(403c) Alkylammonium Formate-Based Protic Ionic Liquids for Methane Hydrate Inhibition: Offshore Flow Assurance

T. Altamash, F. Qureshi, M. Atilhan, M. Tariq and M. Khraisheh*

Department of Chemical Engineering, Qatar University

Author Emails: tausif.Altamash@qu.edu.qa|mQureshi@qu.edu.qa | mert.atilhan@gmail.com

Author for Correspondence*: m.Khraisheh@qu.edu.qa

Abstract

During the transportation of natural gas via pipeline on the sea floor where high pressure and low temperature exist a severe flow assurance problem arises due to formation of gas hydrates. Gas hydrates are solid crystalline compounds that are formed under favorable thermodynamic condition. Practically, the formation of hydrates is a constant threat to the oil and gas industry, as they have the tendency to grow larger in sizes and completely block the pipeline over the period of the time. In addition to that, they can cause major operations shutdown and an explosion leading to large economic losses and posting safety risk to nearby operators.

In order to solve hydrate formation issue some conventional thermodynamic inhibitors like Methanol and Methyl ethylene glycol (MEG) are widely used in industry. However, these inhibitors are highly flammable, toxic in nature required in bulk quantities and leakage may disturb the aquatic environment. Therefore, there is a high demand for new class of low dosage somehow greener gas hydrate inhibitors to keep away from hazards.

Ionic liquids (ILs) are asymmetric structure containing salts that are also known as designer solvents due to their ability to be tailor according to the process requirement. Some classes of ILs are also reported to be environmentally friendly and non-flammable in nature. Generally, the ILs are classified as Aprotic and Protic ILs. The protic ionic liquids are formed by proton transfer from Bronsted acid to Bronsted base. In comparison to Aprotic, the protic ILs are easier methodology and one step reaction process made this class of IL cheaper in cost. Therefore, five different simpler protic ILs have been selected as; Ethyl ammonium formate, Dimethyl ammonium formate , Dimethylethyl ammonium formate, Tributyl ammonium formate, and were tested with methane gas at different pressures and concentrations to find the effect of high dosage by PSL systemtecknik rocking cell assembly.

According to the experimental results, at lower concentration (5wt%) the selected protic ILs act as kinetic hydrate inhibitors. But at higher concentration (10wt%) the selected protic ILs exhibit both thermodynamic and kinetic inhibition effect simultaneously. The methane HVLE curve was shifted by 2.0 ± 0.1 ^oC and hydrate formation was delayed by 2 hrs at high pressure conditions (~120 bars). The kinetic inhibition performance of protic ILs was also significantly enhanced when they were doped with synergents and the hydrate was delayed upto 20 hrs at low pressure conditions (~40 bars) and 10 hrs at high pressure conditions (~120 bars). Moreover, poly ethylene oxide (PEO) were added at lower amount (1wt%) with 5 wt% of said protic ionic liquids. As expected the PEO shown enhanced kinetic effect whereas, no thermodynamic effects were observed.

Acknowledgement

This work was made possible by NPRP grant for # 6-330-2-140 (TA) and GSRA # 2-1-0603-14012 (FQ) for from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.