Mechanism of the formation of carbon oxides under conditions of the oxidative chlorination of methane: III. Kinetics of the reaction of CCl<Subscript>4</Subscript> with oxygen on copper-containing salt catalysts

The kinetics of the oxidative dechlorination of CCl₄ on two supported catalysts for methane oxychlorination (CuCl₂-KCl and CuCl₂-KCl-LaCl₃) at 350–425°C was studied using a gradientless method. Although these catalysts exhibited different activities, the rate of reaction on them was described by one exponential equation at the same activation energy of E ≈ 26.3 kcal/mol. A two-path reaction mechanism was proposed, which involved the dissociative adsorption of initial reactants and chlorine with the formation of phosgene and the oxidation of phosgene to CO₂. The occurrence of two types of active sites on the catalyst surface was assumed.     

Thermochemical Properties of Dissolution of Nicotinic Acid C<Subscript>6</Subscript>H<Subscript>5</Subscript>NO<Subscript>2</Subscript>(s) in Aqueous Solution

Nicotinic acid (also known as niacin) was recrystallized from anhydrous ethanol. X-ray crystallography was applied to characterize its crystal structure. The crystal belongs to the monoclinic system, space group P2₍₁₎/c. The crystal cell parameters are a = 0.71401(4) nm, b = 1.16195(7) nm, c = 0.71974(6) nm, α = 90°, β = 113.514(3)°, γ = 90° and Z = 4. Molar enthalpies of dissolution of the compound, at different molalities m/(mol·kg^?1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. The molar enthalpy of solution at infinite dilution was calculated, according to Pitzer’s electrolyte solution model and found to be \( \Delta_{\text{sol}} H_{m}^{\infty } = ( 2 7. 3 \pm 0. 2) \) kJ·mol^?1 and Pitzer’s parameters (\( \beta_{{\text{MX}}}^{{\text{(0)}L}} \), \( \beta_{{\text{MX}}}^{{\text{(1)}L}} \) and \( C_{{\text{MX}}}^{\phi L} \)) were obtained. The values of apparent relative molar enthalpies (\( {}^{\phi }L \)) and relative partial molar enthalpies (\( \overline{{L_{2} }} \) and \( \overline{{L_{1} }} \)) of the solute and the solvent at different molalities were derived from the experimental enthalpy of dissolution values of the compound. Also, the standard molar enthalpy of formation of the anion \( {\text{C}}_{ 6} {\text{H}}_{ 4} \text{NO}_{2}^{-} \) in aqueous solution was calculated to be \( {\Delta_{\text{f}}^{} H}_{\text{m}}^{\text{o}} ({\text{C}}_{ 6} {\text{H}}_{ 4} {\text{NO}}_{2}^{-} \text{,aq}) = - \left( {603.2 \pm 1.2} \right)\;{\text{kJ}}{\cdot}{\text{mol}}^{-1} \).     

Hydration and proton transport in solid solutions based on Ba<Subscript>2</Subscript>CaWO<Subscript>6</Subscript>

Hydrated alkaline-earth metal tungstates Ba₄Ca_{2 + x} W_{2 ? x} O_{12 ? 2x} with perovskite structure were studied by the thermogravimetry, ¹H NMR, IR, and Raman spectroscopy methods. Electrical conductivity and transfer numbers were measured with varying T, \(p_{O_2 } \) and \(p_{H_2 O} \). The solid solutions are capable of reversibly intercalating water and can exhibit high-temperature proton transport. The localization of protons on oxygen results in the appearance of energetically nonequivalent OH groups; a small fraction of protons are present in the form of H₂O and H₃O⁺.     

Structure of the Cu(Salen) molecule Cuo<Subscript>2</Subscript>N<Subscript>2</Subscript>C<Subscript>16</Subscript>H<Subscript>14</Subscript> according to gas-phase electron diffraction data and quantum chemical calculations

In the framework of synchronous gas-phase electron diffraction and mass spectrometry experiment, the saturated vapor of N,N′-ethylenebis(salicylaldiminate) copper(II) CuO₂N₂C₁₆H₁₄ is studied at a temperature T 574(5) K. It is found that evaporation is congruent and the saturated vapor consists of monomeric molecules. Electron diffraction data are proved to correspond to the geometric model for the CuO₂N₂C₁₆H₁₄ molecule of C ₂ symmetry with an almost planar structure of the CuN₂O₂ coordination fragment and internuclear distances \(r_{h_1 } \)(Cu-O) = 1.917(13) Å and \(r_{h_1 } \)(Cu-N) = 1.931(15) Å. The stuctural parameters obtained are compared to those quantum chemically calculated and molecular parameters in crystals.     

