Enhanced stability of nitrogen-doped carbon-supported palladium catalyst for oxidative carbonylation of phenol

Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.

Boron-doped lamellar porous carbon supported copper catalyst for dimethyl oxalate hydrogenation

Doping heteroatoms on carbon materials could bring some special advantages for using as catalyst support.In this work, a boron doped lamellar porous carbon(B-LPC) was prepared facilely and utilized as carbonbased support to construct Cu/B-LPC catalyst for dimethyl oxalate(DMO) hydrogenation. Doping boron could make the B-LPC own more defects on surface and bigger pore size than B-free LPC, which were beneficial to disperse and anchor Cu nanoparticles. Moreover, the interaction between Cu species and B-LPC could be strengthened by the doped B, which not only stabilized the Cu nanoparticles, but also tuned the valence of Cu species to maintain more Cu^(+). Therefore, the B-doped Cu/B-LPC catalyst exhibited stronger hydrogenation ability and obtained higher alcohols selectivity than Cu/LPC, as well as high stability without decrease of DMO conversion and ethylene glycol selectivity even after 300 h of reaction at 240℃.

N-doped ordered mesoporous carbon as a multifunctional support of ultrafine Pt nanoparticles for hydrogenation of nitroarenes

Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content （9.58 wt%）, high surface area （417 m^2/g）, and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles （NPs）. The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs （about 1.0 ± 0.5 nm） to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger （4.4 ± 1.7 nm） and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity （conversion 100%） and selectivity （〉99%） in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst （conversion 89% and selectivity 90%）. This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.

A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

A carbon nanotube-supported NiP amorphous catalyst （NiP/CNT） was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Preparation and Characterization of Carbon Nanotubes-Coated Cordierite for Catalyst Supports

The carbon nanotubes-coated cordierite （CNTs-cordierite） was fabricated by pyrolysis of ethine on cordierite with iron catalyst, which was penetrated into the cordierite substrate by vacuum impregnation. The cordierite substrate, carbon naontubes, and CNTs-cordierite were characterized by SEM, TEM/HREM, BET, and TGA. The results show that the carbon nanotubes were distributed uniformly on the surface of cordierite. A significant increase in BET surface area and pore volume was observed, and a suitable pore-size distribution was obtained. On the CNTs-cordierite, carbon nanotubes penetrated into the cordierite substrate, which led to a remarkable stability of the CNTs against ultrasound maltreatment. Growth time is an important factor for thermostability and texture of the sample. The mass increased but the purity decreased with the growth time, which caused the exothermic peak shift to low temperature, and the corresponding full width half maximum （FWHM） of the peak in DTG increased.

Study on the Reaction Mechanism for Carbon Dioxide Reforming of Methane over supported Nickel Catalyst

The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalyst were extensively investigated by TPSR and TPD experiments. It showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalyst, while CO2 adsorbed on the catalyst weakly and only existed in one kind of adsorption state. Then the mechanism of interaction between the species dissociated from CH4 and CO2 during reforming was proposed.

Effect of Activated Carbon as a Support on Metal Dispersion and Activity ofRuthenium Catalyst for Ammonia Synthesis

Ten kinds of activated carbon from different raw materials were used as supports to prepare ruthenium catalysts. N_2 physisorption and CO chemisorption were carried out to investigate the pore size distribution and the ruthenium dispersion of the catalysts. It was found that the Ru dispersion of the catalyst was closely related to not only the texture of carbon support but also the purity of activated carbon. The activities of a series of the carbon-supported barium-promoted Ru catalysts for ammonia synthesis were measured at 425 ℃, 10 0 MPa and 10 000 h -1. The result shows that the same raw material activated carbon, with a high purity, high surface area, large pore volume and reasonable pore size distribution might disperse ruthenium and promoter sufficiently, which activated carbon as support, could be used to manufacture ruthenium catalyst with a high activity for ammonia synthesis. The different raw material activated carbon as the support would greatly influence the catalytic properties of the ruthenium catalyst for ammonia synthesis. For example, with coconut shell carbon(AC1) as the support, the ammonia concentration in the effluent was 13 17% over 4%Ru-BaO/AC1 catalyst, while with the desulfurized coal carbon(AC10) as the support, that in the effluent was only 1 37% over 4%Ru-BaO/AC10 catalyst.

