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间歇反应器内醋酸丁酯酯化反应与渗透汽化集成过程的模型计算 总被引:1,自引:0,他引:1
建立了一个间歇反应器内酯化反应与渗透汽化集成过程的数学模型, 用于描述反应和脱水同时进行的过程. 该模型考虑了反应体系中所有组分的渗透量影响以及混合物的非理想热力学行为. 选择乙酸和正丁醇生成醋酸丁酯的酯化反应与 PVA 膜渗透汽化集成过程为研究体系, 将模型结果与文献中已报道的实验数据进行对比, 验证了该模型的有效性. 结果表明, 采用渗透汽化脱除酯化反应的水分将提高酯的产率. 对温度、反应物初始比、膜面积与反应体积比以及催化剂浓度几种操作条件对集成过程性能影响进行了参数的分析. 根据结果讨论得到该膜过程与反应集成过程的优化操作条件. 相似文献
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通过二次生长法在α-Al2O3支撑体表面合成了PHI分子筛膜,考察了晶种合成方式、二次生长合成温度及时间对形成PHI分子筛膜的影响.采用X射线衍射(XRD)、扫描电子显微镜(SEM)对合成膜进行表征.结果表明:载体表面合成出了PHI分子筛;二次生长法合成出的PHI分子筛膜连续、致密,膜厚约为20 μm.利用渗透汽化技术对甲醇、乙醇、异丙醇和叔丁醇等不同分子尺寸的醇/水体系进行分离性能的研究,同时考察原料液中水含量对所制备的PHI分子筛膜的分离性能的影响.结果表明:PHI分子筛膜对几种醇水体系都具有良好的分离效果,随着水含量的增加,水的渗透通量呈增大趋势,乙醇和甲醇的理想分离因子有所降低,异丙醇和叔丁醇的理想分离因子增大. 相似文献
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用聚电解质渗透汽化膜进行乙醇脱水 总被引:5,自引:1,他引:4
渗透汽化 (PV)膜过程由于可用于有机 /有机及有机 /水的恒沸或近沸混合物的分离而成为近年来膜技术研究开发的热点[1,2 ] .德国 GFT公司所制的富马酸交联 PVA脱水膜[3] 对温度为 80℃的 80 %Et OH料液 ,其分离因子为 350 ,渗透通量为 2 0 0 g/ (m2 ·h) .优秀的分离膜要求渗透通量大 ,同时具有较高的分离因子和良好的稳定性 .因此 ,提高膜的分离性能是渗透汽化技术开发应用的关键 .周继青等 [4 ]研究了 PVA/ PVP互穿网络膜的渗透汽化性能 ,发现膜的渗透通量虽有明显提高 ,但膜的选择性下降 .聚电解质具有优良的亲水性 ,可制得高水通… 相似文献
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聚环氧乙烷(PEO)/壳聚糖(CS)共混膜的醇—水渗透蒸发性能研究 总被引:1,自引:0,他引:1
研究了EtOH-H2O,n-PrOH-H2O,i-PrOh-H2O体系在CS膜和PEO/CS共混膜中的渗透蒸发性能。讨论了料液温度、料液浓度、共混膜组成对分离性能的影响,结果发现PEO的掺入能大大提高CS膜的渗透通量,而分离因子下降。同时从膜材料的聚集态结构出发对相关的渗透蒸发行为进行了讨论。对于PEO/CS共混膜,膜内自由体积的大小是影响分离性能的主要因素,小分子在膜中的渗透蒸发行全为主要是由扩 相似文献
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合成了双官能化杯[4]芳烃衍生物,并通过共缩聚的方法制备了主链含杯[4]芳烃的聚对苯二甲酸丁二酯聚二甲基硅氧烷(PBT-PDMS)共聚酯.利用1H-NMR,FTIR,SEC等手段表征了共聚物的组成及分子量.以此共聚物为膜材料,通过刮膜法制备了可用于渗透汽化的致密无孔分离膜,并用SEM表征了无孔膜的膜厚及截面结构.研究了温度和原始液浓度对渗透汽化的影响.该共聚物渗透气化膜分离水中微量苯的分离因子可达491,通量为58 g/(m2h). 相似文献
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The equation of Reilly, Wood, and Robinson was used to predict the osmotic coefficient of seawater and of its concentrates at molal ionic strengths of 0.5 to 6.0 at 25°C. The results agree closely with experimental data at ionic strengths below 5. The average difference in osmotic coefficients over the entire concentration range is 0.0014. The only serious discrepancy is at an ionic strength of 6, where a difference of 0.0068 is found. The accuracy of the predictions of osmotic coefficients prompted the calculation of the activity coefficients of NaCl, Na2SO4, MgCl2, MgSO4, KCl, and K2SO4 in the mixture. The calculated activity coefficients of NaCl and Na2SO4 agree within experimental error with previous measurements. This agreement demonstrates the prediction of activity and osmotic coefficients for complex mixtures. 相似文献
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本文将Bjerrum渗透系数概念推广到混合溶剂体系中,提出了广义渗透系数的概念及其一般定义式,并导出了广义渗透系数与电解质活度系数之间的相互关系式,从而可以借助于广义渗透系数较易实现混合溶剂体系中溶质与溶剂热力学性质之间的相互推算,同时,混合溶剂作为一个整体的非理想性亦可得到具体度量.因此引入广义渗透系数概念具有理论与实际意义. 相似文献
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指出Debye-Htickel离子活度系数公式中,除了静电作用项以外还有另一项,称之为渗透项.渗透项鲜为人知,故着重讨论该项的意义和作用. 相似文献
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Measured values of the pressure of H2O over saturated solutions in equilibrium with the dihydrate, tetrahydrate or hexahydrate of CaCl2 are converted to osmotic coefficients and compared with literature values for solutions of smaller molality. It is found that the osmotic coefficient is constant, within the uncertainty, from about 7 mol-kg–1 to soturation at all temperatures from 25 to 100°C. From this simple approximation, the activity coefficient is calculated for high molalities and at saturation. By combination of these results with other established data, entropies and Gibbs energies of formation are calculated for the crystalline hydrates of CaCl2. 相似文献
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The osmotic pressures of –polyelectrolyte solutions without added salt was measured in the concentration ranges 0.001–0.02
