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Open AccessArticle

Fe Speciation in Iron Modified Natural Zeolites as Sustainable Environmental Catalysts

1
Instituto Politécnico Nacional, ESFM, Departamento de Física, UPALM, Zacatenco, Ciudad de México 07738, Mexico
2
Instituto de Ciencia y Tecnología de Materiales (IMRE)-Universidad de La Habana, Zapata y G s/n, La Habana, C.P. 10400, Cuba
3
Dipartimento di Chimica and NIS Centre, Università di Torino, Via P. Giuria 7, 10125 Torino, Italy
4
Centro Nacional de Electromagnetismo Aplicado (CNEA), Universidad de Oriente, Ave. Las Américas s/n, Santiago de Cuba, C.P. 90400, Cuba
5
Departamento de Nanocatálisis, Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México, Carretera Tijuana-Ensenada, Km 107. Ensenada, C.P. 22860 BC, Mexico
*
Authors to whom correspondence should be addressed.
Catalysts 2019, 9(10), 866; https://doi.org/10.3390/catal9100866
Received: 24 September 2019 / Revised: 15 October 2019 / Accepted: 16 October 2019 / Published: 19 October 2019
(This article belongs to the Special Issue Sustainable and Environmental Catalysis)
Natural purified mordenite from Palmarito de Cauto (ZP) deposit, Cuba, was subjected to a hydrothermal ion exchange process in acid medium with Fe2+ or Fe3+ salts (Fe2+ZP and Fe3+ZP). The set of samples was characterized regarding their textural properties, morphology, and crystallinity, and tested in the NO reduction with CO/C3H6. Infrared spectroscopy coupled with NO as a probe molecule was used to give a qualitative description of the Fe species’ nature and distribution. The exchange process caused an increase in the iron loading of the samples and a redistribution, resulting in more dispersed Fe2+ and Fe3+ species. When contacted with the NO probe, Fe2+ZP showed the highest intensity of nitrosyl bands, assigned to NO adducts on isolated/highly dispersed Fe2+/Fe3+ extra-framework sites and FexOy clusters. This sample is also characterized by the highest NO sorption capacity and activity in NO reduction. Fe3+ZP showed a higher intensity of nitrosonium (NO+) species, without a correlation to NO storage and conversion, pointing to the reactivity of small FexOy aggregates in providing oxygen atoms for the NO to NO+ reaction. The same sites are proposed to be responsible for the higher production of CO2 observed on this sample, and thus to be detrimental to the activity in NO SCR. View Full-Text
Keywords: natural zeolite; mordenite; Iron exchange; FTIR-NO; HRTEM; NO reduction natural zeolite; mordenite; Iron exchange; FTIR-NO; HRTEM; NO reduction
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MDPI and ACS Style

Chávez Rivas, F.; Rodríguez-Iznaga, I.; Berlier, G.; Tito Ferro, D.; Concepción-Rosabal, B.; Petranovskii, V. Fe Speciation in Iron Modified Natural Zeolites as Sustainable Environmental Catalysts. Catalysts 2019, 9, 866.

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