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. 2025 Jan 28;10(5):4516–4525. doi: 10.1021/acsomega.4c08146

Synthesis, Characterization, and Effects of Aliphatic and Aromatic Amines on Thermal and Surface Properties of Zwitterionic Amphiphiles

Muhammad Israr †, Ahmad Mahboob †, Syed Muhammad Shakil Hussain †,*, Muhammad Shahzad Kamal †,*, Theis Solling †, Mohammed Alotaibi ‡, Mohanad Fahmi ‡
PMCID: PMC11822523  PMID: 39959055

Abstract

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Solubility and thermal stability of surfactants are the key properties to consider for their possible oilfield applications. Most commercially available surfactants experience hydrolysis under high temperatures, and prolonged heating exacerbates this process, creating significant challenges for the petroleum industry. To address these complications, a novel class of propylamine and pyridinium-based zwitterionic surfactants was prepared, and their structures were confirmed using nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopies. Salt tolerance tests were performed in distilled water, seawater, and formation water, while thermal stability was evaluated by using thermogravimetric analysis (TGA). Additionally, surface properties such as critical micelle concentration (CMC) and surface tension at the CMC (γCMC) were measured for these surfactants. The surfactants exhibit remarkable solubility in all types of water without any precipitation or cloudiness. TGA data demonstrated that the thermal decomposition temperatures for all of the newly prepared zwitterionic surfactants were around 300 °C, significantly greater than real reservoir temperatures. The CMC values range from 0.07 to 0.26 mmol L–1, where the surface tension at the CMC (γcmc) ranges from 31.16 to 34.54 mmol/L. Moreover, low CMC values of zwitterionic amphiphiles containing a propylamine group in their core structure signify that they can make more tightly compact micelle structures than zwitterionic amphiphiles with a pyridine ring. This research fills the critical gap concerning the solubility and thermal stability of surfactants under harsh conditions by designing and evaluating these novel zwitterionic amphiphiles. The excellent solubility, thermal stability, and surface properties of the synthesized zwitterionic amphiphiles make them ideal choices for effective applications in challenging reservoir conditions, paving the way for enhanced oil recovery approaches.

1. Introduction

Oil has remained the world’s fundamental energy source since its discovery, and the demand continues to grow. The world’s rapid industrialization is the key reason behind the increased demand for oil. Substantial focus has been given to the recovery of trapped oil in aging reservoirs. Although both primary and secondary techniques are used for oil recovery, a significant amount (around two-thirds) of the original oil remains irretrievable in old reservoirs.1 Chemical enhanced oil recovery (cEOR) approaches usually include the injection of specially formulated chemicals to modify the characteristics of reservoir liquids or reservoir rocks by reducing interfacial tension (IFT) between oil and water, altering the rock’s wettability toward a more water-wet state for improved oil displacement, and controlling the mobility ratio of the displacing fluid to ensure a uniform flow front, thus collectively enhancing oil displacements efficiency and maximizing overall recovery.2−6 Surfactants are acknowledged to reduce surface tension and IFT between oil and water, which weakens the capillary forces and increases the capillary number, allowing trapped oil to flow easily toward production wells. Furthermore, surfactants alter the wettability of rocks, often changing it from oil-wet to water-wet states, allowing water to move oil more efficiently from pore spaces.7,8 Upstream applications of surfactants are suffering due to their low solubility, high adsorption on formation rocks, and inadequate thermal stability.9−12

Generally, surfactants are classified into four groups (i.e., anionic, nonionic, cationic, and zwitterionic) according to the property of the polar headgroup. The hydrophilic polar “head” of surfactants is vital in determining their physicochemical characteristics due to their inimitable chemical structure and their interactions with neighboring molecules.13 Choosing the appropriate surfactants for enhanced oil recovery (EOR) is a challenging practice that has to take the wettability, mineralogy, salinity, temperature, and pressure conditions of the reservoir rock into consideration.14 For example, anionic surfactants are favored for use in sandstone reservoirs because of their special chemical characteristics, which lead to less adsorption onto the rock surfaces compared to their cationic counterparts.15 Likewise, the challenges associated with strong absorption in carbonate reservoirs were mitigated by the application of cationic surfactants.16 Moreover, nonionic surfactants are used to increase salt resistance; however, they show greater interfacial tension (IFT) values than anionic surfactants. Zwitterionic amphiphiles have recently gained significant consideration in both academic and industrial applications, owing to their unique physicochemical characteristics. These include remarkable heat resistance, tolerance to highly saline environments, high solubilities, strong foam stability, and biodegradability.17 Given the significance of zwitterionic surfactants, researchers in the petroleum industry have conducted extensive studies on their applicability in enhanced oil recovery.18−23 Moreover, interest in their wettability and alteration performance has surged in recent years. In this context, Deng et al. investigated the wettability alteration performance of zwitterionic amphiphiles on Berea sandstone and Indiana limestone under high salinity (150,000 ppm of NaCl). Their findings suggest that wettability alteration is not affected by calcite dissolution.24 For specific oilfield applications, careful selection of an appropriate headgroup and tail group in the core structure of zwitterionic surfactants is highly important. For instance, adding a carboxylate moiety as a headgroup to a surfactant molecule improves its water solubility by enabling interactions with water molecules via hydrogen bonding.25 In the same way, hydroxy sulfobetaine groups enhance the hydrophilicity of the surfactant molecule. On the other hand, increasing the chain length (tail group) decreases the surfactant water solubility. Surfactants with long nonpolar tail groups were found to be insoluble in aqueous media.26 The addition of ethoxy units (EO) to the tail group of the surfactant generally increases its thermal stability.27 Indeed, the incorporation of EO units eradicates the need for an additional cosolvent to accomplish the much sought-after ultralow interfacial tension (IFT). This change in structure not only enhances the surfactant’s solubility in aqueous media but also improves its solubility in high-salinity environments.28,29 For instance, Afeez et al. studied the thermal stability, salinity tolerance, IFT, and wettability alteration phenomena of betaine-type zwitterionic surfactants on carbonate rocks. These surfactants demonstrated stable and efficient EOR performance, shifting carbonate surfaces toward water-wet conditions with varying effects based on headgroups. Furthermore, the overall recovery efficiency reached 31.3–44.1% of the original oil in place.30 Simultaneously, the addition of the amide functional group derived from either aliphatic or aromatic amines—to the framework of zwitterionic surfactants—demonstrates various advantages compared to those lacking the amide group. These include low CMC, good biodegradability, eco-friendliness, reduced toxicity, and low cost.31,32

