Molecular-Level insights into kinetic and agglomeration inhibition mechanisms of structure I and II gas hydrate formation

Understanding the inhibition mechanisms of gas hydrate inhibitors is vital for maintaining flow assurance in oil and gas pipelines. Hydrate nucleation, growth, and aggregation typically occur at the gas-liquid interface, making the study of these interfacial phenomena critical for designing effective inhibitors. Previous studies have predominantly focused on vinyl-based polymers, limiting insights into how variations in polymer molecular structures influence inhibition mechanisms. To address this knowledge gap, this study investigates etidronic acid-terminated waterborne polyurethane (EA-WPU), a dual-function kinetic and anti-agglomerant hydrate inhibitor. The unique inhibition mechanisms of EA-WPU against structure I and structure II hydrates were unveiled through molecular dynamics simulations. The polymer's hydrophilic carboxyl and phosphate groups destabilize the local structure of water molecules, inducing disorder at the hydrate-water interface and retarding crystal growth. Simultaneously, its hydrophobic chains adsorb onto hydrate surfaces, altering their wettability from hydrophilic to lipophilic. This transition significantly increases water droplet contact angles, effectively mitigating hydrate particle aggregation. By resisting incorporation into hydrate cages and modifying mass transfer at gas-liquid interfaces, EA-WPU extends induction periods and decreases critical nucleus sizes. Its dual functionality reduces dosing requirements and environmental impact, aligning with green chemistry principles. The polymer's molecular flexibility and robust hydrogen bonding interactions allow for rapid structural adaptation, ensuring effective inhibition. These findings emphasize that the interplay between materials and interfaces and gas hydrate formation is foundational for understanding hydrate nucleation and growth. This understanding is crucial for designing multifunctional materials that can effectively control gas hydrate plugging, ultimately enhancing the safety and efficiency of energy transportation in the oil and gas industry.