Search

Acetylene hydration to acetaldehyde is considered as a valuable and potential production route in the acetylene chemical industry. In this work, Zn-La bimetallic catalysts were prepared to improve the catalytic performance and long-term stability of Zn catalyst in the acetylene hydration, and the influence of the impregnation order for the metal components on the catalytic activity of the Zn catalyst was investigated. Moreover, the physicochemical properties of Zn-La bimetallic catalysts could be characterized by XRD, BET, TGA, TEM, XPS, H2-TPR, C2H2-TPD, and ICP-OES. The study indicated that LaCl3 additive could markedly improve the catalytic performance and stability of the Zn catalyst, and the optimal addition amount of LaCl3 was 3 wt%. The characterization results showed the addition of the La additive resulted in strong interaction in the bimetallic catalysts, which can not only enhance the adsorption of reactant acetylene but also improved the dispersion of metal components, effectively inhibited carbon deposition, and prevented the loss of Zn components would contribute to the high performance and stability of bimetallic catalysts. Furthermore, first impregnation ZnCl2 component then that of LaCl3 component could gain the high-performance and stability bimetallic catalyst in the hydration of acetylene. The La additive resulted in strong interaction in the bimetallic catalysts, which can not only enhanced the adsorption of reactant acetylene but also improved the dispersion of metal components, effectively inhibited carbon deposition, and prevented the loss of Zn components would contribute to the high performance and stability of bimetallic catalysts. [ABSTRACT FROM AUTHOR]

Defect sites and nitrogen species in carbon materials directly affect their catalytic activity for acetylene hydrochlorination. However, there is often a negative correlation between the increase of defect sites and nitrogen species. Usually, increasing the density of defect sites by improving the calcination temperature often results in a decrease in the content of nitrogen species. Therefore, it is an important design strategy to improve the active sites of the catalyst by creating abundantly inherent defect sites. In this paper, rosette-like nitrogen doped mesoporous carbon materials (NPCs-T) were synthesized by a self-assembly method. NPCs-T materials have more defect sites than conventional spherical materials. The structure–activity relationship of catalytic performance and nitrogen species demonstrates that pyridine N and pyridinic N+O− are the main active sites. In addition, the synergistic effect of defect sites and suitable nitrogen species is beneficial to the adsorption and activation of acetylene and hydrogen chloride, thus promoting the reaction process of acetylene hydrochlorination. The application of rosette-like mesoporous carbon materials in the hydrochlorination of acetylene leads to outstanding reactivity and stability, stimulating their potential for industrial applications. [ABSTRACT FROM AUTHOR]

In the production of chloroprene rubber, acetylene dimerization over the Nieuwland catalyst is an important step. The addition of Mg2+ to the Nieuwland catalyst improves the acetylene conversion and the selectivity toward vinyl acetylene. In this study, active component crystal structure, the role of Mg2+ in the Nieuwland catalyst, the reason for the catalyst deactivation, and the reaction mechanism were analyzed by different characterization techniques. The results indicate that the main reason for the Nieuwland catalyst deactivation is the loss of Cu2+. The addition of Mg2+ will increase the exposure of active sites, reduce the residence time of acetylene in the catalyst, and inhibit the reduction of Cu2+, thereby improving the catalytic performance and stability of the catalyst. [ABSTRACT FROM AUTHOR]

Considering the economic and environmental advantages of water as a solvent and the drawbacks of Au catalysts prepared in an aqueous solution for acetylene hydrochlorination, such as easy aggregation of active components, insufficient active sites, and serious carbon deposition, supported gold catalysts were prepared by using an ice photochemical method (liquid nitrogen freezing and UV light irradiation). The appropriate ice-photochemical treatment results in ice lattice formation, which inhibits gold nuclei formation during the catalyst preparation and catalytic reaction. In addition, it limits the crystal phase change and aggregation of active species. The freezing and the energy absorbed by the gold component under irradiation at the exact wavelengths may produce a plasma effect on the surface of the Au component and promote the excitation of outer electrons of the Au nucleus to Cl, suppressing the transition of the dispersed atomic active species with a high valence state to the inert Au0 clusters. Therefore, the superior activity of the prepared catalysts Au/AC-F1I1 is probably caused by the synergistic adsorption and activation of reactants by the highly dispersed AuClx-like multi-sites, facilitating the rapid electrophilic addition reaction and impeding the carbon deposition, thus promoting the continuous exposure of active sites. The significantly improved activity and stability, and the environment-friendly preparation strategy provide new inspiration for the design and application of Au-based catalysts for acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

