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Made available in DSpace on 2014-06-12T18:02:35Z (GMT). No. of bitstreams: 2 arquivo164_1.pdf: 3053526 bytes, checksum: 2e5eafdf454df7889e3e5ba1c87ceb2a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A corrosão por ácidos naftênicos a altas temperaturas nas unidades de refino é um dos maiores problemas nas refinarias de todo o mundo, uma vez que, podem causar envenenamento de catalisadores e paradas operacionais de alto custo. Os ácidos naftênicos correspondem a uma mistura complexa de ácidos carboxílicos presentes no petróleo, responsáveis diretamente pela sua acidez e corrosividade. Tais compostos também estão presentes nas frações destiladas do petróleo, causando diversos problemas na qualidade final do produto. Dentre estas frações do petróleo pode-se destacar o querosene de aviação (QAV) que é produzido através do fracionamento por destilação à pressão atmosférica. Os óleos nacionais estão cada vez mais ácidos, estimulando a busca por novos e eficientes métodos de mitigação. Métodos propostos por estudos científicos e industriais para minimizar a corrosão provocada por ácidos naftênicos vêm apresentando custos elevados e problemas de operação. O processo de adsorção tem a vantagem da possibilidade de recuperação dos ácidos orgânicos, que são precursores de surfactantes e aditivos para lubrificantes, não havendo formação de resíduos poluentes e contribuindo com o meio ambiente. As peneiras moleculares mesoporosas (MCM-41) vêm despertando grande interesse na comunidade científica em função da perspectiva da sua aplicação em processos de adsorção e catálise. A fim de reduzir o alto custo dos processos de separação por adsorção, principalmente devido ao elevado valor de alguns adsorventes, a utilização de resíduos agroindustriais como adsorventes vem se destacando como método alternativo. O objetivo deste trabalho foi a remoção da acidez naftênica de uma mistura modelo de QAV (ácido dodecanóico em ndodecano) com uso do adsorvente Sr-MCM-41 e de adsorvente preparado a partir de resíduo agroindustrial. No presente trabalho foi sintetizada a peneira molecular mesoporosa Sr-MCM- 41, na qual a incorporação do estrôncio resultou no aumento da basicidade do material e consequentemente da sua afinidade pelos ácidos. O adsorvente Sr-MCM-41 foi caracterizado por análise termogravimétrica (TG) e termogravimétrica diferencial (DTG), difração de raios- X (DRX), medida de área superficial por adsorção de N2 (BET), espectrometria de emissão óptica com plasma indutivamente acoplado (ICP-OES) e espectroscopia na região do infravermelho com transformada de Fourier (FT-IR). Os resultados da caracterização deste material indicaram que a incorporação do estrôncio não comprometeu a estrutura mesoporosa e que os materiais sintetizados apresentaram um bom grau de organização. Foi utilizada a técnica de planejamento fatorial para otimização do processo adsortivo visando a determinação das melhores condições de operação. Em seguida foram realizados estudos de cinética e equilíbrio de adsorção com o adsorvente Sr-MCM-41, obtendo-se como capacidade máxima adsortiva 2,0 gácido.g-1 adsorvente, a partir do estudo de equilíbrio de adsorção. Os dados de equilíbrio foram ajustados a isoterma de BET tipo IV. A cinética de adsorção foi modelada considerando-se um modelo de força motriz linear. Também foi preparado o carvão ativado a partir da casca da laranja, o qual foi caracterizado através da medida de área superficial por adsorção de N2 (BET) apresentando isoterma do tipo I, característica de materiais microporosos e foram realizados testes para avaliação de sua capacidade adsortiva que foi em torno de 0,40 gácido.g-1 adsorvente. O estudo de adsorção utilizando a Sr-MCM-41 apresentou significativa eficiência, uma vez que o adsorvente apresentou uma alta capacidade adsortiva. Para o adsorvente carvão ativado preparado a partir da casca da laranja constatou-se a potencialidade de sua aplicação por ser um resíduo agroindustrial, porém, verificou-se a necessidade de um estudo mais detalhado

