Lithium insertion property of Li2 2V2O5·nH2O

Lithium vanadium oxides have been prepared by the new solution processing in an aqueous hydrogen peroxide solution with lithium and vanadium alkoxides, LiO-n-C₃H₇ and VO(O-i-C₃H₇)₃, at low temperature, compared with conventional high temperature solid state reaction. Oxides having a layered structure isomorphic to that of γ-phase Li_xV₂O₅ were obtained. This “γ-like phase” oxide can be obtained at the nominal Li/V ratio of 1.5 almost as a single phase. However, formation of ω phase cannot be confirmed. The γ-like phase oxide contained water and organic compounds, and the water content n in Li_xV₂O₅·nH₂O was found to be about 2.4 for the γ-like phase oxide. Further as the result of the atomic absorption spectrometric method, the lithium content x in Li_xV₂O₅·nH₂O was estimated to be 2.2, and water molecules presumably exist in the interlayer space.Water content of the γ-like phase oxides, affects charge and discharge behaviours markedly. The lithium extraction-insertion capacity of the γ-like phase oxides were smaller, but the oxides had higher average potential compared with those of γ-phase oxide. As water content of γ-like phase oxides decreased, the lithium extraction-insertion capacity increased. Moreover, it should be noted that the average potential of γ-like phase oxides is at least 1 V higher than that of γ-LiV₂O₅.     

Structural behaviour of molecular alloys: n-pentacontane (n-C50H102)-n-pentacosane (n-C25H52); n-pentacontane (n-C50H102)-n-tricosane (n-C23H48) at room temperature

This paper displays a study of binary mixtures of n-alkanes whose ratio of chain length is around two. The systems composed of n-tricosane (n-C₂₃H₄₈)-n-pentacontane (n-C₅₀H₁₀₂) and n-pentacosane (n-C₂₅H₅₂)-n-pentacontane (n-C₅₀H₁₀₂) have been studied by means of X-ray analyses. These latter, performed at room temperature, showed in both cases, the existence of a large domain where the phases characteristic of each pure component coexist. These mixtures obey Kravchenko's rule relative to the solubility of the n-alkanes according to the chain length of each component. The mixtures studied do not form an intermediate solid solution. In other words, there is no particular arrangement of the shorter molecules inside the crystallographic unit of the longer.     

Structural-microstructural characterization and optical properties of Eu3+,Tb3+-codoped LaPO4·nH2O and LaPO4 nanorods hydrothermally synthesized with microwaves

Rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄·nH₂O single-crystal nanorods with the compositions La_0.99999-xEu_xTb_0.00001PO₄·nH₂O (x?=?0–0.03), La_0.99999-yTb_yEu_0.00001PO₄·n′H₂O (y?=?0–0.010), and La_0.99999-zTb_zEu_0.000007PO₄·n′′H₂O (z?=?0–0.012) were hydrothermally synthesized with microwaves. It is shown that the Eu³⁺,Tb³⁺ codoping does not affect the thermal stability of these nanorods, which is due to the formation of substitutional solid solutions with both Eu³⁺ and Tb³⁺ replacing La³⁺ in the crystal lattice. Moreover, it is also shown that monazite-type Eu³⁺,Tb³⁺-codoped LaPO₄ single-crystal nanorods can be obtained by calcining their rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄·(n,n′ or n′′)H₂O counterparts at moderate temperature in air, and that they are thermally stable. It is also observed that, for the same Eu³⁺,Tb³⁺-codoping content, the monazite-type Eu³⁺,Tb³⁺-codoped LaPO₄ nanorods exhibit higher photoluminescent efficiency than the rhabdophane-type Eu³⁺,Tb³⁺-codoped LaPO₄· (n,n′ or n′′)H₂O nanorods. Moreover, it is found that the highest photoluminescence emission corresponds to the monazite-type La_0.96999Eu_0.02Tb_0.00001PO₄ nanorods for the La_0.99999-xEu_xTb_0.00001PO₄ system. However, for those compositions energy transfer from Tb³⁺ to Eu³⁺ does not occur. In addition, for an efficient energy transfer to occur, a content of at least 1?mol% Tb³⁺ is needed in all the studied materials.     

