New insights into the kinetic effects of CH3OH on methane hydrate nucleation

Methanol (CH3OH) has been recognized as an effective thermodynamic inhibitor for hydrate blockage. Recently, complimentary to its thermo effect, CH3OH is reported to exhibit complex kinetic roles on hydrate nucleation. Herein, by using the molecular dynamic (MD) simulation and based on newly proposed hydrate nucleation mechanism (ref. 32), the kinetic roles of CH3OH are investigated from perspective of compressions among CH4 hydration layers during hydrate nucleation. Specifically, hydrate nucleation is increasingly mitigated as concentrations of CH3OH increase from 1 wt% to 50 wt%. Such inhibition effects are dominantly contributed by H-bonds between –OH of CH3OH and waters, which promote integrations of CH3OH into CH4 hydration layer and result in following changes: i) inhibiting formation of key water structures that are necessary for hydrate nucleation; ii) hindering the compression probability among CH4 hydration layers. Based on these findings, hydrate inhibition efficiency of CH3OH is suggested to be regulated by changing its H-bond formation ability with waters, and the ideal models in MD simulation validate it. Overall, this study can help to better understand the kinetic roles of CH3OH on hydrate nucleation and provide guidance for the design of effective kinetic hydrate inhibitors.