Diluent Mixtures Research Articles

Phase behavior of polymer/diluent/diluent mixtures and their application to control microporous membrane structure

Rechargeable battery separators containing controlled pores were fabricated via the thermally-induced phase separation (TIPS) process. Based on the idea that pores could be manipulated by controlling the liquid–liquid phase separation temperature in the TIPS process, phase boundaries of the polymer–diluent systems were controlled by using diluent mixtures. Phase behaviors of the polymer/diluent/diluent ternary blends consisting of polyethylene (PE) as polymer, and soybean oil (SBO) and dioctyl phthalate (DOP) as diluents were explored. PE/SBO and PE/DOP binary blends, and PE/SOB/DOP ternary blends exhibited typical upper critical solution temperature (UCST) type phase behaviors, and the phase separation temperatures of the PE/SBO blends were higher than those of the PE/DOP blends. When the mixing ratio of the polymer and diluent-mixture was fixed, the phase separation temperature of the PE/SBO/DOP blend initially increased with increasing SBO content in the diluent-mixture passing through a maximum centered at about 80 wt% SBO and decreased beyond this point. Furthermore, the phase separation temperature of the PE/diluent-mixture blend was always higher than that of the PE/SBO blend when the diluent-mixture contained more than or equal to 50 wt% SBO. To understand the observed phase behavior of the blends, thermodynamic analyses based on the lattice-fluid theory were performed. Larger pore membranes were fabricated from the blend when higher phase separation temperatures of the blend were exhibited.

Preparation of porous PVDF membrane via thermally induced phase separation with diluent mixture of DBP and DEHP

AbstractPoly(vinylidene fluoride) microporous membranes were prepared via the thermally induced phase separation process using diluent mixture of dibutyl phthalate (DBP) and di(2‐ehylhexyl) phthalate (DEHP). The effects of the DBP ratio to DEHP in the diluent mixture on the phase diagrams were investigated. The phase diagrams can be controlled successfully by varying the DBP ratio in the diluent mixture. The compatibility between polymer and diluent mixture was characterized to explain the features in the phase diagram. The cross‐sectional structures of membranes were investigated and related to the DBP ratio in diluent mixtures, initial polymer concentration, and cooling rate. When the DBP ratio to DEHP was 30 wt/70 wt, only spherulites structure was obtained at the polymer concentration of 30 wt % and at the cooling rate of 10°C/min, whereas the cellular structure was detected as the polymer concentration increased or the cooling rate deceased. In the case of the systems with only S‐L phase separation, only spherulites structures were observed and the sizes of spherulites increased with increase in the polymer concentration and with decrease in the cooling rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Studying the chemistry of HCCI in rapid compression machines

The rapid compression machine is an ideal tool to investigate the chemistry of the HCCI engine as important factors controlling both devices are the same. There is no tool that describes, meaningfully, the physical and chemical processes occurring in one of the simplest research tools, the rapid compression machine and typically, processes are simulated based on gross oversimplifications. This study highlights some factors that optimise the RCM as a research tool, and the effect of using diluent mixtures on measured ignition delay times. It shows that there is no straightforward method to define characteristic heat loss associated with diluent mixtures.

Entity-Based Eyring−NRTL Viscosity Model for Mixtures Containing Oils and Bitumens

A segment-based Eyring−NRTL viscosity model was recently presented and evaluated using data from a variety of mixtures containing polymers. In this paper, the segment-based Eyring−NRTL viscosity model is modified to provide a practical theory-based model for the viscosity of liquid mixtures containing complex components that cannot be typically described by the segment-based approach. To reflect these changes, this new model is referred to as an entity-based Eyring−NRTL viscosity model, because entities are viewed as abstract segments that represent complex components but are not well-defined. The entity-based Eyring−NRTL viscosity model provides a theory-based equation for liquid mixture viscosity as a function of composition, temperature, pressure, and shear rate. The correlative and predictive capability of the entity-based Eyring−NRTL viscosity model is demonstrated using component and mixture viscosity data from the following systems: lubricating oil blends, crude oil blends, bitumen−diluent mixtures, heavy oil−diluent mixtures, and acetone−ethanol−2,2,4-trimethylpentane mixtures. Ternary lubricating oil blend viscosities and ternary acetone−ethanol−2,2,4-trimethylpentane mixture viscosities are predicted from component and binary viscosity parameters determined from only component and binary mixture viscosity data. The entity-based model should be useful for modeling viscosity in a number of applications containing complex components, such as petroleum, petrochemicals, polymers, lubricants, coatings, and personal care products.

