Research on the co-feeding of ammonia into the Fischer-Tropsch (FTS) process over ironbased catalysts revealed that the presence of ammonia during the FTS leads to the formation of nitrogen-containing compounds (NCCs). Recent studies on the addition of ammonia to the FTS process, now known as the Nitrogen Fischer-Tropsch (NFTS) process, reported that the production of NCCs during the NFTS process is enhanced by the presence of oxygenates. The studies, therefore, suggested that oxygenates are the primary precursors of NCCs. However, due to the gap in knowledge related to the NFTS reactions mechanisms, the validity of this assumption is still unknown. In this thesis, the aim was to investigate the correlation between the presence of oxygenates under the FTS conditions and the formation of NCCs under the NFTS conditions and check the suitability of various iron-based catalysts for the NFTS process. From literature, four ironbased catalysts, known for yielding a high percentage of oxygenates, were identified, synthesised, characterised and then tested under FTS conditions to determine the optimum reaction conditions for oxygenates formation. It was found that high oxygenates selectivity can be achieved at low temperature and high space velocity as at these operating conditions the occurrence of secondary reactions involving oxygenates are limited. Furthermore, the catalysts were tested under NFTS conditions to determine their catalytic performance and their selectivity towards NCCs. During the NFTS process, in addition to the decrease in the CO conversion, a significant drop in the oxygenates and CO2 selectivity followed by the formation of NCCs were observed. These results confirmed a sight activity inhibiting effect of ammonia and pointed out the correlation between the presence of oxygenates and the formation of NCCs under FTS and NFTS processes respectively. At the conditions applied, selectivities of up to 17.9 C% of NCCs (predominantly nitriles) could be obtained. This modified process may therefore be considered as an important variation of the FTS process with greatly enhanced chemicals production potential.

This research studies the use of class=SpellE>titania (titanium dioxide, TiO2) as a catalyst for deoxygenation of class=SpellE>syngas derived oxygenates. These oxygenates are formed as byproducts when biomass derived syngas (CO & H2) is converted to ethanol on Rhodium or Molybdenum based catalysts. Conversion of these oxygenates to hydrocarbon would enhance the viability of class=SpellE>syngas to gasoline technology. This study revealed that class=SpellE>titania can indeed be used to convert syngas derived oxygenates to hydrocarbon at high temperature and pressure. Acetone condensation to mesitylene was studied very closely. The study revealed that the acid-base dual nature of class=SpellE>titania is key for the success of this reaction. When titaniawas combined with the zeolite H+/ZSM-5, a broad range of gasoline type hydrocarbon could be produced. Ethanol conversion to higher alcohols was studied as part of a partial deoxygenation of ethanol research. While this conversion was possible on class=GramE>titania, zirconia proved to be a better catalyst. Ethanol could be converted to 1-butanol and other higher alcohols at high temperature and pressure. The mechanism by which this occurs was studied as well.

No description available.

