Perovskite-type oxides ammonia oxidation

Some dense inorganic membranes made of metals and metal oxides are oxygen specific. Notable ones include silver, zirconia stabilized by yttria or calcia, lead oxide, perovskite-type oxides and some mixed oxides such as yttria stabilized titania-zirconia. Their usage as a membrane reactor is profiled in Table 8.4 for a number of reactions decomposition of carbon dioxide to form carbon monoxide and oxygen, oxidation of ammonia to nitrogen and nitrous oxide, oxidation of methane to syngas and oxidative coupling of methane to form C2 hydrocarbons, and oxidation of other hydrocarbons such as ethylene, methanol, ethanol, propylene and butene. 

Other types of oxides, non-perovskite oxides including pyrochlores and fluorites, have also been investigated. It was found that the ammonia formation rates from pyrochlore-type membrane were close to that obtained from perovskite-type membranes, although in the case of the fluorite membrane, the formation rates were slightly higher (Liu et al., 2006 Xie et al., 2004 Wang et al., 2005). More comprehensive details about characteristics of each material, fabrication, cell components, and the formation rate can be found in a review presented by Amar et al. (2011). 

Ammonia oxidation was the test reaction chosen by Yu et al. (1992) to investigate connections between structure and catalytic properties in Lai- Sr NiC and Lai i 33iThxNi03 For x < 0.3, both types of solids only showed the reflections corresponding to the perovskite structure. At x 0.3, several other phases appeared, i.e. NiO, La2Ni04 and Th02. As the Sr concentration increases, the number of oxygen... 

RTi02N (R = La, Nd), RTaON2 (R=La-Dy) and LaNbON2 oxynitrides (Marchand et al. 1991b) were prepared at 950°C by reaction between ammonia and the corresponding ternary oxides, and were characterized as orthorhombic perovskites of the GdFe03-type (Muller and Roy 1974). The slight deformation, which induces the loss of cubic... 

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