Policies and Motivations for the CO2 Valorization through the Sabatier Reaction Using Structured Catalysts. A Review of the Most Recent Advances

The current scenario where the effects of global warming are more and more evident, has motivated different initiatives for facing this, such as the creation of global policies with a clear environmental guideline. Within these policies, the control of Greenhouse Gase (GHG) emissions has been defined as mandatory, but for carrying out this, a smart strategy is proposed. This is the application of a circular economy model, which seeks to minimize the generation of waste and maximize the efficient use of resources. From this point of view, CO2 recycling is an alternative to reduce emissions to the atmosphere, and we need to look for new business models which valorization this compound which now must be considered as a renewable carbon source. This has renewed the interest in known processes for the chemical transformation of CO2 but that have not been applied at industrial level because they do not offer evident profitability. For example, the methane produced in the Sabatier reaction has a great potential for application, but this depends on the existence of a sustainable supply of hydrogen and a greater efficiency during the process that allows maximizing energy efficiency and thermal control to maximize the methane yield. Regarding energy efficiency and thermal control of the process, the use of structured reactors is an appropriate strategy. The evolution of new technologies, such as 3D printing, and the consolidation of knowledge in the structing of catalysts has enabled the use of these reactors to develop a wide range of possibilities in the field. In this sense, the present review presents a brief description of the main policies that have motivated the transition to a circular economy model and within this, to CO2 recycling. This allows understanding, why efforts are being focused on the development of different reactions for CO2 valorization. Special attention to the case of the Sabatier reaction and in the application of structured reactors for such process is paid

CO oxidation at low temperature on Au/CePO4: Mechanistic aspects

This work reports the synthesis and characterization of a cerium phosphate supported gold catalyst as well as its catalytic activity for the oxidation of CO. A precipitation method in the presence of an organic modifier followed by a hydrothermal treatment was used for the support synthesis, resulting in high surface area nanometric particles. Gold/cerium phosphate catalyst with a 1% (w/w) nominal gold content was characterized using XRF, XRD, N2 adsorption-desorption measurements, TEM and DRIFTS-MS. The catalyst shows good catalytic activity at low temperature. The activity is related to the generation of oxygen vacancies in the support caused by the elimination of structural oxygen. In situ studies revealed that the reaction of the oxygen vacancies with gaseous oxygen resulted in the formation of peroxo species. These species are responsible for the activity detected at room temperature in both the catalyst and the support. Moreover, the presence of carbonate and hydrogen carbonate acting as reaction intermediates have been observed

Recycling of construction and demolition waste generated by building infrastructure for the production of glassy materials

The use of waste materials generated by construction and demolition industry to yield valuable glassy materials, i.e. enamel for glazed ceramic tiles and cellular glasses is presented in this study. Both types of materials are produced by one-step treatment at moderate temperatures after simple waste chemical composition adjust. The enamels are manufactured directly from the initial waste powder by melting, while the expanded materials result from mixing of the vitreous material obtained after waste vitrification with an adequate foaming agent and posterior thermal treatment. Through the manuscript the feasibility of one step production of second generation profit materials is discussed in order to help achieving sustainable development and environmental protectio

Effect of starch as binder in carbon aerogel and carbon xerogel preparation

Carbon aerogels and carbon xerogels were synthesized through resorcinol – formaldehyde polycondensation using Na2CO3 as catalyst. The effect of soluble starch introduction in the organic gel preparation on the porous surface properties of these materials was studied. The role of the drying process of the organic gels on the changes in the surface and structural properties of these materials after the addition of soluble starch is dis- cussed. The presence of starch in the prepared carbon xerogels results in the development of microporosity while maintaining the characteristic mesoporosity of carbon xerogels. The Brunauer – Emmett -Teller (BET) surface area increases from 309 m2/g in carbon xerogel without soluble starch until 685 m2/g when 10% of soluble starch is added. The R- value and average crystallite lattice parameters, inter-layer spacing, crystallite height, crystallite diameter and the average number of aromatic layers per carbon crystallite are discussed in function of drying step and presence of soluble starch. The surface properties were also studied by Raman and DRIFT spectroscopiesMinisterio de Educación y Competitividad de España (MINECO) y Fondos FEDER de la Unión Europea-ENE2013-47880-C3-2-R y ENE2017-82451-C3-3-

Effects of nonstoichiometry in the melting process of Y2O3 from molecular dynamics simulations

