Catalysts For Acetylene Hydrochlorination Research Articles

Improvement of imidazolium-based ionic liquids on the activity of ruthenium catalyst for acetylene hydrochlorination

Imidazolium-based Ionic Liquids (IBILs) were employed to synthesize Ru-based catalysts using the Supported Ionic Liquid Phase (SILP) technique for acetylene (C2H2) hydrochlorination, combining the characterizations of transmission electron microscopy (TEM), N2 adsorption-desorption (BET), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD), and X-ray photoelectron spectra (XPS), etc. The optimal Ru10%[BMIM]BF4/AC catalyst achieved the C2H2 conversion of 98.9% and the selectivity to vinyl chloride monomer (VCM) of 99.8% under the temperature of 170°C and the C2H2 gas hourly space velocity (GHSV) of 180h−1. Further, other IBILs with different anions were chosen to fabricate Ru-based catalysts, and the catalysts showed high activity and selectivity similar with Ru10%[BMIM]BF4/AC catalyst. It is demonstrated that IBILs additives can significantly improve the dispersion of ruthenium species and prevent the appearance of coke deposition owing to the interactions between Ru species and [BMIM]BF4. Moreover, the oxygen-containing functional groups on the carbon support are associated with the interactions among Ru species and [BMIM]BF4.

Activated Carbon-Supported Tetrapropylammonium Perruthenate Catalysts for Acetylene Hydrochlorination

The Ru-based catalysts, including Ru/AC (activated carbon), TPAP (tetrapropylammonium perruthenate)/AC, TPAP/AC-HNO3, and TPAP/AC-HCl, were prepared and assessed for the direct synthesis of vinyl chloride monomer. The results indicate that the TPAP/AC-HCl catalyst exhibits the best performance with the conversion falling from 97% to 91% in 48 hours’ reaction under the conditions of 180 °C, a GHSV(C2H2) of 180 h−1, and the feed ratio VHCl/VC2H2 of 1.15. The substitution of RuCl3 precursor with high valent TPAP species leads to more ruthenium oxides active species in the catalysts; the acidification treatment of carrier in TPAP/AC catalyst can produce an enhanced interaction between the active species and the modified functional groups on the carrier, and it is beneficial to inhibit the carbon deposition and sintering of ruthenium species in the reaction process, greatly increase the adsorption ability of reactants, and further increase the amount of dominating active species in the catalysts, thus improving the catalytic performance. This also provides a promising strategy to explore high efficient and economic mercury-free catalysts for the hydrochlorination of acetylene.

A novel S, N dual doped carbon catalyst for acetylene hydrochlorination

In this study, a sulphur and nitrogen dual-doped carbon catalyst was prepared via an easy route with p-phenyldiamine and (NH4)2S2O8 as the nitrogen and sulphur source, respectively. The obtained catalyst displayed efficient acetylene conversion for acetylene hydrochlorination, and the presence of sulphur enhanced the catalytic activity of the nitrogen-doped carbon catalyst. These catalysts show that sulphur and nitrogen have a synergistic effect for acetylene hydrochlorination. Furthermore, because of the addition of different sulphur contents, the pyrrolic N content causes certain changes in the catalysts, resulting in differences in the catalytic activity. Theoretical investigations reveal that the adsorption ability of C2H2 was enhanced by the doping of the S and N-doped carbon catalyst. This is an environmentally friendly catalyst with a broad development prospect and is cheap and easy to obtain.

The Kinetics Model and Fixed Bed Reactor Simulation of Cu Catalyst for Acetylene Hydrochlorination

Abstract Acetylene hydrochlorination is an important reaction for vinyl chloride monomer (VCM) production in China. Non-mercury catalysts and related green processes are the urgently needed technologies in this field. In this work, reaction kinetics and a model of fixed bed reactor (FBR) with Cu/AC (activated carbon) catalyst for acetylene hydrochlorination were constructed and verified by experiments. First, the influence of external and internal diffusion was studied and eliminated. Then, reaction activation energy and reaction order to each reactant were determined. Next, catalyst deactivation was considered and the simulation of an FBR including conversion, temperature and pressure distribution was established. Results were consistent with experimental data. The model provided quantitative parameters for evaluating the activity and lifetime of catalysts, thereby establishing criteria for catalyst evaluation. Industrial long-term performance of catalysts was predicted by limited laboratory short-term data. Finally, previous publication results were gathered and compared. The study provided valuable guidance for non-mercury catalyst in PVC industry and other similar systems.

