Kinetic and Thermodynamic Aspects of Clathrate Hydrate Nucleation and Growth

In this study we present results of our investigations on simple CH4-hydrate and mixed hydrates during the initial steps of the hydrate formation process. In situ Raman spectroscopy, microscopic observation and in situ X-ray diffraction were used in our systematic studies. Although these techniques give only a limited view on the molecular level the combined results from the experiments reported here indicate that the labile cluster hypothesis can describe the initial hydrate formation process. Specifically, the guest molecules dissolve in the aqueous phase before they are encaged into single hydrate cavities which agglomerate to a solid phase. Results from Raman spectroscopic measurements suggest that the initially formed solid phase can be characterized by an excess of pentagonal dodecahedrons, whereas the formation of tetrakaidecahedrons or hexakaidecahedrons occurs as a subsequent step. At the time the tetrakaidecahedrons or hexakaidecahedrons are observed with Raman spectroscopy, corresponding X-ray ...