共查询到20条相似文献,搜索用时 125 毫秒
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为了提高D,L-丙交酯的收率,研究了D,L-乳酸为单体,低真空条件下使乳酸单体先缩聚后解聚制备D,L-丙交酯的工艺条件。考察了制备过程中脱水温度、脱水率、催化剂量、聚合温度和解聚温度对丙交酯产率的影响。结果表明,以ZnO为催化剂,用量为1.2%,在全程低真空条件下,乳酸分别在120~160℃脱水和220~250℃解聚,以无水乙醇和乙酸乙酯作为溶剂改进了粗产品的提纯方法,可得到产率达40.2%的丙交酯。毛细管熔点法测定了产物的熔点,并用红外光谱、差示扫描量热法、X-射线衍射分析对产物进行了分析表征。所得产物为高纯的环状丙交酯。 相似文献
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聚乳酸中间体——丙交酯制备工艺 总被引:1,自引:0,他引:1
研究了间接法合成聚乳酸用的中间体丙交酯的制备工艺。以工业D,L-乳酸(lacticacid)为原料,丙交酯粗产物的收率为考查指标,通过正交实验得到了最佳制备工艺条件为:以4%(v/v)的辛酸亚锡为催化剂,脱水温度为180℃,解聚温度为285℃,得到粗产物收率为72.4%。粗品丙交酯1次重结晶后收率为59.3%,熔点为95.0~96.2℃;5次重结晶后总收率为50.7%,熔点为125.2~126.5℃。同时采用FTIR与1HNMR对产物进行了结构表征。 相似文献
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丙交酯交替溶剂重结晶纯化法及其对聚合的影响 总被引:2,自引:1,他引:1
研究了交替溶剂重结晶丙交酯的纯化方法.首先优化了重结晶时间:在乙酸乙酯体系中,每百克溶剂中溶解丙交酯45 ~75 g,重结晶最佳时间为3~5 h;在乙醇体系中,每百克溶剂中溶解丙交酯30 ~45 g,重结晶最佳时间为1 ~3 h,结果表明,通过控制重结晶时间可达到最佳重结晶效果.以聚合效果比较了以上两种溶剂重结晶的结果,结果表明,乙醇体系重结晶率可高出乙酸乙酯体系约10%,但其纯化的丙交酯经聚合获得的产物分子量却远远低于乙酸乙酯体系.为此,采用交替溶剂重结晶法,即先使用乙醇重结晶丙交酯以获得高结晶率,再以乙酸乙酯重结晶则可在高得率的条件下获得高分子量聚丙交酯.用该法纯化得到的丙交酯经聚合后,产物的分子量可达43×104. 相似文献
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采用直接抽滤法、重结晶法和综合法对粗合成的L-丙交酯提纯,对精制L-丙交酯的熔点、旋光纯度以及其中水和乳酸含量进行测定.结果表明,根据粗L-丙交酯中各组份的物理性质的差异对其进行提纯(综合法)是一种较为有效的方法,用综合提纯方法能够得到光学纯度在99.5%以上的精制L-丙交酯. 相似文献
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丙交酯重结晶溶剂考察 总被引:10,自引:0,他引:10
考察了丙交酯在20种常用有机溶剂中从-10℃对96℃不断升温过程中的溶解及冷却后的重结晶,对在相同试验条件下丙交酯在各种溶剂中溶解的数量以及重结晶回收率作了比较,并讨论了各种溶剂对丙交酯重结晶工艺的适用性。 相似文献
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乙烯酮(双乙烯酮)是十分重要的化工中间体,其下游产品较多。江苏某化工厂开发生产乙烯酮(双乙烯酮)下游产品三十多个,年生产规模三万多吨,是国内以乙烯酮(双乙烯酮)为中间体生产精细化学品的综合骨干企业。针对乙烯酮(双乙烯酮)下游产品废水特点,该厂结合企业实际,开展了产品优化,结构调整,清洁生产,资源循环利用,节水降耗等工作,从源头削减了污染物的生产。同时投资二千多万元新建预处理装置三套,6000m3/d废水生化处理装置一套,使全厂乙烯酮(双乙烯酮)下游产品的废水得到了有效的治理。 相似文献
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D. G. Gordeev L. F. Gudarenko M. V. Zhernokletov V. G. Kudel’kin M. A. Mochalov 《Combustion, Explosion, and Shock Waves》2008,44(2):177-189
A semi-empirical equation of state for metals is described. Its capabilities are demonstrated by the example of the equation
of state for aluminum. New experimental data are presented on the location of the isentrope of aluminum for unloading from
the state at p = 229.71 GPa on the shock adiabat to an aerogel (SiO2) of density 0.08 g/cm3.
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Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 61–75, March–April, 2008. 相似文献
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Jorge Marcelo Romero Soledad Bustillo Hugo Enrique Ramirez Maisuls Nelly Lidia Jorge Manuel Eduardo Gómez Vara Eduardo Alberto Castro Alicia H. Jubert 《International journal of molecular sciences》2007,8(7):688-694
A thermochemical rather simple experimental technique is applied to determine the enthalpy of formation of Diperoxide of ciclohexanone. The study is complemented with suitable theoretical calculations at the semiempirical and ab initio levels. A particular satisfactory agreement between both ways is found for the ab initio calculation at the 6–311G basis This set level. Some possible extensions of the present procedure are pointed out. 相似文献
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A perturbation viscometer is a differential capillary viscometer that measures the logarithmic viscosity gradient of the viscosity-composition curve for gas mixtures. Measurements are made at different gas mixture compositions. Integration of the logarithmic viscosity gradients measured over the full composition range gives the mixture viscosity relative to the viscosity of one of the pure components of the gas mixture. This method is attractive because, for measurements of equal precision, integration of the gradients is potentially an order of magnitude more precise than measurement of the viscosities directly. It can also work at high and low temperatures and perhaps high pressures.The perturbation viscometer has been used to make measurements on ideal gas mixtures at ambient and elevated temperatures. The situation is more complicated when the gas mixtures are non-ideal. Extra effects due to density differences, molar volume change on mixing and differential thermal expansion may be measured in addition to the desired viscosity change producing systematic errors in the results. Thus, a more sophisticated apparatus is required. The standard perturbation viscometer has been modified to separate out the extra effects to permit measurement of the true change in viscosity. In addition, the theoretical operation of the modified apparatus has been revised to account for the design changes to permit calculation of the viscosity-composition profiles from the results.The apparatus has been tested using helium-HFC-125 mixtures and two new viscosity-composition profiles are presented for these mixtures at 23 and . Internal consistency tests have been used to confirm that the data produced are of high quality with an estimated uncertainty in the viscosity ratio data at of 0.9% and at of 1.5%. 相似文献
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塔设备改造选型的分析 总被引:2,自引:0,他引:2
就当前扩产增容中塔设备设计和改造时板式塔和填料塔的选型问题加以分析。在评述目前国内常用的几种塔板和新型填料之后,着重介绍一种新型塔板(导向梯形浮阀塔板)和一种新型填料(波环填料——乾隆帕克)。 相似文献