Safety Assessment of Xylene Sulfonic Acid, Toluene Sulfonic Acid, and Alkyl Aryl Sulfonate Hydrotropes as Used in Cosmetics

Xylene sulfonic acid, toluene sulfonic acid, and alkyl aryl sulfonate hydrotropes used in cosmetics as surfactants, hydrotropes, were reviewed in this safety assessment. The similar structure, properties, functions, and uses of these ingredients enabled grouping them and using the available toxicological data to assess the safety of the entire group. The Cosmetic Ingredient Review Expert Panel reviewed relevant animal and human data related to these ingredients. The panel concluded that xylene sulfonic acid and alkyl aryl sulfonate hydrotropes are safe as cosmetic ingredients in the present practices of use and concentrations as described in this safety assessment, when formulated to be nonirritating.

Visualization of a Surfactant Flood of an Oil-Saturated Porous Medium

This paper discusses the viscous fingering that occurs when water or a surfactant solution displaces oil in a porous medium. Such floods were visualized in an porous medium. Such floods were visualized in an oil-wet porous medium composed of fused plastic particles. The flow structure changed significantly within the range of capillary numbers between 10 -4 and 10 -3 . The addition of surfactant resulted in narrower fingers, which developed in a more dispersive fashion. Introduction In describing fluid/fluid displacements in porous media, a useful dimensionless quantity is the capillary number, (1) which corresponds to the ratio of viscous forces to capillary forces. Here, v is the specific fluid discharge or Darcy velocity, it is viscosity, and o is interfacial tension (IFT). It has been shown that the recovery of oil from an underground reservoir increases significantly if the capillary number can be increased beyond the range of 1 × 10 -4 to 2 × 10 -3 during water flooding (see Larson et al. 1 ). To this end, surfactants are used extensively in tertiary oil recovery operations with the objective of reducing IFT and consequently mobilizing the oil ganglia which otherwise would remain trapped. This paper is concerned with the viscous fingering that occurs when water displaces oil in a porous medium, and we present a brief consideration on the effects that surfactants have on fingering. Noting that Peters and Flock have visualized fingering within the range of capillary numbers between 1.6 × 10 -6 and 7.2 × 10 -4, we present here visualizations at capillary numbers of 7.7 × 10 5 and 1.0 × 10 -3. Both our visualizations and the experiments of Peters and Flock involve large viscosity ratios so that only the viscosity of the more viscous fluid is considered when determining the capillary number. In particular, it is observed that as the capillary number increases, ganglia or blobs of displacing fluid are created at the displacement front in correspondence with the capillary numbers at which trapped ganglia are mobilized. This creation of ganglia at capillary numbers above 10 -3 was noted briefly in a previous paper 3 in which heptane displacing glycerine previous paper 3 in which heptane displacing glycerine was described. A secondary objective of this work was to test the Chuoke et al. theory for predicting the wavelength of fingers, wavelength being the peak-to-peak distance between adjacent well-developed fingers. Experimental Procedure The apparatus for these studies was described in Ref. 3. Basically, it consists of a slab of consolidated plastic particles 1.34 × 0.79 × 0.0 1 8 ft [0.44 × 0.26 × 0.006 m] with particles 1.34 × 0.79 × 0.0 1 8 ft [0.44 × 0.26 × 0.006 m] with a porosity of 0.43 and a permeability of 7, 100 darcies. This high permeability, when compared with that of reservoir rocks, should not be important for this study since capillary numbers and residual saturations are independent of pore size. Water (viscosity 1 cp [1 mPa s]) was used to displace paraffin oil (viscosity 68 cp 168 mPa s] at 77F [25C]). The water was dyed with methylene blue (which acts as a mild surfactant). Without the dye, the oil/water IFT was 42 dyne/cm [42 mN/m]. The addition of dye lowered this value to 36 dyne/cm [36 mN/m] for the concentration of dye used. For the surfactant flood, a 1 % sodium alkyl aryl sulfonate solution was used, giving a surfactant-solution/paraffin-oil IFT of 3.0 dyne/cm [3.0 mN/m]. Water Displacing Oil To compare our experiments with previous investigations of fingering, the displacement of paraffin oil by water at an average specific fluid discharge of 1.34 × 10–4 ft/sec [4.1 × 10 -5 m/s], corresponding to a capillary number of 7.7 × 10 -5, was studied (Fig. 1). Chuoke et al .4 and later Peters and Flock 2 have presented a formula for predicting the wavelength of presented a formula for predicting the wavelength of finger, lambda m : (2) where k is permeability, C is a dimensionless parameter which Peters and Flock call the wettability number and suggest would have the value 25 for an oil-wet porous medium, and mu o and mu ware viscosities of the displaced oil and displacing water, respectively. It was observed that the plastic particles of the porous medium considered here were oil wet because of adsorption of oil. SPEJ P. 325

Microemulsion Phase Behavior Observations, Thermodynamic Essentials, Mathematical Simulation

