Potential use of a combined ozone and zeolite system for gaseous toluene elimination

Chao, Christopher Yu Hang; Kwong, Chi Wai; Hui, K.S.

doi:10.1016/j.jhazmat.2006.08.077

Cited by 66 publications

(32 citation statements)

References 41 publications

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“…The band at 1040-1060 cm À1 , at 1080 cm À1 and at 1140 cm À1 could be related to adsorbed molecular ozone on weak Lewis acid sites [25]. The band at 1400 cm À1 has been assigned to atomic oxygen attached to strong Lewis acid sites [21,26]. This surface site has been claimed as responsible of ozone decomposition on natural zeolite [9].…”

Section: 2mentioning

confidence: 93%

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Role of Lewis acid sites of ZSM-5 zeolite on gaseous ozone abatement

Brodu

Manero

Andriantsiferana

et al. 2013

Chemical Engineering Journal

102

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 9735 We report the role played by acidic surface sites of ZSM-5 on ozone removal. Ozone removal is mainly due to ozone decomposition on mild/strong Lewis acid sites. Adsorbed oxygen species appear on ZSM-5 surface because of ozone decomposition. Keywords:Acidic sites Chemical surface properties Lewis acid sites Ozone Synthetic zeolites ZSM-5 zeolite a b s t r a c t In this work, chemical interactions between ozone and zeolite surface active sites are studied in order to propose a process for gaseous ozone removal. Synthetic ZSM-5 zeolites with three different Si/Al 2 ratios and similar specific surface areas and microporous volumes were used in this study. Zeolite samples were characterised using Fourier Transform InfraRed spectroscopy (FTIR) and pyridine sorption IR studies in order to determine acidic site concentrations and strength. Ozone removal experiments were conducted in a quartz fixed-bed flow reactor, at 20°C and 101 kPa. Experiments using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) were conducted in order to identify adsorbed ozone and/or adsorbed oxygen species on zeolite surface. Pyridine IR measurements evidence two kinds of Lewis acid sites induced by extra-framework aluminium species and electronic aluminium defaults inside zeolite structure. Results obtained here evidence the important role of acidic surface sites of ZSM-5 zeolite on gaseous ozone removal. The total amount of removed ozone is found to be directly proportional to the total content of Lewis acid sites. DRIFTS experiments exhibit two bands around 800 and 1400 cm À1 that could correspond to adsorbed oxygen species linked to zeolite surface. DRIFTS experiments also exhibit a band around 1100 cm À1 that correspond to adsorbed ozone on the zeolite surface. Gaseous ozone removal using ZSM-5 zeolite could be largely attributed to ozone decomposition on Lewis acid sites and also to ozone adsorption on the surface of the zeolites.

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Section: 2mentioning

confidence: 93%

“…5 presents DRIFTS spectra of Z-78, the most reactive ZSM-5 toward ozone. DRIFTS spectra were recorded in the absence of ozone (t = 0 min) and after different times of ozone exposure (3,15,26 and 32 min). The main bands are observed in following ranges: 780-820 cm À1 , 1040-1060 cm À1 , 1080 cm À1 , 1140 cm À1 and 1390 cm À1 .…”

Section: 2mentioning

confidence: 99%

Role of Lewis acid sites of ZSM-5 zeolite on gaseous ozone abatement

Brodu

Manero

Andriantsiferana

et al. 2013

Chemical Engineering Journal

102

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“…Chao et al investigated the performance of a combined ozone-zeolite (13X) system to eliminate gaseous toluene at indoor environments. The degradation of toluene seemed to be contributed by active oxygen atoms, generated from the decomposition of molecular ozone at Lewis acid sites of zeolite framework [11]. Furthermore, catalytic ozonation of toluene was conducted over NaX, NaY and MCM-41 for indoor air purification purposes, taking advantage of the strong oxidizing capability of atomic oxygen generated from adsorbed ozone at Lewis acid sites [12].…”

Section: Introductionmentioning

confidence: 99%

Catalytic Ozonation of Toluene Using Chilean Natural Zeolite: The Key Role of Brønsted and Lewis Acid Sites

et al. 2018

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Abstract:The influence of surface physical-chemical characteristics of Chilean natural zeolite on the catalytic ozonation of toluene is presented in this article. Surface characteristics of natural zeolite were modified by acid treatment with hydrochloric acid and ion-exchange with ammonium sulphate. Prior to catalytic ozonation assays, natural and chemically modified zeolite samples were thermally treated at 623 and 823 K in order to enhance Brønsted and Lewis acid sites formation, respectively. Natural and modified zeolite samples were characterised by N 2 adsorption at 77 K, elemental analysis, X-ray fluorescence, and Fourier transform infrared (FTIR) spectroscopy, using pyridine as a probe molecule. The highest values of the reaction rate of toluene oxidation were observed when NH4Z1 and 2NH4Z1 zeolite samples were used. Those samples registered the highest density values of Lewis acid sites compared to other samples used here. Results indicate that the presence of strong Lewis acid sites at the 2NH4Z1 zeolite surface causes an increase in the reaction rate of toluene oxidation, confirming the role of Lewis acid sites during the catalytic ozonation of toluene at room temperature. Lewis acid sites decompose gaseous ozone into atomic oxygen, which reacts with the adsorbed toluene at Brønsted acid sites. On the other hand, no significant contribution of Brønsted acid sites on the reaction rate was registered when NH4Z1 and 2NH4Z1 zeolite samples were used.

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“…Meanwhile, ozone generated from PC unit can be directly used as an effective oxidation species in ozonation unit. Notably, the existence of adsorbent can further enrich the ozone and organics to extend the reaction time between them, which will promote the efficiency of ozonation to remove VOCs and minimize ozone pollution [27].…”

Section: Introductionmentioning

confidence: 99%