Catalytic steam reforming of ethane and propane over CeO2-doped Ni/Al2O3 at SOFC temperature: Improvement of resistance toward carbon formation by the redox property of doping CeO2

Ni/Al₂O₃ with the doping of CeO₂ was found to have useful activity to reform ethane and propane with steam under Solid Oxide Fuel Cells (SOFCs) conditions, 700-900 °C. CeO₂-doped Ni/Al₂O₃ with 14% ceria doping content showed the best reforming activity among those with the ceria content between 0 and 20%. The amount of carbon formation decreased with increasing Ce content. However, Ni was easily oxidized when more than 16% of ceria was doped. Compared to conventional Ni/Al₂O₃, 14%CeO₂-doped Ni/Al₂O₃ provides significantly higher reforming reactivity and resistance toward carbon deposition. These enhancements are mainly due to the influence of the redox properties of doped ceria. Regarding the temperature programmed reduction experiments (TPR-1), the redox properties and the oxygen storage capacity (OSC) for the catalysts increased with increasing Ce doping content. In addition, it was also proven in the present work that the redox of these catalysts are reversible, according to the temperature programmed oxidation (TPO) and the second time temperature programmed reduction (TPR-2) results.During the reforming process, in addition to the reactions on Ni surface, the gas-solid reactions between the gaseous components presented in the system (C₂H₆, C₃H₈, C₂H₄, CH₄, CO₂, CO, H₂O, and H₂) and the lattice oxygen (O_x) on ceria surface also take place. The reactions of adsorbed surface hydrocarbons with the lattice oxygen (O_x) on ceria surface (C_nH_m+O_x→nCO+m/2(H₂)+O_x−n) can prevent the formation of carbon species on Ni surface from hydrocarbons decomposition reaction (C_nH_m⇔nC+m/2H₂). Moreover, the formation of carbon via Boudard reaction (2CO⇔CO₂+C) is also reduced by the gas-solid reaction of carbon monoxide (produced from steam reforming) with the lattice oxygen (CO+O_x⇔CO₂+O_x−1).     

The nucleation and crystallization of MgO-B2O3-SiO2 glass

The nucleation and crystallization of MgO-B₂O₃-SiO₂ (MBS) glass were studied by means of a non-isothermal, thermal analysis technique, X-ray diffraction and scanning electron microscopy. The temperature range of the nucleation and the temperature of the maximum nucleation rate for MBS glass were determined from the dependences of the inverse temperature at the DSC peak (1/T_p) and the maximum intensity of the exothermic DSC crystallization peak ((δT)_p) on the nucleation temperature (T_n). For MBS glass the nucleation occurred at 600-750 °C, with the maximum nucleation rate at 700 °C, whereas the nucleation and crystal growth processes overlapped at 700 °C < T ≤ 750 °C. The analyses of the non-isothermal data for the bulk MBS glass using the most common models (Ozawa, Kissinger, modified Kissinger, Ozawa-Chen, etc.) revealed that the crystallization of Mg₂B₂O₅ was three-dimensional bulk with a diffusion-controlled crystal growth rate, that n = m = 1.5 and that the activation energy for the crystallization was 410-440 kJ/mol.     

Influence of H4SiW12O40 loading on hydrocracking activity of non-sulfide Ni-H4SiW12O40/SiO2 catalysts

The effect of H₄SiW₁₂O₄₀ loading on the catalytic performance of the reduced Ni-H₄SiW₁₂O₄₀/SiO₂ catalysts for hydrocracking of n-decane with or without the presence of thiophene and pyridine is studied. The catalysts were characterized by BET, XRD, Raman, XPS, H₂-TPR, H₂-TPD, NH₃-TPD and FT-IR of pyridine adsorption. It was found that addition of H₄SiW₁₂O₄₀ to the system increases the catalytic activity and the promoting effect is a function of the H₄SiW₁₂O₄₀ loading. The best result was obtained on 5%Ni-50%H₄SiW₁₂O₄₀/SiO₂ catalyst which shows the highest activity for hydrocracking of n-decane and excellent tolerance to the sulfur and nitrogen compounds in the feedstock. The results showed that a suitable amount of H₄SiW₁₂O₄₀ loading on the 5%Ni/SiO₂ catalyst increases the amount of both hydrogen adsorbed and Brønsted acid and Lewis acid sites on the catalyst. The high catalytic performance of the catalyst can be related to the nature of H₄SiW₁₂O₄₀ and the proper balance between metal and acid functions.     

