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Robertson, Claire J. "Novel mesoporous silicates as indoor air pollutant scavengers." Thesis, University of Strathclyde, 2008. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21847.
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A mesoporous silicate has been developed for the removal of volatile organic compounds (VOCs). The indoor air pollutants of interest were formaldehyde, toluene, ethylbenzene, o-xylene, cumene and dichlorobenzene. The indoor air pollutants were actively sampled onto (i) Tenax filled sampling tubes and subsequently analysed by thermal desorption gas chromatography mass spectrometry or (ii) chemically modified C₁₈ silica cartridges analysed by high performance liquid chromatography ultraviolet spectroscopy. A pollutant atmosphere suitable for testing the sorbents chambers were created in-house. Mesoporous silicates were synthesised to control the surface area, pore size and pore volume of the material. Several preparation methods were used to produce the final mesoporous silicate sorbent. The mesoporous silicates were mainly synthesised using tetraethyl orthosilicate as a precursor with either a quaternary ammonia silicate or triblock copolymer as the organic template synthesising MCM-41 and SBA-I5, respectively. A selection of the successfully synthesised mesoporous silicates were modified with propyl amine to investigate the possibility of formaldehyde chemisorption. Material characterisation was performed using powder x-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption and elemental analysis. Sorbents were selected for adsorption efficiency testing based on the characterisation results. The synthesised mesoporous sorbent VOC and formaldehyde adsorption efficiencies were then compared with commercially available sorbents. It was observed that the commercial sorbents were inefficient at adsorbing both the formaldehyde and the selected VOCs. The modified sorbents adsorbed formaldehyde strongly compared to the unmodified parent sorbent. However when using the modified mesoporous silicate an unwanted release of toluene was also recorded. Simulated closed environments were generated with the selected VOCs. SBA-15 was efficient in reducing the VOC chamber concentration over a period of 2 hours. SBA -15 adsorbed ethylbenzene, cumene and dichlorobenzene with efficiency rates of 89.4, 99.9 and 97.7 %, respectively. The adsorption efficiency for toluene was reduced at 35.4 %.
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Dixon, Jacqueline Mary. "Structure, bonding and catalytic activity of modified mesoporous silicates." Thesis, Nottingham Trent University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403081.
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KATIYAR, AMIT. "Development of Novel Mesoporous Silicates for Bioseparations and Biocatalysis." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204765205.
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Gierszal, Kamil. "Synthesis, adsorption and structural properties of carbons with uniform and ordered mesopores." [Kent, Ohio] : Kent State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1207762469.
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Thesis (Ph.D.)--Kent State University, 2008.Title from PDF t.p. (viewed May 28, 2009). Advisor: Mietek Jaroniec. Keywords: mesoporous carbons, inverse replication, hard templating, OMC, CMK-3, CMK-5, mesoporous silicas, OMS, SBA-15, MCM-48, KIT-6, colloids, colloidal crystal, nanomaterials, gas adsorption. Includes bibliographical references (p. 184-194).
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Park, In. "Mesostructured silica for the reinforcement of thermoset epoxy polymers." Diss., Connect to online resource - MSU authorized users, 2006.
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Keene, Matthew T. J. "The structure of kanemite and some related compounds." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339455.
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Ferreira, Paula Celeste da Silva. "Novel microporous silicates and mesoporous MCM materials derivatised with inorganic and organometallic complexes." Doctoral thesis, Universidade de Aveiro, 2000. http://hdl.handle.net/10773/4573.
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Doutoramento em QuímicaOs materiais microporosos e mesoporosos são potenciais catalisadores heterogéneos. Os zeólitos e outros materiais microporosos do tipo zeolítico tradicionais, têm átomos tetracoordenados no esqueleto. Nos últimos anos, um vasto número de titanossilicatos contendo Ti(IV) hexacoordenado e Si(IV) tetracoordenado, com estruturas tridimensionais, têm sido alvo de grande interesse. Um dos objectivos desta tese foi preparar silicatos microporosos, contendo átomos metálicos com número de coordenação superior a quatro, e possuindo quer novas estruturas quer propriedades físicas e químicas interessantes. Neste contexto, foi preparado um novo ítriossilicato de sódio, AV-1, análogo do raro mineral montregianite, Na4K2Y2Si16O38·10H2O. Este material é o primeiro sólido microporoso que contem quantidades estequiométricas de sódio (e ítrio) no esqueleto. Foi, também, sintetizado um silicato de cério, AV-5, análogo estrutural do mineral montregianite com potencial aplicação em optoelectrónica. Nesta tese é, ainda, descrita a síntese e caracterização estrutural de um silicato de cálcio hidratado, AV-2, análogo do raro mineral rhodesite (K2Ca4Na2Si16O38.12H2O). Na continuação do trabalho desenvolvido em Aveiro na síntese de novos titanossilicatos surgiu o interesse de preparar novos zirconossilicatos microporosos por síntese hidrotérmica. Foram preparados dois novos materiais análogos dos minerais petarasite Na5Zr2Si3O18(Cl,OH)·2H2O (AV-3) e kostylevite, K2Si3O9·H2O (AV-8). Foram, também, obtidos análogos sintéticos dos minerais parakeldyshite e wadeite, por calcinação a alta temperatura de AV-3 e de umbite sintética. A heterogeneização de complexos organometálicos na superfície de materiais mesoporosos do tipo M41S permite associar a grande actividade catalítica e a presença de sítios activos localizados típicos dos complexos organometálicos, com a robustez e fácil separação, características dos materiais mesoporosos siliciosos. Nesta dissertação relata-se a derivatização dos materiais MCM-41 e MCM-48 através da reacção de [SiMe2{(h5-C5H4)2}]Fe e [SiMe2{(h5-C5H4)2}]TiCl2 com os grupos silanol das superfícies mesoporosas. Os materiais MCMs derivatizados com ansa-titanoceno foram testados na epoxidação de cicloocteno a 323 K na presença de hidrogenoperóxido de t-butilo. Estudou-se a heterogeneização dos sais de complexos com ligação metal-metal [Mo2(MeCN)10][BF4]4, [Mo2(m-O2CMe)2(MeCN)6][BF4]2 e [Mo2(m- O2CMe)2(dppa)2(MeCN)2][BF4]2 via imobilização nos canais do MCM-41. A imobilização dos catalisadores homogéneos na superfície do MCM-41 envolve a saída dos ligandos nitrilo lábeis, preferencialmente em posição axial, através da reacção com os grupos Si-OH da sílica. Verificou-se que a ligação Mo-Mo se mantém intacta nos produtos finais. É provável que estes materiais sejam eficientes catalisadores heterogéneos em reacções de polimerização. As técnicas de caracterização utilizadas nesta tese foram a difracção de raios-X de pós, a microscopia electrónica de varrimento, a espectroscopia de ressonância magnética nuclear do estado sólido (núcleos 13C, 23Na e 29Si), as espectroscopias de Raman e infravermelho com transformadas de Fourier, as análises termogravimétricas e as análises de adsorção de água e azoto.
Microporous and mesoporous materials have great potential to be used as inorganic heterogeneous catalysts. Traditional zeolites and microporous zeolite-type materials contain four-coordinated framework atoms. A large number of titanosilicates containing six-coordinated Ti(IV) atoms and fourcoordinated Si(IV) atoms, with three-dimensional structures, are extensively described in the literature. One of the aims of this thesis was to prepare new microporous framework oxide materials, containing metal atoms in different coordinations, which may possess novel structures and display interesting physical and chemical properties. In this context, a sodium yttrium silicate analogue of the rare mineral montregianite, Na4K2Y2Si16O38·10H2O (AV-1), was prepared. This material is the first microporous solid containing stoichiometric amounts of framework sodium (and yttrium) cations. A cerium silicate (AV-5) structural analogue of montregianite with potential for applications in optoelectronics was also prepared. In addition, the synthesis and structural characterisation of a calcium silicate hydrate analogue of the rare mineral rhodesite, K2Ca4Na2Si16O38.12H2O, (AV-2) is reported. As a natural extension of the work carried out on microporous titanosilicates, microporous zirconosilicates were prepared via hydrothermal synthesis. Two new synthetic analogues of the minerals petarasite (AV-3), Na5Zr2Si3O18(Cl,OH)·2H2O, and kostylevite (AV-8), K2Si3O9·H2O, were obtained. The preparation of analogues of parakeldyshite and Zr/Ti-wadeite was achieved by calcination at high temperature of AV-3 and synthetic Zr/Ti-umbite. The heterogenisation of homogeneous catalysts on the surfaces of mesoporous materials of the M41S type attempts to bring together the advantages of high activity and single-site active centres of homogeneous catalysts, and the robustness and easy separation of mesoporous siliceous material. The derivatisation of MCM-41 and MCM-48 materials by covalent reaction of [SiMe2{(h5-C5H4)2}]Fe and [SiMe2{(h5-C5H4)2}]TiCl2 with pendant silanol groups is reported. Ti-modified mesoporous silicas were screened as catalysts for the epoxidation of cyclooctene at 323 K with tbutylhydroperoxide. Potential polymerisation catalysts were prepared by grafting of dimolybdenum complexes [Mo2(MeCN)10][BF4]4, [Mo2(m-O2CMe)2(MeCN)6][BF4]2 and [Mo2(m- O2CMe)2(dppa)2(MeCN)2][BF4]2 onto the surface of purely siliceous MCM-41. The mechanism of surface attachment involves the displacement of labile acetonitrile ligands, most likely in the axially coordinated position, from the complexes by reaction with isolated nucleophilic silanol groups at the silica surface. The characterisation techniques used in this work were powder X-ray diffraction, scanning electron microscopy, 13C, 23Na and 29Si solid state nuclear magnetic resonance spectroscopy, Fourier transform infrared and Raman spectroscopies, thermal analysis, nitrogen and water adsorption measurements.
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Kodumuri, Pradeep. "IN-SITU GROWTH OF POROUS ALUMINO-SILICATES AND FABRICATION OF NANO-POROUS MEMBRANES." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243304850.
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Ruan, Juanfang. "Development of electron microscopy towards nano-structured porous materials : focus on novel zeolites from layered silicates and chiral mesoporous nanotubes /." Stockholm : Department of Physical, Inorganic and Structural Chemistry, Stockholm university, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7439.
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Oliveira, Vaeudo Valdimiro 1982. "Sílicas mesoporosas e silicatos lamelares contendo agentes organofuncionalizados : sorção e liberação controlada de fármacos." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250068.
