Thermodynamic properties of gaseous cerium phosphate studied by Knudsen effusion mass spectrometry

Gaseous CePO₂ has been identified by Knudsen effusion mass spectrometry during vaporization of CeO₂ and magnesium diphosphate from tungsten double, two‐temperature effusion cell. Structure and molecular parameters of gaseous cerium phosphate under study were determined using quantum chemical calculations. On the basis of equilibrium constants measured for gas‐phase reaction, standard formation enthalpy of CePO₂ was determined to be ?508 ± 41 kJ ? mol^?1 at the temperature 298 K.     

Thermodynamic measurement of (Al2O3 + B2O3) system by double Knudsen cell mass spectrometry

Thermodynamic properties of B₂O₃ in the (Al₂O₃ + B₂O₃) binary system were investigated by vapor pressure measurement of B₂O₃ in equilibrium with (Al₂O₃ + B₂O₃) compounds or melts using double Knudsen cell mass spectrometry. The Gibbs free energy change of formation of Al₁₈B₄O₃₃ (9Al₂O₃·2B₂O₃) was estimated from the vapor pressure in equilibrium with a mixture of Al₁₈B₄O₃₃ and Al₂O₃ at 1573 K to 1673 K. And activities of B₂O₃ in the two-phase region Al₁₈B₄O₃₃ and B₂O₃-rich liquid, and (Al₂O₃ + B₂O₃) melts were obtained at 1373 K to 1423 K by vapor pressure measurements.     

Thermodynamic excess quantities of ternary Au–Co–Pd melts by computer-aided Knudsen cell mass spectrometry

Computer-aided Knudsen cell mass spectrometry is used for the thermodynamic investigations on ternary Au–Co–Pd melts over the entire range of composition. The “digital intensity-ratio” (DIR)-method has been applied for the determination of the thermodynamic excess quantities, and the ternary thermodynamically adapted power (TAP) series concept is used for algebraic representation of the thermodynamic mixing behavior. The corresponding TAP parameters as well as the values of the molar excess Gibbs energies G^E, of the molar heats of mixing H^E, of the molar excess entropies S^E, and of the thermodynamic activities at 1800 K are presented.     

Thermodynamic properties and phase equilibria in the system MgO-Al2O3-SiO2 at high temperatures

High-temperature differential mass spectrometry was used to examine evaporation processes and to determine activity of components in the system MgO-Al₂O₃-SiO₂ at 1820 K. The results obtained are in good agreement with the data of thermodynamic calculations.     

Enhanced epoxidation of soybean oil by novel Al2O3–ZrO2–TiO2 solid acid catalyst

This study aims to develop highly efficient, recyclable solid catalysts for the epoxidation of vegetable oils. An Al₂O₃–ZrO₂–TiO₂ solid acid catalyst was prepared by a co‐precipitation/impregnation method and characterised through scanning electron microscopy, energy‐dispersive spectroscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, Fourier‐transform infrared and nitrogen adsorption–desorption analyses. The solid acid catalyst with a high surface area and typical slit pore adsorption was successfully synthesised. Al₂O₃–ZrO₂–TiO₂ also exhibits high stability and improved catalytic efficiency in the epoxidation of soybean oil. An oil conversion rate of 86.6%, which is higher than that of conventional catalysts, was obtained with a catalyst loading of 0.8 wt% and was maintained at 76.6% even after recycling the catalyst three times. The performance of the solid catalyst was slightly superior to that of H₂SO₄. Therefore, this novel catalyst may potentially be applicable in catalysing soybean oil epoxidation.     

Study on sublimation of solid electrolyte (AgI)0.5‐(AgPO3)0.5 with Knudsen effusion mass spectrometry

Knudsen high‐temperature mass spectrometry was used to study the process of sublimation of a solid electrolyte (AgI)_0.5‐(AgPO₃)_0.5. Monoatomic iodine ions were found to be the dominant species in the electron ionization mass spectra below 600°C. With an increase in temperature, the relative content of phosphorus oxide ions, mainly [PO]⁺ and [P₄O₁₀]⁺, increased. Under further heating, we observed silver iodide and iodine dimer ions together with phosphorus dimer and tetramer ions and clusters [IPO₂]⁺, [IP₂]⁺, [I₃P]⁺. Using the experimental logarithmic dependencies of ion signal intensities versus the reciprocal absolute temperature of the effusion cell, the apparent sublimation enthalpies Δ_sH of the ions giving the most intense signals were estimated. Copyright © 2008 John Wiley & Sons, Ltd.     

Knudsen effusion mass spectrometric determination of mixing thermodynamic data of liquid Ag–In–Sn alloy

The vaporisation of a liquid Ag–In–Sn system has been investigated at 1273–1473 K by Knudsen effusion mass spectrometry (KEMS) and the data fitted to a Redlich–Kister–Muggianu (RKM) sub-regular solution model. Nineteen different compositions have been examined at six fixed indium mole fractions, X_In = 0.10, 0.117, 0.20, 0.30, 0.40 and 0.50. The ternary L-parameters, the thermodynamic activities and the thermodynamic properties of mixing have been evaluated using standard KEMS procedures and from the measured ion intensity ratios of Ag⁺ to In⁺ and Ag⁺ to Sn⁺, using a mathematical regression technique described by us for the first time. The intermediate data obtained directly from the regression technique are the RKM ternary L-parameters. From the obtained ternary L-parameters the integral molar excess Gibbs free energy, the excess chemical potentials, the activity coefficients and the activities have been evaluated. Using the temperature dependence of the activities, the integral and partial molar excess enthalpies and entropies were determined. In addition, for comparison, for some compositions, also the Knudsen effusion isothermal evaporation method (IEM) and the Gibbs–Duhem ion intensity ratio method (GD-IIR) were used to determine activities and good agreement was obtained with the data obtained from fitting to the RKM model.