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Vinyl chloride, the monomer of polyvinyl chloride (PVC), is industrially synthesized via acetylene hydrochlorination. Thereby, easy to sublimate but toxic mercury chloride catalysts are widely used. It is imperative to find environmentally friendly non-mercury catalysts to promote the green production of PVC. Low-cost copper-based catalysts are promising candidates. In this study, phosphorus-doped Cu-based catalysts are prepared. It is shown that the type of phosphorus configuration and the distribution on the surface of the carrier can be adjusted by changing the calcination temperature. Among the different phosphorus species, the formed P-C bond plays a key role. The coordination structure formed by the interaction between P-C bonds and atomically dispersed Cu2+ species results in effective and stable active sites. Insights on how P-C bonds activate the substrate may provide ideas for the design and optimization of phosphorus-doped catalysts for acetylene hydrochlorination. Copper-based catalysts are widely investigated for the industrially important hydrochlorination of acetylene (PVC production), whereby phosphorus-doped carbon supports have been found to improve the catalyst's properties. Here the interaction between the P-C bond and atomically dispersed Cu2+ species is clarified and the reaction path of C2H2 and HCl revealed. [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]