WO2010096957A1 - 用电场激活稀土氧化物及其复合氧化物催化剂活性的方法 - Google Patents

用电场激活稀土氧化物及其复合氧化物催化剂活性的方法 Download PDF

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WO2010096957A1
WO2010096957A1 PCT/CN2009/070523 CN2009070523W WO2010096957A1 WO 2010096957 A1 WO2010096957 A1 WO 2010096957A1 CN 2009070523 W CN2009070523 W CN 2009070523W WO 2010096957 A1 WO2010096957 A1 WO 2010096957A1
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electric field
oxide
catalyst
oxygen content
rare earth
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French (fr)
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高鹏
白雪冬
王恩哥
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中国科学院物理研究所
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/96—Regeneration, reactivation or recycling of reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90—Regeneration or reactivation
    • B01J23/92—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
    • B01J37/342—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of electric, magnetic or electromagnetic fields, e.g. for magnetic separation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/206—Rare earth metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/206—Rare earth metals
    • B01D2255/2065—Cerium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/908—O2-storage component incorporated in the catalyst

Definitions

  • the invention belongs to the field of catalysis, and in particular relates to a method for activating the activity of a rare earth oxide and a composite oxide catalyst thereof. Background technique
  • Oxides of rare earth elements such as cerium (Ce) are industrially widely used catalysts for purifying exhaust gas, wastewater, and dehydrogenation.
  • TeWC three-way catalysts
  • their main application is currently to treat automobile exhaust.
  • TWC is used to treat some common polluting gases such as C0, N0 X and hydrocarbons without combustion.
  • the function of the TWC is to provide additional oxygen to fully burn the fuel under fuel-rich conditions and to absorb oxygen from the external environment and store it under fuel-poor conditions.
  • cerium (Ce) oxides in TWC The core principle of the action of cerium (Ce) oxides in TWC is that yttrium can exist in the form of positive trivalent (3+) and positive tetravalent (4+), capable of undergoing oxidation-reduction at higher temperatures, and Oxides have a high oxygen mobility.
  • bismuth oxides such as it can easily form rare earth composite oxides with other metals, thereby having high thermal stability and high oxygen storage capacity (Oxygen).
  • Storage capacity, OSC there are some shortcomings in the car tail gas treatment catalyst based on oxides. For example, the problem of cold start is that the car will not reach its working temperature for the next period of time (usually several tens of seconds) after the start of the car.
  • the normal operating temperature of the cerium oxide catalyst refers to the temperature at which two conditions need to be simultaneously satisfied: one is that the gas component to be treated can react with the cerium oxide; the other is the phase with a low cerium oxide oxygen content (ie, Ce 2 0 3 phase) can be stable.
  • C0, NO can react with Ce0 2 at room temperature, and some common hydrocarbons such as decane and ethane can react with Ce0 2 at room temperature (see A.
  • the idea of activating the activity of the catalyst at normal temperature or lower is to design a method for enabling the rare earth oxide and its composite oxide to remain in a low oxygen content phase at normal temperature or lower.
  • an electric field can drive an oxidation-reduction reaction process of a rare earth oxide and a composite oxide catalyst thereof. That is, an electric field is applied to such an oxide material, and oxygen ions in the oxide material will migrate due to the low potential well, and accompany the release of oxygen from the high oxygen content phase (Ce0 2 ) to the low oxygen content. Phase change of phase (Ce 2 0 3 ); After the electric field, the low oxygen content phase can immediately recover from the environment and then return to the high oxygen content phase. This process is reversible. The reversible phase transition of such oxides under the action of an electric field is consistent with the oxidation-reduction process which typically operates at higher temperatures. Therefore, based on this, the present invention proposes a method of using an electric field to activate the performance of a rare earth oxide and a composite oxide catalyst thereof, so that the catalyst can be operated at a normal temperature or even lower temperature.
  • the specific method of the present invention is to intermittently apply an electric field to the rare earth oxide and its composite oxide catalyst to cause a mutual transition from a high oxygen content phase to a low oxygen content phase, thereby activating the catalyst at normal temperature or lower. Activity.
  • the crystal structure of the rare earth oxide present invention relates generally fluorite structure, common materials ceria (CeO 2), praseodymium oxide (Pr0 2), terbium oxide (Tb0 2), and the like.
  • the fluorite structure rare earth composite oxide material refers to a binary solid solution formed by partial cation substitution by other cations. For example, some of the cerium ions in the cerium oxide are replaced by zirconium ions.
  • the substituted elements may also be bismuth, copper, bismuth, aluminum, calcium, strontium, barium, strontium, and the like.
  • the rare earth composite oxide material further includes a solid solution of ternary or even ternary or higher. For example, in the most common solid solution of cerium-zirconium, a third element is introduced, mainly rare earth elements such as lanthanum, cerium, lanthanum and cerium.
