Effect of the reaction bath temperature in a fixed-bed reactor for oxidation of oxylene over V2O5/TiO2 catalysts

Park, Yeung Ho; Kim, Seung Jun; Kang, Shin Choon

doi:10.1007/bf02789258

Cited by 7 publications

(2 citation statements)

References 12 publications

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“…Sharpless' discovery hinges on the use of the right base in the correct quantities to ensure high catalytic activity and diminished epoxide ring-opening. Other nitrogen donors beside pyridine, ,− notably pyrazole − and 3-cyanopyridine, , have now been investigated as additives in methyltrioxorhenium-mediated epoxidations, Figure . Despite these studies, the effects of the basic additives are still a matter for conjecture.…”

Section: 4 Methyltrioxorheniummentioning

confidence: 99%

Metal-Catalyzed Epoxidations of Alkenes with Hydrogen Peroxide

2003

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Section: 4 Methyltrioxorheniummentioning

confidence: 99%

Metal-Catalyzed Epoxidations of Alkenes with Hydrogen Peroxide

2003

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“…Acid sensitive epoxides such as phenyl oxirane are not stable to these conditions, however , The Lewis acidity of the catalyst tends to mediate the ring opening of sensitive epoxides to diols, but Sharpless' group found that pyridine and other basic additives − accelerate the reaction and protect acid sensitive epoxides from ring opening. The solvents used (MeNO 2 or chlorocarbons) are not ideal for process reactions, and there may be problems separating the product from the additive.…”

Section: Introductionmentioning

confidence: 99%

Manganese-Catalyzed Epoxidations of Alkenes in Bicarbonate Solutions

et al. 2002

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This paper describes a method, discovered and refined by parallel screening, for the epoxidation of alkenes. It uses hydrogen peroxide as the terminal oxidant, is promoted by catalytic amounts (1.0-0.1 mol %) of manganese(2+) salts, and must be performed using at least catalytic amounts of bicarbonate buffer. Peroxymonocarbonate, HCO(4)(-), forms in the reaction, but without manganese, minimal epoxidation activity is observed in the solvents used for this research, that is, DMF and (t)BuOH. More than 30 d-block and f-block transition metal salts were screened for epoxidation activity under similar conditions, but the best catalyst found was MnSO(4). EPR studies show that Mn(2+) is initially consumed in the catalytic reaction but is regenerated toward the end of the process when presumably the hydrogen peroxide is spent. A variety of aryl-substituted, cyclic, and trialkyl-substituted alkenes were epoxidized under these conditions using 10 equiv of hydrogen peroxide, but monoalkyl-alkenes were not. To improve the substrate scope, and to increase the efficiency of hydrogen peroxide consumption, 68 diverse compounds were screened to find additives that would enhance the rate of the epoxidation reaction relative to a competing disproportionation of hydrogen peroxide. Successful additives were 6 mol % sodium acetate in the (t)BuOH system and 4 mol % salicylic acid in the DMF system. These additives enhanced the rate of the desired epoxidation reaction by 2-3 times. Reactions performed in the presence of these additives require less hydrogen peroxide and shorter reaction times, and they enhance the yields obtained from less reactive alkene substrates. Possible mechanisms for the reaction are discussed.

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