C2H2 selective hydrogenation over the Pd and S-modified Pd catalysts: Unraveling the role of Pd active site spatial scale caused by S atom in adjusting catalytic performance

Adjusting the active site spatial scale is an effective way to regulate catalytic performance. In this study, combining DFT calculations with microkinetic modeling, the Pd catalysts and S-modified Pd (S/Pd) catalysts were considered. Here, Pd and S/Pd catalysts were simulated by different supercells and different surface S coverage, respectively. The role of S coverage on Pd surface in adjusting Pd active site spatial scale to regulate catalytic performance of C2H2 selective hydrogenation was fully investigated. Our results showed that the catalytic performance closely depend on Pd active site spatial scale caused by the coverage of surface S species due to the change of geometric and/or electronic effects caused by S atom. S/Pd-2 x 2 catalyst with S coverage of 1/4 ML and Pd active site spatial scale of 2.691 & ANGS; is screened out to simultaneously achieve the best C2H4 activity and selectivity, as well as the effective prevention of green oil to present excellent catalyst stability, which is attributed to the synergetic geometric and electronic effects caused by S atom. The comparisons between S/Pd and S/Cu catalysts showed that the effect of metal active site spatial scale caused by S atom on catalytic performance still strongly depend on the type of metal catalysts. This study gives a theoretical insight for promoting the target reaction required smaller active site spatial scale and suppressing the side reaction required larger active site spatial scale, in which the active site spatial scale can be reasonably adjusted by changing the coverage of surface S species over the metal catalysts.

Automated summary

In this study, the role of S coverage in adjusting the active site spatial scale of Pd catalysts was investigated for regulating the catalytic performance of C2H2 selective hydrogenation. It was found that the catalytic performance strongly depends on the Pd active site spatial scale, which is influenced by the coverage of surface S species. The S/Pd-2 x 2 catalyst with a S coverage of 1/4 ML and a Pd active site spatial scale of 2.691 Å showed the best C2H4 activity and selectivity, as well as excellent catalyst stability.