A kinetic and mechanistic investigation of the alcoholysis of phenyl isocyanate using 1-propanol as the alcohol was undertaken. A molecular mechanism of urethane formation in both alcohol and isocyanate excess is explored using a combination of an accurate fourth generation Gaussian thermochemistry (G4MP2) with the Solvent Model Density (SMD) implicit solvent model. These mechanisms were analyzed from an energetic point of view. According to the newly proposed two-step mechanism for isocyanate excess, allophanate is an intermediate towards urethane formation via six-centered transition state (TS) with a reaction barrier of 62.6 kJ/mol in the THF model. In the next step, synchronous 1,3-H shift between the nitrogens of allophanate and the cleavage of the C–N bond resulted in the release of the isocyanate and the formation of a urethane bond via a low-lying TS with 49.0 kJ/mol energy relative to the reactants. Arrhenius activation energies of the stoichiometric, alcohol excess and the isocyanate excess reactions were experimentally determined by means of HPLC technique. The activation energies for both the alcohol (measured in our recent work) and the isocyanate excess reactions were lower compared to that of the stoichiometric ratio, in agreement with the theoretical calculations.
Kinetic parameters of phenyl isocyanate-monoalcohol reactions has been studied using a microreactor system. The monoalcohol components were propan-1-ol, butan-1-ol, propan-2-ol and butan-2-ol. The reactions were conducted in alcohol/THF mixed solvent under pseudo-first-order circumstances at various temperatures. The reaction mixtures were analyzed by off-line HPLC. Reaction rate constants and apparent activation energies have been determined with good precision. The reaction rate constants were higher for the primary alcohols than for the secondary alcohols. Higher apparent activation energy was found for the secondary alcohols compared to the primary ones. The applied technique provides a simple way to study the effects of various factors (e.g. structure of the isocyanate and the alcohol, temperature, solvents, concentration of reagents, catalysis) on the kinetics of the isocyanate-alcohol reactions.
In Latin America and the Caribbean, the suitable processing of waste through the use of landfills is around 55%, while the local governments with municipal solid waste (MSW) management plans are around 20%. In Quito, for instance, approximately 2000 ton/day of solid waste are collected, and disposed in El Inga Landfill. The objective of this study is evaluating the MSW management of Quito through Life Cycle Assessment (LCA) approach. For achieving this goal, the ISO 14040 methodology was followed and SimaPro 8.4 was used as analysis software. The functional unit used is 1 ton of MSW, while, the material of study was the waste generated in households, commercial sector, schools and markets; whose values were obtained by the public companies EMASEO-EP, EMGIRS-EP, as well as from the open-access data of the city. The results show that using of biogas from the landfill allows the maximum saving of greenhouse gases (GHG) emissions. Therefore, the biogas plant is the process with less environmental impact. The compaction and transportation of MSW displayed a slightly higher impact comparing with the previous process, presenting the second-best environmental performance. On the other hand, the leachate treatment shows the greatest environmental impact according to the model, despite of the effluents does not exceed the permissible limits of the environmental Ecuadorian legislation. The researchers consider suitable the analysis of composting and anaerobic digestion techniques as complementary options to reduce this environmental impact, due to the high organic fraction in the analyzed waste
Este trabajo investigativo comprende principalmente de 3 fases. La primera en la que se basa en el análisis de Reportes de Perforación y Mud Loggin de pozos petroleros de los tipos verticales, direccionales y horizontales, que se perforaron en el cantón la joya de los Sachas ubicado en la provincia de Orellana - Ecuador. En segunda instancia, se ha elaborado una correlación estratigráfica de las principales formaciones del subsuelo de este cantón. La que se basa en un análisis manual del historial de los pozos, clasificándolos en unidades estratigráficas previo el ingreso de la información al software GMS® para construir secciones transversales tridimensionales entre perforaciones. Finalmente, se identifica y caracteriza los minerales con algunas de sus propiedades de las formaciones identificadas. Por lo que se encuentran facies de anhidrita que corresponden al material base para la generación de petróleo, paquetes de arenisca, arcillolita y limonita, correspondientes a la formación Tiyuyacu, siendo intercalada por estratos de conglomerado silíceo, pertenecientes a la Formación Orteguaza. Adicional a esto se observa que la facie de anhidrita forma un pliegue anticlinal cuya cresta es cercana a los menos -160msnm, a su vez, por debajo de los paquetes de arenisca, arcillolita y limonita se muestra una facie de carbón formando un pliegue sinclinal desde los -350msnm.
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