Commercial Nonionic Surfactants Research Articles

Quantifying the effect of non-ionic surfactant alkylphenol ethoxylates on the persistence of thiabendazole on fresh produce surface.

Understanding the role of adjuvants in pesticide persistence is crucial to develop effective pesticide formulations and manage pesticide residues in fresh produce. This study investigated the impact of a commercial non-ionic surfactant product containing alkylphenol ethoxylates (APEOs) on the persistence of thiabendazole on apple and spinach surfaces against the 30 kg m-3 baking soda (sodium bicarbonate, NaHCO3 ) soaking, which was used to remove the active ingredient (AI) in the cuticular wax layer of fresh produce through alkaline hydrolysis. Surface-enhanced Raman scattering (SERS) mapping method was used to quantify the residue levels on fresh produce surfaces at different experimental scenarios. Four standard curves were established to quantify surface thiabendazole in the absence and presence of APEOs, on apple and spinach leaf surfaces, respectively. Overall, the result showed that APEOs enhanced the persistence of thiabendazole over time. After 3 days of exposure, APEOs increased thiabendazole surface residue against NaHCO3 hydrolysis on apple and spinach surfaces by 5.39% and 10.47%, respectively. The study suggests that APEOs led to more pesticide residues on fresh produce and greater difficulty in washing them off from the surfaces using baking soda, posing food safety concerns. © 2023 Society of Chemical Industry.

Competitive Adsorption of a Monoclonal Antibody and Nonionic Surfactant at the PDMS/Water Interface.

Interfacial adsorption of monoclonal antibodies (mAbs) can cause structural deformation and induce undesired aggregation and precipitation. Nonionic surfactants are often added to reduce interfacial adsorption of mAbs which may occur during manufacturing, storage, and/or administration. As mAbs are commonly manufactured into ready-to-use syringes coated with silicone oil to improve lubrication, it is important to understand how an mAb, nonionic surfactant, and silicone oil interact at the oil/water interface. In this work, we have coated a polydimethylsiloxane (PDMS) nanofilm onto an optically flat silicon substrate to facilitate the measurements of adsorption of a model mAb, COE-3, and a commercial nonionic surfactant, polysorbate 80 (PS-80), at the siliconized PDMS/water interface using spectroscopic ellipsometry and neutron reflection. Compared to the uncoated SiO2 surface (mimicking glass), COE-3 adsorption to the PDMS surface was substantially reduced, and the adsorbed layer was characterized by the dense but thin inner layer of 16 Å and an outer diffuse layer of 20 Å, indicating structural deformation. When PS-80 was exposed to the pre-adsorbed COE-3 surface, it removed 60 wt % of COE-3 and formed a co-adsorbed layer with a similar total thickness of 36 Å. When PS-80 was injected first or as a mixture with COE-3, it completely prevented COE-3 adsorption. These findings reveal the hydrophobic nature of the PDMS surface and confirm the inhibitory role of the nonionic surfactant in preventing COE-3 adsorption at the PDMS/water interface.

Modelling the partitioning equilibria of nonionic surfactant mixtures within the HLD framework

Commercial non-ionic surfactants are usually blends of species differing in the degree of ethoxylation, characterised by a distribution of surfactants with different affinity for the oil and the aqueous phases. This leads to an unexpected concentration dependence of the phase behaviour and the rationalization of such deviations is necessary for their exploitation in surfactant-based formulations. In this work, the phase behaviour of commercial Novel® nonionic surfactants in presence of brine and oil was studied fixing equal volumes of organic and aqueous phases and changing the amount of surfactant and brine salinity (fish cut). The conditions for the balanced state (microemulsion solubilizing equals amount of water and oil) have been determined for different alkanes. The phase behaviour of the surfactant mixture was described, without a priori information about its actual chemical composition, in terms of two pseudo-components: one hydrophilic, entirely at the interface, and the other lipophilic, able to partition itself between the interface and the oil bulk according to a partition constant P. The pseudo-components effect on the interface is quantified through surfactant characteristic parameters (SCPs), according to the Hydrophilic-Lipophilic-Difference (HLD) model. SCPs and P can be experimentally determined by fitting the dependence of the balanced state on the surfactant concentration. The model is successfully applied to the tested surfactants and can quantitively predict the behaviour of their mixtures.

