Structural characterization and catalytic evaluation of transition and rare earth metal doped ceria-based solid solutions for elemental mercury oxidation
Structural characterization and catalytic evaluation of transition and rare earth metal doped ceria-based solid solutions for elemental mercury oxidation
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DOI：
10.1039/c3ra41441h
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发表时间：
2013-01-01
期刊：
影响因子：
3.9
通讯作者：
Reddy, Benjaram M.
中科院分区：
文献类型：
--
作者：
Jampaiah, Deshetti;Tur, Katie M.;Reddy, Benjaram M.
研究了不同ceo2固溶体ce1 - xtmxo2 - δ （TM = Mn、Fe或Zr）和ce1 - xrexo2 - δ （RE = Pr、La或Sm）对煤源烟气中单质汞（Hg-0 -> Hg2+）的催化氧化行为。采用共沉淀法合成催化剂，并通过x射线衍射（XRD）、拉曼光谱（RS）、高分辨率电子显微镜（HREM）、布鲁诺尔-埃米特-泰勒（BET）表面积、x射线光电子能谱（XPS）、程序升温还原（TPR）和漫反射光谱（UV-DRS）等技术对催化剂进行了表征。XRD结果证实了Mn、Fe、Zr、La、Pr和Sm阳离子进入CeO2晶格并形成纳米固溶体。透射电镜测量确定了固溶体的纳米晶性质。RS测量结果表明，取代过程促进了氧空位的形成，加快了氧的扩散速度，改善了汞的氧化。UV-vis DRS研究证实了O2- -> Ce3+和O2- -> Ce4+电荷转移跃迁的存在。XPS和H-2-TPR结果表明，Ce4+ -> Ce3+的还原是导致氧空位增加的主要原因，这有利于Hg-0的去除。不同掺杂催化剂的汞氧化活性顺序为：CM > CL > CZ > CF > CS > C > CP。
The catalytic behavior of various CeO2-based solid solutions, namely, Ce1-xTMxO2-delta (TM = Mn, Fe, or Zr) and Ce1-xRExO2-delta (RE = Pr, La, or Sm) was studied for the removal of elemental mercury (Hg-0) from coal-derived flue gas by catalytic oxidation (Hg-0 -> Hg2+). The investigated catalysts were synthesized by a coprecipitation method and characterized by various techniques, namely, X-ray diffraction (XRD), Raman spectroscopy (RS), high-resolution electron microscopy (HREM), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR), and diffuse reflectance spectroscopy (UV-DRS). The XRD results confirmed the incorporation of Mn, Fe, Zr, La, Pr, and Sm cations into the CeO2 lattice and the formation of nanocrystalline solid solutions. The TEM measurements established the nanocrystalline nature of the solid solutions. The RS measurements suggested that the substitution process promotes the formation of oxygen vacancies, which hastens the diffusion rate of oxygen and improves the Hg oxidation. UV-vis DRS studies demonstrated the presence of the charge transfer transitions O2- -> Ce3+ and O2- -> Ce4+. The XPS and H-2-TPR results suggested that the reduction of Ce4+ -> Ce3+ is the foremost reason for the increase in oxygen vacancies, which are beneficial for Hg-0 removal. The order of mercury oxidation activity over various doped catalysts is as follows: CM > CL > CZ > CF > CS > C > CP.