• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

S?ntese seca de Ze?lita Beta a partir de precursores Mesoporosos tipo SBA-15 com diferentes m?todos de carboniza??o / Dried Beta Zeolite Synthesis from SBA-15 Mesoporous Precursors with Different Carbonization Methods

S?, Guilherme Raymundo 28 August 2017 (has links)
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

Page generated in 0.0736 seconds