The phase behavior of microemulsions of brine, hydrocarbon, alcohol, and a pure alkyl aryl sulfonate-sodium 4-(1-heptylnonyl) benzenesulfonate (SHBS or Texas 1) was investigated as a function of the concentration of salt (NaCl, MgCl2, or CaCl2), the hydrocarbon (n-alkanes, octane to hexadecane), the alcohol (butyl and amyl isomers), the concentration of surfactant, and temperature. The phase behavior mimics that of similar systems with the commercial surfactant Witco TRS 10–80. The phase volumes follow published trends, though with exceptions.A mathematical framework is presented for modeling phase behavior in a manner consistent with the thermodynamically required critical tie lines and plait point progressions from the critical endpoints. Hand's scheme for modeling binodals and Pope and Nelson's approach to modeling the evolution of the surfactant-rich third phase are extended to satisfy these requirements.An examination of model-generated progressions of ternary phase diagrams enhances understanding of the experimental data and reveals correlations of relative phase volumes (volume uptakes) with location of the mixing point (overall composition) relative to the height of the three-phase region and the locations of the critical tie lines (critical endpoints and conjugate phases). The correlations account, on thermodynamic grounds, for cases in which the surfactant is present in more than one phase or the phase volumes change discontinuously, both cases being observed in the experimental study. Introduction The phase behavior of a surfactant-based micellar formulation is one of the major factors governing the displacement efficiency of any chemical flooding process employing that formulation. Knowledge of phase behavior is, thus, important for the interpretation of laboratory core floods, the design of flooding processes, and the evaluation of field tests. Phase behavior is connected intimately with other determinants of the flooding process, such as interfacial tension and viscosity. Since the number of equilibrium phases and their volumes and appearances are easier to measure and observe than phase compositions, viscosities, and interfacial tensions, there is great interest in understanding the phase-volume/phase-property relationships. Commercial surfactants, such as Witco TRS 10-80, are sulfonates of crude or partially refined oil. While they seem to be the most economically practicable surfactants for micellar flooding, their behavior, particularly with crude oils and reservoir brines, can be difficult to interpret, the phases varying with time and from batch to batch. Phase behavior studies with a small number of components, in conjunction with a theoretical understanding of phase behavior progressions, can aid in understanding more complex behavior. In particular, one can begin to appreciate which seemingly abnormal experimental observations (e.g., surfactant present in more than one phase or a discontinuity in phase volume trends) are merely features of certain regions of any phase diagram and which are peculiar to the specific crude oil or commercial surfactant used in the study.We report here experimental studies of the phase behavior of microemulsions of a pure sulfonate surfactant (Texas 1), a single normal alkane hydrocarbon, a simple brine, and a small amount of a suitable alcohol as cosurfactant or cosolvent. The controlled variables are hydrocarbon chain length, alcohol, salinity, salt type (NaCl, MgCl2, or CaCl2), surfactant purity, surfactant concentration, and temperature. Many of these experimental data were presented earlier. SPEJ P. 747^

On Interfacial Tensions Measured With Alkyl Aryl Sulfonate Surfactants

Tensions of aqueous solutions and dispersions of sodium p (1-heptylnonyl/benzene sulfonate against decane are not ultralow in the absence of salt, but can fall below 0.01 dyne/cm (0.01 mN/m) with 0.3 wt% (3 g/kg) NaCl, depending on order of mixing, preparation age, and decane drop size. A dispersed preparation age, and decane drop size. A dispersed liquid crystalline phase revealed by spectroturbidimetry and microscopy appears responsible for ultralow tensions. Results with petroleum sulfonate Witco TRS 10-80 support this conclusion. Introduction The importance of ultralow [less than 0.01 dyne/ cm (0.01 mN/m)] interfacial tensions between oil and water as the means of achieving high capillary-number displacement in one mechanism of enhancing oil recovery is well recognized. Low tension is related closely to the phase behavior of suitable surfactant with oil, water, and often an alcohol, as well as other additives. Information in the technical and patent literature concentrates on commercial sulfonate surfactant systems. Few studies of the relationship between tension and phase behavior with pure surfactants have appeared. Since the pioneering work of Hartley on molecular structure dependence of interfacial tension, the influences of WOR, salinity, temperature, surfactant molecular-weight distribution, and other factors have been investigated. However, the origins of ultralow interfacial tensions are not yet known.This paper deals with the low-tension regime associated with low surfactant concentrations, i.e., no more than 1 wt% (10 g/kg). In contrast to the second regime, in which microemulsion plays the central role, this regime does not require the presence of a suitable alcohol or other cosurfactant. presence of a suitable alcohol or other cosurfactant. In this regime it is not clear whether ultralow tensions are equilibrium or nonequilibrium properties. Even with compositions capable of producing ultralow tensions, the measured tensions depend on the way the system is prepared, and time effects are seen. Nevertheless, reproducible measurements can be made by observing a fixed experimental protocol. Tensions measured this way with a given surfactant correlate strongly with semiempirical assignment of carbon numbers to a wide range of hydrocarbons. The correlation extends across related sulfonate surfactants and is a potentially useful means of characterizing low-tension formulations. Understanding this correlation may shed light on the mechanism of ultralow tension in the low-surfactant concentration regime and thus may aid process studies. Understanding the factors responsible for nonequilibrium effects is crucial to interpret laboratory and field data and to design surfactant flooding processes rationally. Commercial surfactants are complex mixtures and are characterized inadequately for basic physicochemical study of order-of-mixing effects physicochemical study of order-of-mixing effects and time-varying interfacial tensions. Experience suggested that a representative pure surfactant would display much of the behavior of commercial mixtures, thereby exposing the practically important aspects to systematic scientific study. The U. of Texas group synthesized an agreed-on alkyl aryl sulfonate that is the subject of extensive studies in this laboratory and elsewhere. Results on its phase behavior with brine and with decane are phase behavior with brine and with decane are reported elsewhere. Parallel studies are under way with a petroleum sulfonate surfactant to establish the extent to which a pure surfactant can mimic the behavior of a commercial mixture. Companion investigations are aimed at explaining the unknown microstructures of ultralow tension interfaces. SPEJ p. 71