Effect Of Flow Velocity On Inhibition Performance Of Imidazoline Derivatives With Different Molecule Structure In CO₂Environment

The flow velocity had an important effect on the corrosion of petroleum and gas pipeline material. In this paper, flow velocity and shear stress near the specimen surface were obtained for each rotational rate through the simulation of computational fluid dynamics (CFD), and then the effect of flow velocity on corrosion rate of N80in absence of inhibitor in CO2environment was studied by dynamic weight-loss experiment. The result showed that, the increase of flow velocity would accelerate the CO2corrosion of specimen. The corrosion rate of the maximum value was23.31mm/a, when the flow velocity was5.5m/s. Morphology of corrosion products of specimens under each rotational rate were obtained by SEM, visually observed the effect of flow velocity on Corrosion of N80steel in CO2environment.Thirteen imidazoline derivatives were synthesized, including five imidazoline derivatives which had different alkyl chain length, i.e. IM-5, IM-9, IM-13, IM-17, IM-21; two imidazoline derivatives which had double bond in alkyl chain, i.e. IM-17D, IM-21D; six imidazoline derivatives which had different pendant chain, i.e. OIM, OIMO, OIME-2(i.e. IM-17D), OIME-3, OIME-4, OIME-D. By infrared spectrum analysis and organic element analysis, the synthesized products are the target compounds.Through the contact angle measurement. AFM force curve measurement, dynamic weight loss experiment and SEM analysis, the effect of alkyl chain of imidazoline derivatives on the inhibition performance was studied. It was found that, the inhibition performance of imidazoline derivatives not only related to the alkyl chain length, but also related to flow velocity. When the medium velocity was low (0.3m/s and0.6m/s). IM-17had the best inhibition performance that the inhibition efficiency reached84%and86.7%; when the medium velocity was high (5.5m/s), IM-21had the best inhibition performance that the inhibition efficiency reached91.9%; in addition, although the double bond in alkyl chain of imidazoline had no effect on the hydrophobicity, but it can enhance molecules adsorption on the metal surface, thereby enhancing its inhibition performance.In addition, the effect of pendant chain of imidazoline derivatives on inhibition performance was studied. The result showed that, the difference of pendant chain would influence the hydrophilicity. hydrophobicity and adhesion. When hydroxyl were in pendant chain of imidazoline derivative (OlMO), it can improve its hydrophilicity; while if amino ethylene (OIME-2), it would promote its hydrophobicity. At low flow velocity (0.3m/s and0.6m/s), the imidazoline which had two amino ethylene in pendant chain (OIME-3) reached equilibrium of hydrophilic and hydrophobic, and the inhibition efficiency were93.7%and94.8%under the two flow velocities; when amino ethylene was excessive, the better hydrophobicity led molecules to agglomeration, and result to the variation of inhibition efficiency; at high velocity (5.5m/s). the effect of fierce mixing made imidazoline well dispersed in solution when multiple amino ethylenes existed in pendant chain (OIME-D), and the inhibition efficiency reached96.7%.