Transformation of Sulfur Compounds in the Hydrotreatment of Supercritical Fluid Extraction Subfractions of Saudi Arabia Atmospheric Residua

Abstract

Atmospheric residue from Saudi Arabia (SZAR) was subjected to supercritical fluid extraction fractionation (SFEF) experiments. Four extractable subfractions (SFEF 1−4) and an unextractable end-cut were obtained. SFEF 1−4 were subjected to a hydrotreating (HDT) test in a mini-tubular reactor packed with commercial hydrodemetallization (HDM) and hydrodesulfurization (HDS) catalysts in order to determine the structural composition transformation of sulfur-containing compounds. Experiments were undertaken at a temperature of 360°C, a hydrogen pressure of 14.7 MPa, a liquid hour space velocity (LHSV) of 0.25 h −1 , and a H 2 /feed ratio of 650:1 (m 3 /m 3 ). The SFEF subfractions and their products were subjected to analysis of their sulfur and nitrogen contents, using an ANTEK 7000S analyzer, and their saturates, aromatics, resins, and asphaltenes (SARA) compositions were analyzed using open column liquid chromatography. The detailed molecular composition of sulfur heteroatom species was determined by methylation, followed by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). In ESI FT-ICR analysis, the sulfur-containing compounds were characterized in terms of class, type (double bond equivalence, DBE), carbon number distribution, and relative abundance. According to the different number of sulfur atoms, sulfur-containing compounds can be divided into S 1 and S 2 class species. The results show that, depending on different transformation mechanisms, S 1 class species, which have less-aromatic cores, are easy to convert, no matter the side chain length. In addition, S 2 class species with less-aromatic cores and/or less carbon numbers have better hydrogenation reactivities. Meanwhile, S 2 class species with long and/or complex chains would be easy to cleavage into small ones under the reaction conditions. Compare to S 1 class species, S 2 species are more active. The potential transformation of sulfur compounds in HDT of subfractions of atmospheric residua were inferred from the DBE distribution and carbon number data by involving SFEF, methylation followed by FT-ICR MS for sulfur species of SFEF subfractions and their HDT products. The results may help understanding of the heavy oil sulfur removal sequence and catalyst/ process optimization for heavy oil desulfurization and thereby assist the efficient production of clean transporation fuels.

Low-Level Fusion of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Data Sets for the Characterization of Nitrogen and Sulfur Compounds in Vacuum Gas Oils

“…To get access to these compositions, ultrahigh-resolution mass spectrometry such as Fourier transform ion cyclotron resonance mass spectrometry (noted FT-ICR MS) has been shown to be a very helpful tool providing fast and accurate chemical fingerprinting of heteroatomic compounds contained in crude oils. − Especially, the distributions of heteroatoms, rings, and double bonds can be obtained with this technique. Electrospray ionization (ESI) source is used for the characterization of basic and neutral nitrogen compounds as it is particularly useful for the analysis of polar compounds .…”

Simple Methods for the Separation of Various Subfractions from Coal and Petroleum Asphaltenes

“…Extraction of asphaltenes and their components by supercritical fluids of solvents is represented by a wide range of these solvents. There are works describing processes with supercritical fluid extraction, where asphaltene molecules were treated with supercritical solvents such as carbon dioxide, water, toluene, pentane, benzene, propane, various alcohols, , and mixed compositions . But those are just a small part of the articles in this research area.…”

Application of Laser-Desorption Silver-Ionization Ultrahigh-Resolution Mass Spectrometry for Analysis of Petroleum Samples Subjected to Hydrotreating

“…For characterizing sulfur-containing compounds in petroleum, there are a number of reports regarding the use of UHR-MS along with diverse ionization methods − and chemical reactions. − Laser-desorption ionization (LDI) is an efficient ionization technique that can be coupled with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) for analysis of crude oil at the molecular level, − and cationization with a metal like silver (Ag) is useful for enhancing the specificity of particular compounds by generating silver adduct ions. The potential use of Ag ionization in combination with high-resolution mass spectrometry has been observed in the analysis of polyaromatic hydrocarbons (HCs), aromatic compounds containing long alkyl substituents in heavy petroleum fractions, biologically relevant alkenes, and isomeric flavonoids .…”