SO2 adsorption and transformation on calcined NiAl hydrotalcite-like compounds surfaces: An in situ FTIR and DFT study

Flower-like hydrotalcite-based NiAl mixed oxides with high surface area were synthesized by urea hydrolysis approach, and employed for SO2 removal. The catalyst was well characterized by TGA, ICP, XRD, SEM, TEM and N2 adsorption/desorption isotherm analyses. The calcined NiAlO showed excellent SO2 adsorption and its adsorption equilibrium was of a type I isotherm, which significantly improved the adsorption performance for low-concentration SO2. XPS and TPD methods were conducted to identify the sulfate species. Specifically, in situ Fourier transform infrared spectroscopy revealed that adsorbed SO2 molecules formed surface bidentate binuclear sulfate. Density functional theory based computations interpreted the vibrational data associated with the NiAlO surface and confirmed that sulfate species adopted a binuclear bidentate binding configuration on the surface of NiAlO catalyst.

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► Flower-like hydrotalcite-based NiAl mixed oxides showed excellent SO2 adsorption.
► The SO2 adsorbed on the NiAlO catalyst is converted into SO32–, HSO3–, and SO42–.
► Density functional theory confirmed a binuclear bidentate binding configuration.