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The preparation and use of Guefoams as heterogeneous catalyst is reported. The Guefoam catalyst consists of an open-pore Al-Si foam that accommodates a freely mobile guest phase (Ni/CeO2/Al2O3 particles) in its cavities, with neither a physical nor a chemical matrix-guest bond. A eutectic Al-12Si alloy was used as a low-melting matrix precursor to prevent thermal sintering of the active phase during liquid metal infiltration. CO2 methanation was chosen as the reaction test. The activity and CH4 selectivity (close to 100%) achieved with the Guefoam catalyst were similar to those obtained with a packed bed of the same active phase particles, but with the advantages of a structured reactor such as robustness and ease of handling. The thermal conductivity of the Guefoam catalyst is significantly improved with regard to the packed bed of active phase particles, which reduces the temperature gradients in the catalytic reactor, as demonstrated by computational fluid dynamic modelling. Since the permeability of the Guefoam catalyst is 2.7 times that of the packed bed, the pressure drop caused by the passage of a fluid through the novel material is reduced, resulting in a significantly higher catalytic performance index than the packed bed.

Los objetivos de esta red han sido (i) generar material audiovisual con los contenidos teóricos de la asignatura Química Inorgánica (Grado en Química), (ii) facilitárselo al alumnado empleando la aplicación “Vértice” y (iii) evaluar el grado de utilización del material audiovisual haciendo un seguimiento de las visitas y tiempo de visualización. Se han editado y montado 33 videos, que suman un total de 33 horas 27’ y 13’’, y el tiempo total de visualización por parte del alumnado ha ascendido a 90h 15’ y 29’’. De los 53 alumnos matriculados en la asignatura, el 72 % ha accedido al menos una vez a consultar algún video, poniendo en evidencia el alto interés por parte del alumnado del material audiovisual desarrollado en esta red. El análisis de los datos de visualización sugiere que la utilización de los videos ha tenido dos perfiles. Una parte del alumnado los ha visualizado de forma sistemática y, otra parte, los ha utilizado de forma selectiva para acceder a contenidos concretos. El resultado de la encuesta de opinión del alumnado realizada por el Vicerrectorado de Estudios, Calidad y Lenguas al profesor que ha impartido la asignatura, y coordinador de esta red, ha sido de 10 en la pregunta “Los recursos proporcionados para el aprendizaje de la asignatura (documentos, bibliografía, presentaciones, recursos didácticos, etc.)”. Este resultado pone en evidencia la elevada satisfacción del alumnado con los videos desarrollados, y cobra especial relevancia si se contextualiza comparándolo con los resultados obtenidos en cursos precedentes (en torno a 8) y con los resultados medios alcanzados en esta misma pregunta en el curso 2020/2021 por la Asignatura, Departamento y Titulación, que son de 7, 8 y 8 respectivamente.

The preferential CO oxidation (so-called CO-PROX) is the selective CO oxidation amid H2-rich atmospheres, a process where ceria-based materials are consolidated catalysts. This article aims to disentangle the potential CO–H2 synergism under CO-PROX conditions on the low-index ceria surfaces (111), (110) and (100). Polycrystalline ceria, nanorods and ceria nanocubes were prepared to assess the physicochemical features of the targeted surfaces. Diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) shows that ceria surfaces are strongly carbonated even at room temperature by the effect of CO, with their depletion related to the CO oxidation onset. Conversely, formate species formed upon OH + CO interaction appear at temperatures around 60 °C and remain adsorbed regardless the reaction degree, indicating that these species do not take part in the CO oxidation. Density functional theory calculations (DFT) reveal that ceria facets exhibit high OH coverages all along the CO-PROX reaction, whilst CO is only chemisorbed on the (110) termination. A CO oxidation mechanism that explains the early formation of carbonates on ceria and the effect of the OH coverage in the overall catalytic cycle is proposed. In short, hydroxyl groups induce surface defects on ceria that increase the COx–catalyst interaction, revealed by the CO adsorption energies and the stabilization of intermediates and readsorbed products. In addition, high OH coverages are shown to facilitate the hydrogen transfer to form less stable HCOx products, which, in the case of the (110) and (100), is key to prevent surface poisoning. Altogether, this work sheds light on the yet unclear CO–H2 interactions on ceria surfaces during CO-PROX reaction, providing valuable insights to guide the design of more efficient reactors and catalysts for this process.

