Numerical Investigation of Hydrocarbon Enrichment of Process Gas Mixtures by Permeation through Polymeric Membranes

In membrane‐based gaseous separations, a consensus on the distribution of the components of the permeate stream in the immediate membrane vicinity has yet to be reached and the possibility of an underestimation of selective gas permeance due to lack of gas mixing on the permeate side exists. In this work, a numerical study of the permeation of ethylene and propylene in their binary mixtures with nitrogen through a composite poly(dimethylsiloxane) coated polysulfone membrane was performed. Continuity and momentum equations, along with gas compressibility and permeance properties for individual species of the gas mixture, were introduced into a comprehensive computational fluid dynamics (CFD) model. Simulation results showed that irrespective of the stage‐cut, gases with higher selectivity were well mixed in the vicinity of the membrane on the permeate side.     

Modeling the phase behavior in binary mixtures involving blowing agents and thermoplastic resins

The thermophysical properties of mixtures of thermoplastic resins and blowing agents, together with the knowledge of the solubilities of these components, are the basis for the manufacturing of plastic foams. In this work, the solubilities of blowing agents trichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromehane, and 1,2‐dichloro‐1,1,2,2‐tetrafluoroethane in thermoplastic resins poly(styrene), high density poly(ethylene), low density poly(ethylene), poly(propylene), poly(vinyl chloride), poly(carbonate) and poly(propylene oxide) were modeled by using the Perturbed Chain‐Statistical Associating Fluid Theory (PC‐SAFT) and the Sánchez‐Lacombe equations of state (EoS), fitting a single temperature‐dependent binary interaction parameter. PC‐SAFT is a theoretically based equation of state with three pure component parameters that describe efficiently the thermodynamics of complex systems. Earlier works with this EoS have already predicted the phase coexistence properties of various refrigerants and higher order alkane series compounds, along with their mixtures. The pure component parameters for the blowing agents were obtained by regression of vapor pressure and liquid density data, while the pure component parameters for the thermoplastic resins were obtained by regression of pure liquid PVT data. The parameter estimation was performed by using a modified maximum likelihood method. The solubility results obtained with both EoS have been compared; the results from PC‐SAFT showed a higher accuracy in terms of solubility pressure deviations. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

丙烯/1-丁烯无规共聚物与丙烯/乙烯抗冲共聚物的对比研究

对丙烯/1-丁烯无规共聚物(PPB)与丙烯/乙烯抗冲共聚物(PPE)的结晶行为进行对比,在等温结晶时,通过相对结晶度随时间的变化关系、等温结晶曲线等研究,表明丙烯/1-丁烯无规共聚物结晶速率明显低于丙烯/乙烯抗冲共聚物,同时丙烯/乙烯抗冲共聚物的等温结晶速率随乙烯单元含量增加没有明显降低。根据Avrami方程计算了共聚物的结晶活化能,证明丙烯/1-丁烯无规共聚物的结晶能力较丙烯/乙烯抗冲共聚物低。扫描电镜分析丙烯/1-丁烯无规共聚物在丁烯单元摩尔分数2.39%时没有韧性拉伸,而丙烯/乙烯抗冲共聚物在乙烯单元摩尔分数3%时出现韧性拉伸。     

乙烯和丙烯在低聚物-正己烷溶液中的溶解度及体积传质系数测定

在高压搅拌釜中,利用气体间歇物理吸收技术,在温度343～393 K、压力0.2～1.45 MPa下,测定了乙烯-正己烷、丙烯-正己烷、乙烯-正己烷-低聚物（低分子量聚乙烯）和丙烯-正己烷-低聚物的气体平衡溶解度与液相体积传质系数k_La,并回归出表观溶解热,使用PC-SAFT状态方程关联了汽液平衡数据,拟合得到乙烯/丙烯-正己烷-低聚物的k_La经验关联式,与实验结果吻合良好。实验系统考察了压力、温度和低聚物浓度对平衡溶解度和k_La的影响,结果表明：压力升高,气体溶解度增大,符合亨利定律,k_La略有降低;温度升高,气体溶解度减小,乙烯在正己烷中的k_La增大,丙烯在正己烷中的k_La则减小;低聚物浓度增加,气体溶解度与k_La均降低。     

Die mit Natriumphenolat katalysierte Addition von Äthylenoxid-Propylenoxid-Gemischen an Monophenylmonoalkylenglykole. I. Die Kinetik der Epoxid-Alkohol-Reaktion

Four separate reactions necessary to describe the copolyaddition of ethylene oxide and propylene oxide mixtures to monophenylmonoalkylene glycol with sodium phenoxide as catalyst have been studied kinetically. The rate of reaction for homoaddition of ethylene oxide and propylene oxide at a molar ratio ≥ 1 of epoxide to the corresponding alkylene glycol is proportional to the catalyst concentration. However, for heteroreactions i. e. in case the glycol used as initial OH-component is not of the same nature (as that produced after the first reaction step), the concentration of the initial alcohol also appears in the rate equation.     

