Methane hydrate formation kinetics and structure information in the presence of cyclopentane under different reaction evolution

• Forming Str.I CH 4 hydrate is the key to obtaining high gas uptake when using thermodynamic promoter. • Wall-climbing growth can tune hydrate structure, facilitating Str.I CH 4 hydrate formation. • Gas uptakes are much higher than the theoretical value of forming only Str.II hydrates in this work. To investigate the methane (CH 4 ) hydrate formation kinetics in the presence of cyclopentane (CP) under different reaction evolution scenarios, three typical methods including quiescent, stirring, and liquid pre-dispersion were adopted to obtain different initial hydrate formation states and reaction evolution scenarios in this work. Combining the analysis of morphology, final gas uptake, hydrate phase ratio, guest distribution, and main gas uptake contributor, it can be found that the strong hydrate wall-climbing growth obtained from quiescent cases can facilitate sI CH 4 hydrate formation, achieving high final gas uptake. By contrast, a weaker or no hydrate wall-climbing growth is typically observed from stirring and liquid pre-dispersion cases and only a small amount of sI CH 4 hydrate forms, resulting in low final gas uptakes. Further, stirring triggering at different reaction times and liquid pre-dispersion experiencing different ultrasonic times were used to change the strength of hydrate wall-climbing growth. And experimental results proved that strong hydrate wall-climbing growth is typically conducive to sI pure CH 4 hydrate formation, making it become the main supplier of final gas uptake in the presence of thermodynamic promoter, thereby significantly increasing the final gas uptake. Thus, any strategies that can strengthen the hydrate wall-climbing growth have a positive effect on hydrate gas uptake.