Direct synthesis of dimethyl carbonate(DMC)from CO2 is critical for achieving carbon neutrality,yet the sluggish formation and conversion of the key*CH₃OCOO intermediate-due to the difficulty of C-O coupling-limit ...Direct synthesis of dimethyl carbonate(DMC)from CO2 is critical for achieving carbon neutrality,yet the sluggish formation and conversion of the key*CH₃OCOO intermediate-due to the difficulty of C-O coupling-limit high DMC yields.Herein,we developed a boric acid-assisted recrystallization strategy to fabricate grain-boundary-rich CeO2 hollow nanospheres,which serve as an efficient catalyst for CO2 to DMC synthesis.The introduction of grain-boundary(GBs)induced the electron redistribution,which led a decrease in the electron density of bulk Ce ions and created a localized electron-rich region at homogeneous interface.This unique electronic landscape promoted reactive methoxy formation and stronger CO2 adsorption,thereby enabling more efficient coupling of*CH3O and*CO2 to form the*CH3OCOO.Concurrently,the enhanced CO2 adsorption facilitated the dissociation of*CH3OCOO and subsequent DMC formation.As a result,the 4%BCeO2-GBs achieved an advantageous DMC yield of 19.8 mmol/g.In the assistance of dehydrating agent,the catalyst delivered a remarkable 264.2 mmol/g DMC yield and 7.12%methanol conversion,which was 32 times higher than commercial CeO2.This study elucidated the intrinsic mechanisms governing*CH3OCOO intermediate behavior and offers valuable guidance for CO2 converting into high-value organic chemicals.展开更多
In this paper,the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10-x wt%CeO2(x=0,4,8)alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics ...In this paper,the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10-x wt%CeO2(x=0,4,8)alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics and thermodynamics performances of the alloys were studied in detail.The results show that the Mg85Cu5Ni10 alloys with CeO2 additive have faster hydrogenation/dehydrogenation kinetics and better thermodynamic properties.The dehydrogenation activation energy is reduced to 81.211 kJ/mol from 119.142 by adding 8 wt%CeO2.CeO2 contributes to producing structural defects,nanocrystallines,grain boundaries,partial amorphous,lattice dislocations and cracks which are favorable to provide more hydrogen diffusion channels during hydriding/dehydriding process.Meanwhile,CeO2 additive weakens the bond energy of Mg-H.These micro structural changes caused by CeO2 additive improve the hydrogen storage performance of Mg85Cu5Ni10 markedly.展开更多
High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an...High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an impregnation-coprecipitation method. The influence of Cu atomic content on the catalytic performance was investigated on the steam reforming of ethanol (SRE) for H2 production and the catalysts were characterized by N2 adsorption, inductively coupled plasma (ICP), X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed rerduction (TPR) and H2-pulse chemisorption techniques. The activity and products distribution behaviors of the catalysts were significantly affected by the doped Cu molar content based on the promotion effect on the dispersion of NiO particles and the interactions between Cu-Ni metal and CeO2 support. Significant increase in the ethanol conversion and hydrogen selectivity were obtained when moderate Cu metal was doped into the Ni/CeO2 catalyst. Over both of the 10Ni98.5Cu1.5/CeO2 and 15Ni98.5Cu1.5/CeO2 catalysts, more than 80% of ethanol conversion and 60% of H2 selectivity were obtained in the ethanol steam-reforming when the reaction temperature was above 450 ℃.展开更多
The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that eith...The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that either CuO or CeO 2 ac tivity is quite low for CO oxidation. However, when CuO and CeO 2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu 2+ and Cu+) on the CeO 2 surfa ce, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu 2+ or Cu+. Rietveld analysis s hows that some CuO, which has smaller ion radius than Ce 4+, enters the Ce O 2 lattice after CuO and CeO 2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value i s a maximum (2.86×10 -3), resulting in high surface energy and the best ac tivity for CO oxidation.展开更多
