Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2018-04-04T13:50:36Z No. of bitstreams: 1 2017 - Guilherme Raymundo Sa.pdf: 3173899 bytes, checksum: 9c3276f740106907243c1c187bbc9d77 (MD5) / Made available in DSpace on 2018-04-04T13:50:36Z (GMT). No. of bitstreams: 1 2017 - Guilherme Raymundo Sa.pdf: 3173899 bytes, checksum: 9c3276f740106907243c1c187bbc9d77 (MD5) Previous issue date: 2017-08-28 / Zeolites are microporous aluminosilicates and have assumed the position of most important catalysts in the chemical industry. However, these microporous materials have the limitation of the diffusion of molecules with larger kinetic diameter. Hybrid materials with hierarchical arrangement of pores in the micro-mesoporous scale have attracted great attention and interest in the last decades because they present acidic activity similar to the microporous zeolites and ordered pore diameter of the mesoporous materials. Beta zeolite can be used in a number of applications, including refining, petrochemical and biomass. The generation of mesopores in the beta zeolite enables higher yields by improving mass transfer in the FCC process. In this work, samples of the mesoporous material SBA-15 were synthesized and used as a source of silica for the synthesis of the mesoporous beta zeolite using the Dry Gel Conversion (DGC) technique. Samples of SBA-15 were submitted to three carbonization methods, using as carbon source sucrose, the organic template and both, in order to fill their pores with carbonaceous material and to prevent the collapse of its structure. The aluminization samples were studied at two times, before and during the dry gel synthesis. Three crystallization times were studied. X-ray diffraction (XRD), N2 adsorption / desorption, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and infrared absorption spectroscopy with Fourier transform (FTIR) were used to characterize the samples. The results indicated that there was formation of zeolite beta presenting mesoporosity for the carbonization method that used only the template as carbon source. These samples showed BEA crystalline structure confirmed by XRD and FTIR analysis and formation of isotherms with type I and IV characteristics, with BET area greater than 500 m? / g, a volume of micropores close to 0.20 cm3 / g and with a volume of mesopores greater than 0.15 cm 3 / g. The other carbonization methods formed an amorphous phase, materials with low crystallinity and formation of polymorphs B and C over polymorph A. The samples presented the formation of mesoporosity did not present the mesopores present in the SBA-15, indicating collapse of the structure during the process of dry gel conversion / Ze?litas s?o aluminossilicatos microporosos e assumiram a posi??o de catalisadores mais importantes na ind?stria qu?mica. Entretanto, esses materiais microporosos possuem a limita??o da difus?o de mol?culas com di?metro cin?tico maior. Os materiais h?bridos com arranjo hier?rquico de poros na escala micro-mesoporosa atra?ram grande aten??o e interesses nas ?ltimas d?cadas pois apresentam atividade ?cida similar ?s ze?litas microporosas e di?metro de poros ordenados dos materiais mesoporosos. A ze?lita Beta pode ser usada em diversas aplica??es, incluindo o refino, a petroqu?mica e o processamento de biomassa. A gera??o de mesoporos na ze?lita beta possibilita maior rendimento melhorando a transfer?ncia de massa no processo de FCC. Neste trabalho foram sintetizadas amostras do material mesoporoso SBA-15 e utilizadas como fonte de s?lica para a s?ntese da ze?lita beta mesoporosa em meio seco utilizando a t?cnica de Dry Gel Conversion (DGC). As amostras de SBA-15 foram submetidas a tr?s m?todos de carboniza??o, utilizando como fonte de carbono sacarose, o direcionador de estrutura e ambos, com o objetivo de preencher seus poros com material carbon?ceo e evitar o colapso de sua estrutura. A aluminiza??o das amostras foi estudada em dois momentos, antes e durante a s?ntese do gel seco. Foram estudados tr?s tempos de cristaliza??o. Para caracteriza??o das amostras foram utilizadas as t?cnicas de difra??o de raios-X (DRX), adsor??o/dessor??o de N2, resson?ncia magn?tica nuclear (RMN), microscopia eletr?nica de varredura (MEV) e espectroscopia de absor??o no infra vermelho com transformada de Fourier (FTIR). Os resultados indicaram que houve a forma??o de ze?lita beta apresentando mesoporosidade para o m?todo de carboniza??o que utilizou apenas o direcionador de estrutura como fonte de carbono. Estas amostras apresentaram estrutura cristalina BEA confirmado pelas an?lises de DRX e FTIR e forma??o de isotermas com caracter?sticas do tipo I e IV, com ?rea BET superior a 500m?