Cu promoted hydrotalcite-based NiAl mixed oxides in adsoption and oxidation of SO2 reaction: Experimental and theoretical study

Introduction of copper into hydrotalcite-based NiAl mixed oxides resulted in improved SO2 adsorption and oxidation performance. XRD revealed the formation of a crystalline NiO phase in which some of the Cu2+ cations are dissolved. The pyridine chemisorption, CO2-TPD, XPS, H-2-TPR and SO2-TPD studies revealed that introduction of Cu into NiAlO generates new centers for oxygen storage and release, promotes the enhancement of Bronsted and Lewis acid strength, increases weakly and strongly alkaline sites, and increases ability for SO2 adsorption and oxidation. In situ Fourier transform infrared spectroscopy demonstrated that adsorbed SO2 molecules formed surface bidentate binuclear sulfate. Density functional theory based computations interpreted the vibrational data associated with the NiAlO and CuNiAlO surface and confirmed that sulfate species adopted a binuclear bidentate binding configuration. Taken together, we propose that the addition of Cu2+ to NiAlO acts to improve this compound as major adsorbent for SO2.