Au-Pd/AC as catalysts for alcohol oxidation : effecf of reaction parameters on catalytic activity and selectivity

The oxidation of different alcohols with molecular oxygen in water has been investigated using a range of activated carbon-supported Au–Pd bimetallic catalysts. The effect of the Au–Pd ratio on the conversion and selectivity was observed and a synergistic effect is present in a large range of the Au–Pd ratio, being maximized for Au80–Pd20 composition instead of Au90–Pd10 shown in glycerol oxidation [A. Villa, C. Campione, L. Prati, Catal. Lett. 115 (2007) 133]. Moreover the enhancement of conversion observed by adding a base resulted greater for gold-rich catalysts rather than for palladium-rich ones. The effect of the alcohol concentration and the metal/substrate ratio in the presence or the absence of the base was also studied revealing substantial differences in terms of both activity and selectivity. At 1 M concentration under biphasic conditions benzyl alcohol has been selectively oxidized to benzaldehyde (S90 = 98%) even in the presence of NaOH with a TOF of 18,000 h−1 using Au60–Pd40/AC as the catalyst