Synthesis And Properties Of A Mannich Base Quaternary Ammonium Salt Corrosion Inhibitor

During the exploiting process of oil and gas wells, acidification was usually used to enhance oil recovery (EOR). However, adding acid will cause serious corrosion of production equipments and pipelines, especially in deep wells with high temperature. The corrosion rate of tubing can be reduced greatly by adding acidification inhibitor, and the Mannich base is the most commonly used corrosion inhibitor in the field of oil corrosion inhibitor. However, inhibitors for oil field have some disadvantages such as delamination, coking and unstability at high temperature. In this paper, the novel Mannich base quaternary ammonium salts J-01and Mannich base intermediate M-01were investigated. The optimum synthesis conditions of J-01and M-01had been chosen by orthogonal experiments. The infrared spectroscopies were used to characterize the structures of synthesized M-01and J-01. In order to compare the inhibition performance of M-01and J-01inhibitors in different conditions, static weight loss method was used. Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) and SEM analysis of the corrosion morphology were also used to analyze the inhibition mechanism.In this paper, Mannich base intermediate was synthesized with formaldehyde solution, acetophenone and benzylamine by "two-step in one-pot". The intermediate of Mannich bases identified by orthogonal experiment showed that the optimum synthesis condition of M-01with the reactant ratio of formaldehyde, benzyla amine and acetophenone was1.2:1.2:1. The reaction temperature was110℃, reaction time of6hours, and the pH of4, respectively. By comparing different quaternary ammonium reagent, finalize benzyl chloride and Mannich intermediate, M-01was chosen to synthesize Mannich quaternary ammonium. The best proportion of Mannich bases and benzyl chloride was1:0.8to compound Mannich quarter identified by orthogonal, the reaction temperature was110℃and the reaction time was6hours. Infrared spectroscopy was used to characterize the synthesized product. According to the SY/T5405-1996standard, the Mannich base quaternary J-01inhibitor had good solubility, dispersion performance and storage performance.Static weight loss method was used to evaluate the influence of inhibitor concentration, medium temperature, concentration of hydrochloric acid, Fe3+concentration and I-concentration on inhibition properties of M-01and J-01inhibitors. When the concentrations of inhibitor is greater than0.5%, the inhibition efficiencies of M-01and J-01are both greater than99.5%,which can accord the standard requirements of SY/T5405-1996. Below110℃, two of the corrosion inhibition efficiencies can remain at a high level. At90℃, when the concentration of hydrochloric acid is up to30%, J-01still exhibits good corrosion inhibition efficiency to PI10steel. Adding Fe3+in HC1liquid will reduce the inhibition performance of J-01corrosion inhibitor. When the concentration of I" is400mg/L, it can significantly improve the corrosion inhibition of J-01in hydrochloric acid medium. Compared with the inhibition performance of quatermized inhibitors, J-01inhibitors exhibit better inhibition properties than M-01inhibitor. The inhibition mechanisms of M-01and J-01were discussed by polarization curves, electrochemical impedance, SEM and other means. M-01and J-01inhibitors are hybrid control inhibitors. The inhibition mechanisms are mainly due to the negative catalytic effect caused by active-site absorption and "the geometrical covering effect" in non-polar sites.