Browsing by Author "Bimbela Serrano, Fernando"
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Publication Open Access The 3D-printing fabrication of multichannel silicone microreactors for catalytic applications(MDPI, 2023) Ibáñez de Garayo Quilchano, Alejandro; Imizcoz Aramburu, Mikel; Maisterra Udi, Maitane; Almazán, Fernando; Sanz Carrillo, Diego; Bimbela Serrano, Fernando; Cornejo Ibergallartu, Alfonso; Pellejero, Ismael; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaMicrostructured reactors (MSRs) are especially indicated for highly demanding heterogeneous catalysis due to the small channel dimensions that minimize diffusional limitations and enhance mass and heat transport between the fluid and the catalyst. Herein, we present the fabrication protocol of the fused filament 3D printing of silicone monolithic microreactors based on a multichannel design. Microchannels of 200 to 800 µm in width and up to 20 mm in length were developed following the scaffold-removal procedure using acrylonitrile butadiene styrene (ABS) as the material for the 3D-printed scaffold fabrication, polydimethylsiloxane (PDMS) as the building material, and acetone as the ABS removing agent. The main printing parameters such as temperature and printing velocity were optimized in order to minimize the bridging effect and filament collapsing and intercrossing. Heterogeneous catalysts were incorporated into the microchannel walls during fabrication, thus avoiding further post-processing steps. The nanoparticulated catalyst was deposited on ABS scaffolds through dip coating and transferred to the microchannel walls during the PDMS pouring step and subsequent scaffold removal. Two different designs of the silicone monolithic microreactors were tested for four catalytic applications, namely liquid-phase 2-nitrophenol photohydrogenation and methylene blue photodegradation in aqueous media, lignin depolymerization in ethanol, and gas-phase CO2 hydrogenation, in order to investigate the microreactor performance under different reaction conditions (temperature and solvent) and establish the possible range of applications.Publication Open Access Application of a modeling tool to describe fly ash generation, composition, and melting behavior in a wheat straw fired commercial power plant(MDPI, 2020) Funcia, Ibai; Bimbela Serrano, Fernando; Gil, Javier; Gandía Pascual, Luis; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaAsh behavior is a key operational aspect of industrial-scale power generation by means of biomass combustion. In this work, FactSage™ 6.4 software was used to develop and assess three models of wheat straw combustion in a vibrating grate-fired commercial boiler of 16 MWth, aiming to describe the inorganic elements release as well as fly ash melting behavior and composition. Simulations were carried out solving four consecutive calculation stages corresponding to the main plant sections. Chemical fractionation was adopted in order to distinguish between reactive, inert and partially reactive biomass fractions. The developed models allow take into account different levels of partial reactivity, values of the temperature for each sub-stage on the grate, and ways to apply entrained streams based on data from the elemental analyses of the fly ashes. To this end, two one-week experimental campaigns were conducted in the plant to carry out the sampling. It has been found that considering chemical fractionation is indispensable to describe the entrainment of solid particles in the gas stream. In addition, the best results are obtained by adopting a small reactivity (2%) of the inert fraction. As for fly ash composition, the concentrations of the major elements showed good agreement with the results from the chemical analyses. In the case of S and Cl, calculations revealed a match with gas cooling effects in the superheaters as well as an entrainment effect. The melting behavior together with the presence of KCl and K2SO4 condensates, point out at possible corrosion phenomena in walls at temperatures of 700–750 °C.Publication Embargo Catalizadores soportados de metales de transición para la valorización de CO2 mediante hidrogenación(2023) González Rangulan, Vigni Virginia; Gandía Pascual, Luis; Bimbela Serrano, Fernando; Ciencias; ZientziakEl objetivo general de esta tesis doctoral es contribuir al desarrollo de catalizadores para llevar a cabo la reacción de metanación de CO2. Para la consecución de este objetivo general se han establecido una serie de objetivos específicos: Estudio preliminar y revisión bibliográfica de los aspectos fundamentales para el desarrollo, formulación, preparación y evaluación de catalizadores de Ni y Co soportados para la reacción de hidrogenación