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Published: 4 June 2021
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1

Gallo, Jean Marcel Ribeiro. "Síntese de carbonos cerâmicos mesoporosos para aplicação como eletrodos em células a combustível a metanol direto." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250419.

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Orientadores: Heloise de Oliveira Pastore, Leonardo Marchese
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Esse trabalho teve como objetivo a aplicação de peneiras moleculares mesoporosas de sílica como suporte para metal em aplicações em eletrodos na Célula a combustível a metanol direto (DMFC). As peneiras moleculares mais importantes, MCM-41, MCM-48 e SBA-15, foram escolhidas. Em um primeiro momento a reprodutibilidade das sínteses foi verificada. Como pesquisa lateral foi estudada a acidez de superfície da SBA-15 contendo alumínio obtida por síntese direta. Além disso, foi desenvolvida a primeira síntese direta para a [Al]-SBA-15 Sílica é um isolante elétrico e, portanto, não pode ser utilizada como um eletrodo, deste modo, uma nova família de compósitos chamada Carbonos Cerâmicos Mesoporosos (MCC) foi preparada pela adição de grafite comercial na síntese das sílicas mesoporosas (MCM-41, MCM-48 ou SBA-15). A grafite não influenciou na formação da mesofase de sílica, de qualquer maneira, a MCC-MCM-41 e a MCC-MCM-48 cresceram na superfície da grafite. As MCCs preparadas com razão em massa sílica/carbono de 1/1 e 1/1.25 apresentaram condutividades elétricas similares enquanto MCCs com menos quantidade de carbono se mostraram isolantes elétricos. As MCCs(1/1) modificadas com 20 % em massa de paládio foram usadas na DMFC chegando no máximo a desempenhos 10 vezes menores que o do sistema usando o suporte comercia Vulcan XC-72R. Esse comportamento foi atribuida a menos condutividade elétrica dos MCCs. Para aumentar a condutividade elétrica dos MCCs(1/1), o agente direcionador orgânico usado na síntese da fase silícica foi carbononizado ( ao invez de calcinado, como feito anteriormente) Alternativamente, os MCCs foram sintetizados com uma razão em massa sílica/carbono de 1/3. Os testes dos MCCs contendo 20 % em massa de platina no cátodo da DMFC mostraram melhores resultados para a MCC-SBA-15(1/3) e a MCC-MCM-48(1/1) pirolisada. Por outro lado, o despenho do sistema usando o suporte Vulcan-XC-72R foi o dobro. Modificados com 60 % em massa da liga PtRu, o MCC-SBA-15(1/3) e o MCC-MCM-48(1/1) pirolisado foram aplicados no ânodo da DMFC, alcançando desempenhos 20 e 40 % maiores que a Vulcan XC-72R.
Abstract: The present work aimed at using mesoporous silica as metal support for Direct Methanol Fuel Cell (DMFC) electrodes. The most important mesoporous silica, MCM-41, MCM-48 and SBA-15, were chosen. In a first moment their synthesis were verified with respect to the reproductibility. As side results, the surface acidity of aluminum containing SBA-15 obtained by direct synthesis was also studied and it is also reported the first [Al]-SBA-16 obtained by direct synthesis was reported. Silica is electrically insulating and thus cannot be used directly in a cell electrode, thus it was reported here the preparation of the novel composite named Mesoporous Carbon Ceramics (MCC) obtained by the addition of commercial graphite into the mesoporous silica synthesis (MCM-41, MCM-48 or SBA-15). The graphite did not influence in the formation of the silica mesophase, however, MCC-MCM-41 and MCC-MCM-48 grow on the graphite surface. The MCCs prepared with silica/carbon weight ratio of 1/1 and 1/1.25 presented similar electrical conductivities while lower carbon loading MCCs were found insulating. The MCCs(1/1) modified with 20 wt % of platinum were used on Direct Methanol Fuel Cell electrodes (DMFC) reaching performances more ten 10 times lower than that of a system using the commercial metal support Vulcan XC-72R, probably due to their lower electrical conductivity. To increase the electrical conductivity of the MCCs(1/1), the surfactant used to synthesize the silica phase was carbonized (instead of calcined as done for the previous materials). Alternatively, MCCs was synthesized with silica/carbon weight ratio of 1/3. The test of 20 wt. % platinum-containing MCCs on the cathode of the DMFC showed that the best results were obtained for the MCC-SBA-15(1/3) and for the template-pyrolysed MCC-MCM-48(1/1), however, the performance was approximately half of that of the system using Vulcan-XC-72R. When modified with 60 wt % of PtRu alloy, MCC-SBA-15(1/3) and to the template-pyrolysed MCC-MCM-48(1/1) and applied on the DMFC anode, the performances at 343 K was ca. 20 and 40 % higher that that obtained for the system using Vulcan XC-72R.
Doutorado
Quimica Inorganica
Doutor em Ciências
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2

Tan, Yu-May. "Mesoporous materials." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370067.

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3

Lebold, Timo. "Mesoporous silica nanostructures." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-118194.

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4

Björk, Emma M. "Mesoporous Building Blocks : Synthesis and Characterization of Mesoporous Silica Particles and Films." Doctoral thesis, Linköpings universitet, Nanostrukturerade material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-99858.

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Catalyst supports, drug delivery systems, hosts for nanoparticles, and solar cells are just some examples of the wide range of exciting applications for mesoporous silica. In order to optimize the performance of a specific application, controlling the material’s morphology and pore size is crucial. For example, short and separated particles are beneficial for drug delivery systems, while for molecular sieves, the pore size is the key parameter. In this thesis, mesoporous silica building blocks, crystallites, with hexagonally ordered cylindrical pores were synthesized, with the aim to understand how the synthesis parameters affect the particle morphology and pore size. The synthesis of the particles is performed using a sol-gel process, and in order to increase the pore size, a combination of low temperature, and additions of heptane and NH4F was used. By variations in the amounts of reagents, as well as other synthesis conditions, the particle morphology and pore size could be altered. Separated particles were also grown on or attached to substrates to form films. Also, a material with spherical pore structure was synthesized, for the first time using this method. It was found that a variation in the heptane concentration, in combination with a long stirring time, yields a transition between fiber and sheet morphologies. Both morphologies consist of crystallites, which for the fibers are joined end to end, while for the sheets they are attached side by side such that the pores are accessible from the sheet surface. The crystallites can be separated to a rod morphology by decreasing the stirring time and tuning the HCl concentration, and it was seen that these rods are formed within 5 min of static time, even though the pore size and unit cell parameters were evolving for another 30 min. Further studies of the effects of heptane showed that the shape and mesoscopic parameters of the rods are affected by the heptane concentration, up to a value where the micelles are fully saturated with heptane. It was also observed that the particle width increases with decreasing NH4F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH4F, and the growth mechanism for platelets was further studied. The pore sizes for various morphologies were altered by e.g. variations in the hydrothermal treatment conditions, or the method for removing the surfactants. The separated particles can be attached to substrates, either during the particle synthesis or by post grafting prior to calcination. The film formation during the one-pot-synthesis was studied and a formation mechanism including nucleation of elongated micelles on the substrate was suggested. During the post grafting film synthesis, the medium in which the particles are dispersed, as well as functionalization of both particle and substrate are crucial for the post grafting process. The pores are easily accessible independent of the method, even though they are aligned parallel to the substrate when the one-pot-method is used, while post grafting gives a perpendicular pore orientation. In summary, this work aims to give an understanding for the formation of the synthesized material, and how to tune the material properties by alterations in parameter space. Successful syntheses of four different particle morphologies and two new types of films were performed, and the pore size could easily be tuned by various methods.
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5

Yue, Wenbo. "Mesoporous crystalline metal oxides." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/830.

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6

Liu, Yi. "Mesoporous silica/polymer nanocomposites." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31739.

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Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Jacob. Karl; Committee Member: Griffin. Anselm; Committee Member: Tannenbaum. Rina; Committee Member: Thio. Yonathan S; Committee Member: Yao. Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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7

Sheikh, Shehla Altaf. "Modification of mesoporous silicas." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327599.

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8

Mehlhorn, Dirk, Rustem Valiullin, Jörg Kärger, and Ryong Ryoo. "Diffusion in mesoporous zeolites." Diffusion fundamentals 20 (2013) 96, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13685.

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9

Mehlhorn, Dirk, Rustem Valiullin, Jörg Kärger, and Ryong Ryoo. "Diffusion in mesoporous zeolites." Diffusion fundamentals 16 (2011) 54, S. 1, 2011. https://ul.qucosa.de/id/qucosa%3A13795.

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10

Mehlhorn, Dirk, Rustem Valiullin, Jörg Kärger, and Ryong Ryoo. "Diffusion in mesoporous zeolites." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183854.

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11

Khushalani, Deepa. "Studies of mesoporous inorganic materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35204.pdf.

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12

O'Brien, Stephen. "The chemistry of mesoporous materials." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390532.

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13

Lotsi, Bertha. "Mesoporous Adsorbents for Perfluorinated Compounds." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3729.

