Banca de DEFESA: CARLOS AUGUSTO CABRAL KRAMER

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : CARLOS AUGUSTO CABRAL KRAMER
DATE: 13/12/2021
TIME: 08:00
LOCAL: Remotamente pelo Google Meet
TITLE:

OXIDATION OF BANANA LIGNIN VIA THE CATALYTIC ACTION OF CO3O4 UNDER MILD CONDITIONS AND INVESTIGATION OF STABILITY,PROPERTIES OF THE βO4 BINDING AND INTRAMOLECULAR INTERACTIONS THROUGH THE DFT, QTAIM AND NCI APPROACH 

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PAGES: 169
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Orgânica
SPECIALTY: Química dos Produtos Naturais
SUMMARY:

Lignin is a natural macromolecule that, in general, is formed by the aromatic units S, G and H, depending on their origin. It is noteworthy that from its structure it is possible to obtain molecules of high added value, however, the processes come up against the need to break the bond that unites these aromatic units, the βO4 bond. This work, through computational modeling methods via DFT, QTAIM and NCI, investigated the main intramolecular interactions and their properties related to this bond. The stability was also evaluated, by evaluating the boundary orbitals, of these models and their oxidized equivalents. It can be seen that lignins that have methoxyl linked to the second aromatic unit, that is, the unit that performs the βO4 bond, perform interactions that are totally different from models that do not have them. For some specific conformations, hydrogen bonds between the gamma hydroxyl and the methoxyl of SUA were characterized and these are responsible for making the βO4 bond stronger. However, the methoxylated models are dominated by repulsive and destabilizing interactions that make their βO4 bonds, in general, 4.41% weaker than the models formed by H units that perform attractive and stabilizing dihydrogen interactions. The computational modeling used confirmed that lignins derived from more oxygenated monomers have a smaller HOMO-LUMO gap and, therefore, are less stable. In the developed study, the replacement of alpha hydroxyl by carbonyl (oxidation) was able to abruptly change the electronic topology, reducing the binding energy in βO4 for all models considered. Experimentally, an efficient oxidative method was developed, which was applied in the oxidation of banana organosolv lignin via atmospheric oxygen gas with an oxidizing agent in the presence of Co3O4 as a heterogeneous catalyst at a temperature of 80°C under ambient pressure. The ideal concentration of the catalyst verified was 1% (mol/mol), which after 54 hours of reaction was sufficient for the satisfactory oxidation of the structure, which was confirmed by FTIR analysis.

BANKING MEMBERS:
Interno - 1086214 - ANDERSON DOS REIS ALBUQUERQUE
Externa à Instituição - ANNE GABRIELLA DIAS SANTOS - UERN
Presidente - 1805556 - LUCIENE DA SILVA SANTOS
Externo à Instituição - SAULO GREGORY CARNEIRO FONSECA - IFRN
Externo à Instituição - ÁMISON RICK LOPES DA SILVA