Effect of praseodymium on catalytic graphitization of furan resin carbon

We introduced a new catalyst,rare earth element praseodymium,for the catalytic graphitization of furan resin carbon.The extent of graphitization of the furan resin carbon was examined by X-ray diffraction and Raman spectroscopy.The morphology of furan resin carbon was characterized by scanning electron microscopy.The effects of the praseodymium content and the heat-treatment temperature on the catalytic graphitization of furan resin carbon were also investigated.The results indicated that the praseodymium c...

H_2S Gas Sensitivity of Nanocrystalline Tin Dioxide Doped with Ytterbium (Yb) and Praseodymium (Pr)

<正>The influence of Yb_2O_3 and Pr_2O_3 doping on electrical and gas sensing properties of tin dioxide was studied.A doping content of 0.5wt%～5wt% was investigated by mechanical mixing.The significant improvement on sensitivity and selectivity to 200μg/g hydrogen sulphide gas has been achieved by 3wt% Pr_2O_3 and 5wt% Yb_2O_3 adding.The better response and revovery properties of Pr or Yb doped tin dioxide sensor for 200μg/g hydrogen sulphide gas were found.The maximum sensitivity to H_2S gas is observed at about 120℃.Pr has stronger catalysis than Yb for H_2S reaction on SnO_2 surface.S~ 2-) was oxidized to S~ 6+) on the SnO_2 surface according to XPS.

First-principles study on anatase TiO_2 codoped with nitrogen and praseodymium

The crystal structures, electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory. Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO2 nanocrystal photocatalyst were synthesized by a microwave chemical method. The calculated results show that the photocatalytic activity of TiO2 can be enhanced by N doping or Pr doping, and can be further enhanced by N＋Pr codoping. The band gap change of the codoping TiO2 is more obvious than that of the single ion doping, which results in the red shift of the optical absorption edges. The results are of great significance for the understanding and further development of visible-light response high activity modified TiO2 photocatalyst. The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light. The experimental results show that the codoping TiO2 photocatalytic activity is obviously higher than that of the single ion doping. The experimental results accord with the calculated results.

Synthesis and crystal structure of sodium praseodymium polyphosphate, NaPr(PO_3)_4

Reaction of Na2CO3, Pr6O11 and H3PO4 gave the sodium praseodymium polyphosphate NaPr（PO3）4.The title compound crystallized in the monoclinic P21/n space group with a=0.9965（4） nm, b=1.31437（4） nm, c=0.72271（3） nm, β=90.429（3）°, V=0.9465（4） nm3, Z=4, R=0.0493 and wR=0.1266 for 1855 independent reflections.The structure of NaPr（PO3）4 consisted of PrO8 polyhedra sharing oxygen atoms with phosphoric group PO4 to form a three-dimensional framework, delimiting intersecting tunnels in which the sodium ion was located.Each Na＋ ion was bonded to seven oxygen atoms.

Effect of Lanthanum-praseodymium-cerium Mischmetal on Mechanical Properties and Microstructure of Mg-A1 Alloys

The effects of lanthanum-praseodymium-cerium mischmetal （LPC） on the microstructure and mechanical properties of Mg-Al alloy were investigated. With the addition of LPC, an additional rod-like Al11La3 phase was deposited in the alloy. LPC greatly improves the tensile strength of cast Mg-Al alloys but negatively affects the elongation of cast alloys above 473 K. Cast alloys are strengthened by both precipitation strengthening and dispersion strengthening at ambient temperature. When the temperature exceeds 473 K, only the dispersion operates as a strengthening mechanism.

Molten Salt Electrodeposition of Praseodymium-iron Alloy

The electrochemical behaviour of Pr(III) on iron electrode in molten PrCl3-KCl-NaCl was studied by means of cyclic voltammetry and potential-time curve method. The results show that the reduction of Pr(III) to Pr on the iron electrode proceeds reversibly in one step and forms Pr-Fe alloys. The Pr-Fe alloys are obtained by molten salt electrolysis with molten KCl-NaCl as electrolyte and PrCl3 as raw materials. The composition of electrolytic product is PrFe2 and Pr analysed by X-ray diffraction. Pr recovery efficiency is 90% and the current efficiency is 85%.

