胜利高酸原油馏分油中石油酸的腐蚀性研究

CORROSION RESEARCH OF NAPHTHENIC ACID IN DISTILLATES OF SHENGLI HIGH ACID CRUDE

对胜利高酸原油200～350℃和350～450℃馏分油中的石油酸用醇碱抽提、纯化后,采用元素分析法、蒸气压渗透法、红外光谱法和氢核磁共振波谱法对石油酸结构组成进行了分析,并考察了A20碳钢在两个馏分油中的腐蚀速率随温度的变化。结果表明：胜利原油200～350℃和350～450℃馏分油中石油酸的平均分子式分别为C_15.86H_27.51O_2.06和C_32.86H_54.77O_2.29;石油酸腐蚀不仅与酸含量有关,更与其结构密切相关,随着馏分变重,石油酸的烃支化度由0.197升至0.292,烃支化程度增大,石油酸与羧基相连基团的吸电子能力降低,石油酸酸性减弱,对碳钢腐蚀能力降低,同时,石油酸在与碳钢接触反应时,所受空间位阻增大,减缓了石油酸对碳钢的腐蚀;石油酸的腐蚀性随温度升高而增大,小分子石油酸的腐蚀能力强。

Naphthenic acid in the distillates of 200--350 ℃ and 350--450 ℃ in Shengli high acid crude oil were separated and purified through alkaline-ethanol extraction. The structures and composi- tions of naphthenic acids were confirmed by means of element analysis method, steam osmosis pressure, hydrogen nuclear magnetic resonance （NMR） spectroscopy, and Fourier transform infrared spectroscopy techniques. The corrosion of A_20 carbon steel in the two distillates was conducted at different tempera- tures. The results show that naphthenic acid is monocarboxylic, and the average molecular formulas of naph- thenic acid in the distillates of 200--350 ℃ and 350--450 ℃ are C_15.86 H_27.51 O_2.06 and Ca_2.86 H_54. 77 O_2.29 , respectively. The corrosion ability of naphthenic acid is not only related to acid content, but also closely related with its structure. As the fraction becomes heavier, the branching degree of petroleum acid mol- ecule increases from 0. 197 to 0. 292, and the electron-withdrawing property of the group connected with carboxyl groups in acid reduces, and the acidity decreases, resulting in a lower corrosion rate of carbon steel. At the same time, a larger space sterie hindrance in branched acid molecules would lower the cor- rosion ability of naphthenic acid. The corrosion rate is increased as temperatures go up and the corrosion ability of the small molecular naphthenic acid is stronger.