Thermochemical oxygen pump with praseodymium oxides using a temperature-swing at 403–873 K

The praseodymium oxide redox system releases and incorporates oxygen into an inert gas. Reductions of Pr6O11 to Pr5O9 and Pr5O9 to Pr9O16 were analyzed while heating a mixture of air with N2 at O2 partial pressures of 2 × 102-6 × 103 Pa from 373 to 833 K. Oxidations of Pr9O16 to Pr5O9 and Pr5O9 to Pr6O11 were analyzed while cooling from 873 to 373 K. The enthalpy changes for oxidation reactions (5Pr9O16 + 12O2→9Pr5O9 and 6Pr5O9 + 12O2→5Pr6O11) were determined to be − 128 ± 26 and − 138 ± 10 kJ, respectively. The oxygen pump with praseodymium oxides incorporated can be operated between air and a gas with Po2 of 4 × 102 Pa by using a temperature-swing method between 403 and 873 K. The minimum Po2 in diluent N2 achieved was 0.1 Pa at 403 K.