Can n-Propanol Form Hydrate?

Abstract

Alcohols are generally considered hydrate inhibitors. The fact that 2-propanol, in addition to tert-butanol can form hydrates, suggests further investigation of this issue is required. In light of this, it was decided to assess the potential for hydrate formation by n-propanol. However, there are at present no data concerning its effects on hydrate stability available in the open literature. Here, we present freezing point data of n-propanol solutions (up to 80 mass %). These data suggest existence of a peritectic point at 263.05 K and formation of clathrate hydrate in the n-propanol−water system. To confirm whether n-propanol, like 2-propanol, forms mixed hydrates with structure I formers at elevated pressures, dissociation conditions were measured for aqueous solution of 10, 16.4, and 25 mass % n-propanol in the presence of methane at pressures up to 40 MPa and natural gas at around 10 MPa. The results show that n-propanol does not display a hydrate inhibition effect, which would be expected from an alcohol and may, in fact, take part in clathrate formation. Consequently, n-propanol has been modeled as a hydrate-forming compound by use of a thermodynamic model. Comparisons between experimental hydrate dissociation data and model predictions suggest that n-propanol may take part in structure II hydrate formation, occupying the large cavity of the hydrate structure.