“…On the basis of the study using structural analysis of the VR and visbreakates reported by Fainberg et al 16 and conclusions of Di Carlo and Janis, 6 following mechanistic path for the components can be concluded: Thus, the yields of the various products depend on their relative proportion and the extent of their crackability. In view of the above study, the five feeds covered in the present case and the data on VB feed (taken from the work of Singh 14 ) can be divided into three major classes based on asphaltenes (As) to saturates (Sa) ratio 6 as follows: (i) paraffinic feeds, e.g., BHSR, NGSR, <0.5; (ii) intermediate asphaltenic feeds, e.g., VB Feed, AMSR (0.5-2.0); (iii) the asphaltenic feed, e.g., Haldia Asphalt and AM Asphalt (g2).…”
Section: Resultsmentioning
confidence: 88%
“…6 The lower the difference, the higher is the feed stability. Thermal cracking increases the aromaticity of the asphaltene, 16 and as the reaction proceeds, the difference between the aromaticity of the maltenes phase and the asphaltenes increases. 6 Thus, the stability reduces as the conversion increases.…”
Thermal cracking of vacuum residues and asphalts obtained from operating Indian refineries
were studied in a batch reactor. The temperature was varied in the range 400−430 °C, and the
batch time was varied from 0 to 15 min. The pressure was kept at a constant value of 1.2 MPa
through out the experiment. The variation in the composition of the cracked gas fraction for
each feed was studied by gas chromatography. The resulting visbroken products were further
characterized in terms of its different industrially important boiling cuts. A five lump kinetic
model, comprising of gas (C1−C5), gasoline (IBP-150), LGO (150−350), VGO (350−500), and VR
(500+) has been developed. The variation in the kinetic parameters with change in the feed
properties has been discussed. Also, an attempt has been made to seek a relationship between
the feed properties with the kinetic rate parameters and the activation energies.
“…On the basis of the study using structural analysis of the VR and visbreakates reported by Fainberg et al 16 and conclusions of Di Carlo and Janis, 6 following mechanistic path for the components can be concluded: Thus, the yields of the various products depend on their relative proportion and the extent of their crackability. In view of the above study, the five feeds covered in the present case and the data on VB feed (taken from the work of Singh 14 ) can be divided into three major classes based on asphaltenes (As) to saturates (Sa) ratio 6 as follows: (i) paraffinic feeds, e.g., BHSR, NGSR, <0.5; (ii) intermediate asphaltenic feeds, e.g., VB Feed, AMSR (0.5-2.0); (iii) the asphaltenic feed, e.g., Haldia Asphalt and AM Asphalt (g2).…”
Section: Resultsmentioning
confidence: 88%
“…6 The lower the difference, the higher is the feed stability. Thermal cracking increases the aromaticity of the asphaltene, 16 and as the reaction proceeds, the difference between the aromaticity of the maltenes phase and the asphaltenes increases. 6 Thus, the stability reduces as the conversion increases.…”
Thermal cracking of vacuum residues and asphalts obtained from operating Indian refineries
were studied in a batch reactor. The temperature was varied in the range 400−430 °C, and the
batch time was varied from 0 to 15 min. The pressure was kept at a constant value of 1.2 MPa
through out the experiment. The variation in the composition of the cracked gas fraction for
each feed was studied by gas chromatography. The resulting visbroken products were further
characterized in terms of its different industrially important boiling cuts. A five lump kinetic
model, comprising of gas (C1−C5), gasoline (IBP-150), LGO (150−350), VGO (350−500), and VR
(500+) has been developed. The variation in the kinetic parameters with change in the feed
properties has been discussed. Also, an attempt has been made to seek a relationship between
the feed properties with the kinetic rate parameters and the activation energies.
“…The calculated cmc's increase as the length of the aliphatic chain increases. Although there is no experimental evidence of greater aggregation due to shorter aliphatic chains in the asphaltene molecules, some studies have reported a higher tendency toward flocculation for the asphaltenes with shorter aliphatic chains. − In other words, the asphaltenes with the shorter aliphatic chains flocculate first. 8 (a) Predicted apparent molecular weight as a function of the concentration and (b) predicted cmc values for the series N4C j in benzene at 25 °C.…”
The aggregation behavior of asphaltenes in apolar solvents is studied using a molecular thermodynamic
approach. The theory is based on a molecular model for asphaltene aggregates that describes them as
aromatic cores, composed of stacked aromatic sheets, surrounded by aliphatic chains. Using this simple
molecular model, an analytical expression is developed for the free energy of aggregation that incorporates
five contributions due to (1) transfer of the polyaromatic rings from the solvent into the aromatic core, (2)
mixing of the aliphatic chains with the solvent, (3) deformation of the aliphatic chains, (4) steric repulsion
among the aliphatic chains, and (5) aggregate core−solvent interactions. The proposed approach provides
a qualitative description of the main experimental trends observed for asphaltene aggregation. Specifically,
the experimentally observed variation of cmc values and aggregate size with (1) asphaltene molecular
characteristics, (2) asphaltene concentration, (3) solvent composition, and (4) temperature has been
qualitatively reproduced by the theory. In addition, the thermodynamic molecular model developed does
not utilize any information derived from experiments on asphaltene solutions, and therefore, it is strictly
predictive.
“…For two of the samples, , short residues from Safaniya and from a Heavy Venezuelan crude oil, the theoretical solubility distributions for asphaltenes and resins were used to calculate the compatibility. For the third sample, a short residue from a mix of heavy crude oils, the intersection area between asphaltene distribution and total aromatics distribution, was considered as an index of compatibility of the sample.…”
A theoretical method to calculate solubility parameter distributions was used to study the main factors that affect the stability of residues and products of their visbreaking with respect to asphaltene deposition. With this method it was possible to analyze the changes observed on the solubility parameter distributions of asphaltenes due to visbreaking. The results obtained showed a decrease in easily soluble asphaltenes, while there is an increase in difficult-to-dissolve asphaltenes during processing. To evaluate the instability, a compatibility index between asphaltenes and resins/or aromatics is proposed using the theoretical solubility profiles. By use of this index, it was possible to identify the factors involved in instability and to establish their relative importance for each sample. Among all the factors studied, the characteristics of the asphaltene fraction seem to be the main one. For the group of fractions examined, it was found that the average solubility parameter calculated was directly proportional to the H/C atomic ratio.
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