Molecular insights into the effects of mass transfer ability of anti-agglomerant monolayers with different densities on the growth and wetting behavior of methane hydrate

Abstract

Anti-agglomerants (AAs) have been recognized as an effective method for gas hydrate risk management in oil and gas pipelines. However, a limitation of AAs is their poor inhibitory effect on hydrate growth and aggregation in gas–water systems. In addition, the density of the AAs monolayer is considered one of the main factors affecting the growth and aggregation of hydrate particles, but the mechanism of this effects remains unclear. Herein, molecular dynamics (MD) simulations were employed to investigate the effects of anti-agglomerant (cocamidopropyl dimethylamine) monolayers with different densities on hydrate growth and the wetting behavior of hydrate surface. The results revealed that AA monolayers primarily suppress hydrate growth and reduce the wetted area by modulating mass transfer processes of gas and water molecules. The high-density monolayer can effectively hinder the flattening and diffusion of droplet on the hydrate surface due to its ability to maintain the aggregation state of water molecules and reduce the contact area between droplet and hydrates. The high-density AA monolayers simultaneously enhance the bonding strength between the monolayer and the hydrate, as well as the intermolecular interactions between AA molecules. The Coulomb interaction and h-bonds make the main contributions to the binding strength. Therefore, enhancing the adsorption density of AAs on the hydrate surface and the binding strength between AA molecules in the gas–water system should serve as a strategic approach in designing efficient AAs. These molecular insights on the anti-agglomeration mechanism are beneficial to guide the screening and design of efficient AAs molecules.