Surface polarity and catalytic activity of inorganic solid acids The objective of this work is to quantify solvent influence on the surface polarity and catalytic activity of inorganic solid acids. Kamlet-Taft`s a (hydrogen-bond acidity), b (hydrogen-bond accepting ability) and p* (dipolarity/polarizability) parameters of various silicas, alumina, aluminosilicate, zeolites HZSM-5 and HY as well as of a siliceous MCM-41 material were determined using solvatochromic surface polarity indicators, which have been adsorbed on the solid acids from solvents of different polarity. The surface-mediated hydride-transfer reaction of 1,4-cyclohexadiene with triphenylmethylium induced by the solid acid catalysts, respectively, has been kinetically studied as function of the polarity of the surrounding solvent. The relative rate constant k? has been determined in ten different solvents. Correlation analyses between lg k? and the polarity parameters a, b, and p* of the solvents as well as of the catalysts surfaces are shown and discussed. Acid-base-interactions between solvent and catalyst mainly influence the reactivity and surface polarity of the solid acids. / Oberflächenpolarität und katalytische Aktivität anorganischer Feststoffsäuren Ein zentrales Anliegen der Arbeit ist die Quantifizierung des Lösungsmitteleinflusses auf die Oberflächenpolarität und die katalytische Aktivität anorganischer Feststoffsäuren. Die Oberflächenpolaritätsparameter a (Acidität), b (Basizität) und p* (Dipolarität/Polarisierbarkeit) von unterschiedlichen Kieselgelen und Zeolithen sowie von je einem Aluminiumoxid und Alumosilikat werden mittels solvatochromer Sondenmoleküle in Lösungsmitteln verschiedener Polarität bestimmt. Für die Hydridionenübertragung von 1,4-Cyclohexadien auf oberflächengeneriertes Triphenylmethylium wird in den genannten Fest-/Flüssig-Systemen die katalytische Aktivität untersucht und dazu die für den Katalysator normierte Geschwindigkeitskonstante k? [s-1m-2] ermittelt. Korrelationsanalysen zeigen Zusammenhänge zwischen lg k? und den Parametern a, b und p* der Lösungsmittel bzw. Feststoffoberflächen auf und werden diskutiert. Säure-Base-Wechselwirkungen zwischen Lösungsmittel und Katalysator sowie Solvatationseffekte haben einen entscheidenden Einfluss auf Reaktivität und Oberflächenpolarität. In Bezug auf Diffusionsvorgänge und Aktivierungsenergien spielt die Morphologie der Feststoffsäuren eine wichtige Rolle, wie beim Vergleich zwischen nanoporösem silikatischem MCM-41 und konventionellen Kieselsäuren festgestellt wird.

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

The active sites for epoxydation of alkenes in silica supported titanium catalysts are isolated Ti(IV) ions. The strategy for site isolation consists here to graft titanium isopropoxyde by reaction with surface silanol groups, the density of which is decreased by chemical capping instead of the energy consuming thermal treatment. The molecular stencil patterning technique (MSP) is applied to enforce site isolation. In mesostructured porous silicas, the partly extracted templating surfactant plays the role of a MSP mask during capping. Then, the elimination of the remaining surfactant liberates silanol islands for the grafting of Ti(IV) ions. Quantitative FT-IR and 29Si MAS-NMR studies reveal that the inverse organic stencil made of grafted organosilyls groups is maintained at each synthesis steps. Diffuse reflectance UV spectroscopy in correlation with the catalytic activity in epoxidation of cyclohexene show that these original surfaces favor the formation of a much larger number of isolated mononuclear sites than the unmodified silica surfaces. The demonstration is obtained using a dipodal organosilyl function, 1-2-ethanebis (dimethylsilyl) (EBDMS) that is much more stable than the classic and monopodal, trimethylsilyl (TMS). Besides, it is shown that the inverse organic stencil (from EBDMS or TMS) is stabilized further by thermal treatment while its dispersive effect on titanium can be preserved. The proof relies on a quantitative 29Si solid State NMR study. Finally, a refined description of the grafting mode of titanium was realized by simulation of the UV spectra of a large series of catalysts assuming only 5 different types of species including isolated species and clusters differentiated by the range of sizes.