Improving dispersibility and stability of Cu(II)Cu(I)/activated carbon (AC) is a crucial aspect for enhancing its catalytic performance in the process of gas–solid acetylene dimerization. The Cu(II)Cu(I)/NAC-500 catalyst using nitrogen-modified AC (NAC) as a support, delivered excellent catalytic performance and stability vs undoped Cu(II)Cu(I)/AC at 100 °C and 120 h−1 of C2H2 gas hourly space velocity. Under the optimal conditions, the Cu(II)Cu(I)/NAC-500 catalyst exhibited a stable catalytic performance during a 10 h test with 65% C2H2 conversion; and the selectivity to monovinylacetylene (MVA) reached 86%. The existence of nitrogen species can increase the interaction between copper and the support, and increase dispersion of the copper species on the support, which were benefit for the catalytic performance. [ABSTRACT FROM AUTHOR]

A series of Cu‐pyrrolidone/spherical activated carbon (SAC) catalysts were prepared via a simple incipient wetness impregnation method and then assessed in acetylene hydrochlorination, and the catalytic evaluation result indicated that the 1‐methyl‐2‐pyrrolidinone (NMP) ligand was found to be the most effective one to significantly improve the activity and stability of Cu catalyst. The catalyst with the optimal molar ratio of NMP/Cu = 0.25 showed 94.2% acetylene conversion at 180°C and an acetylene gas hourly space velocity of 180 h−1. Moreover, the acetylene conversion of Cu‐0.25NMP/SAC remained stable over 99.1% for about 220 h under the industrial condition. Transmission electron microscopy (TEM) analyses proved that NMP ligand improved the dispersion of Cu species. In addition, hydrogen temperature‐programmed reduction (H2‐TPR), X‐ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), and Brunner–Emmet–Teller (BET) indicated that the additive of NMP was preferential to stabilize the catalytic active Cu+ and Cu2+ species and inhibit the reduction of Cuα+ to Cu0 during the preparation process and reaction, hence restraining the coke deposition. Furthermore, the steady coordination structure between Cu and NMP was confirmed by Fourier‐transform infrared spectra (FT‐IR) and Raman combining with density functional theory (DFT) calculation, which could effectively lower the adsorption energy of catalyst for C2H2 and inhibit the serious carbon deposition caused by excessive acetylene self‐accumulation. Our findings suggest that the efficient, well‐stabilized cost‐effective, and environmentally friendly Cu catalyst has great potential in acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

Acetylene dimerization is an important step in an acetylene-based process for chloroprene production, and the traditional catalyst for this transformation is the Nieuwland catalyst in a bubble column reactor. However, the drawbacks of this catalyst are the use of high concentration of a copper reagent, low acetylene conversion and monovinylacetylene (MVA) selectivity, and the difficulty to generate or reuse the catalytic system. Therefore, in this study, we first reported a gas–solid acetylene dimerization reaction by applying copper-supported catalysts, which were prepared via an impregnation technique using CuCl as the precursor. The catalytic activity was examined and discussed in detail by modification of the impregnation solvent, Cu loading amount, reaction temperature, and the acetylene gas hourly space velocity. Under optimal conditions, the catalyst exhibited a maximum acetylene conversion of 48.3% and a monovinylacetylene selectivity of 87.4%. The catalysts were characterized by TGA, XRD, H2-TPR, TEM, BET, XPS and ICP-AES. Not only the preparation, isolation and recycling of the supported catalyst were easy in the gas–solid reaction, but also the supported catalyst overcame the shortcomings of the liquid phase catalyst. The loss of the Cu active species is concluded to be the main factor causing the decrease in the catalytic activity. [ABSTRACT FROM AUTHOR]

Etidronic acid (HEDP) and Nitrilotri(methylphosphonic acid) (ATMP) were selected as heteroatoms‐containing ligands to modify Au catalysts for acetylene hydrochlorination. Results from several analytical methods reveal an optimal mole ratio of Au/ligand (L) of 1 : 1, with obvious increments over the Au1‐L1/AC catalyst. The coordination between the Au and the heteroatoms, especially the collocative presence of N, P, and O promoted electron transfer from the heteroatoms to the Aun+ and increased the density of the electron cloud around active centers. This stabilized the Aun+ and increased the difficulty in the reduction of Au species, and re‐oxidized the Au0 to active Aun+ species. Moreover, the coordination inhibited the migration of active components. The increased density of the electron cloud around active centers also weakens the adsorption capacity for C2H2 and strengthens the adsorption ability for HCl of the catalysts, which is conductive for constructing the micro‐environment favorable to the reaction. DFT calculations proved the stabilization effect of the heteroatoms‐containing ligands, and the energy sequence of the transition states supported the experimental results. [ABSTRACT FROM AUTHOR]

A series of Zn–Cu bimetallic catalysts were prepared and used as catalysts for acetylene hydration in our study, and the influence of a copper additive on the performance of zinc catalysts was studied in detail. The activity test results indicate that the addition of copper improved the activity and stability of the bimetallic catalysts. The best catalytic performance was obtained over a Zn–10Cu/MCM catalyst, which gave 98% acetylene conversion. The catalysts were characterised via temperature-programmed reduction, low-temperature N2 adsorption/desorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Analysis results indicate that the Cu interacted synergistically with Zn species and prevented Zn species loss during the reaction, thereby improving the catalytic activity and stability of the bimetallic catalysts for the hydration of acetylene to acetaldehyde. [ABSTRACT FROM AUTHOR]

