Polysaccharide-Stabilized PdAg Nanocatalysts for Hydrogenation of 2-Hexyn-1-ol

Abstract

We used a new one-pot green technique to prepare polysaccharide-based Pd and PdAg nanocatalysts. Catalysts were obtained using a sequentially supporting natural polymer (2-hydroxyethyl cellulose (HEC), chitosan (Chit), pectin (Pec)) and metals on zinc oxide. Nanocatalysts based on a polysaccharide were studied using various physicochemical methods (IR spectroscopy, transmission electron microscopy, X-ray powder diffraction, etc.). The catalyst characterization results indicated the complete adsorption of polysaccharides and metal ions onto the inorganic support (ZnO). We demonstrated the formation of polysaccharide-stabilized Pd nanoparticles with a size of ~2 nm. Metal nanoparticles were uniformly located on the surface of polysaccharide-modified zinc oxide. The synthesized catalysts were tested using liquid-phase hydrogenation of 2-hexyn-1-ol under mild conditions (0.1 MPa, 40 °C). Close conversion values of 2-hexyn1-ol were obtained for all the developed catalysts. The selectivity for cis-hexen-1-ol of the polysaccharide-based PdAg nanocatalysts varied as follows: PdAg-HEC/ZnO > PdAg-Pec/ZnO > PdAg-Chit/ZnO. A similar correlation was obtained in the presence of monometallic Pd-polysaccharide/ZnO catalysts. We determined the optimum reaction temperature and catalyst loading for PdAg catalysts modified using HEC and Chit (40 °C, 0.05 g).