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• 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]

Graphical abstract Highlights • Supported-ionic-liquid-phases as stabilizer of Pd complex active phase. • Different Pd loadings were screened to identify an optimized Pd-based supported-ionic-liquid-phase catalyst. • The catalyst showed superior catalytic activity for acetylene hydrochlorination. • The catalyst displayed stable performance after running for 500 h. • The enhanced catalytic stability may attribute to the confinement of Pd complex. Abstract Vinyl chloride monomer (VCM) is an important platform molecule for the manufacture of polyvinyl chloride (PVC) via the direct hydrochlorination route from acetylene. However it is plagued by the toxicity of the mercury chloride (HgCl 2) catalyst. Here we show that a 0.5Pd-10IL/AC catalyst, working as an environmentally friendly and highly efficient catalyst in supported-ionic-liquid-phase (SILP) system, is an plausible alternative for the commercially used HgCl 2 catalyst for acetylene hydrochlorination. It performs higher activity and more stable conversion than ionic liquid (IL)-free 0.5Pd/AC catalyst during a 10 h reaction. Furthermore, the low-loading 0.15Pd-10IL/AC catalyst demonstrates a stable catalytic performance with a negligible loss of C 2 H 2 conversion after 500 h under typical industrial reaction conditions. After careful characterization of the catalysts and additional catalytic tests, we ascribe the IL influence on the activity and stability of the catalysts to the stabilization and dispersion of active Pd species in the IL layer, the possible coordination of the IL to the Pd atoms, and the confinement of Pd complexes within the pores supports. This efficient and stable non-mercury catalyst provides an opportunity for green route to large-scale vinyl chloride production. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped carbons supported gold catalysts has attracted much attention in a broad range of applications. However, co‐existence of multiple nitrogen species which may have vastly different effect on the gold‐based catalysts, has limited the development of an ideal nitrogen‐doped carbon support. Herein, we have demonstrated that by addition of sulfur species, selective formation of pyrrolic nitrogen against pyridinic nitrogen can be achieved for pyrrolic nitrogen doped carbon support. The gold catalysts synthesized from the pyrrolic nitrogen doped carbon support produced using ionic liquid‐assisted synthetic strategy (Au/N, S‐AC‐700), exhibited excellent catalytic activity and stability for hydrochlorination of acetylene. The outstanding performance was attributed to the π electrons transferred from pyrrolic nitrogen to Au (III) center, which could increase the electron density of Au hence facilitate the adsorption of hydrogen chloride on the catalyst. Green economy? Carbon with surface‐enriched nitrogen and sulfur supported Au catalysts was developed for acetylene hydrochlorination. The presence of sulfur species on the carbon surface inhibited the formation of pyridinic N which was not necessary for the hydrochlorination of acetylene. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate that the less toxic, relatively safe, and recyclable organic aqua regia (OAR) can be employed as a greener alternative solvent to conventional aqua regia to activate Au/AC catalysts for the hydrochlorination of acetylene. We show that Au-based catalysts prepared with HAuCl 4 as precursor can be prepared initially in water (Au(H 2 O)/AC). Although catalysts prepared from aqueous HAuCl 4 showed poor activity, it can be significantly enhanced by catalyst activation in OAR (Au(H 2 O)/AC(OAR)). In contrast to the catalyst activation procedure using aqua regia (Au(aq)/AC), we demonstrate that the new activation procedure leads to both improved activity and stability of the resulting Au(H 2 O)/AC(OAR) catalyst. Further analyses of X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) show that the variations of Au particle size and chemical state caused by OAR treatment promote Au oxidation and high dispersion. In addition, temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) indicated that the presence of residual sulfur and nitrogen species may help stabilize the cationic Au 3+ species and generate a catalyst less prone to deactivation by increasing the reduction temperature of the Au 3+ species and enhancing the adsorption of hydrogen chloride over the Au(H 2 O)/AC(OAR) catalyst. These results suggest that OAR can be substituted for conventional solvents to activate Au/AC catalysts for the hydrochlorination of acetylene. [ABSTRACT FROM AUTHOR]

