Highlyactive and reusable rhodium catalyst for selective hydrogenation of nitrile-butadiene rubber

A recyclable heterogeneous rhodium catalyst (MTS-T-Rh) was prepared by loading Rh species onto an amino-silica support grafted by tannin, an intermediate linker and stabilizer, and fully characterized by X-ray diffraction, infrared spectrometry, scanning electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma. The importance of tannin in improving the activity and stability of the heterogeneous catalyst is discussed. Tannin is a stabilizer for chelating with the Rh-active sites through a chemical bond, which enhances interactions between the Rh nanoparticles and silica. The catalytic hydrogenation of nitrile-butadiene rubber was evaluated in solution. Above 96% conversion and 100% selectivity, the carbon-carbon double bond was obtained at 120 °C and 3.0 MPa H₂ after 8 h over MTS-T-Rh. Compared with Rh/SiO₂, the as-prepared MTS-T-Rh catalyst exhibited considerably improved reusability, which suffered about 11% deactivation for hydrogenation of nitrile-butadiene rubber, whereas Rh/SiO₂ was 53%.