Gaseous Salts Research Articles

Thermochemical Study of Gaseous Salts of Oxygen-Containing Acids: XXIII. Lead Antimonates

Reactions of the gas-phase synthesis of lead antimonates were studied. Standard enthalpies of formation and atomization of gaseous PbSbO2 and PbSb2O4 were determined.

Thermodynamic properties of gaseous BaSnO2 and Ba2 O2 studied by Knudsen effusion mass spectrometry.

BaSnO3 is an interesting technical and industrial ceramic, with uses in many areas of electronic technology. Currently, there is great interest in this ceramic material because of its potential as a transparent conductive oxide. Due to its good chemical stability, it is also used as a surface processing material in the synthesis of electroluminophores. When heated, the stannates of alkaline earth metals can pass into the vapor phase with or without dissociation. Until the present investigation, gaseous salts where SnO plays the role of an anion-forming oxide had been unknown. The formation enthalpy of gaseous Ba2 O2 also needed to be determined. Knudsen effusion mass spectrometry was used to determine the partial pressures of vapor species, equilibrium constants and enthalpies of the studied gas-phase reactions, as well as the formation and atomization enthalpies of gaseous BaSnO2 and Ba2 O2 : a mixture of BaO and SnO2 was evaporated from a platinum effusion cell. For the evaporation of gold (pressure standard), a molybdenum effusion cell was used. A theoretical study of gaseous BaSnO2 and Ba2 O2 was performed by several quantum chemistry methods. Ba, BaO, Ba2 O2 , SnO and BaSnO2 were found to be the main species in the vapor over the BaO-SnO2 mixture in the temperature range of 1680-1920 K. The standard formation enthalpies of gaseous BaSnO2 and Ba2 O2 were determined on the basis of the equilibrium constants of the studied gas-phase reactions. Energetically favorable structures of these gaseous species were found and vibrational frequencies were evaluated in the harmonic approximation. The formation enthalpy of gaseous Ba2 O2 was clarified; in addition, the formation enthalpies of gaseous SrSnO3 and CaSnO3 were estimated. The thermal stability of gaseous BaSnO2 was confirmed by Knudsen effusion mass spectrometry. The reaction enthalpies of gaseous BaSnO2 from gaseous barium and tin oxides were theoretically evaluated and the obtained values were found to be in reasonable agreement with the experimental ones.

Modelling of initial deposition of biomass ash particles on walls of superheater tubes

Condensation of gaseous alkali chloride and sulphate and adhesion of molten ash particles are still an important issue of investigation and gaining more and more attention in biomass utilization. In this work the behaviours for formation of initial deposition layer and condensation of KCl(g) and K2SO4(g) were simulated nu-merically in a 2-D computational domain of an in-line 4?4 tube bundle. The sticking and rebound efficiency of incident particles, condensation rate of gaseous salts and ash deposition rate on both of the windward and the leeward sides of tubes were obtained through transient calculation cases. The ash deposition mass on the windward side of tubes is mainly from impaction and stickiness of large ash particles. The condensation rate of KCl(g) is two orders of magnitude higher than that of K2SO4(g) on both of the windward and the leeward side of tubes. The ash deposition rate and the condensation rate on the windward side of tubes are of equal importance. While on the leeward side of tubes the condensation of salt vapours is more dominant than the inertial impaction in the forming stage of initial layer.

Thermodynamic properties of gaseous cerium molybdates and tungstates studied by Knudsen effusion mass spectrometry.

CeO2 -WO3 and CeO2 -MoO3 catalysts have shown excellent performance in the selective reduction of NOx by ammonia (NH3 -selective catalytic reduction) over a wide temperature range. Strong interaction between CeO2 and WO3 or MoO3 might be the dominant reason for the high activity of these mixed oxides. Studies of ceria-containing gaseous salts involve considerable experimental difficulties, since the transition of such salts to vapor requires high temperatures. To predict the possibility of the existence of gaseous associates formed by cerium and molybdenum (tungsten) oxides it is important to know their thermodynamic characteristics. Until the present investigation, gaseous cerium oxyacid salts were unknown. Knudsen effusion mass spectrometry was used to determine the partial pressures of vapor species and the equilibrium constants of gas-phase reactions, as well as the formation and atomization enthalpies of gaseous cerium molybdates and tungstates. CeO2 was evaporated from molybdenum and tungsten effusion cells containing gold metal as a pressure standard. A theoretical study of gaseous cerium gaseous molybdates and tungstates was performed by several quantum chemical methods. In the temperature range 2050-2400 K, CeO, CeO2 , XO2 , XO3 , CeWO3 , CeXO4 , CeXO5 (X = Mo, W) and CeMo2 O7 were found to be the main vapor species over the CeO2 - Mo (W) systems. On the basis of the equilibrium constants of the gaseous reactions, the standard formation enthalpies of gaseous CeWO3 , CeXO4 , CeXO5 (X = Mo, W) and CeMo2 O7 at 298 K were determined. Energetically favorable structures of gaseous cerium salts were found and vibrational frequencies were evaluated in the harmonic approximation. The thermal stability of gaseous cerium oxyacid salts was confirmed by high-temperature mass spectrometry. Reaction enthalpies of the gaseous cerium molybdates and tungstates from gaseous cerium, molybdenum and tungsten oxides were evaluated theoretically and the obtained values are in reasonable agreement with the experimental one.

