RESUMEN
High surface-area, mesoporous CeO2, ZrO2, and Ce-Zr composite nanoparticles were developed using the hydrothermal template-assisted synthesis method. Samples were characterized using XRD, N2 physisorption, TEM, XPS, and FT-IR spectroscopic methods. The CO2 adsorption ability of the obtained materials was tested under dynamic and equilibrium conditions. A high CO2 adsorption capacity in CO2/N2 flow or CO2/N2/H2O was determined for all studied adsorbents depending on their composition flow. A higher CO2 adsorption was registered for Ce-Zr composite nanomaterials due to the presence of strong O2- base sites and enriched surface oxygen species. The role of the Ce/Zr ratio is the process of the formation of highly active and selective adsorption sites is discussed. The calculated heat of adsorption revealed the processes of chemisorption and physisorption. Experimental data could be appropriately described by the Yoon-Nelson kinetic model. The composites reused in five adsorption/desorption cycles showed a high stability with a slight decrease in CO2 adsorption capacities in dry flow and in the presence of water vapor.
RESUMEN
A series of mesoporous cerium-iron binary oxides was prepared by a hydrothermal technique using CTAB as a template. The influence of the Fe/Ce ratio and the variations in the preparation techniques such as the type of solvent and the precipitation agent, the approach of the template release, and the temperature of calcination on the phase composition, textural, structural, surface, and redox properties of the obtained materials was studied in details by XRD, nitrogen physisorption, TPR, FTIR, UV-vis, XPS, Raman, and Moessbauer spectroscopies. The materials were tested as catalysts in methanol decomposition and total oxidation of ethyl acetate. It was assumed that the binary materials represented a complex mixture of differently substituted ceria- and hematite-like phases. Critical assessment of their formation on the base of a common mechanism scheme was proposed. This scheme declares the key role of the formation of shared Ce-O-Fe structures by insertion of Fe3+ in the ceria lattice and further competitive compensation of the lattice charge balance by the existing in the system ions, which could be controlled by the Fe/Ce ratio and the hydrothermal synthesis procedure used. This mechanism provides proper understanding and regulation of the catalytic behavior of cerium-iron oxide composites in methanol decomposition with a potential for hydrogen production and total oxidation of ethyl acetate as a model of VOCs.
RESUMEN
Surface catalyzed reactions can be a convenient way to deactivate toxic chemical warfare agents (CWAs) and remove them from the contaminated environment. In this study, pure titanium oxide, magnesium hydroxide, and their composites TiO2/Mg(OH2) were prepared by thermal decomposition and precipitation of the titanium peroxo-complex and/or magnesium nitrate in an aqueous solution. The as-prepared composites were examined by XRD, XPS, HRTEM, and nitrogen physisorption. Their decontamination ability was tested on CWA surrogates and determined by high-performance liquid chromatography (HPLC) and gas chromatography coupled with mass spectrometry (GC-MS). Dimethyl methyl phosphonate (DMMP) was used as a G simulant for the nerve agents sarin (GB) and soman (GD) while 2-chloroethyl ethyl sulfide (2-CEES) and 2-chloroethyl phenyl sulfide (2-CEPS) were used as surrogates of sulfur mustard (HD). The activity of the as-prepared composites was correlated with acid-base properties determined by potentiometric titrations and pyridine adsorption studied by in situ DRIFTS. The mixing of Ti and Mg led to an increase of the surface area and the amount of surface -OH groups (with an increasing amount of Ti) that caused improved degradation of DMMP.
RESUMEN
The formation of active sites in the silica supported copper and cerium oxide bi-component catalysts for total oxidation of ethyl acetate was studied by Nitrogen physisorption, XRD, XPS, UV-Vis, Raman, FTIR of adsorbed CO spectroscopies and TPR. It was found that the interaction between the copper oxide nanoparticles and the supported on the silica ceria ones is realized with the formation of interface layer of penetrated into ceria lattice copper ions in different oxidative state. This type of interaction improves the dispersion of copper oxide particles and provides higher accessibility of the reactants to the copper active sites even at low copper amount.