Fuel cells are attractive energy conversion devices with high efficiencies and low emissions, and many studies have been conducted so far. Among them, fuel cells operating at 200-600°C are promising technologies which combine the many advantages of high- and low-temperature fuel cells. However, they have not been developed due to the lack of good ionic-conductors with high thermal stability at intermediate temperatures. Recently, we have developed new proton-conductive electrolytes consisting of solid acid and pyrophosphate, and evaluated their electrochemical, structural and thermal properties at intermediate temperatures. For the composite based on CsH2PO4/SiP2O7, the interfacial chemical reaction between CsH2PO4 and SiP2O7 during heat-treatment gave rise to the formation of a new phase of CsH5(PO4)2. The temperature dependence of conductivity for this composite was different from that for pure CsH2PO4, and the maximum conductivity achieved was 44 mS·cm−1 at 266°C. Using potassium and rubidium salts, MH2PO4 (M = K, Rb), as the solid acids for the composite electrolytes, analogous phenomena were confirmed despite the alkaline metal. Operation of a fuel cell employing CsH2PO4/SiP2O7-based composite electrolyte (thickness: ca. 1.3 mm) was demonstrated at 200°C and generated electricity up to 220 mA·cm−2 at 0.2 V. CsH5(PO4)2 composites with SiP2O7 and SiO2 were fabricated, and the composite effects were investigated at intermediate temperatures based on conductivity measurement, thermal analysis, and wettability evaluation. The melting and dehydration processes of CsH5(PO4)2 in composites were different depending on the matrix species. The composite with SiP2O7 matrix showed the highest conductivity of all composites. The conductivity of the composites appears to correlate with the wettability between the components as examined by contact angle measurement. These findings should be attributed to the differences in the interfacial interactions between CsH5(PO4)2 and the matrix.
Much attention has been devoted to efforts to operate polymer electrolyte fuel cells (PEFCs) at temperatures above 100°C in order to avoid the problem of serious CO poisoning of the anode catalyst. It is also of great concern to operate PEFCs under low-humidity conditions, because the space and energy required for external humidification are eliminated or minimized in the fuel cell system. Thus, proton-conducting materials that can satisfy the above criteria have been proposed, developed, and evaluated worldwide. In particular, recent research efforts have been increasingly focusing on the design of anhydrous proton conductors, since these materials, at least in principle, do not need the presence of water as a charge carrier. We have recently found that In, Al, or Mg-doped SnP2O7 show high proton conductivities>10−1 S·cm−1 between 150 and 350°C under water-free conditions. Attempts to apply these materials as electrolytes in some electrochemical devices were also made. This paper presents an overview of the current status of doped SnP2O7 with principal emphasis on the materials aspect. In addition, the benefits of intermediate-temperature fuel cells using these materials are briefly summarized in terms of cell design, electrolyte and electrode materials.
New proton conductive solid acid composites were prepared by mechanical milling. First, the formation of highly proton conductive cesium-containing sulfate-phosphate double salt composites, and their phase transition are described. Second, a mechanochemical synthesis of "cesium ortho-oxosalt-heteropoly acid composites," and the relationship between proton conductivity and hydrogen bonding network in the composites are discussed. Mechanochemical treatment of mixtures of cesium hydrogen sulfate (CsHSO4) and cesium dihydrogen phosphate (CsH2PO4) using a planetary type of ball mill formed Cs3(HSO4)2(H2PO4) and Cs5(HSO4)3(H2PO4)2. Cs3(HSO4)2(H2PO4) and Cs5(HSO4)3(H2PO4)2 were transformed to the higher temperature phase of Cs2(HSO4)(H2PO4) by heating at around 100°C. Proton conductivity of the treated compound remarkably increased on heating to 2×10−3 S·cm−1 at around 180°C, whereas no steep decrease was observed on cooling. The high proton conductivity was ascribed to the presence of the high temperature phase of Cs2(HSO4)(H2PO4). Milling of Cs-containing ortho-oxosalts (Cs2SO4, Cs2CO3 or CsHSO4) and phosphotungstic acid (H3PW12O40·6H2O: WPA-6) mixtures obtained partially substituted CsxH3−xPW12O40 composites. Chemical durability and proton conductivity of the resultant composites markedly improved under both humidified and dried conditions. In addition, mechanochemically prepared 90CsHSO4·10WPA-6 (mol%) composite maintained high proton conductivity from room temperature to 180°C. Conductivity of the composite was 3.3×10−3 S·cm−1 at 100°C under dry atmosphere, much higher than those of pure CsHSO4 (4×10−7 S·cm−1) and WPA-6 (1×10−7 S·cm−1). The –O(H)···O hydrogen bonding distance in the CsHSO4–WPA-6 composites was estimated from the 1H-isotropic chemical shift of 1H MAS NMR spectra. Proton conductivities of CsHSO4–WPA-6 composites under dry atmosphere were strongly related to the bond distance.