/g, um volume de microporos pr?ximos de 0,20 cm3/g e com um volume de mesoporos superior a 0,15 cm3/g. Os demais m?todos de carboniza??o formaram uma fase amorfa, materiais de baixa cristalinidade e com forma??o dos polimorfos B e C em detrimento ao polimorfo A. Os melhores resultados foram obtidos com o tempo de cristaliza??o de 48 horas. As amostras apresentando a forma??o de mesoporosidade n?o apresentaram os mes n?o apresentaram os mes n?o apresentaram os mesn?o apresentaram os mes n?o apresentaram os mesn?o apresentaram os mes n?o apresentaram os mes n?o apresentaram os mesn?o apresentaram os mes n?o apresentaram os mes n?o apresentaram os mes oporos presentes na SBA oporos presentes na SBA oporos presentes na SBA oporos presentes na SBA oporos presentes na SBA oporos presentes na SBA oporos presentes na SBAoporos presentes na SBAoporos presentes na SBAoporos presentes na SBA-15, indicando colapso da 15, indicando colapso da 15, indicando colapso da 15, indicando colapso da 15, indicando colapso da 15, indicando colapso da 15, indicando colapso da 15, indicando colapso da 15, indicando colapso da estrutura estrutura estrutura durante o processo de s?ntese seca

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-12T14:38:14Z No. of bitstreams: 1 RUCILANA PATRÍCIA BEZERRA CABRAL - TESE (PPGEP) 2008.pdf: 6571244 bytes, checksum: d2b524bd924cc294214a4507138e3b56 (MD5) / Made available in DSpace on 2018-09-12T14:38:14Z (GMT). No. of bitstreams: 1 RUCILANA PATRÍCIA BEZERRA CABRAL - TESE (PPGEP) 2008.pdf: 6571244 bytes, checksum: d2b524bd924cc294214a4507138e3b56 (MD5) Previous issue date: 2008-07-06 / Devido ao aumento na produção de óleo pesado, a indústria do refino voltou-se para os processos de hidrocraqueamento (HCC) que fornecem combustíveis básicos e leves atendendo as exigências da sociedade moderna. O processo HCC é realizado, geralmente, sob temperaturas e pressões elevadas na presença do hidrogênio e de um catalisador de hidrocraqueamento. As cargas de petróleo brasileiras inevitavelmente contêm muitas impurezas, como os compostos orgânicos nitrogenados. Estes compostos de nitrogênio presentes nas cargas de hidrocraqueamento atuam como venenos temporários dos catalisadores, resultando numa diminuição de atividade destes catalisadores. Normalmente, os catalisadores de HCC compreendem de um suporte ácido mais um componente hidrogenante selecionado do Grupo VIB e do grupo VIII da Tabela periódica dos Elementos, na forma de óxido ou sulfeto. Zeólita Beta e SAPO-5 foram propostos para serem usados como suportes ácidos. A respeito do componente hidrogenante, a combinação de metais usados, expressada como óxidos, foi NiO-MoO3. Uma série de catalisadores NiMo suportados em Zeólita Beta e SAPO-5, de diferentes composições, foram preparados por impregnação seqüencial úmida dos materiais utilizando soluções aquosas precursoras de Ni(NO3)2.6H2O e (NH4)6 Mo7O24. 4H2O. Os suportes e catalisadores foram analisados pelas técnicas: Difração de raios-X (DRX), Espectrometria de Emissão Atômica de Plasma Acoplado Induzido (ICPAES), Adsorção Física de N2 pelo método BET, Redução com Temperatura Programada (RTP), Microscopia Eletrônica de Transmissão (MET), Espectroscopia no Infravermelho de piridina adsorvida (IV), Espectroscopia de Refletância Difusa (DRS) e Espectroscopia de Ressonância Magnética Nuclear (RMN). Os catalisadores NiMo sulfetados foram avaliados usando um reator tubular de fluxo contínuo, no hidrocraqueamento do cumeno na presença e ausência de piridina. Foi verificado que os catalisadores suportados em zeólita Beta promoveram maiores conversões que os suportados em SAPO-5, principalmente o que usou zeólita Beta (Si/Al=8,2) com 4%NiO e 15%MoO3. A presença da piridina foi prejudicial à performance de todos os catalisadores, inclusive para os padrões cedidos pelo CENPES. / Due to the increasing of the heavier crude oil feedstocks production, the oil refining industry has turned to hydrocracking (HCK) processes to provide the lighter basic fuels which modern society demands. The HCK process is generally carried out under high temperatures and pressures in the presence of the hydrogen and a HCK catalyst. The feedstocks of the Brazilian crudes inevitably contain many impurities, such as organic nitrogen compounds. These nitrogen compounds present in the feeds of hydrocracking process act as, temporary poisons to the catalysts, thereby decreasing the catalyst activity. Usually, hydrocracking catalysts comprise of an acidic support plus a hydrogenating component selected from the Group VIB metals and Group VIII metals of the Periodic Table of the Elements, in their oxide or sulfide form. Beta zeolite and SAPO-5 are proposed as acidic support materials for hydrocracking. Regarding the hydrogenation component the combination of the metals used in the form of oxides, was NiO-MoO3. A series of NiMo catalysts supported on Beta zeolite and SAPO-5, of different compositions, were prepared by sequential incipient wetness impregnation of the materials with aqueous solutions of Ni(NO3)2 . 