Dependence of Molecular Kinetics of Asphaltene Cracking on Chemical Composition

Rahmani, Samina; Gray, Murray R.

doi:10.1080/10916460601054297

Cited by 19 publications

(8 citation statements)

References 10 publications

(9 reference statements)

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“…Great efforts have also been made to investigate the kinetic behavior of asphaltene conversion under different processes, including thermal cracking, − thermal hydrocracking, catalytic hydrocracking, , and thermal cracking in supercritical water (SCW) . However, the kinetics of asphaltene conversion under non-catalytic hydrogenation conditions, such as selecting THN as a hydrogen donor, were seldom investigated.…”

Section: Introductionmentioning

confidence: 99%

Seven-Lump Kinetic Model for Non-catalytic Hydrogenation of Asphaltene

et al. 2017

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Non-catalytic hydrogenation with a hydrogen donor is a beneficial way for effective conversion of asphaltene to distillate with minimal coke formation. In this work, detailed product distribution, which includes gas, light oil [initial boiling point (IBP)–350 °C], middle oil (350–540 °C), heavy oil (>540 °C), asphaltene, and coke, obtained from non-catalytic hydrogenation of asphaltene with tetralin as a hydrogen donor, was investigated in an autoclave. The effects of reaction conditions, including reaction time, reaction temperature, and hydrogen donor/asphaltene weight ratio, on asphaltene conversion, detailed product distribution, liquid product yield, and liquid product selectivity were studied. Results showed that through controlling the reaction condition, asphaltene conversion and total liquid yield reached 72.72 and 70.34 wt %, respectively, and produced only 2 wt % coke and 0.34 wt % gas. We then developed a seven-lump kinetic model, including an active hydrogen lump to describe the reaction behaviors of asphaltene hydroliquefaction. Activation energies ranged from 106.07 to 237.50 kJ mol–1. The activation energies of the main reaction that asphaltene decomposed and hydrogenated by active hydrogen to produce heavy oil and middle oil were 106.07 and 109.06 kJ mol–1, respectively, which were lower than those of thermal cracking. The activation energy of distillate formation from active hydrogen combined with macromolecule radicals was 143.78 kJ mol–1. The detailed product yield predicted by the developed seven-lump kinetic model exhibited good consistency with the experimental data.

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Section: Introductionmentioning

confidence: 99%

Seven-Lump Kinetic Model for Non-catalytic Hydrogenation of Asphaltene

et al. 2017

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“…Studies related to asphaltene behavior during the thermal cracking are very limited and most of the previous efforts are related to coke formation and kinetic model development. − Hauser et al studied the structural changes in asphaltenes during pyrolysis by solid-state 13 C NMR and X-ray diffraction. They reported more scissioning of side chains than cracking in a more distant position from the aromatic ring.…”

Section: Introductionmentioning

confidence: 99%

Impact of Thermal Treatment on Asphaltene Functional Groups

et al. 2016

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The main objective of this study is to provide an in-depth analysis that reveals the impact of thermal treatment on the different functional groups that exist in asphaltene molecules. This contribution is important to further understand the nature of changes that take place in asphaltenes during distillation and thermal cracking processes. A slight increase was observed in the aromatic −CH groups, compared to aliphatic −CH groups, as crude oil is processed to atmospheric and vacuum residues. A slight decrease was also observed in the intensity ratio between methylene and methyl groups (CH 2 /CH 3 ) with distillation, which suggests a decrease in the average length of alkyl side chains for asphaltene molecules. The Fourier transform infrared (FTIR) results also suggest the possibility of thiophenic compounds oxidation during the atmospheric and vacuum distillations. More obvious differences were noted between asphaltenes exposed to thermal cracking, separated from the pitch samples, and their parent asphaltenes from the vacuum residues. Although the spectra of thermally treated asphaltenes have most of the features that belong to their parent asphaltenes, the results illustrate more aromatic structures as the reaction severity increases. In addition, the ratio of CH 3 to CH 2 groups shifted toward CH 3 with increasing reaction time and/or temperature due to the shortening of alkyl side chains. FTIR results have been further supported by 1 H and 13 C nuclear magnetic resonance (NMR) analysis, which confirmed the conclusion that thermal cracking of residual oils mainly affected the paraffinic side chains while the observed changes in the aromatic core appear to be relatively limited.

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“…A number of research groups have studied asphaltene transformation in hydroprocessing [2,[4][5][6][7][8][9][10][11][12] whereas other studies have focused on the impact of thermal treatment in asphaltene conversion. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Our research group has extensively concentrated on asphaltene characterization over the past few years and has fully studied the impact of thermal treatment on asphaltene molecular structure. For example, Lababidi et al [18] reported notable decrease in asphaltene molecular weight, associated with significant increase in aromaticity, as thermal cracking severity increases.…”

Section: Introductionmentioning

confidence: 99%

Determination of asphaltene structural parameters by Raman spectroscopy

AlHumaidan

Rana

2021

J Raman Spectroscopy

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The objective of this study is to determine the aromatic sheet diameter (L a ) and the number of aromatic sheets per stack (n) for asphaltene molecules from Raman spectra by investigating and optimizing empirical equations proposed in the literature for both crystalline and amorphous carbon materials. The results clearly indicated that the best empirical equation for determining the aromatic sheet diameter for asphaltene was the equation proposed by Tuinstra and Koenig, but only when the graphitization indicator I D /I G would have been determined from the peak integrated ratio, rather than from the peak intensity ratio. The best results of L a were obtained when the Raman spectra were deconvoluted and fitted with three peaks using Gaussian function. The number of aromatic sheets per stack for asphaltene was also determined by examining various empirical equations proposed for crystalline carbon materials. The results indicated that these equations could be applied on asphaltene if the first-order region of Raman spectrum were to be fitted with two peaks, representing the G and D bands. Fitting the spectra with more peaks could result in splitting the G band into two bands (i.e., G and D2 bands), which would shift the G-band position to a wavenumber below 1581.6 cm À1 , and, subsequently, prevent the utilization of these empirical equations.

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Dependence of Molecular Kinetics of Asphaltene Cracking on Chemical Composition

Cited by 19 publications

References 10 publications

Seven-Lump Kinetic Model for Non-catalytic Hydrogenation of Asphaltene

Seven-Lump Kinetic Model for Non-catalytic Hydrogenation of Asphaltene

Impact of Thermal Treatment on Asphaltene Functional Groups

Determination of asphaltene structural parameters by Raman spectroscopy

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