Integrated biorefinery in continuous flow systems using sustainable heterogeneous catalysts

The negative impact of crude oil on the environment has led to a necessary transition toward alternative, renewable, and sustainable resources. In this regard, lignocellulosic biomass (LCB) is a promising renewable and sustainable alternative to crude oil for the production of fine chemicals and fuels in a so-called biorefinery process. LCB is composed of polysaccharides (cellulose and hemicellulose), as well as aromatics (lignin). The development of a sustainable and economically advantageous biorefinery depends on the complete and efficient valorization of all components. Therefore, in the new generation of biorefinery, the so-called biorefinery of type III, the LCB feedstocks are selectively deconstructed and catalytically transformed into platform chemicals. For this purpose, the development of highly stable and efficient catalysts is crucial for progress toward viability in biorefinery. Furthermore, a modern and integrated biorefinery relies on process and reactor design, toward more efficient and cost-effective methodologies that minimize waste. In this context, the usage of continuous flow systems has the potential to provide safe, sustainable, and innovative transformations with simple process integration and scalability for biorefinery schemes. This thesis addresses three main challenges for future biorefinery: catalyst synthesis, waste feedstock valorization, and usage of continuous flow technology. Firstly, a cheap, scalable, and sustainable approach is presented for the synthesis of an efficient and stable 35 wt.-% Ni catalyst on highly porous nitrogen-doped carbon support (35Ni/NDC) in pellet shape. Initially, the performance of this catalyst was evaluated for the aqueous phase hydrogenation of LCB-derived compounds such as glucose, xylose, and vanillin in continuous flow systems. The 35Ni/NDC catalyst exhibited high catalytic performances in three tested hydrogenation reactions, i.e., sorbitol, xylitol, and 2-methoxy-4-methylphenol with yields of 82 mol%, 62 mol%, and 100 mol% respectively. In addition, the 35Ni/NDC catalyst exhibited remarkable stability over a long time on stream in continuous flow (40 h). Furthermore, the 35Ni/NDC catalyst was combined with commercially available Beta zeolite in a dual–column integrated process for isosorbide production from glucose (yield 83 mol%). Finally, 35Ni/NDC was applied for the valorization of industrial waste products, namely sodium lignosulfonate (LS) and beech wood sawdust (BWS) in continuous flow systems. The LS depolymerization was conducted combining solvothermal fragmentation of water/alcohol mixtures (i.e.,methanol/water and ethanol/water) with catalytic hydrogenolysis/hydrogenation (SHF). The depolymerization was found to occur thermally in absence of catalyst with a tunable molecular weight according to temperature. Furthermore, the SHF generated an optimized cumulative yield of lignin-derived phenolic monomers of 42 mg gLS-1. Similarly, a solvothermal and reductive catalytic fragmentation (SF-RCF) of BWS was conducted using MeOH and MeTHF as a solvent. In this case, the optimized total lignin-derived phenolic monomers yield was found of 247 mg gKL-1

Deposition and assembly of magnesium hydroxide nanostructures on zeolite 4A surfaces