[ES] El actual enfoque hacia la desfosilización de la industria química acentúa la necesidad de desarrollar procesos químicos medioambientalmente más sostenibles. El diseño de sistemas catalíticos en tándem para llevar a cabo reacciones mecanísticamente desacopladas en un solo reactor, representa una estrategia prometedora para potencialmente reducir el tamaño de las instalaciones y alcanzar mayores eficiencias energéticas y económicas. El gas de síntesis y sus derivados directos C1 (metanol, DME) representan una atractiva fuente de carbono no derivada del petróleo para la producción de productos químicos. La propagación selectiva de cadena desde compuestos C1 hasta específicamente productos sigue siendo un desafío importante en el campo de la catálisis heterogénea. En esta tesis, se presenta cómo el diseño racional de un sistema catalítico en tándem, multifuncional y heterogéneo, proporciona una ruta novedosa y alternativa para la síntesis directa de productos C3 de interés a partir de compuestos C1. En este trabajo, se ha estudiado la integración en tándem de la reacción de carbonilación de compuestos metoxi (DME) con CO, con la posterior cetonización de los productos carboxílicos C2 intermedios correspondientes en un sistema catalítico multifuncional. La integración de los catalizadores Ag/MOR y Pd/ZrCeOx respectivamente, permite la síntesis directa de acetona a partir de mezclas de DME/gas de síntesis a 548 K y 20 bares. La incorporación de H-FER nanocristalina en un catalizador multifuncional metal/óxido/zeolita Pd/ZrCeOx:FER, como funcionalidad específica de hidrólisis del acetato de metilo, ha permitido la obtención de rendimientos a acetona hasta tres veces mayores en comparación con los obtenidos utilizando solamente el catalizador metal/óxido. La funcionalidad específica de hidrólisis se ha incorporado en base a los resultados de estudios cinéticos realizados para las etapas de reacción por separado, que revelan una limitación general de la velocidad de cetonización a partir del paso de hidrólisis ácida del intermedio acetato de metilo. A una distancia intercatalítica en el rango de micrómetros, se ha mantenido una conversión de DME estable (superior al 94%), junto con una selectividad de acetona del 65-70% (entre los productos orgánicos) durante al menos 10 días de operación continua. Además, la atmósfera de gas de síntesis a alta presión permite la integración de la hidrogenación de grupos carbonilo, abriendo la puerta para la producción de 2-propanol en un solo reactor. En particular, la incorporación del catalizador de hidrogenación Ag-Pt/¿-Al2O3 ha permitido alcanzar una selectividad de 2-propanol del 51% dentro de la fracción de productos C3. Finalmente, el concepto de conversión en tándem mencionado anteriormente se ha extendido a la conversión directa de mezclas de DME/gas de síntesis a propileno. Con este fin, se han desarrollado catalizadores basados en Ag/SiO2 como una funcionalidad de hidrodeshidratación de acetona y se han acoplado al sistema catalítico multifuncional en tándem desarrollado para la producción de acetona. A una temperatura de reacción en el rango de 548-578 K y una presión total de 15 bares, el sistema catalítico en tándem proporciona ratios propileno-a-etileno en el rango 6-9, y selectividades de propileno de hasta el 40%, para una conversión de DME >97%, demostrando que esta ruta de producción es intrínsecamente más selectiva hacia propileno que la mayoría de los procesos de metanol-a-propileno reportados. Además, la temperatura de reacción relativamente suave y el carácter reductor de la atmósfera de gas de síntesis inhiben la deposición de coque, proporcionando un comportamiento estable durante períodos de operación superiores a 214 horas. Aunque se requiere mayor optimización en cuanto al rendimiento a propileno, los resultados abren la puerta a un nuevo proceso para la producción de propileno a partir de materias primas C1, alternativo a los procesos de metanol-a-hidrocarburos. / [CA] L'actual enfocament cap a la desfossilització de la indústria química accentua la necessitat de desenvolupar processos químics mediambientalment més sostenibles. En aquest context, el disseny de sistemes catalítics en tàndem per a dur a terme reaccions mecanísticamente desacoblades en un sol reactor, representa una estratègia prometedora per potencialment reduir la grandària de les instal·lacions i aconseguir majors eficiències energètiques i econòmiques. El gas de síntesi i els seus derivats directes C1 (metanol, DME) representen una atractiva font de carboni no derivada del petroli. La propagació selectiva de cadena des de compostos C1 fins específicament productes C3 continua sent un desafiament important en el camp de la catàlisi heterogènia. En aquesta tesi, es presenta com el disseny racional d'un sistema catalític en tàndem, multifuncional i heterogeni, proporciona una ruta nova i alternativa per a la síntesi directa de productes C3 d'interés a partir de compostos C1. En aquest treball, s'ha estudiat la integració en tàndem de la reacció de carbonilació de compostos metoxi (DME) amb CO, amb la posterior cetonització dels productes carboxílics C2 intermedis corresponents en un sistema catalític multifuncional. La integració dels catalitzadors Ag/MOR i Pd/ZrCeOx respectivament, permet la síntesi directa d'acetona a partir de mescles de DME/gas de síntesi a 548 K i 20 bars. La incorporació d'H-FER nanocristalina en un catalitzador multifuncional metall/òxid/zeolita Pd/ZrCeOx:FER, com a funcionalitat específica d'hidròlisi de l'acetat de metil, intermedi en el procés global, ha permés l'obtenció de rendiments a acetona fins a tres vegades majors en comparació amb els obtinguts utilitzant solament el catalitzador metall/òxid, Pd/ZrCeOx. La funcionalitat específica d'hidròlisi s'ha incorporat sobre la base dels resultats d'estudis cinètics realitzats per a les etapes de reacció per separat, que revelen una limitació general de la velocitat de cetonització a partir del pas d'hidròlisi àcida de l'intermediari acetat de metil. A una distància intercatalítica en el rang de micròmetres, s'ha mantingut una conversió de DME estable (superior al 94%), juntament amb una selectivitat d'acetona del 65-70% (entre tots els productes orgànics) durant almenys 10 dies d'operació contínua. A més, l'atmosfera de gas de síntesi a alta pressió permet la integració de la hidrogenació de grups carbonil, obrint la porta per a la producció no sols d'acetona, sinó també de 2-propanol en un sol reactor. En particular, la incorporació del catalitzador d'hidrogenació Ag-Pt/¿-Al2O3 ha permés aconseguir una selectivitat de 2-propanol del 51% dins de la fracció de productes C3 (és a dir, acetona, 2-propanol, propà i propilé). Finalment, el concepte de conversió en tàndem esmentat anteriorment s'ha estés a la conversió directa de mescles de DME/gas de síntesi a propilé. A aquest efecte, s'han desenvolupat catalitzadors basats en Ag/SiO2 com una funcionalitat de hidro-deshidratació d'acetona i s'han acoblat al sistema catalític multifuncional en tàndem desenvolupat per a la producció d'acetona. A una temperatura de reacció en el rang de 548-578 K i una pressió total de 15 bars, el sistema catalític multifuncional en tàndem proporciona ràtios propilé-a-etilé en el rang 6-9, i selectivitats de propilé de fins al 40%, per a una conversió de DME >97%, demostrant que aquesta ruta de producció és intrínsecament més selectiva cap a propilé que la majoria dels processos de metanol-a-propilé reportats. A més, la temperatura de reacció relativament suau i el caràcter reductor de l'atmosfera de gas de síntesi inhibixen la deposició de coc, proporcionant un comportament estable durant períodes d'operació superiors a 214 hores. Encara que es requereix una major optimització quant al rendiment a propilé, els resultats obrin la porta a un nou procés per a la producció de propilé a partir de matèries primeres C1, alternatiu als processos de metanol-a-hidrocarburs. / [EN] The present focus on advancing towards a defossilized chemical industry underscores the need for developing more environmentally sustainable chemical processes. In this context, the design of tandem-catalytic systems to steer mechanistically decoupled reactions in a cascade fashion, in a single reactor, represents a promising strategy for potentially reduce the installed size of chemical processes and attain higher energy- and cost-efficiencies. Synthesis gas and its direct C1 derivatives (methanol, DME), represent an attractive non-petroleum derived carbon source for the production of commodity chemicals. The selective chain propagation from C1 building blocks to specifically C3 compounds has been demonstrated through biocatalytic routes, however it remains an important challenge for heterogeneous catalysis. In this thesis, we report how the design and engineering of a multifunctional, heterogeneous tandem-catalytic system provides a novel and alternative route for the direct synthesis of C3 compounds from C1 building blocks. The selective obtention of C2+ products with specific chain lengths, surpassing the inherently non-selective C-C chain propagation characteristic of Fischer-Tropsch polymerization reactions, poses a significant challenge. In this work, the tandem integration of the reaction of carbonylation of methoxy compounds (DME) with CO, with subsequent ketonisation of the corresponding C2 carboxylic intermediate products on a multifunctional catalytic system is reported. The integration of an optimized Ag/MOR and Pd/ZrCeOx catalysts, respectively, allows the direct synthesis of acetone from DME/syngas mixtures at 548 K and 20 bar. Enhanced acetone time-yields, i.e. by a factor greater than three, have been obtained by incorporation of nanosized H-FER, as a specific ester hydrolysis functionality in a Pd/ZrCeOx:FER metal/oxide/zeolite multifunctional ketonisation composite catalyst. The specific hydrolysis functionality was implemented based on insights from kinetic studies on the individual reaction steps revealing overall ketonisation rate limitation from the methyl acetate intermediate acid-catalysed hydrolysis step. At the micro-meter range carbonylation/ketonisation intercatalysts spacing, a noticeably stable DME conversion (of >94%), alongside ca. 65-70% acetone selectivity (within all organic products) has been sustained for at least 10 days on-stream. Furthermore, the high-pressure syngas atmosphere allows integrating the hydrogenation of carbonyl groups therefore opening the door for the production of not only acetone but also 2-propanol in a single reactor. Particularly, Ag-Pt/¿-Al2O3 hydrogenation catalyst afforded reaching a 2-propanol selectivity of 51% within the C3 products fraction (i.e. acetone, 2-propanol, propane and propylene). Finally, the above tandem conversion concept has been extended to the direct conversion of DME/syngas mixtures to propylene. To this end, Ag/SiO2 catalysts have been developed as an acetone hydrodehydration functionality and coupled to the multifunctional catalytic-tandem system developed for acetone production from DME/syngas mixtures. At a reaction temperature in the range of 548-578 K and a total pressure of 15 bar, the multifunctional catalytic system affords a remarkably high propylene-to-ethylene molar ratio of 6-9 and overall propylene selectivities up to 40%, at essentially full DME conversion (>97%), proving this production route intrinsically more selective to propylene than most of methanol-to-propylene processes. Moreover, the comparatively mild reaction temperature and the reducing character of the syngas atmosphere inhibit coke deposition, leading to stable performance for times-on-stream in excess of 214 hours. While future improvements in propylene time-yield will be required, the results open the door to a new process for propylene production from C1 feedstocks, alternative to methanol-to-hydrocarbons processes. / I would like to thank the Spanish Ministry of Science, Innovation and Universities (MCIU) for my FPU fellowship (FPU17/04751) and the European Research Council (ERC) under the Horizon 2020 research and innovation program (ERC-CoG- TANDEng; grant agreement 864195), which have made possible the realization of this thesis. BASF SE (Ludwigshafen, Germany) is gratefully acknowledged for their support to fundamental research efforts in catalysis, a portion of which has contributed to the outcomes presented in this PhD thesis. I would also like to thank the Spanish Research Council (CSIC) and, particularly, the Institute of Chemical Technology (ITQ), for providing the infrastructure where I have developed my PhD work. Next, I want to thank the Massachusetts Institute of Technology (MIT) for giving me access to their facilities during my short PhD research stay, and to the ALBA synchrotron, especially to the CLÆSS beamline, for the several beamtimes granted. Finally, I would like to thank the department of Chemical and Nuclear Engineering (DIQN) of the Polytechnic University of Valencia (UPV), for hosting me as a teaching assistant over these years / Andrés Marcos, E. (2024). Tandem Catalysis for Selective C1-to-C3 Chain Propagations towards Platform Chemicals Production [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204891

