Dissertations / Theses on the topic 'Magnetic heterogeneous catalyst'

L'impact environnemental dû à l'utilisation de carburants et de lubrifiants non renouvelables, associé aux préoccupations liées au changement climatique, a accru la demande de sources d'énergie durables. Les produits d'origine biologique, tels que le biodiesel et les biolubrifiants, sont apparus comme des alternatives aux carburants et lubrifiants minéraux en raison de leur disponibilité, de leur caractère renouvelable, de leurs faibles émissions de gaz, de leur non-toxicité et de leur biodégradabilité. Bien que le biodiesel et les biolubrifiants soient généralement produits par la réaction de transestérification avec des catalyseurs homogènes dans des réacteurs conventionnels, deux défis principaux restent à relever. D’abord, l'utilisation de catalyseurs homogènes nécessite de nombreuses et coûteuses étapes de purification. Les catalyseurs hétérogènes qui ont une surface de contact élevée et qui sont réutilisables et faciles à séparer constituent une solution prometteuse pour pallier ces difficultés. Ensuite, la réaction de transestérification est une réaction lente nécessitant un bon transfert de masse entre les deux liquides non miscibles, l’huile et le méthanol. La production de biodiesel dans des réacteurs agités est souvent limitée, en raison d’une surface d’échange réduite entre les phases et des temps de réaction longs. Il en résulte une faible teneur en biodiesel et la formation de produits secondaires indésirables. Des systèmes de mélange qui favorisent un meilleur contact liquide-liquide afin d'intensifier la réaction de transestérification méritent d’être explorés.L'objectif de cette étude est d’examiner comment améliorer la production de biodiesel et de biolubrifiants via deux manières différentes: en développant un nouveau catalyseur hétérogène et en utilisant un système d’agitation vibrant. Tout d'abord, un catalyseur hétérogène appelé « charbon actif magnétique », dérivé de déchets de coquilles d'amandes et modifié par de l'oxyde de calcium (MAC@CaO), a été synthétisé. Ensuite, le potentiel du MAC@CaO comme catalyseur récupérable pour les réactions de transestérification a été exploré, en se concentrant sur la production d'ester méthylique d'acide gras (EMAG) et de triester de triméthylolpropane (TMPTE). Les conditions optimales de réaction ont permis d'obtenir des rendements en EMAG et en TMPTE de 93,2 % et 95,3 %, respectivement. La recyclabilité du catalyseur MAC@CaO a également été évaluée afin de déterminer sa stabilité chimique. Les rendements en FAME et TMPTE sont restés constamment supérieurs à 85% pendant cinq cycles consécutifs, montrant ainsi le potentiel du nouveau catalyseur. Dans la deuxième partie de cette thèse, le système d’agitation vibrant a été caractérisé afin d'évaluer ses capacités de mélange en monophasique et en multiphasique (solide-liquide et liquide-liquide-solide). L'objectif était de mieux comprendre le fonctionnement de ce système en évaluant le temps de mélange, ses performances pour les suspensions liquide-solide et la production d'émulsions de Pickering. Les résultats montrent que le mélange en monophasique et la suspension des solides sont facilités lorsque l'amplitude des vibrations et le diamètre de la plaque du mélangeur augmentent. Les émulsions de Pickering ont une stabilité supérieure à deux mois. Ensuite, les résultats des expériences de synthèse de biodiesel ont montré une tendance similaire. L'augmentation de l'amplitude des vibrations, du diamètre de la plaque et du nombre de trous coniques dans la plaque s'est accompagnée d'une augmentation de la teneur en EMAG. La teneur maximale en FAME atteinte était de 97,8 % après seulement 30 minutes, durée équivalente ou plus courte qu’avec un réacteur agité. Ce résultat s’explique par une bonne circulation du flux et par une rupture efficace des gouttelettes, ce qui améliore de manière significative les processus de transfert de masse impliqués dans la réaction de transestérification des triglycérides en EMAG
The environmental impact caused by the use of non-renewable fuel and lubricant resources, coupled with concerns about climate change, has increased the demand for sustainable energy sources. Biobased products, such as biodiesel and bio-lubricants, have emerged as alternatives to mineral fuels and lubricants due to their availability, renewability, lower gas emissions, non-toxicity and biodegradability. Although biodiesel and bio-lubricants are typically produced through the transesterification reaction with homogeneous catalysts in conventional stirred-tank reactors, there are two primary challenges associated with each of these processes. Firstly, the use of homogeneous catalysts requires numerous and costly purification steps. Heterogeneous basic catalysts that have high surface area and that are reusable and easy to separate are a promising solution to mitigate these challenges. Secondly, the transesterification reaction is a slow mass-transfer limited reaction that involves two immiscible liquids, specifically triglyceride and methanol. For biodiesel production in stirred-tank reactors there are many associated challenges such as inadequate mixing, limited interfacial area between liquids and long process times. This results in low biodiesel content and the formation of undesirable secondary products. Alternate mixing equipment that improves liquid-liquid contacting to intensify and enhance the transesterification may be required.The objective of this study is to explore two different ways to enhance biodiesel and biolubricant production: by developing a new heterogeneous catalyst and by using a vibromixer to enhance mixing. Firstly, a heterogeneous basic catalyst named magnetic activated carbon, derived from almond shell waste and modified by calcium oxide (MAC@CaO), was synthesized. The resulting material underwent comprehensive characterization using various techniques. Subsequently, the potential of the MAC@CaO as a recoverable basic catalyst in transesterification reactions was explored, focusing on the production of fatty acid methyl ester (FAME) and trimethylolpropane triester (TMPTE). Optimal reaction conditions yielded FAME and TMPTE yields of 93.2% and 95.3%, respectively. The recyclability of the MAC@CaO catalyst was also assessed to determine its chemical stability. FAME and TMPTE yields remained consistently above 85% over five consecutive cycles, highlighting the potential of the developed catalyst. In the second part of this thesis, the vibromixer underwent comprehensive testing to evaluate its mixing capabilities for both single-phase and multiphase (solid-liquid and liquid-liquid-solid) mixing operations. The objective of this assessment was to gain a better understanding of the vibromixer device for various mixing processes by quantify mixing time, cloud height, and Pickering emulsion production before applying it to biodiesel production. The results show that single phase mixing and solids suspension improve when increasing the vibration amplitude and mixer plate size. Pickering emulsions characterized with small droplet sizes (approximately 2 microns) have a stability exceeding two months. Subsequently, the results from the biodiesel production experiments using the vibromixer demonstrated a similar trend. With an increase in vibration amplitude, plate size and the number of conical holes in the plate, the FAME content also increased. The maximum FAME content achieved was 97.8% after only 30 minutes; this is equivalent or shorter than for stirred tank reactors. It is expected that the enhanced reaction is due to good flow circulation and excellent breakup of droplets, which consequently increases interfacial area and significantly improves the mass transfer processes involved in the transesterification reaction of triglycerides into FAMEs

