Catalytic performance of a Pt-Rh/CeO_2-ZrO_2-La_2O_3-Nd_2O_3 three-way compress nature gas catalyst prepared by a modified double-solvent method

A Pt-Rh three-way catalyst(M-DS) supported on CeO_2-ZrO_2-La_2O_3-Nd_2O_3 and its analogous supported catalyst(DS) were developed via a modified double-solvent method and conventional double-solvent method, respectively. The as-prepared catalysts were characterized by N_2 adsorption-desorption, X-ray diffraction(XRD), CO-chemisorption, X-ray photoelectron spectroscopy(XPS) and hydrogen temperature-programmed reduction(H_2-TPR). The preformed Pt nanoparticles generated using ethanol as a reducing agent on M-DS presented enhanced Pt dispersion regardless of aging treatment as confirmed by XRD and CO-chemisorption measurements. The textural properties and reduction ability of M-DS were maintained to a large extent after aging treatment. This result was consistent with those of the N_2 adsorption-desorption and H_2-TPR, respectively. Meanwhile, the XPS analysis demonstrated that higher Pt~0 species and larger Ce~(3+) concentration could be obtained for M-DS. In the conversion of a simulated compressed natural gas(CNG) vehicle exhaust, both fresh and aged M-DS showed a significant enhancement in the activity and N_2-selectivity. Particularly, the complete conversion temperature(T_(90)) of CH_4 over the aged M-DS catalyst was 65 oC lower than that over the aged catalyst by conventional double-solvent method.     

One-step synthesis and structural quantitative analysis of La_(2/3)Sr_(1/3)MnO_3/La_(1.4)Sr_(1.6)Mn_2O_7 composites

La2/3Sr1/3MnO3/La1.4Sr1.6Mn2O7 composites with arbitrary weight percentage were prepared using a one-step solid-state reaction method. The experimental results demonstrated that addition of K2CO3 during preparation favored the formation of the composites even though the K+ ions were volatilized under the high temperatures of sintering. Full quantitative analysis with the Rietveld method showed that the content of La1.4Sr1.6Mn2O7 phase decreased and the fraction of the La2/3Sr1/3MnO3 phase increased as the a...     

高纯氧化镧中痕量稀土杂质的ICP-MS测定

本文研究了用等离子质谱法测定高纯氧化镧中１４个稀土杂质；确定了仪器最佳工作条件；选择了测定同位素；用标准加入法校正基体的抑制效应，从而改善了测量精度；做了加料回收和试样分析。本法具有灵敏度高、流程简单、耗样少的优点，可用于５Ｎ～６Ｎ纯度的氧化镧分析。     

Preparation and Structure of Mg2-xRExNi （RE = La, Ce, Pr, Nd, Y） Ternary Alloys

A series of Mg2-xNdxNi (x =0.05, 0.1, 0.2, 0.3) alloys and Mg1.95RE0.05Ni (RE= La, Ce, Pr, Nd, Y)ternary alloys were prepared by ball milling of mixted powder of Mg, Ni, RE and sintering under the protection of argon. XRD analysis shows that Mg2-xNdxNi (x = 0.05, 0.1 ) and Mg1.95RE0.05Ni consist of single phase with the same crystal structure as Mg2Ni. While three-phase alloys including Mg2Ni, NdNi and NdMgNi4 were formed in Mg1.8Nd0.2Ni and Mg1.7Nd0.3Ni alloys respectively. The lattice constants of Mg2Ni in those ternary alloys were calculated. The decomposition of Mg2Ni occurs in the milling process of Mg2Ni and Mg1.95RE0.05Ni alloys respectively. For the latter, another earlier reaction occurs in milling process, which means that atoms of RE are separated from crystal structure of Mg2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.     

Phase equilibria in low basicity region of CaO-SiO_2-Nb_2O_5-(5 wt%,10 wt%,15 wt%) La_2O_3 system

The lack of thermodynamic information,such as primary phase fields and liquidus temperatures,in the CaO-SiO₂-Nb₂O₅-La₂O₃ quaternary system phase diagram has restricted the comprehensive utilization of the niobium(Nb) and rare earth(RE) resources.In this work,the phase equilibria in low basicity region(w(CaO)/w(SiO₂)<1) of CaO-SiO₂-Nb₂O₅-(0-15 wt%)La₂O₃ system at 1373-1873 K...     

Structure and Transport Properties in CMR Materials of La（1-x）2/3Ca1/3MnO3 with Rare Earth Vacancies

Samples of manganese oxides La（1-x）2/3Ca1/3MnO3（x 〈 0.10） with Lavacancy were prepared by standard solid-state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma ）, analyzed by XRD and with Rietveld Refinement. The effect of different La-site vacancies concentration on electronic transport of La（1-x）2/3Ca1/3MnO3 was investigated. The insulator-metal transition temperature （about 267 K） nearly remains unchanged with the increase of vacancy concentration, which indicates that small La-vacancy does not destroy the double exchange interaction. But the electronic resistance increases and MR value decreases with La-vacancy content x 〉 0.04. The maximum of the MR value （8 T） is about 220% at transition temperature （TMI）.     