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Effective adsorbents for polyfluorinated compounds (PFCs) were successfully prepared. And they were tested in the adsorption of perfluorooctanoic and perfluorooctanesulfonic acids. Bridged silsesquioxanes containing secondary and tertiary amino groups were synthesized by sol-gel condensation of bis[3-(trimethoxysilyl)propyl]amine and bis[3-(methylamino)propyl]-trimethoxysilane in acidic media with surfactants. Obtained materials are mesoporous with a high BET surface area. They combine high structural stability with a high concentration of surface amino groups serving as adsorption sites. Batch adsorption tests demonstrated their extremely high adsorption capacity on PFCs: in some experiments, it reached up to 88% of the adsorbent weight. Adsorption of PFCs changed the surfaces of the adsorbent nanoparticles from hydrophilic to hydrophobic thus providing their agglomeration and floatability. Column tests showed fast adsorption of PFCs even at high concentrations and high flow rates. Obtained results can be used in the development of an effective filtration device for clean-up of water contaminated by PFCs.
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14

Wall, Jennifer H. "Spectroscopic characterisation of mesoporous materials." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1963/.

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Commercially available inorganic solids and organically functionalised silicas and silica-polysaccharide composite materials synthesised in the laboratory were characterised by various techniques. These included direct infrared spectroscopic measurements, infrared and UV-visible probing techniques using probe molecules such as water, ammonia, d3-actonitrile, aniline, Reichardt’s dye and iodine and also by the application of the Knoevenagel condensation as a model reaction. As well as the information obtained about the surface activity of the solids, this review of techniques revealed the advantages and limitations of well-known and less frequently used methods. In particular, the use of iodine as a UV-visible probe molecule allowed the observation of differences between materials that are extremely difficult to analyse such as sodium carbonate and sodium acetate. However with current levels of knowledge about the electronic transitions of iodine adsorbed on surfaces, the results are not straight forward to interpret. The silica-polysaccharide composites also showed interesting properties, both in terms of their morphology and their chemistry and merit further study.
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15

Reynhardt, Jan Petrus Karel. "Carbonylation catalysts based on metal complexed PAMAM-dendrimers supported on mesoporous and periodic mesoporous silica supports." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/29253.

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This thesis describes the synthesis and characterization of various polyamidoamine (PAMAM) dendrimer moieties supported on amorphous mesoporous and periodic mesoporous silica supports. The surface characteristics of the supports are investigated using various methods and found to be intricately involved in the success of the dendrimer synthesis. The dendrimers are phophinomethylated and complexed with either palladium or rhodium and used as catalysts for carbonylation reactions. The palladium complexed C6-PAMAM dendrimers supported on aminopropyl silica gel are recyclable catalysts for the hydroesterification of olefins and turnover numbers (TON) of up to 1200 are possible. C2-PAMAM dendrimers supported on LPMCM-41 and Davisil are complexed with rhodium and used as catalysts for the hydroformylation reaction of olefins. These catalysts show how the pore geometry influences the activity and recyclability of the catalysts. The dendrimer-rhodium complexes supported on LPMCM-41 exhibit very high activity and a TOF of up to 1800 h-1 are observed for the hydroformylaton of 1-octene. These catalysts can be recycled effectively by simple filtration. A negative dendrimer effect is observed with the higher generations exhibiting lower activity than the lower generations. The dendrimer-rhodium complexes supported on Davisil also exhibit very high activity and a TOF of up to 1700 h-1 are observed for the hydroformylation of 1-octene. The activity of these catalysts are less dependent on the generation than the LPMCM-41 dendrimers, and excellent activity is observed up to the third generation for the hydroformylation reaction of 1-octene.
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16

Li, Yan. "Periodic mesoporous organosilicas with functional chromophores." Diss., Ludwig-Maximilians-Universität München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-173286.

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17

Jackson, Dominic. "Organic functionalisation of hexagonal mesoporous silica." Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341112.

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18

Schillo, Melissa C. "Mesoporous Inorganic Membranes for Water Purification." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313586746.

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19

Meoto, Silo, and Marc-Olivier Coppens. "Anodic alumina-mesoporous silica hybrid membranes." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184904.

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20

Ronhovde, Cicily J. "Biomedical applications of mesoporous silica particles." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5837.

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Mesoporous silica particles are of significant interest for biomedical applications due to their good general biocompatibility compared to other nanoparticle matrices such as quantum dots, high specific surface areas up to 1000 m2/g, and extreme synthetic tunability in terms of particle size, pore size and topology, core material, and surface functionalization. For one application, drug delivery, mesoporous silica nanoparticles (MSNs) of two pore structures, MCM-41 – parallel, hexagonally ordered pores approximately 3 nm in diameter – and wormhole (WO) – interconnected, disordered pores also approximately 3 nm in diameter – were synthesized with particle diameters under 100 nm. Additionally, a magnetic Fe3O4 nanoparticle core was incorporated into Fe3O4-core WO-MS-shell particles. The particles were loaded with doxorubicin, a chemotherapeutic, and the drug release into phosphate buffered saline (PBS, 10 mM, pH 7.4) at 37 °C was monitored by fluorescence spectroscopy. The data were fit to three models: Korsmeyer-Peppas, first order exponential release, and Weibull. The Korsmeyer-Peppas model provided useful information concerning the kinetics and mechanism of drug release from each MSN type. A small but statistically significant difference in the release kinetics was found due to the different pore topologies. A much larger kinetic effect was observed due to the inclusion of an iron oxide core. Applying a static magnetic field to the Fe3O4-core WO-MS shell particles did not have a significant impact on the doxorubicin release. This is the first time that the effects of pore topology and iron oxide core have been isolated from pore diameter and particle size for these materials. In vitro cell studies were conducted to determine the cytotoxicity of the bare and doxorubicin-loaded materials against three cancerous cell lines – A549 human lung carcinoma cells, HEC50CO human endometrial cancer cells, and CT26 mouse colon cancer cells. The MCM-41 and WO MSNs generally displayed similar toxicities within each cell line, and the Fe3O4-core WO-MS shell particles were less toxic. Doxorubicin-loaded particles generally displayed greater toxicity than bare MSNs, but the A549 cells were very resistant to all concentrations of MSNs tested. For another biomedical application, tissue phantom development, mesoporous silica particles with approximately 10 μm diameters and C18 surface functionalization were evaluated for their use as a substrate for optical tissue phantoms. Tissue phantoms are synthetic imitations of biological material, and C18-modified silica provides a substrate that is simple to load with optically active biological molecules. The molecules are then hydrophobically trapped to maintain a clear optical boundary between the biological loading within the particle and an aqueous suspension gel. Several preparation techniques were evaluated for the dispersal of hydrophobic particles in aqueous media, and qualitative analysis indicated that surfactant coating of the outer surface could fully disperse the hydrophobic particle while maintaining the clear optical boundary. A novel analysis was developed to provide a single numerical indicator of clustering for a quantitative assessment of particle dispersal in tissue phantoms.
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21

TIDDIA, MARIAVITALIA. "Hybrid Mesoporous and Microporous Materials Characterisation." Doctoral thesis, Università degli Studi di Cagliari, 2019. http://hdl.handle.net/11584/259900.

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My thesis research is undertaken to address various challenges in the study of porous hybrid materials. The effect of the insertion of polymer in porous material via an electrochemical process, the analysis of the photocurrent generated by developing a hybrid p-n junction, the stability and the resistance added to the pristine material by the process and the definition of a protocol for mass spectrometry analysis of porous materials and buried interfaces will be presented in the seminar. Two popular analysis techniques; electrochemistry and mass spectrometry, explored the potential to analyse organic inorganic hybrid materials and interfaces using different polymers and different inorganic substrates. Electrochemical and optical study made on porous silicon grafted with a conducting polymer, properties like resistance to attack by basic solution and photocurrent generation will be presented and explained. The possibility to understand how the polymer is attached to the pore walls is investigated by mass spectrometry imaging. This technique requires refinement of measurement parameters for this class of materials, by using models with similar composition and geometry. To do this, I used a focused ion beam (FIB) for milling the surface of a porous micrometric matrix applying a particular cleaning procedure to recover the damaged polymeric component. This method has been successfully applied to other devices to highlight the effectiveness of this technique in section. These studies provide the essential metrological foundation to address frontier issues in surface and nanoanalysis and extend the measurement capabilities of secondary ion mass spectrometry.
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22

Xu, Yeping. "Synthesises of mesoporous materials and studies of host-guest interaction in mesoporous carbon by solid state NMR." Berlin mbv, Mensch-und-Buch-Verl, 2009. http://d-nb.info/995894957/04.

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23

Borisova, Dimitriya. "Feedback active coatings based on mesoporous silica containers." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6350/.

