Lithium cuprate, a multifunctional material for NO selective catalytic reduction by CO, with subsequent carbon oxides capture at moderate temperatures

Li2CuO2 was evaluated as a possible catalyst for the NO selective catalytic reduction (NO SCR) by CO. The initial idea was supported by ab initio thermodynamic analysis. This analysis showed...

On the Structure-Activity Relationship for NO-SCR with NH3 Catalyzed by Cu-exchanged Natural Chabazite and SSZ-13

In spite of their similar structures, the catalytic properties of natural and synthetic (SSZ-13) Chabazite during the selective reduction of NO with NH3 have a different dependence on the Cu exchange level when tested under conditions equivalent to those found in Diesel vehicles. At low (1-2 wt.%) and high copper loadings (6-14 wt.%), their activities differ, because there are variations in the different species of Cu (Cu+, Cu2+, Cu-O-Cu) detected by UV-Vis. At intermediate Cu loadings (2-3 wt.%) they have similar high activities, reaching 100 % conversion. High deNOx activity per Cu site appears to correlate with the predominance of charge compensation Cu2+ species over CuOx moieties. There are changes in the distribution of Cu moieties during operation of both catalysts, evidenced by DR-UV-Vis. Resumen. A pesar de sus estructuras similares, las propiedades catalíticas de Chabazita natural y sintética (SSZ-13) durante la reducción selectiva de NO con NH3 dependen de manera diferente frente al nivel de intercambio con Cu cuando se prueban bajo condiciones equivalentes a las de vehículos Diesel. A bajos (1-2 % p/p) y altos contenidos de Cu (6-14 % p/p) la reducción de NO es diferente debido a variaciones en las distintas especies de Cu (Cu+, Cu2+, Cu-O-Cu) observadas por UV-Vis. Por su parte, los catalizadores intercambiados con 2-3 % p/p de Cu tuvieron alta actividad por sitio de Cu, alcanzando 100 % de conversión de NO, lo que parece deberse a la predominancia de especies de Cu2+ sobre especies CuOx de acuerdo con el análisis por DR-UV-Vis, el que también muestra la existencia de variaciones en la distribución de especies de Cu debido a la reacción.

INCREASES IN SCR ENERGETIC PROTON FLUXES ON EARTH AND THEIR RELATION TO SOLAR SOURCES

Logachev catalog data for solar cycle 23 has been used to study the dependence of measured increases in solar cosmic rays (SCRs) on solar perturbations. The efficiency of recording the SCR increases, driven by proton acceleration in the corona, on Earth and in its vicinity is shown to depend on power of a solar flare that created a shock wave and on position of the flare on the solar disk. As the particle flux moves along the heliolongitude away from the parent flare, the acceleration efficiency decreases, i.e. the maximum energy of the accelerated particles and their intensity at equal energy decrease. As a result, at a certain distance along a heliolongitude from the parent solar flare, the solar proton flux intensity decreases to the galactic background, and there is no SCR increase detected.

INCREASES IN SCR ENERGETIC PROTON FLUXES ON EARTH AND THEIR RELATION TO SOLAR SOURCES

Logachev catalog data for solar cycle 23 has been used to study the dependence of measured increases in solar cosmic rays (SCRs) on solar perturbations. The efficiency of recording the SCR increases, driven by proton acceleration in the corona, on Earth and in its vicinity is shown to depend on power of a solar flare that created a shock wave and on position of the flare on the solar disk. As the particle flux moves along the heliolongitude away from the parent flare, the acceleration efficiency decreases, i.e. the maximum energy of the accelerated particles and their intensity at equal energy decrease. As a result, at a certain distance along a heliolongitude from the parent solar flare, the solar proton flux intensity decreases to the galactic background, and there is no SCR increase detected.

Fe Speciation in Iron Modified Natural Zeolites as Sustainable Environmental Catalysts

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.