6H2O and (NH4)6 Mo7O24.4H2O. The supports and catalysts were analyzed by several techniques such as: X-ray diffraction (XRD), plasma-emission spectrometry (ICP-AES), N2 physical adsorption by BET method, temperature programmed reduction (TPR), transmission electronic microscopy (TEM), infrared spectroscopy of adsorbed pyridine (IR), diffuse reflectance spectroscopy (DRS) and nuclear magnetic resonance (NMR) spectroscopy. The sulfide NiMo catalysts were evaluated using a continuous-flow tubular reactor by the cumene hydrocracking in the presence and absence of pyridine. It was verified that the NiMo catalysts based on Beta zeolite produced the highest cumene conversion than those based on SAPO-5, particularly the one with Beta zeolite (Si/Al=8,2) containing 4%NiO and 15%MoO3. The presence of nitrogen as pyridine was detrimental for the performance of all catalysts, including the standards one, supplied for the CENPES.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Propylene is a chemical compound with high value added, widely used in the industry and usually obtained from petroleum. However, there is the need of the development of alternative routes for the production of this compound from renewable sources. The use of acetone for the production of propylene is a good option, because this oxygenated compound can be obtained by biomass conversion. The use of a one step process also adds an advantage to the propylene production from acetone, uniting in a single reactor two consecutive reactions: acetone hydrogenation, followed by dehydration of the formed isopropanol. For this, there are necessary two catalysts with distinct properties, one containing metallic sites, for hydrogenation, and another where there are acidic sites, for dehydration. The main objective of this work is to obtain propylene from acetone in one single step, using Cu/Zn/Al mixed oxide derived from hydrotalcite-like compounds and acid form of Beta zeolite as catalysts. For that, the catalysts were obtained by the coprecipitation method at variable pH followed by calcination, for the mixed oxide, and by hydrothermal synthesis, for the zeolite. The catalysts were also characterized as their with distinct properties. The hydrogenation and dehydration reactions have been studied individually and together by varying the catalyst or mixture of catalysts employed and the composition and flow rate of the feed. First, they were evaluated the thermodynamic boundaries of the reaction systems in which was observed that the acetone hydrogenation is strongly limited by the equilibrium and which are the preferential products of each reaction. For the reaction test, it was used the factorial experimental design, where the feeding conditions and reaction temperature were varied, and as response variables it was obtained the composition of the organic fraction at the reactor outlet. In the hydrogenation reaction, only isopropanol was obtained and the acetone conversion was close to that of equilibrium. In the dehydration reaction of isopropanol, propylene was preferably formed, with only small concentrations of diisopropyl ether at low temperatures, being obtained complete alcohol conversion in some experimental conditions. The complete process of acetone conversion into propylene was carried out at eleven distinct experimental conditions and the olefin fraction was up to 65 % of the organic fraction. It was possible the parameters estimation of simplified kinetic models, considering the Langmuir-Hinshelwood hypothesis, appropriate to the prediction of the molar fractions of the compounds in the organic fraction for both individual as simultaneous reactions. The kinetic models were used to the analysis of the effect of process variables on the reaction products in the three reaction systems considered. / O propeno é um composto químico de alto valor agregado, largamente empregado na indústria e obtido, geralmente, a partir do petróleo. Entretanto, há a necessidade do desenvolvimento de rotas alternativas para a produção deste composto a partir de fontes renováveis. A utilização de acetona para a produção de propeno é uma boa opção, pois este composto oxigenado pode ser obtido através de conversão da biomassa. A utilização de processo em uma única etapa acrescenta, ainda, mais uma vantagem à produção de propeno a partir de acetona, unindo em um único reator duas reações consecutivas: hidrogenação