Evaluation of lower flammability limits of fuel–air–diluent mixtures using calculated adiabatic flame temperatures

The lower flammability limit (LFL) of a fuel is the minimum composition in air over which a flame can propagate. Calculated adiabatic flame temperatures (CAFT) are a powerful tool to estimate the LFL of gas mixtures. Different CAFT values are used for the estimation of LFL. SuperChems™ is used by industry to perform flammability calculations under different initial conditions which depends on the selection of a threshold temperature. In this work, the CAFT at the LFL is suggested for mixtures of fuel–air and fuel–air–diluents. These CAFT can be used as the threshold values in SuperChems™ to calculate the LFL. This paper discusses an approach to evaluate the LFL in the presence of diluents such as N 2 and CO 2 by an algebraic method and by the application of SuperChems™ using CAFT as the basis of the calculations. The CAFT for different paraffinic and unsaturated hydrocarbons are presented as well as an average value per family of chemicals.

Observations of the cellular structure of fuel–air detonations

Detonation cell widths, which provide a measure of detonability of a mixture, were measured for hydrocarbon–air and hydrogen–air–diluent mixtures. Results were obtained from a 0.43-m-diameter, 13.1-m-long heated detonation tube with an initial pressure of 101 kPa and an initial temperature between 25 and 100 °C. The cell widths of simple cyclic hydrocarbons are somewhat smaller than those of comparable straight-chain alkanes. Cyclic hydrocarbons tested generally had similar cell sizes despite differences in degree of bond saturation, bond strain energy, oxygen substitution, and chemical structure. There was a significant reduction in the cell width of octane, a straight-chain alkane, when it was mixed with small quantities of hexyl nitrate. The effect of a diluent, such as steam and carbon dioxide, on the cell width of a hydrogen–air mixture is shown over a wide range of mixture stoichiometries. The data illustrate the effects of initial temperature and pressure on the cell width when compared to previous studies. Not only is carbon dioxide more effective than steam at increasing the mixture cell width, but also its effectiveness increases relative to that of steam with increasing concentrations. The detonability limits, which are dependent on the facility geometry and type of initiator used in this study, were measured for fuel-lean and fuel-rich hydrogen–air mixtures and stoichiometric hydrogen–air mixtures diluted with steam. The detonability limits are nominally at the flammability limits for hydrogen–air mixtures. The subcellular structure within a fuel-lean hydrogen–air detonation cell was recorded using a sooted foil. The uniform fine structure of the self-sustained transverse wave and the irregular structure of the overdriven lead shock wave are shown at the triple point path that marks the boundary between detonation cells.

Approximation of flammability region for natural gas–air–diluent mixture

The growing implementation of exhaust gas recirculation (EGR) in reducing NO x emissions of engine is of paramount motivation to perform a fundamental research on the flammability characteristics of fuel–air–diluent mixtures. In this work, the influences of EGR on the flammability region of natural gas–air–diluent flames were experimentally studied in a constant volume bomb. An assumption of critical burning velocity at flammability limit is proposed to approximately determine the flammability region of these mixtures. Based on this assumption, an estimation of the flammability map for natural gas–air–diluent mixtures was obtained by using the empirical formula of burning velocity data. The flammability regions of natural gas–air mixtures with EGR are plotted versus the EGR rate. From the comparison of estimated results and experimental measurements, it is suggested that the accuracy of prediction is largely dependent upon the formula of burning velocity used. Meanwhile, the influence of pressure on the critical burning velocity at flammability limit is also investigated. On the basis of the pressure dependence criterion, the estimation was performed for the circumstance of high temperature and pressure, and the prediction results still agree well with those of experiments.

