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The CO2 methanation mechanism over the highly active (TOF=75.1 h−1), selective (>92%) and stable 10% LaNiO3/CeO2-derived catalyst is still unresolved. The surface of the catalyst is monitored under hydrogenation (H2), oxidizing (CO2) and CO2 methanation (H2 +CO2) conditions by near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) using synchrotron radiation. Meanwhile, the main reaction intermediates are identified by in situ FTIR analysis. NAP-XPS experiments confirm that LaNiO3 perovskite reduction leads to the ex-solution of Ni0 nanoparticles and Ni2+single bondCeO2−x and Ni2+single bondLa2O3 interfaces conformation, favouring the CO2 adsorption and the H2 dissociation/transfer. In situ FTIR experiments combined with the C1s spectra (NAP-XPS) suggest that the CO2 activation occurs on CeO2−x (oxygen vacancies and OH–) at low temperatures, in the form of bicarbonates; whereas, mono-/bidentate carbonates are formed on different strength La2O3 sites at increasing temperatures. These species are consecutively reduced to formates, as the main reaction intermediate, and methane by the H spilled from Ni0 nanoparticles near to NiOsingle bondCeO2−x and NiOsingle bondLa2O3 interfaces.

Ni/CeO2 catalysts are very active and selective for total hydrogenation of CO2 to methane, but the nature of the active sites is still unclear. The surface of a Ni/CeO2 catalyst has been monitored under CO2 methanation conditions by Near Ambient Pressure-XPS (NAP-XPS) using synchrotron radiation, and has been concluded that the species involved in the redox processes taking place during the CO2 methanation mechanism are the Ni2+-CeO2/Ni0 and Ce4+/Ce3+ pairs. In addition, a small fraction of nickel is present on the catalyst surface forming NiO and Ni2+-carbonates/hydroxyls (around 20% of the total surface nickel), but these species do not participate in the redox processes of the methanation mechanism. Under CO2 methanation conditions the H2 reduction rate of the Ni2+-CeO2/Ni0 and Ce4+/Ce3+ couples is much faster than their CO2 reoxidation rate (2 times faster, at least, at 300ºC), but a certain proportion of nickel always remains oxidized under reaction conditions. The high activity of Ni/CeO2 catalysts for CO2 methanation is tentatively attributed to the simultaneous presence of Ni2+-CeO2 and Ni0 active sites where CO2 and H2 are expected to be efficiently dissociated, respectively.

La transformación del CO2 ha suscitado gran interés a la comunidad científica en el área de la catálisis heterogénea, no solo por su potencial aplicación y escalado, sino también por estimular la creatividad de la comunidad científica en el diseño de las formulaciones y generación de conocimiento. En este sentido, la conversión (electro/foto) catalítica de CO2 ha experimentado un avance significativo en el desarrollo de nuevos combustibles, productos químicos, farmacéuticos y building-blocks entre otros. La hidrogenación catalítica de CO2 a productos valiosos se considera prometedora en la economía circular y el reciclado de CO2. El uso de CO2 como materia prima para producir componentes básicos ha surgido como un tema candente en la comunidad científica. Desde productos químicos C1 hasta combustibles de cadena larga, la hidrogenación catalítica de CO2 ofrece actualmente una amplia gama de tecnologías escalables para disminuir las emisiones de gases de efecto invernadero. Principalmente, la conversión de CO2 en metano se puede lograr mediante catalizadores funcionales duales a presión ambiente. Bien en sabido que metales como Ni o Ru soportados sobre óxidos reducibles exhiben una alta actividad y selectividad hacia la producción de metano. Es por ello que, este proyecto de tesis doctoral consiste en el diseño integral de catalizadores de Ni y Ru soportados sobre sistemas basados en óxido de cerio para el estudio de la valorización sostenible de CO2. Esto comprende desde la síntesis y optimización de los nuevos materiales, el estudio de sus propiedades físico-químicas mediante técnicas de caracterización convencional, técnicas avanzadas focalizadas en estudios mecanísiticos, el estudio in-situ de la evolución de los estados de oxidación, el estudio de agentes dopantes trivalentes y tetravalentes, el papel de los centros activos implicados en el mecanismo de reacción y la influencia de la morfología cuando se obtienen diferentes interacciones metal/óxido sobre cataliz

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.

The conversion of CO2 towards added valuable products is considered as a potential alternative to achieve the increase of the petrochemical industry while reducing the CO2 emissions. In the present work, the effect of Ru loading on CeO2 supports has been studied for the CO2 methanation reaction, and catalysts with different Ru loading in the 1–5 wt. % range have been prepared, characterized, and tested. The optimum Ru loading has been found to be 2.5 wt. %. Ruthenium cations are reduced at the lowest temperature for this optimum loading according to H2-TPR experiments (even at room temperature), and the highest proportion of ruthenium cations with strong interaction with ceria is achieved, as deduced from XPS. XRD characterization suggests partial insertion of ruthenium cations into the ceria lattice. In situ DRIFTS experiments evidenced that the balance between formation upon CO2 chemisorption and further hydrogenation of surface carbon intermediates is optimum for 2.5 wt. % Ru/CeO2. For low metal contents, the CO2 chemisorption is limited and no relevant, while as the metal content is increased, the hydrogenation of carbon species is less favourable. The 2.5 wt.% Ru/CeO2 catalyst comprises a balance between surface-carbon groups formation and further hydrogenation.

