Preparation and Performance of Modified Red Mud-Based Catalysts for Selective Catalytic Reduction of NO x with NH 3

摘要

Bayer red mud was selected, and the NH 3 -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 NH 3 -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 °C, the denitrification efficiency of calcined acid washing of red mud catalyst (ARM) was more than 70%. The doping of Ce significantly enhanced NH 3 adsorption from weak, medium and strong acid sites, reduced the crystallinity of α-Fe 2 O 3 in ARM, optimized the specific surface area and broadened the active temperature window, which increased the NO x conversion rate by an average of nearly 20% points from 250–350 °C. The denitration efficiency of Ce 0.3 /ARM at 300 °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 NH 3 /NO molar ratio ([NH 3 /NO]) of 1.0. The presence of SO 2 in the feed had an irreversible negative effect on the activity of the Ce 0.3 /ARM catalyst.