Single-atom catalysts (SACs) supported on two-dimensional (2D) materials are highly attractive for maximizing their catalytic activity.However,graphene based SACs are primarily bonded with nitrogen and carbon sites,re...Single-atom catalysts (SACs) supported on two-dimensional (2D) materials are highly attractive for maximizing their catalytic activity.However,graphene based SACs are primarily bonded with nitrogen and carbon sites,resulting in poor performance for the oxygen evolution reaction (OER).Herein,we develop a general bimetal-ion adsorption strategy for the synthesis of individually dispersed Ni SACs anchored on the oxygenated sites of ultrathin reduced graphene oxide as efficient OER electrocatalysts.The resultant Ni SACs for OER in alkaline electrolyte exhibit a highly stable overpotential of 328 mV at the current density of 10 mA cm^-2,and Tafel slope of 84 mV dec^-1 together with long-term durability and negligible degradation for 50 h,which is greatly outperform its counterparts of nitrogen bonded Ni SACs (564 mV,364 mV dec^-1) and Ni(OH)2 nanoparticles anchored on graphene (450 mV,142 mV dec^-1),and most reported Ni based OER electrocatalysts.Furthermore,the extended X-ray absorption fine structure at the Ni K-edge and theoretical simulation reveal that the nickel-oxygen coordination significantly boost OER performance.Therefore,this work will open numerous opportunities for creating novel-type 2D SACs via oxygen-metal bonding as highly robust OER catalysts.展开更多
In this paper dry reforming of methane （DRM） was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesiz...In this paper dry reforming of methane （DRM） was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesized by a co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant, and employed as catalyst support. The prepared samples were characterized by X-ray diffraction （XRD）, N2 adsorption, H2 chemisorption, temperature-programmed reduction （TPR）, temperature-programmed oxidation （TPO）, temperature- programmed desorption （TPD） and transmission and scanning electron microscopies （TEM, SEM） techniques. The obtained results showed that the catalyst support has a nanocrystalline structure （crystal size： about 5 nm） with a high specific surface area （175 m2 g-1） and a mesoporous structure. Increasing in nickel content decreased the specific surface area and nickel dispersion. The prepared catalysts showed high catalytic activity and stability during the reaction. SEM analysis revealed that whisker type carbon deposited over the spent catalysts and increasing in nickel loading increased the amount of deposited carbon. The nickel catalyst with 7 wt% of nickel showed the highest catalytic activity.展开更多
In this paper, three kinds of MgO with different specific surface area were prepared, and their effects on the catalytic performance of nickel catalysts for the carbon dioxide reforming of methane were investigated. T...In this paper, three kinds of MgO with different specific surface area were prepared, and their effects on the catalytic performance of nickel catalysts for the carbon dioxide reforming of methane were investigated. The results showed that MgO support with the higher specific surface area led to the higher dispersion of the active metal, which resulted in the higher initial activity. On the other hand, the specific surface area of MgO materials might not be the dominant factor for the basicity of support to chemisorb and activate CO2, which was another important factor for the performance of catalysts. Herein, Ni/MgO(CA) catalyst with proper specific surface area and strong ability to activate CO2exhibited stable catalytic property and the carbon species deposited on the Ni/MgO(CA) catalyst after 10 h of reaction at 650 ?C were mainly activated carbon species.展开更多