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Metalle werden oft während ihrer Anwendung korrosiven Bedingungen ausgesetzt, was ihre Alterungsbeständigkeit reduziert. Deswegen werden korrosionsanfällige Metalle, wie Aluminiumlegierungen mit Schutzbeschichtungen versehen, um den Korrosionsprozess aktiv oder passiv zu verhindern. Die klassischen Schutzbeschichtungen funktionieren als physikalische Barriere zwischen Metall und korrosiver Umgebung und bieten einen passiven Korrosionsschutz nur, wenn sie unbeschädigt sind. Im Gegensatz dazu kann die Korrosion auch im Fall einer Beschädigung mittels aktiver Schutzbeschichtungen gehemmt werden. Chromathaltige Beschichtungen bieten heutzutage den besten aktiven Korrosionsschutz für Aluminiumlegierungen. Aufgrund ihrer Giftigkeit wurden diese weltweit verboten und müssen durch neue umweltfreundliche Schutzbeschichtungen ersetzt werden. Ein potentieller Ersatz sind Schutzbeschichtungen mit integrierten Nano- und Mikrobehältern, die mit ungiftigem Inhibitor gefüllt sind. In dieser Arbeit werden die Entwicklung und Optimierung solcher aktiver Schutzbeschichtungen für die industriell wichtige Aluminiumlegierung AA2024-T3 dargestellt Mesoporöse Silika-Behälter wurden mit dem ungiftigen Inhibitor (2-Mercaptobenzothiazol) beladen und dann in die Matrix anorganischer (SiOx/ZrOx) oder organischer (wasserbasiert) Schichten dispergiert. Zwei Sorten von Silika-Behältern mit unterschiedlichen Größen (d ≈ 80 and 700 nm) wurden verwendet. Diese haben eine große spezifische Oberfläche (≈ 1000 m² g-1), eine enge Porengrößenverteilung mit mittlerer Porenweite ≈ 3 nm und ein großes Porenvolumen (≈ 1 mL g-1). Dank dieser Eigenschaften können große Inhibitormengen im Behälterinneren adsorbiert und gehalten werden. Die Inhibitormoleküle werden bei korrosionsbedingter Erhöhung des pH-Wertes gelöst und freigegeben. Die Konzentration, Position und Größe der integrierten Behälter wurden variiert um die besten Bedingungen für einen optimalen Korrosionsschutz zu bestimmen. Es wurde festgestellt, dass eine gute Korrosionsschutzleistung durch einen Kompromiss zwischen ausreichender Inhibitormenge und guten Barriereeigenschaften hervorgerufen wird. Diese Studie erweitert das Wissen über die wichtigsten Faktoren, die den Korrosionsschutz beeinflussen. Somit wurde die Entwicklung effizienter, aktiver Schutzbeschichtungen ermöglicht, die auf mit Inhibitor beladenen Behältern basieren.
Metals are often used in environments that are conducive to corrosion, which leads to a reduction in their mechanical properties and durability. Coatings are applied to corrosion-prone metals such as aluminum alloys to inhibit the destructive surface process of corrosion in a passive or active way. Standard anticorrosive coatings function as a physical barrier between the material and the corrosive environment and provide passive protection only when intact. In contrast, active protection prevents or slows down corrosion even when the main barrier is damaged. The most effective industrially used active corrosion inhibition for aluminum alloys is provided by chromate conversion coatings. However, their toxicity and worldwide restriction provoke an urgent need for finding environmentally friendly corrosion preventing systems. A promising approach to replace the toxic chromate coatings is to embed particles containing nontoxic inhibitor in a passive coating matrix. This work presents the development and optimization of effective anticorrosive coatings for the industrially important aluminum alloy, AA2024-T3 using this approach. The protective coatings were prepared by dispersing mesoporous silica containers, loaded with the nontoxic corrosion inhibitor 2-mercaptobenzothiazole, in a passive sol-gel (SiOx/ZrOx) or organic water-based layer. Two types of porous silica containers with different sizes (d ≈ 80 and 700 nm, respectively) were investigated. The studied robust containers exhibit high surface area (≈ 1000 m² g-1), narrow pore size distribution (dpore ≈ 3 nm) and large pore volume (≈ 1 mL g-1) as determined by N2 sorption measurements. These properties favored the subsequent adsorption and storage of a relatively large amount of inhibitor as well as its release in response to pH changes induced by the corrosion process. The concentration, position and size of the embedded containers were varied to ascertain the optimum conditions for overall anticorrosion performance. Attaining high anticorrosion efficiency was found to require a compromise between delivering an optimal amount of corrosion inhibitor and preserving the coating barrier properties. This study broadens the knowledge about the main factors influencing the coating anticorrosion efficiency and assists the development of optimum active anticorrosive coatings doped with inhibitor loaded containers.
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24

Xia, Yanfeng. "SYNTHESIS OF ORDERED MESOPOROUS MATERIALS VIA MICROWAVE PROCESSING AND HIGHLY HETEROATOM DOPED ORDERED MESOPOROUS CARBONS FOR ENERGY STORAGE." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron15270948387105.

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25

Rocha, Lucas Alonso [UNESP]. "Materiais meso-estruturados luminescentes." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/105768.

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Partículas esféricas de sílica mesoporosa foram obtidas a partir da síntese “template” pelo processo de pirólise de aerossol. O processo foi otimizado para a obtenção de materiais mesoporosos sem resíduos orgânicos e preparados em uma única etapa, eliminando assim, a longa etapa de remoção do surfactante na metodologia tradicional (tratamento térmico ou extração soxhlet, podendo durar dezenas de horas). A otimização do processo de pirólise de aerossol proposta nesta tese reduziu este tempo para apenas alguns minutos. Os materiais apresentaram uma área superficial (BET) de até 1028 m2 .g-1 , com volume de poros (BJH) de 0,58 cm3 .g-1 . Os difratogramas de raios-X indicaram um alto grau de organização com um arranjo hexagonal de poros, confirmado também pela microscopia eletrônica de transmissão. Além disto, bandas características de grupos orgânicos não foram observadas nos espectros de absorção na região do infra-vermelho para as amostras obtidas acima de 600ºC. Amostras dopadas com íons Eu3+ também foram preparadas durante a tese. A análise por espectroscopia de luminescência, para íons Eu3+ , indicou que o íon está encapsulado nos canais mesoporosos sem prévia modificação química da matriz. Posteriormente, moléculas de 1,10- Fenantrolina foram coordenadas ao íon Eu3+ aumentando a faixa espectral de excitação do íon (efeito antena). Além disto, partículas luminescentes também foram obtidas pela incorporação do complexo Eu(fod)3 ou rodamina-B nos poros das matrizes. Finalmente, testes de recobrimento (core shell, SiO2 mesoporoso-SiO2) das partículas luminescentes foram realizados e os resultados indicaram que independentemente da espessura obtida pelo processo de recobrimento, o grau de organização dos poros e a fotoluminescência não sofreram alterações
Spherical mesoporous silica particles were obtained using the template synthesis by spray pyrolysis process. The process was optimized for the preparation of the mesoporous materials in one-pot route without organic residues, eliminating thus, the long process of removal of the surfactant, usually used in the available methods (heat treatment or soxhlet extraction, which require several hours or days). The one- pot route proposed in this thesis reduced the extraction process to only a several minutes. These materials presented a surface area value (BET) of 1028m2 .g-1 and pore volume (BJH) was 0,58 cm3 .g-1 . The X-ray diffraction patterns and the transmission electronic micrographs show an ordered typical p6mm 2D hexagonal mesostructure. Characteristics bands of organic groups were not observed in the infra-red absorption spectra for the samples obtained at 600ºC. Moreover, SiO2 mesoporous doped with Eu3+ ions were also prepared. Luminescence data suggest that the Eu3+ ions were successful encapsulated into the channels of mesoporous silica without any preliminary chemical modification of the matrix. Moreover, extra ligands such as 1,10-Phenantroline can be further coordinated, increasing the spectral range excitation (antenna effect). Furthermore, luminescent particles were also prepared by the wet impregnation of Eu(fod)3 complex and rhodamine-B molecules. Finally, tests of coating (core shell, SiO2 mesoporous-SiO2) of luminescent particles had been carried through and the The results obtained show spherical shape and the observation of a highly ordered hexagonal array of mesochannels further confirms the 2D hexagonal p6m structure. Luminescence results reveal that rhodamine-B has been successfully encapsulated into the channels of mesoporous particles. Silica coating has been observed in TEM measurements
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26

Moscofian, Andrea Sales de Oliveira. "Filossilicatos de magnesio e silicas mesoporosas organofuncionalizados para o uso na remoção de corantes industriais." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250079.