de acetona, seguida da desidratação do isopropanol formado. Para tanto, são necessários dois catalisadores com propriedades distintas, um deles contendo sítios metálicos, para a hidrogenação, e outro onde haja sítios ácidos, para a desidratação. O objetivo principal deste trabalho é a obtenção de propeno a partir de acetona em uma única etapa, utilizando óxido misto de Cu/Zn/Al derivado de material do tipo hidrotalcita e forma ácida da zeólita Beta como catalisadores. Para isso, os catalisadores foram obtidos pelo método de coprecipitação a pH variável seguido de calcinação, para o óxido misto, e pela síntese hidrotérmica, para a zeólita. Os catalisadores foram, ainda, caracterizados quanto às suas propriedades físicoquímicas. As reações de hidrogenação e desidratação foram estudadas individualmente e em conjunto variando-se o catalisador ou mistura de catalisadores empregados e a composição e vazão da alimentação. Primeiramente, foram avaliados os limites termodinâmicos dos sistemas reacionais, em que se observou que a hidrogenação de acetona é fortemente limitada pelo equilíbrio e quais são os produtos preferenciais de cada reação. Para os testes reacionais foi utilizado planejamento de experimentos fatorial, onde as condições de alimentação e temperatura de reação foram variadas, e como variáveis resposta obteve-se a composição da fração orgânica na saída do reator. Na reação de hidrogenação, apenas isopropanol foi obtido e a conversão de acetona foi próxima daquela de equilíbrio. Na reação de desidratação de isopropanol, o propeno foi formado preferencialmente, com apenas pequenas concentrações de éter di-isopropílico a baixas temperaturas, sendo obtidas conversões completas do álcool em algumas condições experimentais. O processo completo de conversão de acetona em propeno foi realizado em onze condições experimentais distintas e a fração de olefina foi de até 65 % da fração orgânica. Foi possível a estimação dos parâmetros de modelos cinéticos simplificados, considerando as hipóteses de Langmuir-Hinshelwood, adequados à predição das frações molares dos compostos na fração orgânica tanto para as reações individuais como simultâneas. Os modelos cinéticos foram utilizados para a análise do efeito das variáveis de processo sobre os produtos de reação nos três sistemas reacionais considerados.

<p>Dimerization and oligomerization reactions of alkenes are promising catalytic strategies to convert light alkenes, which can be derived from light alkane hydrocarbons (ethane, propane, butane) abundant in shale gas resources, into heavier hydrocarbons used as chemical intermediates and transportation fuels. Nickel cations supported on aluminosilicate zeotypes (zeolites and molecular sieves) selectivity catalyze ethene dimerization over oligomerization given their mechanistic preference for chain termination over chain propagation, relative to other transition metals commonly used for alkene oligomerization and polymerization reactions. Ni-derived sites initiate dimerization catalytic cycles in the absence of external activators or co-catalysts, which are required for most homogeneous Ni complexes and Ni²⁺ cations on metal organic frameworks (MOFs) that operate according to the coordination-insertion mechanism, but are not required for homogeneous Ni complexes that operate according to the metallacycle mechanism. Efforts to probe the mechanistic details of ethene dimerization on Ni-containing zeotypes are further complicated by the presence of residual H⁺ sites that form a mixture of 1-butene and 2-butene isomers in parallel acid-catalyzed pathways, as expected for the coordination-insertion mechanism but not for the metallacycle mechanism. As a result, the mechanistic origins of alkene dimerization on Ni cations have been ascribed to both the coordination-insertion and metallacycle-based cycles. Further, different Ni site structures such as exchanged Ni²⁺, grafted Ni²⁺ and NiOH⁺ cations are proposed as precursors to the dimerization active sites, based on analysis of kinetic data measured in different kinetic regimes and corrupted by site deactivation, leading to unclear and contradictory proposals of the effect of Ni precursor site structures on dimerization catalysis.</p> <p> Dimerization of ethene (453 K) was studied on Ni cations exchanged within Beta zeotypes in the absence of externally supplied activators, by suppressing the catalytic contributions of residual H⁺ sites via selective pre-poisoning with Li⁺ cations and using a zincosilicate support that contains H⁺ sites of weaker acid strength than those on aluminosilicate supports. Isolated Ni²⁺ sites were predominantly present, consistent with a 1:2 Ni²⁺:Li⁺ ion-exchange stoichiometry, CO infrared spectroscopy, diffuse reflectance UV-Visible spectroscopy and <i>ex-situ</i> X-ray absorption spectroscopy. Isobutene serves a kinetic marker for alkene isomerization reactions at H⁺ sites, which allows distinguishing regimes in which 2-butene isomers formed at Ni sites alone, or from Ni sites and H⁺ sites in parallel. 