The synthesis of vinyl chloride from acetylene by hydrochlorination has gained tremendous interest in coal-based chemistry. Bimetallic gold-cesium(I)/activated carbon (Au-CsI/AC) catalysts were found to have a higher catalytic activity and stability for acetylene hydrochlorination when compared with gold catalysts. Over 1 Au-4CsI/AC catalysts, the maximum conversion of acetylene was 94% and there was only 5% C2H2 conversion loss after 50 h of running time. Moreover, the 1 Au-4CsI/AC catalyst delivered a stable performance during a 500 h test with the conversion of acetylene and the selectivity of vinyl chloride reaching more than 99.8 and 99.9 %, respectively. Temperature- programmed reduction of H2, temperature-programmed desorption of C2H2, and X-ray photoelectron spectroscopy techniques were further applied to detect structural information on the Au-CsI/AC catalysts. Additives of CsCl indeed stabilized the catalytically active Au3+ species and inhibited the reduction of Au3+ to Au0, thereby improving the activity and long-term stability of gold-based catalysts. [ABSTRACT FROM AUTHOR]

Themain goal of this work is to study the relationship betweenthe surface chemistry of activated carbon (AC) and the performanceof respective gold-supported catalysts in the acetylene hydrochlorination.For this purpose, a set of modified activated carbons with differentlevels of oxygenated groups on the surface, but with no major differencesin their textural parameters, was prepared. A strong effect of thesurface chemistry of activated carbon on the Au/AC catalytic activitywas observed. Comparison of characterizations, catalytic results,and DFT calculations suggests that phenol, ether, and carbonyl groupson activated carbon surface are the key members governing the uniquecatalytic activity and stability of Au3熫媗⬭. Thecomprehensive experimental and theoretical study of the surface chemistryof Au3닪榢뭞 on activated carbon support is believedto be of great benefit for the rational design of gold–carboncomposite catalysts for acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

Development of a sustainable process for designing and synthesising an active and stable catalyst for hydrochlorination of acetylene is challenging, yet crucial, for industrial vinyl chloride monomer (VCM) production. Herein, direct synthesis of bimetallic AuCu catalysts using organic aqua regia (OAR) preparation methods was investigated. In comparison with conventional aqua regia (AR), bimetallic AuCu catalysts synthesised from OAR exhibit enhanced activity and stability. After careful characterisation of the catalyst samples using X-ray diffraction patterns (XRD), Scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), and Temperature-programmed desorption (TPD), this observation was justified for the following reasons: 1) the existence of sulphur and nitrogen atoms stabilised the cationic Au active sites, and 2) OAR helped to sustain the function of the Cu promotor by stabilising it. Advanced understanding on the importance of promoter stability has unveiled new perspectives for this research area. [ABSTRACT FROM AUTHOR]

The front cover artwork for Issue 03/2019 is provided by researchers from Industrial Catalysis Institute, Laboratory Breeding Base of Green Chemistry‐Synthesis Technology, Zhejiang University of Technology (P. R. China). The image shows carbon with surface‐enriched nitrogen and sulfur supported Au catalysts for acetylene hydrochlorination. The sulfur species on the carbon surface was considered to be able to selective formation of pyrrolic nitrogen against pyridinic nitrogen, which significantly influence the catalytic performance of Au‐based catalysts.. See the Full Paper itself at https://doi.org/10.1002/cctc.201801555. "An innovative strategy that tunes the nitrogen speciation" This and more about the story behind the research featured on the front cover can be found in this issue's Cover Profile. Read the full text of the corresponding research at https://doi.org/10.1002/cctc.201801555. [ABSTRACT FROM AUTHOR]

The Front Cover shows carbon with surface‐enriched nitrogen and sulfur supported Au catalysts for acetylene hydrochlorination. In their Full Paper, Bolin Wang et al. demonstrate that the sulfur species on the carbon surface was considered to be able to selective formation of pyrrolic nitrogen against pyridinic nitrogen, which significantly influence the catalytic performance of Au‐based catalysts. More information can be found in the Full Paper by Bolin Wang et al. on page 1001 in Issue 3, 2019 (DOI: 10.1002/cctc.201801555). [ABSTRACT FROM AUTHOR]