Two Praseodymium Coordination Complexes with 1,3-Phenylenediacetate:Structural Diversity Tuned by Auxiliary Ligands

Two new coordination complexes, [Pr（1,3-pda）0.5（nbca）2（H2O）2]（1） and [Pr2（1,3-pda）3（2,2ˊ-bpy）2（H2O）2]（2）（H2pda = 1,3-phenylenediacetic acid, Hnbca = 5-nitro [1,1ˊ-biphenyl]-3-carboxylic acid, 2,2ˊ-bpy = 2,2ˊ-bipyridine）, have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. In 1, the nbca ligands bridge the Pr3＋ ions to form a 1D chain. Moreover, these 1D chains are united together through the 1,3-pda ligands to afford a 2D layer. In contrast, due to a different auxiliary ligand, complex 2 is a 2D layer linked through only bridging deprotonated 1,3-pda. Thermal stabilities and solid fluorescence properties of 1 and 2 were also studied.

Kinetics and the difference for extraction of praseodymium and neodymium from nitrate aqueous solution by [A336][NO_3] using the single drop technique

The kinetics and the difference for Pr(Ⅲ)and Nd(Ⅲ)extraction from nitrate aqueous solution using trialkylmethylammonium nitrate([A336][NO3])as extractant were investigated by the single drop technique.The dependence of the extraction rate of Pr(Ⅲ)and Nd(Ⅲ)on the concentrations of free Pr(Ⅲ)and Nd(Ⅲ)ions,the concentrations of Na NO3 and H+in aqueous solutions,and the concentrations of[A336][NO3]in kerosene solutions were discussed and the corresponding extraction rate equations for Pr(Ⅲ)and Nd(Ⅲ)were obtained.These equations demonstrated that the reaction rate constant of Pr(Ⅲ)with[A336][NO3]was double than that of Nd(Ⅲ).The effect of the addition of diethylenetriaminepentaacetic acid(DTPA)on the difference in the extraction rate of Pr(Ⅲ)and Nd(Ⅲ)by[A336][NO3]was also investigated.It was revealed that the difference in the complex formation rates of Pr(Ⅲ)and Nd(Ⅲ)with DTPA made a significant impact on the difference in the extraction rates of Pr(Ⅲ)and Nd(Ⅲ)with[A336][NO3].The ratio of extraction rates of Pr(Ⅲ)to Nd(Ⅲ)with[A336][NO3]was in proportion to the ratio of complex formation rates of Pr(Ⅲ)to Nd(Ⅲ)with DTPA.The extraction rate difference for Pr(Ⅲ)and Nd(Ⅲ)with[A336][NO3]increased due to a higher complex formation rate constant of DTPA with the free and un-complexed Nd(Ⅲ)ions in the aqueous nitrate solution than that with Pr(Ⅲ)ions.Therefore,the addition of DTPA in the aqueous nitrate solution is an effective method to intensify the separation of Pr(Ⅲ)and Nd(Ⅲ)in kinetics.The study on the extraction mechanism indicated that both the extraction of Pr(Ⅲ)and Nd(Ⅲ)by[A336][NO3]were diffusion controlled,and the reactions obeyed SN2 mechanism.The present work highlights a possible approach to strengthen the kinetic separation of Pr(Ⅲ)and Nd(Ⅲ).

Synergistic extraction of praseodymium with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and 8-Hydroxyquinoline

The synergistic extraction of Pr^3＋ from hydrochloric medium using mixture of 2-ethylhexyl phosphonic acid mono- 2-ethylhexyl ester （P507, HL） and 8-Hydroxyquinoline （HQ） in heptane was investigated. The effect of equilibrium of aqueous acidity on extraction of Pr^3＋ was discussed. The effect of extractant concentraction, different diluents, equilibrium time and acetate ion concentration oil extraction reaction were also studied. With a method of double-logarithmic slope, composition of the extracted species on 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and 8-Hydroxyquinoline was derived. The result shows that the synergistic extraction system not only overcomes emulsification of 8-Hydroxyquinoline, but also shows perfect capacity of synergistic extraction. The largest synergistic enhancement factor can be calculated to be 5.49 at pH 3.6 for Pr^3＋.

Preparation and Electrochemical Application of Praseodymium Modified TiO2-NTs/SnO2-Sb Anode by Cyclic Voltammetry Method

A Pr-doped TiO2-NTs/SnO2-Sb electrode was prepared by a simple method, cyclic voltarnmetry （CV）. The methyl orange （MO）aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO2-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseo- dymium oxide was successfully doped into the SnOz-Sb film by CV method. Due to the doped Pr, the oxygen evo- lution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The Ct/C0（φ） was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.099 3 min-1. The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.

Oxygen Storage Capacity and Adsorptive Property of Praseodymium Oxides

Oxygen storage and adsorptive properties of praseodymium oxides were investigated by pulse experiments and temperature - programmed desportion/reduction (TPD/TPR) experiments. Pr2O3 possesses the similar oxygen storage properties to CeO2, and its dynamic oxygen storage capacity is 14.9 mumol.g(-1). The studies on TPD Of O-2, H2O and CO and TPR show that Pr2O3 provides more active surface oxygen species and at a lower temperature than CeO2. It is suggested that Pr2O3 can be a well candidate as an oxygen storage component in automobile three-way catalyst.

Microwave assisted synthesis,spectroscopy and biochemical aspects of lanthanum(Ⅲ) and praseodymium(Ⅲ) complexes with oxadiazole functionalised dithiocarbazinates

The new lanthanum (Ⅲ) and praseodymium (Ⅲ) complexes of the general formula [Ln(L)3] (Ln=La(Ⅲ) or Pr(Ⅲ); LK=potassium salt of dithiocarbazinates) were prepared by both, conventional thermal and by the use of microwave technology. Elemental analyses, electrical conductance, magnetic moment and electronic, infrared, far-infrared, 1H and 13C NMR spectral studies were used to characterize the complexes. The molecular weights of few complexes were determined by FAB-mass spectra. Nephelauxetic ratio, covalency parameter and bonding parameter for these complexes were also calculated. The probable structures of the complexes were proposed. The antifungal and antibacterial activities of the complexes were evaluated. The activities were correlated with the structures of the compounds.

Study on Separation of Lanthanum from Praseodymium Complexes with IMDA by Gel and Macroporous Anion Exchangers

During our studies on separation of rare earth complexes with aminopolycarboxylic acids on anion-exchangers, it is found that the affinity series of these elements with IMDA (Ln 3+ ∶IMDA=1∶2) for the anion-exchanger Dowex 1 in the acetate and IMDA forms is non-typical: Dy 3+ > Ho 3+ > Gd 3+ >Eu 3+ >Er 3+ >Y 3+ >Sm 3+ >Tm 3+ >Nd 3+ >Pr 3+ >>La 3+ . In the affinity series La 3+ is characterised as the lowest affinity in comparison with other rare earth elements, which indicates possibility of purification of La 3+ from all remaining lanthanides as well as Pr 3+ in the macro-micro systems by the frontal analysis technique. In the investigations strongly basic gel anion-exchangers Dowex 1×8 (type 1) and Dowex 2×8 (type 2) and strongly basic and weakly basic macroporous anion-exchangers Dowex MSA-1 and Dowex MWA 1 were used. Macroporous ion-exchangers have a sponge-like matrix which contains pores larger than molecules in size and the exchange of large ions is faster. The studies indicate that both the gel and macroporous anion-exchangers are useful for purification of La 3+ from Pr 3+ complexes with iminodiacetic acid.

Determination of Composition and Stability Constant of Praseodymium(Pr^(3+))Complex with Tribromoarsenazo(TBA)by Dual-Series Linear Regression Method

A new method,dual-series linear regression method,has been used to study the complexation equilibrium of praseodymium(Pr^(3+))with tribromoarsenazo(TBA)without knowing the accurate concentra- tion of the complexing agent TBA.In 1.2 mol/L HCl solution, Pr^(3+)reacts with TBA and forms 1:3 com- plex,the conditional stability constant(lgβ_3)of the complex determined is 15.47,and its molar absorptivity(ε_3^(630))is 1.48×10~5 L·mol^(-1)·cm^(-1).

Synthesis and Crystal Structure of [(Praseodymium)_2(3,5-Binitro Benzoyloxy)_6 (Dimethyl Sulfoxide)_4] Complex

A novel one-dimensional chain complex [Pr2(bnbo)6(DMSO)4] (bnbo=3,5-binitro benzoyloxy, DMSO= dimethyl sulfoxide) with bridging carboxyl groups was synthesized and its structure has been determined by single-crystal X-ray methods. In the complex, a pair of adjacent metal ions are alternately connected by four or two carboxylate groups to form an infinite chain of 8-coordinated Pr3+ ions. The complex (Pr2C50H42N12O40S4 ) crystal system is triclinic, with space group P1, a=14.2890(3), b=14.3427(3), c=20.1601(2)? =76.636(1), b=84.496(1), =60.316(1)? V=3491.4(1)?, Z=2, Mr =1861.02, Dc=1.770 g/cm3, m=1.608mm-1, F(000)=1856, the final R=0.0776 and wR=0.1724 for 8804 reflections with I > 2s(I).

