Estudo da forma??o de mesoporos em ze?litas mordenitas, por tratamentos p?s-s?ntese de dessilica??o

• Autor(a) principal: Almeida, Julio Cesar Gomes de
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/6497
• topic: Ze?lita mesoporosa; Mordenita; Tratamento alcalino; Dessilica??o; Microporos; Mesoporos; Mesoporous zeolite; Mordenite; Alkaline treatment; Desiccation; Micropores; Mesopores; Engenharia Qu?mica

The oil reserves discovered in recent years in Brazil and in the world are mostly made up of heavy oils. For the processing of these oils, it is increasingly necessary the presence of an active matrix in catalysts for catalytic cracking in fluidized bed. Zeolites can be used as catalysts or support for catalysts in separation processes. Thus, it has a wide application in oil refining processes, in the petrochemical and chemical industry and in environmental control. These properties are associated with the presence of pores in its structure, which guarantee a high specific area. One of the most important processes in oil refining is the catalytic cracking of gas oil, which is formed by a complex mixture of hydrocarbons, the molecules of some of which exceed the pore diameter of zeolite Y. This zeolite has the largest pore diameter (~7.4 ?). Thus, the molecules were unable to access the active sites inside the zeolite Y crystals. In order to overcome this difficulty, in this work original microporous Mordenite zeolites were synthesized, and through post-synthesis alkaline treatments, it was tried to transform them from microporous Mordenites, (~ 7.4x10-10 m), into mesoporous Mordenites ( ~7.4x10-9 m). Therefore, the materials and methods used to synthesize, alkaline treat, characterize and catalytically evaluate the Mordenite Zeolites with two types of molar ratios SiO2/Al2O3, SAR 20 and SAR 40 were presented. Mordenite zeolites were synthesized with the following molar compositions: 20 SiO2 : 1.0 Al2O3 : 6.0 Na2O : 600 H2O and 40 SiO2 : 1.0 Al2O3 : 12.0 Na2O : 1600 H2O. The alkaline treatments had: 2 types of temperature, 2 types of hydroxides, 3 types of concentrations and the presence or not of a surfactant. In addition to the alkaline treatment, the samples also underwent ion exchange and calcination at 550?C. To be sure that the synthesis of microporous mordenite and the possible transformation into mesoporous mordenite occurred, the characterization and catalytic evaluation techniques were used. For the characterization were used the techniques of X-ray diffraction (XRD), energy dispersive X-ray fluorescence spectrometry (EDX), nitrogen adsorption/desorption, temperatureprogrammed ammonia desorption (TPD-NH3) and Catalytic Evaluation. It was observed that XRD confirmed the formation of Mordenite Zeolites with two types of molar ratios SiO2/Al2O3, SAR 20 and SAR 40, and that they have excellent crystallinity. EDX showed that all samples had lower SAR than the synthesis gel and that there was very low desilication in the treated samples. The textural analysis showed that the samples do not have a large amount of mesopores. The TPD showed that the samples have predominantly weak to moderate acid strength. The catalytic evaluation showed that the samples treated in the presence of CTABr had a lower rate of deactivation and that the samples that were treated with Tetramethylammonium hydroxide had a higher initial catalytic activity than the samples treated with Sodium Hydroxide. In the experiments of this work, There was no significant formation of mesopores in the mordenite zeolites, by alkaline treatments after desilicon synthesis.