Inspired by these unique properties of zwitterionic surfactants, six novel zwitterionic amphiphiles—three diethylaminopropylamine-based and three pyridinium-based, namely, lauryl polyethoxy amido-carboxylate (LPAC), lauryl polyethoxy amido-hydroxy sulfonate (LPAH), lauryl polyoethoxy amido-sulfonate (LPAS), lauryl polyoxyethylene pyridinium carboxylate (LPPC), lauryl polyoxyethylene pyridinium hydroxy sulfonate (LPPH), and lauryl polyoxyethylene pyridinium sulfonate (LPPS)—were successfully prepared and characterized using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. The influence of aliphatic and aromatic amines as well as various headgroups on the physiochemical properties (thermal and surface) and water solubility was comprehensively investigated. The salt tolerance test was carried out by dissolving them in distilled water, seawater, and formation water and then keeping them at a temperature of 90 °C for 21 days. Moreover, the thermal stability and surface properties were also studied with the help of TGA and a Kruss tensiometer.

2. Experimental Section

2.1. Materials

Glycolic acid ether (Mn ∼ 690), 4-amino pyridine (98%), 3-(diethylamino)-propylamine (98%), sodium chloroacetate (C2H2ClO2Na) (97%), propane sultone (97%), chloro-hydroxypropane-sulfonic acid salt (96%), magnesium sulfate, calcium chloride, sodium sulfate, sodium chloride, and sodium bicarbonate were purchased from Aldrich and Panreac. Anhydrous solvents, NMR solvents, and additional organic solvents were obtained from commercial vendors (e.g., Aldrich) and used without further purification.

2.2. Structural Characterization

NMR and Fourier transform infrared (FT-IR) spectroscopies were used to characterize the chemical structure of newly synthesized zwitterionic surfactants. 1H NMR and 13C NMR spectra were recorded using a 500 MHz Jeol 1500 spectrometer. Chemical shifts (δ) were reported by using tetramethylsilane as the internal standard for both 1H and 13C NMR. The PerkinElmer instrument (16F model) was used for the FT-IR analysis, and values were recorded in cm–1.

2.3. Solubility Studies

Zwitterionic surfactants (LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS) were each solubilized at a concentration of 0.25 wt % in distilled water, seawater, and formation water, and their solubility was monitored over time. The proportion of each salt in seawater and formation water is given in Table 1.

Table 1. Composition of Electrolytes in SW and FW.

ions SW (g L–1) FW (g L–1)
Na+ 18.3 59.5
Ca+ 0.7 19.1
Mg+ 2.1 2.5
SO4+ 4.3 0.4
Cl– 32.2 132.1
HCO3– 0.1 0.4
total 57.7 214
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2.4. Surface Tension

Wilhelmy plate method was used to test the surface tensions of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS using a force tensiometer. The measurements were carried out at 25 °C. To acquire accurate results, the Wilhelmy plate was washed with distilled water and dried by using a blue flame before each cycle. Moreover, the surface tension of distilled water was recorded for comparison.

2.5. TGA Analysis

An SDT Q600 instrument was used to measure the thermal properties, with a consistent heating rate of 10 °C/min. The analysis was carried out within the heating range of 30–1000 °C under a constant nitrogen flow of 40 mL/min.

2.6. Synthesis

2.6.1. Synthetic Protocol of the Amido-Amine Intermediate (3, Method A)

Intermediate 3 was prepared by reacting glycolic acid ether (25 g, 36.2 mmol) with (3-(diethylamino)-1-propylamine) (7.4 g, 72.5 mmol) in the presence of a catalytic amount of sodium fluoride (0.152 g 3.6 mmol) at 165 °C for 12 h (Scheme 1). Aluminum oxide (Al2O3) was used to remove excess water formed during the reaction. After reflexing at 165 °C for 12 h, the reaction mixture was cooled to room temperature, dissolved in 50 mL of acetone, filtered, and dried by a rotary evaporator, which afforded the corresponding intermediate 3.

Scheme 1. Synthesis of Quaternary Ammonium (Propylamine) and Quaternary Pyridinium-Based Zwitterionic Surfactants (LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS).

