Nitrogen and phosphorus co-doped activated carbon induces high density Cu^(+)active center for acetylene hydrochlorination

This work aims to solve the problems of low reaction activity of Cu-based catalysts and agglomeration of active centers in acetylene hydrochlorination.Cu-based catalysts supported by NAP co-doped activated carbon(AC)with different content(mCu-xNP/AC)were manufactured and applied in the acetylene hydrochlorination reaction.It was found that the doping of carriers N and P induced the transformation of Cu^(2+)to Cu^(+),and the catalytic activity was markedly improved.Under the optimal reaction temperature of 220℃,the gas hourly space velocity(GHSV)of C_(2)H_(2)was 90 h^(-1)and V_(HCl):V_(C_(2)H_(2))was 1.15.The initial activity of the 5%Cu-30 NP/AC catalyst reached 95.59%.Through some characterization methods showed the addition of N and P improved the dispersion of Cu in carbon,which increased the ratio of Cu^+/Cu^(2+).The measurement results confirmed that the chemisorption capacity of mCu-xNP/AC for C_(2)H_(2)decreased slightly,and the chemisorption capacity for HCl increased significantly,which was the reason for the increased activity of the catalyst.The conclusion provides a reference for the development of acetylene hydrochlorination Cu catalyst.

Regulating the coordination environment of Ru single-atom catalysts and unravelling the reaction path of acetylene hydrochlorination

In this work,DFT calculations were used firstly to simulate the nitrogen coordinated metal single-atom catalysts(M-N_(x)SACs,M=Hg,Cu,Au,and Ru) to predict their catalytic activities in acetylene hydrochlorination.The DFT results showed that Ru-N_(x)SACs had the best catalytic performance among the four catalysts,and Ru-N_(x)SACs could effectively inhibit the reduction of ruthenium cation.To verify the DFT results,Ru-N_(x)SACs were fabricated by pyrolyzing MOFs in-situ spatially confined metal precursors.The N coordination environment could be controlled by changing the pyrolysis temperature.Catalytic performance tests indicated that low N coordination number(Ru-N_(2),Ru-N_(3))exhibited excellent catalytic activity and stability compared to RuCl_(3)catalyst.DFT calculations further revealed that Ru-N_(2)and Ru-N_(3)had a tendency to activate HCl at the first step of reaction,whereas Ru-N4tended to activate C_(2)H_(2).These findings will serve as a reference for the design and control of metal active sites.

Electron-deficient Cu site catalyzed acetylene hydrochlorination

Rational design of catalytic sites to activate the C≡C bond is of paramount importance to advance acetylene hydrochlorination. Herein, Cu sites with electron-rich and electron-deficient states were constructed by controlling the impregnation solutions. The π electrons flowing from acetylene to Cu site are facilitated over the electron-deficient Cu sites, achieving high activation of C≡C bond. The contradiction between the increased activation of acetylene required for enhanced catalytic activity and the resistance of Cu site to reduction by acetylene required for maintaining catalytic stability can be balanced by establishing strong interactions of Cu site with pyrrolic-N species. The catalytic activity displays a volcano shape scaling relationship as a function of Cu particle size. Tribasic copper chloride is concomitantly generated with the construction of electron-deficient Cu sites. The H–Cl bond of HCl can be activated over the tribasic copper chloride, accelerating the surface reaction of vinyl chloride production. This strategy of inducing electron deficiency provides new insight into the rational design of catalysts for the synthesis of vinyl chloride with a high catalytic performance.

