Catalysts For Acetylene Hydrochlorination Research Articles

Constructing a fragmentary g-C3N4 framework with rich nitrogen defects as a highly efficient metal-free catalyst for acetylene hydrochlorination

Fragmentary g-C3N4 was prepared using a melamine formaldehyde resin precursor, which exhibited an activity 30 times higher than pure g-C3N4 in acetylene hydrochlorination.

Defective graphene@diamond hybrid nanocarbon material as an effective and stable metal-free catalyst for acetylene hydrochlorination.

A defective nanodiamond-graphene material (ND@G) exhibits superior catalytic activity in acetylene hydrochlorination with an acetylene conversion of 50%, selectivity to vinyl chloride of up to 99.5% at 220 °C, and a C2H2 gas hourly space velocity of 300 h-1, which is the first example of a metal-free catalyst with comparable performance to that of the 0.25% Au/C catalyst.

Highly effective carbon-supported gold-ionic liquid catalyst for acetylene hydrochlorination.

The sulfur-containing ionic liquid (IL) trimethylsulfonium iodide (C3H9SI) was used to synthesize an efficient non-mercuric catalyst with HAuCl4·4H2O as a precursor and spherical active carbon (SAC) as a support. Various Au-IL/SAC catalysts were synthesized using the incipient wetness impregnation technique and applied to acetylene hydrochlorination. The 0.3% Au-IL/SAC catalyst showed the best catalytic performance, with an acetylene conversion of 90% at a temperature of 170 °C and gas hourly space velocity (GHSV) of 360 h−1 using water as the solvent. The catalyst also displayed excellent long-term stability: C2H2 conversion was maintained at 97% for up to 200 h (T = 170 °C, GHSV = 90 h−1). Brunauer–Emmett–Teller surface area, thermogravimetric analysis, temperature programmed desorption, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy results together showed that the C3H9SI additive significantly improved the dispersion of Au species and inhibited coke deposition on the catalyst surface during the acetylene hydrochlorination reaction. The superior activity and stability of the Au-IL/SAC catalyst make it a green catalyst for the industrial application of acetylene hydrochlorination.

An efficient Au catalyst supported on hollow carbon spheres for acetylene hydrochlorination.

Mesoporous hollow carbon spheres (HCSs) were prepared using SiO2 spheres as a hard template, and Au nanoparticles were then synthesized using NaBH4 as a reducing agent on the surface of the HCS support. Transmission electron microscopy characterization indicated that Au nanoparticles were much smaller on the HCS support than those on the active carbon (AC) support. HCl-TPD showed that the Au/HCS catalyst displayed a more active site than on Au/AC. The resulting Au/HCS catalyst showed excellent catalytic activity and stability for acetylene hydrochlorination. Acetylene conversion of Au/HCS can be maintained above 92% even after 500 h of lifetime. The excellent catalytic performance of Au/HCS was attributed to the presence of the HCS support, which limited the aggregation of Au nanoparticles.

Supported ionic liquid-palladium catalyst for the highly effective hydrochlorination of acetylene

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 (HgCl2) 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 HgCl2 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 C2H2 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.

Hydrochlorination of acetylene catalyzed by activated carbon supported highly dispersed gold nanoparticles

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.

Achieving Efficient and Low Content Ru‐Based Catalyst for Acetylene Hydrochlorination Based on N,N’‐Dimethylpropyleneurea

AbstractA new Ru‐based catalyst system based on N,N′‐Dimethylpropyleneurea (DMPU) was developed for the acetylene hydrochlorination reaction in this study. The optimal 1 % Ru‐10 %DMPU/AC catalyst exhibits the best activity with the acetylene conversion of 87.6 % under 170 °C and the GHSV (C2H2) of 900 h−1. Additionally, the Ru‐10 %DMPU/AC with lower Ru content (0.2 wt%) displayed excellent activity and stability with acetylene conversion of 81.3 % after 200 h under the conditions of 170 °C and C2H2 GHSV of 180 h−1. The characterization results indicate that the presence of DMPU could improve the dispersion of the catalytic species and provide full protection to prevent the sintering of the ruthenium particles and to inhibit the reduction of active ruthenium oxide component. Moreover, the catalytic property, characterizations and theoretical calculation results reveal that the ability to adsorb and activate HCl reactant with the addition of DMPU via its strong hydrogen bonding plays a significant role on the high stability of the Ru‐DMPU/AC catalyst system.

