Characterisation of the ( 111 ) growth planes of a type I 1 gas hydrate and study of the mechanism of kinetic inhibition by poly ( vinylp yrrolidone )

This work has developed techniques for studying the mechanism by which a hydrate growth inhibitor, i.e. poly(vinylpyrro1idone) (PVP), acts. The topology of a series of (111) faces of the type I1 clathrate hydrate, the postulated growth plane, have been studied in detail and used to calculate hydrogen-bond energy surfaces. N-Ethylpyrrolidone (NEP), the monomeric unit, has been used to sample adsorption on one of the ( 11 1) surfaces. The adsorption sites were found to be located around the large partial cavities, at positions determined by the location of the pendant hydrogens. There is an added van der Waals attraction between the NEP and the hydrate surface which is optimal when the pyrrolidone occupies the partial large (16-hedra) cavities on the hydrate surface.