(425a) Effectiveness of Pyrrolidinium Based Ionic Liquids in Flow Assurance: Preventing Hydrates Formation in Offshore Sub-Sea Pipelines

The formation of hydrates within the offshore subsea pipelines is a major challenge to flow assurance in oil and gas industry. Annually, the industry spends large amount of money on thermodynamic inhibitors like methanol and methyl ethylene glycol (MEG) to prevent hydrates formation. However, large quantity (>30 wt %) of MEG and methanol is required for this process, causing disposal and corrosion issues. MEG is also very expensive and methanol is dangerous to use in offshore facilities due to its high flammability. This has shifted the interest of researchers towards the use of ionic liquids (ILs) to prevent hydrates formation in sub-sea pipelines. Thus, the aim of this work is to test the effectiveness of pyrrolidinium based ILs in preventing hydrates formation and check for exhibition of any dual inhibition behaviour by these ILs.  

We have tested three pyrrolidinium based ILs namely: 1-methyl-1-propyl pyrrolidinium chloride, 1-methyl-1-propyl pyrrolidinium triflate and 1-methyl-1-propyl pyrrolidinium dicyanamide for their effectiveness in hydrate inhibition of a synthetic quaternary gas mixture containing: methane (85%), ethane (10%), nitrogen (2.5%) and carbon dioxide (2.5 %). It is evident that the cation of tested ILs is fixed as ‘‘1-methyl-1-propylpyrrolidinium’’ and anions are changed which will help us to understand the role of anions, if any, in inhibition performance of the tested ILs. These tests were conducted using 1 and 5 wt% concentrations of each IL sample on a rocking cell assembly by PSL Systemtechnik GmBH at different pressures ranging from (40-120) bars.

According to the tests results, the pyrrolidinium based ionic liquids were able to prevent hydrates formation by providing a temperature shift of 1.8  at low pressures and by delaying hydrates formation time by almost one hour at high pressures. These results also confirm the dual inhibition behaviour of pyrrolidinium based ionic liquids, as they were able to show both thermodynamic and kinetic inhibition effects simultaneously. However, no significant effect of anion is observed. The results were also compared with standard industrial thermodynamic inhibitor methanol and the trends are discussed.