Phase diagram for the system KVO3 + NH4HCO3 + NH4VO3 + KHCO3 + H2O at 303 K

Solubility data of the KVO₃ + NH₄HCO₃ + NH₄VO₃ + KHCO₃ + H₂O system at 303 K were determined under varying pressure conditions. The results were used to construct a phase diagram in the oblique projection according to Jänecke's method. At constant p and T this diagram includes two invariant points, five double saturated liquid curves, and four crystallization fields corresponding to KVO₃, NH₄HCO₃, NH₄VO₃, and KHCO₃. It has been found that ammonium meta-vanadate is a sparingly soluble salt. NH₄VO₃ and KHCO₃ compose the stable pair of salts, whereas KVO₃ and NH₄HCO₃ form the unstable salt-pair. A thorough knowledge of the solubility phase diagram for this reciprocal quaternary salt system is the theoretical basis of the carbonation process of the potassium meta-vanadate saturated ammonia solution.     

The electrolyte NRTL model and speciation approach as applied to multicomponent aqueous solutions of H2SO4, Fe2(SO4)3, MgSO4 and Al2(SO4)3 at 230–270 °C

This work presents chemical modeling of solubilities of metal sulfates in aqueous solutions of sulfuric acid at high temperatures. Calculations were compared with experimental solubility measurements of hematite (Fe₂O₃) in aqueous ternary and quaternary systems of H₂SO₄, MgSO₄ and Al₂(SO₄)₃ at high temperatures. A hybrid model of ion-association and electrolyte non-random two liquid (ENRTL) theory was employed to fit solubility data in three ternary systems H₂SO₄–MgSO₄–H₂O, H₂SO₄–Al₂(SO₄)₃–H₂O at 235–270 °C and H₂SO₄–Fe₂(SO₄)₃–H₂O at 150–270 °C. Employing the Aspen Plus™ property program, the electrolyte NRTL local composition model was used for calculating activity coefficients of the ions Al³⁺, Mg²⁺ Fe³⁺ and SO₄²⁻, HSO₄⁻, OH⁻, H₃O⁺, respectively, as well as molecular species. The solid phases were hydronium alunite (H₃O)Al₃(SO₄)₂(OH)₆, hematite Fe₂O₃ and magnesium sulfate monohydrate (MgSO₄)·H₂O which were employed as constraint precipitation solids in calculating the metal sulfate solubilities. A correlation for the equilibrium constants of the association reactions of complex species versus temperature was implemented. Based on the maximum-likelihood principle, the binary interaction energy parameters for the ionic species as well as the coefficients for equilibrium constants of the reactions were obtained simultaneously using the solubility data of the ternary systems. Following that, the solubilities of metal sulfates in the quaternary systems H₂SO₄–Fe₂(SO₄)₃–MgSO₄–H₂O, H₂SO₄–Fe₂(SO₄)₃–Al₂(SO₄)₃–H₂O at 250 °C and H₂SO₄–Al₂(SO₄)₃–MgSO₄–H₂O at 230–270 °C were predicted. The calculated results were in excellent agreement with the experimental data.     

Low-temperature heat capacity and standard molar enthalpy of formation of the complex Zn(Thr)SO4·H2O (s)

Low-temperature heat capacities of the complex Zn(Thr)SO₄·H₂O (s) have been precisely measured with a small sample adiabatic calorimeter over the temperature range from 78 to 373 K. The initial dehydration temperature of the complex (T_d=325.50 K) has been obtained by analysis of the heat-capacity curve. The experimental values of molar heat capacities have been fitted to a polynomial equation by least square method. The standard molar enthalpy of formation of the complex has been determined from the enthalpies of dissolution (Δ_dH_m^Θ) of [ZnSO₄·7H₂O (s) +Thr (s)] and Zn(Thr)SO₄·H₂O (s) in 100 ml of 2 mol dm⁻³ HCl solvent as: Δ_fH_{m,Zn(Thr)SO4·H2O}^Θ=−2111.7±3.4 kJ mol⁻¹. These experiments were made by using an isoperibol solution calorimeter at 298.15 K.     