Photocatalytic degradation of L- acid by TiO_2 supported on the activated carbon

TiO2 sol was prepared by sol-gel technique with tetrabutyl titanate as precursor. Supported TiO2 catalysts on activated carbon were prepared by soak and sintering method. The aggregation of nano-TiO2 particles can be effectively suppressed by added polyethylene glycol （PEG） as a surface modifier. The average particle diameter of TiO2, specific surface area and absorbability of catalyst can be modified. Based on characteristics of the TiO2 photocatalyst with XRD, specific surface area, adsorption valves of methylene blue and the amount of TiO2 supported on the activated carbon, the photocatalytic degradation of L-acid was studied. The effect of the factors, such as pH of the solution, the initial concentration of L-acid on the photocatalytic degradation of L-acid, were studied also. It was found that when the pH of the solution is 1.95, the amount of photocatalyst is 0.5 g, the concentration of the L-acid solution is 1.34×10^3 mol/L and the illumination time is 7 h, the photocatalytic degradation efficiency of L-acid can reach 89,88%, The catalyst was reused 6 times and its degradation efficiency hardly changed.

Enhancement of the formic acid electrooxidation activity of palladium using graphene/carbon black binary carbon supports

Combinations of graphene(Gr)and carbon black(C)were employed as binary carbon supports to fabricate Pd‐based electrocatalysts via one‐pot co‐reduction with Pd2+.The electrocatalytic performance of the resulting Pd/Gr‐C catalysts during the electrooxidation of formic acid was assessed.A Pd/Gr0.3C0.7(Gr oxide:C=3:7,based on the precursor mass ratio)electrocatalyst exhibited better catalytic performance than both Pd/C and Pd/Gr catalysts.The current density generated by the Pd/Gr0.3C0.7catalyst was as high as102.14mA mgPd?1,a value that is approximately3times that obtained from the Pd/C(34.40mA mgPd?1)and2.6times that of the Pd/Gr material(38.50mA mgPd?1).The anodic peak potential of the Pd/Gr0.3C0.7was120mV more negative than that of the Pd/C and70mV more negative than that of the Pd/Gr.Scanning electron microscopy images indicated that the spherical C particles accumulated on the wrinkled graphene surfaces to form C cluster/Gr hybrids having three‐dimensional nanostructures.X‐ray photoelectron spectroscopy data confirmed the interaction between the Pd metal and the binary Gr‐C support.The Pd/Gr0.3C0.7also exhibited high stability,and so is a promising candidate for the fabrication of anodes for direct formic acid fuel cells.This work demonstrates a simple and cost‐effective method for improving the performance of Pd‐based electrocatalysts,which should have potential industrial applications.

Systematic variation of the sodium/sulfur promoter content on carbon-supported iron catalysts for the Fischer–Tropsch to olefins reaction

The Fischer–Tropsch to olefins（FTO） process is a method for the direct conversion of synthesis gas to lower C–Colefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction.The catalytic activity can be improved and undesired formation of alkanes can be suppressed by the addition of sodium and sulfur as promoters but the influence of their content and ratio remains poorly understood and the promoted catalysts often suffer from rapid deactivation due to particle growth. A series of carbon black-supported iron catalysts with similar iron content and nominal sodium/sulfur loadings of 1–30/0.5–5 wt% with respect to iron are prepared and characterized under FTO conditions at 1and 10 bar syngas pressure to illuminate the influence of the promoter level on the catalytic properties.Iron particles and promoters undergo significant reorganization during FTO operation under industrially relevant conditions. Low sodium content（1–3 wt%） leads to a delay in iron carbide formation. Sodium contents of 15–30 wt% lead to rapid loss of catalytic activity due to the covering of the iron surface with promoters during particle growth under FTO operation. Higher activity and slower loss of activity are observed at low promoter contents（1–3 wt% sodium and 0.5–1 wt% sulfur） but a minimum amount of alkali is required to effectively suppress methane and C–Cparaffin formation. A reference catalyst support（carbide-derived carbon aerogel） shows that the optimum promoter level depends on iron particle size and support pore structure.