Crystal structure of CsNbMoO<Subscript>6</Subscript>

Single crystals of CsNbMoO₆ were grown from solution in melt, and their crystal structure was solved by X-ray diffraction (R[I > 2σ(I)]₁ = 0.0386). Crystals were cubic, а = 10.41039(8) Å, Z = 8, space group \(F\bar 43m\). The synthesized crystals were shown to exhibit the second harmonic generation effect, which confirmed the absence of an inversion center in the structure. The structure was built of MO₆ (M = Nb, Mo) octahedra, which share all vertices to form a three-dimensional framework where niobium and molybdenum atoms are randomly distributed. Framework interstices accommodate cesium ions. Crystals of CsNbMoO6 can be considered as pseudo-symmetric with respect to space group \(Fd\bar 3m\) due to a small shift of some oxygen atoms relative to the regular system of points in this group.     

Ab initio investigation of the lower-energy candidate structures for (H<Subscript>2</Subscript>O)<Subscript>10</Subscript><Superscript>+</Superscript> water cluster

Low-lying structures of water cationic clusters and the compounds with the OH radical have become a hot topic in recent years. We here investigate the cluster \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \) and calculate its ideal structures by the quantum chemical calculation together with the particle swarm optimization method. We analyzed the properties of the obtained lower-energy isomers of \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \). Their energies are further re-optimized and demonstrated at three different methods with two basis sets. Based on our numerical calculations, a new cage-like structure of \( {\left({\mathrm{H}}_2\mathrm{O}\right)}_{10}^{+} \) with the lowest energy is obtained at MP2/aug-cc-pVDZ level. Our results showed the comparison of energy order at different conditions and demonstrated the influence of temperature on the relative Gibbs energy and IR spectra. Moreover, we also contained the molecule orbitals to discuss the stability of these representative isomers.     

Crystal and molecular structure of ammonium trinitratouranylate NH<Subscript>4</Subscript>[UO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>]

Ammonium trinitratouranylate NH₄[UO₂(NO₃)₃] (I) single crystals have been synthesized by the reaction of aqueous solutions of diaquadinitratouranyl tetrahydrate and ammonium nitrate in the presence of nitric acid. The structure of the complex has been studied by X-ray diffraction analysis: space group \(R\bar 3c\), a = 9.361(2), c = 18.883(4) Å; V = 1433.0(5) ų, and Z = 6. The structural units of the NH₄[UO₂(NO₃)₃] crystal—NH ₄ ⁺ cations and [UO₂(NO₃)₃]^? complex anions with three bidentate cyclic nitrato groups—are on crystallographic axes \(\bar 3\). A complex three-dimensional packing arranged by the electrostatic attraction forces between counterions and the N-H...O hydrogen bonds between ammonium cations and trinitratouranylate anions is realized in the structure. X-ray diffraction analysis results are confirmed by IR spectra of NH₄[UO₂(NO₃)₃].     

Synthesis of nanocrystalline ZnO by the thermal decomposition of [Zn(H<Subscript>2</Subscript>O)(O<Subscript>2</Subscript>C<Subscript>5</Subscript>H<Subscript>7</Subscript>)<Subscript>2</Subscript>] in isoamyl alcohol

It was studied how the conditions of heat treatment of a [Zn(H₂O)(O₂C₅H₇)₂] solution in isoamyl alcohol at 120–140°C for 2–60 min affect the precursor decomposition mechanism and the characteristics of the obtained nanocrystalline zinc oxide. In all the cases, the product was a crystalline substance with the wurtzite structure and a size of crystallites of 14–18 nm, which was independent of the synthesis conditions. The thermal behavior and microstructure of the separated and dried nanostructured ZnO powder were investigated. It was determined how the duration and temperature of the heat treatment of the precursor solution affects the microstructure of ZnO coatings dip-coated onto glass substrates using dispersions produced at 120 and 140°C. The nanosized ZnO application procedure was shown to be promising for creating a gas-sensing layer of chemical gas sensors for detecting 1% H₂ (\(R_0 /R_{H_2 } \) was 58 ± 2 at an operating temperature of 300°C) and 4 ppm NO₂ (\(R_{NO_2 } /R_0\) were 15 ± 1 and 1.9 ± 0.1 at operating temperatures of 200 and 300°C, respectively).     