A deposition - precipitation method was developed to produce magnesium hydroxide / zeolite 4A (Mg(OH)₂ - Z4A) nanocomposites at mild conditions and the effect of processing variables such as precursor concentration, type of base added, and synthesis time on the composition, size, and morphology of the nanocomposite were studied. It was determined that the precursor concentration, basicity, and synthesis time had a significant effect on the composition, size, and morphology of the deposited magnesium hydroxide (Mg(OH)₂) nanostructures. The properties of the Mg(OH)₂ - Z4A such as surface area, pore volume and composition were characterized. Mg(OH)₂ - Z4A samples and bare zeolite 4A were dispersed in Ultem® polymer to form a mixed matrix membrane. The thermal and mechanical properties of the resulting films were investigated. It was found that the addition of rigid bare zeolites into the polymer decreased the mechanical properties of the polymer composite. However, some of these adverse effects were mitigated in the polymer composite loaded with Mg(OH)₂ - Z4A samples. Isotherms for the adsorption of Mg(OH)₂ petals on zeolite 4A were measured in order to determine the optimum conditions for the formation of magnesium hydroxide / zeolite 4A nanocomposites at ambient conditions. The loading of the Mg(OH)₂ can be determined from the adsorption isotherms and it was also found that the adsorption of Mg(OH)₂ on zeolite A occurs via 3 mechanisms: ion exchange, surface adsorption of Mg²⁺ ions, and surface precipitation of Mg(OH)₂. Without the addition of ammonium hydroxide, the predominant processes are ion exchange and surface adsorption of Mg²⁺ ions. In the presence of ammonium hydroxide, Mg(OH)₂ crystals are precipitated on the surface of zeolite 4A at moderate Mg²⁺ ions concentration and the loading of Mg(OH)₂ was found to increase with increasing Mg²⁺ ions concentration. A detailed examination of the interactions between Mg(OH)₂ and functional groups on the zeolite surface was conducted. Solid-state 29Si, 27Al, and 1H NMR spectra were coupled with FTIR measurements, pH and adsorption studies, and thermogravimetric analyses to determine the interactions of Mg(OH)₂ with surface functional groups and to characterize structural changes in the resulting zeolite after Mg(OH)₂ deposition. It was discovered that acid - base interactions between the weakly basic Mg(OH)₂ and the acidic bridging hydroxyl protons on zeolite surface represent the dominant mechanism for the growth of Mg(OH)₂ nanostructures on the zeolite surface.Ph.D.Committee Chair: Teja, Amyn; Committee Member: Deng, Yulin; Committee Member: Koros, William; Committee Member: Nair, Sankar; Committee Member: Tannenbaum, Rin