and 0.2–1.9 mol kg-1. Our results show that the osmotic coefficients φp were strongly dependent on the chemical structures of polyelectrolyte through the polyion radius and the interaction between
the ionic moiety and counterions. The osmotic pressures in polyelectrolyte solutions without added salt, calculated on the
basis of the counterion contribution, are in agreement with the experimental results. We conclude that the counterion contribution
is dominant in the osmotic pressures and thus, the polymer contribution is negligible in the examined concentration range
0.2–1.9 mol kg-1. The P–B approach gave a fair prediction of the absolute values of the osmotic pressures with λ=4.5, where λ is the charge
density parameter, except for NaPA. In other words, the concentration dependence of the φp values can be explained in terms of the counterion contribution.
Received: 11 June 1997 Accepted: 19 August 1997 相似文献
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Ornella Ortona Gerardino D'Errico Luigi Paduano Vincenzo Vitagliano 《Journal of solution chemistry》2003,32(12):1103-1120
Measurements of osmotic coefficients, mutual diffusion coefficients, and conductivity were performed on the binary system sodium n-octyl sulfonate (C8SO3Na)–water at 25°C both below and above the micellar composition range. The osmotic coefficient data were obtained through vapor-pressure osmometry, while the Taylor dispersion method was used to measure diffusion coefficients. The mass equilibrium model was applied to this self-aggregating system, taking into account the deviation of the activity coefficients from the Debye–Hückel limiting law by using the Guggenheim corrective terms for mixed electrolyte solutions. The expressions derived from the model fit the experimental osmotic and diffusion coefficient data well, when the same values of aggregation number, fraction of condensed counterions, and equilibrium constant are used. Osmotic coefficients were also used to determine the thermodynamic factor required to compute the solute mobility from diffusion data. Conductivity data were used to test two theoretical models, namely, the Onsager–Fuoss and the Mean Spherical Approximation theories. Both models have been found to yield unsatisfactory fits to our experimental data and some arbitrary terms had to be applied to the theoretical expressions to obtain good agreement between experiment and theory. 相似文献
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We report osmotic and activity coefficients of aqueous sodium sulfate solutions. The osmotic coefficients were determined at 40°C by the isopiestic method. Sodium chloride served as the isopiestic standard. The molality ranges covered in this study correspond to about 0.2–3.0. The activity coefficients were calculated from the parameters obtained by fitting the Hamer–Wu and Pitzer equations to the experimental osmotic coefficients. 相似文献
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The osmotic coefficients for aqueous lithium sulfate solutions were experimentally determined at 40°C. Sodium chloride served as the isopiestic standard for the calculation of osmotic coefficients. The molality ranges covered in this study correspond to about 0.1–2.5 mol-kg–1. The system of equations developed by Hamer-Wu and Pitzer were used to fit each set of osmotic coefficients. The parameters obtained from the fit were used to calculate the activity coefficients. 相似文献
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采用等压法研究了308.15K下NaCl-H2O、CaCl2-H2O和NaCl-CaCl2-H2O体系离子强度分别为0.5666~5.9265molkg-1、0.3943~5.5573molkg-1和0.6524~16.6631molkg-1的等压平衡浓度和水活度,计算了渗透系数及饱和蒸汽压,获得了该体系渗透系数和饱和蒸汽压随离子强度的变化规律.应用Pitzer离子相互作用模型,用实验数据用多元线性回归拟合了308.15K下该体系的NaCl和CaCl2的纯盐参数β(0)、β(1)、Cφ分别为0.3181、1.5346、-0.0014和0.07972、0.3067、0.00075,拟合标准偏差分别为0.00072、0.0049;混合离子作用参数θNa,Ca、ψNa,Ca,Cl分别为0.06821、-0.0076,拟合标准偏差为0.0063和0.0064.用Pitzer模型计算的渗透系数与实验结果吻合.本研究为含钠钙海卤水体系热力学模型建立提供了重要的热力学基础数据. 相似文献