RESUMEN

A bulk scale process is implemented for the production of nanostructured film composites comprising unary or multi-component metal oxide nanoparticles dispersed in a suitable polymer matrix. The as-received nanoparticles, namely Al[Formula: see text]O[Formula: see text], SiO[Formula: see text] and TiO[Formula: see text] and binary combinations, are treated following specific chemical and mechanical processes in order to be suspended at the optimal size and composition. Subsequently, a polymer extrusion technique is employed for the fabrication of each film, while the molten polymer is mixed with the treated metal oxide nanoparticles. Transmission and reflection measurements are performed in order to map the optical properties of the fabricated, nanostructured films in the UV, VIS and IR. The results substantiate the capability of the overall methodology to regulate the optical properties of the films depending on the type of nanoparticle formation which can be adjusted both in size and composition.

RESUMEN

Regeneration of the activity of three-way catalytic converters (TWCs) was tested for the first time using a biodegradable metal chelating agent (S, S-ethylenediamine disuccinic acid (S, S-EDDS). The efficiency of this novel environmentally friendly solvent in removing various contaminants such as P, Zn, Pb, Cu and S from commercial aged three-way catalysts, and improving their catalytic performance towards CO and NO pollutants removal has been investigated. Four samples of catalysts from the front and rear inlets of two different TWCs with different mileages and aged under completely different driving conditions were investigated. The catalysts were characterized using various techniques, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements (N(2) adsorption at 77 K). Quantitative ICP-MS analyses and SEM-EDS studies show the removal of Zn, P and Pb. SEM-EDS images obtained at low magnification (50 µm) showed considerable differences in the surface morphology and composition after washing with S, S-EDDS. However, XRD studies indicated neither little to no removal of major contaminant compound phases nor major structural changes due to washing. Correspondingly, little or no enhancement in BET surface area was observed between the used and washed samples. Light-off curves show that the regeneration procedure employed can effectively improve the catalytic performance towards NO pollutant.

Asunto(s)

Automóviles , Quelantes/química , Etilenodiaminas/química , Succinatos/química , Biodegradación Ambiental , Catálisis , Espectrometría de Masas , Metales Pesados/química , Microscopía Electrónica de Rastreo , Porosidad , Polvos , Propiedades de Superficie , Difracción de Rayos X

RESUMEN

Doping of La(2)O(3) crystallites with Ca(2+) ions significantly enhances the intrinsic rate of NO reduction by CH(4) in the presence of 5% O(2) at 550 degrees C compared to pure La(2)O(3) and CaO solids, while the opposite is true after doping of CaO with La(3+) ions. It was found that the 5 wt % La(2)O(3)-95 wt % CaO system has one of the highest intrinsic site reactivities (TOF = 8.5 x 10(-3) s(-1)) reported at 550 degrees C for the NO/CH(4)/O(2) reaction among metal oxide surfaces. The doping process occurred after first dispersing La(2)O(3) and CaO crystallites in deionized water heated to 60 degrees C for 90 min, while the dried material was then ground and heated slowly in air to 800 degrees C and kept at this temperature for 5 h. The doping process had the effect of creating surface oxygen vacant sites (F-type defects) in the oxide lattices the concentration of which is a function of the wt % La(2)O(3) used in the mixed oxide system as revealed by photoluminescence and O(2) chemisorption studies. According to DRIFTS (15)NO transient isotopic experiments (SSITKA), oxygen vacant sites in Ca(2+)-doped La(2)O(3) promote the formation of a more active chemisorbed NO(x) species (NO(2)(-)) that contributes to the enhancement of reaction rate as compared to pure lanthana, calcium oxide, and La(3+)-doped CaO. These results were supported by the kinetic orders of the reaction with respect to NO and O(2) obtained as a function of wt % La(2)O(3) content in the mixed oxide system. Carbon dioxide (a reaction product) competes for the same oxygen vacant sites to form stable adsorbed carbonate-like species, thus lowering the reduction rate of NO. The dependence of the reaction TOF on the wt % La(2)O(3) loading at 550 degrees C was found to follow the trend of the dependence of photoluminescence intensity on the wt % La(2)O(3) content in the La(2)O(3)-CaO oxide system.