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Orientador: Claudio Airoldi
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Filossilicatos de magnésio e sílicas mesoporosas, com grupos orgânicos ligados às estruturas poliméricas inorgânicas, foram estudados na remoção de corantes. Para a síntese dos materiais nanoestruturados organofuncionalizados foram empregados agentes sililantes, (H3CO)3Si-R1, em que R1 é a cadeia carbônica contendo grupos funcionais: 3-aminopropiltrimetoxissilano, cloreto de octadecildimetil(3-trimetoxissilil-propil)amônio, 3-mercaptopropiltrimetoxissilano, 3-etilenodiaminopropiltrimetoxissilano e 3-dietilenotriaminopropiltrimetoxissilano. Através do processo sol-gel foram obtidos filossilicatos com estruturas inorgânicas similares àquelas dos silicatos lamelares naturais e sílicas mesoporosas empregando-se o surfatante CTAB como direcionador da estrutura inorgânica. As moléculas pendentes nos poros dos novos materiais com cargas positivas ou protonadas interagiram com as cargas negativas dos corantes utilizados na indústria têxtil: amarelo reativo GR, vermelho reativo RB e azul reativo RN. O estudo de adsorção mostrou que o filossilicato contendo cloreto de octadecildimetil(3-trimetoxissilil-propil)amônio, Fil-COTA, foi o material que apresentou a maior capacidade de adsorção, 1343 mg gpara o corante amarelo GR, 1286 mg g para o azul reativo RN e 344 mg gpara o vermelho reativo RB. Também foram realizados testes em amostras reais de efluente têxtil. Os resultados mostraram que não é necessário ajustar o pH inicial, a saturação do material ocorre após 3 h, sendo necessária uma massa mínima de 2,5 g dm de Fil-COTA. Portanto, este material é promissor no tratamento de efluentes têxteis reais.
Abstract: Magnesium phyllosilicates and mesoporous silicas, with organic groups anchored onto an inorganic polymeric backbones were studied for dye removal. In the synthesis of the organofunctionalized nanostructured materials, the silylanting agents, (H3CO)3Si-R1, where R1 represents carbonic chain containing functional groups: 3-aminopropyltrimethoxysilane, octadecyl (3-trimethoxysylilpropyl)ammonium chloride, 3 ¿ mercaptopropyltri-methoxysilane, 3-ethylenediaminetrymethoxysilane and 3-diethy-lenetriaminetrymethoxysilane were employed. The sol-gel process was used and phyllosilicates with inorganic lamellar structures similar to those of natural silicate and mesoporous silicas were obtained using the surfactant CTAB as template to direct inorganic structure in the latter case. The pendent molecules in pores of the new material with positive charge interact with the negative charge of the dyes used in the textile industry: reactive yellow GR, reactive red RB and reactive blue RN. The adsorption study showed that the phyllosilicate containing octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, Fil-COTA, presented the highest adsorption capacity, 1343 mg g for reactive yellow GR, 1286 mg g for reactive blue RN and 344 mg g for reactive red RB. Real samples of textile effluents were also tested. The results showed that it is not necessary to ajust the inicial pH, surface saturation occurs after 3 h and the minimum mass necessary is 2,5 g dm of Fil-COTA. Thus, this is a promising material for textile effluent treatement.
Doutorado
Quimica Inorganica
Doutor em Ciências
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27

Badshah, Syed. "Híbridos inorgânico-orgânicos nanoestruturados de sílica mesoporosa e filossilicatos - energética da remoção de cátions na interface sólido/líquido." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250054.

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Orientador: Claudio Airoldi
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: No presente trabalho, híbridos inorgânico-orgânicos nanoestruturados de sílica mesoporosa e de filossilicatos de magnésio lamelares com estrutura similar ao talco foram sintetizados e caracterizados. A máxima capacidade sorptiva de cátions dos híbridos e as características energéticas das interações dos cátions com centros básicos, na interface sólido/líquido, foram também estudadas. A sílica mesoporosa análoga aos materiais SBA-15 tem sido sintetizada por meio do tribloco co-polímero EO20-PO70 -EO20 (P123 - Pluronic®), que atua como um agente direcionador estrutural. Os materiais SBA-15 sintetizados foram funcionalizados com vários agentes sililantes, os quais apresentam os seguintes grupos funcionais: amida, nitrila e marfolina ou base de Schiff do anel tiofênico. Os agentes sililantes com os grupos funcionais mencionados acima foram sintetizados por meio de reações de adição de Michael do aceptor de Michael a,b - insaturado (acrilamida, acrilonitrila e 4- acriloilmarfolina), ou por meio da reação de base de Schiff do 2-tiofenocaboxaldeído com os agentes sililantes aminados, comercialmente disponíveis. As técnicas de espalhamento de raios X a baixa ângulo (SAXS) e de adsorção/desorção de nitrogênio para a SBA-15 pura e a SBA-15 funcionalizada mostraram um arranjo estrutural hexagonal bem-ordenado nos materiais. Os filossilicatos lamelares híbridos com diferentes porções orgânicas presentes dentro dos nanoespaços lamelares foram sintetizados por meio de reações sol-gel de uma única etapa. Com esse intuito, os agentes sililantes com vários grupos funcionais (tiopropanamida, tiocarbamato, nitrila e base de Schiff ou anel tiofênico) foram sintetizados e reagiram com uma solução metanólica de nitrato de magnésio, sob condições básicas. A difratometria de raios X indicou distâncias basais maiores de que 1 nm para os filossilicatos híbridos sintéticos. A técnica de difração de raios X também mostrou que a estrutura inorgânica dos filossilicatos híbridos era similar àquela do talco natural. A estrutura inorgânica do filossilicato híbrido é composta de camadas octaédricas ocupadas pelo átomo de magnésio hexacoordenado presentes entre duas camadas tetraédricas silícicas, em que a porção orgânica está covalentemente ligada à camada tetraédrica da estrutura em camadas. A integridade das porções orgânicas ligadas à rede inorgânica da sílica mesoporosa ou dos filossilicatos foi confirmada por meio da Espectroscopia no Infravermelho com transformada de Fourier e por meio da técnica de Ressonância Magnética no estado sólido para os núcleos Si e C. A máxima incorporação de porções orgânicas foi determinada por meio da análise elementar. As porções orgânicas ligadas aos materiais híbridos contêm: nitrogênio, oxigênio e enxofre, os quais correspondem aos sítios básicos disponíveis para a remoção de espécies como: Pb, Cu, Cd e Ni. As capacidades sorptivas máximas dos materiais híbridos para tais cátions foram obtidas por meio de Isotermas de adsorção de Langmuir. Os resultados revelam que os filossilicatos lamelares híbridos apresentam elevada capacidade para remoção de cátions em comparação com os materiais SBA-15, devido ao elevado grau de funcionalização. A energética das interações entre os cátions e os centros básicos ao longo da interface sólido/líquido foram determinadas através da microcalorimetria. As variações negativas da energia de Gibbs, de entalpia e os valores positivos de variação entrópica indicam interações espontâneas e favoráveis entre os sólidos e os íons metálicos. Esses resultados favoráveis indicam que os híbridos sintetizados podem ser úteis na remoção de cátions tóxicos de soluções aquosas, auxiliando na despoluição de ecossistemas
Abstract: In the present work, nanostructured inorganic-organic hybrids based on mesoporous silica and lamellar magnesium phyllosilicates with talc-like structure were synthesized and characterized. The maximum cations sorption capacity of the hybrids and energetic features from cation- basic center interactions at the solid liquid interface were also studied. The mesoporous silica analogous to SBA-15 materials has been synthesized through the triblock co-polymer EO20-PO70 -EO20 (P123 ¿ Pluronic®) as a structured directing agent. The synthesized SBA-15 materials were functionalized with various silylating agents having organic functional groups of amide, nitrile, and marpholine or Schiff base of thiophenic ring. The silylating agents with the aforementioned functional groups were synthesized either by the Michael addition reactions of a,b-unsaturated Michael acceptor (acrylamide, acrylonitrile and 4-acryloylmarpholine) or by the Schiff base reaction of 2-thiophenecaboxaldehyde with commercially available aminated silylating agents. Small angle X-ray scattering (SAXS) and nitrogen adsorption/desorption experiments for both SBA-15 and functionalized SBA-15 showed well-ordered hexagonal array structure. The lamellar phyllosilicates hybrids with different organic moieties inside the lamellar nanospaces were synthesized through a single step sol-gel reaction. For this purpose, silylating agents with various functional groups (thiopropanamide, thiocarbamate, nitrile and Schiff base of thiophenic ring) were synthesized and reacted with methanolic solution of magnesium nitrate under basic conditions. The X-ray diffraction showed basal distances of more than 1 nanometer for the synthetic hybrid phyllosilicates. The XRD also showed that the inorganic structure of the hybrid phyllosilicates was similar to that of natural talc. The inorganic network of the hybrid phyllosilicate is composed of octahedral sheet occupied by hexacoordinated magnesium atom sandwiched between two tetrahedral silicic sheets, and the organic moiety is covalently bonded to the tetrahedral sheet of the layered structure. The integrity of organic moieties attached to the inorganic network of mesoporous silica or phyllosilicates was confirmed by the Fourier transform infrared spectroscopy and nuclear magnetic resonance in the solid-state for the Si and C nuclei. The maximum incorporation of organic moieties was determined through elemental analysis. The attached organic moieties of the hybrid materials contain nitrogen, oxygen or sulfur basic centers available for divalent lead, copper, cadmium and nickel cation removal. The maximum sorption capacities of the hybrids for such cations were obtained through Langmuir adsorption isotherms. The results reveal that the lamellar magnesium phyllosilicate hybrids present high capacity for cations removal as compared to functionalized SBA-15 materials, due to a high degree of functionalization. The energetic of cation-basic centers interactions at the solid/liquid interface were determined through microcalorimetry. The negative Gibbs energy, exothermic enthalpy and positive entropic values indicate spontaneous and favorable interactions between the solids and metal ions. These favorable results indicated that the synthesized hybrids can be useful for removal of toxic cations from aqueous solutions for the improvement of ecosystem
Doutorado
Quimica Inorganica
Doutor em Ciências
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28

Correia, Leandro Marques. "Fe2O3 ou Co3O4 suportados em sílicas mesoporosas modificadas com NH4F e Ti para adsorção de benzotiofeno e reação de oxidação catalítica seletiva parcial de H2S a S." reponame:Repositório Institucional da UFC, 2017. http://www.repositorio.ufc.br/handle/riufc/27280.

