Infrared spectroscopic study of NO and NH3 adsorption on alumina-supported nickel oxide catalysts

The surface changes of alumina due to supported nickel oxide species (samples are prepared by step-wise pore volume impregnation with formate solutions) are studied in the high frequency region (OH stretches) by the method of in situ FTIR spectroscopy. A hypothesis is made that the nickel species deposite predominatingly on the surface neutral OH groups via hydrogen bonds. The deposition of the nickel oxide species on the coordinatively unsaturated Al3+ ions (obtained as result of the dehydroxylation) is also discussed. The metal concentration increase does not lead to the change in the alumina surface, while the calcination temperature appears to change it. The adsorption and desorption of ammonia species on the nickel-supported samples reveal that the nickel concentration increase results in the increase of the number of the nickel species and in the intensity increase of the bands corresponding to ammonia more weakly bonded to the nickel species. The analysis of the spectra reveals that the sample containing 1.7% NiO and heated at 870 K displays the highest activity with respect to NO oxydation as compared to other samples studied.