The ligand coordination approach for improving the stability of low-mercury catalyst in the hydrochlorination of acetylene

Mercuric chloride supported on activated carbon(HgCl_2/AC) is used as an industrial catalyst for the hydrochlorination of acetylene. Loss of HgCl_2 by sublimating from the surface of activated carbon causes the irreversible deactivation of mercury catalyst and environmental pollution. In this work, a ligand coordination approach based on the Principle of Hard and Soft Acids and Bases(HSAB) was employed to design more stable lowmercury catalyst. The low-mercury catalysts(4% HgCl_2 loading) were prepared by using HgCl_2 and potassium halides(KX, X = Cl, I) as precursors. The HgCl_2-4KI/AC catalyst showed best catalytic stability than HgCl_2/AC and HgCl_2-4KCl/AC in the hydrochloriantion of acetylene. HgCl_2 could form more stable complex with KI,K_2HgI_4 as the main active component of the HgCl_2-4KI/AC catalyst. The characterizations of XRD and EDX analysis illustrated that the active component of HgCl_2-4KI/AC was highly dispersed on the surface of activated carbon.The sublimation rates of HgCl_2 from the catalysts verified that the active component with larger stability constant had better thermal stability. Using Hg(Ⅱ) complexes with high stability constant as the active component may be the research direction of developing highly stable low-mercury catalyst for the hydrochlorination of acetylene.

High nitrogen carbon material with rich defects as a highly efficient metal-free catalyst for excellent catalytic performance of acetylene hydrochlorination

In this work,we developed a simple strategy to synthesize a carbon material with high nitrogen and rich carbon defects.Our approach polymerized diaminopyridine(DAP) and ammonium persulfate(APS).Following a range of different temperature pyrolysis approaches,the resulting rough surface was shown to exhibit edge defects due to N-doping on graphite carbon.A series of catalysts were evaluated using a variety of characterization techniques and tested for catalytic performance.The catalytic performance of the N-doped carbon material enhanced alongside an increment in carbon defects.The NC-800 catalyst exhibited outstanding catalytic activity and stability in acetylene hydrochlorination(C_(2) H_(2) GHSV=30 h^(-1),at 220℃,the acetylene conversion rate was 98%),with its stability reaching up to 450 h.Due to NC-800 having a nitrogen content of up to 13.46%,it had the largest specific surface area and a high defect amount,as well as strong C_(2) H_(2) and HCl adsorption.NC-800 has excellent catalytic activity and stability to reflect its unlimited potential as a carbon material.

Melamine Modification of Spherical Activated Carbon and Its Effects on Acetylene Hydrochlorination

Commercial spherical activated carbon（SAC） was modified by impregnation to enhance the catalytic properties of SAC in acetylene hydrochlorination through melamine modification. Different modification conditions for SAC with nitrogen were compared by changing the SAC-Melamine ratios. The effect of carbonization temperature on the modification was also investigated. Surface chemistry and adsorption properties of the modified and unmodified SACs were studied by scanning electron microscope（SEM）, X-ray photoelectron spectroscopy（XPS）, elementary analysis, BET, and temperature-programmed desorption（TPD）. Moreover, the catalytic properties of SAC in acetylene hydrochlorination under differently modified conditions were also investigated. Elemental analysis showed that the nitrogen content of the modified SAC was greatly improved. XPS revealed that nitrogen mainly exists in Pyrrole nitrogen and Pyridine nitrogen. TPD showed that desorption of C2H2 was changed by modification. The conversion rate of acetylene was up to 70% under the following reaction conditions： temperature, 150 ℃; C2H2 hourly space velocity（GHSV）, 36 h-1; feed volume ratio V（HCl）/V（C2H2） = 1.15. The catalytic properties of SAC were improved significantly via melamine modification.

Hydrochlorination of acetylene over the Ru-based catalysts treated by plasma under different atmospheres

Ru-based catalysts modified in different atmospheres by plasma technology were prepared to catalyze the acetylene hydrochlorination reaction.The(Ru/AC)-N2(AC = activated carbon)catalyst yielded by the plasma modification of Ru/AC catalyst in N2 atmosphere exhibits the best catalytic performance with a stable C2H2 conversion of 87.2%;a relative increase of 27.1%in C2H2 conversion was achieved compared with that of the untreated Ru/AC catalyst.The results of the analysis revealed that the modification produced a mutual effect between the generated function groups on carrier AC and the active components, which can disperse and yield more active species in the fresh catalysts.These are benefits of enhancing the activity of the catalysts.Moreover, the modification can restrain coke formation and inhibit the loss of active species in the reaction, as well as strengthen the adsorption ability of reactants on the catalysts.These are benefits of improving the catalysts’ performance.

