Analysis of a hybrid distillation-pervaporation column in a single unit: Intermediate membrane section in the rectifying and stripping section

Distillation-pervaporation in a single unit (DPSU) column can perform separations that are not possible in conventional distillation by overcoming distillation boundaries. Unlike conventional hybrid distillation-pervaporation columns, in a DPSU system the pervaporation membrane is located inside the column. The separation by distillation and pervaporation is carried out simultaneously inside the same column section. In a previous work, a simplified model was used to design and analyze distillation-pervaporation in a single unit (DPSU) systems with a hybrid rectifying-pervaporation section, where the membrane constitutes the whole section. In this study, this simplified model is applied to DPSU columns where the membrane partially constitutes the rectifying or the stripping sections, including the model derivation of the stripping section and the operation leaves. The simplified model is applied for the separation of two mixtures with different Serafimov's topology classifications: acetone-isopropanol-water (topology type 1.0-2) and ethyl acetate-ethanol-methanol (topology type 2.0-2b). Thermodynamic limitations are identified for the separation of the ethyl acetate-ethanol-methanol mixture. Multiple operation leaves are produced depending on the liquid composition at the beginning of the membrane section, hindering the conditions that help to overcome the distillation boundary through a DPSU column. For some conditions, a section that is partially constituted by a membrane performs better than if the membrane constitutes the whole section.     

Effects of nematic coupling on the phase behaviour of nematogen mixtures

The phase behaviour of binary nematogen mixtures of side‐chain liquid crystal crosslinked polymers and low molecular weight liquid crystals is investigated with particular emphasis on the effects of nematic coupling. The cross nematic quadrupole parameter ν₁₂ is assumed to be proportional to the geometric average of ν₁₁ and ν₂₂ characteristic of single nematogens. In the weak coupling limit, the proportionality constant is lower than 1, and the phase diagram exhibits a reduced miscibility of the nematogens. In the case of strong coupling, the proportionality constant exceeds 1 resulting in higher miscibility. This is characterized by a nematic order that extends to temperatures above the upper nematic–isotropic transition temperature. A wide region of miscibility emerges showing a single nematic phase. Nematogens having similar nematic–isotropic transition temperatures exhibit different phase properties from systems with widely separated transition temperatures. Effects of the polymer volume fraction at crosslinking, rubber elasticity parameters of the network, and the Flory–Huggins interaction parameter on the equilibrium phase diagram of these systems are discussed. © 2001 Society of Chemical Industry     

微乳液最佳中相醇用量和增溶能力与油相等效烷基碳数的定量关系

主要考察了十八烷基三甲基氯化铵(OTAC)和十二烷基硫酸钠(SDS)对油相的增溶规律。通过不同烃类混合,包括两种烃类的混合和4种烃类混合,调整混合油相的等效烷基碳数(EACN),探索最佳中相醇用量(A*)、最佳增溶量(SP*)与EACN的关系。A*、SP*与EACN在两类表面活性剂条件下都呈现二次函数的关系,且在同一表面活性剂体系中,控制其他组分含量恒定的情况下,函数关系与所用的烃无关。     

Catalytic behaviour of M1, M2, and M1/M2 physical mixtures of the Mo–V–Nb–Te–oxide system in propane and propene ammoxidation

Essentially pure orthorhombic M1 and pseudo-hexagonal M2 phases were prepared using the precursor method. Consistent with literature the M1 phase was shown to be effective for propane ammoxidation to acrylonitrile while the M2 phase was essentially inert for propane activation. Both phases convert propene efficiently to acrylonitrile. Both phases show a significant selectivity dependence on the ammonia and oxygen concentrations in the feed, revealing thereby additional insights into the reaction mechanism.

Physical mixtures of the two separately prepared phases exhibited symbiosis in the ammoxidation of propane when finally divided (5 μm), thoroughly mixed and brought into intimate contact with each other. Acrylonitrile yields significantly higher than those obtained with the M1 phase alone were demonstrated with a 50 wt.% M1/50 wt.% M2 physical mixture having a corresponding surface area ratio of about 4:1. The phase cooperation effect is particularly large at high propane conversions and non-existent when the particle size of the phases is too large (e.g. >250 μm) and the inter-particle contact is poor.     

On the Permeability of Silicone Rubber to Acetylene

Abstract

Very high rates have been reported for the permeation of acetylene through silicone rubber. Measurements in this laboratory, while consistent with the reported data for the permeation of other gases through silicone rubber, do not confirm the rates reported for acetylene.     

