Study On The Synthesis Of 3,5-Dimethylaniline By Gas Phase Amination

The current researching of 3,5-dimethylaniline at home and abroad was reviewed in this paper. An integral tubular fixed-bed reactor apparatus was designed and assembled according to self requirements. A new process of synthesizing 3,5-dimethylaniline with 3,5-dimethylphenol and gaseous ammonia by vapor-solid phase amination was developed. The catalyst was selected and the preparation of catalyst was discussed. The effect of process condition such as reaction temperature, reaction press and catalyst ageing time was investigated. Reaction mechanism was demonstrated by experiment results and technology literatures.In the part of catalyst's evaluation, the main catalyst and promoter was selected at first. Secondly, the preparation condition of catalyst influence on reaction process was studied: main catalystγ-Al₂O₃, promoter Fe₂O₃, calcination temperature 550℃, calcination time 5 hours, impregnation concentration 0.017mol/L.In the part of optimizing process conditions, the catalysis activity influence of reaction temperature, solvent selection, reaction press and catalyst ageing time was discussed. The optimum process condition selected was as follows: reaction temperature 430℃, reaction press 0.6MPa, reaction 1 hour. Under the optimum process conditions the conversion of 3,5-dimethylphenol was larger than 97.67%, and the selectivity to 3,5-dimethylaniline was larger than 92.88%.In the part of reaction mechanism investigation, the reaction mechanism was provided based on experiments analysis and research, as follows, NH₂^- wasproduced by NH₃ effecting with O^2- which on catalyst surface, as amination nucleophilic reagent 3,5-dimethylaniline was produced by NH₂^- and3,5-dimethylphenol bimolecular nucleophilic substitution reaction with 3,5-dimethylphenol...