Predicting the classification characteristics of coal. Part 3. Gross calorific value of dry,ash-free coal

For 63 samples of Ukrainian, Russian, and imported coal, equations for predicting the gross calorific value Q_s^daf on the basis of the following coal characteristics are developed: W^a, O_d^daf, Q_s^af, and C_ar. The error is within the standard tolerances (σ ≤ 0.3 MJ/kg). With sufficient accuracy, Q_s^daf may be predicted from equations based on petrographic characteristics such as the vitrinite reflectance, the content of liptinitegroup minerals, and the sum of lean macerals (I + 2Sv/3). In these equations, the coefficients correspond to the heat of combustion of the vitrinite components at different metamorphic stages, the liptinite, and the lean macerals.     

Structure of a biologically active binuclear palladium complex,bis(bis[(μ<Subscript>2</Subscript>-cysteine)(2,2′-dipyridyl)-palladium(II)]) · hexanitrates · novemhydrates

The structure of a biologically active binuclear palladium complex, namely, [(dipy)Pd(μ-cysH) (μ-cys)Pd(dipy)]³⁺ · 3NO ₃ ^? · 4.5H₂O (dipy = 2,2′-dipyridyl, C₁₀H₈N₂; cys = cysteine, C₃H₇NO₂S), has been determined from X-ray diffractometry data. The compound crystallizes in the triclinic system, symmetry space group P1, with the unit cell parameters a = 13.863(1) Å, b = 13.819(1) Å, c = 12.170(1) Å, α = 122.13(1)°, β = 103.61(1)°, γ = 91.40(1)°, V = 1887.02 ų, Z = 2, and ρ = 1.82 g/cm³. The final discrepancy factor is R1 = 0.0495 for 12884 symmetrically nonequivalent reflections with F ₀ ≥ 4σ(F ₀), wR2 = 0.1071, and GooF = 0.978. The unit cell contains two chemically equivalent but crystallographically independent positively charged binuclear palladium complexes, six NO ₃ ^? anions, and nine water molecules. The π-π stacking interaction between the nearest pyridyl rings of the neighboring layers takes place. Moreover, the interlayer and intralayer interactions occur through van der Waals interactions and a complex three-dimensional system of hydrogen bonds, which are formed by water molecules, NH ₃ ⁺ groups, and carboxyl groups.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.     

Structure of a biologically active binuclear palladium complex in the compound (bis[(μ<Subscript>2</Subscript>-2-chloroethylammonium)(1,10-phenanthroline)-palladium(I)]) · tetranitrates · hydrate

The structure of a biologically active palladium complex [(1,10-phenanthroline)Pd(μ₂-2-chloroethylammoniu)] ₂ ⁴⁺ · 4NO ₃ ^? · H₂O has been determined from the diffractometric data. The compound crystallizes in the triclinic crystal system, space group of symmetry P \(\bar 1\), with the unit cell parameters a = 12.8352(8) Å, b = 14.4040(8) Å, c = 12.1668(9) Å, α = 116.16(1)°, β = 115.72(1)°, γ = 91.09(1)°, V = 1756.3 ų, Z = 2, and ρ = 1.892 g/cm³. The final reliability factor is R ₁ = 0.0351 for 7357 nonequivalent reflections with I ≥ 2σ(I), wR ₂ = 0.0970, and S = 1.044. The asymmetric part of the unit cell contains one positively charged binuclear palladium complex, four NO ₃ ^?1 anions, and one water molecule. The nanocomplexes are involved in the stacking π-π interaction by pairs: each complex forms a stacking with only one adjacent complex. The interaction between layers and inside each layer occurs through the van der Waals interactions and a three-dimensional system of hydrogen bonds, which are formed by the N ₃ ⁺ groups and water molecules.     

Structure of a biologically active binuclear palladium complex in the compound bis(bis[(μ<Subscript>2</Subscript>-2-chloroethylammonium) (1,10-phenanthroline)-palladium(I)]) · octanitrates · dihydrates

The structure of a biologically active binuclear palladium complex, namely, [(1,10-phenanthroline) Pd(μ₂-2-chloroethylammonium) ₂ ⁴⁺ · 4NO ₃ ^? · H₂O, has been determined using X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group of symmetry Cc, with the unit cell parameters a = 24.527(3) Å, b = 13.097(1) Å, c = 22.651(3) Å, β = 104.23(1)°, V = 7052(2) ų, Z = 8, and ρ = 1.88 g/cm³. The final discrepancy factor is R1 = 0.0316 for 15581 symmetrically nonequivalent reflections with I ≥ 2σ(I), wR2 = 0.0513, and GooF = 1.047. The palladium atoms reside in the oxidation state of 1+, which is rarely encountered in organometallic compounds. The asymmetric part of the unit cell contains two chemically equivalent but crystallographically independent positively charged binuclear palladium complexes, eight NO ₃ ^? anions, and two water molecules. The π-π stacking interaction between the nearest 1,10-phenanthroline rings of the neighboring layers takes place. Moreover, the interlayer and intralayer interactions occur through electrostatic interaction forces and a complex three-dimensional system of hydrogen bonds, which are formed by water molecules and N ₃ ⁺ groups.     

