Single-atom Au atomically trapped in WO3− catalyst for selective demethoxylation of lignin-derived guaiacols

Utilizing the reducibility of oxygen vacancies and the low hydrogenation of single metal atoms, Au atoms automatically trapped in WO3-x. The resultant catalyst was characterized by many technologies to analyze its structure and morphology and exhibited high activity in the demethoxylation of 4-propylguaiacol, which was attributed to the synergistic effect between single Au atom and oxygen vacancy. The presence of Au enhanced the hydrogen dissociation but its single atom had a low hydrogenation activity, resulting in the total monophenols selectivity and yield of 98.3% and 94.2% at 225 °C, respectively. This Au/WO3-x catalyst also exhibited high stability: both the demethoxylation activity and structure were almost unchanged after 5 cycle runs. This preparation method was suit to fabricate other analogous catalysts such as Pt/WO3-x-R, Pd/WO3-x-R, Ir/WO3-x-R and Ru/WO3-x-R with high demethoxylation activity. In addition, other lignin-derived guaiacols were also successfully converted into the corresponded monophenols on Au/WO3-x catalyst. This study applied single atom catalyst into the demethoxylation of guaiacols, which provided a universal method to fabricate single metal atom trapped in WO3-x catalysts towards upgrading lignin-derived bio-oil into value-added chemicals.