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Orientador: Claudio AiroldiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Na presente investigação foram sintetizados os híbridos inorgânico-orgânicos micro/mesoestruturados: a) silicato lamelar do tipo kanemita sódica, b) sua forma quimicamente modificada com cobre e c) sílica mesoporosa SBA-16. A combinação dos reagentes Na2SiO3/NaOH/etanol e Na2SiO3/NaOH/Cu(NO3)2/etanol propiciaram a obtenção de kanemita sódica e sua forma contendo o cobre incorporado na estrutura inorgânica, através da substituição isomórfica do silício nas razões molares Si/Cu = 50, 100 e 200. Para as sílicas mesoporosas foram usados sistemas formados por copolímeros F127/TEOS/H2O, F127/TEOS/etanol/H2O e F127/TEOS/butanol/H2O em meio ácido. Os materiais organofuncionalizados previamente intercalado com dimetilsulfóxido (DMSO) e etilenodiamina (EN) formam os sólidos lamelares Na-KN-DMSO, Na-KN-EN e Cu-KN-EN, através do processo de pós-síntese com o agente sililante 3-iodopropiltrimetoxissilano, que reagiu subsequentemente com dietil iminodiacetato e benzidina, formando os híbridos mesoporosos. Os híbridos lamelares foram aplicados na sorção de metais e corantes em soluções aquosas. Dentre os cátions bário, cobalto e cobre, o cobre foi mais facilmente sorvido em Na-KN-EN quando comparado com Na-KN-DMSO. No caso dos corantes verde brilhante e azul reativo 15, o primeiro foi também mais eficiente na sorção. No processo de liberação de fármacos amoxicilina e omeprazol foram utilizados os híbridos mesoporosos. Os dados de liberação mostram que o primeiro fármaco apresentou uma cinética de liberação satisfatória no fluido intestinal simulado (FIS), enquanto que o omeprazol liberou em maior quantidade no fluido gástrico simulado (FGS)
Abstract: The present investigation deals with the syntheses of inorganic-organic nano/mesostrutered hybrids: a) sodic lamellar silicate kanemite, b) its chemically modified form with copper and c) SBA-16 mesoporous silicas. The reagents combination Na2SiO3/NaOH/ethanol and Na2SiO3/NaOH/Cu(NO3)2/ethanol enabled to obtain sodic kanemite and its synthesized form containing incorporated copper in the inorganic structure, through the isomorphic substitution of silicon using the molar ratio Si/Cu = 50, 100 and 200. For mesoporous silicas the copolymers F127/TEOS/H2O, F127/TEOS/ethanol/H2O and F127/TEOS/butanol/H2O in acidic condition were used. The synthesized organofunctionalized materials were previously intercalated with dimethylsulfoxide (DMSO) and ethylenediamine (EN) in the Na-KN-DMSO, Na-KN-EN and Cu-KN-EM lamellar solids, through the post-synthesis process with the silylating agent 3-iodopropyltrimethoxysilane, which subsequently reacted with diethyl iminodiacetate and benzidine. The lamellar hybrids were applied for cation and dye sorption processes. Among barium, cobalt and copper, the last cation was more favorable sorbed in Na-KN-EN, when compared with Na-KN-DMSO. In case of brilliant green and reactive blue 15 dyes, the first one was also more efficient in sorption. The controlled drug delivery process, amoxicillin and omeprazole were applied with mesoporous hybrid systems. The delivery data demonstrated that the first drug presented a satisfactory kinetic in the simulated intestinal fluid (SIF), while omeprazole presented high amount in the simulated gastric fluid (SGF)
Doutorado
Quimica Inorganica
Doutor em Ciências
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Matzen-Fredel, Anna. "Immobilisation of metathesis catalysts on mesoporous materials for the conversion of bio sourced fatty compounds." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10174.
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Alors que les ressources fossiles décroissent, le concept de bio-raffinerie est une approche très attrayante pour la production de produits chimiques à partir de ressources renouvelables. Dans ce contexte, les dérivés d’acides gras insaturés, obtenus par hydrolyse de triglycérides issus de végétaux, sont une catégorie importante de substrats. Leur conversion en composés à haute valeur ajoutée est un objectif majeur qui peut être atteint grâce à la catalyse, et plus particulièrement grâce à la métathèse des alcènes. De plus, dans un esprit de meilleure séparation entre produits et catalyseurs, et pour des questions de recyclage, l’emploi de catalyseurs hétérogènes est de grand intérêt. L’hétérogénéisation de catalyseurs commerciaux à base de ruthénium a été entreprise. Les matériaux hybrides ont été préparés en deux étapes: après une cationisation à l’aide de sels d’argent, les espèces organométalliques ont été immobilisées par échange ionique dans les aluminosilicates mésoporeuses de type MCM-41. Ces nouveaux catalyseurs ont été caractérisés par RMN du solide, IR, DRX, BET, analyse élémentaire et ATG. Ils ont été employés avec succès dans différentes réactions de métathèse impliquant le substrat-type, l’oléate de méthyle. Les réactions étudiées sont l’homométathèse, l’éthénolyse et la métathèse croisée avec des oléfines fonctionnalisées issues des acides acrylique et crotonique. Bien que le recyclage n’ait pas été couronné de succès, les catalyseurs supportés permettent de réaliser toutes ces réactions, ce qui représente dans certains cas le premier exemple de telles transformations par catalyse hétérogène avec des activités et sélectivités élevéesAs fossil resources constantly decrease, the concept of bio-refinery is a most attractive approach to generate chemicals from renewable resources. In this context, unsaturated fatty acids derived from the hydrolysis of crops extracted-triglycerides are a major class of substrates. These must be converted to high added-value derivatives: catalytic transformations can play a key role in this, by converting such compounds into other functionalized derivatives. A most attractive reaction to meet this challenge is olefin metathesis. Based on product/catalyst separation and catalyst recycling issues, use of heterogeneous catalysts is of high interest.We thus prepared heterogenized commercial ruthenium catalysts. The hybrid materials were prepared in a two-step procedure: after silver salt-mediated cationization, the organometallic species were immobilized by ion exchange on mesoporous aluminosilicates of the MCM-41 family. The novel catalysts were characterized by solid-state NMR, IR, XRD, BET, elemental analysis and TGA. They were successfully applied in several metathesis reactions involving the archetypic methyl oleate, a C18 unsaturated ester, with different grades of purity. The probed reactions were self-metathesis, ethenolysis and cross-metathesis with functionalized olefins derived from acrylic and crotonic acids. Though recycling was not completely successful, the supported catalysts were able to efficiently catalyze all these transformations, providing in some instances the first heterogeneously examples of such reactions with high activity and selectivity
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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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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 AiroldiTese (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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Saravanapavan, Priyadharshini. "Mesoporous calcium silicate gel-glasses : synthesis, structure and bioactivity." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271675.
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Raimondi, Maria Estelle. "Synthesis and characterisation of novel liquid crystal templated mesoporous solids." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341026.
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Qin, Ling. "Elucidation of the formation of cubic mesoporous silicas." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/elucidation-of-the-formation-of-cubic-mesoporous-silicas(a4130738-065d-4453-b9b1-85c9df418179).html.
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Four cubic mesoporous silicas, SBA-1, SBA-16, AMS-8 and AMS-10, were synthesized and the iso-electron density maps were built based on the amplitudes of structure factors recorded from SAXS and the phases retrieved from reference to HREM. A mesopore fraction to the total volume of the unit cell measured from the nitrogen adsorption was applied to identify the contour of the silica interface.Further, minimal surfaces which correspond to the space groups of the mesostructures were refined in Surface Evolver. The global mean curvatures of the surfaces were adjusted slightly to fulfill the consistent void fractions given by the gas sorption. A comparison has thereby been made between the experimental iso-electron density contours and their corresponding simulated constant-mean-curvature surfaces. A resistance of the silica interface on reducing to the constant-mean-curvature surface was found at the connections between mesocages according to the comparison. It can be concluded that the inorganic moiety undergoes a stronger affinity with the connections where water is filled than the spherical surfactant micelles.Moreover, the surfactant templates of SBA-1 and SBA-16 were removed at temperatures lower than 100 °C in order to maintain the inorganic morphology identical to the as-synthesized samples and avoid any structural shrinkage caused by calcination. The optimum method used was based on the properties of the surfactants: cationic C16TEABr was extracted by the supercritical CO2-MeOH fluid; neutral triblock PEO-PPO-PEO copolymers were broken down by O3.
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Almeida, Ramon Kenned de Sousa 1983. "Sílicas e carbonos mesoestruturados organofuncionalizados e aplicação à liberação controlada de fármacos." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250069.
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Orientador: Claudio AiroldiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: As sílicas mesoporosas SBA-15 e SBA-16 sintetizadas através do método hidrotérmico com os copolímeros direcionadores de estrutura P123 e F127 foram organofuncionalizadas com agentes sililantes que contêm grupos funcionais, como nitrogênio, oxigênio e enxofre. As sílicas foram caracterizadas por análise elementar, espectroscopia na região do infravermelho, ressonância magnética nuclear de carbono e silício no estado sólido, termogravimetria, área superficial, espalhamento de raios X a baixo ângulo, microscopia eletrônicas de varredura e transmissão. As caracterizações comprovam a efetivação das sínteses das sílicas SBA-15 e SBA-16 com estruturas hexagonal e cúbica, respectivamente. As sílicas organofuncionalizadas, mostraram maiores graus de ancoramento obtido quando funcionalizadas com organossilanos contendo nitrogênio. Além das sílicas, foram sintetizados carbonos mesoporosos usando as sílicas como direcionadores rígidos de estrutura. Os mesmos foram funcionalizados com anidrido malêico e subsequentes reações com água e hidreto de alumínio e lítio resultando em grupos carboxílicos e na redução dos mesmos, respectivamente. A efetividade da funcionalização foi comprovada, sobretudo por espectroscopia na região do infravermelho, termogravimetria, ressonância magnética de carbono e espectroscopia de fotoelétrons de raios X. Ensaios de liberação dos fármacos ibuprofeno e genfibrozila foram realizados nas sílicas SBA-15 e SBA-16. Os resultados mostraram que ibuprofeno é liberado de SBA-15 de forma constante e controlada por 77 h. Além disso, os perfis de liberação de genfibrozila mostraram que 67 % do fármaco foram liberados de ambas as sílicas, porém o tempo de equilíbrio foi 70 h quando usada SBA-15 e de 24 h quando usada SBA-16. Além disso, verificou-se que os dados tem um bom ajuste quando aplicado a modelo apropriado e que os mecanismos de liberação são regidos pela influencia da difusão e pelo tempo de liberação
Abstract: Mesoporous SBA-15 and SBA-16 silicas synthesized by hydrothermal method using P123 and F127 copolymers as structure directing agents were organofunctionalized with silylating agents containing functional groups, such as nitrogen, oxygen and sulfur. The silicas were characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance of carbon and silicon nuclei in solid state, thermogravimetry, surface area, X-ray scattering at low angle, scanning electron microscopy and transmission. The characterizations demonstrated the effectiveness of the synthesis of SBA-15 and SBA-16 silicas with hexagonal and cubic structures, respectively. The organofunctionalized silicas showed that the obtained surface modification gave highest degrees of anchoring when functionalized with organosilanes containing nitrogen. Besides the silicas, were also synthesized mesopororous carbons using silicas as hard template, which were functionalized with maleic anhydride and subsequent reaction with water and lithium aluminum hydride, resulting in carboxylic groups due to the reduction process. The effectiveness of the functionalized was proven, mainly by infrared spectroscopy, thermogravimetry, 13C NMR and X-ray photoelectron. Assays with ibuprofen and gemfibrozil releasing were performed on SBA-15 and SBA-16 silicas and the results showed that the ibuprofen is released from SBA-15 in a constant and controlled form for 77 h. Furthermore, release profiles of gemfobrozil gave 67 % of the drug released from both silicas, however the equilibrium time were 70 h when used SBA-15 and 24 h for SBA-16. In addition, it was found that the data has good fitting when applied for appropriate model and the release mechanisms are governed by the influence of diffusion and release time
Doutorado
Quimica Inorganica
Doutor em Ciências
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Fattori, Natália 1985. "Síntese, caracterização e aplicação de novos adsorventes obtidos a partir da modificação de sílicas mesoporosas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249668.
