Glycerol oxidation using MgO and Al2O3 supported gold and gold-palladium nanoparticles prepared in the absence of polymer stabilisers

Au and AuPd nanoparticles supported on MgO and Al2O3 supports were employed for the selective aqueous phase oxidation of glycerol under basic conditions. Catalysts were prepared by sol-immobilisation without the addition of a stabilizing agent such as polyvinyl alcohol (PVA), which is generally added to stabilize the noble metal sol prior to immobilisation on. The obtained materials prepared with and without stabilizing agent were active for glycerol oxidation and showed similar catalytic performances - implying that the stabilizing polymer is not required to obtain active materials. Depending on the support used, it was possible to tailor the selectivity towards desired oxidation products by using catalysts prepared with or without stabilizing agent. PVA-free Au/ Al2O3 exhibited a remarkably high selectivity towards tartronic acid (40% at 97% conversion), which was not observed for the analogous sample prepared with PVA. Selective glycerol oxidation performed under base-free conditions over AuPd/MgO catalysts also corroborated the previous results that the presence of a stabilizing polymer is not required to prepare active catalysts by sol-immobilisation. Thus, a facile way is presented herein to circumvent the inherent drawbacks encountered by the use of polymer stabilizers during catalyst preparation and the experimental results in fact suggest that the presence of the polymer stabilisers can affect the reaction pathways and control selectivity