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-

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

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

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

The role of Au, Cu & CeO2 and their interactions for an enhanced WGS performance

The WGS reaction over multicomponent Au/Ce1-xCuxO2/Al2O3 catalysts is studied in this work. The systems are carefully designed aiming to take advantage of every active phase included in the formulation: gold, ceria and copper. Special emphasis is given to the CeO2-CuO synergy and its influence on the displayed catalytic performance with and without gold. To this aim a meaningful correlation between the physicochemical properties of the mixed materials and their activity/stability is proposed. In general terms the developed catalysts present high activity under realistic WGS reaction conditions, with fairly good long term stability. In addition, the systems successfully withstand start-up/shut-downs situations, indispensable requisite for real applications in the field of pure hydrogen production for fuel cell goals.Junta de Andalucía TEP-8196España Mineco ENE2012-374301-C03-01 ENE2013-47880-C3-2-

Low-temperature CO oxidation on multicomponent gold based catalysts

In this work the development of gold catalysts, essentially based on γ-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 γ-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 activit

Boosting the activity of a Au/CeO2/Al2O3 catalyst for the WGS reaction

Herein a strategy to design highly efficient Au/CeO2/Al2O3 based WGS catalysts is proposed. The inclusion of transition metals, namely Fe, Cu and Zn as CeO2 dopant is considered. All the promoters successfully increased the WGS performance of the undoped sample. The activity improvement can be correlated to structural and/or redox features induced by the dopants. The comparative characterization of the doped samples by means of XRD, Raman spectroscopy and OSC evaluation permits an accurate understanding of the boosted WGS activity arising from the Ce-promoter interaction. This study establishes distinction among both, structural and redox sources of promotion and provides a useful strategy to develop highly active Au/CeO2 based catalysts for the WGS reaction.Junta de Andalucía TEP-8196España Mineco ENE2012-374301-C03-01 ENE2013-47880-C3-2-

Chemical CO2 recycling via dry and bi reforming of methane using Ni-Sn/ Al2O3 and Ni-Sn/CeO2-Al2O3 catalysts

Carbon formation and sintering remain the main culprits regarding catalyst deactivation in the dry and bireforming of methane reactions (DRM and BRM, respectively). Nickel based catalysts (10 wt.%) supported on alumina (Al2O3) have shown no exception in this study, but can be improved by the addition of tin and ceria. The effect of two different Sn loadings on this base have been examined for the DRM reaction over 20 h, before selecting the most appropriate Sn/Ni ratio and promoting the alumina base with 20 wt.% of CeO2. This catalyst then underwent activity measurements over a range of temperatures and space velocities, before undergoing experimentation in BRM. It not only showed good levels of conversions for DRM, but exhibited stable conversions towards BRM, reaching an equilibrium H2/CO product ratio in the process. In fact, this work reveals how multicomponent Ni catalysts can be effectively utilised to produce flexible syngas streams from CO2/CH4 mixtures as an efficient route for CO2 utilisation

Sub-ambient CO oxidation over Au/MO x/CeO 2-Al 2O 3 (M = Zn or Fe)

A series of ZnO and Fe 2O 3 modified ceria/alumina supports and their corresponding gold catalyst were prepared and studied in the CO oxidation reaction. ZnO-doped solids show a superior catalytic activity compared to the bare CeO 2-Al 2O 3, which is attributed to the intimate contact of the ZnO and CeO 2 phases, since an exchange of the lattice oxygen occurs at the interface. In a similar way, Fe 2O 3-modified supports increase the ability of the CeO 2-Al 2O 3 solids to eliminate CO caused by both the existence of Ce-Fe contact surface and the Fe 2O 3 intrinsic activity. All of the gold catalysts were very efficient in oxidising CO irrespective of the doping metal oxide or loading, with the ZnO containing systems better than the others. The majority of the systems reached total CO conversion below room temperature with the ZnO and Fe 2O 3 monolayer loaded systems the most efficient within the series.Ministerio de Ciencia e Innovación ENE2009-14522-C05-01Junta de Andalucía P09-TEP-545