PP—EPR对PP／EPT增容作用的研究

通过δ－ＴｉＣｌ３－Ｅｔ２ＡｌＣｌ催化淤浆聚合合成了不同嵌段箍度的聚丙烯－乙丙橡胶嵌段共聚物（ＰＰ－ＥＰＲ）。作为惭丙橡胶（ＥＰＴ）和ＰＰ的增容性，明显改善的低温耐部性能。实验发现，当ＰＰ－ＥＰＲ中ＰＰ段的聚合时间为５ｍｉｎ。ＥＰＲ段的聚全时间为３０ｍｉｎ时，ＰＰ－ＥＰＲ加入量仅为４％，就可以显著地改善ＰＰ和ＥＰＴ的相容性，使共混物ＰＰ／ＥＰＴ／ＰＰ－ＥＰＲ的拉伸强度只比ＰＰ降低２２％而－２０℃和     

Physical and chemical stress relaxation of elastomers

In this paper we have developed a method whereby physical and chemical relaxation processes can be distinguished, using stress relaxation experiments as a function of temperature. We assumed that there exists some temperature range above the glass transition temperature over which the chemical effects can be neglected for the time scale of the experiments. The data in this low temperature range were then used to determine the WLF constants and other physical relaxation parameters. The physical component of the stress relaxation could then be subtracted from high temperature experiments in order to extract chemical kinetic information. Based on certain reasonable assumptions, an equation was developed for the relaxation modulus of a chemically reacting system. This equation could be used to determine the time dependence of the crosslink density, or conversely could be used to predict the long term relaxation modulus from an assumed kinetic mechanism. These calculations were demonstrated for ethylene propylene and butyl elastomers.     

Surfactants from fatty esters of polyalkoxylated polyol glycosides

The glycoside raw materials used to prepare the surfactants were mixtures produced directly from low cost starch and the polyols by transglycosidation. After alkoxylation with ethylene oxide and propylene oxide, the glycosides were transesterified by the methyl esters of various fatty acids to yield the final products. Monolaurates of the polyalkoxylated glycosides containing a combination of 8 mol ethylene oxide and 4 mol propylene oxide per mole of glycoside showed detergency in an alkaline formulation comparable to two commercial detergents. An advantage in this application is the potential for complete biodegradation because of the fatty ester carbohydrate structures. The two monolaurates of glycerol glycoside polyethers containing 4.8 and 8 mol propylene oxide, in particular, produced oil-inwater emulsions of high stability. ARS, USDA.     

The effect of [bmim][Br] on the solubility of carbon dioxide and methane in glycols at pressures up to 14 MPa and temperatures ranging from 303 to 423 K

Solubility data of methane in ethylene glycol and 1-4 butylene glycol and carbon dioxide in ethylene glycol and 1-2 propylene glycol in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide have been measured in the temperature range (303–423) K at pressures up to 14 MPa. Henry's law constant of each solute in the studied solvent at saturation pressure is given. The experiments were performed in an autoclave type phase equilibrium apparatus using the total pressure method. For mixtures containing carbon dioxide and ethylene glycol no influence was observed. For mixtures containing carbon dioxide and 1-2 propylene glycol it was observed salting-out effect at 303.2 K and 323.2 K and salting-in effect at the remaining temperatures. For mixtures containing methane and ethylene glycol or 1-4 butylene glycol salting-in effect was observed.     

Spheripol工艺生产高抗冲聚丙烯

介绍了Spheripol工艺生产高抗冲聚丙烯产品的方法,采用两步复合工艺生产嵌段聚丙烯,第1步采用环管反应器进行丙烯液相均聚反应,第2步采用流化床反应器进行丙烯均聚物与乙烯单体气相共聚反应,即在气相反应器中,利用来自环管反应器中的均聚物的残余活性,加入乙烯和补充的丙烯及氢气实现乙-丙共聚,共聚物的生成使最终产品的抗冲性能大大提高,尤其是低温下的抗冲性能。     

Emulation of condensed fuel flames with gaseous fuels supplied through a porous copper calorimeter