AgBF_4/[emim][BF_4] supported ionic liquid membrane for carbon monoxide/nitrogen separation

In this paper,AgBF_4/[emim][BF_4] supported ionic liquid membranes(SILMs) were prepared successfully for CO/N_2 separation using nitrogen pressure immobilization procedures.The incorporation of AgBF_4 could decrease membrane weight loss,improve the pressure-resistant ability,and keep the critical pressure(0.45 MPa) of the SILMs.The high viscosity and undissolved Ag BF_4 solids in membrane liquid would disturb gas molecular transport through membrane and give rise to the gas transport resistance.Therefore,the gas permeability decreased remarkably with increasing AgBF_4 carrier content in the membrane.When the molar ratio of AgBF_4 to [emim][BF_4] increased from 0:1 to 0.3:1,the CO/N_2 selectivity of the SILMs showed a great increase from ～1 to ～9 at 20 °C and 0.4 MPa,suggesting that AgBF_4 was an effective carrier for CO facilitated transport.The permeabilities of N_2 and CO increased at higher transmembrane pressure,indicating that molecular transport would dominate the transport process at high pressure.The temperature-dependent gas permeability followed the Arrhenius equation.Moreover,the differences between the activation energies of CO and N_2 became larger after introducing AgBF_4,resulting in more obvious decrease in the CO/N_2 selectivity at higher operating temperature.

Correlation between the surface characteristics of carbon supports and their electrochemical stability and performance in fuel cell cathodes

In this paper,an extensive characterisation of a range of carbon blacks(CB)with similar surface area but different surface chemistry is carried out by flow calorimetry,Raman spectroscopy,dynamic water vapour sorption,instrumental gas analysis,nitrogen adsorption/desorption and high potential chronoamperometry.Using these carbon materials as supports,Pt/CB electrocatalysts are prepared by microwave-assisted polyol-mediated synthesis in gram scale.Structural,morphological and electrochemical properties of the prepared electrocatalysts are evaluated by X-ray diffraction,transmission electron microscopy,rotating disc electrode and in situ fuel cell characterisation of the corresponding membrane-electrode assemblies.The obtained results allow to establish a relationship between surface chemistry and electrochemical properties useful for the design of Pt/C catalyst layers with high performance and stability.

Platinum in-situ catalytic oleylamine combustion removal process for carbon supported platinum nanoparticles

Colloidal synthesis method such as oleylamine(OAm)-stabilized process is of great interest for obtaining uniform and highly dispersed platinum nanoparticle catalysts, yet the ligand may unavoidably inhibit their electro-catalytic performance. Thus, fully removing these ligands is critical to activate catalyst surface. Previous research of OAm removal process pointed that thermal annealing was the most effective way in comparison with other methods such as chemical washing, UV–Ozone irradiation and cyclic voltammetry sweeping, but generally resulting in undesired growth of platinum nanoparticle. Few studies concerning a more efficient ligand removal process have been published yet. In this work we proposed a platinum in-situ catalytic OAm combustion strategy to elucidate the removal mechanism of OAm ligands in thermal process and the key experimental parameters were also optimized. In addition, heat flow signal based on differential scanning calorimetry(DSC) measurement as a sensitive indicator, is suggested to reveal the ligand removal efficiency, which is much more reliable than the traditional spectroscopy.In comparison with commercial Pt/C sample, such a surface clean Pt/C electrocatalyst has shown an enhanced specific activity for oxygen reduction reaction. Our removal strategy and the evaluation method are highly instructive to efficient removal of different organic ligands.

Synthesis and functionalization of carbon xerogels to be used as supports for fuel cell catalysts

The synthesis and properties of carbon xerogels are briefly described in this mini-review, emphasizing the methods used for tuning their surface chemistry and textural properties in order to design efficient electrocatalysts for fuel cells. In particular, the role played by the surface functional groups in determining the loading, dispersion, oxidation state and stability of the metal phases is addressed.

