Isosteric Heats of Adsorption of N2O and NO on Natural Zeolites
Gerardo Domínguez, Rosario Hernández–Huesca,* and Gelacio Aguilar–Armenta
Centro de Investigación de la Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Blvd. 14 sur y Av. San Claudio, Ciudad Universitaria, C.P. 72570, Puebla, Pue. México, *Responsible author: rosario.hernandez@fcquim.buap.mx.
Received November 24, 2009
Accepted May 25, 2010
Abstract
We studied the capacities of three natural zeolites to adsorb N2O or NO using a glass high–vacuum volumetric system that permitted characterization of the energetics of the adsorption process. Adsorption equilibrium data were analyzed using the classical Freundlich equation and the Dual–Langmuir model. We employed the Clausius–Clapeyron relationship to calculate the isosteric heats of adsorption using the equilibrium data of the isotherms measured at 273.15 K and 293.15 K. The isosteric heats of reversible adsorption of both gases were smaller than the heats of total adsorption. The interaction energy of N2O with mordenite was larger than the interaction energies of N2O with either erionite or clinoptilolite. The interaction energy of NO was found to be largest with erionite.
Keywords: Adsorption, NOx, isosteric heats, natural zeolites.
Resumen
Estudiamos la capacidad que presentan tres zeolitas naturales de adsorber N2O y NO, con el objetivo de obtener información sobre la energía característica del proceso de adsorción y mediante el uso de un sistema volumétrico al alto vacío. Las isotermas de adsorción de N2O y NO se ajustaron a las ecuaciones de Dual–Langmuir y Freündlich, respectivamente. La ecuación de Clausius–Clapeyron se utilizó para calcular los calores isostéricos de adsorción a partir de las isotermas de adsorción medidas a 273.15 K y 293.15 K. El calor isostérico de la adsorción reversible de ambos gases presentó valores menores que los de la adsorción total. La energía de interacción del N2O con mordenita fue mayor que con erionita y clinoptilolita, mientras que la energía de interacción de la molécula de NO fue mayor con erionita.
Palabras clave: Adsorción, NOx, calores isostéricos, zeolitas naturales.
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]]>Acknowledgments
We are thankful to Consejo Nacional de Ciencia y Tecnología (CONACyT, Mexico) for financial support via scholarship No. 181781 and Project Ref. I36379–U.
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