Abstract
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 °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 α-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 °C. The denitration efficiency of Ce0.3/ARM at 300 °C was as high as 88%. The optimum conditions for the denitration reaction of the Ce0.3/ARM catalyst were controlled as follows: Gas Hourly Space Velocity (GHSV) of 30,000 h−1, O2 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 Ce0.3/ARM catalyst.
Highlights
Red mud, which is a major solid waste derived from the aluminum industry, has been producing in huge quantities over the decades
The results showed that the Ce0.3 /acid washing of red mud catalyst (ARM) catalyst was adapted to Gas Hourly Space Velocity (GHSV) of 15,000–30,000 h− 1
Bayer red mud from industrial waste was prepared as low-cost red mud-based catalyst to evaluate the performance of denitration with simulated coal-fired flue gas
Summary
Red mud, which is a major solid waste derived from the aluminum industry, has been producing in huge quantities over the decades. Most of the red mud is treated for landfilling, which brings a heavy burden to the environment. Bayer red mud is considered hazardous due to its strong alkalinity (pH = 10–12). Utilization of red mud has become the focus of study and an urgent issue all over the world. Since red mud contains Fe2 O3 (20–50%). The large-scale catalysis application of red mud is limited because of its alkalinity [6], mainly originating from Na and Ca, and their oxides can cause sintering in the catalyst and reduce the catalytic activity [7]. Li et al [8] developed a ball milling and acid-base neutralization method to reuse red mud as an efficient Fe-Ti/Si-Al denitration catalyst free of alkali. Cao et al [9]
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