Enthalpy of Dissociation of Simple and Mixed Carbon Dioxide Clathrate Hydrate

Abstract

The enthalpy of dissociation is an important property of clathrate hydrates. Through it is possible to obtain some conclusions about the microscopic structure formed. It can be obtained by direct methods of measurement or estimated by indirect methods. However, the inherent difficulties of direct methods influence the accuracy of this methodology. Given this, the direct or indirect methods show similar results. In this study, the enthalpy of dissociation of hydrates of carbon dioxide was determined for hydrates formed by simple systems CO2/H2O, CO2/H2O/Sodium Dodecyl Sulfate (SDS) and mixed hydrates CO2/H2O/Tethrahydrofuran (THF) through the indirect method using Equation Clausius Clapeyron. The method was applied to new data equilibrium between the phases H-Lw-V (Hydrate-Liquid rich in CO2 and water Vapor of water) generated in this study and a set of literature data. The values obtained for the systems with SDS proved similar to those obtained without additive systems, since the results for systems with THF were almost double compared to systems CO2/H2O, confirming the change in the type of hydrate structure sI (46 water molecules per unit cell) to a structure of sII (136 water molecules per unit cell). The results were compared and shown in agreement with values reported in the literature for both the direct method, and to the indirect method.