Yttrium chloride-modified Au/AC catalysts for acetylene hydrochlorination with improved activity and stability

The addition of yttrium chloride (YCl3) to an activated carbon-supported Au catalyst (Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer (VCM). The structure and physicochemical features of the YCl3-modified catalysts (Y–Au/AC) were measured by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, C2H2-temperature programmed desorption, and scanning transmission electron microscopy. The presence of YCl3 was found suppressing the reduction of highly oxidized Auδ+ (δ = 1, 3) to metallic Au0 dependently and thus retard the agglomeration of Au nanoparticles during the reaction. In addition, the additive of YCl3 to the Au/AC catalyst greatly inhibits the coke deposition on the catalyst surface. The optimized catalyst with an atomic ratio of Y/Au = 5 (1 wt% Au loading weight) yields an 87.8% acetylene conversion and almost 100% selectivity for VCM under the reaction of GHSV(C2H2) = 800 h−1 at 180 °C. The durability test indicates that the 5Y–1Au/AC catalyst maintains high catalytic activity for more than 2300 h at 30 h−1 GHSV(C2H2) and 180 °C, indicating great promise as a non-mercury catalyst for PVC manufacture.

Surface chemical characterization of deactivated low-level mercury catalysts for acetylene hydrochlorination

Abstract Mercury-containing catalysts are widely used for acetylene hydrochlorination in China. Surface chemical characteristics of the fresh low-level mercury catalysts and spent low-level mercury catalysts were compared using multiple characterization methods. Pore blockage and active site coverage caused by chlorine-containing organics are responsible for catalyst deactivation. The reactions of chloroethylene and acetylene with chlorine free radical can generate chlorine-containing organic species. SiO 2 and functional groups on activated carbon contribute to the generation of carbon deposition. No significant reduction in the total content of mercury was observed after catalyst deactivation, while there was mercury loss locally. The irreversible loss of HgCl 2 caused by volatilization, reduction and poisoning of elements S and P also can lead to catalyst deactivation. Si, Al, Ca and Fe oxides are scattered on the activated carbon. Active components are still uniformly absorbed on activated carbon after catalyst deactivation.

Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN) as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction.

Effective Catalytic Performance of Plasma-Enhanced W2N/AC as Catalysts for Acetylene Hydrochlorination

It is a significant environment goal to find searching green and low-price non-precious metal catalysts to replace HgCl2 in the catalytic hydrochlorination of acetylene to yield polyvinylchloride (PVC). Transition metal nitrides exhibit excellent chemical stability and high performance in many reactions, and may be the desirable candidates for this reaction. Herein, tungsten nitride, W2N, is applied as the active ingredient in the synthesis of vinyl chloride monomer (VCM), for the first time. Two catalysts were prepared. The first was prepared by depositing tungsten onto an activated carbon support, whereas the second was prepared from using the first catalyst via plasma treatment. This treatment increased the interaction between the support material and the active ingredient, and generated nanoparticles that exhibit greater level of aggregation. However, the plasma treatment also turned to enhance the catalytic performance. Additionally, it increased the number of W–N bond in the catalyst and reduced the deposition of coke on the catalyst surface.

Identification of single-site gold catalysis in acetylene hydrochlorination.

There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species.

Deactivation mechanism and regeneration of carbon nanocomposite catalyst for acetylene hydrochlorination

Acetylene hydrochlorination is an important coal-based technology for production of vinyl chloride, the monomer of one of the world mostly used plastics. Despite of the great potentials demonstrated for carbon-based catalysts to replace the toxic mercury chloride, the stability and the deactivation mechanism are rarely discussed, which is essential for real applications. Herein, we present a detailed study on the deactivation mechanism of nitrogen doped carbon based catalyst in acetylene hydrochlorination. The results show that the deactivation was likely caused by the carbon-like deposition over the catalyst, which can be regenerated with high temperature NH3 treatment.

