Separation of kinetics and mass-transfer in a batch alkoxylation reaction

The quantitative aspects of the role of interfacial mass-transfer and reaction kinetics in ethoxylation of lauryl alcohol were examined in a batch recirculation reactor. The liquid droplets falling through a gas column were obtained by utilizing a recirculation loop and a set of spray nozzles. The CO₂/NaOH reaction was employed to characterize the interfacial area. The alkoxylation reaction was studied at temperatures between 124°C and 171°C, at catalyst levels between 0.09 and 0.50 weight percent and at ethylene oxide partial pressures between 68 kPa and 204 kPa. A model was developed which permits the prediction of reactor performance at various operating conditions. The mass-transfer during free fall dominates the interfacial mass-transfer and the contributions during the drop formation and coalescence stages are small. The rate of ethylene oxide (EO) addition to lauryl alcohol was constant during the batch run, indicating similar activity for the unreacted lauryl alcohol and the lauryl alcohol ethoxylated to varying extents. The rate of ethoxylation is first-order in both catalyst and ethylene oxide concentrations. The liquid-phase reaction kinetics and interfacial mass-transfer occur in series, with kinetics dominating the overall ethoxylation rate. As expected, an increasing role of mass transfer is observed at higher temperatures, and/or higher catalyst concentrations where the kinetic rate becomes significantly high. The intrinsic activation energy for the ethoxylation of lauryl alcohol is 55.2 kJ/mole.     

Foam enhancement by short-chain hydrophobe alcohol ethoxylates in light-duty liquids

This study examined linear alcohol ethoxylates as foam-enhancing agents in light-duty liquids. The ethoxylates were formulated as supplementary surfactants to an anionic main surfactant system. The relationship between ethoxylate structure and performance was elucidated, comparisons were made between ethoxylates and other recognized foam-enhancing agents, and a representative light-duty liquid formula was optimized. Performance evaluation focused on manual plate washing capacity but also included agitation foam volume, surface activity, cloud and clear temperatures, viscosity and grease cutting. Shortchain alcohol ethoxylates with a high degree of ethoxylation (such as C₈ with 70% or 7 moles of ethylene oxide) gave optimum performance that was comparable to or better than acknowledged foam-enhancing agents. The substitution of an alcohol ethoxylate for a fatty acid ethanolamide in the test formulation resulted in substantially lower formulation viscosity.     

Die Emulgierung oxidierter Polyäthylen-Wachse mit ionisch - nichtionischen Emulgator-Systemen II

Emulsification of Oxidized Polyethylene Waxes with Ionic-Nonionic Emulsifier Systems II Studies using methods described earlier were extended to emulsification of oxidized polyethylene waxes having varying acid values and molecular weights with nonionic-ionic emulsifier systems. Besides nonylphenolethoxylates C_9/11- and C_13/15-fatty alcohol ethoxylates were also used in the presence of various amines as emulsifiers. The optimum degree of ethoxylation for each emulsifier was determined within each class of ethoxylate as a function of the degree of oxidation of polyethylene waxes. The efficiency of various classes of ethoxylation products and the influence of various amines were compared under different conditions.     

Effect of initiators and ethoxylation degree of non‐ionic emulsifiers on vinyl acetate and butyl acrylate emulsion copolymerization in the loop reactor

Vinyl acetate and butyl acrylate copolymers were synthesized in the presence of ammonium persulfate and potassium persulfate initiators, mixture of non‐ionic and anionic emulsifiers, and polyvinyl alcohol as protective colloid in a loop reactor. The monomer ratio was chosen 85:15. The series of non‐ionic emulsifiers, which have 10–40 moles ethoxylated nonyl phenol, were combined with Nansa 66 (sodium dodecyl benzene sulfonate). The effects of the initiators on the physicochemical properties of copolymers were investigated by measuring conversion, viscosity, molecular weight, molecular weight distribution, and surface tension, respectively by using gravimetric method, Brookfield viscometer, gel permeation chromatograpy (GPC), and ring method. The effects of ethoxylation degrees of the non‐ionic emulsifiers to the same properties of copolymers were also investigated. It was determined that the copolymer viscosities showed different tendency for two initiators. They were increased by the increasing ethoxylation degree of the non‐ionic emulsifier for ammonium persulfate. In contrast, latex viscosity was decreased by increasing the ethoxylation degree in presence of potassium persulfate. Similar changes were also found in number average molecular weights of copolymers. On the other hand, weight average molecular weights of copolymers increased by increasing the ethoxylation degree of the non‐ionic emulsifier for both initiators. In the case of potassium persulfate, the surface tension values of copolymers increased by increasing the ethoxylation degree, but generally increasing the ethoxylation degree did not affect the surface tension of copolymer very seriously for two initiators. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 537–543, 2003     

