Acceleration of CO₂ Hydrate Formation by N₂ Micronanobubbles: Insights from Experiments and Molecular Simulations

Micronanobubbles (MNBs) play a crucial role in the formation and dissociation of gas hydrates. The presence of MNBs has been shown to accelerate hydrate formation even when the composition of the bubbles differs from that of the hydrate guest species. This study was conducted to investigate the influence of N2 MNBs on CO2 hydrate formation using a combination of experimental methods and molecular simulations. The experimental results demonstrated that the presence of N2 MNBs elevated the onset temperature of CO2 hydrate formation, suggesting that the N2 MNBs acted as promoters in the process. The underlying mechanisms were explored through molecular simulations, which revealed two key factors. First, the presence of N2 MNBs led to a high local concentration of CO2 around the bubbles, which facilitated hydrate nucleation. Second, N2 cages formed transiently, with stable 512 and 51262 cages as the predominant structures, which contributed to the stabilization of hydrate precursors. This study was the first to simultaneously involve macroscopic and microscopic approaches to investigating the effects of MNBs on hydrate formation, particularly with an MNB gas type differing from the guest species involved in hydrate formation. The results provide valuable insights into the influence of MNBs on hydrate formation and their molecular behaviors during the formation process.