ABSTRACT
CuO-CeO2/SiO2 catalysts lose activity when they are calcined at 600 °C and temperatures above. This loss of activity was related to a decrease in the amount of highly dispersed Cu species interacting with Ce (CuO-CeO2 interface) over the SiO2 support. These species are highly active in CO oxidation, so this reaction was selected to conduct this study. In order to avoid the activity loss in CuO-CeO2/SiO2 catalysts, the effect of high Ce loads (8, 16, 24, and 36%) on the thermal stability of these catalysts was studied. The results reveal that when increasing calcination temperature from 500 to 700 °C, the catalysts with Ce load equal to or higher than 24% increase the formation of highly dispersed Cu interacting with Ce and therefore the activity (90% of CO conversion at 120 °C). In catalysts with Ce load below 24%, Cu species agglomerate and decrease the activity (less than 5% of CO conversion at 120 °C).
ABSTRACT
The transient combustion of biomass leads to the evolution of a variety of pollutants (NO, CO, organic compounds, and many others) that can react with each other on a suitable catalyst to generate compounds of lower toxicity. Here, the transient reduction of NO with CO and naphthalene in the presence of oxygen was studied on a Ca/Cu/YCeO2-TiO2 catalyst. Response surface methodology was used to identify the optimum amounts of calcium, copper, and cerium. The optimized Ca/Cu/YCeO2-TiO2 catalyst was then extensively studied and characterized. The coupling of yttrium-stabilized ceria with TiO2 provided an active support that effectively activated naphthalene. When calcium and copper were added to the support, the obtained Ca/Cu/YCeO2-TiO2 catalyst achieved the full conversion of CO and naphthalene and 72% conversion of NO. The Ca/Cu/YCeO2-TiO2 catalyst possessed labile oxygen species, which might be related to the high catalytic activity.
ABSTRACT
The effect of the ZrO2 loading was studied on spherical SiO2@ZrO2-CaO structures synthetized by a simple route that combines the Stöber and sol-gel methods. The texture of these materials was determined using SBET by N2 adsorption, where the increment in SiO2 spheres' surface areas was reached with the incorporation of ZrO2. Combined the characterization techniques of using different alcoholic dissolutions of zirconium (VI) butoxide 0.04 M, 0.06 M, and 0.08 M, we obtained SiO2@ZrO2 materials with 5.7, 20.2, and 25.2 wt % of Zr. Transmission electron microscopy (TEM) analysis also uncovered the shape and reproducibility of the SiO2 spheres. The presence of Zr and Ca in the core-shell was also determined by TEM. X-ray diffraction (XRD) profiles showed that the c-ZrO2 phase changed in to m-ZrO2 by incorporating calcium, which was confirmed by Raman spectroscopy. The purity of the SiO2 spheres, as well as the presence of Zr and Ca in the core-shell, was assessed by the Fourier transform infrared (FTIR) method. CO2 temperature programmed desorption (TPD-CO2) measurements confirmed the increment in the amount of the basic sites and strength of these basic sites due to calcium incorporation. The catalyst reuse in FAME production from canola oil transesterification allowed confirmation that these calcium core@shell catalysts turn out to be actives and stables for this reaction.
ABSTRACT
Methane is one of the most important greenhouse gases emitted from natural and human activities. It is scarcely soluble in water; thus, it has a low bioavailability for microorganisms able to degrade it. In this work, the capacity of the fungus Fusarium solani to improve the solubility of methane in water and to biodegrade methane was assayed. Experiments were performed in microcosms with vermiculite as solid support and mineral media, at temperatures between 20 and 35⯰C and water activities between 0.9 and 0.95, using pure cultures of F. solani and a methanotrophic consortium (Methylomicrobium album and Methylocystis sp) as a control. Methane was the only carbon and energy source. Results indicate that using thermally inactivated biomass of F. solani, decreases the partition coefficient of methane in water up to two orders of magnitude. Moreover, F. solani can degrade methane, in fact at 35⯰C and the highest water activity, the methane degradation rate attained by F. solani was 300â¯mgâ¯m-3 h-1, identical to the biodegradation rate achieved by the consortium of methanotrophic bacteria.