Biodiesel is an alternative fuel that can be produced from a variety of lipid feedstocks. It has a number of perceived advantages over conventional petroleum diesel and as a result world production of biodiesel has increased dramatically since the turn of the century. Amongst its reported disadvantages is a widely observed increase in emissions of oxides of nitrogen, or NOx. Several explanations have been proposed for this phenomenon; in reality it is likely to be due to a combination of factors. The interplay of multiple factors affecting NOx emissions means that the increase in NOx when fuelling on biodiesel is not consistent or ubiquitous, but is instead dependent upon operating conditions and the specifics of the fuels being compared. The work documented in this thesis explores the nature and causes of the change in NOx emissions associated with biodiesel. The intention was that, by adjusting operating conditions, and using a wide range of fuels, doped with additives to achieve an even broader range of combustion characteristics, the impact of important variables would be made clearer, making it possible to reduce the problem to its lowest common denominators. In early experiments it was found that NOx emissions from biodiesel tended to be lower than those of petrodiesel under conditions where combustion was relatively highly premixed, but higher under more conventional diesel conditions where diffusion combustion constituted a larger proportion of heat release. The main experimental set revealed a definite increase in NOx emissions when fuelling on biodiesel, for a fixed start of combustion and equivalent degree of premixing. The addition of an oxygenate to petrodiesel elicited comparable NOx emissions to biodiesel, as a function of fuel-bound oxygen content; the data implies that the like-for-like biodiesel NOx increase may be a direct result of fuelbound oxygen. However, the like-for-like biodiesel NOx increase varies dependent upon operating conditions. In part, this may be related to higher apparent heat release rate (AHRR) through the diffusion burn phase when fuelling on biodiesel. This may result from the extended biodiesel injection duration. Across operating conditions, the extent to which smoke emissions when fuelling on petrodiesel exceeded those when fuelling on biodiesel was generally correlated with the magnitude of the biodiesel NOx increase; where the difference in smoke emissions was small, the biodiesel NOx increase was small, and where the difference in smoke emissions was more substantial, so was the difference in NOx emissions. This suggests a possible connection to changes in mixture stoichiometry. When differentiating between fuels, increased cetane number reduces NOx, and increased oxygen content increases NOx. Biodiesel does not necessarily have higher NOx emissions than petrodiesel: the biodiesel NOx increase exists where the difference in cetane number is insuffi cient to counteract the effects of fuel-bound oxygen content.