Divalent Metal Organic Frameworks as Heterogeneous Oxidation Catalysts

[ES] Se ha desarrollado un método de síntesis "verde" de compuestos metal orgánicos en medio acuoso, a temperatura y presión ambientes, fácilmente escalable y con tiempos de cristalización muy cortos (10 min). El método se ha aplicado con éxito a la síntesis de trimesatos de metales divalentes isoreticulares y con fórmula general M3(BTC)2·12 H2O (M = Ni2+, Co2+, Cu2+ y Zn2+; BTC = trimesato). La estructura de estos materiales presenta dos tipos de centros metálicos ("puente" y "ter-minales") en proporción 2 a 1, ambos con coordinación octaédrica y unidos a 4 moléculas de H2O y a dos oxígenos carboxilato del ligando. Usando este método de síntesis, se han preparado también series de compuestos bimetálicos isoreticulares de Co-Ni y Co-Zn en todo el rango de concentraciones, así como compues-tos de Mn-Ni con una concentración máxima de Mn2+ del 50%. Mediante la combinación de difracción de rayos X (en polvo y de monocristal) y microscopía EDX/SEM se ha demostrado que los compuestos bimetálicos forman verdaderas disoluciones sólidas (no meras mezclas de fases) y que los iones metálicos se dis-tribuyen homogéneamente en todo el cristal. Además, el análisis detallado de la variación de los parámetros de celda con la composición en compuestos Co-Ni y Co-Zn aporta fuertes evidencias de que los iones Co2+ ocupan preferentemente las posiciones "terminales". Se ha evaluado la actividad de los compuestos preparados como catalizadores para la oxidación aeróbica de cumeno (CM) a cumeno hidroperóxido (CHP). El com-puesto monometálico de Co2+, Co-BTC, presentó una elevada actividad, aunque la selectividad a CHP obtenida fue relativamente baja (69%), ya que los iones Co2+ catalizan también la descomposición del CHP formado. Una buena estrategia para optimizar esta selectividad consistió en aislar los iones Co2+ en una matriz de Ni-BTC (que es inerte tanto para la oxidación de CM como para la descomposición de CHP). Así, al disminuir la concentración de iones Co2+ en compuestos bimetálicos Co-Ni se observó un aumento de la selectividad a CHP de hasta el 91% para el material con un 5% de Co. Se ha calculado que estadísticamente el 73% de los iones Co2+ en este material se encuentran aislados, por lo que la des-composición/sobreoxidación del CHP se ve muy limitada. Usando una variación del método de síntesis, se han obtenido también compuestos isoreticulares de Co2+ en los que los ligandos trimesato se han reemplazado parcialmente por ligandos isoftálico o 5-aminoisoftálico. Al utilizar estos com-puestos como catalizadores para la oxidación aeróbica de CM, se ha observado que la introducción de este segundo ligando (y en particular del 5-aminoisoftálico) en la red metal-orgánica facilita la descomposición del CHP formado y aumenta la selectividad final a 2-fenil-2-propanol (PP). Esto se ha atribuido a la creación de defectos puntuales en la red del material, que presentan una mayor actividad para la descomposición de CHP. Siguiendo con la oxidación de CM como reacción modelo, se ha evaluado la actividad catalítica de compuestos isoreticulares de cobalto con ligandos bispirazolato funcionalizados con distintos grupos (CoBPZ, CoBPZ-NO2 y CoBPZ-NH2). En este caso se ha observado una clara influencia del ligando utilizado sobre la acti-vidad catalítica y la selectividad a CHP o PP del material. Mientras que el Co-BPZ presenta una baja conversión de CM y una elevada selectividad a CHP, Co-BPZ-NH2 presenta las características opuestas: una elevada velocidad de reacción pero una baja selectividad a CHP. En este último caso, el producto mayoritario forma-do es el PP. Por último, el estudio de MOFs de cationes divalentes como catalizadores de oxidación se ha completado con una reacción de síntesis de quinazolina mediante acoplamiento oxidativo de bencilamina y 2-aminoacetofenona usando TBHP co-mo oxidante. Como catalizadores para esta reacción