A family of novel bio-based zwitterionic surfactants derived from oleic acid

Abstract

Bio-based zwitterionic surfactants have attracted increasing attention due to their renewable resources and excellent surface properties. A family of bio-based zwitterionic surfactants derived from oleic acid was prepared using a facile and high-yield route. All these bio-based zwitterionic surfactants exhibited outstanding surface properties.

---

The current feedstock of the surfactant's hydrophobic part mainly include two categories: (i) fossil resources with priority to petroleum; and (ii) renewable biomass resources. Petroleum products have been used as the main source of surfactant's hydrophobic group, which account for nearly two thirds of the organic carbon embodied in the final surfactants.¹ Since fossil resources are finite and biomass is renewable, the share of traditional petroleum-based surfactants, the resource of which are totally from petroleum chemicals, in surfactant production is gradually declining. Biomass is seen as one of the best alternatives to replace fossil resources.^2–7 Bio-based surfactants as a kind of promising material are different from traditional petroleum-based surfactants and biosurfactants.⁸ Although biosurfactants are absolutely renewable and their surface properties are outstanding, they have not been applied widely due to their low production and high costs.⁹ The main resource of bio-based surfactants is from abundant biomass like vegetable oils,^10,11 proteins,^12,13 and carbohydrates.¹⁴

Many researchers have devoted themselves to the study of bio-based surfactants derived from long-chain unsaturated fatty acid, such as oleic acid, linoleic acid, and erucic acid. The chemical synthesis of ultra long chain zwitterionic surfactants and the surface activities of their solutions have been documented.^{10,11,15–17} These surfactants exhibit lower critical micelle concentrations and lower surface tension, which are attributed to their molecular structures.^17–21

Zwitterionic surfactants, which are electrically neutral compounds have small effective headgroup area due to the proximity of their positive and negative charges.¹⁷ Bio-based zwitterionic surfactants have attracted more attention due to their excellent surface and interfacial properties, low irritation, good detergency, rich foaminess and fine stability;^15,16 while some improvement is still needed to produce zwitterionic surfactants. Previously reported reaction conditions are harsh, requiring high temperatures (>160 °C)^22,23 and expensive catalysts,²⁴ resulting in higher production costs. Looking for low-cost and high-yield routes for the production of renewable materials-derived zwitterionic surfactants with outstanding surface/interfacial properties has become a major focus of research interest.

In the present work, a family of bio-based zwitterionic surfactants showing outstanding surface and interfacial properties was obtained through facile and high-yield chemical modification and transformation of oleic acid molecules (Scheme 1). To the best of our knowledge, none of the surfactant molecules described here have been previously reported.

Scheme 1 Synthetic route of N-phenyloctadecanoicamidopropyl-N,N-dimethylcarboxylbetaine (POAPMB).

To obtain compound POAPMB, the chemical modification of the instable double bond in oleic acid molecules was first carried out through a Friedel–Crafts alkylation reaction using benzene as an alkylation reagent and AlCl₃ as a catalyst. The generated phenyl octadecanoic acid (POA) underwent acyl chlorination by sulfoxide chloride and was then amidated with N,N-dimethyl-1,3- propylenediamine, generating N-phenyloctadecanoicpropyl-N,N-dimethylamine (POAPMA). Eventually, POAPMA was reacted with sodium chloroacetate in methanol/water (v_methanol : v_water = 1 : 4); the product of this reaction was then desalinated in alcohol and recrystallized in ethyl acetate to obtain the final bio-based zwitterionic surfactant, viz. POAPMB, which has 58.1% bio-derived carbon in its molecule.

