El sistema SiO₂-AlPo₄ como catalizador de craqueo de fracciones petrolíferas

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, leída en 1977.Fac. de Ciencias QuímicasTRUEProQuestpu

Transformation of light paraffins in a microwave-induced plasma-based reactor at reduced pressure

In this work, the effects of the plasma chemistry of an argon microwave (2.45 GHz) discharge at reduced pressure on the conversion of three different alkanes (n-pentane, n-hexane and n-heptane) have been studied. Optical emission spectroscopy has been used for identifying the species generated in the plasma and for estimating its gas temperature. Gas chromatography, mass spectrometry, X-ray diffraction and FTIR spectroscopy have been employed for identifying and analyzing all the compounds present as reaction products. Microwave power and hydrocarbon flow rate have been found critically to affect both conversion and selectivity. The main gas products have been hydrogen and ethylene. At low powers (100–150 W) the conversion to hydrogen has been quite selective. However, at high powers (>300 W) or slow hydrocarbon flow rate ethylene has resulted to be the major product. In most cases, an important fraction of a carbon deposit has been obtained which has been characterized as an amorphous hydrogenated carbon film. Some plausible mechanisms explaining the formation of the main reaction products have been discussed

Las tesis doctorales: historia, política y legislación universitaria

Este artículo pretende realizar una panorámica histórica y legislativa de las tesis doctorales en España como elemento fundamental para entender el desarrollo de la educación universitaria y los cambios que ha ido viviendo. Para ello se analiza su evolución desde el contexto histórico y político educativo. Tras una introducción, el texto se divide en dos partes principales. La primera abarca desde los orígenes de las tesis doctorales y las primera legislaciones hasta la Guerra Civil. La segunda parte aborda los cambios en el doctorado y las tesis doctorales desde la legislación y las políticas educativa después de la Guerra Civil hasta la actualidad. Como conclusión, se puede ver cómo ser doctor o doctora ha ido modificando su sentido desde un título más elitista y vinculado a cuestiones de estatus y liturgia a una concepción moderna, académica y científica, con la tesis doctoral como referente, donde la formación investigadora y las aportaciones al incremento del campo de conocimiento disciplinar y a la sociedad han sido una constante, pudiendo constatarse además a través de este análisis los paralelismos entre la propia evolución de la institución universitaria y la de las tesis doctorales

Las tesis doctorales: historia, política y legislación universitaria

This paper aims to provide a historical and legislative overview of doctoral theses in Spain as a fundamental element to understand the development of university education and the changes it has been experiencing. To do this, its evolution is analyzed from the educational, historical and political context. After an introduction, the text is divided into two main parts. The first covers from the origins of doctoral theses and the first legislation to the Civil War. The second part addresses the changes in the doctorate and doctoral theses from educational legislation and policies after the Civil War to the preset. In conclusion, we can see how being a doctor has been changing its meaning from a more elitist title linked to issues of status and liturgy to a modern, academic and scientific conception, with the doctoral thesis as a reference, where research training and the contributions to the increase in the field of disciplinary knowledge and to society have been a constant, and through this analysis the parallels between the evolution of the university institution itself and that of the doctoral theses can also be confirmed.Este artículo pretende realizar una panorámica histórica y legislativa de las tesis doctorales en España como elemento fundamental para entender el desarrollo de la educación universitaria y los cambios que ha ido viviendo. Para ello se analiza su evolución desde el contexto histórico y político educativo. Tras una introducción, el texto se divide en dos partes principales. La primera abarca desde los orígenes de las tesis doctorales y las primera legislaciones hasta la Guerra Civil. La segunda parte aborda los cambios en el doctorado y las tesis doctorales desde la legislación y las políticas educativa después de la Guerra Civil hasta la actualidad. Como conclusión, se puede ver cómo ser doctor o doctora ha ido modificando su sentido desde un título más elitista y vinculado a cuestiones de estatus y liturgia a una concepción moderna, académica y científica, con la tesis doctoral como referente, donde la formación investigadora y las aportaciones al incremento del campo de conocimiento disciplinar y a la sociedad han sido una constante, pudiendo constatarse además a través de este análisis los paralelismos entre la propia evolución de la institución universitaria y la de las tesis doctorales

Efficient Removal of Nonylphenol Isomers from Water by Use of Organo-Hydrotalcites

The presence of potent organic endocrine-disrupting chemicals (EDCs) in natural aquifers can have adverse impacts on public health and the environment. 4-nonylphenol, one such EDC, can be efficiently removed from water by adsorption onto a clayey material. In this work, we created an effective sorbent for this purpose by using co-precipitation and subsequent ion-exchange to intercalate the organic anion deoxycholate into a Mg/Al hydrotalcite. Intercalating deoxycholate ions increased the organophilicity of the hydrotalcite surface. The solid was used to adsorb 4-nonylphenol at different pollutant concentrations and temperatures. The adsorption process was subjected to a kinetic study. Based on the results, the EDC was adsorbed by chemisorption. In addition, based on the equilibrium isotherms used for the process, the Freundlich model was the most accurate in reproducing the adsorption of 4-nonylphenol onto deoxycholate-intercalated hydrotalcite

Three-Dimensional Hierarchical Hydrotalcite–Silica Sphere Composites as Catalysts for Baeyer–Villiger Oxidation Reactions Using Hydrogen Peroxide

The development of effective, environmentally friendly catalysts for the Baeyer–Villiger reaction is becoming increasingly important in applied catalysis. In this work, we synthesized a 3D composite consisting of silica spheres coated with Mg/Al hydrotalcite with much better textural properties than its 2D counterparts. In fact, the 3D solid outperformed a 2D-layered hydrotalcite as catalyst in the Baeyer–Villiger reaction of cyclic ketones with H2O2/benzonitrile as oxidant. The 3D catalyst provided excellent conversion and selectivity; it was also readily filtered off the reaction mixture. The proposed reaction mechanism, which involves adsorption of the reactants on the hydrotalcite surface, is consistent with the catalytic activity results

Etherification of glycerol with tert-butyl alcohol over sulfonated hybrid silicas

The etherification of glycerol with tert-butyl alcohol has been carried out in the liquid-phase on differentsulfonic acid functionalized hybrid silicas obtained by oxidative cleavage of tetrasulfide bridges. Thesematerials exhibited different textural properties and acidities ranging from 0.5 to 2.3 mmol g−1. First ofall, different experimental variables, including the reactant ratio and temperature have been tested andall catalysts were essayed under optimal conditions. The best catalytic behavior of the hybrid silicas wasobtained on S50TS50O (Yh-GTBE= 28%) at 75◦C and autogenous pressure. In fact, the glycerol conversionobtained on S50TS50O, clearly surpassed that obtained on A-15 (74 and 51%, respectively). The acidity andthe hydrophilic character of the sulfonated hybrid silicas solids have been found to be key parametersfor their catalytic activity whereas the surface area and porosity do not seem to be advantageous for thisreaction. All catalysts were reused and subjected to an extensive characterization