Hydrodechlorination of trichloroethene using stabilized Fe-Pd nanoparticles: Reaction mechanism and effects of stabilizers, catalysts and reaction conditions

This study investigated the effects of carboxymethyl cellulose (CMC) as a stabilizer on the reactivity of CMC-stabilized Fe-Pd bimetallic nanoparticles toward trichloroethene (TCE). Overall, the particle stabilization prevented particle agglomeration and resulted in greater particle reactivity. The pseudo-first order TCE degradation rate increased from 0.86 h⁻¹ to 6.8 h⁻¹ as the CMC-to-Fe molar ratio increased from 0 to 0.0124. However, a higher CMC-to-Fe ratio inhibited the TCE degradation. Within the same homologous series, CMC of greater molecular weight resulted in more reactive nanoparticles for TCE hydrodechlorination. Hydrogen (either residual hydrogen from zero-valent iron (ZVI) nanoparticle synthesis or hydrogen evolved from ZVI corrosion) can serve as effective electron donors for TCE dechlorination in the presence of Pd (either coated on ZVI or as separate nanoparticles). Decreasing reaction pH from 9.0 to 6.0 increased the TCE reduction rate by 11.5 times, but enhanced the Fe corrosion rate by 31.4 times based on the pseudo-first order rate constant. Decreasing pH also shifted the rate controlling step of TCE reduction from Fe corrosion to hydrodechlorination. Ionic strength (<0.51 M) did not significantly affect the TCE reduction.     

Formulating middle-phase microemulsions using mixed anionic and cationic surfactant systems

Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane, and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form). The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures advantageous.     

Interaction Between Nonionic and Gemini (Cationic) Surfactants: Effect of Spacer Chain Length

The interaction between mixtures of nonionic surfactant polyethylene glycol p-(1,1,3,3-tetramethyl butyl)-phenyl ether and cationic gemini surfactants alkanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-s-12, where s = 2, 4 and 6) was studied using surface tension and small-angle neutron scattering measurements. Marked interaction was observed for the investigated surfactants mixtures which depend upon the hydrophobic spacer length of the gemini surfactant and also on the fraction of nonionic surfactant in the mixed systems. The results are discussed in terms of interaction parameters calculated according to the theory of regular solutions which uses the critical micelle concentration determined tensiometrically to calculate the molecular interaction parameter and the mole fractions of the two components in the mixed micelles. A relatively high negative molecular interaction parameter value (up to −3.40) obtained for mixtures of nonionic and cationic gemini surfactant indicates a presence of strong attractive interaction in the mixed system that increases with the spacer length of the gemini surfactant. Micellar parameters deduced from small-angle neutron scattering measurements also compliment the surface tension results.     

Morphology,structure, and conductivity of polypyrrole prepared in the presence of mixed surfactants in aqueous solutions

Polypyrrole (PPy) was prepared from different mixed‐surfactant solutions with ammonium persulfate as an oxidant. Three types of combinations were selected, including cationic/anionic, cationic/nonionic, and anionic/nonionic mixed‐surfactant solutions. The surfactants used in the experiments included cetyltrimethylammonium bromide (cationic surfactant), sodium dodecyl sulfate (anionic surfactant), sodium dodecyl sulfonic acid salt (anionic surfactant), poly(vinyl pyrrolidone) (nonionic surfactant), and poly(ethylene glycol) (nonionic surfactant). The morphology, structure, and conductivity of the resulting PPy were investigated in detail with scanning electron microscopy, Fourier transform infrared spectra, and the typical four‐probe method, respectively. The results showed that the interaction between the different surfactants and the interaction between the surfactants and the polymer influenced the morphology, structure, and conductivity of the resulting polymer to different degrees. The cationic surfactant favored the formation of nanofibers, the addition of anionic surfactants produced agglomeration but enhanced the doping level and conductivity, and the presence of a nonionic surfactant weakened the interaction between the other surfactant and the polymer in the system. In comparison with the results for monosurfactant solutions, the polymerization of pyrrole in mixed‐surfactant solutions could modulate the morphologies of PPy, which ranged from nanofibers of different lengths to nanoparticles showing various states of aggregation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1987–1996, 2007     