O presente trabalho descreve a preparação de catalisadores magnéticos para aplicação nos processos de fotocatálise heterogênea e ozonização catalítica heterogênea, visando a degradação de poluentes emergentes. Primeiramente buscou-se preparar nanopartículas magnéticas para posterior aplicação no preparo de catalisadores magnéticos de TiO2. Diversas variáveis experimentais foram avaliadas na preparação das nanopartículas magnéticas, tais como: temperatura de reação, tempo de agitação, tempo no ultrasom, velocidade de agitação, velocidade de agitação da base, tempo de agitação do estabilizante, concentração da base e do estabilizante. A influência destes parâmetros de preparação no diâmetro hidrodinâmico e distribuição de tamanho das partículas foi avaliada por meio de um planejamento estatístico. Dependendo das condições experimentais, obteve-se materiais com um tamanho médio variando entre 11 e 36 nm e entre 23% e 77% de distribuição de tamanho. Na condição otimizada, obteve-se partículas com um tamanho médio, obtido pela técnica de espalhamento de luz dinâmico, de 18 nm e 21% de distribuição. O nanomaterial magnético foi utilizado para preparar os catalisadores híbridos Fe3O2@TiO2 e Fe3O4@SiO2@TiO2. Os materiais foram caracterizados por difratoemtria de raios-X (XRD), microscopia de varredura (MEV) e transmissão (TEM), espectroscopia no infravermelho (FT-IR), análise térmica (TG e DTA), espectrometria de emissão óptica (ICP-OES), medidas de área superficial (BET) e espalhamento dinâmico de luz (DLS). Os catalisadores magnéticos foram empregados na degradação dos poluentes emergentes paracetamol; 4-metilaminoantipirina (4-MAA); ibuprofeno; 17 β-estradiol; 17 α-etinilestradiol, e do fenol. Nos processos de degradação também variou-se o efeito do pH nas respostas dos sistemas. De maneira geral, o material Fe3O4@TiO2 apresentou atividade catalítica nos processos de degradação fotoquímica e de ozonização, com desempenho similar ou, em alguns casos, superior ao TiO2. Em relação a 4-MAA, obteve-se, em 60 minutos de tratamento, 25% de mineralização para o processo de fotólise e 66% para o processo de fotocatálise empregando Fe3O4@TiO2. Para o processo de ozonização em pH 3, obteve-se, em 180 minutos de tratamento, 40 e 60% de mineralização para o processo não catalítico e o processo catalítico empregando Fe3O4@TiO2, respectivamente. Os resultados utilizando-se TiO2 foram semelhantes à ozonização não catalítica, o que demonstra o efeito positivo do núcleo magnético para a atividade do material. Assim, o material híbrido multifuncional Fe3O4@TiO2 mostrou-se eficiente para a degradação de poluentes emergentes empregando-se os processos de fotocatálise e de ozonização catalítica heterogênea, possibilitando uma adicional praticidade de separação do meio de tratamento.
The present work describes the preparation of magnetic catalysts for application in heterogeneous photocatalysis and heterogeneous catalytic ozonation processes, aiming the degradation of emerging pollutants. Magnetic nanoparticles were prepered as substratum of magnetic TiO2 catalysts. Several experimental variables were evaluated in the preparation of the magnetic nanoparticles, such as temperature, stirring time, sonication time, precipitation reaction stirring speed, base addition rate, dispersion stirring time, base concentration and stabilizer percentage. The influence of these parameters on particle hydrodynamic diameter and size distribution were measured by a statistical design. Depending on the experimental conditions, materials with an average size ranging between 11 nm and 35 nm and distribution between 23% and 77% were obtained. In the optimum preparation conditions, Fe3O4 magnetic particles with a hydrodynamic diameter of 18 nm and 21% distribution were obtained. The magnetic nanomaterial was used to prepare the hybrid catalysts Fe3O4@TiO2 and Fe3O4@SiO2@TiO2. The prepared materials were characterized by X-ray diffraction (XRD), field-emiss ion scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG), differential thermal analysis (DTA), inductively coupled plasma optical emission spectrometry (ICP-OES), BET specific surface area and dynamic light scattering (DLS). The magnetic catalysts were employed in the degradation of the emerging pollutants paracetamol; 4-methylaminoantipyrin (4-MAA); ibuprofen; 17 β-estradiol; 17 α-ethinyl estradiol, and phenol. In the treatment processes the effect pH on the systems was also varied. In general, the material Fe3O4@TiO2 showed catalytic activity in the processes of photochemical degradation and ozonation, with performance similar or, in some cases, superior to TiO2. For example, the 4-MAA mineralization, after 60 minutes of treatment, by the photolysis process reached a m aximum value of 25%. In the same treatment time by the photocatalytic process using Fe3O4@TiO2 it was obtained 66% of 4-MAA mineralization. For the ozonation process, in pH 3, after 180 minutes of treatment, 40% of 4-MAA mineralization was achieved by non-catalytic method. On the other hand, in the same treatment time employing Fe3O4@TiO2, 60% of 4-MAA mineralization was obtained. In addition, for the ozonation process using TiO2 similar results to non-catalytic ozonation were observed, which demonstrates the positive effect of the magnetic core for the activity of the catalyst. Thus, the hybrid material Fe3O4@TiO2 was efficient for the degradation of emerging pollutants employing the photocatalysis and heterogeneous catalytic ozonation processes, allowing an additional practicality for separating the catalyst from the treatment medium.

Surface catalysed reactions play an important role in chemical productions. Developments of catalyst requiring high activity whilst improving on product selectivity can potentially have a profound effect in the chemical industry. Traditional catalyst modifications were focused on tuning the size, shape and foreign metal doping to form well defined metal nanoparticles of unique functionalities. Here, we show new approach to engineering of metal nanocatalysts via a subsurface approach can modify the chemisorption strength of adsorbates on the surface. Carbon modified nanoparticles were synthesised using glucose to stabilise Pd nanoparticles at a molecular level. Upon heat treatment, the carbonised glucose encapsulated the Pd nanoparticles with carbon atoms take residence in the octahedral holes (15 at.%). These materials were tested in liquid phase stereoselective hydrogenations of 3-hexyn-1-ol and 4-octyne. The former has importance in the fragrance industry towards the production of leaf fragrance alcohol. It was shown for the first time that the geometrically and electronically modified Pd with interstitial carbon atoms reduced the adsorption energy of alkenes, ultimately leading to higher reaction selectivity. Boron modified Pd nanoparticles was synthesised using BH₃.THF in the liquid phase. The material possess high B interstitial saturation (20 at.%), which can be synthesised for the first time below 100°C. These materials were tested in the liquid phase selective hydrogenation of various alkynes and 2-chloronitrobenzene, of which the latter has importance in the pesticides industry. Kinetic modelling on the hydrogenation of 4-octyne suggests these subsurface occupied B does play a pivotal role on increasing the reaction selectivity, as removal of these species lead to decreased selectivity. Au nanoparticles were synthesised and characterised using H¹³COOH NMR. The new liquid NMR characterisation method is successfully applied to examine the chemisorption strength of metal nanoparticles. An attempt to synthesise PVP capped B modified Pd nanoparticles with the above NMR characterisation was investigated. It is believed the examples of subsurface atom modifications as shown here may offer future catalyst developments in this area.

