Nanotitania-Supported Rhodium(0) Nanoparticles: Superb Catalyst in Dehydrogenation of Dimethylamine Borane

摘要

Rhodium(0) nanoparticles, in situ formed from the reduction of rhodium(II) octanoate in toluene solution, are active catalyst in dehydrogenation of dimethylamine borane, however not very stable. When the same nanoparticle formation reaction is performed in the presence of nanotitania it yields the supported rhodium(0) nanoparticles (Rh(0)/nanoTiO2) with an average size of 3.17 ± 0.52 nm, which can be isolated and characterized by a combination of analytical techniques including inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET) surface area measurement. Rh(0)/nanoTiO2 is highly active and long lived catalyst providing 9700 turnovers in releasing 1 equivalent H2 from dimethylamine borane over 27 h before deactivation and a record initial turnover frequency (TOF) value of 2900 h~(-1) in H2 generation at 60.0 ± 0.5℃, which is the highest TOF value ever reported for dehydrogenation of dimethylamine borane using homogeneous or heterogeneous catalyst. Rh(0)/nanoTiO2 is also quite reusable catalyst preserving 57% of the initial catalytic activity even after the fourth run of dehydrogenation reaction. This report also includes the results of kinetic study on the catalytic dehydrogenation of dimethylamine borane depending on the temperature and catalyst concentration.