Selective hydrogenation of 1,3-butadiene by transition metal compounds immobilized in 1-butyl-3-methyl imidazolium room temperature ionic liquids

Abstract

Os complexos [Co(acac) 2 ], [Co(acac) 3 ], [Fe(acac) 3 ] e [Ni(acac) 2 ] (acac = acetilacetonato) dissolvidos em tetrafluoroborato de 1-butil-3-metilimidazônio (1), trifluorometanosulfonato de 1-butil-3-metilimidazólio (2) ou hexafluorofosfato de 1-butil-3-metilimidazólio (3), catalisam a hidrogenação de 1,3-butadieno em butenos em sistema catalítico tipicamente bifásico. A conversão do 1,3-butadieno, a seletividade e a freqüência de rotação (TOF) são fortemente dependentes do metal de transição e do líquido iônico. Para [Co(acac) 2 ] dissolvido em 1, estudos cinéticos sugerem que a reação ocorre no meio líquido iônico, com uma energia aparente de ativação de of 33.8 kJ mol -1 . A solução iônica do catalisador pode ser recuperada e reutilizada várias vezes sem mudanças perceptíveis na atividade e seletividade da reação.The compounds [Co(acac) 2 ], [Co(acac) 3 ], [Fe(acac) 3 ] and [Ni(acac) 2 ] (acac = acetylacetonate) dissolved in 1-butyl-3-methyl imidazolium tetrafluoroborate (1), trifluoromethanesulphonate (2) or hexafluorophosphate (3) catalyze the reduction of 1,3-butadiene into butenes in a typical two-phase catalytic reaction. The 1,3-butadiene conversion, the selectivity and turnover frequencies (TOF) are strongly dependent on the nature of the transition metal catalyst precursor and the ionic liquid. For [Co(acac) 2 ] dissolved in 1, kinetic studies strongly suggest that the reaction takes place in the ionic solution bulk, having an apparent activation energy for the overall process of 33.8 kJ mol -1 . The recovered ionic catalyst solution can be reused several times without any significant changes on activity and selectivity. Keywords: biphasic hydrogenation, ionic liquids, dienes, cobalt catalysts IntroductionThe hydrogenation of dienes to mono-olefins has several potentially useful applications in industry. In applications where only moderate selectivity is required heterogeneous catalysts excel due to their easy separability from reaction products by decantation or filtration, and the catalyst can be recycled. 1-5 Transition metal catalyst precursors are known to hydrogenate dienes to olefins under homogeneous conditions. 1,2 In these cases, however, C=C bond isomerization reactions are also operative decreasing the selectivity to hydrogenation products. 6 Moreover, the separation of the products from the reaction mixture and recovery of the catalyst represent disadvantages of these homogeneous catalytic reactions. [3][4][5] The catalytic system formed by dissolving cobalt cyanide in water is highly specific and active (compared with the homogeneous systems) for the hydrogenation of conjugated dienes. 7 Given the restriction that the cobalt catalyst is rapidly deactivated, this aqueous system remains the best catalyst for the hydrogenation of dienes as far as selectivity is concerned.Room temperature molten salts (or ionic liquids) have been demonstrated to be the immobilizing agents of choice for various organometallic catalyst precursors. 8 In these reactions, the catalysts maintain their m...

Degradation of chlorinated butenes and butadienes by granular iron

“…1,3-butadiene then appeared to degrade with a normalized pseudo-first-order half-life of 89.2 min (R 2 = 0.89, estimated using data points from peak concentration onward) to a mixture of 1-butene, cis-2-butene and trans-2-butene. This transformation likely occurred via catalytic hydrogenation consistent with Consorti et al [15] where butadiene underwent hydrogenation catalyzed by transition metal complexes resulting in a mixture of 1-butene, cis-2-butene, trans-2-butene and n-butane. N-butane was not observed in this column experiment, however it is unknown if further catalytic hydrogenation would have occurred if residence times had been greater.…”

“…One such pathway is reductive β-elimination [13] in which two chlorine atoms on adjacent carbons (α, β pair) are removed resulting in a unit increase in bond order between the two carbons. Unsaturated bonds in an organic compound can also be reduced via interaction with granular iron through a process known as catalytic hydrogenation [13,15] in which iron acts as a catalyst in the addition of hydrogen to a double or triple bond. Reactive pathways have been proposed where possible.…”

Degradation of chlorinated butenes and butadienes in granular iron columns

“…2e). This is in agreement with Consorti et al [28] who reported that 1,3-butadiene underwent hydrogenation catalyzed by transition metal complexes resulting in a mixture of 1-butene, cis-2-butene, trans-2-butene and nbutane. Although iron is not a commonly used catalyst for hydrogenation, previous studies have shown that iron can function as a catalyst for hydrogenation of PCE and TCE [15,22] dechlorination reactions as well as in conversion of ethene to ethane.…”

Development of a lewis-based catalytic system for biodiesel production: from a batch laboratory scale to a continuous pilot plant

“…Ionic liquids, especially those derived from dialkylimidazolium cation, have been used in several fields, such as electrochemistry 32 and catalysis, 33 because of their interesting physical-chemical behavior. 34 Regarding the use of metal compounds as catalyst, ionic liquids have been described as excellent solvents to obtain bi-phase catalytic system due to their high efficiency to stabilize intermediates and avoid metal leaching.…”