Pd-nanoparticles supported on bacterial nanocellulose as a catalyst for the hydrogenation of polyfunctional reagents containing C=O and C=C bonds

The bacterial nanocellulose (BNC) was synthesized by cultivating the Komagataeibacter medellinensis strain in Hestrin-Schramm medium under static conditions.1 Pd nanoparticles were supported on BNC by impregnating of palladium (II) acetate in acetone, followed by reduction of Pd ions using NaBH4 in methanol. The 2wt% Pd/BNC and 4wt% Pd/BNC catalysts were synthesized and characterized by SEM, TEM, FTIR, XPS, and TA. The catalysts were screened in liquid phase hydrogenation in a batch reactor. Their reactivity in hydrogenation of acetophenone (ACP), furfural (FU), 5-hydroxymethylfurfural (HMF) and cinnamaldehyde (CAL) was tested under mild conditions (p = 4–9 bar H2, T = 30–70°C) in various solvents, including water, isopropanol, ethanol, acetonitrile, and toluene. The catalysts exhibited high selectivity towards 1-phenylethanol (PE) during ACP hydrogenation in water and especially in isopropanol (ca. 100% PE). During FU hydrogenation, Pd/BNC primarily facilitated the formation of furfuryl alcohol, followed by saturation of the furan ring. Surprisingly, Pd/BNC demonstrated low catalytic activity in HMF hydrogenation in both nonpolar and polar solvents. In CAL hydrogenation, Pd/BNC exhibited 100% conversion and up to 96% selectivity towards hydrocinnamaldehyde (C=C bond saturation), almost independently of the solvent (isopropanol/toluene) used. The catalyst demonstrated excellent recyclability in CAL hydrogenation in isopropanol.