The Influence of SO 2 and NO 2 Impurities on CO 2 Gas Hydrate Formation and Stability

The sequestration of industrially emitted CO 2 in gas hydrate reservoirs has been recently discussed as an option to reduce atmospheric greenhouse gas. This CO 2 contains, despite much effort to clean it, traces of impurities such as SO 2 and NO 2 . Here, we present results of a pilot study on CO 2 hydrates contaminated with 1 % SO 2 or 1 % NO 2 and show the impact on hydrate formation and stability. Microscopic observations show similar hydrate formation rates, but an increase in hydrate stability in the presence of SO 2 . Laser Raman spectroscopy indicates a strong enrichment of SO 2 in the liquid and hydrate phase and its incorporation in both large and small cages of the hydrate lattice. NO 2 is not verifiable by laser Raman spectroscopy, only the presence of nitrate ions could be confirmed. Differential scanning calorimetry analyses show that hydrate stability and dissociation enthalpy of mixed CO 2 –SO 2 hydrates increase, but that only negligible changes arise in the presence of NO 2 impurities. X‐ray diffraction data reveal the formation of sI hydrate in all experiments. The conversion rates of ice+gas to hydrate increase in the presence of SO 2 , but decrease in the presence of NO 2 . After hydrate dissociation, SO 2 and NO 2 dissolved in water and form strong acids.