Aqueous biphasic catalytic hydrogenation of olefins and olefin mixtures by the [Rh(μ-Pz)(CO)(TPPMS)]2 complex, Pz = pyrazolate, TPPMS = (C6H5)2P(C6H4SO3Na)

The hydrosoluble complex [Rh(μ-Pz)(CO)(TPPMS)]2, Pz = pyrazolate ligand, and TPPMS = (C6H5)2P(C6H4SO3Na) was used as catalytic precursor in the two phase hydrogenation reaction of the individual olefins (1-hexene, styrene, cyclohexene and 2,3-dimethyl-1-butene) to give the main expected saturated products. Under the best operational conditions (80 °C, 200 psi H2, S/C 535/1, and 600 rpm), the substrates showed the following hydrogenation reactivity order: 1-hexene > styrene > cyclohexene > 2,3-dimethyl-1-butene. The quaternary equimolar mixture of olefin and an olefin mixture that simulates a real composition of olefin present in a naphtha showed a different hydrogenation order; styrene > 1-hexene > cyclohexene > 2,3-dimethyl-1-butene. The catalyst can be recycled without significant loss of activity and showed sulfur tolerance, demonstrated by using benzothiophene in the olefin mixtures.

Graphical abstractThe complex [Rh((-Pz)(CO)(TPPMS)]2 was used as a catalytic precursor for the aqueous biphasic hydrogenation of several olefins and olefins mixtures resembling naphtha cuts. The observed catalytic activity was 1-hexane > styrene > cyclohexene > 2,3-dimethyl-1-butene. The catalyst was shown to be resistant to sulfur poisons and recyclable for five consecutive runs without loss of activity.Figure optionsDownload full-size imageDownload as PowerPoint slide