Nano-deposits of Ni and Co, supported on porous oxide materials, serve as heterogeneous catalysts within Johnson-Matthey plc. in the steam reforming and Fischer-Tropsch processes, with the size, shape and dispersity of the metal crystallites linked to the catalytic profile. Here we study the magnetic properties of nickel systems synthesised on the nano-scale, with the aim of developing an industrially viable technique by which the diameter of the nickel species can be evaluated. A series of nickel nanoparticles, synthesised via the thermal decomposition of Ni(acac)2, are studied as a model for the catalytic systems. The nanoparticles were studied via magnetometry and microscopy to identify the super-paramagnetic and nuclear volume of the particles, respectively. The magnetisation studies demonstrate that the widely used Langevin function based method of particle sizing does not reflect the total nuclear volume, and a surface correction term is introduced based on the low temperature, high applied field magnetisation. To demonstrate the applicability of the proposed analysis, the study of a series of industrially-viable precipitation catalysts are reported. The catalysts are studied via x-ray diffraction (XRD) and gas adsorption to establish comparable values of crystallite diameter. The values of crystallite diameter determined from the magnetic analysis are demonstrated to be consistent with the range of sizes determined from the XRD and gas adsorption studies, with additional sensitivity to the polydispersity of the crystallites. During the study of the precipitation catalysts, the magnetic volume was demonstrated to be reduced from the nuclear volume. This behaviour was also confirmed via small angle neutron scattering experiments, which demonstrated a magnetic scattering volume reduced from the nuclear by = 1 nm, on the order previously reported for nano-ferromagnetic materials. Through these studies we have established the methods for determining the surface correction term to magnetic granulometry studies. We have demonstrated that the corrected values are in agreement with the nuclear volumes determined via TEM, gas adsorption and XRD and that our proposed technique for the study of catalyst crystallites requires a short time scale, is insensitive to the catalytic support and is sensitive to the distribution of crystallite diameters.

Les réactions pallado-catalysées permettant la formation de liaisons carbone-carbone trouvent de nombreuses applications en synthèse organique et constituent l'étape clé de la synthèse d'un grand nombre de molécules. La première partie de cette thèse décrit la préparation et l'étude de catalyseurs hétérogènes et réutilisables comportant du palladium supporté sur un polymère portant des groupements phosphinés, polymère dérivé soit d'une résine de Merrifield soit d'une résine Rasta. De très bons résultats ont été obtenus pour leur utilisation dans les couplages croisés de Hiyama, Heck et Suzuki et dans chaque cas la possibilité de réutilisation jusqu'à 4 fois du catalyseur a été vérifiée. Notre travail constitue une des premières utilisations d'un catalyseur réutilisable dans le couplage de Hiyama. Nous avons aussi mis au point des conditions permettant d'effectuer le couplage de Heck en présence d'une quantité infime de palladium. Notre étude sur les résines Rasta constitue la première application de ces supports en pallado-catalyse. La deuxième partie de la thèse décrit l'étude de la préparation de catalyseurs où le palladium serait supporté sur des nanoparticules superparamagnétiques et qui pourraient donc être récupérés de tout milieu réactionnel grâce à un champ magnétique externe. Des nanoparticules de cobalt ont été préparées puis recouvertes de pyrocarbone par dépôt chimique en phase vapeur. Des groupements organiques ont été fixés sur la coque de carbone, ce qui permet l'introduction de ligands phosphinés. La structure de ces particules a été étudiée par microscopie électronique en transmission et leur préparation optimisée en fonction des résultats structuraux.

The first experimental work discussed in this thesis is a series of reaction studies to look at the effect of four solvents - methanol, propan-1-ol, propan-2-ol and octanol - on the hydrogenation of 4-tertiary butyl phenol (TBP). Experiments are first done in a stirred pot-type reactor with two different sized catalyst particles and the rate and selectivity were compared. The same reaction was also performed in a small trickle bed reactor so that the effect of the reactor could be considered along with the effect of particle size and solvent. The next three areas of experimental work, use NMR to examine the effect of the four solvents on mass transport issues. Firstly the diffusion of solvents within alumina pellets is investigated using a technique known as pulsed-field gradient (PFG) NMR. A two component model is fitted to the data and is explained on the basis that the larger diffusion coefficient gives the pore (or ordinary) diffusion rate, while the smaller diffusion coefficient gives a rate of diffusion which is reduced due to the effect of interaction with the pore wall. The same technique is then exploited to study the effect of the solvent on diffusion of TBP in liquid mixtures. In particular, the effect of concentration is considered, and models for diffusion at infinite dilution are compared with data extrapolated from experimental data. Strong association is seen between the TBP and the smaller polar solvents which weakens with increasing alcohol solvent size. The effect of temperature on the diffusion of solvents is effectively modelled by an Arrhenius equation. Magnetic Resonance Imaging (MRI) is used to look at the effect of the solvent on the hydrodynamics during trickle flow. 2D cross-sectional images were taken through the trickle bed were taken and algorithms were developed and applied to calculate the hold-up and wetting efficiency for each solvent over at least five different liquid flowrates. The solvents were then ranked based on these characteristics and trends seen between solvents were found mainly to depend on the viscosity of the solvent.

In this manuscript, the application of different nanocatalysts derived from metal oxides impregnated on the surface of the magnetite in different reaction of general interest in Organic Chemistry is described. In the First Chapter, a cobalt derived catalyst was used to study the hydroacylation reaction of azodicarboxylates with aldehydes. In the Second Chapter, a catalyst derived from copper was used to perform different reactions, including homocoupling of terminal alkynes and the subsequent hydration reaction to obtain the corresponding 2,5-disubstituted benzofurans, the reaction of alcohols and amines (or nitroarenes) to obtain the corresponding aromatic imines, the cross-dehydrogenative coupling reaction of N-substituted tetrahydroisoquinolines using deep eutectic solvents and air as final oxidant. Finally, the formation of benzofurans from aldehydes and alkynes through a tandem coupling-allenylation-cyclization process has been performed. In the Third Chapter, a bimetallic catalyst derived from nickel and copper was used to study the multicomponent reaction between benzyl bromides, sodium azide and alkynes to obtain the corresponding triazoles. In the Fourth Chapter, a catalyst derived from palladium was used in the direct arylation of heterocycles using iodonium salts. Also the synthesis of 4-aryl coumarins through the Heck arylation reaction and subsequent cyclization using the same catalyst is described. In the last Chapter, the use of different eutectic mixtures were studied as alternative media to perform in a single vessel the cyclation reaction of N-hydroxy imidoyl chlorides and alkynes, without any type of catalyst under oxidizing conditions.

