Co,Ce nanoparticles supported on stacked wire mesh cartridges. Activity and stability in diesel soot combustion.

In this work, Co3O4 nanoparticles were successfully synthesized by precipitating a precursor salt solution in the form of microdroplets generated by a nebulizer, as an efficient, fast and low-cost approach. After drying and calcination, synthesized particles were deposited on stacked wire mesh monoliths by immersing the structures in a suspension containing synthesized Co3O4 particles and commercial ceria nanoparticles as a binder. These structured catalysts were evaluated for the combustion of diesel soot which constitutes a crucial step in the regeneration of catalytic particulate filters (CDPFs). Thermal and mechanical stability of Co,Ce washcoated monoliths were investigated. For this, successive catalytic evaluations of the structured system, with intermediate treatments at 900 °C (accelerated aging), were carried out indicating a very good activity and stability of the catalysts developed. Adherence tests showed good adhesion of the catalytic layer to the metallic substrate. Fresh and aged catalysts were fully characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Laser Raman Spectroscopy (LRS) and Temperature-Programmed Reduction (TPR). It was found that the catalytic coating resulted composed of nanometric CeO2 and Co3O4 along with chromium, iron and manganese oxides coming from the migration of the metallic substrate, in the catalytic cartridge calcined at 600 °C. Despite after calcination at 900 °C spinels of Co, Fe, Cr and Mn were observed, these oxides did not significantly affected the catalytic activity. Although this aging treatment at 900 °C was severe and is not expected under real conditions, it highlights the potential application of the catalytic metallic cartridges here developed.

Novel ceramic paper structures for diesel exhaust purification.

The catalytic combustion of diesel soot is addressed with flexible and structured "paper catalysts". Two different series of catalysts were prepared either by drip impregnation or by a spray method to deposit a mixture of Co, Ba, and K or a mixture of Co and Ce onto SiO2-Al2O3 ceramic paper matrixes. In every case, CeO2 nanoparticles were added to bind the ceramic fibers. SEM images showed that the impregnation method generated catalytic particles concentrated as large chunks (> 10 µm), mainly at ceramic fiber crossings, whereas the spray method produced smaller catalytic particles (< 1 µm) well distributed throughout the ceramic paper. Besides, Co-Ba-K particles appeared better dispersed on the surface of ceramic fibers than Co-Ce due to the presence of K. Additionally, FTIR spectra showed the formation of O22- and O2- species associated with CeO2 (binder) on the samples containing potassium which gave the Co-Ba-K-ceramic paper good catalytic properties, thus making the Co-Ba-K drop impregnated the best catalyst both considering activity and stability. Successive temperature programmed oxidation (TPO) runs up to 700 °C caused the formation of cobalt silicates in the catalytic ceramic paper prepared by the spray method, as indicated by TPR. The formation of these species was probably favored by the smaller size of cobalt particulates and their higher dispersion in the catalysts prepared by the spray method. This provoked the partial loss of the redox properties of Co3O4. TPR experiments also indicated the formation of BaCoO3 in Ba-containing ceramic paper, which could help in maintaining the catalyst activity after several TPO runs through the capacity of this mixed perovskite-type oxide to trap and release NOx.

Ultrasound-Assisted Deposition of Co-CeO2 onto Ceramic Microfibers to Conform Catalytic Papers: Their Application in Engine Exhaust Treatment.

The combination of the selective catalytic reduction technology with catalytic filters constitutes one of the most efficient ways for diesel engine exhaust treatment. In this paper, the development of catalytic ceramic papers as structured systems for the abatement of diesel soot particles is addressed. Ceramic papers were prepared by the dual-polyelectrolyte papermaking method, which is based on the conventional papermaking technique used for cellulosic papers, in which a portion of cellulosic fibers is replaced by ceramic ones. The deposition of Co and Ce as catalytic materials by the wet spray method on ceramic papers was studied for the development of structured catalysts using an ultrasonic nebulizer and different solvents. The use of alcohol-water solutions for the impregnation of cobalt generated smaller particles and a high dispersion of them on the ceramic fibers, greater than that obtained when pure water was employed. Temperature programmed oxidation (TPO) assays showed that the best catalytic performance was acquired with the catalysts generated with alcohol solvents, showing a maximum rate for soot combustion at a temperature close to 400 °C. The adequate soot combustion performance and the high thermal and catalytic stability make catalytic ceramic papers impregnated by the wet spray method, promising systems for their application as diesel particulate filters.

Development of edible films obtained from submicron emulsions based on whey protein concentrate, oil/beeswax and brea gum.

Edible films with whey protein concentrate (WPC) with a lipid component, sunflower oil (O) or beeswax (W), to enhance barrier to water vapor were obtained. Brea gum was used as emulsifier and also as matrix component. In order to achieve emulsion with small and homogeneous droplet size, an ultrasonicator equipment was used after obtaining a pre-emulsion using a blender. The films were made by casting. Effects of lipid fraction on droplet size, zeta potential, mechanical properties, water vapor permeability (WVP), solubility, and optical properties were determined. The droplet size of emulsions with BG decreased when decreasing the lipid content in the formulation. The zeta potential was negative for all the formulations, since the pH was close to 6 for all of them and pI of BG is close to 2.5, and pI of ß-lactoglobulin and α-lactalbumin (main proteins in WPC) are 5.2 and 4.1, respectively. Increasing W or SO content in blended films reduced the tensile strength and puncture resistance significantly. BG and WPC films without lipid presented better mechanical properties. The presence of lipids decreased the WVP, as expected, and those films having BG improved this property. BG films were slightly amber as a result of the natural color of the gum. BG has shown to be a good polysaccharide for emulsifying the lipid fraction and improving the homogeneity and mechanical properties of the films with WPC and beeswax or oil.