Discovery of mesoporous materials by Mobil researchers in 1992 opened a new field in catalytic applications. The materials designated as M41S family are MCM-41 with one-dimensional hexagonal structure, MCM-48 with three-dimensional cubic structure and MCM-51 with unstable lamellar structure. This family of materials have high surface areas up to 1500 m2/g, narrow pore size distributions with pore sizes varying from 20 to 100 &Aring / . These materials can be activated by incorporation of metals or active compounds into their structures. In this study, copper and nickel incorporated MCM-41 type catalytic materials were synthesized via different methods namely, impregnation, high temperature and low temperature direct synthesis methods. The Cu-MCM-41, and Ni-MCM-41, as well as synthesized MCM-41 were characterized by using XRD, TEM, N2 sorption, SEM, XRF, EDS, AAS and TPR. MCM-41 was synthesized with high temperature direct synthesis method. High surface area values up to 1400 m2/g of MCM-41 mesoporous materials were obtained with high pore volumes up to 1.17 cc/g. Cu-MCM-41 type catalytic materials were synthesized with three different methods. Impregnation and high temperature direct synthesis methods gave better results than those of low temperature direct synthesis method. In impregnation, relatively high surface area values (730 m2/g) were obtained with Cu/Si mole ratio as high as 0.3 in the product. For the case of high temperature direct synthesis products, Cu/Si mole ratios as high as 0.26 were obtained with somewhat smaller surface areas (400 m2/g). Low temperature direct synthesis method is the least favorable method in metal loading. Ni-MCM-41 type of catalytic materials were synthesized by impregnation and high temperature direct syntheses methods. Ni incorporation by high temperature direct synthesis method gave high surface area values (560-930 m2/g) having Ni/Si mole ratios of 0.12-0.28.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2017-03-23T19:40:24Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) alenice_ferreira_cruz.pdf: 3398178 bytes, checksum: 4f7c2c8ff0a3c9856be63b637e43306b (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-04-20T16:59:10Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) alenice_ferreira_cruz.pdf: 3398178 bytes, checksum: 4f7c2c8ff0a3c9856be63b637e43306b (MD5) / Made available in DSpace on 2017-04-20T16:59:11Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) alenice_ferreira_cruz.pdf: 3398178 bytes, checksum: 4f7c2c8ff0a3c9856be63b637e43306b (MD5) Previous issue date: 2016 / O bisfenol-A ? um importante produto qu?mico, amplamente utilizado em ind?strias para a produ??o de policarbonatos, resinas epoxi e outros pl?sticos. Existe uma car?ncia em desenvolver m?todos eficazes para remov?-lo de efluentes. Uma vez que, o mesmo faz parte dos chamados poluentes emergentes, pois ? um contaminante prejudicial para os organismos, mesmo em baixas concentra??es, devido ao seu efeito nocivo sobre sa?de. Neste trabalho, buscou-se avaliar o desempenho de dois silicatos mesoporosos (MCM-41 e Co-silicato) frente ? adsor??o do bisfenol-A. Os perfis de difra??o de raio-X dos materiais confirmaram a forma??o da MCM-41 e o material modificado (Co-silicato) demonstrou alterar ao ?nico elemento de ordem estrutural, que ? a disposi??o dos canais paralelos (2?=2). As imagens de MEV mostraram que os materiais n?o apresentaram morfologia definida. Dados indicaram que ambos os materiais apresentam elevada ?rea espec?fica, sendo 988 m2g-1 para MCM-41 e 729 m2g-1 para Co-silicato. O material Co-silicato mostrou elevado potencial como adsorvente, frente ? MCM-41. A elevada ?rea superficial, aliada ao tamanho dos poros, juntamente com a presen?a de ?ons met?licos (cobalto) favoreceram o processo de adsor??o. A forma??o de s?tios ativos no silicato, ap?s a inser??o de cobalto, favoreceu a adsor??o do contaminante. A partir dos testes de adsor??o realizados em pH 3, 6 e 9 foi poss?vel notar que o material que teve uma melhor capacidade de adsor??o foi o material Co-silicato. Diante dos testes de cin?tica, o material Co-silicato nas faixas de pH analisadas demonstrou maior potencial de adsor??o do bisfenol-A, em rela??o ao resultados de remo??o obtidos com o material MCM-41. Os modelos utilizados para os ajustes matem?ticos da adsor??o foram as isotermas de Langmuir, Freundlich, e Redlich-Peterson. O valor do coeficiente de correla??o (R2) 0,9641 pH 3; (R2) 0,9834 pH 6 e (R2) 0,9959 pH 9 dos par?metros de Redlich-Peterson sugeriram que o modelo de Redlich-Peterson descreve melhor o comportamento de adsor??o de bisfenol-A no material Co-silicato, j? que apresenta maior valor do coeficiente de correla??o em pH testados, comparando com os valores de correla??o (R2) de Langmuir e Freundlich. Os dados revelaram que a modifica??o da MCM-41 com ?tomos de cobalto alteraram as propriedades f?sico-qu?mica do material, e potencializou o adsorvente para adsor??o da mol?cula de bisfenol-A. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016. / Bisphenol-A is an important chemical, widely used in industries for the production of polycarbonates, epoxy resins and other plastics. There is a lack of effective methods to remove it from effluents. Since it is part of so-called emerging pollutants, it is a harmful contaminant for organisms, even in low concentrations, because of its harmful effect on health. This work aimed to evaluate the performance of two mesoporous silicates (MCM-41 and Co-silicate) against the adsorption of bisphenol-A. The X-ray diffraction profiles of the materials confirmed the formation of MCM-41 and the modified material (Co-silicate) was shown to change to the only structural element, which is the arrangement of the parallel channels (2? = 2). The SEM images showed that the materials did not present definite morphology. Data indicated that both materials presented a high specific area, being 988 m2g- 1 for MCM-41 and 729 m2g-1 for Co-silicate. Co-silicate material showed high adsorbent potential compared to MCM-41. The high surface area, together with the pore size, together with the presence of metallic ions (cobalt) favored the adsorption process. The formation of active sites in the silicate, after the insertion of cobalt, favored the adsorption of the contaminant. From the adsorption tests carried out at pH 3, 6 and 9 it was possible to observe that the material with the best adsorption capacity was the Co-silicate material. Due to the kinetic tests, the Co-silicate material in the analyzed pH ranges showed a higher adsorption potential of bisphenol-A in relation to the removal results obtained with the MCM-41 material. The models used for the mathematical adjustments of the adsorption were the isotherms of Langmuir, Freundlich, and Redlich-Peterson. The value of the correlation coefficient (R2) 0.9641 pH 3; (R2) 0.9834 pH 6 and (R2) 0.9959 pH 9 of the Redlich-Peterson parameters suggested that the Redlich-Peterson model better describes the adsorption behavior of bisphenol-A in the Co-silicate material, since it presents Higher value of the pH correlation coefficient tested, compared with the Langmuir and Freundlich correlation values (R2). The data revealed that the modification of MCM-41 with cobalt atoms altered the physicochemical properties of the material and potentiated the adsorbent for adsorption of the bisphenol-A molecule.

Made available in DSpace on 2016-06-02T19:56:53Z (GMT). No. of bitstreams: 1 5790.pdf: 8879884 bytes, checksum: 256bcf8b3832d498d50cb0b4fea7cecc (MD5) Previous issue date: 2014-02-25 / Universidade Federal de Sao Carlos / The increasing demand for it in today s world and the problems caused by fossil fuel usage lead to a search for alternative sources that may integrate the world s energy matrix. In this context, because this product is essential to technological, social and environmental development of a country, biofuels like ethanol and biodiesel are strong candidates to minimize the worries about energy availability. Biodiesel is often produced by transesterification reaction using homogeneous catalyst as sodium hydroxide (NaOH) or potassium hydroxide (KOH). However, these materials present issues like the soap formation and need for additional steps in the process to neutralize and purify the product in order to be under specification of Brazilian National Agency of Petroleum, Natural Gas and Biofuels. This fact has stimulated research to find new materials to replace the current route of biofuels production and one promising material is the heterogeneous catalyst. With this motivation, this work presents a new alternative to the synthesis of a solid recently classified as heterogeneous catalyst, the MCM-41, aiming the minimization of costs for its production. The material was synthesized using sodium trisilicate as silica source and it was later tested, without modification, in transesterification reaction between an ester and an alcohol. The results showed catalyst activity and the conversion was around 40%, but its reuse reveals intense loss of activity because of CTA+ cations removal. However, new techniques are under development to guarantee more stability to the catalyst. / A demanda por energia no mundo atual e os problemas que os combustíveis fosseis oca-sionam, tem impulsionado a procura por fontes alternativas de energia que associadas as fontes já utilizadas possam suprir toda a necessidade energetica. Neste