ε-caprolactam Sythesis From Cyclohexane Nitrosation Catalyzed By The Novel Catalysts

Caprolactam is a kind of important chemical raw materials, as intermediates in the production of polyamide fiber and resin process. At present,industrial production methods of caprolactam have many disadvantages such as complex step, complicated operation, low atomic economy, the environmental pollution, serious equipment corrosion,etc. Therefore, the development of the green caprolactam technology has great meaning. This topic about the preparation process of cyclohexane nitrosation to caprolactam are studied, through the preparation of different kinds of catalysts, and the characterization of the catalysts, performance of catalysts were investigated, optimizing reaction conditions of cyclohexane catalyzed nitrosation to caprolactam and catalyst preparation conditions, and the catalytic reaction mechanism was studied. Finally, by sodium nitrite instead of nitroso sulfuric acid as the nitration reagent, developed a new method of cyclohexane nitrosation to compound the caprolactam.This paper firstly examines the catalytic performance of the different types of zeolite molecular sieve for caprolactam preparation by cyclohexane nitrosation. Results show that the best effect at the presence of HZSM-5,through studying different Si/Al ratio of the HZSM-5, finding that when the silica alumina ratio of HZSM–5 was 50 as catalyst, reaction temperature 81 ℃, the reaction time for 48 h, the quality ratio of concentrated sulfuric acid and sulfuric acid nitroso about 3:1, cyclohexane conversion rate reached 6.1%, the selectivity of caprolactam was 77.92%. Again by HZSM-5 molecular sieve which silica alumina ratio was 50 as the carrier, the vanadium oxide as the active component, the preparation of the different loading of V2O5/HZSM-5 catalysts and their catalytic properties were studied. Results show that 5%V2O5/HZSM-5 as catalyst, cyclohexane conversion rate reached 8.08%, caprolactam selectivity of 69.7%.In the research based on previous studies, adopting the carrier of amorphous SiO2-Al2O3, by introducing transition metal oxide to SiO2-Al2O3 catalyst to the preparation of MxOy/SiO2-Al2O3 type catalyst, studying the performance of catalyst,results show that when the V2O5 was loaded at the amorphous SiO2-Al2O3 catalytic,the effect is best. With V2O5/SiO2-Al2O3 as catalyst, through the preparation conditions of the catalyst were optimized, found that when V2O5 loading was 15%, the calcination temperature was 500 ℃, the catalyst particles were uniform and dispersion of active components V2O5 was high,and showed the best catalytic performance. This paper finally choosed 15%V2O5/SiO2-Al2O3 as catalyst, cyclohexane catalyzed nitrosation by process optimization, the optimum reaction conditions: catalyst dosage 0.5 g, reaction temperature 81 ℃, the reaction time for 42 h, cyclohexane conversion rate was 8.01%, the selectivity of caprolactam is up to 73.10%. By catalyst circulation experiment, results show that V2O5/SiO2-Al2O3 catalyst have good stability and cycle performance. This article also on the basis of V2O5/SiO2-Al2O3 as catalyst,cyclohexane catalyzed nitrosation process was studied, and put forward possible catalytic mechanism.In this paper, the nitroso sulfuric acid as the nitration reagent, cyclohexane nitrosation reaction mechanism was studied, through the analysis of the intermediate product for nitroso cyclohexane, determines the cyclohexane nitrosation reaction mechanism. Finally, through replace the nitroso sulfuric acid with sodium nitrite as nitrosation reaction reagent,we had carried on the preliminary research, the qualitative analysis of reaction product shows that the main product of the reaction was nitroso cyclohexane, developed a new route about the preparation of caprolactam from cyclohexane nitrosation with sodium nitrite as nitrosation reagent.