Synthesis And Property Evaluation Of Mannich Base Quaternary Ammonium Salt Corrosion Inhibitor

At present,in the wake of the rapid development of industry,the demand for oil reservoir resources is increasing.Acidification is one of the common measures to increase oil and gas production and injection volume in oil and gas fields.However,the addition of corrosive acid will corrode the tubing and downhole metal equipment.Meanwhile,the formation will be destroyed by dissolved iron ions.Therefore,the addition of acidification corrosion inhibitors has become a universal and economical method to solve such problems.Mannich base is a compound with a stable structure,and the corrosion inhibition effect is excellent when mixed with the synergist.The quaternary ammonium hydrochloric is acid soluble,which it makes its adsorption on the metal surface diverse.As a result,the adsorption film is more stable.Mannich base quaternary ammonium salt corrosion inhibitor has become a research hotspot in academic and industry because of the structure of both Mannich base and quaternary ammonium salt.In this paper,diethanolamine and dimethylamine aqueous solution were respectively reacted with acetophenone and formaldehyde to prepare Mannich bases MB-01 and MB-02.And then the products of previous step were respectively reacted with benzyl chloride to finally prepare two kinds of Mannich base quaternary ammonium salts MJ-01 and MJ-02.The synthesized compounds were characterized using ¹H NMR and FTIR.The effect of the four products on corrosion of N80 sample in 15%HCl solution was studied by atmospheric static weightlessness method.The results indicate that the corrosion inhibition performance of diethanolamine series products is obviously better than that of dimethylamine series products.For the same series of products,the protective effect of the corrosion inhibitor quateinized on the steel sheet is significantly improved.Finally,the quaternized corrosion inhibitors MJ-01and MJ-02 were selected as the subsequent study objects.Electrochemical tests showed that the prepared corrosion inhibitors were both mixed corrosion inhibitors,which were inhibiting the anode and cathode corrosion reaction simultaneously.Meanwhile,the fitted adsorption isotherm model results indicate that the adsorption of the two corrosion inhibitors on the surface conforms to Langmuir adsorption model,and the adsorption process are chemisorption and mixed adsorption respectively.The results of surface morphology analysis further confirm that the corrosion inhibitor molecules can inhibit corrosion by adsorption on the metal surface.In order to further verify the results of traditional experiments,quantum chemistry calculation and molecular dynamics simulation were used to calculate the adsorption mechanism of corrosion inhibitor molecules on the metal surface.The quantum chemical calculation results show that the highest occupied orbital energy(E_HOMO)is more consistent with the change of corrosion inhibition rate,which is used to predict the corrosion inhibition efficiency.The equilibrium adsorption of a single inhibitor molecule on the metal surface was simulated.And the results show that the inhibitor molecule can form a stable adsorption film on the metal sheet.The order of adsorption energy also follows the experimental results.