se ha utilizado el trimesato de[CA] S'ha desenvolupat un mètode de síntesi "verda" de compostos metall orgànics en medi aquós, a temperatura i pressió ambients, fàcilment escalable i amb temps de cristal·lització molt curts (10 min). El mètode s'ha aplicat amb èxit a la síntesi de trimesats de metalls divalents isoreticular i amb fórmula general M3(BTC)2·12 H2O (M = Ni2+, Co2+, Cu2+ y Zn2+; BTC = trimesat). L'estructura d'aquests materials presenta dos tipus de centres metàl·lics ("pon" i "terminals") en una proporció de 2 a 1, ambdós amb coordinació octaèdrica i units a 4 molècules d'aigua i a 2 oxígens carboxilat del lligand. Emprant aquest mètode de síntesi, s'han preparat també sèries de compostos bimetàl·lics isoreticular de Co-Ni i Co-Zn en tot el rang de concentracions, així com compostos de Mn-Ni amb una concentració màxima de Mn2+ del 50%. Mitjançant l'ús combinat de difracció de raigs X (en pols i de monocristall) i microscòpia EDX/SEM s'ha demostrat que els compostos bimetàl·lics formen vertaderes dissolucions sòlides (no simples mescles de fase) i que els ions metàl·lics es distribueixen homogèniament en tot el cristall. A més, l'anàlisi detallat de la variació dels paràmetres de cel·la amb la composició de compostos Co-Ni i Co-Zn aporta fortes evidències de que els ions Co2+ ocupen preferentment les posicions "terminals". S'ha avaluat l'activitat dels compostos preparats com a catalitzador per a l'oxidació aeròbica de cumè (CM) a cumè hidroperòxid (CHP). El compost monometàl·lic de Co2+, Co-BTC, presenta una elevada activitat, encara que la selectivitat a CHP obtinguda és relativament baixa (69%), ja que els ions Co2+ catalitzen també la descomposició del CHP format. Una bona estratègia per optimitzar aquesta selectivitat consisteix en aïllar els ions Co2+ en una matriu de Ni-BTC (que és inert tant per a l'oxidació de CM com per a la descomposició de CHP). Així, a mesura que disminueix la concentració d'ions Co2+ en compostos bimetàl·lics Co-Ni s'observa un augment de la selectivitat a CHP de fins el 91% per al material amb un 5% de cobalt. S'ha calculat que estadísticament el 73% dels ions Co2+ d'aquest material es troben aïllats, de manera que la descomposició/sobreoxidació del CHP es veu molt limitada. Emprant una variació del mètode de síntesi, s'han obtingut també compostosisoreticulars de Co2+ en els que els lligands trimesat s'han reemplaçat parcialment per lligands isoftàlic o 5-aminoisoftàlic. Quan aquest compostos s'usen com a catalitzadors per a l'oxidació aeròbica de CM, sobserva que la introducció d'aquest segon lligand (i en particular del 5-aminoisoftàlic) en la xarxa metallorgànica es facilita la descomposició del CHP format i augmenta la selectivitat final a 2-fenil-2-propanol (PP). Això s'ha atribuït a la creació de defectes puntuals en la xarxa del material, que presenten una major activitat per a la descomposició del CHP. Seguint amb l'oxidació de CM com a reacció model, s'ha avaluat l'activitat catalítica de compostosisoreticulars de cobalt amb lligands bispirazolat funcionalitzats amb distints grups (CoBPZ, CoBPZ-NO2 i CoBPZ-NH2). En aquest cas s'ha observat una clara influència del lligand utilitzat sobre l'activitat catalítica i la selectivitat a CHP o PP del material. Mentre que el CoBPZ presenta una baixa conversió de CM i una elevada selectivitat a CHP, CoBPZ-NH2 presenta les característiques oposades: una elevada velocitat de reacció però una baixa selectivitat a CHP. En aquest últim cas, el producte majoritari format és el PP. Per últim, l'estudi de MOFs amb cations divalent como a catalitzadors d'oxidació s'ha completat amb una reacció de síntesi de quinazolina mitjançant acoblament oxidatiu de benzilamina i 2-aminoacetofenona emprant TBHP como a oxidant. Com a catalitzadors per aquesta reacció s'ha utilitzat el trimesat de coure, HKUST-1, així com materials isoreticular amb lligands mixtes obtinguts reemplaçant pa[EN] A "green" synthesis