Analysis And Phase Equilibrium For N₂O₄-N₂O₅-HNO₃ System And Nitration Of Propylene Oxide By N₂O₅

Advantages of new green nitrating agent of dinitrogen pentoxide in comparison to conventional nitrating agents are: ease of temperature control, simple isolation of the product, high selectivity in position of attack with multifuctional substrates, fasibility towards the reaction in acidic medium to offer strong nitrating system. So it receives more and more concerns.In this study, the N2O4-N2O5-HNO3 system was analyzed by the methods of Raman spectrum, nuclear magnetic resonance spectrum (NMR) and chemical titration. Cloud-point method was used to obtain the data of Liquid-Liquid and Solid-Liquid equilibrium. The nitration reaction of propylene oxide with dinitrogen pentoxide was conducted in a batch reactor.The results of low-temperature Raman spectrum indicated that the integrated intensity of the nitronium cation (NO2+) at 1400cm-1 with the concentrations of pentoxide dinitrogen was approximately linear. Thus this method could be applied to monitor the process of producing dinitrogen pentoxide by electrochemical oxidation of dinitrogen tetroxide in nitric acid.The results from the two-step titration method of redox titration combined with acidity titration were well consistent with that from the method of redox titration combined with NMR. Both analytic methods had high accuracy and were good to analyze the N2O4-N2O5-HNO3 system. In the two-step titration, optimum conditions were cerium sulfate as oxidant, sampling using ampoule ball and distilled water as solvent.Liquid-Liquid and Solid-Liquid equilibrium data for the N2O4-N2O5-HNO3 system was obtained at 258.2K ~281.2 K. The critical points and the solubility of dinitrogen pentoxide in dinitrogen tetroxide and nitric acid, respectively, were determined. The structures of the reaction products in the nitration of propylene oxide were identified by Raman, NMR and GC-MS. The results indicated that 1,2-propanediol dinitrate was the main product in the nitration reaction, 1,2-propanediol nitrate the major byproduct. The effect of reagents, reaction temperature, dinitrogen tetroxide and nitric acid on the yield and purity of 1,2-propanediol dinitrate were also investigated. The results indicated that CHCl3 was optimum reagent and the reaction temperature was better controlled at 10~15℃. Dinitrogen tetraoxide and nitric acidhad a detrimental effect on the yield and purity of 1,2-propanediol dinitrate. When the concentrations of dinitrogen tetroxide and nitric acid were below 1.00% and 5.53% respectively, these detrimental effects could be neglected. Under the optimum conditions, the yields and the purity of 1,2-propanediol dinitrate were 99.01% and 95.89%, respectively.