Study on the Transformation Behavior of Organic Chlorides in Crude Oil and the Corrosion Mechanism of Equipment

Abstract

As the quality of crude oil continues to deteriorate, the corrosion of refining equipment caused by organic chlorides has become increasingly prominent. This study systematically investigates the molecular structure characteristics and occurrence forms of organic chlorides in crude oil, reveals their transformation patterns under thermal and catalytic conditions, and elucidates the intrinsic mechanism through which the transformation products induce equipment corrosion. The results show that organic chlorides are primarily distributed in the intermediate fraction of 180-350℃, with C-Cl bond dissociation energies ranging between 297 and 368 kJ/mol. During pyrolysis, the homolytic cleavage of C-Cl bonds generates chlorine radicals, which initiate chain reactions, while catalytic conditions significantly accelerate the transformation rate by lowering the activation energy. The released hydrogen chloride undergoes chemical adsorption at the metal interface, forming Fe-Cl bonds, and chloride ions accumulate at defects in the passive film, leading to a decrease in the pitting potential and triggering localized electrochemical corrosion. The corrosion layer exhibits a multi-layered structural characteristic, and its microstructural evolution is quantitatively correlated with the corrosion rate. This research provides a theoretical basis for the corrosion protection of refining equipment.