Phenol hydrogenation is a green route to prepare cyclohexanone,an intermediate for the production of nylon 66 and nylon 6.The development of high-performance catalysts still keeps a great challenge.Herein,the activate...Phenol hydrogenation is a green route to prepare cyclohexanone,an intermediate for the production of nylon 66 and nylon 6.The development of high-performance catalysts still keeps a great challenge.Herein,the activated carbon(AC)was modified with an acidic material Nb_(2)O_(5)to adjust the microstructure and surface properties of AC,and the influences of the calcination temperature and Nb_(2)O_(5)content on the catalytic performance of the Pd/AC-Nb_(2)O_(5)catalysts for the phenol hydrogenation to cyclohexanone were investigated.The Nb_(2)O_(5)with proper content can be highly uniformly distributed on the AC surface,enhancing the acidity of the Pd/AC-Nb_(2)O_(5)catalysts with comparable specific surface area and Pd dispersion,thereby improving the catalytic activity.The hybrid Pd/AC-10 Nb_(2)O_(5)-500 catalyst exhibits the synergistic effect between the Pd nanoparticles and AC-10 Nb_(2)O_(5),which enhances the catalytic activity for the hydrogenation of phenol.Furthermore,the as-prepared Pd/AC-10 Nb_(2)O_(5)-500 catalyst shows good reusability during 7 reaction cycles.展开更多
An activated carbon （AC） supported Pd catalyst was used to develop a highly efficient in situ adsorption-catalysis system for the removal of low concentrations of o-xylene. In this study, three kinds of Pd/AC cataly...An activated carbon （AC） supported Pd catalyst was used to develop a highly efficient in situ adsorption-catalysis system for the removal of low concentrations of o-xylene. In this study, three kinds of Pd/AC catalysts were prepared and tested to investigate the synergistic efficiency between adsorption and catalysis for o-xylene removal. The Pd/AC catalyst was first used as an adsorbent to concentrate dilute o-xylene at low temperature. After saturated adsorption, the adsorbed o-xylene was oxidized to CO2 and H20 by raising the temperature of the catalyst bed. The results showed that more than 99% of the adsorbed o-xylene was completely oxidized to CO2 over a 5% Pd/AC catalyst at 140℃. Brunauer-Emmett-Teller （BET） analysis, scanning electron microscopy （SEM）, temperatureprogrammed desorption （TPD）, and temperature-programmed oxidation （TPO） were applied to investigate the physical properties of o-xylene adsorption-desorption and the in situ adsorption-catalysis activity of the AC support and Pd/AC catalyst. A synergistic relationship between the AC support and the active Pd species for the removal of low concentrations of o-xylene was established.展开更多
A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） a...A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.展开更多
Hydrogen generation from formic acid （FA） has received significant attention. The challenge is to obtain a highly active catalyst under mild conditions for practical applications. Here atomic layer deposition （ALD...Hydrogen generation from formic acid （FA） has received significant attention. The challenge is to obtain a highly active catalyst under mild conditions for practical applications. Here atomic layer deposition （ALD） of FeOx was performed to deposit an ultrathin oxide coating layer to a Pd/C catalyst, therein the FeOx coverage was precisely controlled by ALD cycles. Transmission electron microscopy and powder X-ray diffraction measurements suggest that the FeOx coating layer improved the thermal stability of Pd nanoparticles （NPs）. X-ray photoelectron spectroscopy measurement showed that deposition of FeOx on the Pd NPs caused a positive shift of Pd3d binding energy. In the FA dehydrogenation reaction, the ultrathin FeOx layer on the Pd/C could considerably improve the catalytic activity, and Pd/C coated with 8 cycles of FeOx showed an optimized activity with turnover frequency being about 2 times higher than the uncoated one. shape as a function of the number of FeOx ALD The improved activities were in a volcanocycles, indicating the coverage of FeOx is critical for the optimized activity. In summary, simultaneous improvements of activity and thermal stability of Pd/C catalyst by ultra-thin FeOx overlayer suggest to be an effective way to design active catalysts for the FA dehydrogenation reaction.展开更多
The palladium nanoparticles/carbon nanofibers（Pd NPs/CNFs） catalyst was prepared by the electrospinning method, the hydrazine hydrate solution reduction in an ice bath environment, the high temperature carbonization...The palladium nanoparticles/carbon nanofibers（Pd NPs/CNFs） catalyst was prepared by the electrospinning method, the hydrazine hydrate solution reduction in an ice bath environment, the high temperature carbonization. The catalyst was characterized by X-ray diffraction（XRD）, fieldemission scanning electron microscope（FE-SEM）, and transmission electron microscopy（TEM）. The nanofibers are not cross-linked and arranged in order. The surface of Pd NPs/CNFs is smooth, and it can be observed that a large number of particles were loaded and well-dispersed in carbon fiber matrix, and the particle distribution is uniform. The activity center of catalyst is Pd^（0）. The Pd NPs/CNFs exhibited a high efficiency, good reusability and stability in the Suzuki and Heck reactions. It can be used for at least five consecutive runs without significant loss of its catalytic activity. The good recyclability of Pd NPs/CNFs provides a way to greatly reduce the cost of the catalyst.展开更多
