Research On Structure And Composition Of Petroleum Acids In Crude Oil And Distillate From Sudan Daer

In this study, alkali alcohol method was used to separate the petroleum acids in Daer crude oil and column chromatography method was used to separate the acids of its distillate, which is divided into eight distillate products with different ranges of temperature, including 300-320℃,320-345℃,345-395℃,395-425℃,425-460℃,460-480℃,480-500℃and 500-530℃. The acids distribution of the distillate products was mainly studied. The main content is composed of two parts.1. Separation of the Petroleum Acids in Daer Crude Oil by Alkali Alcohol MethodThe petroleum acids in Daer crude oil were separated by alkaline ethanol extraction. By studying solvent mixture ratio, the amount of crude oil, reaction temperature, reaction time on the effect of the removal rate of acids, the conditions of acids removal of Daer crude oil were optimized. The structure and composition of the petroleum acids were confirmed by means of FTIR and Nagative-ion ESI-MS. Results indicate that under the appropriate conditions of the solvent alkaline ethanol solution (p(KOH) 14 g/L, alcohol:water=7:3或3:1 (V:V)), crude oil dosage 6-8 g, reaction temperature 60-75℃and reaction time 30-40 min, the petroleum acids in Daer crude oil can all be extracted. It was found that the petroleum acids in this fraction are aliphatic acids, naphthenic acids (including 1-3-ring naphthenic acids) and aromatic acids (including alylbenzoic acids, naphthenebenzoic acids and dinaphthenebenzoic acids). The amount of naphthenic acids is ranked first, being 56%(Based on mass of the petroleum acids). Aromatic acids are made up 30% and aliphatic acids 14%.2. Separation of the Acids of Distillate by Column Chromatography MethodThe petroleum acids in its distillate were separated by column chromatography method. By studying different conditions on the effect of the removal rate of acids, the conditions of acids removal of distillates were optimized.200-300 mesh silica column chromatography and D290 big hole anion exchange resin separate the acids of distillate. The acids of distillate can be all extracted by acidic methanol solvent. The acid number and density of distillates increase gradually as temperature increasing. The acid number tends to be stable during 440-500℃, increasing of the boiling point has little impact on the acid number change above 440℃. The petroleum carboxylic acids were concentrated in middle and heavy oil. The results of IR and ESI-MS indicate that the composition and structure of petroleum carboxylic acids in the samples are probably mainly composed of 1-ring naphthenic acids and aromatic acid in the form of dimer or polynersomes, proportion of aliphatic acids is relatively little. The petroleum acids of different fractions have the same characteristic functional groups; structure is also roughly the same.The carbon number distribution of petroleum carboxylic methyl esters is 13-59. The petroleum acids in this fraction are aliphatic acids, naphthenic acids (including 1-3-ring naphthenic acids) and aromatic acids (including alylbenzoic acids, naphthenebenzoic acids and dinaphthenebenzoic acids). The highest amount of naphthenic acid can rank 54.6% in 500-530℃fraction, the lowest in 300-320℃fraction also can achieve 38.8%. The highest amount of aromatic acids can occpuy 52.0% in 320-345℃fraction), the lowest also can achieve 30.2%. Meanwhile fatty acids are mainly contained only in 300-320℃fractions, and the amount of fatty acids in other fractions is below 15.0 %., the structure distribution of petroleum acids in fractions high boiling point is more similar to that of crude oil.