Thermal analysis of earlywood and latewood of larch (<Emphasis Type="Italic">Larix gmelinii</Emphasis> (Rupr.) Rupr.) found along the Polar tree line

This work introduces a new method of calculations depending on the essential assumptions of the kinetic methods, with the least amount of approximations to find the apparent kinetic parameters calculated for the crystallization of the Se₉₀Te₁₀ powders with heterogeneous particle sizes and shapes under non-isothermal conditions. The apparent kinetic parameters calculated by the new method are compared with that calculated blindly by applying Málek’s method, ignoring its applicability condition of invariant activation energy. The new method is based on the assumption that the kinetic function \(f\left( \alpha \right)\) parameters are independent of the heating rate \(\beta\) and time \(t\), and the fitting temperature function is assumed to be in the approximated form \(K\left( T \right) = K\left( {t,\beta } \right) = ct^{\text{r}} \beta^{\text{s}}\). The exponents \(r\) and \(s\) are calculated isoconversionally, while the constant \(c\) and the kinetic function \(f\left( \alpha \right)\) parameters are calculated by a curve fitting method using a generalized form of the ?esták and Berggren function, considering the steadily and logarithmic acceleration and deceleration of the curve. According to the data in this work, the fitting temperature function can be roughly approximated to the form \(K\left( T \right) \approx c/t\) which work in with the physical dimensions of the rate constant. Moreover, the Arrhenian and the non-Arrhenian parameters, which describe the fitting temperature function \(K\left( T \right)\), are calculated isoconversionally. The deduced parameters work harmonically together to perfectly fit the experimental and the true data.     

Synthesis and structural organization of ruthenium(IV) cluster Li<Subscript>8</Subscript>Ru<Subscript>2</Subscript>OCl<Subscript>14</Subscript> and its catalytic properties in the water oxidation reaction

The synthesis of binuclear ruthenium(IV) oxochloride complex and reaction of the latter with LiCl in a 2.5 M HCl solution have been carried out. The reaction of Ru(IV) binding in solution leads to the formation of a new cluster compound Li₈Ru₂OCl₁₄ (I) whose molecular structure has been determined by X-ray diffraction. The crystals are tetragonal, space group \(I\bar 42m\), a = 7.08 Å, c = 17.00 Å, V = 852.18 ų, Z = 2. Supramolecular structural self-organization of I includes the formation of layers parallel to the xy plane. The high thermal stability of complex I and retention of its dinuclear structure in an acidic environment have been shown by thermal analysis and IR and electronic spectroscopy. It has been found that cluster I is an efficient catalyst for water oxidation in artificial photosynthesis.     

Syntheses and crystal structures of [Bi(DMSO)<Subscript>8</Subscript>][Fe(NCS)<Subscript>6</Subscript>] and [Al(DMSO)<Subscript>6</Subscript>][Al(NCS)<Subscript>6</Subscript>]

New complexes of composition [Bi(DMSO)₈][Fe(NCS)₆] (1) and [Al(DMSO)₆][Al(NCS)₆] (2) have been prepared, and an octahedral hexarodanoaluminate anion has been structurally characterized for the first time. Crystals of compound 1 are triclinic, space group \(P\bar 1\), a = 11.2368(4) Å, b = 11.4063(4) Å, c = 21.0711(9) Å, α = 92.9520(10)°, β = 99.9430(10)°, γ = 111.9290(10)°, V = 2447.69(16) ų, Z = 2, ρ_calc = 1.680 g/cm³, R ₁ = 0.0564; crystals of compound 2 are cubic, space group \(Pa\bar 3\), a = 15.8201(4) Å, V = 3959.39(17) ų, Z = 4, ρ_calc = 1.462 g/cm³, R ₁ = 0.0475. The bismuth coordination polyhedron BiO₈ in compound 1 is a distorted square antiprism with broken square faces (Bi-O, 2.368-2.582 Å). In the structure of 2, the cation disordered in a complex manner has an octahedral configuration (Al-O, 1.888(11)-1.912(11) Å).     

<Emphasis Type="Italic">Ab initio</Emphasis> study of scandium fluoride molecules: ScF,ScF<Subscript>2</Subscript>, AND ScF<Subscript>3</Subscript>

