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Master's Dissertation
DOI
https://doi.org/10.11606/D.59.2010.tde-26062024-165719
Document
Author
Full name
Heide Regina Airoldi
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2010
Supervisor
Committee
Iamamoto, Yassuko (President)
Assis, Marilda das Dores de
Ribeiro, Anderson Orzari
Title in Portuguese
Manganês porfirinas em materiais nanoestruturados como catalisadores biomiméticos na oxidação de hidrocarbonetos
Keywords in Portuguese
Catálise biomimética
Hidrocarbonetos
Manganêsporfirinas
Oxidação
Sílica hexagonal mesoporosa
Abstract in Portuguese
Cloreto de 5,10,15,20,25-tetrakis(pentafluorofenil)porfirinato de manganês (IlI) (MnP) foi imobilizado em sílica hexagonal mesoporosa (SHM). Os materiais foram preparados pela co-condensação entre tetraetilortossilicato e a metaloporfirina covalentemente ligada à 3-aminopropiltrietoxissilano, ao redor de dois tensoativos distintos, n-dodecilamina (C12) ou n-hexadecilamina (C16), com a finalidade de modular os tamanhos dos poros. Os materiais obtidos MnP-SHMC12 e MnP-SHMC16 foram caracterizados por IV RD UV-Vis, DRX, BET e TGA. As análises de RD UV-Vis e DRX, confirmaram que a imobilização da MnP em SHM a partir dos tensoativos C12 e C16 foi realizada com sucesso. Pode-se observar pelo MEV que os catalisadores apresentam-se como nanopartículas esféricas de 50 a 100 nm que se aglomeram em esferas maiores de 0,5 a 1,5 µm aproximadamente, revelando estruturas organizadas. Nas análises por BET, a MnP-SHMC12 em comparação com a MnP-SHMC16, apresentou valores de área superficial (As: 500 m2.g-1), volume de poro (Pv: 0,96 cm3.g-1 ) e tamanho de poro (PT: 7,7 nm) inferiores aos obtidos para a MnP-SHMC16 (As: 760 m2.g-1; Pv: 1,6 cm3.g-1; PT: 8,8 nm) como esperado. Os resultados mostram que estes materiais apresentam estrutura mesoporosa com grande área superficial. A eficiência catalítica dos materiais foi avaliada na oxidação do (Z)cicloocteno e cicloexano utilizando iodosilbenzeno e H2O2 como oxidante nos solventes dicloroetano, metanol e acetonitrila. Os melhores resultados obtidos na epoxidação (100%) foram em dicloroetano, com iodosilbenzeno como oxidante, enquanto que nas mesmas condições o rendimento de cicloexanol foi de 16%. Com o H2O2 como oxidante os resultados foram em geral menores. As reutilizações dos catalisadores MnP-SHMC12 e MnP-SHMC16 na oxidação do (Z)-cicloocteno foram estudadas em 10 ciclos e apresentam alta estabilidade e eficiência catalítica, com número de turnover de 903 e 740 respectivamente.
Title in English
Não informado.
Keywords in English
Biomimetic catalysis
Hexagonal mesoporous silica
Hydrocarbons
Manganese porphyrin
Oxidation
Abstract in English
5,10,15,20,-tetrakis (pentafluorophenyl) porphyrin manganese (IlI) chloride (MnP) was immobilized onto hexagonal mesoporous silica (HMS). The materials were prepared by co-condensation of tetraethylorthosilicate and metalloporphyrin covalently linked to 3-aminopropyltriethoxysilane, around two different surfactants, n-dodecylamine (C12) or n-hexadecylamine (C16), in order to adjust the pare size. The obtained materials MnP-HMS C12 and MnP-HMS C16 were characterized by IR, RD UV-Vis, XRD, BET, and TGA. RD UV-Vis and XRD analyses confirmed that the immobilization of MnP onto HMS from surfactants C12 and C16 was successful. The SEM micrographs revealed that the catalysts consist of spherical nanoparticles measuring 50-100 nm, which aggregate into larger, well organized spheres with sizes varying between 0.5 and 1.5 µm. BET analysis showed that MnP-HMS C12 has a surface area (SA) of 500 m2.g-1), pore volume (Pv:) of 0.96 cm3.g-1, and pore size (PT) of 7.7 nm, which are lower than the values obtained for MnP-HMS C16 (SA: 760 m2.g-1; Pv: 1.6 cm3.g-1, and PT: 8.8 nm, respectively) as expected. The results demonstrate that these materials exhibit mesoporous structure with large surface area. The catalytic efficiency of the materials was evaluated in the oxidation of (Z)-cyclooctene and cyclohexane by iodosylbenzene or H2O2 in the solvents dichloroethane, methanol, or acetonitrile. The best epoxidation results (100%) were achieved in dichloroethane, using iodosylbenzene as oxidant, whereas under the same conditions the yield of cyclohexanol was 16%. When H2O2 was utilized as oxidant, the results were generally lower. The reuse of the catalysts MnP-HMS C12 and MnP-HMS C16 in the oxidation of (Z)-cyclooctene was studied in 10 cycles, revealing that they are highly stable and catalyticaly efficient, with a turnover number of 903 and 740, respectively.
 
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