Effect of Support and Polymer Modifier on the Catalytic Performance of Supported Palladium Catalysts in Hydrogenation

In this study, we investigated the influence of polymer nature and support characteristics on the performance of Pd-based heterogeneous catalysts. Catalysts were prepared via sequential adsorption of poly(4-vinylpyridine) (P4VP) or chitosan (CS) and palladium ions onto MgO and SBA-15 supports under ambient conditions. The resulting hybrid materials were characterized by IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). TEM analysis revealed that Pd nanoparticles with an average size of 2-3 nm were well-dispersed on P4VP/MgO, while larger and less uniformly distributed particles (8-10 nm) were observed on SBA-15-based systems. Catalytic tests in the hydrogenation of 2-propen-1-ol, phenylacetylene, and 2-hexyn-1-ol under mild conditions (40 °C, 1 atm H₂, ethanol) demonstrated that both the support and polymer type significantly influence activity and selectivity. P4VP-modified catalysts outperformed CS-containing analogs in all reactions. MgO-based systems showed higher activity and selectivity in 2-propen-1-ol hydrogenation compared to SBA-15-based catalysts. The 1%Pd-P4VP/MgO catalyst exhibited the best performance, with a reaction rate of 5.2 × 10^-6 mol/s, 83.4% selectivity to propanol, and stable activity over 30 consecutive runs. In phenylacetylene and 2-hexyn-1-ol hydrogenation, all catalysts showed high selectivity to styrene (93-95%) and cis-2-hexen-1-ol (96-97%), respectively. The incorporation of P4VP polymer into the Pd/MgO catalyst leads to smaller and better-distributed palladium particles, resulting in enhanced catalytic activity and stability during hydrogenation reactions. These results confirm that the choice of polymer modifier and inorganic support must be tailored to the specific reaction, enabling the design of highly active and selective polymer-modified Pd catalysts for selective hydrogenation processes under mild conditions.