Search

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]

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]

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]

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]

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]

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]

• Intermetallic Pd-Sn catalysts with designed composition are successfully synthesized. • A composition-performance relationship was established to demonstrate acetylene conversion, ethylene selectivity and stability. • |Eads(C2H2)-Eads(C2H4)| was used as a unified descriptor for the intrinsic catalytic properties of Pd-Sn catalysts. • This research provides an insight into the design principle of hydrogenation catalysts with desirable activity and selectivity. In Pd catalyzed acetylene semi-hydrogenation, high selectivity always comes at the expense of activity while improving both selectivity and activity is challenging. In this work, the performance of Pd alloy catalysts was enhanced by inserting Sn phase to modify both surface Pd ensembles and electronic structures. Compared with Pd/C, the optimal Pd 2 Sn/C catalyst exhibits higher selectivity at the same acetylene conversion level, with its selectivity increased from 10 % to nearly 95 % at ca 100 % acetylene conversion. Both experimental and DFT calculation results reveal that the specific performance is attributed to the redispersion of surface Pd ensembles by Sn insertion and down-shift of d-band center of catalysts, thus changing the adsorption behavior of the reaction gases. This design principle provides an efficient method for tailoring and optimizing durable Pd-based catalysts with desirable reactivity and ethylene selectivity for selective hydrogenation of acetylene. [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]