  • An electrode is placed on either side of the fluorite structure oxide or its composite oxide, and an electric field is applied in the case of a fuel rich, even if the temperature at this time is even lower near normal temperature, the stable phase of the fluorite structure oxide or the composite oxide It will change from a high oxygen content phase to a low oxygen content phase. This is because the surface lattice oxygen of such oxides is very active and can react with C0, NO, etc. at room temperature. Under the action of the electric field, the lattice oxygen on the surface of the oxide is more active, reacting more easily with the fuel molecules adsorbed on the surface, producing oxygen vacancies and products of complete combustion.
  • Oxygen vacancies on the surface continue to diffuse into the body; oxygen ions continue to diffuse from the body to the surface, filling the oxygen vacancies generated on the surface, preparing for the next reaction.
  • the existence of an electric field will make this diffusion process proceed more quickly. Until a large amount of oxygen ions are consumed, a large amount of oxygen vacancies are generated, and the oxide is converted from the original high oxygen content phase to the low oxygen content phase.
  • the effect of the electric field actually breaks the chemical equilibrium that was originally maintained by the oxidation potential, allowing the chemical reaction to proceed from the high oxygen content phase to the low oxygen content phase. Under the new chemical equilibrium maintained by the electric field and the oxidation potential, their low oxygen content phase can remain stable.
  • the stable phase of the fluorite structure oxide or its composite oxide is converted from a low oxygen content phase to a high oxygen content phase.
  • Driving in the oxidative potential Under the action, the oxide will absorb oxygen from the external environment and spontaneously recover to the high oxygen content phase.
  • the magnitude of the electric field strength applied in the method of the present invention depends on the type of fluorite structure oxide material, as well as the environmental conditions at which it is exposed to temperature and external oxygen pressure. Whether the stable phase of the material is high oxygen or low oxygen is determined by the chemical potential of oxygen, which is a function of temperature and ambient oxygen partial pressure. The higher the temperature, the less the intensity of the applied electric field.
  • phase-change process of the electric field driven by the present invention is comparable to the speed of the phase transition process driven by the oxidation potential, depending on the type of material, specific surface area, crystal defects, ambient temperature and oxygen pressure.
  • the rare earth oxides and composite oxide materials thereof according to the method of the present invention include film materials, nanocrystalline materials and bulk materials.
  • FIG. 1 is a structural view of a structure according to an embodiment of the present invention.
  • TEM transmission electron microscope
  • Figure 3a is an electron diffraction diagram of the Ce0 2 film of the present invention when no electric field is applied;
  • Figure 3b is an electron illuminating diagram of the Ce0 2 film of the present invention when an electric field is applied;
  • 4a is a graph showing an electron energy loss spectrum (EELS) oxygen K-side change of a Ce0 2 film of the present invention, wherein 1 is data when no electric field is applied, 2 is data when an electric field is applied, and 3 is data when an electric field is removed;
  • EELS electron energy loss spectrum
  • 4b is a white line diagram of the electron energy loss spectrum (EELS) of the Ce0 2 film of the present invention, wherein 1 is data when no electric field is applied, 2 is data when an electric field is applied, and 3 is data when an electric field is removed.
  • EELS electron energy loss spectrum
  • a ruthenium dioxide film is grown on a conductive substrate.
  • Fig. 2b is a TEM high resolution diagram of the Ce0 2 film when an electric field is applied. Compared with Fig. 2a, there are obvious modulation fringes, and the appearance of such modulation fringes proves that ordered oxygen vacancies are produced.
  • the selected area electron diffraction pattern of the CeO 2 film when no electric field is applied is the reciprocal of the quadruple lattice constant.
  • Figure 3b is a selected electron diffraction pattern of the CeO 2 film when an electric field is applied, with the appearance of superstructure spots, which justify the generation of ordered oxygen vacancies.
  • the spot spacing reflects the distance of the space, which is four times the lattice constant.
  • the lattice constant at this time has an increase of about 3% as compared with Fig. 3a, demonstrating that the oxide has been converted to Ce 2 0 3 at this time.
  • Fig. 4b is a graph showing the white line change of Ce in the EELS spectrum of the Ce0 2 film, 1 is data when no electric field is applied, 2 is data when an electric field is applied, and 3 is data when an electric field is removed.
  • Figure 4b shows that M5 is lower than M4 when no electric field is applied; M5 is higher than M4 after applying electric field; M5 is lower than M4 when the electric field is removed; and the relative height reversal of M5 and M4 is positive trivalent The characteristic of mutual transition between Ce and positive tetravalent Ce.
  • the present invention is described by taking only the Ce0 2 film as an example, and the application of the oxide of other rare earth elements and the composite oxide thereof will not be repeated. .
  • the nanocrystalline material and the bulk material of Ce0 2 have the same properties as the film of the film, but the material forms are different, the description will not be repeated here.