EPR and optical studies on binary mixed alkali-alkaline earth oxide borate glasses doped with Cu<Superscript>2+</Superscript> ions

Mixed alkali alkaline earth oxide borate glasses of the composition (25 – x)Li₂O–xK₂O–12.5BaO–12.5MgO–49B₂O₃–1CuO (x = 0, 5, 10, 15 and 20 mol %) were prepared by the melt quenching technique. The X-ray diffractograms of all the glass samples were recorded at room temperature. Peak free X-ray spectra revealed the amorphous nature of all the prepared glasses. Modulated differential scanning calorimetry (MDSC) was used to determine the glass-transition temperature (T _g ). The probable mixed alkali effect was investigated using experimental techniques like density, molar volume, MDSC, electron paramagnetic resonance (EPR), and optical absorption studies. From the EPR spectra the spin-Hamiltonian parameters were evaluated. The spin-Hamiltonian parameter values indicated that the ground state of \(C{u^{2 + }}is{\kern 1pt} {d_{{x^2} - {y^2}}}\) orbital (²B_1g) and the site symmetry around Cu² is tetragonally distorted octahedral. The variation of g _|| and A _|| as a function of Li₂O content was found to be nonlinear. A broad optical absorption band was observed in all the glasses containing Cu² ions corresponding to ²B_1g → ²B_2g transition. From the optical absorption studies the values of the optical band gap (E _opt) for indirect, direct transitions and Urbarch energy (ΔE) have been evaluated. By co-relating the EPR and optical absorption data, bonding parameters α², β² and β ₁ ² were evaluated.     

IR Spectroscopy in Rank and Group Assignment of Coal

The possibility of express determination of the characteristics V _IR ^daf , R_{o, IR}, y_IR, ΣLC_IR, and A _IR ^d used in the ranking of coal on the basis of IR spectroscopy is assessed for a specific example: Kuznetsk coals of different maceral composition and metamorphic development. The IR characteristics are compared with values obtained by standard methods (V^daf, R_{o, r, y}, ΣLC, and A^d).     

Synthesis and crystal structure of a new oxohalide CdPb<Subscript>2</Subscript>O<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

A new compound, CdPb₂O₂Cl₂, is synthesized by the method of solid-phase reactions. The compound has monoclinic symmetry, space group C2/m, a = 12.392(8) Å, b = 3.8040(14) Å, c = 7.658(5) Å, β = 122.64(5)°, and V = 304.0(3) ų. The structure contains one symmetrically independent position of the Pb²⁺ cation coordinated by three O^2? anions (Pb²⁺-O^2? = 2.29–2.34 Å) and five Cl^? anions (Pb²⁺-Cl^? = 3.35–3.57 Å). The Cd²⁺ cation has a symmetric coordination with the formation of two bonds Cd-O = 2.15 Å and four bonds Cd-Cl = 2.73 Å. The oxygen atom is tetrahedrally coordinated by three Pb²⁺ cations and one Cd²⁺ cation, which leads to the formation of oxo-centered heterometallic OPb₃Cd tetrahedra. The tetrahedra are linked together into chains through common Pb atoms and into layered complexes due to sharing of the equatorial Cd atoms. The chlorine atoms are located above the cavities of the oxo-centered layer.     

