Hidroformilação e hidroaminometilação de ésteres ômega-insaturados oriundos da biomassa

Abstract

Vegetable oils, such as soybean oil and castor oil, are sources of methyl esters of fatty acids, abbreviated by FAMEs (Fatty Acid Methyl Ester), which can be precursors of several products of high added value, for example polymers and pharmaceuticals. Methyl 10-undecenoate (UME) and methyl 9-decenoate (DME) are omega-unsaturated methyl esters obtained from the pyrolysis of castor oil and the ethenolysis of soybean biodiesel, respectively. By the hydroformylation and hydroaminomethylation of the UME and DME, aldehydes and amines can be obtained, respectively, they are potential application in the synthesis of bio-renewable polymers. Hydroaminomethylation is a tandem catalytic process comprised of three stages: hydroformylation of the alkene resulting in an aldehyde; condensation of an amine with aldehyde and hydrogenation of the enamine or imine formed in the second step, which gives rise to linear or branched amines. This reaction is environmentally interesting, because it generates less waste compared to non-catalytic processes, and it is also economically attractive, as it allows high selectivity for the main product in a few hours of reaction, in addition to the fact that the various steps take place in a single reactor. The hydroformylation and hydroaminomethylation of the UME were studied under different reaction conditions: the temperature, the auxiliary ligand and the solvents were varied. The linear aldehyde 12-methyl oxododecanoate was obtained with 98% of selectivity when the catalytic precursor [Rh(COD)(OMe)]2, the auxiliary ligand Xantphos and the solvent toluene were used at 100ºC. The linear amine from the hydroaminomethylation of methyl 10-undenoate with 4-methylpiperidine was obtained in 89% of selectivity when the system [Rh(COD)(OMe)]2/ Xantphos (P / Rh = 5), in the solvent mixture toluene: methanol 1:1 was used in 5 hours reaction time. The use of the ethanol solvent in this same reaction conditions allowed 80% of selectivity for the linear amine in just two hours of reaction, which represents an environmentally friendly and more economically viable alternative. The DME was obtained from the ethenolysis of the FAMEs of soybean biodiesel with first generation Grubbs catalyst, conversion of 62% and 13.9 ± 2.0% mass yield for DME (purity = 90%).