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Description

用电场激活稀土氧化物及其复合氧化物催化剂的活性 技术领域
本发明属于催化领域， 具体涉及一种激活稀土氧化物及其复合氧化 物催化剂活性的方法。 背景技术
铈（Ce)等稀土元素的氧化物是工业上广泛使用的催化剂， 用来净 化废气， 废水和脱氢等。 作为三效催化剂 （ three-way catalysts, 以下 简称 "TWC" ), 目前它们最主要的应用是处理汽车尾气。 TWC是用来处理 一些常见的污染气体， 如 C0、 N0X和没有燃烧的碳氢化合物等等。 TWC的 功能是在富燃料的条件下提供额外的氧使燃料充分燃烧， 而在燃料不足 的条件下， 从外界环境中吸收氧并存储起来。 铈（Ce) 的氧化物在 TWC 中的作用的核心原理是铈能够以正三价 （ 3+)和正四价 （4+) 的形式存 在， 能够在较高温度下发生氧化 -还原反应， 而且其氧化物有很高的氧迁 移率。 与其他材料相比， 工业上选择铈的氧化物还有其他一些因素， 比 如它能容易地与其它金属形成稀土复合氧化物， 从而具有较高的热稳定 性和高的氧存取容量（Oxygen storage capacity, OSC )。 但基于饰氧化 物的汽车尾气处理催化剂存在一些不足， 比如冷启动的问题， 就是汽车 在开始启动后接下来的一段时间内 （一般是几十秒）， 催化剂会因为达不 到它的工作温度而不具有催化性能， 造成发动机排放的有害气体不能被 氧化处理， 而达不到净化的效果。 铈氧化物催化剂的正常工作温度指的 是有两个条件需要同时满足的温度： 一是待处理气体成分与铈氧化物能 够发生反应； 二是铈氧化物氧含量低的相 （即 Ce203相） 能够稳定存在。 C0、 NO在室温就能与 Ce02反应， 一些常见的碳氢化合物如曱烷、 乙烷在 室温附近也能与 Ce02发生反应（见 A. Trovarelli, Catalytic properties of ceria and Ce02-containing materials, Catalysis Reviews-Science and Engineering, 1996, 38： 439-520 )0 但是这些反应仅仅局限于 匕 物表面的少数氧离子。 因为在室温附近， 铈氧化物的稳定相是高氧含量 相（即 Ce02相）。 氧的化学势维持着整个化学平衡， 在室温附近它会阻碍 铈氧化物失氧， 从而保持铈氧化物处于高氧含量相。 因此， 这类氧化物 在室温或较低温度下不具有催化性能。 早在 1964年， D. J. M. Bevan和 J. Kordis (见 D. J. M. Bevan, J. Kordis, Mixed Oxides of the Type M02 ( Fluor i te) -M203, 1. Oxygen Dissociation Pressures and Phase Relationships in the System Ce02_Ce203 at High Temperatures, J. Inorg. Nucl. Chem, 1964, 26: 1509- 1523 ) 尤发现铈 可以在正四价和正三价之间转换， 也就是说该氧化物可以在缺氧的条件 下释放氧， 又能在富氧的条件下吸收氧。 汽车尾气处理的研究开始于上 个世纪 60年代，在 70年代有了很大的进展， Ce02开始作为汽车尾气处理 催化剂的一种关键成分来使用。 1975年， 美国开始使用 Ce02去除含有有 毒物质的汽车尾气， 日本和欧洲在 80年代也开始使用这种催化剂。现在， 世界上大部分的小汽车， 大汽车， 卡车都安装有用这种催化剂制作的尾 气处理装置 (见 A. Trovarel 1 i , Catalytic properties of ceria and Ce02-containing materials , Catalysis Reviews-Science and Engineering, 1996, 38： 439-520和 M. Shelef , R. W. McCabe, Twenty-five years after introduction of automotive catalysts： what next? Catalyst today, 2000, 62： 35—50 )。
