A series of Ni/La2Zr2O7 pyrochlore catalysts prepared by impregnation method and treated by dielectric barrier discharge（DBD） plasma in different atmospheres and varied sequences were prepared and applied for dry re...A series of Ni/La2Zr2O7 pyrochlore catalysts prepared by impregnation method and treated by dielectric barrier discharge（DBD） plasma in different atmospheres and varied sequences were prepared and applied for dry reforming of methane（DRM）. It is found that all of the plasma treated catalysts show evidently improved activity and coke resistance in comparison with the non-plasma treated one. The best performance is achieved on Ni/La2Zr2O7–H2P–C,a catalyst treated in H2 plasma before calcination. TGA-DSC and SEM demonstrate that carbon deposition is significantly suppressed on all of the plasma treated samples. Moreover,XRD and TEM results testify that both Ni O and Ni sizes on the calcined and reduced samples treated by plasma are also decreased,which results in higher Ni metal dispersion on the reduced and used catalysts and enhances the interactions between Ni sites and the support. It is believed that these are the inherent reasons accounting for the promotional effects of plasma treatment on the reaction performance of the Ni/La2Zr2O7 pyrochlore catalysts.展开更多
In this study, Ni/YZrOcatalysts prepared with impregnation method and treated by dielectric barrier discharge plasma(DBD) in different atmospheres have been investigated for methane dry reforming. It is revealed by H-...In this study, Ni/YZrOcatalysts prepared with impregnation method and treated by dielectric barrier discharge plasma(DBD) in different atmospheres have been investigated for methane dry reforming. It is revealed by H-TPR that plasma treatment can enhance the interaction between Ni O/Ni particles and the YZrOpyrochlore support. Therefore, catalysts with smaller Ni O and Ni grains sizes, higher metallic Ni active surface areas can be achieved, as evidenced by XRD, TEM and Hadsorption-desorption measurements. As a consequence, the plasma-treated catalysts show significantly improved activity, stability and coke resistance, as testified by the TEM and TGA-DSC results. Plasma treatment in H/Ar gas mixture is found to be the best condition to prepare Ni/YZrO, which can be used to obtain a catalyst with the highest activity, stability and most potent coke resistance. It is believed that the smaller Ni grain size and higher metallic Ni active surface area induced by plasma treatment are the inherent reasons accounting for the promoted reaction performance of the Ni/YZrOpyrochlore catalysts.展开更多
In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3O...In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3OH conversion and H_(2)yield,the reaction perfo rmance of the catalysts ranks as Cu/Sm_(2)O_(3)-M>Cu/Sm_(2)O_(3)-C>Cu/Gd_(2)O_(3)-M>Cu/Gd_(2)O_(3)-C>Cu/Eu_(2)O_(3)-M>Cu/Eu_(2)O_(3)-C.For the same kind of REO,Cu supported on the monoclinic support shows better performance than on the cubic one.Despite the phase structure difference,Sm_(2)O_(3) is the best support among all the three kinds of REOs.Compared with Cu/REO catalysts prepared with cubic supports,the corresponding catalysts prepared with monoclinic supports generally possess mo re surface oxygen vacancies,which can generate mo re surface active oxygen(O_(2)^(-)) and moderate basic sites.Moreover,the contents of Cu^(+) on the catalysts follow the same sequence.The reaction performance is positively related to the amount of these three types of surface sites.But metallic Cuo species is necessary to maintain the Cu^(+)■Cu^(0) redox cycle.Furthe rmore,on a catalyst with good perfo rmance,those vital surface reaction intermediates can be stabilized during the reaction.Cu/Sm_(2)O_(3)-M possesses the largest quantities of these surface sites,and has the appropriate amount of Cu^(+) and Cu^(0) after reduction,thereby displaying the optimal performance in all the catalysts.In conclusion,evident support crystal structure effect is observed for Cu/REO catalysts,and a monoclinic phase REO is a better support than the respective cubic phase one.展开更多
Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM...Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^(-2),equaling to a weight percentage around 4.5%.It has been revealed that the quantities of surface active oxygen(O_(2)^(-))and acid sites are crucial for the reaction,which can adsorb and activate NO_(x)and NH_(3)reactants effectively.Below the monolayer dispersion threshold,Co_(3)O_(4)is finely dispersed as sub-monolayers or monolayers and in an amorphous state,which is favorable to generate the two kinds of active sites,hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide.However,the formation of crystalline Co_(3)O_(4)above the capacity is harmful to the reaction performance.4%Co_(3)O_(4)/ZSM-5,the catalyst close to the monolayer dispersion capacity,possesses the most abundant active O_(2)^(-)species and acidic sites,thereby demonstrating the best reaction performance in all the samples.It is proposed the optimal Co_(3)O_(4)/ZSM-5 catalyst can be prepared by loading the capacity amount of Co_(3)O_(4)onto HZSM-5 support.展开更多
