EXPERIMENTAL SOLID STATE NMR OF GAS HYDRATES: PROBLEMS AND SOLUTIONS

Abstract

Solid State NMR spectroscopy has taken a very prominent place among the many spectroscopic techniques employed for the characterization of clathrate hydrates. Exceptionally high sensitivity of the spectra to the molecular environment and dynamic processes, together with the ability to provide accurate and quantitative data make NMR spectroscopy a highly desirable and versatile approach for studying hydrates. Application of the method to its full capacity, however, requires some extensive instrumental developments to adapt it to the specific experimental requirements of hydrate studies, for example, very low temperatures and high pressures. In this presentation we will give an overview of recent Solid State NMR advances in various areas of hydrate research. Examples will include analysis of the composition and structure of mixed gas hydrates prepared from multi-component mixtures of hydrocarbons, characterization of the natural gas hydrates from different sources, and evaluation of formation conditions and properties of mixed hydrogen hydrates. 13 C NMR with Magic Angle Spinning (MAS) at -100C has been the main approach in the first two examples. We will discuss the requirements and the necessary instrumental developments to make the experiments of this type successful. The detailed characterization of mixed hydrogen hydrates required low temperature 1 H MAS. Problems of quantification in these experiments will be discussed. We expect that all these recent experimental developments will prompt wider application of Solid State NMR in hydrate research.