Abstract
Four kinds of cryptomelane-type octahedral molecular sieve (OMS)-2-X (the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), temperature programmed reduction by H2 (H2-TPR) and X-ray photoelectron spectroscopy (XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity (RH) of 90% and gas hourly space velocity of 585,000 h−1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The efficiency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.
Highlights
Stratosphere ozone protects the human beings from ultraviolet light irradiation (Wang et al 2015)
The ozone in the troposphere can react with nitrogen oxides (NOx) (Wang et al 2011) and volatile organic compounds (VOCs), and the interaction among them is accelerated by light from the sun (Cooper et al 2010; Afonso and Pires 2017), to form photochemical smog as a secondary air pollutant
Four kinds of octahedral molecular sieve (OMS)-2 with different molar ratios were prepared by chemical thermal synthesis involving both potassium permanganate and MnAc2
Summary
Stratosphere ozone protects the human beings from ultraviolet light irradiation (Wang et al 2015). Zhang’s group (Liu and Zhang 2017; Jia et al 2016a, b, 2017) have reported that oxygen vacancies are the main factor for the outstanding behavior of MnO2 in ozone decomposition under wet conditions due to different crystal structures and morphologies of MnO2. The mechanism for catalytic decomposition of ozone mainly involves several redox steps, and oxygen vacancies are deemed as the active center (Zhu et al 2017; Stoyanova et al 2006; Lian et al 2015; Liu and Zhang 2017; Jia et al 2016a, 2017). OMS-2-X catalysts were prepared with different molar ratios of KMnO4/MnAc2 and characterized by a variety of means including N2 adsorption–desorption, XRD, TEM, SEM, H2-TPR and XPS These as-prepared OMS-2-X samples were used as catalysts under relatively high humidity for ozone decomposition
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