Study of Coke Formation in SARA Fractions by Means of Thermogravimetry

Coke formation process is studied by the example of SARA fractions - saturated (S) and aromatic (A) hydro-carbons, resins (R) and asphaltenes (A) - naphthenic and methane crude oils by means of thermogravimetry. The studied oil samples are characterized as heavy, high-sulphur, high-resin and contain large amounts of asphaltenes. They differ from each other in the content of resins, asphaltenes, sulphur, and in the yields of fractions with the initial boiling point (IBP)-360 degrees C. Thermogravimetric analysis was carried out heating the samples from 25 to 650 degrees C at a rate of 10 degrees C/min in argon. It is demonstrated that the yield of coke-like condensation products (coke) depends on the composition and structure of SARA fractions. During thermal analysis, the yield of coke is lower from the fractions of saturated and aromatic hydrocarbons and resins of naphthenic oil than from similar frac-tions of methane oil. The amount of solid products formed during thermal analysis of asphaltenes from naphthen-ic oil is larger than for asphaltenes of methane oil. Experimental and calculation data on coke yield from thermal analysis of model mixtures are presented. It is determined that coke formation during thermal analysis of model mixtures is not a direct function of the additive contribution from each of the components of the mixture.