The recently discovered mesoporous molecular sieve MCM-41 was synthesized, modified, and characterized and proposed as an alternative adsorbent for VOC control. The synthesis conditions for pure-silica and aluminosilicate MCM-41 were optimized as follows: 4.5Na2O:30SiO2:5.2C16H33(CH3)3N + :2500H2O and 7.5Na2O:30SiO2:xAl2O3:7.2C16H33(CH3)3N + :3500H2O (x < 1), respectively, and at 373 K for 4 days. Our studies showed that MCM-41 is not stable in the presence of water vapor. For example, a hydrothermal treatment of MCM-41 at 723 K for 2 hour resulted in 50 % of structure collapses. Again, when a template-free MCM-41 sample was exposed to air with a relative humidity of 60 % for three months, almost total pore structure collapses were observed. Adsorption equilibrium results showed that MCM-41 has a narrow pore size distribution and exhibits extraordinary pore volume compared to the classical microporous adsorbents, such as molecular sieves and activated carbons. Despite the impressive adsorption capacities of this material, the Type IV isotherm behavior requires the VOCs, in the gas phase, to be at high partial pressure. This is not the case with most industrial VOC streams. A real VOC stream requires an adsorbent with not only a high adsorption capacity but also a high adsorption affinity at a low VOC concentration. To overcome the above mentioned two problems, both the surface chemistry and the pore-opening sizes of MCM-41 were modified. To modify the surface chemistry, one has to better understand the surface chemistry. Our pioneering study of the surface chemistry of MCM-41 using FTIR, 29 Si CP/MAS NMR, pyridine-TPD, and TGA demonstrated that three types of silanol groups, i.e. single, (SiO)3Si-OH, hydrogen-bonded, (SiO)3Si-OH---OH-Si(SiO)3 and geminal, (SiO)2Si(OH)2 are distributed over the surface of MCM-41. The number of silanol groups per unit nm 2 , aOH, varies between 2.5 and 3.0 depending on the template-removal method. To improve the hydrothermal stability and enhance the hydrophobicity, the surface chemistry of MCM-41 was modified by silylation. Though both the free and hydrogen-bonded SiOH groups were found to be the active sites for adsorption of pyridine with desorption energies of 91.4 and 52.2 kJ mol -1 , respectively, only the free SiOH groups are highly accessible to the silylating agent, chlorotrimethylsilane. The surface coverage of the modifying agent was found to has a linear relationship with the surface free silanol groups which can be controlled by different heating temperatures. Modification by silyaltion can significantly improve hydrophobicity and stability. Rehydration/dehydration experiments demonstrate that the surface-silylated MCM-41 is highly tolerable to water vapor due to the complete replacement of surface-hydrophilic silanols. A novel modification method, namely selective tailoring (ST), was developed to tailor the pore-opening sizes of MCM-41 (rather than the entire pores). The novelty is that only the pore mouths at both ends of a cylindrical pore of MCM-41 was modified by deposition of some alkoxides. By doing so, the types of adsorption isotherms of VOCs can be changed from Type IV to Type I while the pore volume can be significantly preserved. This is of course significance in VOC removal since the adsorption affinity has been drastically enhanced. Adsorption equilibria and kinetics for VOCs in the pore-opening-modified MCM-41 materials were measured, modeled and compared to that of activated carbons and hydrophobic molecular sieves. The pore-modified MCM-41 has a much higher adsorption capacity than that of the traditional microporous adsorbents such as activated carbons and molecular sieves. The adsorption equilibrium data fit the Langmuir-Uniform distribution (Unilan) models very well. Upon the equilibrium parameters being obtained and considering the pore structure of our pore-modified MCM-41 adsorbents, the kinetic data were further modeled using the literature-existed models recently developed by Do and coworkers, i.e. the constant surface diffusivity macropore, surface and micropore diffusion (CMSMD) model and the macropore and surface diffusion (MSD) model. Results demonstrated that the CMSMD model can predict our kinetic uptake curves reasonably fine. Some key kinetic parameters including pore and surface diffusivities, apparent diffusivity, activation energy for adsorption, and pore tortuosity factor can be readily obtained. The porosity of the MCM-41 materials were