A systematic study of the kinetics of supported-ionic-liquid-phase (SILP) Au catalysis (Au-IL/AC) has been established in the continuous gas-phase hydrochlorination of acetylene. We reveal that the effect of ionic liquid (IL) film on substrate diffusion can be eliminated. The reaction order of the catalyst indicates that Au is confirmed to exist as a monomer in the IL film of the Au-IL/AC system, which is different from the fast equilibrium of the "Au dimer and monomer" for the classical Au/AC catalyst. The homogeneous reaction micro-environment is confirmed for Au-IL/AC since the activation energy was little changed under both heterogeneous and homogeneous catalysis, further verifying the monatomic characteristics of Au in Au-IL/AC. Due to the supported IL film, the reaction order of hydrogen chloride was decreased from 1 to 0.5 while creating a hydrogen chloride enrichment system around Au, which provides the possibility of producing vinyl chloride with an equal substrates feed ratio. This kinetic-perspective-based revelation of the catalytic behavior of the metal active sites confined in IL film enriches and expands the SILP catalytic system for acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

• Nitrogen-doped carbon catalysts with a layered structure were synthesized by the dual-template method. • An efficient non-metallic catalyst for the environmentally friendly synthesis of acetylene hydrochlorination. • Catalysts with higher specific surface area and nitrogen content exhibit superior catalytic performance. • The protonated pyridinic nitrogen and pyridinic N + O exhibit moderate adsorption strength towards hydrochloric acid, serving as active sites for the catalyst. Non-metallic catalysts present significant potential for environmentally friendly industrialization of acetylene hydrochlorination. However, the challenge of low activity in non-metallic catalysts hampers their practical application. In this study, we propose the use of a dual-template method to fabricate a layered N-doped carbon catalyst, subsequently applying it to acetylene hydrochlorination reactions. Experimental results indicate that the catalyst exhibits exceptional catalytic performance in acetylene hydrochlorination. Combined with characterization results, the catalyst's performance is positively correlated with its surface area and nitrogen content. Furthermore, DFT calculations suggest that protonated pyridinic nitrogen and pyridinic N + O − have moderate adsorption on HCl, potentially serving as active sites for the catalyst. This study analyzes the impact of various parameters of N-doped carbon catalysts on catalytic performance, providing direction for developing non-metallic catalysts suitable for industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • Inactive Au/TiO 2 can be activated by Cl radicals. • Once Cl is consumed, the reaction will be terminated, although a large amount of supported cationic Au remains. • The Au(I)–Au(III) redox couple is responsible for triggering the reaction. Supported cationic gold (Au) has been recognized as an active site of acetylene hydrochlorination for decades; however, it remains ambiguous why its loading on carbon-based materials is active but that on metal oxides (e.g., titania, TiO 2) is virtually inactive. For the inactive Au/TiO 2 catalyst, the Au(I)–Au(III) redox couple cannot be constructed in the presence of oxidizing gas (NO, N 2 O, and NO 2), which is thermally desorbed from the catalyst synthesis when aqua regia is used. Surprisingly, the inactive Au/TiO 2 can be activated when it is impregnated with trichloromethane, CHCl 3 , which releases the radical (Cl) to trigger the Au(I)–Au(III) redox couple. Once Cl radicals are consumed, the reaction will be terminated, although a large amount of supported cationic Au remains. The terminated Au/TiO 2 catalyst can be reactivated by adding Cl again. In contrast to the carbon-supported cationic Au system, the inability to build Au(I)–Au(III) redox couples is the dominant reason for the inactivity of metal-oxide-supported Au catalysts and provides a new perspective on activating metal-oxide-supported metal-based hydrochlorination catalysts. [ABSTRACT FROM AUTHOR]

Ru-Based catalysts with distinct active phases from Ru0, to RuO2, RuCl3 and RuCl2N were synthesized and evaluated in acetylene hydrochlorination. RuCl2N is identified as the efficient active phase due to its co-activation of acetylene and hydrogen chloride. This discovery holds great potential to accelerate the large-scale application of Ru-based catalysts in industry. [ABSTRACT FROM AUTHOR]

Boron-doped carbon nanodot materials, comprising evenly distributed BC3-nanodots in a layered carbon matrix, are prepared through a pre-assembly assisted carbonization synthetic strategy. The prepared materials are endowed with high electron affinity and distortion resistance, which provides a stable framework while generating affinity to substrates. [ABSTRACT FROM AUTHOR]