In fire debris analysis, substrate contribution refers to compounds present within the material collected that can interfere with the instrumental detection of ignitable liquids or contribute petroleum or alcohol-based compounds, which may complicate the interpretation. The concept of substrate contribution was brought to light by "The petroleum-laced background" by Lentini et al. focusing on commercial products (e.g. tennis shoes, magazines, etc.), the publication successfully illustrated that these products can produce chromatograms similar to those generated by the presence of petroleum-based ignitable liquids (ILs). As a result, Lentini et al. demonstrated that fire debris analysts can identify the presence of ignitable liquids without realizing the compounds in question might be the result of the manufacturing processes, and are inherent to the substrate in question. Therefore, the findings may or may not be probative. Gasoline is easily accessible and is frequently used by arsonists. As such, fire debris analysis focuses primarily on petroleum-based compounds. However, oxygenated solvents, which encompass all oxygen-containing compounds as defined by the American Society for Testing and Materials (ASTM) classification scheme, can also be used in an arson event. Despite the potential to be used as ILs, little is known regarding the recovery of these compounds. Previous thesis projects from the Biomedical Forensic Sciences program at Boston University School of Medicine explored and optimized the use of zeolites in recovering low molecular weight oxygenated ignitable liquids. An isothermal gas chromatography/mass spectrometry (GC/MS) method was also developed to detect these oxygenated ILs. The results from these projects show that zeolites have the potential to be used in forensic casework. Inspired by previous publications and thesis research, the goal of this project was to first develop a reference library on substrate contribution from oxygenates (e.g. ethanol, isopropanol and acetone) present in commercial products using the isothermal GC/MS methods. The development of this reference library included a specific interest in wood treatment products, considering wood is one of the most commonly submitted fire debris materials. The second stage involved an attempt at evaluating extraction efficiencies of activated charcoal strip and zeolites. The results of this project suggested that automotive and food products examined contained only acetone and ethanol respectively, while the variety of oxygenates found in household and personal care products indicated further analysis of additional products in these categories would be beneficial. Moreover, the results also reaffirmed zeolites' role in recovering oxygenated ILs in a controlled testing environment using KimWipes as a non-contributing substrate. However, the instrumental method required some modifications, as there was partial separation between ethanol and acetone. The results from applying products onto wooden blocks suggested that activated charcoal strips recovered more oxygenates than zeolites. This unexpected result prompted an investigation into the existing extraction parameters. The investigation suggested that the wooden blocks themselves were responsible for the unexpected recovery results, and future studies would be needed to understand if this recovery was substrate-specific.