contexto, sabendo que esse produto e essencial para o desenvolvimento tecnológico, social e ambiental de um país, os combustíveis líquidos baseados em biomassa sao fortes candidatos a garantir a se¬gurança energetica mundial, o etanol e o biodiesel são exemplos de produtos com potencial para esse fim. O biodiesel e comumente obtido atraves da reação de transesterificação na presença de catalisadores homogêneos como o hidróxido de sodio (NaOH) ou de potassio (KOH). Entretanto o uso desses materiais apresenta problemas como a possibilidade de formação de sabões e a necessidade de etapas adicionais ao processo para neutralizar e purificar o biodiesel deixando-o dentro das especificações estabelecidas pela Agencia Naci¬onal do Petroleo, Gás Natural e Biocombustóveis. Este fato tem estimulado pesquisas no sentido de sugerir materiais que possam substituir o caminho utilizado atualmente, um desses materiais seria o catalisador heterogeneo. Diante deste cenario, o presente trabalho propoe uma rota alternativa para a síntese de um solido recentemente classificado com catalisador heterogeneo, a CTA-MCM-41, visando minimizar os custos de obtenção deste catalisador. O sílido foi sintetizado utilizando como fonte de sílica o trissilicato de sodio e posteriormente testado sem nenhuma modificacao numa reação modelo entre um ester e um alcool e na reação de transesterificação de oleos vegetais. Os resultados mostram que o catalisador apresentou atividade nas duas reacães, atingindo conversões em torno 40% porém o reuso do catalisador revela uma intensa perda de atividade devido a remoçcaão dos cations CTA+. Entretanto novas tecnicas estao sendo desenvolvidas para garantir uma maior estabilidade ao catalisador.

Submitted by Rosana Amâncio (rosana.amancio@ufcg.edu.br) on 2018-07-11T16:43:30Z No. of bitstreams: 1 Tacia Thaisa de Lima Silva UFCG PPGCNBio.pdf: 3218128 bytes, checksum: 07c42fd45987f76fb62c91ebfa9dad6e (MD5) / Made available in DSpace on 2018-07-11T16:43:30Z (GMT). No. of bitstreams: 1 Tacia Thaisa de Lima Silva UFCG PPGCNBio.pdf: 3218128 bytes, checksum: 07c42fd45987f76fb62c91ebfa9dad6e (MD5) Previous issue date: 2016-07-22 / Capes / A pirólise de biomassa utiliza rejeitos orgânicos por conversão termoquímica produzindo compostos oxigenados de menor peso molecular, visando principalmente à produção de energia. O teor dos componentes lignocelulósicos (celulose, hemicelulose, lignina) além da umidade e cinzas é o que confere os produtos finais do processo, sendo eles o bio-óleo, carvão e gás. O presente trabalho teve como objetivo avaliar a influência do catalisador Ni/MCM-41 no processo de pirólise rápida do bagaço de sisal (Agave sisalana). A biomassa foi caracterizada segundo sua composição lignocelulósica, análise termogravimétrica, miscroscopia eletrônica de varredura, espectroscopia de infravermelho e por fim foi realizado o estudo cinético para avaliar a energia de ativação aparente da decomposição térmica dos componentes lignocelulósicos do bagaço do sisal. O catalisador foi sintetizado e caracterizado por difração de raios X, espectroscopia na região do infravermelho e análise termogravimétrica e por fim foram realizadas as pirólises num micro pirolisador da CDS 5200 HP-R da CDS Analytical, em uma faixa de temperatura 500°C. Foram analisados 31 picos no cromatograma produzido pelo processo pirolítico do bagaço de sisal. Pela análise das influências dos resultados da pirólise rápida, com a catalítica contendo apenas o MCM-41 e outra com Ni/MCM-41. Os resultados da caracterização do bagaço de sisal mostraram que esta biomassa tem um alto teor de celulose, O uso do catalisador de Ni/MCM-41 não favoreceu significativamente a redução dos compostos oxigenados. Além disso, o bagaço de sisal como rejeito orgânico pode ser aproveitado por meio de processos termoquímicos gerando novos produtos e reduzindo os impactos ambientais causados pelo seu acúmulo. / The pyrolysis of biomass use organic waste thermochemical conversion of oxygenates to produce lower molecular weight, aiming at the production of energy. The content of the lignocellulosic components (cellulose, hemicellulose, lignin) in addition to the moisture and ash is what gives the end products of the process, namely bio-oil, coal and gas. This study aimed to evaluate the influence of Ni / MCM-41 catalyst in the fast pyrolysis process sisal bagasse (Agave sisalana). Biomass was characterized according to their lignocellulosic composition, thermal analysis, scanning electron miscroscopia, infrared spectroscopy and finally was performed kinetic study to evaluate the apparent activation energy of thermal decomposition of lignocellulosic components sisal bagasse. The catalyst was synthesized and characterized