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Na-Based materials are emerging as promising high-temperature CO2 sorbents. In this work, we provide a detailed study on the synthesis of Na(2)TiO(3)via a solid-state route using NaOH and TiO2 as starting reactants. The CO2 sorption properties of the synthesized Na2TiO3 were evaluated by thermogravimetric analysis. A subsequent comprehensive study on the complex reaction mechanism of Na2TiO3 at high temperatures under carbonation conditions was performed via real time in situ synchrotron X-ray diffraction analysis. In situ experiments performed under different conditions revealed the occurrence of thermally-driven phase transitions derived from the structural instability of the material at high temperatures. These reactions could be differentiated from carbonation processes, allowing the proposal of a reaction mechanism of the material as a CO2 sorbent. The obtained results can explain the abnormal dynamic thermogram displayed by Na2TiO3 in the presence of CO2 within a temperature range that is of interest for practical applications and serve as a basis for evaluating the feasibility of using this material in CO2 capture schemes., Reaction Chemistry & Engineering, 6 (10), ISSN:2058-9883

The feasibility of the reduction of CO2 to CH4 employing MgH2 in the presence and absence of cobalt as catalyst was investigated for the first time, exploring different non-independent reaction conditions such as the grade of microstructural refinement, the molar ratio MgH2:CO2, reaction time and temperature. For the un-catalyzed process a methane yield of 44.6% was obtained after 24 h of thermal treatment at 400°C employing a molar ratio of 2:1, through a methanation mechanism that involves the direct reduction of CO2 and the generation of CH4 via C as an intermediary. For the MgH2 catalyzed process a methane yield of 78% was achieved by heating at 350 °C for 48 h, being 4:1 the optimal molar ratio. The global mechanism responds to a Sabatier process favored by Co as an active catalyst, together with reversed water gas shift reaction followed by methanation of CO in presence of steam. On account of the fact that it was proved that the use of catalyst allows lowering the operational temperature without collapsing the methane yield, this research provides an interesting insight of a thermochemical method for CO2 reduction to CH4 employing a solid hydrogen storage medium as H2 source.

CO2 emissions have been continuously increasing during the last half century with a relevant impact on the planet, being the main contributors of the greenhouse effect and global warming. The development of new technologies to mitigate these emissions poses a challenge. Herein, it is demonstrated the recycling of CO2 to produce CH4 selectively by using Mg2FeH6 and Mg2NiH4 complex hydrides as dual conversion promoters and hydrogen source. Magnesium based-metal hydrides containing Fe and Ni catalyze the hydrogenation of CO2 and their total conversion is obtained at 400°C after 5 h and 10 h, respectively. The complete hydrogenation of CO2 depends on the complex hydride, H2:CO2 mol ratio and experimental conditions: temperature and time. For both hydrides, the activation of CO2 on the metal surface and its subsequent capture bring about the formation of MgO. Investigations on Mg2FeH6-CO2 system indicate that the main process occurs via the reversed water-gas shift reaction (WGSR) followed by the methanation of CO in presence of steam. In contrast, the reduction of CO2 by Mg-based hydride in the Mg2NiH4-CO2 system has a strong contribution on the global process. Complex metal hydrides are promising dual promoter-hydrogen source for the CO2 recycling and conversion into valuable fuels like CH4., The present work is part of the CO2MPRISE, "CO2 absorbing Materials Project- RISE", a project that has received funding from the European Union's Horizon 2020 research and innovation programme, under the Marie Skłodowska-Curie Grant Agreement No 734873. The work was also supported by CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), ANPCyT– (Agencia Nacional de Promoción Científica y Tecnológica), CNEA (Comisión Nacional de Energía Atómica) and HZG (Helmholtz– ZentrumGeesthacht). The authors also thank Bernardo Pentke (Departamento Fisicoquímica de Materiales) for the SEM micrographs and Sebastian Anguiano for the Raman measurements (Laboratorio de Fotónica y fotoelectrónica). This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 712949 (TECNIOspring PLUS) and the Government of Catalonia's Agency for Business Competitiveness (ACCIÓ).

El comienzo del siglo XXI trae consigo importantes desafíos asociados con la futura economía energética. Por un lado, a nivel mundial hay un crecimiento continuo de la demanda de energía, que está siendo satisfecha en más de un 80% por combustibles de origen fósil (petróleo, carbón y gas). Estos recursos son limitados y generan una fuerte dependencia de la economía del mundo industrializado de su disponibilidad. Por otro lado, el empleo masivo de los combustibles fósiles ha incrementado las emisiones de CO2 con un claro impacto sobre el medioambiente. Por lo tanto, es necesario un cambio en la matriz energética desde portadores de energía fósil a energías renovables. Frente a este panorama, proponemos combinar el ciclo del hidrógeno con el del carbono. El hidrógeno producido a partir de fuentes renovables constituye un vector energético renovable y no contaminante, que puede ser almacenado para su posterior empleo. Además, su obtención posibilita la combinación con el CO2 capturado de la atmósfera para producir combustibles sintéticos. Este ciclo combinado, requiere el desarrollo de materiales y procesos que posibiliten la producción de hidrógeno empleando catalizadores adecuados, su almacenamiento en matrices sólidas tipo hidruros, la captura selectiva de CO2 en los sitios de generación y su posterior transformación a productos de valor agregado. En cada una de estas etapas nuestro grupo de trabajo ha realizado importantes avances. En este trabajo se presentarán los principales resultados obtenidos en los últimos años por nuestro grupo, asociados con el desarrollo de materiales almacenadores de hidrógeno tipo amiduros. Estos materiales muestran una importante flexibilidad estructural, que permite modificar la termodinámica y/o la cinética de reacción, manteniendo capacidades de almacenamiento de hidrógeno atractivas. The beginning of the 21st century brings important challenges associated with the future energy economy. There is a continuous growth of energy demand, which is being satisfied by more than 80% of fossil fuels (oil, carbon and gas). These resources are limited and generate a strong dependence on the economy of the industrialized world of their availability. The massive use of fossil fuels has increased the CO2 emissions with a clear impact on the environment. Then, a change in the energy matrix from fossil energy carriers to renewable energies is necessary. The proposal is to combine the hydrogen cycle with the carbon cycle. Hydrogen produced from renewable sources constitutes a renewable and non-polluting energy carrier, which can be stored for later use. Their production allows the combination with CO2 captured from the atmosphere to produce synthetic fuels. This combined cycle requires the development of materials and processes that allow the production of hydrogen using suitable catalysts; the hydrogen storage in hydride - type solid matrices; the selective capture of CO2 at the generation sites and its subsequent transformation to value-added products. In each of these stages, our work group has made important progresses. In this paper we present results obtained in the last years, associated with the development of amides for hydrogen storage applications. These materials exhibit significant structural flexibility, which allows the modification of thermodynamics and/or reaction kinetics, while maintaining attractive hydrogen storage capacities. Fil: Gennari, Fabiana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina