双曼尼希碱缓蚀性能的量子化学研究

Quantum Chemical Study on Corrosion Inhibition Performance of Double Mannich Base

以4-甲基苯乙酮、甲醛和正己胺为原料合成了单曼尼希碱(MPE)和双曼尼希碱(DMPE),研究2种曼尼希碱在酸性介质中对N80试片的缓蚀作用及电化学性能。结果表明:DMPE对N80试片缓蚀性能优于MPE;DMPE降低了N80试片表面的腐蚀电流密度而使电荷转移电阻显著提高,有效抑制了N80试片的电极反应过程。采用量子化学密度泛函理论(DFT)计算2种曼尼希碱的最高占据轨道能级(E _(HOMO))、最低未占轨道能级(E _(LUMO))、Hirshfeld电荷、简缩Fukui指数和分子范德华表面静电势极小点(V_(s,min))。结果表明:最高占据轨道能级比较,DMPE高于MPE;最低未占轨道能级比较,DMPE低于MPE;与MPE相比,DMPE更容易接受和给出电子;DMPE的V _(s,min)低于MPE,DMPE更易电离形成质子化的季铵盐;DMPE的4-甲基苯环、2个β-羰基的氧原子、叔胺基的N原子能够与N80试片的Fe原子的前线轨道成键。采用分子动力学模拟方法构建了MPE与DMPE在Fe不同晶面上的6个吸附模型,MPE与DMPE在不同Fe晶面上的吸附能绝对值由大到小的顺序均为Fe(110)、Fe(100)、Fe(111),在同一Fe晶面上DMPE的吸附能绝对值均大于MPE,说明DMPE比MPE在Fe表面吸附更稳定。

Mono Mannich base(MPE)and double Mannich base(DMPE)were synthesized from raw materials such as 4-methylacetophenone,formaldehyde and n-hexylamine,so as to investigate the corrosion inhibition and electrochemical properties of the two Mannich bases on N80 test pieces in acidic media.The corrosion inhibition efficiency of the two Mannich bases was measured by mass loss experiment.The results show that the corrosion inhibition of N80 test pieces by DMPE is better than by MPE.DMPE can decrease the corrosion current density on the surface of N80 test pieces,thus leading to a significant increase in the charge transfer resistance and effectively inhibiting the electrode reaction process of N80 test pieces.Density functional theory(DFT)of quantum chemistry was used to calculate the highest occupied molecular orbital energy level(E _(HOMO)),the lowest unoccupied molecular orbital energy level(E _(LUMO)),Hirshfeld charge,the condensed Fukui index and the molecular van der Waals surface minimal electrostatic potential(V s,min)of the two Mannich bases.The results show that the highest occupied orbital energy level,DMPE is higher than MPE;and the lowest unoccupied orbital energy level,DMPE is lower than MPE.Compared with MPE,DMPE is easier to accept and give electronics.The V _(s,min) of DMPE is lower than that of MPE,and DMPE is more likely to ionize to form protonated quaternary ammonium salts.The 4-methylbenzene ring of DMPE,two oxygen atoms ofβ-carbonyl group and N atom of tertiary amine can form bonding with the frontier orbital of Fe atom of N80 test pieces.Six adsorption models of MPE and DMPE on different crystalline surfaces of Fe were constructed using the molecular dynamics simulation method.The molecular dynamics simulations results show that the absolute values of the adsorption energies of MPE and DMPE on the different Fe crystal planes are in the descending order of Fe(110),Fe(100),Fe(111);the absolute values of adsorption energy of DMPE on the same Fe crystalline surface are greater than those of MPE,indicating that DMPE is more stable than MPE during adsorption on Fe surface.