We reported a novel in situ synthesis of ZIF-8 following carbonization route to modulate the morphology of spherical activated carbon (SAC). It is illustrated that the highly dispersed nanoparticles with the average size about 10.50 nm and bamboo-shaped carbon nanotubes (B-CNTs) with the average diameter of 40-80 nm were appeared on the surface of the modified SAC. Such modified SAC showed superior catalytic performance toward acetylene hydrochlorination, with the highest acetylene conversion of 81% and the selectivity to VCM above 99%. The enhanced catalytic performance is attributed that the highly dispersed ZIF-8-derived nanoparticles can easily generate more active sites, which can efficiently access to the reactants of hydrogen chloride and acetylene in acetylene hydrochlorination. Additionally, B-CNTs change the porosity of the materials, which inhibits the formation of coke deposition. TPD and TGA analysis results also prove that the optimal 17% ZIF-8/SAC catalyst can not only enhance the adsorption of reactants, but also inhibit the adsorption of product, resulting in the decrease in the amount of coking deposition. Such synthetic approach is promising to be applied in morphological modulation of other porous materials. [ABSTRACT FROM AUTHOR]

A series of catalysts with different ruthenium and chloride ratios were prepared and evaluated in the acetylene hydrochlorination reaction, in combination with several characterization techniques. The results indicate that the catalyst with the optimum ratio of Ru/Cl = 5/7 exhibits the highest initial acetylene conversion above 96.1% at 180 °C, an GHSV(C2H2) of 180 h−1, and a feed ratio VHCl/VC2H2 of 1.15. Appropriate coordination numbers of ruthenium and chloride could increase the amount of ruthenium oxides, improve the dispersion of Ru species on the carrier and enhance the adsorption ability of the catalyst, consequently improving the catalytic performance. TPPB additives can further enhance the activity and stability of the catalyst, which also provides a promising strategy to explore highly efficient and economic mercury-free catalysts for the hydrochlorination of acetylene. [ABSTRACT FROM AUTHOR]

A series of ruthenium-based catalysts were prepared using spherical activated carbon as a support with the treatment of oxidation or reduction. The catalytic performances of the prepared catalysts were assessed in the hydrochlorination of acetylene based on their characterisation by BET, TG, TEM, TPR, Raman, and XPS. The best catalytic performance was achieved with the oxidised catalyst Ru/SAC-C300, which exhibited a stable acetylene conversion at 96.5% in 48 h at 170 °C and a GHSV (C 2 H 2 ) of 180 h −1 . It is proposed that there exist three major active sites on the surface of Ru-based catalysts for acetylene hydrochlorination, i.e., the oxidised site (RuO 2 ), the reduced state (metallic Ru) and the complexes of Ru/RuOy. Compared with the active ingredient of metallic Ru and Ru/RuOy through the reductive treatment, the active ingredient of RuO 2 is key for improving the catalytic performance of Ru-based catalysts through the oxidative treatment, which provides a promising route to explore high efficient non-mercuric catalysts for acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

Nieuwland catalyst is a key step in the dimerization of acetylene. Various zirconium metal additives incorporating Nieuwland catalysts were prepared, and their catalytic performances were assessed in acetylene dimerization. Different characterization techniques (i.e., thermogravimetric analysis, temperature-programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen ion concentration measurement and transmission electron microscopy) were employed in this study. The best catalytic performance was obtained over zirconium-acetylacetonate-incorporated Nieuwland catalysts, with an acetylene conversion of 53.3% and a monovinylacetylene selectivity of 87.4%. Based on these results, the zirconium acetylacetonate additive could reduce the types of transition state complexes, and it could also change the morphology of the catalyst. In addition, the additives could significantly inhibit the occurrence of trimerization products and polymers. Hence, the conversion of acetylene, monovinylacetylene selectivity, and stability of the Nieuwland catalysts were enhanced. [ABSTRACT FROM AUTHOR]

Several gold-based catalysts including Au, Au–La(iii), Au–Co(ii), and Au–Co(iii) were prepared and assessed for acetylene hydrochlorination, combining with characterizations of low-temperature N2 adsorption/desorption, thermogravimetric analysis, X-ray diffraction, temperature-programmed reduction, inductively coupled plasma-atomic emission spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The best catalytic performance was obtained over Au1Co(iii)3/SAC catalysts with an acetylene conversion of 92% and a selectivity to VCM of 99.9%. It is indicated that the additives of Co(iii), Co(ii) and La(iii) are preferential to stabilize the catalytic active Au+ species and inhibit the reduction of Au3+ to Au0 in the preparation process of Au-based/SAC catalysts. The addition of these additives can greatly inhibit the occurrence of coke deposition on the catalyst surface, and also inhibit the catalyst sintering, thereby improving the activity and long-term stability of the Au-based catalysts. [ABSTRACT FROM AUTHOR]