The burning rate emulator (BRE) is a burner that emulates condensed fuel flames using gaseous fuel/inert mixtures by matching four properties: the heat of combustion; the heat of gasification; the laminar smoke point; and the surface temperature. Matching the heat of gasification requires measuring the burner heat flux, for which the BRE has embedded heat flux gauges and a copper top-plate calorimeter. Seven condensed fuels were emulated: acetone, ethanol, methanol, polyethylene, polymethylmethacrylate, polypropylene, and polystyrene. The gaseous fuels were methane, ethylene, and propylene, diluted with nitrogen. Emulation data and flame images are shown to demonstrate emulation accuracy. A new method of emulation is developed that shifts the focus on which properties are prioritized and yields ~15% improvement in flame height. Calibration and use of the calorimeter are shown to have improved accuracy (within 5%) which provides confidence in the results.     

THE SEPARATION OF METHYL ACETATE FROM METHANOL BY EXTRACTIVE DISTILLATION

Methyl acetate cannot be completely removed from methyl acetate-methanol mixtures by distillation because of the presence of the minimum binary azeotrope. Methyl acetate can be readily removed as overhead product from mixtures containing it and methanol by using extractive distillation in which the extractive distillation agent is a higher boiling oxygenated, nitrogenous and/or sulfur containing organic compound or a mixture of these. Typical examples of effective agents are dimethylsulfoxide, glycerine plus propylene glycol, ethylene glycol plus dimethylsulfoxide plus 1,5-pentanediol. Methanol can be removed as the overhead product from methyl acetate when the extractive distillation agent is nitrobenzene, propylene carbonate or ethylene glycol phenyl ether.     

THE SEPARATION OF METHYL ACETATE FROM METHANOL BY EXTRACTIVE DISTILLATION

Methyl acetate cannot be completely removed from methyl acetate-methanol mixtures by distillation because of the presence of the minimum binary azeotrope. Methyl acetate can be readily removed as overhead product from mixtures containing it and methanol by using extractive distillation in which the extractive distillation agent is a higher boiling oxygenated, nitrogenous and/or sulfur containing organic compound or a mixture of these. Typical examples of effective agents are dimethylsulfoxide, glycerine plus propylene glycol, ethylene glycol plus dimethylsulfoxide plus 1,5-pentanediol. Methanol can be removed as the overhead product from methyl acetate when the extractive distillation agent is nitrobenzene, propylene carbonate or ethylene glycol phenyl ether.     

环氧丙烷与乙二胺合成2-甲基吡嗪的研究

本文研究了以乙二胺和环氧丙烷为原料,经气固相接触催化合成2-甲基吡嗪的新工艺。试验中采用自制的复合催化剂,最佳工艺条件为:预热温度260℃,反应温度380℃,原料环氧丙烷和乙二胺摩尔比为1 2∶1,流量为6mL h,反应过程中氢气、氮气流量均为4L h。2-甲基吡嗪的反应收率大于89%(质量分数),经分离得到纯度大于99%(质量分数)的2-甲基吡嗪。     

Explosionskenngrößen von Ethylenoxid und Ethylenoxid/Propylenoxid‐Gemischen

Gas phases of ethylene oxide and propylene oxide, commonly used for technical alcoxylation reactions, can decompose explosively with an enormous temperature and pressure rise even without the presence of air. For the estimation of consequences of such reactions explosion pressures and rates of pressure rise of EO and certain mixtures of ethylene oxide and propylene oxide at temperatures between 100 °C and 200 °C and pressures between 1 bar and 10 bar were determined experimentally using vessels with volumes of 3 dm³ and 100 dm³.     

Polymerization of olefins through heterogeneous catalysis—V. Gas-liquid mass transfer limitations in liquid slurry reactors

Many processes for polymerization of olefins employ laboratory, pilot plant, or full-scale liquid-phase polymerization reactors with monomer introduced as a gas. Criteria for the presence of gas-liquid mass transfer resistance in these systems are determined in terms of observed reaction rate or loading of a heterogeneous catalyst of given intrinsic activity. The effects of variables such as reactor size and configuration, temperature, and soluble polymer are also examined. The equilibrium monomer concentrations of ethylene in hexane and propylene in heptane are calculated through a modified Benedict-Webb-Rubin equation, and some calculations for ethylene-propylene mixtures are tabulated. The general methodology for predicting gas-liquid mass transfer resistance is readily extendible to copolymerization systems.     