Clay-Sand Wettability Evaluation for Heavy Crude Oil Mobility

In this work, the effect of distilled water, a biodiesel viscosity reducer, and a commercial nonionic surfactant on the apparent permeability of clay-sand cores through the analysis of contact angle, linear swelling, and porous media fluid flow for a northern Mexico crude oil was evaluated. The results showed that the clay content influences the contact angle values having a lower wettability effect in the rocky medium. The addition of biodiesel produces a fluid movement similar to the addition of distilled water. Biodiesel-based flow enhancer not only reduces the crude oil viscosity but also improves the flowability through porous media. However, this behavior is only valid if the soil is not saturated with salty water.

Novel surfactants for stable biodiesel-water emulsions to improve performance and reduce exhaust emissions of a light-duty diesel engine

Emulsified biodiesel is a viable alternative to fossil diesel to reduce carbon footprint, oxides of nitrogen (NOx) and soot emissions. However, widespread commercial utilization of biodiesel-water emulsions requires cost-effective novel surfactants for producing stable emulsions. Studies on neat biodiesel-water emulsions are scarce, and the available studies are done with surfactants developed for diesel-water emulsions. The present work explores the efficacy of different surfactants in producing stable biodiesel-water emulsions and their effects on engine characteristics. The surfactants investigated include a commercial nonionic surfactant, viz. Span80-Tween80 and two novel surfactants, viz. polyglycerol poly ricinoleate (PGPR) and raw Karanja oil (RKO). The water concentrations in biodiesel-water emulsions are fixed at 6, 12 and 18% (by mass) with 2% surfactant. The emulsions prepared using a hot-plate magnetic stirrer were stable for over five months. The experiments were carried out on a light-duty diesel engine at rated speed and varying loads with the prepared emulsions. The results obtained with stable biodiesel-water emulsions with different water concentrations and surfactant types are compared with neat biodiesel as a reference fuel. At low water concentrations, the cylinder pressure increased with PGPR and RKO, whereas it was nearly the same as biodiesel with the Span-Tween combination. However, the trends between Span-Tween and RKO were reversed at higher water concentrations. The diffusion phase heat release rate increased and the combustion phasing advanced in general, with all the surfactants at all water concentrations. The engine brake thermal efficiency (BTE) increased, the brake specific fuel consumption (BSFC) reduced with emulsions, and the benefits increased at higher water concentrations with a maximum variation of 8% and 20% in BTE and BSFC, respectively. From the emission reduction perspective, biodiesel-water emulsions with RKO surfactant and 18% water concentration perform better, resulting in a maximum reduction of 40%, 52% and 69% in NOx, smoke and carbon monoxide (CO) emissions. Overall, the present study shows that alternative low-cost surfactants produced from renewable sources have stable biodiesel-water emulsions that effectively reduce exhaust emissions and improve engine performance.

Key factor of sponge phase formation in commercial polyethoxylated nonionic surfactant/cosurfactant/water systems and its unique feature at interface

A sponge phase is particularly interesting in terms of its features, such as its transparency, low viscosity, low interfacial tension and so on. However, most past research on the sponge phase have focused on pure surfactants, whereas little research exists on commercial polyethoxylated nonionic surfactants that are used in cosmetics and household products. The reason is attributed to the polyethyleneoxide, hydrophilic group of nonionic surfactants, having large distributions in polymerization degree, resulting in many irregular behaviors in the phase equilibrium. In this study, the phase sequence of the sponge phase formation in a commercial polyethoxylated nonionic surfactant/cosurfactant/water system was investigated based not only on HLB, but also on the distribution of polymerization degree of the hydrophilic group to reveal the irregularity of the phase sequence. As a result, in commercial nonionic surfactant systems, the important points for sponge phase formation were revealed to be (1) selecting a surfactant having intermediate HLB, and (2) selecting a structure with sufficient lipophobicity. These factors are for preventing cosurfactant phase separation that is attributed to the wide distribution of polymerization degree of polyethyleneoxide groups. Furthermore, we demonstrated the phenomenal wetting behavior on a hydrophobic surface with unevenness and clarified that the low interfacial tension and low viscosity of the sponge phase among various self-assembling structures were the critical for the wetting behavior.

