Acetylene hydrochlorination over supported ionic liquid phase(SILP)gold-based catalyst:Stabilization of cationic Au species via chemical activation of hydrogen chloride and corresponding mechanisms

The activation of HCl by cationic Au in the presence of C2H2 is important for the construction of active Au sites and in acetylene hydrochlorination.Here,we report a strategy for activating HCl by the Au-based supported ionic liquid phase(Au–SILP)technology with the[N(CN)2^–]anion.This strategy enables HCl to accept electrons from[N(CN)2^–]anions in Au–[N(CN)2^–]complexes rather than from pure[Bmim][N(CN)2],leading to notable improvement in both the reaction path and the stability of the catalyst without changing the reaction triggered by acetylene adsorption.Furthermore,the induction period of the Au–SILP catalyst was shown to be absent in the reaction process due to the high Au(III)content in the Au(Ⅲ)/Au(Ⅰ)site and the high substrate diffusion rate in the ionic liquid layer.This work provides a facile method to improve the stability of Au-based catalysts for acetylene hydrochlorination.

Oxygen and nitrogen-doped metal-free carbon catalysts for hydrochlorination of acetylene

Activated carbon was tested as metal-free catalyst for hydrochlorination of acetylene in order to circumvent the problem of environment pollution caused by mercury and high cost by noble metals. Oxygen-doped and nitrogen-doped activated carbons were prepared and characterized by XPS, TPD and N2 physisorption methods. The influences of the surface functional groups on the catalytic performance were discussed base on these results. Among all the samples tested, a nitrogen-doped sample, AC-n-US00, exhibited the best performance, the acety- lene conversion being 92% and vinyl chloride selectivity above 99% at 240 ~C and C2H2 hourly space velocity 30 h- 1. Moreover, the AC-n-US00 catalyst exhibited a stable performance during a 200 h test with a conversion of acetylene higher than 76% at 210 ~C at a C2H2 hourly space velocity 50 h 1. In contrary, oxygen-doped catalyst had lower catalytic activities. A linear relationship between the amount of pyrrolic-N and quaternary-N species and the catalytic activity was observed, indicating that these nitrogen-doped species might be the active sites and the key in tuning the catalytic performance. It is also found that the introduction of nitrogen species into the sample could significantly increase the adsorption amount of acetylene. The deactivation of nitrogen- doped activated carbon might be caused by the decrease of the accessibility to or the total amount of active sites.

Highly Active and Stable Ni_2P/SiO_2 Catalyst for Hydrogenation of C_9 Petroleum Resin

Catalytic hydrogenation is an appropriate method for the improvement of C9 petroleum resin（C9PR） quality. In this study, the Ni2P/SiO2（containing 10% of Ni） catalyst prepared by the temperature-programmed reduction（TPR） method was used for hydrogenation of C9 petroleum resins. The effect of reaction conditions on catalytic performance was studied, and the results showed that the optimum reaction temperature, pressure and liquid hourly space velocity（LHSV） was 250 ℃, 6.0 MPa, and 1.0 h-1, respectively. The bromine numbers of hydrogenated products were maintained at low values（250 mg Br/100g） within 300h, showing the high activity and stability of Ni2P/SiO2 catalyst. The fresh and spent catalysts were characterized by X-ray diffraction（XRD）, BET surface area（BET） analysis, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared（FTIR） pyridine adsorption, and X-ray photoelectron spectroscopy（XPS）. Compared with the traditional sulfurated-Ni W catalysts, Ni2P possessed globe-like structure instead of layered structure like the active phase of Ni WS, thereof exposing more active sites, which were responsible for the high activity of Ni2P/SiO2 catalyst. The stability of Ni2P/SiO2 catalyst was probably attributed to its high sulfur tolerance, antisintering, anti-coking and carbon-resistance ability. These properties might be further ascribed to the special Ni-P-S surface phase, high thermal stability of Ni2P nanoparticles and weak surface acidity for the Ni2P/SiO2 catalyst.

Controllable synthesis of novel nanoporous manganese oxide catalysts for the direct synthesis of imines from alcohols and amines

