Banca de DEFESA: RAFAEL BARBALHO DE LIMA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : RAFAEL BARBALHO DE LIMA
DATE: 29/04/2024
TIME: 09:00
LOCAL: Videoconferência
TITLE:

Formation of mesopores in zeolitic material of MWW topology by alkaline treatment

KEY WORDS:

Zeolite; MCM-22; Desilication; hierarchization; accessibility

PAGES: 80
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Físico Química Inorgânica
SUMMARY:

Due to their unique characteristics, zeolites have a wide range of applications. However, the presence of a uniquely microprose structure restricts its use in reactions involving bulky molecules. Therefore, to solve the problem of accessibility of bulky molecules to the active sites of zeolites, the focus has been on the development of zeolites with hierarchical structures. Hierarchical zeolites present a combination of microporosity, characteristic of zeolites, with an additional level of porosity that can be in the range of mesopores or macropores, allowing greater accessibility. Given the methods developed to obtain hierarchical zeolites (Top-down and Bottom-up), alkaline treatment, one of the processes that constitutes the Top-down method, has been widely used due to its simplicity and efficiency. Alkaline treatment through the desilication process promotes the formation of secondary porosity by removing silicon atoms from the zeolitic structure. In alkaline treatment, several factors can influence the formation of secondary porosity, such as Si/Al ratio, morphology, structure, pore-directing agents, among others. In this work, alkaline treatment was carried out on MCM-22 zeolite with a Si/Al ratio equal to 15 and 50, with a two-dimensional and three-dimensional structure, obtained in rotational and static form, and with different types and quantities of pore-directing agents (CTAB and TPAOH). All synthesized materials presented crystalline phases referring to the MWW zeolite structure. The synthesis in the rotational form presented a rounded and thin platelet cluster morphology, while the static form presented more homogeneous and thick rounded platelets. All samples subjected to alkaline treatment showed lower crystallinity than the starting sample, due to partial destruction of the structure, caused by the removal of silicon atoms, however samples with two-dimensional structures showed greater crystallinity when compared to three-dimensional structures.

COMMITTEE MEMBERS:
Externo à Instituição - ADONAY RODRIGUES LOIOLA - UFC
Interno - 350509 - ANTONIO SOUZA DE ARAUJO
Externa à Instituição - IANE MAIARA SOARES DE SOUZA - UFRN
Externa à Instituição - LINDIANE BIESEKI - UFRN
Presidente - 1308577 - SIBELE BERENICE CASTELLA PERGHER
Externo à Instituição - VINÍCIUS PATRÍCIO DA SILVA CALDEIRA - UERN