Reversible sorption of nitrogen oxides in Mn-Zr oxide

Removal of NO (900 ppm) was investigated using several mixed metal oxide systems in the presence and absence of gaseous O-2. At 200-300 degrees C Mn-Zr oxide exhibited the highest NO removal among the oxides investigated and it was facilitated in the presence of O-2. The removal was accompanied by the sorption of oxidized NO species on or in the solid and stored via formation of nitrate. Since the sorption and desorption was reversible, the oxide sorbent was regenerated on heating the sample at 400 degrees C after NO uptake. The stored NOx species were also eliminated from the solid by reduction with C3H8 or C2H5OH at 300 degrees C. The amorphous phase of the Mn-Zr oxide which is formed after heating this oxide at 450 degrees C was extremely effective for NO removal due to good mixing between Mn and Zr oxides. The surface area of the oxide was a maximum and the amorphous phase was dominant for the oxide with Mn/Zr = 1. The removal of NO was not influenced by coexisting CO2 and was promoted by the presence of H2O. (C) 1996 Academic Press, Inc.