The present doctoral thesis focused mainly on the use of α-imino esters in 1,4-conjugated addition reactions (Michael-type additions) which have been optimized using phosphines acting as organocatalysts. On the other hand, α-imino esters have been evaluated in heterogeneous systems functionalizing carbonaceous matrices through 1,3-dipolar cycloaddition reactions and their subsequent application in catalysis. Chapter 1 describes a new approach for the preparation of glutamates and pyroglutamates surrogates without the use of bases, through Michael-type addition reactions between different imino esters and conjugated alkenes in the presence of a phosphine that acts as an organocatalyst. Chapter 2 reports the results obtained from the functionalization of single-walled nanotubes (SWCNT) with different imino esters through the microwave-assisted 1,3-dipolar cycloaddition reaction; the pyrrolidine rings-functionalized material was characterized by using several techniques and subsequently the synthesis of a heterogeneous catalyst using an iridium complex was afforded. This supported catalyst was evaluated, as a proof of concept, in the hydrogen-transfer reaction of acetophenone to yield 1-phenyletanol. In Chapter 3 the covalent functionalization of multilayer graphene (MLG) via microwave-assisted 1,3-dipolar cycloaddition with azomethine ylides generated by thermal 1,2-prototropy from various imino esters is described. In particular, this strategy allows to anchor an imino ester containing a 2,2’-bipyridine unit in order to obtain a functionalized material capable of assembling a ruthenium atom to achieve a heterogeneous supported complex. This new catalyst was tested, as a proof of concept, in the photocatalytic aerobic oxidative hydroxylation reaction of 4-methoxyphenylboronic acid. / The present work has been possible thanks to the Spanish Ministerio de Ciencia, Innovación y Universidades (project RED2018-102387-T) the Spanish Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) (MCIN/AEI/10.13039/501100011033) and Fondo Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2017-82935-P, PID2019-107268GB-I00 and PID2021-123079OB-I00), the Generalitat Valenciana (IDIFEDER/2021/013, GVACOVID19/2021/079 and CIDEGENT/2020/058), Medalchemy S. L. (Medalchemy-18T) and the University of Alicante (VIGROB-068, UAUSTI21-05). Additionally, I would like to thanks the Generalitat Valenciana for the Grisolía’s fellowship (GRISOLIAP/2020/111) from the Santiago Grisolía program and for the CIBEFP/2022/17 grant to carry out a three-months research stay in the Department of chemical and pharmaceutical sciences at the University of Trieste-Italy.

[ES] La presente tesis doctoral se basa en la síntesis, caracterización y uso de catalizadores basados en especies de Pd soportadas sobre matrices sólidas en reacciones de interés en química fina. En general, se ha pretendido obtener catalizadores multifuncionales, estables y reutilizables que se puedan separar fácilmente de la mezcla de reacción y que contribuyan a desarrollar protocolos más sostenibles que den lugar a compuestos orgánicos de interés. En primer lugar, el material [Pd/Al2O3], constituido por nanoagregados de Pd(0) de un tamaño medio de 2.8 nm y soportados sobre una matriz de tipo ¿-Al2O3 con elevada densidad de sitios ácidos, ha demostrado ser altamente activo y eficiente en la ciclación deshidrogenativa entre ureas y 1,2-dioles para la síntesis de imidazol-2-onas. Al utilizar ureas y 1,2-dioles desactivados, la cooperatividad Pd-Zn ha demostrado ser imprescindible para el éxito del proceso, obteniendo los mejores resultados al emplear el sistema de [Pd/Al2O3]-ZnO. Ambos materiales, [Pd/Al2O3] y [Pd/Al2O3]-ZnO, han demostrado ser reusables y estables bajo las condiciones de reacción al no presentar problemas de lixiviación. Además, este protocolo catalítico ha permitido obtener hasta 28 imidazol-2-onas con buenos resultados, demostrando su amplio potencial sintético. Por otra parte, el nanomaterial [Pd(0.75%)/Mg3Al-LDH]-300(D), constituido por nanopartículas de Pd(0) de un tamaño medio de 2.8 nm y soportado sobre una matriz básica de tipo dh-LDH, ha demostrado ser altamente activo para mediar la síntesis de propiolamidas mediante la aminocarbonilación oxidativa entre alquinos terminales y aminas secundarias, en presencia de CO/O2. Se ha determinado que un soporte con estructura dh-LDH con una relación de Mg/Al de 3 es el idóneo para estabilizar especies de [PdI2] generadas in situ en el medio de reacción así como para promover la activación de los reactivos de partida. El sistema catalítico ha demostrado ser reusable y estable bajo las condiciones de reacción, además de poseer una elevada aplicabilidad sintética al haber obtenido más de 60 propiolamidas diferentes, destacando el uso por primera vez en este tipo de procesos de aminas N-aromáticas y N-heterocíclicas. Finalmente, se ha llevado a cabo la síntesis de materiales híbridos derivados de soportar mediante interacciones no covalentes complejos de Pd con geometría plano-cuadrada sobre matrices grafénicas. Los resultados de caracterización apuntan a que estos materiales están constituidos, principalmente, por especies aisladas de Pd(II), demostrando el papel estabilizante de los ligandos utilizados al evitar la agregación del metal. Esos materiales han sido, en general, altamente activos y selectivos como catalizadores en la semi-hidrogenación de alquinos, y lo que es más relevante, se ha demostrado una sinergia complejo - grafeno en la actividad catalítica estudiada. El material de [Pd-Phen/OGr-C] ha sido reutilizado en varios ciclos y es estable bajo las condiciones de reacción. Además, este protocolo catalítico posee una elevada aplicabilidad, al