Sponge-like carbon monoliths with tailored channel architecture and porosity were prepared by combining sol-gel polymerization and 3D printing technology. The pore size distribution (PSD) and macropore volume were controlled by varying the water concentration used in the synthesis. The size and interconnection degree of primary particles, and consequently the pore width and macropores volume, increases by increasing the water concentration. However, a more heterogeneous PSD was detected at high water concentration, due to the better-defined spheres-like morphology of primary particles which leaves voids and corners between fused spheres together with bigger macropores leaves by the coral-like structure. The role of this porosity control on the CuO/CeO2 catalytic performance was pointed out in the CO-PrOx reaction. The CuO/CeO2 dispersion and distribution along the carbon network increases by increasing the water concentration, i.e. the pore width and macropore volume, enhancing the catalytic activity. However, this improvement is not observed at high water concentration in which preferential flow pathways are created favored by the heterogeneous PSD. This manifest that the porosity control plays an important role in the catalytic performance of monolithic catalysts and thus, the monolithic support must be specifically designed to optimize the catalytic performance of active phases for each application.

Esta tesis consiste en la implementación de la tecnología de impresión 30 como una herramienta para el diseño y fabricación de soportes monolíticos que mejoran las prestaciones de los soportes convencionales. En un primer enfoque se ha empleado la estereolitografía (impresión 30) para la preparación directa de estructuras monolíticas de resina polimérica. Estos monolitos poliméricos con diferentes diseños geométricos se han empleado como soporte de la fase activa Cu0/Ce02 y su rendimiento fue estudiado en la reacción de oxidación preferencial de C0 (C0-Prüx). Un segundo enfoque ha consistido en la preparación de plantillas (moldes) mediante la tecnología de impresión 30 de modelado por deposición fundida, las cuales junto con un procedimiento de síntesis de hidrogeles de resorcinol y formaldehído han permitido obtener estructuras monolíticas de carbón con diferentes configuraciones geométricas de sus canales y una porosidad definida por las condiciones de síntesis. Estos monolitos de carbón se han empleado con éxito como soportes de las fases activas Cu0/Ce02 y Ni/Ce02, y su rendimiento catalítico fue estudiado en la reacción C0-Prüx y la reacción de metanación de C02, respectivamente.

A new method to synthesize integral carbon monoliths with a controlled channel morphology has been developed in this work by combining 3D-printing technology and sol–gel polymerization. By this method, robust and consistent carbon monoliths were obtained with a perfect replica of the channel architecture at a microscale range. As a proof of concept, a carbon monolith with tortuous channels that split and join successively along the monolith length has been designed, fabricated and tested as a CuO/CeO2 support for the preferential oxidation of CO in the presence of H2 (CO-PrOx), which is a topic of ongoing research for H2 purification in fuel cells. The behavior of this novel carbon monolith catalyst has been compared with that of a counterpart catalyst prepared with a conventional honeycomb design. Results shown that the wide macroporosity of the carbon network favors the anchoring and dispersion of the active phase both in the channel surface and the carbon network. The channel architecture affects the gas diffusion both through the channel and the carbon network and consequently, affects the active phase accessibility and activity. T50 (the temperature to achieve 50% CO conversion) decreases by almost 13 °C at 240 mL min−1 in the carbon monolith with tortuous channels (T50 = 79.7 °C) compared to the honeycomb monolith (T50 = 93.1 °C). The turbulent path created by the tortuous channels favours the active phase–gas contact and even the gas diffusion inside the macropores of the carbon skeleton improving the catalytic performance of the active phase compared to that by the conventional honeycomb design. Thus, this work demonstrates the potential of 3D printing to improve the catalytic supports currently available.

Honeycomb monoliths are the preferred supports in many industrial heterogeneous catalysis reactions, but current extrusion synthesis only allows obtaining parallel channels. Here, we demonstrate that 3D printing opens new design possibilities that outperform conventional catalysts. High performance carbon integral monoliths have been prepared with a complex network of interconnected channels and have been tested for carbon dioxide hydrogenation to methane after loading a Ni/CeO2 active phase. CO2 methanation rate is enhanced by 25% at 300 °C because the novel design forces turbulent flow into the channels network. The methodology and monoliths developed can be applied to other heterogeneous catalysis reactions, and open new synthesis options based on 3D printing to manufacture tailored heterogeneous catalysts.