Strength and Static Fatigue of Abraded Glass Under Controlled Ambient Conditions: IV, Effect of Surrounding Medium

The strength and static fatigue behavior of abraded glass specimens tested in various surrounding media have been studied. The test media included distilled water, nitrogen atmospheres of varying humidity, methyl and isopropyl alcohol and mixtures of these with distilled water, and various acidic and basic solutions. For intermediate durations of load the strength values in atmospheres of 0.5 and 43% relative humidity were 45 and 20% greater, respectively, than in distilled water. The value of t_0.5, the characteristic duration for static fatigue, under these three test conditions was 3500, 200, and 8 seconds, respectively, for the particular grit-blast abrasion studied, indicating that liquid water is the most effective agent for promoting a high rate of static fatigue and very dry air with a small concentration of water vapor is least effective. In reagent-grade methyl or isopropyl alcohol (0.01 to 0.05% H₂O) the strength at an intermediate load duration of 10 seconds was about 40% greater than in distilled water and the slope of the static fatigue curve differed somewhat from that obtained for tests in water. With the addition of water to the alcohol solutions the fatigue curve became parallel to that for water, and as the water content was increased, the curves shifted toward the water curve. For tests in acidic and basic solutions the strength at an intermediate load duration was independent of pH over the range pH 1 to 13. For more acidic solutions the strength was slightly less and for more basic solutions slightly greater than in this range. The results are discussed in terms of possible mechanisms for static fatigue. It is concluded that the static fatigue of abraded glass results from changes in the shape or size of surface abrasion cracks under the combined action of stress and the surrounding medium. In general, water or water vapor is the primary agent in promoting fatigue, and, unlike the usual chemical attack, the interaction appears to involve primarily the neutral water molecule and the SiO₂ network of the glass. The presence of other ions or molecules is relatively unimportant except as it may serve to reduce the concentration of water and its availability to the tip of the abrasion crack.     

Component distribution of alcohol ethylene oxide adducts

The relative reaction constants for the base-catalyzed ethoxylation of primary straight chain alcohols have been determined for the unreacted alcohol and the first three ethylene oxide adducts. The distribution of the ethoxylates was found using molecular distillation, nuclear magnetic resonance analysis and gas liquid partition chromatography. A mathematical model describing the distributions was set up and programmed on a 7090 digital computer. Solution of the program gave the relative reaction constants for the alcohol and the first three adducts. The relative reactivities of the adducts in the base-catalyzed ethoxylation of primary straight chain alcohols are shown to increase with adduct number, but tend to a constant value as the adduct number increases. Results also show that alcohols from C₆ to C₁₈ are equally reactive to ethylene oxide on a molar basis.     

Tuning Interfacial Activity of Polymeric Resin–Surfactant/<Emphasis Type="Italic">n</Emphasis>-Alcohol Solution Interactions

Measurements of surface tension were carried out for several aqueous solutions of different amphiphilic systems. This research studied the interaction between two polymeric resins (more structure definition) (PR) and nonyl phenol ethoxylates (NP) with degrees of ethoxylation varying from 10 to 20 ethylene oxide groups. The results show that in mixtures of PR and NP₂₀EO, the adsorption on the surface was lower, with the molecules tending to remain within the liquid. On the other hand, mixtures of PR and NP₁₀EO have resulted in greater surface adsorption. The effect of the added alcohols was to tune the interfacial activity of the PR as function of the PR and alcohol concentrations. The general tendency of the surface tension curves to decrease with increasing PR/alcohol concentration in solutions was not significantly modified with the addition of alcohols; however, the surface tension values changed due to the addition of alcohols and a model is proposed to explain these changes, as they depend on both alcohol chain length and the PR/alcohol concentration. An emulsion stability test was performed on polymeric resins–surfactant systems to determine the correlation between their surface properties. Nonionic surfactants present in these mixtures are mainly responsible for the emulsion stability. It was concluded that mixtures of the less hydrophilic PR (PR_B) with NP₁₀EO have good interfacial properties, including a high interfacial concentration and a low critical micellar concentration.     