This thesis describes the preparation and characterization of core-shell noble metal-magnetite hybrid hollow nanocomposites utilizing hierarchical architecture. The hollow magnetite (hFe3O4) nanoparticles were prepared by hydrothermal method, forming the cavity via Oswald ripening. Further surface modifications involved both inorganic and organic coatings, conferring the intracellular drug delivery ability and the catalytic enhancement. In the first part, a series of hierarchical core-shell nanostructures flower-like hFe3O4@AlOOH was synthesized through solvothermal method and sol-gel process. The formation of cavity accessible hFe3O4@γ-AlOOH was achieved using silica-templated solvothermal treatment where the Kirkendall effect was observed. The morphologies of the as-prepared nanocomposites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). Then, the nano-encapsulation of platinum drug using hollow magnetite and its derivatives, has been developed with improved loading efficiency via co-solvent system. A dimethylformamide/water co-solvent system was found to be the most efficient system to encapsulate water-insoluble cisplatin. The platinum content was further quantitatively and qualitatively analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and FTIR spectroscopy. The enhancement of loading efficiency could be driven by emulsification due to the diffusion of hydrophobic cisplatin into the hollow cavity of iron oxide nanoparticles. By incorporating water, the loading efficiency of hFe3O4 and hFe3O4@γ-AlOOH increased from 1-2% to 27% and from 6% to 54%, respectively. The grafting of cisplatin on AlOOH nanoflakes might account for the high loading efficiency of flower-like hFe3O4@AlOOH. As a complement to naked hFe3O4, a cell-penetrating poly(disulfide)s (CPD)-decorated hollow iron oxide nanoparticle was synthesized by immobilizing both cysteine and MPTMS as an initiator, followed by in situ polymerization to form hFe3O4-Cys-CPD-CONH2 and hFe3O4-MPS-CPD-CONH2. The morphologies were characterized by TEM/energy-dispersive X-ray spectroscopy (TEM/EDX) and the compositions of the as-prepared iron oxide nanocomposites were characterized by TGA, FTIR and X-ray photoelectron spectroscopy (XPS) and ICP-MS. The CPD coating not only serve as a protective layer, but also prevent the encapsulated cisplatin from a premature release. The hFe3O4-MPS-CPD-CONH2 exhibit promising features for the intracellular delivery of cisplatin, demonstrating a glutathione (GSH)-responsive drug release. Comparing with other hFe3O4 nanoparticles, an enhancement of cellular uptake of hFe3O4-MPS-CPD-CONH2 could be observed by optical microscope, showing rapid accumulation of the hFe3O4-MPS-CPD-CONH2 nanocomposites in the primary human renal proximal tubular epithelial cells (HRPTEpiCs) cell in 2 h. At 24 h, hFe3O4 (F), hFe3O4-MPS (FS) and hFe3O4-MPS-CPD-CONH2 (FSC) together with cisplatin treatment did not cause any significant cytotoxicity to the cells when the particle concentration is less than 10 µg/mL. Interestingly, FSCC showed a certain extent of toxicity with increasing Fe and Pt concentration along with the treated time. It may suggest that the hFe3O4-MPS-CPD-CONH2 nanoparticle, as a cisplatin carrier, could enhance the drug efficiency by increasing cellular uptake of the nanoparticles in HRPTEpiCs together with the boosted cytotoxicity. Based on these data, cisplatin- hFe3O4-MPS-CPD-CONH2 (FSCC) treatments with the concentration less than 20 µg/mL and duration no more than 24 h could maintain around 70% of the cell viability of the HRPTEpiCs. The hypothesis, at which CPD serves as an efficient carrier for intracellular cisplatin delivery, could be confirmed by both microscopic images and the cell viability test. In the second part, a series of Au/Fe3O4 hybrid nanocomposites was prepared to investigate their catalytic efficiencies using 4-nitrophenol reduction as a model system. The flower-like hFe3O4@γ-AlOOH@SiO2-NH2@Au was prepared by using protonated ammonium on hFe3O4@γ-AlOOH@SiO2-NH2 to entangle gold nanoparticles (AuNPs) via electrostatic attraction. In comparison to numerous of catalytic studies, the turnover frequency (TOF) of hFe3O4@γ-AlOOH@SiO2-NH2@Au shows a superior conversion rate up to 7.57 min-1 (4-nitrophenol per Au per min) for the 4-nitrophenol using sodium borohydride as a reductant. A rapid conversion of 4-nitrohpenol was observed using flower like composites that converted the 4-nitrophenol within 2 min. Our result suggests that silica residue hinders the reduction rate of the 4-nitrophenol. A significant deviation from pseudo first order was observed for densely AuNPs-functionalized nanoflower system, hFe3O4@γ-AlOOH@SiO2-NH2@Au2X, which is different from most of the 4-nitrophenol reductions reported in literature. The hFe3O4@γ-AlOOH@SiO2-NH2@Au also demonstrates catalytic activity when heated up to 800 °C before reduction. The recyclability was examined using magnetically recycled hFe3O4@γ-AlOOH@SiO2-NH2@Au, which showed insignificant decrease in the catalytic efficiency. To prove the concept, platinum nanoparticles (PtNPs) immobilized hFe3O4@γ-AlOOH@SiO2-NH2@Pt and hFe3O4@γ-AlOOH@SiO2-NH2@Pt/Au were also prepared via electrostatic attraction to verify the feasibility of endowing modular functionality via post modification.

During this PhD thesis, cobalt (Co) catalysts have been prepared, characterized and studied in the carbon monoxide hydrogenation (CO+H2) reaction (also known as “Fischer-Tropsch” (FT) reaction). In industry, the FT synthesis aims at producing long chain hydrocarbons such as gasoline or diesel fuels. The interest is that the reactants (CO and H2) are obtained from other carbonaceous sources than crude oil: natural gas, coal, biomass or even petroleum residues. As it is well known that the worldwide crude oil reserves will be depleted in a few decades, the FT reaction represents an attractive alternative for the production of various fuels. Moreover, this reaction can also be used to produce high value specialty chemicals (long chain alcohols, light olefins…).

Two different types of catalysts have been investigated during this thesis: cobalt with magnesia used as support or dispersant (Co/MgO) and cobalt with silica used as support (Co/SiO2). Each catalyst from the first class is prepared by precipitation of a mixed Co/Mg oxalate in acetone. This coprecipitation is followed by a thermal decomposition under reductive atmosphere leading to a mixed Co/MgO catalyst. On the other hand, Co/SiO2 catalysts are prepared by impregnation of a commercial silica support with a chloroform solution containing Co nanoparticles. This impregnation is then followed by a thermal activation under reductive atmosphere.

The mixed Co/Mg oxalates and the resulting Co/MgO catalysts have been extensively characterized in order to gain a better understanding of the composition, the structure and the morphology of these materials: thermal treatments under reductive and inert atmospheres (followed by MS, DRIFTS, TGA and DTA), BET surface area measurements, XRD and electron microscopy studies have been performed. Moreover, an original in situ technique for measuring the H2 chemisorption surface area of catalysts has been developed and used over our catalysts.

The performances of the Co/MgO and Co/SiO2 catalysts have then been evaluated in the CO+H2 reaction at atmospheric pressure. Chemical Transient Kinetics (CTK) experiments have been carried out in order to obtain information about the reaction kinetics and mechanism and the nature of the catalyst active surface under reaction conditions. The influence of several experimental parameters (temperature, H2 and CO partial pressures, total volumetric flow rate) and the effect of passivation are also discussed with regard to the catalyst behavior.

Our results indicate that the FT active surface of Co/MgO 10/1 (molar ratio) is entirely covered by carbon, oxygen and hydrogen atoms, most probably associated as surface complexes (possibly formate species). Thus, this active surface does not present the properties of a metallic Co surface (this has been proved by performing original experiments consisting in switching from the CO+H2 reaction to the propane hydrogenolysis reaction (C3H8+H2) which is sensitive to the metallic nature of the catalyst). CTK experiments have also shown that gaseous CO is the monomer responsible for chain lengthening in the FT reaction (and not any CHx surface intermediates as commonly believed). Moreover, CO chemisorption has been found to be irreversible under reaction conditions.

The CTK results obtained over Co/SiO2 are quite different and do not permit to draw sharp conclusions concerning the FT reaction mechanism. More detailed studies would have to be carried out over these samples.

