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| 1 | Synthesis of hexaaluminate catalysts for methane combustion by reverse microemulsion medium显示文摘The aim of this study is to synthesize the catalysts of Fe-and Mn-substituted hexaaluminate by reverse microemulsion medium for methane catalytic combustion application.Pseudo-ternary phase diagrams in quaternary microemulsion systems of cetyltrimethylammonium bromide(CTAB),n-butanol,n-octane,and water [or Al(NO3)3 solution] were presented.The effects of the alcohol chain length,ratio of sur-factant to cosurfactant,and salt concentration on the formation and stability of microemulsion systems were studied.The phase behavior of microemulsion systems was confirmed through the varying of the conductivity with the water content.The performance and structure of the catalysts,La(Mnx/Fex)Al12-x-O19-δ synthesized with the optimal parameter in the phase diagrams of microemulsions systems were characterized by BET,TG-DTA,and XRD.The micro fix-bed reactor was used to measure the catalytic activities of catalysts to methane combustion.The results showed that this synthesis method could yield non-agglomerated and highly dispersed precursors that would undergo crystallization at the lower temperature of 950℃.When temperature was raised up to 1050℃,the complete crystalline La-hexaaluminate was shaped.The hexaaluminate substituted with Fe had high-catalytic activity and stability at high temperature,while the Mn-substituted had higher catalytic activity at lower temperature.When the cooperation of Fe and Mn occurred,i.e.,LaFeMnAl10O19-δ exhibited a high surface area and catalytic activity to CH4 combustion,the CH4 light-off temperature was only 475℃ and the complete combustion temperature was 660℃.This was attributed to the synergistic effect between Fe and Mn. | BAI ShouLi WANG LiangShi SHI BingJie YANG PengCheng CUI MeiSheng LONG ZhiQi LI DianQing CHEN AiFan | 2009 | Science China Chemistry2009，52，1： | 6 |
| 2 | Effect of grain size on thermal stability and oxygen storage capacity of Ce_(0.17)Zr_(0.73)La_(0.02)Nd_(0.04)Y_(0.04)O_2 solid solutions显示文摘Nanostructured CeO_2-ZrO_2 materials are an irreplaceable constituent in catalytic systems for automobile exhaust purification due to their unique oxygen storage capacity(OSC). However, traditional CeO_2-ZrO_2 materials are easy to sinter at high temperature, which causes a sharp decrease of OSC. In this paper,La^(3+) , Nd^(3+) and Y^(3+) are chosen as dopants for CeO_2-ZrO_2 to improve anti-sintering and OSC properties.The Ce_(0.17) Zr_(0.73) La_(0.02) Nd_(0.04) Y_(0.04) O_2 powders(CZLNY) were prepared by co-precipitation method. The effects of grain sizes with different mixed chlorinated solution concentrations on performances were investigated. X-ray diffraction(XRD) and transmission electron micrograph(TEM) were performed to calculate the grain sizes of CZLNY. The specific surfaces, OSC and redox properties were investigated by N_2 adsorption/desorption and temperature programmed reduction(H2-TPR). The results show that introducing La^(3+) , Nd^(3+) and Y^(3+) into CeO_2-ZrO_2 lattice can improve the stability of phase structure and anti-sintering ability. Moreover, low concentration of mixed chlorinated solution remarkably improves structural and textural properties of CZLNY. Relatively large fresh grain exhibits superior thermal stability and OSC under the condition of being calcined at 800℃ for 3 h. The specific surface and OSC are42.37 m^2/g and 333.13 mmol/g after calcining at 1000℃ for 10 h, respectively. This is owing to the low sintered driving force of large grain and long-range migration energy of large pores during the sintering process, which are beneficial to the stability of structure in CZLNY materials. | Yuhui Zhang Meisheng Cui Yongke Hou Xiaowei Huang Yongqi Zhang Qiannan Xue | 2019 | Journal of Rare Earths2019，37，2： | 3 |
