Selective hydrogenation of acetylene (C2H2) to ethylene (C2H4) has been recognized as an important strategic reaction for the removal of trace acetylene from ethylene. Palladium‐based alloys are one of the most commonly used catalysts for this reaction but bear a high price and unsatisfactory catalytic performance. Here, we develop a feasible strategy toward the synthesis of a palladium‐silver dilute alloy catalyst (PdxAg/Al2O3), which contains the Pd1Ag single‐atom‐alloy (SAA) and Pd2Ag dimer‐alloy (DA) species. This catalyst exhibits a high ethylene (C2=) yield of 90.1 % even after 100 hours at 60 °C, which is 11.9 times higher than that of the PdAg/Al2O3 alloy catalyst. Based on in‐situ spectroscopic investigations and theoretical calculations, both Pd1Ag SAA and Pd2Ag DA species in PdxAg/Al2O3 are easier to desorb C2H4 compared with PdAg/Al2O3, and they experience the possible hydrogenation paths with the low energy barriers to yield C2=. Furthermore, PdxAg/Al2O3 is beneficial to restraining coking due to the endothermic C−H bond cleavage. Thus, these combined merits contribute to the superior catalytic performance for PdxAg/Al2O3.

Alumina is widely used as support in the industrial catalytic process. As a common impurity, the sulfur species, which are often considered a harmful component, play a positive role in some petrochemical reactions. Herein, the S-modified catalysts were fabricated using the exogenous/endogenous deposition method to study the effect of the sulfur induced by introduction approaches. Series characterizations reveal that the exogenous sulfur from the sulfidation treatment affects the active metals by poisoning the low-coordinated sites, leading to the active metal sites decrease. As for the endogenous deposition method, besides the poison effect, the removal of the endogenous sulfur from the S-contain alumina support can produce oxygen vacancies, which can not only act as acid sites but work as an electron acceptor that optimizes the catalyst electronic structure. Benefits from the effect of endogenous sulfur, the catalyst with a suitable catalytic metal/acid microenvironment exhibit the best dehydrocyclization performance.