Macroscopic kinetics of hydrate formation of mixed hydrates of hydrogen/tetrahydrofuran for hydrogen storage

Abstract

Hydrogen/Tetrahydrofuran mixed hydrate formation studies were conducted in a stirred tank reactor. Hydrate formation kinetics at driving forces of 2 MPa, 5 MPa and 7 MPa were studied. Tetrahydrofuran (THF) concentration was varied between 1 mol% and 5 mol% and its effect on hydrate formation kinetics was investigated. With an increase in the driving force there was an increase in gas uptake till super saturation. However, the increased driving force had little effect on the reduction of induction time even at high promoter (THF) concentration. 5 mol% THF solutions behave distinctly exhibiting an increased hydrate growth compared to low promoter concentrations due to the occurrence of multiple nucleation events (observed based on temperature spikes and gas uptake). Rate of hydrate formation increased with an increase in driving force for a given concentration of THF promoter. Water conversion to hydrates in the range of 2.8–10.8% was achieved for all the experiments. Addition of Sodium Dodecyl Sulphate (SDS) surfactant had no effect in improving the kinetics of mixed hydrogen/THF hydrates. This study highlights the kinetic challenges that need to be overcome in storing hydrogen as clathrate hydrates.