1-butene and 2-butenes formed at Ni sites were not equilibrated and their distribution was invariant with ethene site-time, revealing the primary nature of butene double-bond isomerization at Ni sites as expected from the coordination-insertion mechanism. <i>In-situ</i> X-ray absorption spectroscopy showed that the Ni oxidation state was 2+ during dimerization, also consistent with the coordination-insertion mechanism. Moreover, butene site-time yields measured at dilute ethene pressures (<0.4 kPa) increased with time-on-stream (activation transient) during initial reaction times, and this activation transient was eliminated at higher ethene pressures (≥ 0.4 kPa) and while co-feeding H₂. These observations are consistent with the <i>in-situ</i> formation of [Ni(II)-H]⁺ intermediates involved in the coordination-insertion mechanism, as verified by H/D isotopic scrambling and H₂-D₂ exchange experiments that quantified the number of [Ni(II)-H]⁺ intermediates formed.</p> <p> The prevalence of the coordination-insertion cycles at Ni²⁺ cations provides a framework to interpret the kinetic consequences of the structure of Ni²⁺ sites that are precursors to the dimerization active sites. Beta zeotypes predominantly containing either exchanged Ni²⁺ cations or grafted Ni²⁺ cations show noteworthy differences for ethene dimerization catalysis. The deactivation transients for butene site-time yields on exchanged Ni²⁺ cations indicate two sites are involved in each deactivation event, while those for grafted Ni²⁺ cations indicate involvement of a single site. The site-time yields of butenes extrapolated to initial time, and then further extrapolated to zero ethene site-time, rigorously determined initial ethene dimerization rates (453 K, per Ni) that showed a first-order dependence in ethene pressure (0.05-1 kPa). This kinetic dependence implies the β-agostic [Ni(II)-ethyl]⁺complex to be the most abundant reactive intermediate for the Beta zeolites containing exchanged and grafted Ni²⁺ cations. Further, the apparent first-order dimerization rate constant was two orders of magnitude higher for exchanged Ni²⁺ cations than for grafted Ni²⁺ cations, reflecting differences in ethene adsorption or dimerization transition state free energies at these two types of Ni sites. </p> <p> The presence of residual H⁺ sites on aluminosilicate zeotypes, in addition to the Ni²⁺ sites, causes formation of saturated hydrocarbons and oligomers that are heavier than butenes and those containing odd numbers of carbon atoms. The reaction pathways on Ni²⁺ and H⁺ sites are systematically probed on a model Ni-exchanged Beta catalyst that forms a 1:1 composition of these sites <i>in-situ</i>. The quantitative determination of apparent deactivation orders for the decay of product space-time yields provides insights into the site origins of the products formed. Further, Delplot analysis systematically identifies the primary and secondary products in the reaction network. This strategy shows linear butene isomers to be primary products formed at Ni²⁺-derived sites, while isobutene is formed as a secondary product by skeletal isomerization at H⁺ sites. In addition, propene is formed as a secondary product, purportedly by cross-metathesis between linear butene isomers and the reactant ethene at Ni²⁺-derived sites. Also, ethane is a secondary product that forms by hydrogenation of ethene at H⁺ sites, with the requisite H₂ generated <i>in-situ</i> likely by dehydrogenation and aromatization of ethene at H⁺ sites.</p> <a>The predominance of the coordination-insertion mechanism at Ni²⁺-derived sites implies kinetic factors influence isomer distributions within the dimer products, providing an opportunity to influence the selectivity toward linear and terminal alkene products of dimerization. In the case of bifunctional materials, reaction pathways on the Ni²⁺ and H⁺sites dictate the interplay between kinetically-controlled product selectivity at Ni sites and thermodynamic preference of product isomers formed at the H⁺ sites. </a>In summary, through synthesis of control catalytic materials and rigorous treatment of transient kinetic data, this work presents a detailed mechanistic understanding of the reaction pathways at the Ni²⁺ and H⁺ sites, stipulating design parameters that have predictable consequences on the product composition of alkene dimerization and oligomerization.