Process monitoring of the Au-S bond conversion in acetylene hydrochlorination

The continuous expansion of vinyl chloride production increases environmental pollution caused by mercury catalysts,which is an issue that urgently needs to be solved.Green and stable catalysts should be researched to alleviate this issue.In this research,Thiolactic acid acts as a ligand where sulfhydryl groups form a stable complex with Au on the surface of a spherical activated carbon(SAC).An Au-thiolactic acid/SAC catalyst was designed with a Au theoretical loading of 0.5%(mass)to overcome the disadvantages of traditional Au-based catalysts,such as a low conversion rate and poor life cycle.The ratio of Au to ligand was screened,and the activity was best when Au/S=1:8.The formation of the Au-S bond was proven by FT-IR and UV-vis.The longevity test of the Au1 S8/SAC catalyst was carried out at 1200 h^(-1) for 50 h.Samples with reaction times of 0 h,5 h,10 h,20 h,and 50 h were taken to monitor the catalyst status.The XPS and TPR tests proved that the Au-S bond broke as the acetylene hydrochlorination reaction proceeded,The DFT calculation proved that the Au-S bond is the active site,and the sulfur atom promotes the adsorption of C_(2)H_(2) by the catalyst.

Stabilizing supported gold catalysts in acetylene hydrochlorination by constructing an acetylene–deficient reaction phase

In the process of acetylene hydrochlorination,the rapid deactivation of supported gold(Au)catalysts by acetylene is still a huge challenge.Here,we provide an innovative strategy for constructing an acetylene–deficient reaction phase on the active site by coating an ionic liquid film on the Au(H2O)/C surface.The reactant ratio of C2H2 to HCl in this acetylene–deficient reaction phase is 1:132,in contrast to the 1:1 M ratio in the gas phase,thus boosting the catalytic stability of Au(H2O)/C catalysts.The kinetic and theoretical analysis showed that the reduction of cationic gold by C2H2 and the generation of carbon deposition can be inhibited in this constructed reaction phase during reaction.The current work not only broadens the scope of supported Au catalysts in acetylene hydrochlorination,but also verifies the perspective of the tunability of stoichiometric balance,which can be used in other catalytic applications.

Free radicals induced ultra-rapid synthesis of N-doped carbon sphere catalyst with boosted pyrrolic N active sites for efficient acetylene hydrochlorination

Activated carbon-supported HgCl2 catalysts have seriously impeded the development of the polyvinyl chloride(PVC)industry due to the sublimation of Hg species and environmental pollution problems.Herein,the template-free and organic solvent-free strategy was devised to synthesize non-metallic based nitrogen-doped carbon(U-NC)sphere catalyst for acetylene hydrochlorination.This green strategy via ultrasonic chemistry initiates resin crosslinking reactions between aminophenol and formaldehyde resin by free radicals,leading to the ultra-rapid formation of U-NC with remarkably high pyrrolic N content in only 5 min.This U-NC catalyst exhibited an outstanding space-time-yield(1.6 gVCM·gcat^(−1)·h^(−1)),even comparable to the reported metallic catalyst.By combining kinetic analysis,advanced characterizations,density functional theory,it is found that the amount of pyrrolic N is in linear with C_(2)H_(2)conversion,pyrrolic N in U-NC can effectively improve acetylene hydrochlorination performance by mediating HCl adsorption.This work sheds new light on rationally constructing metal-free catalyst for acetylene hydrochlorination.

Manipulating micro-electric field and coordination-saturated site configuration boosted activity and safety of frustrated single-atom Cu/O Lewis pair for acetylene hydrochlorination