The selective catalytic reduction(SCR) of NOx using MnOx and CeO2 supported on viscose-based active carbon fibers(ACF) at 120 ℃~270 ℃ relatively lower than the temperature when using V2O5/TiO2-anatase catalyst was ...The selective catalytic reduction(SCR) of NOx using MnOx and CeO2 supported on viscose-based active carbon fibers(ACF) at 120 ℃~270 ℃ relatively lower than the temperature when using V2O5/TiO2-anatase catalyst was studied.As a result,CeO2/ACF shows a better catalysis than MNOx/ACF,which is not affected by the reaction temperature. NO conversion of 85% is reached with the 10%-CeO2/ACF catalyst at the whole temperature window.Furthermore,a series of MnOx-CeO2/ACF composite catalysts were studied.The results show that the loading method of catalyst affects its activity.展开更多
Elucidation of the CuOx-CeO2 interactions is of great interest and importance in understanding complex CuOx-CeO2 interfacial catalysis in various reactions. In the present work, we have investigated structures and cat...Elucidation of the CuOx-CeO2 interactions is of great interest and importance in understanding complex CuOx-CeO2 interfacial catalysis in various reactions. In the present work, we have investigated structures and catalytic activity in CO oxidation of CuOx species on CeO2 rods, cubes and polyhedra predominantly exposing {110}+{100}, {100} and {111} facets by the incipient wetness impregnation method with the lowest Cu loading of 0.025%. The structural evolution of CuOx species was found to depend on both the Cu loading and the CeO2 morphology. As the Cu loading increases, CuOx species are deposited preferentially on the surface defect of CeO2 and then aggregate and grow, accompanied by the formation of isolated Cu ions, CuOx clusters strongly/weakly interacting with the CeO2, highly dispersed Cu O nanoparticles, and large Cu O nanoparticles. The isolated Cu^+ species and CuOx clusters weakly interacting with the CeO2 were observed mainly on the O-terminated CeO2{100} facets. Meanwhile, more Cu(I) species are stabilized during CO reduction processes in CuOx/c-CeO2 catalysts than in CuOx-CeO2 and CuOx/p-CeO2 catalysts. The catalytic activities of various CuOx/CeO2 catalysts in CO oxidation vary with both the CuOx species and the CeO2 morphology. These results comprehensively elucidate the CuOx-CeO2 interactions and exemplify their morphology-dependence.展开更多
CO methanation on Ni/CeO2 has recently received increasing attention.However,the low-temperature activity and carbon resistance of Ni/CeO2 still need to be improved.In this study,plasma decomposition of nickel nitrate...CO methanation on Ni/CeO2 has recently received increasing attention.However,the low-temperature activity and carbon resistance of Ni/CeO2 still need to be improved.In this study,plasma decomposition of nickel nitrate was performed at ca.150℃ and atmospheric pressure.This was followed by hydrogen reduction at 500 ℃ in the absence of plasma,and a highly dispersed Ni/CeO2 catalyst was obtained with improved CO adsorption and enhanced metal-support interaction.The plasma-decomposed catalyst showed significantly improved low-temperature activity with high methane selectivity(up to 100%)and enhanced carbon resistance for CO methanation.For example,at 250 ℃,the plasma-decomposed catalyst showed a CO conversion of 96.8% with high methane selectivity(almost 100%),whereas the CO conversion was only 14.7% for a thermally decomposed catalyst.展开更多
Praseodymium (Pr) was impregnated to CeO2-ZrO2 solid solution by an impregnation method. The as-obtained Pr modi- fied CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts. The structure and reducibilit...Praseodymium (Pr) was impregnated to CeO2-ZrO2 solid solution by an impregnation method. The as-obtained Pr modi- fied CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts. The structure and reducibility of the fresh and hydrother- really aged catalysts were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), CO chemi- sorption and H2 temperature-programmed reduction (H2-TPR). The oxygen storage capacity (OSC) was evaluated with CO serving as probe gas. Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated. The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones. The scheme of structural evolutions of the catalysts with and without Pr was also established. Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing, which inhibited the sintering, and increased the amount of oxygen vacancies in CeO2-ZrO2 support. Furthermore, those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.展开更多
