Synthesis Of Thiourea Imidazoline Quaternary Ammonium Salt And Its Effect On Corrosion Of X80 Pipeline Steel In Simulated Oil-field Water

With the wide application of CO₂ gas displacement technology in the exploitation of oil and gas fields,CO₂ will lead to the aggravation of corrosion of metal pipelines and even the phenomenon of corrosion perforation in the process of exploitation and transportation of oil and gas fields,thus causing fire and explosion accidents.And cause huge economic losses and environmental pollution and other problems.Adding corrosion inhibitor to corrosion medium has become one of the important means to solve the corrosion of metal pipeline.Imidazoline corrosion inhibitors are widely used in corrosion and protection of oil and gas pipelines because of their green,high efficiency and environmental protection.In this study,Imidazoline quaternary ammonium salt and thiourea Imidazoline quaternary ammonium salt were prepared by amidation,cyclization and quaternary ammonium reaction with organic oleic acid?ester?and diethylenetriamine as raw materials.The corrosion inhibition mechanism and inhibition law of Imidazoline quaternary ammonium salt and thiourea Imidazoline quaternary ammonium salt on X80 pipeline steel were studied by simulating the produced aqueous solution of Xinjiang oilfield.The research results provide a theoretical basis for the application of thiourea Imidazoline quaternary ammonium salt corrosion inhibitor in the water environment produced by CO₂ gas flooding technology in oil field.In this study,stearic acid and diethylenetriamine were used as raw materials by decompression operation.The suitable reaction conditions for preparing Imidazoline intermediate IP-1,by amidation and cyclization are as follows:feed ratio 1:1.10,amidation reaction temperature 160?,amidation reaction pressure 8.11 kPa,amidation reaction time 3h,The yield of amidation was over 98%.The cyclization reaction temperature was 200?,the cyclization reaction pressure was 5.07 kPa,and the cyclization reaction time was 3 h.the yield of cyclization reaction was 98%.Imidazoline quaternary ammonium salt inhibitor IM-1,with high solubility was obtained by quaternization of Imidazoline intermediate IP-1 with benzyl chloride and then reacted with thiourea to prepare thiourea Imidazoline quaternary ammonium salt inhibitor IM-S1.The thermal performance analysis shows that the thiourea Imidazoline quaternary ammonium salt IM-S1 corrosion inhibitor has good thermal stability,and the weight loss rate is only 1.02%at30?-378?.The corrosion weightlessness was investigated in simulated oilfield aqueous solution.the experimental results show that IM-S1 corrosion inhibitor has remarkable corrosion inhibition effect and has a good inhibition effect on the corrosion of X80 pipeline steel.Corrosion weightlessness,potentiodynamic polarization,electrochemical impedance spectroscopy,micromorphology and micro-area electrochemical?SVET?were used.The corrosion inhibition properties of IM-S1 thiourea Imidazoline quaternary ammonium salt inhibitor on X80 pipeline steel in aqueous solution containing CO₂ at different pH values and temperatures were studied systematically.The results show that IM-S1 thiourea Imidazoline quaternary ammonium salt inhibitor can be effectively adsorbed on the surface of metal steel in neutral solution and medium and low temperature conditions?25?-40??,so as to achieve the protection of matrix metal.It has remarkable corrosion inhibition effect.The adsorption of IM-S1 inhibitor on the steel surface reduces the ion current density on the steel surface,thus effectively reducing the corrosion rate of the steel.From the point of view of adsorption thermodynamics and adsorption kinetics,the adsorption behavior of IM-S1 thiourea Imidazoline quaternary ammonium salt inhibitor on the surface of metal steel was calculated theoretically by simulating oilfield aqueous solution.The results show that the adsorption behavior of IM-S1 inhibitor on the surface of metal steel accords with Langmuir isothermal adsorption,and the adsorption free energy?G_0ads is-38.57kJ/mol,.The adsorption activation energy E_A value is 6.61 kJ/mol,and the corrosion inhibitor particles are easily adsorbed on the surface of metal steel.The corrosion inhibition efficiency is high.