Zirconium promoter effect on catalytic activity of Pd based catalysts for heterogeneous hydrogenation of nitrile butadiene rubber.

A facile strategy to regulate the structural and electronic state of Pd active sites on silica supports via Zr incorporation with different introduction sequences has been demonstrated. Pd-Zr/N-SiO 2 prepared with Zr incorporation then Pd loading exhibits superior catalytic activity for the hydrogenation of nitrile butadiene rubber. • PdZr/SiO 2 catalysts were prepared via different methods and utilized for NBR hydrogenation. • The geometric and electronic effects of Zr component on Pd active sites were revealed. • Zr can improve the catalytic activity but the sequence of Zr introduction affects the performance. Three PdZr bi-component catalysts supported on modified silica have been successfully synthesized via different Zr introduction methods and utilized for the hydrogenation of nitrile butadiene rubber (NBR) to produce high value-added hydrogenated NBR. It is demonstrated that the introduction of Zr can lead to the formation of small-sized and electron-rich Pd nanoparticles and the order of adding Zr can significantly affect the catalytic activity. In particular, the PdZr bi-component catalyst obtained by introducing Zr followed by adding Pd is found to be more stable on the silica support, which exhibits a high hydrogenation degree of 90.9% with 100% selectivity to C C bond, close to the single Pd catalyst with double Pd contents. The electronic structure and reaction mechanism analysis from density functional theory calculations further reveal that the addition of Zr component leads to negatively charged Pd species with lower energy barrier for the hydrogenation of C C bond. Our findings provide a useful guidance for the design of efficient and low-cost bi-component catalysts for the selective hydrogenation of unsaturated polymers. [ABSTRACT FROM AUTHOR]