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The oxygenation constants(Ko_2)of cobalt(Ⅱ)hydroxamates(CoL_2~1-CoL_2~3)with benzo-15-crown-5(B15C5)pendants were measured over the range of-5 to 20℃,and the values of thermodynamic parameters(ΔH~0 andΔS~0)were calculated based on these(No_2)values.Meanwhile,these crowned complexes were employed to the oxidation for p-xylene to p-toluic acid with air at 110Δunder normal atmospheric pressure.The effects of B15C5 pendant and the length of chain bonded to B15C5 in these complexes on the O_2-binding capabilities and oxidation for p-xylene were investigated with the comparison of crown-free analogues CoL_2~4.  相似文献   

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Calcium titanofluoride CaTiF5(s) was prepared by solid-state reaction of CaF2(s) with TiF3(s) and characterized by X-ray diffraction method. The standard molar isobaric heat capacity (Cp,m) of CaTiF5(s) was determined by a power compensated differential scanning calorimeter in the temperature from 230 K to 710 K. A solid-state galvanic cell with CaF2 as electrolyte was used to determine the standard molar Gibbs energy of formation (ΔfGm) of CaTiF5 in the temperature range from 803 K to 1005 K. The galvanic cell can be depicted as:(-)Pt,O2(g,101.325kPa)/{CaO(s)+CaF2(s)}//CaF2//{CaTiF5(s)+CaTiO3(s)}/O2(g,101.325kPa),Pt(+)The second law analysis of present data were carried out to derive the standard entropy Sm(298.15K) and the enthalpy of formation ΔfHm(298.15K) and the values derived are 68.7 J · K−1 · mol−1 and −2848.4 kJ · mol−1, respectively.  相似文献   

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Standard molar Gibbs free energy of formation of ternary oxides Pb5CrO8(s), Pb2CrO5(s), and PbCrO4(s) were determined by measuring equilibrium oxygen partial pressures over relevant phase fields using manometry and solid oxide electrolyte based emf methods and are given by: ΔfGm°Pb5CrO8(s)±0.55/(kJ·mol-1)=-1809.4+0.6845(T/K)(837T/K1008),ΔfGm°Pb2CrO5(s)±0.30/(kJ·mol-1)=-1161.3+0.4059(T/K)(859T/K1021),ΔfGm°PbCrO4(s)±0.17/(kJ·mol-1)=-909.8+0.3111(T/K)(863T/K1093),  相似文献   

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The standard molar Gibbs free energy of formation of Co2TiO4, CoTiO3, and CoTi2O5 as a function of temperature over an extended range (900 to 1675) K was measured using solid-state electrochemical cells incorporating yttria-stabilized zirconia as the electrolyte, with CoO as reference electrode and appropriate working electrodes. For the formation of the three compounds from their component oxides CoO with rock-salt and TiO2 with rutile structure, the Gibbs free energy changes are given by:ΔfG(ox)°(Co2TiO4)±104/(J·mol-1)=-18865-4.108(T/K)ΔfG(ox)°(CoTiO3)±56/(J·mol-1)=-19627+2.542(T/K)ΔfG(ox)°(CoTi2O5)±52/(J·mol-1)=-6223-6.933(T/K)Accurate values for enthalpy and entropy of formation were derived. The compounds Co2TiO4 with spinel structure and CoTi2O5 with pseudo-brookite structure were found to be entropy stabilized. The relatively high entropy of these compounds arises from the mixing of cations on specific crystallographic sites. The stoichiometry of CoTiO3 was confirmed by inert gas fusion analysis for oxygen. Because of partial oxidation of cobalt in air, the composition corresponding to the compound Co2TiO4 falls inside a two-phase field containing the spinel solid solution Co2TiO4–Co3O4 and CoTiO3. The spinel solid solution becomes progressively enriched in Co3O4 with decreasing temperature.  相似文献   

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