Thermochemical study of gaseous salts of oxygen-containing acids: XXII.1 Lead salts

Reactions of gas-phase synthesis of lead phosphates and tellurates have been studied. Standard enthalpies of formation and atomization of gaseous PbPO2, PbPO3, PbP2O6, PbTeO3, and Pb2TeO4 salts have been determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXI. Zinc phosphate

A gas–phase reaction involving zinc phosphate was studied by the high-temperature massspectrometry method. Standard enthalpies of formation and atomization of the molecules ZnPO3(gas) were determined.

Thermodynamic study of gaseous tin molybdates by high-temperature mass spectrometry.

Molybdenum and tin are components of various construction materials which are often used at high temperature and in an oxidizing atmosphere. Oxides of molybdenum and tin, with their high reactivity, can, in their turn, form a number of gaseous compounds. To predict the possibility of the existence of gaseous associates formed by tin and molybdenum oxides it is important to know their thermodynamic characteristics. Until the present investigation only a few gaseous salts of tin were known. High-temperature Knudsen effusion mass spectrometry was used to determine the partial pressures of vapor species over the SnO(2) -MoO(3) system. The formation enthalpies of gaseous SnMoO(4), Sn(2) MoO(5) and SnMo(2)O(7) were derived. Measurements were performed with a MS-1301 mass spectrometer. Vaporization was carried out using a molybdenum effusion cell containing the samples under study and pure gold as the reference substance. A theoretical study of gaseous tin molybdates was performed by several quantum chemical methods: wave function based explicitly correlated F12 methods and DFT M0(6) methods. In the temperature range of 1200-1400 K, SnO, Sn(2)O(2), SnMoO(4), Sn(2) MoO(5), SnMo(2)O(7), MoO(3), Mo(2)O(6) and Mo(3)O(9) were found to be the main vapor species over the samples studied. On the basis of the equilibrium constants of gaseous reactions, the standard formation enthalpies of gaseous SnMoO(4) (-699 ± 29 kJ/mol), Sn(2) MoO(5) (-1001 ± 38 kJ/mol) and SnMo(2)O(7) (-1456 ± 60 kJ/mol) at 298 K were determined. Energetically favorable structures were found and vibrational frequencies were evaluated in the harmonic approximation. The stability of gaseous species, SnMoO(4), Sn(2) MoO(5) and SnMo(2)O(7), was confirmed by high-temperature mass spectrometry. A number of gas-phase reactions involving tin-containing gaseous salts were studied. The enthalpies of reactions of gaseous tin molybdates were evaluated theoretically and the obtained values are in agreement with those obtained experimentally.

Thermochemical study of gaseous salts of oxygen-containing acids: XX. Germanium salts

Reactions of the gas-phase synthesis of germanium vanadate, borate, and molybdate have been studied. Standard enthalpies of formation and atomization of gaseous salts GeV2O6, GeB2O4, and SnMo2O7 have been determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XIX. Tin salts

Reactions of the gas-phase synthesis of tin vanadates, borates, and molybdates were studied. Standard enthalpies of formation and atomization of gaseous salts SnV2O6, SnB2O4, Sn2B2O5, SnMoO4, Sn2MoO5, and SnMo2O7 were determined.

Formation and thermodynamics of gaseous germanium and tin vanadates: a mass spectrometric and quantum chemical study.

