Cette étude présente la préparation et l’évaluation de l’activité d’un nouveau catalyseur monolithique en microréacteur. La réaction d’hydrogénation du p-nitrophénol par transfert d’hydrogène avec l’acide formique a été choisie comme réaction modèle pour comparer les performances du monolithe à celles d’un catalyseur commercial en lit fixe.Cette thèse comporte une partie expérimentale importante. D’un côté, un montage expérimental et des protocoles d’analyse en ligne ont été mis au point pour faire une étude quantitative précise de la réaction modèle. De l’autre côté, les conditions de préparation d’un monolithe de silice fonctionnalisée dans le tube-réacteur en acier chemisé de verre ont été optimisées. Il a été chargé en nanoparticules de Pd par une méthode en écoulement. Le monolithe comporte un réseau de macropores pour l’écoulement et une organisation hexagonale typique de mésopores et micropores, et cela presque sans retrait au séchage. L’activité des 2 types de catalyseurs dans la réaction modèle a été comparée par leur cinétique de réaction et leur comportement dynamique dans la phase de mise en régime du microréacteur. Une partie théorique présente la modélisation du microréacteur en régime stationnaire pour l’établissement des cinétiques et en régime transitoire pour rationaliser les observations expérimentales. Le monolithe Pd@silice et le catalyseur commercial Pd@alumine ont des comportements différents et obéissent à des lois cinétiques différentes. Un modèle réactionnel impliquant un changement de propriétés de la surface catalytique pourrait expliquer le profil de concentration inhabituel observé avec le catalyseur commercial. La comparaison démontre la supériorité du nouveau catalyseur monolithe, et lui ouvre de bonnes perspectives industrielles. / This study presents the preparation and the evaluation of performance of a new monolithic catalyst in microreactor. The transfer hydrogenation of p-nitrophenol by formic acid is chosen as the model reaction for the comparison of the monolith with a traditional packed-bed microreactor containing commercial catalyst.This thesis includes an important experimental part. On the one hand, experimental set-up and protocols involving on-line analysis have been developed in order to study quantitatively the model reaction; On the other hand, the conditions of preparation of functionalized silica monolith in a stainless steel tube with the inner wall pre-coated by glass were optimized, and the palladium nanoparticles were immobilized by a continuous flow method. The monolith possesses the flow-through macropores, typical hexagonal organization of mesopores and micropores, and scarcely any shrinkage. The comparison of the two types of catalysts mainly focuses on the activity of catalysts in the model reaction, their kinetic model and their dynamic behavior in the start-up phase of the flow microreactor. In the theoretical part, the modelisation of reactor has been investigated both under stationary conditions for kinetics determination and under transient conditions for the rationalization of experimental observations. Pd@silica monolith and commercial Pd@alumina powder have different behavior and gives different kinetic laws. A reaction model with change in the catalytic surface properties could explain the unusual profile of concentrations observed with commercial catalyst. The superior performance of monolithic catalyst is demonstrated, which also exhibits particular industrial interests.

De nombreuses mesures pour réduire les émissions anthropiques de gaz à effet de serre et plus particulièrement de CO2, existent déjà, elles restent cependant insuffisantes. C’est dans ce cadre qu’a vu le jour le projet ANR VItESSE2 visant à développer un procédé de conversion de CO2,issu de certaines industries, en méthanol par réduction à l’hydrogène produit par électrolyse de l’eau à partir d’électricité fournie par des énergies faiblement émettrices de CO2 (énergie nucléaire et les énergies renouvelables). Ce procédé permet aussi d’assurer, une fonction de gestion du système électrique en reliant la production d’hydrogène aux quantités d’électricités disponibles sur le réseau. Les principaux objectifs de la thèse sont la synthèse et la caractérisation de catalyseurs performants ainsi que la mise au point des conditions réactionnelles conduisant à la meilleure productivité en méthanol. L’optimisation des systèmes catalytiques a permis de développer un catalyseur de type CuO-ZnO-ZrO2 compétitif par rapport aux catalyseurs commerciaux actuellement sur le marché. / Numerous measures to reduce anthropogenic emissions of greenhouse gases, especially CO2, already exist; however they are still insufficient. It is in this context that the ANR project VItESSE2 emerged to develop a method for converting CO2 produced by industries. The aim of this project is to transform CO2 into methanol, by reduction with hydrogen produced by water electrolysis using electricity provided by decarbonised energies (nuclear and renewable energies). This process also allows to secure a management function of the electrical grid by connecting the production of hydrogen to the available quantity of electricity in the network. The main objectives of this thesis are the synthesis and the characterization of efficient catalysts for CO2 hydrogenation into methanol and the development of reaction conditions leading to improved methanol productivity. The optimization of catalyst systems allowed to develop a CuO-ZnO-ZrO2 catalyst competitive in relation to commercial catalysts currently on the market.