With the objective to develop catalysts having application potential for oxidative coupling of methane (OCM) at relatively lower temperature. A series of Ln2Zr2O7 compounds with varied rare earth A sites have been pre...With the objective to develop catalysts having application potential for oxidative coupling of methane (OCM) at relatively lower temperature. A series of Ln2Zr2O7 compounds with varied rare earth A sites have been prepared by a co-precipitation method. XRD and Raman have proved that pure Ln2Zr2O7 compounds have been successfully prepared for all the catalysts. By decreasing the rA/rB ratio, their crystalline structure transform from an ordered pyrochlore (La2Zr2O7) to a less ordered pyrochlore (Pr2Zr2O7 and Sm2Zr2O7) and eventually to a defective cubic fluorite phase (Y2Zr2O7). H2-TPR, O2-TPD and XPS have testified that the amount of surface active O2-species follows the order of La2Zr2O7>Pr2Zr2O7>Sm2Zr2O7 > Y2Zr2O7, which is well consistent with the reaction performance, indicating that the abundance of surface O2- sites is a critical factor influencing the reaction performance. CO2-TPD has demonstrated that a better catalyst generally possesses a larger amount of surface moderate alkaline sites, which is another factor to affect the reaction performance. It is concluded that the concerted interaction between the two types of surface active sites controls the reaction performance of the Ln2Zr2O7 catalysts. In comparison with the state-of-the art Mn/Na2WO4/SiO2, La2Zr2O7, the best catalyst, exhibits much improved reaction performance below 750 ℃.展开更多
A2B2O7 pyrochlore is a kind of important functional materials for different purposes,which has been investigated extensively by crystallographers and material scientists.However,the catalytic chemistry of this type of...A2B2O7 pyrochlore is a kind of important functional materials for different purposes,which has been investigated extensively by crystallographers and material scientists.However,the catalytic chemistry of this type of special compounds has rarely been documented,though a few researchers have tried to synthesize some pyrochlore compounds with different chemical compositions for a variety of green energy production and air pollution control reactions in the history.With the expectation to help catalysis scientists to get better acquaintance with,and gain deeper understanding on this type of compounds as heterogeneous catalysts,the major publications over the past several decades have been screened and reviewed in this paper,based also on our own experience of studying on this type of catalytic materials.The crystalline phase transformations of the compounds with the change of the A and B site cations,the phase change’s influences on the surface and bulk properties,and their subsequent impact on the catalytic performance for different reactions have been summarized.Furthermore,the future work which needs to be performed to perceive in depth this kind of important materials as catalysts has been proposed and suggested.We trust that this short review contains valuable information,which will provide great help for people to get better cognition for A2 B2 O7 pyrochlore compounds,and assist them to develop better catalysts for various reactions.展开更多
基金supported by the Chinese Natural Science Foundation (21263015 and 21203088)the Education Department of Jiangxi Province (KJLD14005 and GJJ14205)the Natural Science Foundation of Jiangxi Province (20142BAB213013)
文摘A series of Ni/La2Zr2O7 pyrochlore catalysts prepared by impregnation method and treated by dielectric barrier discharge（DBD） plasma in different atmospheres and varied sequences were prepared and applied for dry reforming of methane（DRM）. It is found that all of the plasma treated catalysts show evidently improved activity and coke resistance in comparison with the non-plasma treated one. The best performance is achieved on Ni/La2Zr2O7–H2P–C,a catalyst treated in H2 plasma before calcination. TGA-DSC and SEM demonstrate that carbon deposition is significantly suppressed on all of the plasma treated samples. Moreover,XRD and TEM results testify that both Ni O and Ni sizes on the calcined and reduced samples treated by plasma are also decreased,which results in higher Ni metal dispersion on the reduced and used catalysts and enhances the interactions between Ni sites and the support. It is believed that these are the inherent reasons accounting for the promotional effects of plasma treatment on the reaction performance of the Ni/La2Zr2O7 pyrochlore catalysts.