Extraction, characterization and evaluation of saponin-based natural surfactant for enhanced oil recovery

To minimize environmental impact and costs, natural surfactants are suggested as an ecologically sustainable replacement for synthetic surfactants. The aim of this work is to evaluate the efficiency of low-cost saponin-based natural surfactant (SBNS) from Vernonia amygdalina (VA) leaves for enhanced oil recovery (EOR). Furthermore, the study investigated the IFT behaviour of SBNS at oil-water interface and the emulsion behaviour and oil displacement efficiency of SBNS. The SBNS was obtained via ultrasonic extraction of dried VA leaves in a water bath, centrifuging the obtained liquid mixture and freeze drying to evaporate to dryness. Thereafter, Fourier-transform infrared spectroscopy (FTIR) and high-performance liquid chromatography were used to characterize the extracted SBNS. Moreover, tensiometer (Easy-Dyne KRUSS) was used to study the interfacial tension (IFT) behaviour of the SBNS at oil-water interface. Also, the SBNS ability to form stable emulsion in the presence of crude oil was determined. Finally, oil displacement by SBNS solution was investigated under simulated reservoir conditions (3000 psi and 100 °C) with high-pressure high-temperature (Fars EOR) core flooding equipment. The performance of SBNS was compared to commercial non-ionic surfactant 4-octylphenol polyethoxylated (TX-100). Experimental result indicated that the SBNS reduced the IFT at oil-water interface. The natural surfactant lowered the IFT of the oil-water interface from 18.0 to 0.97 mN/m. Moreover, emulsions formed with SBNS showed good stability characterized by a decrease in the median drop diameter with an increase in SBNS concentration. Finally, oil displacement test shows that oil recovery of TX-100 and SBNS increased by 9% and 15% original-oil-in-place (OOIP), respectively. Hence, SBNS is recommended as an appropriate substitute for conventional surfactant due to its inexpensive raw material, lower toxicity, and higher efficiency.

Abatement of chlorobenzenes in aqueous phase by persulfate activated by alkali enhanced by surfactant addition

Sites polluted by dense non-aqueous phases (DNAPLs) constitute an environmental concern. In situ chemical oxidation (ISCO) application is limited since oxidation often occurs in the aqueous phase and contaminants are usually hydrophobic. In this work, ISCO enhanced by the surfactant addition (S–ISCO) was studied for a complex liquid mixture of chlorinated organic compounds (COCs) using persulfate (PS) activated by alkali (PSA) as oxidant and Emulse-3® as a commercial non-ionic surfactant. The reaction between E3 and PSA was investigated in the absence and presence of solubilized COCs in the following concentration ranges: COCs 1.2–50 mM, PS 84–336 mM, NaOH:PS molar ratio of 2, and surfactant concentration 1–10 g·L−1.In the experiments carried out in the absence of COCs, the unproductive consumption of PS was studied. The higher the surfactant concentration, the lower the ratio PS consumed to the initial surfactant concentration due to more complex micelle structures hindering the oxidation of surfactant molecules. This hindering effect was also noticed in the oxidation of solubilized COCs. The reduction of chlorobenzenes by PSA was negligible at surfactant concentrations above 2.5 g·L−1, independently of the COCs concentration solubilized. Instead, a surfactant concentration of about 1 and PS concentration of 168 mM yielded a significant decrease in the time required to abate a mass of DNAPL, compared with an ISCO process, with a bearable increase in the unproductive consumption of PS.

Non‐linearchanges in phase inversion temperature for oil and water emulsions of nonionic surfactant mixtures

