【作者】 陈国浩；

【导师】 赵景茂；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2012， 博士

【摘要】 CO₂腐蚀是油气田生产过程中最为常见的一种腐蚀形式，它严重的威胁了石油化工行业的安全生产，往往会造成巨大的经济损失，甚至危及到人身安全。有鉴于此，如何有效的抑制CO₂腐蚀一直是研究热点。在诸多抑制CO₂腐蚀的措施中，添加缓蚀剂是一种简单有效，成本低廉的手段，被广泛的应用于各大油气田实际生产中。然而，目前有关缓蚀剂的机理研究相对较少，特别是缓蚀协同效应机理的研究相当匮乏。为了对缓蚀剂的缓蚀机理进行深入的研究，本论文合成了一系列缓蚀剂，利用红外光谱对它们的结构进行了表征。利用失重法、极化曲线、电化学阻抗谱（EIS）、零电荷电位测试等电化学技术，配合X射线光电子能谱（XPS）、量子化学计算等手段，对缓蚀剂的缓蚀机理及缓蚀协同效应机理进行了深入的研究。主要工作如下：1、利用极化曲线和EIS电化学测试技术，系统的研究了CO₂腐蚀体系中咪唑啉衍生物（OIMQ）、硫脲（TU）和两者复配使用的复配缓蚀剂的电化学行为。结果表明：OIMQ和TU之间具有良好的缓蚀协同效应，当使用浓度为10mg/L时，两者的最佳配比为5mg/L+5mg/L。分析两者的电化学行为可以发现，OIMQ是一种抑制阳极为主的混合型缓蚀剂，通过对阳极过程的负催化作用而起到缓蚀作用；TU是一种混合型缓蚀剂，作用机理为几何覆盖效应；当两者复配使用后，缓蚀剂表现出的作用机理为几何覆盖效应，极化曲线上出现了吸附/脱附平台区；EIS图谱上出现了Warburg阻抗，表明在碳钢表面形成了一种双层缓蚀剂的膜层结构，验证了之前的XPS试验结果。即硫脲分子主要存在于缓蚀剂膜的底部，而咪唑啉主要存在于缓蚀剂膜的上部。2、研究发现在CO₂体系中，咪唑啉类缓蚀剂（OIMA）和苯甲酸钠（SB）之间存在协同效应，此结论在国内外均未见相关报道。应用静态失重法、动电位极化曲线和EIS电化学测试技术研究了二者之间的缓蚀协同效应机理，并提出了吸附模型。结果表明，OIMA能够有效地抑制Q235钢在CO₂饱和盐水溶液中的腐蚀，而SB基本上对Q235钢在CO₂饱和盐水溶液中的腐蚀没有缓蚀作用。但是当两者复配使用时，有明显的缓蚀协同作用。通过EIS和零电荷电位测试技术，辅以XPS测试，推测OIMA与SB的缓蚀协同效应机理如下：首先，在CO₂饱和盐水溶液中，OIMA会被质子化，质子化的OIMA分子能够通过物理吸附的方式吸附在金属表面的阴极区，由此使得零电荷电位向正的方向移动，除了物理吸附，OIMA还将通过化学吸附方式吸附在金属表面。当SB添加到溶液中后，将会发生水解反应，形成苯甲酸根离子（phCOO-），由于静电引力吸附到Q235钢表面，使得缓蚀剂的膜层更加的致密，从而对Q235钢起到更好地保护作用，两者表现出良好的缓蚀协同效应。即这两种缓蚀剂在金属表面上的吸附是分步进行的，在本试验条件下，首先发生咪唑啉分子吸附，大约20min后SB分子才开始吸附在Q235钢表面。3、合成了一种新型多吸附中心的抗CO₂腐蚀的缓蚀剂——聚酰胺聚脲（MPA）。动态失重法结果表明它能够有效地抑制CO₂腐蚀；且随着使用浓度增大，缓蚀率提高。动电位极化曲线测试结果表明它是一种抑制阳极过程为主的混合型缓蚀剂。通过计算MPA分子单体的Fukui指数，发现它在金属表面吸附的最主要的活性点为S原子，S原子既可以向金属提供孤对电子，与Fe形成共价键；也可以通过得到Fe的电子形成反馈键，从而牢固的吸附在金属的表面；N33、N34两个杂原子可以通过获得Fe的电子形成反馈键，使MPA分子更加牢固的吸附在金属的表面，有效的阻断了腐蚀介质与金属表面接触，起到保护金属的作用。4、研究了咪唑啉分子中苯环的数量以及位置对其缓蚀性能的影响。合成了三种含苯环的咪唑啉类缓蚀剂，即2-氨乙基-1-苯基咪唑啉（PIMA）、2-苯甲酰氨乙基-1-苯基-咪唑啉（PIMAA）、2-氨乙基苯亚甲基-1-苯基咪唑啉季铵盐（PIMQ），并通过静态失重法研究了它们的缓蚀性能。结果表明：三种缓蚀剂都能够有效地抑制Q235钢在CO₂饱和盐水溶液中的腐蚀，其中PIMQ效果最好，PIMAA的缓蚀效果次之，PIMA的缓蚀效果在三种缓蚀剂之中最差。极化曲线测试结果表明三种缓蚀剂都是抑制阳极过程为主的阳极型缓蚀剂。通过热力学计算，发现三种缓蚀剂在Q235钢表面的吸附服从Langmuir等温吸附方程；吸附过程为自发过程，吸附类型属于化学吸附；吸附过程是吸热过程，升高温度有利于缓蚀剂的吸附；吸附过程是一个熵增过程。量子化学计算发现PIMQ的ΔE最小，表明在三种缓蚀剂之间，PIMQ最易于吸附于金属表面，从而具有最高的缓蚀效率，这主要是由EHOMO的差异所引起的，表明相比于其他两种缓蚀剂，PIMQ更易于提供电子给Fe原子的d空轨道，形成牢固的配位键。5、利用EIS和旋转圆盘电极，系统的研究了两种具有不同亲水基的咪唑啉类缓蚀剂，即2-氨乙基-1-十七烯基咪唑啉（OIMA）和2-羟乙基-1-十七烯基咪唑啉（OIMO）在不同转速和不同浓度下对Q235钢的缓蚀性能。结果表明，两种缓蚀剂都能够有效地抑制Q235钢在流动条件下的CO₂腐蚀，且OIMA具有更好地缓蚀性能。当电极旋转时，在低频段出现Warburg阻抗，表明电极过程由活化控制转为浓差控制；高频段出现了另一个时间常数（除了较低转速下，低浓度OIMO时），表明缓蚀剂膜层更加厚实。从EIS图谱的拟合结果可以发现电荷转移电阻随着转速的增加先增大后减小，表现出流速对于缓蚀剂缓蚀性能影响的两面性。量子化学计算结果表明，OIMA的ΔE更小，表明其在金属表面的吸附强度更大，因此表现出比OIMO更好地缓蚀性能。在流动条件下将PIMA与TU、SP和OP复配后发现，PIMA和TU具有良好的缓蚀协同效应，和SP和OP之间表现出拮抗效应。最后，构建了一个4-9-1的BP神经网络，较为准确的预测咪唑啉类缓蚀剂在流动条件下的缓蚀率，具有良好的外延性，误差很小，能够满足实际应用的要求。更多还原

【Abstract】 Carbon dioxide （CO₂） is a naturally occurring constituent in oil andgas production and is found in amounts varying from trace levels to asmuch as50%. Dissolved CO₂in the produced brine is very corrosive tocarbon steel pipelines. Therefore CO₂corrosion has a very importanteconomic impact in this industry. The problem has caused theapplication of many corrosion control methods and research around theworld. One of the most cost-effective methods is the injection of organicinhibitors into oil wells, gas wells and pipelines. However, there are fewstudied about the corrosion inhibition mechanism, especially