The mechanism of selective NOx reduction by hydrocarbons in excess oxygen on oxide catalysts: V. Adsorption properties of a commercial Ni-Cr oxide catalyst

摘要

According to X-ray diffraction analysis data, the test catalyst was a Ni-Cr spinel with an impurity of NiO. With the use of in situ IR spectroscopy, it was found that nitrite, nitrate, and acetate surface complexes occurred under the reaction conditions of the selective catalytic reduction of nitrogen oxides by propane in the presence of oxygen on the nickel-chromium catalyst. As the temperature was increased, the nitrite complexes were converted into nitrate species. The molar absorption coefficient of surface nitrate complexes was determined. According to IR-spectroscopic and TPD data, the nitrate complexes were bound relatively weakly to the surface. The temperature region of their existence was 50-200 degrees C. The temperature region of existence of the surface acetate complexes was 200-400 degrees C. The individual adsorption of oxygen was not observed; however, oxygen-containing surface sites (Cr5+=O) participated in the formation of the surface complexes ofreactants.