de CO2: naturaleza del soporte, método de preparación, incorporación de la carga de metal, condiciones de Capítulo 1 activación y condiciones de operación durante la reacción, entre otros, a fin de establecer las bases que guíen el diseño de un catalizador activo, selectivo y estable. Desarrollo de catalizadores de Ni y Co en forma de polvo empleando diversos óxidos metálicos como soportes, a fin de poner de manifiesto el efecto de la interacción metal-soporte en la conversión del CO2. Estudio del efecto las variables operacionales más relevantes en la reacción: temperatura de reacción, tiempo de reacción y temperatura de reducción de los catalizadores, prestando especial atención a la conversión del reactante evaluado (CO2) y el rendimiento a CH4 y a CO. Realización de ensayos de actividad catalítica que permitan efectuar la evaluación del comportamiento de los diferentes catalizadores preparados en la reacción de hidrogenación de CO2 mediante la determinación de la actividad específica por centro activo y la energía de activación aparente. Relacionar las propiedades de los catalizadores con su comportamiento durante la reacción de hidrogenación del CO2 para obtener claves que guíen el diseño racional de los mismos a través del análisis conjunto de los resultados de los ensayos catalíticos y de caracterización físico-química. Análisis de los resultados y selección de aquellos catalizadores con resultados más prometedores, a fin de evaluarlos con el sistema de análisis mediante espectroscopía de infrarrojo operando FTIR y obtener información relevante que permita contribuir a elucidar el mecanismo de reacción para la metanación del CO2.Publication Open Access Catalytic hydroprocessing of lignin β-O-4 ether bond model compound phenethyl phenyl ether over ruthenium catalysts(Springer, 2017) Gómez Monedero, B.; Faria, J.; Bimbela Serrano, Fernando; Ruiz, M. P.; Química Aplicada; Kimika AplikatuaThe catalytic hydroprocessing of phenethyl phenyl ether (PPE), a model compound of one of the most significant ether linkages within lignin structure, β-O-4, has been studied. Reactions were carried out using two ruthenium-based catalysts, supported on different materials: 3.8 wt.% Ru/C and 3.9 wt.% Ru/Al2O3. Aiming at studying the reaction mechanism, experiments were carried out at 150 °C and 25 bar in H2 atmosphere, with varying feed to catalyst mass ratios and reaction time. Differences between the relative importance of the steps of the mechanism were observed when using those two catalysts. The most significant finding was the predominance of the cleavage of Cβ-O bonds compared to the cleavage of the Caryl-O when using Ru/Al2O3 as catalyst; whereas with Ru/C, the two routes were nearly equivalent. It has been observed that the kinetic model describes the general tendencies of consumption and formation of the different products, but some over/under estimation of concentrations occurs. Finally, the effect of temperature was also explored by carrying out reactions at 100 and 125 °C, observing that decreasing temperature from 150 to 125 or 100 °C favored the dimer hydrogenation route versus the hydrogenolysis of the ether bonds.Publication Open Access Clean syngas production by gasification of lignocellulosic char: state of the art and future prospects(Elsevier, 2021) Moreira, Rui; Bimbela Serrano, Fernando; Gil-Lalaguna, Noemí; Sánchez, José Luis; Portugal, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2Using lignocellulosic char instead of the original biomass avoids the need for costly cleaning and conditioning stages of the producer gasification gas. However, lignocellulosic char gasification has been less extensively studied than gasification of lignocellulosic biomass, and a review of published works on this topic was missing. In this review the present status of char gasification technologies and their future prospects are critically discussed, including possible research opportunities. To date, most studies on char gasification have been performed in thermogravimetric analyzers (TGA) or TGA-like experimental setups. The major setback of TGA and TGA-like equipment is that they do not mimic the actual reaction conditions occurring in gasification reactors, which impedes a direct extrapolation of the findings during the scale-up of different gasification technologies. For this reason, in this literature review focus was put on studies undertaken in industrially relevant reactors, both in batch and continuous configurations. Overall, char gasification can be deemed a valid alternative for clean syngas production, contributing to an integral valorization of lignocellulosic residues within different biorefinery schemes. Of these, process intensification by