In this study, the preferential CO oxidation (CO-PROX) reaction is simulated under advection–diffusion conditions in a CuO/CeO2 catalyst-supported monolith built by 3D-printing. The simulation incorporates the mass balances in the bulk of the fluid, the momentum balance, and the heterogeneous chemical reactions. In the monolith constricted channels, the fluid velocity is 80% larger than in the wider channels. Three reactive regimes are identified: the CO oxidation-dominated regime governing up to 85 °C and the early and late transition regimes where the H2 oxidation eventually increases. Up to 175 °C, a H2 oxidation-dominated reactive regime was not identified. The simulation accurately predicts experimental results of CO conversion and selectivity in the range from 25 to 175 °C. A sensitivity analysis demonstrates that the composition of gas mixture fed significantly affects the ratio of reaction rates and, consequently, the CO conversion and CO selectivity; meanwhile, the rate of gas injection yields moderate changes in reactivity.

Three-dimensional (3D)-printed catalysts are being increasingly studied; however, most of these studies focus on the obtention of catalytically active monoliths, and thus traditional channeled monolithic catalysts are usually obtained and tested, losing sight of the advantages that 3D-printing could entail. This work goes one step further, and an advanced monolith with specifically designed geometry has been obtained, taking advantage of the versatility provided by 3D-printing. As a proof of concept, nonchanneled advanced monolithic (NCM) support, composed of several transversal discs containing deposits for active phase deposition and slits through which the gas circulates, was obtained and tested in the CO-PrOx reaction. The results evidenced that the NCM support showed superior catalytic performance compared to conventional channeled monoliths (CMs). The region of temperature in which the active phase can work under chemical control, and thus in a more efficient way, is increased by 31% in NCM compared to the powdered or the CM sample. Turbulence occurs inside the fluid path through the NCM, which enhances the mass transfer of reagents and products toward and from the active sites to the fluid bulk favoring the chemical reaction rate. The nonchanneled monolith also improved heat dispersion by the tortuous paths, reducing the local temperature at the active site. Thus, the way in which reactants and products are transported inside the monoliths plays a crucial role, and this is affected by the inner geometry of the monoliths.

El objetivo general de esta intervención educativa es dar al alumnado la oportunidad de tener una experiencia anticipada en tareas de investigación previa a la realización del TFG en química. Con esto se pretende que el alumnado disponga de un mejor criterio cuando tenga que tomar la decisión de qué hacer en su TFG y con quién, sabiendo qué implica la elección de tutor y de línea de trabajo. Asimismo, nos permitirá a los docentes detectar de forma temprana aquellos alumnos con aptitudes hacia la investigación, permitiéndoles planificar su trabajo TFG con un enfoque que permita un máximo aprovechamiento de esa asignatura y, si fuese el caso, de su formación futura como investigador. Las actividades desarrolladas han incluido reuniones informativas sobre las actividades de la red, visitas guiadas a los laboratorios y realización de prácticas supervisadas en nuestros laboratorios. Con una población total de 43 alumnos, el 40 % ha mostrado interés por participar en parte de las actividades de la red y el 12 % ha optado por realizar todas las actividades propuestas, lo que se valora como unos porcentajes muy satisfactorios.

Honeycomb-shaped cordierite monoliths are widely used as supports for a large number of industrial applications. However, the high manufacturing cost of cordierite monoliths only justifies its use for high temperatures and aggressive chemical environments, demanding applications where the economic benefit obtained exceeds the manufacturing costs. For low demanding applications, such as the preferential oxidation of CO (CO-PrOx), alternative materials can be proposed to reduce manufacturing costs. Polymeric monoliths would be an interesting low-cost alternative; however, the limitations of the active phase incorporation to the polymeric support must be overcome. In this work, the implementation and use of polymeric monolithic structures obtained by three-dimensional printing to support CuO/CeO2 catalysts for CO-PrOx have been studied. Several approaches were used to anchor the active phase into the polymeric monoliths, such as adding inorganic materials (carbon or silica) to the polymer previous to the printing process, chemical attack with solvents of the printed resin before or during the active phase incorporation, and consecutive impregnation and modification of the channel wall design. Among those approaches, best results were obtained by the addition of silica and by channel modification. Independent of the strategy followed, a subsequent thermal treatment in N2 was required to soften the resin and favor the active phase anchoring. However, catalyst particles become embedded on the polymeric resin being not active, and thus, a final cleaning thermal treatment under air was needed to recover the active phase activity, after which the supported active phase demonstrated good catalytic activity, stability, and reusability.