Comparative bioelectrochemical study of two types of myoglobin layer-by-layer films with alumina: Vapor-surface sol-gel deposited Al2O3 films versus Al2O3 nanoparticle films

Two types of layer-by-layer films of myoglobin (Mb) and Al₂O₃ were assembled on different surfaces and compared in Mb electrochemistry and bioelectrocatalysis. One type, designated as {SG-Al₂O₃/Mb}_n, was assembled by alternate deposition of Al₂O₃ by vapor-surface sol-gel method from liquid aluminum butoxide and Mb by adsorption from its solution. Another type, designated as {NP-Al₂O₃/Mb}_n, was constructed by alternate adsorption of Al₂O₃ nanoparticles and Mb from their dispersion or solution in the conventional layer-by-layer way. Quartz crystal microbalance (QCM), UV-vis spectroscopy, and cyclic voltammetry (CV) were used to monitor the growth of the two types of {Al₂O₃/Mb}_n films. UV-vis and IR spectroscopy demonstrated that Mb in both types of {Al₂O₃/Mb}_n films retained its near native structure. While both Mb films assembled on pyrolytic graphite (PG) electrodes exhibited a pair of well-defined, nearly reversible CV reduction-oxidation peaks for Mb heme Fe(III)/Fe(II) redox couple and good electrocatalytic reactivity toward reduction of oxygen and hydrogen peroxide, the {SG-Al₂O₃/Mb}_n films demonstrated distinct advantages over the {NP-Al₂O₃/Mb}_n films in larger maximum surface concentration of electroactive Mb and better biocatalytic performances. This may be mainly attributed to the higher porosity of {SG-Al₂O₃/Mb}_n films than that of {NP-Al₂O₃/Mb}_n films, which may be beneficial to counterion transport in the charge-hopping mechanism and the diffusion of catalytic substrates through the films.     

Combustion synthesis of (Ti1−xNbx)2AlC solid solutions from elemental and Nb2O5/Al4C3-containing powder compacts

Preparation of the (Ti_1−xNb_x)₂AlC solid solution (formed from the M_n+1AX_n or MAX carbides, where n = 1, 2, or 3, M is an early transition metal, A is an A-group element, and X is C) with x = 0.2-0.8 was investigated by self-propagating high-temperature synthesis (SHS). Nearly single-phase (Ti,Nb)₂AlC was produced through direct combustion of constituent elements. Due to the decrease of reaction exothermicity, the combustion temperature and reaction front velocity decreased with increasing Nb content of (Ti_1−xNb_x)₂AlC formed from the elemental powder compacts. In addition, the samples composed of Ti, Al, Nb₂O₅, and Al₄C₃ were adopted for the in situ formation of Al₂O₃-added (Ti,Nb)₂AlC. The SHS process of the Nb₂O₅/Al₄C₃-containing sample involved aluminothermic reduction of Nb₂O₅, which not only enhanced the reaction exothermicity but also facilitated the evolution of (Ti,Nb)₂AlC. Based upon the XRD analysis, two intermediates, TiC and Nb₂Al, were detected in the (Ti,Nb)₂AlC/Al₂O₃ composite and their amounts were reduced by increasing the extent of thermite reduction involved in the SHS process. The laminated microstructure characteristic of the MAX carbide was observed for both monolithic and Al₂O₃-added (Ti,Nb)₂AlC solid solutions synthesized in this study.     

