车用多缸直喷柴油机燃用二甲醚的燃烧和排放特性研究

开展了4缸直喷柴油机燃用二甲醚时的燃烧和排放特性的研究。结果表明，适当增加喷油器伸出缸盖底平面的距离，采用流通截面较大的喷油器，降低启喷压力，可以提高CA498发动机燃用二甲醚时的热效率。燃用二甲醚时，发动机缸内的最大爆发压力和压力升高率低于燃用柴油时的情况。二甲醚发动机在所有工况下均可实现无碳烟排放，NO，排放约为柴油机的50％，CO和HC排放与柴油机相当。试验结果表明二甲醚是一种高效、低排放、燃烧噪声低的柴油机新型代用燃料。     

A highly active and stable Pt modified molybdenum carbide catalyst for steam reforming of dimethyl ether and the reaction pathway

To improve the stability of molybdenum carbide catalysts in dimethyl ether steam reforming (DSR), the inactivation mechanism and the performance of Pt modified catalyst has been investigated. The Mo₂C oxidation induced by H₂O is verified to be the main reason of catalytic deactivation. After modified with Pt, the H₂ production rate and selectivity are greatly enhanced, reaches 1605 μmol min⁻¹·g_cat⁻¹ at 350 °C, in comparison to that of the Mo₂C/Al₂O₃ catalyst. Moreover, the 2%Pt–Mo₂C/Al₂O₃ catalyst is more stable with only 20% activity loss after 50 h on stream compares to the 73% activity loss in 12 h with Mo₂C/Al₂O₃ catalyst. By means of in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the enhancement brought by Pt is ascribed to the consumption acceleration of intermediate oxygen species on catalyst surface and the decline of onset temperature of DSR reaction. It is expected that these findings can lead us to more practical molybdenum carbide catalysts in DSR.     

Modification of polymers for cardiovascular applications—some routes to bioactive hydrophilic polymers

This paper is concerned with the activation of platelets by polymers, a key-process in the behaviour of prosthetic devices in contact with blood. Platelets are activated by contact with many different types of polymer surfaces, which must therefore be regarded as thrombogenic. Two procedures for reducing thrombogenicity are discussed: (i) the chemical attachment of inhibitors of platelet aggregation and (ii) gross modification of the nature of the surface, e.g. by making it more hydrophilic. For purposes of (i) the potent prostaglandin analogue BW 245C has been used, while for (ii) grafting of poly(ethylene glycol) (PEG) has been explored. Both methods give greatly reduced platelet adhesion inin vitro tests. The second part of the paper deals with the properties of adducts of inhibitors of platelet aggregation (BW 245C, dipyridamole) with water-soluble macromolecules [poly(N-vinyl pyrrolidone), PEG, dextran]. Adducts have been synthesized with terminal and side-chain coupling. On adduction the two inhibitors mentioned show opposite types of behaviour: the molar activity of BW 245C is dramatically reduced, but that of dipyridamole is significantly increased. Remarkable synergistic effects have been recorded for BW 245C adducts. These observations are interpreted in terms of differences in stereochemistry in the drug-receptor interactions. Appropriate chemical techniques for coupling are outlined, attention being drawn to the special uses of haloalkyl- and haloacyl-isocyanates and 2-isocyanatoethyl methacrylate as reagents.     

聚(α-甲基苄基)酚聚氧乙烯醚的电子电离质谱研究

采用直接进样法 ,研究了聚 (α 甲基苄基 )酚聚氧乙烯醚的电子电离质谱 (EI/MS) ,分析了其特征峰、碎片离子 ,揭示了其断裂规律并根据一系列特征峰来确定 α 甲基苄基和聚氧乙烯的缩合度大小     

Studies of the halogenation of dissolved organic material during the chlorination of saline cooling waters,the model compounds resorcinol diacetate and resorcinol dimethyl ether

Chlorination of seawater containing resorcinol diacetate or resorcinol dimethyl ether results primarily in the formation of brominated products. At low chlorine concentrations (cf. model compound), ring substitution products dominate whilst at higher chlorine levels ring cleavage occurs and trihalomethanes are produced. Electrophilic chlorination of the model compounds in seawater therefore appears to be slower than the formation of HOBr by oxidation of naturally occurring bromide. The influence of solution acidity on the nature and extent of halogenation is described and reaction mechanisms postulated.     

Photocrosslinking of a maleimide functionalized polymethacrylate

A polymethacrylate bearing pendent maleimide (MI) groups has been crosslinked by UV irradiation of the photoinitiator‐free functionalized polymer. The reaction was followed in situ by real‐time IR spectroscopy and shown to proceed with an initial quantum yield of two maleimide double bonds polymerized per photon absorbed, the value expected for a photocycloaddition mechanism. A twofold increase of the reaction rate was achieved by performing the UV irradiation in the presence of a thioxanthone photosensitizer (1 wt%). Insolubilization of the photoresist requires the reaction of at least 18 MI double bonds per polymer chain, thus implying the occurrence of an intramolecular coupling process between neighbouring MI groups located on the same polymer chain. In the presence of an electron donor monomer, like the divinylether of triethyleneglycol used, the cycloaddition reaction gives way to a radical‐induced copolymerization of maleimide and vinyl ether double bonds, which becomes the only crosslinking process in a stoichiometric mixture of the two components. Copyright © 2003 Society of Chemical Industry     

双(4-(对氟苯甲酰基)苯基)苯基氧化膦的合成与表征

以双(4-羧苯基)苯基氧化膦、氟苯等为原料,合成了标题化合物,并采用差示扫描量热法、红外光谱和核磁共振等对产品的结构进行了表征。     

5种E型环氧树脂的基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)表征

应用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术,研究了E-12、E-31、E-42、E-44和E-51五种牌号环氧树脂.获得了该类树脂的聚合度及其不同聚合度所对应的分子结构;发现了该类树脂中有一定量的环氧氯丙烷的聚合物,并给出了可能的分子结构.     

Ion-chromatographic characterization of ethoxylated anionic surfactants

Alkyl ether sulfates (AES), analyzed by nonsuppressed or single-column ion chromatography with conductivity detection, generate profiles that are characteristic of the ethoxylate content. Identification of ethoxylation content was accomplished by calculating the slope of the log of the peak area for each homologue vs. the number of ethoxyl groups in the homologue. Quantitation of ethylene oxide content as well as quantitation of mixed alkyl sufates in the presence of AES in mixed surfactant systems is possible. Raw materials require only dilution in mobile phase, while finished products must be subjected to a solid-phase extraction by means of a reverse-phase cartridge and an ion-pair reagent. The chromatogram of the anionic surfactant yields the moles of ethoxylation and the characterization of the ethoxyl chain distribution. Anionic surfactant mixtures in products are identified and quantitated by reference to AES raw materials with a similar slope.     

Kinetic analysis of benzyl alcohol oxidation by alcohol oxidase in aqueous—organic two-phase systems

Alcohol oxidase-catalyzed oxidation of benzyl alcohol to benzaldehyde was studied in three two-liquid phase systems involving butyl acetate, xylene and n-decane. A more highly hydrophobic solvent resulted in more favorable partitioning of the substrate into the aqueous phase and less deleterious effect on the enzyme activity. As a result, the overall production of aldehyde was highest with the n-decane system and lowest with the butyl acetate system. In addition, the organic solvent served as an extractant for the product, which acted both as a competitive inhibitor and as a denaturant of the enzyme. The time courses of benzaldehyde production were simulated by a simple mathematical model assuming Michaelis–Menten kinetics in the aqueous phase, enzyme deactivation by organic solvents and the equilibrium partitioning of the reagents between the two phases.