Theoretical investigations on the SO2 + HO2 reaction and the SO2–HO2 radical complex

The mechanism of the SO₂ + HO₂ reaction was studied theoretically for the first time. Three product channels were revealed, namely, O₂ + HOSO, O₂ + HSO₂, and OH + SO₃. The O₂ + HOSO channel dominates the reaction under combustion conditions. A five-member-ring complex [SO₂–HO₂] exists at the entrance of the reaction. The structure and binding energy (D_e and D₀) of the SO₂–HO₂ complex have been calculated. In view of D₀ = 21.2 ± 2.0 kJ mol⁻¹, the SO₂–HO₂ complex should be stable at low temperature. The infrared spectra and frequency shifts were calculated for both SO₂–HO₂ and SO₂–DO₂, and compared with the available experimental data.     

H_2O对SO_2在CaO表面上吸附的影响理论研究

采用密度泛函理论研究了H_2O对SO_2在CaO(001)表面上吸附的影响。结果表明,以四种形式(-H_2O、-H、-OH和-H-OH)存在的H_2O使SO_2在CaO表面上的吸附构型发生改变。SO_2在不同形式H_2O基团邻位吸附时,-H使S原子的p轨道态密度峰明显左移且吸附能比洁净表面大90 kJ/mol,其余基团表面吸附能无明显变化;SO_2吸附于-OH和-H-OH生成HSO_3基团,吸附能相比于洁净表面较小,可能作为暂态结构;SO_2吸附于-H_2O生成SO_3基团,H_2O断键生成的H基团起主要吸附作用,CaO表面上生成类似Ca(OH)_2的局部结构且吸附能比洁净表面大45 kJ/mol。     

Hydroformylation of propylene in supercritical CO2 + H2O and supercritical propylene + H2O

Hydroformylation of propylene has been carried out in supercritical CO₂ + H₂O and in supercritical propylene + H₂O mixtures using Rh(acac)(CO)₂ and triphenylphosphine trisulfonate trisodium salt (TPPTS), P(m-C₆H₄SO₃Na)₃, as catalyst. Visual observation of the reaction mixtures indicates that in both systems a single phase is present at supercritical temperatures and pressures so that the reaction occurs under homogeneous conditions. After reaction is complete, a biphasic system is formed when the pressure and temperature are reduced to ambient. This facilitates separation of the products in the organic phase and the rhodium catalyst in the aqueous phase. The rhodium concentration in the organic phase was found to be negligible (1.0 × 10⁻⁶ mg/ml). Furthermore, compared with traditional hydroformylation technology, the supercritical reactions also show better activity and selectivity.     

SO_2和H_2O(g)对新疆高钠煤中钠挥发和形态迁移的研究

在水平管式炉上进行了400-1 100℃新疆高钠煤恒温燃烧实验,并利用逐级提取的方法分析煤及煤灰中钠的赋存形态,研究煤中钠的释放和形态迁移特性。重点考察700和1100℃下H_2O(g)和SO_2(g)单因素及双因素对煤中无机钠挥发和形态迁移的影响。结果表明,随着温度的升高,煤中钠的释放比例逐渐增大,其中,有机态钠最先析出,其次是水溶态无机钠,硅铝酸盐形式的无机钠则由于高热稳定性不易分解或挥发。低温下(700℃)H_2O(g)的存在降低了钠的挥发,而较高温度下(1 100℃)焦炭与水蒸气反应生成的局部还原性气氛促进煤中钠的挥发,但当入口气氛中H_2O(g)浓度高于20%时,促进作用减小。SO_2的存在抑制了煤中钠的挥发,随着燃烧温度升高,SO_2对钠的抑制作用减弱。H_2O和SO_2双因素作用下,低温下(700℃)抑制了煤中钠的挥发,而较高温度下(1 100℃)钠的挥发特性取决于两者在入口气氛中的浓度。对于选取的高钠煤,20%H2O和2.0×10-3SO_2入口气氛下,1 100℃煤燃烧钠的挥发比例由86%提高到了87.1%。     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