Hydrodechlorination of 2,4,6-trichlorophenol for a permeable reactive barrier using zero-valent iron and catalyzed iron

Dehalogenation of toxic organic compounds has been intensively studied during the last decade by using zero-valent iron (ZVI). However, the reactivity of iron is compound specific and very low reactivities were reported for aromatic compounds including chlorophenols. In this study, hydrodechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) was conducted in a batch system by using ZVI and catalyzed iron. No degradation was observed with ZVI over the 40 days experiments. Catalyzed ZVIs removed 2,4,6-TCP and palladium-coated iron (Pd/Fe) and nickel-coated iron (Ni/Fe) showed relatively enhanced reactivity while copper-coated iron (Cu/Fe) and platinum-coated iron (Pt/Fe) showed lower reactivities. The surface area normalized kinetic constants (k _SA ) of Pd/Fe, Ni/Fe, Cu/Fe, Pt/Fe are 2.54×10⁻⁴, 1.01 × 10⁻⁴, 2.24×10⁻⁵, 2.56×10⁻⁵ L m⁻² h⁻¹, respectively. The identification of less chlorinated phenols and phenol confirmed that the removal is dechlorination. Pd/Fe system exerts relatively low pH compared with the ZVI system, and the low pH is favorable for the dechlorination. The reactivity enhancement of catalyzed iron was discussed in terms of catalytic effects and the corrosion potential by the bimetal coupling. Variable Pd content on the Pd/Fe was tested, and the degradation rate of 2,4,6-TCP increased in proportion to the increase of Pd content.     

Adsorption mechanism of surfactants on nonwoven fabrics

For improved surface properties, nonwoven fabrics of polypropylene and poly(ethylene terephthalate) were treated with several kinds of surfactants, including anionic, cationic, and nonionic types. The adsorption isotherms of the anionic, cationic, and nonionic surfactants on the nonwoven fabrics were different. The adsorption isotherm of the cationic surfactant (dodecyl dimethylbenzyl/ammonium chloride) exhibited a maximum. The adsorption isotherm of the anionic surfactant (sodium dodecylbenzene sulfonate) was in the shape of the fifth Brunauer adsorption isotherm, and that of the nonionic surfactant (alkylphenol/ethylene oxide condensate) was similar to the fourth Brunauer adsorption isotherm. The time of the adsorption equilibrium was constant for the same types of adsorbate and adsorbent, and it was not related to the initial concentration. The specific surface resistance of the nonwoven fabrics decreased substantially after the adsorption of ionic surfactants. The nonwoven fabrics with the surfactants were characterized with scanning electron microscopy and X‐ray photoelectron spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3210–3215, 2003     

Synergistic Effect of Mixed Surfactant Systems on Foam Behavior and Surface Tension

Foam and surface tension behaviors of different ionic/nonionic surfactant solutions along with their different combinations have been investigated. Among different surfactants, sodium dodecyl sulfate showed the highest foamability over other surfactants. Mixed surfactant systems were always found to have higher foamability than the individual surfactant. It was also noticeable that nonionic surfactants show good foamability when they combine with anionic and cationic surfactants. In the case of mixed surfactant systems, nonionic/cationic surfactant mixtures showed lower surface tension than nonionic/anionic surfactant mixture due to a synergistic effect.     

Synergistic effect of polymer-surfactant mixtures on the stability of aqueous silica suspensions

The aim of the present work was to investigate the effect of cationic/nonionic surfactant mixtures on the dispersion and flocculation behavior of aqueous silica suspensions. In the study dodecylamine (DDA) was used as the cationic surfactant and polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO–PPO–PEO) triblock copolymers were employed as the nonionic surfactant. The dispersion and flocculation behavior of aqueous silica suspensions were studied mainly by turbidity measurements at low solids loading (0.05 vol.%) to observe the stability of the system for a given time period. Rheological measurements were performed at higher solids loadings to determine the viscosity as a function of shear rate. Adsorption behavior of single and mixed surfactants onto silica surface was studied using a total organic carbon analyzer.Results of the study showed that dispersion and flocculation behavior of aqueous silica suspensions depends on the type and concentration of surfactant, cationic/nonionic surfactant ratio and surfactant addition sequence to the system.     