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...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.展开更多
Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the T...Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the TiO_(2)materials on the catalytic performance of Pd/TiO_(2)-101 and Pd/TiO_(2)-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene.The PdfTiO_(2)-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield.To understand these effects,the catalysts were characterized by H_(2)temperature-programmed desorption(H_(2)-TPD),H_(2)temperature-programmed reduction(H=-TPR),transmission electron microscopy(TEM),pulse CO chemisorption,X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The TEM and CO chemisorption results confirmed that Pd nanoparticles(NPs)on the TiO_(2)-101 support had a smaller average particle size(1.53 nm)and a higher dispersion(15.95%)than those on the TiO_(2)-001 support(average particle size of 4.36 nm and dispersion of 9.06%).The smaller particle size and higher dispersion of Pd on the Pd/TiO_(2)-101 catalyst provided more reaction active sites,which contributed to the improved catalytic activity of this supported catalyst.展开更多
The one-pot synthesis of methyl isobutyl ketone(MIBK)from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein.we report a series of ...The one-pot synthesis of methyl isobutyl ketone(MIBK)from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein.we report a series of Pd supported on mixed metal oxide(MMO)catalysts with controllable acidic/basic/metallic sites on the surface.We study the relationship between the nature,synergy,and proximity of active sites and the catalytic performance of the multifunctional catalyst in the tandem reaction,in detail.In the existence of Lewis acid and base sites,the catalysts with medium-strength acidic/basic sites show preferred activity and/or MIBK selectivity.For multifunctional catalysts,the catalytic properties are more than just a collection of active sites,and the Pd/Mg_3Al-MMO catalyst possessing 0.1%Pd loading and~0.4 acid/base molar ratio exhibits the optimal 42.1%acetone conversion and 37.2%MIBK yield,which is among the best reported so far for this tandem reaction under similar conditions.Moreover,the proximity test indicates that the intimate distance between acidic/basic/metallic sites can greatly shorten the diffusion time of the intermediate species from each active site,leading to an enhancement in the catalytic performance.展开更多
Deactivation of Pd/C catalyst often occurs in liquid hydrogenation using industrial materials. For in-stance, the Pd/C catalyst is deactivated severely in the hydrogenation of N-(3-nitro-4-methoxyphenyl) acetamide. In...Deactivation of Pd/C catalyst often occurs in liquid hydrogenation using industrial materials. For in-stance, the Pd/C catalyst is deactivated severely in the hydrogenation of N-(3-nitro-4-methoxyphenyl) acetamide. In this study, the chemisorption of sulfur on the surface of deactivated Pd/C was detected by energy dispersive spec-trometer and X-ray photoelectron spectroscopy. Sulfur compounds poison the Pd/C catalyst and increase the forma-tion of azo deposit, reducing the activity of catalyst. We report a mild method to regenerate the Pd/C catalyst: wash the deposit by N,N-dimethylformamide and oxidize the chemisorbed sulfur by hot air. The regenerated Pd/C cata-lyst can be reused at least ten runs with stable activity.展开更多
Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annea...Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annealing process to stabilize nitrogen‐mesoporous carbon supported Pd single‐atom/cluster(Pd/NMC)material,which provided a catalyst with superior performance for Suzuki coupling reactions.In comparison with commercial palladium/carbon(Pd/C)catalysts,the Pd/NMC catalyst exhibited significantly boosted activity(100%selectivity and 95%yield)and excellent stability(almost no decay in activity after 10 reuse cycles)for the Suzuki coupling reactions of chlorobenzenes,together with superior yield and excellent selectivity in the fields of the board scope of the reactants.Moreover,our newly developed rapid annealing process of precursor solutions is applied as a generalized method to stabilize metal clusters(e.g.Pd,Pt,Ru),opening new possibilities in the construction of efficient highly dispersed metal atom and sub‐nanometer cluster catalysts with high performance.展开更多
A multifunctional porous organic polymer of POP-Nixantphos-PPh_(3)-PhSO_(3)Na was prepared by free radical tricopolymerization.Further loading of Pd(OAc)2 led to the catalyst of Pd/POP-Nixantphos-PPh_(3)-PhSO_(3)Na.In...A multifunctional porous organic polymer of POP-Nixantphos-PPh_(3)-PhSO_(3)Na was prepared by free radical tricopolymerization.Further loading of Pd(OAc)2 led to the catalyst of Pd/POP-Nixantphos-PPh_(3)-PhSO_(3)Na.In this catalyst,Nixantphos ligand moieties were employed to enhance the catalytic hydrocarboxylation activity of palladium.Additionally,PPh_(3)ligand moieties were utilized to construct a porous framework of catalyst that facilitated the dispersion of Pd nanoparticles as well as the diffusion of reactants and products.Furthermore,the incorporation of PhSO_(3)Na moieties improved the hydrophilicity of the support.With H_(2)O as the reaction solvent,under the initial CO pressure of 0.1 MPa,Pd/POP-Nixantphos-PPh3-PhSO3Na-catalyzed hydrocarboxylation of alkynes to afford the correspondingα,β-unsaturated carboxylic acids in good yields(76%~96%).Various alkynes,such as diaromatic alkynes,arylalkyl alkynes and dialkyl alkynes,worked well in the process.Additionally,the catalyst showed excellent recyclability with no significant yield loss over five cycles.展开更多