Simultaneously boosting acetylene hydrochlorination activity and avoiding formation of explosive copper acetylide over Cu-based catalyst,which represented a promising alternative to Hg-based and noble metal catalysts,remained challenging.Herein,we fabricated a frustrated single-atom Cu/O Lewis pair catalyst(Cu/O-FLP)by coupling epoxide group(C-O-C)with atomdispersed Cu-cis-N_(2)C_(2)Cl center to address this challenge.The basic epoxy site modulated the electron-deficient state of Lewisacidic Cu center and paired with the Cu-cis-N_(2)C_(2)Cl moiety to preferentially break HCl into different electronegative Cu-Clδ-and C-O-H^(δ+)intermediates,which further induced both an extra localized electric field to polarize acetylene and a upshift of the dband center of catalyst,thereby promoting adsorption and enrichment of acetylene by enhancing the dipolar interaction between acetylene and active intermediates.Moreover,the generated Cu-Clδ-and C-O-H^(δ+)drastically reduced the energy barrier of ratelimiting step and made vinyl chloride easier to desorb from the Lewis-basic oxygen-atom site rather than traditional Lewis-acidic Cu center.These superiorities ensured a higher activity of Cu/O-FLP compared with its counterparts.Meanwhile,preferential dissociation of HCl endowed single-atom Cu with the coordination-saturated configuration,which impeded formation of explosive copper acetylide by avoiding the direct interaction between Cu and acetylene,ensuring the intrinsic safety during catalysis.

Application of SnO_(x)/AC catalyst for the acetylene hydrochlorination

In this work,SnO_(x)/activated carbon(AC)was synthesized by hydrothermal method,which was applied to acetylene hydrochlorination.Characterizations showed the SnO_(x)nanoparticles were uniformly dispersed on the carbon,with the coexistence of SnO and SnO_(2).The acetylene conversion of SnO_(x)/AC was 75%,much higher than that of SnCl_(4)/AC.It was shown that the adsorption of reactants on SnO_(x)was stronger than on SnCl_(4).Theoretical calculations showed the adsorption energies of reactants on SnO_(x)were thermodynamically favorable and suggested that Sn^(4+)and Sn^(2+)in SnO_(x)have different adsorption capacities for reactants.Through adjusting the valence ratio of SnO_(x),SnO_(x)/AC O 4 h(O for oxidation)exhibited the best catalytic performance and had the strongest adsorption capacity for the reactants.However,the SnO_(x)/AC catalyst was easily deactivated during acetylene hydrochlorination due to the loss of Sn.The doping of N effectively reduced the loss of Sn and improved the stability of the catalyst due to the anchoring effect of N on the SnO_(x)particles.

Hydrochlorination of Acetylene Using SiC Foam Supported Structured C/Au Catalysts

AuCl3 loaded structured catalysts were prepared on SiC foam supported with pre-coated activated carbon layers. The catalytic properties of the structured catalysts towards hydrochlorination of acetylene were tested in a fixed- bed reactor with the AuCl3 loaded on activated carbon pellets as a reference. For isopyknic catalysts, the structured catalyst with only one fifth of the Au amount as that was used on the reference catalyst exhibited even a little higher acetylene conversion and much better stability than the latter no matter what the gas hourly space velocities of acetylene were used. The results indicated that the more homogeneous distribution of AuCl3 particles and better heat transfer along the fixed-bed reactor originated from the low pressure drop and high thermal conductivity of the SiC foam supported structured catalysts might be able to account for their improved efficiency and stability. It is befieved that these novel structured C/Au catalysts can be potentially applied in VCM industrialization in view of their greatly reduced cost and much prolonged life.

Improvement of the stability of Hg/AC catalysts by CsCl for the high-temperature hydrochlorination of acetylene

Activated carbon-supported mercuric chloride（HgCl2） is used as an industrial catalyst for acetylene hydrochlorination. However, the characteristic of easy sublimation of HgCl2 leads to the deactivation o the catalyst. Here, we showed that the thermal stability of the Hg/AC catalyst can be evidently improved when Cs Cl is added into the Hg/AC catalyst. Compared with the pure Hg/AC catalyst, the sublimation rate of HgCl2 from the Hg–Cs/AC catalyst decreased significantly and the Hg–Cs/AC catalyst showed bette catalytic activity and stability in the reaction. This promoting effect is related to the existence of cesium mercuric chlorides（CsxHgyCl（x＋2y）） highlighted by XRD, HR-TEM and EDX analyses. Thus, reacting HgCl2 with alkali chlorides to form alkali-mercuric chlorides may be a key to design highly efficient and thermally stable mercuric chloride catalyst for hydrochlorination reactions.