Scheme 1

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2.6.2. Intermediate (3)

Pale-yellow oil (yield 98%). 1H NMR (500 MHz, CDCl3) δ: 7.59 (s, NH), 3.95 (s, CH2), 3.69–3.54 (m, (OCH2CH2)n), 3.48–3.28 (m, CH2), 2.59–2.29 (m, CH2), 1.72–1.60 (m, CH2), 1.59–1.51 (m, (CH2)n), 1.35–1.16 (m, CH2), 0.99 (t, J = 7.0 Hz, CH3), 0.85 (t, J = 6.4 Hz, CH3). 13C NMR (125 MHz) δ: 169.6, 71.4, 70.7, 70.4, 70.2, 69.9, 51.0, 46.7, 38.0, 31.8, 29.5, 29.4, 29.2, 26.3, 26.0, 22.6, 14.0, 11.4.

2.6.3. General Procedure for the Synthesis of the Pyridinium-Amide Intermediate (3′, Method B)

Glycolic acid ether (25 g, 36.2 mmol), 4-amino pyridine (6.8 g, 72.46 mmol), and 25 mL of toluene were added to a 250 mL three-necked flask under argon atmosphere. The reaction mixture was stirred at 110 °C for 18 h. A Dean–Stark apparatus was used to remove excess water formed during the reaction. The excess toluene was evaporated with a rotary evaporator. The viscous material was then dissolved in cold acetone, filtered, and dried under high vacuum, which afforded the corresponding intermediate (3′).

2.6.4. Intermediate (3′)

Pale-yellow gel (yield 95%). 1H NMR (500 MHz, methanol-d4) δ: 8.57 (s, NH), 8.09–8.05 (m, ArCH), 6.80–6.78 (m, CH2), 3.99–3.65 (m, CH2), 3.62–3.56 (m, (OCH2CH2)n), 3.46–3.44 (m, CH2), 1.54–1.50 (m, CH2),1.32–1.28 (m, (CH2)n), 0.89 (t, J = 6.3 Hz, CH3). 13C NMR (125 MHz) δ: 176.7, 169.0, 159.1, 142.0, 108.8, 71.0, 70.4, 70.21, 70.1, 70,0, 69.8, 69.8, 31.7, 29.5, 29.4, 29.4, 29.1, 22.4, 13.2.

2.6.5. Synthesis of (LPAC/LPPC)

Sodium chloroacetate (0.92 g, 7.75 mmol) and intermediate 3 or 3′ (6.4 mmol) were dissolved in ethanol/water (37.5:7.5 mL) and refluxed at 85 °C for 12 h. After 12 h, the reaction was cooled to room temperature, filtered, extracted with ethyl acetate (3 × 25 mL), and dried over magnesium sulfate. The viscous crude product was then passed through a short column on silica gel (ethanol, 100%) to give the desired product (LPAC/LPPC).

2.6.6. LPAC

Colorless viscous material (yield 96%). 1H NMR (500 MHz, CDCl3) δ: 7.62 (s, NH), 3.88–4.01 (m, CH2), 3.53–3.74 (m, (OCH2CH2)n), 3.47–3.37 (m, CH2), 3.35–3.29 (m, CH2), 2.68–2.71 (m, CH2), 1.84–1.72 (m, CH2), 1.51–1.54 (m, CH2), 1.22–1.30 (m, (CH2)n), 1.10 (t, J = 7.2 Hz, CH3), 0.84 (t, J = 6.7 Hz, CH3).13C NMR (125 MHz) δ: 170.0, 164.8, 71.4, 70.7, 70.4, 69.9, 61.5, 58.8, 55.7, 53.5, 50.0, 46.2, 44.5, 37.2, 35.7, 31.8, 29.5, 25.9, 25.3, 22.6, 14.0, 10.1. FT-IR υ (cm–1): 3382, 2927, 2854, 1639, 1461, 1353, 1257, 1107, 1044, 948.

2.6.7. LPPC

Colorless gel (yield 95%). 1H NMR (500 MHz, methanol-d4) δ: 8.45 (s, NH), 7.98 (d, J = 6 Hz, ArCH), 6.78(d, J = 6 Hz, ArCH), 3.85–3.84 (m, CH2), 3.60–3.55 (m, (OCH2CH2)n), 3.50–3.39 (CH2), 1.50–1.48 (m, CH2), 1.24–1.21 (m, (CH2)n), 0.82 (t, J = 6.0 Hz, CH3). 13C NMR (125 MHz) δ: 177.6, 174.4, 169.8, 162.1, 141.1, 110.3, 72.6, 71.5, 71.4, 71.3, 70.8, 70.7, 33.3, 31.1, 31.0, 30.8, 30.7, 24.0, 14.7. FT-IR υ (cm–1): 3463, 3213, 2947, 2869, 1650, 1535, 1377, 1157, 1029, 833.

2.6.8. Synthesis of (LPAH/LPPH)

Chloro-hydroxy-propanesulfonic acid salt (1.5 g 7.75 mmol), intermediate 3 or 3′ (6.4 mmol), and sodium carbonate (1.86 g, 15.94 mmol) were added to ethanol/water (36:12 mL) and heated to 85 °C for 12 h. After 12 h, the reaction was cooled to room temperature, filtered, extracted with ethyl acetate (3 × 25 mL), and dried over magnesium sulfate. The excess solvent was removed by a rotary evaporator and the crude mixture was passed through a short pad of silica that acquired the desired product (LPAH/LPPH).