Rheological properties of water solutions of syndiotactic poly(vinyl alcohol) of different molecular weights

To precisely identify the effect of the molecular weight of syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA) on the rheological properties of s‐PVA/water solutions, we prepared four s‐PVAs with a syndiotactic dyad content of 57%, a degree of saponification (DS) of 99.9%, and number‐average degrees of polymerization (P_n's) of 300, 1300, 2700, and 4000. Through a series of experiments, we found that the molecular weight of poly(vinyl alcohol) had a significant influence on the rheological properties of s‐PVA/water solutions. Over a frequency range of 10^?1 to 10² rad/s, the s‐PVA/water solution with the highest P_n value showed the largest values of the complex viscosity, storage modulus, and loss modulus at similar syndiotacticity and DS values of s‐PVA, and this suggested that the higher P_n was, the stronger the internal ordered structure was in the molecules. All the s‐PVA/water solutions showed shear‐thinning behavior, which implied heterogeneity. In a modified Casson plot, Bingham flow behaviors, which gave rise to non‐zero yield stress, were evident. This suggested that some pseudostructure existed in the s‐PVA/water solutions. The yield stress increased with P_n, and this implied that the pseudostructure was developed as P_n increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1426–1431, 2004     

Viscosity measurements on nylon-6/ethyl alcohol solutions in presence of inorganic salts

In this work shear viscosity data are reported for nylon-6/ethyl alcohol solutions in the presence of LiCl or LiNO₃ at different concentrations of nylon and salts up to the solubility. These data have been obtained mostly at 45°C; higher temperatures have been used in a few cases to avoid precipitation at short times. For comparison, some viscosity measurements have been performed on nylon-6/formic acid solutions also in presence of salts. The results seem to confirm interpretations already advanced by other authors both for the solubility and the solution properties of nylon-6 in the presence of similar salts.     

Effect of prolonged heating at elevated temperatures on the phase composition and textures of portland cement clinker

Two kinds of portland cement clinker with widely different MgO and SO₃ content were reheated for a long time at elevated temperature. With the clinker rich in MgO and SO₃, alite increased while belite decreased in quantity after reheating. The alite crystals, overgrown with new precipitates, gave zonal structures. Thin platy hexagonal crystals were occasionally nucleated and grown separately in the bulk liquid. High degree of supercooling produced dismembered dendritic crystals of belite. The C/S ratio of the interstitial phase decreased with reheating. The above changes occur in association with the process in which the interstitial liquid, initially variable in basicity, is transformed to the uniform and most acidic one. This process is controlled by the counterdiffusion of CaO and SiO₂, the rate of which is such that, in normal clinker processing, the clinkering reaction terminates before reaching this stage. Rise in firing temperature increases the concentration of SiO₂ in the interstitial liquid and leads to higher solid C₃S/C₂S ratio in clinker. The presence of MgO and SO₃ in abundance lowers the viscosity of the liquid and hence accelerates the changes. No appreciable change could be recognized for the clinker low in MgO and SO₃ content.     

Spherical capped gas bubbles rising in aqueous media

The rising velocity of spherical capped bubbles in water and in PVA solutions, showed the viscosity to have little influence below 2P. Solutions with high viscosities caused some retardation especially with smaller bubbles.Measurements of the mass transfer coefficient during the absorption of CO₂ from bubbles rising in water gave similar values to those obtained during the desorption of CO₂ from saturated solutions into inert bubbles which had been formed under mercury to prevent premature transfer. Instantaneous values of the mass transfer coefficient from CO₂ bubbles into water and PVA solutions were found to decay as the bubble rose in the column. The rate of decay was especially rapid when small amounts of PVA were dissolved in water and this effect was probably due to the influence of surfactants.A qualitative study was also carried out on the shapes of wakes behind spherical cap bubbles and on the exchange between the liquid in the wake and the surroundings.     

Characteristics of Lactic Acid Transport in Supported Liquid Membranes

Abstract

Transport of lactic acid in supported liquid membranes containing tertiary amines (Alamine 336, Henkel Corp.) as the carrier was investigated. Both equilibrium extraction constants (K _t) and effective diffusion coefficients (D) of the acid-amine complex were measured for systems with various diluents. Larger K _t values and, thus, more efficient extraction were found when diluents were used, especially with oleyl alcohol which improved the polarity of the oil membrane and led to an approximately sixtyfold increase in the K _t value. Experimental results of D for different supported liquid membranes were found in the range of 2 to 7 × 10^?7 cm²/s. Although much lower than those predicted by the Wilke-Chang equation, the values are consistent in the orders of magnitude with the literature results for other permeates in similar supported liquid membranes.     

