Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

Abstract

As the foundation of energy industry moves towards gas, flow assurance technology preventing pipelines from hydrate blockages becomes increasingly significant. However, the principle of hydrate inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic hydrate inhibitors (KHIs), and investigated hydrate inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in hydrate inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of hydrate formation for natural gas exploitation and the utilization of hydrates as next-generation gas capture media.

Kinetic study of amino acids inhibition potential of Glycine and l -leucine on the ethane hydrate formation

“…Secondly, the amino acids of Glycine and L -leucine, which are termed hydrophobic, have hydrophilic character due to their carboxylic acid and amine groups. Hence, they can form the stronger hydrogen bonds with water molecules than hydrogen bonds between water molecules; so they cause the perturbation in hydrate crystal lattice (Figure 2) [27]. The inhibition potential of amino acids depend the side chain long of alkyl and their hydrophobicity extent.…”

“…Amino acids are as a new group of kinetic inhibitors during hydrate formation which their physical and chemical properties are strongly dependent on the particular side chain [27]. Among of thermodynamic and kinetic inhibitors, the amino acids have the various advantages such as the easy recovery capability in pipelines due to stability and compatibility with environment.…”

“…The molecular structure of amino acids is composed of a hydrophilic and a hydrophobic head. The molecular structure and physical properties of Glycine and L -leucine were presented in Table (1) [10,27,28]. The mechanism of amino acids in inhibiting of hydrate formation is described as Figure (2); there are two sensible features of hydrophobic amino acids that contribute them to be known as kinetic hydrate inhibitor.…”

Natural gas hydrate formation and inhibition in gas/crude oil/aqueous systems

“…Several new techniques are under development in order to replace or improve conventional methods (methanol injection, temperature increase) for hydrates -plugging prevention. Several chemical and biologic kinetic inhibitors have been developed and investigated as alternative solutions to these traditional thermodynamic inhibitors [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Some compounds naturally found in sea water and reservoir fluids also act as inhibitors [25,26].…”

Optimization of inhibition conditions of tetrahydrofuran hydrate formation via the fractional factorial design methodology

“…They can be used as an analog to study the gas hydrates without the requirement of high pressures (Dirdal et al, 2012;Varaminian, 2013, 2014;Naeiji et al, 2014). L-leucine is a natural hydrophobic amino acid that has been previously studied as KHIs (kinetics hydrate inhibitors) for CO 2 hydrate inhibition (Sa et al, 2013). It is environmentally friendly KHIs with enhanced biodegradability.…”