by X-ray diffraction, spectroscopy in the infrared region and thermogravimetric analysis were performed and finally the pyrolysis in a micro pyrolyser CDS HP 5200-R CDS Analytical, in a temperature range of 500 ° C. They analyzed 31 peaks in the chromatogram produced by the pyrolytic process sisal bagasse. The analysis of the influences of the results of fast pyrolysis with the catalyst only containing MCM-41 and another Ni / MCM-41. The results of the characterization of sisal pulp showed that biomass has a high cellulose content, the use of the catalyst Ni / MCM-41 did not significantly favors the reduction of oxygenated compounds. Furthermore, sisal pulp as organic waste can be passed through thermochemical processes generate new products, and reducing the environmental impact caused by its accumulation.

Made available in DSpace on 2016-06-02T19:55:37Z (GMT). No. of bitstreams: 1 5340.pdf: 5522610 bytes, checksum: 3e81291c16e96817f4a95ed87273242d (MD5) Previous issue date: 2013-03-07 / Universidade Federal de Sao Carlos / The search for clean and renewable fuels has aroused great interest in the industry and scientific community with the growing demand for energy. The transesterification reaction of triglycerides is one way of achieving a sustainable fuel and less harmful to the environment. This has encouraged researchers to develop new routes of synthesis of heterogeneous catalysts. The CTA-MCM-41 silica has basic catalytic sites called siloxy (≡SiO-) and may be used in transesterification reactions. Its use in base catalysis has shown promising results, but the reuse reveals extensive loss of activity due to the removal of CTA cations from the channels. The catalyst modification may improve the catalytic stability, in which the insertion of polymeric species together the micelles within the silica is one method studied by our group. Given this perspective, this study aimed at evaluating the modification of the basic catalyst CTA-MCM-41. The polymers encapsulation and ultraviolet irradiation on silicas containing monomer were performed in this study. It was possible to prove by means of small angle X-ray scattering conducted on the emulsion and silicas, the polymeric and monomeric species were inside the micelles causing micellar and silica expansion. The infrared absorption spectroscopy, X-ray diffraction and chemical analysis showed that these species remained inside the micelles after encapsulation. The catalytic evaluation demonstrated that the modified silica with low amounts of monomer added showed improved catalytic stability. / A busca por combustíveis considerados limpos e renováveis tem despertado grande interesse da comunidade científica e industrial com a crescente demanda por energia. A reação de transesterificação de triacilgliceróis é uma das formas de se obter um combustível sustentável e menos agressivo ao meio ambiente. Esse ideal vem estimulando pesquisadores a desenvolverem rotas de síntese de novos catalisadores heterogêneos capazes de atender essa necessidade. A sílica tal como sintetizada CTA-MCM-41 apresenta sítios catalíticos básicos denominados de siloxi (≡SiO-) e pode ser utilizada em reações de transesterificação. Seu uso em catálise básica tem mostrado resultados promissores, no entanto sua reutilização revela uma intensa perda de atividade devido à remoção dos cátions CTA do interior dos canais da sílica. A modificação dessas sílicas pode melhorar a estabilidade catalítica, sendo a inserção de espécies poliméricas no interior das micelas que formam a sílica um meio viável e que vem sendo estudado por nosso grupo. Diante dessa perspectiva, esse trabalho teve por objetivo principal o estudo de síntese e modificação do catalisador básico CTA-MCM-41. O encapsulamento de polímeros e irradiação ultravioleta sobre sílicas contendo monômeros foram os métodos de modificação realizados nesse estudo. Foi possível comprovar através de espalhamento de raios X a ângulos pequenos realizado sobre as emulsões e sílicas, que as espécies monoméricas e poliméricas se encontravam no interior das micelas provocando expansão micelar e dos canais das sílicas. Para o método de encapsulamento, observou-se por meio de fisissorção de nitrogênio que as sílicas modificadas apresentaram a formação de um sistema de poros secundário. Através de espectroscopia de absorção na região do infravermelho, difratometria de raios X e análise química observou-se que parte das espécies monoméricas e das poliméricas continuava no interior das micelas após o encapsulamento. A avaliação catalítica na reação de transesterificação demonstrou que as sílicas modificadas com baixos teores de monômero adicionados à síntese apresentaram melhora na estabilidade catalítica.