Effect of diluent on poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membrane formation via thermally induced phase separation

AbstractPoly(ethylene‐co‐vinyl alcohol) hollow‐fiber membranes with a 44 mol % ethylene content were prepared by thermally induced phase separation. A mixture of 1,3‐propanediol and glycerol was used as the diluent. The effects of the ratio of 1,3‐propanediol to glycerol in the diluent mixture on the phase diagram, membrane structure, and membrane performance were investigated. As the ratio increased, the cloud point shifted to lower temperatures, and the membrane structure changed from a cellular structure due to liquid–liquid phase separation to a particulate structure due to polymer crystallization. Better pore connectivity was obtained in the hollow‐fiber membrane when the ratio of 1,3‐propanediol to glycerol was 50:50, and the membrane showed about 100 times higher water permeability than the membrane prepared with pure glycerol. For the prepared hollow‐fiber membrane, the solute 20 nm in diameter was almost rejected. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 219–225, 2005

Monodisperse Poly (Styrene-co-Divinylbenzene) Particles (3.2 ?m) with Relatively Small Pore Size as HPLC Packing Material

Monodisperse 3.2-μm porous poly(styrene-co-divinylbenzene) particles have been prepared by a new multistage polymerization procedure, so-called ‘modified seeded polymerization’. In the synthesis of the particles sufficient porosity was generated by use of a diluent mixture with relatively low viscosity. The use of relatively high diluent/seed latex ratio resulted in the formation of particles with an average pore size of 13 nm. The particles were used as column-packing material in HPLC and their performance was compared with that of larger particles (dn = 7.8 μm) obtained by the same method. The SEC plot for the 3.2 μm particles showed that the proposed material was particularly suitable for separation of analytes in the molecular weight range 100–2000. In reversed-phase mode alkylbenzenes were separated with resolution >2 by use of a relatively small column (50 mm × 4.6 mm i.d.) packed with 3.2-μm particles. Theoretical plate numbers (TPN) in excess of 35 000 plates m−1 could be achieved with benzene as analyte. Whereas the ratio of TPN determined with pentylbenzene to that determined with benzene was less than 0.7 for the 7.8-μm particles, the same ratio was 0.95 for the 3.2-μm particles. With the 3.2-μm packing material proposed no significant decrease in resolving power was observed when the mobile-phase flow rate was increased sevenfold.

Suportes poliméricos para catalisadores sulfônicos: síntese e caracterização

Suportes poliméricos foram sintetizados por meio da copolimerização de estireno (S) e divinilbenzeno (DVB) em suspensão aquosa na presença de misturas diluentes constituídas por tolueno e n-heptano, solventes esses considerados como bom e mau para o polímero respectivamente, em composições variadas. Foram usados dois teores de DVB (60 e 80%) e dois graus de diluição (100 e 200%). Os suportes foram caracterizados no estado seco e no estado inchado e suas propriedades foram relacionadas com os parâmetros de síntese. No estado seco, os copolímeros foram analisados quanto à densidade aparente, à área específica, ao volume de poros e à morfologia. No estado inchado foi observado o comportamento dos copolímeros em tolueno e em n-heptano. Neste trabalho são comentadas as vantagens do uso desses suportes para a preparação de catalisadores sulfônicos e se faz uma comparação entre esses catalisadores e os catalisadores homogêneos convencionais comumente usados em sínteses orgânicas.

Challenges Inherent in the Development of Predictive Deposition Tools for Asphaltene Containing Hydrocarbon Fluids

The correlation and prediction of deposit formation are at the core of flow assurance, risk assessment, and other reservoir fluid management issues and are equally important for heavy oil or bitumen partitioning and upgrading. Asphaltene deposition in particular is a key topic in both sectors. Hydrocarbons from condensate-rich reservoir fluids to bitumen + diluent mixtures share constituents, from asphaltenes and resins to pentane, and can all be classified as asymmetric from a phase behavior perspective. The phase dia-grams for these asymmetric fluids are characterized by zone of four-phase behavior surrounded by three-phase and two-phase regions in both pressure-composition at constant temperature, and pressure–temperature at constant composition diagrams. Adherent asphaltenic solid and liquid deposits only arise within some multiphase zones. Zones such as the SL1, SL1V, L1L2V, and L1L2 are prone to the production of adherent asphaltenic deposits particularly when combined with intermittent or laminar flow. By incorporating incomplete approaches prevalent in both sectors into qualitative four component phase diagrams, one can illustrate key aspects of the phase diagrams for the entire range of fluids, as well as the challenges faced with respect to the prediction of specific phase behaviors. In this article we present and illustrate some of these challenges and propose a path toward their resolution.

