Hydrocarbon Composition of Native Asphalt Thermolysis Products

Abstract

Springer Science+Business Media New York Thermolysis of Karmal and Ashal'cha native asphalts is conducted at 450C. It is shown that in the thermolysis process the content of resins decreases and of oils (hydrocarbons) increases.Chromatomass spectrometry is used to analyze the hydrocarbon composition of the oils. Thermolysis of Karmal native asphalts leads to increased content of both saturated and alkyl-and naphthenesubstituted mono-, bi-and tricyclic arenes. Thermolysis of Ashal'cha native asphalt, on the other hand, leads to reduced content of cyclanes, alkyl-and naphthenobenzenes, and naphthene-substituted naphthalenes and phenanthrenes, but increased content of alkanes and alkyl-substituted naphthalenes and phenanthrenes.In order to solve problems associated with intensification of processing of heavy hydrocarbon stocks with high contents of resinous and asphaltenous components (heavy crudes, native asphalts, oil resids, etc.), information is needed on the composition and properties of the components of the obtained products. This is bound up with the fact that yield of light fractions is increased essentially by degrading resins and asphaltenes [1][2][3][4][5][6][7]. No less important are the data on the change in the hydrocarbon composition of heavy crudes in the thermolysis process. The behavior of the hydrocarbons in the thermal degradation process depends on their chemical composition and structure, molecular weight, etc., which determine their volatility and reactivity in 213 Table 1 Specimen Content, wt. %, of oils resins asphaltenes Karmal NA Initial NA 72.2 23.7 4.1 Thermolysate 76.3 17.1 4.3 Ashal'cha NA Initial NA 67.6 26.2 6.2 Thermolysate 70.5 15.1 5.6cracking and condensation reactions [8,9]. Changes in the hydrocarbon composition occur partly due to thermal degradation of resins and asphaltenes, which leads to formation of low-molecular hydrocarbon fragments [10,11]. This work is a part of the studies of thermal conversions of components of heavy crudes and native asphalts (NA) [2,3] and is aimed at finding out the paths of conversion of alkanes, cyclanes, and aromatic hydrocarbons of NA under thermal effect.Ashal'cha and Karmal NAs (Tatarstan Republic) having densities of 978 and 959 kg/m 3 and sulfur contents of 4.6 and 3.8 wt. %, resin contents of 26.1 and 23.7 wt. %, and asphaltene contents of 6.2 and 4.1 wt. %, respectively, were taken for the study.Thermolysis of the NA was carried out in autoclaves 12 cm 3 in volume at 450C for 2 h in air atmosphere.As shown in [3], these conditions ensure maximum yield of liquid products and acceptable yield of gas and solid phases. The yield of gaseous thermolysis products was determined from the weight loss of the reactor containing the specimen after opening of the reactor. The liquid products were extracted by washing the reactor with chloroform.To determine the asphaltene content, the liquid thermolysis products were treated with 40-fold excess of n-hexane by the procedure described in [12]. The malthenes obtained after deasphalting were put on A...