Synthesis and thermo-decomposition mechanism of rare earth complexes with phenylacetic acid

Rare earth complexes with phenylacetic acid (LnL(3) . nH(2)O, Ln is Ce, Nd, Pr, Ho, Er, Yb and Y, L is phenylacetate, n = 1-2) were prepared and characterized by elemental analysis, IR spectroscopy, chemical analysis, and X-ray crystal structure. The mechanism of thermal decomposition of the complexes was studied by means of TG-DTG, DTA and DSC. The activation energy and enthalpy change for the dehydration and melting processes were determined.

The conductivity behavior of a polymer gel electrolyte

A new kind of polymer gel electrolyte which is composed of polytriethylene glycol dimethacrylate(PTREGD), propylene carbonate(PC) and LiPF6 has been prepared by thermal polymerization. The conductivity was measured as a function of temperature, and it was found that the Arrhenius equation was held very well through out the salt concentration studied. Maximum room temperature conductivity of 4.95 x 10(-4) S/cm, as well as a minimum activation energy value of 18.90 kJ/mol were obtained at the same salt concentration of 0.22 mol/L.

Ionic conductivity of gel electrolyte based on polydiethylene glycol dimethacrylate and its copolymer

Gel electrolytes were prepared by thermal polymerization of diethylene glycol dimethacrylate (DIEGD) or its copolymer with methoxy polyethylene glycol monomethacrylate, molecular weight 400 (PEM(400)), at a molar ratio of 3/1 in the presence of propylene carbonate (PC) and LiClO4. Conductivity was measured by impedance spectroscopy. It was found that the conductivity data follow the Arrhenius equation in the homopolymer gel system, while the VTF equation holds true in the copolymer gel system. An increase in conductivity was observed in the copolymer gel system. However, whether in the homopolymer or in the copolymer gel system, a maximum ambient temperature conductivity was found at a salt concentration near 1.50 mol/l. Further, the activation energy values calculated from Arrhenius plots for the homopolymer gel system tended to reach a minimum value with increasing salt concentration. (C) 1996 Elsevier Science Ltd

Ionic conductivity of polymer gel electrolytes based on poly(polyethylene glycol dimethacrylate)

Gel electrolytes have been prepared by thermal polymerization of poly(polyethylene glycol dimethacrylate) (P(PEGD)) in the presence of propylene carbonate (PC) and alkali metal salts, such as LiClO4, LICF(3)SO(3) and LiBF4. The conductivity was studied by means of impedance spectroscopy, and it is found that the temperature dependence of conductivities follow a Arrhenius relationship when the molar percentage of PC is higher than 75% or LiClO4 concentration is lower than 0.9 mol/l. However, when LiCF3SO3 or LiBF4 is used instead of LiClO4 as the salt, the situation is different. For LICF(3)SO(3), the Arrhenius relationship almost holds true for all the salt concentrations studied; while for LiBF4, the Arrhenius equation hardly fits for any salt concentration. The dependence of activation energy on salt concentration is also examined, both for LiClO4 and LiCF3SO3, the values of E(a) tend to reach a minimum value with increasing salt concentration. Copyright (C) 1996 Elsevier Science Ltd.

Local chain motions in a dilute solution of phenolphthalein poly(ether sulfone)

C-13 and H-1 relaxation times were measured as a function of temperature in two magnetic fields for dilute solutions of phenolphthalein poly(ether sulfone) (PES-C) in deuterated chloroform. The spin-lattice relaxation times were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (J. S. model). The phenyl group rotation is treated as a stochastic diffusion by the J. S. model. The restricted butterfly motion of the phenyl group attached to the cardo ring in PES-C is mentioned but is not discussed in detail in this work. Correlation times for the segmental motion are in the picosecond range which indicates the high flexibility of PES-C chains. The correlation time for the phenyl group internal rotation is similar to that of the segmental motion. The temperature dependence of these motions is weak. The apparent activation energy of the motions considered is less than 10 kJ/mol. The simulating results for PES are also reasonable considering the differences in structure compared with PES-C. The correlation times and the apparent activation energy obtained using the J. S. model for the main chain motion of PES-C are the same as those obtained using the damped orientational diffusion model and the conformational jump model.

CRYSTAL STRUCTURE AND THERMAL ANALYSIS OF ERBIUM COMPLEX WITH BENZENE ACETIC ACID

The crystal structure of erbium (III) complex of benzene acetic acid is reported. The complex crystallizes in the monoclinic space group P2(1)/a with a = 0,9008(3)nm, b=1.4242(5) nm, c=1.8437(7) nm, beta=98.80(3)degrees, V = 2.337(1) nm(3), Z = 4. The mechanism of thermal decomposition of complex has been studied by TG-DTG-DTA. The activation energy for dehydration reaction has been calculated by Freeman Carroll method. The enthalpy change for dehydration and phase change process has been determined.

Isolation, characterization and electron microscopic single particle analysis of the NADH : ubiquinone oxidoreductase (complex I) from the hyperthermophilic eubacterium Aquifex aeolicus

The proton-translocating NADH:ubiquinone oxidoreductase (complex I) has been purified from Aquifex aeolicus, a hyperthermophilic eubacterium of known genome sequence. The purified detergent solubilized enzyme is highly active above 50 degreesC. The specific activity for electron transfer from NADH to decylubiquinone is 29 U/mg at 80 degreesC. The A. aeolicus complex I is completely sensitive to rotenone and 2-n-decyl-quinazoline-4-yl-amine. SDS polyacrylamide gel electrophoresis shows that it may contain up to 14 subunits. N-terminal amino acid sequencing of the bands indicates the presence of a stable subcomplex, which is composed of subunits E, F, and G. The isolated complex is highly stable and active in a temperature range from 50 to 90 degreesC, with a half-life of about 10 h at 80 degreesC. The activity shows a linear Arrhenius plot at 50-85 degreesC with an activation energy at 31.92 J/mol K. Single particle electron microscopy shows that the A. aeolicus complex I has the typical L-shape. However, visual inspection of averaged images reveals many more details in the external arm of the complex than has been observed for complex I from other sources. In addition, the angle (90degrees) between the cytoplasmic peripheral arm and the membrane intrinsic arm of the complex appears to be invariant.

