Rodriguez-Castellon E.,Cristalografia y Mineralogia
Journal of Molecular Catalysis A: Chemical | Year: 2011
A complex between Cu(II) and a polyampholyte synthesized from methacrylic acid, imidazole and ethyleneglycol diglycidyl ether was used as a heterogeneous catalyst for hydrogen peroxide activation and degradation of chlorophenols. The material was characterized by XPS and by measurements of the zeta potential. The isoelectric point determined experimentally was 8.0, differing from that obtained by titration (6.4), which indicated the presence of fixed positive charges in disubstituted imidazole units. The XPS N 1s signal for pyridinic nitrogen in the imidazole units, and the O 1s signals from the carbonyl, hydroxyl and carboxylate groups shifted to higher binding energies after copper uptake, proving the chemical nature of Cu(II) adsorption on the polyampholyte. The XPS spectrum of the complex showed a Cu 2p3/2 peak at 934.7 eV and the characteristic shake-up satellite of Cu(II). When the complex was used as a heterogeneous catalyst for H2O2 activation, Cu(I) was proved to be a probable intermediate species and contributed to elucidate the mechanism. The Auger CuLMM spectrum supports the presence of Cu(I) with a kinetic energy value of 914.8 eV. The complex was applied in the oxidation of chlorinated phenols in aqueous solution at room temperature without any loss in efficiency. © 2011 Elsevier B.V. All rights reserved.
Alonso D.M.,CSIC - Institute of Catalysis |
Vila F.,CSIC - Institute of Catalysis |
Mariscal R.,CSIC - Institute of Catalysis |
Ojeda M.,CSIC - Institute of Catalysis |
And 2 more authors.
Catalysis Today | Year: 2010
A series of CaO solids have been prepared by means of thermal treatment of the following precursors: carbonate, acetate, oxalate, nitrate, and two hydroxides obtained previously by precipitation of calcium acetate and nitrate in basic medium. These solids show distinct reaction rates in the catalytic transesterification of triglycerides with methanol to obtain biodiesel. An exhaustive characterization study using X-ray diffraction, N2 adsorption-desorption isotherms, infrared spectroscopy of pyrrole adsorbed, and temperature-programmed desorption of CO2 allowed us to determine the influence of the physicochemical properties (crystallite size, surface area and porosity) and surface basicity (amount and distribution of basic sites with different strength) on the overall catalytic activity. We have found that CaO obtained by decomposition of calcium carbonate, which shows the highest amount and surface density of very strong base sites, catalyzes triglycerides transesterification with higher rates. © 2010 Elsevier B.V. All rights reserved.
Ruiz M.L.,CONICET |
Lick I.D.,CONICET |
Ponzi M.I.,CONICET |
Rodriguez-Castellon E.,Cristalografia y Mineralogia |
And 2 more authors.
Applied Catalysis A: General | Year: 2011
The diesel soot combustion was studied using catalysts prepared by impregnation with cesium nitrate and/or gold on zirconium oxide (ZrO 2), hydrated zirconium oxide and silica (SiO2). Catalysts were characterized by colorimetry, elemental analysis, atomic absorption spectrophotometry, XRD, FTIR, TPR and XPS. Measurements of catalytic activity were performed in a thermobalance with air and in a fixed bed reactor with a NO/O2 feed. All catalysts containing cesium nitrate exhibit a good activity for soot oxidation and the addition of gold substantially increases the CO2 generation leading the selectivity to 100% in CO2. © 2010 Elsevier B.V. All rights reserved.
Cecilia J.A.,Cristalografia y Mineralogia |
Garcia-Sancho C.,Cristalografia y Mineralogia |
Franco F.,Cristalografia y Mineralogia
Microporous and Mesoporous Materials | Year: 2013
Porous clay heterostructures (PCHs) with increasing amounts of Zr were prepared from natural montmorillonite. The texture, structure and acidic properties of the obtained PCH samples were characterized by SEM, BET, XRD, FTIR, DTA-TG, NH3-TPD and 1-butene isomerization. These studies show that the addition of Zr has a noticeably effect in the structural order of the PCH along the câ̂ --axis with lower influence of random displacements between layers along a and b-axis. This addition causes a decrease of the specific surface area, an increase of the density of acid sites generating Brönsted-type acidity when zirconium content increases.© 2013 Elsevier Inc. All rights reserved.
Rubio-Caballero J.M.,Cristalografia y Mineralogia |
Saravanamurugan S.,Technical University of Denmark |
Maireles-Torres P.,Cristalografia y Mineralogia |
Riisager A.,Technical University of Denmark
Catalysis Today | Year: 2014
Acetalization is a viable method to protect carbonyl functionalities in organic compounds and offers a potential synthetic strategy for synthesizing derived chemicals. In this work, several families of commercial zeolites have been employed as solid acid catalysts in the acetalization of furfural to form furfural diethyl acetal at room temperature using ethanol as a renewable solvent. Among the tested catalysts, H-USY (6) provided the highest catalytic activity (79% acetal yield), excellent selectivity and reusability in five consecutive reaction runs. Process parameters such as, e.g. reaction time, catalyst loading and applicability of different lower alcohols were evaluated and optimized. © 2014 Elsevier B.V.
Jimenez-Morales I.,Cristalografia y Mineralogia |
Del Rio-Tejero M.A.,Cristalografia y Mineralogia |
Braos-Garcia P.,Cristalografia y Mineralogia |
Santamaria-Gonzalez J.,Cristalografia y Mineralogia |
And 2 more authors.
Fuel Processing Technology | Year: 2012
Stable sulfated zirconia can be prepared by impregnation with sulfuric acid of a zirconium doped mesoporous MCM-41 silica and ulterior calcination at 750 °C. Two catalysts with nominal sulfur contents of 1.3 and 4 wt.% were prepared. After the thermal activation at this temperature, some sulfate ions (sulfur content of 0.15 and 0.69 wt.%) are strongly retained onto the superficial zirconia, thus generating acidic catalysts which are able to produce the esterification of oleic acid with methanol at 75 °C in 5 h. The experimental results reveal that the unique way to obtain stable catalysts without leaching of sulfate species to the liquid medium of reaction is by thermal treatment at high temperature as 750 °C. Only with 1 g of this stable catalyst a conversion close to 98% was attained. The conversion of this catalyst is well maintained in a high extend (76%) after three cycles of catalysis without any treatment and is stable in the presence of 5 wt.% of water. © 2012 Elsevier B.V.