Commercially important hydrogenation reactions make use of precious noble metal catalysts which are becoming increasingly scarce, and the search for capable alternative catalysts prevails. Transition metal carbides of group IV-VI metals show similar catalytic behavior to platinum and are $103/kg lower in price than the precious metal catalysts. Tungsten carbide, studied in this work, can form in different stoichiometries and phase compositions depending upon synthesis methods. Synthesis of high surface area tungsten carbide with control over its phase composition remains a challenge currently. In this work, the novel isothermal synthesis method of tungsten carbide (WC, W2C) in a CH4/H2 carburization atmosphere with synthesis temperature and presence or absence of a silica support in the catalyst precursor (WO3) as process variables was investigated. The amounts of CO and H2O formed during synthesis corresponded to the amount of oxygen in the WO3 precursor. The catalysts were further characterized by X-ray diffraction to determine phase composition and crystallite size, by scanning electron microscopy to determine morphology, and by CO chemisorption to determine metallic surface area. X-ray diffraction analysis indicated the carbide catalysts to contain W2C, WC, and metallic W phases. The use of a silica-supported precursor favored the formation of a nearly phase pure, high surface area W2C rich catalyst whereas high synthesis temperature and absence of silica precursor favored formation of a low surface area WC rich catalyst. Further, the catalysts were tested for steady state activity at a W/F (weight catalyst/toluene feed rate) of 0.20-0.30 h-1, addition of H2 to a total pressure of 21 bar absolute and 250 °C, and the effect of phase composition and surface area on the activity was studied. This work resulted in the successful synthesis of 4 tungsten carbide catalysts with varying phase compositions and surface areas and correlation of their compositions and surface areas with their corresponding toluene hydrogenation activities.

In this project, the TMP method was employed to produce “active sites.” These active sites are for influencing and controlling the Co₃O₄ growth. One of the aims was to investigate what effect the grafting of the molecular precursor has on the nature and distribution of active sites on the various support materials. The second aim was to investigate the effect an increase in molecular precursor loading, in various impregnation steps, has on the nature and distribution of the active sites. The third aim was to investigate the effect of the steric constraints of ligand groups, by changing the molecular precursor, on the nature and distribution of active sites. The fourth aim was to use the different aspects discussed above and apply them to investigate what effect the above-mentioned modifications have on Co₃O₄ morphology. While another aim was to investigated what effect varying the quantity of Co(NO₃)₂•6H₂O has on Co₃O₄ morphology. Lastly, we investigated what effect varying the impregnation procedure and calcination temperature have on the Co₃O₄ morphology. The effect the support has on the phase of titanium molecular precursor was investigated using molecular precursor, ⁱPrOTi[OSi(O[superscript(t)]Bu₃)]₃. The supports used were Silica 922, NanoDur, Aerosil 200, Stöber spherical silica, SBA-15, mod MCM-41 and sMCM-41. The molecular precursor ⁱPrOTi[OSi(O[superscript(t)]Bu₃)]₃ was revealed to be in the orthorhombic TiO₂ with space group P(cab), normal brookite lattice, on Silica 922 after calcination but only an isolated area displaying this morphology. Generally we do not observe any TiO₂ on the support, which indicates that we have produce site-isolated sites, suggesting the TMP method has been successful on all of the various supports. The emphasis is placed on the effect of this molecular precursor and the respective support has on the Co₃O₄ morphology in Chapter 3. In this Chapter, a unique morphology was observed on Silica 922 which showed Co₃O₄ nanorods of cubic Co₃O₄ in the space group Fd-3m. Silica 922 was used for the remainder of the thesis to investigate the effect the quantity of molecular precursor has on the nature of active sites and Co₃O₄ morphology in Chapter 4. This support was also used to investigate the effect the amount of Co(NO₃)₂•6H₂O has on Co₃O₄ morphology in Chapter 5. This support was lastly used to investigate the steric constraints of the ligand groups, Ti[OSi(O[superscript(t)]Bu)₃]₄ (TiSi4), ⁱPrOTi[OSi(O[superscript(t)]Bu)₃]₃ (TiSi3), (OtBu)₃TiOSi(O[superscript(t)]Bu)₃ (TiSi) and the least sterically constrained Ti(OⁱPr)₄ has on the loading of precursor and Co₃O₄ morphology in Chapter 6.