Evaluation of the pyrolytic and kinetic characteristics of Enteromorpha prolifera as a source of renewable bio-fuel from the Yellow Sea of China

The pyrolytic and kinetic characteristics of Enteromorpha prolifera from the Yellow Sea were evaluated at heating rates of 10, 20 and 50 degrees C min(-1), respectively. The results indicated that three stages appeared during pyrolysis; dehydration, primary devolatilization and residual decomposition. Differences in the heating rates resulted in considerable differences in the pyrolysis of E. prolifera. Specifically, the increase of heating rates resulted in shifting of the initial temperature, peak temperature and the maximum weight loss to a higher value. The average activation energy of E. prolifera was 228.1 kJ mol(-1), the pre-exponential factors ranged from 49.93 to 63.29 and the reaction orders ranged from 2.2 to 3.7. In addition, there were kinetic compensation effects between the pre-exponential factors and the activation energy. Finally, the minimum activation energy was obtained when a heating rate of 20 degrees C min(-1) was used. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Kinetic study of the accelerating effect of coal-burning additives on the combustion of graphite

The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.

Investigation of ideal zirconium-doped perovskite-type ceramic membrane materials for oxygen separation

Zirconium-doped perovskite-type membrane materials of BaCo0.4Fe0.6-xZrxO3-delta (x = 0-0.4) with mixed oxygen ion and electron conductivity were synthesized through a method of combining citric and EDTA acid complexes. The results of X-ray diffraction (XRD), oxygen temperature-programmed desorption (O-2-TPD) and hydrogen temperature-programmed reduction (H-2-TPR) showed that the incorporation of proper amount of zirconium into BaCo0.4Fe0.6O3-delta could stabilize the ideal and cubic structure of perovskite. Studies on the oxygen permeability of the as-synthesized membrane disks under air/He gradient indicated that the content of zirconium in these materials had great effects on oxygen permeation flux, activation energy for oxygen permeation and operation stability. The high oxygen permeation flux of 0.90 ml cm(-2) min(-1) at 950degreesC, the single activation energy for oxygen permeation in the range of 600-950 degreesC and the long-term operation stability at a relatively lower operational temperature of 800 degreesC under air/He gradient were achieved for the BaCo0.4Fe0.4Zr0.2O3-delta material. Meanwhile, the effect of carbon dioxide on structural stability and oxygen permeability of this material was also studied in detail, which revealed that the reversible stability could be attained for it. (C) 2002 Elsevier Science B.V. All rights reserved.

Synthesis and characterization of gallium-based perovskite-type dense membrane with oxygen semipermeability

La0.15Sr0.85Ga0.3Fe0.7O3-delta (LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-delta (LSCFO) mixed oxygen-ion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding dense membranes were fabricated. The properties of the oxide powders and membranes were characterized with combined SEM, XRD, H-2-TPR, O-2-TPD techniques, mechanical strength and oxygen permeation measurement. The results showed that LSGFO had much higher thermochemical stability than LSCFO due to the higher valence stability of Ga3+. After the temperature-programmed reduction by 5% H-2 in Ar from 20 degreesC to 1020 degreesC, the basic perovskite structure of LSGFO was successfully preserved. LSGFO also favors the oxygen vacancy formation better than LSCFO. Oxygen permeation measurement demonstrated that LSGFO had higher oxygen permeation flux than LSCFO, but they had similar activation energy for oxygen transportation, with a value of 110 and 117 kJ . mol(-1), respectively The difference in oxygen permeation fluxes was correlated with the difference in oxygen vacancy concentrations for the two materials.

A novel zirconium-based perovskite-type membrane material for oxygen permeation

A novel zirconium-based membrane material of BaCo0.4Fe0.4Zr0.2O3-6 with cubic perovskite structure was synthesized for the first time through a method of citric and EDTA acid combined complexes. The structural stability was characterized by XRD, O-2-TPD and H-2-TPR techniques respectively. The high oxygen permeation flux of 0.873 mL/cm(2) min at 950 degreesC was obtained under He/Air gradient. Meanwhile, the single activation energy for oxygen permeation and the long-term steady operation of 200 h at 800 degreesC were achieved.

CO adsorption and correlation between CO surface coverage and activity/selectivity of preferential CO oxidation over supported Ag catalyst: an in situ FTIR study

In situ IR measurements for CO adsorption and preferential CO oxidation in H-2-rich gases over Ag/SiO2 catalysts are presented in this paper. CO adsorbed on the Ag/SiO2 pretreated with oxygen shows a band centered around 2169 cm(-1), which is assigned to CO linearly bonded to Ag+ sites. The amount of adsorbed CO on the silver particles ( manifested by an IR band at 2169 cm(-1)) depends strongly on the CO partial pressure and the temperature. The steady-state coverage on the Ag surface is shown to be significantly below saturation, and the oxidation of CO with surface oxygen species is probably via a non-competitive Langmuir Hinshelwood mechanism on the silver catalyst which occurs in the high-rate branch on a surface covered with CO below saturation. A low reactant concentration on the Ag surface indicates that the reaction order with respect to Pco is positive, and the selectivity towards CO2 decreases with the decrease of Pco. On the other hand, the decrease of the selectivity with the reaction temperature also reflects the higher apparent activation energy for H-2 oxidation than that for CO oxidation.