method has been developed for the preparation of metal organic frameworks in aqueous media, which is easily scalable, at room tempera-ture, ambient pressure and very short crystallization times (10 min). This method has been successfully applied to the synthesis of isoreticular divalent metal trimesates of general formula M3(BTC)2·12 H2O (M = Ni2+, Co2+, Cu2+ y Zn2+; BTC = trimesate). The structure of these compounds features two types of metal centers ("bridging" and "terminal") in a 2 to 1 ratio, both with octahedral coordina-tion and linked to 4 water molecules and 2 carboxylate oxygens of the ligand. Using this method, two series of bimetallic isoreticular compounds of Co-Ni and Co-Zn have also been prepared in all range of compositions, as well as bimetallic Mn-Ni compounds up to a maximum concentration of 50% of Mn2+. A combined X-ray diffraction (powder and single crystal) and EDX/SEM has shown that these bimetallic compounds form true solid solutions (not simple mixture of phases) and that both ions distribute homogeneously throughout the crystal. A detailed analysis of the variation of cell parameters with the composition strongly sug-gests that Co2+ ions occupy preferentially the "terminal" positions of the frame-work. The materials obtained with the above method have been evaluated as catalysts for the aerobic oxidation of cumene (CM) to cumene hydroperoxide (CHO). The monometallic Co2+ compound, Co-BTC, showed a high catalytic activity, but a relatively low selectivity to CHP 69%), since the Co2+ ions can also catalyze the decomposition of the formed CHP. A good strategy to optimize the CHP selectivity consisted in isolating the Co2+ ions into a Ni-BTC (which is inert for both CM oxidation and CHP decomposition). In this way, as the concentration of Co2+ ions in the bimetallic Co-Ni compound decreases, a parallel increase of the CHP selec-tivity was observed, up to 91% for the material with 5% of Co. In this compound, 73% of the total Co2+ ions are statistically isolated, so that decomposi-tion/overoxidation of CHP is unlikely to occur. By using a variation of the above synthesis method, additional isoreticular Co2+ compounds have been prepared in which the trimesate ligands have been partially replaced by either isophthalic or 5-aminoisophthalic. When these compounds were used as catalysts for the aerobic oxidation of cumene, we observed that the introduction of this second ligand (in particular in the case of 5-aminoisophthalic) into the framework facilitates decomposition of CHP and in-creases the final selectivity to 2-phenyl-2-propanol (PP). This has been attributed to the progressive creation of point defects in the framework, having a higher activity for CHP decomposition. Following with the aerobic oxidation of CM as model reaction, we evaluated the catalytic activity of isoreticular cobalt compounds having bispyrazolate ligands bearing differnent functional groups (CoBPZ, CoBPZ-NO2 and CoBPZ-NH2). In this case, there is a clear influence of the ligand used on the catalytic activity of the material and the obtained selectivity to CHP or PP. While CoBPZ showed a low CM conversion and high CHP selectivity, the opposite properties are obtained for the Co-BPZ-NH2: i.e., a high reaction rate but a low CHP selectivity. In this latter case, the major product of the reaction was PP. Finally, the evaluation of divalent MOFs as oxidation catalysts has been complet-ed by addressing the synthesis of quinazoline through the oxidative coupling reaction of benzylamine and 2-aminoacetophenone using TBHP as oxidant. As catalysts for this reaction we have used a copper trimesate, HKUST-1, as well as isoreticular mixed-ligand compounds obtained by partially replacing trimesate ligands by 5-hydroxyisophthalic (OH-isophthalic).Nowacka, AE. (2019). Divalent Metal Organic Frameworks as Heterogeneous Oxidation Catalysts [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/129872TESI

