Synthesis,Performance Test And Theoretical Calculation Of Bis-mannich Base Acidizing Corrosion Inhibitor

Oil well acidizing is a commonly used means of increasing production during oilfield exploitation,and acidification corrosion inhibitors are widely used in the acidification process to prevent corrosion of mining equipment and pipelines due to a series of advantages such as low cost and convenient use.With the development of the petroleum industry,the expectation for corrosion inhibitors increases constantly.Corrosion inhibitors that are resistant to high temperature,easy to dissolve,non-toxic and environmentally friendly,and have good corrosion inhibition effects are more and more becoming the focus of research.Mannich base acidification corrosion inhibitors have been widely studied because of the above advantages,but so far,there are few studies on bis-Mannich base corrosion inhibitors.In this paper,two kinds of isomers: 1,2-propanediamine and 1,3-propanediamine,were reacted with paraformaldehyde and acetophenone to prepare two bis-Mannich bases:3-[1-Methyl-2-(3-oxo-3-phenyl-propylamino)-ethylamino]-1-phenyl-propan-1-one(M-23-M)and 3-[3-(3-oxo-3-phenyl-propylamino)-propylamino]-1-phenyl-propan-1-one(M-3-M).Then the corrosion inhibition performances of the two were studied by static weight loss method and electrochemical experiment.The results show that when 0.3 % acid corrosion inhibitor was added to 15 % HCl solution at 90 ℃,the corrosion efficiencies of M-23-M and M-3-M are 96.79 % and 91.79 %,respectively.Both corrosion inhibitors are mixed control corrosion inhibitors,and their adsorptions on the surface of the N80 steel sheet conform to the Langmuir isotherm adsorption line.Surface analysis experiments verified that the inhibitor molecules did form a protective film on the surface of the N80 steel sheet.In addition,the results of quantum chemistry calculations and molecular dynamics simulations are consistent with experimental results.In this paper,static weight-loss method,electrochemical test,scanning electron microscope,contact Angle measurement,Quantum chemical calculation and molecular dynamics simulation were used to study the inhibition performance of three kinds of novel bis-mannich base acidification corrosion inhibitors:3-[4-(3-Oxo-3-phenyl-propylamino)-butylamino]-1-phenyl-propan-1-one(M-4-M),3-[6-(3-Oxo-3-phenyl-propylamino)-hexylamino]-1-phenyl-propan-1-one(M-6-M)and3-[8-(3-Oxo-3-phenyl-propylamino)-octylamino]-1-phenyl-propan-1-one(M-8-M)in 15 %HCl solution to N80 steel.The results show that the corrosion efficiency increases with the increase of the corrosion inhibitor concentration and alkyl chain length.In addition,when the addition of the corrosion inhibitor is 0.3 % in weight-loss method,M-8-M has the highest corrosion inhibition rate for N80 steel,up to 98.20 %.Electrochemical tests show that the three corrosion inhibitors are all mixed type.The surface analysis results show that the corrosion inhibitors form dense adsorption layers on the surface of N80 steel,thereby protecting the steel sheets and slowing their erosion by acid.The adsorption of the three corrosion inhibitors on the surface of the steel sheet follows the Langmuir isotherm,which is a mixed adsorption type where physical adsorption and chemical adsorption exist simultaneously.Combining quantum chemistry calculations and molecular dynamics simulation analysis,the corrosion inhibition performance of corrosion inhibitors increasing with the increase of the alkyl chain length mainly due to the following two reasons: First,the molecular flexibility of the corrosion inhibitors increases with the growth of the alkyl chain.The molecule with longer alkyl chain can be adsorbed on the surface of the steel sheet in a more pocking form,thereby forming a tighter adsorption film.Second,the increase of alkyl chain length will improve the hydrophobicity of corrosion inhibitor molecules,which makes the corrosive particles in the aqueous solution more difficult to contact with the Fe surface.