In the current study simultaneous reactions of hydrodesulfurization(HDS) of dibenzothiophene(DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic(Co-Mo/Al2O3 and Ni-Mo/Al2O3) and t...In the current study simultaneous reactions of hydrodesulfurization(HDS) of dibenzothiophene(DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic(Co-Mo/Al2O3 and Ni-Mo/Al2O3) and tri-metallic(Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3) catalyst systems which were prepared by incipient impregnation method.In situ hydrogen utilization and low Pd loadings were the major targets of this study.For comparison purpose,catalytic activity was separately determined for both the methanol reforming and HDS of DBT reactions as well.Ni based catalysts were confirmed with better activity than Co ones for both the reactions with Pd promoted ones ranking at the top i.e.Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 where Pd-Ni-Mo/Al2O3 showed 91% DBT conversion at 380 ℃ and 12 h reaction time.Some of the selected organic additives on catalytic activity were tested for their effect toward HDS reaction which was unique with close relation to their chemical nature.Reaction products were quantitatively and qualitatively analyzed via HPLC and GC-MS techniques respectively which helped in elucidating reaction mechanism.展开更多
In this study,supported Pd catalysts were prepared and used as heterogeneous catalysts for the activation of peroxymonosulfate(PMS)which successfully degrade bisphenol F(BPF).Among the supported catalysts(i.e.,Pd/SiO_...In this study,supported Pd catalysts were prepared and used as heterogeneous catalysts for the activation of peroxymonosulfate(PMS)which successfully degrade bisphenol F(BPF).Among the supported catalysts(i.e.,Pd/SiO_(2),Pd/CeO_(2),Pd/TiO_(2)and Pd/Al2O3),Pd/TiO_(2)exhibited the highest catalytic activity due to the high isoelectric point and high Pd0 content.Pd/TiO_(2)prepared by the deposition method leads to high Pd dispersion,which are the key factors for efficient BPF degradation.The influencing factors were investigated during the reaction process and two possible degradation pathways were proposed.Density functional theory(DFT)calculations demonstrate that stronger BPF adsorption and BPF degradation with lower reaction barrier occurs on smaller Pd particles.The catalytic activities are strongly dependent on the structural features of the catalysts.Both experiments and theoretical calculations prove that the reaction is actuated by electron transfer rather than radicals.展开更多
Pd-based catalysts have been extensively studied in the catalytic oxidation of methane,but their longterm stability and water resistance are unsatisfactory as the active sites are susceptible to water toxicity.The add...Pd-based catalysts have been extensively studied in the catalytic oxidation of methane,but their longterm stability and water resistance are unsatisfactory as the active sites are susceptible to water toxicity.The addition of Pt to Pd-based catalysts is found to be the most effective and promising method.However,distinct states of existence of Pt can affect the catalytic performance to different degrees,even negatively.Therefore,the impact mechanism of Pt on Pd-based catalysts needs to be further understood.In this work,A-site defective La_(0.9)AlO_(x)perovskite was used as a support,and the state of Pt in catalysts was regulated by adjusting the introducing sequence of Pd and Pt,It is found that only when Pt is introduced preferentially,the activity and water resistance of the bimetal can be improved.Combining a series of characterization results of the fresh catalysts,reduced catalysts,and the samples after reduction and use,it is found that the higher Pt^(2+)content in the catalyst is the main reason for promoting bimetallic properties,while more Pt0has an inhibitory effect.This work provides a new understanding of the promotion effect of Pt on Pd-Pt bimetal in the catalytic oxidation reaction of methane.展开更多
Electrocatalytic water splitting for hydrogen production is a key approach to tackling the current energy crisis.Among the catalysts,the traditional Pd@C catalysts are remarkable for their efficiency in hydrogen evolu...Electrocatalytic water splitting for hydrogen production is a key approach to tackling the current energy crisis.Among the catalysts,the traditional Pd@C catalysts are remarkable for their efficiency in hydrogen evolution.However,the high cost and scarcity of Pd catalysts,as well as the instability caused by the corrosiveness of carbon-based substrates,hinder their large-scale application.To overcome this challenge,an effective strategy is to construct highly dispersed Pd single atoms to improve palladium utilization and choose more stable materials as supports.In this study,TiO_(2-x)carriers with abundant oxygen vacancies were prepared and loaded with Pd by photoreduction deposition.Adjusting the palladium content resulted in three forms of Pd-loaded TiO_(2-x):nanoparticles(Pd@TiO_(2-x)(6%,10%)),nanoclusters(Pd@TiO_(2-x)(3%))and single atoms(Pd@TiO_(2-x)(1.5%)).The oxygen vacancies