Oxypropylation of fatty alcohols,and the sulfation products

Reaction of propylene oxide, rather than ethylene oxide, with fatty alcohols, gives a higher yield (50%) of mono-oxyalkylation product because the secondary alcohol formed is less reactive than the primary alcohol formed with ethylene oxide. Rate of further reaction is about half the rate of the parent primary alcohol. Distributuon of propylene oxide reaction products follows the Weibull-Nycander equation. Analysis of reaction products was accomplished by gas-liquid chromatography of the acetylated ether alcohol mixtures. Pure mono-oxypropylated alcohols ROCH₂CHOHCH₃ and in some cases dioxypropylated alcohols R[OCH₂CH(CH₃)]₂OH were separated by fractional distillation. Individual ether alcohols and products with a known average number of oxypropyl groups were sulfated and evaluated in terms of Krafft point, critical micelle concentration, detergency, foam height and lime soap dispersing properties. Incorporation of one oxypropyl group was more effective than the same degree of oxyethylation, and improved solubility with no significant loss in foaming and detergency. Ether alcohol sulfates from propylene oxide are stable to alkaline hydrolysis and nearly equal to the sulfates from ethylene oxide in their stability to acid hydrolysis. Presented at the AOCS Meeting in Cincinnati, 1965. E. Utiliz. Res. Dev. Div., ARS. USDA.     

Fabrication and characterization of PDMS coated PES membranes for separation of ethylene from nitrogen

Composite membranes were prepared for separation of ethylene from nitrogen using polyethersulfone (PES) as support and polydimethylsiloxane (PDMS-a grade of silicone rubber) as active layer at various concentrations. Permeance and ideal selectivity were measured for all membranes under the transmembrane pressure of 2 to 6 bars. Influences of affecting parameters on membrane performance (i.e. permeance and selectivity) were investigated. The studied parameters include: PES concentration in casting solution, solvent type, PDMS concentration in coating layer, support thickness, coating thickness and coagulation atmosphere. For all coated membranes, the ethylene permeance was higher compared to the nitrogen permeance except for 5% coated air coagulated membrane. This membrane was more permeable for N₂ in comparison with ethylene under the pressures higher than 2 bars. The nitrogen permeance exhibited a rather constant value. There was no significant change in nitrogen permeance with respect to the coating layer, whereas ethylene permeance was highly influenced by coating layer composition and support thickness. The governing mechanism for the separation is solution-diffusion of ethylene in PDMS layer (solution-diffusion model). The SEM study was carried out for investigation of membrane morphology. In a run ethylene was passed through the membrane after the passage of nitrogen. In the second run ethylene was passed through the membrane before nitrogen. The nitrogen selectivity was reduced in the later test. This is due to the ethylene high solubility in membrane matrix.     

Crystalline characteristics of ethylene/propylene/1,4-hexadiene terpolymers and related ethylene copolymers

An improved differential thermal analytical technique which permits the rapid, convenient characterization of the thermal behavior of crystalline polymers free of any influence of prior thermal history is presented. Characterization of both crystallization and fusion phenomena is described for ethylene/propylene copolymers subjected to well-controlled thermal scanning techniques. Parameters describing these phenomena are derived. While they are nonequilibrium parameters, they are reproducible and capable of correlation with polymer composition. the crystallization onset temperature determined by this cooling technique was found to relate to the molar ethylene content of the copolymers by an equation similar to the one derived by Flory⁵ based on equilibrium melting point. The relationship was found to hold true for a number of ethylene copolymers, including samples of linear and branched polyethylene, commercial EPDM, and ethylene/vinyl acetate copolymers.     

Propylene-induced plasticization in silver polymer electrolyte membranes

Silver polymer electrolyte membranes consisting of AgBF₄ or AgCF₃SO₃ dissolved in poly(2-ethyl-2-oxazoline) (POZ) or poly(N-vinyl pyrrolidone) (PVP) have previously shown outstanding separation performance for propylene/propane mixtures. The ideal separation factor (i.e. pure gas selectivity) of propylene over propane reached 15,000, but the actual selectivity (i.e. mixed gas selectivity) was approximately 50. In this study, the origin of large difference between pure and mixed gas selectivities has been elucidated in terms of membrane plasticization by propylene molecules. The membrane plasticization was confirmed by the decrease of selectivity with increasing propylene concentration in the feed, resulting from the increase of both propylene and propane permeances. The decrease of glass transition temperature (T_g) in silver polymer electrolytes upon the sorption of propylene also supported the membrane plasticization, determined by in situ high-pressure differential scanning calorimetry (HPDSC). Further analysis of configuration entropy model revealed that the interaction of propylene/silver ion in POZ/AgBF₄ was approximately 2-fold stronger than that in POZ/AgCF₃SO₃, which is in good agreement with the results of propylene solubility and FT-IR spectra.