| Summary: | Surfactants have been reported as the most efficient gas hydrate promoters (GHPs) for gas storage and transportation; however, slow kinetics of nucleation and growth of hydrate crystals and foam formation during hydrate dissociation severely impact their applications. Here, a new class of chemical additives based on ethylenediaminetetraacetic acid bisamides was developed to control methane hydrate formation for gas storage and flow assurance applications. Synthesized molecules contain both polar fragments (carboxyl and amide groups) and hydrophobic alkyl groups with different sizes and branching. The obtained results revealed that bisamides with short alkyl chains ( n -propyl and isopropyl) promoted the formation of methane hydrate and significantly reduced foam stability during hydrate decomposition compared to sodium dodecyl sulfate (SDS). Moreover, by increasing the length of the alkyl substituent up to propyl, the nucleation time increased. However, the conversion of gas to hydrate escalated remarkably. A transition from promotion to inhibition properties is observed with a further increase in the alkyl chain from propyl to butyl. Nevertheless, bisamides with hexyl groups showed surfactant properties, which is responsible for their poor promotion efficiency. In addition, the studied compounds practically do not form foam and are less toxic compared to SDS as a well-known GHP. The results of this study can be useful for the design and development of effective additives for gas storage and flow assurance applications.
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