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CORREIA, L. M. Fe2O3 ou Co3O4 suportados em sílicas mesoporosas modificadas com NH4F e Ti para adsorção de benzotiofeno e reação de oxidação catalítica seletiva parcial de H2S a S. 2017. 233 f. Tese (Doutorado em Engenharia Química)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017.
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The presence of sulfur (S) in automotive fuels must be retrain, once it generates air pollution and promotes damage to the motor (corrosion), affecting the health of living beings. The conventional process of hydrodesulfurization (HDS) for sulfuric compounds removal, used by petrochemical industries, generates large amount of H2S, which can be used in selective partial oxidation reaction of H2S to S. The HDS treatment process is not effective to remove refractory compounds at low concentrations of S, making polish techniques, such as adsorption, necessary due to environmental constraints increase. This situation has led to a need of deeper research in the area of sulfur compounds removal in fossil fuels (gas and diesel). Thus, the development of methodologies to prepare and characterize new adsorbents with high sulfur removal are necessary. The adsorption of BT (standard organic molecule contained in gas and diesel) was investigated using a regular mesoporous silica SBA-15 type and modified with NH4F, and impregnated with Fe and Co respectively. The experiments were done in batch, with different initial BT concentrations (3-15 mmol.L-1) at different temperatures (30 °C, 40 °C and 50 °C). In the second part of the research, the H2S was partially oxidized to S and SO2 using a tubular fixed bed catalytic reactor, containing mesoporous silica HMS, SBA-15, and MCM-41 modified with NH4F and Ti, and respectively Fe2O3 and Co3O4. The catalytic tests were conducted at 180 °C and 170 oC. Reactional conditions were a catalyst mass of 100 mg (40-60 mesh), operating with a 125 mL.min-1 total flow, with molar ratio H2S/Air/He (1/5/94). The brackets, adsorbents and active phases of mesoporous catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), adsorption and desorption isotherms at -196°C, x-ray photoeletronic spectroscopy (XPS), Fourier transform infrared (FTIR), Elemental analysis (CHNS) and spectroscopy of UV-visible region. The results show that mycotoxin adsorbents are promising for the hydrodesulfurization process for BT removal, especially, the sample (15Co/SBA-15/NH4F). All the prepared catalysts are active and promising for the elementary S production. The most stable catalyst was 15Fe/MCM-41, obtaining conversion values of H2S (89.72%), selectivity of S (96.19%), and selectivity of SO2 (3.81%) at 180 °C and 360 min of reaction time in the H2S to S selective oxidation partial reaction in gas phase
A presença de enxofre (S) nos combustíveis automotivos deve ser combatida, uma vez que gera a poluição atmosférica e traz prejuízos ao motor (corrosão), afetando também à saúde dos seres vivos. O processo convencional de hidrodessulfurização (HDS) para remoção dos compostos de S, utilizado pelas indústrias petroquímicas, gera elevada quantidade de H2S, o qual pode ser utilizado na reação de oxidação seletiva parcial de H2S a S. O processo de tratamento por HDS não é eficaz para remoção de compostos refratários em baixas concentrações de S, o que torna necessário a técnicas de acabamento como a adsorção, devido a um aumento nas restrições ambientais. Essa situação tem levado a uma necessidade de maiores pesquisas na área de remoção de sulfurados nos combustíveis (gasolina e diesel). Assim, busca-se desenvolver metodologias para preparar e caracterizar novos adsorventes com elevada capacidade de remoção de enxofre. A adsorção de BT (molécula orgânica modelo contida na gasolina e diesel) foi investigada utilizando-se sílicas mesoporosas do tipo SBA-15 e modificadas com NH4F, e impregnadas respectivamente com Fe e Co. Os experimentos foram feitos em batelada, com diferentes concentrações iniciais de BT (3-15 mmol/L) e temperaturas distintas (30 oC, 40 oC e 50 oC). Na segunda parte da pesquisa o H2S foi parcialmente oxidado a S e SO2 utilizando um reator catalítico de leito fixo do tipo tubular, contendo sílica mesoporosa do tipo HMS, SBA-15, e MCM-41 modificadas com NH4F e Ti, e respectivamente Fe2O3 e Co3O4. Os testes catalíticos foram conduzidos a uma temperatura de reação de 180 ºC e 170 oC. As condições reacionais foram massa do catalisador de 100 mg (40-60 mesh), operando com uma vazão total de 125 mL min-1, com razão molar H2S/Ar/He (1/5/94). Os suportes, adsorventes e as fases ativas dos catalisadores mesoporosos foram caracterizados por difração de raios-X (DRX), microscopia eletrônica de transmissão (MET), isotermas de adsorção e dessorção a -196 oC, espetroscopia fotoeletrônica de raios-X (XPS), infravermelho com transformada de Fourier (FTIR), análise elementar (CHNS) e espectroscopia da região do UV-visível. Os resultados demonstram que os adsorventes são promissores para o processo de hidrodessulfurização para a remoção da molécula de BT, especialmente, a amostra (15Co/SBA-15/NH4F). Todos os catalisadores preparados são ativos e promissores para produção de S elementar. O catalisador mais estável foi 15Fe/MCM-41, obtendo-se valores de conversão de H2S (89,72%), seletividade a S (96,19%), e seletividade a SO2 (3,81%) na temperatura de 180 oC e tempo reacional de 360 min na reação parcial de oxidação seletiva de H2S a S em fase gás
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29

Klichko, Yaroslav Vladimirovich. "Functional mesoporous silica films for nanosystems applications." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1998520791&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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30

Tokay, Kenan Cem. "Dimethyl Ether Synthesis Over Novel Mesoporous Catalysts." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609817/index.pdf.

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Due to overconsumption, fossil reserves are rapidly being depleted and various sources predict that they will not last until the end of 21st century. Moreover, the increase in the rate of global warming and the polluting matter emitted by the vehicles consuming fossil fuels has increased the search for renewable and clean energy sources. Alcohols and ethers, which contain fewer pollutants and have better burning properties, are commonly thought among clean fuel alternatives. Among the potential clean energy sources, dimethyl-ether is already in use in the automotive industries of many countries such as China and Japan, due to its low NOx and CO2 emissions, high cetane rating and efficient combustion characteristics, especially in diesel engines. In this work, dimethyl-ether synthesis is achieved using methanol dehydration reaction over solid acid catalysts. For this purpose, three different mesoporous MCM-41 type aluminum silicates have been synthesized with direct hydrothermal synthesis method and aluminum is added to the synthesized SBA-15 catalyst using impregnation method. Apart from the catalysts synthesized, different commercial catalysts such as aluminum oxide in different forms (&
#945
and &
#947
), Nafion NR-50 and Nafion SAC-13 have also been tested in this reaction. These materials were characterized by methods such as XRD, EDS, SEM, and N2 physical adsorption and DRIFTS were also investigated in terms of paramters such as the conversion of methanol to products, selectivity and yield. The analyses have shown that AlSi1 is the most active of all the aluminum silicates synthesized in both 0.136 and 0.27 s.g/cm3 space times, with up to 80% methanol conversion in all temperatures tested. AlSi1 also has low by-product formation and similar to other aluminum silicates, its dimethyl-ether selectivity approaches 1 at 4000C. Among all synthesized catalysts, the dimethyl-ether yield was seen to be the highest for Al-SBA-15, which approaches 0.5 at 4000C for both space times. For all aluminum silicates synthesized, about 40% dimethyl-ether yield was obtained at the same temperature and space times. Among the aluminum oxides, &
#945
-alumina was seen to be superior to others in &
#947
forms in terms of conversion selectivity and yield, especially at low temperatures. As to Nafion catalysts, due to its much higher surface area and high Bronsted acidity, Nafion SAC-13 has shown higher activity compared to Nafion NR-50 for all temperatures and space times tested.
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31

Schloßbauer, Axel. "Biofunctionalized Mesoporous Silica for Controlled Release Applications." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-124262.

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32

Nissfolk, Jarl. "Charge Transport Processes in Mesoporous Photoelectrochemical Systems." Doctoral thesis, KTH, Organisk kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9849.

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During the last decade, the dye sensitised solar cell (DSC) has attracted much attention. The technology has a potential to act as a new generation of photovoltaic device, it has also increased our knowledge within the field of photoelectrochemistry. The materials used in the DSC have been used in other technologies, such as electrochromic displays. This thesis examines how such systems can be analysed to understand their properties from their components. Both of the considered device technologies consist of a thin mesoporous semiconductor film immersed in an electrolyte. The study starts by investigating some of the fundamental properties of the mesoporous semiconductor and its interface with the electrolyte. This gives rise to the charge-voltage relationship for the devices, which is related to the chemical capacitance and electronic energy levels for the materials. In particular,special attention is given to the DSC and the properties of the charge carriers in the semiconductor. For the DSC, several techniques have been developed in order to understand the processes of transport and recombination for the charge carriers in the semiconductor film, which are vitally important for performance. In this thesis, particular focus is given to light modulation techniques and electrical analysis with impedance spectroscopy. The transportproperties show for both techniques a nonlinear behaviour, which is explained with the trapping model. The DSC solar cell is analysed in order to interpret the transport measurements for film thickness optimisation. DSC cells with new semiconductor materials, such as ZnO, were analysed with impedance measurements to provide new insights into the optimisation of the performance of the photoelectrochemical solar cell technology.
QC 20100804
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33

Wang, Wenhui. "Preparation and characterization of periodic mesoporous organosilicas." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26798.