Structure of a catalytically active oxo-centered trinuclear cobalt complex triaqua-(μ<Subscript>3</Subscript>-oxo)-hexa(μ<Subscript>2</Subscript>-pivalato-O,O′)-tricobalt(III)

The structure of a catalytically active oxo-centered trinuclear cobalt complex, namely, [triaqua-(μ₃-oxo)-hexa(μ₂-pivalato-O,O′)-tricobalt(III)]¹⁺ · NO ₃ ^? · 3H₂O, has been determined using X-ray diffraction analysis. The compound crystallizes in the hexagonal crystal system, space group of symmetry P6₃/mmc, with the unit cell parameters a = 12.328(1) Å, c = 22.625(1) Å, V = 2978.1(4) ų, Z = 2, and ρ = 1.075 g/cm³. The final discrepancy factor is R1 = 0.0596 for 589 symmetrically nonequivalent reflections with I ? 2σ(I), wR2 = 0.1612, and GooF = 1.035. The high-symmetry complex [C₃₀H₆₀O₁₆Co₃]¹⁺ with symmetry D _6h and a diameter of ～11 Å is an oxo-centered trinuclear cluster consisting of three symmetrically equivalent Co(III) atoms. Among the oxo-centered trinuclear metal complexes known to date, this complex has the highest symmetry and differs by the presence of two chemically equivalent bridges between the metal atoms. Apart from the two positively charged symmetrically equivalent trinuclear complexes, the unit cell contains two symmetrically equivalent NO ₃ ^? ions (statistically disordered over four positions) and six crystal water molecules.     

Moisture-holding capacity of coals

As a result of a comprehensive study of 63 samples of coal concentrates (from Ukraine, Russia and countries outside the former Soviet Union), it was established that the prediction of the moisture-holding capacity of coals can be appropriately performed according to their values of W ^a, R ₀, O _d ^daf , and O _s ^daf . It was found that the oxidation of coal increased its moisture-holding capacity; however, in this case, the absolute change in this parameter was smaller than the error of its determination (0.5%). Therefore, upon the oxidation of almost 30% of the organic matter of coal, the moisture-holding capacity increased by only 0.4%. There is a close correlation between the maximum moisture capacity of coals and the water pore volume, and this correlation was described by a linear equation in the studies.     

Effect of heat transfer conditions on the critical pressure of metal ignition in oxygen

Experimental data on the critical pressure of ignition of titanium alloy fragments in gaseous oxygen are analyzed. The fragments are obtained after fracture of alloy samples in the dynamic mode (p₂^*) and under natural convection conditions (p₁^*). The results are analyzed with allowance for the heat transfer coefficients from material ignition initiators under similar conditions. Based on the shape of the experimental thermograms of plate cooling, the coefficient of heat transfer from microcraters with a juvenile surface formed due to knockout of metal particles from the plate by the high-velocity flow is found: α₂ ≈ 11 kW(m² ·K). The value of α₂ is close to the value of this coefficient calculated with the use of the coefficient α₁ ≈ 5 kW/(m² · K) of heat transfer from titanium rod microfragments (with the size of the order of metal grains) formed during titanium rod fracture in oxygen under conditions of natural convection with allowance for the ratio p₂^*/p₁^*.     

Crystal structure of Pb<Subscript>6</Subscript>O[(Si<Subscript>6</Subscript>Al<Subscript>2</Subscript>)O<Subscript>20</Subscript>]

The crystal structure of Pb₆O[(Si₆Al₂)O₂₀)] is investigated using X-ray diffraction. The compound has tetragonal symmetry, space group I4/mmm, a = 11.7162(10) Å, c = 8.0435(12) Å, and V = 1104.13(2) ų. The structure is refined to R ₁ = 0.036 for 562 unique reflections with [F ₀] ≥ 4σF. The structure contains two symmetrically independent positions of the Pb²⁺ cations coordinated by five O atoms (Pb²⁺-O^2? = 2.34–2.68 Å). The TO₄ tetrahedra (T = Si, Al) form tubular [(Si₆Al₂)O₂₀] chains extended along the c axis. The O₄ oxygen atom is not bonded to the Si and Al atoms and is octahedrally coordinated by six Pb atoms with the formation of an oxo-centered OPb₆ octahedron. The assumption is made that, in some of lead silicate and aluminosilicate glasses, a number of oxygen atoms are located outside the tetrahedral structure and represent segregation centers of the Pb²⁺ cations due to the formation of oxo-centered complexes.     

Properties of the solid thermolysis products of brown coal impregnated with an alkali

The mechanism of formation of a porous active carbon framework is considered, and the properties of the solid thermolysis products of brown coal (Aleksandriisk deposit, Ukraine) with potassium hydroxide are studied. The yields of the solid thermolysis products (Y _STP, %) and potassium humates, the rate of the interaction of the solid thermolysis products with KOH at 700–900°C, the specific surface areas (S _BET, m²/g), the adsorption capacities for methylene blue (A _MB, mg/g) and iodine (A _I, mg/g), and the specific activities of surface areas A _MB ^′ = A _MB/S _BET and A _I ^′ = A _I/S _BET (mg/m²) are determined under variation of the KOH/coal ratio (R _KOH < 18 mol/kg) and temperature (110–900°C).     