Reductive transformation and dechlorination of chloronitrobenzenes in UASB reactor enhanced with zero‐valent iron addition

BACKGROUND: Zero‐valent iron (ZVI) is increasingly being applied in biological wastewater treatment to enhance the conversion of various contaminants. The objective of this present study was to investigate the effect of ZVI on the anaerobic biotransformation and dechlorination of chloronitrobenzenes (3,4‐DClNB and 4‐ClNB). Experiments were conducted in two upflow anaerobic sludge blanket (UASB) reactors, one (R2) with 30 g L^?1 ZVI added, and the other (R1), serving as control reactor. RESULTS: ZVI‐based anaerobic granular sludge (ZVI‐AGS) composed of bacteria associated with precipitated FeCO₃ and FeS was successfully developed within 5 months in reactor R2. ZVI addition obviously enhanced 3,4‐DClNB transformation and dechlorination efficiencies under high 3,4‐DClNB loads, and further promoted dechlorination of 4‐chloroaniline (4‐ClAn) to aniline. Compared with the AGS formed in R1 reactor, iron and its corrosion products were observed and colonized with anaerobes such as methanothrix in ZVI‐AGS, and the specific transformation rates of 3,4‐DClNB and 4‐ClNB using ZVI‐AGS were improved by 34.0% and 64.4%, respectively. Furthermore, ZVI‐AGS provided higher 3,4‐dichloronailine and 4‐ClAn dechlorination efficiency than AGS. Abiotic transformation of ClNBs by ZVI, appropriate concentration of iron corrosion products, lower redox potential and greater hydrogen production were the main factors providing enhanced transformation and dechlorination of ClNBs in the UASB reactor. CONCLUSION: Addition of ZVI to a UASB reactor enhanced the reductive transformation and dechlorination of ClNBs. It provides a feasible proposal for the design and optimization of a high‐rate anaerobic wastewater treatment technique for industrial wastewater. Copyright © 2010 Society of Chemical Industry     

Electrochemically Reversible Solubilization of Polycyclic Aromatic Hydrocarbons by Mixed Micelles Composed of Redox-active Cationic Surfactant and Conventional Nonionic Surfactant

Reduplicate utilization of surfactants is a key factor for Surfactant-Enhanced Remediation (SER) technology to reduce its high operation costs. In order to achieve the reuse of surfactants, this study attempted to construct a novel reversible solubilization system for SER. Three typical polycyclic aromatic hydrocarbons (PAHs) pyrene, phenanthrene, and acenaphthene were controllably solubilized and released by the mixed micelles composed of redox-active cationic surfactant (11-Ferrocenylundecyl) trimethylammoniunm bromide (FTMA) and conventional nonionic surfactant Tween80. Solubilization of PAHs is assumed to be controlled by changing the redox states of FTMA. Cyclic voltammograms tests of FTMA showed the oxidation and reduction potential were 0.4570 and 0.4068 V, respectively, and the peak currents ratio of FTMA and FTMA⁺ was 1.26, verified that FTMA possesses electrochemically reversible property. In FTMA-Tween80 mixed solutions, CMC values demonstrated the nonideal interaction between the two surfactants and the interaction parameters (β) was -5.5296 when the mass ratio was FTMA:Tween80 = 2:8. Due to the synergistic solubilization effect, the apparent water solubilities of PAHs were significantly enhanced by the mixed surfactant, and they were much higher than those in single surfactant. After oxidation, more than 50% of the PAHs in mixed micelles could be released, the cumulative release efficiency of selected PAHs followed the order of pyrene > pherantherene > acenaphthene. Briefly, such results in this article provide a facile method to meliorate the SER technology.     