improved the stability of the titanium dioxide materials by providing more active hydrogen adsorption sites and increasing the affinity of Pd for active hydrogen.Single atom loading increased the frequency of oxygen holes in the support and the high activity of monatomic Pd promoted the adsorption of active hydrogen and facilitated the formation of active hydrogen intermediates.The synergistic effect of single atoms and oxygen vacancies improved the stability and catalytic activity of the composite material.Pd@TiO_(2-x)(1.5%)showed outstanding performance in hydrogen evolution in an acidic medium with an overpotential of only 24 m V at a current density of 10 m A/cm^(2)and a low Tafel rise of 41.9 m V/dec.This study provides an effective strategy for the development of high-performance hydrogen evolution(HER)catalysts.展开更多
A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon...A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon - carbon double bonds systems and reusability. Furthermore, XPS and IR spectra shouted that active component in the composite catalysts is atomic Pd(0). An addition of a small amount of Fe2O3 has a promotive action upon hydrogenation activity of the catalysts, which indicated that there are some strong interactions (electron transfer) between Pd(0) and Fe(Ⅲ) species. Based on these results, a possible catalytic hydrogenation mechanism was also suggested.展开更多
A robust bulky bornylimidazo[1,5-a]pyridin-3-ylidene allylic Pd complex was synthesized and well characterized.DFT calculations indicated that the ligand acts as a strongσ-donor andπ-acceptor endowing the active Pd(...A robust bulky bornylimidazo[1,5-a]pyridin-3-ylidene allylic Pd complex was synthesized and well characterized.DFT calculations indicated that the ligand acts as a strongσ-donor andπ-acceptor endowing the active Pd(0)center with high electron density and good coordination towards olefin.The introduction of a bulky,rigid bornyl ring further improved the catalytic efficacy due to the matched steric effects.This catalyst showed high efficiency and versatility in theα-arylation and Heck cyclization/Suzuki crosscoupling reactions at mild reaction conditions.Desired 3,3-disubstituted oxindoles,especially featuring an allylic-derived C3-quaternary stereocenter were obtained in high yields.Furthermore,the concise synthesis of bioactive heterocycle-fused indoline alkaloids was successfully proved.展开更多
Zeolites are a promising support for Pd catalysts in leanmethane(CH_(4))combustion.Herein,three types of zeolites(H-MOR,H-ZSM-5 and H-Y)were selected to estimate their structural effects and deactivation mechanisms in...Zeolites are a promising support for Pd catalysts in leanmethane(CH_(4))combustion.Herein,three types of zeolites(H-MOR,H-ZSM-5 and H-Y)were selected to estimate their structural effects and deactivation mechanisms in CH_(4)combustion.We show that variations in zeolite structure and surface acidity led to distinct changes in Pd states.Pd/H-MOR with external high-dispersing Pd nanoparticles exhibited the best apparent activity,with activation energy(Ea)at 73 kJ/mol,while Pd/H-ZSM-5 displayed the highest turnover frequency(TOF)at 19.6×10^(−3)sec^(−1),presumably owing to its large particles with more step sites providing active sites in one particle for CH_(4)activation.Pd/H-Y with dispersed PdO within pore channels and/or Pd2+ions on ion-exchange sites yielded the lowest apparent activity and TOF.Furthermore,Pd/H-MOR and Pd/H-ZSM-5 were both stable under a dry condition,but introducing 3 vol.%H_(2)O caused the CH_(4)conversion rate on Pd/H-MOR drop from 100%to 63%and that on Pd/H-ZSM-5 decreased remarkably from 82%to 36%.The former was shown to originate fromzeolite structural dealumination,and the latter principally owed to Pd aggregation and the loss of active PdO.展开更多
基金The financial supports from the National Natural Science Foundation(21776127,21921006)the Jiangsu Province Key R&D Program(BE2018009-2)+3 种基金the Jiangsu Province natural science research of College and university general project(20KJB540003)a project funded by the priority academic program development of Jiangsu higher education institutions(PAPD)the State Key Laboratory of Materials-Oriented Chemical Engineering(ZK201902)the outstanding young teacher’s project of Changzhou Vocational Institute of Textile and Garment of China。
文摘Phenol hydrogenation is a green route to prepare cyclohexanone,an intermediate for the production of nylon 66 and nylon 6.The development of high-performance catalysts still keeps a great challenge.Herein,the activated carbon(AC)was modified with an acidic material Nb_(2)O_(5)to adjust the microstructure and surface properties of AC,and the influences of the calcination temperature and Nb_(2)O_(5)content on the catalytic performance of the Pd/AC-Nb_(2)O_(5)catalysts for the phenol hydrogenation to cyclohexanone were investigated.The Nb_(2)O_(5)with proper content can be highly uniformly distributed on the AC surface,enhancing the acidity of the Pd/AC-Nb_(2)O_(5)catalysts with comparable specific surface area and Pd dispersion,thereby improving the catalytic activity.The hybrid Pd/AC-10 Nb_(2)O_(5)-500 catalyst exhibits the synergistic effect between the Pd nanoparticles and AC-10 Nb_(2)O_(5),which enhances the catalytic activity for the hydrogenation of phenol.Furthermore,the as-prepared Pd/AC-10 Nb_(2)O_(5)-500 catalyst shows good reusability during 7 reaction cycles.