Catalytic Behavior of Metal-Organic Framework UiO-66 in Conversion of Saccharide Biomass

UiO-66 (Universitet i Oslo 66) is a zirconium-based metal-organic framework (MOF) material. Due to the superior thermal, chemical and mechanical stability, UiO-66 is one of the most attractive MOF platforms to enabling catalysis. This thesis explored the catalytic behavior of UiO-66 in saccharide biomass conversion. The Brønsted acidity in UiO-66 enabled depolymerization of inulin into monosaccharides, which has distinct high activity than inorganic BEA zeolite and aqueous hydrogen chloride (HCl) acid catalysts. The catalytic mechanism of UiO-66 stays in-between pore mouth catalysis and random chain splitting which are prevalent mechanisms in BEA and HCl acid, respectively. The UiO-66 was further explored as catalyst for synthesis of alkyl lactates from saccharide biomass via one-pot multiple step reaction approach. The Lewis and Brønsted acidity in UiO-66 enabled this reaction network, and produced methyl and ethyl lactate from methanol and ethanol solvents by using mono-, di- and polysaccharide feedstocks

Metal-Organic Frameworks and Covalent Organic Frameworks as single site catalysts for organic transformations

Els Metal-Organic frameworks (MOFs) i Covalent Organic Frameworks (COFs) són nous tipus de materials porosos que han atret una gran atenció a causa de la seva combinació única de propietats: alta porositat, bona estabilitat química, estructures ben ordenades i gran capacitat d'ajustament estructural. Entre les seves aplicacions possibles, la catàlisi és una de les més prometedores a causa del potencial dels MOFs i COFs per formar catalitzadors de centre únic que estan ben definits i romanen accessibles en estat sòlid. En aquesta línia de recerca, aquesta tesi té com a objectiu desenvolupar i estudiar nous catalitzadors basats en MOFs i COFs per a transformacions orgàniques. El treball presentat en aquesta tesi mostra un mètode simple per immobilitzar lligands de perilè fotocatalíticament actius dins de MOF-520, cosa que permet estudiar els lligands com a unitats aïllades i emprar els MOF com a fotocatalitzadors heterogenis per a l'acoblament reductiu d'enllaços C=O i C =N. Aquesta tesi també descriu la síntesi i caracterització d'una sèrie de COFs que porten lligands donadors de N a la seva estructura. La incorporació de Co a aquestes estructures va donar com a resultat MCOFs, que es van emprar com a catalitzadors d'hidroboració i borilació. Finalment, es van fer estudis per explorar la naturalesa de centre únic dels centres catalítics. Aquest treball mostra el potencial de MOF i COF com a catalitzadors heterogenis eficients i reciclables per a transformacions orgàniques i aplana el camí per al desenvolupament de nous sistemes catalítics de centre únic.Los Metal-Organic frameworks (MOFs) y Covalent Organic Frameworks (COFs) son nuevos tipos de materiales porosos que han atraído una gran atención debido a su combinación única de propiedades: alta porosidad, buena estabilidad química, estructuras bien ordenadas y gran capacidad de ajuste estructural. Entre sus muchas aplicaciones posibles, la catálisis es una de las más prometedoras debido al potencial de MOFs y COFs para formar catalizadores de centro único que estén bien definidos y permanezcan accesibles en estado sólido. En esta línea de investigación, la presente tesis tiene como objetivo desarrollar y estudiar nuevos catalizadores basados en MOFs y COFs para transformaciones orgánicas. El trabajo presentado en esta tesis muestra un método simple para inmovilizar ligandos de perileno fotocatalíticamente activos dentro de MOF-520, lo que permite estudiar los ligandos como unidades aisladas y emplear los MOF como fotocatalizadores heterogéneos para el acoplamiento reductivo de enlaces C=O y C=N. Esta tesis también describe la síntesis y caracterización de una serie de COFs que portan ligandos donantes de N en su estructura. La incorporación de Co en estas estructuras dio como resultado MCOFs, que se emplearon como catalizadores de hidroboración y borilación. Finalmente, se realizaron estudios para explorar la naturaleza de centro único de los centros catalíticos. Este trabajo muestra el potencial de MOF y COF como catalizadores heterogéneos eficientes y reciclables para transformaciones orgánicas y allana el camino para el desarrollo de nuevos sistemas catalíticos de centro único.Metal-organic frameworks (MOFs) and Covalent Organic Frameworks (COFs) are new types of porous materials that have attracted great attention due to their unique combination of properties: high porosity, good chemical stability, well-ordered structures and great structural tuneability. Among their many possible applications, catalysis is one of the most promising due to the potential of MOFs and COFs to form single-site catalysts that are well defined and remain accessible in the solid state. In this line of research, the current thesis aims to develop and study new MOF and COF-based catalysts for organic transformations. The work presented in this thesis shows a simple method to immobilize photocatalytically active perylene ligands inside MOF-520, allowing this way to study the ligands as isolated units, and to employ the MOFs as heterogeneous photocatalysts for the reductive coupling of C=O and C=N bonds. This thesis also describes the synthesis and characterization of a series of COFs bearing N-donor ligands in their structure. Incorporation of Co into these structures resulted in MCOFs, which were employed as hydroboration and borylation catalysts. Finally, studies were performed to explore the single-site nature of the catalytic centers. This work showcases the potential of MOFs and COFs as efficient and recyclable heterogeneous catalysts for organic transformations, and paves the way for the development of new single-site catalytic systems

Catalytic Methods in Flow Chemistry

The chemical industry is essential in the daily humn life of modern society; despite the misconception about the real need for chemical production, everyone enjoys the benefit of the chemical progress. However, the chemical industry generates a large variety of products, including (i) basic chemicals, e.g., polymers, petrochemicals, and basic inorganics; (ii) specialty chemicals for crop protection, paints, inks, colorants, textiles, paper, and engineering; and (iii) consumer chemicals, including detergents, soaps, etc. For these reasons, chemists in both acdemia and industry are challenged with developing green and sustainable chemical production towrad the full-recycling of feedstocks and waste. Aiming to improve the intensification of the process, chemists have established chemical reactions based on catalysis, as well as alternative technologies, such as continuous flow. The aim of this book is to cover promising recent research and novel trends in the field of novel catalytic reactions (homogeneous, heterogeneous, and enzymatic, as well as their combinations) in continuous flow conditions. A collection of recent contribution for conversion of starting material originated from petroleum resources or biomass into highly-added value chemicals are reported