The effect of hydrogen peroxide on properties of Ce_(0.35)Zr_(0.55)La_(0.055)Pr_(0.045)O_2 oxides and the catalytic performance used on Pd supported three-way catalyst

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.     

Calculation of RECl_3-CaCl_2-LiCl Phase Diagrams(RE=La, Ce, Pr, Nd)

ＣａｌｃｕｌａｔｉｏｎｏｆＲＥＣｌ_３－ＣａＣｌ_２－ＬｉＣｌＰｈａｓｅＤｉａｇｒａｍｓ（ＲＥ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ）ＱｉａｏＺｈｉ－Ｙｕ（乔芝郁）；ＸｉｎｇＸｉａｎ－Ｒａｎ（邢献然），ＤｕａｎＳｈｕ－Ｚｈｅｎ（段淑贞）（ＤｅｐａｒｔｍｅｎｔｏｆＰｈ...     

Study on Electrolytes (CeO_2 )_( 0.7-x) (MO) _x (La_2O_3)_(0.3)(M=Mg,Ca, Sr)

ＳｔｕｄｙｏｎＥｌｅｃｔｒｏｌｙｔｅｓ（ＣｅＯ_２）_（０．７－ｘ）（ＭＯ）_ｘ（Ｌａ_２Ｏ_３）_（０．３）（Ｍ＝Ｍｇ，Ｃａ，Ｓｒ）ＣｈｅｎＧｕａｎｇｙｕ（陈广玉），ＬｉｕＪｉａｎｇ（刘江），ＨｅＬａｎｙｉｎｇ（何岚鹰），ＳｕＷｅｎｈｕｉ（苏文辉），Ｈｕ...     

Thermochemical Properties of the Complexes RE(HSal)3·2H2O(RE = La, Ce, Pr, Nd, Sm)

Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(HSal)₃·2H₂O(RE = La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE³⁺ ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, Δ_cU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, Δ_cH_m^θ, and standard molar enthalpies of formation, Δ_fH_m^θ, were calculated.     

Thermochemical Properties of the Complexes RE(HSal)3·2H2O (RE=La, Ce, Pr, Nd, Sm)

Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(Hsal)3·2H2O(RE=La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE3 ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, ΔcU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated.     

Catalytic combustion of toluene on Pt/Al2O3 and Pd/Al2O3 catalysts with CeO2,CeO2-Y2O3 and La2O3 as coatings

CeO₂,La₂O₃,and CeO₂-Y₂O₃ oxides were coated on the surface of spherical granular AI₂O₃(3-5 mm)through impregnation method,and proved as better supports of Pd and Pt catalysts.The influences of rare earth metal doping on the adsorption rates of Pd and Pt ions,as well as the catalytic performance,were investigated.Results show that the H₂PtCl₆·6H₂O adsorption rates of the Al     

Study of cerium ion in (Y0.95La0.05)2O3:Ce

(Y0.95La0.05)2O3: Ce3+ nano-powder was synthesized by co-precipitation method and sintered at 800 and 900 oC. All the samples were cubic phase characterized by X-ray diffraction (XRD) analysis. The samples sintered at the lower temperature exhibited luminescence. According to the distinguishable structure of Ce 3d peaks and the shift of O 1s lines in the X-ray photoelectron spectroscopy (XPS), luminescence was further confirmed to originate from Ce3+ ions. Effects of introducing La3+ into Y2O3 were discusse...     

Study on Rare Earth Electrolyte of Ce_(0.9)RE_(0.1)O_(2-δ) (RE=Pr, Nd, Sm, Gd, Dy)

Thesolidelectrolyteisakeycomponentofsolidoxidefuelcell (SOFC) .Dopedceriaisoneofpromis inghigh conductingsolidelectrolyteinSOFC[1,2 ] .Butitiswell knownthatitisdifficulttosinterdopedceriabysolidstatereactioninair .TheCe0 .9RE0 .1O2 -δelectrolytematerialswerepreparedbythesol gelmethod .Thesinteringtemperatureofthesamplescandecreasetoabout 4 0 0K .Theionicconductivityandlinearthermalexpansionpropertiesofsol gelpreparedCe0 .9RE0 .1O2 -δinawidetemperaturerangewerein vestigated .Thepowder…     

Enhancing (de)hydrogenation kinetics properties of the Mg/MgH_2 system by adding ANi_5(A=Ce,Nd,Pr,Sm,and Y) alloys via ball milling

