Inhibition of gold and platinum catalysts by reactive intermediates produced in the selective oxidation of alcohols in liquid water

Inhibition of a Gold-Based Catalyst in Benzyl Alcohol Oxidation: Understanding and Remediation

“…They also reported the alleviation of this inhibition when NaOH was present. Zope and Davis [3] reported similar effects for the selective oxidation of glycerol to glyceric acid. They performed the reaction in the presence of 19 different compounds: either products or intermediates in the glycerol oxidation reaction, or species that might be formed from condensation of intermediates and/or products.…”

“…Furthermore, the solubility in water is enhanced when organics are oxygenated, which can be either problematic or advantageous. It is now widely recognized that the chemical industry will need to adapt to the new situation [1][2][3]. Once the catalytic abilities of gold had been discovered [4], its high activity for oxidation reactions at mild conditions, down to room temperature, was quickly noticed.…”

“…However, the chemistry of biomass-derived molecules differs significantly from oil-derived molecules [1,3]. Their higher oxygen content renders them more sensitive to oxidation, requiring milder conditions in selective oxidation processes.…”

“…Because of this, catalysts tested in the oxygen mass-transfer limited regime can exhibit higher activity [1,11,14] than might be predicted based on data in the kinetic regime. It is generally accepted that gold-based catalysts are resistant to overoxidation [1,3,11], making them promising candidates for oxidation reactions over extended periods of time. However, a reaction intermediate or the product itself can be an inhibiting entity.…”

“…Alcohol selective oxidation is often carried out in the presence of a base as "promoter" or "co-catalyst" [1][2][3]7,8,11,12,14,15]. The base enhances the deprotonation of the alcohol, thereby ensuring that the rate-limiting step is the catalytic oxidation step [1,15].…”