Gas-phase catalytic conversion of glycerol to value added chemicals was investigated over zinc-supported copper and nickel catalysts.The addition of aluminum in the support was also investigated in glycerol conversion...Gas-phase catalytic conversion of glycerol to value added chemicals was investigated over zinc-supported copper and nickel catalysts.The addition of aluminum in the support was also investigated in glycerol conversion and the results indicate an increase in the acidity and adsorption capacity for both copper and nickel catalysts.HRTEM and XRD analysis revealed Ni Zn alloy formation in the Ni/ZnO catalyst.The XRD patterns of the prepared Zn Al mixed oxide catalysts show the presence of Gahanite phase(ZnAl2O4).In addition,H2 chemisorption and TPR results suggest a strong metal-support interactions(SMSI)effect between Ni and Zn O particles.Bare supports Zn O and ZnAl(Zn/Al=0.5)were investigated in the glycerol conversion and they did not present activity.Copper supported on ZnO and ZnAl mixed oxide(Zn/Al=0.5)was active towards hydroxyacetone formation.Nickel was active in the hydrogenolysis of glycerol both for C–C and C–O bonds cleavage of glycerol producing CH4.Strong metal-support interactions(SMSI)between Ni and ZnO has a remarkable suppression effect on the methanation activity during the glycerol conversion.展开更多
The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO const...The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO constituted 62.0% of cement clinker. The physicochemical characterization of the catalysts revealed 32-folds increment of BET surface area （SBET） with the addition of nickel metal into the cement clinker, which was also corroborated by FESEM images. Significantly, XRD results suggested different types of Ni oxides formation with Ni loading, whilst Ca3SiO5 and Ca2Al0.67Mn0.33FeO5 were the main crystallite species for pure cement clinker. Temperature-programmed reduction analysis yielded three domains of H2 reduction peaks, viz. centered at approximately 750 K referred to as type-Ⅰ peaks, another peaks at 820 K denoted as type-Ⅱ peaks and the highest reduction peaks, type-Ⅲ recorded at above 1000 K. 20 wt% Ni was found to be the best loading with the highest XG and H2 yield, whilst the lowest methanation activity. Syngas with lower H2/CO ratios （0.6 to 1.5） were readily produced from glycerol dry reforming at CO2-to-Glycerol feed ratio （CGR） of unity. Nonetheless, carbon deposit comprised of whisker type （Cv） and graphitic-like type （Cc） species were found to be in majority on 20 wt%Ni/CC catalysts.展开更多
The colloidal carbon microspheres(CMS)were prepared by the hydrothermal method.The nickel catalysts supported on carbon microspheres(Ni/CMS)were further prepared and were characterized by the Fourier transform infrare...The colloidal carbon microspheres(CMS)were prepared by the hydrothermal method.The nickel catalysts supported on carbon microspheres(Ni/CMS)were further prepared and were characterized by the Fourier transform infrared spectroscopy(FTIR),the X-ray diffraction(XRD),the scanning electron microscopy(SEM),the transmission electron microscopy(TEM),and the N_(2)adsorption technique.The selective hydrogenation of maleic anhydride(MA)to succinic anhydride(SA)over the Ni/CMS catalysts was investigated.The results indicated that the Ni/CMS catalyst,which was prepared with glucose as carbon source and calcined at 500℃,exhibited the best performance.The hydrogen pressure,reaction temperature,and reaction time could significantly affect the conversion of maleic anhydride during the hydrogenation reaction.A 98.4%conversion of MA and an 100%selectivity to SA were achieved over the Ni/CMS catalyst in acetic anhydride solvent under mild conditions covering a temperature of 90℃,a H2 pressure of 1.0 MPa,and a reaction time of 3 h.展开更多
The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glyco...The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.展开更多
Four perovskite-type complex oxides (LaNiO_3, La_2NiO_4, LaCoO_3 andLa_2CoO_4) were successfully prepared using two sol-gel methods, the Pechini method (PC) and thecitric acid complexing method (CC). The catalysts wer...Four perovskite-type complex oxides (LaNiO_3, La_2NiO_4, LaCoO_3 andLa_2CoO_4) were successfully prepared using two sol-gel methods, the Pechini method (PC) and thecitric acid complexing method (CC). The catalysts were characterized by XRD and TPR. Afterreduction, the activity of the catalysts in the CO_2 reforming of methane was tested. Ni-basedcatalysts from La_2NiO_4 precursors were the most active and stable catalyst after calcination above850 ℃, which gave a methane conversion of 0.025 mmol/(g·s) for those prepared by the PC methodand 0.020 mmol/(g·s) by the CC method. It was proposed that the well-defined structure and lowerreducibility is responsible for the unusual catalytic behavior observed over the pre-reducedLa2NiO_4 catalyst.展开更多
Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly（ethylene glycol）-block-poly（propylene glycol）-block-poly（ethylene glycol） （PEG-PPG...Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly（ethylene glycol）-block-poly（propylene glycol）-block-poly（ethylene glycol） （PEG-PPG-PEG, MW： 5800） as a surfactant. They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction （XRD）, N2 adsorption （BET）, temperature-programmed reduction and oxidation （TPR-TPO）, and scanning electron microscopy （SEM） techniques. Catalysts showed a relatively high catalytic activity and stability. TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced. TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C12A7 catalysts with higher CaO amount were effective against coke deposition.展开更多
The structure of polyolefin has an important influence on its performance and application.Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin.However,research on ...The structure of polyolefin has an important influence on its performance and application.Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin.However,research on the ethylene/1-hexene copolymerization catalyzed by nickel complexes with different steric ligands remains to be refined.Here,three α-dimine nickel catalysts are used to study the ligand effect on catalytic performance in the ethylene/1-hexene copolymerization.Reaction activity,molecular weight,phase-transition temperature and branching density of the resultant copolymer are measured to evaluate the catalytic performance.The results indicate that the steric ligands could exert great effect on the copolymerization.As for the chemical valence of Ni species,detailed EPR demonstrate that the presence of excess xo-catalyst can reduce Ni(Ⅱ)to the lower valence and affect the catalytic performance.展开更多
Decomposition of methane in the presence of coprecipitated nickel-basedcatalysts to produce carbon fibers was investigated. The reaction was studied in the temperaturerange of 773 K to 1073 K. At 1023 K, the catalytic...Decomposition of methane in the presence of coprecipitated nickel-basedcatalysts to produce carbon fibers was investigated. The reaction was studied in the temperaturerange of 773 K to 1073 K. At 1023 K, the catalytic activities of three catalysts kept high at theinitial period and then decreased with the reaction time. The lifetimes of Ni-Cu-Al and Ni-La-Alcatalysts are longer than that of Ni-Al catalyst. With three catalysts, the yield of carbon fiberswas very low at 773 K. The yield of carbon fibers for Ni-La-Al catalyst was more than those forNi-Al and Ni-Cu-Al catalysts. For Ni-La-Al catalyst, the elevation of temperature from 873 K up to1073 K led gradually to an increase in the yield of carbon fibers. XRD studies on the Ni-La-Alcatalyst indicate that La_2NiO_4 was formed. The formation of La_2NiO_4 is responsible for theincrease in the catalytic lifetime and the yield of carbon fibers synthesized on Ni-La-Al at773-1073 K. Carbon fibers synthesized on Ni-Al catalyst are thin, long carbon nanotubes. There arebamboo-shaped carbon fibers synthesized on Ni-Cu-Al catalyst. Carbon fibers synthesized on Ni-La-Alcatalyst have large hollow core, thin wall and good graphitization.展开更多
A series of Ni/ZSM-5 containing a small amount of Ni was prepared by an ion exchanged method.The impact of the n(SiO_(2))/n(Al_(2)O_(3))ratio on the catalytic activity was studied using the samples 0.09Ni/ZSM-5(60)and...A series of Ni/ZSM-5 containing a small amount of Ni was prepared by an ion exchanged method.The impact of the n(SiO_(2))/n(Al_(2)O_(3))ratio on the catalytic activity was studied using the samples 0.09Ni/ZSM-5(60)and 0.09Ni/ZSM-5(130).To determine the interaction between the Ni species and acid sites on the surface of the catalyst,the catalysts were characterized by N2 adsorption-desorption,X-ray diffraction(XRD),scanning electron microscopy(SEM),and UV-vis spectroscopy.The performance of the catalysts for the catalytic oligomerization of 1-hexene was investigated in detail.The nickel species were found to be uniformly distributed in all the catalysts.It was discovered that the oligomerization activity of the catalyst can be improved using Ni species;however,the contribution of Brønsted acids in oligomerization reactions is greater than that of Ni sites and Lewis acids.展开更多