The ordered mesoporous Zr-modified MCM-41 materials were synthesized by using four different preparation methods including impregnation method, precipitation method, ultrasound method and trituration method, respectively; active zinc species were immobilized on the modified materials with different methods for introducing zirconia species as effective catalysts for the acetylene hydration. All the synthesized materials were characterized by various techniques including BET, FTIR, XRD, TGA, TEM, XPS, NH 3 -TPD, H 2 -TPR, and solid-stated UV–vis. The correlation between structural properties of zirconia modified support and catalytic performance of the Zn catalysts was evaluated in detailed in the acetylene hydration. It is demonstrate that the Zr-modified materials showed the excellent thermostability, and zirconia species addition could enhance the interactions between active metal and support, as well as control the metal particles size with better dispersion. In addition, the substantial enhancement of acid sites and total acid quantity for the modified materials were contributed to the zirconia species addition. Besides, activity evaluation confirms that the Zn/ZM-P catalyst showed more optimistic catalytic performance above 92% C 2 H 2 conversion and 85% selectivity to acetaldehyde in the acetylene hydration due to the stronger metal-support interactions and more acid sites. The study would provide scientific basis for the design of metal catalysts. [Display omitted] • Zr-modified MCM-41 materials were synthesized by different preparation methods. • The correlation between structural properties of Zr-MCM-41 and catalytic performance of the catalysts was evaluated. • Zr-modified MCM-41 markedly improved catalytic performance of Zn catalyst. • Zr-modified MCM-41 enhanced stronger metal–support interactions, provided more acid sites and active sites. [ABSTRACT FROM AUTHOR]

• Volcanic correlation is found between reduction potential and catalytic activity. • Data-informed guide the discovery of high-performance Cu-MPPO catalysts. • Acetylene conversion up to 96%, catalyst life of more than 600 h. • Detailed study of electron transfer between Cu-MPPO catalyst and reactant. Understanding the relationship between catalyst structure and performance is essential for the rational design of active sites for high-performance Cu-ligand catalysts for acetylene hydrochlorination. Herein, two descriptors are informed by data to screen efficient ligands and predict high-performance Cu-ligand catalysts: (1) the reduction potential of Cu2+-Cu+ and catalytic performance were correlated in a volcano-like manner; (2) the C≡C bond length of C 2 H 2 and catalytic performance were linearly related within the Cu2+-Cu+ reduction limit. By using the two descriptors, the MPPO (3-methyl-1-phenyl-2-phospholene 1-oxide) ligand was successfully identified and developed into an effective Cu-MPPO catalyst. The conversion of C 2 H 2 of 96.11 % and the selectivity of VCM of 99 % were obtained under the conditions of 180 h−1, 180 °C, and V HCl : V C2H2 = 1.2. The C 2 H 2 conversion was still above 90 % after running for more than 600 h at 50 h−1. The excellent activity and exceptional stability of the Cu-MPPO catalyst validate the developed model for optimal ligand selection. Detailed structural characterization and density function theory calculations of the designed catalysts were performed to reveal the relationship between catalyst structure and activity. The results indicated that the addition of MPPO altered the local microenvironment of Cu. The simultaneous increased electron density around Cu and Cl resulted in strengthened HCl adsorption and weakened acetylene adsorption, inhibiting the generation of carbon deposition. In addition, MPPO contributed to suppressing the reduction of Cu species, thus stabilizing the active species. This research provides valuable insights and reference strategies for screening efficient ligands in Cu-ligand catalysts. [ABSTRACT FROM AUTHOR]