Magnesium(Mg)-based alloys have already been widely studied as the hydrogen storage materials because of their high reversible hydrogen storage capacity,low cost,light weight,etc.However,the poor de/hydrogenation kinetic properties dramatically hinder the practical applications.In this work,the MgH_2-ANi_5(A=Ce,Nd,Pr,Sm,and Y) composites were prepared by a high-energy ball milling method.which can effectively refine the particle size thus improving the kinetic properties.Experimental results reveal that the MgH_2-ANi_5 composites mainly consist of Mg_2 NiH_4,MgH_2 and rare earth(RE) hydride,which will be dehydrogenated to form Mg_2 Ni,Mg and stable RE hydride reversibly.Accordingly,the asmilled MgH_2-ANi_5(A=Ce,Nd,Pr,Sm,and Y) composites with various A-elements can respectively contribute to a reversible hydrogen storage capacity of 6.16 wt%,5.7 wt%,6.21 wt%,6.38 wt%,and 6.5 wt%at a temperature of 300℃,and show much better kinetic properties in comparison to the pure MgH_2 without any additive.In-situ formed Mg_2 Ni and stable RE hydride(such as CeH_(2.73) and YH_2) might act as effective catalysts to significantly improve the hydrogen storage properties of MgH_2.The present work provides a guideline on improving the kinetic properties of the Mg-based hydrogen storage alloys.     

Effect of Yttrium on Microstructures and Preparation and Structure of Mg2-xRExNi (RE=La,Ce,Pr,Nd,Y) Ternary Alloys

A series of Mg2-xNdxNi(x=0.05,0.1,0.2,0.3)alloys and Mg1.95RE0.05Ni(RE= La,Ce,Pr,Nd,Y)ternary alloys were prepared by ball milling of mixted powder of Mg,Ni,RE and sintering under the protection of argon.XRD analysis shows that Mg2-xNdxNi(x=0.05,0.1)and Mg1.95RE0.05Ni consist of single phase with the same crystal structure as Mg2Ni.While three-phase alloys including Mg2Ni,NdNi and NdMgNi4 were formed in Mg1.8Nd0.2Ni and Mg1.7Nd0.3Ni alloys respectively.The lattice constants of Mg2Ni in those ternary alloys were calculated.The decomposition of Mg2Ni occurs in the milling process of Mg2Ni and Mg1.95RE0.05 Ni alloys respectively.For the latter,another earlier reaction occurs in milling process,which means that atoms of RE are separated from crystal structure of Mg2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.     

[Y(dbm)_3(H_2O)]:Synthesis,thermal behavior and spin-coating precursor for Y_2O_3 layer formation

The synthesis,structure and thermal behavior of [Y(dbm)_3(H_2 O)](3)(dbm = 1,3-diphenyl-1,3-propandionate) and its use as a spin-coating precursor for Y_2 O_3 deposition is reported. Complex 3 was prepared by the reaction of [Y(NO_3)_3·6 H_2 O](1) with 3 equiv of Hdbm(2) in presence of NaOH. The molecular structure of 3 in the solid-state was determined by single X-ray crystal diffraction. Both C_1 symmetric crystallographically independent species of 3 possess a YO7 coordination setup with minor deviation from an ideal capped octahedron coordination geometry(∧ enantiomer). Complex 3 forms a1 D chain, due to intermolecular hydrogen bonds between the coordinated H_2 O molecule and the 0 atom of the dbm ligand, respectively. The thermal decomposition behavior of 3 was investigated by thermogravimetric studies in the temperature range of 40-800 ℃ and 40-1300 ℃ under an oxygen and argon atmosphere, respectively. Powder X-ray diffraction(PXRD) measurements of the residues confirmed the formation of Y_2 O_3. Complex 3 was applied as a spin-coating precursor for yttrium oxide film formation on either Si wafers with a continuous 100 nm thick SiO_2 film, or with a native oxide layer.The as-deposited Y_2 O_3 layers are smooth, conformal, dense and transparent and are of a thickness of 27 and 30 nm, respectively.     

Flotation performance and adsorption mechanism of styrene phosphonic acid as a collector to synthetic(Ce,La)_2O_3

The flotation performances of styrene phosphonic acid(SPA) to synthetic(Ce,La)_2O_3(REO), calcium fluorite(CaF_2) and fluorapatite(Ca_5F(PO_4)_3) were investigated by flotation tests, flotation of synthetic mixed mineral, the surface adsorption capacity and the polarizing microscopy to solve the flotation separation problem of rare earth oxides from roasted concentrate. The flotation test results indicated that compared with CaF_2 and Ca_5F(PO_4)_3, SPA exhibited superior collecting performance to direct flotation recovery of REO and floated out above 90% REO at pH 3–6. However, the collecting ability of SPA to CaF_2 and Ca_5F(PO_4)_3 was extremely weak and the highest recovery was only 20% at pH 2–11. The flotation of synthetic mixed mineral showed that SPA was a good collector reagent for flotation of synthetic REO at pH 5, so REO, CaF_2 and Ca_5F(PO_4)_3 could be separated from roasted concentrate by using SPA as a collector. The surface adsorption capacity tests and polarizing microscopy results confirmed that SPA was adsorbed on REO surface, while CaF_2 and Ca_5F(PO_4)_3 were not. The adsorption mechanism of SPA to synthetic REO was studied by solution chemistry analysis of collector, the ζ-potential tests, infrared spectroscopy and X-ray photoelectron spectroscopy(XPS) analyses. The results indicated that SPA was physically adsorbed onto REO surface, which exhibited excellent flotation selectivity to REO against CaF_2 and Ca_5F(PO_4)_3.