| 3 | The effect of hydrogen peroxide on properties of Ce0.35Zr0.55La0.055Pr0.045O2 oxides and the catalytic performance usedon Pd supported three-way catalyst显示文摘In this study,two series of cerium zirconium mixed oxides Ce_(0.35)Zr_(0.55)La_(0.055)Pr_(0.045)O_2 were prepared under traditional co-precipitation and oxidation co-precipitation methods respectively. The physicochemical properties of the samples were compared under these two methods and assessed by XRD,Raman,BET,TEM,H_2 TPR,OSC,XPS and catalysts measurements. The formation of homogeneity phase structure can be facilitated by changing the precipitating properties of Ce3+ under oxidation coprecipitation method, which is helpful to enhance the homogeneity of Ce and Zr at atomic level.What's more, it is conducive to remove impurities Na^+ and Cl^-by oxidation co-precipitation with hydrogen peroxide. The catalysts activities are related to both the redox properties and the textural properties of mixed oxides. The Pd-only TWCs supported on the CZLP-H-F exhibits better catalytic performance and thermal stability with wider air/fuel ratio operation window, lower light-off and full conversion temperatures of C_3 H_8 and NO. The homogeneity of phase structure for cerium zirconium mixed oxide can be predicted and deduced from detecting the atomic distribution uniformity of its precursor. So this work not only provides insights into the mechanisms for phase segregation of cerium zirconium mixed oxide, but also provides a guidance to improve homogeneity of cerium zirconium mixed oxide by adding additives. | Qi wang Meisheng Cui Xiaowei Huang Yongke Hou Mei Yue Qiang Zhong YongqiZhang | 2017 | Journal of Rare Earths2017，35，11： | 3 |
| 4 | SO_(4)^(2-)-modified La,Y-doped ceria-zirconia with high oxygen storage capacity and its application in Pd-only three-way catalysts显示文摘As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials,many strategies have been utilized to improve the oxygen storage capacity.Here in this study,we report a simple and facile approach to prepare a SO_(4)^(2-)-modified La,Y-doped ceria-zirconia material(SO/CZLY-f)with high oxygen storage capacity.Due to the additional redox process between SO_(4)^(2-)and S^(2-),oxygen storage capacity of SO/CZLY-f(745.3μmol O_(2)/g)is about 1.6 times higher than that of La,Ydoped ceria-zirconia material without SO_(4)^(2-)modification.Moreover,the catalytic activities and stability of the corresponding Pd-only three-way catalyst were measured.Compared to that of Pd@CZLY-f,the operation window of CO,full conversion temperature of HC and NO over Pd@SO/CZLY-f are obviously widened and lowered,respectively.After aging treatment at 1100℃for 4 h,the superiority of aged Pdloading composite is still maintained. | Hao Wang Yongke Hou Yongqi Zhang Meisheng Cui Fang Chen Xiaowei Huang Juanyu Yang Zongyu Feng | 2022 | Journal of Rare Earths2022，40，5： | 2 |
| 5 | Effects of precursor moisture and inert N_2 atmosphere calcinations on structure and properties of alumina modified CeZrLaNd mixed oxides显示文摘CeO_2-ZrO_2 mixed oxides are widely used in the three-way catalysts due to their unique reversible oxygen storage and release capacity. Large surface area, high oxygen storage capacity and good thermal stability of cerium zirconium mixed oxides are the key properties for the automotive catalysts so as to meet the strict emission regulations. In this work, alumina modified CeZrLaNd mixed oxides were prepared by a co-precipitation method. The effects of moisture in precursor and inert N2 atmosphere during calcinations on the structure and properties were investigated by Brunauer-Emmett-Teller(BET) surface area measurements, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), hydrogen temperature-programmed reduction(H_2-TPR), oxygen storage capacity(OSC), Raman spectroscopy, and X-ray photoelectron spectroscopy(XPS). The