Polymerization of 1,3-butadiene with VO(P204)2 and VO(P507)2 activated by alkylaluminum

The oxovanadium phosphonates (VO(P₂₀₄)₂ and VO(P₅₀₇)₂) activated by various alkylaluminums (AlR₃, R = Et, i-Bu, n-Oct; HAlR₂, R = Et, i-Bu) were examined in butadiene (Bd) polymerization. Both VO(P₂₀₄)₂ and VO(P₅₀₇)₂ showed higher activity than those of classical vanadium-based catalysts (e.g. VOCl₃, V(acac)₃). Among the examined catalysts, the VO(P₂₀₄)₂/Al(Oct)₃ system (I) revealed the highest catalytic activity, giving the poly(Bd) bearing M_n of 3.76 × 10⁴ g/mol, and M_w/M_n ratio of 2.9, when the [Al]/[V] molar ratio was 4.0 at 40 °C. The polymerization rate for I is of the first order with respect to the concentration of monomer. High thermal stability of I was found, since a fairly good catalytic activity was achieved even at 70 °C (polymer yield > 33%); the M_n value and M_w/M_n ratio were independent of polymerization temperature in the range of 40-70 °C. By IR and DSC, the poly(Bd)s obtained had high 1,2-unit content (>65%) with atactic configuration. The 1,2-unit content of the polymers obtained by I was nearly unchanged, regardless of variation of reaction conditions, i.e. [Al]/[V], ageing time, and reaction temperature, indicating the high stability of stereospecificity of the active sites.     

Living cationic random copolymerization of β-pinene and isobutylene with 1-phenylethyl chloride/TiCl4/Ti(OiPr)4/nBu4NCl

The first example of living cationic random copolymerization of β-pinene and isobutylene was achieved with 1-phenylethyl chloride/TiCl₄/Ti(OiPr)₄/nBu₄NCl (TiCl₄/Ti(OiPr)₄ mole ratio: 3/1) initiating system in CH₂Cl₂ at −40 °C. β-Pinene and isobutylene was consumed at almost the same rate, suggesting that the two monomers exhibit almost equal reactivity. At any monomer feed ratio, the number-average molecular weight (M_n) of the copolymers increased in direct proportion to the total monomer conversion, and the molecular weight distribution was relatively narrow (M_w/M_n=1.1-1.2) throughout the reaction. The reactivity ratios determined by the Kelen-Tüdõs method were rβ-pinene=1.1 and r_isobutylene=0.89, which indicated that the composition of copolymer is approximately identical to the monomer feed ratio. The analysis of the structure and sequence distribution of the copolymers by ¹H NMR spectroscopy further confirmed that perfectly random copolymers were obtained by this living cationic polymerization system. The glass transition temperatures of the copolymers obtained with varying monomer compositions were also determined by DSC method.     

Studies on stoichiometry and ionic conductivity of the pyrochlore type Tl1+xTa1+xW1−xO6 . nH2O system

The system Tl_1+xTa_1+xW_1?xO₆. nH₂O with 0 ≤x≤1 has been studied by means of TGA, X-ray diffraction and impedance measurements in the temperature region 300–700 K. The samples possess the cubic pyrochlore structure over the entire compositional and temperature range studied. At 575 K the conductivity σ = 1.4 × 10^?2 (Ω cm)^?1 for x = 0.80. The compositional dependence of the ionic conductivity at this temperature can be described by the equations

and

where a and b are the occupancy factors of the Tl⁺ ions at the crystallographic sites (16d) and (8b), respectively.At room temperature water is reversibly adsorbed. The content increases from n = 0.05 for x = 0 to n = 1.0 for x = 0.75 decreasing thereafter to 0.25 for x = 1. At 298 K the ionic conductivity of Tl_1.75Ta_1.75W_0.25O₆. nH₂O increases from 5.5 × 10^?8 (Ω cm)^?1 to 4.1 × 10^?5 (Ω cm)^?1 as n increases from 0. to 1.0.     

