Epoxidation of Cyclohexene on Heterogenized Molybdenum Compounds

Barradas, E.F.M.; Cestari, Antonio R.; Airoldi, Cláudio; Buffon, Regina

doi:10.1590/s0104-66321998000200008

Cited by 14 publications

(4 citation statements)

References 12 publications

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“…It turned out that all systems contained mainly Mo(VI) species but in different environments. 18 All catalysts were tested in the epoxidation of cyclohexene (Table 1) 6 ] but that the presence of one or two ethylenediamine groups in the support had no significant effect on the catalytic activity of the resulting systems. In recycling experiments with SiEt1/ [MoO 2 (acac) 2 ] no leaching was observed but the catalytic activity decreased slightly.…”

Section: Anchoring On Functionalized Silicamentioning

confidence: 99%

Heterogenization of alkene epoxidation catalysts

Buffon¹,

Schuchardt²

2003

J. Braz. Chem. Soc.

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Este trabalho descreve nosso esforço em heterogeneizar catalisadores para epoxidação. Tanto o molibdênio ancorado quanto o engaiolado pelo método de sol-gel mostraram grande seletividade, mas possuem suas atividades fortemente reduzidas. Por outro lado, silicatos de molibdênio foram muito ativos e estáveis até a formação de diols na mistura reacional. Catalisadores heterogeneizados de rênio foram menos ativos, mas permitiram o uso do peróxido de hidrogênio anidro como oxidante. Contudo, o alto custo e a dificuldade de regeneração impedem a aplicação industrial destes catalisadores. Durante estas investigações, descobrimos que a alumina sozinha é ativa para epoxidação com peróxido de hidrogênio anidro, fornecendo boas conversões para epóxidos com alta seletividade. Mais pesquisa é necessária para esclarecer a natureza dos grupos hidroxilas responsáveis pela atividade catalítica, para produzir materiais que permitem a obtenção de epóxidos com alta seletividade em condições industriais.This account describes our efforts to heterogenize epoxidation catalysts. Anchored and sol-gel entrapped molybdenum were shown to be very selective, but had a strongly reduced activity. On the other hand, molybdenum silicates were very active and stable as long as no diols were present in the reaction mixture. Heterogenized rhenium catalysts were less active but allowed the use of anhydrous hydrogen peroxide as oxidant. However, the high cost and difficult regeneration prevents the industrial use of these catalysts. During these investigations, we found that alumina alone is active in the epoxidation with anhydrous hydrogen peroxide, giving good conversions to epoxides with high selectivity. More research is needed in order to clarify the nature of the hydroxyl groups responsible for its catalytic activity and thus to produce an appropriate material which would allow the obtention of epoxides with high selectivity under industrial conditions.

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Section: Anchoring On Functionalized Silicamentioning

confidence: 99%

Heterogenization of alkene epoxidation catalysts

Buffon¹,

Schuchardt²

2003

J. Braz. Chem. Soc.

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“…Chemically modified silicas are used extensively in many scientific and technological applications, for example, as HPLC bonded phases for specific separations [2,3,[9][10][11], supports for catalysts in specific organic reactions [12], and supports for microorganisms [13] and pesticides [14], as well as for the immobilization of humic acid [15] and the extraction of metallic cations from aqueous and nonaqueous solvents, by forming immobilized metallic complexes, which present variable compositions and distorted geometries [16]. Our research group has extensively studied this last application, in order to find kinetic and thermodynamic data on the interactions between metals and modified surfaces [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Kinetics and equilibrium parameters of Hg(II) adsorption on silica–dithizone

Cestari

Vieira

Lopes

et al. 2004

Journal of Colloid and Interface Science

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“…Chemically modified silicas are used extensively in many scientific and technological applications, for example, as HPLC bonded phases for specific separations (2,3,(9)(10)(11), supports for catalysts in specific organic reactions (12), supports for microorganisms (13) and pesticides (14), and the immobilization of humic acid (15) and the extraction of metallic cations from aqueous and nonaqueous solvents by forming immobilized metallic complexes, which present variable composition and distorted geometries (16). This last application has been extensively studied 1 To whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%