Electrochemical Synthesis Of A New Green Nitrating Agent Of N₂O₅

Nitration products find many applications in pharmaceutical products, agricultural and pest control chemicals, pigments, precursors for polyurethane or polyamide production and high energy materials. Conventional nitration of organic compounds normally involves nitric acid in conjunction with other reagents such as sulphuric acid. However, undesirable side reactions often occurred and serious pollution problem was caused in the conventional processes. In addition, it can not meet with the requirements of selective nitration and deactivated substrates.Dinitrogen pentoxide (N2O5) could be a promising alternative nitrating agent. In contrast to the conventional nitrating agent, N2O5 had several advantages such as simple isolation of the product, ease of temperature control and absence of spent acid for disposal. Furthermore, in many reactions, higher reactivity and selectivity can be obtained with the use of N2O5. So the followings had been studied in this thesis in order to produce N2O5 by electric oxidation of N2O4.A divided electrolytic cell was designed. The effect of the configuration of the electrolytic cell on the electric process was investigated, and the optimum condition of the electrolytic cell was determined. Ti was selected as the electrode substrate, and Pt, RuO2-IrO2 and IrO2 were used as the electrode coat. It was found that the electrolysis results were the best, when IrO2/Ti as the anodic electrode material, and IrO2/Ti as the cathodic electrode material. The hydrophobic PTFE membrane was used as the separator of the electroyzer. The effects of physical parameters of PTFE membrane, such as hydrophobility, pore size on the N2O5 electrosynthesis were investigated. The hydrophilic surface favored the transport of water and N2O4 through PTFE membrane and the chemical yield was decreased. The higher hydrophobicity would restrain the charge transport and increase the special energy of the electrolysis. The low hydrophobicity with an angle contact of water at about 92~110°is preferred. Thick membrane could not inhibit the transports of water and N2O4 through membrane. So the perfect thickness of membrane was 60-200μm. The current efficiency could be improved by using the aperture of PTFE membrane less than 0.2μm. With the above optimized electrolytic conditions, the yield of N2O5 was 86.95wt% for 8 hours electrolysis under 2.5 V voltage. The current efficiency was 89.23%, and the specific energy was 0.72 kWh/kgN2O5.