>Magister Scientiae - MSc / This study explores the use of UV-assisted reduction method to synthesise the catalysts, aiming at reducing synthesis time. The Pd and Au catalyst loading is kept at 5 wt% in order to reduce the cost associated with high loading (20 wt%) of platinum group metals. The synthesised catalysts have SnO2 incorporated in them for two purposes, one being to activate the chemical reaction by absorbing UV-light and the second one is to serve as a promoter for binary and ternary catalysts. All the synthesised electrocatalysts in this study were denoted as Au/10wt%SnO2-C, Au/15wt%SnO2-C, Au/20wt%SnO2-C, Au/40wt%SnO2-C, Au/60wt%SnO2-C, Pd/10wt%SnO2-C, Pd/15wt%SnO2-C, Pd/20wt%SnO2-C, Pd/40wt%SnO2-C, Pd/60wt%SnO2-C and PdAu/10wt%SnO2-C respectively. The UV-assisted reduction method was proved to be effective with the obtained results from TEM, SEM, XRD and electrochemical studies. TEM micrographs revealed nanoparticles of Pd, Au and SnO2 which were proved by the measured d-spacing values corresponding to the element’s structures. The measured average particle size ranged from 3.05 to 14.97 nm for the electrocatalysts. The XRD profiles confirmed the face centred cubic of Pd, Au and tetragonal structures of SnO2. These electrocatalysts showed varied activity towards the oxidation of alcohols namely, methanol, ethanol, ethylene glycol and glycerol in alkaline electrolyte The cyclic voltammetry results showed improved performance towards the oxidation of glycerol on Au-based electrocatalysts, highest current density of 22.08 mA cm-2 than on Pd-based electrocatalysts. Pd-based electrocatalysts were more active towards the oxidation of ethanol than Au-based electrocatalysts with the highest current density of 19.96 mA cm-2. The co-reduced PdAu on 10wt%SnO2-C electrocatalysts showed the lowest current density of 6.88 mA cm-2 for ethanol oxidation when compared to Pd/10wt%SnO2-C and Au/10wt%SnO2-C. Linear sweep voltammograms showed more negative onset potentials on Pd-based electrocatalysts than Au-based electrocatalysts. The more negative onset potential obtained on Pd-based electrocatalysts was observed for ethanol oxidation. These results correspond to the trend observed in literature for ethanol oxidation being more favoured on Pd-based electrocatalysts whereas the polyalcohol oxidation is more favoured on Au-based electrocatalysts. The best performing and most stable electrocatalyst among the Au-based electrocatalysts is Au/10wt%SnO2-C and Pd/10wt%SnO2-C for the Pd-based electrocatalysts.

A bench-scale tubular reactor with recirculation was built in order to study the efficiency of the photocatalytic oxidation of phenol on fluidized titanium oxide-coated silica gel beads. A UV-C lamp placed along the central vertical axes of the reactor was used as source of photons. A bed of silica gel beads was fluidized by means of fluid recirculation and forced to follow upward helical flow around the lamp. Anatase was successfully synthetized on silica gel particles of average diameters 224, 357 and 461 µm, as confirmed by scanning electron micrographs, through a sol-gel technique using a titanium (iv)isopropoxide / hydrochloric acid / ethanol precursor. Data was obtained from multiple 8-hours photocatalytic experiments using a determined mass of beads fluidized in an aqueous solution of known initial phenol concentration. Contaminant degradation with irradiation time was measured as COD. Beads that had been subjected to three consecutive coating procedures produced an 8-h removal efficiency 10% higher than beads with a single coat. 20 g L-1 of silica beads was found to be the optimum load for the experimental reactor configuration regardless of beads size, although efficiency increased with decreasing size of the latter. Experimental results confirmed that the efficiency of phenol photocatalytic degradation decreases with increasing pollutant concentration. Also, the highest removal was achieved with initial pH 3, and it decreased with increasing pH. When NaCl was added to the solution, COD removal increased with increasing salinity. Additionally, it was found that dissolved oxygen is indispensable for photocatalysis to proceed, and that saturation of the treated mixture with oxygen was effectively achieved by keeping the liquid surface in contact with pure oxygen at 1 atm. Finally, statistical analysis of the data showed that photocatalytic mineralization of phenol-derived COD under the experimental conditions follows exponential decay. Based on this finding, a correlation model was proposed for the accurate prediction (minimum R2 = 0.9840) of the COD removal efficiency of the reactor for any given initial COD.

