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.

Natural purified mordenite from Palmarito de Cauto (ZP) deposit, Cuba, was subjected to a hydrothermal ion exchange process in acid medium with Fe 2+ or Fe 3+ salts (Fe 2+ ZP and Fe 3+ ZP). The set of samples was characterized regarding their textural properties, morphology, and crystallinity, and tested in the NO reduction with CO/C 3 H 6 . Infrared spectroscopy coupled Prime Archives in Chemistry 3 www.videleaf.com 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 Fe 2+ and Fe 3+ species. When contacted with the NO probe, Fe 2+ ZP showed the highest intensity of nitrosyl bands, assigned to NO adducts on isolated/highly dispersed Fe 2+ /Fe 3+ extra-framework sites and Fe x O y clusters. This sample is also characterized by the highest NO sorption capacity and activity in NO reduction. Fe 3+ ZP showed a higher intensity of nitrosonium (NO + ) species, without a correlation to NO storage and conversion, pointing to the reactivity of small Fe x O y aggregates, and providing oxygen atoms for the NO to NO + reaction. The same sites are proposed to be responsible for the higher production of CO 2 observed on this sample, and thus to be detrimental to the activity in NO SCR.