haberse podido utilizar hasta con 37 alquinos diferentes obteniendo muy buenos resultados de rendimiento y quimioselectividad. / [CA] La present tesi doctoral es basa en la síntesi, caracterització i ús de catalitzadors basats en espècies de Pd suportades sobre matrius sòlides en reaccions d'interés en química fina. En general, s'ha pretès obtenir catalitzadors multifuncionals, estables i reutilitzables que es puguen separar fàcilment de la mescla de reacció i que contribuïsquen a desenvolupar protocols més sostenibles que donen lloc a compostos orgànics d'interès. En primer lloc, el material [Pd/Al2O3], constituït per nanoagregats de Pd(0) d'una grandària mitjana de 2.8 nm i suportats sobre una matriu de tipus ¿-Al2O3 amb elevada densitat de llocs àcids, ha demostrat ser altament actiu i eficient en la ciclació deshidrogenativa entre urees i 1,2-diols per a la síntesi d'imidazol-2-ones. En utilitzar urees i 1,2-diols desactivats, la cooperativitat Pd-Zn ha demostrat ser imprescindible per a l'èxit del procés, aconseguint els millors resultats emprant el sistema de [Pd/Al2O3]-ZnO. Tots dos materials, [Pd/Al2O3] i [Pd/Al2O3]-ZnO, han demostrat ser reutilitzables i estables sota les condicions de reacció ja que no presenten problemes de lixiviació. A més, aquest protocol catalític ha permès obtenir fins a 28 imidazol-2-ones amb bons resultats, demostrant el seu ampli potencial sintètic. D'altra banda, el nanomaterial [Pd(0.75%)/Mg3Al-LDH]-300(D), constituït per nanopartícules de Pd(0) d'una grandària mitjana de 2.8 nm suportades sobre una matriu bàsica de tipus dh-LDH, ha demostrat ser altament actiu per a catalitzar la síntesi de propiolamides mitjançant l'aminocarbonilació oxidativa entre alquins terminals i amines secundàries, en presència de CO/O2. S'ha determinat que un suport amb estructura dh-LDH amb una relació de Mg/Al de 3 és l'idoni per a estabilitzar les espècies de [PdI2] generades in situ en el medi de reacció així com per a promoure l'activació dels reactius de partida. El sistema catalític ha demostrat ser reutilitzable i estable sota les condicions de reacció, a més de posseir una elevada aplicabilitat sintètica en haver obtingut més de 60 propiolamides diferents, destacant l'ús per primera vegada en aquesta mena de processos d'amines N-aromàtiques i N-heterocícliques. Finalment, s'ha dut a terme la síntesi de materials híbrids derivats de suportar mitjançant interaccions no covalents complexos de Pd amb geometria pla-quadrada sobre matrius grafèniques. Els resultats de caracterització apunten a que aquests materials estan constituïts, principalment, per espècies aïllades de Pd(II), demostrant el paper estabilitzant dels lligands utilitzats per a evitar l'agregació del metall. Aquests materials han sigut, en general, altament actius i selectius com a catalitzadors en la semi-hidrogenació d'alquins, i el que és més rellevant, s'ha demostrat una sinèrgia complex - grafè en l'activitat catalítica estudiada. El material [Pd-Phen/OGr-C] ha sigut reutilitzat en diversos cicles i es estable sota les condicions de reacció. A més, aquest protocol catalític posseeix una elevada aplicabilitat i s'ha pogut aplicar a 37 alquins diferents obtenint molt bons resultats de rendiment i quimioselectivitat. / [EN] The present PhD thesis is focused on the synthesis, characterisation and use of catalysts based on Pd species supported on solid matrixes in reactions of interest in fine chemistry. In general, the aim is to obtain multifunctional, stable and reusable catalysts that can be easily separated from the reaction mixture and that contribute to the development of more sustainable protocols leading to relevant organic compounds. Firstly, the [Pd/Al2O3] material, consisting of Pd(0) nanoaggregates with an average size of 2.8 nm and supported on a ¿-Al2O3-type matrix with a high density of acid sites, has been designed as a highly active and efficient catalyst in the dehydrogenative cyclisation between ureas and 1,2-diols for the synthesis of imidazole-2-ones. When using ureas and deactivated 1,2-diols, Pd-Zn cooperativity has been shown to be essential for the success of the process, with the best results obtained using a [Pd/Al2O3]-ZnO system. Both materials, [Pd/Al2O3] and [Pd/Al2O3]-ZnO, have proved to be reusable and stable under the reaction conditions as they do not present leaching problems. Moreover, this catalytic protocol has allowed to obtain up to 28 imidazole-2-ones with good results, demonstrating it is wide synthetic potential. On the other hand, the nanomaterial [Pd(0.75%)/Mg3Al-LDH]-300(D), consisting of Pd(0) nanoparticles with an average size of 2.8 nm and supported on a basic dh-LDH-type matrix, has been shown to be highly active for catalysing the synthesis of propiolamides via oxidative aminocarbonylation between terminal alkynes and secondary amines in the presence of CO/O2. A dh-LDH-structured support with an Mg/Al ratio of 3 has been found to be suitable for stabilising [PdI2] species generated in situ in the reaction medium, as well as for promoting the activation of the starting reagents. The catalytic system has proved to be reusable and stable under the reaction conditions, besides having a high synthetic applicability as more than 60 different propiolamides have been obtained. It is especially relevant the use of N-aromatic and N-heterocyclic amines for the first time in this type of processes. Finally, the synthesis of hybrid materials derived from supporting Pd complexes with planar square geometry on graphene matrices through non-covalent interactions has been carried out. The characterisation results show that these materials are mainly constituted by isolated Pd(II) species, demonstrating the stabilising role of the ligands to avoid the aggregation of the metal. These materials have been, in general, highly active and selective as catalysts in the semi-hydrogenation of alkynes, and what is more relevant, a complex - graphene synergy has been demonstrated in the studied catalytic activity. In addition, [Pd-Phen/OGr-C] has shown to be reusable in several catalytic cycles and stable under the reaction conditions. Moreover, this catalytic protocol has demonstrated a high applicability, in fact it has been applied to 37 different alkynes with very good results, in terms of yield and chemoselectivity. / Arango Daza, JC. (2023). Materiales basados en especies de Pd soportadas sobre matrices sólidas como catalizadores eficientes para reacciones de interés en química fina [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/201576