Finally, Co/MgO catalysts have also been studied on a combined DRIFTS/MS experimental set-up in Belfast. CTK and Steady-State Isotopic Transient Kinetic Analysis (SSITKA) experiments have been carried out. While formate and methylene (CH2) groups have been detected by DRIFTS during the FT reaction, the results indicate that these species play no role as active intermediates. These formates are most probably located on MgO or at the Co/MgO interface, while methylene groups stand for skeleton CH2 in either hydrocarbon or carboxylate. Unfortunately, formate/methylene species have not been detected by DRIFTS over pure Co catalyst without MgO, because of the full signal absorption.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

Master of Science
Department of Chemical Engineering
Keith Hohn
Acid catalysts have been shown to be very successful in the pretreatment of cellulosic biomass to improve glucose yield and improve overall yield of ethanol. This report presents the results of a techno-economic study that looks into the use of nanoscale magnetic solid acid catalysts for glucose production. Magnetic solid acid catalysts are an improvement over using diluted acid due to eliminating acid-waste generation and corrosion hazards. Their magnetic nature also allows them to be easily separated from reaction products by an external magnetic force. After the technology is analyzed, a series of unit operations is proposed to go from the laboratory scale to the industrial plant scale. The next step was to develop material and energy balances using HYSYS process simulation software. Capital and operating costs are estimated and all the information is combined into a discounted cash flow economic model. The economic portion of the report uses a probabilistic cost assessment. It is used to quantify the range of risks in the project from swings in feedstock costs, differences in yield from catalysts, and any other significant variables. Both capital costs (initial equipment & construction investment) and operating costs (feedstock supply, chemicals, and personnell) are included with ranges of error based on databases and expert opinion. This method of evaluating investment efficiency can be helpful for predicting the cost benefits of proposed future research. The yield and percent catalyst magnetically recovered is assumed based on laboratory research to simplify the model. A 2000 metric tons of biomass per day facility was analyzed. Using the magnetic solid acid catalyst technology, the capital costs are estimated to be $160 million and this technology saves around 10% of capital costs compared to ethanol plants that uses conventional acid hydrolysis. The yield of the magnetic solid acid catalysts should be around 75% to compete with existing ethanol technologies. The metric used for this report is the discount profitability index (DPI) which is the ratio of future cash flows divided by investment. A DPI “hurdle rate” of 1.3 is used, which is similar to industry economic metrics of projects that include new process plants. The calculated DPI for the project is 1.38 DPI which is higher than using conventional cellulose treatment technologies. The recommendation is continue to study this technology’s large scale applicability before attempting any plant pilot studies.

El present manuscrit presenta estudis científics que versen sobre la síntesi i aplicacions en catàlisi de nanopartícules metàl·liques (Pd, Pt, Au, Ni) dipositades sobre nanoesferes de Co i Fe2O3. En primer lloc s’ha estudiat l’activitat en acoblament creuat de tipus Suzuki-Miyaura d’un catalitzador format per nanopartícules de pal·ladi dipositades a la superfície de nanoesferes de Co recobertes de carboni. S’ha observat alta activitat catalítica per a l’acoblament d’àcid fenilborònic amb iodurs i bromurs d’aril, emprant càrregues de catalitzador baixes i temps de reacció curts. També s’ha estudiat el recobriment de la capa de carboni amb sílica per a la incorporació d’un complex de pal·ladi per tal de minimitzar el lixiviat de metalls cap a la dissolució, observat amb el catalitzador anterior. D’aquesta manera es van assolir altes activitats catalítiques minimitzant la quantitat de Pd i Co lixiviada. La deposició de nanopartícules de Pt, Au i Ni petites (5 nm) i amb activitat catalítica a les mateixes nanoesferes es va estudiar a continuació. Nanopartícules d’or actives i de menys de 5 nm de mida van ser obtingudes per reducció de HAuCl4 en presència de PVP i se’n va avaluar el seu potencial per a la hidrogenació catalítica de para-nitrophenol. En contrast, la síntesi d’un catalitzador de platí suportat va resultar més problemàtica. Tot i assolir alts nivells de funcionalització, la formació d’agregats de Pt sobre la superfície del suport magnètic va fer inviable la catàlisi. De manera anàloga, la formació de NiO i aglomeració de Ni metàl·lic va fer impossible la formació de catalitzadors actius.
nanopartículas metálicas (Pd, Pt, Au, Ni) depositadas sobre nanoesferas de Co y Fe2O3. En primer lugar se ha estudiado la actividad en acoplamiento cruzado de tipo Suzuki-Miyaura de un catalizador formado por nanopartículas de paladio depositadas en la superficie de nanoesferas de Co recubiertas de carbono. Se ha observado alta actividad catalítica para el acoplamiento de ácido fenilborónico con yoduros y bromuros de arilo, empleando cargas de catalizador bajas y tiempos de reacción cortos. También se ha estudiado el recubrimiento de la capa de carbono con sílica para la incorporación de un complejo de paladio para minimizar el lixiviado de metales hacia la disolución, observado con el catalizador anterior. De esta manera se alcanzaron altas actividades catalíticas minimizando la cantidad de Pd y Co lixiviada. La deposición de nanopartículas de Pt, Au y Ni pequeñas (5 nm) y con actividad catalítica a las mismas nanoesferas se estudió a continuación. Nanopartículas de oro activas y de menos de 5 nm de tamaño fueron obtenidas por reducción de HAuCl4 en presencia de PVP y se evaluó su potencial para la hidrogenación catalítica de para-nitrophenol. En contraste, la síntesis de un catalizador de platino soportado resultó más problemática. A pesar de alcanzar altos niveles de funcionalización, la formación de agregados de Pt sobre la superficie del soporte magnético hizo inviable la catálisis. De forma análoga, la formación de NiO y aglomeración de Ni metálico hizo imposible la formación de catalizadores activos.
The present dissertation presents a scientific work focused on the synthesis and catalytic evaluation of catalysts based on metallic nanoparticles (Pd, Pt, Au, Ni) deposited on magnetic nanobeads of Co and Fe2O3. Firstly, the evaluation of the activity for the Suzuki-Miyaura cross-coupling reaction of a catalyst composed by palladium nanoparticles deposited on the surface of the carbon-coated Co nanobeads was studied. High catalytic activity was observed for the coupling of phenylboronic acid with aryl iodides and bromides, employing low metal loading and short reaction times. A functionalisation consisting on a silica coating over the carbon shell and further incorporation of a palladium complex was also investigated in order to minimize leaching of metals observed with the previous catalyst. High catalytic activity was performed and the metal leaching (Pd and Co) was minimized. The deposition of small (~ 5 nm) catalytically active Pt, Au and Ni nanoparticles on the magnetic nanobeads was afterwards investigated. Active gold nanoparticles of less than 5 nm in size were obtained by reduction of HAuCl4 in presence of PVP and their potential for the catalytic hydrogenation of para-nitrophenol was evaluated. Contrarily, synthesising an active supported platinum catalyst proved to be more challenging. High metal loadings were achieved however formation of Pt clusters on the surface of the magnetic support precluded the activity of the samples. Similarly, formation of NiO and agglomeration of metallic Ni prevented the formation of active catalysts.