Molecular dynamics simulations in the microcanonical ensemble of liquid yttrium oxide were performed at a temperature of 3100 K. Three different Y/O ratios were used in order to find out what the role of nonstoichiometry is in the process of melting and disordering of the liquid at high temperatures. Our simulations indicate that when no oxygen vacancies are generated there is no disordering process and the crystalline structure should remain. We conclude that the melting process occurs, in the real system, when a large enough number of oxygen vacancies is generated as a result of the large thermal vibrations of superficial oxygen atoms. The apparent high coordination number for yttrium found experimentally is explained based on the overlapping of the partial radial distribution functions, which cannot be elucidated from the x-ray diffraction data but can be clearly seen from our simulations.Comisión Interministerial de Ciencia y Tecnología MAT97-071

Low-temperature CO oxidation on multicomponent gold based catalysts

In this work the development of gold catalysts, essentially based on ¿-alumina with small superficial fraction of Ce-Fe mixed oxides as support for the low temperature CO oxidation is proposed. Characterization results obtained by means of TEM, OSC, XPS, UV-Vis spectroscopy and H2-TPR are employed to correlate the activity data with the catalysts composition. The bare ¿-alumina supported gold catalyst demonstrates the poorest activity within the series. The addition of CeO2 or FeOX improves the catalytic performance, especially observed for the CeO2-FeOx mixed oxide doped samples. This enhanced CO oxidation activity was related to the Ce-Fe interaction producing materials with promoted redox properties and therefore oxidation activity.Peer Reviewe

Amber imitation? Two unusual cases of Pinus resin-coated beads in Iberian Late Prehistory (3rd and 2nd millennia BC)

A group of beads from the artificial cave of La Molina (Lora de Estepa, Sevilla) and Cova del Gegant (Sitges, Barcelona) were made from a biogenic raw material and intentionally covered by a layer of resin. This is the first time this type of treatment has been documented on elements of adornment in the Late Prehistory of the Iberian Peninsula. The composition and nature of the coatings are analysed and the symbolic role of such alterations and imitations of prehistoric adornments is discussed.Ministerio de Economía y Competitividad HAR2012- 34620, HAR2017-83474-

Ru–Ni Catalyst in the Combined Dry-Steam Reforming of Methane: The Importance in the Metal Order Addition

Biogas is one of the main biomass-energy resources. Its use for syngas production with a H2/CO ratio close to two would have huge environmental, social and economic impact in the actual energetic scenario. However, the use of dry reforming, where the two main components are transformed into syngas, does not allow the desired H2/CO ratio. For this reason, the addition of water is proposed. The process was performed with two Ru–Ni catalysts where the metal order in the impregnation process was varied. The catalysts were prepared either by simultaneous or consecutive impregnation of the active phases and its catalytic performance in the combined dry-steam reforming of methane was tested. The catalysts were characterized by XRF, XRD, SBET, TPR-H2 and Raman spectroscopy. The existence of a strong Ni–Ru interaction is evidenced by Raman spectroscopy and TPR-H2 in the sample synthesized by the simultaneous impregnation. Concerning the catalytic activity, this sample presents the highest CH4 and CO2 conversion values in the entire composition rate and the lowest amount of carbon deposits after reaction. After pulse, and reactivity tests it was concluded that the higher Ni–Ru interaction displayed by the catalyst synthesized by the simultaneous impregnation, enhances the carbon gasification.España Mineco ENE2012-374301-C03-01 ENE2013-47880-C3-2-RJunta de Andalucía FEDER TEP-819

Molecular-dynamics simulations of liquid aluminum oxide

The total and partial radial distribution functions g(r) and the corresponding structure factors S(q) were calculated based on molecular-dynamics simulations in the microcanonical ensemble of liquid aluminum oxide. The simulations were performed in the temperature range 2300-3000 K in order to explore the temperature dependence of the structure, finding that the liquid structure is invariant as a function of temperature. With the aid of the partial radial distribution functions, it is possible to reinterpret the experimental data leading to a new assignment of peaks which differs from the one reported in a previously published work by Ansell et al. [Phys. Rev. Lett. 78, 464 (1997)]. The structural model for liquid aluminum oxide obtained from our simulations is essentially the same as that reported in the experimental work.Dirección General de Investigaciones Científicas y Técnicas PB95-124

Structuring Pt/CeO2/Al2O3 WGS catalyst: Introduction of buffer layer

This work is devoted to the development of novel structured catalytic system for WGS reaction. The new concept is related to the presence of a pre-catalytic “buffer” layer formed by WGS-inert oxide, i.e. not involved in CO conversion, but able to increase the number of participating sites in water dissociation step during the reaction. The performance of the proposed systems appears to depend strongly on the stream composition, being its effect beneficial in highly reducing atmospheres making it ideal for clean-up application. An increment of the partial kinetic order for water species is observed and reveals the key role of the water activation for superior catalytic behavior.Junta de Andalucía TEP-819