[ES] La presente tesis doctoral se centra en la investigación y desarrollo de catalizadores avanzados con aplicaciones en la industria química. Desde la síntesis de nanopartículas de Rh2P hasta la exploración de catalizadores de cobalto dopados con heteroátomos, se ha buscado no sólo la eficiencia catalítica, sino también minimizar el impacto de estos procesos, permitiendo la producción de productos químicos esenciales con un menor consumo de recursos. Se ha investigado el proceso de síntesis de nanopartículas de Rh2P soportadas por impregnación húmeda seguida de pirólisis para su uso en reacciones de hidroformilación. Para ello, se han descrito y comparado dos métodos que se diferencian en los precursores empleados: uno a partir de un único precursor de fósforo y rodio y el otro a partir de dos precursores separados. Posteriormente, se ha realizado una caracterización de los materiales que ha permitido relacionar la forma de incorporar el fósforo con la composición de las partículas, determinando que el contenido de óxido de rodio es mayor cuando se emplean dos precursores. Para analizar la contribución del fósforo en el sistema se han preparado nanopartículas de rodio metálico soportadas para estudiar la influencia del fósforo en la composición y el tamaño de partícula. Se han analizado otros aspectos como la carga metálica, la temperatura de pirólisis y el uso de diferentes soportes empleando la microscopía electrónica; y se ha estudiado su capacidad de disociación de hidrógeno mediante ensayos de intercambio isotópico. Tras la caracterización de los materiales, éstos se han empleado como electrocatalizadores en la reacción de evolución del hidrógeno, en la que se ha estudiado su aplicabilidad a pH ácido, básico y neutro con bajas cargas de metal. Se ha demostrado que las especies de Rh2P son más activas que las de Rh metálico en la producción de hidrógeno y que el método de síntesis influye en la actividad catalítica. Para completar los ensayos experimentales, se han realizado cálculos DFT que han permitido comprobar por un lado la influencia de los defectos en la red de Rh2P y por otro, si las capas de carbono son efectivas en la protección de las nanopartículas. Se han aplicado los materiales de Rh y Rh2P en la hidroformilación de olefinas donde se ha estudiado la actividad catalítica, la influencia del fósforo y la estabilidad de los catalizadores. Se ha demostrado que el material Rh2P-1@C, obtenido a partir de un solo precursor de rodio y fósforo, es un sustituto viable del catalizador homogéneo RhCl(PPh3)3 ya que las energías de activación calculadas son muy cercanas entre sí. Se ha estudiado la influencia de algunos parámetros en la estabilidad del catalizador, como la temperatura de pirólisis a la que se sintetiza el material, demostrando que existe una relación inversa entre la temperatura de pirólisis y la cantidad de metal lixiviado durante la reacción. Otro factor estudiado es el del soporte, donde además del carbón se han empleado óxidos inorgánicos (Al2O3, CeO2, La2O3, ZnO), poniendo de manifiesto la superioridad del carbón como soporte no sólo en términos de actividad catalítica, sino de estabilidad del material. El catalizador Rh2P-1@C ha sido satisfactoriamente probado en reacciones de hidroformilación de etileno en un reactor de lecho fijo y en la reacción de hidroaminometilación. Como alternativa a los materiales de rodio, se han desarrollado catalizadores de cobalto dopados con heteroátomos (fósforo y nitrógeno). Éstos se han empleado en la hidroformilación de olefinas, donde se ha evaluado la influencia del dopaje en la actividad catalítica y en su estabilidad. Se ha comprobado la efectividad del recubrimiento del carbón dopado con nitrógeno al aumentar su estabilidad en comparación con las nanopartículas de cobalto sin recubrir y se ha demostrado que las nanopartículas de Co2P, al contrario que las Rh2P, no son más activas que las de Co metálico. / [CA] Aquesta tesis doctoral es centra en la investigació i la síntesis de nous catalitzadors amb aplicacions en reaccions químics d'interès industrial. Durant el transcurs de la síntesis de les nanopartícules fins a l'estudi de nous catalitzadors, s'ha cercat no únicament l'eficiència catalítica dels processos sinó la disminució de l'impacte dels mateixos. S'ha investigat el procés de síntesis de nanopartícules de Rh2P suportades a través del mètode d'impregnació humida seguida d'un procés de piròlisis, per al posterior ús d'aquests materials en reaccions d'hidroformil·lació. Per tal fi, s'han descrit i comparat dos mètodes de síntesis que es diferencien en els precursors utilitzats: un a partir d'un únic precursor com a font de fòsfor i rodi, i l'altre a partir dels dos precursors - de rodi i fòsfor - per separats. Posteriorment, s'ha portat a terme una caracterització completa de cadascun dels materials preparats que a permès relacionar la forma com s'incorpora el