Lu Pei,Yue Huifang,Xing Yi,Wei Jianjun,Zeng Zheng,Li Rui,Wu Wanrong
In this study, series of Ce x Zr y Mn z O 2 /r-Al 2 O 3 catalysts were prepared by impregnation method and explored to co-purification of NO x and Hg 0 at low temperature. The physical and chemical properties of the catalysts were investigated by XRD, BET, FTIR, NH 3 -TPD, H 2 -TPR, and XPS. The experimental results showed that 10% Ce 0.2 Zr 0.3 Mn 0.5 O 2 /r-Al 2 O 3 yielded higher conversion on co-purification of NO x and Hg 0 than the other prepared catalysts at low temperature, especially at 200–300 °C. 91% and 97% convert rate of NO x and Hg 0 were obtained, respectively, when 10% Ce 0.2 Zr 0.3 Mn 0.5 O 2 /r-Al 2 O 3 catalyst was used at 250 °C. Moreover, the presence of H 2 O slightly decreased the removal of NO x and Hg 0 owing to the competitive adsorption of H 2 O and Hg 0 . When SO 2 was added, the removal of Hg 0 first increased slightly and then presented a decrease due to the generation of SO 3 and (NH 4 ) 2 SO 4 . The results of NH 3 -TPD indicated that the strong acid of 10% Ce 0.2 Zr 0.3 Mn 0.5 O 2 /r-Al 2 O 3 improved its high-temperature activity. XPS and H 2 -TPR results showed there were high-valence Mn and Ce species in 10% Ce 0.2 Zr 0.3 Mn 0.5 O 2 /r-Al 2 O 3 , which could effectively promote the removal of NO x and Hg 0 . Therefore, the mechanisms of Hg 0 and NO x removal were proposed as Hg (ad) + [O] → HgO (ad), and 2NH 3 /NH 4 + (ad) + NO 2 (ad) + NO (g) → 2 N 2 + 3H 2 O/2H + , respectively.
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Jing Yang,Heng-Quan Chen,Fen Qiao,Xifeng Zhu,Tao Wang,Wei-Ping Pan
Engineering metal-based nanoarchitectures and their atomic-scale arrangement is a promising avenue for enhanced mercury adsorbent activities. Interactions between metal single atoms and substrates result in regulated transitions between distinct reaction processes that boost mercury adsorption activity. Herein, a novel sorbent of porous Co 3 O 4 with Palladium atomic dispersed was successfully prepared by one-step pyrolysis of zeolitic imidazolate framework 67 (ZIF-67) precursors. Via engineering single Pd atoms into ZIF-derived Co 3 O 4 (Pd 1 /Co 3 O 4 -ZIF), the strong metal-support interaction (SMSI) activated the reducibility of Co 3+ in porous Co 3 O 4 to efficiently adsorb and oxidize Hg 0 , enhancing its mercury removal efficiency. Specifically, Pd 1 /Co 3 O 4 -ZIF exhibited superior sorption performance for Hg 0 over a broad range of temperatures (30–350 °C) and high gaseous hourly space velocity (about 555,500 hr −1 ) with the average Hg 0 removal efficiency higher than 98%. The strategy of constructing atomic active sites on the surface of porous metal-oxide to convert adsorbed Hg 0 into HgO is a promising approach to solve the problem that Hg 0 in flue gas is challenging to remove. Density functional theory (DFT) calculation further proved that the existence of a single Pd site on the surface of Co 3 O 4 significantly reduced the energy barrier of Hg 0 to HgO at the atomic level. This work contributed to a thorough comprehension of the structural and adsorption properties of the ZIF-derived Co 3 O 4 sorbent engineering with a single atom and enabled the efficient capture of elemental mercury in flue gas by such ZIF-derived sorbent.
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