Equilibrium geometric parameters, normal mode frequencies and intensities in IR spectra, atomization enthalpy, and relative energies of low-lying electronic states of scandium fluoride molecules (ScF, ScF₂, and ScF₃) are calculated by the coupled-cluster method (CCSD(T)) in triple-, quadruple, and quintuple-zeta basis sets with the subsequent extrapolation of the calculation results to the complete basis set limit. The ScF molecule is also studied by the CCSDT technique. The error in the approximate calculation of triple excitations in the CCSD(T) method does not exceed 0.002 Å for the equilibrium internuclear distance R _e, 4 cm^?1 for the vibrational frequency, and 0.2 kcal/mol for the dissociation energy of the molecule. In the ground electronic state \(\tilde X^2 \) A ₁(C _2ν ) of ScF₂ molecules, R _e(Sc-F) = 1.827 Å and α_e(F-Sc-F) = 124.2°; the energy barrier to bending (linearization) h = E _min(D _g8h ) ? E _min(C_2ν) = 1652 cm^?1. The relative energies of Ã²Δ _g and \(\tilde B^2 \)Π _g electronic states are 3522 cm^?1 and 14633 cm^?1 respectively. The bond distance in the ScF₃ molecule (\(\tilde X^1 \) A′₁, D _3h ) is refined: R _e(Sc-F) = 1.842 Å. The atomization enthalpies Δ_at H ₂₉₈ ⁰ of ScF _k molecules are 139.9 kcal/mol, 289.0 kcal/mol, and 444.8 kcal/mol for k = 1, 2, 3 respectively.     

Conductivity and thermal expansion of the Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>1.9</Subscript> solid electrolyte in the oxidizing and reducing atmospheres

Highly compact (99%) solid electrolyte Ce_0.8Gd_0.2O_1.9 with submicron (0.3 μm) grains is synthesized. The dilatometric (20–850°C) and conductivity (180–350°C) measurements are performed on the electrolyte in air and as a function of the partial oxygen pressure \(p_{O_2 } \) (0.21?1×10^?25 atm) at 600, 700, and 800°C. An inflection is found in the temperature dependences of the thermal coefficient of linear expansion and conductivity (impedance measurements) at ～230°C, which is the evidence for a phase transition. The activation energies for conduction in the grain bulk and boundaries differ only slightly, indicating that the grain boundaries’ resistance is caused not by the precipitation of the second phase at the boundaries, but most probably by the presence of intergranular nanopores. The dilatometric measurements confirm a significant increase in the linear dimensions of Ce_0.8Gd_0.2O_1.9 in the reducing atmospheres with a parallel increase in its electron conductivity. The electron conductivity and specific elongation increase proportionally to \(p_{O_2 }^{ - 1/4} \) at all temperatures. The \(p_{O_2 } \) values, at which the transport numbers of ions t _i = 0.5, are determined. They are 10^?22.5, 10^?20, and 10^?18 atm at 600, 700, and 800°C, respectively.     

Combined Application of Optical Emission Spectroscopy and Kinetic Numerical Modelling to Determine the Ions Densities in a Flowing N<Subscript>2</Subscript> Post-Discharge

The combined application of optical emission spectroscopy (OES) and kinetic numerical modelling was employed to determine the N₂⁺(X²\( \Sigma_{\text{g}}^{ + } \)), N₃⁺, and N₄⁺ densities in the post-discharge (pink afterglow; PA) of a nitrogen flowing DC discharge. We measured the relative densities of the N₂(C³Π_u) and N₂⁺(B²\( \Sigma_{\text{u}}^{ + } \)) states along the post-discharge region by OES. The density values were attained as functions of the post-discharge residence time. We fitted the experimental densities with densities calculated from a kinetic numerical model developed to calculate the temporal density of several nitrogen species in the nitrogen afterglow. Analysis of the rate balance equations of these ions indicated that these densities can be determined from data generated from both the model and experimental N₂⁺(B²\( \Sigma_{\text{u}}^{ + } \)) density. Thus, we determined the ions density profiles in the nitrogen post-discharge and observed that the N₃⁺ density is dominant in the PA. This is followed by that of the N₂⁺(X²\( \Sigma_{\text{g}}^{ + } \)) and N₄⁺ ions. Such behaviour has been previously reported in a study that employed mass spectrometry to analyse the ions in the PA generated by a nitrogen high-frequency discharge. In our study, the DC discharge was operated at a gas flow rate of 0.9 Slm^?1, a discharge current of 30 mA, and a gas pressure range of 400–700 Pa.     