primarily evaluated using the traditional methods based on nitrogen adsorption/desorption data. Results indicated that the BJH method always underestimates the true pore diameter of MCM-41. An comparison plot (t-plot or as-plot) method was suggested and improved. Plotting of nitrogen adsorption data at 77 K versus the statistical film thickness reveals three distinct stages, with a characteristic of two points of inflection. The steep intermediate stage is caused by capillary condensation occurred in the highly uniform mesopores. From the slope of the section after condensation, the external surface area can be obtained. Therefore, the true surface area of the mesopores is readily calculated. The linear portion of the last section is extrapolated to the adsorption axis of the comparison plot, and this intercept is used to obtain the volume of the mesopores. From the surface area and pore volume, average mesopore diameter is calculated, and the value thus obtained is in good agreement with the pore dimension obtained from powder X-ray diffraction measurements. The principle of pore size calculation, the thickness of adsorbed nitrogen film, and the problems associated with the BJH method were discussed in detail. It has been found that at a given relative pressure, the smaller the pore radius, the thicker the adsorbed film. Thermodynamics analysis established that the stability of the adsorbed film is determined by interface curvature and the potential of interaction between adsorbate and adsorbent. A semi-empirical equation is proposed to describe the state of stable adsorbed films in cylindrical mesopores. It is also shown to be useful in calculations of pore size distributions of mesoporous solids. The desorption of four representative volatile organic compounds (VOCs), i.e. n-hexane, cyclohexane, benzene, and methanol from MCM-41 were also investigated and compared with the hydrophobic zeolite, silicalite-1, using the technique of temperature programmed desorption (TPD). The desorption energies of these organics to MCM-41 were evaluated and compared with the adsorption isosteric heats. The affinity of organics to MCM-41 and silicalite-1, which represents surface hydrophobicity/hydrophilicity were studied and discussed. Results showed that only one desorption peak can be found for all organics from MCM-41, different from that from the microporous adsorbents (activated carbons and hydrophobic molecular sieves). The activation energies for desorption of non-polar molecules are slightly higher than their latent heats of evaporation, whereas the activation energy for desorption of methanol is well above its latent heat of evaporation. These results are consistent with those derived from the adsorption isotherm measurements. The very high activation energy for the desorption of methanol is due to the hydrogen bonds between methanol molecules and silanol groups over MCM-41 surfaces. The affinity of volatile organics to MCM-41 are in the order of methanol > n-hexane > benzene > cyclohexane.

La incorporación de titanio en la estructura de tamices moleculares ha dado lugar a la obtención de catalizadores altamente efectivos en procesos de oxidación selectiva. En particular, la síntesis de la zeolita de poro grande Ti-Beta y del material mesoporoso Ti-MCM-41, ha permitido ampliar el campo de aplicación de estos materiales en procesos de Química Fina ya que el mayor diámetro de poro de estas estructuras permite la oxidación de sustratos muy voluminosos para los que la Ti-Siliclita-1, único material disponible hasta el momento, era prácticamente inactiva. En el presente trabajo se ha llevado a cabo un estudio sobre la actividad catalítica de la Ti-Beta y la Ti-MCM-41 para, a partir del mismo, diseñar los procedimientos de síntesis de estos tamices moleculares de poro grande y ultragrande más adecuados para la oxidación de diferentes sustratos orgánicos tales como olefinas, alcoholes y alcanos empleando peróxidos como oxidantes. Durante el estudio se ha puesto de manifiesto la influencia de parámetros concernientes tanto al propio catalizador (composición química, carácter hidrófilo/hidrófobo) como a la propia reacción química (estructura del sustrato, tipo de oxidante, naturaleza del disolvente, ...) sobre la actividad catalítica de la zeolita Ti-Beta. Por último, se estudió la aplicación de la Ti-Beta y la Ti-MCM-41 en procesos de oxidación con un claro interés comercial como son la epoxidación de ácidos y ésteres de ácidos grasos y la epoxidación de terpenos y donde se ha observado la viabilidad de estos catalizadores como alternativas reales a los catalizadores actuales que se emplean en estos procesos / Esteve Ciudad, P. (1998). Oxidación selectiva de hidrocarburos sobre tamices moleculares de poro grande conteniendo titanio [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/5763 / Palancia