• Ru-based catalyst improved by quaternary ammonium IL has high catalytic performance in acetylene hydrochlorination. • TBAH IL enhanced the Ru dispersion and stabilized the Ru valence. • The interaction mechanism of TBAH IL with Ru active species and AC support has been revealed. Five quaternary ammonium ionic liquids (QAILs) were employed to synthesize Ru-based catalysts with the purpose of exploring an efficient non-mercuric catalyst for the acetylene hydrochlorination reaction. The activity and stability of Ru-QAILs/AC catalysts were investigated. Importantly, the method and sequence of impregnation were compared. The 0.1Ru15TBAH/AC catalyst prepared by co-impregnation method achieved 95% initial conversion of acetylene and 99.5% selectivity of vinyl chloride, and remained stable in the 200 h life evaluation under the conditions of T = 170 °C, GHSV (C 2 H 2) = 90 h−1 and V (HCl): V (C 2 H 2) = 1.1. A series of characterizations demonstrated that the addition of TBAH could improve the dispersion of Ru species, effectively prevent the appearance of coke deposition and increase the content of Ru4+ active species. Particularly, the mechanism of coke inhibition by adding TBAH IL was discussed via Temperature-programmed desorption (TPD) analysis, and the interaction mechanism of TBAH IL with the AC support and with the Ru species were revealed via XPS spectrum combined with density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • The acetylene hydrochlorination was evaluated on non-precious Cu based catalysts. • The Cu@MOMTPPC catalysts showed the highest catalytic performance among non-precious metal. • Carbon deposition, aggregation and loss of Cu species were inhibited after MOMTPPC addition. • The synergistic effect is due to hydrogen bond and steric hindrance of MOMTPPC ionic liquid. The development of environmentally friendly nonmercuric catalysts for acetylene hydrochlorination reaction mainly focuses on precious metal like Au, Pd and Ru. Non-precious metal based catalyst had much lower activity and stability in this reaction, limiting its practical application. In this work, a novel ionic liquid improved Cu-based heterogeneous catalyst has been designed and successfully synthesized, and it showed the highest catalytic activity and stability among the reported non-precious metal based catalyst used in the reaction of acetylene hydrochlorination. Among many ionic liquids, the (Methoxymethyl) triphenylphosphonium chloride (MOMTPPC) ionic liquid improved Cu-based heterogeneous catalysts has the highest catalytic performance. The optimal 15%Cu@15%MOMTPPC/SAC achieved the conversion of C 2 H 2 of 92.2% under the reaction condition of T =180℃, GHSV (C 2 H 2) of 180 h−1 and V HCl / V C2H2 = 1.2. And under the industrial GHSV (C 2 H 2) of 36 h−1, C 2 H 2 conversion maintains above 98.7% within 360 h. A series of experimental characterizations combined with theoretical calculations indicated that the addition of MOMTPPC ionic liquid can inhibit carbon deposition, prevent the aggregation of Cu species, enhance the dispersion of Cu species and the adsorption of HCl reactant. The stabilization effect of MOMTPPC to Cu is mainly through the hydrogen bond, steric hindrance of MOMTPPC cation and electrostatic effect. The development of Cu@MOMTPPC/SAC catalyst with high efficiency shed light on the potential of replacing the toxic mercuric catalyst with non-precious Cu-based catalyst in the polyvinyl chloride (PVC) industry. [ABSTRACT FROM AUTHOR]

• The AC after adsorbing dyeing wastewater was synthesized to N-doped catalyst. • NR/CAC catalysts showed superior performance in acetylene hydrochlorination. • Mechanism of pyridinic nitrogen doping process on the support was revealed. • Catalytic mechanism of different N species was analyzed by DFT calculation. Dyeing wastewater led to the water pollution and mercury contamination originated from polyvinyl chloride (PVC) production are both environmental problems derived with industrial development. In this work, the coconut activated carbon (CAC) was used to adsorb neutral red (NR), a representative dye in dyeing wastewater. Then, the spent CAC was calcined to be N-doped metal-free catalyst to realize the resource recovery. The metal-free catalyst showed a superior catalytic performance in acetylene hydrochlorination which is the important reaction for PVC production industry. The optimal 3NR/4CAC catalyst exhibited preferable catalytic activity with C 2 H 2 conversion of 97.9% and competitive stability in the 200 h lifetime test. A series of experimental characterizations combined with ReaxFF molecular dynamics simulations as well as density functional theory (DFT) calculations have been carried out to reveal the structural and electronic properties of the N-doped CAC catalysts, the nitrogen doping process as well as the catalytic mechanism of different N species for the acetylene hydrochlorination. This work provides a novel way for the reutilization of the waste adsorbent produced from dyeing wastewater treatment to support the sustainable development of PVC industry. [ABSTRACT FROM AUTHOR]

Graphical abstract The catalytic activity of the Au catalyst is closely linked with the intrinsic properties of the solvents used in the preparation process. Highlights • Au catalysts were prepared using several solvents for acetylene hydrochlorination. • The activity of the catalysts is linked with the intrinsic properties of solvents. • The optimal solvent can highly disperse and anchor the active species. • The optimal solvent greatly improves the catalytic performance of the catalysts. • Au-isopropanol/AC catalyst exhibits the outstanding activity. Abstract A series of Au catalysts were prepared with several representative solvents and evaluated for acetylene hydrochlorination. The results revealed that the activity of the catalyst is closely linked with the intrinsic properties of solvents. The catalytic performance of the catalysts increased with decreasing polarity of the solvents, and superior performance was achieved over the Au-isopropanol/AC catalyst, with a 84% stable conversion under reaction conditions of 180 °C and a gas hourly space velocity (GHSV) of 1200 h−1; relative increases of 700.0% and 483.3%, respectively, in acetylene conversion were achieved compared with that achieved with traditional catalysts prepared with water and aqua regia. The substitution of the highly polar water and aqua regia with weakly polar and volatile alcohols altered the crystallization process of Au nanoparticles (NPs) during their formation. The various edges or defects in the formed multiple-twinned or polycrystalline particles provided new active sites for reactants. The altered solvents may enhance the interaction between the support and the Au species, highly dispersing and anchoring the active species and inhibiting their agglomeration and loss during the reaction. Moreover, the interaction also strengthens the adsorption capacity for reactants of the catalysts, enhancing their catalytic performance. This approach may provide an effective reference for exploring environmentally benign mercury-free catalysts for acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