AbstractHydrophilic–lipophilic deviation (HLD) is a semiempirical framework for surfactant‐oil–water (SOW) formulation that has effectively assimilated SOW properties such as phase inversion temperature (PIT) and Winsor Type I ↔ II ↔ III ↔ IV microemulsion behavior. The HLD system's reliance on surfactant and oil parameters necessitates their experimental determination when relevant and accurate values are not available. In this study, experiments have been of the type commonly used to generate test surfactant HLD parameters based on perturbation of a well‐defined SOW reference system and assumption of linear mixing behavior for PIT versus component mole fractions. The reference SOW compositions comprisedn‐octane, 0.01 M aqueous NaCl, and puren‐decyl tetraethylene glycol ether (C10E4) reference surfactant. Test surfactants were primary alcohol ethoxylates and nonylphenol ethoxylates comprising disperse PEG (polyethylene glycol) chain lengths that are inherent to commercial production of nonionic ethoxylate surfactants. We observe non‐linear behavior of PIT versus test surfactant mole fraction, even when accounting for surfactant concentration effects, so the desired linear correlation that could otherwise be used to assign an HLD parameter has not been obtained. Since an objective of this study has been to improve the predictive utility of the HLD framework for commercial nonionic surfactants, relevant terms in the HLD equation have been assessed in terms of their potential contributions to non‐linear behavior. One current working‐explanation relates substantial non‐linear PIT contribution to oil‐like surfactant components in disperse commercial ethoxylates.

Nonylcyclohexanol ethoxylates, a green alternative of nonylphenol ethoxylate, on the interfacial physiochemical properties aspects

AbstractNonylphenol ethoxylates (NPEOn), typically NPEO10, are the second popular nonionic surfactants that have been banned or restricted from use and production by Europe since 1990 due to their poor degradability and high genetic toxicity. The hypothesis of this work is that the nonylcyclohexanol ethoxylates (NCEOn) may possess similar interfacial properties but lower biotoxicity and better biodegradability compared with NPEOn according to their structures. To verify this and to find the optimal alternative of NPEO10, the interfacial properties of NCEOn were compared with the typical commercial ethoxylates nonionic surfactants, such as nonylphenol ethoxylated‐10 (NPEO10), alcohol ethoxylated‐9 (AEO9), secondary alcohol ethoxylated‐9 (SAE9), and isomeric alcohol ethoxylated‐9 (TO9). It is the NCEO7 that shows excellent emulsifying ability similar to that of NPEO10. NCEO11 performed stronger detergency than other assayed commercial nonionic surfactants. Additionally, NCEOn possessed lower biological toxicity to aquatic organisms. Hence, NCEOn could be considered as a green substitute for NPEOn in the assayed application fields.

Degradation of octylphenol polyethoxylates with a long ethoxylate chain using the laccase-mediated systems.

Alkylphenol polyethoxylates (APEOn) are the second-largest category of commercial nonionic surfactants, which are difficult to degrade naturally in the environment. This study examined the degradation of octylphenol polyethoxylate (OPEOn) by laccase and its laccase-mediated systems. The results showed that OPEOn was poorly degraded by laccase alone. 2,2'-azino-bis [3-ethylbenzothiazoline-6-sulphonic acid] (ABTS), 1-hydroxybenzotriazole (HBT), and 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) were selected as the redox mediators. Experimental results also indicated that 52.4% of the initial OPEOn amount was degraded by laccase in the presence of TEMPO. The degradation efficiency was analyzed using high-performance liquid chromatography. Furthermore, the structural characteristics of the degradation products were measured using matrix-assisted laser desorption/ionization-time of flight mass spectrometry and nuclear magnetic resonance spectroscopy, and it could be found that the laccase-TEMPO system could gradually shorten the ethoxylate chain by oxidizing the primary hydroxyl group of OPEOn, thereby degrading the OPEOn of the macromolecule into small molecules. The maximum of the ion peak distributions of OPEOn decreased from n = 8 finally down to 3. The novel enzymatic system introduced by this study will become a promising alternative method for high-efficiency APEOn conversion and had great potential value in wastewater treatment.

