Coking Kinetics of Asphaltenes as a Function of Chemical Structure

Abstract

The dependence of coking kinetics on the chemical structure of asphaltenes was examined by reacting five different asphaltenes in 1-methylnaphthalene and tetralin at 430 °C and ca. 9.8 MPa. The selected heptane-insoluble asphaltenes were Athabasca asphaltenes from Canada, Arabian Light and Arabian Heavy from Saudi Arabia, Maya from Mexico, and Gudao from China. The 13C NMR aromaticity of the asphaltenes ranged from 0.40 to 0.61, and the sulfur contents ranged from 4.44 wt % to 7.47 wt %. The cracking kinetics of the asphaltenes were consistent with a modified kinetic model for coke formation, incorporating phase separation and hydrogen transfer to the asphaltenes. The rate of cracking of asphaltenes in 1-methylnaphthalene correlated with the content of aliphatic sulfur, and the yield coefficient for coke correlated with the aromaticity. These correlations allowed prediction of coking kinetics for Iranian Light and Khafji asphaltenes on the basis of average structural properties of asphaltenes. Hydrogen transfer to the different asphaltenes did not correlate with any single average structural property.

Pentane-Insoluble Matter from Conventional and Heavy Crudes: Relationships Between Thermal Characteristics and Molecular Parameters

“…Figure 2 demonstrates that aromaticity (f a ), H/C atomic ratios, molecular weight (MW), equivalent diameter (D), and mean aliphatic side-chain length (L) are significantly correlated with coke yields. The dominant influence of aromaticity on thermal behavior of asphaltenes was reported earlier (Banerjee et al, 1986;Dutta et al, 2000;Gary, 2003;Rahmani et al, 2003;Speight, 1981). With the exception of the Chinese Daqing end cut, coke formation also correlated reasonably well with the structural parameters H au /C A , δ, n, R a , and C f (Figure 3).…”

Investigation on sediment formation in residue thermal conversion based processes

“…Its boiling point distribution range is between 230 and 580°C according to ASTM D-2887 (simulated distillation) while the VROs boil above 540°C. The H/C atomic ratio of the FCC slurry oil (0.96) is very close to that of the asphaltenes [39][40][41][42] and it is much lower than that of the investigated VROs (VRO H/C atomic ratio variation between 1.36 and 1.53). 4 presents the results of pyrolysis of the investigated VROs at different severities (reaction time at constant reaction temperature of 410°C and constant pressure of 10 bars).…”

Composition of Initiated Cracking Products of High-sulfur Natural Bitumen

“…Amount of resins and asphaltenes defines bitumen properties of both dispersion medium and dispersed phase, as well as natural bitumen aggregate stability of in the thermolysis conditions [2][3][4][5][6][7] . These compounds have high molecular weight, tend to condense and coke formation during processing, and deactivate catalysts [8][9][10] .…”