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Orientador: Yoshitaka GushikemDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: O presente trabalho descreve a preparação e caracterização de novos materiais adsorventes obtidos a partir da modificação química de dois diferentes substratos mesoporosos: uma sílica mesoporosa constituída de uma estrutura porosa altamente ordenada e uniforme, composta de poros ou canais cilíndricos dispostos paralelamente e empacotados em arranjo hexagonal (SBA-15), e uma sílica mesoporosa caracterizada por uma rede desordenada de poros, de tamanho e forma variados, distribuídos e interconectados aleatoriamente ao longo da estrutura porosa (SMD). Os dois substratos mesoporosos foram modificados com dois diferentes agentes funcionalizantes derivados da molécula 4,4'-bipiridina, imobilizados sobre a superfície da sílica tanto na forma monossubstituída (Bipy), como na forma dissubstituída (Bipy). A eficiência dos materiais obtidos como adsorventes de íons cobre (II) em solução etanólica foi testada, visando à utilização destas matrizes na purificação de etanol combustível. Os valores de capacidade efetiva de adsorção e constantes de equilíbrio heterogêneo foram obtidos. O processo de adsorção de CuCl2 ocorre na interface sólido-solução pela formação de complexos aniônicos de cobre (CuCl4 e CuCl3), que agem como contra-íons dos cátions bipiridínio (Bipy e Bipy). Os valores das constantes de equilíbrio heterogêneo obtidos expressam a habilidade dos materiais em reter os complexos anionicos de cobre na superficie, pela interacoes com o grupo organico 4,4 '-bipiridinio
Abstract: This work describes the preparation and characterization of new adsorbent materials obtained from two different chemically modified substrates: i) a mesoporous silica constituted by a highly ordered and uniform porous framework, with parallel cylindrical pore channels packed in a hexagonal array (SBA-15), ii) a mesoporous silica characterized by a disordered porous framework, with non-uniform size and shape, distributed and interconnected randomly throughout the porous structure (Disordered Mesoporous Silica, DMS). The two mesoporous substrates were chemically modified with two different silylating agents, derived from the organic molecule 4,4'-bipyridine, immobilized on the surface of the silica in the monosubstituted form (Bipy), as well as in the disubstituted form (Bipy). The materials obtained were tested as practical adsorbents for cooper ions from ethanol solution, aiming their use in the purification of ethanol fuel. The effective sorption capacities and the heterogeneous equilibrium constants were obtained. The adsorption process of CuCl2 occurs in the solid/solution interface, through the formation of anionic copper complexes (CuCl4 and CuCl3), that act as counter-ions of the bipyridinium cations (Bipy e Bipy). The heterogeneous equilibrium constants values obtained express the ability of the materials to retain the anionic copper complexes on the adsorbent surface, through electrostatic interactions with the organic molecule 4,4'-bipyridine
Mestrado
Quimica Inorganica
Mestre em Química
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Ritchie, Lyndsey Kay. "Large pore mesoporous silicas for application in protein adsorption, enzyme immobilisation and drug delivery /." St Andrews, 2009. http://hdl.handle.net/10023/747.
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Donado, Sainz de la Maza Esther. "Cobalt supported on mesoporous silicas for the Fischer-Tropsch synthesis." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-158473.
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This thesis deals with the study of several catalysts for the Fischer-Tropsch synthesis in the Biomass-To-Liquid process. In this work two groups of catalysts were tested. On the one hand, two series of catalysts with cobalt loadings of 6 and 12 wt% over SiO2 and some of them containing 5wt% of TiO2 were tested. One the other hand, other two series of mesoporous short channel SBA-15, all of them with cobalt loadings of 12wt% and some with 5wt% of titania. The first series was supported on SBA-15 DeWitte and the second one on SBA-15 Martinez. On the one hand, the influence of water addition to the feed, titania content and cobalt loading to the catalyst and was studied, as well as the consequences of a GHSV. The FT reaction was carried out along 5 periods of 24 hours each, in which conditions such as feed and water content were modified, enabling the study of these parameters. It was found that water provokes an increase of the CO conversion and has a positive kinetic effect on the rate to hydrocarbons. However, this fact reaction is followed by a quick deactivation, enhanced by high water partial pressures. Most of that deactivation is irreversible since it is not completely recovered after water removal. On the other hand, differences between the supports were studied. Some SBA-15 supported catalysts show CO diffusion limitations at longer channel lengths than what applies for conventional 3D porous supports. Titania grafting increases the rate to hydrocarbons, showing positive results for FT catalysts development.
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Wang, Wei. "High nickel- and titania-containing mesoporous silicas : synthesis and characterisation." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/7782.
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In order to heighten the nickel content in mesoporous silica frameworks, a new direct synthesis method, called modified DS method, has been developed instead of the commonly used direct synthesis method. In addition, with the aim of incorporating a high amount of titania into SBA-15 mesoporous silica without blocking its mesopores, a multistep impregnation method, called the MSI method, has also been developed. By using the two developed methods, high nickel- and high titania-containing mesoporous silicas obtained werc synthesized. The nickel- and titania-containing mesoporous silicas were characterised by various techniques, i.e. XRD, TEM, EDX, SENI, N2-sorption, XPS, FTIR, UV-Vis-DRS, UV-VIS, TPR, and Raman spectroscopy. For nickel-containing mesoporous silicas synthesized by the modified DS method, satisfactory mesostructures were obtained and the nickel content was increased up to 14.7 wt.%. So far, no reports have been published on synthesis of mesoporous MCM-41-type silica with higher nickel content than 3.6 wt.% using DS method. Via our modified IDS method, high BET surface area (>840 rný/g) and pore volume (>-0.73 cm3/g were also achieved. Nickel was found to be incorporated into the silica frameworks. Formation of nickel phyllosilicates was also confirmed. After activation, mesostructurcs were still intact. Small nickel clusters embedded in the silica walls were found. A high amount of titania (up to 24.4 wt.%) was incorporated into the mesoporous SBA-15 silica via the multistep impregnation method. No damage to the SBA-15 silica mesostructures was caused. The existence of small titania nano-domins was confirmed to be present by Raman and UV-vis-DRS measurements. High dispersion of them was realized via this method according to the results of low-anglc XRD, TEM and N2-sorption measurements. Importantly, no blockage of mesopores was observed. Photo-activity tests showed the superiority of the materials synthesized by the MSI method to those by one-step impregnation method.
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Mdoe, James Epiphan Gabriel. "Organically modified mesoporous silicas as base catalysts for green chemistry." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310988.
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Mauder, Daniel. "Investigation of structure and surface properties of mesoporous silica materials by solid state NMR." Berlin mbv, Mensch-und-Buch-Verl, 2009. http://d-nb.info/998069116/04.
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Orman, Sultan. "Zr And Silicotungstic Acid Incorporated Silicate Structured Mesoporous Catalysts For Dimethyl Ether Synthesis." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613499/index.pdf.
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Due to high consumption rates of petroleum derived fuels and environmental regulations, significant search has been initiated for the development of environmental friendly and efficient fuels, which were derived from more abundant feedstocks. Dimethyl ether (DME), as having a good combustion quality and high cetane number, is an efficient alternative for diesel fuel. With improved combustion quality, the emissions from DME used engines are greatly decreased. DME synthesis can be carried out via two different methodsmethanol dehydration on acidic catalysis and syn-gas conversion on bifunctional catalysis. In this study, the aim is to synthesize acidic catalysts using direct hydrothermal synthesis method for DME synthesis as using methanol as feed stock via dehydration and to characterize these materials. The support of the synthesized materials comprises of MCM-41 structure and silicotungstic acid (STA) and metals (Zr / Ni / Cu) were incorporated into the MCM-41 structure during synthesis. Two different techniques were used to extract the surfactant (CTMABr) from catalyst matrix. First one is the conventional calcination technique (at 350°
C) and the second is supercritical fluid extraction (at various operating conditions) with methanol modified CO2. The effect of metal loading on extraction performance is analyzed through characterizations of Ni and Cu incorporated materials. In addition, The effect of operation parameters on catalyst properties are also investigated with performing extraction at different pressures for different durations. By changing the type of metal incorporated into the catalyst, the extraction performance is also monitored. The characterization results indicated that, SFE process is also a promising method for surfactant removal. The activities of zirconium added catalysts are tested in methanol dehydration reaction towards DME. It is concluded that the conversion of methanol and selectivity of DME in presence of extracted samples are lower (maximum yield -0.54- obtained at 450°
C with sceSZ1) compared to the calcined materials (maximum yield -0.80- obtained at 300°
C with cSZ6). This result can also be foreseen by DRIFTS analysis of pyridine adsorbed samples. The acid sites of extracted materials are not as strong as in the calcined catalysts.
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Ritchie, Lyndsey K. "Large pore mesoporous silicas for application in protein adsorption, enzyme immobilisation and drug delivery." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/747.
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A range of mesoporous materials based on SBA-15, KIT-6 and FDU-12 have been prepared using neutral block copolymers Pluronic P123 and F127 and characterised using methods including electron microscopy and nitrogen adsorption. Typically the materials have a hexagonal (p6mm) or cubic (Fm3m and Ia-3d) symmetry and pore geometry and are rendered porous by either calcination or solvent extraction. Organic functional groups were incorporated into the silica walls of the materials by co-condensation in the form of propyl thiols and additives in the form of alkanes were added to control pore size and geometry. The effects of temperature, additives, organic functionalisation, synthesis time and sol-gel composition were investigated and the resulting materials were tested as supports for protein adsorption, enzyme immobilisation, and drug delivery. Two FDU-12 materials of differing entrance and cavity sizes were used to adsorb a range of proteins with molecular weight 17 to 160 kDa to determine if there was a size exclusion effect. It was seen that the larger pore material was able to adsorb proteins of a larger size (molecular weight 105 kDa) and an exclusion effect was observed when the dimension of the proteins became too great (larger than 130 kDa). There was no clear trend for the smaller pore material where each protein was adsorbed to some extent by the material but apart from the smallest protein, myoglobin, mainly on the surface and not within the pores. The adsorption of the lipase B from Candida Antartica, CALB, was studied on a range of mesoporous supports with their templates removed by either calcination or extraction. The effect of pore size and functionalisation was investigated in terms of maximum loading and rate of loading. By functionalising the KIT-6 material the maximum loading of CALB was reduced from 45.5 to 32 mg/g whereas functionalising the FDU-12 material increased the maximum from 33 to 42.5 mg/g. The activity of the immobilised CALB was measured by enantioselective transesterification of (R)-1-phenylethanol in methyltetrabutyl ether (MTBE). The effect of loading, surface functionalisation and reusability in organic media were investigated. Functionalisation with propyl thiol was seen to increase the rate of conversion after 30 minutes for both KIT-6 and FDU-12 materials. Selected FDU-12 and KIT-6 materials with window sizes from 6 to 12 nm and with and without functionalisation were used to carry out a drug release study using Bovine serum albumin (BSA). BSA was loaded onto the material and the uptake quantified using nitrogen adsorption, elemental analysis, and thermogravimetric analysis. The release of BSA into simulated body fluid at 37 ºC was measured using HPLC. Functionalisation was seen to have little effect. The type of cubic morphology controlled the rate at which the BSA was released. The KIT-6 3D channel material exhibited a burst release initially followed by a steady release of BSA whereas the mesocage FDU-12 material had a slower and more linear release profile, closer to that desired.
