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Abstract
This study concerns with distribution, type, and structure of carboxylic acids in the 200–550°C distillates of Bohai crude oil. The acids, isolated by aqueous alcoholic sodium hydroxide, were converted into corresponding methyl esters with BF3 as catalyst. The chemical structure of these carboxylic acids and distribution of their various components in different distillates were studied in detail by IR, VPO, MS, and elemental analysis. The results show that the carboxylic acids in Bohai crude oil are mainly composed of naphthenic acids and branched chain fatty acids, and the content is high in distillates at about 405°C and 505°C. With increase of boiling temperature of distillates, the content of naphthenic acids increases gradually. The ring numbers of naphthenic acids in diesel distillate are mainly 1–3, and those in lubricant distillate are mainly 1–6.