No description available.

The use of transition metal catalysts - either homogeneous (discrete well-defined metal complexes) or heterogeneous (more poorly-defined metal surfaces) - play an important role in the transformations of small substrates into larger, value-added compounds. Although heterogeneous catalysts have the greater industrial applicability, there has been enormous interest in homogeneous transition metal systems for effecting selective transformations of small substrate molecules. The bulk of these homogeneous systems are mononuclear. Perhaps surprisingly, very little research has focuses on systems with adjacent metal centres. Binuclear systems possess adjacent metals that may interact and possibly lead to transformations not observed in monometallic systems. It is this opportunity for adjacent metal involvement in substrate activation that is the focus of this dissertation. the goal of this research is to gain an increased understanding of metal-metal cooperativity and adjacent metal involvement in substrate transformations; how can adjacent metal involvement lead to substrate activation not seen in monometallic counterparts, and what role does each metal play in these interactions, particularly when the two metals are different. Throughout this dissertation examples of transformation unique to systems with at least two metals are presented and examined with a particular focus on the roles of the two metals and any associated binding modes in these transformations. In addition, by comparing the RhOs, RhRu and IrRu systems, the influence of metal substitution is also examined. For example, diazoalkane activation and C-c bond formation promoted by the Rh-based systems is investigated, the roles of the adjacent metals of the IrRu system in the conversion of methylene groups to oxygenates is examined, and the unusual geminal C-H bond activation of olefinic substrates is explored. Overall, the work presented within this thesis adds to the growing understanding of adjacent metal cooperativety, leading us toward a more rational approach to the design of homogeneous homo- and heterobimetallic catalysts, heterogeneous catalyst and nanoparticle catalysts for selective substrate transformations.

No description available.

No description available.