催化学报 ›› 2022, Vol. 43 ›› Issue (3): 862-876.DOI: 10.1016/S1872-2067(21)63870-6

• 论文 • 上一篇    下一篇

In-Co二元金属氧化物上CO2催化加氢反应的选择性转变: 催化反应的机理和构效关系

李龙泰a,, 杨彬b,c,, 高彪a, 王逸夫a, 张玲霞b,c, 石原达已d, 齐伟e,f,*(), 郭利民a,#()   

  1. a华中科技大学环境科学与工程学院, 湖北武汉 430074, 中国
    b中国科学院大学杭州高等研究院, 化学与材料科学学院, 浙江杭州 310000, 中国
    c中国科学院上海陶瓷研究所, 高性能陶瓷与超细微结构国家重点实验室, 上海 200050, 中国
    d九州大学国际碳中性能源研究所, 福冈, 日本
    e华中科技大学化学与化工学院, 生物无机化学与材料学湖北省重点实验室, 湖北武汉 430074, 中国
    f华中科技大学电气工程学院, 先进电子工程与技术国家重点实验室, 湖北武汉 430074, 中国
  • 收稿日期:2021-06-10 修回日期:2021-06-10 出版日期:2022-03-18 发布日期:2022-02-18
  • 通讯作者: 齐伟,郭利民
  • 作者简介:第一联系人:

    共同第一作者

  • 基金资助:
    国家自然科学基金(21878116);湖北省自然科学基金(2019CFA070)

CO2 hydrogenation selectivity shift over In-Co binary oxides catalysts: Catalytic mechanism and structure-property relationship

Longtai Lia,, Bin Yangb,c,, Biao Gaoa, Yifu Wanga, Lingxia Zhangb,c, Tatsumi Ishiharad, Wei Qie,f,*(), Limin Guoa,#()   

  1. aSchool of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China
    bChemistry and Material Science College, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310000, Zhejiang, China
    cState Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
    dInternational Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 8190395, Japan
    eHubei Key Laboratory of Bioinorganic Chemistry & Materia Medica, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China
    fState Key Laboratory of Advanced Electronic Engineering and Technology, School of Electrical and Electrical Engineering, Huazhong Universi-ty of Science and Technology, Wuhan 430074, Hubei, China
  • Received:2021-06-10 Revised:2021-06-10 Online:2022-03-18 Published:2022-02-18
  • Contact: Wei Qi, Limin Guo
  • About author:First author contact:

    Contributed equally to this work.

  • Supported by:
    National Natural Science Foundation of China(21878116);Natural Science Foundation of Hubei Province(2019CFA070)

摘要:

