Synthesis of Amphiphilic Mesoporous Silica Nanoparticles to Stabilize Pickering Emulsions for Enhanced Oil Recovery

Pickering emulsions stabilized by nanoparticles offer significant potential for enhanced oil recovery (EOR). Nanoparticle morphology critically governs emulsion stability. This study successfully synthesized novel amphiphilic mesoporous silica nanoparticles (MSNs) modified with alkyl chains (propyl, hexyl, octyl; denoted MSNs-Cn, n = 3, 6, 8) via a two-step method and systematically investigated their structure-performance relationship in stabilizing Pickering emulsions for EOR. The morphology and surface properties of MSNs and MSNs-Cn were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), zeta potential analysis, water contact angle measurements, and interfacial tensiometry. The emulsification capacity was evaluated through optical microscopy, static multiple light scattering (Turbiscan), and rotational rheometry, and it was found that MSNs modified with optimal hexyl chain grafting (MSNs-0.2C6) exhibited superior interfacial activity. Atomic force microscopy (AFM) and N₂ adsorption-desorption isotherms confirmed that enhanced surface roughness and a larger specific surface area (728.9 m²/g) significantly contributed to the emulsifying performance by promoting nanoparticle adsorption energy and capillary interactions at the oil-water interface. Core flooding experiments demonstrated that the MSNs-0.2C6-stabilized emulsion exhibited excellent EOR performance, with an increase in oil recovery of up to 19.6%. This study revealed the correlation and mechanism between the porous morphological characteristics of mesoporous silica nanoparticles and their interfacial activity, established a relevant theoretical model, and thereby promoted the development of nanoparticles in the field of EOR.