Never before have refiners faced the challenges caused by dramatic changes in crude prices and refinery margins. However some worldwide trends have not changed, such as the need to shift refinery product distributions to a more diesel-oriented slate and to reduce residue fuel oil production. The required shift from gasoline to distillate fuels cannot be accomplished solely by modifications to current hydrocracking or FCC operations. New technologies will be required that achieve higher non-distillable conversion and increased selectivity to distillate-range products. Ideally, these technologies should be both cost-effective and commercially proven. UOP has responded to the needs for increased distillate yield and non-distillable conversion with the introduction of its latest residue upgrading technology offering, the UOP Uniflex Process. This high-conversion slurry hydrocracking technology contains elements of a commercially-proven slurry reaction system and the UOP UnicrackingTM and UnionfiningTM technologies. The Uniflex Process can achieve non-distillable conversion levels in excess of 90 wt% with distillate yield over 50 vol%. This paper discusses the features of the Uniflex Process technology, its yield and economic advantages over conventional residue upgrading technologies, and other applications of the technology.
Immiscible liquid dispersions are widely used in chemical process, petroleum industries, polymerization, heterogeneous chemical synthesis, etc. In most of these chemical processes, the rate of inter-phase heat and mass transfer is known to strongly affect the overall performance and depends on the interfacial contact area between the phases. This study at CFD simulations of immiscible liquid dispersion has been performed on a vertical pipe. With specific reference to dispersed liquid-liquid flows, it was seen that the two-fluid approach (Eulerian-Eulerian approach) was extensively used for multiphase modeling, especially when detailed predictions are desirable over a range of holdups in exchange for a reasonable amount of computation power. The results of CFD predictions for water as a continuous and kerosene as a dispersed phase have been compared with the experiments of Farrar and Bruun and Al-Deen and Bruun. These simulations have also been done to understand the effect of various significant forces in turbulent liquid dispersions (drag, lift, turbulent dispersion and added mass). Several expressions for these forces were tested in order to choose the best combination. Further, the problem has been simulated using two different turbulence models. It has been found that lift force is more important than turbulent dispersion and added mass. Inter-phase closure guidelines for liquid-liquid bubbly flows were developed based on simulation results that yielded the best agreement with experimental data.
A nascent surface has high activity to catalyze the decomposition of lubricants under boundary lubrication conditions. The effects of sulfur-containing, nitrogen-containing, phosphorus-containing additives and phosphate-containing ionic liquid were investigated on the decomposition of synthetic hydrocarbon oil (multialkylated cyclopentane, MAC). The decomposition processes of the lubricants on the nascent surface of bearing steel AISI 52100 were investigated using a ball-on-disk friction tester in a vacuum chamber with a quadrupole mass spectrometer. Three parameters related to the decomposition process were observed: the induction period for the decomposition, the desorption rate of gaseous products, and the critical load for the activation of the decomposition. The order of efficiency of additives in extending the induction period was: sulfur-containing additive (S)<nitrogen-containing additive (N)<phosphorus-containing additive (P)<phosphate-containing ionic liquid (P-IL). The order of efficiency in increasing the critical load was: N<S<P<P-IL, and the order of efficiency in decreasing the decomposition rate was: N<S<P<P-IL. These results suggest that additives which can form iron salts (such as iron phosphate and iron sulfide) will deactivate the nascent surface, decreasing the decomposition rate and increasing the critical load.
Through comparisons of dielectric constant (ε) and Hansen solubility parameter (HSP) of supercritical water (SCW) with those of typical solvents, conditions of SCW which has good miscibility with heavy oils were determined. The required conditions of SCW were found to be 2.2 ≤ ε ≤ 10.4 and HSP for hydrogen bonding, δh, < 10.0 MPa0.5. Validity of the optimum conditions estimated was confirmed by some experimental results.