Melting and thermal decomposition of [Ni(H2O)6](NO3)2

The two-stage melting process and the thermal decomposition of [Ni(H₂O)₆](NO₃)₂ was studied by DSC, DTA and TG. The first melting point at 328 K is connected with the small and the second melting point at 362 K with the large enthalpy and entropy changes. The thermal dehydration process starts just above ca. 315 K and continues up to ca. 500 K. It consists of three well-separated stages, but the sample mass loss at each stage depends on the experimental regime. However, irrespective of the chosen regime, the total of registered mass losses in stage one and two amounts to three H₂O molecules per one [Ni(H₂O)₆](NO₃)₂ molecule. The remaining three H₂O molecules are gradually freed in the temperature range of 440–500 K in the third stage of the dehydration. Above 580 K, anhydrous Ni(NO₃)₂ decomposes into NO and NiO. The gaseous products were identified by quadrupole mass spectrometer (QMS), and the solid product was identified by X-ray diffraction (XRD) analysis.     

Thermodynamic properties of the system NH4NO3 + (NH4)2SO4 + H2O at 298.15 K

In this investigation, the mixed aqueous electrolyte system of nitrate and sulfate with common ammonium cation has been studied with the hygrometric method at the temperature 298.15 K. The water activities of the system [yNH₄NO₃ + (1 − y)(NH₄)₂SO₄](aq) are measured at total molalities from 0.4 mol kg⁻¹ up to saturation for different ionic-strength fractions y of NH₄NO₃ with y = 0.2, 0.5 and 0.8. The obtained data allow the deduction of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii–Stokes–Robinson (ZSR), Leitzke and Stoughton (LSII), Kusik and Meissner (KM), and Pitzer models. From these measurements, new Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture. The obtained results are used to calculate the excess Gibbs energy at total molalities for different ionic-strength fractions y.     

Synthesis and enthalpy of formation of SrB4O7·3H2O

Hydrated strontium borate, SrB₄O₇·3H₂O, has been synthesized and characterized by XRD, FT-IR, DTA-TG and chemical analysis. The molar enthalpy of solution of SrB₄O₇·3H₂O in 1 mol dm⁻³ HCl(aq) was measured to be (21.15 ± 0.29) kJ mol⁻¹. With incorporation of the previously determined enthalpies of solution of Sr(OH)₂·8H₂O(s) in [HCl(aq) + H₃BO₃(aq)] and H₃BO₃ in HCl(aq), and the enthalpies of formation of H₂O(l), Sr(OH)₂·8H₂O(s) and H₃BO₃(s), the enthalpy of formation of SrB₄O₇·3H₂O was found to be −(4286.7 ± 3.3) kJ mol⁻¹.     

Noncentrosymmetric K2Mn3(SO4)3F2·4H2O and Rb2Mn3(SO4)3F2·2H2O with pseudo-KTP structures

Two fluoride sulfates,K₂Mn₃(SO₄)₃F₂·4H₂O(Ⅰ) and Rb₂Mn₃(SO₄)₃F₂·2H₂O (Ⅱ) are obtained by water solution method.Single-crystal X-ray diffraction analysis indicated that they crystallize in space groups of Cmc2_1.Their structures feature a pseudo-KTP structure consisting of interconnecting[Mn₃(SO₄)3F₂(H₂O)2]_∞ layers,which are further packing along the a axis with alkali metal cations balancing the charges.The structure relationships between the two compounds are discussed.Secondharmonic generation measurements manifest that Ⅰ and Ⅱ have similar second-harmonic generation responses of about 0.2 and 0.25 times that of KH₂PO₄.     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

Radiation induced scavenging of NOx, SO2, H2S from exhaust gases

The theoretical model of exhaust gases radiation induced oxidation was developed. NO, SO₂ and H₂S concentrations curves vs dose calculated by use of this model for mixtures containing N₂ (80.5%), O₂ (11%), H₂O (8.4%), NO (100–600 ppm), SO₂ (150–500 ppm) and H₂S (300–1000 ppm) have been obtained. It has been shown that NO and SO₂ conversion reactions with acids formation go simultaneously with oxidizing reaction of H₂S giving SO₂ as an intermediate substance. These processes were evaluated for different initial concentrations of NO, SO₂ and H₂S. Data established by our simulation calculations show that the electron beam process can be judged as a promising technology for simultaneous removal of SO₂, NO and H₂S from exhaust gases.     