BaTiO3 nanotubes by co-axial electrospinning: Rheological and microstructural investigations

BaTiO₃ (BT) nanotubes (NT_s) were synthesized using a co-axial electrospinning process. BT precursor/PVP-ethanol and heavy mineral oil were used as the shell solution and core liquid, respectively. The rheological studies indicated that NT_s could be formed by a stable jet at a range of viscosities of the shell solution. Due to the shear thinning behavior of the shell solutions, their actual viscosity values at the time of jet formation will be lower than the viscosity of the core liquid. The morphology of the obtained NT_s was strongly influenced by the viscosity of the shell solution. By increasing the concentration of BT precursor, the morphology of the BT NT_s was changed from porous to more dense structure. XRD analysis revealed that the crystallization of BT NT_s occurs at 550–630 °C calcination temperature range. Raman spectra confirmed the presence of tetragonal phase at early stage of crystallization.     

Ethoxylation of detergent-range oxo alcohols derived from fischer-tropsch α-olefins

Detergent-range alcohols currently are produced from a variety of basic raw materials including natural fats and oils, natural gas, and petroleum. Joining this list of basic raw materials is coal. Olefins are formed in the conversion from coal via the Fischer-Tropsch (F-T) process and are then converted to alcohol via the oxo process. This paper describes the characteristics of Fischer-Tropsch oxo alcohol and its ethoxylation properties in comparison with other common detergentrange alcohols. This work shows that oxo 1213 alcohol (i.e., a mixture of primary fatty alcohols containing both 12 and 13 carbons in their hydrocarbon backbone) reacts with ethylene oxide similarly to linear alcohol, yielding low levels of unethoxylated alcohol. Substitution at the C₂ position has more impact on the ethoxylation of an alcohol than the degree of linearity.     

Viscosity-structure relationship of dilute triglycerides’ solutions correlation to retention time in reversed-phase liquid chromatography

The dynamic viscosity (η) of dilute solutions of the trigly-cerides triolein, trilinolein, trimyristin, tristearin and tripalmitin in benzene at temperatures in the range of 25–37°C can be expressed in terms of the viscosity of the solvent (η₀), the triglycerides’ concentration (C) and structural characteristics, such as the length of the carbon chains (CN) and the number of double bonds (DB). The simple empirical equation ln η=k₀+k₁ ln η₀+k₂ CN+k₃ DB+k₄ C satisfactorily describes (within the experimental error of 0.002 cp) the solution viscosity of triglycerides inp-xylene when using the coefficients derived from the benzene solutions. In addition, a relation is derived extending the application of the above-mentioned empirical equation to multicomponent dilute solutions. This last one describes the dilute solution viscosity of natural oils in benzene and agrees with the experimental values. Furthermore, the triglycerides that have equal partition numbers in reversed-phase liquid chromatography (RPLC) exhibit equal values for the solution viscosity. This relationship is similar to the equation expressing the retention time of RPLC in terms of the structure of the solute. Hence, it is suggested that the shape of the solute, which is a significant factor for the solution viscosity of triglycerides, also plays an important role in the retention mechanism of RPLC.     

Effect of hydrotropes on the aqueous solution behavior of surfactants

Aqueous solutions of surfactants—cationic: tetradecyltrimethylammonium bromide (C₁₄TABr); anionic: sodium dodecyl sulfate (SDS); and nonionic: polyoxyethylene t-octylphenol (trade name Triton X-102, also called OPE-8)— in the presence of three hydrotropes, viz., sodium xylene sulfonate, sodium p-toluene sulfonate, and sodium chlorobenzene sulfonate, were examined by measuring surface tension, viscosity, and cloud points for the nonionic surfactant. The results show a marked decrease in the critical micelle concentration with increase in hydrotrope concentration for C₁₄TABr, a marginal decrease for SDS, and very little change for OPE-8 up to 0.1 M hydrotrope. The viscosity of cationic surfactant solutions showed a remarkable increase in the presence of trace amounts of hydrotropes (up to 15 mM). In contrast, the SDS solution showed only a slight increase in viscosity at high hydrotrope concentration (150 mM), and the viscosity of the OPE-8 solution remained constant. The cloud point of OPE-8 increased in the presence of hydrotropes, unlike its behavior with the simple salt NaCl. The strong dependence of the solution behavior of cationic surfactants on the presence of hydrotropes is discussed in terms of electrostatic interaction.     