与三十年前相比， 今天的汽车尾气处理催化剂有了很大的发展， 如 P. Fornasiero等人发现， Ce02和 Zr02的混合物比单纯的 Ce02具有更高的 0SC和更低的工作温度（见 P. Fornasiero, J. Kaspar, M. Graziani, Redox behavior of high surface area Rh-loaded Ce0.5Zr0.502 mixed oxide, Journal of Catalysis, 1997, 167: 576-580 ), 所以从本世纪开始， 工 业上就开始使用这种混合物来代替单纯的 Ce02, 同时， 与催化剂一起使 用的硬件设施也在不断得到改善。 不过令人遗憾的是， 冷启动的问题始 终没有得到解决。
本专利激活常温或更低温度下催化剂活性的思路是， 设计一种方法， 使稀土氧化物及其复合氧化物能够在常温或更低温度下能够保持在低氧 含量相。 发明内容
本申请的发明人经过研究发现， 用电场可以驱动稀土氧化物及其复 合氧化物催化剂的氧化-还原反应过程。 也就是， 对这类氧化物材料施加 电场， 氧化物材料中的氧离子将由于势阱变低而发生迁移， 并伴随着氧 的释放而发生从高氧含量相（Ce02)到低氧含量相（Ce203 )的相变； 撤去 电场后， 低氧含量相立即又能从环境中吸收氧再次发生相变而恢复到高 氧含量相。 这个过程是可逆的。 这类氧化物在电场作用下的可逆相变过 程与通常它们在较高温度下工作的氧化-还原过程是一致的。 因此， 基于 此， 本发明提出一种方法， 釆用电场激活稀土氧化物及其复合氧化物催 化剂的性能， 使催化剂可以在常温甚至更低的温度下工作。
本发明的具体方法是对稀土氧化物及其复合氧化物催化剂间歇式地 施加电场， 使其发生从高氧含量相到低氧含量相之间的相互转变， 从而 激活常温或更低温度下催化剂的活性。
本发明涉及的稀土氧化物的晶体结构一般为萤石结构， 常见的材料 有二氧化铈（Ce02 ), 二氧化镨（Pr02 ), 二氧化铽（ Tb02 ), 等等。 萤石结 构稀土复合氧化物材料指的是部分阳离子被其他阳离子取代后， 而形成 的二元固溶体。 如二氧化铈中部分铈离子被锆离子取代。 取代的元素还 可以是镧、 铜、 钡、 铝、 钙、 镨、 铽和钇等。 稀土复合氧化物材料还包 括三元甚至三元以上的固溶体。 如最常见的在铈锆的固溶体中， 再引入 第三种元素， 主要是稀土元素如镧、 钇、 镨和铽等。
本发明涉及的常温或更低温度下萤石结构氧化物及其复合氧化物催 化剂的工作过程和原理如下：
在萤石结构氧化物或其复合氧化物两侧放置电极， 在富燃料的情况 下施加电场， 即使这时的温度在常温附近甚至更低一些， 萤石结构氧化 物或复合氧化物的稳定相都会由高氧含量相转变为低氧含量相。 这是因 为这类氧化物的表面晶格氧非常活泼， 在室温下就能与 C0、 NO等发生反 应。 在电场的作用下， 氧化物表面的晶格氧会更加的活泼， 与吸附在表 面的燃料分子更容易发生反应， 产生氧空位和完全燃烧的产物。 表面产 生的氧空位又会持续向体内扩散； 氧离子则持续不断的从体内向表面扩 散， 填充表面产生的氧空位， 准备下一次的反应。 而电场的存在又会使 得这个扩散过程更加迅速的进行。 直到大量的氧离子被消耗掉， 大量的 氧空位产生后， 氧化物由原来的高氧含量相转变成低氧含量相。 电场的 作用实际上是打破了原来由氧化学势维持的化学平衡， 使得化学反应从 高氧含量相向低氧含量相的方向进行。 在电场和氧化学势共同维持的新 的化学平衡下， 它们的低氧含量相就可以保持稳定存在。