Bimetallic Au-Li/SAC catalysts for acetylene hydrochlorination

A series of Au-Li/SAC catalysts for acetylene hydrochlorination were prepared with HAuCl4⋅4H2O and LiCl as precursors by an incipient wetness impregnation method and characterized by XRD, BET, TEM, TG, XPS and TPR techniques. It is found that Au1Li0.5/SAC shows the highest activity and stability with the acetylene conversion of 91.3% after 48 h reaction running. The addition of Li can disperse the Au species well and inhibit coke formation on the catalyst surface, Li additives can also inhibit the reduction of active gold species during the reaction time, thereby improving the activity and the long-term stability of gold-based catalysts.

Synthesis and characteristics of organotin-based catalysts for acetylene hydrochlorination

Organotin-based catalysts prepared by a facile and green synthesis route were used in the acetylene hydrochlorination reaction. In detail, organotin-based catalysts were directly synthesized by supporting both organotin and nitrogen compounds on a coal-based columnar activated carbon (AC) using both incipient wetness impregnation and calcination methods. Interestingly, upon addition of nitrogen compounds, the resultant (SnCl4 + C16H34Cl2Sn)/AC catalysts showed higher activity and stability when compared the its (SnCl4 + C16H34Cl2Sn + C2N4H4)/AC counterpart at 200 °C and a gas hourly space velocity (GHSV, C2H2 based) of 30 h−1. According to the results, organotin was demonstrated to be the active site, whereas the incorporation of nitrogen allowed partial mitigation of the loss of active components.

The Effect of N‐Doping in Activated Carbon‐Supported Au‐Sr Catalysts for Acetylene Hydrochlorination to Vinyl Chloride

AbstractWe used N‐doped activated carbon (NAC) as support to prepare a novel Au−Sr catalyst and evaluated the effect of N‐dopants on the performance of Au−Sr catalyst in acetylene hydrochlorination. A promoting effect was observed when N atoms were incorporated into AC framework, and the prepared SrAu/NAC catalyst demonstrated optimal activity compared with the undoped Au/AC and SrAu/AC catalysts. The SrAu/NAC also showed an excellent stability during the 500 h test, with acetylene conversion and vinyl chloride selectivity both exceeding 99.9%. A detailed characterization was investigated through XPS, TPD, TPR, TGA, PXRD, TEM, AAS, and BET to reveal the physicochemical properties of the related catalysts. It is demonstrated that the NAC can function as an effective support to enhance activity and life of Au‐based catalysts with unique electronic property, and the presence of doped nitrogen species as anchor sites is beneficial to increasing the electron density of active Au(III) center through electron transfer from doped N atoms to the active Au(III) species, and stabilizing active Au(III) ions and retarding its reduction within catalyst preparation and use process. Moreover, the combination of N‐dopants and strontium additive may promote a synergistic effect to make active Au species disperse better and significantly enhance the adsorption of HCl, remarkably suppress the reduction of active cationic Au(III), and effectively inhibit carbon deposition in the catalytic reaction.

Novel nitrogen-doped Au-embedded graphene single-atom catalysts for acetylene hydrochlorination: A density functional theory study

Abstract The mechanisms of an Au-embedded graphene (AuG) single-atom catalyst (SAC) and AuG-SACs doped with nitrogen at different locations for acetylene hydrochlorination were investigated through density functional theory (DFT). The density functional dispersion correction was calculated with the DFT-D3 method. We studied the adsorption characteristics of HCl and C2H2 on these SACs and simulated the corresponding reaction mechanism. We also found that adding the heteroatom N to AuG-SACs can reduce the reaction activation energy. Furthermore, we found the optimal location of the N atom of the N–substituted SAC to reduce the activation energy. The results suggest that N-doped AuG-SACs could find potential in catalyzing acetylene hydrochlorination to vinyl chloride and reduce the amount of noble metal used in mercury-free catalysts.

Sulfur and nitrogen co-doped mesoporous carbon with enhanced performance for acetylene hydrochlorination

Acetylene hydrochlorination is a major technology for producing vinyl chloride in coal-rich areas, but its development is restricted by its utilizing the toxic mercury chloride (HgCl2) catalyst. Lately, several nitrogen-doped carbon materials have been studied and are considered to be a feasible alternative. Here, we propose an approach based on sulfur doping to effectively improve the pyridinic N content in N-doped carbon material. According to high-resolution XPS and C2H2 TPD results, C atoms adjacent to pyridinic N were proved to be active sites, and thus the co-doped carbon catalyst exhibited a higher acetylene conversion than the N-doped carbon sample. Furthermore, the co-doped catalyst processed in NH3 exhibits preferable catalytic activity and competitive stability owing to its high specific surface area, mesoporous structure, and high nitrogen level. Good performance, combined with the features of low cost and ecofriendliness, makes sulfur and nitrogen co-doped carbon a promising catalyst for acetylene hydrochlorination.

