Experimental and theoretical study on dissociation thermodynamics and kinetics of hydrogen-propane hydrate

Hydrate-based hydrogen storage is a promising technology in the clean energy field. In this study, propane was selected as the accelerator guest molecule for hydrogen storage in hydrates. Hydrogen-propane (0.67/0.33, mole ratio) hydrate dissociation properties are investigated by experiment and molecular dynamics simulation. The hydrogen-propane hydrate phase equilibrium is measured by different methods and the average dissociation heat is 77.03 J/g under 0.98-1.72 MPa. While hydrate dissociation heat flow curves show the characteristic of two-step dissociation, which is further confirmed via Raman spectroscopy. Simultaneously, hydrogen-propane hydrate dissociation driven by depressurization and heating are also investigated by Raman spectroscopy. During dissociation, the Raman peak area of hydrogen in hydrate continues to decrease, whereas it is relatively stable for propane before the hydrate dissociation complete. In addition, hydrogen-propane hydrate reformation occurs more intensely during the heating process, especially when the temperature exceeds 273 K than with depressurization. This indicates that depressurization is more feasible for continuous hydrogen releasing, a concept of recycling hydrate clathrate structure was proposed to shorten hydrate formation time and accelerates hydrogen storage rate. In addition, the molecular dynamics simulation results confirmed that the hydrogen release rate from hydrate is higher than that of propane from the microscopic view point. The results of this study provide a potential pathway of hydrogen storage using hydrates.

Automated summary

This study investigates the dissociation properties of hydrogen-propane hydrates through experiments and simulations, revealing the characteristics of the dissociation process and the impact of different dissociation driving mechanisms on hydrogen release. The results indicate that the release rate of hydrogen from hydrates is higher than that of propane, and propose the concept of recycling hydrate clathrate structure to accelerate hydrogen storage rate.