microwave heating offers interesting opportunities for research and scaling-up, though efforts must be directed toward developing continuous microwave-assisted gasification processes.Publication Open Access CO2 methanation over nickel catalysts: support effects investigated through specific activity and operando IR spectroscopy measurement(MDPI, 2023) González Rangulan, Vigni Virginia; Reyero Zaragoza, Inés; Bimbela Serrano, Fernando; Romero Sarria, Francisca; Daturi, Marco:; Gandía Pascual, Luis; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaRenewed interest in CO2 methanation is due to its role within the framework of the Power-to-Methane processes. While the use of nickel-based catalysts for CO2 methanation is well stablished, the support is being subjected to thorough research due to its complex effects. The objective of this work was the study of the influence of the support with a series of catalysts supported on alumina, ceria, ceria–zirconia, and titania. Catalysts’ performance has been kinetically and spectroscopically evaluated over a wide range of temperatures (150–500 °C). The main results have shown remarkable differences among the catalysts as concerns Ni dispersion, metallic precursor reducibility, basic properties, and catalytic activity. Operando infrared spectroscopy measurements have evidenced the presence of almost the same type of adsorbed species during the course of the reaction, but with different relative intensities. The results indicate that using as support of Ni a reducible metal oxide that is capable of developing the basicity associated with medium-strength basic sites and a suitable balance between metallic sites and centers linked to the support leads to high CO2 methanation activity. In addition, the results obtained by operando FTIR spectroscopy suggest that CO2 methanation follows the formate pathway over the catalysts under consideration.Publication Open Access Comparative study of supported Ni and Co catalysts prepared using the All-in-One method in the hydrogenation of CO2: effects of using (Poly)Vinyl Alcohol (PVA) as an additive(MDPI, 2024) Navarrete Rodríguez, Luisa Fernanda; Atienza Martínez, María; Reyero Zaragoza, Inés; Urroz Unzueta, José Carlos; Amorrortu, Oihana; Sanz Iturralde, Oihane; Montes, Mario; Garcés, Siby I.; Bimbela Serrano, Fernando; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; IngeniaritzaTwo series of Ni and Co catalysts supported onto La-Al2O3 were prepared and the CO2 hydrogenation reactions investigated. The catalytic performance was evaluated in terms of the evolution with the reaction temperature of the CO2 conversion and product (CH4 and CO) yields, as well as specific activities (TOF) and apparent activation energies. CH4 was the favored product over both metals while the TOF for CH4 formation was about three times higher for Ni than Co at 240–265 °C. Metallic particle size effects were found, with the TOF for CH4 formation decreasing over both Ni and Co as the mean metallic size decreased. In contrast, the TOF for CO formation tended to increase at a decreasing particle size for the catalysts with the smallest Ni particle sizes. The apparent activation energies for Ni and Co were very similar and significantly decreased to values of 73–79 kJ/mol when the metallic dispersion increased. The catalysts were prepared using the all-in-one method, resulting in (poly)vinyl alcohol (PVA) being a key additive that allowed us to enhance the dispersion of Ni and Co to give very effective catalysts. This comparative study joins the few existing ones in the literature in which catalysts based on these metals operated under strictly the same reaction conditions.Publication Open Access Desarrollo de catalizadores basados en rodio y otros metales de transición para la producción de gas de síntesis a partir de biogás(2021) Navarro Puyuelo, Andrea; Gandía Pascual, Luis; Bimbela Serrano, Fernando; Reyero Zaragoza, Inés; Ciencias; ZientziakEl objetivo último de esta tesis doctoral es formular catalizadores de Rh y Co y desarrollar, a partir de las mejores formulaciones, sistemas catalíticos estructurados para la producción de gas de síntesis mediante el reformado de biogás. Se han considerado como rutas de reformado las reacciones de reformado seco y su combinación con la oxidación parcial de metano, a través del reformado combinado de tipo ‘oxy‐CO2’.Publication Open Access Desarrollo de catalizadores de cobalto y rodio para la producción de gas de síntesis por oxidación parcial de metano(2017) Moral Larrasoaña, Ainara; Gandía Pascual, Luis; Bimbela Serrano, Fernando; Química Aplicada; Kimika AplikatuaLos procesos Gas-to-Liquid (GTL), basados en la transformación de gas natural en hidrocarburos sintéticos, son