Submitted by Kilvya Braga (kilvyabraga@hotmail.com) on 2018-04-20T11:49:44Z No. of bitstreams: 1 LILIANE ANDRADE LIMA - TESE (PPGEQ) 2015.pdf: 2336965 bytes, checksum: 3c30300b9a2863d952cc2c8242889a4f (MD5) / Made available in DSpace on 2018-04-20T11:49:44Z (GMT). No. of bitstreams: 1 LILIANE ANDRADE LIMA - TESE (PPGEQ) 2015.pdf: 2336965 bytes, checksum: 3c30300b9a2863d952cc2c8242889a4f (MD5) Previous issue date: 2015 / Este trabalho teve como objetivo sintetizar e caracterizar a peneira molecular mesoporosa MCM-41, utilizando diferentes fontes de sílica, e desenvolver catalisadores a base de cobalto e rutênio. As peneiras moleculares MCM-41 foram sintetizadas utilizando-se como fonte de sílica as cinzas de casca de arroz, cinzas de bagaço de cana-de-açúcar, argila chocolate B e Sílica Aerosil 200 com a seguinte base molar: 1,0 CTMABr:4,0 SiO2:1 Na2O:200 H2O. As peneiras moleculares MCM41 obtidas foram calcinadas em mufla a 600 °C por 7 horas. A deposição dos metais (cobalto e rutênio) sobre o suporte MCM-41 foi realizada por meio de impregnação úmida e depois calcinada. As amostras obtidas foram caracterizadas pelas técnicas de Espectroscopia de Fluorescência e Raios X por Energia Dispersiva (FRX-ED), Difração de raios X (DRX), Adsorção Física de Nitrogênio, Microscopia Eletrônica de Varredura (MEV) e Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR). Os resultados mostraram ser possível obter a peneira molecular MCM-41 com diferentes fontes de sílica, pelas micrografias observa-se que os materiais apresentam morfologias similares, constituídas por aglomerados com forma esponjosa. Os difratogramas dos catalisadores mostraram que após a impregnação dos metais e calcinação, não ocorreram modificações na estrutura hexagonal. A partir dos resultados de Adsorção Física de N2, observou-se isotermas de adsorção do tipo IV, típico de materiais mesoporosos e altos valores de área superficial. Os catalisadores apresentaram composições de metais nas proporções pré-definidas e após impregnação do rutênio obteve melhor dispersão dos metais sobre a peneira molecular. Os espectros apresentaram bandas na região de 500 - 4000 cm-1, características das vibrações fundamentais dos grupos funcionais específicos presentes na estrutura da peneira molecular MCM-41 e bandas referentes a estrutura do óxido de cobalto (Co3O4). / This study aimed to synthesize and characterize the molecular sieve mesoporous MCM-41, using different sources of silica, and develop cobalt-based catalysts and ruthenium. The MCM-41 molecular sieves were synthesized using as silica source the rice husk ash, ash from sugarcane bagasse, clay chocolate B and silica Aerosil 200 with the following molar basis: 1.0 CTMABr: 4.0 SiO2: 1 Na2O: 200 H2O. The MCM-41 molecular sieves were obtained calcined in a muffle at 600 ° C for 7 hours. The deposition of metals (cobalt and ruthenium) on the supporting MCM-41 was performed by wet impregnation and then calcined. The samples obtained were characterized by spectroscopy techniques Fluorescence and X-rays by Energy Dispersive (FRX-ED), X-ray diffraction (XRD), Adsorption Nitrogen Physics, Scanning Electron Microscopy (SEM) and Fourier transform infrared spectroscopic (FTIR). The results proved possible to obtain MCM-41 molecular sieve having different silica sources, the micrographs it is noted that the materials have similar morphology, consisting of spongy form agglomerates. The XRD patterns of the catalysts showed that after impregnation and calcination of the metal, there were no changes in the hexagonal structure. From the results of Physical Adsorption of N2 was observed adsorption isotherms of type IV, typical of mesoporous materials and high surface area values. The metal catalyst compositions presented in predefined proportions and after impregnation of the obtained ruthenium better dispersion of metals on the molecular sieve. The spectra showed bands in the region of 500 - 4000 cm-1, characteristic of the fundamental vibrations of the specific functional groups present in the structure of the molecular sieve MCM-41 and bands related to the structure of the cobalt oxide (Co3O4).

