Photocatalysis is a process to convert light energy into chemical energies. This advanced process has been extensively applied in different areas, such as water splitting to evolve hydrogen, organic/ inorganic pollutants decomposition, artificial photosynthesis (CO2 reduction), disinfection, heavy metal recovery, organic synthesis and nitrogen fixation (reduction). The difficulty for photocatalysis applied in practical is primarily due to the low quantum yield as for the high recombination of photogenerated charge carriers. Various strategies have been implemented to overcome these challenges. As recently developed advanced materials, two dimensional materials have attracted lots of attentions as for their superiorities such as large specific surface area and high conductivity. These advantages for two dimensional materials make them be promising cocatalysts in enhance catalytic activity. In this thesis, various two dimensional materials (such as MoS2, SnS, BN as well as C3N4) other than graphene were prepared and investigated in the promotion of photocatalytic activity. Specifically, the focus of present work is on two dimensional materials enhanced photocatalysis in environmental remediation, including organic pollutants detoxification as well as bacteria inactivation. It was found that two dimensional materials, including MoS2, SnS, BN, may be excellent candidates as cocatalysts to enhanced visible-light-driven photocatalytic activity. And g-C3N4 as an effective photocatalyst exhibited excellent photocatalytic oxidation activity, and its activity can be further enhanced with surface modification by hydroxyl functional groups (a modification method reported in the thesis). Suggestions for future work were also proposed in this thesis.

Orientador: Maurício Boscolo / Banca: Newton Luiz Dias Filho / Banca: Camila de Almeida Melo / Resumo: A produção e o consumo de biodiesel no Brasil e no mundo vem aumentando a cada ano em decorrência da busca por combustíveis menos poluentes e processos de produção mais baratos. Este biocombustível é produzido pela esterificação ou transesterificação de óleos ou gorduras com álcoois de cadeia curta. A catálise homogênea alcalina é a mais empregada na transesterificação gerando grandes quantidades de resíduos ao final do processo, já os catalisadores heterogêneos, menos usados em razão do custo e eficiência, são facilmente separados do produto final e ainda melhoram a qualidade do glicerol residual. O uso do etanol na produção do biodiesel fortalece a agroindústria brasileira, porém possui como principal desvantagem a sua higroscopicidade, o que pode favorecer a reação de saponificação afetando a qualidade do biodiesel e dificultando seu processo de produção. Neste trabalho, hidróxidos duplos lamelares tipo hidrotalcitas e piroauritas com substituição parcial de Mg e Al por Ba, Cu, Zn e Fe foram estudados como precursores de óxidos metálicos com atividade catalítica transesterificante na produção de biodiesel etílico de óleo de soja e caracterizados por TGA, DSC, FTIR-ATR, BET, XRD e SEM. Cromatografia em fase gasosa (GC-FID) foi empregada na quantificação dos produtos. Foram testadas 40 variações dos catalisadores, sendo 20 em cada temperatura de calcinação (450 e 600ºC). Dentre os materiais estudados, aqueles contendo Ba houve formação de fase secundária e os materiais com zinco e cobre obtiveram alta cristalinidade, maior perda de massa quando calcinados e altas áreas superficiais. Nos testes catalíticos em recipientes fechados com pressão autogerada a 120ºC por 12 horas utilizando razão 1:20 (massa óleo/massa etanol) e com 20% (massa catalisador/massa óleo). Os materiais de referência (hidrotalcita e piroaurita sem... / Abstract: Both the production and consumption of biodiesel have constantly increased worldwide and in Brazil due to a search for fuels which pollute less and production processes which cost less as well. Such biofuel is produced by means of esterification and transesterification of oils or fat with short-chain alcohols. Alkaline homogeneous catalysis is still widely used in transesterification, even though it generates a massive amount of residues at the end of the process; however, heterogeneous catalysts are not employed so frequently because they are more costly and less efficient. Nevertheless, they can be easily separated from the final product and improve the quality of residual glycerol. Although the use of ethanol in the production of biodiesel strengthens the Brazilian agro-industry, it poses a disadvantage: its hygroscopicity, which can generate a saponification reaction and, thus, affect the quality of the biodiesel and make its production process more difficult. In this study, we analyzed lamellar double hydroxides from hydrotalcite and pyroaurite types, with a partial substitution of Mg and Al for Ba, Cu, Zn, and Fe. We studied as metal oxide precursors with a transesterification catalytic activity on production of ethyl biodiesel from soybean oil and characterized them through TGA, DSC, FTIR-ATR, BET, XRD, and SEM. Gas chromatography (GC-FID) was used for products quantification. We conducted tests with 40 variations of catalysts, 20 for each calcination temperature (450 and 600ºC). Among the studied materials, those with Ba presented a secondary phase formation and materials with zinc and copper showed high crystallinity, high mass loss when calcined and high surface areas. In closed containers with auto-generated pressure at 120ºC for 12h using the ratio 1:20 (oil mass/ ethanol mass) and 20% (catalyst mass/ oil mass), the reference materials (hydrotalcite and ... / Mestre

