Thermodynamic inhibition of CO2 hydrate by Na-montmorillonite: implications for hydrate-based CO2 sequestration
Yunting Liu, Junjie Ren, Dnyaneshwar R. Bhawangirkar, Jianzhong Zhao, Praveen Linga, Zhenyuan Yin
Abstract
Abstract With the growing global focus on reducing greenhouse gas emissions, hydrate-based CO 2 sequestration in marine sediments has gained wide attention due to its high storage capacity and thermodynamic stability of CO 2 hydrate. However, the limited understanding of the CO 2 hydrate stability zone, particularly in the presence of abundant swelling type clays, i.e., Na-montmorillonite, warrants further investigation. This study examines the thermodynamic effects of Na-montmorillonite on the phase equilibria of CO 2 hydrate under varying water contents (30–80 wt%). The results reveal that Na-montmorillonite inhibits CO 2 hydrate formation thermodynamically with a significant inhibition effect as the water content decreases. A notable leftward shift of up to 2.7 K in the phase equilibrium temperature was observed at 3.90 MPa with 30 wt% water content. A thermodynamic model was developed integrating the diffuse double layer theory and Hu-Lee-Sum water activity correlation model into the classical Chen-Guo model. The proposed model demonstrated high accuracy with the measured data with an absolute average deviation of pressure below 0.5%. The thermodynamic inhibition effect is attributed to the decrease in water activity caused by the Na + exchange in the diffuse double layer on the clay surface. This study also presents the implication of swelling type clay on the CO 2 hydrate stability zone in a permafrost setting, highlighting its impact on the CO 2 storage site selection and CO 2 storage capacity. These findings provide valuable insights for optimizing hydrate-based CO 2 sequestration strategies, contributing to CO 2 mitigation technology.