Syntheses and structural determination of nine-coordinate K3[Nd(nta)2(H2O)]·6H2O and K3[Er(nta)2(H2O)]·5H2O

The syntheses and structural determination of Nd^III and Er^III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K₃[Nd^III(nta)₂(H₂O)]·6H₂O complex belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm³, Z=8, M=763.89, D_c=1.930 g cm⁻³, μ=2.535 mm⁻¹ and F(000)=3048. The final R₁ and wR₁ are 0.0390 and 0.0703 for 4501 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd^IIIN₂O₇ part in the [Nd^III(nta)₂(H₂O)]³⁻ complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly. The crystal of the K₃[Er^III(nta)₂(H₂O)]·5H₂O complex also belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm³, Z=8, M=768.89, D_c=1.987 g cm⁻³, μ=3.833 mm⁻¹ and F(000)=3032. The final R₁ and wR₁ are 0.0321 and 0.0671 for 4445 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er^IIIN₂O₇ part in the [Er^III(nta)₂(H₂O)]³⁻ complex anion has the same structure as Nd^IIIN₂O₇ part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Multiphoton ionization vibrational state selection of H2O, D2O and HDO

We present a study of single color (2 + 1) resonance-enhanced multiphoton ionization (REMPI) of H₂O, D₂O, and HDO via several Rydberg states lying in the energy range from 80 000 to 86 000 cm⁻¹. Photoelectron spectra (PES) show that the corresponding cations can be vibrationally state-selected for most vibrational states. The exception is the bend of H₂O⁺ and HDO⁺, where mixing in the REMPI intermediate level results in weak ion intensity and only 50% state purity.     

Polarized absorption spectra and polarized Raman spectra of single crystals of trans(Cl2)-[CoCl2(NH3)n(H2O)4−n]Cl complexes (n = 2, 3, 4)

The title cobalt(III) complexes have been investigated by polarized absorption and Raman spectroscopies of the single crystals. The symmetry properties of the d-electron orbitals and of the vibrational modes attributable to the Raman bands of trans(Cl₂)-[CoCl₂(NH₃)_n(H₂O)_4−n]Cl complexes (n = 2, 3, or 4) were examined to elucidated the peculiar observation that ligand substitution causes no splitting of the 15 200-cm⁻¹ absorption band and the 250-cm⁻¹ Raman band. Effects of replacing the NH₃ ligand with H₂O on the electronic structure, atom–atom force constants and vibrational modes of these complex ions are briefly described.     

FTIR and computational studies of pure and water containing SO3 species in solid argon matrices

The FT infrared spectrum in the 4000–400 cm⁻¹ range of SO₃ vapors, matrix isolated in argon and in water doped argon solid layers, is reported. Vibrational bands are assigned to pure SO₃ monomeric and polymeric species and to SO₃H₂O complexes, on the basis of theoretical B3LYP and MP2 calculations employing the aug-cc-pVTZ basis sets. The spectroscopic evidence suggests that in addition to the monomer, both the dimeric and the cyclic trimeric (SO₃)_n complexes are the only other SO₃ forms present in the matrix. The spectra also indicate the presence of the 1:1 and the 1:2 SO₃·H₂O complexes as well as traces of H₂S₂O₇ and water complexed H₂SO₄, but no evidence for a stable 2:1 SO₃H₂O complex was found. The occurrence of the various species is discussed in the light of their calculated energies.