HIGHLY DISPERSED GOLD SILICA CATALYST PREPARED IN ONE STEP BY THE AEROSOL-ASSISTED SOL-GEL PROCESS

Van der Verren, Margot [UCL] Aprile, Carmela [UNamur] Debecker, Damien P. [UCL] et al.

Owing to their unique physical and chemical properties gold nanoparticles are ubiquitous in many fields of nanotechnology. In heterogeneous catalysis, supported gold nanoparticles are attractive for the selective oxidation of bio-based platform molecules to obtain added-value chemicals. Catalysis on gold is strongly structure-sensitive, so gold particle formation should be finely controlled; their size should remain below 5 nm. Among the different supports, SiO2 is attractive for its high stability, low cost and tuneable porosity. However, combining gold with silica either leads to large particles – when following conventional methods – or requires to work with multi-steps methods, unattractive from an industrial and sustainability point of view. [1] The aerosol-assisted sol-gel process is primed to solve such synthesis challenges, as it allows to produce heterogeneous catalysts with a fine control on the particle shape, size, surface chemistry and textural properties in a limited number of steps. [2] Direct synthesis of mesostructured metal-based catalysts is possible via the addition of a metal precursor in the aerosol feed. Hampsey et al. reported a direct synthesis of Pd-SiO2 catalysts [3] and we recently reported the synthesis of Cu-SiO2 catalysts. [4] Such one-pot aerosol strategy has, however, never been reported for Au-SiO2 materials. Here, we present a modified aerosol process for the preparation of Au-SiO2 catalyst with highly dispersed gold nanoparticles. We showed that the addition of a gold-stabilizer – a thiol-based molecule – during synthesis is the key to obtain small gold nanoparticles (size of 3.1 ± 0.4 nm after calcination, compared to 11 ± 2 nm without the gold-stabilizer) (Figure 1). The catalyst displayed advantageous textural properties (SSA = 440 m².g-1; Vp = 0.09 cm³.g-1; Dp = 5 nm) with a successful incorporation of gold. The catalytic activity for glycerol oxidation was highly improved when gold was stabilized (glycerol conversion of 51% compared to 5% without stabilization).