de gran interés para la valorización de los nuevos recursos que emergen actualmente fruto de la aparición de nuevos yacimientos y fuentes de gas natural no convencional (GNNC). La primera etapa del proceso GTL consiste en la conversión del CH4 en gas de síntesis, una mezcla de H2, CO y CO2, aunque también puede contener N2. Entre las distintas alternativas para producir gas de síntesis, la oxidación parcial de metano (OPM) resulta ventajosa, ya que se podrían suavizar considerablemente las condiciones de operación de las tecnologías industriales existentes, con el consiguiente ahorro económico y mejoras en seguridad. Con el fin de obtener altos rendimientos a gas de síntesis se requieren altas temperaturas y/o catalizadores adecuados. Así, el diseño del catalizador es clave para obtener una conversión de metano a gas de síntesis exitosa y eficiente. El objetivo de esta tesis ha sido el de desarrollar catalizadores de Co y Rh para llevar a cabo la reacción de oxidación parcial de metano (OPM) a gas de síntesis; pretendiendo avanzar asimismo en el conocimiento del desarrollo de esta importante reacción por vía catalítica. Para la consecución de este objetivo general, se han abordado diversos objetivos específicos: - conocer en mayor profundidad cómo se desarrolla la reacción sobre este metal desarrollando un estudio paramétrico de la influencia de las principales variables de operación sobre la conversión de metano, rendimiento a H2 y CO y estabilidad, así como un estudio cinético. En este contexto, entre los resultados más destacables de la tesis cabe destacar que el estudio cinético llevado a cabo ha permitido plantear un modelo cinético para la reacción de OPM, el cual permite describir de manera satisfactoria los resultados experimentales obtenidos y poder modelar adecuadamente el complejo esquema de la reacción global de OPM en base a la combinación de cuatro reacciones elementales sencillas, como son: la combustión de metano, el reformado de metano con vapor de agua, la reacción de desplazamiento del gas de agua reversa (RWGS) y la combustión de hidrógeno. - investigar el efecto de las condiciones de activación de catalizadores de Co así como del desarrollo de la propia reacción sobre el comportamiento catalítico con el fin de obtener información sobre el papel de la función metálica en el proceso de oxidación parcial. Para lograr una adecuada evolución de la reacción de OPM hacia la producción estable y prolongada en el tiempo de gas de síntesis resulta esencial mantener el Co en estado metálico durante el transcurso de la reacción y sobre todo en los instantes iniciales, que condicionan notablemente la estabilidad de los catalizadores. Ello delimita la ventana de condiciones de operación para la reacción de OPM catalítica y, concretamente, el intervalo óptimo de temperaturas de reacción, idealmente entre 700 y 800 oC. - Realizar un amplio estudio exploratorio considerando elementos básicos de la formulación del catalizador: naturaleza del soporte, método de preparación, incorporación de promotores del Co y del soporte, carga de metal, etc. con el fin de establecer las bases que guíen el diseño de un catalizador de Co para OPM. Los resultados obtenidos en los ensayos de actividad catalítica efectuados con un catalizador Co/Mg-Al preparado en el laboratorio por coprecipitación y calcinado a 500 oC se encuentran a la vanguardia del estado del arte en el arriba citado campo de investigación. Estos resultados mejoran ampliamente los existentes hasta el momento, permitiendo alcanzar conversiones de metano y selectividades hacia la producción de gas de síntesis muy próximas a las de los valores dictados por el equilibrio termodinámico de la reacción de OPM a 800 oC de manera estable y prolongada durante tiempos de reacción tan largos como 48 h y a GHSV tan elevadas como 1000 L N/(gcat•h). - Finalmente, también se ha planteado como objetivo explorar el papel de la OPM en la valorización del biogás mediante reformado para la obtención de gas de síntesis. Estrategias de reformado combinado de tipo “oxy-CO2” pueden constituir una opción interesante para la valorización de este recurso renovable cada vez producido en mayor volumen. En este sentido, el desarrollo de catalizadores de Rh en combinación con la introducción de pequeñas cantidades de oxígeno en la alimentación supone una estrategia exitosa que puede conducir a la viabilidad del proceso a escalas mayores si se logra desarrollar catalizadores de Rh con menores cargas en el catalizador que las utilizadas en esta tesis, esto es, contenidos de Rh inferiores al 0,5 % en masa del catalizador final.Publication Open Access Effect of oxygen addition, reaction temperature and thermal treatments on syngas production from biogas combined reforming using Rh/alumina catalysts(Elsevier, 2019) Navarro Puyuelo, Andrea; Reyero Zaragoza, Inés; Moral Larrasoaña, Ainara; Bimbela Serrano, Fernando; Bañares, Miguel A.; Gandía Pascual, Luis; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2Dry reforming and partial oxidation of biogas were studied using 0.5 wt.