Non-premixed fluidized bed combustion of C1-C4n-alkanes

The non-premixed combustion of C₁-C₄n-alkanes with air was investigated inside a bubbling fluidized bed of inert sand particles at intermediate temperatures: 923 K ? T_B ? 1123 K. For ethane, propane and n-butane, combustion occurred mainly in the freeboard region at bed temperatures below T₁ = 923 K. On the other hand, complete conversion occurred within 0.2 m of the injector at: T₂ = 1073 K. For methane, the measured values of T₁ and T₂ were significantly higher at 1023 K and above 1123 K, respectively. The fluidized bed combustion was accurately modeled with first-order global kinetics and one PFR model to represent the main fluidized bed body. The measured global reaction rates for C₂-C₄n-alkanes were characterized by a uniform Arrhenius expression, while the global reaction rate for methane was significantly slower. Reactions in the injector region either led to significant conversion in that zone or an autoignition delay inside the main fluidized bed body. The conversion in the injector region increased with rising fluidized bed temperature and decreased with increasing jet velocity. To account for the promoting and inhibiting effects, an analogy was made with the concept of induction time: the PFR length (b_i) of the injector region was correlated to the fluidized bed temperature and jet velocity using an Arrhenius expression. These results show that the conversion of C₂-C₄n-alkanes can be estimated with one set of critical bed temperatures and modeled with one Arrhenius kinetics expression.     

Effects of substrates on the capacitive performance of RuOx·nH2O and activated carbon-RuOx electrodes for supercapacitors

The electrochemical energy storage and delivery on the electrodes composed of hydrous ruthenium oxide (RuO_x·nH₂O) or activated carbon-hydrous ruthenium oxide (AC-RuO_x) composites are found to strongly depend on the substrate employed. The contact resistance at the active material-graphite interface is much lower than that at the active material-stainless steel (SS) mesh interface. Thin films of gold plus RuO_x·nH₂O deposited on SS meshes (RuO_x/Au/SS) are found to greatly improve the poor contact between SS meshes and electrode materials. The maximum specific capacitance (C_S,RuOx) of RuO_x·nH₂O, 1580 F g⁻¹ (measured at 1 mV s⁻¹), very close to the theoretic value, was obtained from an AC-RuO_x/RuO_x/Au/SS electrode with 10 wt.% sol-gel-derived RuO_x·nH₂O annealed in air at 200 °C for 2 h. The highly electrochemical reversibility, high-power characteristics, good stability, and improved frequency response of this AC-RuO_x/RuO_x/Au/SS electrode demonstrate its promising application potential in supercapacitors. The ultrahigh specific capacitance of RuO_x·nH₂O probably results from the uniform size distribution of RuO_x·nH₂O nanoparticles, ranged from 1.5 to 3 nm which is clearly observed from the high-resolution transmission electron microscopy (HRTEM).     

Thermoelectric properties of Bi2O3-added WO3 ceramics

Tungsten trioxide (WO₃) ceramics were prepared by firing Bi₂O₃-added WO₃ compacts with atomic ratios of Bi/W?=?0.00, 0.01, 0.03, or 0.05, in which Bi₂O₃ was mixed as a sintering agent. Dense ceramics consisting of remarkably grown WO₃ grains were obtained for Bi-containing samples with Bi/W?=?0.01, 0.03, and 0.05. The grain growth was enhanced by the liquid phase of Bi₂W₂O₉ formed among the WO₃ grains while firing. The XRD patterns did not show evidence for Bi inclusion into the WO₃ lattice, but the SEM-EDX showed an intensive distribution of Bi into the grain boundaries. Electrical conductivity σ and Seebeck coefficient S were measured in a temperature range of 373–1073?K. The temperature dependences indicated that the Bi₂O₃-added WO₃ ceramics were n-type semiconductors. It was considered that the electron carriers were generated from oxygen vacancies included into the WO₃ grains. The thermoelectric power factors S²σ for the ceramics ranged from 1.5?×?10^?7 W?m^?1 K^?2 to 2.8?×?10^?5 W?m^?1 K^?2, and the highest value occurred at 970?K for the ceramic with Bi/W?=?0.01.     

Electrooxidation of acetaldehyde on platinum-modified Ti/Ru0.3Ti0.7O2 electrodes

In this study, the electrochemical oxidation of acetaldehyde was investigated at activated massive DSA^® electrodes in acid medium, using differential electrochemical mass spectrometry (DEMS) and high-performance liquid chromatography (HPLC). The electrodes were prepared either by platinum electrodeposition or by depositing a highly nanodispersive-supported catalyst (Pt and Pt-Ni) over electrode surfaces with a Ti/Ru_0.3Ti_0.7O₂ nominal composition. Bulk electrolysis shows evidence of CO₂ and acetic acid formation. The electrocatalytic efficiency of the electrode material was also investigated as a function of the amount of catalyst added over the DSA^® electrode surface. The presence of RuO₂-active sites on the DSA^® substrate plays an important role in the reaction overall efficiency. The addition of platinum to DSA^® enhances the oxidation of acetaldehyde to CO₂. The role of the substrate on the direct activation of acetaldehyde oxidation is discussed on the basis of the direct application of the metal nanoparticle catalyst over conductive oxide surface based on Magneli phase (mixture of Ti_nO_2n−1 and other phases) from Ebonex^®.     

