The role of MgO in the binding of SO<Subscript>2 </Subscript>by lime-containing materials

Summary The results of investigation of MgO participation in the binding of SO₂ with lime-containing materials as sorbents are presented. Experiments of SO₂ binding into solid phase using model samples of reactive grade MgO and CaO varying the mole ratio of MgO/CaO from 9:1 to 1:9 were carried out. Besides, dolomite and limestone samples with different MgO/CaO mole ratio (from 1.24 to 0.13) and samples of ashes formed at combustion of Estonian oil shale (containing 35-40% of carbonates) and its semicoke were studied Initial samples, intermediate and final products were subjected to chemical, IR-spectroscopy, X-ray and BET specific surface area analyses. The results of the present study confirmed the active participation of MgO in the binding of SO₂ into the solid phase. In addition to CaSO₄ the formation of Ca,Mg-double sulphate CaMg₃(SO₄)₄ and -MgSO₄ was observed. The presence of CaMg₃(SO₄)₄ was fixed in a large temperature range 400-900°C and that of -MgSO₄ in between 500-700°C. The optimum temperature range for formation and durability of CaMg₃(SO₄)₄ was 700-800°C.     

CO<Subscript>2</Subscript> and SO<Subscript>2</Subscript> uptake by oil shale ashes

In the present research, CO₂ and SO₂ binding ability of different oil shale ashes and the effect of pre-treatment (grinding, preceding calcination) of these ashes on their binding properties and kinetics was studied using thermogravimetric, SEM, X-ray, and energy dispersive X-ray analysis methods. It was shown that at 700 °C, 0.03–0.28 mmol of CO₂ or 0.16–0.47 mmol of SO₂ was bound by 100 mg of ash in 30 min. Pre-treatment conditions influenced remarkably binding parameters. Grinding decreased CO₂ binding capacities, but enhanced SO₂ binding in the case of fluidized bed ashes. Grinding of pulverized firing ashes increased binding parameters with both gases. Calcination at higher temperatures decreased binding parameters of both types of ashes with both gases studied. Clarification of this phenomenon was given. Kinetic analysis of the binding process was carried out, mechanism of the reactions and respective kinetic constants were determined. It was shown that the binding process with both gases was controlled by diffusion. Activation energies in the temperature interval of 500–700 °C for CO₂ binding with circulating fluidized bed combustion ashes were in the range of 48–82 kJ mol⁻¹, for SO₂ binding 43–107 kJ mol⁻¹. The effect of pre-treatment on the kinetic parameters was estimated.     

Chemisorption of SO<Subscript>2</Subscript> on the Zn-modified In<Subscript>2</Subscript>O<Subscript>3</Subscript> surface

Chemisorption of SO₂ and O₂ on the In₂O₃ surface containing a zinc additive (0.4–2.7 at.%) was studied in a temperature range of 22–200 °C. At least three forms of sorbed SO₂ exist on the modified In₂O₃ surface. The temperature affects the contribution of single forms of SO₂ sorption and, hence, the change in the electric conductivity. The preliminary sorption of O₂ favors the formation of a donor form of chemisorbed SO₂. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2228–2232, October, 2005.     

Interaction of Cl<Subscript>2</Subscript> and SO<Subscript>2</Subscript> with Finely Divided In<Subscript>2</Subscript>O<Subscript>3</Subscript>

The effect of O₂, Cl₂, and SO₂ on electrophysical and sorption properties of powdered In₂O₃ with a large specific area is studied at 23–200°C. The specimen is most sensitive to Cl₂ and SO₂ at near-room temperatures.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 529–536.Original Russian Text Copyright © 2005 by Vinokurova, Derlyukova.     

Effect of the Composition of Modified SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack>/ZrO<Subscript>2</Subscript> on Catalytic Properties in Reduction of NO by Hydrocarbons

We have shown that the activity of cobalt-containing catalysts based on sulfated zirconium dioxide in selective catalytic reduction (SCR) of NO by methane depends on the amount of sulfur and the preparation method. Modification of Fe and Mn improves the catalytic behavior of SO ₄ ²⁻ /ZrO₂ as a result of the increase in the concentration of active sites.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 121–125, March– April, 2005.     

