The effect of temperature on the molecular structure of Raman asphaltenes during pyrolysis

Asphaltenes were precipitated from Raman heavy crude oil subjected to pyrolysis at temperatures of 350, 400 and 450 °C for holding times ranging from 10 to 120 min using sandbath. Product fractions were separated as gas, maltene, remaining asphaltene and coke. The time and temperature dependence of product distributions were determined. Molecular structure of remaining asphaltenes was characterized by elemental analysis, Proton Nuclear Magnetic Resonance (1H NMR), Gel Permeation Chromatography (GPC). These data provide insights into the distribution of heteroatoms and the aromaticity within both original and remaining asphaltenes as well as to the coke formation reactions occurring during the asphaltene pyrolysis. The temporal structural variations of remaining asphaltene allowed discernment of asphaltene thermal pathways.