fòsfor el material en funció de la composició de les partícules. Amb l'objectiu d'analitzar la contribució de les espècies de fòsfor en el sistema s'han preparat un material basat en nanopartícules de rodi metàl·lic suportades. S'han analitzat, mitjançant la microscòpia electrònic, com influeixen en aquest paràmetre altres aspectes, com ara: la càrrega metàl·lica, la temperatura de piròlisis i l'ús de diferents suports. Tanmateix, s'ha estudiat la capacitat dissociativa de l'hidrogen per part d'aquests materials mitjançant assajos d'intercanvi isotòpic. Després de la caracterització dels materials, aquests s'han utilitzat com a electrocatalitzadors en la reacció d'evolució de l'hidrogen en la què s'ha estudiat la utilització d'aquests materials, utilitzant una baixa càrrega metàl·lica, en diferents medis (pH àcid, bàsic i neutre). Els treballs han demostrat que les espècies de Rh2P són més actives que les de Rh metàl·lic i que el mètode de síntesis també influeix en l'activitat catalítica. Per a completar la part experimental, s'han realitzat càlculs DFT que han permès comprovar tan la influència dels defectes de la xarxa de Rh2P com la influència de les capes de carboni en quant a la protecció de les pròpies nanopartícules. Tot seguit, els materials de Rh y Rh2P s'han aplicat en la reacció d'hidroformil·lació d'olefines on s'ha estudiat l'activitat catalítica, la influència de les espècies de fòsfor i l'estabilitat dels catalitzadors utilitzats. S'ha demostrat que el material de Rh2P-1@C, obtingut a partir d'un sol precursor de rodi i fòsfor, pot convertir-se en un possible candidat per a substituir el catalitzador homogeni RhCl(PPh3)3. També, s'ha estudiat la influència d'alguns paràmetres relacionats amb l'estabilitat del catalitzador, com ara la temperatura de piròlisis i la quantitat de metall lixiviat durant la reacció. Una altre factor que ha estat objecte d'estudi és el suport, on a més a més del carboni s'han utilitzat òxids inorgànics - Al2O3, CeO2, La2O3 i ZnO - posant de manifest la superioritat del carboni com a suport; no només en termes d'activitat catalítica sinó d'estabilitat del propi material. A més a més, el catalitzador Rh2P-1@C s'ha provat satisfactòriament en reaccions d'hidroformil·lació de l'etilè en un reactor de tipus llit fix, i en la reacció d'hidroaminometil·lació. Com a alternativa als materials de rodi, s'han sintetitzat catalitzadores de cobalt dopats amb heteroàtoms (fòsfor i nitrogen). Aquests materials, s'han utilitzat en la reacció d'hidroformil·lació d'olefines, on s'ha estudiat la influència del dopatge en l'activitat catalítica i en la seva estabilitat. S'ha comprovat que l'efectivitat del recobriment del carbó dopat amb nitrogen augmenta l'estabilitat del catalitzador en front de les nanopartícules de cobalt sense recobriment, i s'ha aconseguit demostrar que les nanopartícules de Co2P, a diferència de les de Rh2P, no resulten ser més actives que les de Co metàl·lic. / [EN] The present doctoral thesis focuses on the research and development of advanced catalysts with applications in the chemical industry. From the synthesis of Rh2P nanoparticles to the exploration of cobalt catalysts doped with heteroatoms, the primary goal has been to enhance not only the catalytic efficiency but also to minimize the environmental impact of these processes. In a time where the transition to clean energy sources and environmentally friendly processes is of utmost importance, advances in catalysis and material synthesis play a crucial role in the quest for more sustainable solutions in the chemical industry. The synthesis of supported Rh2P nanoparticles by wet impregnation followed by pyrolysis has been investigated. Two methods, differing only in the precursors employed, have been described and compared: one using a single precursor of phosphorus and rhodium, and the other using two separate precursors. Material characterization has revealed the relationship between the method of phosphorus incorporation and particle composition, demonstrating that the rhodium oxide content is higher when two separate precursors are used. Additionally, supported metallic rhodium nanoparticles were prepared to study the influence of phosphorus on particle size and composition. In this chapter, other factors have also been analyzed such as metal loading, pyrolysis temperature, and the use of different supports, employing electron microscopy. Finally, the hydrogen dissociation capacity of the catalysts has been compared through isotopic exchange assays, and the presence of carbon patches around the nanoparticles has been studied using Raman spectroscopy. Following material characterization, these materials have been employed as electrocatalysts in the hydrogen evolution reaction, where their applicability at acidic, basic and neutral pH at one of the lowest metal loadings described has been studied. It has been demonstrated that Rh2P species are more active than metallic Rh species in hydrogen production, and the synthesis method influences catalytic activity. To complement experimental assays, DFT calculations have been performed, allowing for an examination of the influence of defects in the Rh2P lattice and an assessment of the effectiveness of carbon layers in protecting the nanoparticles. Rh and Rh2P materials have been applied in the hydroformylation of olefins, where catalytic activity, the influence of phosphorus, and catalyst stability have been investigated. It has been shown that the material Rh2P-1@C, obtained from a single precursor of rhodium and phosphorus, is a viable substitute for the homogeneous catalyst RhCl(PPh3)3, as their apparent activation energies are very close. The influence of parameters affecting catalyst stability, such