?rea de concentra??o: Produtos e coprodutos.
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A diversifica??o da matriz energ?tica, por raz?es econ?micas, ambientais e da pr?pria pol?tica energ?tica das na??es, tem suscitado foco especial nos biocombust?veis, particularmente no bioetanol e no biodiesel. Na ind?stria, o biodiesel (?steres de ?cidos graxos com um ?lcool de cadeia molecular curta) ?, mais comumente, produzido pela transesterifica??o de triacilglicer?is de ?leos vegetais ou gordura animal, com metanol ou etanol, sob cat?lise homog?nea com uma base (KOH ou NaOH). Por representarem alternativas potencialmente mais sustent?veis, dos pontos de vistas econ?micos e ambientais, o presente trabalho foi dedicado a avaliar a efici?ncia qu?mica de catalisadores heterog?neos baseados em materiais de min?rios: (i) de ni?bio, enriquecido em Nb2O5 (Geo.Nb2O5); (ii) de areia monaz?tica (Geo.Mona), uma fonte mineral de terras raras, e (iii) de rejeitos de minera??o de fosfato, ricos em magnetita (Geo.Mag.CMT e Geo.Mag.CMA). Os materiais minerais foram preparados em mistura com componentes ?cidos (H2SO4; HCl ou HF) ou b?sicos (KOH; , KBr, NaOH; CaO; KI; KF ou KCl). As rea??es de transesterifica??o foram conduzidas sob refluxo, com ?leo de soja comercial e metanol, sob a??o dos catalisadores s?lidos. A raz?o molar padr?o ?leo:metanol foi de 1:100, com 10% de catalisador em rela??o ao ?leo, a 60 ?C. Dos testes realizados com os materiais preparados com CaO sint?tico comercial, nas mesmas condi??es, a mistura calcinada a 800 ?C por 4 h rendeu ?steres met?licos sempre acima de 99%; o menor tempo de rea??o (2 h, para completar a transesterifica??o) foi conseguido com o catalisador baseado na Geo.Mona, em rela??o ao Geo.Nb2O5 (5 h), ao Geo.Mag.CMT (3 h) e o Geo.Mag.CMA tamb?m (2 h). Analisou-se o reuso consecutivo do catalisador. Ap?s cada rea??o, o catalisador s?lido era lavado com metanol e seco a 100 oC. O melhor resultado foi obtido com o rejeito magn?tico com CaO calcinados a 200 ?C por 4 h, para o que se conseguiu at? 8 rea??es consecutivas. Nas impregna??es com ?cidos e bases, os melhores resultados foram com a mistura Geo.Nb2O5 e KOH calcinada a 600 ?C, para a qual conseguiu 8 rea??es consecutivas, com rendimento qu?mico em ?steres met?licos de praticamente 100% e tempo reacional de 10 min, no primeiro uso. O efeito catal?tico sin?rgico mais significativo foi conseguido com o catalisador baseado em cada um dos tr?s materiais avaliados em mistura com CaO: nenhum efeito catal?tico significativo na rea??o de transesterifica??o de triacilglcier?is do ?leo foi observado apenas com o material mineral puro calcinado. O CaO puro como catalisador, tamb?m calcinado e usado em rea??o, levou a rendimentos qu?micos pouco acima de 80%. A mistura individual do material mineral com CaO, nas mesmas condi??es de prepara??o anteriores, levaram a rendimentos qu?micos de efetivamente 100%. Os presentes resultados revelam a excepcional potencialidade, dos pontos de vista qu?mico, econ?mico e ambiental, dos catalisadores mistos, dos materiais minerais com CaO, ora avaliados, nos processos de produ??o industrial de biodiesel.
Tese (Doutorado) ? Programa de P?s-gradua??o em Biocombust?veis, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017.
The diversification of the energy matrix has been drawing special attention to biofuels, especially bioethanol and biodiesel, mainly for economic and environmental reasons and national energy policies. In industry, biodiesel (esters of fatty acids with a short-chain alcohols) is most commonly produced by the transesterification of triacylglycerols in vegetable oils or animal fats with methanol or ethanol using homogeneous catalysis with a base (KOH or NaOH). The present work was devoted to the evaluation of the chemical efficiency of heterogeneous catalysts based on mineral materials: (i) niobium, enriched in Nb2O5 (Geo.Nb2O5); (ii) monazite sand (Geo.Mona), a mineral source of rare earths, and (iii) phosphate mining tailings, rich in magnetite (Geo.Mag.CMT e Geo.Mag.CMA). The mineral materials were prepared in admixture with acidic (H2SO4, HCl or HF) or basic (KOH, KBr, NaOH, CaO, KI, KF or KCl) components. The transesterification reactions were conducted under reflux with commercial soybean oil and methanol in the presence of the solid catalysts. The standard molar ratio of oil:methanol was 1:100, using 10% catalyst relatively to the quantity of oil, at 60 ?C. According to the tests performed with the materials prepared with commercial synthetic CaO under the same conditions, the yield of methyl esters with the mixture calcined at 800 ?C for 4 h was always greater than 99%. The shortest reaction time (2 h to complete the transesterification) was achieved with the Geo.Mona catalyst; the reaction times with Geo.Nb2O5 (5 h), the Geo.Mag.CMT (3 h) and the Geo.Mag.CMA also (2 h) were longer. The consecutive reuse of the catalyst was also verified. After each reaction, the solid catalyst was washed with methanol and dried at 100 ?C. The best result was obtained with the magnetic waste with CaO calcined at 200 ?C for 4 h, with which up to eight consecutive reactions were achieved. On impregnating with acids or bases, the best results are obtained with the Geo.Nb2O5 and KOH mixture calcined at 600 ?C, with which eight consecutive reactions were completed. Virtually 100% yields of methyl esters were obtained in a reaction time of 10 min in the first use. The most significant synergistic catalytic effect was achieved with each of the three minerals mixed with CaO. No significant catalytic effect on the transesterification reaction of triacylglycerols in the oil was observed with the pure calcined minerals. When the calcined CaO is used alone as catalyst, the reaction yielded just over 80%. For the mixture of the individual minerals with CaO under the same preparation conditions described above, the transesterification reaction led to virtually 100% yields. The present results reveal an outstanding potential regarding the chemical, economic and environmental aspects of the mixed catalysts (the mineral material with CaO) for chemical processes leading to the industrial production of biodiesel.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The Knoevenagel condensation is one of the most important methods to perform new C-C bonds in organic compounds, and it was used at least in one-step on the synthesis of several molecules. The N-acylhydrazones, in turn, are molecules with considerable biological activity, which increased the number of papers involving the synthesis of N-acylhydrazones in the last years. This present work consists of the use of magnetic nanoparticles functionalized as catalysts in the Knoevenagel condensations and the synthesis of N-acylhydrazones. The magnetic nanoparticles, Fe3O4, were prepared by the chemical co-precipitation method, coated with sílica, Fe3O4@SiO2, and functionalized with amino groups (Fe3O4@SiO2-3N, which 3N = N1-(3-trimethoxysilylpropyl)diethylenetriamine) and lanthanide ions (Fe3O4@SiO2-1N-EDTA-Tb3+, which 1N = (3-aminopropyl)trimethoxysilane). These materials were characterized by absorption spectroscopy in infrared region, X-ray diffraction (X-RD), thermogravimetric analysis, elemental analysis of carbon, hydrogen and nitrogen, and magnetization measurements. The Fe3O4@SiO2-3N magnetic nanoparticles were used as catalysts in the Knoevenagel condensation, showing good isolated yields (71-100%) and reaction times (10-45 min). The amino groups in the functionalized magnetic nanoparticle act as bases, promoting the desprotonation of methylene group, and as catalyst in the reaction, activating the carbonylic carbon by the iminium ion formation. The Fe3O4@SiO2-1N-EDTA-Tb3+ magnetic nanoparticles were used as catalysts in the synthesis of N-acylhydrazones, showing also good isolated yields (65-95%) and reaction times (2-180 min). In conclusion, the magnetic nanoparticles synthetized showed a good catalytic activity, easilly recovered by magnetic separation and reused in subsequent reactions.
A reação de condensação de Knoevenagel é uma das reações mais utilizadas em síntese orgânica para formação de ligação C–C, sendo usada como uma das etapas para a síntese de várias moléculas. As N-acilidrazonas, por sua vez, são moléculas que apresentam considerável atividade biológica, o que impulsionou os trabalhos envolvendo a síntese das mesmas nos últimos anos. O presente trabalho consiste na utilização de nanopartículas magnéticas funcionalizadas como catalisadores nas reações de condensação de Knoevenagel e na síntese de N-acilhidrazonas. As nanopartículas magnéticas (magnetita, Fe3O4) foram sintetizadas pelo método de coprecitação química, revestidas com sílica (Fe3O4@SiO2) e funcionalizadas com grupos aminos (Fe3O4@SiO2-3N, em que 3N = N1-(3-trimetoxisililpropril)dietilenotriamina) e com íons terras raras adsorvidos (Fe3O4@SiO2-1N-EDTA-Tb3+, em que 1N = 3-aminopropiltrimetoxissilano). Elas foram caracterizadas por espectroscopia de absorção na região do infravermelho, DR-X, análises termogravimétricas, análise elementar de carbono, hidrogênio e nitrogênio e medidas de magnetização. As nanopartículas magnéticas Fe3O4@SiO2-3N foram usadas como catalisadores nas reações de condensação de Knoevenagel, apresentando bons rendimentos isolados (71-100%) e tempos reacionais (10-45 min). Os grupos aminos presente no material atuam como base, promovendo a desprotonação do metileno, e como catalisador na reação, ativando o carbono carbonílico através da formação do íon imínio. Já as nanopartículas magnéticas Fe3O4@SiO2-1N-EDTA-Tb3+ foram utilizadas como catalisadores na síntese das N-acilidrazonas, também apresentando bons rendimentos isolados (65-95%) e tempos reacionais (2-180 min). Em linhas gerais, as nanopartículas magnéticas sintetizadas apresentaram boa atividade catalítica, sendo facilmente recuperada por separação magnética e reutilizada em reações subsequentes.