Effect of reduction temperature on the preparation of zero-valent iron aerogels for trichloroethylene dechlorination

Zero-valent iron (ZVI) aerogels have been synthesized by sol-gel method and supercritical CO₂ drying, followed by H₂ reduction in the temperature range of 350–500 °C. When applied to trichloroethylene (TCE) dechlorination, the ZVI aerogel reduced at 370 °C showed the highest performance in the conditions employed in this study. Thus, the effect of reduction temperature in preparing ZVI aerogels has been investigated by several characterizations such as BET, XRD, TPR, and TEM analyses. As the reduction temperature decreased from 500 to 350 °C, the BET surface area of the resulting aerogels increased from 6 to 30 m²/g, whereas their Fe⁰ content decreased up to 64%. It was also found that H₂ reduction at low temperatures such as 350 and 370 °C leads to the formation of ZVI aerogel particles consisting of both Fe⁰ and FeO _x in the particle cores with a different amount ratio, where FeO _x is a mixture of maghemite and magnetite. It is, therefore, suggested that reduction at 370 °C for ZVI aerogel preparation yielded particles homogeneously composed of Fe⁰ and FeO _x in the amount ratio of 87/13, resulting in high TCE dechlorination rate. On the other hand, when Pd- and Ni-ZVI aerogels were prepared via cogellation and then applied for TCE dechlorination, we also observed a similar effect of reduction temperature. However, the reduction at 350 or 370 °C produced Pd- or Ni-ZVI aerogel particles in which Fe⁰ and Fe₃O₄ co-exist homogeneously. Since both Fe⁰ and Fe₃O₄ are advantageous in TCE dechlorination, the activities of Pd- and Ni-ZVI aerogels reduced at 350 °C were comparable to those of both aerogels reduced at 370 °C, although the former aerogels have less Fe⁰ content.     

Synthesis and characterization of nanosized polypyrrole–polystyrene composite particles

Nanosized polypyrrole–polystyrene (PPy–PS) composite particles were synthesized by the polymerization of pyrrole on PS nanoparticles in the presence of FeCl₃. The PS nanoparticles were prepared from microemulsion polymerizations using the cationic nonpolymerizable surfactant cetyltrimethylammonium bromide (CTAB), the nonionic polymerizable surfactant ω‐methoxy[poly(ethylene oxide)₄₀]undecyl α‐methacrylate (PEO–R–MA‐40), or the cationic polymerizable surfactant ω‐acryloyloxyundecyltrimethylammonium bromide (AUTMAB). For the latexes stabilized by CTAB, the resulting PPy–PS composite particles exhibited relatively poor colloidal stability and the pressed pellets exhibited relatively low electrical conductivities (～10^?7–10^?3 S cm^?1). However, for the latexes stabilized by polymerizable surfactants, the resulting PPy–PS composite particles exhibited relatively good colloidal stability and relatively high conductivities (～10^?5–10^?1 S cm^?1). The effect of polymerizable surfactants on the colloidal stability of composite particles and the conducting mechanism of the composites are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1360–1367, 2004     

Surfactant-Induced Wettability Alteration of Oil-Wet Sandstone Surface: Mechanisms and Its Effect on Oil Recovery

Different analytical methods were utilized to investigate the mechanisms for wettability alteration of oil-wet sandstone surfaces induced by different surfactants and the effect of reservoir wettability on oil recovery. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is more effective than the nonionic surfactant octylphenol ethoxylate (TX-100) and the anionic surfactant sodium laureth sulfate (POE(1)) in altering the wettability of oil-wet sandstone surfaces. The cationic surfactant CTAB was able to desorb negatively charged carboxylates of crude oil from the solid surface in an irreversible way by the formation of ion pairs. For the nonionic surfactant TX-100 and the anionic surfactant POE(1), the wettability of oil-wet sandstone surfaces is changed by the adsorption of surfactants on the solid surface. The different surfactants were added into water to vary the core surface wettability, while maintaining a constant interfacial tension. The more water-wet core showed a higher oil recovery by spontaneous imbibition. The neutral wetting micromodel showed the highest oil recovery by waterflooding and the oil-wet model showed the maximum residual oil saturation among all the models.     