Decarbonization of Natural Lime-containing Materials and Reactivity of Calcined Products Towards SO2 and CO2

The results obtained by studying decarbonization of different samples of Estonian limestone and dolomite and the following sulphation or carbonation of calcined products to estimate their SO2 and CO2 binding ability were presented. Experiments were carried out with thermogravimetric equipment(Q-Derivatograph, MOM and Labsys™, SETARAM) – calcination of the samples in the atmosphere of air with the heating rate 10 K per minute using multiplate crucibles, the following sulphation or carbonation of the calcined products after cooling to the fixed temperature (temperature range 400–900°C) under isothermal conditions in the flow of air-SO₂ or air-CO₂ mixture. Chemical, X-ray, BET nitrogen dynamic desorption, etc. methods for the characterization of the initial samples, intermediate and final products were used. In addition, the possibilities of recurrent use of oil shale ashes taken from different technological points at operating thermal power plants (Estonian and Baltic TTPs, Estonia) as sorbents for SO₂ binding from gaseous phase were studied, as well as the possibilities of activation of these ashes towards SO₂ binding. The results of these studies confirmed the high reactivity of Estonian limestone and dolomite towards SO₂ and CO₂. Dependence of SO₂ binding mechanism on the SO₂ concentration has been established. Modelling of SO₂ capture of dolomite and limestone was carried out to establish the kinetic parameters of these processes. The possibilities of activation of oil shale ashes and their effective recurrent use for binding SO₂ and CO₂ from gaseous phase were confirmed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of phase formation upon the treatment of La<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript> and La<Subscript>2</Subscript>O<Subscript>2</Subscript>SO<Subscript>4</Subscript> in a hydrogen flow

The sequence of phases occurring during treatment of lanthanum sulfate, La₂(SO₄)₃ and lanthanum oxysulfate, La₂O₂SO₄ in a hydrogen flow is established. The temperature ranges in which homogeneous La₂O₂S is produced are revealed: when La₂(SO₄)₃ is a precursor, the range is 770–1220 K; in the case of La₂O₂SO₄, the interval is 950–1220 K. The kinetic curves showing the time dependence of the yield of La₂O₂S is constructed and treated using the Avrami-Erofeev and contracting volume equations. The activation energies of the reactions are determined.     

Phase equilibriums,ion association,and mechanisms of solvation in the LiN(CF<Subscript>3</Subscript>SO<Subscript>2</Subscript>)<Subscript>2</Subscript>-(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>SO<Subscript>2</Subscript> system

The phase diagrams, isotherms of the electrical conductivity, Raman spectra, and time correlation functions of vibrational dephasing are studied for the LiN(CF₃SO₂)₂-(CH₃)₂SO₂ system, which is promising for use as an electrolyte in medium-temperature lithium-ion batteries. The phase diagram of this system contains a broad supercooled region. It is shown that the concentration dependences of the electrical conductivity are typical for solutions of strong electrolytes. The Raman spectra and the time correlation functions of vibrational dephasing for the anion and the solvent indicate that in the supercooling range, cations are weakly solvated by solvent molecules and form ion pairs.     

Simultaneous removal of NO and SO<Subscript>2</Subscript> in a plasma reactor packed with TiO<Subscript>2</Subscript>-coated glass beads

We analyzed the dielectric pellet bed discharge-photocatalyst hybrid process for NO and SO₂ removal. A cylindrical-wire type discharge reactor was packed with glass beads as dielectric pellets and the plasmas were generated by dielectric pellet bed discharge. The TiO₂ photocatalysts were coated onto the glass beads by the dip-coating method and were activated by the light from discharge. Experiments were carried out for three cases: NO removal only, SO₂ removal only, and simultaneous NO and SO₂ removal. As the voltage applied to the plasma reactor increased, or as the residence time increased, the NO and SO₂ removal efficiencies increased. With increasing initial NO and SO₂ concentrations, the NO and SO₂ removal efficiencies decrease. The removal efficiencies for simultaneous NO and SO₂ removal are lower than those for NO only or SO₂ only.     

