Development of Anionic Surfactant from Neem Seed Oil for Enhanced Oil Recovery (ROE) Applications

Abstract

The demand for sustainable and eco-friendly alternatives in the oil and gas industry has intensified interest in bio-based surfactants for enhanced oil recovery (EOR). This study investigates the synthesis and characterization of an anionic surfactant derived from Azadirachta indica (neem) seed oil, offering a biodegradable and cost-effective substitute for conventional synthetic surfactants used in sandstone reservoirs. Neem seeds were cleaned, air-dried, milled, and subjected to solvent extraction using Soxhlet apparatus with n-hexane. The extracted oil underwent proximate and physicochemical analyses to assess its surfactant-producing potential. Proximate analysis revealed a moisture content of 28.76%, oil content of 14.44%, protein content of 16.67%, and ash content of 5.10%. Physicochemical parameters such as acid value (1.88 mg KOH/g), saponification value (184.80 mg KOH/g), oil yield (23.00%), viscosity (32.45 mPa·s), and surface tension (31.55 mN/m) supported its suitability for surfactant production. An anionic surfactant was synthesized via saponification followed by sulfonation with concentrated sulfuric acid under controlled temperature and agitation. The pale-yellow final product exhibited foam formation, indicating surface activity. The results of FTIR analysis confirmed the chemical transformation, with characteristic peaks at 3290 cm⁻¹ (O–H), 1640 cm⁻¹ (C=C), and 1104 cm⁻¹ (S=O), validating the presence of alcohol, alkene, and sulfonate functional groups essential for amphiphilic behavior. SEM analysis of the synthesized surfactant at varying magnifications (500x, 1000x, and 1500x) revealed granular and vesicle-like structures. These micelle-forming features are indicative of self-assembly, crucial for interfacial tension reduction, emulsion stability, and wettability alteration in EOR applications. The results demonstrate that neem seed oil is a promising renewable feedstock for the production of effective anionic surfactants. Its favorable chemical profile, successful structural modification, and supportive morphology confirm its potential in green chemical applications such as EOR, detergents, and emulsifiers. Future work should include performance testing under simulated reservoir conditions to validate field applicability and scale-up potential, especially in regions rich in neem resources.