Solubility of Two Disperse Dyes Derived from <Emphasis Type="Italic">N</Emphasis>-Alkyl and <Emphasis Type="Italic">N</Emphasis>-Carboxylic Acid Naphthalimides in the Presence of Gemini Cationic Surfactants

The solubility of naphthalimide-based monoazo dyes containing N-ethyl and N-ethanoic acid groups was investigated in the presence of a conventional monomeric counterpart (DTAB) and two cationic gemini surfactants (12-4-12 or 14-4-14) individually. The effective parameters on dye solubility such as temperature, time and concentration of surfactants were investigated by UV–Visible spectrophotometry. The results demonstrate that the solubility of both dyes was considerably increased at concentrations above the surfactant CMC. The wavelength for the maximum absorbance of dyes in the aqueous solution shifts toward longer wavelengths with changes in the concentration of the cationic surfactants. A kinetic study of solubilization of dyes in cationic surfactants solution showed that the rate of solubilization follows the pseudo-first-order reactions. Rates of solubilization were in the range of 0.5 × 10⁻³ to 6.8 × 10⁻³ min⁻¹ for both dyes. The disperse dye containing a carboxylic acid group (dye 2) has a higher solubility rate than the dye containing an alkyl group (dye 1). The type of surfactant has a very low effect on adsorption of dye 1 onto the polyester fibers, whereas changing the surfactant type from DTAB to 12-4-12 or 14-4-14 causes adsorption of dye 2 on polyester to decrease.     

水溶性铑-膦络合物催化烯烃氢甲酰化反应--阳离子表面活性剂的加速作用

介绍了以水溶性铑-膦络合物RhCl(CO)(TPPTS)₂作为催化剂前体在水/有机两相体系中催化烯烃氢甲酰化反应研究的进展,阐述了阳离子表面活性剂的加速作用和介稳态胶束-离子对协同作用机理关系.通过两相体系中界面分子组装和选择与烯烃分子链长相匹配的表面活性剂, 设计制备了高区域选择性复合催化剂体系.当采用双长链表面活性剂与铑-膦络合物组成的复合催化体系时,在不搅拌的情况下就显示出极高的催化活性.     

Polymer‐Cationic Surfactant Interaction: 1. Surface and Physicochemical Properties of Polyvinyl Alcohol (PVA)‐S‐Alkyl Isothiouronium Bromide Surfactant Mixed Systems

Surface properties of polyvinyl alcohol (nonionic polymer) and three synthesized cationic surfactants, namely, S‐alkyl isothiouronium bromide at different mole fractions of 1:9, 3:7, 5:5, 7:3, and 9:1, were investigated. The values of the surface parameters were discussed according to the type of interaction between the cationic surfactant and type of polymer studied. The S‐alkyl isothiouronium bromide surfactant molecules are positively charged molecules, and the PVA chains contain hydroxyl groups that are partially negatively charged centers. The comparison between the surface properties of the individual cationic surfactants and their mixture with PVA polymer showed that the mixed systems have some advantages over the individual cationic surfactants.     

Precipitation and Micellar Properties of Novel Mixed Anionic Extended Surfactants and a Cationic Surfactant

Surfactant-modified mineral surfaces can provide both a hydrophobic coating for adsorbing organic contaminants and, in the case of ionic surfactants, a charged exterior for adsorbing oppositely charged species. This research evaluates the precipitation phase boundaries and synergistic behavior of the mixtures of carboxylate-based anionic extended surfactants with a pyridinium-based cationic surfactant. One cationic surfactant (cetylpyridinium chloride) and four anionic extended surfactants were studied. The anionic surfactants studied were ethoxy carboxylate extended surfactants with average carbon chain lengths of either 16 and 17 or 16 and 18 with 4 mol of a propylene oxide group and a different number of moles of an ethylene oxide group (2 and 5 mol). Precipitation phase boundaries of mixed anionic extended surfactants and cationic surfactant were evaluated to ensure that the surface tension studies are in regions without precipitate. Surface tension measurements were conducted to evaluate the critical micelle concentration of individual and mixed surfactant systems. Precipitation phase boundaries of these novel mixed surfactant systems showed greatly reduced precipitation areas as compared to a conventional mixed surfactant system which is attributed to the presence of the ethylene oxide and propylene oxide groups and resulting steric hindrances to precipitation. Moreover, it was demonstrated that the CMC of mixed surfactant systems were much lower than that of individual surfactant systems. Synergism was evaluated in the four systems studied by the β parameter which found that all systems studied exhibited synergism. From these results, these novel mixed surfactant systems can greatly increase formulation space (reduce the precipitation region) while maintaining synergism, although slightly reduced from conventional anionic-cationic mixtures reported previously.     