Transport selectivity of carbonate and chloride ions througha strongly alkaline anion-exchange membrane before and after its modification with sodium alginate

The transport selectivity of carbonate ions relative to chloride ions \(\left( {P_{Cl^ - }^{CO_3^{2 - } } } \right)\) through an anion-exchange membrane during electrodialysis is investigated before and after the membrane was modified by the electrolytic precipitation of sodium alginate on its surface, as well as by pretreating the membrane in a solution of sodium alginate. It is established that the experimental value of \(P_{Cl^ - }^{CO_3^{2 - } } \) is appreciably smaller than the calculated value for the unmodified membrane at low values of current density. At large currents the calculated value of \(P_{Cl^ - }^{CO_3^{2 - } } \) is 0.83, and the experimental value is 0.64. During electrodialysis of the working solution, which contains sodium alginate at a concentration of 1–2 g l^?1, \(P_{Cl^ - }^{CO_3^{2 - } } \) decreases by 2–3 times in the current-density range 0.25–1 A dm^?2. Pretreatment of the membrane in a solution of sodium alginate having a concentration of 10 g l^?1 for 72 h decreases \(P_{Cl^ - }^{CO_3^{2 - } } \) from 0.50 (unmodified membrane) to 0.35.     

Solvent extraction of calcium and strontium into nitrobenzene by using synergistic mixture of hydrogen dicarbollylcobaltate and diphenyl-<Emphasis Type="Italic">N</Emphasis>-butylcarbamoylmethyl phosphine oxide

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^?) in the presence of diphenyl-N-butylcarbamoylmethyl phosphine oxide (DPBCMPO, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, \( {\text{HL}}_{2}^{ + } \), \( {\text{ML}}_{2}^{2 + } \), \( {\text{ML}}_{3}^{2 + } \) and \( {\text{ML}}_{4}^{2 + } \) (M²⁺ = Ca²⁺, Sr²⁺) are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined. In the considered nitrobenzene medium, it was found that the stability of the \( {\text{SrL}}_{2,{\text{org}}}^{2 + } \) complex is somewhat higher than that of species \( {\text{CaL}}_{2,{\text{org}}}^{2 + } \), while the stability constants of the remaining strontium complexes \( {\text{SrL}}_{3,{\text{org}}}^{2 + } \) and \( {\text{SrL}}_{4,{\text{org}}}^{2 + } \) are smaller than those of the corresponding complex species \( {\text{CaL}}_{n}^{2 + } \) (n = 3, 4).     

High-pressure defect phase Nd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

A perovskite-like oxide Nd _x Cu₃V₄O₁₂ (space group Im \(\bar 3\) Z = 2, a = 7.278–7.322 Å) with cationic vacancies was prepared for the first time under triaxial compression of p = 6.0–9.0 GPa at 700–1300°C. The compound has a metal-type conductivity, paramagnetic properties, and a phase transition.     

Theoretical prediction of the new high-density lithium boride LiB<Subscript>11</Subscript> with polymorphism and pseudoplasticity

We predict the possibility of existence of the new lithium boride LiB₁₁ with polymorphism. For energy reasons, the preferred type is α′-LiB₁₁ (trigonal space group R3m, a _h = 0.4982 nm, c _h = 1.1123 nm, z _h = 3, ρ = 2.63 g/cm³), with a framework built of tetrahedra and one-capped octahedra. α′-LiB₁₁ is pseudoplastic because of twinning via the high-symmetry state of α-LiB₁₁ (cubic space group \(F\bar 43m\), a = 0.6810 nm, z = 4, ρ = 2.65 g/cm³) and a bipolaron semiconductor. α → α′ transition is accompanied by the 0.0627-nm displacement of 1/11 B atoms. The β′ polymorph (tetragonal space group \(I\bar 4m2\), a = 0.4404 nm, c = 0.7708 nm, ρ = 2.80 g/cm³) is transformation hardened because of the transition to the α′ phase. We infer that LiB₁₁ formation is possible under high pressure.     

Sodium perborate/NaNO<Subscript>2</Subscript>/KHSO<Subscript>4</Subscript>-triggered synthesis and kinetics of nitration of aromatic compounds

Sodium perborate (SPB) was used as efficient green catalyst for NaNO₂/KHSO₄-mediated nitration of aromatic compounds in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds was achieved under both conventional and solvent-free microwave conditions. Reaction times were comparatively shorter in the microwave-assisted than conventional reaction. The reaction kinetics for nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [Phenol], [NaNO₂], and [SPB]. Reaction rates accelerated with introduction of electron-donating groups but retarded with electron-withdrawing groups. Kinetic results did not fit well quantitatively with Hammett’s equation. Observed deviations from linearity were addressed in terms of exalted Hammett’s constants (\( \bar{\sigma } \) or σ_eff), para resonance interaction energy (ΔΔG_p) parameter, and Yukawa–Tsuno parameter (r). This term provides a measure of the extent of resonance stabilization for a reactive structure that builds up charge (positive) in its transition state. The observed negative entropy of activation (?ΔS^#) suggests greater solvation and/or cyclic transition state before yielding products.