1,4,8,11,15,18,22,25-octabutoxy phthalocyanine nickel(Ⅱ) was synthesized by refluxing 3,6-dibutoxy phthalonitrite with anhydrous nickel chloride in n-amyl alcohol solvent in the presence of 1,8-diazabicycloundec-7-en...1,4,8,11,15,18,22,25-octabutoxy phthalocyanine nickel(Ⅱ) was synthesized by refluxing 3,6-dibutoxy phthalonitrite with anhydrous nickel chloride in n-amyl alcohol solvent in the presence of 1,8-diazabicycloundec-7-ene(DBU).The product was characterized by elemental analysis.IR,UV-Vis and fluorescence emission spectra.The thermal stability was studied by TG and TDG.The redox potentials was measured using cyclic voltammetry(CV).展开更多
基金supported by the National Natural Science Foundation of China(Grants 51702078,51572259,and 51872283)National Key R&D Program of China(Grants 2016YFB0100100 and 2016YFA0200200)+5 种基金Liao Ning Revitalization Talents Program(Grant XLYC1807153)Natural Science Foundation of Liaoning Province(Grant 20180510038)DICP(DICP ZZBS201708,DICP ZZBS201802)DICP&QIBEBT(Grant DICP&QIBEBT UN201702)Dalian National Laboratory For Clean Energy(DNL),CASDNL Cooperation Fund,CAS(DNL180310,DNL180308)。
文摘Single-atom catalysts (SACs) supported on two-dimensional (2D) materials are highly attractive for maximizing their catalytic activity.However,graphene based SACs are primarily bonded with nitrogen and carbon sites,resulting in poor performance for the oxygen evolution reaction (OER).Herein,we develop a general bimetal-ion adsorption strategy for the synthesis of individually dispersed Ni SACs anchored on the oxygenated sites of ultrathin reduced graphene oxide as efficient OER electrocatalysts.The resultant Ni SACs for OER in alkaline electrolyte exhibit a highly stable overpotential of 328 mV at the current density of 10 mA cm^-2,and Tafel slope of 84 mV dec^-1 together with long-term durability and negligible degradation for 50 h,which is greatly outperform its counterparts of nitrogen bonded Ni SACs (564 mV,364 mV dec^-1) and Ni(OH)2 nanoparticles anchored on graphene (450 mV,142 mV dec^-1),and most reported Ni based OER electrocatalysts.Furthermore,the extended X-ray absorption fine structure at the Ni K-edge and theoretical simulation reveal that the nickel-oxygen coordination significantly boost OER performance.Therefore,this work will open numerous opportunities for creating novel-type 2D SACs via oxygen-metal bonding as highly robust OER catalysts.
文摘In this paper dry reforming of methane （DRM） was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesized by a co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant, and employed as catalyst support. The prepared samples were characterized by X-ray diffraction （XRD）, N2 adsorption, H2 chemisorption, temperature-programmed reduction （TPR）, temperature-programmed oxidation （TPO）, temperature- programmed desorption （TPD） and transmission and scanning electron microscopies （TEM, SEM） techniques. The obtained results showed that the catalyst support has a nanocrystalline structure （crystal size： about 5 nm） with a high specific surface area （175 m2 g-1） and a mesoporous structure. Increasing in nickel content decreased the specific surface area and nickel dispersion. The prepared catalysts showed high catalytic activity and stability during the reaction. SEM analysis revealed that whisker type carbon deposited over the spent catalysts and increasing in nickel loading increased the amount of deposited carbon. The nickel catalyst with 7 wt% of nickel showed the highest catalytic activity.
基金supported by the South-Central University for Nationalities(CZZ12002)
文摘In this paper, three kinds of MgO with different specific surface area were prepared, and their effects on the catalytic performance of nickel catalysts for the carbon dioxide reforming of methane were investigated. The results showed that MgO support with the higher specific surface area led to the higher dispersion of the active metal, which resulted in the higher initial activity. On the other hand, the specific surface area of MgO materials might not be the dominant factor for the basicity of support to chemisorb and activate CO2, which was another important factor for the performance of catalysts. Herein, Ni/MgO(CA) catalyst with proper specific surface area and strong ability to activate CO2exhibited stable catalytic property and the carbon species deposited on the Ni/MgO(CA) catalyst after 10 h of reaction at 650 ?C were mainly activated carbon species.
基金financial support from Fondecyt.R.J.Chimentao is grateful to Fondecyt 1180243Fondecyt 1161660+3 种基金the Universitat Rovira i VirgiliUniversidad de Costa Rica for the financial supportICREA Academia programGC 2017 SGR 128.