The stabilities of gaseous germanium and tin vanadates were confirmed by high temperature mass spectrometry, and its structures were determined by quantum chemical calculations. A number of gas-phase reactions involving these gaseous salts were studied. On the basis of the equilibrium constants, the standard formation enthalpies of gaseous GeV2O6 (-1520 ± 42 kJ mol(-1)) and SnV2O6 (-1520 ± 43 kJ mol(-1)) were determined at a temperature of 298 K.

Gaseous titanium molybdates and tungstates: thermodynamic properties and structures.

Titanium is a component of various construction materials, which is often used at high temperature and in an oxidizing atmosphere. Thermally stable even at high temperatures, titanium compounds may appear in the condensed phase. To predict the possibility of existence of gaseous associates formed by titanium oxides it is important to know their thermodynamic characteristics. Until the present investigation no gaseous salts of titanium were known. Measurements were performed by high-temperature Knudsen effusion mass spectrometry with a MS-1301 mass spectrometer. Vaporization was carried out using molybdenum and tungsten effusion cells containing samples of pure Au, Ti3O5 and SiO2. A theoretical study of gaseous titanium molybdates and tungstates in different spin states was performed by quantum chemical density functional theory (DFT) B3LYP and M06 methods. On the basis of the equilibrium constants of gaseous reactions, the standard formation enthalpies of gaseous TiMoO3 (-424 ± 28 kJ/mol), TiWO3 (-400 ± 22 kJ/mol), TiMoO4 (-795 ± 29 kJ/mol), TiWO4 (-750 ± 24 kJ/mol), TiMoO5 (-1146 ± 23 kJ/mol) and TiWO5 (-1125 ± 22 kJ/mol) at 298 K were determined. Energetically favorable structures were localized and vibrational frequencies were evaluated in the harmonic approximation. Natural atomic charges, bond orders, and valence indices were calculated for all relevant structures. The stability of gaseous species TiMoOn and TiWOn (n = 3, 4, 5) was confirmed by high-temperature mass spectrometry. A number of gas-phase reactions involving titanium-containing gaseous salts were studied. Enthalpies of reactions of gaseous TiXOn (X = Mo, W; n = 3, 4, 5) formation were evaluated theoretically and the obtained values are in agreement with the experimental ones.

Thermal stability and structures of gaseous GeB2O4 and GeMo2O7

The stability of gaseous GeMo2O7 and GeB2O4 were confirmed by Knudsen effusion mass spectrometry. To get structure parameters of these gaseous salts quantum chemical investigation of molecules was undertaken.

Thermochemical study of gaseous salts of oxygen-containing acids: XXVIII. Gallium borates

Reactions of the gas-phase synthesis of gallium borate from oxides and its dimerization were studied. It was found that the molecules Ga2O, B2O3, GaBO2, and (GaBO2)2 are present in the vapor above the Ga2O3-B2O3 system. Enthalpies of formation and atomization of gaseous gallium borates were determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXVII. Antimonites of alkali metals

Vaporization of sodium, potassium, rubidium, and cesium antimonates was studied. Vapors above the studied antimonates contain dimeric (MSbO2)2 molecules in addition to monomeric antimonites MSbO2. Standard enthalpies of formation of these gaseous molecules were determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXVI. Iodates of alkali metals

Vaporization of iodates of alkali metals was studied. Vapor above the iodates contains dimeric molecules alongside monomers. Standard enthalpies of formation of the gaseous molecules MIO3 and M(IO3)2 were determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXV. Magnesium borates

Standard enthalpies of formation and atomization of gaseous magnesium borates MgBO2 and MgB2O4 were determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXIV. Polymers of alkali metals perrenates

The vaporization of alkali metals perrhenates was studied. Standard enthalpies of formation of the gaseous molecules (MReO4)2 were determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXIII. Molecules MnB2O4, MnNbO2, MnNbO3 and MnTiO3

Gas-phase equilibria involving manganese borate, niobates, and titanate were studied. Standard enthalpies of formation and atomization of the gaseous molecules MnB2O4, MnNbO2, MnNbO3, and MnTiO3 were determined.

Thermochemical study of gaseous salts of oxygen-containing acids: XXII. Tin molybdates

Gas-phase reactions involving tin molybdates were studied. Standard enthalpies of formation and atomization of gaseous salts SnMoO4 and Sn2MoO5 were determined.

Gaseous salts of oxygen-containing acids: Thermal stability, structure, and thermodynamic properties

Experimental data and results of quantum-chemical calculations on the structure and thermodynamic properties of gaseous salts of oxygen-containing acids were systematized. A criterion of thermal stability of these compounds was offered and regularities in the atomization enthalpies were established.