基金supported by the National Natural Science Foundation of China (No. 20607029)the Ministry of Science and Technology of China (No. 2007AA061402)
文摘An activated carbon （AC） supported Pd catalyst was used to develop a highly efficient in situ adsorption-catalysis system for the removal of low concentrations of o-xylene. In this study, three kinds of Pd/AC catalysts were prepared and tested to investigate the synergistic efficiency between adsorption and catalysis for o-xylene removal. The Pd/AC catalyst was first used as an adsorbent to concentrate dilute o-xylene at low temperature. After saturated adsorption, the adsorbed o-xylene was oxidized to CO2 and H20 by raising the temperature of the catalyst bed. The results showed that more than 99% of the adsorbed o-xylene was completely oxidized to CO2 over a 5% Pd/AC catalyst at 140℃. Brunauer-Emmett-Teller （BET） analysis, scanning electron microscopy （SEM）, temperatureprogrammed desorption （TPD）, and temperature-programmed oxidation （TPO） were applied to investigate the physical properties of o-xylene adsorption-desorption and the in situ adsorption-catalysis activity of the AC support and Pd/AC catalyst. A synergistic relationship between the AC support and the active Pd species for the removal of low concentrations of o-xylene was established.
基金Supported by the "863" Program of Science and Technology Ministry of China(Nos.2006AA05Z137, 2007AA05Z143 and 2007AA05Z159)National Natural Science Foundation of China(Nos.20433060, 20473038, 20573057 and 20703043)the Natural Science Foundation of Jiangsu Province, China(No.BK2006224).
文摘A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.
基金This work was supported by the National Natural Science Foundation of China （No.51402283 and No.21473169）, One Thousand Young Talents Program under the Recruitment Program of Global Experts, the Fundamental Research Funds for the Central Universi- ties （No.WK2060030017）, and the Startup Funds from University of Science and Technology of China.
文摘Hydrogen generation from formic acid （FA） has received significant attention. The challenge is to obtain a highly active catalyst under mild conditions for practical applications. Here atomic layer deposition （ALD） of FeOx was performed to deposit an ultrathin oxide coating layer to a Pd/C catalyst, therein the FeOx coverage was precisely controlled by ALD cycles. Transmission electron microscopy and powder X-ray diffraction measurements suggest that the FeOx coating layer improved the thermal stability of Pd nanoparticles （NPs）. X-ray photoelectron spectroscopy measurement showed that deposition of FeOx on the Pd NPs caused a positive shift of Pd3d binding energy. In the FA dehydrogenation reaction, the ultrathin FeOx layer on the Pd/C could considerably improve the catalytic activity, and Pd/C coated with 8 cycles of FeOx showed an optimized activity with turnover frequency being about 2 times higher than the uncoated one. shape as a function of the number of FeOx ALD The improved activities were in a volcanocycles, indicating the coverage of FeOx is critical for the optimized activity. In summary, simultaneous improvements of activity and thermal stability of Pd/C catalyst by ultra-thin FeOx overlayer suggest to be an effective way to design active catalysts for the FA dehydrogenation reaction.