Gas Transport in Polymers Prepared via Metathesis Copolymerization of exo-N-Phenyl-7-oxanorbornene-5,6-dicarboximide and Norbornene

This work reports the synthesis of exo-N-phenyl-7-oxanorbornene-5,6-dicarboximide and its ring-opening metathesis copolymerization with norbornene to yield poly(exo-N-phenyl-7-oxanorbornene-5,6-dicarboximide-co-norbornene), with molar ratio 50/50. The glass transition temperature of the copolymer is 125 °C. Permeation and sorption processes of different gases (hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, methane, ethylene, and ethane) were measured in membranes prepared by casting from solutions of the copolymer in chloroform. The Langmuir capacity of the gases is relatively small due to the nearness of the glass transition temperature of the polymer to the working temperature. The solution of the most condensable gases in the continuous phase of the membrane is apparently described by the Flory−Huggins theory of polymer−diluent mixtures. In general, the membranes exhibit a reasonably high separation coefficient of hydrogen with respect to ethane, ethylene, nitrogen, and methane. The value...

The influence of the diluent system on the porous structure formation of copolymers based on 2-vinylpyridine and divinylbenzene. Diluent system. III. heptane/methylethylketone

The effects of the diluent mixture's composition and crosslinking degree [divinylbenzene (DVB)] on the porous characteristics of the anion-exchange resins based on 2-vinylpyridine (2VP) and DVB, synthesized by suspension polymerization, in the presence of a diluent mixture constituted of heptane (HEP) and methyl ethyl ketone (MEK) at different proportions, were evaluated. The resins were characterized by mercury porosimetry, nitrogen adsorption (Brunauer–Emmett–Teller (BET) method surface area determination), apparent density, and swelling in methanol. The optical appearance of the copolymer beads was examined by optical microscopy. It was found that the development of porosity was attained whenever the content of methyl ethyl ketone in the diluent mixture was increased for all DVB contents employed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 666–669, 2004

Crosslinking of vinyl-terminated side-chain liquid crystalline polyethers using low molecular weight analogous mesogenic esters as reactive diluents

We have synthesized two methyl 4′-(ω-alkenoxy)-4-biphenylcarboxylates and two methyl 6-(ω-alkenoxy)-2-naphthalenecarboxylates and used them as reactive diluents in the crosslinking of vinyl-terminated side-chain liquid-crystal polyepichlorohydrin derivatives containing analogous mesogenic moieties. The crosslinking was done with a 10 mol% of a free radical initiator system. Differential scanning calorimetry, polarized optical microscopy and X-ray diffraction measurements show that the mixtures of polymers with the reactive diluents had the same mesophases as pure polymers. We obtained liquid crystal thermosets from the biphenyl derivatives but, because of the low isotropization temperatures of the polymer–diluent mixtures, the naphthalene derivatives did not produce crosslinked anisotropic materials.

Laminar flame velocity determination for H2-air-steam mixtures using the spherical bomb method

The present work reports experimental results on the determination of laminar flame velocities of hydrogen- air - diluent mixtures initially at 100 kPa and for 2 different initial temperatures 298 and 353 K. The diluent was water vapor or a mixture containing helium and carbon dioxide. The data obtained in this study are compared with the literature ones. The experimental setup consists of a spherical bomb coupled to a schlieren system and a high speed camera. The effect of the stretch on the flame velocity is characterized for all the investigated mixtures. Computed laminar flame velocities are obtained using PREMIX and CHEMKIN codes. Two different kinetic mechanisms are used, and the computed values are compared to the experimental ones.

Removal of 230Th by solvent extraction from high grade uranium ore liquid tailings to arrest 226Ra production in the tailings

AbstractPrimene JM‐T, D2EHPA and TBP were used as solvents to extract 230Th from sulphuric acid uranium leachate and barren solutions from a Saskatchewan, Canada uranium mill. This was done with the objective of eliminating the source for 226Ra production in the tailings in perpetuity. A 0.1 vol% Primene JM‐T, 5 vol% isodecanol (modifier), and kerosene diluent mixture was found to completely remove thorium from the solutions. The thorium was stripped from the loaded organic with a 15 wt% ammonium carbonate solution.

