Effect of sodium montmorillonite clay on the kinetics of CH4 hydrate-implication for energy recovery

Silty-clayey host sediments have been widely identified in naturally-occurring hydrate-bearing sediments in the South China Sea. However, the effect of clay minerals on the kinetics of CH4 hydrate (MH) formation and dissociation remains unknown and warrants further investigation. The objective of this paper is to elucidate the effect of montmorillonite (MMT) clay particles on the formation and dissociation kinetics of MH. A series of experiments involving kinetics and morphological observations were designed to investigate the kinetics of MH in MMT suspensions with mass fractions ranging from 0.1 wt% to 9.0 wt%. The experimental results reveal that MMT promotes nucleation but delays the growth kinetics of MH. The diffuse double layer (DDL) on clay minerals is quantified to explain the observed kinetic behavior. The electric field induced on the clay surface resulted in a shorter induction time. The morphology observed indicated that MH initially forms at the gas-liquid interface and develops upward along the reactor surface, resulting in the hydrate-clay stratification behavior. The upward migration of water due to hydrate growth promotes the agglomeration of MMT clay and reduces the conversion of free water to hydrate. The findings of this study are essential in understanding the mechanisms of the naturally occurring negatively-charged clay particles on the kinetics of MH. Moreover, the results have implications for the occurrence of MH in clay-rich sediments in nature and the development of energy-efficient recovery strategies from silty-clayey hydrate-bearing sediments.

Automated summary

This study investigates the effects of montmorillonite clay particles on the formation and dissociation kinetics of methane hydrate (MH). The experimental results reveal that clay particles promote nucleation but delay the growth kinetics of MH. The findings provide insight into the mechanisms of clay particles on the kinetics of MH and have implications for energy recovery from clay-rich hydrate-bearing sediments.