基金the support of the National Natural Science Foundation of China(No.21266016)
文摘The palladium nanoparticles/carbon nanofibers（Pd NPs/CNFs） catalyst was prepared by the electrospinning method, the hydrazine hydrate solution reduction in an ice bath environment, the high temperature carbonization. The catalyst was characterized by X-ray diffraction（XRD）, fieldemission scanning electron microscope（FE-SEM）, and transmission electron microscopy（TEM）. The nanofibers are not cross-linked and arranged in order. The surface of Pd NPs/CNFs is smooth, and it can be observed that a large number of particles were loaded and well-dispersed in carbon fiber matrix, and the particle distribution is uniform. The activity center of catalyst is Pd^（0）. The Pd NPs/CNFs exhibited a high efficiency, good reusability and stability in the Suzuki and Heck reactions. It can be used for at least five consecutive runs without significant loss of its catalytic activity. The good recyclability of Pd NPs/CNFs provides a way to greatly reduce the cost of the catalyst.
基金supported by the National Natural Science Foundation,China(Nos.21506138,21606199,21575097 and21375092)the Natural Science Foundation of Zhejiang Province,China(No.LQ15B060001)the China Postdoctoral Science Foundation(No.2016M592015)
文摘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.
文摘Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the TiO_(2)materials on the catalytic performance of Pd/TiO_(2)-101 and Pd/TiO_(2)-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene.The PdfTiO_(2)-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield.To understand these effects,the catalysts were characterized by H_(2)temperature-programmed desorption(H_(2)-TPD),H_(2)temperature-programmed reduction(H=-TPR),transmission electron microscopy(TEM),pulse CO chemisorption,X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The TEM and CO chemisorption results confirmed that Pd nanoparticles(NPs)on the TiO_(2)-101 support had a smaller average particle size(1.53 nm)and a higher dispersion(15.95%)than those on the TiO_(2)-001 support(average particle size of 4.36 nm and dispersion of 9.06%).The smaller particle size and higher dispersion of Pd on the Pd/TiO_(2)-101 catalyst provided more reaction active sites,which contributed to the improved catalytic activity of this supported catalyst.
文摘The one-pot synthesis of methyl isobutyl ketone(MIBK)from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein.we report a series of Pd supported on mixed metal oxide(MMO)catalysts with controllable acidic/basic/metallic sites on the surface.We study the relationship between the nature,synergy,and proximity of active sites and the catalytic performance of the multifunctional catalyst in the tandem reaction,in detail.In the existence of Lewis acid and base sites,the catalysts with medium-strength acidic/basic sites show preferred activity and/or MIBK selectivity.For multifunctional catalysts,the catalytic properties are more than just a collection of active sites,and the Pd/Mg_3Al-MMO catalyst possessing 0.1%Pd loading and~0.4 acid/base molar ratio exhibits the optimal 42.1%acetone conversion and 37.2%MIBK yield,which is among the best reported so far for this tandem reaction under similar conditions.Moreover,the proximity test indicates that the intimate distance between acidic/basic/metallic sites can greatly shorten the diffusion time of the intermediate species from each active site,leading to an enhancement in the catalytic performance.
基金Supported by the Natural Science Foundation of Zhejiang Provincial （LYI2B03009） and Program for Zhejiang Leading Team of Science and Technology Innovation （2011 R09020-03）.
文摘Deactivation of Pd/C catalyst often occurs in liquid hydrogenation using industrial materials. For in-stance, the Pd/C catalyst is deactivated severely in the hydrogenation of N-(3-nitro-4-methoxyphenyl) acetamide. In this study, the chemisorption of sulfur on the surface of deactivated Pd/C was detected by energy dispersive spec-trometer and X-ray photoelectron spectroscopy. Sulfur compounds poison the Pd/C catalyst and increase the forma-tion of azo deposit, reducing the activity of catalyst. We report a mild method to regenerate the Pd/C catalyst: wash the deposit by N,N-dimethylformamide and oxidize the chemisorbed sulfur by hot air. The regenerated Pd/C cata-lyst can be reused at least ten runs with stable activity.
文摘Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annealing process to stabilize nitrogen‐mesoporous carbon supported Pd single‐atom/cluster(Pd/NMC)material,which provided a catalyst with superior performance for Suzuki coupling reactions.In comparison with commercial palladium/carbon(Pd/C)catalysts,the Pd/NMC catalyst exhibited significantly boosted activity(100%selectivity and 95%yield)and excellent stability(almost no decay in activity after 10 reuse cycles)for the Suzuki coupling reactions of chlorobenzenes,together with superior yield and excellent selectivity in the fields of the board scope of the reactants.Moreover,our newly developed rapid annealing process of precursor solutions is applied as a generalized method to stabilize metal clusters(e.g.Pd,Pt,Ru),opening new possibilities in the construction of efficient highly dispersed metal atom and sub‐nanometer cluster catalysts with high performance.
