Estudo da síntese de zeólitas lamelares contendo átomos de alumínio, boro e gálio

• Ano de defesa: 2016
• Autor(a) principal: Catuzo, Gabriel Liscia [UNESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Zeólitas lamelares; Substituição Isomórfica; Zeólita MWW; Zeólita FER; Desidratação do glicerol; Lamellar zeolites; Isomorphous Substitution; MWW zeolite; FER zeolite; Glycerol dehydration
• Link de acesso: http://hdl.handle.net/11449/143500

Glycerol is the major by-product of biodiesel production. This organic compound has received much attention in recent years due to its growing supply, which has easily surpassed the demand. Therefore, there is a relevant necessity to find a destination for this product. Dehydration reaction is one of the most interesting and challenging routes, which produces acrolein in the presence of an acid catalyst. In order to have a catalytic dehydration of glycerol with high conversion and acrolein selectivity, it’s important to develop an efficient acid catalyst. This outlook will be achieved from the coherent combination of several physicochemical characteristics of the catalyst, such as suitable acid strength and porosity. With respect to acidity control, the isomorphous substitution of heteroatoms in zeolite framework may reduce the Brønsted acidity, resulting in decreased coke formation during the catalytic reaction. With respect to porosity, it’s possible to obtain hierarchically structured zeolites, which play an important role in molecular diffusion. In this way, the study of the synthesis of MWW and FER lamellar zeolites, incorporated with gallium and boron atoms is proposed. Lamellar zeolites are very interesting materials because they can be exfoliated, enhancing accessibility to active sites. The MWW and FER zeolites were synthesized with boron, aluminum and gallium atoms. The XRD patterns of the samples show that different heteroatoms induce the formation of different crystalline phases for MWW structure. These phases were qualified and quantified. Additionally, the SEM images were obtained for the different crystal phases. On the other hand, X-ray diffraction patterns of FER structure show no formation of contaminant crystalline phases. The materials were also characterized by Infrared Spectroscopy and Thermal Analysis. The first one provided important structural informations especially for the materials incorporated with B, providing evidence of the non-incorporation of this heteroatom in the structure of the material synthesized with HMI. In addition, the thermal analysis of the materials provided relevant informations about structural nature of the catalysts, confirming the lamellar nature of the MWW and ferrierite materials. Finally, the characterization by Temperature-Programmed Desorption of Ammonia for FER zeolites structure was performed. From this, it was possible to confirm a lower acidity for B-FER zeolite. On the other hand, the low concentration of acid sites for Al-FER zeolite suggests that the heteroatom was slightly incorporated in the structure. Additionally, the greatest acid strength for Al-MCM-22 zeolite in comparison to Ga-MCM-22 was verified.