Removal of volatile odorous organic compounds over NiAl mixed oxides at low temperature

In this paper, a series of NiAl hydrotalcite-like compounds (HTLCs) were prepared by the urea-decomposition method. Removal of carbonyl sulfide (COS) and methyl mercaptan (CH₄S) over the hydrotalcite-derived oxides (HTO) at low temperature was studied. The Ni3Al-HTO exhibited higher catalytic activities than Ni3Al mixed oxides prepared by physical mixing method (Ni3Al-PM) or impregnation/calcination method (Ni3Al-IC). Based on the characterization, it was found that desulfurization activities are closely tied to the surface acid-base properties of catalysts. CO₂-TPD indicates that the basic characteristic of the Ni3Al-HTO is prominent. XPS results showed that there was a strong interaction between Ni and Al element on Ni3Al-HTO. The first principle calculation based on density function theory was applied with the aim to study the change of basic sites. The results showed that Ni3Al-HTO presents a half-metallic characteristic. Electron transfer from the Al and O atom to the Ni atom was observed, which is helpful for the transfer of electrons from the surface and improves the catalytic activity. Analysis of the DRIFT spectra suggests that sulfate species was formed by the action of surface basic sites, resulting in the formation of H₂O on the surface.