Enhancement of the sulfur resistance of gold-based catalysts is significantly relevant and highly desirable for the development and large-scale applications of these catalysts. In this study, a supported gold-based imidazolium ionic liquid catalyst was shown to be ultra-high resistant towards sulfur poisoning during the acetylene hydrochlorination reaction. To explore the impact of H2S on the as-prepared catalysts, accelerated laboratory-scale poisoning tests were performed, and characterization was achieved by various instruments. The adsorption of H2S on the active sites of Au/AC catalysts, occupying gold species, prevented the reactants, including C2H2 and HCl, from being adsorbed on the catalyst surface. With respect to the Au–IL/AC catalysts, the unique Au–IL colloid complexes, formed from ionic liquids, impart resistance towards H2S; moreover, the ionic liquid layer on the activated carbon surface can prevent the deposition of sulfur impurities on catalysts; in addition, the adsorption of H2S on the ionic liquid layer is a dynamic equilibrium process, and the adsorption equilibrium constant at 180 °C (453 K) is 0.24 L mg−1. The interaction between H2S and the ions in the ionic liquid is weaker than the binding force within ions in the ionic liquid itself. [ABSTRACT FROM AUTHOR]

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]

Au catalysts supported with carbon‐based carriers have been extensively studied for the hydrochlorination of acetylene and expected to replace toxic mercury catalysts. However, removal of the highly corrosive aqua regia used in the preparation of carbon‐based catalysts while maintaining catalytic activity and stability remains a key challenge. Herein, we present a green technology carrier, activated carbon fibers (ACF), to support gold catalysts for the hydrochlorination of acetylene. TPD and XPS analyses confirmed the presence of surface oxygen‐containing functional groups (SOGs) and pyrrolic N species on the ACF. The Au/ACF−H2O catalyst exhibited better catalytic activity and stability than Au/ROX0.8(AQ)−H2O. Characterization results revealed that the catalytic properties of Au/ACF−H2O could be attributed to the anchoring and stabilization of gold active species on the SOGs, leading to atomic dispersion, and to the improvement of HCl adsorption with the synergistic effect of electron‐donating pyrrolic N groups. The results indicated that usage of this green carrier can be considered as the a new approach to reduce or eliminate the use of strong oxidizing reagents in the preparation of Au catalysts. [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]

Activated carbon fiber (ACF) carbon materials with different graphitization degrees were prepared by impregnation with iron salt solutions, where the graphitization degree was found to increase with the elevated impregnation concentration. Examining these materials for acetylene hydrochlorination demonstrated that their catalytic performances do not monotonically depend on the graphitization degree. Both density functional theory (DFT) calculations and experimental results revealed that the interface between the graphite layer and the support serves as the catalytic active site, and further clarified that the difference in the degree of exposure of the active interface results in the difference in catalytic activity. [Display omitted] • This synthetic method can avoid the conventional high-temperature roasting. • The degree of graphitization affects the properties of catalysts. • Theoretical calculation reveals the model of the active sites. • The degree of active site exposure has a significant effect on catalytic performances. [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]

Adsorption and activation for substrates and the stability of Pd species in Pd-based catalysts are imperative for their wider adoption in industrial and practical applications. However, the influence factor of these aspects has remained unclear. This indicates a need to understand the various perceptions of the structure–function relationship that exists between microstructure and catalytic performance. Herein, we revisit the catalytic performance of supported-ionic-liquid-phase stabilized Pd-based catalysts with nitrogen-containing ligands as a promoter for acetylene hydrochlorination, and try to figure out their regulation. We found that the absolute value of the differential energy, |Eads(C2H2)-Eads(HCl)|, is negative correlated with the stability of palladium catalysts. These findings imply that the optimization of the electron structure provides a new strategy for designing highly active yet durable Pd-based catalysts. [ABSTRACT FROM AUTHOR]

We studied the acetylene hydrochlorination in gas–liquid phase reactions using ionic liquids (IL) as the reaction media and CuCl2 as the catalyst. The Cu-IL catalyst showed strong synergy between the IL and the Cu(II) active catalytic species. For [PrMIm]Cl, the Cu-IL catalyst exhibited significant enhancement of the catalytic activity in comparison with the CuCl2 catalyst supported on activated carbon and the IL alone as the catalyst. We have also performed DFT calculations of the reaction process, which provides a good explanation of our experimental results and for the synergetic effect. Our result suggests that ILs may be used to improve the activity of other metallic catalysts for the hydrochlorination reaction of acetylene. [ABSTRACT FROM AUTHOR]