Potential of Palm Kernel Alkanolamide Surfactant for Enhancing Oil Recovery from Sandstone Reservoir Rocks

The interest in using benign surfactants has been steadily increasing in the context of enhanced oil recovery (EOR). Palm kernel alkanolamide surfactant (PKA), a nonionic surfactant synthesized from palm kernel oil, was preliminarily assessed for EOR from sandstone reservoir rocks. The performance factors determined were silica adsorption for surfactant loss and crude oil solubilization for oil solubilizing efficiency. The performance of PKA was compared to two commercial ionic surfactants, SDS (anionic surfactant) and CTAB (cationic surfactant). The results show that PKA was less absorbed on silica than CTAB or SDS. The adsorption kinetics were well fit with a pseudo-second order model for all three surfactants. The adsorption equilibrium data for CTAB and PKA were fitted with Langmuir isotherm, while for SDS Freundlich isotherm fit well, indicating multilayer SDS adsorption on silica surfaces. The adsorption of PKA was not significantly affected by added salt or increased temperature. In addition, the solubilization equilibrium constant (Ks) had the rank order PKA > CTAB > SDS, and proportionally increased with added salt. PKA performance was also compared to two commercial nonionic surfactants, Tergitol 15-S-9 and Tergitol TMN-6, and the results indicate that PKA was the least adsorbed, and had the highest Ks among the tested nonionic surfactants.

Gas hydrate nucleation and growth in the presence of water-soluble polymer, nonionic surfactants, and their mixtures

We investigated the effect of mixtures of commercial nonionic surfactants Sintanol ALM-7 (A7), Sintanol ALM-10 (A10), Surfynol 465 (S6), Surfynol 485 (S8), and well-known kinetic hydrate inhibitor Luvicap 55W (sample P) on nucleation and growth of sII gas hydrate. The ramp method (cooling at a constant rate of 1 °C × h−1) was employed to determine hydrate onset temperature and subcooling of individual and mixed samples. The dosage of reagents varied within 0.25–1.0 mass% range. A7 and A10 were tested at concentrations of 1.6∙10−4–2.5∙10−3 mass% (about or lower than CMC) as well. All surfactants were found to be weak antinucleators of gas hydrates. The inhibition performance of the surfactants was significantly lower in comparison with Luvicap 55W. We observed that ethoxylated fatty alcohols (A7 and A10) at low concentrations demonstrated a hydrate-inhibiting action at nucleation and growth stages.The Luvicap 55W – surfactant mixtures were tested as KHIs with a total dosage of 0.5 mass%, and in the ratio of 1:1, 1:2, and 1:5. Several mixed samples (1:1 P + A10), (1:2 P + A10), (1:2 P + S6) have demonstrated the same or higher efficacy in inhibition of hydrate nucleation than pure KHI. The results obtained indicate the presence of a synergistic effect of kinetic inhibition of gas hydrate with mixtures of the polymer and ethoxylated nonionic surfactants. Among the mixtures, the best results were obtained for the sample (1:2 P + S6). Surfynol 465 is characterized by high solubility in water, low foaming (compared to other surfactants), and lower cost than vinyl lactam-based KHI. Thus, the Surfynol 465 is a promising synergist for the vinyl lactam polymeric KHI and allows reducing the dosage of the expensive polymer.

Biosurfactants from Waste: Structures and Interfacial Properties of Sophorolipids Produced from a Residual Oil Cake

AbstractSophorolipids (SL) are microbial biosurfactants that have entered the market as detergent and cosmetic formulation ingredients. Current research is focused on the use of wastes to decrease the final production costs of SL and the environmental impacts. SL from wastes will help to move toward the circular economy only if the SL produced this way are pure enough and as efficient as current commercial SL. This manuscript focuses on the study of the structures and the interfacial properties of a crude SL natural mixture produced by solid‐state fermentation from a residual sunflower oil cake from the oil‐refining industry. Liquid chromatography–mass spectrometry (LC–MS) demonstrated that the diacetylated lactonic 18:1 SL was the most abundant SL of the mixture, followed by the correspondent acidic form. The surface tension‐lowering capacity was studied in a water–air interface at temperatures ranging from 15 to 50 °C. The minimum surface tension and critical micelle concentration were determined. The emulsion properties were similar to those obtained for the commercial nonionic surfactant Triton X‐100. The efficiency of the SL natural mixture was also proven successful for the displacement of a diesel slick. These results confirmed the effectiveness of SL produced from a real waste.