Boron-modified activated carbon supporting low-content Au-based catalysts for acetylene hydrochlorination

A series of boron-modified low-gold-content Au-based catalysts were prepared by impregnation. Characterization by N2 adsorption/desorption, XPS, H2–TPR, HCl/C2H2–TPD, TG, TEM, and SEM was applied to analyze the catalyst. Compared with the unmodified catalyst, B-modified Au0.25%/BAC-20% exhibited better performance (acetylene conversion increase by 21.4% and selectivity to VCM of more than 99.5%) at a space velocity of 770h−1 and 150°C. The results indicated that the presence of boron species is favorable to the stabilization of catalytically active Au3+ species and the inhibition of Au3+ to Au0 during acetylene hydrochlorination, and hence improves the catalytic stability. In addition, the presence of boron species can effectively inhibit carbon deposition and also inhibit the catalyst sintering during the reaction. TPD experiments revealed that not the adsorption ability of C2H2 but the adsorption ability of the HCl played a crucial role in boron-modified Au-based catalysts.

Activated carbon supported VN, Mo 2 N, and W 2 N as catalysts for acetylene hydrochlorination

Abstract The development of green catalysts for the calcium carbide acetylene method synthesis of vinyl chloride monomer (VCM), is essential material to industrial polyvinyl chloride production. The original catalyst HgCl2 easy to volatile during the reaction lead to environmental pollution. Here we present three different transition metal nitride load into activated carbon (AC): VN/AC, Mo2N/AC, and W2N/AC as novel catalysts. W2N/AC and Mo2N/AC was a relatively stable catalyst to compared with VN/AC. All of them VCM selectivity can maintain 98%. More HCl ratio for Mo2N/AC lead its acetylene conversion reach 80%. The former two catalysts are promising candidates for acetylene hydrochlorination.

Trimetallic Au‐Cu‐K/AC for acetylene hydrochlorination

AbstractThe metal chloride of KCl was chosen to modify Au‐Cu/AC to decrease the noble metal of gold and enhance the catalytic performance. Then a mercury‐free catalyst of Au‐Cu‐K/AC was prepared by the impregnation method. The catalytic performances of mercury‐free catalyst for acetylene hydrochlorination were conducted for 1600 h in a fixed bed reactor by a single‐tube pilot unit. The fresh and used catalysts were also characterized in comparison. The results showed that the acetylene conversion on mercury‐free catalyst decreased slowly from 98 % to 89 %, and the vinyl chloride monomer (VCM) selectivity was kept at 99.7 % under reaction conditions of temperature 165 °C, gas hourly space velocity (GHSV) 40 h−1, and feed volume ratio of HCl to C2H2 of 1.05 during 1600 h on stream. The results showed that the additives of K with Cu can make the active species of gold dispersed well and retard the aggregation of particles. The reason for the slow decline of acetylene conversion for Au‐Cu‐K/AC catalyst was the whisker carbon deposition, shown in a faint yellow colour over the catalyst surface, which consisted of short‐chain hydrocarbon molecules. Further study for accelerated deactivation of sole metal in the catalyst gives the clues that the non‐noble metal of Cu in Au‐Cu‐K/AC catalyst plays a key role to form the deposition.

Nitrogen-doped Carbon Derived from ZIF-8 as a High-performance Metal-free Catalyst for Acetylene Hydrochlorination

Acetylene hydrochlorination is a major industrial technology for manufacturing vinyl chloride monomer in regions with abundant coal resources; however, it is plagued by the use of mercury(II) chloride catalyst. The development of a nonmercury catalyst has been extensively explored. Herein, we report a N-doped carbon catalyst derived from ZIF-8 with both high activity and quite good stability. The acetylene conversion reached 92% and decreased slightly during a 200 h test at 220 °C and atmospheric pressure. Experimental studies and theoretical calculations indicate that C atoms adjacent to the pyridinic N are the active sites, and coke deposition covering pyridinic N is the main reason for catalyst deactivation. The performance of those N-doped carbons makes it possible for practical applications with further effort. Furthermore, the result also provides guidance for designing metal-free catalysts for similar reactions.

Oxidation modification of Ru-based catalyst for acetylene hydrochlorination

Oxidation modification enhances the interaction between the oxygenated functional groups and Ru species, strengthens the adsorption of reactants, and augments the amount of active species, enhancing the catalytic performance of the catalysts.