Synthesis, Structure and Luminescent Properties of a Nine-Coordinated Praseodymium Complex

The Pr(TTA)_3phen(C_2H_5OH)quarternary complex with 2-thenoyltrifluoro-acetone(TTA), 1,10-phenanthroline(phen)and ethanol were synthesized and characterized by single-crystal X-ray diffraction. The central Pr^(3+) ion is nine-coordinated. The infrared(IR)spectrum, diffuse reflectance(DR)spectrum and fluorescence measurements of the complex were investigated.

Adsorption and Desorption of Praseodymium (Ⅲ) from Aqueous Solution Using D72 Resin

In this work, the feasibility of using a macroporous strong acid ion exchange resin (D72) as an adsorbent for praseodymium (Ⅲ) was examined. The adsorption behavior and mechanism were investigated with various chemical methods and IR spectrometry. The results showed that the loading of Pr (III) ions was strongly dependent on pH of the medium and the optimal adsorption condition is in HAc-NaAc medium with pH value of 3.0. Adsorption kinetics of Pr (III) ions onto D72 resin could be best described by pseudo-second-order model. The maximum adsorption capacity of D72 for Pr (Ⅲ) was evaluated to be 294 mg·g 1 for the Langmuir model at 298K. The apparent activation energy, E a , was 14.71 kJ·mol 1 . The calculated data of thermodynamic parameters, ΔSΘ value of 100 J·mol 1 ·K 1 and ΔHΘ value of 8.89 kJ·mol 1 , indicate the endothermic nature of the adsorption process, while a decrease of ΔGΘ with increasing temperature indicates the spontaneous nature of the adsorption process. Finally, Pr (Ⅲ) can be eluted by using 1.00 mol·L 1 HCl-0.50 mol·L 1 NaCl solution and the D72 resin can be regenerated and reused. Thomas model was successfully applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The characterization before and after adsorption of Pr (Ⅲ) ions on D72 resin was conformed by IR.

Crystal Structure of Praseodymium Complex with L－proline，Pr_2（L－Pro）_6（H_2O）_4·6ClO_4

Pr2(L-Pro)6(H2O)4]·6ClO4(Pro= proline), Mr=1641.4, monoclinic, P21,α=9. 879(3),b=21. 883(4),c=13. 393(2) A, β=91. 23(2) A, V=2895(1) A3, Z=2,Dc=1. 88g/cm3,μ( MoKα)=20. 5cm￣(-1) . F(000)=1648, R =0. 035 for 5032 observed reflections. The coordination polyhedron of Pr( Ⅲ) ion comprises six oxygen atoms from the L-Pro molecules and two from the water molecules, Each L-Pro molecule coordinates to two Pr(Ⅲ) ions through the carboxyl oxygens in a bidentate bridging mode, thus creating one-dimensional chain structure.

Effects of Praseodymium Doping on Conductivity and Oxygen Permeability of Cobalt-Free Perovskite-Type Oxide BaFeO3-δ

Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation. In order to stabilize the cubic perovskite structure of BaFeO3-δ material at room temperature, iron was partially substituted by praseodymium. BaFe1-yPryO3-δ powders were synthesized by a solid state reaction method, and sintered samples were prepared from the synthesized BaFe1-yPryO3-δ powders. X-ray diffraction results reveal that the BaFe1-yPryO3-δ samples remain cubic structure at praseodymium substitution amount of y 0.05, 0.075, 0.1. Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe1-yPryO3-δ increase monotonically with the increase of the praseodymium doping amount, praseodymium doping promotes the grain size growth. Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe1-yPryO3-δ and BaFe0.9Pr0.1O3-δ composition has an electrical conductivity of 6.5 S/era and an oxygen permeation of 1.112 mL/（cm^2.min） at 900 ℃, respectively. High temperature XRD in- vestigation shows that the crystal structure of BaFe0.975Pr0.025O3-δ membrane completely transform to cubic phase at 700℃. The present test results have shown that partially substitution of Fe by praseodymium in BaFeO3 can stabilize the cubic structure and improve the properties.