Prospective acid microemulsions development for matrix acidizing petroleum reservoirs

The oil exploration and drilling processes cause damage to the reservoir that result in decreasing production. Well stimulation processes are performed to repair this damage and restore the oil flow. Among them, matrix acidizing aims to unblock the pores by dissolving the rock, organic or inorganic scale through reaction with the injected acid, causing the dilation of the deeper pores to form long wormholes that provide a path for oil to flow from the reservoir to the production well. In this work, acid microemulsions were developed aiming to improve the stimulation process and reduce the problems caused by using acidic solutions, such as fast reaction with the reservoir rocks. The solvents used as the oil phase were kerosene and Solbrax Eco 175/235, while the aqueous phase consisted of hydrochloric acid (32%) and commercial nonionic surfactants based on ethoxylated lauryl alcohol containing different ethylene oxide units in their chains, and the cosurfactants were propanol and butylglycol. Initially, pseudo-ternary phase diagrams were constructed with the described components to determine the best concentrations of surfactant, cosurfactant, oil phase and aqueous phase to obtain microemulsions. The acidic microfluids prepared were characterized in terms of appearance, stability, particle size, density, viscosity, pH and type of emulsion. The most stable systems were selected for performance testing, where the rock-fluid reaction rate was measured. The results showed that a stable acid microemulsion was formed at room temperature, but not all the hydrochloric acid remained in the microemulsion. The best systems to retard the rock-fluid reaction rate were those containing ethoxylated lauryl alcohol with 1 unit of ethylene oxide.

Prediction of the cloud point of polyethoxylated surfactants and their mixtures by the thermodynamic model of Flory-Huggins-Rupert

The cloud point curves of polyethoxylated surfactants are established experimentally. These experimental data are preliminary to the development of the cloud point extraction process, which appears as an interesting alternative to the usual solvent extraction unit operation. Starting from the thermodynamic model developed by Flory and Huggins for phase separation of polymer aqueous solutions, this paper aims at the prediction of cloud point curves. In this work, Rupert’s approach is extended to commercial nonionic surfactants, mixtures of homologous species, namely a few alkylphenol and alcohol ethoxylates. The limit of such an approach is clearly demonstrated, provided that a fitting parameter is finally required for a successful model application to pilot-plant manufactured surfactants, like C8ΦEn (n = 7.5, 10, 12), C9ΦEn (n = 8, 10, 12), C12E4, C12E6 and commercial Tergitol 15-S-7 (linear C12-C14 secondary alcohol with an average of 7 ethylene oxide units).GRAPHICAL ABSTRACT

Formulation of oil-in-water emulsions for pesticide applications: impact of surfactant type and concentration on physical stability.

Oil-in-water (O/W) emulsions can be utilized as effective pesticide delivery systems in the agricultural industry. In this study, the effects of hydrophile-lipophile balance (HLB), concentration, and location of surfactants on the formation and physical stability of O/W emulsions suitable for pesticide applications was investigated using dynamic light scattering and vertical laser profiling. A non-polar pesticide (lambda-cyhalothrin) was used as a model. The pesticide emulsion with the highest stability was obtained using a commercial non-ionic surfactant (polyoxyethylene castor oil ether, EL-20) with a required HLB value of 10.5. Emulsion stability increased as the surfactant concentration was increased from 2 to 6%, which was attributed to the formation of smaller oil droplets during emulsification. Emulsions prepared with the surfactant initially in the oil phase were more stable than those prepared with it initially in the aqueous phase. The optimum formulation of the pesticide emulsion was determined as follows: 5% lambda-cyhalothrin (active ingredient) and 6% EL-20 (surfactant) dissolved in 5% S-200 (aromatic hydrocarbon, as oil phase), then deionized water up to 100%, which met the quality indicators set by the FAO standards. The present study is expected to provide useful information to improve the stability of pesticide emulsions for commercial applications.

