Weakened Mn-O bond in Mn-Ce catalysts through K doping induced oxygen activation for boosting benzene oxidation at low temperatures

Xi Chen; Xiaoyan Wang; Ziliang Jia; Chao Yang; Zhihong Liu; Yuexing Wei; Mengxue Wang; Meisheng Liang

doi:10.1016/j.jcis.2024.04.018

Weakened Mn-O bond in Mn-Ce catalysts through K doping induced oxygen activation for boosting benzene oxidation at low temperatures

J Colloid Interface Sci. 2024 Jul 15:666:88-100. doi: 10.1016/j.jcis.2024.04.018. Epub 2024 Apr 3.

Authors

Xi Chen¹, Xiaoyan Wang², Ziliang Jia², Chao Yang³, Zhihong Liu², Yuexing Wei², Mengxue Wang², Meisheng Liang⁴

Affiliations

¹ College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong 030600, China; Shanxi Key Laboratory of Compound Air Pollutions Identification and Control, Jinzhong 030600, China; Shanxi Institute of Eco-Environmental Planning and Technology, Taiyuan 030009, China.
² College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong 030600, China.
³ College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong 030600, China; Shanxi Key Laboratory of Compound Air Pollutions Identification and Control, Jinzhong 030600, China.
⁴ College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong 030600, China; Shanxi Key Laboratory of Compound Air Pollutions Identification and Control, Jinzhong 030600, China. Electronic address: liangmeisheng@tyut.edu.cn.

PMID: 38583213
DOI: 10.1016/j.jcis.2024.04.018

Abstract

K-doped Mn-Ce solid solution catalysts were synthesized using a combination of coprecipitation and hydrothermal methods, demonstrating excellent performance in benzene oxidation. The catalyst K₁Ce₅Mn₅ exhibited comparable activity to noble metal catalysts, achieving a 90 % benzene conversion at approximately 194 ℃. Durable tests under dry and moist conditions revealed that the catalyst could maintain its activity for 50 h at 218 ℃ and 236 ℃, respectively. Characterization results indicated that the catalyst's enhanced activity resulted from the weakened Mn-O bonding caused by the introduction of K⁺, facilitating the activation of oxygen and its involvement in the reaction. CeO_x, the main crystalline phase of Mn-Ce solid solutions, provided abundant oxygen vacancies for capturing and activating oxygen molecules for the weakened Mn-O structures. This conclusion was further supported by partial density of state analysis from density functional theory computations, revealing that the introduction of K⁺ weakened the orbital hybridization of Mn3d and O2p. Finally, in situ diffuse reflectance infrared Fourier-transform spectroscopy (in situ DRIFTS) studies on Ce₅Mn₅ and K₁Ce₅Mn₅ catalysts suggested that the introduction of K⁺ promoted the conversion of adsorbed benzene. Furthermore, intermediate products were transformed more rapidly for K₁Ce₅Mn₅ compared to Ce₅Mn₅.

Keywords: Benzene oxidation; Mn–Ce solid solutions; Mn–O bonding; Quantum calculations.