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992.
A series of novel nonionic functional polyurethane surfactants were synthesized by the polycondensation of 2,4‐toluene diisocyanate with poly(propylene oxide) (weight‐average molecular weight = 400, 1000, or 2000) and monoallyl‐end‐capped poly(ethylene oxide). The chemical structure of the polyurethane surfactants was determined by Fourier transform infrared and 1H‐NMR, and the effects of the concentration, salt, rest time, and temperature on the surface tension were investigated. These polymeric surfactants exhibited excellent surface activity. Sample III, which was synthesized with monoallyl‐end‐capped poly(ethylene oxide) (number‐average molecular weight = 1000), poly(propylene oxide) (number‐average molecular weight = 2000), and tolylene diisocyanate, could reduce the surface tension to 37.6 mN/m at a concentration of 0.06 mol/L at 25°C. All polyurethane surfactants synthesized in this study had low critical micelle concentrations (ca. 10?4 to 10?5 mol/L) and could reduce the surface tension even at very low concentration levels. Moreover, the surface tension decreased with an increase in the temperature or the concentration of the polyurethane surfactants. The addition of salt resulted in a decrease in the surface tension, and it took some time for the polyurethane surfactants to reach a constant surface tension value. UV spectra were found to be very useful for determining the critical micelle concentration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2956–2962, 2006 相似文献
993.
994.
气固下行流化床反应器Ⅱ气固两相的流动规律 总被引:1,自引:1,他引:1
气固下行流化床反应器气固两相流动过程是比较复杂的,沿轴向气固两相运动可分为第一加速、第二加速和恒速3个运动段,沿径向局部气体速度、颗粒速度和颗粒浓度都具有不同程度的不均匀性。而这种不均匀性是由气固两相顺重力场湍动运动所决定的。和循环床提升管相比,下行管反应器气固两相沿径向分布的不均匀性得到有效地改善,气固可以实现超短接触操作,因而是一种新型高效气固超短接触反应器 相似文献
995.
Matthias Berger Manfred P. Schnelder 《Journal of the American Oil Chemists' Society》1992,69(10):961-965
Regioisomerically pure 1(3)-rac-monoacylglycerols are conveniently prepared in high yields (>75%) and in multigram quantities by enzymatic esterification
of glycerol in the presence of various lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) with a variety of different acyl donors, such as free fatty acids, fatty acid alkyl esters, vinyl esters and triacylglycerols,
as well as natural fats and oils. All reactions are carried out in aprotic organic solvents with low water content, namelyn-hexane, diethyl ether, tBuOMe or mixtures of these solvents. Essential for the success of these transformations were the
following two factors. First, the creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol
and the hydrophobic reaction medium by its adsorption onto a solid support. Second, a facile system for the separation of
the desired monoacylglycerol from the reaction mixture, coupled with the continuous recycling of acyl donor and undesirable
by-products. 相似文献
996.
一种新型含氟菊酸的合成 总被引:1,自引:0,他引:1
本文以4-甲基-3-戊烯-2-酮为原料,经三步反应,合成了一种新型的拟除虫菊酯中间体反-3-(1-甲基-2,2-二氟乙烯基)-2,2-二甲基环丙烷羧酸,总产率为50.0%。 相似文献
997.
The equilibrium phase compositions of iron have been calculated for gas compositions that could be encountered during the Fischer–Tropsch synthesis. The gas compositions measured experimentally for CO conversion levels in the 30–90% range show that iron should be present as the carbide phase. However, experimental characterization of iron catalysts show that a significant fraction of the iron is present as Fe3O4 following synthesis for several days. A model that can account for the experimental catalyst phase composition and the gases present in the reactor would have a core of Fe3O4 and an outer layer of iron carbides. 相似文献
998.
研究建立了同时测定三磷酸胞苷二钠中乙醇、丙酮、氯甲醚、甲苯、苯乙烯5种有机溶剂残留量的毛细管气相色谱法。样品以乙腈为溶剂,经DB-FFAP(30 m×0.32 mm×0.25μm)毛细管柱分离,氢火焰离子化检测器检测,这5种有机溶剂呈良好的线性响应,平均回收率在98.3%~99.5%,精密度RSD在0.21%~1.92%,最低检出限可达5.0~7.5 mg/kg。本方法简单、灵敏、准确,完全能满足药品中所述有机溶剂残留量的测定要求。 相似文献
999.
《Fuel》2003,82(2):147-151
The aim of this paper is to show how a cheap carbonaceous material such as low rank coal-based carbon (or char) can be used in the combined SO2/NO removal from exhaust gas at the linear gas velocity used in commercial systems (0.12 m s−1). Char is produced from carbonization and optionally activated with steam. This char is used in a first step to abate the SO2 concentration at the following conditions: 100 °C, space velocity of 3600 h−1, 6% O2, 10% H2O, 1000 ppmv SO2, 1000 ppmv NO and N2 as remainder. In a second step, when the SO2 concentration in the flue gas is low, NO is reduced to N2 and steam at the following experimental conditions: 150 °C, space velocity of 900 h−1, 6% O2, 10% H2O, 0-500 ppmv SO2, 1000 ppmv NO, 1000 ppmv NH3 and N2 as remainder.It has been shown that the presence of NO has no effect on SO2 abatement during the first step of combined SO2/NO removal system and that low SO2 inlet concentration has a negligible effect on NO reduction in the second step. Moreover, this char can be thermally regenerated after use for various cycles without loss of activity. On the other hand, this regenerated char shows the highest NO removal activity (compared to parent chars, either carbonized or steam activated) which can be attributed to the activating effect of the sulfuric acid formed during the first step of the combined SO2/NO removal system. 相似文献
1000.
以低轨环境下无拖曳卫星控制器设计为研究对象,对于给定结构的无拖曳卫星,考虑推进器增益存在不确定时的鲁棒控制器设计。首先,简要介绍无拖曳卫星的概念及原理;之后,对带有不确定性的无拖曳卫星控制系统进行分析与建模,并对其进行LFT不确定性建模,最后利用μ分析和D-K迭代设计出满足鲁棒性能的鲁棒控制器。仿真结果说明鲁棒控制器的有效性。 相似文献