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51.
Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion 总被引:1,自引:0,他引:1
The effects of support and additive on the oxidation state and catalytic activity of Pt catalyst in the low temperature propane combustion were systematically investigated on Pt/MgO, Pt/Al2O3 and Pt/SiO2–Al2O3. The catalytic activity varied much with both support materials and additives. The catalyst on the more acidic support showed higher activity, and the catalytic activity on every support materials increased as the electronegativity of additives increased, while some additives decreased the activity. The oxidation state of platinum, estimated by white line intensity of Pt LIII-edge XANES spectrum, also varied with the support and additives, and additives with higher electronegativity greatly prevented the platinum from its oxidation under oxidising atmosphere. Among almost all the catalysts with various supports and various additives, a clear relationship was observed between the oxidation state of platinum and the catalytic activity; the more metallic platinum showed higher activity. Thus, it was concluded that the total electrophilic/electrophobic property derived from those of the support and additive controls the oxidation state of platinum, which intensively affects the catalytic activity; i.e. higher electrophilic property provides less oxidised platinum, resulting in high catalytic activity. The mechanism of this effect was also discussed on the basis of thermochemical data, and it was proposed that the electrophobic materials promote the noble metal oxidation since the noble metal oxo-anion such as PtOδ− is more stabilised with electrophobic cation. 相似文献
52.
Summary The synthesis of poly(-thiophenediyl)benzylidene (PTB) with high molecular weight is described. Number-average degrees of polymerization reached about 74. The characterizations of the polymer was investigated by 1H-NMR, 13C-NMR, IR, and UV-VIS spectra. The polymer with well-defined structure and high molecular weight was obtained by polymerization at low temperature and in polar solvent. This polymer was thermally stable and a thermal decomposition took place at 391°C under nitrogen and at 370°C under air. The glass transformation temperature was 117°C and this PTB was nonfusible. 相似文献
53.
Masahiro Takehara Ippei Yoshimura Kouichi Takizawa Ryonosuke Yoshida 《Journal of the American Oil Chemists' Society》1972,49(3):157-161
Long chain N-acylglutamic acid was prepared in a high yield by a reaction of glutamic acid with fatty acid chloride in a mixed
solvent of water and a water miscible organic solvent such as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran,t-butyl alcohol or cyclohexanone. In this reaction the composition of the mixed solvent influenced the yield of N-acylated
glutamic acid and the best yield was obtained when the reaction was carried out in the mixed solvent comprising 30–60% v/v
of the organic solvent. Long chain N-acylaspartic acid was also obtained in a high yield by the same method. As the other
method to obtain N-lauroyl-D L-glutamic acid, it was examined that N-acyl-α-aminoglutarodinitrile which was obtained by a reaction of α-aminoglutarodinitrile
with fatty acid chloride was hydrolyzed with an aqueous alkaline solution. The salts of long chain N-acylglutamic acid are
known as the surface active agents that react mildly on the human skin. 相似文献
54.
Uniaxial drawing experiments of the polystyrene films plasticized by a sorption of compressed CO2 gas at pressures up to about 18 MPa were carried out with strain rates ε of 0.0290 and 0.0079 s?1. The drawing was performed successfully with draw ratio λ up to 4 at the temperatures of 308.15, 318.15, 328.15, and 338.15 K. The Hermans orientation function f of the drawn samples was determined from the dichroic ratio measured by an infrared spectrophotmeter. While f value increases with increasing ε or λ, it decreases with increasing CO2 pressure or temperature. © 1995 John Wiley & Sons, Inc. 相似文献
55.
A new Ag/Al2O3 catalyst for removing NOx in lean exhaust gas was developed. Oxidized Ag/Al2O3 catalyst is highly active for reduction of NOx with ethanol and propene, whereas reduced Ag/Al2O3 catalyst is less active for these reactions. Selectivity to N2 is also high on the oxidized Ag/Al2O3 compared to that on the reduced Ag/Al2O3. XRD and SEM studies of these two types of Ag catalysts suggest that oxidation induces an interaction between Ag and the
support, where the particles are grown in large size. In contrast, the metallic Ag particles are finely dispersed by the reduction
process. Although dispersion of Ag particles is decreased by the oxidation process, the catalytic activity is increased. This
suggests that the Ag-alumina sites created in the high temperature oxidizing environment are active in catalytic reduction
of NOx.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
56.