ABSTRACT COMPARISON OF SORPTION CAPACITIES OF HYDROCARBONS ON DIFFERENT SAMPLES OF MCM-41 AYDOGDU, Birsu M. Sc., Department of Chemical Engineering Supervisor: Prof. Dr. Hayrettin Y&Uuml / CEL Co-Supervisor: Prof. Dr. G&uuml / rkan KARAKAS January 2013, 69 pages MCM-41(Mobil Composition Matter-41) is one of the three members of M41S family and has a highly ordered hexagonal honeycomb like structure with a narrow pore size distribution in mesopore range, high surface area, high pore volume and high thermal stability. These features make MCM-41 proper to use for adsorption, catalysis, ion exchange and separation processes. . In this study sorption capacities of C8 aromatics (o-, m-, p-xylene and ethylbenzene at 30 &deg / C, 50 &deg / C and 65 &deg / C) on a MCM-41 sample synthesized in our laboratory were determined gravimetrically by using a commercial automated electro balance system and compared with results obtained in a previous and similar MSc thesis study with a sample of different origin and characteristics / specifically low BET surface area (492 m2/g). MCM-41 sample was synthesized by hydrothermal synthesis method with cetyltrimethylammoniumbromide (CTAMBr as surfactant) and tetraethyl ortosilicate (TEOS as silica source) in basic conditions. This MCM-41 sample was calcined at 540 oC for 8 h and characterized by XRD, nitrogen adsorption at 77 K, TGA, TEM, SEM and SEM-EDX. According to XRD data, main characteristic peak for synthesized MCM-41 was obtained at 2&theta / =2.28&deg / . Three small reflection peaks can be seen at 2&theta / values of 2.59, 4.27&deg / and 4.5&deg / . XRD pattern of the MCM-41, indicated that the desired structure of MCM-41 was successfully synthesized. Surface area, pore volume and average pore diameter were obtained from the nitrogen adsorption data at 77 K as 1154 m2/g, 1.306 cm3/g and 2.75 nm respectively. TGA analysis showed that the 540 oC is proper for the calcination. SEM -EDX analysis gave an oxygen atomic concentration 66.40% and silicon atomic concentration 33.60%. These results showed that the chemical composition of the synthesize material was in almost pure SiO2 form. The adsorbed amount for all isomers at the same pressure decreased as the temperature of the adsorption isotherms increases as expected for physical adsorption. Nitrogen adsorption of MCM-41 in this study showed type IV isotherm with H2 type hysteresis loop according the IUPAC classification. However, for o-,m-, and p-xylene an approximately linear increase in the adsorbed amount as a function of relative pressure was observed from the adsorption isotherms. Except for adsorption isotherms of m-xylene and p-xylene at 65 oC all isotherms of xylenes showed hysteresis loops. Hysteresis loops narrowed down with increasing temperature. p-xylene and m-xylene adsorption isotherms at 65 oC were reversible and did not show any hysteresis loop. Ethylbenzene adsorption isotherms at 30 oC, 50 &deg / C and 65 oC also showed a linear increase in the adsorption amount as a function of relative pressure like xylenes. At 50 &deg / C and 65 oC adsorption isotherms of ethylbenzene were reversible without a hysteresis loop. For all adsorbates volume of adsorbed amounts were calculated on the assumption that they exist as saturated liquids at the isotherm temperature and found to be significantly lower than pore volume obtained from nitrogen adsorption isotherm at 77K. Sorption capacities of these hydrocarbons on MCM-41 were also very low when compared to values found in a previous study which involved a MCM-41 sample of significantly lower surface area ( 492 m2/g ). This may be attributed to structure degradation which requires further investigation.

