Siloxane-modified MnOx catalyst for oxidation of coal-related o-xylene in presence of water vapor

Yingjian Chen; Kening Yao; Xiao Zhang; Boxiong Shen; Richard Lee Smith Jr; Haixin Guo

doi:10.1016/j.jhazmat.2022.129109

Siloxane-modified MnO_x catalyst for oxidation of coal-related o-xylene in presence of water vapor

J Hazard Mater. 2022 Aug 15:436:129109. doi: 10.1016/j.jhazmat.2022.129109. Epub 2022 May 14.

Authors

Yingjian Chen¹, Kening Yao¹, Xiao Zhang², Boxiong Shen³, Richard Lee Smith Jr⁴, Haixin Guo⁴

Affiliations

¹ School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China; Tianjin Key Laboratory of Clean Energy and Pollution Control, Hebei University of Technology, Tianjin, China.
² School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China; Tianjin Key Laboratory of Clean Energy and Pollution Control, Hebei University of Technology, Tianjin, China. Electronic address: zhangxiao@hebut.edu.cn.
³ School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China; Tianjin Key Laboratory of Clean Energy and Pollution Control, Hebei University of Technology, Tianjin, China. Electronic address: shenbx@hebut.edu.cn.
⁴ Graduate School of Environmental Studies, Tohoku University, Aramaki Aza Aoba 6-6-11, Aoba, Sendai 980-8579, Japan.

PMID: 35594674
DOI: 10.1016/j.jhazmat.2022.129109

Abstract

In coal-combustion energy production, presence of water vapor in flue gas causes catalyst deactivation and leads to the release of large quantities of volatile organic compounds (VOCs). In this study, design of a low-temperature, hydrophobic catalyst for flue gas purification was achieved by modifying support material with inorganic siloxane. Introduction of 5% water vapor into simulated flue gas at 300 °C reduced oxidation efficiency for o-xylene removal by 26% with unmodified MnO_x/γ-Al₂O₃ catalyst, whereas with modified catalyst MnO_x-Si_0.9/γ-Al₂O₃ oxidation efficiency was reduced by only 5%. MnOx-Si_0.9/γ-Al₂O₃ exhibited stable catalytic efficiency for o-xylene gas oxidation containing water vapor for over 200 min. Water-resistance of the catalyst was effective for removal of multi-coal combustion pollutants (Hg⁰ and NO) and moreover, hydrophobicity of the catalyst led to a reduction in surface sulfate deposition, thereby lowering toxicity of SO₂ from simulated flue gas. DRIFTS analysis showed that the hydrophobic catalyst surface not only reduces water adsorption, but also promotes water volatilization. Based on molecular adsorption energies, catalyst support modification with siloxane inhibits water adsorption and promotes organic adsorption and thus provides a new strategy for preparing water-resistant catalysts for flue gas purification.

Keywords: Catalytic oxidation; Coal combustion; Hydrophobic modification; VOCs; Water vapor.