Metal nanoparticles in ionic liquid‐cosolvent biphasic systems as active catalysts for acetylene hydrochlorination

Ionic liquid (IL)‐stabilized metal nanoparticles (NPs) have attracted increased attention as novel catalysts for various reactions due to their excellent stability and high activity. However, the high viscosity of ILs limits their applications. Here, for the first time, we reported an NPs@IL‐cosolvent liquid–liquid biphasic system for metal NPs catalysis. The NPs were successfully confined to IL phase, and abundant IL droplets containing NPs were generated under the reactant flow. The NPs@IL droplets served as microreactors for the catalysis; while the low viscosity organic phase enabled the rapid mass transfer of substances. The biphasic system exhibited improved performance for acetylene hydrochlorination than that of the pure IL system. An acetylene conversion of 98% and a selectivity of 99.5% were achieved along with a 90% decrease on IL usage. The tolerable gas hourly space velocity in the biphasic system for a satisfactory conversion was almost double that of the pure IL system. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2536–2544, 2018

The activity and stability of PdCl2/C-N catalyst for acetylene hydrochlorination

Carbon supported PdCl2 is highly active in catalyzing acetylene hydrochlorination reaction, but deactivates rather quickly. Upon nitrogen doping in the carbon structure, the stability of the PdCl2 catalysts is significantly improved. Furthermore, the results show that 900 °C is a preferred doping temperature. The acetylene conversion keeps above 90% even after 1200 min time on stream whereas the one without nitrogen doping drops to below 10% after 450 min. The stabilizing mechanism of nitrogen doping on catalyst was studied.

Descriptors for High-Performance Nitrogen-Doped Carbon Catalysts in Acetylene Hydrochlorination

Nitrogen-doped carbons are promising materials for a broad range of applications. However, their rational design is greatly hampered by the lack of efficient methods to control the nitrogen speciation, which not only causes controversy about the roles of specific nitrogen functionalities but also hinders investigations into other physicochemical characteristics of these materials. We herein present a cutting-edge strategy that allows a systematic tuning of the electrical conductivity of polyaniline-derived N-doped carbons at a defined nitrogen speciation and content, and similar porous properties. By application of these model systems in acetylene hydrochlorination, a major industrial technology for the production of polyvinyl chloride, we provide insights into the active sites and the reaction mechanism and disclose two key catalytic descriptors for N-doped carbons in this reaction: (i) a high content of pyrrolic-N functionalities, promoting the adsorption of the reactants, and (ii) good electrical condu...

Heterogeneous non-mercury catalysts for acetylene hydrochlorination: progress, challenges, and opportunities

The replacement of mercuric chloride with non-mercury catalysts in acetylene hydrochlorination for the production of a vinyl chloride monomer, a precursor to polyvinyl chloride, would meet the requirements of green chemistry and have a great significance in the industrial field.

Effect of acidity and ruthenium species on catalytic performance of ruthenium catalysts for acetylene hydrochlorination

Carbon-supported ruthenium catalysts are promising mercury-free catalysts for acetylene hydrochlorination, due to their high activity and relatively low price. The deactivation mechanism was identified and solved by a simple ammonia treated method.

Ionic liquids-coordinated Au catalysts for acetylene hydrochlorination: DFT approach towards reaction mechanism and adsorption energy

A DFT study of Au–IL catalysts for acetylene hydrochlorination was carried out and consistency with experimental data was obtained.

Nitrogen doped nanoflower porous carbon as a nonmetal catalyst for acetylene hydrochlorination

The performance of nanoflower-like morphology NPC-T catalysts on acetylene hydrochlorination was related to the nitrogen content of species as well as specific surface area.

Wheat flour-derived N-doped mesoporous carbon extrudate as superior metal-free catalysts for acetylene hydrochlorination.

N-Doped mesoporous carbon extrudate with a major quaternary N species has been successfully prepared through direct carbonization of wheat flour/gluten with silica, which is a cheap and convenient method for scale-up production approach. The obtained carbon extrudate metal-free catalyst enables highly efficient production of vinyl chloride monomer through acetylene hydrochlorination, with a superior catalytic performance and excellent stability (>85% conversion and vinyl chloride selectivity over 99% at 220 °C).