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The heterogeneous selective hydrogenation of nitrile butadiene rubber (NBR) is an efficient method to generate high value‐added hydrogenated NBR. Nevertheless, the inherent large molecular size and high spatial hindrance of polymers lead to poor activity and metal loss. Herein, we report a simple support ammonia pretreatment strategy for the synthesis of efficient N‐doped Pd catalyst and applied for the NBR hydrogenation. The results reveal that N doping enhances electron transfer from the support to Pd more effectively than oxygen‐rich vacancy support, thereby substantially enhancing the electron cloud density and stability of the Pd sites. The formation of more electron‐rich Pd sites not only significantly enhances the adsorption‐activation ability of C=C and H2, but also lowers the apparent activation energy of the reaction. As a result, the Pd/N‐TiO2‐R demonstrates best activity with a hydrogenation degree (HD) of 98 % and a TOF value of 335 h−1, significantly higher than that of Pd/TiO2−R (HD=83 %, 282 h−1) and Pd/TiO2 (HD=74 %, 204 h−1). This strategy will provide new inspiration to improve the activity and stability of Pd/TiO2 catalysts for the hydrogenation of unsaturated polymers. [ABSTRACT FROM AUTHOR]

Heterogeneous hydrogenation is an effective way to improve the performance of unsaturated polymers, but the preparation of supported catalysts with high metal dispersion and stability remains challenging. Herein, we synthesize a SiO2-based support wrapping with carbon nitride on the surface (CNx@SiO2) via the thermal polycondensation of melamine, on which Pd nanoclusters with highly exposed active sites are formed and stably anchored via the strong interaction between N and Pd. The thermal temperature affects the properties of CNx, which further modulates the electronic and structural state of Pd nanoclusters. The Pd/CNx @SiO2-500 catalyst, prepared at 500 °C with an optimal CNx structure (g-C3N4) and high nitrogen content, features highly dispersed and electron-rich Pd nanoclusters (1.3 nm). This catalyst exhibits a hydrogenation activity of 98.0% for nitrile rubber, with a selectivity of 100% for C=C bonds. This work provides a facile method to prepare Pd catalysts with high activity and stability, paving the way for the upgrading of unsaturated polymers via hydrogenation. [ABSTRACT FROM AUTHOR]