for thesynergistic mechanism of corrosion inhibitors in sweet system. In orderto make deeper studies on the corrosion inhibition mechanism andsynergistic inhibition effect, several inhibitors were synthesized andcharacterized by infrared spectroscopy in the paper. Their inhibitionperformance was investigated by weight-loss method andelectrochemical techniques. Based on these results, as well as X-rayphotoelectron spectroscopy analysis and quantum chemical calculationsresults, the inhibition mechanism and synergistic mechanism were proposed to explain the inhibition behavior of the inhibitors in sweetsystem.1. The electrochemical behavior of imidazoline derivates （OIMQ）and/or thiourea （TU） was studied by using polarization curves and EIS.The results indicated that a synergistic effect existed between TU andOIMQ. The optimum proportion of them was1:1（wt%） when the totalusing concentration was10mg/L. OIMQ was an anodic-type inhibitorand caused by negative catalytic effect; while TU was a mixed-typeinhibitor and caused by geometrical blocking effect. For TU+OIMQcombination, it was also a mixed-type inhibitor and caused bygeometrical blocking effect, and the inhibitor molecules could desorbfrom the metal surface when the potential applied on the metal was overthe adsorption potential. EIS results showed that the Warburg impedanceemerged on the Nyquist plots, which can be attributed to formation of abi-layer inhibitor film on the metal surface. This result was inaccordance with the XPS result reported by previous studies, that TUmolecules mainly exist on the bottom of the inhibitor film; however,OIMQ molecules mainly exist on the top of the inhibitor film.2. The synergistic inhibition effect of OIMA and SB inCO²-saturated solution was found by weight-loss method, polarizationcurves and EIS, which was not reported before. The results showed thatOIMA could prevent the mild steel from CO²corrosion to some extent and its inhibition can be strengthened by the combination use of SB. Thesynergistic inhibition effect of OIMA and SB is obvious. Based on theEIS, XPS and PZC measurement results, an adsorption model wasproposed to elucidate the synergistic effect between OIMA and SB.When10mg/L OIMA and10mg/L SB were added into theCO₂-saturated solution, N3atom in OIMA ring was combined withhydrogen ion to form an ammonium ion and the positive charged OIMAmolecules physically adsorbed onto the negative charged surface of theelectrode in the test solution. The chemical adsorption might take placesimultaneously which involving the charge sharing or transfer fromOIMA to the metal surface. Consequently, parts of the negative chargeson the metal surface were neutralized and the metal surface had extrapositive charge. And then, SB, mainly in the form of phCOO^-, will bemoved toward to the metal surface by coulomb force and then adsorb onit and make the inhibitor film more compact and thicker. EISmeasurements showed that OIMA adsorbed first on the metal surfaceand followed by the adsorption of SB after20min later when OIMA andSB were added into solution.3. A new inhibitor for CO₂corrosion-modified polyamide （MPA）was