Abstract
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.
Highlights
Hydroformylation of olefins is one of the most important homogeneous catalytic reactions in the chemical industry with a worldwide oxoaldehyde production [1]
The homogeneous catalyst system for hydroformylation has high catalytic activity, good selectivity, and other advantages, the transition metal complex used in the catalyst system may dissolve in the product, resulting in difficulties in the recovery of the catalyst [6,7]
We report the design and synthesis of Rh-catalysts supported by TiO2 nanotubes (TNTs) of different surface acidity
Summary
Hydroformylation of olefins is one of the most important homogeneous catalytic reactions in the chemical industry with a worldwide oxoaldehyde production [1]. There are two technical and scientific issues; one is the separation of the homogeneous catalyst from the product, and the other is preventing active components from loss. We used TiO2 nanotubes-supported Rh nanoparticles and amorphous Co–B catalysts to catalyze the hydroformylations of vinyl acetate [15] and cyclohexene [16]. The addition of B in the catalyst should be able to improve the catalytic activity of catalysts by increasing the Lewis acid positions [19,20]. We used boron-modified TiO2 nanotubes-supported Rh-nanoparticle catalysts to catalyze the hydroformylations of styrene, and the TOF of aldehydes was up to 18,458 h−1 [21]
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