Effects of Surface Features on Sulfur Dioxide Adsorption on Calcined NiAl Hydrotalcite-like Compounds

Abstract

The hydrotalcite-based NiAl mixed oxides were synthesized by coprecipitation and urea hydrolysis approaches and employed for SO₂ removal. The samples were well characterized by inductively coupled plasma (ICP) elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption/desorption isotherm analyses. The acid-base properties were characterized by pyridine chemisorption and CO₂ temperature-programmed desorption (TPD). The calcined NiAlO from the urea method showed excellent SO₂ adsorption and its adsorption equilibrium showed a type I isotherm, which significantly improved the adsorption performance for low-concentration SO₂. Both the physical structure and the acidic-basic sites were found to play important roles in the SO₂ adsorption process. In situ Fourier transform infrared spectroscopy (FTIR) investigation revealed that adsorbed SO₂ molecules formed surface bisulfite, sulfite, and bidentate binuclear sulfate. The mechanisms for SO₂ adsorption and transformation are discussed in detail.

Catalytic pyrolysis of natural algae over Mg-Al layered double oxides/ZSM-5 (MgAl-LDO/ZSM-5) for producing bio-oil with low nitrogen content

“…This means that the prepared catalyst MgAl-LDH /ZSM-5 successfully obtained the crystal structure of ZSM-5 and MgAl-LDH. However, in the XRD pattern of MgAl-LDO/ZSM-5 composites, besides the peaks of ZSM-5, only peaks at 42.9°and 62.3°, which belonged to MgO phase (JCPDS 4-829), was detected, and no diffraction peaks attributed to crystalline Al 2 O 3 phase could be observed for the high dispersion of Al species in the composite, which was consistent with the literature reports (Zhao et al, 2011).…”

Kinetic study of adsorption and desorption of SO2 over γ-Al2O3 and Pt/γ-Al2O3

“…The peak located at 1350 cm -1 is the characteristic band of surface sulfates, which we also observed when the catalyst was exposed to SO2 and O2 (not shown for brevity). The broad feature in the 950-1100 cm -1 range was attributed to the cooperative effects of surface sulfites and sulfates [23].…”

“…As shown in Figure 2, the intensity of this band significantly decreased after SO2 was removed from the gas-phase and the sample was purged with He. This is explained by the interaction of SO2 with surface hydroxyls leading to the formation of water and bisulfite species (HSO3 -), according to the reaction pathway proposed by Zhao et al [23]:…”

“…According to the adsorption mechanism proposed by Zhao et al [23], when O2 is present in the gas phase, it can adsorb on the surface, forming surface-active oxygen thereby facilitating further oxidation of bisulfite and sulfite species to sulfate. According to our DRIFTS results, the participation of surface oxygen, either originating from residual gas-phase O2 or from the molecular structure of alumina, in the formation of surface sulfate became important upon heating the sample to 450°C.…”

Production of added-value materials from a hazardous waste in the aluminium tertiary industry: Synergistic effect between hydrotalcites and glasses

“…Several environmental uses involving the successful application of hydrotalcites have been reported in the literature, generally focused on the adsorption of pollutant gases such as NO x , SO 2 , CO 2 , etc. [14][15][16][17] or the removal of organic dyes, toxic metals and anions present in wastewaters such as NO 3 À , Cr(VI), Mo(VI), As(V), Se(VI), Pb(II), etc. [18][19][20][21][22][23].…”