Synthesis and Characterization of Rh/B⁻TNTs as a Recyclable Catalyst for Hydroformylation of Olefin Containing ⁻CN...

The TiO₂-based nanotubes (TNTs, B⁻TNTs) of different surface acidities and their supported Rh catalysts were designed and synthesized. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), tempera⁻ture⁻programmed desorption of ammonia (NH₃⁻TPD), atomic emission spectrometer (ICP), and Brunauer⁻Emmett⁻Tellerv (BET) surface-area analyzers. Images of SEM and TEM showed that the boron-decorated TiO₂ nanotubes (B⁻TNTs) had a perfect multiwalled tubular structure; their length was up to hundreds of nanometers and inner diameter was about 7 nm. The results of NH₃-TPD analyses showed that B⁻TNTs had a stronger acid site compared with TNTs. For Rh/TNTs and Rh/B⁻TNTs, Rh nanoparticles highly dispersed on B⁻TNTs were about 2.79 nm in average diameter and much smaller than those on TNTs, which were about 4.94 nm. The catalytic performances of catalysts for the hydroformylation of 2-methyl-3-butennitrile (2M3BN) were also evaluated, and results showed that the existence of B in Rh/B⁻TNTs had a great influence on the catalytic performance of the catalysts. The Rh/B⁻TNTs displayed higher catalytic activity, selectivity for aldehydes, and stability than the Rh/TNTs.