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Branton, Peter James. "The adsorption of gases and vapours by a model mesoporous alumino-silicate and related solids." Thesis, University of Exeter, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239304.
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Voß, Rebecca. "Mesoporous organosilica materials with amine functions : surface characteristics and chirality." Phd thesis, Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2005/528/.
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In this work mesoporous organisilica materials are synthesized through the silica sol-gel process. For this a new class of precursors which are also surfactant are synthesized and self-assembled. This leads to a high surface area functionality which is analysized with copper (II) and water adsorption.Im Rahmen dieser Arbeit werden mesoporöse Amin-funktionalisierte Organo-Silikate durch den Silika Sol-Gel Prozess hergestellt. Dabei werden neue Alkoxysilyl-Precursoren synthetisiert und condensiert die die gewünschte Funktion auf die Oberfläche dirigieren. Herstellt werden primäre, secundäre und chirale Amine. Die Oberflächenfunktionalität wird mit Kupfer (II) und Wasser Adsorption analysiert.
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Nell, Kara. "Functionalized Nano-structured Silicas for Trace Collection from Natural Waters." Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20681.
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Throughout this body of work, three classes of sorbent materials were created and optimized, each designed to selectively capture organics or desired metals from natural water sources. These target species included toxic heavy metals, uranium, rare earths, and simple organics, such as benzene. Each class of sorbent materials is functionalized nanostructured silicas, created by the development of several functionalization methods: utilizing thiol-ene click chemistry, aromatic interactions, and the formation of inclusion complexes.
Thiol-ene click surface modification gave rise to sorbent materials with impressive affinities for both soft metals, such as gold, and harder metals, such as uranium and rare earth elements. Applications of these materials for aqueous mining of uranium and rare earth elements from various natural water sources are presented.
Two classes of materials based on supramolecular functionalization methods were prepared. In the first class, aromatic interactions allowed for surface functionalization with thiol containing aryl ligands. These materials proved to have an excellent affinity for heavy metals from natural waters, and hold promise for regenerable nanostructured silica sorbents. The second class of materials utilizes the ability of β-cyclodextins to form inclusion complexes with small molecule organics, such as benzene. The formation of inclusion complexes drove both surface functionalization and the capture of small molecule organics from aqueous solutions. This work serves to inspire the development of novel functionalized nanostructured sorbents for trace collection of toxic organics from aqueous streams. These supramolecular methods for surface medication can be expanded to nanomaterials at large.
This dissertation includes both previously published/unpublished and co-authored material.10000-01-01
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Dreifke, Michael [Verfasser], and Michael [Akademischer Betreuer] Fröba. "Cozy and Pleasant Surroundings - Coenzyme Regeneration in Mesoporous Silicas / Michael Dreifke ; Betreuer: Michael Fröba." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/114448569X/34.
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Fulvio, Pasquale Fernando. "Synthesis and Characterization of Ordered Mesoporous Inorganic Nanocomposite Materials." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1258990927.
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El, Gamouz Abdelaziz. "From calixpyrrole derivatives to mesoporous hybridised silicas : synthesis, characterisation and their interaction with polluting species." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/843597/.
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This research deals with two main topics; The first one concerns an investigation on meso-tetramethyl-tetrakis-(4-N,N- diethylacetamide phenoxymethyl]calix[4]pyrrole (CPA) and it includes: i) A bibliographical review about calixpyrroles ii) The synthesis and characterisation (structural and thermodynamic) of CPA in different solvents. iii) A detailed study of the interaction of CPA with different ionic species using different techniques (1H NMR, conductance and calorimetry). It is demonstrated that CPA and its parent compound not only interact with anions but also with cations, and thermodynamic data for cation complexation processes involving these receptors are first reported. The second topic of this work concerns: i) A general review about silica and its different forms with a discussion on hexagonal mesoporous silicas. ii) Synthesis and characterisation (XRD, IR, TGA-DTA, elemental analysis and N2 sorption).of these materials. iii) An investigation of the applications of synthesized silicas for the removal of a wide range of pollutants (polyphenols, pesticides, dyes and ionic species) from aqueous medium. Parameters aiming to establish the optimal experimental conditions for the removal of pollutants from water (mass: solution ratio, pH and temperature effects) as well as the kinetics of the extraction processes have been investigated.. Conclusions, suggestions and perspectives for future work are included.
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Mascotto, Simone, Bernd M. Smarsly, Dirk Wallacher, and Andreas Brandt. "In-situ-SANS investigations of C5F12 condensation in mesoporous silicas with a hierarchical pore structure." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-191435.
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Mascotto, Simone, Bernd M. Smarsly, Dirk Wallacher, and Andreas Brandt. "In-situ-SANS investigations of C5F12 condensation in mesoporous silicas with a hierarchical pore structure." Diffusion fundamentals 11 (2009) 94, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A14067.
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Lin, Jun. "Radiation-induced alterations in mesoporous silicas : The effect of electronic processes involving ions and electrons." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2022. http://theses.enscm.fr/ENSCM_2022_LIN.pdf.
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Les matériaux utilisés dans le nucléaire (combustible, matrice de conditionnement, matériaux de structure…) sont soumis à des contraintes importantes liées à la création de défauts qui modifient leurs propriétés. Plusieurs études ont montré que les interfaces peuvent agir comme un puits pour les défauts causés par l'irradiation, ce qui suggère que les nanomatériaux pourraient avoir une plus grande résistance à l'irradiation que les matériaux présentant une structure « micrométrique ». Par ailleurs, les silices mésoporeuses ont gagné en popularité ces dernières années et sont envisagées pour le traitement des effluents radioactifs (séparation, conditionnement…). Bien que de nombreuses études aient été réalisées sur le comportement de silices non poreuses sous irradiation, très peu de travaux s’intéressent à celui de la silice mésoporeuse en particulier lorsqu’elle est irradiée en régime d‘électronique.Le but de cette thèse est de comprendre et d'expliquer les modifications induites par irradiation dans les silices mésoporeuses en régime électronique. Ce travail a permis de quantifier l’évolution de propriétés physico-chimiques (polymérisation du réseau, création de défauts…) et structurales (volume poreux, diamètre et distribution des pores…) de la silice mésoporeuse irradiée par des faisceaux d'ions de haute énergie dans une gamme de pouvoirs d'arrêt variant entre 1 keV/nm et 12 keV/nm, ainsi que par des électrons (10 - 300 keV et 0.6 - 2.4 MeV). Des méthodes de caractérisation post-irradiation (réflectivité des rayons X, adsorption de gaz, SAXS et FTIR, etc.) ont été utilisées, ainsi que le suivi in situ de la structure des pores à l'aide de microscopie électronique. Les résultats expérimentaux ont indiqué que la structure des pores était sensible à l'irradiation conduisant dans certaines conditions à son effondrement, tandis que le réseau de silice lui-même évolue peu par rapport à la silice non poreuse. Parallèlement, un modèle TS3D (modèle de pointe thermique 3D) a été utilisé avec succès pour décrire et expliquer le comportement de contraction des pores observé en réponse à l'irradiation ionique. De plus, le mécanisme de contraction des pores sous irradiation par des électrons a été délimité en fonction du domaine des énergies incidentes des électrons et de la dose. Cette recherche a montré que par rapport à une silice non poreuse, la présence de pores nanométriques réduit l’accumulation des dommages causés par les irradiations. Conjointement à cet effet bénéfique, le pore se contracte jusqu’à disparaitre sous l’impact de l’irradiation. Par conséquent, d’un point de vue applicatif cette caractéristique pourrait être mise à profit pour imaginer de nouvelles voies de traitement des effluents radioactifs, par une stratégie de type « séparation/conditionnement » ou pour l'autoguérison des couches de gel poreux formées à la surface des colis de déchets vitrifiés dont l’exutoire envisagé est le stockage géologique profondMaterials used in nuclear energy (fuel, packaging matrix, structural materials...) are subject to significant stresses due to the creation of defects that modify their properties. Several studies have shown that interfaces can act as a sink for defects caused by irradiation, which suggests that nanomaterials could have a higher resistance to irradiation than materials with a "micrometric" structure. Simultaneously, mesoporous silica materials have grown in popularity in recent years and are becoming more involved in the domain related to radiation conditioning, such as the prospective use of conditioning for nuclear waste. While research has begun to focus on the behavior of non-porous silica materials when exposed to radiation, no extensive investigations have been conducted on the behavior of mesoporous silica when exposed to radiation, particularly at electronic irradiation regime.This thesis aims to comprehend and explain the radiation-induced changes in mesoporous silicas under electronic regimes. This work quantified the evolution of physical (pore volume, pore diameter and distribution...) and structural (polymerization of the network, creation of defects...) properties of mesoporous silica irradiated with high-energy ion beams with stopping powers ranging from 1 keV/nm to 12 keV/nm, and with electron beams (10 - 300 keV and 0.6 - 2.4 MeV). Post-irradiation characterization methods (X-ray reflectivity, gas adsorption, SAXS, FTIR, etc.) have been used, as well as in-situ pore structure monitoring using electron microscopes. The experimental findings indicated that pore structures were susceptible to a certain degree of irradiation-induced shrinking. In contrast, evidence shows that the silica network itself does not alter much in porous silica compared to non-porous silica. Meanwhile, a 3DTS (3D thermal spike) model has been successfully applied to describe and explain the observed pore contraction behavior in response to ionic irradiation. Additionally, the mechanism of pore contraction under electron irradiation has been delineated according to the domain of incident electron energies. When compared to non-porous silica, this research has demonstrated that the existence of nanoscale pores reduces the accumulation of damage induced by irradiation. In conjunction with this effect, the pore contracts until it completely disappears under the impact of irradiation. This characteristic could, from an applicative point of view, be of interest to practitioners in the context of new methods of treating radioactive effluents, such as through the use of a "separation/conditioning" strategy, or in the context of the self-healing of porous gel layers formed on the surface of vitrified waste packages whose final destination is deep geological disposal
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Alkimim, Isabella Pereira. "Influência de álcoois na síntese e propriedades das sílicas mesoporosas." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/4162.
