Electrochemical synthesis of N 2O 5 by oxidation of N 2O 4 in nitric acid with PTFE membrane

Abstract

Electrochemical synthesis of dinitrogen pentoxide (N 2O 5) by oxidation of dinitrogen tetroxide (N 2O 4) in a plate-and-frame electrolyzer was investigated. As the separator, different porous polytetrafluoroethylene (PTFE) membranes were tested in this process and the effects of hydrophilicity and of hydrophobicity on the electrolysis were discussed. The transport of N 2O 4 and water from catholyte to anolyte through membrane occurred in the electrolysis, especially at the end of the electrolysis. The water transport had a much more effect on the electrolysis than that of the N 2O 4 diffusion. The hydrophobic PTFE membranes had better performance on control of water transport from catholyte to anolyte than that of the hydrophilic ones. Hydrophobicity can increase the chemical yield of N 2O 5. The membranes with a low hydrophobic surface were preferred. All the hydrophobic PTFE membranes with low resistance have the specific energy of 1.1–1.5 kWh kg −1 N 2O 5. The current efficiency of 67.3–80.2% and chemical yield of 58.9–60.9% were achieved in production of N 2O 5. The technique of replacing the catholyte with fresh nitric acid can minimize the transport of N 2O 4 and water to a great extent, it can further improve the chemical yield and reduce the specific energy.