Development of microemulsions to reduce the viscocity of crude oil emulsions

The formation of water-in-oil (W/O) emulsions during extraction of petroleum is a major problem, because these emulsions increase the oil’s viscosity and thus significantly lower the production rates. In these situations, chemical products called emulsion viscosity reducers (EVRs) can be injected during crude oil production. The development of EVRs consisting of oil-in-water (O/W) microemulsions can attract a good deal of attention due to the possibility of reducing costs and increasing environmental friendliness (they are mostly composed of water instead of large volumes of organic solvents). This article describes the preparation of O/W microemulsions, using the solvents kerosene, Solbrax or xylene as components of the oil phase and three commercial nonionic polymer surfactants based on poly(ethylene oxide) as the aqueous phase. For this purpose, first ternary phase diagrams (water/oil/surfactant) were constructed to determine the optimal concentrations of these components to prepare the O/W microemulsions, selecting 16wt% surfactant, 4wt% oil phase and 80wt% aqueous phase as the common composition of all the systems studied. The efficiency of the microemulsion systems was investigated by rheological tests in synthetic water/oil emulsions prepared from a heavy crude oil (°API 20). The microemulsion systems were tested regarding their interfacial activity by analyzing the interfacial tension and the average size of the water droplets dispersed in the crude oil, before and after adding the systems developed. The results showed that the performance of the O/W microemulsions did not depend on the type of oil phase, but that the insertion of an oil phase (i.e., the formation of an O/W microemulsion) improved the performance of the surfactant in the medium compared to the efficiency of the aqueous surfactant solutions.

Critical Microemulsion Concentration and Molar Ratio of Water-to-Surfactant of Supercritical CO2 Microemulsions with Commercial Nonionic Surfactants: Experiment and Molecular Dynamics Simulation

The critical microemulsion concentration (cμc) and the molar ratio of water-to-surfactant (W0) of supercritical CO2 (scCO2) microemulsion that uses different nonionic hydrocarbon surfactants (LS-36, LS-45, LS-54, DYNOL-604, TMN-6) were examined at temperatures from 35 to 45 °C and pressures up to 19 MPa. The results show that the cμc mainly depends on the structure of the surfactant. The surfactant with more hydrophilic structure, such as the ethylene oxide (EO) group and hydroxyl, tends to produce a higher cμc. In addition, the cμc increases with the increase of the ratio of ethylene oxide (EO) group number to the propylene oxide (PO) group number of the surfactant. The capacity of the microemulsion system to dissolve water, which is characterized by W0, is related to the concentration and structure of surfactant. It is found that a higher solubility of surfactant in CO2 favors the system to dissolve water at lower pressure. At higher pressure, the stronger hydrophilicity of surfactant and the higher sur...

A New Type of Sulfobetaine Surfactant with Double Alkyl Polyoxyethylene Ether Chains for Enhanced Oil Recovery

AbstractA new type of sulfobetaine with double alkyl polyoxyethylene (n) ether chains, dicoconut oil alcohol polyoxethylene (n) ether methylhydroxylpropyl sulfobetaine (diC12–14EnHSB) was synthesized using a commercial nonionic surfactant, coconut oil alcohol polyoxethylene (n) ether, as raw material and its properties as a surfactant for enhanced oil recovery (EOR) in the absence of alkali was studied. The purified product is a mixture of homologues with mainly C12/C12, C12/C14 and C14/C14 alkyl chains and widely distributed EO chains (n = 2.2 on average) with an average molar mass of 742.6 g/mol. The diC12–14E2.2HSB has an improved aqueous solubility at 25 °C compared with didodecylmethylhydroxylpropyl sulfobetaine (diC12HSB), a homologue without an EO chain, and is highly surface active as reflected by its low CMC (4.6 × 10−6 mol/L), high saturated adsorption (6.8 × 10−10 mol/cm2) and small cross sectional area (0.24 nm2/molec.) at the air/water interface. With a hydrophile–lipophile balance well matched with Daqing crude oil/connate water system, the sulfobetaine can reduce Daqing crude oil/connate water interfacial tension to ultra‐low values at 45 °C in the absence of alkali, and displays a low saturated adsorption at the sandstone/water interface (0.0024 mmol/g), reduced by 69 and 92 % respectively in comparison with that of the corresponding carboxyl betaine, diC12–14E2.2B and its homologue without an EO chain, didodecylmethylcarboxyl betaine (diC12B). With these excellent properties diC12–14E2.2HSB gives a high tertiary recovery, 18.4 % original oil in place, when mixed with other hydrophobic and hydrophilic sulfobetaines in surfactant‐polymer (SP) flooding free of alkali. The insertion of EO chains in combination with the replacement of carboxyl betaine by sulfobetaine is therefore very efficient for improving the properties of the double chain hydrophobic carboxyl betaines as surfactants for SP flooding free of alkali.