• Isolated Ru SACs supported by mesoporous N-doped carbon nanospheres were prepared. • Single-site-dispersed Ru-N-C domains were constructed by metal-support interactions. • The Ru–N–C structure enhanced the adsorption and activation of reactants. • DFT calculation shows that Ru–N–C active domains reduce the reaction energy barrier. Single-atom catalysts (SACs) have sparked gigantic attention due to their high activity, atomic utilization, and unique metal–host coordination environment. A hard-template method with Lewis acid modification strategy was adopted to obtain mesoporous N-doped carbon nanospheres as the host to prepare a Ru SAC for acetylene hydrochlorination. The single site scattered Ru-N-C active structure constructed by the interaction between the metal–support and the heteroatom-rich mesoporous g-NC nanosphere material provides a rich defect structure that promotes the mass transfer of reactants and products. Furthermore, the N-doped support anchors, disperses and modulates the catalytic active domains, stabilizing their active state and enhancing the adsorption and activation of initial reactants. As a result, the obtained Ru SAC possesses excellent catalytic properties and lasting life in a 500-h test, which render it highly promising for industrial applications. Moreover, the clarified catalytic mechanism provides a reference for the preparation of other SACs. Efficient acetylene hydrochlorination:The single-site-dispersed Ru-N-C local active centers facilitate the mass transfer of reactants and products, modulate the electronic properties of the metal centers, stabilizing their active state and improving the adsorption and activation of reactant molecules. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of trimetallic Ru-Co(III)-Cu(II)/SAC catalysts were synthesized and assessed for acetylene hydrochlorination, combining with characterizations of TPR, TPD, TGA, TEM, XPS, EXAFS, etc. Compared with the monometallic and bimetallic catalysts, the trimetallic Ru1Co(III)3Cu(II)1/SAC catalyst with 0.1 wt% Ru loading shows a superior activity with the acetylene conversion of 99.0%. It is illustrated that co-addition of Co(III) and Cu(II) can make the ruthenium active species dispersed highly on the carrier, and Cu(II) species can not only inhibit the reduction of RuCl 3 precursors, but also make Co 2+ or Co° transform to high valent species of Co(III), resulting in more ruthenium oxides and low valent Cu + /Cu° species. The Ru1Co(III)3Cu(II)1/SAC is a promising non-mercuric catalyst for acetylene hydrochlorination reaction with the advantages of environmental benign and low cost. [ABSTRACT FROM AUTHOR]

• Multistage porous carbon materials rich in C-N local active domains were constructed. • Reactants were synergistically activated by C-N active sites and π-containing groups. • The structure-performance relationship was also clarified using DFT calculations. • The disadvantages of acetylene hydrochlorination catalyzed by AC were resolved. • Significantly improved stability endows the catalyst a bright application prospect. The benchmark carbon-based catalyst, activated carbon (AC), has a low catalytic activity due to its uniform surface charge distribution and stable structure. To overcome these problems, melamine-phenol-formaldehyde (MPF) resin, which is rich in pyridinic N and pyrrolic N, multi-porous C-N materials rich with defect sites were synthesized in situ by heat treatment using silica sol as the template and phenol, melamine, and formaldehyde as the carbon and nitrogen sources. The experimental results and characterization techniques revealed that carbon materials with abundant hierarchical pores and local C-N active sites were constructed by incorporating heteroatom-containing groups. Hydrogen chloride and acetylene molecules were activated due to the high electronegativity of defective sites, and the synergistic interactions between pyridinic N and π-containing functional groups (C=C, triazine ring, etc.). The structure-performance relationship was also clarified using DFT calculations. In addition, the strong interactions between heteroatomic sites and metal species also made MPF-800 an admirable metal catalyst support. Overall, the disadvantages of acetylene hydrochlorination catalyzed by benchmark AC were resolved. : The non-metallic carbon materials (MPF- T) exhibit remarkable catalytic performance and maintain outstanding long-term stability in the hydrochlorination of acetylene [Display omitted] [ABSTRACT FROM AUTHOR]

