228 research outputs found

    Methane hydrate: shifting the coexistence temperature to higher temperatures with an external electric field

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    In the present work, we used molecular dynamic simulations of the equilibrium NPT ensemble to examine the effect of an external electric field on the three-phase coexistence temperature of methane gas, liquid water and methane hydrate. For these simulations, we used the TIP4P/Ice rigid water model and a single-site model for methane. The simulations were implemented at two pressures, 400 and 250bar, over temperatures ranging from 285 to 320K and from 280 to 315K, respectively. The application of an external electric field in the range of 0.1-0.9caused the effect of the thermal vibrations of the water molecules to become attenuated. This resulted in a shift of the three-phase coexistence temperature to higher temperatures. Electric fields below this range did not cause a difference in the coexistence temperature, and electric fields above this range enhanced the thermal effect. The shift had a magnitude of 22.5K on average.Peer ReviewedPostprint (author's final draft

    Mechanical recycling of plastic wastes. Case of study: high impact polystyrene for manufacturing TV components shelf

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    En este trabajo se presenta una introducción sobre la situación actual del reciclaje de los materiales plásticos a nivel mundial, con un especial interés en la situación en la que se encuentra el estado Europeo. A pesar de que existen numerosas técnicas de reciclado de plásticos, el método de reciclado mecánico ha llamado mucho la atención por parte de las industrias transformadoras del plástico debido a la capacidad de producción que puede llevarse a cabo mediante el uso de técnicas como la extrusión y la inyección de plásticos. La parte final de este trabajo se enfoca en un caso práctico que se llevó a cabo en el Centre Català del Plàstic (CCP) y la empresa SONY para la obtención de materiales plásticos reciclables para manufacturar carcasas de televisiones. El trabajo realizado en el CCP fue el estudio de la viabilidad de la sustitución de materiales vírgenes por materiales reciclados procedentes de residuos industriales. El estudio consistió en analizar la viabilidad de sustituir un poliestireno antichoque (HIPS) virgen por el mismo material de origen pero reciclado. De esta manera, se compararon las propiedades de cuatro materiales HIPS reciclados (HIPS-RA, -RB, -RC y -RD) así como un estudio de su morfología. Se observó que el índice de fluidez del HIPS aumentó con la proporción de material reciclado y con el número de procesos de transformación. La propiedad mecánica más afectada resultó ser la resistencia al impacto, y se observaron dos tipos de morfologías claramente diferentes. El material reciclado que mostró mejores propiedades fue el HIPS-RB, y fue escogido para sustituir al HIPS virgen en la producción de componentes de electrónica de consumo. Finalmente, el estudio realizado permitió analizar los factores que intervienen en el estudio de materiales reciclados, conocer las posibilidades de su aplicación en el caso concreto de componentes de electrónica de consumo y crear las bases para poder establecer una metodología para realizar futuros estudios de introducción de materiales reciclados en otras aplicaciones tecnológicas. Por lo anterior, el trabajo presenta una completa introducción en el área del reciclaje mecánico y las tendencias del mercado así como la viabilidad del reaprovechamiento de materiales de residuo para el desarrollo de componentes no estructurales y de elevada producción industrial.Postprint (published version

    Engineering covalent organic frameworks in the modulation of photocatalytic degradation of pollutants under visible light conditions

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    Mixtures of triphenylamine (TPA) and phenyl phenothiazine (PTH) fragments have been incorporated into a series of extended polyimine structures that have been applied in the photodegradation of pollutants of different nature under visible light irradiation. Results obtained revealed that materials containing PTH as the sole photoactive unit resulted in the most active photocatalytic material in the degradation of polybrominated diphenyl ether-1 and Sudan Red III. In contrast, the covalent organic framework containing only TPA acted as the best photocatalyst for the degradation of Methylene Blue. These different trends are related to the versatility of PTH moiety to trigger both photoredox and energy transfer processes, while TPA is only an effective energy transfer catalystFinancial support was provided by the European Research Council (ERC-CoG, contract number: 647550), Spanish Government (PID2019-110637RB-I00, RTI2018-095038-B-I00 and RTI2018-095622-B-I00), “Comunidad de Madrid” and European Structural Funds (S2018/NMT-4367). It was also funded by the CERCA Program/Generalitat de Catalunya. ICN2 is supported by the Severo Ochoa program from the Spanish MINECO (Grant No. SEV-2017-0706). Alberto López-Magano thanks to UAM for FPI-UAM predoctoral fellowship

    Metal- and covalent-organic framework mixed matrix membranes for CO2 separation: A perspective on stability and scalability

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    Membrane technology has attracted great industrial interest in carbon capture and separation owing to the merits of energy-efficiency, environmental friendliness and low capital investment. Conventional polymeric membranes for CO2 separation suffer from the trade-off between permeability and selectivity. Introducing porous fillers in polymers is one approach to enhance membrane separation performance. Metal-organic frameworks (MOFs), with ordered porous structure and diverse chemical functionalities, are promising fillers to prepare mixed matrix membranes (MMMs) for CO2 separation. However, the main issue of MOF based MMMs in industry is their stability and processability. This review analyses recent work on stable and scalable MOF based MMMs for CO2 separation. The typical stable MOFs, MOF-based MMMs and the scalable MOF synthesis are summarized. A large number of MOF-based MMM suffer from instability upon exposure to contaminants. For that reason, we also discuss the use of covalent organic frameworks (COFs) as an alternative to prepare MMMs for CO2 separation, considering their excellent stability and good compatibility with polymers. Finally, a brief conclusion and current challenges on obtaining scalable and stable MMMs are outlined. This review may provide some guidance for designing high performance MMMs for industrial CO2 capture and separation to help achieving carbon neutrality.publishedVersio

    Selective CO₂ capture in metal-organic frameworks with azine-functionalized pores generated by mechanosynthesis

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    Two new three-dimensional porous Zn(II)-based metal-organic frameworks, containing azine-functionalized pores, have been readily and quickly isolated via mechanosynthesis, by using a nonlinear dicarboxylate and linear N-donor ligands. The use of nonfunctionalized and methyl-functionalized N-donor ligands has led to the formation of frameworks with different topologies and metal-ligand connectivities and therefore different pore sizes and accessible volumes. Despite this, both metal-organic frameworks (MOFs) possess comparable BET surface areas and CO₂ uptakes at 273 and 298 K at 1 bar. The network with narrow and interconnected pores in three dimensions shows greater affinity for CO compared to the network with one-dimensional and relatively large pores-attributable to the more effective interactions with the azine groups
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