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Periodic mesoporous organosilicates (PMOs) are hybrid materials whose framework is comprised of alternating organic and inorganic species. These materials are prepared via supramolecular templating assembly using bridged silsesquioxanes (RO)3Si-R'-Si(OR) 3 as precursors, and surfactants as templates. This thesis is devoted to the preparation and characterization of phenyl- and ethenylene-bridged PMOs. The phenylene-containing precursor (bis(triethoxysilyl)benzene was synthesized by Barbier-Grignard reaction, whereas the ethylene derivative bis(triethoxysilyl)ethylene was prepared by self-metathesis reaction. They were characterized by 1H and 13C NMR, and mass spectrometry. The corresponding mesoporous materials were prepared using these precursors in the presence of different types of surfactants including oligomeric alkyl polyethylene oxide, triblock polyalkylene oxide copolymer and alkyltrimethylammonium surfactants. To obtain highly ordered mesoporous organosilicates, different synthesis conditions were employed and optimized. All materials were characterized using XRD, TEM, SEM, nitrogen adsorption, 29Si and 13C solid state NMR. In addition, some post-synthesis reactions using these materials were investigated.
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34

Chen, Hung-Ting. "Multifunctionalized mesoporous silica nanoparticles for selective catalysis." [Ames, Iowa : Iowa State University], 2007.

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35

Lund, Kristina. "Structural and morphological studies of mesoporous crystals /." Stockholm : Department of Physical, Inorganic and Structural Chemistry, Stockholm university, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7110.

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36

Miller, Catherine J. "Catalytic applications of mesoporous silica-supported organometallics." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400204.

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37

Mehreteab, Tesfamariam. "Preparation of mesoporous Ti - Organosilicate epoxidation catalysts." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2009. http://digitalcommons.auctr.edu/dissertations/85.

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Following the methodology used in sol—gel chemistry to functionalize amorphous silica, organic functionalized mesoporous silica were prepared by the co-condensation of tetraethoxysilane and organoalkoxysilanes in the presence of surfactant templates. A series of titanium catalysts containing Ti-MCM-41 with different bridging and pendant organic functional groups (such as methyl triethoxysilane (MTEOS), phenyl triethoxysilane (PTEOS), diphenyl triethoxysilane (DPTEOS), bis (triethoxysilyl) ethane (BTSE), 1,4 bis(triethoxysiyl) benzene (BTSB), bis( triethoxysilyl) biphenyl (BTSDP) and two catalysts with different organic-inorganic ratios (90% TEOS with 10% phenyl, 70% TEOS with 30% phenyl) were synthesized. The catalysts were characterized by elemental analysis, XRD, FTIR, UVDRS, by solid state 13C and 29Si MAS NMR, and BET surface area analysis. The catalytic activities of the synthesized materials were evaluated for epoxidation of cyclohexene with TBIIP. The materials yielded improved conversion compared to the conversion results obtained from the traditional titanium containing mesoporous silica (Ti-MCM-41). The hydrophobic character of the synthesized catalysts was tested in the epoxidation of cyclohexene by using wet TBIIP. Ti-MCM41 with bridged organosilane showed almost the same conversion in the presence of water, while for Ti-MCM-41 with organosilane pendant groups. conversion decreased almost 36%. This implies that the silylation of the surface ofTi-MCM4I protected the active sites. The effect of substrate: oxidant molar ratio in these reactions were studied and high conversion, high selectivity were achieved at 1:1 molar ratio.
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38

Weiß, Veronika Ortrud Sophie. "Mesoporous silica nanoparticles as drug delivery platforms." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-185595.

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39

Hassler, Julia. "Mesoporous metal oxides for perovskite solar cells." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-263064.

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40

Mandlmeier, Benjamin. "Templated macro/mesoporous titania and carbon nanostructures." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-168114.

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41

Kim, Hyung Ju. "Modified mesoporous silica membranes for separation applications." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52175.

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The main theme of this dissertation is the fabrication and analysis of modified mesoporous silica membranes for separation applications. Synthesis methods for mesoporous silica membranes have been developed to enhance the transport performance and quality of the membranes, such as permeability, pore volume, and surface area. Then, synthesized membranes were modified with different organic groups to tailor selectivity in separations. The collected studies of modified mesoporous silica membranes showed that appropriate functionalization on newly synthesized novel membranes leads to promising structural and permeation properties. First, a seeded growth method was developed for synthesis of MCM-48 membranes on alumina supports, thereby extending the seeded growth technique used for zeolite membranes to mesoporous silica membrane synthesis. The surface properties of the MCM-48 membranes were then modified by silylation with hexamethyldisilazane (HMDS). In comparison to MCM-48 membranes previously synthesized by the in situ growth technique, much less silica infiltration into the alumina support was observed. The pore structure of the MCM-48 membranes demonstrated that a large accessible pore volume was available for molecular permeation and pore modification to tailor selectivity. The gas permeation properties of the calcined and silylated MCM-48 membranes were consistent with a Knudsen-like mechanism, albeit with a substantial influence of gas-solid interactions in the mesopores. The silylated MCM-48 membranes were evaluated for pervaporative separation of ethanol (EtOH), methyl ethyl ketone (MEK), and ethyl acetate (EA) from their dilute aqueous solutions. The synthesized membranes exhibited high pervaporative separation factors and organic fluxes. The selective separation of organic/water mixtures with MCM-48 membranes were attributed to both the organophilic nature of the surface and the effective pore size of the silylated mesopores. Next, the synthesis and organic/water separation properties of mesoporous silica membranes supported on low-cost and scalable polymeric (polyamide-imide) hollow fibers and modified by trimethylsilylation with HMDS was studied. Thin, defect-free membranes that exhibited high gas permeances consistent with Knudsen-like diffusion through the mesopores were prepared. Silylation of these membranes did not affect the integrity of the mesoporous silica structure and the underlying polymeric hollow fiber, but led to capping of the surface silanol groups in the mesopores with trimethylsilyl groups. The silylated mesoporous membranes were evaluated for pervaporative separation of EtOH, MEK, EA, iso-butanol, and n-butanol from their dilute aqueous solutions. The membranes showed higher separation factors than those of flat membranes, along with high organic fluxes. The large increase in hydrophobicity of the membranes upon silylation allowed upgrading of the feed mixtures to permeate streams with considerably higher organic content. The selective separation of organic/water mixtures with the fiber-supported mesoporous silica membranes was attributed to both the organophilic nature of the surface (yielding good adsorption selectivity) and the effective pore size of the silylated mesopores (giving good fluxes). Comparison with other types of organic/water separation membranes revealed that the present silylated membrane platform shows good promise for use in organic/water separation applications due to its high flux, scalable and low-cost fabrication methodology, and good separation factors that can be further enhanced by tailoring the mesopore modification chemistry. Further, the gas transport properties of aziridine-functionalized mesoporous silica membranes on polymeric hollow fibers have also investigated. The mesoporous membranes were amine-functionalized with aziridine and their transport properties were studied to understand the effects of surface functionalization on gas separations. This new hybrid aminosilica membrane showed interesting and counter-intuitive N₂ selective permeation properties in dry CO₂/N₂ separations. Detailed characterization of the membrane structure and its permeation behavior showed that such behavior was due to the strong adsorption of CO₂, leading to reduced gas flux because of CO₂-induced amine crosslinking in the mesopores. This hyper-branched aminosilica membrane showed CO₂ selective properties when applied to humid gas permeation. Water molecules in the humid gas affected the adsorption of CO₂ molecules by causing a lower degree of crosslinking, allowing facilitated transport of CO₂.
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42

Leclerc, Stephane Alfred Andre. "Direct liquid crystal templating of mesoporous metals." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340513.

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43

Geite, Patrik. "Medical Implant Applications of Mesoporous Silica Films." Thesis, Linköpings universitet, Nanostrukturerade material, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-154463.

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A literature review of medical implant applications of mesoporous silica films was written, highlighting the advantages and limitations of different film synthesis methods. Both films synthesized through the EISA sol-gel method and particulate films, including those synthesized through the direct growth method, were reviewed and discussed. All films were found to have their strengths and weaknesses, however, the films synthesized through the direct growth method was found to be the most promising type for coating implants. In addition to the literature review, copper-doped mesoporous silica films were synthesized on titanium grade 2 substrates. SEM shows that particles grown on all the films and EDX elemental analysis confirms the presence of copper in the material. Nitrogen physisorption measurements show that particles with incorporated copper have a higher specific surface area, and pore volume compared to un-doped particles. No copper content could be confirmed through FTIR. The particles grown on titanium substrates were more rod-like compared to the ones grown on the silicon substrates as control.
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44

Jones, Matthew David. "Studies of catalysts anchored to mesoporous materials." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619937.

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45

Puron, Zepeda Holda Maria. "Novel mesoporous catalysts for vacuum residue hydrocracking." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18912.