• The catalysts were prepared by coordinating Ru precursor with triazine-based ligands. • The coordination contributes to the dispersion of active species. • The interaction enhanced the adsorption and activation of reactants. • DFT calculation shows that the complexation can reduce the reaction energy barrier. Ru/AC catalyst used in acetylene hydrochlorination reaction has several drawbacks such as poor dispersion, metal loss, serious carbon deposition, and insufficient active sites. To address these issues of traditional Ru/AC, in this study, the supported Ru-L x /AC catalysts were synthesized by the coordination of ruthenium precursor and several structural triazine ligands. The complexation of heteroatomic structure to Ru atom formed a local active domain, which is more conducive to the synergistic adsorption and activation of the initial reactants, and further optimizes the reaction microenvironment. The spatial topological structure with conjugated structures effectively promoted the transfer of electrons between the heteroatoms and the ruthenium precursors, facilitating the stabilization of active Ru species. The newly developed synthetic process also increased dispersion of reaction components and impeded the sintering of ruthenium components promoted by the local structural forces. The optimum Ru-1,3,5-triazine/AC (Ru-L 1 /AC) catalyst exhibited 162% higher acetylene conversion than the benchmark Ru/AC catalyst. The significantly improved activity and stability of the optimized catalyst will have a huge application prospect in industry. Efficient acetylene hydrochlorination: The coordination between ruthenium and heteroatom ligands promotes the transfer of electrons between the heteroatoms and the metal precursor, ensuring the continuous and efficient catalysis of the catalyst. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering the disadvantages of Cu-based catalyst for acetylene hydrochlorination, such as poor dispersion, severe carbon deposition and insufficient active sites, supported Cu-complex catalysts were synthesized by using phosphine-oxide organic compounds as ligands. A local active domain was successfully constructed based on the complexation of Cu atom to heteroatomic structure in meticulously selected ligands, in which the phenyl group acts as an electron donor to change the CuCl 2 active site electronic structure. The density functional theory calculation proved the existence of a strong interaction between triphenylphosphine oxide and CuCl 2 , and synchronously, electrons on the benzene ring were transferred to the Cl atom in CuCl 2 , stabilizing the Cu species. This superior activity may be attributed to the heightened adsorption of HCl and weakened C 2 H 2 and vinyl chloride adsorption by the constructed local active domain, which impedes the carbon deposition that promotes the continuous exposure of active sites. Under the reaction conditions: T = 180 ℃, GHSV C2H2 = 180 h−1 and V HCl /V C2H2 = 1.2, the C 2 H 2 conversion of 15%Cu7%TPPO/AC reaches 88%, which was over 30% higher than 15%Cu/AC catalyst. The significantly improved activity and stability of the proposed catalyst provides a reference for green and sustainable production of vinyl chloride. [Display omitted] • Complexation of TPPO with CuCl 2 establishes a locally active domain catalyst. • 15%Cu7%TPPO/AC catalyst improves the performance over 30% than 15%Cu/AC catalyst. • Significantly improved stability endows the catalyst a bright application prospect. • The electrons transfer from the benzene ring to the Cl atom in CuCl 2. [ABSTRACT FROM AUTHOR]

• The catalysts were prepared by coordinating the Au precursor with heteroatom ligands. • The adsorption and activation capacity of HCl was improved because of the heteroatom. • N- or P-containing ligands contributed to the anchoring and dispersion of Au species. • P-containing ligand also increased the relative content of active Aun+ species. • O-containing ligands enhanced the activity by weakening the adsorption of acetylene. In line with the fulfillment of international Minamata Convention and the urgent need for developing non-mercury catalysts, Au-L x /AC catalysts were synthesized and evaluated for the hydrochlorination of acetylene. The results showed that the interaction between ligands and Au species contributed to the enhanced catalytic activity with important and different roles of each ligand. Depending on the high electronegativity of heteroatoms, all the prepared catalysts had effectively improved their adsorption and activation capacity of hydrogen chloride. Specifically, the N-containing ligands in catalysts increased the dispersion of Au species and an enhanced adsorption of acetylene was observed. Whilst, the coordination of P-containing ligands with Au can increase the relative content of active Aun+ species and the O-containing ligands rather decreased the adsorption of acetylene. Furthermore, all the prepared Au-L x /AC catalysts showed good stabilities based on the inhibition of the agglomeration of Au components or of coking deposition. [ABSTRACT FROM AUTHOR]

• A melamine-formaldehyde-PVA coating-pyrolysis method was developed to prepare the N-doped activated carbon (N@CBC-FE). • N@CBC-FE presented the highest conversion of 75 % under 220 °C and 50 h−1 acetylene GHSV in 120 h. • N@CBC-FE showed excellent activity due to the polymeric network coating generated by formaldehyde, PVA and melamine. N-doped carbon-based materials have been regarded as promising alternative metal-free catalysts for the production of vinyl chloride monomer. In this work, N-doped carbon-based catalysts were synthesized via a melamine/formaldehyde/ polyvinyl alcohol (PVA) coating-pyrolysis method, and the performances of the resultant catalysts (N@CBC-FE) were investigated and compared with those of the control samples. The optimal N@CBC-FE catalyst presented the highest acetylene conversion of 75 % at 220 °C and an acetylene gas hourly space velocity of 50 h−1 in 120 h. N 2 sorption, Raman spectroscopy, attenuated total Reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed desorption analysis results revealed that the excellent performance of N@CBC-FE was mainly attributed to the unique nitrogen intercalation pathway generated by the polymeric network coating, which was produced by the reactions among formaldehyde, PVA and melamine. Moreover, the abundant mesopores of N@CBC-FE facilitated the transfer of the reactants and retarded the deactivation process. This work is expected to provide new insights for the preparation of N-doped activated carbon-based catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catalytic performance of activated carbons prepared from different precursors were evaluated for acetylene hydrochlorination. • The relationships between catalytic activity and typical feature of ACs were disclosed. • The superior activity of ACs attributed to higher conductivity, lower graphitization, higher adsorption of reactants but less acidic sites. A number of commercial activated carbons (ACs) produced from different sources including pitch, coal, coconut and wood were evaluated as the catalyst for the hydrochlorination reaction of acetylene. To disclose the structure-activity relationship, a series of characterizations were performed including texture, porosity, surface graphitization, conductivity, surface functional groups, surface adsorption properties and surface acidic sites distribution for these ACs. The results illustrate that the higher catalytic activity of ACs is attributed to higher conductivity, lower graphitization, less surface strong acidic sites and higher adsorption ability to reactants. This work would shed light on the rational design of carbon-based catalysts and their potential application in acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