% Rh/Al2O3 catalysts, both inhouse prepared and commercial. The effects of O2 addition on syngas yield and biogas conversion were studied at 700 C using different O2/CH4 ratios in the gas feeding stream: 0 (dry reforming), 0.12, 0.25, 0.45 and 0.50. The highest CH4 conversion, H2 yield and H2/CO molar ratio were obtained with an O2/CH4 ratio of 0.45, even though simultaneous valorization of both CH4 and CO2 could be best attained when the O2/CH4 ratio was 0.12. Increased biogas conversions and syngas yields were obtained by increasing reaction temperatures between 650 and 750 C. A detrimental influence on catalytic activity could be observed when the catalyst was subjected to calcination. Increasing the hold time of the thermal conditioning of the catalyst under inert flow altered Rh dispersion, though had no significant impact on catalyst performance in the dry reforming of methane at 700 C and 150 N L CH4/(gcat h). Characterization of spent samples after reaction by Raman spectroscopy revealed the presence of carbonaceous deposits of different nature, especially on the commercial(named as Rh com) and calcined (Rh calc) catalysts, though oxygen addition in the biogas feed significantly reduced the amount of these deposits. The Rh catalysts that had not been calcined after impregnation (Rh prep) did not present any noticeable characteristic peaks in the G and D bands. In particular, scanning transmission electron microscopy (STEM) images of the spent Rh prep sample revealed the presence of very highly dispersed Rh nanoparticles after reaction, of particle sizes of about 1 nm, and no noticeable C deposits. Combined oxy-CO2 reforming of biogas using highly dispersed and low metal-loading Rh/Al2O3 catalysts with low O2 dosage in the reactor feed can be used to effectively transform biogas into syngas.Publication Open Access Encuesta de satisfacción de un proyecto de mejora de calidad del servicio aragonés de salud(Universidad de Murcia, 2015) Bimbela Serrano, María Teresa; Bimbela Serrano, Fernando; Bernués Vázquez, Luis; Ciencias; ZientziakIntroducción: Según el informe de 2008 del Sistema Nacional de Salud, existe un 4,7% de los usuarios que opina que el sistema sanitario debería rehacerse por completo y casi un 27%, que es necesario introducir cambios importantes para su mejora. Hipótesis: El desarrollo de un programa específico de control de peso para pacientes obesos en Atención Primaria mejora la calidad de la actuación percibida por el paciente de Atención Primaria. Objetivos: Valorar la influencia de un proyecto de mejora de calidad de Atención Primaria en los resultados globales de una encuesta de satisfacción de los usuarios de dicha Zona Básica de Salud. Material y Métodos: Estudio prospectivo de intervención cuasiexperimental centrado en el tratamiento de la obesidad en Atención Primaria realizado desde Enero de 2012 a Diciembre 2013, en cuya evaluación final se realizó una encuesta autoadministrada de Satisfacción de los usuarios y se comparó con los resultados obtenidos con el mismo cuestionario por el Servicio Aragonés de Salud en dicha Zona Básica de Salud. Para el análisis estadístico de estos datos se empleó el programa informático SPSS.15. Resultados principales: Se observa un aumento destacable en los apartados ‘Interés del personal de enfermería’, ‘Satisfacción de los cuidados sanitarios’ (medicina y enfermería) y ‘Solución dada a problemas’. No hubo aspectos negativos y el 100% de los encuestados expresó una satisfacción general y un 88% destacó el aspecto de la paciencia del profesional hacia los pacientes. Conclusión: El proyecto de mejora de calidad realizado con pacientes crónicos de la consulta de enfermería de Atención Primaria, ha sido valorado muy satisfactoriamente, llegando a mejorar la puntuación de los resultados globales del Sistema Aragonés de Salud en esta Zona Básica de Salud.Publication Embargo Estudio de la hidrogenación de CO2 con catalizadores de níquel y cobalto soportados(2024) Navarrete Rodríguez, Luisa Fernanda; Gandía Pascual, Luis; Bimbela Serrano, Fernando; Garcés Polo, Siby Inés; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaEl objetivo general de la presente tesis doctoral es evaluar el desempeño de catalizadores de Ni y de Co soportados en la hidrogenación de CO2 como ruta de valorización de este compuesto hacia la obtención de productos químicos con baja huella de