Behaviour of the FeOSH system under coal liquefaction conditions

The behaviour of the iron-sulphur system in the presence of water and hydrogen under coal liquefaction conditions has been investigated by using a high-pressure differential thermal analysis technique. The iron compounds used were Fe₂O₃, Fe₃O₄ and FeS₂. DTA was performed under 10.1 MPa (initial pressure) N₂ or H₂, heating to 450 °C (2.5 °C min⁻¹). Sulphate ions were detected by BaCl₂ addition to the product aqueous solution; sulphides were formed as gaseous and solid products. The results suggest that the catalytic behaviour of the sulphate and sulphides formed under the conditions employed must be considered for the iron-sulphur system in coal liquefaction.     

Stabilite thermodynamique des phases dans le systeme CaOAl2O3CO2H2O

The paper presents a theoretical investigation on the nature of thermodynamical stable precipitating phases in the CaOAl₂O₃CO₂H₂O system when monocalcium aluminate (CA) with or without an excess of lime or alumina is mixed with water in equilibrium with gaseous carbon dioxide. Basing on the nature of ions in solution (A10₂⁻, Ca⁺⁺, CO_{3_}⁻⁻, OH⁻ and H⁺). and supposing that only $\text{C}\text{C}$, AH₃, CH, CAH₁₀, C₂AH₈ and C₄ACH₁₁ are the possible stable phases, the system was mathematically described taking into account the values of solubility products, the equilibrium between atmospheric carbon dioxide and the solution, ionic dissociation constant of water, matter balance of calcium and aluminate ions and condition of the solution electroneutrality. For a given system of initial parameters, computer calculation has allowed to determine the only possible solid-liquid system among the 22 theoretically possible cases (zero, one or two solids in equilibrium with the solution). So, varying the initial parameters has led to draw isobaric and isosteric phase diagramms, what shows that, in the conditions of the study, CAH₁₀ is the only stable phase at 21°C. The result suggests that the precipitation of C₂AH₈ and $\text{C}{}_4\text{A}\text{C}\text{H}{}_{11}$ can only be a consequence of saturations of the solution with respect to CAH₁₀.     

Passivity of iron and nickel in a CH3OHOH2OH2SO4 system

The passivity of iron and nickel has been investigated in methanolic solutions of sulphuric acid with various water content. The stable oxide-hydroxide film can be formed on the metal surface only in the solutions with the molar ratio of acid to water lower than 1:4. In the solutions with higher ratio water molecules are bound in the hydratation shell of hydrogen ions. In such solutions the anodic behaviour of iron and nickel is similar to the behaviour of these metals in aqueous concentrated solutions of sulphuric acid. A thick unprotective anodic layer covers the nickel surface during anodic polarization whereas iron undergoes anodic dissolution without forming an anodic film.     

Effect of NaCl or NaOH on the formation of CSH

Formation field and composition of CSH in the presence of NaCl and/or NaOH were investigated to clarify their effects on the durability of concrete. The CSH and other hydrates were prepared from the mixtures of various solutions. The silica gel, CSH and calcium hydroxide are precipitated in turn with increasing initial Ca/Si mole ratio of mixture. On the formation of hydrate, the liquid composition moves to and then situates on each solubility product curve regardless of ionic species or concentration. The CSH formed in this experiment has lower Ca/Si mole ratio than that of normal CSH formed in water and contains sodium ion. However, this CSH easily returns to normal CSH after dispersing in water. These characteristic of CSH are confirmed thermodynamically.     

Electrochemical and thermal behaviour of solid AgIAgIO3 and AgIAg3AsO4

Solid AgIAgIO₃ and AgIAg₃AsO₄ of various compositions were investigated by conductivity, thermal and electrochemical methods. Both systems show dependences on composition and temperature enabling determination of the activation energy of conductivity. Glassy phases are formed at appropriate rates of cooling of molten samples. By thermal analysis (DSC), the glass transition and crystallization processes of the glassy phases were identified. Processes of anodic and cathodic decomposition of the electrolyte were investigated. The energy of activation for the cathodic redox (Ag⁺ → Ag) process was determined. It was also shown how the capacity of the Pt/electrolyte phase boundary depends on the dc potential and ac frequency.     

