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Ru-based catalysts have shown great potential for the environmentally friendly industrialization of acetylene hydrochlorination. However, the high cost and reduction of active sites in Ru catalysts have limited their practical applications. In this study, we propose a strategy to optimize the electronic structure of Ru single-atom catalysts by leveraging the strong coordination ability of ligands with the metal and apply this strategy to acetylene hydrochlorination. The experimental results verify that the performance of the catalyst increases with the increase of the ligand. Characterization results indicate that ligands not only optimize the electronic properties of Ru single atoms by forming a RuCl 2 -N structure, but also enhance the adsorption of reactants on the catalysts. DFT calculations reveal that the ligand-modified Ru species can efficiently adsorb and activate acetylene molecules, while the adjacent excessive ligand can adsorb and dissociate HCl molecules. This ultimately leads to an addition reaction between acetylene and HCl through a hydrogen overflow mechanism. [Display omitted] ● The single-atom catalyst with RuCl 2 -N structure are successfully synthesized. ● Enhances catalyst stability by optimising the electronic structure of Ru single atoms. ● Pre-dissociative activation of HCl facilitates the acetylene hydrochlorination reaction. ● This research provides an insight for the design of non-mercury catalysts for vinyl chloride. [ABSTRACT FROM AUTHOR]

There is great potential for carbon-supported gold catalysts to replace toxic mercuric chloride-based catalysts in the acetylene hydrochlorination, which is a key process for producing PVC. However, the catalyst design is essentially hindered by the difficulties in enhancing the catalytic activity of cationic gold and suppressing the deactivation of active species. We report a strategy for self-oxidation of Au3+ by the Au-SILP system with the [Bmim][Cl 3 ] ILs. This strategy can stabilize all gold species in the state of highly oxidized Au3+ instead of coexisting in the Au3+/Au+ site, which makes the catalyst exhibit excellent catalytic activity. High coordination numbers Au-Cl entities reduce the electron transfer between Au3+ and C 2 H 2 and weaken the adsorption of C 2 H 2 on the Au active sites. Furthermore, [Bmim][Cl 3 ] ILs can self-oxidize gold nanoparticles on the support surface into Au3+. This study provides a new method for improving the stability and activity of gold-based acetylene hydrochlorination catalysts. [Display omitted] • The self-oxidation of Au3+ catalyst are successfully synthesized. • Self-oxidation of high-valence gold via sacrificial [Bmim][Cl 3 ] high activity and long lifetime catalyst design of Au-SILP catalysts. • High coordination numbers Au-Cl entities reduce the electron transfer between Au3+ and C 2 H 2 and weaken the adsorption of C 2 H 2 on the Au active sites. [ABSTRACT FROM AUTHOR]

• Nitrogen and phosphorus codoped carbon-based catalyst was successfully prepared. • Catalysts with NP-C600 gave excellent activity and stability for acetylene hydrochlorination. • The conversion of C 2 H 2 over NP-C600 is almost identical to that over Au/C. • Phosphorus atoms bonded with nitrogen in a pyridine structure are the active sites for the best-performing NP-C600 catalyst. Catalyzed acetylene hydrochlorination for vinyl chloride monomer (VCM) production is of great industrial importance, as VCM is the precursor for polyvinyl chloride. Carbon-based materials have recently been proposed as environmentally friendly and cost-efficient substitutes for highly toxic mercuric chloride catalyst, which is currently used for VCM manufacture. However, their practical application has been limited because of their relatively low reactivity, due to the lack of efficient active sites. Structural engineering of carbon-based materials has been proved a powerful strategy for tuning their physical and chemical properties, which are directly related to their catalytic properties. Here we present a novel and highly active nitrogen- and phosphorus-codoped carbon-based catalyst prepared using 1-ethylsulfonate-3-methylimidazolium dihydrogen phosphate [ESO 3 HMim+H 2 PO 4 −] as a phosphorus source and 1-ethyl-3-methylimidazolium dicyanamide [EMim]+N(CN) 2 −] as a nitrogen source, which has shown unexpectedly high acetylene hydrochlorination activity with space-time yield comparable to that of some well-developed Au-based catalysts. Experimental observations in combination with density functional theory calculations demonstrated that phosphorus atoms bonded with nitrogen in the pyridine structure are the active sites for the best-performing NP-C600 catalyst. This work provides a promising method of structure tuning of carbon-based metal-free materials to effectively optimize their catalytic mechanism and applications. [ABSTRACT FROM AUTHOR]

• Palladium-based catalysts with distinct nanostructures are successfully synthesized. • Pd SAC exhibits excellent activity and stability for acetylene hydrochlorination. • Pyridinic nitrogen is responsible for stabilizing palladium species. • Reaction mechanism is affected by pyridinic nitrogen. Alternative palladium (Pd)-based catalysts to toxic mercuric chloride catalysts in vinyl chloride manufacture via acetylene hydrochlorination is currently limited by the lack of efficient and durable active sites. Here, the catalytic behavior of Pd-based catalysts with tunable nanostructures and coordination bonds were investigated. The evolution of Pd entities were precisely regulated by controlled thermal treatment. Pyridinic nitrogen is shown to regulate the nanostructures and coordination bonds of Pd sites, improve the thermal stability of Pd atoms, promote the adsorption of acetylene and enrich hydrogen chloride. These results indicate that Pd single-atom is more active than Pd nanoparticle or Pd cluster. The catalytic performance of Pd single-atom catalyst can be further improved by substituting Pd-Cl bond with Pd-N bond, with PdN 2 identified as the efficient and durable active sites. Furthermore, the enrichment of hydrogen chloride enables the Pd single-atom catalysts to produce vinyl chloride via a non-hydrogen chloride excess method, which is a breakthrough in the existing industrial system. Our strategy for controlling the catalytic behavior of Pd sites is of a broad application prospect for the precise control and design of metal active sites. [ABSTRACT FROM AUTHOR]