Promoting effect of FeOx addition on the mechanochemically prepared vanadium-based catalyst for real PCDD/Fs removal and mechanism insight

Industrial-use VOx-based catalysts usually have a higher active temperature window (> 250-300°C), which becomes a "bottleneck" for the practical application of PCDD/Fs catalytic degradation technology. In this work, VOx-FeOx/TiO2 catalyst prepared via mechanochemically method was investigated for the catalytic removal of PCDD/Fs. The removal efficiency of 1,2-DCBz, pure PCDD/Fs gas generated in the lab, PCDD/Fs from actual flue gas, long-term were studied, and the degradation mechanism was explored using FTIR and TOFMS. The degradation efficiency of 1,2-DCBz and PCDD/Fs on VOx-FeOx/TiO2 were higher than that of VOx/TiO2 catalyst, and the optimal FeOx addition ratio was 3 wt.%. The characterization results show that the addition of FeOx can effectively improve the pore structure, surface acidity, and VOx dispersion of the catalyst, thus contributing to increasing the V5+ content and surface-active oxygen, which is conducive to the improvement of adsorption and redox performance of the catalyst. Under the actual MSWI (municipal solid waste incineration) flue gas, the PCDD/Fs removal efficiency over VTi-3Fe-MC maintained long-term stability, higher than 85% for 240 min. This result was not significantly reduced compared with the data obtained in the laboratory. According to the analysis results of intermediate products by FTIR and GC-TOFMS, it can be inferred that the epoxidation fracture of benzene ring is the rate-limiting step of dioxin catalytic degradation reaction. This work gives an in-depth view into the PCDD/Fs removal over VOx-FeOx/TiO2 catalysts and could provide guidelines for the rational design of reliable catalysts for industrial applications.

A sulfur-resistant CuS-modified active coke for mercury removal from municipal solid waste incineration flue gas

Adsorption is a typical method for air pollutant removal from flue gas. A CuS-modified active coke (CuS/AC) sorbent was developed to improve the elemental mercury removal efficiency from municipal solid waste incineration (MSWI) flue gas. The influences of the loading amount of CuS, reaction temperature, and flue gas components including O₂, SO₂, H₂O, and HCl on Hg⁰ removal efficiency were investigated, respectively. The results showed that the mercury adsorption capacity of CuS/AC_(20%) sorbent was about 7.17 mg/g with 50% breakthrough threshold, which is much higher than that of virgin active coke. The analysis of XPS indicated that HgS was the main species of mercury on spent CuS/AC, which implied that adsorption and oxidation were both included in Hg⁰ removal. S₂^2- played a vital role in the oxidation of physically adsorbed Hg⁰. Meanwhile, the common components of MSWI flue gas exhibited no significant inhibition effect on Hg⁰ removal by CuS/AC sorbent. CuS/AC sorbent is a promising sorbent for the mercury removal from MSWI flue gas.