Researches On Structure Of A Novel N-Benzylquinolinium Chloride Derivative (BQD) And Its Corrosion Inhibitive Performance

As the technical progress in oil and gas field development,both the concentration of acid solution and the temperature of oil wells are becoming higher in acidizing engineering.Therefore,novel acidizing corrosion inhibitors with effective corrosion inhibition are still in need.N-Benzylquinolinium chloride(BQC)is extensively used as corrosion inhibitor in acidizing engineering,but its synthetic reaction conditions much different and the corrosion inhibition of the products are distinctive apparently.The synthesis of BQC was researched in detail,and the pure BQC was separated.The corrosion inhibition of the pure BQC to N80 steel in 15% hydrochloric acid at 90?was evaluated by static gravimetric measurement.The result showed that corrosion rate was 232.68 g·m-2·h-1 at the concentration of 7.31×10-2 mol·L-1,which indicated that the performance of the BQC do not satisfied all requirements in practice.Another red substance which was named N-Benzylquinolinium Chloride Derivative(BQD)was separated from the products mixture,and the corrosion inhibition of BQD was evaluated.The results showed that corrosion rate was 1.98 g·m-2·h-1 at the concentration of 7.44×10-4 mol·L-1,which displayed excellent corrosion inhibition.The compound of BQD and its corrosion inhibition have not been researched so far.Evidently,it is BQD rather than BQC that play the role of inhibitor in so called N-Benzylquinolinium chloride inhibitors used in acidizing engineering.The molecular formula of BQD was determined as C32H23N2 Cl by High Performance Liquid Chromatography /High Resolution Mass Spectromettry(HPLC-HRMS).The structure of BQD was determined by H-NMR,C-NMR and FT-IR.According to the structure,the formation mechanism of BQD from two BQC by Michael addition reaction was proposed reasonably.Based on the calculation of the data from the static gravimetric measurement,the adsorption of BQD on the steel surface obeyed Langmuir adsorption isotherm.The standard free energy of adsorption of BQD was-54.48 kJ·mol-1,which indicated a strong chemisorption of BQD on the steel surface.The corrosion inhibitions of BQD were also investigated by EIS,and potentiodynamic polarization,and the results were in good agreements with the results from static gravimetric measurement.All the results indicated that the inhibitive performance of BQD is far better than that of BQC.Based on the structural difference between BQD and BQC,the mechanism of effective corrosion inhibitions of BQD was discussed.