carbono, en particular metano, como tecnología facilitadora de la integración del hidrógeno de origen renovable en la industria química y el mix energético.Publication Embargo Evaluación de catalizadores soportados para la hidrogenación de CO2(2023) Urbiola Los Arcos, Irati; Bimbela Serrano, Fernando; Navarro Puyuelo, Andrea; Escuela Técnica Superior de Ingeniería Agronómica y Biociencias; Nekazaritzako Ingeniaritzako eta Biozientzietako Goi Mailako Eskola TeknikoaRecientemente se ha desarrollado un notable interés en diversas estrategias encaminadas a valorizar CO2 proveniente de diferentes efluentes industriales, como pueda ser el CO2 obtenido en la producción de biometano a partir de biogás. Dicha valorización puede efectuarse a través de su hidrogenación con H2 producido a partir de electricidad renovable, bien para producir CH4, pudiendo ser empleado como gas natural sustituto (SNG), o CO, con el que se puede producir gas de síntesis. En este proceso, las dos principales reacciones son la metanación de óxidos de carbono, altamente exotérmicas, y la reacción inversa de desplazamiento de gas a agua, moderadamente endotérmica. Debido a las limitaciones termodinámicas y a la alta estabilidad de la molécula de CO2, es de suma importancia la selección de las condiciones de operación en las que se lleva a cabo la reacción, así como el empleo de un catalizador adecuado. Por ello, en este Trabajo Fin de Grado se han diversos catalizadores de Co soportados en la reacción de hidrogenación de CO2, con el fin de poder analizar el efecto de distintas variables sobre su comportamiento catalítico: método de síntesis, contenido de metal activo o soporte utilizado, entre otras. Los catalizadores 15 % Co/Al2O3 y 5 % Co/Al2O3 (IHI), preparados mediante el mismo método de impregnación a humedad incipiente, han obtenido resultados prometedores en cuanto a actividad y rendimiento y selectividad a CH4. Por otro lado, los catalizadores que contenían Mg en su soporte han presentado un mayor rendimiento y selectividad a CO, a pesar de obtener menores conversiones de CO2.Publication Open Access Exploring a low-cost valorization route for amazonian cocoa pod husks through thermochemical and catalytic upgrading of pyrolysis vapors(American Chemical Society, 2023) Villasana, Yanet; Armenise, Sabino; Ábrego, Javier; Hablich, Karina; Bimbela Serrano, Fernando; Cornejo Ibergallartu, Alfonso; Gandía Pascual, Luis; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaEcuador as an international leader in the production of cocoa beans produced more than 300 000 tons in 2021; hence, the management and valorization of the 2 MM tons of waste generated annually by this industry have a strategic and socioeconomic value. Consequently, appropriate technologies to avoid environmental problems and promote sustainable development and the bioeconomy, especially considering that this is a megadiverse country, are of the utmost relevance. For this reason, we explored a low-cost pyrolysis route for valorizing cocoa pod husks from Ecuador’s Amazonian region, aiming at producing pyrolysis liquids (bio-oil), biochar, and gas as an alternative chemical source from cocoa residues in the absence of hydrogen. Downstream catalytic processing of hot pyrolysis vapors using Mo- and/or Ni-based catalysts and standalone γ-Al2O3 was applied for obtaining upgraded bio-oils in a laboratory-scale fixed bed reactor, at 500 °C in a N2 atmosphere. As a result, bimetallic catalysts increased the bio-oil aqueous phase yield by 6.6%, at the expense of the organic phase due to cracking reactions according to nuclear magnetic resonance (NMR) and gas chromatography–mass spectrometry (GC–MS) results. Overall product yield remained constant, in comparison to pyrolysis without any downstream catalytic treatment (bio-oil ∼39.0–40.0 wt % and permanent gases 24.6–26.6 wt %). Ex situ reduced and passivated MoNi/γ-Al2O3 led to the lowest organic phase and highest aqueous phase yields. The product distribution between the two liquid phases was also modified by the catalytic upgrading experiments carried out, according to heteronuclear single-quantum correlation (HSQC), total correlation spectroscopy (TOCSY), and NMR analyses. The detailed composition distribution reported here shows the chemical production potential of this residue and serves as a starting point for subsequent valorizing technologies and/or processes in the food and nonfood industry beneficiating society, environment, economy, and research.Publication Open Access Extraction of phenolic compounds from populus salicaceae bark(MDPI, 2022) Autor, Elsa; Cornejo Ibergallartu, Alfonso; Bimbela Serrano, Fernando; Maisterra Udi, Maitane; Gandía Pascual, Luis; Martínez