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2019. / A shortage of water has resulted in the need to enhance the quality of wastewater that is released into the environment. The advanced oxidation process (AOP) using heterogeneous catalysis is a promising treatment process for the management of wastewater containing recalcitrant pollutants as compared to conventional processes. As AOP is a reliable wastewater treatment process, it is expected to be a sustainable answer to the shortage of clean water. AOP using heterogeneous catalysis based on Co3O4 particles and PMS, in particular has been found to be a powerful procedure for the degradation and mineralization of recalcitrant organic contaminants. In addition, due to the growing application of Co3O4 in lithium batteries, large quantities of these particles will be recovered as waste from spent lithium batteries, so there is a need to find a use for them. Although this method has received some promising feedback, challenges still need to be addressed, such as the toxicity of cobalt particles, the poor chemical and thermal stability and particle aggregation, and the prompting of lower catalytic efficiency in long haul application. Furthermore, the removal of the catalyst after the treatment of pollutants is also an issue. In order to be applicable, a novel catalyst must be produced requiring the combination of Co3O4 with a support material in order to inhibit cobalt leaching and generate better particle stability. From the available literature, TiO2 was found to be the best support material because it not only provides a large surface area for well dispersed Co3O4, but it also forms strong Co-O-Ti bonds which greatly reduced cobalt leaching as compared to other support materials. Moreover, it also greatly encourages the formation of surface Co–OH complexes, which is considered a crucial step for PMS activation. Therefore, the issues cited above could be avoided by producing a Co3O4/TiO2 heterojunction catalyst.

Catalisadores de óxido de vanádio suportados sobre titânia foram preparados pelo processo sol-gel. A secagem do material foi efetuada em condições supercríticas (aerogel) e pelo método convencional (xerogel). As características texturais foram determinadas por adsorção de N2 à 77K para obtenção de isotermas de adsorção, área superficial BET, distribuição, forma e tamanho de poros. A morfologia do material foi verificada por microscopia eletrônica de varredura. A estrutura e a identificação dos grupos superficiais foram determinadas por difratometria de raios-X e espectroscopia de infravermelho. Obteve-se sólidos com áreas superficiais ate três vezes superiores que os valores médios encontrados na literatura. Porosidade de ate 300 cm3g-1 para os aerogéis. Três tipos de espécies vanádio foram identificados nos catalisadores: grupos superficiais vanadis monoméricos, grupos vanadatos poliméricos e cristalitos de V2O5. O suporte e formado por TiO2 nas formas anatásio e rutilo com predominância da primeira forma nos aerogeis. A análise de microscopia mostrou urna granulometria ligeiramente esférica com partículas em torno de 6OMEGAm e boa dispersão do óxido de vanádio sobre a titânia. / In this work, catalysts of V2O5/ TiO2 were obtained by sol-gel method, and dried under two different conditions: supercritical (aerogel) and conventional one (xerogel). The textural characterization was carried out by adsorption of N2 at 77K, determining the adsorption isotherm, BET surface area and size, shape and distribution of porous structure. The morphology of synthesized material was studied by SEM, the structure and surface groups were characterized by XDR and FTIR, respectively. The surface area was about three time of reported in the literature. The porosity achieves values of 300 cm3g-1for aerogels. Three surface species were identified for vanadium: monomeric vanadyl, polymeric vanadates groups and V2O5 in crystallites forms. Two different forms of crystallization, rutile and anatase, were found for TiO2 support, being the first of them predominant for aerogels. The analysis of SEM micrographies exhibited a spheric granulation of particles of about 6OMEGAm and showed a good dispersion of vanadium oxide on titanium.

