Abstract
Palladium catalysts modified with chitosan (CS) and supported on MgO, SiO2, TiO2, and Al2O3 were prepared by a precipitation method and evaluated in the low-temperature hydrogenation of 2-propen-1-ol. Chitosan was first deposited onto the oxide supports by adjusting the suspension pH to 7.5, followed by immobilization of palladium via reductive deposition using NaBH4. For comparison, analogous non-modified catalysts were synthesized. Physicochemical characterization (TGA, XPS, HAADF-STEM, SEM, viscosimetry, and elemental analysis) confirmed successful incorporation of Pd (1 wt.%) and CS (10 wt.%). HAADF-STEM revealed that Pd particle size and aggregation strongly depended on the support nature, with the most uniform distribution observed for Al2O3-supported catalysts. Chitosan modification reduced Pd nanoparticle size from 4–11 to 3–4 nm and improved dispersion. XPS showed a pronounced increase in the fraction of oxidized Pd species for the Al2O3- and TiO2-supported catalysts, whereas only minor changes were observed for the SiO2-based system. For unmodified catalysts, the nature of the oxide support strongly influenced their performance, resulting in a wide variation in catalytic activity (TOF = 1650–13,100 h−1) and selectivity toward propanol (65–75%). Chitosan modification resulted in a support-dependent convergence of catalytic activity (TOF = 3130–8840 h−1) and selectivity (76–81%). Stability tests were performed for Pd–CS(10%)/MgO and Pd–CS(10%)/Al2O3, which showed stable performance over 20 cycles without significant loss in catalytic activity. Overall, chitosan modification significantly influences Pd dispersion, oxidation state, and catalytic performance, with effects strongly dependent on the oxide support.