Quaternary Ammonium Salts from Hydrolyzed Fatty Oil Based on Novel Tertiary Amines Used as Corrosion Inhibitors for Pipelines Carbon Steel at Acid Job in Petroleum Industry

Abstract

Ten new quaternary ammonium salts (QASs) were designed and synthesized from hydrolyzed fatty oils; the hydrolyzed oils were used as a source of alkyl halides to prepare the QASs by refluxing the fatty alkyl halide with ethoxylated amines as untraditional 3° amines in acetone. The structure of the prepared QASs were characterized by FTIR and ¹H NMR spectroscopy. The prepared cationic surfactants QASs were tested as corrosion inhibitors for carbon steel in 1 M HCl solution. The corrosion inhibition efficiency was measured using weight loss and potentiodynamic polarization methods. The inhibition efficiencies obtained from the two employed methods are in good agreement with each other. In generally, the inhibition efficiency increased with increasing the inhibitor concentration. From the obtained data it was found that the inhibition efficiency of QASs, which, based on ethoxylated aromatic tertiary amine, is greater than the efficiencies of the QASs based on ethoxylated aliphatic tertiary amine. The QASs based on fatty alkyl halide from palm oil exhibited the best inhibition efficiency than QASs based on fatty alkyl halides from coconut oil. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir's adsorption isotherm. The free energy of adsorption processes was calculated and discussed. The surface active properties were calculated on the basic of surface tension measurements. The obtained data of inhibition efficiencies were discussed on the light of surface active properties of these QASs and their chemical structures. The quantum chemical calculations was proceeded for QHL1,4,5 and QHP3,4,5 the following quantum chemical indices such as the bond length, bond angle, charge density distribution, highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), energy gap ΔE˭HOMO –LUMO, and dipole moment (u) were considered.The surface morphology of carbon steel sample was investigated by scanning electron microscopy.

Keywords:

• Cationic surfactant
• corrosion inhibitors
• potentiodynamic
• quantum chemistry
• quaternary ammonium salts
• weight loss