Partition of <Emphasis Type="Italic">n</Emphasis>-Butanol Among Phases and Solubilization Ability of Winsor type III Microemulsions

The partition of n-butanol in Winsor type III (W-III) microemulsions was investigated in this work. Three kinds of anionic surfactants (sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (DSS), and sodium dodecyl benzene sulfonate (SDBS)) and two kinds of anionic/cationic surfactant mixtures (SDS/octadecyl trimethyl ammonium chloride (OTAC) mixtures and DSS/OTAC mixtures) were studied. Internal standard gas chromatography was employed in n-butanol content analysis. The results showed that no water exists in the excess oil (EO) phase and no oil exists in the excess water (EW) phase. For the W-III microemulsions obtained by salinity scanning, relatively constant n-butanol content in the EO (11–12 v%) and EW (1–4 v%) was found under different salinities. Accurate measurement of n-butanol content in each phase is important for those systems having low solubilization ability. For the W-III microemulsions prepared using SDS/OTAC surfactant mixture, the percentage of n-butanol distributed into the interfacial layer decreased while the fraction of n-butanol in the interfacial layer first increased sharply and then tended to be stable with the addition of n-butanol. For the different optimum W-III microemulsion systems tested, most of the surfactant-to-alcohol molar ratio data are near 1:3, but obvious deviation could be observed for some data. On the basis of the accurate measurement of n-butanol content in the EO and EW phases, the standard free energy, ΔG _o→in ^* (T = 298.15 K) of n-butanol transferring from the EO phase to the interfacial region was calculated. The results show negative ΔG _o→in ^* values. For microemulsions with the same components, n-butanol content is an important factor influencing the ΔG _o→in ^* value, and a high absolute value of ΔG _o→in ^* leads to high solubilization ability.     

Reusability and selective adsorption of Pb<Superscript>2+</Superscript> on chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-<Emphasis Type="Italic">co</Emphasis>-acrylic acid) hydrogel

Reusability and selective adsorption toward Pb²⁺ with the coexistence of Cd²⁺, Co²⁺, Cu²⁺ and Ni²⁺ ions on chitosan/P(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic acid) [CS/P(AMPS-co-AA)] hydrogel, a multi-functionalized adsorbent containing –NH₂, –OH, –COOH and –SO₃H groups was studied. The CS/P(AMPS-co-AA) was prepared in aqueous solution by a simple one-step procedure using glow discharge electrolysis plasma technique. The reusability of adsorbent in HNO₃, EDTA-2Na and EDTA-4Na was investigated in detail. The competitive adsorption of the metal ions at the initial stage was compared between their equal mass concentration and equal molar concentration. In addition, the adsorption mechanism of the adsorbent for adsorption of Pb²⁺ was also analyzed by XPS. The results showed that the optimum pH of adsorption was 4.8, and time of adsorption equilibrium was about 180 min. Adsorption kinetics fitted well in the pseudo second-order model. The equilibrium adsorption capacities of Pb²⁺, Cd²⁺, Co²⁺, Cu²⁺, and Ni²⁺ at pH 4.8 were obtained as 673.3, 358.3, 176.7, 235.0 and 171.7 mg g^?1, in their given order. The adsorbent displayed an excellent reusability using 0.015 mol L^?1 EDTA-4Na solution as the eluent, and the desorption ratio could not correctly reflect the true characteristics of adsorption/desorption process. Moreover, the adsorbent showed good adsorption selectivity for Pb²⁺. The molar adsorption capacity at the initial stage with equal molar concentration was more reliable than the mass adsorption capacity during the study of selective adsorption. According to the XPS results, the adsorption of Pb²⁺ ions by the CS/P(AMPS-co-AA) absorbent could be attributed to the coordination between N atom and Pb²⁺ and ion-exchange between Na⁺ and Pb²⁺.     