The world&rsquo / s being alerted to the global warming danger and the depletion of fossil fuel resources, has increased the importance of the clean and renewable hydrogen energy. Bioethanol has high potential to be used as a resource of hydrogen since it is a non-petroleum feedstock and it is able to produce hydrogen rich mixture by steam reforming reactions. Discovery of mesoporous MCM-41 type high surface area silicate-structured materials with narrow pore size distributions (20-100 &Aring / ) and high surface areas (up to 1500 m2/g) opened a new avenue in catalysis research. Catalytic activity of such mesoporous materials are enhanced by the incorporation of active metals or metal oxides into their structure. Nickel and copper are among the most active metals to be used in steam reforming of ethanol to produce hydrogen. In this study, copper and nickel incorporated MCM-41 type catalytic materials were tested in the steam reforming of ethanol. Two Ni-MCM-41 samples having different Ni/Si ratios were prepared by high temperature direct synthesis method and two Cu-MCM-41 samples having same Cu/Si ratios were synthesized by two different methods namely, high temperature direct synthesis method and impregnation method. The synthesized materials characterized by XRD, EDS, SEM, N2 physisorption and TPR techniques. XRD results showed that Ni-MCM-41 and Cu-MCM-41 catalysts had typical MCM-41 structure. The d100 and lattice parameter values of Ni-HT (I) (Ni-MCM-41 sample having 0.036 Ni/Si atomic ratio) was obtained as 3.96 and 4.57 nm., respectively. In addition Ni-HT (I) was found to have a surface area of 860.5 m2/g and 2.7 nm pore diameter. The d100 and lattice parameter values for a typical Cu-MCM-41 prepared by impregnation method having Cu/Si atomic ratio of 0.19 were obtained as 3.6 and 4.2 nm., respectively. This sample also has a 631 m2/g surface area and 2.5 nm pore diameter. Steam reforming of ethanol was investigated in the vapor phase by using Ni-MCM-41 and Cu-MCM-41 catalysts between 300&deg / C and 550&deg / C. Results proved that Ni incorporated MCM-41 type catalytic materials were highly active in hydrogen production by steam reforming of ethanol and actualized almost complete ethanol conversion for Ni-MCM-41 having Ni/Si atomic ratio of 0.15 over 500&deg / C . The side products obtained during reforming are methane and formaldehyde. Although the Cu-MCM-41 samples were not as active as Ni-MCM-41, it was observed that Cu-MCM-41 catalyst synthesized by the impregnation method showed an ethanol conversion of 0.83. However, the main product was ethylene with the copper incorporated catalysts. Effects of space time, the operating conditions (reaction temperature), metal/Si ratio of the catalyst and the preparation method on the product distributions were also investigated and best reaction conditions were searched.

Noble metal incorporated MCM-41 based nanostructured mesoporous materials have attracted the attention of material researchers in recent years. Sorption characteristics of MCM materials can be improved by surface modification techniques. Besides surface modification, metal nanoparticles can also be produced within the pores of mesoporous materials. MCM-41 can act as host for several metal nanoparticles such as palladium. The present study is focused on the synthesis of Pd-MCM-41 nanocomposite catalytic materials by using different direct synthesis procedures, as well as an impregnation method. Impregnated samples were used to synthesize Pd nanoparticles inside the pores of MCM-41. In the direct hydrothermal synthesis of Pd-MCM-41, incorporation of the Pd metal was achieved by adding PdCl2, K2PdCl4 and Pd(NH3)4(NO2)3 solutions into the synthesis mixture. Syntheses were performed in acidic and basic routes. Hydrothermal synthesis was carried out in an autoclave at 120 oC. The solid product was filtered, washed, dried, calcined at 550 oC in a stream of dry air and reduced in a stream of hydrogen at 200 oC. In the case of impregnation, PdCl2 solution was added to a suspension of MCM-41. The product was evaporated to dryness, dried under vacuum and reduced with H2 gas at 200 oC. Physical and chemical properties and surface morphology of Pd-MCM-41 nanomaterials were characterized by using XRD, XPS, EDS, BET, SEM, TEM and TPR techniques. Very high Pd/Si ratios, as high as 0.45 and 0.18 were obtained in the mesoporous materials produced by the basic and acidic direct synthesis routes, respectively. The BET surface areas of these materials were found as 999 m2/g and 694 m2/g, respectively. These results showed that the basic direct synthesis procedure was highly successful for the incorporation of Pd into the mesoporous Si structure. In addition, EDS analysis of the Pd-MCM-41 materials prepared by the impregnation technique showed that Pd/Si ratios were 0.24 and 0.12 in the two samples having surface areas of 527 m2/g and 883 m2/g, respectively. In conclusion, high surface area of the material synthesized by the basic route together with a higher Pd/Si ratio makes this material more attractive for catalytic and hydrogen storage applications.

