite catalysts under the optimized conditions. However, it was found that the Mn-Al-VPO composite catalyst gives the best results with 20.2% of conversion and 48.9% of selectivity toε-caprolactam among present reductive VPO composite catalysts. It should be noted that the reductive-supported Mn/AlVPO give the remarkable results with 9.8% of conversion and 72.9% of selectivity toε-caprolactam among these reductive-supported VPO composite catalysts under the optimized conditions.Moreover, the effects of supported metal-oxide, some indiscerptible salts (such as barium sulphate, calcium sulphate et al.) and silica gel as catalyst on nitrosation reaction of cyclohexane were researched, and the reuse of catalyst was examined. The results show that these catalysts give better catalytic performance on nitrosation reaction, and barium sulphate and silica gel play the same catalytic role on this reaction. Furthermore, some influence factors on nitrosation reaction were explored. The results indicate that the main factors are catalyst, reaction temperature and reaction time; especially, the effects of catalyst and reaction temperature are very remarkable in this reaction.In addition, the catalytic liquid-phase Beckmann rearrangement of cyclohexanone oxime toε-caprolactam over solid sulfonic acid resin in dimethyl sulfoxide (DMSO) has been successfully performed. The influences of solvent, catalyst, reaction temperature and reaction time on the rearrangement of cyclohexanone oxime in the liquid phase were examined. The results indicate that conversion of oxime can reach 100% with 97.9% of selectivity toε-caprolactam under optimal reaction conditions. This catalytic system involved is environmentally harmless, easily separate, and the catalyst can be conveniently recovered for recycled use. Moreover, the adsorption of cyclohexanone oxime and caprolactam on solid sulfonic acid resin was studied. The results indicate that the adsorption behavior on sulfonic acid resin accords with Langmuir adsorption model and the adsorption kinetics can be described by Langmuir isotherm and speed equation.This discovery establishes a potential new one-step process for makingε-caprolactam from cyclohexane. It might have potential applied prospect and prominent theoretical signification.
Keywords/Search Tags:VPO composite catalysts, cyclohexane, nitrosation reaction, nitrosyl sulfuric acid, ε-caprolactam
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