Thermogravimetric Studies on Pyrolysis and Combustion Behavior of a Heavy Oil and Its Asphaltenes

Abstract

A thermogravimetric analyzer (TGA) was used to obtain information on the pyrolysis and combustion behavior of both crude oil (Neilburg) and its asphaltenes, each mixed with reservoir sand. Of all the saturate, aromatic, resin, and asphaltene fractions, asphaltenes contribute the most to the formation of coke (fuel). Temperatureramped as well as the isothermal pyrolysis experiments on whole oil and asphaltenes were analyzed to determine the temperature at which coke formation was maximized. Furthermore, isothermal combustion curves for coke derived from whole oil and asphaltenes were obtained to provide reliable data for calculating the kinetics of the reactions. The classical Arrhenius model was applied, and the activation energy for the combustion of coke formed from pure asphaltenes and from the whole oil was calculated. The results showed that the Arrhenius model fitted the data well in the entire range of temperatures the experiments were conducted. The source material for the coke led to modest differences in its reactivity. The observed activation energy for asphaltenes was 117.7 kJ/mol, and for the whole oil it was 129.5 kJ/mol, which indicates that they were in close agreement. Also, the combustion of coke from asphaltenes showed a reaction order of 0.4 at 375°C, which gradually increased to 0.9 at 525°C. For whole oil, it increased from 0.5 at 375°C to 0.7 at 500°C.

A study of the combustion chemistry of petroleum and bio-fuel oil asphaltenes

“…The two petroleum asphaltenes have similar mass loss profiles and they have, as shown in experimental results here for the loss of the volatiles follow kinetic rates which are similar to those found in our previous studies [15] and by other research groups [17][18][19] as discussed later.…”

Effect of low-temperature oxidation on the pyrolysis and combustion of whole oil

“…The production of coke is maximized at the isothermal pyrolysis temperature of 425 C [13]. This was confirmed by the nonisothermal pyrolysis experiment, which was discussed in the previous section.…”

TG/DTG, FT-ICR Mass Spectrometry, and NMR Spectroscopy Study of Heavy Fuel Oil

“…In the LTO region, the fuel is partially oxidized and pyrolyzed via heterogeneous reactions, and the oxidation rate of asphaltenes is very slow with almost no mass loss. 46 The LTO region is followed by homogenous (gas phase) reactions in the FD region to form the fuel compounds for the HTO region. The reactions in the third region appear to be in the mode of hydrocarbon/char reactions 9,46 .…”

“…46 The LTO region is followed by homogenous (gas phase) reactions in the FD region to form the fuel compounds for the HTO region. The reactions in the third region appear to be in the mode of hydrocarbon/char reactions 9,46 . Similar trends of the activation energies were obtained in 9, 46 with slightly higher values, which is most likely due to the higher asphaltenes content in the current sample.…”