Tesis por compendio / [ES] El Proyecto de investigación aquí descrito se estructura en dos partes. La primera parte se centra en la investigación fundamental con el objetivo de crear un protocolo para la síntesis de zeolitas. La segunda parte se refiere al diseño, síntesis y caracterización de nuevas zeolitas, particularmente utiles para aplicaciones DeNOx,, pero también podría ser útil para aplicaciones MTO. La investigación fundamental sugiere un Nuevo modelo de preparación de zeolitas utilizando otras zeolitas como simiente. Este proceso se llama transformación zeolita-zeolita o también conversión interzeolita. El alto rendimiento obtenido, la rápida cristalización y la mejor utilización y rendimiento de los materiales de partida se han tenido en cuenta para mejorar el proceso en base a un proyecto de doctorado financiado por una empresa. Este método se ha ilustrado utilizando varias zeolitas como semilla, entre otras FAU y CHA, para la preparación de las dos zeolitas objetivo: AEI y AFX. En la segunda parte, la investigación se centra en el diseño de nuevas zeolitas de poro medio. Se han seleccionado tres zeolitas hipotéticas de una base de datos de 933611 estructuras. Esta selección se ha realizado utilizando descriptores específicamente diseñados en base a la aplicabilidad de estas zeolitas en procesos DeNOx zeolitas. A continuación se han buscado los agentes directores de estructura (ADE) más apropiados, con la ayuda de métodos computacionales, algunos de los cuales se han sintetizado posteriormente. El uso de dichos ADE en el gel de síntesis ha permitido la obtención de una zeolita cuya topología (ERI) ha sido identificada mediante análisis por PXRD, y cuya morfología y tamaño de cristal (particularmente pequeño) la hacen muy adecuada para su uso como catalizador en algunos procesos. El trabajo de síntesis también reveló la aparición de una nueva zeolita de alta densidad, llamada 'paracelsio-K'. Este nuevo material se ha obtenido al explorar el espacio de fases que cristalizan al utilizar 1-methyl-DABCO como ADE. La síntesis de esta zeolita tiene un especial interés porque el ADE no se incorpora en los canales de la zeolita, pero más bien influyendo en la nucleación y cristalización. La caracterización reveló que la composición del material es próxima al mineral microcline, estructuralmente cercano al paracelsio, ambos feldespatos. A diferencia de los feldespatos el paracelsio-K contiene moléculas de agua en su interior (1 molécula por cavidad) y puede describirse como el material más simple de la familia de las zeolitas que contiene cadenas del tipo 'doble-cigüeñal'. Utilizando los elementos topológicos correspondientes a esta estructura es posible generar estructuras zeolíticas ya conocidas, como GIS, APC, MER, PHI, SIV y algunas otras zeolitas hipotéticas. / [CA] El Projecte d'investigació aquí descrit s'estructura en dos parts. La primera part se centra en la investigació fonamental amb l'objectiu de crear un protocol per a la síntesis de zeolites. La segona part es refereix al disseny, síntesis i caracterització de noves zeolites, particularment útils per a aplicacions DeNOx , però també podria ser útil per a aplicacions MTO. La investigació fonamental suggereix un nou model de preparació de zeolites utilitzant altres zeolites com a llavor. Aquest procés s'anomena transformació zeolita-zeolita o també conversió interzeolita. L'alt rendiment obtingut, la ràpida cristal·lització i la millor utilització i rendiment dels materials de partida s'han tingut en compte per millorar el procés en base a un projecte de doctorat finançat per una empresa. Aquest mètode s'ha il·lustrat utilitzant diverses zeolites com a llavor, entre altres FAU i CHA, per a la preparació de les dues zeolites objectiu: AEI i AFX. A la segona part, la investigació se centra en el disseny de noves zeolites de porus mitjà. S'han seleccionat tres zeolites hipotètiques d'una base de dades de 933.611 estructures. Aquesta selecció s'ha realitzat utilitzant descriptors específicament dissenyats sobre la base de l'aplicabilitat d'aquestes zeolites en processos DeNOx zeolites. A continuació s'han buscat els agents directors d'estructura (ADE) més apropiats, amb l'ajuda de mètodes computacionals, alguns dels quals s'han sintetitzat posteriorment. L'ús d'aquests ADE al gel de síntesi ha permès l'obtenció d'una zeolita la topologia (ERI) ha estat identificada mitjançant anàlisi per