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Previous issue date: 2015-02-23Universidade Federal de Sao Carlos
In recent years there has been growing interest in studies on the use of heterogeneous catalysts in the biodiesel production, since such materials have some advantages over homogeneous catalysts such as ease of separation of product generated and the possibility of being reused. Among these catalysts, it is important to emphasize the mesoporous molecular sieves, since they have some advantages that enable its catalytic application. This study aimed to synthesize spheres of hybrid silica, with mesoporous occluded by the driver structure (CTA-SiO2), and to investigate the influence of different alcohols in the properties of these materials and evaluate their catalytic activity in the transesterification reaction. The mesoporous silicas were synthesized with varying the length of the alkyl chain (C1-C3) and amount of alcohol in the reaction mixture. The silicas were characterized by different techniques, such as X-ray scattering at small angles (SAXS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis. The results showed that the structure and morphology of the mesoporous silica containing organic driver may be controlled during synthesis by varying alcohol content, leading to the formation of materials with different phases, levels of organization and morphology, with the best results obtained from the samples synthesized with methanol and ethanol. For the evaluation of activity and catalytic stability, hybrid silicas were tested in transesterification reaction between ethyl acetate and methanol. The materials showed activity, and when the pore structure is well organized, larger amount of catalytic sites is available resulting in higher conversions. Thus synthesized materials with lower amounts of alcohol had higher catalytic activity compared with other materials. Silicas synthesized showed little catalytic stability compared to successive uses in the transesterification reaction. Thus, materials synthesized with the use of smaller amounts of alcohol tended to stability in comparison to other samples. Part of the activity is due to the presence of basic species formed as a result of leaching of cations CTA+, promoting the reaction also in the homogeneous phase.
Nos últimos anos tem sido crescente o interesse por estudos sobre o emprego de catalisadores heterogêneos na produção de biodiesel, uma vez que esses materiais possuem algumas vantagens em relação à catálise homogênea, tais como a facilidade de separação dos produtos gerados e possibilidade de serem reutilizados. Dentre esses catalisadores, torna-se importante salientar as peneiras moleculares mesoporosas, pois apresentam algumas vantagens que viabilizam sua aplicação catalítica. O presente estudo teve como objetivo sintetizar sílicas híbridas em formato de esferas, com mesoporos ocluídos pelo direcionador de estrutura (CTA-SiO2), bem como investigar a influência de diferentes álcoois nas propriedades desses materiais e avaliar sua atividade catalítica na reação de transesterificação. As sílicas mesoporosas foram sintetizadas com variação do comprimento da cadeia alquílica (C1-C3) e quantidade de álcool na mistura reacional. Foram caracterizadas por diferentes técnicas, como: espalhamento de raios X a ângulos pequenos (SAXS), difratometria de raios- X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET) e análise termogravimétrica. Os resultados mostraram que a estrutura e morfologia das sílicas mesoporosas contendo direcionador orgânico podem ser controladas durante a síntese através da variação do teor de álcool, levando à formação de materiais com diferentes fases, níveis de organização e morfologia, sendo os melhores resultados obtidos a partir das amostras sintetizadas com metanol e etanol. Para avaliação da atividade e a estabilidade catalítica, as sílicas híbridas foram testadas na reação de transesterificação entre o acetato de etila e metanol. Os materiais apresentaram atividade, sendo que quando a estrutura dos poros é bem organizada, maior quantidade de sítios catalíticos fica disponível resultando em maiores conversões. Consequentemente, os materiais sintetizados com menores teores de álcool apresentaram maior atividade catalítica em comparação com os demais materiais. As sílicas sintetizadas mostraram pouca estabilidade catalítica frente a sucessivos usos na reação de transesterificação. Assim, os materiais sintetizados com emprego de menores teores de álcool apresentaram uma tendência à estabilidade em relação às demais amostras. Parte da atividade se deve à presença de espécies básicas formadas em consequência da lixiviação dos cátions CTA+, promovendo a reação também na fase homogênea.
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Hondow, Nicole S. "The synthesis of new heterogeneous Fischer-Tropsch catalysts : the incorporation of metal aggregates in mesoporous silicas." University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0083.
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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.
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BRAGANCA, LAURINDA FATIMA DA FONSECA PEREIRA GUIMARAES. "SYNTHESIS AND CHARACTERIZATION OF CO-FE NANOCRYSTALS SUPPORTED ON MESOPOROUS SILICAS FOR THE FISCHER-TROPSCH SYNTHESIS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15921@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRONeste trabalho foram sintetizadas amostras bimetálicas de cobalto e ferro suportadas em sílicas mesoporosas do tipo SBA-15 e HMS. A preparação das mesmas ocorreu pelo método de impregnação incipiente do ponto úmido com soluções aquosas de nitratos de Co e Fe para obtenção de amostras com 25% p/p total de metal. Para estudos de efeitos comparativos das diversas propriedades, amostras monometálicas de Co ou Fe foram também preparadas com o mesmo teor metálico. Para investigar o efeito de diferentes direcionadores de estrutura, duas séries da sílica mesoporosa HMS foram preparadas utilizando dois tipos de direcionadores: dodecilamina (DDA) e tetradecilamina (TDA). As amostras foram caracterizadas por medidas de fisissorção de N(2), análise de difração de Raios-X (DRX), redução com temperatura programada (RTP), microscopia eletrônica de transmissão (TEM), quimissorção de H(2) e espectroscopia fotoeletrônica de raios-X (XPS). A quantidade de metal incorporado foi estimada por espectroscopia de absorção atômica (EAA). Os suportes foram também caracterizados por análise diferencial termogravimétrica (ATG/ATD). As curvas ATG evidenciaram que os direcionadores de estrutura foram, em grande parte, removidos até 700 K. As propriedades de textura mostraram que após a introdução metálica no suporte SBA-15, a área específica, o volume de poros e o diâmetro de poro decresceram em menor extensão para a amostra bimetálica em relação às monometálicas. As análises de DRX detectaram a formação das fases de Co(3)O(4) e CoFe(2)O(4) para todas as amostras bimetálicas; sendo que para a amostra de Co-Fe/HMS (TDA), a fase a-Fe(2)O(3) foi também indicada. A presença do suporte HMS (TDA) resultou na formação de fases cristalitas de maiores dimensões. Os valores das espessuras de parede para os suportes do tipo HMS foram maiores em relação aos encontrados na literatura, sugerindo a formação de materiais mais estáveis. Os perfis de RTP foram similares entre as amostras monometálicas e bimetálicas, entretanto, maiores temperaturas de redução do óxido de cobalto na amostra bimetálica foi indicada em relação às amostras monometálicas de cobalto, no suporte HMS (TDA). Uma interação metal-suporte mais forte foi evidenciada para a amostra Co-Fe/SBA-15. As medidas de quimissorção de H(2) indicaram valores das dispersões metálicas maiores para as amostras bimetálicas em comparação as monometálicas de ferro e menores em relação às monometálicas de cobalto. A partir das micrografias obtidas por MET, foi observada uma menor formação (percentual) de aglomerados para a amostra de Co-Fe/SBA-15 em relação à de Co-Fe/HMS (DDA). O espectro Co2p resultante da análise de XPS, para a amostra bimetálica de Co-Fe/HMS (DDA) indicou a presença de Co(3)O(4). O catalisador de Co-Fe/HMS (DDA) apresentou maiores seletividades para C(5+) e álcoois em relação ao catalisador Fe/HMS (DDA) na síntese de Fischer-Tropsch. O parâmetro de probabilidade de crescimento da cadeia (a) foi maior para o catalisador bimetálico Co-Fe/HMS (DDA) em comparação ao catalisador Co-Fe/SBA-15. Ambos os catalisadores bimetálicos exibiram uma seletividade (%) maior para a fração de leves, C2-C4.
In this work, cobalt and iron bimetallic samples supported on SBA-15 or HMS mesoporous sílicas were prepared by incipient wetness impregnation. Cobalt nitrate and iron salts were used to obtain samples containing 25 wt% total of metal content. Also, a series of supported monometallic cobalt or iron samples were synthesized, with the same metal loading, and compared to bimetallic ones. In order, to investigate the effect of different templates, a series of HMS sílicas have been prepared using two types of structure direction: dodecylamine (DDA) and tetradecylamine (TDA). The samples were cheracterized by N(2)-physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), transmission electron microscopy (TEM), H(2) chemisorption and X-ray photoelectron spectroscopy (XPS) analysis. The amount of incorporated metal was estimated by atomic absorption spectroscopy (AAS). The supports were, also, characterized by thermogravimetric (TGA), as well as differential thermal (DTA) analyses. The TGA/DTA curves showed that the templates were mainly removed until 700 K. The textural properties revealed that after metal introduction to SBA-15 support, specific area, pore volume and pore diameter decreased in a lesser extension for the bimetallic sample compared to monometallic ones. XRD measurements detected the formation of Co(3)O(4) and CoFe(2)O(4) phases for all bimetallic samples. For Co-Fe/HMS (TDA) sample, the a-Fe(2)O(3) phase formation and a higher Co(3)O(4)/CoFe(2)O(4) crystallite sizes were also observed. The wall thickness valour for HMS supports was higher than previously reported values, suggesting more stable materials. The TPR profiles indicated similar behavior between bimetallic and monometallic samples. In case of cobalt oxide on bimetallic sample, higher reduction temperatures were indicated compared to monometallic ones for HMS (TDA) support. A higher interaction metal-support was showed for Co-Fe/SBA- 15. According to hydrogen chemisorption, the bimetallic samples dispersions were higher than iron monometallic and lower than cobalt monometallic samples. From TEM microphotografs, it was observed a lesser fraction of agglomerates to Co-Fe/SBA-15 than Co-Fe/HMS (DDA) sample. XPS spectrum of Co2p region indicated the presence of Co(3)O(4) for the bimetallic sample, Co-Fe/HMS (DDA). The Fe-Co/HMS (DDA) bimetallic catalyst showed higher C(5+) and alcohols selectivities than Fe/HMS (DDA) on the Fischer-Tropsch reaction. Also, the bimetallic cobalt and iron based catalyst supported on HMS (DDA) recorded a higher value for the chain growth parameter (a) than Co-Fe/SBA-15. Both bimetallic catalysts exhibited highter selectivities (%) for lighter fractions, C2-C4.
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Prosenjak, Claudia. "Experimental and theoretical adsorption studies in tuneable organic-inorganic materials." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4150.
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Adsorption processes are widely used for the storage and separation of gases in many industrial and environmental applications. The performance of the process depends strongly on the adsorbent and its interaction with the gases. Therefore, the idea of tailoring the adsorbent to the application by adapting the pore size and/or the chemical composition is very attractive. This work focuses on two groups of customizable hybrid materials: Firstly, in crystalline metal-organic frameworks (MOFs) the chemical and structural properties can be modified by changing the metal-oxide corner or the organic linker. Secondly, periodic mesoporous silica materials can be prepared with different pore sizes and geometries depending on the surfactant and its concentration and additionally modified with organic surface groups. The adsorption behaviour of the materials can be predicted by molecular simulation and thus the influence of modifications can be studied without the need of synthesising the material. For MOFs, the coordinates of the atoms can be obtained from XRD measurements. The quality of the predicted adsorption results was investigated for pure gas (methane, ethane, propane, nitrogen and carbon dioxide) and gas mixture (methane – carbon dioxide) adsorption on the metal-organic framework CuBTC. The comparison showed a good agreement between experimental and simulated results especially at low pressures. In order to create atomistic models for the mesoporous silica structures that are amorphous on the atomistic level, two existing simulation methods to model MCM-41-type materials were combined: micellar structures from coarse grained simulations that capture the phase separation in the surfactant/silica/solvent mixtures were used as input in kinetic Monte Carlo simulation that created the pore model on the atomistic level. The model created with this new methodology showed similar adsorption behaviour compared with a model created only with the kMC method using an ideal geometrical structure as micelle. The influence of modifications of the MOF structures (exchange of metal, linker length/composition and catenation) was investigated by Grand Canonical Monte Carlo simulations for hydrogen adsorption at low temperature and temperature controlled desorption. The peaks in the desorption spectra could be related to steps in the adsorption isotherms at 20 K.