基金supported by the National Natural Science Foundation of China(21567016,21666020)the Natural Science Foundation of Jiangxi Province(20181ACB20005,20171BAB213013,20181BCD40004,20181BAB203017)+2 种基金the Innovation Fund Designated for Graduate Students of Jiangxi Province(YC2018-B015)the Education Department Foundation of Jiangxi Province(KJLD14005)the Opening Fund of Key Laboratory of Process Analysis and Control of Sichuan Universities(2017002)~~
基金supported by the National Natural Science Foundation of China (21567016, 21566022, 21263015)the Natural Science Foundation of Jiangxi Province (20151BBE50006, 20151BAB203024)the Education Department of Jiangxi Province (KJLD14005, GJJ150016)
文摘In this study, Ni/YZrOcatalysts prepared with impregnation method and treated by dielectric barrier discharge plasma(DBD) in different atmospheres have been investigated for methane dry reforming. It is revealed by H-TPR that plasma treatment can enhance the interaction between Ni O/Ni particles and the YZrOpyrochlore support. Therefore, catalysts with smaller Ni O and Ni grains sizes, higher metallic Ni active surface areas can be achieved, as evidenced by XRD, TEM and Hadsorption-desorption measurements. As a consequence, the plasma-treated catalysts show significantly improved activity, stability and coke resistance, as testified by the TEM and TGA-DSC results. Plasma treatment in H/Ar gas mixture is found to be the best condition to prepare Ni/YZrO, which can be used to obtain a catalyst with the highest activity, stability and most potent coke resistance. It is believed that the smaller Ni grain size and higher metallic Ni active surface area induced by plasma treatment are the inherent reasons accounting for the promoted reaction performance of the Ni/YZrOpyrochlore catalysts.
基金the Natural Science Foundation of China(21567016,21503106)the Natural Science Foundation of Jiangxi Province(20171BAB213013)+3 种基金the Education Department Foundation of Jiangxi Province(KJLD14005)National Key Research and Development Program of China(2016YFC0209302)the Innovation Fund Designated for Graduate Students of Jiangxi Province(YC2015-B017)the Innovation Fund Designated for Undergraduate Students of China(201701035)~~
基金Project supported by the National Natural Science Foundation of China(22172071,22102069,22062013,22262021,21962009)Natural Science Foundation of Jiangxi Province,China(20202BAB203006,20212BAB203030)Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis,China(20181BCD40004).
文摘In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3OH conversion and H_(2)yield,the reaction perfo rmance of the catalysts ranks as Cu/Sm_(2)O_(3)-M>Cu/Sm_(2)O_(3)-C>Cu/Gd_(2)O_(3)-M>Cu/Gd_(2)O_(3)-C>Cu/Eu_(2)O_(3)-M>Cu/Eu_(2)O_(3)-C.For the same kind of REO,Cu supported on the monoclinic support shows better performance than on the cubic one.Despite the phase structure difference,Sm_(2)O_(3) is the best support among all the three kinds of REOs.Compared with Cu/REO catalysts prepared with cubic supports,the corresponding catalysts prepared with monoclinic supports generally possess mo re surface oxygen vacancies,which can generate mo re surface active oxygen(O_(2)^(-)) and moderate basic sites.Moreover,the contents of Cu^(+) on the catalysts follow the same sequence.The reaction performance is positively related to the amount of these three types of surface sites.But metallic Cuo species is necessary to maintain the Cu^(+)■Cu^(0) redox cycle.Furthe rmore,on a catalyst with good perfo rmance,those vital surface reaction intermediates can be stabilized during the reaction.Cu/Sm_(2)O_(3)-M possesses the largest quantities of these surface sites,and has the appropriate amount of Cu^(+) and Cu^(0) after reduction,thereby displaying the optimal performance in all the catalysts.In conclusion,evident support crystal structure effect is observed for Cu/REO catalysts,and a monoclinic phase REO is a better support than the respective cubic phase one.
基金the financial supporting by the National Natural Science Foundation of China(Grant Nos.21962009,22172071,22102069,22062013)the Natural Science Foundation of Jiangxi Province(Grant Nos.20202BAB203006,20181ACB20005)the Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis(Grant No.20181BCD40004).