CO2混合物热物性在CCS研究中的作用:实验数据、理论模型和典型应用

二氧化碳捕集与封存（CCS）各工艺过程的设计、运行都依赖于对CO₂及其混合物热物理性质的深入理解。同时，CCS的规模化发展和商业化进程，对CO₂混合物及其热物性的准确性提出了更高的要求。本文从实验数据、理论模型和典型应用3个方面综述了CO₂及其混合物热物性的发展现状，并尝试对发展趋势进行归纳。在实验研究方面，CO₂混合体系的研究进展视组分不同，差异较大，其中CO₂-N₂、CO₂-CH₄、CO₂-H₂O和CO₂-H₂二元体系已形成较完善的物性数据库，而CO₂-NH₃、CO₂-NO _x 和CO₂-CO体系的物性数据还比较欠缺；在物性估算方面，面向CCS的物性估算模型研究自2008年开始活跃，基于不同理论构架，目前已逐步形成面向CCS的多元化的物性估算体系。物性研究在CCS中的应用主要体现在物性是支撑CCS过程研究的基础，其不准确性在过程模拟或计算中会被“放大”，从而影响过程评估的准确性，本文从物性在循环构建和能效分析中的作用以及CO₂水合物的形成3个方面入手做了说明。文章最后对面向CCS的物性研究趋势进行了梳理，对分子模拟技术、通用性强的物性估算模型和物性在过程设计和循环分析中的角色进行了展望。     

Dynamics of concentrated solutions of low molecular weight phenolics and poly(2-vinylpyridine): Role of intermolecular hydrogen bonding

The molecular dynamics of solutions of poly(2-vinylpyridine) (P2VPy) and a series of low molecular weight phenols containing from one to six hydroxyl groups were investigated using broadband dielectric spectroscopy (DRS). Dynamic mechanical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, small-angle X-ray scattering and wide-angle X-ray diffraction were employed in a complementary role. Segmental relaxation times for the α processes of all solutions follow expectations from T_gs derived from DSC experiments. For three of the model mixtures at 30 and 50 mol% [i.e., those containing bis (4-hydroxyphenyl) methane, 2,6 dihydroxynaphthalene, and 2,2-methylenebis[6-(2-hydroxy-5-methylbenzyl)-p-cresol] significantly broadened dielectric α relaxation time distributions were observed, indicating dynamic heterogeneity. On the other hand, 4-ethyphenol-P2VPy solutions display dynamic homogeneity. P2VPy with 10 mol% 2,3,3,4,4,5-hexahydroxybenzophenone behaved differently than all mixtures investigated in this study: it displayed a T_g (and T_α) significantly higher than that of the neat components, a small SAXS scattering peak, and an additional dielectric relaxation that we propose originates from Maxwell-Wagner-Sillars interfacial polarization. We propose that this behavior is a result of a phase separation of different types of hydrogen-bonded complexes, one rich in P2VPy and the other involving the type of 2,3,3,4,4,5-hexahydroxybenzophenone hydrogen-bonded structures found in the neat state. Intermolecular hydrogen bonding in all of the P2VPy-phenol mixtures suppresses, in some cases completely, the local P2VPy β relaxation by decreasing the mobility of the pyridine side groups.     

Development of a multi-fluid model for poly-disperse dense gas-solid fluidised beds, Part II: Segregation in binary particle mixtures

Particle mixing and segregation rates in a bi-disperse freely bubbling fluidised bed have been studied with a new multi-fluid model (MFM) based on the kinetic theory of granular flow for multi-component systems (see Part I). The MFM simulation results have been compared with digital image analysis experiments obtained by Goldschmidt et al. [2003. Digital image analysis of bed expansion in dense gas-fluidised beds. Powder Technology 138, 135-159] for bi-disperse mixtures of glass beads. In strong contrast to MFMs previously described in the literature, that strongly overestimate the segregation rates, the new MFM seems to underestimate the segregation rates at longer times. This underprediction of the segregation rate is probably related to the neglect of frictional stresses associated with long-term multiple-particle contacts resulting in an overestimation of the mobility of the emulsion phase, which is corroborated by discrete particle simulations without friction between the particles and the particles and the wall. The level of the granular temperature of the segregating system, as computed with the new MFM, compares reasonably well with the granular temperatures found in the DPM simulation.     

内置水平管的振动流化床中混合物的临界流化速度

在内置水平管的矩形振动流化床内研究了玉米粒和塑料珠混合物(Geldart D颗粒)中的流体力学性质。考察了颗粒质量分数、振动频率、振幅和内置水平管对混合颗粒的临界流化速度的影响。实验表明,振动的加入降低了混合物的临界流化速度。根据振动流化床的动力学特性,分析床层中颗粒受力情况,建立了混合颗粒物在振动流化床中临界流化速度的两类数学模型。通过实验数据建立两种模型的关联式所得的计算值和实验值误差控制在10%以内,吻合较好。