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Article

Preparation of Pd/SiO2 Catalysts by a Simple Dry Ball-Milling Method for Lean Methane Oxidation and Probe of the State of Active Pd Species

by 1,2, 1,2, 1,2, 1, 1,*, 1,*, 1, 1 and 1,2,*
1
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China
2
University of the Chinese Academy of Sciences, Beijing 100049, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Anil Banerjee
Catalysts 2021, 11(6), 725; https://doi.org/10.3390/catal11060725
Received: 26 May 2021 / Revised: 9 June 2021 / Accepted: 10 June 2021 / Published: 11 June 2021
(This article belongs to the Special Issue Advances in Catalytic Oxidation of Methane and Carbon Monoxide)
A series of Pd/SiO2 catalysts were prepared with different Pd precursors by a dry ball-milling method and used in the catalytic oxidation of lean methane at low temperature. The effect of Pd precursors on the catalytic performance was investigated and the state of the most active Pd species was probed. The results indicate that dry ball-milling is a simple but rather effective method to prepare the Pd/SiO2 catalysts for lean methane oxidation, and palladium acetylacetonate is an ideal precursor to obtain a highly active Pd/SiO2-Acac catalyst with well- and stably dispersed Pd species, owing to the tight contact between acetylacetonate and Si–OH on the SiO2 support. Besides the size and dispersion of Pd particles, the oxidation state of Pd species also plays a crucial role in determining the catalytic activity of Pd/SiO2 in lean methane oxidation at low temperature. A non-monotonic dependence of the catalytic activity on the Pd oxidation state is observed. The activity of various Pd species follows the order of PdOx >> Pd > PdO; the PdOx/SiO2-Acac catalysts (in particular for PdO0.82/SiO2-Acac when x = 0.82) exhibit much higher activity in lean methane oxidation at low temperature than Pd/SiO2-Acac and PdO/SiO2-Acac. The catalytic activity of PdOx/SiO2 may degrade during the methane oxidation due to the gradual transformation of PdOx to PdO in the oxygen-rich ambiance; however, such degradation is reversible and the activity of a degraded Pd/SiO2 catalyst can be recovered through a redox treatment to regain the PdOx species. This work helps to foster a better understanding of the relationship between the structure and performance of supported Pd catalysts by clarifying the state of active Pd species, which should be beneficial to the design of an active catalyst in lean methane oxidation at low temperature. View Full-Text
Keywords: lean methane mitigation; catalytic oxidation; Pd/SiO2; ball-milling method; active Pd species lean methane mitigation; catalytic oxidation; Pd/SiO2; ball-milling method; active Pd species
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MDPI and ACS Style

Yang, L.; Fan, C.; Luo, L.; Chen, Y.; Wu, Z.; Qin, Z.; Dong, M.; Fan, W.; Wang, J. Preparation of Pd/SiO2 Catalysts by a Simple Dry Ball-Milling Method for Lean Methane Oxidation and Probe of the State of Active Pd Species. Catalysts 2021, 11, 725. https://doi.org/10.3390/catal11060725

AMA Style

Yang L, Fan C, Luo L, Chen Y, Wu Z, Qin Z, Dong M, Fan W, Wang J. Preparation of Pd/SiO2 Catalysts by a Simple Dry Ball-Milling Method for Lean Methane Oxidation and Probe of the State of Active Pd Species. Catalysts. 2021; 11(6):725. https://doi.org/10.3390/catal11060725

Chicago/Turabian Style

Yang, Li, Chao Fan, Li Luo, Yanyan Chen, Zhiwei Wu, Zhangfeng Qin, Mei Dong, Weibin Fan, and Jianguo Wang. 2021. "Preparation of Pd/SiO2 Catalysts by a Simple Dry Ball-Milling Method for Lean Methane Oxidation and Probe of the State of Active Pd Species" Catalysts 11, no. 6: 725. https://doi.org/10.3390/catal11060725

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