采用催化加氢的方式将CO2转化为甲醇, 既可以减少CO2排放, 又制备了化学品, 该反应具有重要的研究意义. 氧化铟(In2O3)作为CO2加氢制甲醇催化剂, 由于其较高的CO2活化能力和甲醇选择性, 被科研工作者广泛研究. 其中, 将具有良好解离H2能力的过渡金属元素引入In2O3(M/In2O3)是有效提高催化剂性能的策略之一, 然而, M/In2O3体系催化CO2加氢反应机理及活性位点仍不清楚. 本文引入Co制备了In-Co二元金属氧化物催化剂应用于CO2加氢制甲醇, 结果表明, 相较于In2O3, In-Co催化剂性能有很大提升, 其中In1-Co4催化剂上甲醇时空产率(9.7 mmol·gcat‒1 h‒1)是In2O3(2.2 mmol·gcat‒1 h‒1)的近5倍(反应条件: P = 4.0 MPa, T = 300 oC, GHSV = 24000 cm3STP gcat‒1 h‒1, H2/CO2 = 3). 值得注意的是, 尽管Co是金属元素的主体, In-Co催化剂中Co催化CO2甲烷化的活性受到明显抑制. 本文还通过多种技术系统研究了催化剂结构与反应选择性转变间的关系.
采用电感耦合等离子体发射光谱、粉末X射线衍射、拉曼光谱、X射线光电子能谱和透射电子显微镜等对催化剂结构以及表面性质进行了表征. 结果表明, 在H2还原气氛诱导下, In-Co催化剂表面发生重构, 形成以CoO为核, 以In2O3为壳的核壳结构, 其在高压反应后仍能保持稳定; 更重要的是, 该核壳结构可以显著增强In-Co催化剂吸附及活化CO2的能力. CO2加氢反应动力学研究表明, Co催化剂上H2分压对CO2加氢为零级反应, 而H2分压在In-Co上的反应级数为正数; In-Co催化剂上, CO2分压的反应级数接近于零, 表明CO2及其衍生物在In-Co的表面吸附饱和, 但在纯Co上, 则不会发生这种饱和吸附.
通过原位DRIFTS研究了催化反应路径和关键中间物种的吸附及反应行为, 发现CO2加氢在纯Co和In-Co上的催化机理均遵循甲酸盐路径. 在该催化路径中, CO2首先加氢为甲酸盐(*HCOO)物种, 随后加氢为甲氧基(*CH3O). *CH3O在Co催化剂上进一步加氢生成CH4, 而*CH3O在In-Co催化剂上则会脱附生成CH3OH. 根据表征结果, 本文认为, 在还原性气氛下, In-Co发生了重构并生成表面富In2O3的核壳状结构, 显著提高了催化剂对CO2和含碳物种的吸附能力. Co和In-Co催化剂对CO2加氢反应选择性的差异归因于催化剂对CO2和对*HCOO等含碳中间物种的吸附稳定性不同. CO2及其衍生的含碳中间物种在In-Co催化剂上的吸附能力比在Co催化剂上强, 形成了较合适的催化剂表面C/H比, 从而使*CH3O能够脱附为CH3OH, 而不是进一步加氢为CH4. 综上, 本文研究为高活性In-Co催化剂体系在CO2加氢反应中的催化机理及行为提供了解释, 为金属-氧化铟(M-In2O3)催化剂体系的设计提供了参考.

关键词: 氧化铟, 钴, CO2加氢, 甲醇合成, 核壳结构, 表面C/H比

Abstract:

The hydrogenation of CO2 into methanol has attracted much attention and In2O3 is a promising catalyst. Introducing metal elements into In2O3 (M/In2O3) is one of the main strategies to improve its performance. However, its mechanism and active sites remain unclear and need to be further elucidated. Here, the noble-metal-free Inx-Coy oxides catalysts were prepared. Much-improved performance and obvious product selectivity shift were observed. The optimized catalyst (In1-Co4) (9.7 mmol gcat-1 h-1) showed five times methanol yields than pure In2O3 (2.2 mmol gcat-1 h-1) (P = 4.0 MPa, T = 300 °C, GHSV = 24000 cm3STP gcat-1 h-1, H2:CO2 = 3). And the cobalt-catalyzed CO2 methanation activity was suppressed, although cobalt was most of the metal element. To unravel this selectivity shift, detailed catalysts performance evaluation, together with several in-situ and ex-situ characterizations, were employed on cobalt and In-Co for comparative study. The results indicated CO2 hydrogenation on cobalt and In-Co catalyst both followed the formate pathway, and In-Co reconstructed and generated a surface In2O3-enriched core-shell-like structure under a reductive atmosphere. The enriched In2O3 at the surface significantly enhanced CO2 adsorption capacity and well stabilized the intermediates of CO2 hydrogenation. CO2 and carbon-containing intermediates adsorbed much stronger on In-Co than cobalt led to a feasible surface C/H ratio, thus allowing the *CH3O to desorb to produce CH3OH instead of being over-hydrogenated to CH4.

Key words: Indium oxide, Cobalt, CO2 hydrogenation, Methanol synthesis, Core-shell structure, Surface C/H ratio