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

Abstract

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.