Spectroscopic and conductometric studies on the interactions of thionine with anionic and nonionic surfactants

In this study, the interaction of thionine, a cationic dye, with anionic [sodium dodecyl sulphate (SDS), lithium dodecyl sulphate (LiDS), and sodium dodecylbenzene sulphonate (SDBS)], nonionic (Tween 20 and Triton X‐100), and binary mixtures of anionic and nonionic surfactants was studied by conductometric and spectrophotometric measurements. The degree of ionisation, the counterion binding parameters, and the equilibrium constants in the premicellar region were obtained from conductivity data. Binding constants of thionine to anionic, nonionic, and mixtures of anionic and nonionic micelles were determined by spectrophotometric measurements. The binding tendency of thionine to anionic micelles followed the order SDBS > SDS > LiDS. The presence of nonionic surfactants increased significantly the binding affinity of thionine to anionic micelles, and the highest binding constant was calculated in the presence of Tween 20. The results obtained from conductometric studies correlated with those obtained from spectroscopic studies. Data concerning dye–surfactant interaction are important for a fundamental understanding of the performance of single and mixed surfactants and for their industrial application.     

Importance of micellar relaxation time on detergent properties

As we enter the new millennium, manufacturers of laundry detergents would like to provide new products for the twenty-first century. With the goal of achieving new and better performance characteristics, design strategies for research and development should be defined. This paper highlights the importance of micellar relaxation kinetics in processes involved in detergency. Earlier Shah and coworkers showed that the stability of sodium dodecyl sulfate (SDS) micelles plays an important role in various technological processes. The slow relaxation time (τ₂) of SDS micelles, as measured by the pressure-jump technique, was in the range of 10⁻⁴ to 10¹ s, depending on the surfactant concentration. A maximal relaxation time and thus a maximal micellar stability was found at 200 mM SDS (5 s), corresponding to the least-foaming, largest bubble size, longest wetting time of textile, largest emulsion droplet size, and the most rapid solubilization of oil. These results are explained in terms of the flux of surfactant monomers from the bulk to the interface, which determines the dynamic surface tension. More stable micelles lead to less monomer flux and hence to a higher dynamic surface tension. The relaxation time for nonionic surfactants (as measured by the stopped-flow technique) was much longer than for ionic surfactants because of the absence of ionic repulsion between the head groups. The τ₂ was related to dynamic surface-tension experiments. Stability of SDS micelles can be greatly enhanced by the addition of long-chain alcohols or cationic surfactants. In summary, relaxation time data of surfactant solutions enable us to predict the performance of a given surfactant solution. Moreover, results suggest that one can design appropriate micelles with specific stability, or τ₂, by controlling surfactant structure, concentration, and physicochemical conditions, as well as by mixing anionic/cationic or ionic/nonionic surfactants for a desired technological application, e.g., detergency.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-(3-Oxapropanoxyl)dodecanamide and its Application in Surfactant-Polymer Flooding

Alkali-surfactant-polymer (ASP) flooding has been considered to be one of the useful tertiary oil recovery techniques. However, field tests in China have revealed that serious side effects may occur due to using alkali. Thus alkali-free SP flooding is more favorable in China. Unfortunately, surfactants effective in ASP flooding are usually ineffective in the absence of alkali and new surfactants need to be designed. In this paper N-(3-Oxapropanoxyl)dodecanamide as a pure compound and a mixture of homologues with narrow EO number distribution, synthesized by the reaction of lauroyl chloride with diglycolamine and addition of one ethylene oxide to coconut monoethanolamide respectively, are examined for their adaptability in SP flooding. It is found that, when mixed with betaines, both products can reduce Daqing crude oil/connate water interfacial tension to a magnitude of 10⁻³–10⁻⁴ mNm⁻¹ at 45 °C in a wide surfactant concentration range, 0.01–0.5 wt%, and oil displacement tests using natural cores indicates that a tertiary oil recovery of 18.6 ± 0.4% OOIP can be achieved by SP flooding with the N-(3-Oxapropanoxyl)dodecanamide as the main surfactant without adding any alkaline agent and neutral electrolyte. N-(3-Oxapropanoxyl)dodecanamide, as a nonionic surfactant without a cloud point and producible industrially from renewable materials, is an ideal surfactant for SP flooding in the absence of an alkaline agent.