Banca de DEFESA: OSEAS SILVA SANTOS
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.DISCENTE : OSEAS SILVA SANTOS
DATA : 28/06/2019
HORA: 09:00
LOCAL: Instituto de Química
TÍTULO:
N2O assisted methanol conversion over acid and base catalysts
PALAVRAS-CHAVES:
Nitrous oxide; Methanol: Oxidation; dehydration; Formaldehyde; Dimethyl ether.
PÁGINAS: 150
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Físico Química Inorgânica
RESUMO:
Nitrous oxide (N2O), a pollutant that contributes to the greenhouse effect and depletion of the ozone layer, is one of the main protagonists, along with methanol, in this study. In this sense, this work was developed to evaluate nitrous oxide as an oxidizing agent in basic and acidic reactions using methanol to obtain formaldehyde and dimethyl ether, respectively. In the basic catalysis catalysts of cobalt oxides derived from lamellar double hydroxides were used as catalysts for the conversion of methanol to formaldehyde in the presence of nitrous oxide. The catalysts were characterized by various techniques. The test results showed 100% methanol conversion and 91% selectivity to formaldehyde were simultaneously obtained with 100% N2O conversion at 440 ºC over a Co,Mg,Al-mixed oxide catalyst. Higher hydrogen yields and lower CO and CO2 yields were obtained than when air was used as oxidizing agent, under the same conditions. At another time, as a complementary study, these same oxides catalysts were prepared by inserting cerium by the co-precipitation method. In this study, Cobalt and Cerium doped oxides were characterized and tested in the selective catalytic oxidation of methanol assisted by N2O. It was obtained 100% methanol conversion, 100% N2O conversion and 91% formaldehyde yield were obtained on the CoMgAl catalyst. The catalysts containing cerium were more active in the conversion of N2O at lower temperatures (350 - 400 ºC), but presented lower formaldehyde yields, due to the increase of oxidation products (CO and CO2) formation. In general, the basic reaction with oxides derived from HDLs suggests that the reaction occurs on a combination of redox and basic catalytic sites. On the other hand, acidic catalysts were used for H-ZSM-5 and Co-ZMS-5 acid catalysts for the dehydration reaction of methanol to N2O-assisted dimethyl ether (DME). During this study, high conversion of methanol (78 %) and yield and selectivity to DME of 70 and 90 %, respectively, were obtained at 300 °C. During the stability test the Co-ZSM-5 catalyst was shown to be thermally stable and catalytically in the N2O/CH3OH reaction (1:3) with low generation of polyoxymethylene dimethyl ethers (POMEs) (<10%). In conclusion N2O acts in the removal of the carbon deposits avoiding the intensive coking of the acid catalyst. On the other hand, the formation of surface oxygen species due to N2O decomposition generated a higher number of moderate (or density) sites, contributing to the selective formation of DME. N2O can be used as an oxidizing agent in industrial processes of economic importance, such as assisting in the reaction of selective oxidation of methanol to formaldehyde or in the dehydration reaction of methanol to dimethyl ether.
MEMBROS DA BANCA:
Presidente - 282610 - HELOYSA MARTINS CARVALHO ANDRADE
Interno - 2356272 - ARTUR JOSE SANTOS MASCARENHAS
Interno - 1861434 - VALERIA CRISTINA FERNANDES
Interno - 2362069 - RAILDO ALVES FIUZA JUNIOR
Interno - 1488945 - ADRIANE VIANA DO ROSARIO
Externo à Instituição - SUZANA MODESTO DE OLIVEIRA BRITO - UEFS
Externo à Instituição - CARINE TONDO ALVES - UFRB
Externo à Instituição - TEREZA SIMONEMASCARENHAS SANTOS