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41.
Purification of solvents containing air – Alternative methods. Different processes are used for the purification of solvents containing air: condensation, absorption, adsorption, combustion, membrane permeation, and biofilters or bioscrubbers. The processes will be explained by examples. The specifications required by “TA Luft” often cannot be reached only by condensation and membrane permeation. The success of absorption depends on the scrubbing liquid. Glycol ethers are useful scrubbing liquids – especially for chlorinated hydrocarbons. The choice of the process depends on the volume flow rate, the solvent concentration, and the kind of solvent. Recycling of the solvents reduces the costs of the process. 相似文献
42.
Nitrate radicals are being recognized as key intermediates in a growing list of important chemical processes in the atmosphere. Here, the role of nitrate radicals (NO3) in tropospheric chemistry is discussed, with special emphasis on results from field measurements, most of which have been made by differential optical absorption spectroscopy (DOAS), with matrix-isolation electron spin resonance being an alternative technique. Nitrate radicals were observed in the atmosphere at peak mixing ratios of 350 ppt. Long-term observation of NO3 shows that 24-h averages in rural air masses are closer to a few ppt. Nevertheless, the NO3 radical plays an important role in the non-photochemical conversion of NOx to HNO3. Also, NO3 is a strong oxidizing agent and initiates the night-time removal of atmospheric trace species such as olefins, aromatic hydrocarbons, and organic sulfur compounds. Finally, night-time peroxy radical production and release of reactive halogen species from sea salt aerosol might be initiated by NO3 reactions. 相似文献
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Summary: This paper describes a step on the ambitious aim to “design” application properties of ldPE by first simulating the detailed molecular structure of a high‐pressure tubular reactor product. The reactor of a certain configuration produces under well‐defined operating conditions. The next step is to correlate the structure with the application properties. Finally, the sequence will be reversed in order to deduce the operating conditions, which lead to the desired product quality. Two‐dimensional distributions, in molecular weight and branching frequency, as well a two compartment models with a core and a shell stream were simulated and compared with experimental results. Therefore, CFD simulations were carried out to discretize the reaction medium. Samples were taken from both pilot and commercial plants. The TREF‐SEC analytical method was successfully applied in order to measure the microscopic structure of the material. The tremendous numerical problems were solved with the help of the software PREDICI .
46.
Roland Schmidt Ulrich Hammon Stefan Gottfried M. Bruce Welch Helmut G. Alt 《应用聚合物科学杂志》2003,88(2):476-482
The synthesis of iron(II) complexes with various tridentate di(imino)pyridine ligands and their potential as ethene oligomerization catalysts are described. The ligands are characterized by 1H‐ and 13C‐NMR spectroscopy and the complexes only by mass spectrometry due to their paramagnetism. After activation either with methylalumoxane (MAO) or with a heterogeneous cocatalyst consisting of partially hydrolyzed trimethylaluminum and silica gel, the prepared complexes proved to be good catalysts for the oligomerization of ethene. 1‐Octene, 1‐hexene, and 1‐decene were the major products, formed in very high isomeric purity (99.9 %). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 476–482, 2003 相似文献
47.
Maria Casapu Jan-Dierk Grunwaldt Marek Maciejewski Meike Wittrock Ulrich Gbel Alfons Baiker 《Applied catalysis. B, Environmental》2006,63(3-4):232-242
The formation and stability of BaAl2O4 and BaCeO3 in Pt-Ba/Al2O3 and Pt-Ba/CeO2 based NOx storage-reduction (NSR) catalysts has been investigated using kinetic measurements, X-ray diffraction, thermal analysis and X-ray absorption spectroscopy. In as-prepared state, the Ba-component in the NSR catalysts was made up of amorphous BaO and BaCO3. The formation of BaAl2O4 started above 850 °C, whereas the formation of BaCeO3 was already observed at 800 °C and was faster than that of BaAl2O4. The stability of BaAl2O4 and BaCeO3 in various liquid and gaseous atmospheres was different. BaAl2O4 was rapidly hydrated at room temperature in the presence of water and transformed to Ba(NO3)2 and γ-alumina in the presence of HNO3, whereas BaCeO3 was decomposed to much lower extent under these conditions. Interestingly, BaCeO3 was transformed to Ba(NO3)2/CeO2 in the presence of NO2/H2O at 300–500 °C. Also, the presence of CO2 led to decomposition of barium cerate, which has important consequences for the catalyst ageing under NOx-storage conditions and can be exploited for regeneration of thermally aged NSR-catalysts. 相似文献
48.