Merino, Víctor; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako UnibertsitateLignocellulosic residues have the potential for obtaining high value-added products that could be better valorized if biorefinery strategies are adopted. The debarking of short-rotation crops yields important amounts of residues that are currently underexploited as low-grade fuel and could be a renewable source of phenolic compounds and other important phytochemicals. The isolation of these compounds can be carried out by different methods, but for attaining an integral valorization of barks, a preliminary extraction step for phytochemicals should be included. Using optimized extraction methods based on Soxhlet extraction can be effective for the isolation of phenolic compounds with antioxidant properties. In this study, poplar bark (Populus Salicaceae) was used to obtain a series of extracts using five different solvents in a sequential extraction of 24 h each in a Soxhlet extractor. Selected solvents were put in contact with the bark sample raffinate following an increasing order of polarity: n-hexane, dichloromethane, ethyl acetate, methanol, and water. The oily residues of the extracts obtained after each extraction were further subjected to flash chromatography, and the fractions obtained were characterized by gas chromatography coupled with mass spectrometry (GC–MS). The total phenolic content (TPC) was determined using the Folin–Ciocalteu method, and the antioxidant activity (AOA) of the samples was evaluated in their reaction with the free radical 2,2-Diphenyl-picrylhydrazyl (DPPH method). Polar solvents allowed for higher individual extraction yields, with overall extraction yields at around 23% (dry, ash-free basis). Different compounds were identified, including hydrolyzable tannins, phenolic monomers such as catechol and vanillin, pentoses and hexoses, and other organic compounds such as long-chain alkanes, alcohols, and carboxylic acids, among others. An excellent correlation was found between TPC and antioxidant activity for the samples analyzed. The fractions obtained using methanol showed the highest phenolic content (608 g of gallic acid equivalent (GAE)/mg) and the greatest antioxidant activity.Publication Open Access Highly selective CO formation via CO2 hydrogenation over novel ceria-based high-entropy oxides (HEOs)(Elsevier, 2025-03-01) Cortázar, María; Lafuente Adiego, Marta; Navarro Puyuelo, Andrea; García, Xènia; Llorca Piqué, Jordi; Reyero Zaragoza, Inés; Bimbela Serrano, Fernando; Gandía Pascual, Luis; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaIn the present study, new ceria-based high-entropy oxides (HEOs) were investigated as CO2 hydrogenation catalysts. The nominal composition was (Ce0.5Ni0.1Co0.1Cu0.1Zn0.1Mg0.1)Ox and the synthesis was accomplished through the citrate complexing sol-gel method. Characterization techniques utilized including ICP-AES, in situ XRD and in situ XPS, SEM-EDS, HR-TEM and HAADF-STEM, Raman spectroscopy, H2-TPR, CO2-TPD and N2 physical adsorption. The physicochemical characterization and the catalytic results revealed that the conditions of the thermal treatments at which the oxides were subjected critically determined the catalytic performance, especially the CO2 hydrogenation products selectivities. Calcination in air and/or reduction in hydrogen conducted at temperatures below 500 °C led to active but poorly selective catalysts that produced both methane and CO with significant yields. This was mainly attributed to the presence of metallic Cu, Ni and Co on the catalysts that appeared to be supported on ceria doped with the rest of the formulation elements. In contrast, thermal treatments at 750 °C favored the formation of a rocksalt entropy-stabilized (NiCoCuZnMg)Ox HEO supported on ceria that has stood out for showing an excellent selectivity towards the reverse water¿gas shift (RWGS) reaction. This catalyst led to CO selectivities of almost 100 % over a very wide range of reaction temperatures (300-700 °C). Long-term stability tests (100 h) showed only a slight decrease in CO2 conversion, while CO selectivity remained stable at nearly 100 % at 400 °C. XRD characterization of the used catalysts evidenced that, whereas the basic catalyst structure remained, some metallic copper exsolved during reduction and reaction period. These results are relevant and very promising, opening a door to the development of new catalysts for the valorization of CO2 through the RWGS reaction, thus expanding the low-temperature limit at which this process can be carried out selectively.Publication Embargo How bimetallic CoMo carbides and nitrides improve CO oxidation(Elsevier, 2023) Villasana, Yanet; García Macedo, Jorge A.; Navarro Puyuelo, Andrea; Reyero