Synthesis and Performance Evaluation of Multialkylated Aromatic Amide Oligomeric Surfactants as Corrosion Inhibitor/Drag Reducing Agents for Natural Gas Pipeline

Drag reducing agents (DRAs) including amphiphiles and polymers can enhance energy efficiency and transmission volume in natural gas pipelines. However, the correlation between DRA molecular structure and drag reduction efficiency remains unclear. In this paper, the multialkylated aromatic amides (MAA) oligomeric surfactants with different numbers of amide group/<i>n</i>-dodecane chain (from 1 to 3) were first synthesized and characterized. Then, the potential efficiency of MAA as the corrosion inhibitors (CIs)/DRAs for natural gas pipelines was investigated by interfacial activity analysis, film-forming property test, electrochemical polarization curve measurement, and in-door loop test. The results showed that the molecular structure is the key factor influencing the performance of MAA. By increasing the number of amide group/<i>n</i>-dodecane chains, the interfacial activity of MAA improves greatly, thus outstandingly affecting the film-forming property of the MAA on the carbon steel sheet. For MAA-1, the formed film is too thin to cover the surface roughness, and then the corrosion inhibiting (78.64%)/drag reducing (0-2%) rates are the lowest. For MAA-3, the formed film is the thickest and smooth, thus imparting the largest corrosion inhibiting (93.88%)/drag reducing (10-14%) rates to MAA-3. For MAA-2, the formed film is thicker but not smooth, and the corrosion inhibiting (89.88%)/drag reducing (4-6%) rates are intermediate. We speculate that the structure of the MAA greatly influences the adsorption and self-assembly of MAA on the inner pipe wall and then generates different performances. This work is helpful for guiding the development of natural gas DRAs with high efficiency.