PXRD, i la morfologia i mida de vidre (particularment petit) la fan molt adequada per al seu ús com a catalitzador en alguns processos. El treball de síntesi també va revelar l'aparició d'una nova zeolita d'alta densitat, anomenada 'paracelsio-K'. Aquest nou material s'ha obtingut a explorar l'espai de fases que cristal·litzen en utilitzar 1-methyl-DABCO com ADE. La síntesi d'aquesta zeolita té un especial interès perquè el ADE no s'incorpora en els canals de la zeolita, però més aviat influint en la nucleació i cristal·lització. La caracterització va revelar que la composició del material és propera al mineral microcline, estructuralment proper al paracelsio, tots dos feldspats. A diferència dels feldspats el paracelsio-K conté molècules d'aigua al seu interior (1 molècula per cavitat) i pot descriure com el material més simple de la família de les zeolites que conté cadenes del tipus 'doble-cigonyal'. Utilitzant els elements topològics corresponents a aquesta estructura és possible generar estructures zeolítiques ja conegudes, com GIS, APC, MER, PHI, SIV i algunes altres zeolites hipotètiques. / [EN] The research project described herein is structured in two parts. The first part is focused on the fundamental research with the aim of creating a toolbox for zeolite preparation. The second part deal with the design, synthesis and characterization of novel zeolites particular useful for DeNOx applications, but could be also useful for MTO applications. The fundamental research is addressing a novel approach of preparing zeolites by using other zeolites as raw materials. This process is known as zeolite-to-zeolite transformation or interzeolite conversion. The high yield obtained, fast crystallization time and the better utilization of the raw materials (e.g. parent zeolite, organic structure directing agent (OSDA)), are important benefits of interzeolite conversion technic, which answer the objectives formulated for an industrial PhD project. The method has been exemplified by using various raw materials as parent zeolites, such as FAU and CHA for the preparation of two target small pore zeolites AEI and AFX. In the second part the focus has been on the design of novel small pore zeolites. Three hypothetical frameworks have been selected by narrowing down a database containing 933611 structures. The selection has been performed by using the general descriptors for the state-of-the-art DeNOx zeolites (e.g. CHA). This was followed by finding suitable OSDAs for the selected frameworks, by using computational methods. The usage of the theoretically predicted OSDAs in synthesis gels made possible the synthesis of a novel high-silica zeolite. PXRD analysis, revealed that the zeolite has the ERI framework topology. The obtained material has a distinct particle morphology and smaller crystallites, which are key parameters for various catalytic processes. The synthesis work revealed also a novel dense zeolite, named K-paracelsian. The new material has been obtained while exploring the phase space using 1-methyl-DABCO as OSDA. The synthesis of this zeolite is especially interesting in the sense that the OSDA is not being incorporated into the zeolite channels, but rather influencing the nucleation and crystallization. Further characterization revealed a material compositionally closely related to the mineral microcline and structurally closely related to the mineral paracelsian, both of which are feldspars. In contrast to the feldspars, K-paracelsian contains intrazeolitic water corresponding to one molecule per cage and can be described as the simplest endmember of a family of dense double-crankshaft zeolite topologies. By applying the identified building principle, a number of known zeolite frameworks (e.g. GIS, APC, MER, PHI, SIV) and hypothetical zeolite topologies can be constructed. / The authors thank Haldor Topsoe A/S and Innovation Fund Denmark for financial support under the Industrial PhD programme (Case no. 1355-0174B). We thank MINECO of Spain for funding (SEV-2016- 0683 and RTI2018-101033-B-100) and ASIC-UPV for the use of computational facilities. We also thank Prof. M. M. J. Treacy for assistance with the Database of Prospective Zeolite Structures. / Boruntea, C. (2020). Design, synthesis and characterization of small-pore zeolites for industrial environmental applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/141094 / TESIS / Compendio