Sustainable energy management has become a high priority for many countries. A great majority of our energy stocks comes from non-renewable fossil fuels, which are currently dwindling. Biofuels are one of the most promising solutions being researched to address this urgent problem. In particular, using transesterified Jatropha curcas L. oil appears to be a promising method of producing biofuels due to several properties of the plant, such as the high oil yield of its seeds and the fact that it does not compete with food crops. The literature mentions many attempts of using zeolites as solid acid catalysts in transesterification reactions of vegetable oils with high free fatty acid (FFA) content. The acid catalysis prevents soap formation and emulsification, which can be observed in the basic process. The use of a solid catalyst makes the separation and purification of the final products steps easier to implement in comparison to catalysis in homogeneous conditions. However, the efficiency of the zeolite in the heterogeneous transesterification reaction of vegetable oil is not well-known yet and varies on the structure of the catalyst used. This project aims at better understanding the relationship between the type of zeolite used and the yield of this particular reaction using reconstituted Jatropha oil from Sesame seed oil, which has a similar composition. Five different types of zeolites were compared: Y, X, Beta, Mordenite & ZSM-5. Non-catalyzed reactions as well as homogeneously catalyzed - with H2SO4 - reactions were also implemented. Since we take advantage of the catalytic properties of different zeolites, the one that were not already in hydrogen form were ion-exchanged and the ion-exchanged species were then analyzed by Energy-Dispersive X-Ray spectroscopy (EDX). Three alcohol-to-oil ratios were tested at atmospheric pressure and at T=115°C for each catalyst in order to determine the influence of this ratio. All experiments were conducted in an airtight autoclave with butan-1-ol in order to obtain a biofuel whose cetane index is higher than regular petroleum-based diesels.

This Dissertation describes the development of chemical looping for selective oxidations. Chemical looping is a reactor technology that achieves simultaneous reaction and separation. For a large subset of reactions (viz. abstraction or insertion of oxygen), this technology is based upon the use of oxygen carriers. These materials, typically metal oxides, reversibly store and release oxygen, and there is growing interest in using these materials for selective oxidations. This Dissertation describes work on the development of oxygen carriers for selective oxidations, including foundational work on a method for analysing periodic non-catalytic gas-solid reactions, of which chemical looping selective oxidations are a subset. The oxygen chemical potential of Ca2Fe2O5 was exploited to improve the efficiency of the steam-iron process to produce hydrogen. The ability of reduced Ca2Fe2O5 to convert a higher fraction of steam to hydrogen than chemically unmodified Fe was demonstrated in a packed bed. This demonstrates how the oxygen chemical potential might be manipulated and exploited for chemical looping reactions. The oxygen chemical potential determines the selectivity in thermodynamically-controlled selective oxidations, and, depending on the reaction mechanism, kinetically-controlled selective oxidations. A generic method for enhancing the oxygen-carrying capacity of oxygen carriers for use in selective oxidations is presented, where one material that is selective in the reaction is deposited on the surface of a second material acting as a reservoir of oxygen and as a support. The presence of ceria in the support was found to supply lattice oxygen additional to that provided by the bismuth oxide, without affecting the selectivity of bismuth oxide. The surface chemistry was decoupled from the bulk properties of the support, thus simplifying the design and formulation of composite oxygen carriers. Building upon the concepts of oxygen chemical potential and composite oxygen carriers, chemical looping epoxidation was demonstrated for the first time. The oxygen carrier was composed of Ag, for its unique catalytic properties, and SrFeO3 as the support, for its high oxygen chemical potential at low temperatures. A reaction mechanism was proposed based on the observations. Nonlinear frequency response theory was used to analysis a periodic non-catalytic gas-solid reaction. Generalised frequency response functions (which are higher order analogues to traditional, linear transfer functions) were derived to obtain the nonlinear frequency response of the archetypal reactor. Such a method lies between the traditional frequency response theorem and numerical methods in terms of accuracy and speed. A niche application was proposed for the analysis of experimental kinetics, avoiding convolution of measurements with the response time of measuring equipment. In summary, this Dissertation describes how materials might be formulated for selective oxidations in chemical looping mode. This was demonstrated for an industrially-significant reaction for the production of ethylene. A novel application of nonlinear frequency response theory was also demonstrated for chemical looping reactions.

