Summary. Mixtures of different surfactant types have been proposed for application in polymer/micellar flooding processes. In some cases, severe fractionation of such mixtures is found even in short core experiments. In this paper, a new theory of surfactant partitioning between phases is developed and tested. Polydisperse nonionic surfactants blended with an anionic surfactant are considered. Important parameters in the theory are the critical micelle concentrations (CMC's) of surfactant mixtures in water and the partition coefficients of the surfactant between oil and water measured at total surfactant concentrations less than the CMC. From these simple experiments, surfactant fractionation in microemulsion systems can be modeled. We also show that the fractionation of polydisperse ethoxylated nonionic surfactants between excess oil and water phases is not as severe in the presence of anionic surfactants as it is in systems containing only nonionic surfactants. Introduction Mixed surfactant systems have been proposed for application in polymer/micellar flooding processes. Generally, the purpose of blending different surfactant types is to achieve a desirable phase behavior in environments that are difficult or perhaps impractical to cope with using a single surfactant. On the other hand, there is general reluctance to apply mixtures of different surfactant types because of the chromatographic separation that will occur if surfactant molecules partition selectively into fluid phases that are moving at different velocities. phases that are moving at different velocities. Difficulties of this type have been reported for mixture of disulfonates and monosulfonates. Other surfactant mixtures appear to resist separation to the extent that detecting it in laboratory experiments is difficult. Why are some mixtures readily separated and others are not? If surfactant partioning is the key factor, how can it be modeled? Can simple laboratory experiments yield the appropriate parameters needed for the model? Is there an underlying thermodynamic theory that will help select surfactant systems that resist chromatographic separation? These are the questions addressed in this paper. The particular system studied is a mixture of nonionic and anionic surfactants; however, the same principles applied to this system will also apply to others. The concept used is similar to one previously reported and to that originally proposed by Biais et al. The interfacial region is treated as a separate phase called a pseudophase to emphasize that this is a conceptual model rather than an actual picture of the true system. In accordance with this theory, it will be shown that those surfactant systems that form mixed micelles with an attendant strong interaction will be far less susceptible to chromatographic separation than systems that form ideal mixed micelles. Systems that resist the formation of mixed micelles will, accordingly, be more susceptible to separation than surfactant systems that form ideal mixed micelles. These qualitative observations are made quantitative in this paper, and the theoretical predictions are shown to predict with considerable accuracy the partitioning of nonionic surfactants between phases when a partitioning of nonionic surfactants between phases when a surfactant system consisting of a mixture of anionic and nonionic surfactants is used. The theory predicts that because of the strong interaction between nonionic and anionic surfactants, such systems will exhibit a smaller degree of fractionation than do non-ionic surfactants when applied alone. Experiments show this unexpected trend to be correct. The approach used will also apply to mixtures of anionic surfactants and to mixtures of anionic surfactants with added alcohol cosolvent. It can therefore be used in connection with thermodynamic models of micellar phase behavior, such as that recently reported by Prouvost et al., permitting the fractionation of surfactant to be analyzed. permitting the fractionation of surfactant to be analyzed. Theory SPERE p. 305
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency therecf. nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, complettiness. or usefulness of any Information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.