The reactions of trans-2,5-dimethoxy-4′-aminostilbene with poly(maleic anhydride-co-methylvinyl ether) and trans-2,5-dimethoxy-4′-isocyanatostilbene with poly(oxy-1,4-phenyleneisopropylidene:1,4-phenyleneoxy-2-hydroxytrimethylene) yield polymeric systems which undergo rapid crosslinking upon short exposure to ultraviolet light. The extent of photocrosslinking as a function of exposure time was determined by the decrease of the trans-stilbene ultraviolet absorption at 350 nm. 相似文献
49.
Lenssen K Jantscheff P von Kiedrowski G Massing U 《Chembiochem : a European journal of chemical biology》2002,3(9):852-858
Here we describe the first synthesis-screening approach for the identification and optimization of new cationic lipids for gene transfer in various cell lines. Combinatorial solid-phase chemistry was used to synthesize a library of new cationic lipids based on 3-methylamino-1,2-dihydroxypropane as the polar, cationic lipid part. As the nonpolar lipid part, different hydrocarbon chains were bound to the amino group of the scaffold and the amino group was further methylated to afford constantly cationic lipids. Lipids were synthesized in both configurations and as racemates, and the counter ions were also varied. By using a fully automated transfection screening method and COS-7 cells, the cationic lipid N,N-ditetradecyl-N-methyl-amino-2,3-propanediol (KL-1-14) was identified as a candidate lipid for the development of an improved transfection reagent. Screening the transfection properties of KL-1-14 in numerous combinations with the helper lipids dioleoylphosphatidylethanolamine (DOPE) and cholesterol (Chol) revealed that Chol is the most suitable helper lipid and the best KL-1-14/Chol ratio is 0.5-0.7. Compared to the standard transfection lipid N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl sulfate (DOTAP), transfection efficiency was improved by a factor of about 40. Furthermore, by using R- and S-configured KL-1-14, it could be shown that the configuration of the lipids had no significant influence on its transfection efficiency. The highest transfection efficiencies were achieved with chloride as the counter ion. The new lipofection reagent was further tested to transfect the cell lines MDA-MB-468, MCF-7, MDCK-C7, and primary dentritic cells (DC), which are important for the development of new anticancer gene therapy strategies. Even in these cells, KL-1-14/Chol (1:0.6) had improved transfection efficiencies, which were about two to four times higher than for DOTAP. 相似文献
50.
Ulrich Frank 《Software and Systems Modeling》2014,13(3):941-962
The paper presents a method for multi- perspective enterprise modeling (MEMO) and a corresponding (meta-) modeling environment. An extensive analysis of requirements for enterprise modeling serves to motivate and assess the method. The method is based on an elaborate conception of multi-perspective enterprise models and on an extensible language architecture. The language architecture is comprised of a meta modeling language and an extensible set of integrated domain-specific modeling languages (DSML). The DSML are supplemented with process models and with guidelines for their reflective use. The corresponding modeling environment integrates editors for various DSML into multi-language model editors. It includes a meta model editor which enables the convenient use, development and extension of the set of supported DSML and supports the generation of respective graphical model editors. Thus, it also serves as a foundation for method engineering. MEMO covers both software engineering as well as social, managerial and economic aspects of the firm. The presentation of MEMO is supplemented with a comparative overview of other approaches to enterprise modeling. The paper concludes bys summarizing fundamental technical, epistemological and political challenges for enterprise modeling research and discusses potential paths for future research. 相似文献