文摘Gas-phase catalytic conversion of glycerol to value added chemicals was investigated over zinc-supported copper and nickel catalysts.The addition of aluminum in the support was also investigated in glycerol conversion and the results indicate an increase in the acidity and adsorption capacity for both copper and nickel catalysts.HRTEM and XRD analysis revealed Ni Zn alloy formation in the Ni/ZnO catalyst.The XRD patterns of the prepared Zn Al mixed oxide catalysts show the presence of Gahanite phase(ZnAl2O4).In addition,H2 chemisorption and TPR results suggest a strong metal-support interactions(SMSI)effect between Ni and Zn O particles.Bare supports Zn O and ZnAl(Zn/Al=0.5)were investigated in the glycerol conversion and they did not present activity.Copper supported on ZnO and ZnAl mixed oxide(Zn/Al=0.5)was active towards hydroxyacetone formation.Nickel was active in the hydrogenolysis of glycerol both for C–C and C–O bonds cleavage of glycerol producing CH4.Strong metal-support interactions(SMSI)between Ni and ZnO has a remarkable suppression effect on the methanation activity during the glycerol conversion.
基金supported by Ministry of Education,Malaysia through MTUN(No.RDU121216)
文摘The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO constituted 62.0% of cement clinker. The physicochemical characterization of the catalysts revealed 32-folds increment of BET surface area （SBET） with the addition of nickel metal into the cement clinker, which was also corroborated by FESEM images. Significantly, XRD results suggested different types of Ni oxides formation with Ni loading, whilst Ca3SiO5 and Ca2Al0.67Mn0.33FeO5 were the main crystallite species for pure cement clinker. Temperature-programmed reduction analysis yielded three domains of H2 reduction peaks, viz. centered at approximately 750 K referred to as type-Ⅰ peaks, another peaks at 820 K denoted as type-Ⅱ peaks and the highest reduction peaks, type-Ⅲ recorded at above 1000 K. 20 wt% Ni was found to be the best loading with the highest XG and H2 yield, whilst the lowest methanation activity. Syngas with lower H2/CO ratios （0.6 to 1.5） were readily produced from glycerol dry reforming at CO2-to-Glycerol feed ratio （CGR） of unity. Nonetheless, carbon deposit comprised of whisker type （Cv） and graphitic-like type （Cc） species were found to be in majority on 20 wt%Ni/CC catalysts.
基金The authors are grateful for the financial supports of the Project of Research and Development Fund of Nanchong City(19YFZJ0107,18YFZJ0041)the Meritocracy Research Funds of China West Normal University(17YC041)the Undergraduate Training Program for Innovation of China West Normal University.(cxcy2020186).
文摘The colloidal carbon microspheres(CMS)were prepared by the hydrothermal method.The nickel catalysts supported on carbon microspheres(Ni/CMS)were further prepared and were characterized by the Fourier transform infrared spectroscopy(FTIR),the X-ray diffraction(XRD),the scanning electron microscopy(SEM),the transmission electron microscopy(TEM),and the N_(2)adsorption technique.The selective hydrogenation of maleic anhydride(MA)to succinic anhydride(SA)over the Ni/CMS catalysts was investigated.The results indicated that the Ni/CMS catalyst,which was prepared with glucose as carbon source and calcined at 500℃,exhibited the best performance.The hydrogen pressure,reaction temperature,and reaction time could significantly affect the conversion of maleic anhydride during the hydrogenation reaction.A 98.4%conversion of MA and an 100%selectivity to SA were achieved over the Ni/CMS catalyst in acetic anhydride solvent under mild conditions covering a temperature of 90℃,a H2 pressure of 1.0 MPa,and a reaction time of 3 h.
基金the support of the Smart Mix Program of The Netherlands Ministry of Economic Affairs, Agriculture and Innovation and The Netherlands Ministry of Education, Culture and Science (Grant no. 053.70.011)
文摘The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.
文摘Four perovskite-type complex oxides (LaNiO_3, La_2NiO_4, LaCoO_3 andLa_2CoO_4) were successfully prepared using two sol-gel methods, the Pechini method (PC) and thecitric acid complexing method (CC). The catalysts were characterized by XRD and TPR. Afterreduction, the activity of the catalysts in the CO_2 reforming of methane was tested. Ni-basedcatalysts from La_2NiO_4 precursors were the most active and stable catalyst after calcination above850 ℃, which gave a methane conversion of 0.025 mmol/(g·s) for those prepared by the PC methodand 0.020 mmol/(g·s) by the CC method. It was proposed that the well-defined structure and lowerreducibility is responsible for the unusual catalytic behavior observed over the pre-reducedLa2NiO_4 catalyst.
