Inhibiting COx formation on WOx-loaded Au/TiO2 photocatalyst for selective oxidation of p-xylene to p-methyl benzaldehyde

Photocatalytic selective oxidation of p -xylene with O 2 offers a mild pathway to synthesize p -methyl benzaldehyde ( p -MBA), which is one of the primary precursors in the manufacture of fine chemicals. Here, we report that Au/WO x /TiO 2 photocatalyst selectively catalyzes the oxidation of p -xylene to p -MBA with 88.6% selectivity at 1.0% conversion, the formation of CO x is suppressed to 0.8%. Kinetic experiments indicate that p -methylbenzyl alcohol and p -MBA are initial products. p -Methylbenzyl alcohol is further oxidized to form p -MBA, p -methylbenzyl acid and CO x ; p -MBA is further oxidized to p -methylbenzyl acid and CO x . On TiO 2 surface, p -methylbenzyl alcohol is more prone to directly combust to CO x by O 2 – . Loading of WO x can weaken the adsorption ability of p -methylbenzyl alcohol on the catalyst surface to avoid the combustion. Meanwhile, WO x and Au can facilitate the separation of photo-generated carriers to attain high activity and suppress the O 2 – formation to obtain high selectivity.