Banca de DEFESA: ARNALDO CARLOS LUCAS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : ARNALDO CARLOS LUCAS
DATA : 20/04/2020
HORA: 10:00
LOCAL: on line
TÍTULO:

Investigation of the Unimolecular Reactions in the Pyrolysis and Combustion Mechanisms for 2,5-dimethylfuran

PALAVRAS-CHAVES:

2,5-dimethylfuran, pyrolysis, density functional theory, transition state theory

PÁGINAS: 86
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Cinética Química e Catálise
RESUMO:

Furans are alternative fuels that can be mixed with diesel, increasing the energy balance and improving combustion performance. Among them, 2,5-dimethylfurane (DMF) is found. It is well established that, among initiation reactions, unimolecular decompositions are predominant. Therefore, the study of the reaction pathways that represent the main routes for the unimolecular decomposition of DMF and for the reactions of the main primary products was carried out. Theoretical calculations were performed at CCSD (T)/aug-cc-pVTZ//M06 2X/aug-cc-pVTZ level including geometry optimizations, vibrational frequency calculations and reaction paths. Kinetic parameters were predicted at the level of canonical variational transition state theory. The dependence of the rate coefficients with the temperature was evaluated. Migration paths 2-3 of CH₃ and 3-2 of hydrogen were calculated. The migration of methyl 2-3 leads to 3,5‑dimethylfuran-2(3H)-ildene, which dissociates, forming methylketene and prop-1-yne. The 3-2 hydrogen migration leads to 2,5‑dimethylfuran-3(2H)-ildene, which dissociates, forming the hexa‑3,4-dien-2-one. This last intermediate undergoes isomerization and another hydrogen migration with simultaneous C - C dissociation, leading to ketene and but-1-ino. The migration of hydrogen 3-4 leads to hexa‑4‑in-2‑one and then undergoes a dissociation leading to ketene and but‑2-ine. Breaking the C - O bond leads to the same intermediate as the 3-2 hydrogen migration. The dissociation of a methyl hydrogen from DMF was calculated leading to (5‑methylfuran‑2-yl)methyl. The rate coefficients were calculated and the global rate coefficients, as a function of temperature, for the unimolecular decomposition of DMF are adjusted to the Arrhenius expression: kglobal = 4.32x10¹⁵exp (-77.62 / RT) s^-1 with the expressed parameters in units s^-1 and kcal.mol^-1. Reactions of the intermediate DMF-H, a product of unimolecular dissociation, were also investigated. The 3-2 migration path leads to 5‑oxohexa‑2,3‑dien-1-yl. It undergoes isomerization and dissociation until it reaches cetene and buta‑1,2‑dien‑4‑yl. Another route is initiated by the migration of hydrogen 4-5, leading to 2‑methyl‑5‑methyldiene‑2,5‑dihydrofuran‑3‑yl, where this has a dissociation reaching 1‑[(but‑3‑yn‑2‑yl)oxy]ethenyl until it reaches cetene and but‑1‑yn‑3‑yl. The migration of a 5‑4‑methyl leads to 3‑methyl‑5‑methylideneoxolan‑4‑yl‑2‑ylidene, which goes through another three stages until it reaches carbonyl and penta‑1,2,4‑triene. The last route starts with the breaking of the C ‑ O bound leading to the 5 ‑oxohexa‑1,2‑dien‑4‑yl and then goes through three more steps reaching the ketene and buta‑1,2‑dien‑4‑yl. This work presents new data on the study of DMF pyrolysis with results close to the experimental and unimolecular reaction paths not previously seen.

MEMBROS DA BANCA:
Presidente - 1716351 - GLAUCO FAVILLA BAUERFELDT
Interna - 1354432 - CLARISSA OLIVEIRA DA SILVA
Externo ao Programa - 1808284 - MARCIO SOARES PEREIRA
Externo à Instituição - LEONARDO BAPTISTA - UERJ
Externo à Instituição - THIAGO MESSIAS CARDOZO - UFRJ