在缺燃料的情况下， 只需要撤去电场， 此时， 萤石结构氧化物或其 复合氧化物的稳定相由低氧含量相转变为高氧含量相。 在氧化学势的驱 动下， 氧化物会从外界环境中吸收氧， 从而自发的恢复到高氧含量相。 本发明方法中所施加的电场强度的大小取决于萤石结构氧化物材料 的种类， 以及它所处的温度和外界氧压强等环境条件。 材料的稳定相是 高氧含量还是低氧含量， 这是由氧的化学势决定的， 它是温度和外界氧 分压的函数。 温度越高， 所需施加的电场强度就越小。 （以往这种催化剂 的工作方式是， 要加热催化剂到很高温度， 使其稳定相变成低氧含量相， 这样催化剂才能工作 )。 本发明电场驱动的相变过程的快慢跟氧化学势驱 动的相变过程的快慢相当， 具体取决于材料的种类、 比表面积、 晶体缺 陷、 环境的温度和氧压强等。
本发明方法所涉及的稀土氧化物及其复合氧化物材料包括其薄膜材 料、 纳米晶材料和块体材料。 附图说明
图 1为本发明实施举例的结构实物图；
图 2a为本发明 Ce02薄膜没有施加电场时的透射电子显微镜 ( TEM ) 高分辨图；
图 2b为本发明 Ce02薄膜施加电场时的 TEM高分辨图；
图 3a为本发明 Ce02薄膜没有施加电场时的电子衍射图；
图 3b为本发明 Ce02薄膜施加电场时的电子^ ί汙射图；
图 4a为本发明 Ce02薄膜的电子能量损失谱（EELS )氧 K边变化图， 其中， 1是没有施加电场时的数据， 2是施加电场时的数据， 3是撤去电 场时的数据；
图 4b为本发明 Ce02薄膜电子能量损失谱（EELS )铈的白线变化图， 其中， 1是没有施加电场时的数据， 2是施加电场时的数据， 3是撤去电 场时的数据。 具体实施举例
下面以 Ce02薄膜材料为例， 对本发明作进一步的详细说明。
( 1 ) 在导电衬底上生长二氧化铈薄膜。
( 2 ) 用金属针尖电极与薄膜接触， 将导电衬底和金属针尖连接到电压源 的两个电极上， 电压为几伏到几十伏。 见附图 1。
( 3 ) 为了证明电场作用前后 Ce02所发生的相变，即 Ce02释放氧和吸收氧 的氧化 -还原过程，我们把上述装置放入透射电子显微镜（ TEM )中， 和表征。
具体观察和表征结果如下：
如图 2a所示， 没有施加电场时的 Ce02薄膜 TEM高分辨图， 图中下半 部分为上半部分中红色矩形框部分的放大图。
图 2b为 Ce02薄膜施加电场时的 TEM高分辨图， 与图 2a相比， 有明 显的调制条紋出现， 这种调制条紋的出现证明产生了有序氧空位。
如图 3a所示， 没有施加电场时的 Ce02薄膜的选区电子衍射图， 图中 标明的间距为四倍晶格常数的倒数。
图 3b为施加电场时的 Ce02薄膜的选区电子衍射图，有超结构斑点出 现， 这种斑点恰好证明了有序氧空位的产生。 斑点间距反映的是空间的 距离， 是晶格常数的四倍。 而且， 此时的晶格常数与图 3a相比， 有大约 3 %的增大， 证明此时氧化物已经转换为 Ce203。
通过施加电场前后元素电子能量损失谱（EELS ) 的实验数据变化能 够进一步证明 Ce02相变的发生。 如图 4a中 Ce02薄膜 EELS谱中氧 K边的 变化所示， 1是没有施加电场时的数据， 2是施加电场时的数据， 3是撤 去电场时的数据。 该图表明， 施加电场的时候， 与 Ce的 4 f 电子和 0的 2p电子杂化的特征峰 A消失； 撤去电场该峰又会出现。 这表明在电场作 用下 4f 电子态发生了变化， 并且这种变化是可逆的。
图 4b为 Ce02薄膜 EELS谱中 Ce的白线变化图， 1是没有施加电场时 的数据， 2是施加电场时的数据， 3是撤去电场时的数据。 图 4b表明， 没有施加电场时， M5要低于 M4 ; 加电场后 M5要高于 M4 ; 撤去电场， M5 又低于 M4 ;而 M5和 M4的这种相对高度的反转变化正是正三价 Ce和正四 价 Ce之间相互转变的特征。
由于稀土元素的氧化物及其复合氧化物具有基本相同的特性， 因此， 本发明仅以 Ce02薄膜为例对本发明进行说明， 对于其他稀土元素的氧化 物及其复合氧化物的应用不再赘述。 另外， 由于 Ce02的纳米晶材料和块 体材料与其薄膜性质相同， 只是材料形式不同， 因此， 在此也不再重复 说明。