Made available in DSpace on 2016-06-02T19:56:53Z (GMT). No. of bitstreams: 1 Retido.pdf: 19733 bytes, checksum: 6aad255badc436a06364517de2344ab6 (MD5) Previous issue date: 2014-02-20 / Universidade Federal de Sao Carlos / The masters work presented is result of a great effort provided by the group, which has worked with changes in the synthesis of CTA-MCM-41. The synthesis of the M41S family (composed of mesoporous silica MCM-41, MCM-48 and MCM-50) was developed by Mobil Oil Corporation in 1992 due to necessity to processing of molecules larger than 0.75 nm, which is the pore diameter of zeolite Y. Among the silica, the most studied is the MCM-41. When the MCM-41 containing cations CTA in your pores, has catalytic sites with basic character because of the presence of anions siloxy (&#8801;SiO-) associated. In evaluating the basic character of the CTA-MCM-41 in transesterification reactions of monoesters, we obtained satisfactory conversions, but when catalyst was reused, there was loss of catalytic activity due to leaching of cations CTA. With the objective of providing more stability in catalytic transesterification reactions of monoester, have changed the routes of synthesis through the use of monomers like acrylate, methacrylate esters and styrene. For this particular research, arises the innovative proposal to replace the CTABr surfactant (Cetyltrimethylammonium bromide) used in the synthesis of mesoporous silica by the surfactant synthesized, CADMABr (Cetylallyldimethylammonium bromide), which differs from CTABr by the substitution of a methyl group of the hydrophilic head group by the polymerizable allyl group. To check the formation of the surfactant and the degree of polymerization solution was held elementary chemical analysis (CHN) and nuclear magnetic resonance of 13C (NMR 13C), it was done also the small angles X-ray scattering (SAXS) of dispersions of different concentrations of CTABr and CADMABr to compared the micellar behavior. For characterization of the catalysts synthesized with this new polymerizable surfactant (Surfmer) was held X-ray diffraction for phase identification characteristic of silica, electron microscopy and thermogravimetry. The results were promising, although the catalytic stability was not achieved in significant way yet. However, the study conducted opens up a range of possibilities for continuation of this theme, as the replacement CTABr by CADMABr makes possible the polymerization without inserting of monomers inside the micelles. / O trabalho de mestrado apresentado é resultado de um grande esforço proporcionado pelo grupo, que tem trabalhado com modificações na síntese da CTA-MCM-41. A síntese da família M41S (composta pelas sílicas mesoporosas MCM-41, MCM-48 e MCM-50) foi divulgada pela Mobil Oil Corporation em 1992 devido à necessidade de processamento de moléculas maiores que 0,75 nm, que é o diâmetro dos poros da zeólita Y. Entre as sílicas, a mais estudada é a MCM-41. Quando a MCM-41 contém cátions CTA em seus poros, possui sítios catalíticos com caráter básico devido à presença dos ânions siloxi (&#8801;SiO-) associados. Ao avaliar o caráter básico da CTA-MCM-41 em reações de transesterificação de monoésteres, obteve-se conversões satisfatórias, porém à medida que o catalisador foi reutilizado houve perda de atividade catalítica devido à lixiviação dos cátions de CTA. Com o objetivo de proporcionar maior estabilidade catalítica nas reações de transesterificação de monoéster, modificaram-se as rotas de síntese por meio da utilização de monômeros do tipo ésteres acrilatos, metacrilatos e estireno. Para esta pesquisa em particular, surge à proposta inovadora de substituir o surfactante CTABr (Brometo de Cetiltrimetilamônio) utilizado na síntese das sílicas mesoporosas pelo surfactante sintetizado, CADMABr (Brometo de Cetilalildimetilamônio), que se distingue do CTABr pela substituição de um grupo metil da cabeça hidrofílica por um grupo alila polimerizável. Para comprovar a formação do surfactante e seu conversão da polimerização em solução, realizou-se análise química