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Crude oil will continue to be an essential primary energy source during this century. The decline in light crude oil has increased the share of heavy oils in the crude slate fed to refineries. The development of new catalysts that can withstand deactivation by heavy feeds can be readily applied in industry. The aims of this work centred in the development and characterisation of novel NiMo mesoporous catalysts along the testing of such materials in hydrocracking reactions using a heavy hydrocarbon feed, Maya vacuum residue (VR). Four categories of catalytic supports were synthesised: mesoporous alumina (Al2O3), mesoporous alumina doped with Cr (Al2O3-Cr), mesoporous silica alumina (MSA) and carbon nanofibres (CNF). An experimental method was developed for one hour hydrocracking reactions between 400 and 450 °C in a batch reactor using VR. Selected catalysts were utilised in a second reaction with fresh feed. The catalysts short term deactivation was investigated and related to the product distribution and reaction conditions. It was found that reaction temperature had an important impact on conversions and product distributions. The conversion of materials with a boiling point above 450 °C was mainly thermally driven. NiMo catalysts supported on Al2O3, Al2O3-Cr and CNF led to high asphaltene conversions without suffering significant deactivation. On the other hand, the MSA supported catalyst was active mainly due to thermal reactions and its pores were blocked by coke deposits by the first hour of reaction. The Al2O3-Cr support allowed not only higher NiMo dispersion than Al2O3, but also better dispersion of the coke deposits after reaction. NiMo catalysts supported on CNF showed they could be very active in VR hydroprocessing, depending on their synthesis conditions.
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46

Frykstrand, Ångström Sara. "Mesoporous magnesium carbonate : Synthesis, characterization and biocompatibility." Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-281522.

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Mesoporous materials constitute a promising class of nanomaterials for a number of applications due to their tunable pore structure. The synthesis of most mesoporous materials involves a surfactant liquid crystal structure to form the pores. As well as the many advantages associated with this method of synthesis, there are disadvantages such as high production costs and a substantial environmental impact which limit the possibilities for large scale production. Therefore there is a need for other synthesis routes. The aim of the work described herein was to contribute to this field by developing a synthesis route that does not rely on surfactants for pore formation. A mesoporous magnesium carbonate material was therefore formed by self-assemblage of the particles around carbon dioxide gas bubbles, which functioned as pore templates. It was also possible to vary the pore diameter between 3 and 20 nm. The biocompatibility of the formed magnesium carbonate material was evaluated in terms of in vitro cytotoxicity and hemocompatibility, in vivo skin irritation and acute systemic toxicity. The results from the in vitro cytotoxicity, in vivo skin irritation and acute systemic toxicity test using a polar extraction vehicle showed that the material was non-toxic. While signs of toxicity were observed in the acute systemic toxicity test using a non-polar solvent, this was attributed to injection of particles rather than toxic leachables. In the in vitro hemocompatibility test, no hemolytic activity was found with material concentrations of up to 1 mg/ml. It was further shown that the material had anticoagulant properties and induced moderate activation of the complement system. The anticoagulant properties were ascribed to uptake of Ca2+. Finally, the ability of the material to increase the dissolution rate of the poorly soluble drug itraconazole was analyzed.  Itraconazole was dissolved up to 23 times faster from the magnesium carbonate pores than when the free drug was used. The release rate from the delivery vehicle was dependent on the pore diameter. The work presented herein is expected to be useful for the development of alternative synthesis routes for mesoporous materials and also for encouraging the development of biomedical applications for these materials.
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47

Dougherty, Troy Allen. "Synthesis and characterisation of ordered mesoporous materials." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1023.

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Ordered mesoporous materials have attracted much attention recently for use in a wide range of applications. The oxidising materials, ceria (CeO₂) and CGO (Ce₀.₉Gd₀.₁O[subscript(2-δ)]) have both been synthesised with ordered mesopores, but a method for the simple fabrication of these materials in high yields with crystalline pore walls has not yet been reported in the literature. This thesis details the development of the vacuum impregnation method for the synthesis of ordered mesoporous materials with emphasis on ceria and CGO. Using the vacuum impregnation method both materials were successfully prepared. The materials exhibited the porous single crystal morphology in high yields, with unusual crystallographic features. Nitrogen physisorption, transmission electron microscopy (TEM), TEM tomography and temperature programmed studies were employed. Temperature programmed studies showed the materials to be catalytically active at lower temperatures than traditionally-prepared ceria. Photovoltaic studies showed that the materials exhibited efficient exciton quenching. The observation of nanowire extrusion during the synthetic procedure assisted in the postulation of a mechanism for product formation in the vacuum impregnation method. The vacuum impregnation method was subsequently shown to be applicable to the synthesis of other materials, with encouraging results presented for ordered mesoporous carbon and Zr₀.₈₄Y₀.₁₆O[subscript(2-δ)]. The syntheses of ordered mesoporous La₀.₈₅Sr₀.₁₅GaO[subscript(3-δ)] and La₀.₇₆Sr₀.₁₉CoO[subscript(3-δ)] were unsuccessful.
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48

Bernardo, Ricardo Douglas de Sousa. "Immobilization of complex ruthenium in mesoporous silica." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11972.

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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
In recent years, mesoporous silica has attracted considerable scientifical and industrial interest. This material possess physical and chemical properties, which makes it to be used in a variety of applications. These properties include thermal stability, mechanical strength and low solubility, which makes it an ideal matrix support for catalysts. The heterogeneous catalysis has the advantage of separating catalyst from the reaction medium, which justifies the interest in heterogeneous catalysts. Coordination compounds are widely used in homogeneous catalytic processes, based on this there is a growing interest in producing catalytic systems onto heterogeneous silica matrices making very interesting materials. In this work, ruthenium complexes, [RuIICl2(dppb)(PPh3)] and [RuIIICl3(dppb)(OH2)] were synthesized and immobilized onto mesoporous silica matrices modified with aminopropyl and bipyridine groups forming the systems known as Si-apts-bipy-RuIICl2dppb and Si-apts-[bipy-RuIIICl2dppb]Cl-. These systems were characterized by spectroscopic techniques (FTIR, NMR and electronic absorption), electrochemical (cyclic and square wave voltammetry), thermogravimetry (TG), isotherms of adsorption / desorption of N2 and elemental analysis (CHN). The N2 adsorption isotherms using BJH (Barret, Joyner and Halenda) method for matrices shows the synthesized material has characteristics of micro and mesoporous with predominantly mesopore size. Si-apts-bipy-RuIICl2dppb system was the only one that showed catalytic activity in the reaction of hydrogenation of acetophenone with a yield of 53%. The development of catalysts in solid matrices is an area of great interest, which has justified this work.
A sÃlica mesoporosa à um material bastante versÃtil, com porosidade fÃcil de ser moldada tanto em forma quanto em tamanho, alÃm de possuir propriedades fÃsicas e quÃmicas que lhe possibilitam diversas aplicaÃÃes. Dessas propriedades destacamos a sua estabilidade tÃrmica, sua resistÃncia mecÃnica e sua pouca solubilidade as quais a tornam um suporte ideal para catalisadores. Nesse sentido, o uso de compostos de coordenaÃÃo ancorados em matrizes sÃlidas torna-se um interessante sistema a ser estudado, tendo em vista as propriedades, jà bem conhecidas, de alguns complexos metÃlicos de atuarem em catÃlise homogÃnea. De acordo com dados na literatura hà um contÃnuo interesse na sÃntese e caracterizaÃÃo de materiais mesoestruturados aplicados a heterogeinizaÃÃo de catalisadores, como por exemplo, o uso de compostos de coordenaÃÃo. Neste trabalho os complexos de rutÃnio, [RuIICl2(dppb)(PPh3)] e [RuIIICl3(dppb)(OH2)] foram sintetizados e imobilizados em matrizes de sÃlica mesoporosa modificada com grupos aminopropil e bipiridinÃcos, formando os sistemas denominados como Si-apts-bipy-RuIICl2dppb e Si-apts-[bipy-RuIIICl2dppb]Cl. Estes sistemas foram caracterizados por tÃcnicas espectroscÃpicas (FTIR, UV-Vis e RMN de 13C, 29Si e 31P), eletroquÃmicas (voltametria CÃclica e Voltametria de onda quadrada), termogravimÃtricas (TG), isotermas de adsorÃÃo/desorÃÃo de N2 e anÃlise elementar (CHN). As isotermas de N2 para adsorÃÃo pelo mÃtodo BJH (Barret, Joyner e Halenda) para as matrizes indicam que o material sintetizado neste trabalho apresenta caraterÃsticas micro e mesoporosas com predominÃncia de mesoporos. Dos materiais sintetizados apenas o sistema Si-apts-bipy-RuIICl2dppb apresentou atividade catalÃtica na reaÃÃo de hidrogenaÃÃo da acetofenona com um rendimento de 53%. O desenvolvimento de catalisadores em matrizes sÃlidas à uma Ãrea ampla e de grande interesse o que justifica o desenvolvimento deste trabalho.
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49

Madadi, Sara. "Mesoporous catalysts for aerobic epoxidation of limonene." Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/70277.