Following the chemical synthesis of compound POAPMB, the structural diversity of bio-based zwitterionic surfactants was also investigated using toluene and ethyl benzene as well as two other diamines (N,N-dimethylethylenediamine and N,N-diethylethylenediamine) for the modification of the double bond and the carboxyl of oleic acid, respectively (Fig. 1). All the above compounds were analyzed and characterized by EI-MS/ESI-HRMS and ¹H NMR (see ESI†). Surface tensions (SFT) were measured using a surface tensiometer by the plate method and the interfacial tensions (IFT) were measured using an interface tensiometer by the spinning drop method. The contact angle θ of the saturated surfactant solution was measured using the sessile drop technique on hydrophobic solid substrates, which has an average contact angle of 92° on the three phase contact gas/double distilled water/solid. Ultimate biodegradation (ultimate biodegra.) of the bio-based zwitterionic surfactants was determined using the EPI Suite, BIOWIN3 biodegradation model, which is frequently used to estimate the degradation of organic chemicals.²⁵ Variation of the surface tension with the concentration of the bio-based surfactants at 25 °C is shown in Fig. 2.

Fig. 1 Structural diversity of bio-based zwitterionic surfactants derived from oleic acid.

Fig. 2 Variation of the surface tensions with the concentration of the bio-based surfactants at 25 °C. The error bars represent standard deviations of the mean for triplicate measurements.

Dynamic interfacial tension between Daqing crude oil (the composition and fundamental properties of the crude oil were listed in ESI,† section “Material”) and water at the concentration of 0.5 g L⁻¹ bio-based zwitterionic surfactants in water solutions at 50 °C (the average temperature of the stratum in the Daqing oil field, China) are shown in Fig. 3.

Fig. 3 Dynamic interfacial tensions between Daqing crude oil and bio-based surfactant solutions at 50 °C.

The final yield, surface/interfacial properties (calculation method and formula are listed in ESI,† section “Surface and interfacial properties”) and ultimate biodegradation of bio-based zwitterionic surfactants are listed in Table 1. As shown in Table 1, bio-based zwitterionic surfactants were successfully prepared in high yields at relatively lower temperatures (below 75 °C) and atmospheric pressure. Compared with other methods, which require at least 160 °C,^22,23 higher temperatures could be avoided in this approach.

Table 1 Final yield, surface/interfacial properties and ultimate biodegradation of the bio-based zwitterionic surfactants

Surfactant	Final yield (%)	CMC (μmol L^−1)	SFTCMC (mN m^−1)	SFTmin (mN m^−1)	Γmax (μmol m^−2)	Amin (nm^2 per molecule)	Average θ	IFTmin (mN m^−1)	Ultimate biodeg.
4a POAPMB	85.4	5.58	28.1	27.9	7.71	0.22	47.83	0.0022	2.6417
4b TOAPMB	83.6	4.32	30.6	26.4	5.56	0.30	50.32	0.0081	2.5139
4c EOAPMB	84.2	3.31	32.7	27.8	5.29	0.31	51.40	0.0518	2.4829
4d POAEMB	88.5	4.08	28.4	25.8	7.08	0.23	46.70	0.0019	2.6727
4e POAEEB	84.3	3.13	33.6	28.9	5.38	0.31	54.04	0.0249	2.4519

---

In addition to the moderate synthetic condition, it is satisfactory that the bio-based surfactants synthesized in the present work exhibit excellent surface and interfacial properties. It is noteworthy that these surfactants (modified both at the double bond and the carboxyl group, Fig. 1 and Table 1) showed better surface and interfacial properties than those without the modification of the double bond by the addition of aromatic hydrocarbon.²¹ This observation indicates the importance of the addition of an aromatic hydrocarbon ring into the structure of bio-based zwitterionic surfactants. It is important to mention that surfactants with a benzene ring in the molecules have been commonly used in oil recovery;²⁶ thus, the bio-based zwitterionic surfactants could be considered potent alternatives in oil recovery.