The Preparation of Cu-g-C3N4/AC Catalyst for Acetylene Hydrochlorination

A novel catalyst based on g-C3N4/activated carbon was prepared by adding CuCl2. The catalytic performance of the as-prepared catalyst was investigated in the acetylene hydrochlorination reaction. X-ray photoelectron spectroscopy, temperature programmed desorption, low temperature N2 adsorption/desorption (Brunauer–Emmett–Teller), and thermal gravity analysis showed that Cu-g-C3N4/AC significantly enhanced the catalytic performance of the original catalyst by increasing the relative pyrrolic N content. Cu-g-C3N4/AC also affected the adsorption of hydrogen chloride and acetylene, as well as inhibited the coke deposition during acetylene hydrochlorination.

A density functional theory study on the performance of graphene and N-doped graphene supported Au3 cluster catalyst for acetylene hydrochlorination

Density functional theory (DFT) calculation was used to investigate the mechanism of Au3 clusters, separately supported on pure graphene (Au3/graphene) and one graphitic N-doped graphene (Au3/N-graphene). These supported Au3 clusters were used to catalyze acetylene hydrochlorination. Results show that the graphene supporter could obviously enhance the adsorption of reactants. Also, N-atom doping could broaden the energy gap between the HOMO of graphene and the LUMO of Au3, leading to the significantly attenuated interaction between the Au3 cluster and graphene by more than 19 kcal/mol (1 cal = 4.184 J). The two catalysts possessed extremely similar reaction mechanisms with activation energy values of 23.26 and 23.89 kcal/mol, respectively. The calculated activation barrier declined in the order of Au3 < Au3/N-graphene < Au3/graphene, suggesting that Au3/N-graphene could be a potential catalyst for acetylene hydrochlorination.

MOF-derived nitrogen-doped porous carbon as metal-free catalysts for acetylene hydrochlorination

A series of ZIF-derived nitrogen-doped carbon materials were prepared using melamine as the additional nitrogen sources for acetylene hydrochlorination. The results indicated that the optimal complex of Z4M1 exhibits the highest acetylene conversion of 60% under the reaction conditions of 180°C, C2H2 gas hourly space velocity (GHSV)=50h−1, VHCl/VC2H2=1.15, suggesting a promising metal-free catalyst for acetylene hydrochlorination. It is illustrated that the additions of melamine not only make the complex of Z4M1 displays special morphological structure and proper pore structure, but also adjust the relative content ratio of three nitrogen species in ZIF-derived nitrogen-doped carbon materials.

Effect of K promoter on the stability of Pd/NFY catalysts for acetylene hydrochlorination

Pd and PdK bimetallic catalysts were prepared and applied in acetylene hydrochlorination reaction. Using NFY zeolites as supports, the Pd-K/NFY catalyst showed both high activity and excellent stability, with a C2H2 conversion of 99% more than 50h. Characterized results indicate that the K promoter can stabilize the Pd2+ species and weaken the occurrence of carbon deposition on the catalyst surface, thus improving the stability of the Pd-based catalysts.

One-pot synthesis of nitrogen and sulfur co-doped activated carbon supported AuCl 3 as efficient catalysts for acetylene hydrochlorination

Abstract Commercialization of acetylene hydrochlorination using AuCl3 catalysts has been impeded by its poor stability. We have been studying that nitrogen-modified Au/NAC catalyst delivered a stable performance which can improve acetylene hydrochlorination activity and has resistance to catalytic deactivation. Here we show that nitrogen and sulfur co-doped activated carbon supported AuCl3 catalyst worked as efficient catalysts for the hydrochlorination of acetylene to vinyl chloride. Au/NSAC catalyst demonstrated high activity comparative to Au/AC catalyst. Furthermore, it also delivered stable performance within the selectivity of acetylene, reaching more than 99.5%, and there was only a 3.3% C2H2 conversion loss after running for 12 h under the reaction conditions of a temperature of 180 °C and a C2H2 hourly space velocity of 1480 h−1. The presence of the sulfur atoms may serve to immobilize/anchor the Au and also help prevent reduction and sintering of the Au and hence improve the catalytic activity and stability. The excellent catalytic performance of the Au/NSAC catalyst demonstrated its potential as an alternative to mercury chloride catalysts for acetylene hydrochlorination.