不同碳链长度咪唑啉缓蚀剂在CO_(2)驱采油环境中的腐蚀防护作用

Corrosion Protection of Imidazoline Corrosion Inhibitors with Different Carbon Chain Length in CO_(2) Driving Oil Environment

目的合成制备适用于CO_(2)驱油环境中井筒材料的腐蚀防护的咪唑啉缓蚀剂,探究碳链长度对咪唑啉缓蚀剂腐蚀防护性能的影响机制。方法以辛酸、月桂酸、硬脂酸和二乙烯三胺等为原料,经酰胺化和环化后制备得到3种碳链长度(C7、C11和C17)的咪唑啉缓蚀剂。通过傅里叶变换红外光谱、量子化学计算、失重法、电化学方法以及表面观察技术,对合成缓蚀剂在CO_(2)驱油环境中对井筒材料的腐蚀防护性能进行了评价。结果红外测试观察到3种链长(C7、C11和C17)的咪唑啉缓蚀剂的特征吸收峰,表明3种链长咪唑啉缓蚀剂成功制备。量子化学计算表明,合成的C17咪唑啉缓蚀剂具有最优的供电子能力和最佳的疏水能力。腐蚀失重和电化学测试结果显示,所合成的3种不同碳链长度的咪唑啉缓蚀剂均对CO_(2)驱腐蚀环境中N80钢具有良好的腐蚀防护作用,随着缓蚀剂浓度的提升,其缓蚀效率逐渐增高。其中含有17个碳链的咪唑啉缓蚀剂(C17)在10 mg/L时缓蚀效率达到了90%以上。拉曼光谱观察到N80钢表面C=N和C—N的吸收峰,表明合成的3种缓蚀剂在N80表面上吸附。SEM结果发现,添加C17咪唑啉的N80表面腐蚀最为轻微,其腐蚀防护效果最优。结论合成的C17碳链的咪唑啉缓蚀剂具有优异的腐蚀防护效果,随着碳链长度的增加,碳链的推电子能力增强,使得咪唑啉缓蚀剂更容易在N80钢表面吸附,同时长碳链形成的缓蚀剂膜层也具有更好的疏水作用,导致咪唑啉中缓蚀剂越长其缓蚀效果越好。

The work aims to synthesize three imidazoline corrosion inhibitors with different carbon chain length for corrosion protection of N80 carbon steel and explore the effect mechanism on the corrosion protection performance in carbon dioxide miscible oil displacement environment.The imidazoline corrosion inhibitors with C7,C11 and C17 carbon chains were synthesized by amidation and cyclization reaction with octanoic acid(OA),lauric acid(LA),stearic acid(SA)and diethylenetriamine(DETA),respectively.Fourier transform infrared spectroscopy(FTIR),quantum chemical calculation,weight loss method,electrochemical measurements including electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization curve(PDP),Raman spectroscopy and surface observation technologies were employed to study the anti-corrosion mechanism of the synthesized three corrosion inhibitors.FT-IR results proved that imidazoline corrosion inhibitors with different carbon chains were successfully prepared.Quantum chemical calculations showed that the synthesized C17 imidazoline corrosion inhibitor had the best electron donating ability and hydrophobic ability.The results of weight loss indicated that all the synthesized inhibitors had good inhibition effect on N80 steel in CO_(2)miscible oil displacement corrosion environment.The inhibition effect of inhibitors increased as the inhibitor concentration and carbon chain length increased,and reached over 90%for imidazoline inhibitor with 17 carbon chain at 10 mg/L.The EIS results indicated that the capacitive arc radius increased with the increase of imidazoline concentration and carbon chain length.The polarization curve results suggested that the imidazoline corrosion inhibitor behaved as an anodic corrosion inhibitor in the test environment,and its self-corrosion current density decreased sharply with the increase of imidazoline concentration and carbon chain length.It could be seen that the same trend of inhibition efficiency was obtained by the method of weight loss and electrochemical test.Raman spectroscopy results indicated that corrosion inhibitors with C7,C11 and C17 carbon chain length were adsorbed on the N80 surface after immersion in test solution for 48 h due to the C=N and C—N character absorption peaks.The electron pushing effect of alkyl could enhance the adsorption effect of inhibitor onto steel surface.The SEM results showed that the surface of N80 added with C17 imidazoline was smooth and flat,and grinding marks could be clearly observed.This result proved that the imidazoline with C17 carbon chain length had the best corrosion protection effect compared to those with C7 and C11 carbon chain length.The adsorption film formed by inhibitor with longer carbon chain had better hydrophobic effect,which led to the better inhibition effect of synthesized imidazoline inhibitor.The synthesized imidazoline corrosion inhibitor with C17 carbon chain has excellent corrosion protection effect for N80 carbon steel.With the increase of carbon chain length,the electron donating ability of the imidazoline is enhanced,which makes the imidazoline corrosion inhibitor easier to be adsorbed on the surface of N80 steel.At the same time,the longer the carbon chain of the imidazoline corrosion inhibitor is,the better the hydrophobic effect of the adsorption film formed on the surface of the carbon steel is,so imidazoline inhibitor with C17 carbon chain has the best protection for N80 steel.