A novel template-free oxalate route was applied to synthesize different mesoporous manganese oxides(amorphous manganese oxide(AMO),Mn5 O8,Mn3 O4,Mn O2)in the narrow temperature range from 350°C to 400°C by controlling the calcination conditions,which were employed as the efficient catalysts for the oxidative coupling of alcohols with amines to imines.The chemical and structural properties of the manganese oxides were characterized by the methods of thermogravimetry analysis and heat flow(TG-DSC),X-ray diffraction(XRD),nitrogen sorption,scanning electron microscope(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),H2 temperature-programmed reduction(H2-TPR),and inductively coupled plasma optical emission spectrometry(ICP-OES)techniques.The structures of different manganese oxides were confirmed by characterization.The M-350(AMO)presented the maximum surface area,amorphous nature,the lowest reduction temperature,the higher(Mn3++Mn4+)/Mn2+ratio,and the higher adsorbed oxygen species compared to other samples.Among the catalysts,M-350 showed the best catalytic performance using air as an oxidant,and the conversion of benzyl alcohol(BA)and the selectivity of N-benzylideneaniline(NBA)reached as high as 100%and 97.1%respectively at the lower reaction temperature(80°C)for 1 h.M-350 had also the highest TOF value(0.0100 mmol·mg-1·h-1)compared to the other manganese oxide catalysts.The catalyst was reusable and gave 95.8%conversion after 5 reuse tests,the XRD pattern of the reactivated M-350 did not show any obvious change.Lattice oxygen mobility and(Mn3++Mn4+)/Mn2+ratio were found to play the important roles in the catalytic activity of aerobic reactions.

Study on the Precursor Phase Composition of Fused Iron Catalyst for Fischer-Tropsch Synthesis

The effect of the precursor composition of fused iron catalyst on the performance of Fischer-Tropsch synthesis was investigated. XRD, BET and CO2 adsorption experiments were carried out to provide better insight into the relationship therein. The results showed that the selectivity of C5＋ hydrocarbon products was dependent on the mole ratio of Fe^2＋/Fe^3＋, which was represented by a hump-shaped curve. Catalysts with precursors containing Fe3O4 phase favored the magnetite spinal formation during F-T reaction, while Fe（1-x）O-based catalysts were more likely to favor the formation and growth of the iron carbide crystals.

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.

Graphdiyne anchoring to construct highly dense palladium trimer active sites for the selective hydrogenation of acetylene

Semi-hydrogenation of acetylene is of growing interest and popularity but subjects to a major challenge in selective hydrogenation to ethylene.Here,we report a strategy that uses graphdiyne(GDY)as a carrier to prepare single-cluster catalysts(SCCs),which on average clusters composed of three atoms(denoted as Pd3 trimer)and applied it to the acetylene semihydrogenation in the presence of large amounts of ethylene.Based on experimental results and systematic quantum chemical research and computational screening,we found that there are multiple active Pd structures on GDY and the Pd3 trimer anchored on GDY is a specific and durable cluster with great potential for accurate and efficient heterogeneous catalysis.The synergetic effects between neighboring atoms in Pd trimer guarantee easy desorption of ethylene and the absence of unselective hydride species thereby preventing excessive hydrogenation to generate unwanted byproducts,which is a crucial mechanism for the excellent selectivity of the catalyst.This new method for precise synthesis Pd clusters provides accurate ways for designing selective hydrogenation catalysts at the atomic scale.

Research progress in green synthesis of ammonia as hydrogen-storage carrier under‘hydrogen 2.0 economy’

Hydrogen energy is characterized by its environmental friendliness,high efficiency,lack of carbon emissions and wide range of applications.However,its transportation and storage are challenges that limit further development of the hydrogen-energy industry.Ammonia is a carbon-free hydrogen-rich carrier.The storage of hydrogen in ammonia has unique advantages of high energy density,easy storage and transportation,reliable safety,a mature industrial foundation and no tail-end carbon emissions.However,industrial ammonia synthesis still heavily relies on the Haber-Bosch process,which accounts for significant energy consumption and greenhouse gas emissions.Therefore,the development of green and sustainable ammonia-synthesis methods is extremely important and urgent.Recently,ammonia-synthesis technologies such as electrocatalysis,photocatalysis,photoelectrocatalysis and biocatalysis have successfully produced ammonia from nitrogen and water,resulting in lower costs.The nitrogen-reduction-reaction conditions of these methods are mild and can be carried out under ambient temperatures and atmospheric pressure with low energy consumptions.Meanwhile,these methods bypass the traditional hydrogen-production section and their routes are simpler.Therefore,these technologies can be used to flexibly integrate renewable energy,including intermittent renewable energy,to achieve distributed ammonia synthesis.These benefits contribute to both global energy and environmental sustainability goals.In this study,the mechanisms of ammonia synthesis under ambient conditions are reviewed and the technical difficulties of various catalysts for ammonia synthesis are summarized.Based on the optimization strategies reported for various catalysts,the high-performing catalysts reported for ammonia synthesis are reviewed and the developmental trend of this field has been forecasted.

Benzene alkylation with methanol over phosphate modified hierarchical porous ZSM-5 with tailored acidity

The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently. The acid strength and sites amount of Br?nsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.