Effect of hybrid polymer coating of Bioglass® foams on mechanical response during tensile loading

A simplified two-dimensional finite elements model was created for a polyvinyl alcohol (PVA) coated Bioglass^® strut undergoing tensile stresses (loading mode I). The strengthening contributions due to the infiltration of coating into surface cracks and coating's stiffness were evaluated in terms of stress intensity factor K_I and tensile stresses σ_yy in the proximity of the crack tip. The infiltration of the coating until the crack tip resulted as the most effective criterion for the struts strengthening. Bioglass^® based scaffolds were dip coated into PVA and PVA/microfibrillated cellulose (MFC) aqueous solutions and tested in tensile load. Coated samples exhibited remarkably higher tensile strength than non-coated ones, which further raised with the increased amount of MFC. Contact angle θ and linear viscosity η measurements of PVA/MFC solutions showed that MFC caused a reduction in θ and a drastic increase in η, indicating that a balance between these two effects must be achieved.     

Micellization Behavior of the 14-2-14 Gemini Surfactant with Some Conventional Surfactants at Different Temperatures

Mixed micellization behavior of the dimeric cationic surfactant ethanediyl-1,2-bis(dimethyl tetradecyl ammonium bromide) with monomeric cationic surfactants cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) was studied in aqueous and aqueous polyethylene glycol (PEG) solutions at various temperatures (298.15, 308.15 and 318.15 K) using conductometric and viscometric methods. The behavior of these mixed systems was analyzed in light of Rubingh’s regular solution theory. The conductivity study indicates that the above systems behave nonideally with mutual synergism at 298.15 and 308.15 K, whereas antagonistic behavior is exhibited at 318.15 K. In the presence of PEG solution, various thermodynamic parameters associated with transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound mixed micelles like ∆G _t^o, ∆H _t^o and ∆S _t^o at various temperatures were evaluated and discussed. The viscosity study shows that in aqueous solutions all these combinations exhibit significant negative departure in the relative viscosity (η_r) from the additivity rule at 298.15 and 308.15 K, whereas at 318.15 K these combinations (except in the case of C14BCl) follow the additivity rule. In presence of 5% PEG solution, all the combinations show positive departure from the additivity rule except the combination with C14BCl which shows negative departure at all the studied temperatures.     

A comparison of inlet- and exit-region flow of viscoelastic fluids in capillary tubes

It is shown, in confirmation of earlier work, that when a viscoelastic liquid flows into a capillary tube, a definite fraction of the inlet pressure drop is required to overcome effects of elastic origin. This pressure drop, ΔP_E, is proportional to the same power of shear rate as the steady-state first normal stress difference measured by means of the jet thrust method. The values of ΔP_E are some 1.6–8.6 times higher than the values of the first normal stress difference, the amount depending on the fluid in use but not on the elastic power-law exponent m. The importance of the extensional mode of deformation in entry region flow is discussed. It is shown by examining dilute polymer solutions after varying periods of degradation that changes in ΔP_E are closely related to changes in the turbulence suppression characteristics of the solutions. The extensional mode of deformation is presumably important in both types of experiment. Both n-pentanol and a mineral oil, tested in the same small-diameter capillary tubes as the polymeric solutions, give well-defined values of ΔP_E, which are compared with previously published normal stress figures. The mineral oil is shown to develop particularly high stresses in elongational flow, though the viscous stresses were also higher than for the polymeric solutions used. Previous evidence of the existence of shear elasticity in organic liquids is listed and the potential importance of the case of mineral oil is emphasized.     

Computational rheology of carbonaceous mesophases

Mesophase pitches are multicomponent discotic nematic liquid crystals (DNLCs), whose characteristic molecular weight is intermediate between low molar mass and polymeric nematic liquid crystals. Flow modelling of these fluids is performed using a previously formulated mesoscopic viscoelastic rheological theory [J. Non-Newtonian Fluid Mech. 94 (2000) 87] that takes into account flow-induced texture transformations. A complete extra stress tensor equation is developed from first principles for liquid crystal materials under non-homogeneous arbitrary flow. This mesoscopic viscoelastic model has been adapted to describe the rheology of flow-aligning thermotropic DNLCs as models of mesophase pitches. We develop a fundamental understanding of the relations between rheology and flow of carbonaceous mesophases using theory and simulation by characterizing the steady and transient shear rheological material functions of flow-aligning DNLCs. Predictions for simple shear flow (under non-homogeneous conditions) for the apparent shear viscosity and first normal stress differences are presented. The predicted relations among rheological properties, shear-induced microstructure, processing conditions and material parameters of discotic mesophases are characterized and discussed.