The Synthesis And Research On Inhibition Mechanism Of Two Efficient Inhibitors Imidazoline And Alcohol Amine

Due to the presence of acidic substances in oil and gas extraction andtransportation process, corrosion of metal pipes is becoming more serious. Metalinhibitors is playing a very important role to solve this problem, as thestrengthening of environmental awareness, toxicity, feasibility poor inhibitorsgradually replaced by green, renewable, environmentally mild inhibitors, thesecorrosion inhibitors have gradually become a national focus, this paper in view ofhigh CO2content of the Daqing oilfield gas pipeline, through molecular structure,material ratio, synthetize two efficient inhibitors such as imidazolines andalcamines, and explore the corrosion mechanism.Through molecular structure design, increase of polar groups, make themolecular structure has good water solubility, and more able to provides the lonepair electrons for metal rail complexation.Using oleic acid and diethylenetriamine（DETA） and triethylene tetramine（TETA） under the condition of vacuum byamidation, cyclization, synthetize imidazoline intermediates, then respectivelyreaction with benzyl chloride and thiourea, obtained corresponding thiourea baseimidazoline salt （IM-S1, IM-S2）, and define the structure characterization ofproducts by infrared spectrum and nuclear magnetic. Change the raw materialproportioning of DETA, yield calculation, corrosion weight loss, polarization curveand ac impedance test results are shown the best proportion of oleic acid, DETA,benzyl chloride, and thiourea is1:1.3:1:1, namely the IM-S1has the best corrosioninhibition ability. Corrosion inhibitor added concentration of70mg/L, the corrosionrate is above97%.Compound with different concentration of thiourea, the corrosion inhibitionability is obviously improved, with the thiourea concentration gradually increased,the corrosion rate showed a trend of decrease after the first increased, dynamiccontact angle test from a macro perspective to observe inhibitor dynamic adsorptionin the surface of sheet steel, when thiourea and IM-S1ratio is1:1,contact angle isthe minimum,adsorption is the best. SEM test from microscopic aspect comparedsurface corrosion of the steel,test results are consistent with the above.Adsorption mode explore the mixed type imidazoline corrosion inhibitor on themetal surface adsorption state, the ΔG theoretical calculated value of mixed typeinhibitor gradually decreases with the increase of the coverage,and gentle erosionperformance has increased spontaneous adsorption ability, and corrosion inhibitionturn better. Coverage test results show that the corrosion inhibitor adsorb on the metal surface needs a certain time, the early corrosion inhibition effect is poorer, theaddition of surfactant OP-10, reduces the macromolecular entanglement betweenIM-S1, improve the speed and penetration ability, make its synergies with thioureamore ideal.Alcohol amine compound corrosion inhibitor, after the screening of rawmaterial, mainly adopting MDEA corrosion inhibitor, mixing different adjuvant,obtain two kinds of diversification alcohol amine inhibitor.Simulated corrosive environment, by selecting the frother, mixing solution andliquid film solvent, prepared a foam drainage agent with appropriate foaming heightand defoaming time under the condition of high temperature and large pH value, toprompted liquid alcohol amine form bubbles,covered the surface of steel bodyevenly, improve the penetration ability of the corrosion inhibitor molecules, reducesthe gravity limits. AES, MDEA and CDEA optimal mix proportion is5:5:1. Besttemperature and pH value for foaming height and defoaming time respectively are50℃and11.Adding the same concentration of trace foaming agent in corrosion inhibitor,Both binary mixture and ternary mixture’corrosion performance are better thansingle MDEA. Binary mixture with the order for corrosion inhibition:Thiourea>MEA>Sodium Molybdate>DETA. The corrosion weight loss,polarization curve and ac impedance test results show that both kind of ternarycompound corrosion inhibitor corrosion rate is less than the national standards. Theresults of alcohol amine corrosion inhibitor from the macroscopic （contact angle）and micro observation（sSEM）are very consistent, lowest contact angle is10.16°,surface morphology shows that corrosion inhibition of compound with thiourea orsodium molybdate is better than the compound with MEA and DETA, the bestproportion for10:3:6, the latter for10:3:3.