2.6.9. LPAH

Colorless gel (yield 94%). 1H NMR (500 MHz, CDCl3) δ: 7.58 (s, NH), 4.26–3.84 (m, CH2), 3.70–3.54 (m, (OCH2CH2)n), 3.46–3.38 (m, CH2), 3.38–3.28 (m, CH2), 2.48 (p, J = 6.9 Hz, CH2), 1.70–1.61 (m, CH2), 1.59–1.49 (m, CH2), 1.36–1.21 (m, (CH2)n), 0.99 (t, J = 7.2 Hz, CH3), 0.85 (t, J = 6.6 Hz, CH3). 13C NMR (125 MHz) δ: 169.6, 71.4, 70.8, 70.3, 69.9, 68.3, 65.0, 62.8, 54.5, 53.7, 51.0, 46.7, 38.0, 31.8, 29.4, 29.4, 29.2, 26.3, 26.0, 22.6, 14.0, 11.4. FT-IR υ (cm–1): 3394, 2923, 2858, 1658, 1531, 1357, 1253, 1191, 1095, 948.

2.6.10. LPPH

Colorless viscous material (yield 92%). 1H NMR (500 MHz, methanol-d4) δ: 8.4 (s, NH),7.97–7.90 (m, ArCH), 6.79–6.75 (m, ArCH), 3.85–3.79 (m, CH2), 3.78–3.57 (m, OCH2CH2)n, 3.54–3.35 (CH2), 1.49–1.45 (m, −CH2), 1.16–1.12 (m, (−CH2)n), 0.78 (t, J = 6 Hz, CH3). 13C NMR (125 MHz) δ: 177.8, 161.1, 157.1, 149.8, 145.2, 110.5, 72.6, 71.3, 71.1, 70.7, 70.6, 68.6, 63.1, 33.3, 31.0, 31.0, 30.8, 23.9, 14.7. FT-IR υ (cm–1): 3425, 3294, 2927, 2862, 1627, 1596, 1461, 1373, 1107, 948.

2.6.11. Synthesis of (LPAS/LPPS)

In a dried three-necked flask charged with a magnetic bar, intermediate 3 or 3′ (6.4 mmol) and propane sultone (1.19 g, 9.75 mmol) were added in the presence of ethyl acetate (50 mL), and the mixture was heated at 80 °C for 12 h. After cooling to room temperature, the excess ethyl acetate was removed, and the crude product was passed through a short column to give the desired surfactant (LPAS/LPPS).

2.6.12. LPAS

Colorless sticky material (yield 93%). 1H NMR (500 MHz, CDCl3) δ: 7.78 (s, NH), 3.95–3.97 (m, CH2), 3.69–3.51 (m, (OCH2CH2)n), 3.45–3.36 (m, CH2), 3.31–3.20 (m, CH2), 2.96–2.84 (m, CH2), 2.67–2.56 (m, CH2), 2.16–1.92 (m, CH2), 1.66–1.41 (m, CH2), 1.41–1.15 (m, (CH2)n), 0.84 (t, J = 6.7 Hz). 13C NMR (125 MHz) δ: 170.8, 71.4, 70.8, 70.4, 69.9, 68.6, 61.5, 53.5, 49.5, 46.6, 43.9, 35.8, 31.8, 29.5, 29.3, 26.0, 24.1, 23.5, 22.6, 14.0, 8.4. FT-IR υ (cm–1): 3409, 2920, 2854, 1662, 1539, 1454, 1253, 1107, 1041, 956.

2.6.13. LPPS

Colorless gel (yield 91%). 1H NMR (500 MHz, methanol-d4) δ: 7.76 (d, J = 6.5 Hz ArCH), 6.58–6.56 (m, ArCH), 3.90–3.89 (CH2), 3.37–3.34 (m, (OCH2CH2)n), 3.03–3.30 (m, CH2), 2.60–2.58 (m, CH2), 1.73–1.69 (m, CH2), 1.27–1.26 (m, CH2), 1.03–1.00 (m, (CH2)n), 0.60 (t, J = 6.5 Hz). 13C NMR (125 MHz) δ: 173.0, 172.5, 162.2, 141.1, 110.4, 73.9, 72.6, 72.1, 71.8, 71.4, 71.0, 69.4, 64.9, 62.4, 62.1, 33.3, 31.0, 30.8, 30.7, 27.5, 24.0, 14.7. FT-IR υ (cm–1): 3429, 3236, 2927, 2858, 1747, 1650, 1461, 1353, 1103, 948.

3. Results and Discussion

Six zwitterionic amphiphiles—three quaternary ammonium (propylamine)-based (LPAC, LPAH, LPAS) and three quaternary pyridinium-based (LPPC, LPPH, LPPS)—were successfully synthesized. This was accomplished by reacting glycolic acid ether with 4-amino pyridine (6.8 g, 72.46 mmol) or (3-(diethylamino)-1-propylamine) and 10 mol % of sodium fluoride (NaF) at 165 °C for 12 h. The intermediate (3 or 3′) was then reacted with different headgroups—propanesulfone (1.19 g, 9.75 mmol), sodium chloroacetate (0.92 g, 7.75 mmol), and chlorohydroxypropanesulfonic acid salt (1.5 g 7.75 mmol)—to acquire LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS (Scheme 1).

3.1. Structural Identification

LPAC was used as a representative example to confirm its chemical structure among the newly prepared zwitterionic amphiphiles. In the 1H NMR spectra of LPPC (Figure 1), two characteristic triplet signals at δ 0.84 and δ 1.10 ppm correspond to the terminal CH3 group in both the hydrophilic headgroup and saturated nonpolar tail. A multiplet peak at δ 1.22–1.30 ppm represents the CH2 moieties in the long lipophilic tail of the surfactant. The CH2 groups of ethoxy units give rise to multiplet peaks at δ 3.53–3.74 ppm, while a multiplet peak at δ 3.88–4.01 is a signature of the CH2 groups next to the carbonyl functional group. Furthermore, a downfield singlet at δ 7.61 ppm is likely retributed to the amide proton [−C=O–NH−].

