Defect Engineered Alginate-Derived Carbon Supported Pd Catalyst for Hydrogenation of Nitrile Butadiene Rubber

Abstract

Selective hydrogenation of nitrile butadiene rubber (NBR) is a key process for producing high-performance hydrogenated nitrile butadiene rubber (HNBR). Nevertheless, the large molecular size (105–106 g/mol) and strong steric hindrance of NBR polymers lead to severe mass transfer limitations and significant metal leaching via multiple interconnected mechanisms, resulting in low catalytic activity and poor catalyst stability. To address this challenge, a functionalized hierarchically porous carbon catalyst with highly dispersed Pd NPs (Pd/CSA-AIR-300) was rationally constructed from sodium alginate via acid etching and controlled oxidation. Oxygen-containing functional groups derived from sodium alginate promote the high dispersion of Pd NPs. Meanwhile, acid etching introduces abundant surface defect sites, which further regulate the electronic structure of Pd. On the other hand, the loose and interconnected pore structure of the carbon skeleton significantly reduces the diffusion limitation of polymer chains, improving the accessibility of active sites. Pd/CSA-AIR-300 (1 wt %) exhibited superior NBR hydrogenation performance over commercial Pd/C (5 wt %), achieving 92.0% conversion and 100% C═C selectivity at 60 °C and 4 MPa H2. Herein, a synergistic strategy combining defect engineering and oxygen-containing functionalization of biomass-derived carbon is proposed, enabling efficient and sustainable hydrogenation of high-viscosity polymers while reducing cost and offering a practical route to enhance rubber properties.