Facile synthesis of oxazolidinones catalyzed by n-Bu4NBr3/n-Bu4NBr directly from olefins,chloramine-T and carbon dioxide

A binary catalyst system composed of n-Bu₄NBr₃/n-Bu₄NBr was developed for facile synthesis of 5-substituted 2-oxazolidinones with perfect regioselectivity in a single operation directly from olefins, chloramine-T and CO₂. The choice of efficient binary catalysts for two steps, i.e. aziridination and cycloaddition, and the optimization of reaction condition are keys to the one-pot synthesis of 5-substituted 2-oxazolidinones. A possible mechanism for the present one-pot synthesis of oxazolidinones was also proposed.     

Pure and mixed gas CH4 and n-C4H10 permeability and diffusivity in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ permeability coefficients in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures from −20 to 35 °C. CH₄ partial pressures range from 1.1 to 14.6 atm, and n-C₄H₁₀ partial pressures range from 0.02 to 1.8 atm. CH₄ permeability decreases with increasing n-C₄H₁₀ upstream activity (f/f_sat) in the feed. For example, at −20 °C, CH₄ permeability decreases by more than an order of magnitude, from 52,000 to 1700 Barrer, as n-C₄H₁₀ activity increases from 0 to 0.73. In contrast, n-C₄H₁₀ mixed gas permeability is essentially unaffected by the presence of CH₄. The depression of CH₄ permeability in mixtures is a result of competitive sorption and blocking effects, which reduce both CH₄ mixture solubility and diffusivity, respectively. Diffusion coefficients of n-C₄H₁₀ and CH₄ in mixtures were calculated from mixture permeability and mixture solubility data. The CH₄ concentration-averaged diffusion coefficient generally decreases as n-C₄H₁₀ activity increases. On the other hand, the n-C₄H₁₀ diffusion coefficient is essentially unaffected by the presence of CH₄. Pure and mixed gas activation energies of permeation and diffusion of CH₄ and n-C₄H₁₀ are reported. The mixed gas n-C₄H₁₀/CH₄ permeability selectivity increases with increasing n-C₄H₁₀ activity and decreasing temperature, and it is higher than pure gas estimates would suggest. Mixture diffusivity selectivity also increases with increasing n-C₄H₁₀ activity. The difference between pure and mixed gas permeability selectivity arises from both solubility and diffusivity effects. The dual mode mixed gas permeability model describes the mixture permeability data reasonably well for n-C₄H₁₀. However, the model must be modified to accurately describe the methane data by accounting for the decrease in methane diffusivity due to the presence of n-C₄H₁₀ (i.e., blocking). Even though the penetrant concentrations are rather significant at some of the conditions considered, no evidence is observed for phenomena such as multicomponent coupling that would require a model more complex than the binary form of Fick's law. That is, Fick's law in its simplest form adequately describes the experimental data.     

Pure and mixed gas CH4 and n-C4H10 sorption and dilation in poly(1-trimethylsilyl-1-propyne)

