高等学校化学学报 ›› 2022, Vol. 43 ›› Issue (4): 20210816.doi: 10.7503/cjcu20210816

• 物理化学 • 上一篇    下一篇

CeO2负载的PdO与Ce1‒x Pd x O2‒δ 物种的甲烷催化燃烧性能

王明智, 郑燕萍, 翁维正()   

  1. 厦门大学化学化工学院, 固体表面物理化学国家重点实验室, 醇醚酯化工清洁生产国家工程实验室, 厦门 361005
  • 收稿日期:2021-12-03 出版日期:2022-04-10 发布日期:2022-01-15
  • 通讯作者: 翁维正 E-mail:wzweng@xmu.edu.cn
  • 基金资助:
    国家自然科学基金(21872111);国家重点研发计划项目(2020YFB0606401)

Catalytic Methane Combustion over CeO2 Supported PdO and Ce1‒x Pd x O2‒δ Species

WANG Mingzhi, ZHENG Yanping, WENG Weizheng()   

  1. State Key Laboratory of Physical Chemistry of Solid State Surfaces,National Engineering Laboratory for Green Chemical Productions of Alcohols,Ethers and Esters,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China
  • Received:2021-12-03 Online:2022-04-10 Published:2022-01-15
  • Contact: WENG Weizheng E-mail:wzweng@xmu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21872111);the National Key Research&Development Program of China(2020YFB0606401)

摘要:

通过调控Pd前驱物在CeO2上的沉积方式, 分别制备了以PdO和离子态的Ce1?x Pd x O2?δ 物种为主的 Pd/CeO2催化剂, 并采用X射线光电子能谱(XPS)和拉曼(Raman)光谱确证了这两种Pd物种的存在. 氧气程序升温脱附(O2-TPD)和氢气程序升温还原(H2-TPR)的表征结果显示, 相比于与载体相互作用较弱的PdO物种, 与CeO2相互作用较强的Ce1?x Pd x O2?δ 物种具有更加稳定的Pd—O键. 催化剂的甲烷燃烧反应起燃活性测试结果显示, 以PdO物种为主的催化剂表现出了良好的低温催化性能, 在原料气配比为1%CH4/4%O2-Ar, 空速为60000 mL·gcat-1·h?1的条件下, T10T90分别为275和367 ℃, 而两种以Ce1?x Pd x O2?δ 物种为主的催化剂的T10均超过420 ℃. 催化剂的甲烷程序升温还原(CH4-TPR)表征结果表明, 在升温过程中只有当PdO或Ce1?x Pd x O2?δ 物种被CH4还原后, 催化活性才开始上升. 由于PdO物种的Pd—O键强度较弱, 有利于Pd物种上的晶格氧在较低温度下参与CH4的氧化过程. 而Ce1?x Pd x O2?δ 物种的Pd—O键较稳定, 且在反应条件下离子态Pd2+与反应体系中氧物种的作用较强, 进而抑制了其与CH4的反应, 因此反应的起燃温度较高. 以γ-Al2O3为载体采用相同的方法制备了Pd/γ-Al2O3催化剂, 相关的表征结果进一步证实, 与载体相互作用较弱的PdO物种更容易被CH4还原, 进而具有较高的催化活性. 据此可以认为Pd/CeO2上氧化态的Pd物种被CH4的还原性能是决定其甲烷催化燃烧反应活性的重要因素之一.

关键词: 氧化铈, 钯, 甲烷, 催化氧化, 氧化钯, Ce1?x Pd x O2?δ, 还原性

Abstract:

Pd/CeO2 catalysts containing mainly PdO and Ce1?x Pd x O2?δ species were prepared by modulating the deposition method of Pd species on CeO2. The Raman and XPS characterizations of the catalysts confirmed the presence of these two types of Pd species on the prepared catalysts. The characterization results of O2-TPD and H2-TPR showed that the Ce1?x Pd x O2?δ species with stronger interactions with CeO2 featured more stronger Pd—O bonds compared to the PdO species. The results of catalytic performance testing for the CH4 combustion reaction showed that, the Pd/CeO2 catalyst dominated with PdO species showed a good activity during the light off process with a T10 and T90 of 275 and 367 ℃, respectively, at a feed gas ratio of 1%CH4-4%O2-Ar and gaseous hourly space velocity(GHSV) of 60000 mL·gcat-1·h?1, while the catalysts dominated with Ce1?x Pd x O2?δ species possessed poor activity with T10 in excess of 420 ℃ under the same condition. The CH4-TPR characterization of the catalysts showed that the catalytic activity started to increase only when the PdO or Ce1?x Pd x O2?δ species started to be reduced by CH4 during the light off process. For the PdO species, the relatively weak Pd—O bonding allows the lattice oxygen on the Pd species to participate in the oxidation of CH4 at lower temperatures, and CeO2 support contributes to the reoxidation of the PdO x through oxygen migration, which in turn completes the process of catalysis by PdO/Pd0 cycle. The low activity of the ionic Ce1?x Pd x O2?δ should attribute to its strong Pd—O—Ce linkages which are difficult to be reduced by CH4 during the reaction. Furthermore, we prepared Pd/γ-Al2O3 catalysts by the same method using γ-Al2O3 as the support, and the characterization results further confirmed that the PdO species with weaker interaction with γ-Al2O3 are more easily be reduced by CH4 and thus exhibit better catalytic activity. It can be concluded that the reducibility of the oxidized Pd species on Pd/CeO2 by CH4 is one of the important factors determining the activity of the catalyst for the methane combustion reaction.

Key words: CeO2, Pd, CH4, Catalytic oxidation, PdO, Ce1?x Pd x O2?δ, Reducibility

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