Natural gas thermodynamic hydrate inhibitors

Gas hydrate formation is a critical issue that can threaten the safe flow of the natural gas stream. The best gas hydrate mitigation strategy is the injection of inhibitors, most importantly thermodynamic hydrate inhibitors (THIs). These materials form hydrogen bonds with water molecules, reducing water activity and shifting the hydrate phase boundary to lower temperatures and higher pressures. In this study, the focus is on the utilization of conventional THIs in natural gas processing as well as the introduction of novel materials as alternatives. The properties, advantages, and disadvantages of the conventional THIs were illustrated, and their inhibition strengths were compared against pure water. The drawbacks of conventional THIs motivate scientists to focus on novel THIs, which not only prevent gas hydrate formation effectively but are also environmentally friendly and have low cost. Novel THIs are classified into ionic liquids (ILs), natural amino acids (NAAs), and sugar-derived compounds (SDCs), which benefit from environmental merits. Furthermore, alkanolamines with dual-purpose sweetening and hydrate inhibition effects were also reviewed. In all of the aforementioned cases, the complete databank of the experimental studies was reported. This study can provide a guideline for screening and use of THIs for natural gas inhibition.