Pure and mixed gas n-C₄H₁₀ and CH₄ sorption and dilation in poly(1-trimethylsilyl-1-propyne) (PTMSP) are reported at temperatures ranging from −20 to 35 °C. The presence of n-C₄H₁₀ in the mixture considerably reduces CH₄ solubility. For example, CH₄ solubility (in the limit of zero CH₄ fugacity) at 25°C decreases from 4.0 (pure gas) to 0.78 cm³(STP)/(cm³ polymer atm) in the presence of n-C₄H₁₀ at an activity of 0.60. At −20 °C, CH₄ solubility decreases by almost an order of magnitude, from 10.2 (pure gas) to 1.22 cm³(STP)/(cm³ polymer atm) in the presence of n-C₄H₁₀ at an activity of 0.61. In contrast, n-C₄H₁₀ mixture sorption properties are not measurably affected by the presence of CH₄. The dual mode sorption model parameters for CH₄ and n-C₄H₁₀ in PTMSP were determined from pure and mixed gas sorption measurements, and this model can adequately describe the sorption data. The n-C₄H₁₀/CH₄ mixed gas solubility selectivity in PTMSP decreases as temperature increases and as n-C₄H₁₀ activity increases. For example, at 25 °C, the n-C₄H₁₀/CH₄ solubility selectivity decreases from 250 to 120 as n-C₄H₁₀ activity increases from 0.02 to 0.25. At −20 °C and an n-C₄H₁₀ activity of 0.24, the n-C₄H₁₀/CH₄ solubility selectivity is 590. Penetrant-induced volume dilation of PTMSP can be adequately modeled by assuming that all swelling is caused by penetrant molecules sorbed in the polymer's dense equilibrium region (i.e., the Henry's law region) during sorption. However, the best fit partial molar volumes in the Henry's law region for the dilation data are considerably lower than the penetrant partial molar volumes in liquids, suggesting that further theoretical efforts are needed to develop predictive models of volume dilation in high free volume glassy polymers.     

Conductivity of commercial zirconia electrolytes—I. Ionic and n-type conductivities of 15 m/o CSZ at oxygen pressures of Cr(s)-Cr2O3(s) mixture

The total and n-type conductivities of commercial 15 m/o calcia stabilized zirconia (CSZ) electrolyte have been measured by applying ac and blocking electrode techniques respectively on cells Mo/Cr(s)-Cr₂O₃(s)/CSZ/Cr(s)-Cr₂O₃(s)/Mo and (+) Mo/Cr(s)-Cr₂O₃(s)/CSZ/Pt-Rh 10%/Mo (?).The ionic and n-type conductivity activation energies are reported in the temperature range 1195–1917 K as in the n-type conductivity dependence on the equilibrium oxygen partial pressure of the Cr(s)-Cr₂O₃(s) mixture.The t_ion has been evaluated and chronoamperometric technique to measure it is also reported.Some consideration has been given on the physicochemical behaviour of the Cr(s)-Cr₂O₃(s) mixture deriving from certain anomalies observed in the conductivity trends at the highest temperature values.     

Catalytic effects of NaOH and ZrO2 for partial oxidative gasification of n-hexadecane and lignin in supercritical water☆

Partial oxidative gasification of n-hexadecane (n-C₁₆) and organosolv-lignin (lignin) was studied by use of a batch type reactor in supercritical water: 673 K, 0.52 cm⁻³ of water density (40 MPa of water pressure at 673 K), and 0.3 of O/C ratio for the n-C₁₆ experiments; 673 K, 0.35 cm⁻³ of water density (30 MPa of water pressure at 673 K), and 1.0 of O/C ratio for the lignin experiments. The experiments without O₂ were also conducted for lignin (lignin decomposition). For all the cases (n-C₁₆ partial oxidation, lignin decomposition, lignin partial oxidation), NaOH or zirconia (ZrO₂) was added in the system as catalysts. Through n-C₁₆ studies, the catalytic effect of NaOH and ZrO₂ on partial oxidation in supercritical water were examined. In the case of lignin partial oxidation, we studied the possibility of partial oxidation in supercritical water for gasification technique of wastes. The yield of H₂ from n-C₁₆ and lignin with zirconia was twice as same as that without catalyst at the same condition. The H₂ yield with NaOH was 4 times higher than that without catalyst. Thus, a base catalyst has a positive effect on partial oxidation of n-C₁₆ and lignin to produce H₂. The catalytic effect of NaOH and ZrO₂ was found to be enhancement of decomposition of intermediate (aldehyde and ketone) into CO, through n-C₁₆ studies. In the case of lignin studies, the enhancement of decomposition of the carbonyl compounds by catalytic effect of NaOH and ZrO₂ inhibit char formation and promotes CO and thus H₂ formation.