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Ferreiro, Rangel Carlos Augusto. "Molecular simulation studies in periodic mesoporous silicas SBA-2 and STAC-1 : model development and adsorption applications." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5272.
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Adsorption is a low-energy separation process especially advantageous when the components to be separated are similar in nature or have a low molar concentration. The choice of the adsorbent is the key factor for a successful separation, and among them periodic mesoporous silicas (PMS) are of importance because of their pore sizes, shapes and connectivity. Furthermore, they can be modified by post-synthesis functionalisation, which provides a tool for tailoring them to specific applications. SBA-2 and STAC-1 are two types of PMS characterised by a three-dimensional pore system of spherical cages interconnected by a network of channels whose formation process was until now obscure. In this work the kinetic Monte Carlo (kMC) technique has been extended to simulate the synthesis of these complex materials, presenting evidence that the interconnecting network originates from spherical micelles touching during their close-packing aggregation in the synthesis. Moreover, for the first time atomistic models for these materials were obtained with realistic pore-surface roughness and details of the possible location of its interaction sites. Grand Canonical Monte Carlo (GCMC) simulations of nitrogen, methane and ethane adsorption in the materials pore models show excellent agreement with experimental results. In addition, their potential as design tools is explored by introducing surface groups for enhancing CO2 capture; and finally, application examples are presented for carbon dioxide capture from flue gases and for natural gas purification, as well as in the separation of n-butane / iso-butane isomers.
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Akinlalu, Ademola V. "Structural analysis and characterization of synthesized ordered mesoporous silicate (MCM-41) using small angle X-rays scattering and complementary techniques." Thesis, Rensselaer Polytechnic Institute, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10158526.
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Mesoporous silicate have widespread potential applications, such as drug delivery, supports for catalysis, selective adsorption and host to guest molecules. Most important in the area of scientific research and industrial applications is their demand due to its extremely high surface areas (> 800m 2g−1) and larger pores with well defined structures.
Mesoporous silicate (MCM-41) samples were prepared by hydrothermal method under various chemo-physical conditions and various experimental methods such as small angle X-rays scattering (SAXS), Nitrogen adsorption-desorption analysis at 77 K, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to investigate the changes in the structural morphology and subtle lattice parameter changes. With regards to the subtle changes in the structural characteristics of the synthesized mesoporous silicate, we seek to understand the electron density function changes as the synthesis parameter are varied from low molar concentration of ATAB/Si to higher concentration, the system becoming more acidity due to increase in the hydrolysis time of pH regulator as a result of increased production of ethanol and acetic acid and the changes due to extended reaction time.
This Ph.D. research tries to understand the influence of various parameters like surfactant-Si molar ratio, reaction time, and the hydrolysis of the pH regulator on the orderliness/disorderliness of the lattice order, lattice spacing and electron density function. The stages during synthesis are carefully selected to better understand where the greater influence on the overall structural morphology exist so as to be able to ne tune this parameter for any desired specification and application.
The SAXS measurement were conducted on a HECUS S3-Micro X-ray system at Rensselaer Polytechnic Institute, Troy, NY. while the data evaluation and visualization were carried in 3DView 4.2 and EasySWAXS software. The electron density functions were generated with a proprietary software called edens.
In this dissertation, the following observations have been revealed resulting from SAXS measurement.
1. As one increases the hydrolysis duration of ethyl acetate, a gradual collapse of the lattice spacing of the mesoporous silcate MCM-41 is observed. We found from SAXS that there is a slight right shift of the spectra toward the higher q-values indicating that we are gradually losing orderliness in the lattice spacing and hexagonal structure of the mesoporous silica. Also, the intensity of the peak of second and third peaks are diminutive when compared to sample with shorter hydrolysis time.
2. A comparison of the SAXS spectra for the different molar concentration sample reveals that the 0:5M samples shows a deteriorating structural characteristics as compared to the 0:25 and 0:75M samples respectively and a clear decrease in the (100) reflection planes. Also noticed is the slight rightward shift in the overall spectrum prole. This observation suggest that further analysis is needed so as to better understand the result.
3. We establish that during MCM-41 synthesis, longer reaction time is needed to produce quality sample with well defined structurally characteristic for its intended application because according to spectrum for the sample with a longer reaction time (aging), a shift towards the lower q-values indicates that a sample with a larger lattice parameter and wall thickness but the intensities of its peak are diminishing when compared to the other of relatively shorter reaction time.
Other complementary techniques were used to corroborated the result obtained from SAXS. Nitrogen adsorption-desorption analysis at 77K was used to generate the isotherms while B.E.T method was used in conjunction with the isotherms to obtained the very important surface area information. SEM provide a visual structural morphology of the samples and FTIR gave the fingerprint detail of the bonds and vibration types between particle present.
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Coelho, Jakelyne Viana. "Síntese de catalisadores baseados em silicatos mesoporosos contendo ferro ou nióbio para uso em sistemas catalíticos heterogêneos." Universidade Federal de Minas Gerais, 2013. http://hdl.handle.net/1843/SFSA-9JLT5T.
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This thesis deals with the development of new materials based on mesoporous silicate, modified with iron and niobium atoms, for use in catalytic processes. The focus of this work was to develop mesoporous materials with high specific area, that act as a catalyst in the oxidation and isomerization, to obtain fine chemicals and in the oxidation/degradation of molecules model, simulating textile dyes an industrial waste. The synthesis of these materials was performed by polymerizing tetraethoxysilane (TEOS) as silica source, supramolecular arrengements of cetyltrimethylammonium bromide (CTAB) as structure drivers, with iron and niobium salts. The materials were characterized by various characterization techniques, and the Mossbauer spectroscopy and XRD indicated the incorporation of Fe and Nb in the silicate structure. Studies textural point materials with high surface area, with values of 1165 and 799 m2 g-1 for Fe3+-MCM and Fe2+-MCM, respectively, and 960 to 910 m2g-1 to Nb-MCM and Nb-MCM//H2O2 respectively. The reactions involving the oxidation of -pinene using niobium catalysts showed that the presence of niobium assisted the conversion of -pinene into oxidized products of high added value. It was possible to observe the oxidation/degradation of Rhodamine-B molecule using ESI-MS analysis and the same catalyst. For the isomerization of -pinene catalysts modified with iron atoms were used. It was possible to observe a greater conversion of -pinene into value added products, highlighting the higher catalytic efficiency of the modified materials with iron when compared with MCM-41. The reactions of oxidation/degradation of methylene blue model molecule were performed, also using the modified catalysts with iron, and monitored by ESI-MS. It was observed that the iron-containing materials are able to generate oxygen radicals, which react with the methylene blue molecule (conversion of about 90%). In conclusion this study aimed to cooperate, in a general way, for the understanding of the effects of metal ions in the structure of mesoporous silicates, such as MCM-41, as well as improve to potential interest of these materials for the industry.Essa tese de doutorado trata do desenvolvimento de novos materiais à base de silicatos mesoporosos modificados com átomos de ferro e nióbio para uso em processos catalíticos. O principal objetivo desse trabalho foi desenvolver materiais mesoporosos, com alta área específica, para atuarem como catalisadores em reações que envolvam sítios oxidantes ou ácidos, para a obtenção de produtos da química fina e na oxidação de compostos orgânicos em meio aquoso. A síntese dos materiais foi executada através da polimerização de tetraetilortossilicato (TEOS) como fonte de sílica, sobre arranjos supramoleculares de brometo de cetiltrimetilamônio (CTAB), utilizados como direcionadores de estrutura, juntamente com os sais de ferro e nióbio. Os materiais foram caracterizados por diversas técnicas de caracterização, sendo que a DRX e a Espectroscopia Mossbauer indicam a incorporação de Fe e Nb na estrutura do silicato. Estudos texturais apontam materiais com elevada área superficial, com valores de 1165 e 799 m2g-1 para Fe3+-MCM e Fe2+-MCM, respectivamente, e 960 e 910 m2g-1 para Nb-MCM e Nb-MCM//H2O2, respectivamente. As reações envolvendo a oxidação do a-pineno, utilizando os catalisadores de nióbio, mostraram que a presença do nióbio auxiliou na conversão do a-pineno em produtos oxidados de alto valor agregado. Utilizando estes mesmos catalisadores, foi permitido, através da análise por ionização por eletrospray acoplado ao espectrômetro de massas (ESI-MS) observar a oxidação/degradação da molécula de Rodamina-B, simulando a degradação de um corante têxtil. Para a isomerização do ß-pineno foram utilizados os catalisadores modificados com átomos de ferro. Foi possível observar uma maior conversão do ß-pineno em produtos de valor agregado, destacando a maior eficiência catalítica dos materiais modificados com ferro, quando comparados com a MCM-41. As reações de oxidação/degradação da molécula modelo azul de metileno foi realizada utilizando também os catalisadores modificados com ferro e monitorada por ESI-MS. Foi possível observar que os materiais que contém ferro são capazes de gerar radicais oxidantes que reagem com a molécula azul de metileno (conversão de aproximadamente 90%. Dessa forma, esse trabalho visou colaborar, de uma maneira geral, para a compreensão dos efeitos da presença de íons metálicos em silicatos mesoporosos, como a MCM-41, assim como a contribuição para possíveis aplicações industriais desses materiais.
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Celer, Ewa B. "Thermal and Hydrothermal Stability of Polymer-Templated Siliceous Mesostructures." Kent State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=kent1185232734.
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Lu, Xinnan. "Optimizing vanadium dispersion in mesoporous silicas using different anchoring metal ions for C-C catalytic bond cleavage in lignin degradation." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN070/document.