Nieuwland catalyst (NC) was modified with different phosphonic acids (P x) and evaluated for their acetylene dimerization activity in monovinyl acetylene (MVA) production. Nearly 49.2% of acetylene conversion and 80.3% of MVA selectivity were obtained in 5 mol% risedronic acid (P 2)-modified NC under an acetylene-gas space velocity of 105 h−1 at 80 °C, which was 17.8% higher than the yield of the control NC. The characterization results of NC and P 2 –NC indicated that the addition of P 2 effectively enhanced the stability of the Cu ions and inhibited oxidation of the active component Cu+, improving their catalytic activity and long-term stability. Unlabelled Image • Phosphonic acids modification Nieuwland is firstly used for acetylene dimerization. • Risedronic acid (P 2)-modified Nieuwland catalyst showed excellent performance and long-term stability. • Addition of P 2 effectively enhances the stability of the Cu ions and inhibits oxidation of the active component Cu+. [ABSTRACT FROM AUTHOR]

• The catalysts were prepared by coordinating the Ru precursor with azole ligands. • The Ru-L 8 /AC catalyst exhibited the superior performance to the other catalysts. • The coordination helps to stabilise high valence Ru and produce more active species. • The coordination contributes to the anchoring and dispersion of active species. • The interaction enhanced the adsorption ability for reactants. Supported Ru-L x /AC catalysts were synthesised by coordinating a Ru precursor with several azole ligands and assessed for acetylene hydrochlorination. The results demonstrated that the coordinated Ru-imidazole/AC (Ru-L 1 /AC) catalyst exhibited superior catalytic activity compared to that of catalysts coordinated with other ligands. In addition, the substitution of hydrogen on the imidazole ring by electron-donating substituents further improved the catalytic performance. Specifically, the coordination between the ruthenium precursor and heteroatom in the ligands, which contain a conjugated structure and an electron-donating substituent, promoted the transfer of electrons from the heteroatom to Ru cation and augmented the electron cloud density around the active centres, which helps stabilise high-valence Ru and produce more active Run+ species. In addition, the coordination contributed to the anchoring and dispersion of active species, which improved the catalytic hydrochlorination of acetylene. Thus, the as-designed Ru-1-isopropyl imidazole/AC (Ru-L 8 /AC) catalyst exhibits a superior performance and good application prospect. [ABSTRACT FROM AUTHOR]

• A series of high efficiency Cu complex catalysts were prepared with phosphoramide ligands in acetylene hydrochloride. • The catalyst with optimal HMPA ligand exhibited good stability in the 100 h lifetime test. • HMPA ligand can restrain coke deposition, suppress loss of loading Cu, and stabilize valence state of active Cu species. • Due to the electron transfer mechanism, a stable coordination structure formed between the Cu and HMPA via Cu-O binding. In order to develop a cut-price, high-efficiency non-mercuric catalyst for acetylene hydrochlorination reaction, several kinds of supported Cu-based catalysts containing phosphoramide ligands have been synthesized by wet impregnation method. The outstanding catalytic activity was obtained over 15 %Cu10 %HMPA/SAC catalyst with acetylene conversion of 87.25 % in the test conditions of T =180 °C, GHSV (C 2 H 2) =180 h−1 and V (HCl): V (C 2 H 2) = 1.2. The catalyst with optimal HMPA ligand also exhibited splendid stability in 100 h lifetime test. The analysis for XRD, TEM, TGA, ICP, H 2 -TPR and XPS indicated that HMPA ligand can improve Cu species dispersion, restrain coke deposition, suppress loss of loading Cu, and stabilize valence state of active Cu species. Due to electron transfer mechanism, steady coordination structure between Cu and HMPA led to favorable properties of Cu-based catalyst, which was further proved by FT-IR, Raman spectra, O 1s XPS spectra integrated with DFT calculations. [ABSTRACT FROM AUTHOR]