results show that the moisture in precursor during calcinations increases the crystal grain size of the cerium zirconium mixed oxides, improving the thermal stability. And the aged surface area of sample after being calcined at1000 ℃ for 4 h reaches 68.8 m^2/g(5.7% increase compared with the common sample). The inert N2 atmosphere endows a great pore-enlarging effect, which leads to high fresh surface area of 148.9 m2/g(13.5% increase compared with the common sample) and big pore volume of 0.5705 mL/g. The redox and oxygen storage capacity are also improved by inert N2 atmosphere with high OSC value of 241.06μmolO_2/g(41.3% increase compared with the common calcination), due to the abundant formation of the crystal defects and oxygen vacancies. | Meisheng Cui Zhizhe Zhai Hao Wang Yongke Hou Yongqi Zhang Xiaowei Huang | 2019 | Journal of Rare Earths2019，37，6： | 2 |
| 6 | Transforming Growth Factor (TGF)-β-Induced MicroRNA-216a Promotes Acute Pancreatitis Via Akt and TGF-β Pathway in Mice显示文摘 | Jian Zhang Xianfeng Ning Wei Cui Meisheng Bi Dianliang Zhang Jianli Zhang | 2015 | Digestive Diseases and Sciences2015，，1： | 1 |
| 7 | Effects of ammonia concentration in hydrothermal treatment on structure and redox properties of cerium zirconium solid solution显示文摘Cerium zirconium solid solution is a key washcoat material for automotive three-way catalysts(TWCs).However,improving the redox ability and high temperature thermal stability of cerium zirconium solid solution is still a challenge.In this paper,the cerium zirconium solid solution was prepared by a coprecipitation-hydrothermal method,and the effects of the ammonia concentration on their structures and redox properties were investigated.The results show that when the ammonia concentration is 0.8 mol/L,the aged sample(1100℃/10 h)of cerium zirconium solid solution has the highest specific surface area of 23.01 m^(2)/g.Additionally,the increase of ammonia concentration improves the uniformity of phase compositions and increases the oxygen vacancies.When the ammonia concentration reaches 0.4 mol/L,the cerium zirconium solid solution exhibits the best redox activity,with the lowest reduction temperature of 565℃.Therefore,increasing ammonia concentration in the hydrothermal treatment is beneficial to the thermal stability and redox performance of cerium zirconium solid solution. | Yunhan Zhang Meisheng Cui Hao Wang Zheng Zhao Liangshi Wang Yongke Hou | 2021 | Journal of Rare Earths2021，39，4： | 1 |
| 8 | Synthesis of La-hexaaluminate catalyst for methane combustion by a reverse SDS microemulsion显示文摘La-hexaaluminate catalyst for methane catalytic combustion was synthesized by a reverse microemulsion.Pseudo-ternary phase diagrams of a quaternary microemulsion system of sodium dodecyl sulfate(SDS),n-pentanol,n-octane,and water(or Al(NO3)3 solution) were presented.The effects of alcohol chain length,cosurfactant-to-surfactant ratio,and salt concentration on the formation and stability of the microemulsion system were studied.The phenomenon that the conductivity changed with water supported the phase behavior of the microemulsion system.La(Mnx/Fex)Al12-xO19-δ catalysts,applied in methane combustion and with high-temperature stability,were synthesized within the stable areas of the phase diagram of the microemulsion system,when SDS was chosen as surfactant,n-pentanol as cosurfactant,and n-octane as oil phase.The physical properties and structure of the catalysts were characterized by BET method,transmission electron microscope(TEM),and X-ray diffraction(XRD).A micro-fixed-bed reactor was used to measure the catalytic activity of hexaaluminates in methane combustion.The results show that the reverse microemulsions can be used to produce discrete La-hexaaluminate nanoparticles that display excellent methane combustion activity owing to their high surface area and high thermal stability. | YU Ying WANG Liangshi CUI Meisheng SHI Yongxi LUO Ruixian CHEN Aifan | 2011 | Rare Metals2011，30，4： | 0 |