Orientador: Renato Sprung
Tese doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Materiais do tipo hidrotalcita foram sintetizados, calcinados e caracterizados, assim como utilizados na conversão catalítica de etanol. As sínteses foram realizadas com razões molares AI/(AI + Mg) iguais a 0,20; 0,25 e 0,33; em todos os casos os difratogramas de raios-X demonstraram que, efetivamente, fases de hidrotalcitas tinham sido obtidas. Esses materiais apresentaram áreas superficiais BET de cerca de 50 a 70 m2.g-l, à exceção da hidrotalcita sintetizada com agentes precipitantes contendo amônio, em que a área superficial foi de cerca de 7 m2g -I. A quimissorção de CO2 desses materiais revelou que hidrota1citas calcinadas são sólidos básicos e tal basicidade relaciona-se com o teor de magnésio substituído e também com a temperatura de ca1cinação. Os testes catalíticos foram realizados a temperaturas de 3000 C a 4000 C e verificou-se o aumento da taxa de reação com o incremento da temperatura. Os produtos de condensação éter etílico e nbutanol foram obtidos em maior proporção. Hidrotalcitas da série sódio apresentaram maior rendimento de n-butanol independentemente do teor de alumínio presente na amostra. Todas as amostras utilizadas apresentaram, a baixas conversões, quantidades significativas de n-butanol, o que pode indicar que, além da via de condensação aldólica, a formação desse produto também ocorre via condensação direta do etanol, ou seja, sem a dessorção para a fase gasosa da molécula de acetaldeído. Testes catalíticos comparativos realizados com óxido de magnésio e alumínio resultaram principalmente em acetaldeído e etileno, respectivamente. Traços de n-butanol foram identificados no óxido de magnésio quando testado a 4000 C, e éter etílico foi observado em maior quantidade no óxido de alumínio quando testado a 3000 C
Abstract: Hydrotalcites-like materiaIs were prepared, calcined and characterized as well as used in the catalytic reaction of ethanol. The synthesis were perfonned with AI/(AI + Mg) ratios of 0.20; 0.25 and 0.33; in all cases the x-ray showed hydrotalcites phases. These materiaIs resulted in BET areas of 50 at 70 m2.g-1, except for the hydrotalcite synthesized with NH3, that resulted in a BET area 00 m2g-1. The CO2 chemisorption on these materiaIs revealed that calcined hydrotalcites are basic catalysts and their basicity was related to the quantity of substituted magnesium and to the calcination temperature. The catalytic reactions were performed at 300, 350 and 4000 C; the reaction rate increasing with reaction temperature. The main reaction products identified were ether and n-butanol. The hydrotalcite synthesized with cation sodium presented the highest yield of n-butanoI independent of aluminum content present in the samples. The results of Iow conversions showed significant yield of n-butanoI, and this could indicate that the formation of that product occurs by aldoI condensation and aIso by straight condensation of ethanoI molecule, without acetaldehyde desorption to gas fase. Comparative catalytic tests performed with MgO and AI203 showed acetaldehyde and ethylene predominantly as reaction products. Traces of n-butanoI were identified with MgO when the reaction occurred at 4000 C, and ether was identified with AI203 when the reaction occurred at 3000 C
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química

碩士
國立中興大學
環境工程學系所
104
Metal Organic Frameworks (MOFs) represents one of the most versatile nanomaterials nowadays. MOF-derived materials also become diversification. In this study, we develop a one-step carbonization process to prepare carbon-supported cobalt material, named as Magnetic Carbon/Cobalt Composite (MCCC), derived from a cobalt-based Metal Organic Framework (ZIF-67). The detailed characterization of MCCC is analyzed by FE-SEM, TEM, XRD and XPS. The magnetism, porosity and cobalt content of MCCC make it exhibit good controllability and catalytic ability. In the first application, MCCC is used to catalyze NaBH4 hydrolysis for H2 production. While nano-scale cobalt catalyst is recognized as one of the most efficient catalysts for H2 production from NaBH4 hydrolysis, it tends to aggregate and decreases the catalytic activities. The cobalt is uniform loaded on MCCC that can avoid the aggregation. Effects of catalyst loading, temperature and sodium hydroxide concentration were thoroughly examined. Under alkaline conditions, the activation energy of the hydrolysis is 28.45 kJ mol-1. MCCC shows a superior catalytic capability with a low activation energy. Finally, an experiment of providing NaBH4 continuously is used to test the stability of MCCC catalyzing NaBH4 hydrolysis. MCCC shows efficient recyclability to hydrolyze NaBH4 over 5 cycles without rinsing. Based on the above experiments, we know that MCCC is an effective and practical heterogeneous catalyst for H2 production from hydrolyzing of NaBH4. The second application, MCCC is used to activate peroxymonosulfate (commercial name : Oxone) for the decolorization of rhodamine B. Normally, the oxidation reaction with Oxone activated by transition metal is faster than by Oxone alone. For the investigation of parameters, this MCCC-activated Oxone process is found to be the most effective when the concentration of MCCC is 50 mg L-1 and the concentration of Oxone is 250 mg L-1; the higher temperatures improved the decolorization efficiency significantly; alkaline solution will be harmful to the generation of sulfate radical and weaken the oxidation reaction; UV photocatalyzation and ultrasonication are both found to enhance the MCCC-activated Oxone process. The recyclability test demonstrated that MCCC can be continuously used with effective catalytic activity. Above these features enable MCCC to be an effective catalyst for the oxone oxidation process.