Metal organic frameworks have gained much attention due to their tunable pore sizes and very high surface areas. With the discovery many of these type materials the need has raised to look into new applications of theses porous frameworks. This thesis focuses on the synthesis of a new perovskite-type metal organic framework and measurement of its thermal conductivity in search of its applicability as a thermoelectric material. The second part of this work focuses on the synthesis of a metal organic framework incorporated with a Lewis pair for the first time. The optimum loading amount of the Lewis pair into the framework was also investigated.

Light intensity distribution studies in the heterogeneous photocatalytic reactors were carried out successfully with potassium ferrioxalate chemical actinometry, reproducible light intensity estimates of the irradiation source were obtained. The increased light intensity in the reactor system increased the absorption as determined by actinometry. It was found that reflectivity was a dependent variable but mesh opening area was an independent variable. The photocatalytic mineralization of dichoroacetic acid DCAA, in the presence of TiO2 immobilized on a plate in an externally irradiated bubble column photoreactor had been investigated. The mass transfer and activity evaluation were measured. It was found that increasing the catalyst thickness, increased the photoactivity until it reaches the optimum loading, further loading increase caused the reaction rate to remain constant. This phenomenon was observed with increased lamp power (intensity) and initial solute concentration. However, the catalyst activity was not influenced by the increasing concentration of dissolved oxygen. The reaction rate for DCAA photomineralization was expressed using the Langmuir-Hinsheldwood model.

Transition metals have been extensively studied as catalysts, and certain metals are known to be highly selective and active for certain processes. It is possible to use metal clusters as models for reactions occurring at metal surfaces, but it is often found that in practical applications these complexes are unstable and break down. It is possible to support or stabilise a metal species on, or in, an inorganic framework, making heterogeneous catalysts. A study of metal cluster chemistry with mixed-donor phosphine ligands was conducted, with several new ruthenium complexes synthesised. The chemistry of metal-sulfur interactions is applicable to the removal of sulfur from crude oil, and in an investigation to this chemistry, the bifunctional ligand HSCH2CH2PPhH was added to ruthenium clusters (Chapter 2). The addition of this sulfur-phosphine ligand to the cluster [Ru3([mu]-dppm)(CO)10] produced the carbonyl substituted cluster [Ru3([mu]-dppm)(H)(CO)7(SCH2CH2PPhH)] and the bridged complex [Ru3([mu]-dppm)(H)(CO)8(SCH2CH2PPhH)Ru3([mu]-dppm)(CO)9], as well as recovery of the starting material. Further reactions with this ligand were examined with [Ru3(CO)12] and other complexes were synthesised with different clusters and ligands (Chapter 2). The M41S materials, MCM-41 and MCM-48, are well ordered porous materials with high surface areas (Chapter 3). The incorporation of three different types of metal species, metallosurfactants, metal clusters and nanoparticles, into these materials was examined in an attempt to make heterogeneous catalysts for the Fischer-Tropsch process. The success of this was studied using characterisation techniques such as powder X-ray diffraction, transmission electron microscopy and BET surface area measurements. Metallosurfactants containing either copper or cobalt were added directly to the synthesis of the porous materials in an attempt to incorporate the metals into the framework structure of the porous silica (Chapter 3). This resulted in well ordered iv porous materials, but the successful incorporation of the metal species was found to be dependent on several factors. Organometallic clusters containing metals such as copper, iron and ruthenium, with supporting carbonyl ligands, were added post-synthesis to MCM-41 and MCM-48 (Chapter 4). Various reaction conditions were examined in attempts to ensure small particle formation. The optimum incorporation of nanoparticles containing iron and platinum was found to occur when a suspension of pre-made and purified nanoparticles was added post-synthesis to the M41S materials (Chapter 4). These materials resulted in porous silicas with well dispersed, small metal particles. The optimum conditions for the calcination of these new materials were determined, in an attempt to remove the ligands and stabilisers and retain the small metal particle size (Chapter 5). Testing for the Fischer-Tropsch process was conducted in a fixed bed reactor through which a flow of synthesis gas containing carbon monoxide and hydrogen could pass over the material (Chapter 5). Analysis by gas chromatography showed that the major product produced by all materials tested was methane, but other hydrocarbons were produced in small amounts, including hexane.

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.