文摘Based on monolayer dispersion theory,Co_(3)O_(4)/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia.Co_(3)O_(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m^(-2),equaling to a weight percentage around 4.5%.It has been revealed that the quantities of surface active oxygen(O_(2)^(-))and acid sites are crucial for the reaction,which can adsorb and activate NO_(x)and NH_(3)reactants effectively.Below the monolayer dispersion threshold,Co_(3)O_(4)is finely dispersed as sub-monolayers or monolayers and in an amorphous state,which is favorable to generate the two kinds of active sites,hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide.However,the formation of crystalline Co_(3)O_(4)above the capacity is harmful to the reaction performance.4%Co_(3)O_(4)/ZSM-5,the catalyst close to the monolayer dispersion capacity,possesses the most abundant active O_(2)^(-)species and acidic sites,thereby demonstrating the best reaction performance in all the samples.It is proposed the optimal Co_(3)O_(4)/ZSM-5 catalyst can be prepared by loading the capacity amount of Co_(3)O_(4)onto HZSM-5 support.
基金the Natural Science Foundation of China (Nos. 21567016, 21566022, 21666020)the Natural Science Foundation of Jiangxi Province (Nos. 20181ACB20005, 20171BAB213013 and 20181BAB203017)+4 种基金the Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis(No. 20181BCD40004) the Education Department of Jiangxi Province (Nos. GJJ150016, GJJ150085 and KJLD14005)the China Postdoctoral Science Foundation(No. 2018M631294)Innovation Fund Designated for Undergraduate Students of Nanchang University of China (No. 201802369)the Graduate Student Creativity Funding of Nanchang University(No. 201802062)
文摘With the objective to develop catalysts having application potential for oxidative coupling of methane (OCM) at relatively lower temperature. A series of Ln2Zr2O7 compounds with varied rare earth A sites have been prepared by a co-precipitation method. XRD and Raman have proved that pure Ln2Zr2O7 compounds have been successfully prepared for all the catalysts. By decreasing the rA/rB ratio, their crystalline structure transform from an ordered pyrochlore (La2Zr2O7) to a less ordered pyrochlore (Pr2Zr2O7 and Sm2Zr2O7) and eventually to a defective cubic fluorite phase (Y2Zr2O7). H2-TPR, O2-TPD and XPS have testified that the amount of surface active O2-species follows the order of La2Zr2O7>Pr2Zr2O7>Sm2Zr2O7 > Y2Zr2O7, which is well consistent with the reaction performance, indicating that the abundance of surface O2- sites is a critical factor influencing the reaction performance. CO2-TPD has demonstrated that a better catalyst generally possesses a larger amount of surface moderate alkaline sites, which is another factor to affect the reaction performance. It is concluded that the concerted interaction between the two types of surface active sites controls the reaction performance of the Ln2Zr2O7 catalysts. In comparison with the state-of-the art Mn/Na2WO4/SiO2, La2Zr2O7, the best catalyst, exhibits much improved reaction performance below 750 ℃.
基金Project supported by the National Natural Science Foundation of China(21962009,21567016,21666020)Natural Science Foundation of Jiangxi Province(20181ACB20005,20171BAB213013,20181BAB203017)Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis(20181BCD40004)。
文摘A2B2O7 pyrochlore is a kind of important functional materials for different purposes,which has been investigated extensively by crystallographers and material scientists.However,the catalytic chemistry of this type of special compounds has rarely been documented,though a few researchers have tried to synthesize some pyrochlore compounds with different chemical compositions for a variety of green energy production and air pollution control reactions in the history.With the expectation to help catalysis scientists to get better acquaintance with,and gain deeper understanding on this type of compounds as heterogeneous catalysts,the major publications over the past several decades have been screened and reviewed in this paper,based also on our own experience of studying on this type of catalytic materials.The crystalline phase transformations of the compounds with the change of the A and B site cations,the phase change’s influences on the surface and bulk properties,and their subsequent impact on the catalytic performance for different reactions have been summarized.Furthermore,the future work which needs to be performed to perceive in depth this kind of important materials as catalysts has been proposed and suggested.We trust that this short review contains valuable information,which will provide great help for people to get better cognition for A2 B2 O7 pyrochlore compounds,and assist them to develop better catalysts for various reactions.
