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

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

作　　者：Yuqing Tang Yanjun Chen Aqsa Abid Zichun Meng Xiaoying Sun Bo Li Zhen Zhao 汤雨晴;陈彦君;Aqsa Abid;孟子淳;孙晓颖;李波;赵震(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;中国石油大学(北京)重质油国家重点实验室,北京102249;中国科学院金属研究所,辽宁沈阳110016)

机构地区：[1]Institute of Catalysis for Energy and Environment,College of Chemistry and Chemical Engineering,Shenyang Normal University,Shenyang 110034,Liaoning,China [2]State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,China [3]Institute of Metal Research,Chinese Academy of Sciences,ShenYang 110016,Liaoning,China

出　　处：《Chinese Journal of Catalysis》2025年第1期272-281,共10页催化学报(英文)

基　　金：国家自然科学基金(22172100,22372105);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资助(LJ212410166043);沈阳师范大学(BS202208);沈阳师范大学“百人计划”。

摘　　要：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(Zr_(cus))around the oxygen vacancies.The origin of the enhanced catalytic activity of ZrO_(2)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 Zr_(cus).Notably,however,the desorption of both propene and hydrogen molecules from Zr_(cus)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.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(Zr_(cus))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ZrO_(2)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Zr_(cus)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C_(3)H_(7)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Zreus,丙烷与Zr_(cus)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0.49eV,相比于完整晶面上分别降低了0.52和0.93eV.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Zreus的不饱和配位,丙烯和氢在Zreus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850K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.T

关 键 词：Propane dehydrogenation Zirconium oxide Oxygenvacancy Densityfunctional theory Microkinetic 

分 类 号：O64[理学—物理化学]