## 4 Discussion  
The proper characterization of petroleum oils is important not only for distillation column design but also for correct evaluation of the existent separation equipment performance [26; 27; 28]. [PERSON] [25] states that an ASTM D 1160 apparatus can be used to extend the crude TBP data. He pointed out that the ASTM D 1160 distillation better approximates a TBP distillation because it is carried out under vacuum; can distill heavier materials than a TBP; much simpler to run than TBP; and it is the best test for refinery vacuum distillation unit calculations [25]. [PERSON] considers the gas chromatographic simulated distillation method to be an unreliable method for conversion to TBP curve, and due to the fact that it derives the boiling data by using standard mixtures of n-paraffins, it is deemed to report inaccurate results for streams with significant aromatic content [25]. [PERSON] et al. [26; 27; 28], however, argue that the use of the ASTM D 1160 method is worse than employing inaccurate TBP data in the design process of a vacuum distillation column. They conclude that few designers know the proper feed characterization techniques, including the use of a modern ASTM D 7169 chromatographic method. [PERSON] et al. summarize that more than 50 vacuum distillation units have been field tested to confirm the validity of using ASTM D 7169 as a TBP curve to model crude and vacuum distillation unit operation [35]. While [PERSON] [25] seems to prefer using ASTM D 1160 for heavy oil characterization, [PERSON] et al. [26; 27; 28] categorically deny ASTM D 1160, and strongly recommend the use of ASTM D 7169 for characterization of heavy oils. The data shown in Figure 5 appear similar to the comparison of distillation curves of the ASTM D 86 and the simulated distillation (ASTM D 2887) reported by [PERSON] [30]. The data in Figure 5 also look similar to the ASTM D 86 and TBP curves reported by [PERSON] [30] Both the TBP and simulation distillation curves lie below the ASTM D 86 and the ASTM D 1160 curves for evaporation lower than 50% and lie above these curves for evaporation higher than 50%. [PERSON] [30] argues that the ASTM D 86 distillation data do not represent actual boiling point of components in a petroleum fraction, while the TBP, due to the high degree of fractionation, gives accurate component distribution for mixtures. [PERSON] also concludes that ASTM D 1160 distillation data is measured more accurately than ASTM D 86 since it is conducted at low pressure [34]. For this reason, ASTM D 1160 curves are closer to TBP curves at the same pressure base. Nevertheless, the similar appearance of the difference in the distillation curves between TBP and ASTM D 86 and that observed in the data of Figure 5 for ASTM D 7169 and ASTM D 1160 may suggest that ASTM D 7169 could be closer to TBP than the ASTM D 1160. Moreover, in our earlier research [24], we proved that the simulated distillation method ASTM D 2887 is equivalent to TBP, even for high aromatic oils like the fluid catalytic cracking light and heavy gas oils. All these findings suggest that the gas chromatographic HTSD (ASTM D 7169) should be closer to the TBP than the physical vacuum distillation method ASTM D 1160, and therefore, it should better characterize the heavy petroleum fractions. The data in Table 2 show that the LNB FCC feed hydrotreating section operated at the same conditions in the hydrotreating reaction section (the same reaction temperature = 357 \({}^{\circ}\)C; the same feed rate = 160 t/h; and the same reaction pressure = 41 bar (g)) for both studied cases. Considering the same quality of the feed for the LNB FCC feed hydrotreating section (see the data in Table S5), one can expect the same vacuum gas oil conversion to take place in the hydrotreating reaction section, and thus, the same amount of generated diesel fraction in this section for both studied cases.