文摘Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly（ethylene glycol）-block-poly（propylene glycol）-block-poly（ethylene glycol） （PEG-PPG-PEG, MW： 5800） as a surfactant. They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction （XRD）, N2 adsorption （BET）, temperature-programmed reduction and oxidation （TPR-TPO）, and scanning electron microscopy （SEM） techniques. Catalysts showed a relatively high catalytic activity and stability. TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced. TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C12A7 catalysts with higher CaO amount were effective against coke deposition.
基金Financial support from the National Key Research and Development Program(2016YFB0302403)is gratefully acknowledged.
文摘The structure of polyolefin has an important influence on its performance and application.Ethylene/1-hexene copolymerization is one of the important ways to control the structure of the polyolefin.However,research on the ethylene/1-hexene copolymerization catalyzed by nickel complexes with different steric ligands remains to be refined.Here,three α-dimine nickel catalysts are used to study the ligand effect on catalytic performance in the ethylene/1-hexene copolymerization.Reaction activity,molecular weight,phase-transition temperature and branching density of the resultant copolymer are measured to evaluate the catalytic performance.The results indicate that the steric ligands could exert great effect on the copolymerization.As for the chemical valence of Ni species,detailed EPR demonstrate that the presence of excess xo-catalyst can reduce Ni(Ⅱ)to the lower valence and affect the catalytic performance.
基金Supported by the National Natural Science Foundation of China (No. 20263003)Natural Science Foundation of Jiangxi province (No. 0250009)
文摘Decomposition of methane in the presence of coprecipitated nickel-basedcatalysts to produce carbon fibers was investigated. The reaction was studied in the temperaturerange of 773 K to 1073 K. At 1023 K, the catalytic activities of three catalysts kept high at theinitial period and then decreased with the reaction time. The lifetimes of Ni-Cu-Al and Ni-La-Alcatalysts are longer than that of Ni-Al catalyst. With three catalysts, the yield of carbon fiberswas very low at 773 K. The yield of carbon fibers for Ni-La-Al catalyst was more than those forNi-Al and Ni-Cu-Al catalysts. For Ni-La-Al catalyst, the elevation of temperature from 873 K up to1073 K led gradually to an increase in the yield of carbon fibers. XRD studies on the Ni-La-Alcatalyst indicate that La_2NiO_4 was formed. The formation of La_2NiO_4 is responsible for theincrease in the catalytic lifetime and the yield of carbon fibers synthesized on Ni-La-Al at773-1073 K. Carbon fibers synthesized on Ni-Al catalyst are thin, long carbon nanotubes. There arebamboo-shaped carbon fibers synthesized on Ni-Cu-Al catalyst. Carbon fibers synthesized on Ni-La-Alcatalyst have large hollow core, thin wall and good graphitization.
基金Financial support was obtained from the State Key Laboratory of Petroleum Molecular&Process Engineering(24-ZC0607-0099)the Natural Science Foundation of China(21706177 and 22378293).
文摘A series of Ni/ZSM-5 containing a small amount of Ni was prepared by an ion exchanged method.The impact of the n(SiO_(2))/n(Al_(2)O_(3))ratio on the catalytic activity was studied using the samples 0.09Ni/ZSM-5(60)and 0.09Ni/ZSM-5(130).To determine the interaction between the Ni species and acid sites on the surface of the catalyst,the catalysts were characterized by N2 adsorption-desorption,X-ray diffraction(XRD),scanning electron microscopy(SEM),and UV-vis spectroscopy.The performance of the catalysts for the catalytic oligomerization of 1-hexene was investigated in detail.The nickel species were found to be uniformly distributed in all the catalysts.It was discovered that the oligomerization activity of the catalyst can be improved using Ni species;however,the contribution of Brønsted acids in oligomerization reactions is greater than that of Ni sites and Lewis acids.
文摘1,4,8,11,15,18,22,25-octabutoxy phthalocyanine nickel(Ⅱ) was synthesized by refluxing 3,6-dibutoxy phthalonitrite with anhydrous nickel chloride in n-amyl alcohol solvent in the presence of 1,8-diazabicycloundec-7-ene(DBU).The product was characterized by elemental analysis.IR,UV-Vis and fluorescence emission spectra.The thermal stability was studied by TG and TDG.The redox potentials was measured using cyclic voltammetry(CV).