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Dans le cadre du développement durable, les procédés rapides, propres et peu énergivores sont très recherchés particulièrement en chimie pour les réactions d’oxydation. A part les solutions de génie des procédés, la catalyse est l’un des meilleurs atouts pour améliorer le processus. Le vanadium étant l’un des meilleurs métaux catalytiques pour de tels réactions, nous avions à nous attaquer son problème de relargage dans le milieu réactionnel en vue d’applications acceptables pour l’environnement. Nous proposons donc dans cette thèse des catalyseurs au vanadium fixé à l’intérieur des nano pores de silices mésoporeuses hexagonales de type MCM-41. La grande dispersion et la rétention du vanadium sont promues grâce à la présence d’ion d’ancrage : Al(III), Ti(IV), Zr(IV) and Ce(IV). Une grande variété de catalyseurs de type V-(Al/Ti/Zr/Ce)-MCM-41 ont été préparés à partir de trois méthodes de synthèse: l’une, ultra-rapide en une étape assistée par micro-onde, la seconde à étapes séquentielles multiples mettant en œuvre une technique de pochoir moléculaire et la troisième à nombre d’étapes réduites utilisant un traitement thermique partiel d’une surface préalablement organosilylée avant le greffage des métaux. Un large panel de techniques physicochimiques fut appliqué à la caractérisation de ces solides avec une attention particulière portée à l’analyse de la bande de transfert de charge ligand-métal du vanadium au degré d’oxydation +5 dont le décalage vers le bleu est corrélé à la taille des clusters d’oxyde de ces ions. La rétention du vanadium dans le méthanol a été corrélée à la dispersion du vanadium comme la dégradation à l’air du 1,2-diphényle-2-méthoxyéthanol. Ce substrat fut choisi comme modèle pour étudier la dégradation de la lignine par clivage C-C ou C-O. Notons que ce bio-polymère produit du phénoxypropanol methylé bio-sourcé utilisé dans les bio-carburants et comme précurseur en chimie fine. Dans le cas présent, un balayage à haut débit de la dégradation de cette molécule mettant en œuvre 96 mini-réacteurs en parallèle a permis de sélectionner le solvant, le métal d’ancrage et la teneure des deux métaux donnant la plus haute conversion. Contrairement aux catalyseurs homogènes, nos catalyseurs présentent une très haute sélectivité en clivage C-CThe search for practical large-scale, fast, clean and energy saving chemical processes are highly regarded in the frame of a sustainable development, particularly for the most problematic oxidation reactions. Apart from chemical engineering solutions, improving the process using heterogeneous catalysis is one of the most adapted solution. Vanadium being considered the best metal for such kind of reactions, one had to tackle the problem of its high dispersion on a support to minimize its high propensity for leaching and to optimize its stability for practicable, safe and clean uses. In the present thesis, vanadium is supported inside the nanopores of a mesoporous silica of MCM-41 type where the high dispersion is assisted by the presence of anchoring ions such as Al(III), Ti(IV), Zr(IV) and Ce(IV) ions. A large set of V-(Al/Ti/Zr/Ce)-MCM-41 catalysts was prepared according to three different methods of preparation: i) ultra-fast one-pot synthesis protocol using the assistance of microwave, ii) post-synthesis modification using molecular stencil patterning (MSP) technique and iii) partial thermal treatment (PTT) of the organo-silylated support. The catalysts were characterized thoroughly using a panel of physical techniques and, particularly, the blue shift of the optical gap measured from the vanadium charge transfer band known to correlated with the dispersion of the metal. In complement, the stability was tested from metal leaching using methanol as a corrosive solvent while their catalytic reactivity was estimated in the aerobic oxidation of 1,2-diphenyl-2-methoxyethanol. This is a model reaction that simulates the oxidative C-C bond cleavage in lignin, the most difficult and crucial step in the degradation of this biopolymer, then producing in a clean way valuable methoxylated phenoxy propanol units useful for biomass fuels or bio-sourced precursors for fine chemistry. A high throughput screening approach was applied to test this aerobic oxidation reaction running over 96 reactors in parallel at the same temperature and sorting out the best catalysts with the most suitable anchoring ions and metal loading for the highest catalytic efficiency
在可持续发展的背景下，对于清洁高效节能可行的大规模化工过程尤其是存在诸多问题的氧化反应过程的探索倍受瞩目。除化学工程解决方案之外，通过多相催化来改进反应过程也是最可行的途径之一。钒被认为是最适合于催化此类反应的金属之一，其亟待解决的问题是实现钒在载体上的高度分散，并最大限度地降低其浸出倾向，改善其稳定性，从而实现对其安全清洁有效的利用。本文提出将钒负载于MCM-41型六方介孔二氧化硅的纳米孔道中，通过锚定离子如Al(III)、 Ti(IV)、Zr(IV)、Ce(IV)离子的存在促进钒的高度分散和固载。采用三种不同的方法制备了一系列V-(Al/Ti/Zr/Ce)-MCM-41催化剂：1、超快微波一步合成法，2、使用分子复刻版技术改性的后嫁接法，3、对有机硅烷化载体进行部分热处理改性的后嫁接法。通过一系列物理化学技术对合成的催化剂进行了充分表征，特别是对与金属分散度相关的钒的电荷跃迁带的测量和与其对应的光谱带隙蓝移进行了分析。随后，以甲醇作为腐蚀溶剂对合成的钒催化剂进行了金属析出的稳定性测试。通过一种木质素模型化合物1,2-diphenyl-2-methoxyethanol的需氧氧化反应测试了所合成负载型钒催化剂的催化活性。在相同温度及反应条件下，用96通道高通量微反应器技术评价了所制催化剂对该反应的催化性能，筛选出具有最高催化效率的负载型钒催化剂及其最适合的锚定离子。该反应中的碳-碳键裂解反应是木质素降解的最关键也是最困难的步骤之一，可通过这类生物聚合物的降解以清洁的方式生产有用的生物质燃料或生物来源高附加值精细化学品前驱体。
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Gutierrez, Luis Felipe. "Production of lactobionic acid by oxidation of lactose over gold catalysts supported on mesoporous silicas - Reaction optimization and purification process proposal." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29991/29991.pdf.
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Le surplus mondial et le faible prix du lactose ont attiré l’attention de chercheurs et de l’industrie pour développer des procédés novateurs pour la production de dérivés du lactose à valeur ajoutée, tels que l’acide lactobionique (ALB), qui est un produit à haute valeur ajoutée obtenu par l’oxydation du lactose, avec d’excellentes propriétés pour des applications dans les industries alimentaire et pharmaceutique. Des recherches sur la production d’ALB via l’oxydation catalytique du lactose avec des catalyseurs à base de palladium et de palladium-bismuth, ont montré des bonnes conversions et sélectivités envers l’ALB. Cependant, le principal problème de ces catalyseurs est leur instabilité par lixiviation et désactivation par suroxydation au cours de la réaction. Les catalyseurs à base d’or ont montré une meilleure performance que les catalyseurs de bismuth-palladium pour l’oxydation de glucides. Cependant, trouver un catalyseur robuste pour l’oxydation du lactose est encore un grand défi. Dans cette dissertation, des nouveaux catalyseurs à base d’or supportés sur des matériaux mésostructurés de silicium (Au/MSM) ont été synthétisés par deux méthodes différentes, et évalués comme catalyseurs pour l’oxydation du lactose. Les catalyseurs ont été caractérisés à l’aide de la physisorption de l’azote, DRX, FTIR, TEM et XPS. Les effets des conditions d’opération, telles que la température, le pH, la charge d’or et le ratio catalyseur/lactose, sur la conversion du lactose ont été étudiés. Finalement, le procédé de déminéralisation de la solution de lactobionate de sodium à la sortie du réacteur a été étudié à l’aide de deux approches: l’électrodialyse avec des membranes bipolaires (EDMB) et la technologie d’échange d’ions. Des catalyseurs Au/MSM hautement actifs ont été synthétisés avec succès par la co-condensation d’un mélange de bis [3-(triéthoxysilyl) propyle] tétrasulfide (BTESPTS), tétra-éthyle ortho-silicate (TEOS) et le précurseur d’or (HAuCl4) en milieu acide, avec le tribloc co-polymère EO20PO70EO20 utilisé comme agent structurant. Il a été trouvé que l’augmentation du ratio molaire BTESPTS/TEOS provoque un changement dans la structure des matériaux, laquelle passe d’une structure 2D-hexagonal très ordonnée à une structure mixte de type hexagonal-vésicule et mousse cellulaire. Dans les conditions opératoires optimales (charge d’or = 0.7% en poids, T = 65ºC, catalyseur/lactose ratio = 0.2, pH = 8-9, débit d’air = 40 mL·min-1), le lactose a été complètement converti en ALB après 80-100 min de réaction, lorsqu’on a utilisé les catalyseurs synthétisés à partir des mélanges contenant une concentration molaire de BTESPTS entre 6-10%. Ces catalyseurs ont été caractérisés par une structure de type « wormhole-like », favorable pour l’accessibilité des réactifs aux nanoparticules d’or (AuNPs) d’environ 8 nm intercalées dans les murs de la silice. AuNPs d’environ 5-6 nm ont été aussi chargées avec succès sur les matériaux mésoporeux SBA-15 et SBA-15-CeO2, par l’adsorption du complexe [Au(en)2]3+ (en=éthylènediamine) en milieu alcalin. Ces catalyseurs ont conservé la structure hexagonale 2D très ordonnée typique de la SBA-15, et ils ont présenté une grande activité pour l’oxydation du lactose. Après 60 min de réaction, les catalyseurs Au/SBA-15-CeO2 (ratio molaire Ce/Si = 0.2) ont présenté l’activité catalytique la plus élevée (100% conversion du lactose) et 100% de sélectivité envers l’ALB, lorsqu’ils ont été utilisés dans les conditions optimales décrites ci-dessus. Ces résultats suggèrent que l’oxyde de cérium joue un rôle dans l’augmentation de l’activité catalytique, où la coordination et les états d’agglomération des atomes du Ce pourraient avoir un effet important. En général, les résultats des analyses XPS sur les états d’oxydation de l’or à la surface des Au/MSM, ont montré la coexistence d’espèces d’or métalliques et oxydées, avec une abondance relative suivant l’ordre Au0 >>>Au+1 > Au+3. Dans le cas des catalyseurs Au/SBA-15-CeO2, la présence des deux états d’oxydation Ce3+ et Ce4+ a été aussi observée. Les expériences de recyclage des catalyseurs ont montré que l’activité des échantillons Au/SBA-15 et Au/SBA-15-CeO2 a été significativement réduite (40-65%) après des cycles de réaction d’oxydation consécutifs, lorsque le lavage avec de l’eau a été utilisé comme procédé de régénération. Par contre, les catalyseurs ont conservé leur activité catalytique, en utilisant la calcination comme méthode de régénération, ce qui indique qu’une des causes de désactivation des catalyseurs Au/MSM pourrait être due à une forte adsorption d’espèces organiques sur la surface des catalyseurs. De plus des quantités significatives d’or ont été trouvées dans la solution après des cycles de réaction consécutifs, ce qui démontre la désactivation est aussi due à la lixiviation de la phase active dans la solution de réaction. Les données expérimentales ont révélé que tant l’EDMB que la technologie d’échange d’ions pourraient être utilisées pour produire l’ALB à partir de son sel de sodium. Cependant, en tenant compte du fait que l’EDMB a été utilisée pour la première fois pour cette application, ce procédé a donc besoin d’une amélioration pour des applications industrielles. En effet, une déminéralisation de 50% a été atteinte après l’application d’une différence de potentiel de 5.0-5.5 V pendant 100-180 min aux bornes d’une cellule d’électrodialyse à trois compartiments, tandis que la solution de lactobionate de sodium a été complètement dépourvue de sodium après 10-30 min, lorsqu’on a utilisé une résine échangeuse de cations commerciale fortement acide (AmberliteTM FPC23 H).The worldwide surplus and low cost of lactose have drawn the attention of researchers and industry to develop innovative processes for the production of value-added lactose derivatives, such as lactobionic acid (LBA), which is a high value-added product obtained from lactose oxidation, with excellent properties for applications in the food and pharmaceutical industries. Investigations on LBA production by means of catalytic oxidation of lactose over palladium and bismuth-palladium supported catalysts have shown good conversion rates and selectivities towards LBA, but the main problem of these catalysts is their instability by leaching and deactivation by over-oxidation during the reaction. Supported gold catalysts have shown to outperform palladium and bismuth-palladium catalysts for the oxidation of carbohydrates. However, there is still a big challenge in finding a robust catalyst for the lactose oxidation. In this dissertation, new gold catalysts supported on mesoporous silica materials (Au/MSM) have