SO2 binding into the solid phase during thermooxidation of blendsestonian oil shale semicoke

Approximately one million tons of semicoke (SC) is formed and stored in open air dumps every year in the production of shale oil by processing Estonian oil shale (OS). The content of different harmful compounds as sulphides, PAH, phenols, etc. in SC make these dumps one of the most serious sources of environmental contamination. The aim of this work was to study the behaviour of sulphur compounds in OS and its SC, formation of SO₂ and possibilities of binding it into the solid phase during thermooxidation of fuel blends based on SC. Blends modified with SC ash addition were studied as well. It was determined that SO₂ emission in thermooxidation of SC samples started at 280-300°C and proceeded with a steady speed up to 580-600°C and the amount of sulphur evolved was 5-10% from the total content of sulphur in the sample. The amount of SO₂ emitted decreased depending on the mass ratio of the composite fuels from 49-56 to 15-35% during thermooxidation of OS samples studied or their blends with SC, respectively, from 43-80% for coal samples to 13-60% for their blends with SC and to 2-13% during thermooxidation of these blends modified with SC ash addition. In the products of thermooxidation formed at 800-900°C the only sulphur containing phase was CaSO₄, at 650°C also traces of CaS and CaMg3(SO₄)₄ were fixed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrodeposition of PbO<Subscript>2</Subscript>-ZrO<Subscript>2</Subscript> composite materials

The regularities of electrodeposition of composite materials based on PbO₂ containing zirconium dioxide particles are studied. The contents of various phases in the composite depend on the electrolyte composition and conditions of deposition. When a dispersed phase is incorporated into the composite coating, the dimensions of lead dioxide crystals decrease to submicrons.     

Homogeneous catalytic fluoroalkylation of thiophenols,phenols and pyrrole by Freons BrCF<Subscript>2</Subscript>CF<Subscript>2</Subscript>Br and CF<Subscript>2</Subscript>ClCFCl<Subscript>2</Subscript>

The use of sulfur dioxide as an electron transfer mediator in the presence of nitrogen bases permits the rather selective fluoroalkylation of thiophenols, phenols, and pyrrole by Freons BrCF₂CF₂Br and CF₂ClCFCl₂ under mild conditions. In the case of thiophenols, the fluoroalkylation occurs to give polyfluoroalkyl aryl sulfides, while phenols and pyrrole are alkylated in the ring. Effects were found for the electronic structure of the substrates and basicity of the medium (pK_α of the pyridines) on the oxidation-reduction properties of the reagents and the efficiency of the reactions studied. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 315–322, September–October, 2007.     

Glass formation in the Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>-Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system

Glass formation boundaries in the Al₂(SO₄)₃-Al(NO₃)₃-H₂O system were determined. IR spectra were studied. Schemes of structural rearrangements within the boundaries of a second glass formation region in the Al(NO₃)₃-H₂O binary subsystem are suggested. A structure is suggested for glassy Al(NO₃)₃H₂O.     

Calorimetric and volumetric data of nucleating bovine albumin solutions at various NaCl,Li<Subscript>2</Subscript>SO<Subscript>4</Subscript> and (NH4)<Subscript>2</Subscript>SO<Subscript>4</Subscript> concentrations

Summary Heat effects and densities of bovine albumin solutions in Na-acetate buffer pH 4.2 at various NaCl, Li₂SO₄ and (NH₄)₂SO₄ concentrations were determined by a LKB 10700-2 microcalorimeter and an Anton Paar 60/602 densimeter (25&deg;C). The density measurements were made after 1 and 48 h of the dissolution of bovine albumin in the buffer. The correlations between the changes of the enthalpy of salting and apparent molar volumes vs. concentrations of salts were determined.     

Dual course of bisacetonation of D-xylose in a system Me<Subscript>2</Subscript>CO-Me<Subscript>2</Subscript>C(OMe)<Subscript>2</Subscript>-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

In the course of formation of a bisisopropylidene protective group by keeping D-xylose in a mixture Me₂CO-(MeO)₂CMe₂-H₂SO₄ alongside the expected 1,2:4,5-O-diisopropylidene derivative formed minor dimethylacetal, 2,3:4,5-O-diisopropylidene-D-xylose, inseparable from the main product by the chromatography on SiO₂. The conditions were found for the selective formation and isolation of the latter, some its one-pot transformations were studied resulting in synthetically promising orthogonally protected acyclic C⁵-synthons.     