as the pyrolysis temperature at which the material is synthesized, has been studied, demonstrating an inverse relationship between pyrolysis temperature and the amount of leached metal during the reaction. Another factor studied is that of the support, where, in addition to carbon, inorganic oxides (Al2O3, CeO2, La2O3, ZnO) have been employed, highlighting the superiority of carbon as support not only in terms of catalytic activity but also material stability. At the end of this chapter, the Rh2P-1@C catalyst has been applied in the hydroformylation of ethylene in a fixed-bed reactor and in the hydroaminomethylation reaction. As an alternative to rhodium materials, cobalt catalysts doped with heteroatoms (phosphorus and nitrogen) have been developed. These catalysts have been employed in the hydroformylation of olefins, where the influence of doping on the catalytic activity and leaching has been evaluated. The effectiveness of nitrogen-doped carbon coating in suppressing leaching has been demonstrated compared to undoped cobalt nanoparticles, and it has been shown that Co2P nanoparticles, unlike Rh2P, are not more active than metallic Co nanoparticles. / Galdeano Ruano, CP. (2024). Catalizadores heterogéneos de rodio y cobalto para la hidroformilación de olefinas y la reacción de evolución del hidrógeno [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/203121

After introducing fundamentals of catalysis with noble metal surfaces especially Pt metal for CO oxidation and subsequent developments on nano-crystalline Pt metals supported on oxide supports, an idea of Pt ion in reducible oxide supports acting as adsorption sites is proposed in chapter 1. Idea of red-ox cycling of an ion in an oxide matrix is presented taking Cu ion in YBa2Cu3O7 as an example. Noble metal ions in reducible oxides such as CeO2 or TiO2 acting as adsorption sites and hence a red-ox catalyst was arrived at from chemical considerations. Among several reducible oxide supports, TiO2 was chosen from crystal structure and electronic structure considerations. A good redox catalyst for auto exhaust and related applications should have high oxygen storage capacity (OSC). Any new material that can work as a redox catalyst should be tested for its OSC. Therefore we designed and fabricated a temperature programmed reduction by hydrogen (H2¬TPR) system to measure OSC. This is presented in chapter 2. We have synthesized a number of oxides by solution combustion method. Structures were determined by powder XRD and Rietveld refinement methods. Fe2O3, Fe2-xPdxO3-δ, Cu1-xMnAl1+xO4, LaCoO3, LaCo1-xPdxO3-δ, CeO2, Ce1¬xPdxO2-δ, TiO2, Ti1-xPdxO2-δ and many other oxide systems were synthesized and their structures were determined. OSC of these systems were determined employing the H2/TPR system. TPR studies were carried out for several redox cycles in each case. Except Pd ion substituted CeO2 and TiO2 other oxide systems decomposed during redox cycling. Pd ion substituted TiO2 gave highest OSC and also it was stable paving way to choose this system for further study. In chapter 3, we have described lattice oxygen of TiO2 activation by the substitution of Pd ion in its lattice. Ti1-xPdxO2-x (x = 0.01 to 0.03) have been synthesized by solution combustion method crystallizing in anatase TiO2 structure. Pd is in +2 oxidation state and Ti is in +4 oxidation state in the catalyst as seen by XPS. Pd is more ionic in TiO2 lattice compared to Pd in PdO. Oxygen storage capacity defined by ‘amount of oxygen that is used reversibly to oxidize CO’ is as high as 5100 μmol/g of Ti0.97Pd0.03O1.97. Oxygen is extracted by CO to CO2 in absence of feed oxygen even at room temperature. Rate of CO oxidation is 2.75 μmol.g-1.s-1 at 60 0C over Ti0.97Pd0.03O1.97 and C2H2 gets oxidized to CO2 and H2O at room temperature. Catalyst is not poisoned on long time operation of the reactor. Such high catalytic activity is due to activated lattice oxygen created by the substitution of Pd ion as seen from first-principles density functional theory (DFT) calculations with 96 atom supercells of Ti32O64, Ti31Pd1O63, Ti30Pd2O62 and Ti29Pd3O61. The compounds crystallize in anatase TiO2 structure with Pd2+ ion in nearly square planar geometry and TiO6 octahedra are distorted by the creation of weakly bound oxygens. Structural analysis of Ti31Pd1O63 which is close to 3% Pd ion substituted TiO2 shows that bond valence of oxygens associated with both Ti and Pd ions in the lattice is 1.87. A low bond valence of oxygen is characteristic of weak oxygen in the lattice compared to oxygens with bond valence 2 and above in the same lattice. Thus, the exact positions of activated oxygens have been identified in the lattice from DFT calculations. Pt has two stable valencies: +2 and +4. Ti ion in TiO2 is in +4 state. Is it possible to substitute Pt exclusively in +2 or +4 state in TiO2? Implications are that Pt in +2 will have oxide ion vacancies and Pt in +4 states will not have oxide ion vacancies. Indeed we could synthesize Pt ion substituted TiO2 with Pt in +2 and +4 states by solution combustion method. In chapter 4, we have shown the positive role of an oxide ion vacancy in the catalytic reaction. Ti0.97Pt2+0.03O1.97 and Ti0.97Pt4+0.03O2 have been synthesized by solution combustion method using alanine and glycine as the fuels respectively. Both are crystallizing in anatase TiO2 structure with 15 nm average crystallite size. X-ray photoelectron spectroscopy (XPS) confirmed Pt ions are only +2 state in Ti0.97Pt0.03O1.97 (alanine) and only in +4 state in Ti0.97Pt0.03O2 (glycine). CO oxidation rate with Ti0.97Pt2+0.03O1.97 is over 10 times higher compared to Ti0.97Pt4+0.03O2. The large shift in 100 % hydrocarbon oxidation to lower