Ion-exchange properties of 4-vinylpyridine–divinylbenzene-based anion exchangers for ferric chloride complex anions

4-Vinylpyridine–divinylbenzene-based anion exchangers were synthesized by suspension polymerization. Diluent mixtures containing a range of cyclohexane to cyclohexanone ratio were employed to dilute monomers at the time of polymerization. The ion exchangers were characterized for porosity, ion exchange capacity and t 1/2 for exchange of (FeCl 4) − ions adsorbed on resins and those in the surrounding solution. A gradual increase of cyclohexane fraction in the diluents from 0% to 100% resulted in: a gradual increase in pore volume from 0.1 to 1.6 ml/g; shift of pore diameter of major fraction of pores from <0.01 to >0.5 μm; and a decrease in breakthrough volume capacity for (FeCl 4) − from 0.7 to 0.2 meq/ml. The t 1/2 value decreased from 63 to 8 s followed by an increase to 70 s at 0%, 50% and 100% cyclohexane in the diluents, respectively.

Studies on cross-linked polyurethane acrylate-based electrolyte consisting of reactive vinyl/divinyl diluents

A series of cross-linked polyurethane acrylate (PUA) electrolytes have been prepared by using 4,4′-methylene bis(phenyl isocyanate), polyethylene glycol, hydroxyethyl methacrylate and different reactive vinyl/divinyl diluents, such as methyl methacrylate (MMA), ethyl acrylate and acrylonitrile, tripropylene glycol diacrylate (TPGDA). The electrolytes were prepared by UV radiation induced cross-linking of the PUA–diluent mixture followed by swelling in a liquid electrolyte (LP-30). Depending upon the composition of the components, these electrolytes exhibited a wide range of mechanical and electrical properties. The system containing MMA as reactive diluent showed highest conductivity, but poor mechanical properties and stability in the liquid electrolyte. The TPGDA cross-linked system possesses a good combination of ionic conductivity and stability in liquid electrolytes. These systems showed good compatibility with Li-electrodes and sufficient electrochemical stability to allow safe operation in rechargeable Li-batteries.

The influence of the diluent system on the porous structure formation of copolymers based on 2-vinylpyridine and divinylbenzene. Diluent system: II-n-heptane/toluene

Anion-exchange resins based on 2-vinylpyridine (2VP) and divinylbenzene (DVB) were synthesized by suspension polymerization in the presence of a diluent mixture of n-heptane (HEP) and toluene (TOL) at different compositions. The effects of the composition of the diluent mixture and crosslinking degree (DVB content) on the porous properties of the resins were evaluated. It was found that the development of porosity was attained whenever the content of n-heptane in the diluent mixture was increased for all DVB contents employed. The resins were characterized by mercury porosimetry, BET surface area determination, and apparent density, swelling in methanol. The optical appearance and surface morphology of the copolymer beads were examined by optical and scanning electron microscopies (SEM), respectively.

Laminar Burning Velocity of Methane–Air–Diluent Mixtures

An experimental facility for measuring burning velocity has been designed and built. It consists of a spherical constant volume vessel equipped with a dynamic pressure transducer, ionization probes, thermocouple, and data acquisition system. The constant volume combustion vessel allows for the determination of the burning velocity over a wide range of temperatures and pressures from a single run. A new model has been developed to calculate the laminar burning velocity using the pressure data of the combustion process. The model solves conservation of mass and energy equations to determine the mass fraction of the burned gas as the combustion process proceeds. This new method allows for temperature gradients in the burned gas and the effects of flame stretch on burning velocity. Exact calculations of the burned gas properties are determined by using a chemical equilibrium code with gas properties from the JANAF Tables. Numerical differentiation of the mass fraction burned determines the rate of the mass fraction burned, from which the laminar burning velocity is calculated. Using this method, the laminar burning velocities of methane–air–diluent mixtures have been measured. A correlation has been developed for the range of pressures from 0.75 to 70 atm, unburned gas temperatures from 298 to 550 K, fuel/air equivalence ratios from 0.8 to 1.2, and diluent addition from 0 to 15 percent by volume.