文摘A multifunctional porous organic polymer of POP-Nixantphos-PPh_(3)-PhSO_(3)Na was prepared by free radical tricopolymerization.Further loading of Pd(OAc)2 led to the catalyst of Pd/POP-Nixantphos-PPh_(3)-PhSO_(3)Na.In this catalyst,Nixantphos ligand moieties were employed to enhance the catalytic hydrocarboxylation activity of palladium.Additionally,PPh_(3)ligand moieties were utilized to construct a porous framework of catalyst that facilitated the dispersion of Pd nanoparticles as well as the diffusion of reactants and products.Furthermore,the incorporation of PhSO_(3)Na moieties improved the hydrophilicity of the support.With H_(2)O as the reaction solvent,under the initial CO pressure of 0.1 MPa,Pd/POP-Nixantphos-PPh3-PhSO3Na-catalyzed hydrocarboxylation of alkynes to afford the correspondingα,β-unsaturated carboxylic acids in good yields(76%~96%).Various alkynes,such as diaromatic alkynes,arylalkyl alkynes and dialkyl alkynes,worked well in the process.Additionally,the catalyst showed excellent recyclability with no significant yield loss over five cycles.
基金Fundamental Research Foundation of Sinopec(X505015)
文摘In the current study simultaneous reactions of hydrodesulfurization(HDS) of dibenzothiophene(DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic(Co-Mo/Al2O3 and Ni-Mo/Al2O3) and tri-metallic(Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3) catalyst systems which were prepared by incipient impregnation method.In situ hydrogen utilization and low Pd loadings were the major targets of this study.For comparison purpose,catalytic activity was separately determined for both the methanol reforming and HDS of DBT reactions as well.Ni based catalysts were confirmed with better activity than Co ones for both the reactions with Pd promoted ones ranking at the top i.e.Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 where Pd-Ni-Mo/Al2O3 showed 91% DBT conversion at 380 ℃ and 12 h reaction time.Some of the selected organic additives on catalytic activity were tested for their effect toward HDS reaction which was unique with close relation to their chemical nature.Reaction products were quantitatively and qualitatively analyzed via HPLC and GC-MS techniques respectively which helped in elucidating reaction mechanism.
基金supported by the National Natural Science Foundation of China(NSFC)(No.21978137).
文摘In this study,supported Pd catalysts were prepared and used as heterogeneous catalysts for the activation of peroxymonosulfate(PMS)which successfully degrade bisphenol F(BPF).Among the supported catalysts(i.e.,Pd/SiO_(2),Pd/CeO_(2),Pd/TiO_(2)and Pd/Al2O3),Pd/TiO_(2)exhibited the highest catalytic activity due to the high isoelectric point and high Pd0 content.Pd/TiO_(2)prepared by the deposition method leads to high Pd dispersion,which are the key factors for efficient BPF degradation.The influencing factors were investigated during the reaction process and two possible degradation pathways were proposed.Density functional theory(DFT)calculations demonstrate that stronger BPF adsorption and BPF degradation with lower reaction barrier occurs on smaller Pd particles.The catalytic activities are strongly dependent on the structural features of the catalysts.Both experiments and theoretical calculations prove that the reaction is actuated by electron transfer rather than radicals.
基金Project supported by the National Key Research and Development Program(2022YFB3504200)National Natrual Science Foundation of China(22376061,21922602,22076047,U21A20326)+1 种基金Shanghai Science and Technology Innovation Action Plan(20dz1204200)Fundamental Re search Funds for the Central Universities。
文摘Pd-based catalysts have been extensively studied in the catalytic oxidation of methane,but their longterm stability and water resistance are unsatisfactory as the active sites are susceptible to water toxicity.The addition of Pt to Pd-based catalysts is found to be the most effective and promising method.However,distinct states of existence of Pt can affect the catalytic performance to different degrees,even negatively.Therefore,the impact mechanism of Pt on Pd-based catalysts needs to be further understood.In this work,A-site defective La_(0.9)AlO_(x)perovskite was used as a support,and the state of Pt in catalysts was regulated by adjusting the introducing sequence of Pd and Pt,It is found that only when Pt is introduced preferentially,the activity and water resistance of the bimetal can be improved.Combining a series of characterization results of the fresh catalysts,reduced catalysts,and the samples after reduction and use,it is found that the higher Pt^(2+)content in the catalyst is the main reason for promoting bimetallic properties,while more Pt0has an inhibitory effect.This work provides a new understanding of the promotion effect of Pt on Pd-Pt bimetal in the catalytic oxidation reaction of methane.