Zaragoza, Inés; Lara, Hugo; Bimbela Serrano, Fernando; Gandía Pascual, Luis; Brito, Joaquin L.; Méndez, Franklin J.; Institute for Advanced Materials and Mathematics - INAMAT2CO elimination is an important step for the proper management of gaseous effluents from various processes, thus avoiding adverse impacts on the environment and human health. In this study, different bimetallic Al2O3-supported CoMo catalysts have been developed, characterized, and tested in the CO oxidation reaction, based on their respective oxides, carbides, and nitrides phases. The parent CoMo-oxide catalyst (CoMo) was prepared by impregnation and then transformed to its carburized (CoMoC) and nitrided (CoMoN) forms using temperatureprogrammed reaction methods under controlled atmospheres of CH4/H2 and NH3, respectively. The catalytic results demonstrate that the CoMoC catalyst exhibits higher activity compared to its CoMoN counterpart, and both are more active than the parent CoMo catalyst. Furthermore, the reduction temperature and space velocity were key process factors, which notably influenced activity and kinetic parameters, while the increase of reduction time does not seem to improve catalytic behavior. These results were associated with a better metal dispersion, and relatively higher reduction grade and metallic surface area on the carbides and nitrides, opening the possibility that new adsorption sites may be created. The catalytic results compare favorably with other nonnoble metal catalysts, such as Cr-, Cu-, Fe-, and Ni-based samples, and highlight the potential of using carbides and nitrides as alternative formulations to enhance the performance of CO oxidation.Publication Open Access Innovative flow-through reaction system for the sustainable production of phenolic monomers from lignocellulose catalyzed by supported Mo2C(Wiley, 2024) Maisterra Udi, Maitane; Atienza Martínez, María; Hablich Alvarracin, Karina Lissett; Moreira, Rui; Martínez Merino, Víctor; Gandía Pascual, Luis; Cornejo Ibergallartu, Alfonso; Bimbela Serrano, Fernando; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra - Nafarroako Unibertsitate PublikoaMolybdenum carbide supported on activated carbon (β-Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow-Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT-RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT-RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13-15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT-RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two-step non-equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs.Publication Open Access Modelizado y estudio experimental del comportamiento de las cenizas en instalaciones industriales de combustión de biomasa con tecnología de parrilla(2021) Funcia, Ibai; Bimbela Serrano, Fernando; Ciencias; ZientziakEl presente trabajo tiene por objetivo general el desarrollo de una metodología para el análisis y predicción del comportamiento de cenizas y compuestos inorgánicos generados en la combustión de biomasa a alta temperatura (450-1300 ºC) a partir de la composición de la materia prima. Más concretamente, en esta tesis doctoral se estudia el empleo de paja de cereal como materia prima en una instalación industrial con tecnología de parrilla móvil. La metodología desarrollada se validará frente a pruebas reales realizadas en una planta de escala comercial (15-25 MWe).Publication Open Access Oxidative steam reforming of glycerol. A review(Elsevier, 2021) Moreira, Rui; Bimbela Serrano, Fernando; Gandía Pascual, Luis; Ferreira, Abel; Sánchez, José Luis; Portugal, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThis review article presents the state-of-the-art on the catalytic oxidative steam reforming (OSR) of glycerol to produce syngas. Concerning the different technologies proposed for the catalytic OSR of glycerol, the following key points can be highlighted: (1) the robustness is much higher than other reforming technologies, (2) several catalysts can work with low deactivation, some of which can recover almost full activity by suitable regeneration, (3) syngas production by catalytic OSR of glycerin is higher than with concurrent technologies, (4) their scaling-up remains an unrealized task, (5) the thermodynamics of the process has been sufficiently covered in the literature, (6) there is a significant lack of kinetic and mechanistic studies that could help gaining deeper insight on the process, (7) novel concepts and reactor designs must be proposed for their development at larger scales, (8) new catalyst formulations must be developed for attaining higher resistance against oxidation and (9) process intensification could help developing them at larger scales.