Study on the Mechanism of Preventing Hydrate Adhesion Based on Oleic Acid Imidazoline

This study systematically investigates the inhibitory effect and underlying mechanism of an adsorption film-type corrosion inhibitor, oleic acid imidazoline, on the adhesion force between natural gas hydrates and pipeline walls, employing an integrated approach of experimental measurement and molecular dynamics (MD) simulation. High-pressure visual micromanipulation experiments were conducted using a specialized apparatus to directly measure the adhesion force under simulated pipeline conditions (1 °C, 4.69 MPa). The results demonstrate that oleic acid imidazoline significantly reduces the hydrate-wall adhesion force in a concentration-dependent manner. Specifically, at concentrations of 0.1 wt%, 0.5 wt%, and 1.0 wt%, the glass fiber deformation decreased to 1.420 mm, 1.251 mm, and 1.001 mm, respectively. These values correspond to substantial reductions of 39.57%, 46.77%, and 57.40% compared to the control group without the inhibitor. To elucidate the mechanism at the molecular level, MD simulations were performed on three systems: hydrate-iron plate, oleic acid imidazoline-iron plate, and hydrate-oleic acid imidazoline. The simulations revealed that the hydrophilic imidazoline ring of the inhibitor forms strong adsorption onto the iron surface via nitrogen atoms, with a high van der Waals interaction energy reaching 36,044 kJ/mol. This prompts the hydrophobic chains to extend outward, forming a dense film. This film effectively acts as a barrier, preventing direct contact between hydrates and the metal surface. Furthermore, the interaction energy between the hydrophobic chains of oleic acid imidazoline and the hydrate structure was found to be relatively weak, stabilizing at approximately 1,237 kJ/mol, which further contributes to the reduction in adhesion force. The research confirms that adsorption film-type corrosion inhibitors like oleic acid imidazoline offer a dual functionality—corrosion inhibition and hydrate adhesion suppression—providing a novel and promising strategy for developing multi-functional inhibitors to mitigate hydrate blockages in natural gas pipelines.