基金supported by the Key Project of Tianjin Natural Science Foundation(No.23JCZDJC00570)Special Funding of China Postdoctoral Science Foundation(No.2023T160268)+3 种基金China Postdoctoral Science Foundation(No.2023M741362)the National natural science foundation of China(Nos.22276209 and 21822608)Research Center for Eco-Environmental Science(No.RCEES-TDZ-2021-7)the support from the Youth Innovation Promotion Association of CAS(No.Y2021019)。
文摘Electrocatalytic water splitting for hydrogen production is a key approach to tackling the current energy crisis.Among the catalysts,the traditional Pd@C catalysts are remarkable for their efficiency in hydrogen evolution.However,the high cost and scarcity of Pd catalysts,as well as the instability caused by the corrosiveness of carbon-based substrates,hinder their large-scale application.To overcome this challenge,an effective strategy is to construct highly dispersed Pd single atoms to improve palladium utilization and choose more stable materials as supports.In this study,TiO_(2-x)carriers with abundant oxygen vacancies were prepared and loaded with Pd by photoreduction deposition.Adjusting the palladium content resulted in three forms of Pd-loaded TiO_(2-x):nanoparticles(Pd@TiO_(2-x)(6%,10%)),nanoclusters(Pd@TiO_(2-x)(3%))and single atoms(Pd@TiO_(2-x)(1.5%)).The oxygen vacancies improved the stability of the titanium dioxide materials by providing more active hydrogen adsorption sites and increasing the affinity of Pd for active hydrogen.Single atom loading increased the frequency of oxygen holes in the support and the high activity of monatomic Pd promoted the adsorption of active hydrogen and facilitated the formation of active hydrogen intermediates.The synergistic effect of single atoms and oxygen vacancies improved the stability and catalytic activity of the composite material.Pd@TiO_(2-x)(1.5%)showed outstanding performance in hydrogen evolution in an acidic medium with an overpotential of only 24 m V at a current density of 10 m A/cm^(2)and a low Tafel rise of 41.9 m V/dec.This study provides an effective strategy for the development of high-performance hydrogen evolution(HER)catalysts.
文摘A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon - carbon double bonds systems and reusability. Furthermore, XPS and IR spectra shouted that active component in the composite catalysts is atomic Pd(0). An addition of a small amount of Fe2O3 has a promotive action upon hydrogenation activity of the catalysts, which indicated that there are some strong interactions (electron transfer) between Pd(0) and Fe(Ⅲ) species. Based on these results, a possible catalytic hydrogenation mechanism was also suggested.
基金Financial supports from the National Natural Science Foundation of China(No.22101133)Natural Science Foundation of Jiangsu Province(No.BK20200768)+1 种基金Nanjing Forestry University,the National Natural Science Foundation of China(the Outstanding Youth Scholars(Overseas,2021)project)the Lab project of the State Key Laboratory of Physical Chemistry of Solid Surfaces are greatly acknowledged.
文摘A robust bulky bornylimidazo[1,5-a]pyridin-3-ylidene allylic Pd complex was synthesized and well characterized.DFT calculations indicated that the ligand acts as a strongσ-donor andπ-acceptor endowing the active Pd(0)center with high electron density and good coordination towards olefin.The introduction of a bulky,rigid bornyl ring further improved the catalytic efficacy due to the matched steric effects.This catalyst showed high efficiency and versatility in theα-arylation and Heck cyclization/Suzuki crosscoupling reactions at mild reaction conditions.Desired 3,3-disubstituted oxindoles,especially featuring an allylic-derived C3-quaternary stereocenter were obtained in high yields.Furthermore,the concise synthesis of bioactive heterocycle-fused indoline alkaloids was successfully proved.
基金supported by the National Key R&D Program of China(No.2022YFC3701603)the National Natural Science Foundation of China(Nos.22106133,52070168)+1 种基金the Key R&D Plan of Zhejiang Province(No.2023C03127)the Fundamental Research Funds for the Central Universities(No.226-2022-00150).
文摘Zeolites are a promising support for Pd catalysts in leanmethane(CH_(4))combustion.Herein,three types of zeolites(H-MOR,H-ZSM-5 and H-Y)were selected to estimate their structural effects and deactivation mechanisms in CH_(4)combustion.We show that variations in zeolite structure and surface acidity led to distinct changes in Pd states.Pd/H-MOR with external high-dispersing Pd nanoparticles exhibited the best apparent activity,with activation energy(Ea)at 73 kJ/mol,while Pd/H-ZSM-5 displayed the highest turnover frequency(TOF)at 19.6×10^(−3)sec^(−1),presumably owing to its large particles with more step sites providing active sites in one particle for CH_(4)activation.Pd/H-Y with dispersed PdO within pore channels and/or Pd2+ions on ion-exchange sites yielded the lowest apparent activity and TOF.Furthermore,Pd/H-MOR and Pd/H-ZSM-5 were both stable under a dry condition,but introducing 3 vol.%H_(2)O caused the CH_(4)conversion rate on Pd/H-MOR drop from 100%to 63%and that on Pd/H-ZSM-5 decreased remarkably from 82%to 36%.The former was shown to originate fromzeolite structural dealumination,and the latter principally owed to Pd aggregation and the loss of active PdO.
