How Recyclability can Reduce Induction Period of Gold Nanocatalysts

The effect of recyclability on the catalytic activity of supported Au101(PPh3)21Cl5 nanoparticles (1.0 wt% Au101/AC) was investigated for benzyl alcohol oxidation under mild conditions. The influence of recyclability on the catalytic activity of activated Au101/AC nanocatalysts was studied trough a comparison of gold particle diameter and also catalysts conversion between the fresh (as synthesized) and recycled gold catalysts. The monitoring of gold particle diameters by transmission electron microscopy (TEM) showed that the gold particles size gradually increased during the catalytic reaction. The mean diameter of the fresh gold catalysts increased from approximately 3 to 3.2, 5.1 and 5.3 nm after 1, 2 and 3 h reaction time, respectively. Whereas the average gold particle diameter of the recycled samples were slightly enlarged from approximately 5.3 (the sample recycled after 3 h of the first catalytic test) to 5.7, 5.9 and 6.2 nm with durations of 1, 2 and 3 h reaction time, respectively. Therefore, larger gold particles gradually formed for fresh and also recycled gold catalysts during reaction tests. Meanwhile, the catalytic activity of activated 1.0 wt% Au101/AC catalysts jumped to full conversion when the recycled gold catalysts were utilized due to removing ligand stabilizer from gold particles and so bigger particles had formed.