Changes in asphaltene surface topography with thermal treatment

Determination of asphaltene structural parameters by Raman spectroscopy

“…The figure clearly shows that the best results, in terms of L a size and expected trend, were obtained when Tuinstra and Koenig's equation was used with integrated area (TK-A). The results of TK-A are in agreement with the L a values reported in the literature [12,19,22,48] and also follow the expected trend with thermal cracking, where the size of L a is expected to slightly decrease as the thermal cracking severity increases. Such trend was not observed for the equations proposed by Mallet-Ladeira et al [45] and Maslova et al, [49] where the aromatic sheet diameter tends to increase with thermal cracking severity.…”

“…The results obtained from the intensity ratio (i.e., TK-I) give fairly comparable results with the other equations proposed by Cançado et al, [42] Mallet-Ladeira et al, [45] and Maslova et al [49] However, the sizes of L a from these equations are relatively higher than those reported in the literature for asphaltene, [46][47][48] as well as those measured by XRD and TEM for asphaltene from similar origin. [19,22] On the other hand, the L a sizes obtained from Tuinstra and Koenig's equation but with peak integrated area (i.e., TK-A) happened to be more comparable with those reported in literature (i.e., $0.8-2.2 nm) and with those measured by different techniques for similar asphaltene ($0.7-1.2 nm). Table 1 also indicates that the equations proposed by Maslova et al [49] and Mallet-Ladeira et al [45] are very sensitive to the number of peaks used in spectra fitting, and these equations tend to oversize L a with the rise in the number of peaks.…”

“…The vulnerability of LF asphaltene toward thermal cracking was reported and thoroughly explained in previous studies, inferring that LF asphaltene has different structure and different reactivity than asphaltenes from RB and EC. [ 18–23 ]…”

“…[19] The observed reduction in the cluster diameter and the number of aromatic sheets per stack with thermal treatment were also reported and thoroughly explained in our previous studies. [19][20][21][22] The slight variation between the different correlations and the different analytical techniques (i.e., Raman and XRD) in Figure 6 is expected and within an acceptable range. Based on these findings, it can be concluded that the methods proposed in the literature for determining the number of layers in crystalline carbon materials from Raman spectra could also be used for asphaltene but only when the first-order region were to be fitted with two peaks (G band and the D band).…”

“…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.…”