Presently, the surfactants used in oil recovery are mainly petroleum sulfonates^27–29 and alkyl benzene sulfonates,^30,31 which are entirely derived from petroleum chemicals. Accompanying these surfactants, a strong alkali, which can cause well bore scaling, stratum damage and permeability decline,^32,33 is added to reduce oil-water interfacial tension to ultralow values and enhance oil recovery.^34–37 Therefore, it will be of a great significance to find a new kind of surfactant that can reduce the oil–water interfacial tension to ultralow values with the aid of a weak base or even in the absence of alkali. Bio-based zwitterionic surfactants can reduce oil–water interfacial tension to ultralow values in the absence of alkali; hence, they may have important applications in enhanced oil recovery.

Ultimate biodegradation scores for bio-based zwitterionic surfactants ranged from 2.4519 (POAEEB)–2.6727 (POAEMB), indicating that the expected total degradation time was in the order of “months” for these compounds. These results also showed that bio-based zwitterionic surfactants are biodegradable, and the degradation time is suitable for EOR, in which the stability of surfactants for several months is needed.

Conclusion

In summary, starting with oleic acid, a family of novel bio-based zwitterionic surfactants, which have excellent interfacial properties was successfully synthesized via a facile and high-yield chemical modification. More derivatives of these kinds of bio-based zwitterionic surfactants could be obtained from other unsaturated fatty acids through this facile and high-yield chemical modification. Generally, waste cooking oils and non-edible oils contain significant amounts of long chain fatty acids. Therefore, it is advantageous to consider these useless or pernicious oils to prepare bio-based zwitterionic surfactants. On the strength of the renewable resource and outstanding interfacial properties, bio-based zwitterionic surfactants will be of great interest for many surfactant application fields, such as detergents, cosmetics, etc., and more specifically, in enhanced energy recovery.

Acknowledgements

This research was supported by National Science Foundation of China (Grant no. 21203063) and the 863 Program (Grant no. 2013AA064403).

