Hydrophobized particles can accelerate nucleation of clathrate hydrates

Abstract

This paper reports the effects of glass particles coated by N,N-dimethyl-N-octadecyl-3-aminopropyl trimethoxysilyl chloride (DMOAP) and octadecyltrichlorosilane (OTS) on the nucleation of tetrahydrofuran (THF), cyclopentane (CP), tetra-n-butyl ammonium bromide (TBAB) and methane (CH4) hydrates under static conditions with no agitation. Induction-time data were collected and statistically processed in the form of probability (P) distribution of samples undergoing no formation of clathrate hydrates as a function of time. Nucleation rate was calculated by fitting the P values to an equation based on the classical nucleation theory. It was found that within 12h, the nucleation rates of all four hydrates were significantly increased by introducing OTS-coated (hydrophobic) surfaces. In contrast, DMOAP-coated (partly hydrophobic) glass surfaces and clean (hydrophilic) glass surfaces had no effect on the formation of CP and CH4 hydrates but showed relatively weak promotion effect on the formation of THF and TBAB hydrates. It was also found that the position where OTS-coated particles were loaded was of paramount importance for the nucleation of the hydrates with water-immiscible CP and CH4, and the appropriate loading position was at the guest/water interface. These results suggest that foreign particles when properly hydrophobized and loaded can accelerate clathrate hydrate nucleation.