27 research outputs found

    4to. Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad. Memoria académica

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    Este volumen acoge la memoria académica de la Cuarta edición del Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad, CITIS 2017, desarrollado entre el 29 de noviembre y el 1 de diciembre de 2017 y organizado por la Universidad Politécnica Salesiana (UPS) en su sede de Guayaquil. El Congreso ofreció un espacio para la presentación, difusión e intercambio de importantes investigaciones nacionales e internacionales ante la comunidad universitaria que se dio cita en el encuentro. El uso de herramientas tecnológicas para la gestión de los trabajos de investigación como la plataforma Open Conference Systems y la web de presentación del Congreso http://citis.blog.ups.edu.ec/, hicieron de CITIS 2017 un verdadero referente entre los congresos que se desarrollaron en el país. La preocupación de nuestra Universidad, de presentar espacios que ayuden a generar nuevos y mejores cambios en la dimensión humana y social de nuestro entorno, hace que se persiga en cada edición del evento la presentación de trabajos con calidad creciente en cuanto a su producción científica. Quienes estuvimos al frente de la organización, dejamos plasmado en estas memorias académicas el intenso y prolífico trabajo de los días de realización del Congreso Internacional de Ciencia, Tecnología e Innovación para la Sociedad al alcance de todos y todas

    Cr(salophen) Complex Catalyzed Cyclic Carbonate Synthesis at Ambient Temperature and Pressure

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    The combination of a chromium(III) salophen bromide complex and tetrabutylammonium bromide is shown to catalyze the reaction between terminal epoxides and carbon dioxide at ambient temperature and 1 bar carbon dioxide pressure and between internal epoxides and carbon dioxide at 80 °C and 10 bar carbon dioxide pressure to form cyclic carbonates. The optimal conditions involve the use of 1.5-2.5 mol % of both the chromium(III) salophen bromide complex and tetrabutylammonium bromide and result in the formation of cyclic carbonates in 57-92% isolated yields after a reaction time of 24 h. Under these conditions, no polycarbonate formation is observed except when cyclohexene oxide is used as substrate. The reactions were found to proceed with retention of epoxide stereochemistry. A study of the reaction kinetics revealed that the chromium(III) complex and tetrabutylammonium bromide react together to form a six-coordinate anionic chromium complex which is the actual catalyst, and a catalytic cycle is proposed which explains the experimentally observed results

    A Powerful Aluminum Catalyst for the Synthesis of Highly Functional Organic Carbonates

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    An aluminum complex based on an amino triphenolate ligand scaffold shows unprecedented high activity (initial TOFs up to 36 000 h–1), broad substrate scope, and functional group tolerance in the formation of highly functional organic carbonates prepared from epoxides and CO2. The developed catalytic protocol is further characterized by low catalyst loadings and relative mild reaction conditions using a cheap, abundant, and nontoxic metal

    Efficient and Greener Synthesis of Propylene Carbonate from Carbon Dioxide and Propylene Oxide

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    Several heterogeneous catalysts have been investigated for solvent-free synthesis of propylene carbonate (PC) for cycloaddition reaction of propylene oxide (PO) and carbon dioxide (CO2). The characterization of different heterogeneous catalysts has been successfully carried out using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. Batch cycloaddition reaction of PC and CO2 has been conducted in a high pressure reactor. The effect of various parameters that could influence the conversion of PO and the selectivity and yield of PC such as catalyst types, catalyst loading, CO2 pressure, reaction temperature, and reaction time has been studied to find the optimum conditions and the best preferred catalyst for this reaction. Ceria and lanthana doped zirconia (Ce–La–Zr–O) catalyst has been found to be the most active and selective for synthesis of PC as compared to other heterogeneous catalysts that were tested as part of this research. Catalyst reusability studies have been conducted to investigate the long-term stability of the best performed catalyst for synthesis of PC, and it has been found that the catalyst could be reused several times without losing its catalytic activity. An artificial neural network (ANN) model has been developed for PC synthesis by cycloaddition reaction of PO and CO2 using Ce–La–Zr–O catalyst to compare the experimental data and the predicted results by ANN model. The ANN model predicted values are in good agreement with the experimental results
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