Portal de Programas de Pós-Graduação (UFAL)

SIGAA - Sistema Integrado de Gestão de Atividades Acadêmicas

PPGM PROGRAMA DE PÓS-GRADUAÇÃO EM MATERIAIS CENTRO DE TECNOLOGIA Phone: Not available E-mail: Not available

Banca de DEFESA: JULYANE DA ROCHA SANTOS SOLANO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JULYANE DA ROCHA SANTOS SOLANO
DATE: 22/07/2022
TIME: 14:30
LOCAL: Ambiente virtual
TITLE:

SYNTHESIS OF ZEOLITE SSZ-13 WITH THE COMBINED USE OF STRUCTURE-DIRECTING AGENTS AND SEED CRYSTALS

KEY WORDS:

Zeolite SSZ-13; Synthesis; Structure-directing agents; Seeds Crystal

PAGES: 128
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

Zeolites with inorganic crystalline structures have been widely used in industry because of their excellent properties. The development of zeolite synthesis strategies facilitates the creation of new zeolite materials, the improvement of synthetic efficiency and the adjustment of the physicochemical properties of the material. Recent efforts have focused on improving the SSZ-13 synthesis routes with minimal maintenance cost while maintaining, or even increasing, its performance. The present research addressed the optimization of the synthesis of SSZ-13 zeolite. For this, the synthesis was carried out using choline chloride, hexamethylenetetramine, betaine, 1-(cis-3- chloroallyl)-3,5,7-triazo-1-azoniaadamantane chloride and 5-ethyl-1-azo- 3,7- dioxabicyclo[3.3.0]octane as structure-directing agents combined with seed crystals. The seed crystals, with CHA structure, were synthesized from an inorganic gel obtained by the interzeolitic transformation of faujasite zeolite. Some important synthesis parameters for obtaining SSZ-13 zeolite were evaluated, such as: directing/SiO2 molar ratio = 0.10, 0.40 or 0.8, OH/SiO2 molar ratio = 0.4 or 0.8, percentage of seed crystals 2.5% or 10% and crystallization times between 24 to 72 hours. The samples were characterized by X-ray diffractometry, energy dispersive Xray spectroscopy, thermal analysis, scanning electron microscopy, nitrogen adsorption-desorption and ammonia desorption at programmed temperature. The catalysts that presented better textural properties were submitted to the catalytic test with n-hexane cracking model reaction. The XRD results revealed that among the structure- directing agents used, only choline chloride and hexamethylenetetramine were effective for the formation of pure SSZ-13 with 24 hours and 48 hours of crystallization, respectively. It was found, in all cases, in the region of lower alkalinity (OH/SiO2 = 0.4), the presence of amorphous materials even with a crystallization time of 72 hours. For choline chloride syntheses, the increase in alkalinity (OH/SiO2 = 0.8) promoted nucleation and crystal growth leading to the formation of SSZ-13 with high purity and crystallinity, regardless of the percentage of seed crystals. However, the syntheses with hexamethylenetetramine were only efficient with the percentage of seed crystals of 10%. The EDX results showed that the samples containing the SSZ13 phase presented very close values of SiO2/Al2O3 ratio, between 9 and 11, indicating a restricted range of SSZ-13 zeolite formation. The samples showed morphology of agglomerates of cubic intergrown crystals and textural and acidic properties characteristic of the CHA structure. The catalytic activity results showed that the sample synthesized with choline chloride suffered a greater deactivation of parts of its acid sites by the deposition of coke, resulting in a lower conversion (about 21%) when compared to the sample synthesized with hexamethylenetetramine, which presents a total acidity lower, but achieved a conversion of approximately 25% and a coke content of only 8.3%.

BANKING MEMBERS:
Presidente - 1545506 - ANTONIO OSIMAR SOUSA DA SILVA
Externo à Instituição - ANTONIO SOUZA ARAÚJO - UFRN
Externo à Instituição - BRUNO JOSÉ BARROS DA SILVA - UFPE
Interna - 426640 - FABIANE CAXICO DE ABREU GALDINO
Interno - 1797785 - LUCAS MEILI

Notícia cadastrada em: 20/07/2022 10:53