Modulating the Aggregation Behavior of 1-Methyl-3-Octylimidazolium Chloride by Alcohols in Aqueous Media

The self-organization and aggregation behavior of a surface active ionic liquid (SAIL) 1-methyl-3-octylimidazolium chloride [C₈mim]Cl, was investigated in aqueous solutions of alcohols 1,2-propanediol and 1-propanol in different compositions using conductivity, surface tension and fluorescence measurements at room temperature. This surface active ionic liquid was synthesized by the reaction of 1-methylimidazole with 1-chlorooctane. Fluorescence spectroscopy was employed to get detailed insight into the local microenvironment of the aggregates, critical aggregation concentrations (CAC) and aggregation number (N _agg.). Degree of ionization (α), CAC and various thermodynamic parameters like the standard Gibbs free energy of aggregation (ΔG _agg. ⁰ ), standard enthalpy of aggregation (ΔH _agg. ⁰ ) and standard entropy of aggregation (ΔS _agg. ⁰ ) were calculated using conductivity measurements at different temperatures (288.15, 298.15 and 308.15 K). The surface activity of the IL in various mixed solvents was evaluated from surface tension measurements by calculating various surface parameters like the minimum surface area occupied by a single ionic liquid molecule (A _min), adsorption efficiency (pC ₂₀), maximum excess concentration at the surface (Γ _max), effectiveness of surface tension reduction(Π _CAC), surface tension at CAC (γ _CAC), p (packing parameter) and CAC at different compositions. Increases in the CAC values were observed with the increase in the amount of alcohols which is attributed to the balancing between electrostatic and hydrophobic interactions. The results from different techniques show that the CAC increases with increase in the amount of the alcohol which is due to the solubilization of the IL molecules which delays the aggregation process. This shows that the spontaneity of the aggregation process of IL decreases with the increase in the concentration of alcohols in water.     

On the critical displacement of excited kinetic units in liquids and glasses

The critical displacement of an atom (a group of atoms) in inorganic glasses Δr _m, which corresponds to the maximum of the interatomic attractive force, is calculated using available data on the surface tension and elastic constants. It is found that the critical atomic displacement Δr _m is close in order of magnitude to the linear dimension of the activation volume of atomic excitation v _h ^1/3 for glasses in the As-S and Ge-As-S systems with a chain structure and is considerably less than the value of v _h ^1/3 for alkali silicate glasses and glasses in the Cd-As system with a structure involving ionic sublattices. A relationship for calculating the activation volume of the atomic excitation from data on the glass transition temperature and elastic constants is derived within the model of an excited state.     

Parameters of luminescence and the local structure of Eu<Superscript>3+</Superscript> centers in fluorogermanate glasses

The influence of the chemical nature of the local environment of Eu³⁺ ions on the parameters of luminescence of these centers in glasses of the (BaGeO₃)_{1 ? x ? y} (Al₂O₃) _x (0.45CaF₂ · 0.55MgF₂) _y (x = 0.25, y = 0; x = 0.17, y = 0.17; x = 0.15, y = 0.22; x = 0.07, y = 37.00; x = 0, y = 0.45) system is investigated. The oxidation state of europium atoms and the degree of homogeneity of their local environment in the glasses are determined using ¹⁵¹Eu Mössbauer spectroscopy.     

Excess volume and excess enthalpy of binary mixtures composed of 1,2-dichloropropane and 1-alkanol (C5-C8)

The excess molar volumes and excess molar enthalpies at T=298.15 K and atmospheric pressure for the binary systems {CH₃CHClCH₂Cl (1)+CH₃(CH₂) _n?1OH (2)} (n=5 to 8) have been determined over the whole range of composition from the density and heat flux measurements using a digital vibrating-tube densimeter and an isothermal calorimeter, respectively. The measured excess molar volumes of all binary mixtures showed positive symmetrical trend with values increasing with chain length of 1-alkanol. Similarly, excess enthalpy values of all binary mixtures showed skewed endothermic behavior with values increasing with chain length of 1-alkanol. The maxima of excess molar enthalpy values were observed around x₁=0.65 with excess enthalpy value ranging from 1,356.8 J/mol (1-pentanol) to 1,543.4 J/mol (1-octanol). The experimental results of both H _m ^E and V _m ^E are fitted to a modified version of Redlich-Kister equation using the Padé approximant to correlate the composition dependence. The experimental H _m ^E data were also fitted to three local-composition models (Wilson, NRTL, and UNIQUAC). The correlation of excess enthalpy data in these binary systems using UNIQUAC model provides the most appropriate results.     

Kinetics of Sedimentation of a Coagulating Suspension

The coagulation–sedimentation kinetics in a spatially heterogeneous disperse system is theoretically analyzed. The expression for the suspension concentration c as a function of time t and depth h is obtained in the form c ～ t ^?ε h ^εν. The concentration of the dispersed phase formed in coagulant hydrolysis depends on the coagulant concentration c ₀ as c ～ c ₀ ^{? γ} . It is determined how the exponents in the expressions derived are related to the characteristics of the coagulation kinetics and the aggregate size distribution. The results obtained are compared with published experimental data.