temperature was observed by Pt2+ ion substituted TiO2 from that by Pt4+ ion substituted TiO2. After reoxidation of the reduced compound by H2 as well as CO, Pt ions are stabilized in mixed valences, +2 and +4 states. The role of oxide ion vacancy in enhancing catalytic activity has been demonstrated by carrying out the CO oxidation and H2 + O2 recombination reaction in presence and in absence of O2. There is no deactivation of the catalyst by long time CO to CO2 catalytic reaction. We analyzed the activated lattice oxygens upon substitution of Pt2+ ion and Pt4+ ion in TiO2, using first-principles density functional theory (DFT) calculations with supercells Ti31Pt1O63, Ti30Pt2O62, Ti29Pt3O61 for Pt2+ ion substitution in TiO2 and Ti31Pt1O64, Ti30Pt2O62, Ti29Pt3O61 for Pt4+ ion substitution in TiO2. We find that the local structure of Pt2+ ion has a distorted square planar geometry and that of Pt4+ ion has an octahedral geometry similar to Ti4+ ion in pure TiO2. The change in coordination of Pt2+ ion gives rise to weakly bonded oxygens and these oxygens are responsible in high rates of catalytic reaction. Thus, the high catalytic activity results from synergistic roles of oxide ion vacancy and weakly bonded lattice oxygen. In chapter 5, we have shown high rates of H2 + O2 recombination reaction by Ti0.97Pd0.03O1.97 catalyst coated on honeycomb monolith made up of cordierite material. This catalyst was coated on γ¬Al2O3 coated monolith by solution combustion method using dip-dry-burn process. This is a modified conventional method to coat catalysts on honeycombs. Formation of Ti0.97Pd0.03O1.97 catalyst on monolith was confirmed by XRD. Form the XPS spectra of Pd(3d) core level in Ti1-xPdxO2-δ, Pd ion is the formed to be +2 state. Ti0.97Pd0.03O1.97 showed high rates of H2 + O2 recombination compared to 2 at % Pd(metal)/γ-Al2O3, Ce0.98Pd0.02O2-δ, Ce0.98Pt0.02O2-δ, Ce0.73Zr0.25Pd0.02O2-δ and Ti0.98Pd0.02O1.98. Activation energy of H2 + O2 recombination reaction over Ti0.97Pd0.03O1.97 is 7.8 kcal/mole. Rates of reaction over Ti0.97Pd0.03O1.97 are in the range of 10 – 20 μmol/g/s at 60 0C and 4174 h-1 space velocity. Rate is orders of magnitude higher compared to noble metal catalysts. From the industrial point of view, solvent-free hydrogenation of aromatic nitro compounds to amines at nearly 1 bar pressure is an important process. In chapter 6, we showed that Ti0.97Pd0.03O1.97 is a good –nitro to –amine conversion catalyst under solvent-free condition at 1.2 – 1.3 bar H2 pressure. Nitrobenzene, p-nitrotoluene and 2-chloro-4-nitrotoluene are taken for the catalytic reduction reaction. The amine products were analyzed by gas chromatography and mass spectrometry (GCMS). Further, confirmation of compounds was done by FTIR, 1H NMR and 13C NMR. In presence of alcohol as solvent, 100% conversion of aromatic nitro compounds to amines took place at higher temperature and it required more times. In n-butanol solvent, 100% conversion of nitrobenzene and p-nitrotoluene occurred within 10 h and 12 h at 105 °C respectively. We have compared solvent-free reduction of p-nitrotoluene over different catalysts at 90 °C. Catalytic activity for reduction of p¬nitrotoluene over Ti0.97Pd0.03O1.97 is much higher than that reaction over 3 atom % Pd on TiO2 and Pd metal. Turnover frequencies (TOF) for nitrobenzene and 2-chloro-4-nitrotoluene conversion are 217 and 20 over Ti0.97Pd0.03O1.97 respectively. With increase of temperature, TOF of aromatic nitro compound reduction is also increased. We have compared the solvent-free reduction of aromatic nitro compound over Ti0.97Pd0.03O1.97 with others in the literature. Upto 3 cycles of reduction reaction, there was no degradation of Ti0.97Pd0.03O1.97 catalyst and stability of catalyst structure was analyzed by XRD, XPS and TEM images. Catalyst is stable under reaction condition and the structure is retained with Pd in +2 state. Finally, we have proposed the mechanism of -nitro group reduction reaction based on the structure of Ti0.97Pd0.03O1.97. Instead of handling nano-crystalline materials we proceeded with coating our catalysts on cordierite honeycombs. In chapter 7, we have shown high catalytic activity towards Heck reaction over Ce0.98Pd0.02O2-δ and Ti0.97Pd0.03O1.97 coated on cordierite monolith. XRD patterns of Ce0.98Pd0.02O2¬δ coated on cordierite monolith were indexed to fluorite structure. Heck reaction of aryl halide with olefins over Ce0.98Pd0.02O2-δ and Ti0.97Pd0.03O1.97 coated on cordierite monolith were carried out at 120 °C. The products were first analyzed by GCMS and for the confirmation of compounds, we have recorded 1H NMR and 13C NMR. Heck reaction was carried out with different solvents and different bases for choosing the good base and a solvent. Hence, we have chosen K2CO3 as base and N,N¬dimethylformamide (DMF) as solvent. We have compared the rates of Heck reactions over these two catalysts and Ti0.97Pd0.03O1.97 catalyst showed much higher catalytic activity than Ce0.98Pd0.02O2-δ. With increase of temperature from 65 °C to 120 °C, the catalytic activity of Ti0.97Pd0.03O1.97 on Heck reaction is also increased. The catalyst was reused for next Heck reaction without significant loss of activity. A mechanism for Heck reaction of aryl halide with alkyl acrylate has been proposed based on the structure of Ti0.97Pd0.03O1.97. In chapter 8, we have provided a critical review of the work presented in the thesis. Critical issues such as noble metal ion doping in TiO2 vs noble metal ion substitution, difficulty of proving the substitution of low % noble metal ion in TiO2, need for better experimental methods to study noble metal ion in oxide matrix have been discussed. Finally, conclusions of the thesis are presented.

