Molecular Insights into Aggregation Kinetics of Methane Hydrate Particles and Anti-agglomerant Mechanism

Understanding the microscopic mechanisms governing methane hydrate aggregation and the inhibition effects of antiagglomerants (AAs) is essential for flow assurance in deep-water–oil and gas pipelines. Using large-scale molecular dynamics simulations, this study investigates the aggregation kinetics of methane hydrate particles in the presence of different types and interfacial densities of AAs. Three representative AAs─cocamidopropyl dimethylamine (CDA), cocamidopropyl betaine (CAB), and cocamidopropyl trimethylammonium chloride (CATC)─were simulated at 277 K and 10 MPa. The results indicate that all three AAs inhibit hydrate particle aggregation by adsorbing onto the hydrate surface, modifying surface wettability, and enhancing dispersion in the hydrocarbon phase. Among them, CDA exhibits the optimal inhibition performance of particle mobility and provides the highest surface coverage, whereas CAB and CATC show relatively weaker inhibitory performance. The antiagglomeration mechanism depends on the interparticle separation: steric hindrance from hydrophobic tails dominates at short distances, while interfacial coverage and adsorption strength govern dispersion at larger separations. Increased surface coverage improves dispersion stability in the hydrocarbon phase. At lower interfacial densities, reduced coverage weakens CDA’s ability to lower interfacial tension, thereby diminishing its inhibition of hydrate motion. Overall, the surface coverage follows the order CDA > CAB ≈ CATC. These findings clarify the molecular-level mechanisms of AA-mediated inhibition and provide a theoretical basis for the design of effective hydrate AAs.