摘要Direct synthesis of dimethyl carbonate(DMC)from CO2 is critical for achieving carbon neutrality,yet the sluggish formation and conversion of the key*CH₃OCOO intermediate-due to the difficulty of C-O coupling-limit high DMC yields.Herein,we developed a boric acid-assisted recrystallization strategy to fabricate grain-boundary-rich CeO2 hollow nanospheres,which serve as an efficient catalyst for CO2 to DMC synthesis.The introduction of grain-boundary(GBs)induced the electron redistribution,which led a decrease in the electron density of bulk Ce ions and created a localized electron-rich region at homogeneous interface.This unique electronic landscape promoted reactive methoxy formation and stronger CO2 adsorption,thereby enabling more efficient coupling of*CH3O and*CO2 to form the*CH3OCOO.Concurrently,the enhanced CO2 adsorption facilitated the dissociation of*CH3OCOO and subsequent DMC formation.As a result,the 4%BCeO2-GBs achieved an advantageous DMC yield of 19.8 mmol/g.In the assistance of dehydrating agent,the catalyst delivered a remarkable 264.2 mmol/g DMC yield and 7.12%methanol conversion,which was 32 times higher than commercial CeO2.This study elucidated the intrinsic mechanisms governing*CH3OCOO intermediate behavior and offers valuable guidance for CO2 converting into high-value organic chemicals.
基金Project supported by the National Natural Science Foundation of China(51761032,51901105,51871125)。
摘要In this paper,the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10-x wt%CeO2(x=0,4,8)alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics and thermodynamics performances of the alloys were studied in detail.The results show that the Mg85Cu5Ni10 alloys with CeO2 additive have faster hydrogenation/dehydrogenation kinetics and better thermodynamic properties.The dehydrogenation activation energy is reduced to 81.211 kJ/mol from 119.142 by adding 8 wt%CeO2.CeO2 contributes to producing structural defects,nanocrystallines,grain boundaries,partial amorphous,lattice dislocations and cracks which are favorable to provide more hydrogen diffusion channels during hydriding/dehydriding process.Meanwhile,CeO2 additive weakens the bond energy of Mg-H.These micro structural changes caused by CeO2 additive improve the hydrogen storage performance of Mg85Cu5Ni10 markedly.
基金Project supported by the National Natural Science Foundation (21076047)the Natural Science Foundation of Zhongkai University of Agriculture and Engineering (G3100026)
摘要High surface area CeO2 was prepared by the surfactant-assisted route and was employed as catalyst support. The 0-3 at.% Cu doped Cu-Ni/CeO2 catalysts with 10 wt.% and 15 wt.% of total metal loading were prepared by an impregnation-coprecipitation method. The influence of Cu atomic content on the catalytic performance was investigated on the steam reforming of ethanol (SRE) for H2 production and the catalysts were characterized by N2 adsorption, inductively coupled plasma (ICP), X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed rerduction (TPR) and H2-pulse chemisorption techniques. The activity and products distribution behaviors of the catalysts were significantly affected by the doped Cu molar content based on the promotion effect on the dispersion of NiO particles and the interactions between Cu-Ni metal and CeO2 support. Significant increase in the ethanol conversion and hydrogen selectivity were obtained when moderate Cu metal was doped into the Ni/CeO2 catalyst. Over both of the 10Ni98.5Cu1.5/CeO2 and 15Ni98.5Cu1.5/CeO2 catalysts, more than 80% of ethanol conversion and 60% of H2 selectivity were obtained in the ethanol steam-reforming when the reaction temperature was above 450 ℃.