Characterization of a soldering system consisting of a glass from the system CaOAl2O3B2O3SiO2 and wollastonite

In this work, the characterization of a soldering system with wollastonite as filler added as powder to the powdered base glass is shown. A soldering system consisting of the base glass and a coexisting crystalline phase is created which is then pressed to pellets and sintered to maximum density.Wollastonite increases the thermal expansion coefficient of the base glass after sintering the samples. In the present paper, the sintering behavior of the soldering system and possible interactions between glass and filler are analyzed. Also, density and porosity after sintering and the resulting crystalline phases are characterized.The mixtures with wollastonite contents up to 30% showed suitable sintering behavior and good density (low porosity). From 40% wollastonite on, the sintering of the samples was not satisfying and porosity was still high after sintering. The main crystalline phases were anorthite, wollastonite and pseudowollastonite, which occurred in all samples. This shows that all three phases are coexisting phases of the glass composition.     

Separation of COCO2N2 gas mixture for high-purity CO by pressure swing adsorption

A pressure swing adsorption (PSA) process for separating CO from a COCO₂N₂ mixture is proposed. The adsorbent used in this process is active carbon supported copper, which has been developed by this laboratory. By cycling the pressure of a bed of this adsorbent between ambient pressure and 20–30 Torr at room temperature, high purity CO can be obtained from the COCO₂N₂ gas mixture with a high recovery. The CO product purity depends crucially on the step of CO cocurrent purge after adsorption in the cycle and the regeneration of sorbent.     

Study of carbon deposits formed on an AlCoMo catalyst during hydrocracking and hydrorefining using derivatography

• 1.1. Carbon deposits formed on an industrial AlCoMo catalyst, in model reactions from n-heptane, cyclohexane, benzene, styrene and cumene were examined. The amount of carbon deposited is influenced considerably by the type of feed hydrocarbon, and by the duration and temperature of contact with the catalyst.
• 2.2. Thermal decomposition studies of concentrates of these carbon deposits reveals that their weight decreases within the range of 13·5 to 16·6 wt.%, and that the gaseous reaction products contain hydrogen and methane.
• 3.3. Comparison of the temperature ranges of reaction of carbon deposits and standard carbon-containing substances with ambient oxygen, suggests that the structure of carbon deposits is similar to the structure of natural carbon. No carbon-black or graphite-like fragments were found in the structure of carbon deposits.

     

Epoxidation of ethylene over AgNaCl catalysts

Epoxidation of ethylene over sodium chloride-doped and granular sodium chloride-supported silver catalysts was performed at atmospheric pressure using conventional flow reactors. Although the stationary activity was somewhat low, each type of catalyst has shown high selectivity, 84–87%, under an ethylene-rich atmosphere. The selectivity was almost independent of reaction temperature, contact time, and catalyst composition. The total reaction rate rose exponentially with temperature until an apparent activation energy of 75.3 kJ mol⁻¹ was obtained. Under oxygen-rich atmospheres, marked drops in activity were observed. In exposing the deactivated catalysts to a stream of hydrogen, carbon dioxide was desorbed. The strongly enhanced adsorption of carbon dioxide promoted the formation of silver chloride. Silver particles on the granular sodium chloride were homogeneously dispersed and ~200 nm in size. In addition, the crystallite size of silver was 43–50 nm, which was not altered after the reaction or even after heating at 673 K in oxygen gas. In a pulse reaction using an ethylene-rich gas mixture, acetaldehydes other than ethylene oxide were formed, and, as the catalyst surface had been oxidized by irreversible adsorption of oxygen, the formation of carbon dioxide was promoted and that of acetaldehyde decreased.     

Electrical properties of electroless NiP thin films

The influence of the pH and temperature of the electroless solution on the electrical characteristics of the deposited NiP thin films has been determined. The phosphorous content of the films increases when the pH of the solution is decreased giving rise to a diminution of the temperature coefficient of the resistance (TCR). Low TCR films (TCR ⩽ 100 ppm °C⁻¹ are obtained for pH = 3.4. In this pH range the deposition rate can be increased by heating the electroless solution to moderate temperatures.     

Blackening of magnesia grains in MgOC refractory

MgO grains in MgOC refractory usually blacken after being used at high temperature. In this paper, the cause and mechanism of blackening of the MgO grains were investigated. Fused MgO crystal grains, which are generally used in MgOC refractory, contain many micropores below 1 μm in size. When the MgO grain with micropores is heated in an atmosphere with high partial pressure of Mg, i.e. with low partial pressure of O₂, Mg diffuses from the grain surface to the micropores, and excess Mg condenses during cooling. Blackening of the MgO grain is caused mainly by condensation of Mg in the microdefects — in particular, in the micropores.     