Figure 1.

Figure 1

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1H NMR of the LPAC zwitterionic surfactant.

The 13C NMR spectra of LPAC (Figure 2) reveal peaks at δ 10.2 and δ 14.1 ppm, representing the terminal CH3 group of the lipophilic tail and quaternary nitrogen [(CH3)2CH2–N−]. Moreover, the peaks appearing in the range of δ 22.7–35.7 ppm correspond to the methylene CH2 units in the lipophilic tail of LPAC. The methylene CH2 groups [(CH3)2CH2–N−] of the quaternary ammonium headgroup could be correlated to the signal at δ 55.7 ppm, while the CH2 moieties [−CH2–N–(CH2CH3)2–CH2−] connected with the ammonium headgroup give rise to the signals at δ 61.5 and δ 58.8 ppm. An overlapped peak at δ 69.9–71.4 ppm may correspond to methylene CH2 groups of the ethoxy unit (−CH2–CH2–O–CH2–CH2–O−) in the tail. The two downfield signals at δ 164.8 and 170.0 ppm could refer to carboxylate carbonyl [−CH2C=O−] and amide carbonyl [−CH2C=O–NH−], respectively.

Figure 2.

Figure 2

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13C NMR of the LPAC zwitterionic surfactant.

In FT-IR spectra of LPAC (Figure 3), a broad band at 3382 cm–1 is associated with the amide NH stretch (RC=O–NH), while the symmetric and asymmetric vibrations of the C–H bond of a long saturated chain of LPAC appear at 2927 and 2854 cm–1. The sharp bands at 1639 cm–1 are an indication of the presence of the C=O stretching vibration. The C–H stretching and bending vibrations of ether (C–O–C) give rise to peaks at 1096 and 1353 cm–1.

Figure 3.

Figure 3

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FT-IR of the LPAC zwitterionic surfactant.

3.2. Solubility Studies

The surfactant solubility in injection water (seawater) and formation brine (FW), as well as their stability at reservoir temperature, are prerequisites for their oilfield applications. In our previous work, it was observed that surfactants with long tails (nonpolar) tend to exhibit poor solubility in both seawater and formation water.33 However, the introduction of ethoxy units in the surfactant skeleton can increase its water solubility through hydrogen bonds between the hydrogen atoms of water molecules and oxygens of ethoxy units.28 Surfactant solutions were prepared in distilled water, seawater, and formation water and then were kept in an oven at 90 °C for 1 week. Table 1 presents the electrolyte composition in seawater and formation water. All newly prepared surfactants (LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS) exhibited excellent solubility in all types of water, and no insoluble materials were observed. Regardless of the nature of amines (aliphatic or aromatic), the solutions of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS remained clear for 1 week at 90 °C, without phase separation and precipitation (Figures 4, 5, and 6).

Figure 4.

Figure 4

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Camera images taken after 7 days at 90 °C demonstrate clear surfactant solutions in deionized water.

Figure 5.

Figure 5

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Camera images taken after 7 days at 90 °C demonstrate clear surfactant solutions in seawater.

Figure 6.

Figure 6

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Camera images taken after 7 days at 90 °C demonstrate clear surfactant solutions in formation water.

3.3. Thermal Stability

The thermal stability of surfactants under reservoir conditions is an important consideration for their potential oilfield applications: Thermally unstable amphiphiles are not suitable candidates. In this study, we used TGA measurements to examine the heat tolerance of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS. The results show that all six surfactants displayed stability ranges up to 300 °C. The initial weight loss of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS was 9, 11, 6, 6, 8, and 7% respectively. This loss is attributed to the evaporation of solvent, residual water, and other impurities. The sharp weight loss was observed at 282, 292, 296, 291, 302, and 333 °C for LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS, respectively (Figure 7). The thermal degradation temperature behavior of all of the surfactants is quite similar. However, there is a slight difference in the thermal stabilities of those that are synthesized from aliphatic amines (LPAC, LPAH, and LPAS) compared with aromatic amine-containing surfactants (LPPC, LPPH, and LPPS). The amphiphiles having aromatic amine structural units are more thermally stable than those with an aliphatic amine in their core structure. This greater thermal stability is likely due to the resonance stabilization and structural rigidity. In aromatic compounds, the pi electrons are delocalized over the cyclic structure, allowing for more efficient energy dispersion and absorption, which help to avert thermal degradation. In contrast, aliphatic amines lack this resonance structure, making them more prone to bond cleavage under heat. Additionally, the rigid structure of the aromatic amine further stabilizes the surfactants, unlike the flexible nature of aliphatic amines.34 Overall, these features account for the higher thermal stability of surfactants containing an aromatic amine.

Figure 7.

Figure 7

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TGA results for LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS.

3.4. Interface Properties

The influence of aliphatic and aromatic amines, as well as various headgroups, on the surface properties of the zwitterionic amphiphile remedies was analyzed at a temperature of 25 °C. Figure 8 displays the surface tension results for the newly prepared zwitterionic amphiphiles, along with other surface properties given in Table 2. The surface tension of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS exhibited almost similar behavior at different concentrations. The surface tension is not significantly affected by the addition of an extra surfactant beyond the CMC. Moreover, the surface tension was used for determining the additional properties, such as CMC, surface tension at CMC (γcmc), maximum surface access (Γmax), and minimum area per molecule (Amin).

Figure 8.

Figure 8

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Surface tensions of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS at various concentrations.

