催化学报 ›› 2025, Vol. 68: 272-281.DOI: 10.1016/S1872-2067(24)60163-4

• 论文 • 上一篇    下一篇

氧化锆催化剂在丙烷催化脱氢中优异性能的再探索: 氧空位的两面性

汤雨晴a, 陈彦君b, Aqsa Abidc, 孟子淳a, 孙晓颖a, 李波a,*(), 赵震a,b,*()   

  1. a沈阳师范大学化学化工学院, 能源与环境催化研究所, 辽宁沈阳 110034
    b中国石油大学(北京)重质油国家重点实验室, 北京 102249
    c中国科学院金属研究所, 辽宁沈阳 110016
  • 收稿日期:2024-08-01 接受日期:2024-09-30 出版日期:2025-01-18 发布日期:2025-01-02
  • 通讯作者: * 电子信箱: boli@synu.edu.cn (李波), zhenzhao@cup.edu.cn (赵震).
  • 基金资助:
    国家自然科学基金(22172100);国家自然科学基金(22372105);辽宁省教育厅高校基本科研重点攻关项目(JYTZD2023183);辽宁省属本科高校基本科研业务费专项资金(LJ212410166043);沈阳师范大学(BS202208);沈阳师范大学“百人计划”

Revisiting the origin of the superior performance of defective zirconium oxide catalysts in propane dehydrogenation: Double-edged oxygen vacancy

Yuqing Tanga, Yanjun Chenb, Aqsa Abidc, Zichun Menga, Xiaoying Suna, Bo Lia,*(), Zhen Zhaoa,b,*()   

  1. aInstitute of Catalysis for Energy and Environment, College of Chemistry and Chemical Engineering, Shenyang Normal University, Shenyang 110034, Liaoning, China
    bState Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
    cInstitute of Metal Research, Chinese Academy of Sciences, ShenYang 110016, Liaoning, China
  • Received:2024-08-01 Accepted:2024-09-30 Online:2025-01-18 Published:2025-01-02
  • Contact: * E-mail: boli@synu.edu.cn (B. Li), zhenzhao@cup.edu.cn/zhaozhen1586@163.com (Z. Zhao).
  • Supported by:
    National Natural Science Foundation of China(22172100);National Natural Science Foundation of China(22372105);Basic Research Project of Education Office of Liaoning Province(JYTZD2023183);Fundamental Research Funds for the Liaoning Universities(LJ212410166043);Shenyang Normal University(BS202208);Program for Excellent Talents in Shenyang Normal University

摘要:

丙烯作为一类重要的化工原料, 近年来市场需求快速增长, 然而目前传统工业路线制丙烯面临着高能耗、低选择性的难题, 难以满足高速发展需求. 丙烷催化脱氢(PDH)作为一种高效制备丙烯的生产工艺, 近年得到迅猛发展. 之前研究结果表明, 氧化锆在丙烷催化脱氢过程中具有优异的催化性能, 并且指出氧空位周围的配位不饱和锆(Zrcus)是反应中的活性中心. 在本文中, 通过使用密度泛函理论(DFT)计算和微观反应动力学模拟, 揭示了四方氧化锆(001)和(100)完整晶面以及含氧空位的(001)-vac和(100)-vac晶面上的丙烷脱氢反应过程. 通过与完整晶面催化剂进行比较, 对缺陷四方ZrO2催化剂反应性能提高的原因进行研究.
本文通过态密度(DOS)分析发现, 与完整晶面相比, 缺陷表面氧空位的产生会出现新的电子局域态, 并且引起电荷的重新排布. 实空间轨道波函数分析进一步证实这些电子主要局限于氧空位内, 使得Zrcus成为一个很好的电子给体, 从而促进丙烷中的C-H键活化. PDH反应路径包括连续两次脱氢和产物(丙烯和氢分子)脱附. 在完整晶面上, 金属-氧作为活化丙烷C-H键的活性位点, 丙烷分解产物C3H7和H分别吸附在锆和氧位点上. 在含有氧空位的晶面上, 活性位点变为Zrcus, 丙烷与Zrcus之间的相互作用与完整晶面相比明显增强, 有利于后续的脱氢步骤. 相比于完整晶面, 在含有氧空位晶面的氧空位上第一个C-H键反应能垒大大降低, 在(100)-vac和(001)-vac晶面上的反应能垒分别为0.47和0.49 eV, 相比于完整晶面上分别降低了0.52和0.93 eV. 然而, 缺陷表面上的第二个C-H键活化性能并没有显著提高. 此外, 由于Zrcus的不饱和配位, 丙烯和氢在Zrcus位点上吸附较强, 阻碍了产物的快速脱附. 通过微观反应动力学模拟发现在反应温度为850 K时, 在(100)-vac, (001)-vac, (100)和(001)晶面上丙烯生成的转化频率(TOF)依次降低. TOF结果表明缺陷表面比完整表面具有更好的催化性能, 说明氧空位在反应中的重要作用. 速率控制度分析结果表明, 完整表面上的速率控制步骤是第一个C-H键断裂, 而缺陷表面上的速率控制步骤是氢气的形成, 该结果表明完整晶面与缺陷表面之间反应机理的具有较大差异.
综上, 本工作通过使用DFT计算和微观反应动力学模拟, 揭示了氧化锆催化剂完整晶面和含有氧空位晶面之间活性差异的根本原因, 指出了局域电子在C-H键活化过程中的关键作用, 给出了进一步提高催化性能的可行方案.

关键词: 丙烷脱氢, 氧化锆, 氧空位, 密度泛函理论, 微观反应动力学

Abstract:

Recent studies have revealed the extraordinary performance of zirconium oxide in propane dehydrogenation, which is attributed to the excellent reactivity of the coordinatively unsaturated zirconium sites (Zrcus) around the oxygen vacancies. The origin of the enhanced catalytic activity of ZrO2 with defective tetrahedral Zr sites was examined by direct comparison with its pristine counterpart in the current study. Electronic-structure analysis revealed that electrons from oxygen removal were localized within vacancies on the defective surface, which directly attacked the C-H bond in propane. The involvement of localized electrons activates the C-H bond via back-donation to the antibonding orbital on the defective surface; conversely, charge is transferred from propane to the pristine surfaces. The barrier for the first C-H bond activation is clearly significantly reduced on the defective surfaces compared to that on the pristine surfaces, which verifies the superior activity of Zrcus. Notably, however, the desorption of both propene and hydrogen molecules from Zrcus is more difficult due to strong binding. The calculated turnover frequency (TOF) for propene formation demonstrates that the pristine surfaces exhibit better catalytic performance at lower temperatures, whereas the defective surfaces have a larger TOF at high temperatures. However, the rate-determining step and reaction order on the defective surface differ from those on the pristine surface, which corroborates that the catalysts follow different mechanisms. A further optimization strategy was proposed to address the remaining bottlenecks in propane dehydrogenation on zirconium oxide.

Key words: Propane dehydrogenation, Zirconium oxide, Oxygen vacancy, Density functional theory, Microkinetic