Oxydehydrogenation of propane catalyzed by VSiO cogels: enhancement of the selectivity to propylene by operation under cyclic conditions

The selectivity to propylene in the oxydehydrogenation of propane is improved when the reaction is carried out under cyclic, redox-decoupled conditions rather than under stationary, co-feeding conditions, and using vanadium oxide dispersed in silica as the catalyst. However, the improvement in selectivity is possible only in samples having a V content which is lower than 10 wt% V₂O₅. This points out the importance of having dispersed vanadium oxide to limit the consecutive combustion of propylene.     

Influence of milling time on the synthesis,microstructure and mechanical properties of ZrB2SiCZrO2f ceramic composites

Zirconium diboride toughened by silicon carbide and zirconia fiber (ZrB₂SiCZrO_2f) was prepared by using planetary ball mill and the effect of milling time was investigated. The results showed that both the length of fiber and particle size of ZrB₂SiC-matrix were reduced as the ball milling time increased. When milling time varied from 8 h to 12 h, the accumulated fibers and agglomerated particles were observed. The production of a homogeneous ceramic could be successfully achieved by using a combination of 20 h milling time and hot-pressing at 1850 °C for 60 min under a uniaxial load of 30 MPa. The optimal flexural strength and fracture toughness of the hot-pressed ZrB₂SiCZrO_2f ceramics reached 1084 MPa and 6.8 MPa m^1/2, respectively. The main toughening mechanisms were fiber debonding, fiber pull-out and transformation toughening. The results indicated that the ball milling technique was proposed as a potential and simple method to obtain usable quantities of ZrB₂SiCZrO_2f ceramic.     

Intrinsic stress evolution in diamond films prepared in a CH4H2NH3 hot filament chemical vapor deposition system

The intrinsic stress in diamond films prepared in a CH₄H₂NH₃ hot filament chemical vapor deposition system has been investigated by the substrate curvature technique as a function of film thickness (2.2–50 μm) and ammonia concentration (0–1.4%). Our results indicated that the film stress changed from compressive to tensile with the increase of film thickness and diamond quality at a constant ammonia concentration of 0.5%. The existence of a non-diamond phase was found to be beneficial to the relaxation of intrinsic tensile stress in the films. The intrinsic stress in diamond films was tensile at an ammonia concentration from 0 to 1.4%, while the maximum tensile stress existed at 0.75% NH₃. The possible origin of intrinsic tensile stress was discussed.     

Densification and characterization of SiO2B2O3CaOMgO glass/Al2O3 composites for LTCC application

A glass/ceramic composite using lead-free low melting glass (SiO₂B₂O₃CaOMgO glass) with Al₂O₃ fillers was investigated. X-ray diffraction analysis revealed that the anorthite and cordierite phase appeared in the sintered composites. The dilatometric analysis showed that the onset of shrinkage took place at ∼624 °C for all the samples and the onset temperature was independent on the content of glass. The low melting glass significantly promoted densification of the composites and lowered the sintering temperature to ∼875 °C. The addition of 50 wt% glass sintered at 875 °C showed ε_r of 7.3, tan δ of 1.15×10⁻³, TEC of 5.41 ppm/°C, thermal conductivity of 3.56 W/m °C, and flexural strength of 184 MPa. The results showed that the SiO₂B₂O₃CaOMgO glass/Al₂O₃ composites were strong potential candidates for low temperature cofired ceramic substrate applications.     

Hydrocracking of Athabasca bitumen over binary metal oxide (SiO2MoO3 and CoO/SiO2MoO3) catalysts

The hydrocracking of Athabasca bitumen was studied over SiO₂MoO₃ (80: 20wt%), 2.92 and 5.54 wt% CoO on SiO₂MoO₃, and commercially available CoOMoO₃/Al₂O₃ catalysts at temperatures in the range 648–698 K for 2 h under an initial hydrogen pressure of 7.0 M Pa in a batch reactor. The reaction products were separated into coke, asphaltenes, resins, aromatics, saturates and gases. The severity of cracking increased with increased reaction temperature. At 698 K, asphaltene and resin yields were low (0.59 and 13.22 wt%, respectively) and gas yields high (40.5 wt%). SiO₂MoO₃ and CoO/SiO₂MoO₃ catalysts showed higher activity than commercial CoOMoO₃/Al₂O₃ catalyst in the conversion of heavy fractions (asphaltenes and resins) and in the formation of light fractions (saturates and aromatics).