Lanthanum ferrite membranes in ammonia oxidation: Opportunities for ‘pocket-sized’ nitric acid plants

This paper reports the application of mixed conducting perovskite membranes for simultaneous in situ O2 separation and catalytic oxidation of ammonia to nitric oxide. Calcium and strontium-substituted lanthanum ferrite perovskites (La1−xAxFeO3−δ, with A = Ca, Sr and x = 0.1–0.2) were prepared by a conventional wet complexation route with citric acid. Dense membrane disks were obtained by uniaxial pressing of the calcined powders followed by sintering. The oxidation of ammonia over these catalytic membranes in the temperature range of 1000–1333 K leads to NO selectivities up to 98% with no N2O production, showing stable performance during several days on stream. This novel process demonstrates the great potential for intensification of nitric acid manufacture into miniaturized plants and is considered to be particularly attractive for on-site production of this important bulk chemical.