Table 2. Surface Properties of LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS at 25 °C.

surfactant temp (°C) CMC (mmol L–1) γcmc mN m–1 Γmax (mol mm–2) × 10–12 Amin (nm2)
LPAC 25 0.0711 32.384 2.67 0.619
LPAS 25 0.1017 33.288 2.81 0.589
LPAH 25 0.1075 34.545 3.06 0.541
LPPC 25 0.1298 31.169 4.75 0.349
LPPS 25 0.1327 31.306 4.09 0.505
LPPH 25 0.2601 34.440 3.12 0.531
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The following equations were used to calculate the surface data21

3.4. 1
3.4. 2

The slope below the CMC is illustrated by dγ/d ln C, where R denotes the gas constant, C is the surfactant concentration, T is the temperature, NA is Avogadro’s number, and n is 1 for the zwitterionic surfactant. The data in Table 2 deliver the effect of aliphatic/aromatic amines and different headgroups on the surface properties. The critical micelle concentration is determined by the interaction of surfactant molecules in the bulk phase. In general, surfactant adsorption at the interface can reflect the critical micelle concentration. Any modification in the chemical structure of surfactants may lead to a reduction of the surface tension and CMC. Surfactants having aliphatic amine in their core structure displayed a low CMC compared to the CMC of the corresponding surfactants having aromatic amines. Moreover, the surfactant’s headgroup also affects the surface properties. Surfactants with polar headgroups can display a lower CMC due to strong interactions between the polar headgroups and water molecules. These interactions, primarily hydrogen bonding and electrostatic interactions, enhance the surfactant’s hydrophilicity and stability at the interface. For example, LPAC that has a carboxylate headgroup reveals lower CMC values compared to those with sulfonate and hydroxy sulfonate groups because the carboxylate group effectively reduces surface tension through strong interactions with water. This high affinity for water helps stabilize the surfactant molecules at the interface, allowing them to aggregate and form micelles more easily.35 The maximum CMC (0.26 mmol L–1) was observed for the surfactant having a hydroxy sulfonate headgroup (LPPH). While higher hydrophilicity generally enhances stability at the interface, in the case of LPPH, the hydroxy sulfonate group may introduce steric hindrance or disrupt the optimal packing arrangement. This effect could elevate its CMC compared to LPPS. On the other hand, the surfactants with the carboxylate headgroup (LPAC) showed the lowest CMC. In addition, the surfactants having the hydroxy sulfonate headgroup (LPAH) displayed the highest γcmc, while the carboxylate headgroup (LPPC) showed the lowest γcmc value. Amphiphiles having an aliphatic amine in their core structure showed similar (close to each other) CMC and γcmc values compared to those with an aromatic amine. Changing the headgroups of amphiphiles induces variations in the value of minimum surface area per molecule (Amin). As a whole, the newly prepared zwitterionic amphiphiles demonstrated excellent surface properties that make them ideal candidates for real oilfield applications.

4. Conclusions

In conclusion, six novel zwitterionic amphiphiles were prepared, and their structures were determined by FT-IR, 1H NMR, and 13C NMR spectroscopies. The influence of aliphatic and aromatic amines on the physiochemical properties of zwitterionic amphiphiles particularly surface and thermal properties was studied. The data demonstrate that the type of the amine (aliphatic or aromatic) has a small effect on the surface and thermal characteristics of the prepared surfactants. All six surfactants (LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS) exhibited excellent solubility along with salinity tolerance in DW, SW, and FW water. The solutions also displayed no cloudiness, phase separation, or precipitation for up to 7 days at 90 °C. It was observed that the CMC of the zwitterionic amphiphiles having aliphatic amine in their structure was lower compared to surfactants with the aromatic amine. Furthermore, the nature of the headgroup of the surfactant also affects the CMC value. For example, amphiphiles with a carboxylate headgroup (LPPC) showed the lowest CMC. TGA analysis revealed that the prepared zwitterionic surfactants decomposed at elevated temperatures than the real oilfield temperature. The decomposition temperatures for LPAC, LPAH, LPAS, LPPC, LPPH, and LPPS are 282, 296, 292, 291, 302, and 333 °C, respectively. The surfactants containing the aromatic amine (rigid structure) were revealed to be more thermally stable than those having the aliphatic amine. Based on their excellent solubility (salt tolerance), remarkable thermal stability, and surface properties, we estimated that these surfactants have high potential for real oilfield applications. Further studies on different applications, including clay swelling and scale inhibition, are ongoing in our laboratories.

Acknowledgments

The authors are grateful to the College of Petroleum Engineering and Geosciences at King Fahd University of Petroleum and Minerals for providing the support through Project Number CIPR2350.

The authors declare no competing financial interest.