Hiromi Yoshida Mikiko Tatsumi Goro Kajimoto 《Journal of the American Oil Chemists' Society》1991,68(8):566-570
Effects of microwave heating on the oxidative stability ofd-tocopherols were studied in relation to the production of fatty acids in oils. During microwave heating, the stability of
tocopherols decreased in the orderδ>β>γ>α. This order did not depend on the types of ethyl esters of fatty acids or oils present. But, the shorter the chainlength
and the lower the degree of unsaturation of the fatty acid ethyl esters, the greater was the reduction in amount of individual
tocopherols. A similar tendency was observed when tocopherol-stripped vegetable oils, with equimolar mixtures of tocopherols
added, were treated under the same conditions. The reduction in tocopherols became greater with increasing levels of free
fatty acids. 相似文献
57.
Electrochemical Ni-Mo alloying of the surface of a nickel substrate was investigated using alternating pulsed electrolysis in an aqueous solution containing only molybdate ions (MoO42−) as a metal ion component. In this electrochemical process, the nickel substrate was slightly dissolved during the anodic pulses, providing nickel ions into the solution in the vicinity of the substrate, while Ni and Mo were both electrodeposited on the substrate surface during the subsequent cathodic pulses. Through the optimization of anodic and cathodic conditions independently based on a set of direct-current electrolysis data, amorphous Ni-Mo alloy layers were found to be formed at the surface of the nickel substrate by the alternating pulsed electrolysis using the MoO42− solution of pH 3.0-5.0. The conditions for Ni-Mo alloy formation were discussed in terms of the dissolving regime of ionic species in the electrolytes determined by an equilibrium calculation. 相似文献
58.
The free‐radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free‐radical graft polymerization of vinyl acetate in ethyl acetate with 2,2′‐azobis(2,4‐dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer‐grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy–determined topology of the polymer‐grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular‐weight distribution for free‐radical polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 300–310, 2003 相似文献
59.
Summary The permeabilities of various cellulose ester membranes and cellulose membranes were investigated using pure water and aqueous solution of glycerol as feed. In all membranes, the permeation rate for aqueous solution of glycerol was greater than for pure water. The permeation rates of cellulose ester membranes increased with an increase in number of carbon atoms of the substituent group in cellulose ester. 相似文献
60.
Jinhua Chen Upita Septiani Masaharu Asano Yasunari Maekawa Hitoshi Kubota Masaru Yoshida 《应用聚合物科学杂志》2007,103(3):1966-1972
In this study the fluoropolymers, poly(ethylene‐co‐tetrafluoroethylene) (ETFE) and poly(vinylidene fluoride) (PVDF) films, together with the radiation‐induced crosslinked polytetrafluoroethylene (cPTFE) film were compared on the basis of their preparation and properties of radiation‐grafted polymer electrolyte membranes. The polymer electrolyte membranes were prepared by radiation grafting of styrene into the base films and subsequent sulfonation. The proton conductivity and chemical stability of the three types of membranes with a similar ion exchange capacity (IEC) near 1.0 mmol/g were investigated and are discussed in detail. Although the ETFE‐based polymer electrolyte membrane was relatively more stable, its proton conductivity was lower than those of the PVDF‐ and cPTFE‐based membranes. On the other hand, the cPTFE‐based membrane showed a significantly higher proton conductivity, but its chemical stability was shorter than that of the ETFE‐based membrane. It is considered that the difference in the preparation and properties of the polymer electrolyte membranes was due to the difference in the degree of crystallinity as well as in the chemical structure of the fluoropolymer base films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1966–1972, 2007 相似文献