Amine-stabilized small gold nanoparticles supported on AlSBA-15 as effective catalysts for aerobic glucose oxidation

Abstract

The preparation of gold nanoparticles (AuNPs) supported on the alumina- and amine-modified silica SBA-15 and systematic studies of their structural properties and behaviour in glucose oxidation are presented. The AuNPs were deposited using either direct reduction or colloidal deposition method. Catalysts were characterized by nitrogen adsorption, XRD, XPS, STEM, HRTEM, 27Al MAS NMR, 1H NMR, DLS, HPLC, ICP MS and thermogravimetry to determine structure/activity relationship in the aerobic glucose oxidation. The highest catalytic activity ca. 800mmolGA/gAumin was achieved for AuNPs prepared by a direct reduction method using SBA-15 first modified with alumina (1wt.%) and then with aminopropyl groups serving as strong adsorption sites. It was notably larger than shown by commercial Au/Al2O3 and Au/TiO2 catalysts (380 and 340mmolGA/gAumin, respectively). Owing to excellent and stable dispersion of AuNPs and their small sizes <6nm, the catalysts showed very good stability, demonstrated in 7 reaction cycles. The impact of specific functionalities on the size, dispersion and stability of AuNPs was discussed and high selectivity towards gluconic acid formation was demonstrated.