One-pot synthesis of nitrogen and sulfur co-doped activated carbon supported AuCl_3 as efficient catalysts for acetylene hydrochlorination

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.

Hydrochlorination of acetylene using expanded multilayered vermiculite(EML-VMT)-supported catalysts

Catalyst supports have very important effects on catalyst performance.A novel expanded multilayered vermiculite（EML-VMT） is successfully used as the catalyst support for the acetylene hydrochlorination.By mixing carbon on the surface of EML-VMT[i.e.,EML-VMT-C）,the HgCl2/EML-VMT-C achieved a high acetylene conversion of 97.3%,a vinyl chloride selectivity of 100%and a turn over frequency（TOF） value of 8.83 × 10^-3s^-1 at a temperature of 140 C,an acetylene gas hourly space velocity（GHSV） of 108 h^-1,and a feed volume ratio V（HC1）/V（C2H2） of 1.15.Moreover,the HgCl2/EML-VMT-C shows good stability.The EML-VMT also shows potential in the preparation of other EML-VMT-supported catalysts.

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

The addition of yttrium chloride(YCl) 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 YCl-modified catalysts(Y-Au/AC)were measured by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, CH-temperature programmed desorption, and scanning transmission electron microscopy.The presence of YClwas found suppressing the reduction of highly oxidized Au(δ=1,3) to metallic Au~0 dependently and thus retard the agglomeration of Au nanoparticles during the reaction. In addition,the additive of YClto 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(CH) = 800 hat 180 ℃.The durability test indicates that the 5 Y-1 Au/AC catalyst maintains high catalytic activity for more than2300 h at 30 hGHSV(CH) and 180 ℃, indicating great promise as a non-mercury catalyst for PVC manufacture.

Active carbon supported S-promoted Bi catalysts for acetylene hydrochlorination reaction

In the present work, the sulfur doped bismuth-based catalysts were prepared by incipient wetness impregnation method and used for the hydrochlorination of acetylene to vinyl chloride monomer （VCM） in a fixed-bed reactor. The effect of introduction of S was characterized by N2 adsorption-desorption, powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, temperature-programmed reduction and X-ray photoelectron spectroscopy. The characterization results indicated that the doping of S resulted in the increase of Brunauer-Emmett-Teller （BET） surface areas and decrease of active species particle size for the Bi-based catalysts, which led to more accessible active sites, and consequently boosted the catalytic hydrochlorination activity. The effect of H2SO4 concentration on the activity of this type catalyst was examined, and the results showed that there is an optimal loading of H2SO4 （S/Bi=0.5 mol/mol）, at which the conversion of C2H2 was enhanced to 81% under the reaction condition and coke deposition is a main reason for the deactivation of catalyst.

Catalyst-free hydrochlorination protocol for terminal arylalkynes with hydrogen chloride

We present a simple and straightforward protocol for hydrochlorination of terminal arylalkynes to vinyl chlorides using hydrogen chloride under mild reaction conditions. This protocol does not involve any metal catalysts or additives. It is simple, inexpensive, and easy to prepare, and exhibits good reaction activity. The hydrochlorination proceeds smoothly to yield unique regioselective products via the Markovnikov addition rule.

Nitrogen doped carbon catalyzing acetylene conversion to vinyl chloride

Commercial production of vinyl chloride from acetylene relies on the use of HgCla as the catalyst, which has caused severe environmental problem and threats to human health because of its toxicity. Therefore, it is vital to explore alternative catalysts without mercury. We report here that N-doped carbon can catalyze directly transformation of acetylene to vinyl chloride. Particularly, N-doped high surface area mesoporous carbon exhibits a rather high activity with the acetylene conversion reaching 77% and vinyl chloride selectivity above 98% at a space velocity of 1.0 mL.min-l.g-1 and 200 ~C. It delivers a stable performa℃nce within a test period of 100h and no obvious deactivation is observed, demonstrating potentials to substitute the notoriously toxic mercuric chloride catalyst.