Inhibition of crystal growth in methane hydrate

Abstract

Computer modelling has been used to investigate the viability of using a non-toxic, water-soluble polymer, polyvinylpyrrolidone (PVP), to inhibit gas hydrate formation. Monte Carlo calculations have been used to study the adsorption of monomer, dimer, tetramer and octamer PVP units on different {001} surfaces of a type I hydrate; various polymer tacticities have also been considered. Adsorption has been found to occur predominantly through the formation of two hydrogen bonds between the pyrrolidone oxygen and the water surface, and thus the location of adsorption sites depended on the availability of pendant hydrogens on the hydrate surface. PVP chains were generally found to lie flat on the surface, although there was some evidence of loops forming for the octamer. The results indicate that inhibition via adsorption of PVP at hydrate growth sites is viable, but that the main factors influencing the adsorption are inherently statistical.