On the kinetics of iridium nanoparticles formation in ionic liquids and olefin hydrogenation

The in situ formation of an iridium nanoparticles dispersion obtained from the reduction of the organometallic precursor [Ir(cod)Cl]2 in 1-n-butyl-3-methyl imidazolium hexafluorophosphate ionic liquid by molecular hydrogen is an autocatalytic process. These nanoparticles possess a small size and a monomodal size distribution of 2.0 ± 0.4 nm iridium nanoparticles can be confirmed by TEM and XRD analysis before and after the catalytic process. The 1-decene hydrogenation by the Ir(0) nanoparticles in the ionic liquid follows the classical monomolecular surface reaction mechanism v=kcK[S]1+K[S]. The reaction rate is a mass controlled process under hydrogen pressure <4 atm. The catalytic kinetic constant (kc) and the adsorption constant (K) under hydrogen pressures ≥4 atm are independent of the hydrogen concentration indicating zero order dependence on hydrogen pressure and the reaction depends only of the 1-decene concentration in the ionic liquid.

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