Examinando por Autor "Bravo, M."

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Modified wacker TBHP oxidation of 1- DODECENE
(ELSEVIER, 2008) Escola, J. M.; Botas, Juan Ángel; Aguado, José; Serrano, D. P.; Vargas, C.; Bravo, M.
A higher 1-olefin (1-dodecene) was oxidized to 2-dodecanone and other ketones in a modified Wacker system featured by omitting the use of copper chloride and employing tert-butylhydroperoxide (TBHP) as oxidant. Acetonitrile was the solvent of choice due to its higher selectivity towards 2-dodecanone, the reaction occurring mostly in the interface. A maximum in conversion and selectivity was measured for a ratio [CH3CN] / [1-dodecene] = 10. The temperature abatement enhances the 2-dodecanone selectivity (61% at 40ºC) because of the lower extent of the competing isomerization reactions. An optimum in 2-dodecanone selectivity was found for a [TBHP] / [1-dodecene] ratio = 7. The use of H2O2 as oxidant led towards slower oxidation rates than TBHP. Other palladium salts (PdSO4 and Pd(CH3COO)2) and several R-CN solvents (propionitrile, benzonitrile, isobutyronitrile) yielded lower performances than palladium chloride and acetonitrile, respectively. On the contrary, ß-ciclodextrin, a phase transfer catalyst, improved the selectivity towards 2-dodecanone.
Oxidation of heavy 1- olefins (C12= - C20=) with TBHP using a modified Wacker system
(ELSEVIER, 2010) Escola, J. M.; Botas, Juan Ángel; Vargas, C.; Bravo, M.
The oxidation of heavy olefins (CB12 B¿ CB20B) was carried out using a modified Wacker system with TBHP as oxidant and acetonitrile as solvent at 80ºC. This system allowed the oxidation of 1-octadecene giving rise to 90% conversion with 60% selectivity towards 2-octadecanone after 2 h while the addition of ß-cyclodextrins did not increase the production of 2-octadecanone. The oxidation of a equimolar mixture of n-dodecane + 1-dodecene enhanced markedly the selectivity towards 2-dodecanone yielding 63% instead of 34% in n-paraffin absence after 2 h, likely due to a dilution effect of the n-dodecane which reduces the extent of the isomerisation reactions. The oxidation of a equimolar mixture CB12PB=P + CB16PB=P + CB20PB=P in presence of equimolar amounts of their corresponding n-paraffins gave rise to practically complete conversion and selectivities towards 2-methylketones within 70 ¿ 90%, enhancing with decreasing chain length due to their higher solubility in the biphasic system. The activity of the catalyst dropped after two reaction cycles, indicating its deactivation by formation of palladium clusters. However, it was possible to obtain similar results in terms of activity and selectivity by decreasing the [1-dodecene]/[PdClB2B] ratio to 100, which is expected to increase the catalyst lifetime by decreasing the extent of palladium aggregation. In this regard, the reported system is rather promising for the oxidation of heavy 1-olefins towards methyl ketones.