elementar (CHN) e ressonância magnética nuclear de 13C (RMN 13C), realizou-se também espalhamento de raios X a ângulos pequenos (SAXS) de dispersões coloidais com diferentes concentrações de CTABr e CADMABr para comparação do comportamento micelar. Para caracterização dos catalisadores sintetizados com esse novo surfactante polimerizável ( Surfmer ) efetuou-se difratometria de raios X para identificação da fase característica das sílicas, microscopia eletrônica de varredura e termogravimetria. Os resultados mostraram-se promissores, embora a estabilidade catalítica ainda não tenha sido alcançada de modo significativo. No entanto, a pesquisa desenvolvida abre um leque de possibilidades para continuação desse tema, pois a substituição do CTABr pelo CADMABr torna possível a polimerização sem a inserção de monômeros no interior das micelas.

Made available in DSpace on 2015-05-14T13:21:44Z (GMT). No. of bitstreams: 1 parte1.pdf: 1266396 bytes, checksum: a4c7a57bd0fd6230873b3e69c5c52c4f (MD5) Previous issue date: 2010-12-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Molecular sieves have been applied to the processing of triacylglycerols, to produce biofuels. In this context, the mesoporous catalyst Al-MCM-41 was proposed in this work as an alternative to acid heterogeneous transesterification of cottonseed oil with ethanol. This material was prepared using various Si/Al molar ratios (25, 50, 75 and 100) with reaction times of 8, 10, 12 or 14 hours at 170°C. The solids were characterized by XRD, FTIR, 29 Si and 27Al MAS NMR, TG/DTA and nitrogen adsorption, which confirmed the mesoporous phase and allowed an estimate of the acidity associated whit the increase of aluminum content in the structure of MCM-41. The catalytic runs were carried out in a PAAR 4843 reactor, with an oil:ethanol molar ratio of 1:9 and catalyst loading of 1,5% at 200°C for 0-180 min; the reaction product was characterized by gas chromatography and 1H and 13C NMR. Gas chromatographic analysis, shoed that the conversion to ethyl esters is linearly dependent on catalyst loading, and Al-MCM-41 (Si/Al=50) was the most active material under the conditions tested. The results of GC-FID and 1H NMR analysis were corroborated by thermal analysis (TGA) and FTIR measurements, which were used to evaluate the Brønsted acidity of the materials. Overall, the yeld of the fatty acid ethyl ester (FAEE) transesterification increased with an increase in catalyst acidity. / Peneiras moleculares têm sido aplicadas para o processamento de triacilgliceróis, visando à produção de biocombustíveis. Nesse contexto, no presente trabalho, o catalisador mesoporoso Al-MCM-41 foi proposto como uma alternativa para a transesterificação ácida heterogênea do óleo de algodão com etanol. Esse material foi preparado variando a razão molar Si/Al (25, 50, 75 e 100) nos tempos de 8, 10, 12 e 14 horas sob temperatura de 170°C. Os sólidos obtidos foram caracterizados por DRX, FTIR, RMN MAS 29Si e 27Al, TG/DTA e área superficial por adsorção de nitrogênio, de modo que se pôde confirmar a fase mesoporosa e estimar a acidez gerada do incremento de alumínio na estrutura do MCM-41. O teste catalítico foi realizado num reator PAAR 4843, com razão molar óleo:etanol de 1:9, 1,5% de catalisador, a 200°C nos tempos de 0-180 min., sendo o produto obtido caracterizado por cromatografia gasosa e RMN 1H e 13C. Através da análise cromatográfica pôde-se verificar que os catalisadores apresentaram perfis lineares de conversão em etil ésteres, sendo o Al-MCM-41 (Si/Al=50) o material mais ativo nas condições utilizadas. Os resultados observados por CG-FID e RMN 1H, foram corroborados pela análise térmica (TG) e FTIR previstos para a geração de acidez de Bronsted, mostrando que o rendimento em FAEE da reação de transesterificação etílica aumenta com o incremento da acidez nos catalisadores.