Natural zeolite reactivity towards ozone: The role of compensating cations

Váldes, Héctor; Alejandro-Martín, Serguei; Zaror, Claudio A.

doi:10.1016/j.jhazmat.2012.04.067

Cited by 48 publications

(40 citation statements)

References 23 publications

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“…Results obtained here are in accordance with those reported elsewhere [23,24]. X-ray powder diffraction (XRD) patterns of natural and modified zeolite samples have been previously reported [25,26]. XRD patterns indicate that chemical modification treatments of natural zeolite do not cause any significant changes in the zeolite framework.…”

Section: Physical-chemical Characteristics Of Natural and Modified Zesupporting

confidence: 92%

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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Section: Physical-chemical Characteristics Of Natural and Modified Zesupporting

confidence: 92%

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

et al. 2018

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“…Standard assays using temperature-programmed desorption of carbon dioxide (CO 2 -TPD) were applied in order to determine the total number and strength of basic sites as described elsewhere [9]. No peaks were observed after the CO 2 -TPD assays.…”

Section: Characterisation Of Zeolite Samplesmentioning

confidence: 99%

“…DRIFTS measurements were carried out using a Nicolet 6700 FTIR spectrometer equipped with a smart collector diffuse reflectance mirror system and a high-temperature/high-pressure DRIFTS cell (Thermo Scientific) as described in a former publication [9].…”

Section: Drifts Experimentsmentioning

confidence: 99%

“…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]. Moreover, the presence of the band frequency related to adsorbed peroxide would indicate that ozone decomposition takes place as described by Eqs.…”

Section: 2mentioning

confidence: 99%

“…They have been applied as catalysts in advanced oxidation processes in combination with ozone for the oxidation of volatile organic compounds from industrial emissions [5][6][7]. Concerning to gaseous ozone abatement over zeolites at ambient conditions, there are only few reported investigations [8][9][10][11]. Two mechanisms are proposed: decomposition on strong Lewis acid sites and adsorption of ozone on weak acidic sites.…”

Section: Introductionmentioning

confidence: 99%

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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

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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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Influence of Impregnation and Ion Exchange Sequence on Metal Localization, Acidity and Catalytic Performance of Cobalt BEA Zeolite Catalysts in Fischer‐Tropsch Synthesis

et al. 2018

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Cobalt distribution between the external surface and micropores and acidity of the large pore BEA zeolite were controlled by choosing the sequence of impregnation and ion exchange procedures. Higher concentration of ion exchangeable cobalt was observed in the catalyst prepared by ion‐exchange of the zeolite proton form. The presence of Na+ instead of H+ ions in the exchange positions of zeolite favored deposition of cobalt on the external surface. The acid sites in the zeolite micropores can be then restored by subsequent ion exchange of sodium with ammonium nitrate and calcination. The catalytic performance of the cobalt zeolite catalysts prepared using different impregnation and ion exchange procedures was tested in the Fischer‐Tropsch synthesis. Higher reaction rates were observed over the catalysts, which did not contain cobalt ions in the cation sites of the zeolite. Lower methane selectivity, higher selectivity to long chain hydrocarbons and high fraction of isomerized products are observed when cobalt species are located on the zeolite outer surface and acid sites inside the BEA zeolite micropores.

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Natural zeolite reactivity towards ozone: The role of compensating cations

Cited by 48 publications

References 23 publications

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

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

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

Influence of Impregnation and Ion Exchange Sequence on Metal Localization, Acidity and Catalytic Performance of Cobalt BEA Zeolite Catalysts in Fischer‐Tropsch Synthesis

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