Notes and references

1. P. Foley, A. Kermanshahi pour, E. S. Beach and J. B. Zimmerman, Chem. Soc. Rev., 2012, 41, 1499–1518.
2. J. A. Melero, J. Iglesias and A. Garcia, Energy Environ. Sci., 2012, 5, 7393–7420.
3. A. Corma, S. Iborra and A. Velty, Chem. Rev., 2007, 107, 2411–2502.
4. I. Johansson and M. Svensson, Curr. Opin. Colloid Interface Sci., 2001, 6, 178–188.
5. Z. Y. Fan, M. Corbet, Y. Zhao, F. De Campo, J. M. Clacens, M. Pera-Titus, P. Métivier and L. M. Wang, Tetrahedron Lett., 2013, 54, 3595–3598.
6. M. J. Climent, A. Corma and S. Iborra, Green Chem., 2014, 16, 516–547.
7. C. S. K. Lin, L. A. Pfaltzgraff, L. Herrero-Davila, E. B. Mubofu, S. Abderrahim, J. H. Clark, A. A. Koutinas, N. Kopsahelis, K. Stamatelatou, F. Dickson, S. Thankappan, Z. Mohamed, R. Brocklesby and R. Luque, Energy Environ. Sci., 2013, 6, 426–464.
8. N. R. Biswal and S. Paria, RSC Adv., 2014, 4, 9182–9188.
9. K. Das and A. K. Mukherjee, Process Biochem., 2007, 42, 1191–1199.
10. Q. Y. Xu, Z. S. Liu, M. Nakajima, S. Ichikawa, N. Nakamura, P. Roy, H. Okadome and T. Shiina, Bioresour. Technol., 2010, 101, 3711–3717.
11. Z. L. Chu and Y. J. Feng, ACS Sustainable Chem. Eng., 2013, 1, 75–79.
12. M. Sreenu, R. R. Nayak, R. B. N. Prasad and B. Sreedhar, Colloids Surf., A, 2014, 449, 74–81.
13. M. Sreenu, B. V. S. K. Rao, R. B. N. Prasad, P. Sujitha and G. K. Chityala, Eur. J. Lipid Sci. Technol., 2014, 116, 193–206.
14. F. Rajabi and R. Luque, RSC Adv., 2014, 4, 5152–5155.
15. L. Y. Qi, Y. Fang, Z. Y. Wang, N. Ma, L. Y. Jiang and Y. Y. Wang, J. Surfactants Deterg., 2008, 11, 55–59.
16. L. P. Nong, C. L. Xiao and Z. S. Zhong, J. Surfactants Deterg., 2011, 14, 433–438.
17. R. Kumar, G. C. Kalur, L. Ziserman, D. Danino and S. R. Raghavan, Langmuir, 2007, 23, 12849–12856.
18. S. R. Raghavan and E. W. Kaler, Langmuir, 2001, 17, 300–306.
19. M. Dierker and H. J. Schäfer, Eur. J. Lipid Sci. Technol., 2010, 112, 122–136.
20. K. Huang, P. Zhang, J. W. Zhang, S. H. Li, M. Li, J. L. Xia and Y. H. Zhou, Green Chem., 2013, 15, 2466–2475.
21. D. Feng, Y. M. Zhang, Q. S. Chen, J. Y. Wang, B. Li and Y. J. Feng, J. Surfactants Deterg., 2012, 15, 657–661.
22. Z. L. Chu and Y. J. Feng, Synlett, 2009, 2655–2658.
23. A. Behr, M. Fiene, C. Buß and P. Eilbracht, Eur. J. Lipid Sci. Technol., 2000, 102, 467–471.
24. Y. R. Jiang, Z. G. Xu, J. M. Luan, P. Q. Liu, W. H. Qiao and Z. S. Li, J. Surfactants Deterg., 2007, 10, 131–136.
25. S. Song, M. Song, L. Zeng, T. Wang, R. Liu, T. Ruan and G. Jiang, Environ. Pollut., 2014, 186, 14–19.
26. Y. W. Zhu, R. H. Zhao, Z. Q. Jin, L. Zhang, L. Zhang, L. Luo and S. Zhao, Energy Fuels, 2013, 27, 4648–4653.
27. J. Yang, W. H. Qiao, Z. S. Li and L. B. Cheng, Fuel, 2005, 84, 1607–1611.
28. J. Qi, J. Luan, Q. Hou, W. Qiao and Z. Li, Energy Sources, Part A, 2011, 33, 89–99.
29. W. L. Ng, D. Rana, G. H. Neale and V. Hornof, J. Appl. Polym. Sci., 2003, 88, 860–865.
30. A. M. Al-Sabagh, M. M. Zakaa and M. R. N. El-Din, J. Dispersion Sci. Technol., 2009, 30, 1237–1246.
31. X. H. Dai, J. S. Suo, X. Duan, Z. W. Bai and L. Zhang, J. Surfactants Deterg., 2008, 11, 111–115.
32. F. Z. Chen, H. Q. Jiang, X. H. Bai and W. Zheng, J. Ind. Eng. Chem., 2013, 19, 450–457.
33. J. R. Hou, Z. C. Liu, S. F. Zhang, X. A. Yue and J. Z. Yang, J. Pet. Sci. Eng., 2005, 47, 219–235.
34. L. F. Chen, G. C. Zhang, J. J. Ge, P. Jiang, J. Y. Tang and Y. L. Liu, Colloids Surf., A, 2013, 434, 63–71.
35. M. G. Tang, G. C. Zhang, J. J. Ge, P. Jiang, Q. H. Liu, H. H. Pei and L. F. Chen, Colloids Surf., A, 2013, 421, 91–100.
36. X. T. Zhao, Y. R. Bai, Z. B. Wang, X. S. Shang, G. M. Qiu and L. F. Chen, J. Dispersion Sci. Technol., 2013, 34, 756–763.
37. Q. Liu, M. Z. Dong, X. G. Yue and J. R. Hou, Colloids Surf., A, 2006, 273, 219–228.

---

Footnote

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c4ra06851c

---