碩士
國立中興大學
環境工程學系所
107
Cobalt nanoparticles (Co NPs) immobilized on N-doped carbonaceous substrates are attractive heterogeneous catalyst for activating Oxone to degrade pollutants. However, conventional preparation of Co NPs/N-doped carbon composites involves multi-step syntheses of N-doped carbon substrates, and then immobilization of Co NPs on substrates which are complicated and time-consuming. In this study, a convenient one-step fabrication technique is developed for preparing a composite of Co/N-doped carbon via carbonization of a mixture of melamine and cobalt acetate. The resulting Co@CN is comprised of Co NPs evenly distributed over a carbon nitride (CN) matrix. Co@CN could exhibit porous structures and magnetic controllability, making it an appealing catalyst for Oxone activation. Catalytic activities for Oxone activation by Co@CN are investigated via batch-type degradation experiments of amaranth (AMR) dye. In comparison to the other reported catalysts, Co@CN demonstrates the much lower activation energy for AMR degradation. The mechanism of AMR degradation by Co@CN-activated Oxone is also determined by investigating Electron paramagnetic resonance (EPR) analysis and effects of radical inhibitors on AMR degradation. These comparisons indicate the promising features of Co@CN as a heterogeneous catalyst for activating Oxone. The synthesis technique proposed here can be also adopted to develop similar composites of metallic NPs distributed over CN matrices for various catalytic applications.

碩士
東海大學
環境科學與工程學系
100
This study used modified magnetic silver nanoparticles (Fe3O4/SiO2/Ag) for the heterogeneous catalytic ozonation to remove humic acid (HA) in water. While hydroxyl radical (․OH) scavengers were added to the system in order to investigate the catalytic ozonation mechanisms. Coumarin is known to react with․OH to generate intermediate (7-hydroxycoumarin). The formation of the intermediate can be used to indicate the presence of․OH in the system. Compared to ozonation alone, Fe3O4/SiO2/Ag combined with ozone to produce more intermediate. This is due to the decomposition of ozone to produce more ․OH by Fe3O4/SiO2/Ag. Added another․OH scavengers of TBA can be observed production of intermediate will be reduced because the․OH was captured, while the intermediate produced in Fe3O4/SiO2/Ag combined with ozone is still higher than the ozonation alone. The results showed that Fe3O4/SiO2/Ag combined with ozone to improve the content of․OH in the system. To remove of humic acid by Fe3O4/SiO2/Ag combined with ozone, the humic acid removal rate is only higher than ozonation alone in acidic condition, this is due to the ozone self-decomposition inhibits the effect of the catalyst at high pH cases. Comparison of first-order ozone decay rate constants, the Kd values of this study of 7.0×10-4 s-1 and is 1.75 times than that of ozonation alone. The results indicated the presence of Fe3O4/SiO2/Ag could improve the oxidizing power of overall system and leading to the HA removal rate increased.

Rozprawa doktorska rozwija tematykę heterogenicznych katalizatorów metaloorganicznych znajdujących się na powierzchni magnetycznej fazy stałej (na nanocząstkach magnetycznych). W części literaturowej przedstawiono przegląd stosowanych nanocząstek magnetycznych oraz powłok je stabilizujących. Dodatkowo zestawiono różne rodzaje katalizatorów oraz przedyskutowano właściwości katalityczne kompleksów metaloorganicznych zaczepianych na magnetycznej fazie stałej. W części badawczej opisano dwie strategie syntezy takich katalizatorów: 1. bezpośrednią syntezę ligandów na powierzchni nanocząstek oraz 2. wprowadzanie ligandów za pomocą reakcji polimeryzacji RAFT/MADIX inicjowanej bezpośrednio z powierzchni fazy stałej. W obu metodach kompleks z metalem (pallad bądź miedź) był syntezowany bezpośrednio na powierzchni nanocząstek (taka strategia tworzenia kompleksów jest najczęściej wykorzystywana). W obu metodach wykorzystano nanocząstki tlenków żelaza jako fazę stałą. Nanocząstki te pokryto powłoką siloksanową zawierającą terminalne grupy aminowe, które w następnych etapach posłużyły jako substraty do syntezy ligandów NHC oraz zaczepienia ditiowęglanu (wykorzystanego w reakcji polimeryzacji RAFT/MADIX). W niniejszej pracy podjęto się próby porównania aktywności katalizatorów palladowych otrzymanych różnymi metodami. Dodatkowo badano wpływ budowy ligandu na tą aktywność (podejście pierwsze) oraz budowy powłoki polimerowej (podejście drugie) na aktywność katalityczną otrzymanych kompleksów.
Doctoral thesis develop a wide topic of heterogenic, organometallic catalysts, which were anchored on magnetic solid support (magnetic nanoparticles). In the theoretical part one can find a review about usage of magnetic nanoparticles as solid support for catalysis. Also commonly used ligands and capping agents applied for stabilization of nanoparticles were catalogued. Catalytic properties, stability and recycling of heterogeneous catalysts were compared and discussed. The research part was divided into two parts which represent two strategies of anchoring catalysts on the magnetic surface. Nanoparticles which were used for the preparation of the catalysts were iron oxides. First strategy was direct synthesis of ligands on the surface of magnetic nanoparticles (MNP). Second strategy is RAFT/MADIX polymerization which is initiated direct from the surface of MNP. In both strategies final catalyst (organometallic complex with palladium or copper) was synthesized directly on the solid phase (as an ultimate step of catalyst preparation) – this is the most commonly used approach for preparation of magnetically separable heterogeneous catalysts. The first step of the catalysts preparation was stabilization of MNP by siloxane coating which was further modified to form NHC precursor or CTA agent. Herein, comparison of activity of palladium catalysts which were made by different methods was attempted. Additionally, the influence of the ligands structure (first strategy) and the influence of the polymeric shell structure (second strategy) on the heterogeneous catalysts activity was studied.
NINIEJSZA PRACA POWSTAŁA DZIĘKI FINANSOWEMU WSPARCIU NARODOWEGO CENTRUM NAUKI:Grant PRELUDIUM, 2016/21/N/ST5/01316, kierownik Iwona Misztalewska-Turkowicz; Grant ETIUDA, 2017/24/T/ST5/00214, kierownik Iwona Misztalewska-Turkowicz; Grant OPUS, 2011/03/B/ST5/02691, kierownik dr hab. Agnieszka Z. Wilczewska.
Uniwersytet w Białymstoku. Wydział Biologiczno-Chemiczny. Instytut Chemii