Synthesis And Inhibition Performance Of Degradable Dissymmetric Bis-quaternary Ammonium Salt With Imidazoline Ring

Bis-quaternary ammonium salt with imidazoline ring is a kind of inhibitor withexcellent inhibition performance, which can effectively inhibit CO2corrosion. Due tothese excellent performance such as low toxicity, high surfactant, high water-solubleand a good bactericidal properties, bis-quaternary ammonium with imidazoline ring isa promising corrosion inhibitor. Dissymmetric bis-quaternary ammonium salt withimidazoline ring and ester, which is good for the environment, should be a highperformance and green corrosion inhibitor.In this paper a new type of dissymmetric bis-quaternary ammonium salt withimidazoline ring and ester group was designed and synthesized. The structures ofintermediates and final products were identified by IR spectra and UV spectra.Inhibition performance and inhibition mechanism for Q235steel in2％NaClsolution saturated CO2were investigated using weight loss, polarization curve,electrochemical impedance spectroscopy (EIS), surface morphology methods andquantum chemistry calculations. Bactericidal properties for sulfate-reducing bacteria(SRB) were investigated using extinction dilution method.Long-chain alkylimidazoline was synthesized by long-chain alkyl fatty acid anddiethylenetriamine, tertiaryamine intermediate with ester group was synthesized bylong-chain alkyl fatty acid and N, N-dimethyl ethanolamine and dissymmetricbis-quaternary ammonium salt with imidazoline ring and ester was synthesized bysingle quaternary ammonium salt with ester and long chain alkylimidazoline. The bestsynthesis process of tertiaryamine intermediate with ester is that the molar ratio ofN, N-dimethyl ethanolamine and long-chain alkyl fatty acid is1.5:1, the reactiontemperature is150-160°C, the reaction time is8-10h, the catalyst amount is3‰ofthe total mass of the material and the water carrier amount is about40%of the total mass. The IR spectra of synthetic intermediates and target product showed theexistence of the products.Weight loss method showed that dissymmetric bis-quaternary ammonium salt hadgood inhibition performance for Q235steel in solution at25℃,40℃,60℃and80℃.The inhibition efficiency increased with increasing the concentration of inhibitor andreached maximum near the CMC. The inhibition efficiency were more than90％in150mg/L dissymmetric bis-quaternary ammonium solution at25℃,40℃and60℃.The polarization curves revealed that the corrosion potential for Q235steel shiftedtoward to postive potential after adding150mg/L. The change of Ecorrvalue was notmore than30mV and the anodic interaction coefficient was close to the cathodicinteraction coefficient indicating the corrosion inhibitor was a kind of anodicinhibitor.The results of EIS showed that the dissymmetric bis-quaternary ammonium saltcould form a protective film on the Q235steel surface to inhibit corrosion at25℃,40℃,60℃and80℃. The film was stability at25℃. As the temperature rised, thestability of the film deteriorated.The surface morphology showed that Q235steel corroded seriously in the solution,especially at40℃and occurred local corrosion at80℃when the inhibitor was notadded. The dissymmetric bis-quaternary ammonium salt had a good protective effectfor Q235steel at the concentration of150mg/L.The bactericidal experiment showed that the dissymmetric bis-quaternaryammonium salt had a good bactericidal bactericidal rate (97%) at the concentration of150mg/L.The quantum chemistry calculation results showed that the dissymmetricbis-quaternary ammonium salt had many activated centers and a lower ELUMO, whichis a good electron acceptor and should have a good inhibition performance.