Tri-synergistic design of Pd-Ni/TiO2-Al2O3 porous catalysts for selective and stable hydrogenation of nitrile butadiene rubber

Hydrogenated nitrile butadiene rubber (HNBR) is a crucial material for high-performance sealing applications; however, conventional solution hydrogenation is often limited by high noble-metal consumption and the challenges in simultaneously achieving high activity, selectivity and stability. Herein, a synergistic design strategy integrating mass transfer enhancement, bimetallic electronic synergy, and support interface stabilization is proposed for efficient NBR hydrogenation. A Pd-Ni bimetallic-doped TiO 2 -Al 2 O 3 porous composite catalyst was synthesized through a sol–gel method, in which the pore size distribution was tuned to 15–18 nm by using an F127 template to facilitate macromolecular diffusion. Partial substitution of Pd with Ni modulates the electronic structure of Pd sites, promoting H 2 dissociation and selective C=C bond hydrogenation, while the TiO 2 -Al 2 O 3 composite support provides Lewis acid–base sites and oxygen vacancies that enhance metal dispersion and catalyst stability. The optimized Pd–1Ni catalyst achieves a hydrogenation degree of 92% at 120 °C and 4 MPa, and retains over 80% of its activity after five consecutive cycles. This work demonstrates an effective strategy for balancing catalytic activity, noble-metal utilization, and operational stability in heterogeneous NBR hydrogenation systems, providing a practical reference for catalyst design in polymer hydrogenation processes.