Synthesized high-silica hierarchical porous ZSM-5 and optimization of its reaction conditions in benzene alkylation with methanol

In our present work, the high-silica hierarchical porous ZSM-5 with appropriate Br(o|¨)nsted acidity and hierarchical porous structure was synthesized by sol-gel method for continuously catalytic conversion of benzene alkylation with methanol to xylene. The effects of temperature, pressure, benzene/methanol molar ratio and weight hour space velocity(WHSV) on the catalytic performance of the catalyst were investigated as well. As a result, the high-silica hierarchical porous ZSM-5 showed great performance as the yield of xylene was up to 41.1% under the optimum reaction conditions(500 ℃,0.1 MPa,M_(benzene)/M_(methanol)= 1:1.5 and WHSV=4 h 1), while the selectivity to by-product, ethylbenzene, was well suppressed(below 0.1%). In addition, the catalyst structure and properties were characterized by the means of XRD, IR, TPD,SEM, TEM and N_2 physical adsorption technologies.

Behavior of adsorbed diphenyl-sulfide on the Pd/C catalyst for o-chloronitrobenzene hydrogenation

A series of diphenyl-sulfide （Ph2S）-immobilized Pd/C catalysts （Pd-Ph2Scx）/C） were prepared using the wetness-impregnation and immobilization method. Pd-Ph2S（x）/C catalysts employed for the hydro- genation of o-chloronitrobenzene showed very high selectivity. The structure of Pd-Ph2Scx）/C with different molar ratio of ligand （x-values） was characterized by XPS and TG-DSC-MS. The results suggest a ＂saturated＂ surface ratio of Ph2S/Pd （about 0.3） was formed on the Pd-Ph2S（x）[C catalysts surface. The Ph2S immobilized on the Pd particle is quite stable, and the desorption of Ph2S or dissociative loss of phenyl group was only found at temperatures above 500 K. The possible catalytic mechanism of the Pd-Ph2S（x）/C catalyst was also discussed.

Synthesis of carbon-supported Pd/SnO_2 catalyst for highly selective hydrogenation of 2,4-difluoronitrobenzene

Halogenated anilines have a wide range of applications in the production of pharmaceuticals and agrochemical substances, and thus it is of great importance to develop highly active and selective catalysts for the hydrogenation of halogenated nitrobenzenes. We approach this challenge by probing noble metal/non-noble metal oxide nanoparticles（NPs） catalysts. Carbon-supported Pd/SnO2catalysts were synthesized by the chemical reduction method, and their catalytic activity was evaluated by the hydrogenation reaction of 2,4-difluoronitrobenzene（DFNB） to the corresponding 2,4-difluoroaniline（DFAN）, showing a remarkable synergistic effect of the Pd and SnO2 NPs. The as-prepared Pd/SnO2/C catalysts were characterized using TEM, XRD, H2 TPD and XPS techniques. Modifications to the electronic structure of the Pd atoms through the use of SnO2 led to the suppression of the hydrogenolysis of the C–F bond and the acceleration of nitrosobenzene（DFNSB） conversion and consequently, resulted in the inhibition of the formation of reactive by-products and may be responsible for the enhancements observed in selectivity.

High halogenated nitrobenzene hydrogenation selectivity over nano Ir particles

The selective hydrogenation of halogenated nitrobenzene over noble metal catalysts(Pd, Pt, and Ir) has attracted much attention owing to its high efficiency and environmental friendliness. However, the effect of size on the catalytic performance varies among different metal catalysts. In this study, sub-nano(<3 nm) Ir and Pd particles were prepared, and their catalytic properties for hydrogenation of halogenated nitrobenzene were evaluated.Results show that high selectivity(N 99%) was achieved over small Ir nanoparticles, in which the selectivity over the Pd with same size was much lower than that on Ir nanoparticles. Meanwhile, Ir and Pd have different hydrogen consumption rates and reaction rates. Density functional theory calculations showed that p-chloronitrobenzene(CNB) has different adsorption properties on Ir and Pd. The distance between oxygen(cholorine) and Ir is much shorter(longer) than that between oxygen and Pd. The reaction barriers of dechlorination of p-CNB and p-chloroaniline over different Ir models are much larger than those on Pd. Especially,lower coordination of Ir leads to larger barriers of dechlorination reaction. These theoretical results explain the difference between Ir and Pd on hydrogenation of halogenated nitrobenzene.

Highly selective hydrogenation of halonitroaromatics to aromatic haloamines by ligand modified Ni-based catalysts

Ligand modification of Ni-based catalysts by coordination of dicyandiamide to Ni metal leads to enhanced selectivity for the selective hydrogenation of halonitroaromatics.The selectivity of above 99.9%to aromatic haloamines can be achieved at the conversion of 100%.The results of H_2-TPD and FT-IR experiments show that Ni^-H~＋ species possessing the properties of Lewis acid site on the surface of Raney Ni could be responsible for the hydrodehalogenation.When Raney Ni was treated by dicyandiamide,Ni^-H~＋ species interacted with N atom from the dicyandiamide.This interaction was stable even at reaction temperature,which reduced the possibility to form the intermediate state of Ar-Cl...H~＋Ni^-.And then C-Cl bond could not be polarized and activated.The hvdrodechlorination process was suppressed effectively.