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Climatic changes, largely induced by the use of fossil fuels and the concern with the sustainable development, has become renewable sources of energy extremely important. Nowadays, renewable sources of energy can be obtained, among several available processes, starting from transesterification, esterification and pyrolysis reaction. The esterification reaction can be carried out with homogeneous and heterogeneous catalysts, being them acids or basic. The use of heterogeneous acid catalysis it is preferable when intend to reduce significantly thr number separation and purifications stages the products, as well as, the possibility of reuse of the catalyst. In this context, researches have been developed using heterogeneous catalysts with the aim to study the biofuels obtaining. The aim os this work was to develop sulphated mesoporosos catalysts and it application in the biofuels production. The sample of MCM-41 was synthesized by the hydrothermal method, and it sample was submeted to sulphatation aiming obtain acid catalysts with different sulfphate concentrations. The catalysts were characterized by X-ray diffraction and infrared spectrocopy. The catalytic activity of the materials was evaluated in a batch reactor through the model reaction of oleic acid esterification. Through the X-ray diffaction results was observed that MCM-41 was obtained with success, because it presented the characteristic picks of the mesopouros structure mesoporosa. Infrared spectroscipy showed that calcination method carried out sucefuly with the elimination of the organic template, and, they were observed the main vibrational bands regarding the sulphate linked on the MCM-41 structure. The results obtained from the catalytic activity, in the esterification reactions were promising, because all the catalysts samples presented catalytic activity for the reaction at several temperatures. Levels of conversion of the sulphated MCM-41 were observed near to the of the reference catalysts, the sulphated zirconia and niobia. / As mudanças climáticas, induzidas em grande parte pelo uso de combustíveis fósseis e a preocupação com o desenvolvimento sustentável, tem tornado as fontes renováveis de energia extremamente importantes. Nos dias atuais, fontes renováveis de energia podem ser obtidas, dentre vários processos disponíveis, a partir de reações de transesterificação, esterificação ou pirólise. A reação de esterificação pode ser conduzida tanto com catalisadores homogêneos quanto heterogêneos, sendo eles ácidos ou básicos. O emprego da catálise ácida heterogênea é preferível quando se pretende reduzir significativamente o numero de etapas de purificação dos produtos, bem como a possibilidade de reuso do catalisador. Neste contexto, pesquisas têm sido desenvolvidas utilizando catalisadores heterogêneos com o objetivo de estudar a obtenção de biocombustíveis. Este trabalho teve como finalidade desenvolver catalisadores mesoporosos sulfatados para a aplicação na produção de biodiesel via catálise ácida. A amostra de MCM-41 foi sintetizada pelo método hidrotérmico e foi submetida à sulfatação, de modo a se obter catalisadores ácidos com diferentes teores de sulfato no MCM-41. Os catalisadores foram caracterizados por difração de raios-X e espectroscopia na região do infravermelho. A atividade catalítica dos materiais foi medida em reator de batelada, através da reação modelo de esterificação etílica de acido oléico. Através dos resultados de difração de raios-X, foi observado que o MCM-41 foi obtido com sucesso, pois apresentou os picos característicos da estrutura mesoporosa. As análises de espectroscopia na região do infravermelho mostraram também que o método de calcinação foi promissor na eliminação do direcionador orgânico, tendo sido também observadas as principais bandas vibracionais referentes ao sulfato, ligado na estrutura do MCM-41. Os resultado obtidos em relação à atividade catalítica na reação de esterificação foram promissores, visto que todas as amostras obtidas apresentaram atividade catalítica para a reação de esterificação, a várias temperaturas. Foram observados níveis de conversão do MCM-41 sulfatados, próximos aos dos catalisadores de referência, à base de zircônia e nióbia sulfatados.