The mechanism of selective NOx reduction by hydrocarbons in excess oxygen on oxide catalysts: III. Adsorption properties of the commercial STK catalyst

摘要

According to X-ray diffraction data, the STK catalyst is a mixture of Fe2O3 and Cr2O3. The temperature-programmed reduction spectrum exhibited two reduction peaks: one, with T-max = 250 degrees C, corresponds to the reduction process Cr2O3 --> CrO and the other, with T-max = 360 degrees C, corresponds to the reduction Fe2O3 --> Fe3O4. The results of thermal desorption measurements suggest that the individual adsorption of oxygen on the surface of the STK catalyst is low; in this case (according to IR-spectroscopic data), an atomic form is the main species. Surface nitrite-nitrate complexes are formed upon the adsorption of NO. Nitrite and nitrate complexes desorbed at maximum rates at 105 and 160 degrees C, respectively. Unlike the NTK-10-1 catalyst, the NO species, which desorbed at high temperatures (250-400 degrees C), was absent from the surface of STK. Propane adsorbed at room temperature to form surface compounds containing an acetate group. The interaction of propane with the surface of the STK catalyst at reaction temperatures resulted in strong surface reduction.