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
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
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
Monolithic catalysts have been widely investigated for CO_(2) methanation due to their fast mass and heat transfer rate,but the effect of the interaction between the catalyst layer and the monolithic support has been ...Monolithic catalysts have been widely investigated for CO_(2) methanation due to their fast mass and heat transfer rate,but the effect of the interaction between the catalyst layer and the monolithic support has been little studied.In this work,Ni/Al_(2)O_(3)/SiC monolithic catalysts,Ni/Al_(2)O_(3) powder catalysts and Ni/Al_(2)O_(3)/SiC-M catalysts were prepared to explore the effect of Si-Al interaction between the catalyst layer and SiC ceramic for CO_(2) methanation performance.Ni/Al_(2)O_(3)/SiC exhibited a CO_(2) conversion of 53% and a CH_(4) specific reaction rate of 0.05 m mol·g^(-1)·s^(-1) under conditions of 0.1 M Pa,4 00℃,and a WHSV of 60000 ml·g^(-1)·h^(-1).The CO_(2) conversion raised by 0.15-fold and the CH_(4) specific reaction rate raised by 0.25-fold compared to Ni/Al_(2)O_(3) with the same catalyst content.SEM,XRD,Raman,and other characterization results revealed that the formation of Si-Al interaction between the catalyst layer and SiC ceramic could weaken the interaction between Ni and Al_(2)O_(3),thereby improving the catalytic activity of Ni/Al_(2)O_(3)/SiC catalyst.However,the Si-Al interaction was further strengthened during the hightemperature reaction process,which significantly weakened the interaction between Ni and Al_(2)O_(3),thereby leading to a decline in the catalytic performance of Ni/Al_(2)O_(3)/SiC catalyst during an 80-h stability test.This study provides valuable insights for future research and development of monolithic catalysts.展开更多
Conventional synthesis of monolith-supported zeolite catalysts is based on a hydrothermal strategy.Here,we report a solvent-free crystallization process to coat ZSM-5 zeolite crystals on a monolithic SiC foam with a h...Conventional synthesis of monolith-supported zeolite catalysts is based on a hydrothermal strategy.Here,we report a solvent-free crystallization process to coat ZSM-5 zeolite crystals on a monolithic SiC foam with a honeycomb structure(ZSM-5/SiC).Characterizations of the ZSM-5/SiC by scanning electron microscopy,N2 sorption,and X-ray diffraction indicate that the zeolite sheath has been ideally coated on the surface of the SiC foam with high purity and crystallinity.Fixing Pd nanoparticles within the ZSM-5 zeolite crystals delivers a bifunctional Pd@ZSM-5/SiC catalyst,which exhibits high activity and selectivity toward diesel range paraffins in the hydrodeoxygenation of methyl oleate,a model molecule for biofuel.In comparison to the powder Pd@ZSM-5,the Pd@ZSM-5/SiC monolith catalyst shows more efficiency,which is attributed to the fast mass transfer and high heat conductivity on the honeycomb SiC structure.The durability test indicates that the Pd@ZSM-5/SiC catalyst is stable under the reaction and high-temperature regeneration conditions.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
Pd/Ce0.67Zr0.33O2 catalyst was pretreated in different atmosphere respectively, and characterized by CO chemical adsorption, XPS, HR-TEM, H2-TPR, Raman, OSC and in situ DRIFTS to investigate the effect of the structur...Pd/Ce0.67Zr0.33O2 catalyst was pretreated in different atmosphere respectively, and characterized by CO chemical adsorption, XPS, HR-TEM, H2-TPR, Raman, OSC and in situ DRIFTS to investigate the effect of the structure properties of PdOx species on the catalytic performance for CO, HC and NOx elimination. The results show that Pd/CZ catalyst pretreated in air atmosphere has higher oxidation activity of HC due to having high Pd dispersion and strong interaction between PdOx and CZ support. Pd/CZ-H catalyst pretreated in reducing atmosphere exhibits better catalytic performance of NOx elimination because of having relatively big Pd particle size, more Pd species in metallic state and higher concentration of oxygen vacancies. While for the Pd/CZ-RG catalyst pretreated in reactant atmosphere, strong adsorption of HC species on the surface of catalysts would lead to a part of active sites being covered, which inhibits HC and NO conversions.展开更多
N2O is a major by-product emitted during low-temperature selective catalytic reduction of NO with NH3(NH3-SCR), which causes a series of serious environmental problems. A full understanding of the N2O formation mechan...N2O is a major by-product emitted during low-temperature selective catalytic reduction of NO with NH3(NH3-SCR), which causes a series of serious environmental problems. A full understanding of the N2O formation mechanism is essential to suppress the N2O emission during the low-temperature NH3-SCR, and requires an intensive study of this heterogeneous catalysis process. In this study, we investigated the reaction between NH3 and NO over a Pd/CeO2 catalyst in the absence of O2, using X-ray photoelectron spectroscopy, NH3-temperature-programmed desorption, NO-temperature-programmed desorption, and in-situ Fourier-transform infrared spectroscopy. Our results indicate that the N2O formation mechanism is reaction-temperature-dependent. At temperatures below 250 ℃, the dissociation of HON, which is produced from the reaction between surface H· adatoms and adsorbed NO, is the key process for N2O formation. At temperatures above 250 ℃,the reaction between NO and surface N·, which is produced by NO dissociation, is the only route for N2O formation, and the dissociation of NO is the rate-determining step. Under optimal reaction conditions, a high performance with nearly 100% NO conversion and 100% N2 selectivity could be achieved. These results provide important information to clarify the mechanism of N2O formation and possible suppression of N2 O emission during low-temperature NH3-SCR.展开更多
Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The o...Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The oxygen released from CeO_(2) enables the oxidation of CH_(x) species to serve as carbon precursors,thus providing Ni/CeO_(2) catalysts with stronger resistance to carbon deposition compared with Ni catalysts.The Ni/CeO_(2) catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics.Under 500℃for 25 h of ESR reaction,the ethanol conversion rate over Ni/CeO_(2) catalysts(n_(CeO_(2)):n_(Ni)=7)is sustained up to 100%and H_(2) selectivity is essentially kept at 74%.The by-product selectivity declines stepwise with increasing content of CeO_(2),which is attributed to the adsorption and oxidation of CO and of CH_(x) species as CH_4 precursor from CeO_(2).The scanning electron microscopy(SEM)and transform electron microscopy(TEM)results reveal that further loading of CeO_(2) on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles.Furthermore,carbon deposition on Ni/CeO_(2) catalysts preferentially outgrow filamentous rather than amorphous carbon,with a tendency for the latter to be more deactivated.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
Hierarchical Si C nanowire-supported Pd nanoparticles showed high photocatalytic activity for the C–X(X = Br, I) borylation of aryl halides at 30 °C. The Si C/Pd Mott-Schottky contact enhances the rapid transfer...Hierarchical Si C nanowire-supported Pd nanoparticles showed high photocatalytic activity for the C–X(X = Br, I) borylation of aryl halides at 30 °C. The Si C/Pd Mott-Schottky contact enhances the rapid transfer of the photogenerated electrons from Si C to the Pd nanoparticles. As a result, the concentrated energetic electrons in the Pd nanoparticles can facilitate the cleavage of C–I or C–Br bonds, which normally requires high-temperature thermal processes. We show that the present Pd/Si C photocatalyst is capable of catalyzing the transformation of a large variety of aryl halides to their corresponding boronate esters under visible light irradiation, with excellent yields.展开更多
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the National Natural Science Foundation of China (22325804 and 22308148)the Natural Science Foundation of Jiangsu Province (BK20230344)the Natural Science Research Project of Jiangsu University (22KJB610001)。
文摘Monolithic catalysts have been widely investigated for CO_(2) methanation due to their fast mass and heat transfer rate,but the effect of the interaction between the catalyst layer and the monolithic support has been little studied.In this work,Ni/Al_(2)O_(3)/SiC monolithic catalysts,Ni/Al_(2)O_(3) powder catalysts and Ni/Al_(2)O_(3)/SiC-M catalysts were prepared to explore the effect of Si-Al interaction between the catalyst layer and SiC ceramic for CO_(2) methanation performance.Ni/Al_(2)O_(3)/SiC exhibited a CO_(2) conversion of 53% and a CH_(4) specific reaction rate of 0.05 m mol·g^(-1)·s^(-1) under conditions of 0.1 M Pa,4 00℃,and a WHSV of 60000 ml·g^(-1)·h^(-1).The CO_(2) conversion raised by 0.15-fold and the CH_(4) specific reaction rate raised by 0.25-fold compared to Ni/Al_(2)O_(3) with the same catalyst content.SEM,XRD,Raman,and other characterization results revealed that the formation of Si-Al interaction between the catalyst layer and SiC ceramic could weaken the interaction between Ni and Al_(2)O_(3),thereby improving the catalytic activity of Ni/Al_(2)O_(3)/SiC catalyst.However,the Si-Al interaction was further strengthened during the hightemperature reaction process,which significantly weakened the interaction between Ni and Al_(2)O_(3),thereby leading to a decline in the catalytic performance of Ni/Al_(2)O_(3)/SiC catalyst during an 80-h stability test.This study provides valuable insights for future research and development of monolithic catalysts.
文摘Conventional synthesis of monolith-supported zeolite catalysts is based on a hydrothermal strategy.Here,we report a solvent-free crystallization process to coat ZSM-5 zeolite crystals on a monolithic SiC foam with a honeycomb structure(ZSM-5/SiC).Characterizations of the ZSM-5/SiC by scanning electron microscopy,N2 sorption,and X-ray diffraction indicate that the zeolite sheath has been ideally coated on the surface of the SiC foam with high purity and crystallinity.Fixing Pd nanoparticles within the ZSM-5 zeolite crystals delivers a bifunctional Pd@ZSM-5/SiC catalyst,which exhibits high activity and selectivity toward diesel range paraffins in the hydrodeoxygenation of methyl oleate,a model molecule for biofuel.In comparison to the powder Pd@ZSM-5,the Pd@ZSM-5/SiC monolith catalyst shows more efficiency,which is attributed to the fast mass transfer and high heat conductivity on the honeycomb SiC structure.The durability test indicates that the Pd@ZSM-5/SiC catalyst is stable under the reaction and high-temperature regeneration conditions.