Carbon-Supported Silver Catalysts for CO Selective Oxidation in Excess Hydrogen

Carbon materials were used as supports for Ag catalysts that are prepared using the conventional wet impregnation method, and their catalytic properties for CO selective oxidation in excess hydrogen at temperatures below 483 K were tested. A variety of techniques, e.g. N2 adsorption, XPS, TPD, UV-Vis DRS, TEM and SEM, were used to determine the influence of physical and chemical properties of the carbon on the properties of Ag catalyst. It was found that defects on the carbon surface served as nucleation sites for silver ions, while functional groups on carbon surface induced their reduction to the metallic form. The formation of silver particles on carbon was governed by homogeneous and/or heterogeneous nucleation during the impregnation and subsequent activation processes. The best catalytic performance was obtained with a Ag/carbon black catalyst with a uniform size distribution of silver nanoparticles （about 12 nm）, moderate BET surface area （with a mesoporous structure）, and a limited amount of carbon-oxygen groups. The research indicates that carbon materials are potentially good supports for silver catalysts for preferential oxidation of CO in excess hydrogen.

Correlation between catalytic activity of supported gold catalysts for carbon monoxide oxidation and metal–oxygen binding energy of the support metal oxides

The effect of a wide variety of metal oxide （MOx） supports has been discussed for CO oxidation on nanoparticulate gold catalysts. By using typical co‐precipitation and deposition–precipitation methods and under identical calcination conditions, supported gold catalysts were prepared on a wide variety of MOx supports, and the temperature for 50%conversion was measured to qualita‐tively evaluate the catalytic activities of these simple MOx and supported Au catalysts. Furthermore, the difference in these temperatures for the simple MOx compared to the supported Au catalysts is plotted against the metal–oxygen binding energies of the support MOx. A clear volcano‐like correla‐tion between the temperature difference and the metal–oxygen binding energies is observed. This correlation suggests that the use of MOx with appropriate metal–oxygen binding energies （300–500 kJ/atom O） greatly improves the catalytic activity of MOx by the deposition of Au NPs.

Methane oxidative carbonylation catalyzed by rhodium chalcogen halides over carbon supports

Gas phase carbonylation of methane is studied in the presence of molecular oxygen over pure carbon carriers and carbon supported rhodium chalcogen halides. Activated carbons and fullerene blacks have been used as carbon supports. XPS and IR-spectroscopy data show the formation of rhodium chalcogen halides in solids prepared by different methods. We have found that the productivity of acetic acid by carbon supported rhodium chalcogen halides depends strongly on the carbon carrier and the method of the catalyst preparation. Namely, the catalyst with highest productivity for the acetic acid is prepared by synthesizing the rhodium chalcogen halide over the carbon support followed by thermal destruction. We have also found that rhodium chalcogen halides over activated carbons are more active compared with fullerene supported catalysts.

Prediction of Henry Constants and Adsorption Mechanism of Volatile Organic Compounds on Multi-Walled Carbon Nanotubes by Using Support Vector Regression

Support vector regression （SVR） combined with particle swarm optimization for its parameter optimization is employed to establish a model for predicting the Henry constants of multi-walled carbon nanotubes （MWNTs） for adsorption of volatile organic compounds （VOCs）. The prediction performance of SVR is compared with those of the model of theoretical linear salvation energy relationship （TLSER）. By using leave-one-out cross validation of SVR test Henry constants for adsorption of 35 VOCs on MWNTs, the root mean square error is 0.080, the mean absolute percentage error is only 1.19~, and the correlation coefficient （R2） is as high as 0.997. Compared with the results of the TLSER model, it is shown that the estimated errors by SVR are ali smaller than those achieved by TLSER. It reveals that the generalization ability of SVR is superior to that of the TLSER model Meanwhile, multifactor analysis is adopted for investigation of the influences of each molecular structure descriptor on the Henry constants. According to the TLSER model, the adsorption mechanism of adsorption of carbon nanotubes of VOCs is mainly a result of van der Waals and interactions of hydrogen bonds. These can provide the theoretical support for the application of carbon nanotube adsorption of VOCs and can make up for the lack of experimental data.

Inactivated properties of activated carbon-supported TiO_2 nanoparticles for bacteria and kinetic study

The activated carbon-supported TiO2 nanoparticles(TiO2/AC)were prepared by a properly controlled sol-gel method.The effects of activated carbons(AC)support on inactivated properties of TiO2 nanoparticles were evaluated by photocatalytic inactivation experiments of Escherichia coli.The key factors affecting the inactivation effciency were investigated,including electric power of lamp, temperature,and pH values.The results show that the TiO2/AC composites have high inactivation properties of E.coli in compari...