synthesized and its structure was characterized by IR spectra.Weight-loss measurement and polarization curves were used toinvestigate its inhibition. The results showed that MPA belongs to a mixed-type inhibitor and controls anodic process principally, whichcould inhibit N80steel from CO₂corrosion efficiently and the inhibitionefficiency improved with the increase of MPA concentration. In viewthat the MPA had many active centers in molecules, Fukui function wascalculated by quantum chemical calculation to find the effectiveadsorption centers of MPA. The results showed that S atoms of MPAcould donated electrons to form chemical bonds with iron atoms on themetal surface and also accepted the negative charge from the metalsurface to form back-donation bonds. N33and N34could formback-donation bonds too. As a result, MPA could adsorb on the metalsurface firmly and protect metal efficiently.4. In order to study the effect of benzene ring number and locationon the inhibition efficiency of imidazoline, three kinds of imidazolinewith benzene ring（s） were synthesized and characterized by IR spectra.Weight loss method and potentiodynamic polarization method werecarried out to evaluate their inhibition. The results showed that the threeimidazoline derivates can inhibit CO₂corrosion effectively and PIMQprovides the highest inhibition efficiency among them. They mainlyrestrain the anodic dissolution and belong to a kind of anodic-typeinhibitors. By thermodynamic calculations, we found that the adsorptionof these derivates on the mild steel surface accords with Langmuiradsorption isothermal equation and belongs to chemical adsorption; the adsorption process is endothermic process, increasing temperature is ofbenefit of improving corrosion inhibition; the adsorption process is anentropy increasing process. Quantum-chemical calculation found thatthe energy gap of PIMQ was lowest. The difference of inhibitionefficiency among the three inhibitors was mainly caused by differencesin EHOMO.5. EIS and RDE were employed to study the inhibition efficiency oftwo imidazolines with different hydrophilic group, OIMA and OIMO,under flow conditions. The results showed that OIMA and OIMO caninhibit Q235steel from CO₂corrosion efficiently under flow conditionsand OIMA had better performance. Under flow condition, Warburgimpedance emerges in Nyquist plots, indicating that the electrodeprocess is controlled by concentration diffusion. And another phaseangle maximum at high frequency region appears in Bode plots underflow conditions （except low concentration of OIMO at low rotationspeed）. R_ctincreases with the increasing of rotation speed, and thendecreases. Quantum chemistry calculation results showed that the energygap of OIMA was lower than OIMO. The corrosion inhibition of PIMAwith TU, SP and OP was studied respectively, the results showed that thesynergistic inhibition effect of PIMA and TU is obvious, but PIMA+OPand PIMA+SP have antagonistic effect. A neuronic network with4-9-1structure was established, by which the inhibition efficiency of imidazoline and its derivates under flow condition can be predictedaccurately.更多还原