Dissociation kinetics of propane–methane and butane–methane hydrates below the melting point of ice

Abstract

Understanding the dissociation mechanism of gas hydrates below the melting point of ice is crucial for expanding the practical applications of solid hydrates in gas storage. The kinetic processes for gas hydrates have not been clarified, except for those of pure CH₄ hydrate and CO₂ hydrates. In this study, using in situ X-ray diffraction analysis, the low-temperature onset of the dissociation of C₃H₈ and C₄H₁₀ hydrate fine particles encapsulating CH₄ as a secondary guest was investigated during temperature ramping. At ∼200 K, the C₃H₈ + CH₄ hydrate, n-C₄H₁₀ + CH₄ hydrate, and iso-C₄H₁₀ + CH₄ hydrate all dissociated in a single step, similar to pure C₃H₈ and pure iso-C₄H₁₀ hydrate. The dissociation of C₃H₈ hydrate was also found to accelerate the dissociation of CH₄ hydrate. Based on the experimental results, it was confirmed that the C₃H₈ and C₄H₁₀ molecules released from the dissociating hydrates accelerated hydrate dissociation.