Several ligands derived from D-glucosamine, designed for different catalytic reactions havebeen synthesized. The ligands for homogeneous catalysis based on 1,2-glucodiamine wereprepared, and used in reactions of allylic alkylation, hydrogenation and Michael addition.Supported Aqueous Phase Catalyst (SAPC) system was prepared from D-glucosamine anduse with very good results in Suzuki Miyaura cross coupling reactions. Catalyst was alsorecycled. Attempt to prepare ligands grafted on SBA-silica matrix were made as well asligands containing poly(ethylene) glycol moiety.

A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal–organic frameworks is developed. Our synthesis strategy, which uses known porous structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Biomass is one of the most promising replacements for fossil fuels as a feedstock for chemical and transportation fuel production. The combination of low vapor pressure and high polarity of most biomass derived molecules makes water the ideal solvent for biomass upgrading reaction schemes. Metal oxide and metal oxide supported catalysts are heavily used in oil refining and petrochemical production, and are capable of upgrading biomass molecules as well. However, the surface chemistries that dictate the behavior of aqueous phase biomass upgrading reactions over metal oxide catalysts are not nearly as well understood as in the case of gas phase hydrocarbon refining systems. This dissertation aims to investigate the surface chemistries of biomass derived oxygenate molecules on metal oxide and metal oxide supported metal catalysts. There are three main objectives in this dissertation: to understand how two and three carbon polyols interact with metal oxide surfaces, to elucidate the role of various surface sites on polyol-metal oxide interactions, and to discover the surface species of kinetic importance in aqueous phase reforming reactions of biomass molecules. Transmission infrared spectroscopy and density functional theory modeling were the major techniques used to demonstrate that polyols with alcohol groups on the first and third carbons, 1,3-propanediol and glycerol, form a multidentate surface species with a bridging alkoxide bond and an acid/base interaction through their two primary alcohol groups with Lewis acid sites of g-Al₂O₃. These interactions occur in the presence of bulk water. Polyols with alcohol groups only on the first and second carbons, ethylene glycol and 1,2-propanediol, only formed alkoxy bonds with the g-Al₂O₃ surface when bulk water was not coadsorbed, and these bonds were removed by re-adsorbing water. Glycerol also forms the same surface species on other metal oxides with strong Lewis acidic character: TiO₂ anatase, ZrO₂, and CeO₂. Glycerol only forms hydrogen bonds with MgO, which lacks strongly Lewis acidic sites. Basic surface hydroxyls and surface oxygen atoms of the metal oxides only played a minor role in interacting with the adsorbed glycerol. In-situ attenuated total reflectance infrared spectroscopy demonstrated that the aqueous phase reforming of glycerol over a 5 wt% Pt on g-Al₂O₃ catalyst is hindered by residual platinum bound hydrogen or oxygen atoms from commonly utilized catalyst reduction or cleaning procedures, respectively. A pretreatment consisting of multiple iterations of dissolved oxygen, dissolved hydrogen, and dissolved helium in water flow periods provides the cleanest Pt surface for monitoring carbon monoxide formation dynamics, and allows for observing the rate limiting step of the aqueous phase reforming reactions water-gas shift removal of Pt bound carbon monoxide. The bridging bound carbon monoxide is preferentially removed over the linearly bound species via water gas shift reactions even at room temperature.