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L'intérêt pour le développement de ressources bio-renouvelables pour la production de polymères a excessivement augmenté récemment. Le limonène époxydé est une source très prometteuse de bio-monomères. Son abondance et le faible coût de sa matière première les rendent appropriés comme alternatives à leurs homologues pétroliers conventionnels. L'oxyde de 1,2 limonène et le dioxyde de limonène, les dérivés de l'époxydation du limonène, sont en effet utilisés pour la synthèse de matériaux durables tels que les polycarbonates de limonène verts et les polyuréthanes sans isocyanates. Par conséquent, l'étude des moyens efficaces et économiques d'époxydation du limonène est d'un grand intérêt. L'activation de l'oxygène moléculaire en tant qu'oxydant dans l'époxydation sélective d'alcènes est une cible tentante en raison de son faible coût et de la nature écologique de cet oxydant. Cependant, l'oxygène moléculaire est inactif et il n'est activé qu'en présence de catalyseurs à base de métaux de transition réactifs et hautement sélectifs. Dans ce travail de recherche, une technique de post-greffage a d'abord été utilisée pour la substitution du cobalt dans la SBA-16 mésoporeuse comme support en utilisant directement l'acétylacétonate de cobalt comme précurseur. La silice mésoporeuse ordonnée, spécifiquement SBA-16 avec une surface spécifique élevée, un grand volume de pores et des tailles de pores uniformes s'est avérée efficace pour fournir des sites actifs haute mentdispersés pour l'époxydation de molécules d'alcène volumineuses comme le limonène. En utilisant cette méthode, une charge élevée de cobalt finement dispersé sur de la silice SBA16 a été obtenue. Les catalyseurs Co / SBA-16 (Co / Si = 4.5%) ont présenté une conversion et une sélectivité élevées dans l'époxydation aérobie Mukaiyama du limonène avec de l'oxygène moléculaire, l’oxydant le plus souhaitable, et de l'isobutyraldéhyde comme coréducteur dans des conditions très douces en présence du solvant vert l’acétate d'éthyle. Pour optimiser le rendement de la formation d'époxyde, un plan expérimental statistique a été appliqué pour une étude systématique des conditions de réaction par Central Composite Design (CCD) et le modèle Response Surface Methodology (RSM). 99% de conversion de limonène, 50% d'oxyde de 1,2 limonène et 32% de dioxyde de limonène ont été obtenus en200 minutes de temps de réaction dans les conditions de réaction optimisées : concentration d'isobutyraldéhyde de 1 mmol / ml (rapport IBA / limonène = 3.3) et 14.3 mg / ml de ivcatalyseur à 28 °C et 10 ml/min de débit d'O2. Pour améliorer davantage l'activité du catalyseur, l'incorporation de Co2+ à faible coordination dans la structure de la silice mésoporeuse SBA-16 a été réalisée par une méthode facile et verte « d’ajustement du pH »et le résultat a été comparé par rapport à notre méthode de post-greffage précédente. Ce catalyseur avec Co/Si = 1.1%, a montré une réactivité bien plus élevée pour l'époxydation aérobie du limonène avec des rendements d'époxyde plus élevés (~ 100%) (1,2 et 8,9-oxydede limonène et dioxyde de limonène) sous une pression d'oxygène de 44 psi. Une analyse cinétique approfondie de l'époxydation aérobie du limonène a été effectuée pour permettre de proposer un schéma réactionnel. Un nouveau mécanisme, dans lequel une réaction de surface entre un intermédiaire Co3+ OOperoxo et le limonène s'est avérée impliquée dans la formation du limonène époxydé. Malgré l'excellent résultat obtenu dans la première partie de cette étude pour l'époxydation aérobie du limonène en présence d'un aldéhyde comme coréducteur et de l'acétate d'éthylecomme solvant, la mise au point d'un procédé catalytique sans solvant ni réducteur est vraiment intéressante en termes de chimie verte. L'activité et la sélectivité des catalyseurs au ruthénium supportés sur divers charbons actifs ont été étudiées dans l'époxydation aérobie du limonène dans des conditions de réaction sans solvant / réducteur et sans initiateur. Le catalyseur préparé par échange de cations en utilisant le charbo activé Darco G60, avec la plus grande surface de mésopore et le plus grand volume de pores et la plus petite taille de particule de Ru (1.8 nm), s'est avéré donner la meilleure combinaison de conversion de limonène de 35% et de sélectivité d'époxyde de 57% (1,2 et 8,9-oxyde de limonène et dioxydede limonène) à 80 °C et 3 bars de pression d'oxygène.
The incentive for the development of bio-renewable resources for production of polymers has been excessively raised recently. Limonene epoxides are very promising sources of biomonomers which their abundance and low cost of raw material make them suitable as alternatives to their conventional petroleum derived counterparts. 1,2 limonene oxide and limonene dioxide, the products of limonene epoxidation, are utilized for synthesis of sustainable materials such as green limonene polycarbonates and non-isocyanate polyurethanes. Therefore, investigation of effective and economic ways of epoxidation of limonene is of high interest. Activation of molecular oxygen as an oxidant in selective epoxidation of alkenes is a tempting target owing to its low cost and environmentally friendly nature. However, molecular oxygen is inactive, and it is activated only in the presence of potent and highly selective transition metal catalysts.In this research work, first a post grafting technique was used for substitution of cobalt inmesoporous SBA-16 as a support, using directly cobalt acetylacetonate as the precursor. Ordered mesoporous silica specifically SBA-16 with high surface area, large pore volume and uniform pore sizes were found effective to provide highly dispersed active sites for the epoxidation of bulky alkene molecules like limonene. Using this method, a high loading of cobalt finely dispersed on SBA-16 silica was obtained. The Co/SBA-16 (Co/Si= 4.5%) catalysts exhibited high conversion and selectivity in aerobic Mukaiyama epoxidation of limonene with molecular oxygen as the most desirable oxidant and isobutyraldehyde as a coreductant under very mild conditions in the presence of the green solvent ethylacetate. Tooptimize the yield of epoxide formation, a statistical experimental design was applied for systematic investigation of reaction conditions by Central Composite Design (CCD) and Response Surface Methodology (RSM) model. 99% limonene conversion, 50% 1,2 limoneneoxide and 32 % limonene dioxide were obtained with in 200 minutes of reaction time under the optimized reaction conditions: 1 mmol/ml isobutyraldehyde concentration(IBA/limonene ratio=3.3) and 14.3 mg/ml catalyst amount at 28°C and 10 ml/min O2 flowrate. To further enhance the activity of catalyst, incorporation of low coordination Co2+within the structure of mesoporous silica SBA-16 has been accomplished through a facile and green “pH adjusting” method and the result compared with those of our previous postgrafting method. This catalyst with Co/Si=1.1%, showed quite higher reactivity for the aerobic epoxidation of limonene with higher epoxide yields (∼100%) (1,2 and 8,9- limoneneoxide and limonene dioxide) under 44 psi oxygen pressure. A thorough kinetic analysis of aerobic epoxidation of limonene was performed to allow proposing a reaction scheme. A new mechanism, in which a surface reaction between a Co3+OO−peroxo intermediate and limonene was found to be involved in the formation of the epoxidized limonene. Despite the excellent result obtained in the first part of this study for aerobic epoxidation of limonene in the presence of an aldehyde as a coreductant and ethylacetate as a solvent,developing a solvent- and reductant-free catalytic process is really appealing in terms of green chemistry. The activity and selectivity of ruthenium catalysts supported on various activated carbons have been investigated in aerobic epoxidation of limonene undersolvent/reductant and initiator free reaction conditions. The catalyst prepared by cation exchange using activated carbon Darco G60, with the highest mesopore surface area and pore volume and the lowest Ru particle size (1.8 nm), was found to give the best combination of limonene conversion of 35% and epoxide selectivity of 57% (1,2 and 8,9- limonene oxideand limonene dioxide) at 80 °C and 3 bar oxygen pressure.
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50

Gordon-Smith, Tobias James. "Direct liquid crystal templating of mesoporous silica." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/192581/.

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The work described in this thesis is concerned with the development of ordered mesoporous silicas by direct templating from lyotropic liquid crystal phases of the surfactants Pluronic PI23, Pluronic F127, CTAB and Brij 78. The factors affecting the regularity, morphology, pore diameter and wall thickness of the templated mesoporous silicas were examined by exploring the reaction composition space and plotting the structural properties on TMOS/surfactant/water ternary diagrams. The silicas were studied using the complementary techniques of small angle X-ray diffraction, transmission electron microscopy and N? adsorption isotherms. Mesoporous silicas with hexagonal (H,) pore morphologies templated from the Hi phase of CTAB were prepared from fumed silica/CTAB/water/NaOH mixtures under hydrothermal conditions. The mesostructure showed very good long-range order and very narrow pore size distributions, with -3.4 mn diameter pores and -1.4 mn thick walls. In addition, mesoporous silicas were prepared using a sol-gel route from TMOS/surfactant/0.5 M HCl(aq) mixtures at 45°C. The central regions of the ternary diagrams of these mixtures were explored. Using Pluronic PI23, mesoporous silicas with hexagonal (Hi) pore morphologies were formed with pore diameters in the range of 5 - 10 nm. With Brij 78 and Pluronic F127, mesoporous silicas with 3d cubic pore morphologies were formed with pore diameters in the range of 2.9 - 4.5 mn and 4 - 1 0 nm for Brij 78 and Pluronic F127 respectively. The mesoporous silicas produced via the sol-gel route had the most ordered structures with a TMOS:water molar ratio in the range of 1:5 to 1:7, leaving little water present after hydrolysis. For ordered silicas, the sum of the pore diameter and wall thickness is roughly constant, where the pore diameter decreases with increasing TMOS content and decreasing surfactant content there is commensurate increase in wall thickness. Finally, 1,3,5 trimethyl benzene was used to swell the hydrophobic core of Pluronic PI 23 and F127 micelles, allowing the templating of mesoporous silica with pore diameters up to 14 nm.
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