摘要The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that either CuO or CeO 2 ac tivity is quite low for CO oxidation. However, when CuO and CeO 2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu 2+ and Cu+) on the CeO 2 surfa ce, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu 2+ or Cu+. Rietveld analysis s hows that some CuO, which has smaller ion radius than Ce 4+, enters the Ce O 2 lattice after CuO and CeO 2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value i s a maximum (2.86×10 -3), resulting in high surface energy and the best ac tivity for CO oxidation.
摘要The selective catalytic reduction(SCR) of NOx using MnOx and CeO2 supported on viscose-based active carbon fibers(ACF) at 120 ℃~270 ℃ relatively lower than the temperature when using V2O5/TiO2-anatase catalyst was studied.As a result,CeO2/ACF shows a better catalysis than MNOx/ACF,which is not affected by the reaction temperature. NO conversion of 85% is reached with the 10%-CeO2/ACF catalyst at the whole temperature window.Furthermore,a series of MnOx-CeO2/ACF composite catalysts were studied.The results show that the loading method of catalyst affects its activity.
摘要Elucidation of the CuOx-CeO2 interactions is of great interest and importance in understanding complex CuOx-CeO2 interfacial catalysis in various reactions. In the present work, we have investigated structures and catalytic activity in CO oxidation of CuOx species on CeO2 rods, cubes and polyhedra predominantly exposing {110}+{100}, {100} and {111} facets by the incipient wetness impregnation method with the lowest Cu loading of 0.025%. The structural evolution of CuOx species was found to depend on both the Cu loading and the CeO2 morphology. As the Cu loading increases, CuOx species are deposited preferentially on the surface defect of CeO2 and then aggregate and grow, accompanied by the formation of isolated Cu ions, CuOx clusters strongly/weakly interacting with the CeO2, highly dispersed Cu O nanoparticles, and large Cu O nanoparticles. The isolated Cu^+ species and CuOx clusters weakly interacting with the CeO2 were observed mainly on the O-terminated CeO2{100} facets. Meanwhile, more Cu(I) species are stabilized during CO reduction processes in CuOx/c-CeO2 catalysts than in CuOx-CeO2 and CuOx/p-CeO2 catalysts. The catalytic activities of various CuOx/CeO2 catalysts in CO oxidation vary with both the CuOx species and the CeO2 morphology. These results comprehensively elucidate the CuOx-CeO2 interactions and exemplify their morphology-dependence.
基金This work was supported by the National Natural Science Foundation of China(21476157,21536008 and 21621004)the National Key R&D Program of China(2016YFB0600902)~~
摘要CO methanation on Ni/CeO2 has recently received increasing attention.However,the low-temperature activity and carbon resistance of Ni/CeO2 still need to be improved.In this study,plasma decomposition of nickel nitrate was performed at ca.150℃ and atmospheric pressure.This was followed by hydrogen reduction at 500 ℃ in the absence of plasma,and a highly dispersed Ni/CeO2 catalyst was obtained with improved CO adsorption and enhanced metal-support interaction.The plasma-decomposed catalyst showed significantly improved low-temperature activity with high methane selectivity(up to 100%)and enhanced carbon resistance for CO methanation.For example,at 250 ℃,the plasma-decomposed catalyst showed a CO conversion of 96.8% with high methane selectivity(almost 100%),whereas the CO conversion was only 14.7% for a thermally decomposed catalyst.
基金supported by National Natural Science Foundation of China(51202116)Ministry of Science and Technology,China(2010CB732304,2013AA065302)
摘要Praseodymium (Pr) was impregnated to CeO2-ZrO2 solid solution by an impregnation method. The as-obtained Pr modi- fied CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts. The structure and reducibility of the fresh and hydrother- really aged catalysts were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), CO chemi- sorption and H2 temperature-programmed reduction (H2-TPR). The oxygen storage capacity (OSC) was evaluated with CO serving as probe gas. Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated. The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones. The scheme of structural evolutions of the catalysts with and without Pr was also established. Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing, which inhibited the sintering, and increased the amount of oxygen vacancies in CeO2-ZrO2 support. Furthermore, those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.