Nanoscale Pd-based catalysts for selective oxidation of glycerol with molecular oxygen: Structure–activity correlations

Abstract

This work investigates selective oxidation of glycerol with molecular oxygen, one of the viable routes to obtain value-added products from bio-glycerol, using nanosized Pd-based catalysts. For this, three types of 1wt.% Pd catalysts supported on activated carbon (Ac), hydrotalcite (HTc), and activated carbon–hydrotalcite composite (Ac–HTc) were prepared. The physicochemical properties of the catalysts are characterized using various techniques, such as XRD, BET, XRF, H2-TPR, CO2-TPD, and TEM. The TEM images reveal the formation of Pd nanoparticles with an average diameter of 9.01, 9.10, and 11.16nm on the surface of HTc, Ac, and Ac–HTc supports, respectively. The CO2-TPD results show that the Pd@HTc catalyst exhibits higher concentration of basic sites compared with that of Pd@HTc-Ac and Pd@Ac catalysts. The H2-TPR profiles show that the reducibility of Pd species is highly dependent on the nature of the supports. Catalytic activity results reveal that the conversion of glycerol over Pd catalysts increased in the following order: Pd/Ac<Pd@HTc-Ac<Pd@HTc, while selectivity of the glyceric acid increased in the following order: Pd@HTc-Ac<Pd@Ac<Pd@HTc. The presence of more number of basic sites and high dispersion of Pd nanoparticles are found to be key factors for excellent catalytic performance of Pd@HTc catalyst in the oxidation of glycerol with molecular oxygen.