C2H2 Semi-hydrogenation over S-modified PdM IMCs: Tuning catalytic performance by surface S Atom, and metal M type and ratio

The space region of metal active site and metal types and ratios plays a crucial role in tuning product selectivity based on the molecule size of target product and by-product. This work employs DFT calculations and microkinetic modeling to perform C2H2 semi-hydrogenation over a series of S-modified PdM IMCs with different M types (Cu, Ag and Au) and ratios (1: 1, 3: 1 and 1: 3). The results show that the catalytic performance of C2H2 semi-hydrogenation strongly depends on the space region of metal active site and the electronic properties induced by S atoms and the M type and ratio. Only S/Pd1Ag1 and S/Pd1Au1 are screened out to show higher H-2 dissociation activity, C2H4(g) selectivity and production activity, moreover, green oil can be well inhibited. Compared to Pd1Ag1 and Pd1Au1, the d-band center over S/Pd1Ag1 and S/Pd1Au1 farther away from the Fermi level increased C2H4(g) selectivity and production activity. More importantly, the greatly decreased space region of active site over S/Pd1Ag1 and S/Pd1Au1 caused by S atoms inhibited green oil production. This finding in this work provides the valuable theoretically structural information for designing and screening PdM catalysts by S modification in alkyne semi-hydrogenation.