CO2 methanation has been studied with Pr-doped Ru/CeO2 catalysts, and a dual effect of Pr has been observed. For low Pr content (i.e., 3 wt %) a positive effect in oxygen mobility prevails, while for high Pr doping (i.e., 25 wt %) a negative effect in the Ru–CeO2 interaction is more relevant. Isotopic experiments evidenced that Pr hinders the dissociation of CO2, which takes place at the Ru–CeO2 interface. However, once the temperature is high enough (200 °C), Pr improves the oxygen mobility in the CeO2 support, and this enhances CO2 dissociation because the oxygen atoms left are delivered faster to the support sink and the dissociation sites at the interface are cleaned up faster. In situ Raman spectroscopy experiments confirmed that Pr improves the creation of oxygen vacancies on the ceria lattice but hinders their reoxidation by CO2, and both opposite effects reach an optimum balance for 3 wt % Pr doping. In addition, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments showed that Pr doping, regardless of the amount, decreases the population of surface carbon species created on the catalysts surface upon CO2 chemisorption under methanation reaction conditions, affecting both productive reaction intermediates (formates and carbonyls) and unproductive carbonates.

Cryptomelane is an abundant mineral manganese oxide with unique physicochemical features. This work investigates the real capabilities of cryptomelane as an oxidation catalyst. In particular, the preferential CO oxidation (CO-PROX), has been studied as a simple reaction model. When doped with copper, the cryptomelane-based material has revealed a great potential, displaying a comparable activity to the high-performance CuO/CeO2. Despite stability concerns that compromise the primary catalyst reusability, CuO/cryptomelane is particularly robust in the presence of CO2 and H2O, typical components of realistic CO-PROX streams. The CO-PROX reaction mechanism has been assessed by means of isotopic oxygen pulse experiments. Altogether, CuO/CeO2 shows a greater oxygen lability, which facilitates lattice oxygen enrolment in the CO-PROX mechanism. In the case of CuO/cryptomelane, in spite of its lower oxygen mobility, the intrinsic structural water co-assists as active oxygen species involved in CO-PROX. Thus, the presence of moisture in the reaction stream turns out to be beneficial for the stability of the cryptomelane structure, besides aiding into the active oxygen restitution in the catalyst. Overall, this study proves that CuO/cryptomelane is a promising competitor to CuO/CeO2 in CO-PROX technology, whose implementation can bring the CO-PROX technology and H2 purification processes a more sustainable nature.

A model of sustainable community rural tourism is complex, so the objective of this study is to assess the influence of factors such as social cohesion and territorial roots in the locality of Usme (Bogotá-Colombia), a territory with natural and cultural heritage very significant. A documentary study is carried out to analyze national and international experiences and a field study through semi-structured interviews and direct observation on the ground. The results confirm that the aforementioned factors are key to the success of the turism entrepreneurships., Un modelo de turismo rural comunitario sostenible es complejo, por lo que el objetivo de este estudio es valorar la influencia de factores como la cohesión social y el arraigo territorial en la localidad de Usme (Bogotá-Colombia), territorio con un significativo patrimonio natural y cultural. Se realiza un estudio documental para analizar experiencias nacionales e internacionales y un estudio de campo, mediante entrevistas semiestructuradas y observación directa sobre el terreno. Los resultados confirman que los factores mencionados son claves para el éxito de los emprendimientos turísticos., Un modèle de tourisme rural communautaire durable est complexe, donc l'objectif de cette étude est d'évaluer l'influence de facteurs tels que la cohésion sociale et les racines territoriales dans la ville d'Usme (Bogotá-Colombie), un territoire avec un patrimoine naturel important et culturel. Une étude documentaire est réalisée pour analyser les expériences nationales et internationales et une étude de terrain, à travers des entretiens semi-structurés et une observation directe sur le terrain. Les résultats confirment que les facteurs susmentionnés sont essentiels au succès des entreprises touristiques.

The preferential CO oxidation (CO-PROX) reaction is paramount for the purification of reformate H2-rich streams, where CuO/CeO2 catalysts show promising opportunities. This work sheds light on the lattice oxygen recovery mechanism on CuO/CeO2 catalysts during CO-PROX reaction, which is critical to guarantee both good activity and selectivity, but that is yet to be well understood. Particularly, in situ Raman spectroscopy reveals that oxygen vacancies in the ceria lattice do not form in significant amounts until advanced reaction degrees, whereas pulse O2 isotopic tests confirm the involvement of catalyst oxygen in the CO and H2 oxidation processes occurring at all stages of the CO-PROX reaction (Mars–van Krevelen). Further mechanistic insights are provided by operando near-ambient pressure X-ray photoelectron spectroscopy (NAP–XPS) and near edge X-ray absorption fine structure (NEXAFS) experiments, which prove the gradual CuO reduction and steady oxidized state of Ce ions until the very surface reduction of CeO2 at the point of selectivity loss. Experiments are complemented by density functional theory (DFT) calculations, which reveal a more facile oxygen refill according to the trend CuO > CeO2 > Cu2O. Overall, this work concludes that the oxygen recovery mechanism in CO-PROX switches from a direct mechanism, wherein oxygen restores vacancy sites in the partially reduced CuO particles, to a synergistic mechanism with the participation of ceria once CuxO particles reach a critical reduction state. This mechanistic switch ultimately results in a decrease in CO conversion in favor of the undesired H2 oxidation, which opens-up future research on potential strategies to improve oxygen recovery.