References

  1. Kumar A.; Mandal A. Synthesis and Physiochemical Characterization of Zwitterionic Surfactant for Application in Enhanced Oil Recovery. J. Mol. Liq. 2017, 243, 61–71. 10.1016/j.molliq.2017.08.032. [DOI] [Google Scholar]
  2. Nabipour M.; Ayatollahi S.; Keshavarz P. Application of Different Novel and Newly Designed Commercial Ionic Liquids and Surfactants for More Oil Recovery from an Iranian Oil Field. J. Mol. Liq. 2017, 230, 579–588. 10.1016/j.molliq.2017.01.062. [DOI] [Google Scholar]
  3. Shaban S. M.; Aiad I.; Fetouh H. A.; Maher A. Amidoamine Double Tailed Cationic Surfactant Based on Dimethylaminopropylamine: Synthesis, Characterization and Evaluation as Biocide. J. Mol. Liq. 2015, 212, 699–707. 10.1016/j.molliq.2015.10.024. [DOI] [Google Scholar]
  4. Babu K.; Pal N.; Bera A.; Saxena V. K.; Mandal A. Studies on Interfacial Tension and Contact Angle of Synthesized Surfactant and Polymeric from Castor Oil for Enhanced Oil Recovery. Appl. Surf. Sci. 2015, 353, 1126–1136. 10.1016/j.apsusc.2015.06.196. [DOI] [Google Scholar]
  5. Kamal M. S.; Hussain S. M. S.; Fogang L. T. A Zwitterionic Surfactant Bearing Unsaturated Tail for Enhanced Oil Recovery in High-Temperature High-Salinity Reservoirs. J. Surfactants Deterg. 2018, 21 (1), 165–174. 10.1002/jsde.12024. [DOI] [Google Scholar]
  6. Mandal A.; Ojha K.. Enhanced Oil Recovery; CRC Press: Boca Raton, 2023. [Google Scholar]
  7. Abbas A. H.; Sulaiman W. R. W.; Jaafar M. Z.; Gbadamosi A. O.; Ebrahimi S. S.; Elrufai A. Numerical Study for Continuous Surfactant Flooding Considering Adsorption in Heterogeneous Reservoir. J. King Saud Univ., Eng. Sci. 2020, 32 (1), 91–99. 10.1016/j.jksues.2018.06.001. [DOI] [Google Scholar]
  8. Howe A. M.; Clarke A.; Mitchell J.; Staniland J.; Hawkes L.; Whalan C. Visualising Surfactant Enhanced Oil Recovery. Colloids Surf., A 2015, 480, 449–461. 10.1016/j.colsurfa.2014.08.032. [DOI] [Google Scholar]
  9. Pal N.; Saxena N.; Mandal A. Studies on the Physicochemical Properties of Synthesized Tailor-Made Gemini Surfactants for Application in Enhanced Oil Recovery. J. Mol. Liq. 2018, 258, 211–224. 10.1016/j.molliq.2018.03.037. [DOI] [Google Scholar]
  10. Pal N.; Saxena N.; Laxmi K. V. D.; Mandal A. Interfacial Behaviour, Wettability Alteration and Emulsification Characteristics of a Novel Surfactant: Implications for Enhanced Oil Recovery. Chem. Eng. Sci. 2018, 187, 200–212. 10.1016/j.ces.2018.04.062. [DOI] [Google Scholar]
  11. Saxena N.; Pal N.; Dey S.; Mandal A. Characterizations of Surfactant Synthesized from Palm Oil and Its Application in Enhanced Oil Recovery. J. Taiwan Inst Chem. Eng. 2017, 81, 343–355. 10.1016/j.jtice.2017.09.014. [DOI] [Google Scholar]
  12. Afolabi F.; Mahmood S. M.; Yekeen N.; Akbari S.; Sharifigaliuk H. Polymeric Surfactants for Enhanced Oil Recovery: A Review of Recent Progress. J. Pet Sci. Eng. 2022, 208, 109358 10.1016/j.petrol.2021.109358. [DOI] [Google Scholar]
  13. Wu G.; Yuan C.; Ji X.; Wang H.; Sun S.; Hu S. Effects of Head Type on the Stability of Gemini Surfactant Foam by Molecular Dynamics Simulation. Chem. Phys. Lett. 2017, 682, 122–127. 10.1016/j.cplett.2017.06.017. [DOI] [Google Scholar]
  14. Ma K.; Cui L.; Dong Y.; Wang T.; Da C.; Hirasaki G. J.; Biswal S. L. Adsorption of Cationic and Anionic Surfactants on Natural and Synthetic Carbonate Materials. J. Colloid Interface Sci. 2013, 408 (1), 164–172. 10.1016/j.jcis.2013.07.006. [DOI] [PubMed] [Google Scholar]
  15. Kwok W.; Hayes R. E.; Nasr-El-Din H. A. Modelling Dynamic Adsorption of an Anionic Surfactant on Berea Sandstone with Radial Flow. Chem. Eng. Sci. 1995, 50 (5), 769–783. 10.1016/0009-2509(94)00450-6. [DOI] [Google Scholar]
  16. Hussain S. M. S.; Kamal M. S. Effect of Large Spacer on Surface Activity, Thermal, and Rheological Properties of Novel Amido-Amine Cationic Gemini Surfactants. J. Mol. Liq. 2017, 242, 1131–1137. 10.1016/j.molliq.2017.07.128. [DOI] [Google Scholar]
  17. Dong S. J.; Li Y. L.; Song Y. B.; Zhi L. F. Synthesis, Characterization and Performance of Unsaturated Long-Chain Carboxybetaine and Hydroxy Sulfobetaine. J. Surfactants Deterg. 2013, 16 (4), 523–529. 10.1007/s11743-013-1441-9. [DOI] [Google Scholar]
  18. Hussain S. M. S.; Mahboob A.; Kamal M. S. Synthesis and Evaluation of Zwitterionic Surfactants Bearing Benzene Ring in the Hydrophobic Tail. Materials 2020, 13 (8), 1858 10.3390/MA13081858. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Hussain S. M. S.; Kamal M. S.; Fogang L. T. Synthesis and Physicochemical Investigation of Betaine Type Polyoxyethylene Zwitterionic Surfactants Containing Different Ionic Headgroups. J. Mol. Struct. 2019, 1178, 83–88. 10.1016/j.molstruc.2018.09.094. [DOI] [Google Scholar]