| 9 | Tailoring thermal stability of ceria-zirconia mixed oxide by doping of rare earth elements:From theory to experiment显示文摘Ceria-zirconia mixed oxides(CZMO)are widely used in many important catalysis fields.However,pure CZMO is known to have poor thermal stability.In this paper,a strategy was proposed to design Ce_(0.475)Zr_(0.475)M_(0.05)O_(2)(M=La,Y,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Er,Lu,and,Yb)oxide surface with high thermal stability by using first-principles molecular dynamics(FPMD)simulation and experiment method.Through the structure stability analysis at different temperatures,the surface energyγas a function of R_(ion)/D_(ave)is identified as a quantitative structure descriptor for analyzing the doping effect of rare earth(RE)elements on the thermal stability of Ce_(0.475)Zr_(0.475)M_(0.05)O_(2).By doping the suitable RE,γcan be adjusted to the optimal range to enhance the thermal stability of Ce_(0.475)Zr_(0.475)M_(0.05)O_(2).With this strategy,it can be predicted that the sequence of thermal stability improvement is Y>La>Gd>Nd>Pr>Pm>Sm>Eu>Tb>Er>Yb>Lu,which was further verified by our experiment results.After thermal treatment at 1100℃for 10 h,the specific surface area(SSA)of aged Y-CZ and La-CZ samples can reach 21.34 and 19.51 m~2/g,which is 63.02%and 49.04%higher than the CZMO sample without doping because the surface doping of Y and La is in favor of inhibiting the surface atoms thermal displacement.In a word,the strategy proposed in this work can be expected to provide a viable way for designing the highly efficient CZMO materials in extensive applications and promoting the usages of the high-abundance rare-earth elements Y and La. | Zheng Zhao Xiaowei Huang Yongqi Zhang Juanyu Yang Meisheng Cui Yongke Hou Zongyu Feng | 2022 | Journal of Rare Earths2022，40，8： | 0 |
| 10 | Catalytic activity of Mn-substituted barium hexaaluminates for methane combustion显示文摘The catalysts of hexaaluminate (BaMnxAl12-xO19-δ , x = 1.0, 2.0, 3.0, 4.0) to be used in methane combustion have been successfully synthesized by co-precipitation method and supercritical drying. The crystalline structure and surface area of catalyst were characterized by X-ray diffraction (XRD) and nitrogen adsorption analysis of BET method. BET analysis revealed that the preparing and drying method proposed here provides stable materials with higher surface area of 51.4 m2/g in comparison to materials prepared using conventional ambient drying method for BaMnxAl12?xO19-δ calcined at 1200℃ under oxygen. XRD analysis indicated that formation of a pure single phase BaMnxAl12-xO19-δ occurred up to x = 3 in the case of Mn-substituted barium hexaaluminates. Incorporation of Mn in excess leads to BaAl2O4 phase formation. As far as the valence state of Manganese ions was concerned, the introduced Mn ions were either divalent or trivalent. The first Mn ions were introduced in the matrix essentially as Mn2+ and only for BaMn3Al9O19-δ does manganese exist exclusively as Mn3+; the higher the Mn concen- tration, the higher the proportion of Mn3+. Catalytic activity for methane combustion has been measured for Mn-substituted barium hexaaluminates, light-off temperature was observed in the 512-624℃ range. The highest activity was obtained for catalysts containing 3 Mn ions per unit cell, which reveals that the BaMnxAl12-xO19-δ catalyst was a promising methane combustion catalyst with high activity and good thermal stability. Temperature programmed reduction (TPR) under hydrogen has been used to correlate the catalytic activity with the amount of easily reducible species. | MA LiJing SHI BingJie CUI MeiSheng WANG LinHong LI DianQing CHEN AiFan | 2008 | Science China Chemistry2008，51，3： | 0 |
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