Zeolites: A Theoretical and Practical Approach with Uses in (Bio)Chemical Processes

This review provides a state-of-the-art summary of distributed zeolite technology, as well as identifying strategies to further promote the absorption of these materials in various areas of study. Zeolites are materials that can be synthesized or found in natural rock deposits a with a basic composition consisting in Al, Si, and O. Zeolite’s consideration as a future material is due to many facile synthesis methods to obtain different structures with variations in pore size, surface area, pore volume and physical properties. These methods are developed using the control of relevant synthesis parameters that influences structure formation, such as crystallization temperature, time of aging and/or crystallization, stoichiometric relationships between components of synthesis gel, pH of the medium, and in some cases the type of structure-directing agent. Each method will lead to geometric changes in the framework formation, making possible the formation of typical chemical bonds that are the fingerprint of any zeolitic structure (O-Si-O and Al-O-Si), forming typical acid sites that give specificity in zeolite and allows it to act as a nanoreactor. The specificity is a characteristic that in some cases depends on selectivity, a fundamental property derived of the porosity, mostly in processes that occur inside the zeolite. In processes outside the structure, the surface area is the main factor influencing this property. Moreover, there are many natural sources with adequate chemical composition to be used as precursors. Some of these sources are waste, minimizing the deposition of potential hazardous materials that can be recalcitrant pollutants depending on the environment. Besides its uses as a catalyst, zeolite serves as a support for many bioprocesses; therefore, this review aims to explain relevant aspects in chemical nature, physical properties, main methods of synthesis, main precursors used for synthesis, and relevant applications of zeolites in chemical catalysis and biological processes

NMR-Spectroscopic Investigations in Brønsted Acid Catalysis.

Die Arbeit befasst sich hauptsächlich mit der NMR-spektroskopischen Untersuchung von binären Komplexen bestehend aus chiralen Brønstedsäure Katalysatoren und Iminen. Dazu wurden Tieftemperaturmessungen bei bis zu 130 K durchgeführt und die Strukturen der untersuchten Komplexe mit Hilfe von NOE Analysen identifiziert und mit durch DFT berechneten Strukturen verglichen. Des Weiteren wurden die Wasserstoffbrückenbindungen der Komplexe durch Messung der skalaren Kopplungen über die Wasserstoffbrücke und durch Anfertigung einer Steiner-Limbach Kurve beschrieben und die daraus resultierende Geometrie untersucht. Auch hier erfolgte der Vergleich mit theoretischen Rechnungen. Weiterhin wurde der Einfluss der Substituenten der Katalysatorklasse auf die Reaktivität und Selektivität der Transferhydrierung von Iminsubstraten untersucht. Dazu wurde die Struktur eines weiteren chiralen Brønstedsäure Katalysators im binären Komplex mit Iminen aufgedeckt und die Wasserstoffbrücken von insgesamt drei Katalysatoren in Komplexen mit verschiedenen Iminen analysiert und diskutiert. Zusätzlich erfolgte die Untersuchung und Aufklärung des Mechanismus einer solvothermalen Syntheserute für Chinolinderivate mit Hilfe von NMR-Spektroskopie

Design of modified metal-organic frameworks for the catalytic application in liquid phase fine chemistry

Due to the highly versatile design, the defined metal sites and the high porosity, metal-organic frameworks (MOFs) are interesting materials for catalytic applications combining the beneficial characteristics of homogeneous and heterogeneous catalysts. In the present thesis, novel concepts for the synthesis and modification of metal-organic frameworks were developed to obtain innovative and highly active heterogeneous catalysts