been synthesized by two different methods, and evaluated as catalysts in the oxidation of lactose. The catalytic materials were characterized by nitrogen physisorption, XRD, FTIR, TEM and XPS. The effects of the operating conditions such as temperature, pH, gold loading and catalyst/lactose ratio on the lactose conversion were investigated. Finally, the demineralization process of the sodium lactobionate solution obtained at the reactor outlet has been studied using two approaches: bipolar membrane electrodialysis (BMED) and ion-exchange technology. Highly active Au/MSM were successfully formulated by the co-condensation of a mixture of bis [3-(triethoxysilyl) propyl] tetrasulfide (BTESPTS), tetraethyl orthosilicate (TEOS) and the gold precursor (HAuCl4) in acidic media, using the triblock co-polymer EO20PO70EO20 as template. It was found that by increasing the BTESPTS/TEOS molar ratio, the structure of the synthesized materials changed from a highly ordered 2D hexagonal structure to a mixed hexagonal-vesicle and cellular foam structure. Under the optimal operating conditions (gold loading = 0.7%wt, T = 65ºC, catalyst/lactose ratio = 0.2, pH = 8-9, air flow = 40 mL·min-1), the lactose was completely converted into LBA after 80-100 min reaction, when using the catalysts synthesized from mixtures containing 6-10% molar concentration of BTESPTS. These catalytic materials were characterized by the predominance of a wormhole-like structure, favorable for the reagent accessibility to the gold nanoparticles (AuNPs) of about 8 nm intercalated in the silica walls. AuNPs of about 5-6 nm were also successfully loaded of mesoporous SBA-15 and SBA-15-CeO2 materials, by the wet adsorption of the gold cationic complex [Au(en)2]3+ (en=ethylenediamine) in alkaline media. These catalysts retained the well-ordered 2D hexagonal structure typical of SBA-15, and showed high activity to lactose oxidation. After 60 min of reaction, the Au/SBA-15-CeO2 catalysts (Ce/Si = 0.2) showed the highest catalytic activity (100% lactose conversion) and 100% selectivity towards LBA, when used at the optimal operating reaction conditions described above. These results suggest that ceria plays a role in the enhancement of the catalytic activity, where the coordination and agglomeration states of Ce atoms could have an important effect. In general, the XPS study on the oxidation states of gold on the Au/MSM surfaces revealed the coexistence of metallic and oxidized Au species, whose relative abundance followed the order Au0 >>>Au+1 > Au+3. In the case of Au/SBA-15-CeO2 catalysts, the presence of both Ce3+ and Ce4+ oxidation states was also observed. Catalysts’ recycling experiments showed that the activity of Au/SBA-15 and Au/SBA-15-CeO2 was significantly reduced (40-65%) after consecutive oxidation reaction cycles, when washing with water was used as regeneration process. On the contrary, these catalytic samples conserved their catalytic activity when calcination was used as regeneration method, indicating that one of the causes of deactivation of Au/MSM might be the strong adsorption of organic species on the catalyst surface. Moreover, significant amounts of Au were found in the solution after consecutive reaction cycles, demonstrating that the leaching of the active phase into the reaction solution is another important cause of the catalyst’ deactivation. Experimental data showed that both BMED and ion exchange technology might be used for producing LBA from its sodium salt. However, taking into account that it is the first time that BMED is used for this application, this process still needs further improvement for industrial applications, since a demineralization rate of 50% was achieved after applying a voltage difference of 5.0-5.5 V during 100-180 min to a three-compartment electrodialysis stack, while a complete sodium removal was achieved after 10-30 min when using a commercial strong cation exchange resin (AmberliteTM FPC23 H).
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Zhang, Jiaxin, and 張家新. "Syntheses and spectroscopic studies of luminescent surfactant rhenium(I) and ruthenium(II) diimine complexes: potential applications as functional materials forsecond-harmonic generation and mesoporous silicate formation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B45015272.
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Donzel, Nicolas. "Nouveaux matériaux mésoporeux catalytiques et leur application pour l'amélioration du gazole." Montpellier 2, 2006. http://www.theses.fr/2006MON20237.
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Zhang, Jiaxin. "Syntheses and spectroscopic studies of luminescent surfactant rhenium(I) and ruthenium(II) diimine complexes : potential applications as functional materials for second-harmonic generation and mesoporous silicate formation /." View the Table of Contents & Abstract, 2004. http://sunzi.lib.hku.hk/hkuto/record/B30267791.
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Gierszal, Kamil Piotr. "Synthesis, adsorption and structural properties of carbons with uniform and ordered mesopores." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1207762469.
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Bibent, Nicolas. "Propriétés d'adsorption et mobilité des charges ioniques dans des silices mésoporeuses fonctionnalisées de type SBA-15." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20014.
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Ce travail traite du rôle joué par les fonctions de surface sur le transport et le piégeage de cations alcalins en présence d'eau, dans des SBA-15 fonctionnalisées. Il s'agit aussi d'étudier les effets de confinement sur la thermodynamique de l'eau adsorbée. La première étape a consisté à synthétiser les différentes SBA-15, contenant des groupements fonctionnels acides du type PO(OH)2, SO3H, COOH ainsi que leurs équivalents alcalins contenant du Li, Na, K ou Rb. Les solides obtenus ont été caractérisés à l'état sec par DRX, adsorption-désorption de N2 et par RMN du solide, afin de rendre compte respectivement de l'organisation du réseau poreux, des caractéristiques texturales et de la structure locale des motifs organiques. Puis, nous avons étudié ces solides en présence d'eau adsorbée. Nous avons mis en évidence l'instabilité des solides alcalins contenant des ions Na+, K+ et Rb+. Nous proposons également une étude thermodynamique de la fusion de l'eau confinée par DSC, pour laquelle nous montrons que déplacement de la température de transition solide/liquide de l'eau adsorbée dépend de la taille des pores. Ensuite, nous avons analysé les dynamiques ionique et moléculaire de l'eau confinée par Spectroscopie d'Impédance Complexe (SIC) et par diffusion quasi-élastique des neutrons (QENS). L'étude par SIC nous a permis, pour les solides acides, de révéler une conduction protonique selon un mécanisme de Grötthus, et de montrer une dépendance entre les valeurs de conductivité et le pKa des fonctions acides. Finalement par QENS, nous avons observé deux régimes de mobilité des protons, de part et d'autre de 220K, que nous avons associés à des populations différentes de protonsThis work deals with the role played by the functions of surface transport and trapping of alkali cations in the presence of water in SBA-15 functionalized. It is also to study the effects of confinement on the thermodynamics of the adsorbed water. The first step was to synthesize the different SBA-15 containing acidic functional groups of type PO (OH) 2, SO3H, COOH and alkali equivalents containing Li, Na, K or Rb. The solids obtained were characterized in the dry state by XRD, N2 adsorption-desorption and solid state NMR, respectively, to reflect the organization of the pore network, and textural characteristics of the local structure of organic patterns. Then, we studied the solid presence of adsorbed water. We have highlighted the instability of solids containing alkali ions Na +, K + and Rb +. We also study the thermodynamics of melting of water confined by DSC, for which we show that displacement of the transition temperature of solid / liquid water adsorbed depends on the pore size. Then, we analyzed the ionic and molecular dynamics of water confined by Complex Impedance Spectroscopy (CIS) and by quasi-elastic neutron scattering (QENS). The CIS study allowed us, for strong acids, reveal a proton conduction mechanism in a Grotthus, and show a dependence between conductivity values and the pKa of the acid functions. Finally by QENS, we have observed two regimes of mobility of protons, on both sides of 220K, which we associated with different populations of protons
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Kerdi, Fatmé. "Nouveaux carbones mésostructurés comme supports de nanoparticules d’or pour des oxydations sélectives aérobies." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10170/document.
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Des nanoparticules d’or dispersées dans un carbone mésoporeux CMK-n (n = 1,3 et 8) ont été obtenues par une méthode originale qui consiste à répliquer des silices mésoporeuses dans lesquelles les particules d’or ont été préalablement formées. La taille des particules d’or est plus petite lorsque la surface de la silice est fonctionnalisée par un thiol (MPTMS) (dAu ~ 2 nm) que par un ammonium (TPTAC) (dAu ~ 6 nm). La taille des particules d’or dans les répliques peut être contrôlée à la fois par la température de calcination du moule et par la température de pyrolyse de la source de carbone. Bien que les répliques carbonées soient beaucoup mieux dispersées dans le milieu réactionnel apolaire que les moules siliciques correspondants, elles sont moins actives dans les oxydations aérobies du cyclohexène et du trans-stilbène en phase liquide. Les meilleures performances dans l'oxydation de ces deux molécules ont été obtenues sur les répliques pyrolysées à 750°C et contenant des particules d’or de taille moyenne d'environ 2 nm. Les très petites particules sont moins actives, probablement parce qu'elles sont complètement enrobées par du carbone, donc inaccessibles. Les performances catalytiques de nos répliques ont été comparées avec celles d'un catalyseur Au/CMK-3 préparé par dépôt colloïdal sur un carbone mésoporeux pré-formé. Les résultats montrent que nos catalyseurs sont beaucoup moins actifs que celui préparé par dépôt colloïdal, car la majorité des particules dans nos répliques sont recouvertes par du carbone. L'inaccessibilité des particules aux gaz a été confirmée par une mesure de chimisorption d’hydrogène sur un catalyseur Pt/CMK-3 préparé par une méthode identiqueHighly dispersed gold nanoparticles in ordered mesoporous carbons CMK-3 have been obtained by an original method which consists in replicating mesoporous SBA-15 silicas containing gold nanoparticles. The gold particle size is smaller when the silica surface is functionalized with a thiol (mercaptopropyl graft, MPTMS) (dAu ~ 2 nm) than with an ammonium (TPTAC) (dAu ~ 6 nm). The gold particle size in replicas can be controlled by both the calcination temperature of the silica template and the pyrolysis temperature of the carbon source. Although the carbon replicas are much better dispersed in non polar solvents than the corresponding silica templates, they are less active in the aerobic oxidations of cyclohexene and trans-stilbene in the liquid phase. The best performances in the oxidation of these two molecules have been obtained on replicas pyrolysed at 750°C and containing gold particles with an average size of about 2 nm. The very small particles are unexpectedly less active probably because they are completely coated by carbon, and thus inaccessible. The catalytic performances of our replicas have been compared with those of a Au/CMK-3 catalyst prepared by colloidal deposition onto a preformed mesoporous carbon replica. The results show that our catalysts are much less active than that prepared by colloidal deposition because the majority of particles in our replicas are covered by carbon. The inaccessibility of particles to gases has been confirmed by hydrogen chemisorption on a Pt/CMK-3 catalyst prepared by an identical method