Preparation and Performance of Modified Red Mud-Based Catalysts for Selective Catalytic Reduction of NOx with NH3

Bayer red mud was selected, and the NH3-SCR activity was tested in a fixed bed in which the typical flue gas atmosphere was simulated. Combined with XRF, XRD, BET, SEM, TG and NH3-Temperature Programmed Desorption (TPD) characterization, the denitration characteristics of Ce-doped red mud catalysts were studied on the basis of alkali-removed red mud. The results showed that typical red mud was a feasible material for denitration catalyst. Acid washing and calcining comprised the best treatment process for raw red mud, which reduced the content of alkaline substances, cleared the catalyst pore and optimized the particle morphology with dispersion. In the temperature range of 300-400 degrees C, the denitrification efficiency of calcined acid washing of red mud catalyst (ARM) was more than 70%. The doping of Ce significantly enhanced NH3 adsorption from weak, medium and strong acid sites, reduced the crystallinity of alpha-Fe2O3 in ARM, optimized the specific surface area and broadened the active temperature window, which increased the NOx conversion rate by an average of nearly 20% points from 250-350 degrees C. The denitration efficiency of Ce-0.3/ARM at 300 degrees C was as high as 88%. The optimum conditions for the denitration reaction of the Ce-0.3/ARM catalyst were controlled as follows: Gas Hourly Space Velocity (GHSV) of 30,000 h(-1), O-2 volume fraction of 3.5-4% and the NH3/NO molar ratio ([NH3/NO]) of 1.0. The presence of SO2 in the feed had an irreversible negative effect on the activity of the Ce-0.3/ARM catalyst.