Highly selective oxidation of amines to imines by Mn2O3 catalyst under eco-friendly conditions

Enhancing the selectivity of imines for the oxidative self-coupling of primary amines was found to be challenging in the heterogeneous catalysis.Three different manganese oxides(M-3,M-4,M-5) were synthesized by controlling the calcination temperature using a simple template-free oxalate route.The prepared manganese oxides were systematically characterized using XRD,N2 sorption,SEM,TEM,XPS,H2-TPR techniques.M-4 gave 96.2% selectivity of imine at 100% conversion of benzylamine,which was far more superior than other existing protocols.Mn^3+/Mn^4+ ratio was found to affect the selectivity of the imines.The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time.

Highly Selective Gas-phase Synthesis of 1,1-Dichloroethylene from 1,1,2-Trichloroethane over Supported Amine Catalysts

The manufacture of 1,1-dichloroethylene（1,1-DCE） usually employs liquid phase method to perform the dehydrochlorination of 1,1,2-trichloroethane（TCE）, where large amounts of high-concentration salty wastewater is produced inevitably. It has been a long-term goal to achieve the gas phase synthesis of 1,1-DCE via supported cata- lysts. In this work, the gas-phase synthesis of 1,1-DCE from TCE was studied in the presence of pentaethylenehexamine（PEHA） supported on silica. High and stable selectivity to 1,1-DCE（up to 98%） was obtained, which could be ascribed to the relatively strong basicity of PEHA according to a proposed E2 mechanism. The formation of PEHA chloride from the HCI generated in situ was detected and was considered to be the main reason for the deactivation of PEHA catalyst.

Nitridation:A simple way to improve the catalytic performance of hierarchical porous ZSM-5 in benzene alkylation with methanol

Nitrided hierarchical porous ZSM-5 was synthesized by nitridation of hierarchical porous ZSM-5 with flowing ammonia at elevated temperature.The samples were characterized by XRD,SEM,Nitrogen sorption isotherms,NH3-TPD and Py-IR,and evaluated in alkylation of benzene and methanol.The result indicated that the high specific surface area of parent ZSM-5 was maintained,while the Bronsted acidity was effectively adjusted by nitridation.Moreover,the high suppression of ethylbenzene was observed on nitrided catalyst and this could be attributed to the decrease of Bronsted acidity which suppressed the methanol to olefins reactions.

Pd/C modified with Sn catalyst for liquid-phase selective hydrogenation of maleic anhydride to gamma-butyrolactone

Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride（MA） to gamma-butyrolactone（GBL）.Thus,Pd/C catalysts modified with different Sn loadings were synthesized,and characterized by XRD,XPS,TEM and elemental mapping.The types of alloy phase and the amounts of the surface Pd-SnOx sites altered along with Sn/Pd mass ratios from 0-1.0synthesized in the process of preparation.The maximum reaction rate was 0.57 mol-GBL/（mol-Pd min）and selectivity was 95.94%when the Sn/Pd mass ratio was 0.6.It might be attributed to the formation of Pd2Sn alloy and less amounts of Pd-SnOx sites.

One pot synthesis of N-ethylaniline from nitrobenzene and ethanol

A novel method for the one pot synthesis of N-alkyl arylamines from nitro aromatic compounds and alcohols is proposed through the combination of the aqueous-phase reforming of alcohol for hydrogen production, the reduction of nitro aromatic compounds for the synthesis of aromatic amine and the N-alkylation of aromatic amine for the production of N-alkyl arylamine over an identical catalyst under the same conditions of temperature and pressure in a single reactor. In this process, hydrogen generated from the aqueous-phase reforming of alcohols was used in-situ for the hydrogenation of nitro aromatic compounds for aromatic amine synthesis, followed by N-alkylation of aromatic amine with alcohols to form the corresponding N-alkyl arylamines at a low partial pressure of hydrogen. For the system composed of nitrobenzene and ethanol, under the conditions of 413 K and PN2 = 1 MPa, the conversion degrees of nitrobenzene and aniline were 100%, the selectivity to N-ethylaniline and N, N-diethylaniline were 85.9% and 0%-4%, respectivity, after reaction for 8 h at the volumetric ratio of nitrobenzene:ethanol:water = 10:60:0. The selectivity for N, N-diethylaniline production is much lower than that through the traditional method. In this process, hydrogen and aromatic amines generated from the aqueous-phase reforming of alcohols and hydrogenation of nitro aromatic compounds, respectively, could be promptly removed from the surface of the catalyst due to the occurrence of in-situ hydrogenation and N-alkylation reactions. Thus, this may be a potential approach to increase the selectivity to N-alkyl arylamine.

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.