title: Oxidative regeneration of toluene-saturated natural zeolite by gaseous ozone: the influence of zeolite chemical surface characteristics.
abstract: In this study, the effect of zeolite chemical surface characteristics on the oxidative regeneration of toluene saturated-zeolite samples is investigated. A Chilean natural zeolite (53% clinoptilolite, 40% mordenite and 7% quartz) was chemically modified by acid treatment with hydrochloric acid and by ion-exchange with ammonium sulphate. Thermal pre-treatments at 623 and 823K were applied and six zeolite samples with different chemical surface characteristics were generated. Chemical modification of natural zeolite followed by thermal out-gassing allows distinguishing the role of acidic surface sites on the regeneration of exhausted zeolites. An increase in Brønsted acid sites on zeolite surface is observed as a result of ammonium-exchange treatment followed by thermal treatment at 623K, thus increasing the adsorption capacity toward toluene. High ozone consumption could be associated to a high content of Lewis acid sites, since these could decompose ozone into atomic active oxygen species. Then, surface oxidation reactions could take part among adsorbed toluene at Brønsted acid sites and surface atomic oxygen species, reducing the amount of adsorbed toluene after the regenerative oxidation with ozone. Experimental results show that the presence of adsorbed oxidation by-products has a negative impact on the recovery of zeolite adsorption capacity.
authors.affiliation: Laboratorio de Tecnologías Limpias (F. Ingeniería), Universidad Católica de la Santísima Concepción, Alonso de Ribera 2850, Concepción, Chile; Núcleo de Energías Renovables (F. Ingeniería), Universidad Católica de Temuco, Rudecindo Ortega 02950, Temuco, Chile.
authors.forename: Serguei
authors.initials: S
authors.lastname: Alejandro
authors.affiliation: Laboratorio de Tecnologías Limpias (F. Ingeniería), Universidad Católica de la Santísima Concepción, Alonso de Ribera 2850, Concepción, Chile. Electronic address: hvaldes@ucsc.cl.
authors.forename: Héctor
authors.initials: H
authors.lastname: Valdés
authors.affiliation: Université de Toulouse; INPT, UPS; Laboratoire de Génie Chimique, 4, Allée Emile Monso, F-31030 Toulouse, France; CNRS; Laboratoire de Génie Chimique; F-31030 Toulouse, France.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Manéro
authors.affiliation: Departamento de Ingeniería Química (F. Ingeniería), Universidad de Concepción, Concepción, Correo 3, Casilla 160-C, Chile.
authors.forename: Claudio A
authors.initials: CA
authors.lastname: Zaror
mesh_terms: D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D059027:Recycling; D013499:Surface Properties; D014050:Toluene / Q000737:chemistry*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D016877:Oxidants; D017641:Zeolites; D014050:Toluene; D010126:Ozone
keywords: Brønsted acid sites; Lewis acid sites; Ozone; Toluene; Zeolite