Improving THF hydrate formation in the presence of nonanoic acid

Abstract

Numerous experiments of tetrahydrofuran (THF) hydrate formation are conducted to investigate the potential of nonanoic acid, which is an organic phase change material, as a kind of novel promoters for hydrate formation. The mixture of THF + nonanoic acid + H2O was stirred using an ultra-sonication bath to prepare emulsion. Nonanoic acid forms a series of small crystal particles when the temperature of the emulsion is lowered. These small crystal particles of organic phase change material promote THF hydrate nucleation and growth. The induction time of THF hydrate formation reduces and the rate of hydrate growth increases with the increase of the mass fraction of nonanoic acid when nonanoic acid mass fraction is <3 wt%. However more additives of nonanoic acid do not further promote THF hydrate formation. The average induction time of THF hydrate formation is the smallest with 3 wt% nonanoic acid in this work. The conversion degree of THF hydrates formed with 3 wt% nonanoic acid is about 82.9% at 0.2 °C under static conditions. The experimental results also show that the nucleation of THF hydrate is a stochastic process but nonanoic acid improves the scatter of hydrate induction time. THF hydrate can form within 73 min under 0.2 °C with 3 wt% nonanoic acid in quiescent conditions. The induction time of THF hydrate formation reduces and the rate of hydrate growth increases with the decrease of experimental temperature.