Claims

权 利 要求
1. 利用电场激活稀土氧化物及其复合氧化物催化剂活性的方法， 该方法 具体为： 对稀土氧化物及其复合氧化物催化剂施加电场， 使其发生从高 氧含量相到低氧含量相之间的相互转变， 从而激活常温或更低温度下催 化剂的活性。
2. 如权利要求 1所述的方法， 其特征在于， 所述稀土氧化物及其复合氧 化物从高氧含量相到低氧含量相之间的相互转变， 具体为： 在电场作用 下， 氧化物中的氧离子的势阱变低， 阳离子从正四价变为正三价， 氧化 物从高氧含量相转变为低氧含量相； 撤去电场后， 氧化物又会自动从周 围的环境中吸收氧， 阳离子恢复成正四价， 低氧含量相又恢复成高氧含 量相； 即， 稀土氧化物及其复合氧化物在电场作用下发生可逆的氧化-还 原反应。
3. 如权利要求 1所述的方法， 其特征在于， 该方法是完全用电场或者辅 助用电场来激活催化剂的活性， 从而降低催化剂的工作温度。
4. 如权利要求 1所述的方法， 其特征在于， 所施加的电场由直流电压或 交流电压或脉冲电压产生。
5. 如权利要求 1所述的方法， 其特征在于， 所述催化剂是基于单一稀土 元素氧化物， 或基于稀土氧化物的复合氧化物， 即基于稀土氧化物的二 元、 三元以及三元以上的固溶体或者混合物， 氧化物的形式可以是薄膜 或纳米晶或块体材料。
6. 如权利要求 1所述的方法， 其特征在于， 该方法用于汽车冷启动处理 尾气， 还用于其它电器以及这些电器在各种温度下处理废气。
PCT/CN2009/070523 2009-02-25 2009-02-25 用电场激活稀土氧化物及其复合氧化物催化剂活性的方法 WO2010096957A1 (zh)

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CN108204267A (zh) * 2018-03-21 2018-06-26 吉林大学 一种电场强化的三元催化器
EP3603807A1 (en) * 2018-07-31 2020-02-05 Baotou Research Institute of Rare Earths Scr catalyst and its preparation method and applications
KR20200060615A (ko) 2018-11-22 2020-06-01 한국에너지기술연구원 바이오가스 전환용 전기장 부과 촉매반응 시스템

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CN1817447A (zh) * 2006-01-05 2006-08-16 四川大学 低铈型储氧材料及其制备方法
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CN1419965A (zh) * 2001-11-20 2003-05-28 罗姆和哈斯公司 电活化催化
CN1817447A (zh) * 2006-01-05 2006-08-16 四川大学 低铈型储氧材料及其制备方法
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CN108204267A (zh) * 2018-03-21 2018-06-26 吉林大学 一种电场强化的三元催化器
CN108204267B (zh) * 2018-03-21 2024-04-16 吉林大学 一种电场强化的三元催化器
EP3603807A1 (en) * 2018-07-31 2020-02-05 Baotou Research Institute of Rare Earths Scr catalyst and its preparation method and applications
KR20200060615A (ko) 2018-11-22 2020-06-01 한국에너지기술연구원 바이오가스 전환용 전기장 부과 촉매반응 시스템

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