Catalytic performance of a single atom Pd1Ag10/Al2O3 catalyst for the selective hydrogenation of acetylene: The role of CO-induced segregation

The single-atom Pd catalysts based on silver-rich bimetallic compositions are known for their extremely high ethylene selectivity in the acetylene hydrogenation reaction; however, their activity is noticeably lower than that of traditional monometallic Pd catalysts. The aim of the work was to apply a method of CO-induced segregation to increase the concentration of single atom Pd-1 sites on the surface of Pd1Ag10/Al2O3 catalyst without noticeable formation of multiatomic Pd-n (n >= 2) ensembles. It has been experimentally established by DRIFTS-CO and XPS methods that the effect of 30 vol% CO exposure temperature on the increase of surface Pd-1 sites concentration in the range of 50 to 350 degrees C has a volcano-like dependence with a maximum at similar to 200-250 degrees C. The catalytic tests show a considerable enhancement in activity for samples treated in CO at 200-250 degrees C (the temperature of 100 % acetylene conversion is reduced by similar to 30 degrees C), while the C2H4 selectivity was similar for both freshly reduced and CO-treated catalysts. These results demonstrate the use of CO-induced segregation as a promising method for the controlled increase in the concentration of isolated Pd-1 sites to improve the activity of silver-rich palladium catalyst without compromising its selectivity.