Synthesis And Performance Evaluation Of Symmetric Bisimidazoline And Its Benzyl Quaternary Ammonium Salt Corrosion Inhibitor

Corrosion is always a very prominent problem to trouble the development of oil and gas industry.Corrosion inhibitor was widely used in oil and gas field development because of its advantages of high efficiency,economy and strong adaptability.Imidazoline corrosion inhibitor has many advantages such as low toxicity,high efficiency,environmental and other features,so it is widely used as a acidification corrosion inhibitor.So the development of more efficient,environmentally friendly imidazoline corrosion inhibitor is the focus of current research.In this paper,the starting poiint is the symmetric bis-imidazolines.the purpose is to investigate the impact of a different hydrophobic chain length,increase the number of activity of' adsorption groups and solubility of' inhibitors on the corrosion inhibition efficiency and the research methods are the laboratory evaluation combined with quantum chemistry calculation.Then the symmetric bis-imidazolines and its benzyl quaternary ammonium salt corrosion inhibitor with a different hydrophobic chain length(7,9,11,13)was synthesised successfully)and its structure was evaluated with FTIR and 1H NMR.We found that the laboratory evaluation results are coincident with the quantum chemistry calculation by studying the inhibitors with the static weight-loss experimen.electrochemical test.SEM and quantum chemistry calculation.The results are as follows:(1)The symmetric bis-imidazolines and its benzyl quaternary ammonium salt Corrosion inhibitors with a different hydrophobic chain length(7,9,11,13)were successfully synthesised by Caprylic acid,Capric acid,Dodecanoic acid.Myristic acid and Tetraethylenepentamine,Benzyl chloride,Synthesis conditions are as follows:the first step reaction(symymetric dis-imidazolines):The molar ratio of fatty,acid and tetraethylenepentamine is 1:0.6.the reaction temperature is 240?,the reaction time is 8h:The second step reaction(benzyl quaternary ammonium salt):The molar ratio of symmetrical bis-imidazolines and benzyl chloride is 1:2.5,the reaction temperature is 100?.the reaction time is 4h.The solubility test shown that the solubility enhanced obviously after quaternary ammoniun reaction by adding benzyl chloride.(2)With increasing the length of the hydrophobic chain,the global activities and corrosion inhibition efficiency of symmetric bis-imidazolines and its benzyl quaternary ammonium salt corrosion inhibitors increased.The impact of hydrophobic chain length on corrosion inhibition efficiency is tiny when the hydrophobic chain length is greater than 9.The corrosion inhibition efficiency increased with the increase of the concentration in the hydrochloric acid solution of 1mol/L at 60?.The best inhibition efficiency is 98%and the inhibitors obtained the best inhibition efficiency at a concentration around 15 mg/L.The inhibition efficiency no longer increased obviously when the inhibitors concentration is greater than 15 mg/L.(3)After the quaternary ammonium reaction of symmetrical bis-imidazolines with different hydrophobic chain length by adding benzyl chloride,the global reaction activities and inhibition efficiency increased.The inhibition efficiency also increased when the concentration rose.The maximum inhibition efficiency rose and the amount of inhibitors decreased while obtained the same inhibition efficiency(adsorption efficiency enhancement).when the hydrophobic chain length is greater than 9,the symmetric bis-imidazolines and its benzyl quaterary ammonium salt does not have much difference in inhibition efficiency and the global reaction activities.(4)These symmetric bis-imidazolin.es and benzyl quaternary ammonium salt corrosion inhibitors belongs to the mixed type inhibitors.In the hydrochloric acid solution of 1mol/L,the corrosion inhibitors can form a compact and stable film on the surface of steel sheets quickly.It can block the steel sheet to contact with the corrosion medium effectively and stop the anodic dissolution and cathodic hydrogen evolution reaction.(5)The adsorption of these symmetric bis-imidazolines and its benzyl quaternary ammonium salt on the steel surface accord with Langmuir adsorption isotherm in the hydrochloric acid solution of lmol/L after fitting with the adsorption model and adsorption thermodynamic calculation.The adsorption process is spontaneous and the adsorption type is chemical adsorption by sharing or transferring the charge to form covalent bonds.