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Project supported by the Key Program of Science Technology Department of Zhejiang Province(2018C03037)
文摘Pd/Ce0.67Zr0.33O2 catalyst was pretreated in different atmosphere respectively, and characterized by CO chemical adsorption, XPS, HR-TEM, H2-TPR, Raman, OSC and in situ DRIFTS to investigate the effect of the structure properties of PdOx species on the catalytic performance for CO, HC and NOx elimination. The results show that Pd/CZ catalyst pretreated in air atmosphere has higher oxidation activity of HC due to having high Pd dispersion and strong interaction between PdOx and CZ support. Pd/CZ-H catalyst pretreated in reducing atmosphere exhibits better catalytic performance of NOx elimination because of having relatively big Pd particle size, more Pd species in metallic state and higher concentration of oxygen vacancies. While for the Pd/CZ-RG catalyst pretreated in reactant atmosphere, strong adsorption of HC species on the surface of catalysts would lead to a part of active sites being covered, which inhibits HC and NO conversions.
基金support of the National Key Research and Development Program of China(2017YFB0310403)the National Natural Science Foundation of China(51872260,51390474,91645103)+2 种基金the Ministry of Science and Technology of China(2016YFE0105700)the Environmentally Sustainable Management of Medical Wastes in China(C/V/S/10/251)the Zhejiang Provincial Natural Science Foundation of China(Z4080070,LD19B030001)~~
文摘N2O is a major by-product emitted during low-temperature selective catalytic reduction of NO with NH3(NH3-SCR), which causes a series of serious environmental problems. A full understanding of the N2O formation mechanism is essential to suppress the N2O emission during the low-temperature NH3-SCR, and requires an intensive study of this heterogeneous catalysis process. In this study, we investigated the reaction between NH3 and NO over a Pd/CeO2 catalyst in the absence of O2, using X-ray photoelectron spectroscopy, NH3-temperature-programmed desorption, NO-temperature-programmed desorption, and in-situ Fourier-transform infrared spectroscopy. Our results indicate that the N2O formation mechanism is reaction-temperature-dependent. At temperatures below 250 ℃, the dissociation of HON, which is produced from the reaction between surface H· adatoms and adsorbed NO, is the key process for N2O formation. At temperatures above 250 ℃,the reaction between NO and surface N·, which is produced by NO dissociation, is the only route for N2O formation, and the dissociation of NO is the rate-determining step. Under optimal reaction conditions, a high performance with nearly 100% NO conversion and 100% N2 selectivity could be achieved. These results provide important information to clarify the mechanism of N2O formation and possible suppression of N2 O emission during low-temperature NH3-SCR.
基金Project supported by the Natural Science Foundation of Hunan Province,China (2022JJ30133)。
文摘Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The oxygen released from CeO_(2) enables the oxidation of CH_(x) species to serve as carbon precursors,thus providing Ni/CeO_(2) catalysts with stronger resistance to carbon deposition compared with Ni catalysts.The Ni/CeO_(2) catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics.Under 500℃for 25 h of ESR reaction,the ethanol conversion rate over Ni/CeO_(2) catalysts(n_(CeO_(2)):n_(Ni)=7)is sustained up to 100%and H_(2) selectivity is essentially kept at 74%.The by-product selectivity declines stepwise with increasing content of CeO_(2),which is attributed to the adsorption and oxidation of CO and of CH_(x) species as CH_4 precursor from CeO_(2).The scanning electron microscopy(SEM)and transform electron microscopy(TEM)results reveal that further loading of CeO_(2) on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles.Furthermore,carbon deposition on Ni/CeO_(2) catalysts preferentially outgrow filamentous rather than amorphous carbon,with a tendency for the latter to be more deactivated.
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.
基金supported by the National Natural Science Foudation of China(21473232,21673271,U1710112)
文摘Hierarchical Si C nanowire-supported Pd nanoparticles showed high photocatalytic activity for the C–X(X = Br, I) borylation of aryl halides at 30 °C. The Si C/Pd Mott-Schottky contact enhances the rapid transfer of the photogenerated electrons from Si C to the Pd nanoparticles. As a result, the concentrated energetic electrons in the Pd nanoparticles can facilitate the cleavage of C–I or C–Br bonds, which normally requires high-temperature thermal processes. We show that the present Pd/Si C photocatalyst is capable of catalyzing the transformation of a large variety of aryl halides to their corresponding boronate esters under visible light irradiation, with excellent yields.
