(26a) Effect of Low-Dosage Aminoacids Based Kinetic Hydrate Inhibitors

Gas hydrates are metastable crystalline compounds that are formed when small gas molecules like ethane and methane gets trapped within the water molecules, at higher pressure and lower temperature conditions. These gas hydrates tend to accumulate in the offshore subsea lines and over the period tend to completely block the pipeline, halting the gas and oil supply to the onshore stations. Therefore, annually the industry spends over 100 million dollars on hydrate prevention procedures. These procedures include mainly the use of chemical thermodynamic hydrate inhibitors (THI) and Kinetic hydrate inhibitors (KHI). The THI like Mono-ethylene glycol (MEG) and Methanol are mainly used in industry. However, these THI are required in bulk quantities, which causes a major disposal issue and also post a major safety threat to nearby operators due to high flammability of Methanol. These commercial THI are also not suitable for environmental, so there is a strong research interest in finding a new class of low dosage KHI and THI inhibitors that are environmentally friendly and effective as commercial THI and KHI.

Amino acids are biological organic compounds containing amine (-NH₂) and carboxylic acid functional groups (-COOH) that have been previously reported to be an environmentally friendly corrosion inhibitors. So the feasibility of using amino acids as a potential KHI and THI have been tested using pure methane gas on a rocking cell assembly within the pressure range of 40-120 bars. The types of amino acids tested include: L-Alanine, L-Phenylalanine, Glycine, Histadine and L-Asparagine.

The experimental results obtained show that the amino acids with lower solubility provided significant KHI effect, but no THI effect. However, the amino acids with higher solubility provided both THI and KHI effect simultaneously. The amino acids with higher solubility were able to shift hydrate vapour liquid equilibrium curve (HLVE) by 0.7 ^o C at both lower (~40 bars) and higher (~100 bars) pressures. These amino acids were also able to delay methane hydrate crystal formation by up to 1 hour at both lower (~40 bars) and higher (~100 bars) pressures. However, the addition of synergents with amino acids delayed the hydrate inhibition by almost 24 hrs at lower (~40 bars) and by 6 hrs at higher (~100 bars) pressures. Thus, the selected amino acids with higher solubility were found to have a have a potential to act as a KHI and THI both simultaneously.

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