Experimental study on in situ dissociation kinetics of CO₂ hydrate in pure water and water/sediments systems

Abstract

Recently, hydrate technology as a newly emerging field has been attracting more and more attention. To support its potential applications, the dissociation behaviors and kinetics of CO 2 hydrate in pure water and water/sediments systems at specified temperatures were studied experimentally by depressurization method. This work reveals two novel aspects of CO 2 hydrate dissociation. Firstly, it is remarkable that the dissociation rate of CO 2 hydrate in water/sediments is faster than that of CO 2 hydrate in pure water, which has not been conscious previously. Secondly, a pseudo first-order kinetic equation including the kinetic constant and activation energy was formulated to describe the dissociation process. Temperature plays an important role and the dissociation rate constant (k d ) and activation energy ( E a ) were obtained through the dissociation experiments at different temperatures. For CO 2 hydrate in pure water, the dissociation rate constant increased from 0.02 to 0.13 mol/(dm 2 MPamin) at the temperature from 273.86 to 276.11 K, and the activation energy was 469.06 kJ mol −1 . For CO 2 hydrate in water/sediments, the dissociation rate constant was from 0.03 to 0.15 mol/(dm 2 MPamin) at the temperature ranging from 273.45 to 276.11 K, and the activation energy was 346.30 kJ mol −1 .