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-20T21:00:39Z No. of bitstreams: 1 AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-21T20:23:04Z (GMT) No. of bitstreams: 1 AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) / Made available in DSpace on 2016-01-21T20:23:04Z (GMT). No. of bitstreams: 1 AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) Previous issue date: 2014-09-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Diversos materiais est?o atualmente em estudo para o processo de captura de CO2, a exemplo dos ?xidos met?licos e ?xidos met?licos mistos, ze?litas, materiais carbon?ceos, estruturas metal-org?nicas (MOF?s), organos?lica e superf?cies de s?lica modificadas. Neste trabalho, analisou-se a capacidade de adsor??o de CO2 em materiais mesoporosos de diferentes estruturas, como o MCM-48 e SBA-15, sem impregna??o e impregnados com n?quel nas propor??es 5 %, 10 % e 20 % (m/m), denominados como 5Ni-MCM-48, 10NiMCM-48, 20Ni-MCM-48 e 5Ni-SBA-15, 10Ni-SBA-15, 20Ni-SBA-15. Os materiais foram caracterizados atrav?s das an?lises de difra??o de raios X (DRX), an?lise t?rmica (TG e DTG), espectroscopia na regi?o do infravermelho com transformada de Fourier (FT-IR), adsor??o e dessor??o de N2 (BET) e microscopia eletr?nica de varredura (MEV) com EDS. O processo de adsor??o foi realizado variando-se a press?o de 100 - 4000 kPa e mantendo-se a temperatura constante e igual a 298 K. Na press?o de 100 kPa, as maiores concentra??es de adsor??o ocorreram para os materiais 5Ni-MCM-48 (0,795 mmol g-1 ) e SBA-15 (0,914 mmol g -1 ) n?o impregnado, e, na press?o de 4000 kPa, para os materiais MCM-48 (14,89 mmol g-1 ) e SBA-15 (9,97 mmol g-1 ) n?o impregnados. Os resultados mostraram que a capacidade de adsor??o varia positivamente com a ?rea espec?fica, no entanto, apresenta uma depend?ncia direta com o tipo e geometria dos canais da estrutura porosa. Os dados obtidos foram ajustados atrav?s dos modelos de Langmuir e Freundlich e os par?metros termodin?micos avaliados foram energia livre de Gibbs e entropia do sistema de adsor??o / Several materials are currently under study for the CO2 capture process, like the metal oxides and mixed metal oxides, zeolites, carbonaceous materials, metal-organic frameworks (MOF's) organosilica and modified silica surfaces. In this work, evaluated the adsorption capacity of CO2 in mesoporous materials of different structures, such as MCM-48 and SBA- 15 without impregnating and impregnated with nickel in the proportions 5 %, 10 % and 20 % (m/m), known as 5Ni-MCM-48, 10Ni-MCM-48, 20Ni-MCM-48 and 5Ni-SBA-15, 10NiSBA-15, 20Ni-SBA-15. The materials were characterized by means of X-ray diffraction (XRD), thermal analysis (TG and DTG), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption and desorption (BET) and scanning electron microscopy (SEM) with EDS. The adsorption process was performed varying the pressure of 100 - 4000 kPa and keeping the temperature constant and equal to 298 K. At a pressure of 100 kPa, higher concentrations of adsorption occurred for the materials 5Ni-MCM-48 (0.795 mmol g-1 ) and SBA-15 (0.914 mmol g-1 ) is not impregnated, and at a pressure of 4000 kPa for MCM-48 materials (14.89 mmol g-1) and SBA-15 (9.97 mmol g-1) not impregnated. The results showed that the adsorption capacity varies positively with the specific area, however, has a direct dependency on the type and geometry of the porous structure of channels. The data were fitted using the Langmuir and Freundlich models and were evaluated thermodynamic parameters Gibbs free energy and entropy of the adsorption system