2CaO·3B2O3·H2O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and
TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B2O3·H2O in HCl·54.572H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HCl·54.501H2O and of CaO in (HCl+H3BO3) solution, together with the standard molar enthalpies of formation of CaO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol−1 of 2CaO·3B2O3·H2O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.
Authors:L. T. Vlaev, S. D. Genieva, and G. G. Gospodinov
Summary The solubility of CoSeO3-SeO2-H2O system in the temperature region 298-573 K was studied. The phase diagram of cobalt(II)selenites was drawn and the crystallization fields for the different phases were determined. Depending on the conditions for hydrothermal synthesis, CoSeO3×2H2O, α-CoSeO3×1/3H2O, β-CoSeO3×1/3H2O, CoSeO3, Co(HSeO3)2×2H2O and CoSe2O5 were obtained. The different phases were proved and characterized by chemical and X-ray analyses, as well as IR spectroscopy.
Authors:L. Vlaev, Svetlana Genieva, and Velyana Georgieva
The solubility of NiSeO3–SeO2–H2O
system in the temperature region 298–573 K was studied. The compounds
of the three-component system were identified by the Schreinemakers’
method. The phase diagram of nickel(II) selenites was drawn and the crystallization
fields for the different phases were determined. Depending on the conditions
for hydrothermal synthesis, NiSeO32H2O,
NiSeO3 and NiSe2O5
were obtained. The different phases were proved and characterized by chemical,
powder X-ray diffraction and thermal analyses as well as IR spectroscopy.
The solubility of MnSeO3-SeO2-H2O system was studied in the temperature region 25–300°C. The compounds of the three-component system were identified by the
Schreinemaker’s method. The phase diagram of manganese(II) selenites was drawn and the crystallization fields for the different
phases were determined. Depending on the conditions for hydrothermal synthesis, MnSeO3·H2O, MnSeO3·3/4H2O, MnSeO3·l/3H2O and MnSe2O5 were obtained. The different phases were proven and characterized by chemical, powder X-ray diffraction and thermal analyses,
as well as IR spectroscopy. The kinetics of dehydration and decomposition of MnSeO3·H2O was studied under non-isothermal heating. Based on 4 calculation procedures and 27 kinetic equations, the values of activation
energy and pre-exponential factor in Arrhenius equation were calculated for both processes.
Authors:M. Iwan, R. Łyszczek, A. Ostasz, and Z. Rzączyńska
Properties of lanthanide 1,2,4-benzenetricarboxylates and lanthanide
1,2,4,5-benzenetetracarboxylates obtained by a classical synthesis method
and under hydrothermal conditions were compared. Solid 1,2,4-benzenetricarboxylates
and 1,2,4,5-benzenetetracarboxylates of cerium, neodymium and erbium were
prepared by a classical precipitation method. The same lanthanide compounds
were obtained also from hydrothermal reaction. All obtained products were
examined by elemental analysis. General formulae of complexes were: Ln(1,2,4-btc)xH2O and Ln4(1,2,4,5-btec)3yH2O. The thermal analysis
shows that hydrothermal conditions cause the coordination of less number of
water molecules to complex molecule. Because lanthanide ions exhibit the most
often the coordination number equal 8 or 9 one can conclude that the coordination
ability of carboxylic groups under hydrothermal conditions is different from
that under mild ones. Probably, in hydrothermal conditions the carboxylic
groups of 1,2,4-benzenetricarboxylate ions are able to form more coordination
bonds with lanthanide ions than under normal pressure.
Authors:A. Martínez-de la Cruz, D. B. Hernández-Uresti, Leticia M. Torres-Martínez, and S. W. Lee
method to prepare PbMoO 4 oxide. The hydrothermalsynthesis provides a simple method to obtain oxides under mild conditions without a thermal post-treatment. The hydrothermal conditions rule the morphology of the final product by controlling experimental
Ti-SBA-15, one of the latest titanium silicalite catalysts, has been prepared according to the literature by the direct hydrothermal synthesis using Pluronic 123 as structure-directing agent. The characterization of the catalyst was performed by means of the following methods: XRD, IR, UV–Vis, X-ray microanalysis and SEM. The catalytic properties of the Ti-SBA-15 catalyst have been tested in the epoxidation of allyl alcohol, methallyl alcohol, crotyl alcohol and 1-butene-3-ol with hydrogen peroxide. The process has been described by the following main functions: the selectivity to epoxide compound in relation to allylic compound consumed and the conversion of allylic compound.