Preparation and Characterization of Copper Nanoparticles Stabilized by Poly(vinyl alcohol) for Catalytic Oxidation of 1-Propanol

Abstract

The aqueous solution of copper (II) complex of poly(vinyl alcohol) (PVA-Cu(II)) was characterized by conductimetric titration, UV-Vis spectroscopy and FTIR. The molar composition of the PVA-Cu(II) complex was determined to be equimolar. Subsequently, the PVA-Cu(II) complex was reduced by sodium borohydride to prepare copper nanoparticles (CuNPs) stabilized by PVA (PVA-CuNPs). According to DLS measurements in aqueous solution the average size of PVA-CuNPs was varied from 10 to 25 nm depending on the amount of sodium borohydride used for reduction. The optimal volume of sodium borohydride to obtain 96 % PVACuNPs with 10 nm size was found to be 3 mL of NaBH4 (0.5 molL–1). The PVA-CuNPs were then deposited onto SiO2 support to obtain SiO2/PVA-CuNPs nanocatalyst for the oxidation of 1-propanol. The SEM image and XRD spectrum of SiO2/PVA-CuNPs nanocatalyst showed the deposition of PVA-CuNPs on the surface of SiO2. The resulting SiO2/PVA-CuNPs nanocatalyst was used for the oxidation of 1-propanol to propionaldehyde by molecular oxygen in a batch-type catalytic reactor at 20oС and atmospheric pressure. The optimum catalyst mass and reaction time were found for the conversion of 1-propanol to propionaldehyde with yields ranging from 61.4 % to 87.8 %. Criteria of hydrodynamic and diffusive similarity (Re, Pr’, Sh), overall volumetric mass transfer coefficient (𝑘𝐿 𝑎), and economic metric (STY) were evaluated. 1-Propanol reacted with the decomposed atomically adsorbed oxygen atoms on the Cu(111), (220) surfaces to form propionaldehyde and water.