Electrochemical Behavior of Cobalt-Dimethylglyoxime Complex Co(DMG)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript> in the Carbon Dioxide Reduction Process

The electrochemical behavior of a complex of cobalt with dimethylglyoxime Co(DMG)₂(H₂O)₂ is studied by cyclic voltametry. Peaks corresponding to redox transitions Co(III)/Co(II) and Co(II)/Co(I) are observed in the potential region 0.4 to ?1.8 V (Ag/AgCl). The product of reduction of the initial complex interacts with carbon dioxide to form a stable compound, probably an intermediate product of electrocatalytic reduction of CO₂ to CO in the presence of N₄-macrocyclic complexes of cobalt.     

K<Subscript>2</Subscript>SO<Subscript>4</Subscript>-K<Subscript>2</Subscript>HPO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O phase diagram in the region of heterogeneous supercritical fluids

Our experimental study of phase equilibria in the K₂SO₄-K₂HPO₄-H₂O system at temperatures up to 500°C and pressures up to 100 MPa was directed to determine the sequence of phase transformations that generate heterogeneous supercritical fluids whose existence region propagates from the K₂SO₄-K₂HPO₄-H₂O subsystem into the ternary system. We found that supercritical fluids become heterogeneous as a result of addition of K₂HPO₄ starting with l ₁-l ₂ critical phenomena in saturated solutions, with the attendant amalgamation of the stable immiscibility region that propagates from the K₂HPO₄-H₂O system and the metastable liquid-liquid phase separation that originates from the K₂SO₄-H₂O system. Our experimental results and the topological analysis of phase equilibria in the vicinity of the critical point of water gave us the full scenario of the phase behavior of the title ternary system in the region of the subcritical and supercritical parameters of state.     

Study of the combustion mechanism of oil shale semicoke in a thermogravimetric analyzer

Oil shale semicoke, formed in retort furnaces, is a source of severe environmental pollution and is classified as a dangerous solid waste. For the industrial application of oil shale semicoke in combustion, this present work focused on the thermal analysis of its combustion characteristics. The pyrolysis and combustion experiments of semicoke were conducted in a Pyris thermogravimetric analyzer. From the comparison of pyrolysis curves with combustion curves, the ignition mechanism of semicoke samples prepared at different carbonization temperatures was deduced, and was found to be homogeneous for semicoke samples obtained at lower carbonization temperature, shifting to heterogeneous with an increase in the carbonization temperature. The effect of carbonization temperatures and heating rates on the combustion process was studied as well. At last, combustion kinetic parameters of semicoke were calculated with the binary linear regression method, showing that activation energy will increase with increasing the heating rate.     

Study on the non-isothermal kinetics of decomposition of 4Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O<Subscript>2</Subscript>·NaCl

The non-isothermal decomposition kinetics of 4Na₂SO₄·2H₂O₂·NaCl have been investigated by simultaneous TG-DSC in nitrogen atmosphere and in air. The decomposition processes undergo a single step reaction. The multivariate nonlinear regression technique is used to distinguish kinetic model of 4Na₂SO₄·2H₂O₂·NaCl. Results indicate that the reaction type Cn can well describe the decomposition process, the decomposition mechanism is n-dimensional autocatalysis. The kinetic parameters, n, A and E are obtained via multivariate nonlinear regression. The n ^th-order with autocatalysis model is used to simulate the thermal decomposition of 4Na₂SO₄·2H₂O₂·NaCl under isothermal conditions at various temperatures. The flow rate of gas has little effect on the decomposition of 4Na₂SO₄·2H₂O₂·NaCl.     

Glass formation in the Al(IO<Subscript>3</Subscript>)<Subscript>3</Subscript>-Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>-HIO<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system

On the basis of experimental data obtained in the study of glass-formation boundaries in the Al₂(SO₄)₃-HIO₃-H₂O, Al(IO₃)₃-Al₂(SO₄)₃-H₂O, and Al(IO₃)₃-HIO₃-H₂O systems and using geometrical analysis, we predict the positions of glass-formation boundaries in the Al(IO₃)₃-Al₂(SO₄)₃-HIO₃-H₂O four-component system along 60, 40, and 25 wt % H₂O sections.