Effects of Preparation Conditions on the Performance of Simultaneous Desulfurization and Denitrification over Ni/Fe Hydrotalcite-like Compounds

The effects of a series divalent metals, ratios of metals, and calcination temperature on the performance of simultaneous desulfurization and denitrification over the hydrotalcite-like compound (HTLC) catalyst were investigated, and the removal mechanism of HTLCs was characterized by X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, temperature-programmed desorption–mass spectroscopy (TPD–MS), and Fourier transform infrared spectroscopy (FTIR) analyses. The results showed that Ni/Fe HTLCs had the best adsorption property to remove SO2 and NO among the three HTLCs: Ni/Fe, Mg/Fe, and Co/Fe HTLCs. The optimum preparation conditions of the adsorbent were at the Ni/Fe mole ratio of 2 and calcined at 300 °C. The high specific surface area as well as the existence of Fe2O3 phases resulted in excellent NO and SO2 adsorption capacities. The removal rate of SO2 and NO still remained at 95 and 50% when the reaction time had extended to 40 min. A total of 13% CO2 of the simulated flue gas had no significant effect on the adsorption of NO and SO2. The NO adsorption capacity decreased slowly with the increase of the H2O concentration, and a total of 2% H2O enhanced the SO2 adsorption capacity but inhibited the SO2 adsorption slightly when the H2O concentration still increased to 5%. SO2 was chemisorbed on the Ni/Fe HTLCs, and the products were sulfate and sulfite according to the characterization results. However, NO was physisorbed and chemisorbed on the Ni/Fe HTLCs, and the chemisorption products were nitrate and nitrite.