  20. Kumar A.; Mandal A. Characterization of Rock-Fluid and Fluid-Fluid Interactions in Presence of a Family of Synthesized Zwitterionic Surfactants for Application in Enhanced Oil Recovery. Colloids Surf., A 2018, 549, 1–12. 10.1016/j.colsurfa.2018.04.001. [DOI] [Google Scholar]
  21. Hussain S. M. S.; Kamal M. S.; Fogang L. T. Effect of Internal Olefin on the Properties of Betaine-Type Zwitterionic Surfactants for Enhanced Oil Recovery. J. Mol. Liq. 2018, 266, 43–50. 10.1016/j.molliq.2018.06.031. [DOI] [Google Scholar]
  22. Chen S.; Liu H.; Sun H.; Yan X.; Wang G.; Zhou Y.; Zhang J. Synthesis and Physiochemical Performance Evaluation of Novel Sulphobetaine Zwitterionic Surfactants from Lignin for Enhanced Oil Recovery. J. Mol. Liq. 2018, 249, 73–82. 10.1016/j.molliq.2017.11.021. [DOI] [Google Scholar]
  23. Da C.; Alzobaidi S.; Jian G.; Zhang L.; Biswal S. L.; Hirasaki G. J.; Johnston K. P. Carbon Dioxide/Water Foams Stabilized with a Zwitterionic Surfactant at Temperatures up to 150 °C in High Salinity Brine. J. Pet Sci. Eng. 2018, 166, 880–890. 10.1016/j.petrol.2018.03.071. [DOI] [Google Scholar]
  24. Deng X.; Alotaibi M. B.; Fahmi M.; Patil S.; Mahmoud M.; Kamal M. S.; Hussain S. M. S. Locally Synthesized Zwitterionic Surfactants as EOR Chemicals in Sandstone and Carbonate. ACS Omega 2024, 9, 43081–43092. 10.1021/acsomega.4c06804. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Wang Y.; Zhang Y.; Liu X.; Wang J.; Wei L.; Feng Y. Effect of a Hydrophilic Head Group on Krafft Temperature, Surface Activities and Rheological Behaviors of Erucyl Amidobetaines. J. Surfactants Deterg. 2014, 17 (2), 295–301. 10.1007/s11743-013-1496-7. [DOI] [Google Scholar]
  26. Hussain S. M. S.; Animashaun M. A.; Kamal M. S.; Ullah N.; Hussein I. A.; Sultan A. S. Synthesis, Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail. J. Surfactants Deterg. 2016, 19 (2), 413–420. 10.1007/s11743-016-1788-9. [DOI] [Google Scholar]
  27. Barry B. W.; Wilson R. C. M. C. Counterion Binding and Thermodynamics of Ethoxylated Anionic and Cationic Surfactants. Colloid Polym. Sci. 1978, 256 (3), 251–260. [Google Scholar]
  28. Negin C.; Ali S.; Xie Q. Most Common Surfactants Employed in Chemical Enhanced Oil Recovery. Petroleum 2017, 3 (2), 197–211. 10.1016/j.petlm.2016.11.007. [DOI] [Google Scholar]
  29. Lim J. C.; Kang E. K.; Lee H.; Lee B. M. Synthesis and Interfacial Properties of Ethoxylated Cationic Surfactants Derived from N-Dodecyl Glycidyl Ether. J. Ind. Eng. Chem. 2015, 22, 75–82. 10.1016/j.jiec.2014.06.027. [DOI] [Google Scholar]
  30. Gbadamosi A.; Alotaibi M.; Kalam S.; Patil S.; Abu-Khamsin S. A.; Hussain S. M. S.; Kamal M. S.; Fahmi M. Static Adsorption of Novel Synthesized Zwitterionic Surfactants on Carbonates. Energy Fuels 2024, 38 (11), 9458–9466. 10.1021/acs.energyfuels.4c01015. [DOI] [Google Scholar]
  31. Taleb K.; Mohamed-Benkada M.; Benhamed N.; Saidi-Besbes S.; Grohens Y.; Derdour A. Benzene Ring Containing Cationic Gemini Surfactants: Synthesis, Surface Properties and Antibacterial Activity. J. Mol. Liq. 2017, 241, 81–90. 10.1016/j.molliq.2017.06.008. [DOI] [Google Scholar]
  32. Ezzat A. O.; Al-Lohedan H. A.; Atta A. M. New Amphiphilic Pyridinium Ionic Liquids for Demulsification of Water Arabic Heavy Crude Oil Emulsions. ACS Omega 2021, 6, 113407 10.1021/acsomega.1c00188. [DOI] [PMC free article] [PubMed] [Google Scholar] [Retracted]
  33. Hussain S. M. S.; Kamal M. S.; Solling T.; Murtaza M.; Fogang L. T. Surface and Thermal Properties of Synthesized Cationic Poly(Ethylene Oxide) Gemini Surfactants: The Role of the Spacer. RSC Adv. 2019, 9 (52), 30154–30163. 10.1039/C9RA06577F. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Hernandez C.; Dreisch S.; Horn J.; Neuenfeld S. Thermal Stability of Amine Compounds and Dichloromethane. Chem. Eng. Trans. 2016, 48, 763–768. 10.3303/CET1648128. [DOI] [Google Scholar]
  35. Mozrzymas A. On the Head Group Effect on Critical Micelle Concentration of Cationic Surfactants Using Molecular Connectivity Indices and Atomic Partial Charges. J. Solution Chem. 2019, 48 (6), 875–890. 10.1007/s10953-019-00887-x. [DOI] [PMC free article] [PubMed] [Google Scholar]

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