Dependence of chemical composition of calcined hydrotalcite-like compounds for SOx reduction

Binary and ternary hydrotalcite-like (HT) materials containing copper, nickel, zinc, iron, magnesium and/or aluminum were synthesized by coprecipitation and characterized by elemental analysis, powder X-ray diffraction and N2 adsorption–desorption at −196 °C. Samples were calcined at 700 °C for 4 h, obtaining mixed oxides which were tested for sulfur oxides (SOx) removal. Their performance was compared with a commercial SOx reducing additive by thermogravimetric SOx uptake. SOx adsorption was carried out by contacting the calcined solid with a mixture of 1% SO2 in air at 650 °C. The adsorbed species were reduced with H2 at 550 °C, 650 °C and 700 °C, in order to study their stability and the solid's regenerability. It was found that the isomorphic incorporation of a transition metal in the HT layers increased the mixed oxide's reduction ability. This was reflected on higher reduction rates and sulfate reduction amounts at 550 °C. Furthermore, these materials showed greater adsorption–reduction properties than the commercial additive.