Comparison of CO ₂ and N ₂O hydrate formation kinetics in organo-mineral suspension

The phenomenon of gas hydrate is a feasible reduction strategy for greenhouse gases (GHGs) such as CO ₂, N ₂O, and CH ₄. In this study, CO ₂ and N ₂O hydrate formation kinetics in organo-mineral suspensions (starch-kaolinite) were investigated by comparing the hydrate induction times under hydrate forming conditions (273.4 K and 30 bar). In spite of their similar physico-chemical (molecular weight and Van der Waals diameter), hydrate induction times of CO ₂ and N ₂O were remarkably different. The average induction time of N ₂O hydrate was approximately 200 min but formation of CO ₂ hydrate was not observed to form during the experimental run. Ab inito molecular dynamics simulation was conducted to explain the different hydrate formation mechanisms. The molecular system did not consider the initial positions of starch, water and N ₂O (or CO ₂) molecules with respect to mineral surfaces (1×10×10 kaolinite unit cell) for the simulations. Significant differences in structural (radial distribution functions and coordination numbers) and energy (binding and potential energies) characteristics of the adsorption of starch molecules on the tetrahedral and octahedral surfaces of kaolinite were observed to describe the different formation mechanisms of organo-mineral complex (starch-kaolinite) with respect to CO ₂ and N ₂O. The identification of this complex is significant as a potential key precursor in forming a larger fragment of hydrate-like structure.