Molecular Transformation of Vacuum Gas Oil in Hydrodesulfurization.

A Novel Desulfurization Process for Fuel Oils Based on the Formation and Subsequent Precipitation of S-Alkylsulfonium Salts. 4. Desulfurization and Simultaneous Denitrogenation of Vacuum Gas Oil

“…This resonance agrees well with that for the S-methylsulfonium salts for benzothiophenes (BTs) and dibenzothiophenes (DBTs) 7,10,11 and also for the precipitate obtained from the light oils. 7,9 As described previously, 7 the S-methylsulfonium salts for BTs and DBTs demonstrate a distinctive resonance at 30-32 ppm in the 13 C NMR spectrum, due to the methyl carbons for S + -CH 3 . However, as shown in Figure 1b, the resonance for the methyl carbons also lies on that for the alkyl carbons on the aromatic or thiophenic ring (C alkyl ), and hence the presence of the methyl carbons can, therefore, hardly be determined by the 13 C NMR spectrum, as was the case for light oils.…”

“…7,9 As described previously, 7 the S-methylsulfonium salts for BTs and DBTs demonstrate a distinctive resonance at 30-32 ppm in the 13 C NMR spectrum, due to the methyl carbons for S + -CH 3 . However, as shown in Figure 1b, the resonance for the methyl carbons also lies on that for the alkyl carbons on the aromatic or thiophenic ring (C alkyl ), and hence the presence of the methyl carbons can, therefore, hardly be determined by the 13 C NMR spectrum, as was the case for light oils. 7 The IR spectrum for the precipitate showed a strong absorption band at 1000-1100 cm -1 , attributable to a counterion, BF 4 -.…”

“…Compared to this value, the current HDS process is reported as being able to decrease the sulfur content of VGO to 14% of the feed value at the conditions of reaction temperature of 633 K, hydrogen pressure of 8 MPa, and LHSV of 2.0 1/h. 12,13 The results, therefore, indicate the present process to be both comparatively more energy-efficient and also more effective for the desulfurization of the VGO, as compared to the HDS process. As shown in Figure 2, the decrease obtained in the residual percentage of sulfur for the VGO is lower than that for straightrun light gas oil (LGO), but higher than that for commercial light oil (CLO) and also for LCO, produced by the catalytic-cracking of VGO, with the desulfurization efficiency obtained lying in the ranking order LGO > VGO > CLO > LCO.…”

“…The desulfurization reactivity of the individual sulfur-containing compounds in the VGO was then studied, in detail, by means of FI-MS. Based on the molecular weight data obtained, the sulfur compounds in the VGO were classified into seven compound fractions, as described previously 6 and where and where the sulfur compounds, having the same number of naphthenic and aromatic rings, are involved in each U value. The relationship between the U value and the compound structure is shown in Table 2, according to Aoyagi et al 12,13 and our other previous work. 6 The distributions of the sulfur compound fraction, for each value of U, both in the feed and in the treated VGO, following desulfurization in the presence of 10-fold molar excess of AgBF 4 based on the initial sulfur content of the feed VGO, are summarized in Figure 3, together with the residual percentage obtained for each sulfur compound fraction.…”

“…7 This is because the VGO contains sulfur and nitrogen compounds of rather higher molecular weight, and hence a higher carbon mass, than those present in the light oils. 6 The 1 H and 13 C NMR spectra, for the precipitate obtained from the VGO, are shown in Figure 1. The 1 H NMR spectrum shows a strong resonance at 3.0-3.4 ppm, owing to methyl protons for S + -CH 3 .…”