This study focuses on the development of novel two-stage esterification-transesterification synthesis of biodiesel from used cooking oil (UCO) using novel heterogeneous catalysts. The esterification of the UCO was investigated using three types of ion exchange resins catalysts including Purolite D5081, Purolite D5082 and Amberlyst 15. Of all the catalysts investigated, Purolite D5081 resin showed the best catalytic performance and was selected for further optimisation studies. From the optimisation study, it was found that the external and internal mass transfer resistance has negligible effect on the esterification reaction. At the optimum reaction conditions, Purolite D5081 achieved 92% conversion of FFA. During reusability study, the conversion of FFA dropped by 10% after each cycle and it was found that progressive pore blockage and sulphur leaching were dominant factors that decreased the catalytic performance of the Purolite D5081 catalyst. A kinetic modelling for FFA esterification was carried out using Purolite D5081 as a catalyst. Three types of kinetic models were investigated i.e. pseudo homogeneous (PH), Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHHW). Experimental data obtained from the batch kinetic studies was successfully represented by the PH model and a good agreement between experimental and calculated values was obtained. The activation energy for esterification and hydrolysis reaction was found to be 53 and 107 kJ/moL. The transesterification of pre-treated cooking oil (P-UCO) was investigated using various types of heterogeneous catalysts including Purolite CT-122, Purolite CT-169, Purolite CT-175, Purolite CT-275, Purolite D5081, Diaion PA306s and Cs-supported heteropolyacids catalysts. Of all the catalysts investigated, Diaion PA306s catalyst showed the highest conversion of triglycerides and was selected for further optimisation studies. At the optimum reaction conditions, Diaion PA306s achieved ca. 75% of triglycerides conversion. During the reusability study, Diaion PA306s catalyst gave a similar conversion of triglycerides after being reused once. Therefore, it was concluded that the resin can be used several times without losing catalytic activity. Several purification methods have been investigated and dry washing method was chosen as the best alternative for biodiesel purification.

In der vorliegenden Arbeit werden Al2O3-geträgerte Eisenoxid-Katalysatoren auf ihre Eignung in der Nachbehandlung von Dieselabgasen getestet. Hierbei werden die Oxidationsreaktionen von Kohlenmonoxid, Propen, Stickstoffmonoxid sowie Ammoniak getestet. Weiterhin wird die Katalysatoraktivität bei der Stickoxidminderung nach dem SCR-Verfahren untersucht. Basierend auf einer detaillierten Charakterisierung wird eine Struktur-Aktivitäts-Korrelation entwickelt, auf deren Basis ein Verständnis für die Art der aktiven Zentren solcher Katalysatoren generiert wird. Zudem wird ein Modell entwickelt, mit Hilfe dessen die spezifische Aktivität der verschiedenen Typen an aktiven Zentren bewertet werden kann. Darüber hinaus wird in dieser Arbeit auf die Stickoxidminderung nach dem SCR-Verfahren fokussiert, was die Untersuchungen des Reaktionsmechanismus sowie die Struktur-Aktivitäts-Korrelation an hydrothermal gealterten Katalysatoren beinhaltet.

Cette thèse s’intéresse à la conversion du glycérol en acide lactique (AL) et 1,2-propanediol (1,2-PDO) par catalyse hétérogène. Le mécanisme de la réaction fait débat, particulièrement au sujet de la première étape, qui peut être une déshydratation ou une déshydrogénation. Il est attendu que ces étapes élémentaires soient influencées par le pH et la nature de l’atmosphère. Ces paramètres ont donc été étudiés expérimentalement, en présence d’un catalyseur au rhodium supporté sur charbon. D’autre part, il y avait un manque de connaissances sur le comportement du glycérol à la surface métallique du catalyseur. Une approche théorique sur une surface modèle a donc été mise en oeuvre dans le champ de la théorie de la fonctionnelle de la densité (DFT), pour examiner les étapes élémentaires et calculer les états de transition correspondants. La combinaison de ces études a montré que la déshydrogénation du glycérol en glycéraldéhyde est la première étape de la réaction sur le catalyseur Rh/C en milieu basique sous atmosphère d’hélium et d’hydrogène. Cette étude a ensuite été étendue à un catalyseur iridium supporté sur charbon, qui a mené à de meilleurs rendements en 1,2-PDO et AL. L’utilisation de ce métal supporté sur carbonate de calcium a permis d’améliorer le rendement en AL, mais l’activité est plus faible. Cependant, ce catalyseur s’est révélé relativement actif dans l’eau à pH neutre, ce qui pourrait conduire à une synthèse plus verte de l’AL. Enfin, les aspects prédictifs de la chimie théorique ont été examinés, pour voir si la réactivité de ce polyol complexe (du point de vue de la chimie théorique) pouvait être modélisée par celle d’un monoalcool sur la surface. / This thesis reports a study of the heterogeneously catalysed conversion of glycerol into 1,2-propanediol (1,2-PDO) and lactic acid (LA). The mechanism and the first step of the reaction are especially debated, as it can be either dehydration or dehydrogenation. It is expected that these elementary steps can be influenced by pH variations and by the nature of the gas phase. These parameters were consequently investigated experimentally in the presence of a carbon supported rhodium catalyst. On the other hand, there was a lack of knowledge in the behaviour of glycerol at the surface of the metallic catalyst. A theoretical approach on a model Rh(111) surface was thus implemented in the framework of Density Functional Theory (DFT) to look over the alementary reactions and to calculate the corresponding transition states. The combination of experimental and theoretical results has shown that dehydrogenation into lyceraldehyde is the first step of the reaction on the Rh/C catalyst in basic media under He or H2 atmosphere. The study was then extended to carbon supported iridium catalyst that lead to the best 1,2-PDO and LA yields. The use of iridium catalyst supported on calcium carbonate allowed obtaining higher yields in LA, but catalytic performances were lower. This latter catalyst was surprisingly quite active when performing the reaction in neutral water, which provides opportunities for a greener synthesis of LA. Last, the predictive aspects of the theoretical chemistry were investigated to determine whether the reactivity of this polyalcohol can be modelized by the reactivity of a simpler monoalcohol on the surface.