This article shows the results of the study whose purpose is to disseminate the experience of the transfer and technological appropriation of the utility model in greenhouse sowing through the application of the social research methodology. El Edén de Cris case, corregimiento of the Elvira, period 2012 - 2016. The results revealsthat when applying the methodology in the project, the technological tranfer appropriation and adoption of sowing under greenhouse was achieved through a utility model; however the continuity of the project involving more agricultural producers would generate a socioeconomic impact in the town.The utility model allowed the application of new forms of agricultural production through the Sustainable Agricultural Productive Units, the replication of more producers could contribute to reducing the gaps of social exclusion and inequality existing in the town of Elvira, reconfiguring the territory from design of a sustainable productive micro-circuit with agroecosystems, through the social construction of forms of productive relations in networks of rural producers. JEL Classification: F18, J43, L83, 013, Q57, Resumo O artigo apresenta os resultados do estudo, cujo objetivo é disseminar a experiência da transferência e apropriação tecnológica do modelo de utilidade na semeadura em estufa através da aplicação da metodologia de pesquisa social, caso El Edén de Cris, corregimiento (é usado na Colômbia para definir um tipo de subdivisão da área rural dos diferentes municípios do país) de La Elvira, período de 2012 - 2016. Os resultados revelam que, ao aplicar a metodologia no projeto, a transferência tecnológica, a apropriação e a adoção da semeadura em casa de vegetação foram realizadas por meio de um modelo de utilidade; no entanto, a continuidade do projeto envolvendo mais produtores agrícolas geraria um impacto socioeconómico na localidade. O modelo de utilidade permitiu a aplicação de novas formas de produção agrícola por meio das Unidades Produtivas Agrícolas Sustentáveis, a replicação de mais produtores poderia contribuir para reduzir as lacunas de exclusão social e desigualdade existentes no corregimiento de La Elvira, reconfigurando o território de projeto de um microcircuito produtivo sustentável com agroecossistemas, através da construção social de relações Produtivas Em Redes De Produtores Rurais. Classificações JEL: F18, J43, L83, 013, Q57, Resumen El artículo muestra los resultados del estudio cuyo propósito es divulgar la experiencia de la transferencia y apropiación tecnológica del modelo de utilidad en la siembra bajo invernadero mediante la aplicación de la metodología investigación social, caso El Edén de Cris, corregimiento de La Elvira, período 2012 - 2016. Los resultados revelan que al aplicar la metodología en el proyecto, se logró la transferencia tecnológica, la apropiación y adopción de siembra bajo invernadero por medio de un modelo de utilidad; sin embargo, la continuidad del proyecto involucrando más productores agrícolas generaría un impacto socioeconómico en la localidad. El modelo de utilidad permitió aplicar nuevas formas de producción agrícola a través de las Unidades Productivas Agrícolas Sostenibles, la réplica a más productores podría contribuir a disminuir las brechas de exclusión social e inequidad existentes en la localidad de la Elvira, reconfigurar el territorio a partir del diseño de un micro-circuito productivo sostenible con el agroecosistema, mediante la construcción social de relaciones productivas en redes de productores rurales. Clasificación JEL: F18, J43, L83, 013, Q57

Actualmente, la optimización de los equipos de la industria de procesos en base a criterios económicos (sin dejar de lado el impacto medioambiental) está creciendo de manera significante. Una de las grandes limitaciones, en este sentido, es el tiempo de computación debido a la necesidad de optimizar uno o varios objetivos (coste e impacto ambiental generalmente) utilizando modelos complejos basados en ecuaciones diferenciales. En este trabajo, se ha propuesto una estructura sistemática para el diseño de reactores tubulares (aplicado a la producción de propilenglicol a partir de óxido de propileno) que combina un método riguroso de optimización con un modelo surrogado (del inglés, “surrogate”) con el objetivo de minimizar los costes de procesado de la materia prima. Los resultados obtenidos muestran tanto las condiciones de operación como el diseño óptimo de entre los tres casos de estudio realizados. De forma complementaria, se ha creado una aplicación con carácter docente como material complementario a la asignatura Diseño de Reactores I del Grado en Ingeniería Química. Con esta aplicación, generada a partir de la herramienta Application Builder provista en COMSOL Multiphysic’s, se pretende que el alumno pueda visualizar los gradientes radiales, así como los fenómenos de transporte implicados en un reactor tubular cuando sucede una reacción de primer orden. Del mismo modo, también permite calcular la conversión en estas condiciones para poder estimar el error que se comete al utilizar los modelos ideales de flujo unidimensional.