Reactivity and Structure Changes of Coal Tar Asphaltene during Slurry-Phase Hydrocracking

Abstract

Coal tar asphaltene (CT-asp) is one of the important heavy components of coal tar. It has significant influences on the conversion efficiency of slurry-phase hydrocracking. The reactivity and structure changes of CT-asp in a slurry-phase process were investigated. Experimental results showed that the conversion of CT-asp reached 66.5 wt % with a significant decrease of sulfur and oxygen contents as the reaction time increased. The CT-asp obtained from the hydrocracking reaction carried out for different time has been analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and 1 H/ 13 C nuclear magnetic resonance. The chemical structural analysis results confirmed that CT-asp was mainly composed of more aromatic rings with oxygen functional groups and possessed a higher aromaticity and shorter aliphatic chains after hydrocracking. Moreover, the effective cracking of carbonyl groups, pyrrolic nitrogen, and alkyl sulfides in CT-asp was found during the slurry-phase hydrocracking. It was considered that a structure with an average of two aromatic rings per aromatic sheet existed in the average molecule of CT-asp, and the aromatic sheets were condensed with each other through diphenyl-like structures or oxo-bridged linkages. In addition, a free radical reaction pathway of CT-asp in slurry-phase hydrocracking was proposed on the basis of the main detected products and the molecular structural changes.

Formation of Ni–MoS3 Hollow Material with Enhanced Activity in Slurry-phase Hydrogenation of Heavy Oil

“…The oil-soluble compound catalyst of molybdenum naphthenate and nickel naphthenate has been shown to have a high activity of hydrogenation and to inhibit the coking in slurry-phase hydrogenation reaction; − however, it could be seen from Table and Figure that the prepared Ni–MoS 3 hollow material exhibited higher activity than that of the compound catalyst of molybdenum naphthenate and nickel naphthenate with similar metal composition at a catalyst dosage of 150 μg·g –1 . In the presence of the Ni–MoS 3 hollow material, reduced coke yield and increased H 2 consumption, R c and light oil yield could be obtained.…”

Exploratory Investigation on the Slurry-Phase Hydrocracking Reaction Behavior of Coal Tar and Petroleum-Based Heavy Oil Mixed Raw Material

“…Du , found that TI in coal tar contained organic aromatic compounds and inorganic minerals and Fe in inorganic minerals and catalyst metals had a certain synergistic effect, which promotes the ability of hydrogenation and inhibiting coking of the catalyst. Du also found that the asphaltene of coal tar was mainly composed of aromatic rings with oxygen functional groups and the asphaltene after the slurry-phase hydrocracking reaction possessed higher aromaticity and shorter aliphatic chains by the effective cracking of carbonyl groups, pyrrolic nitrogen, and alkyl sulfides in the coal tar asphaltene. Considering these reaction characteristics, coal tar can mix with inferior heavy oil for the slurry-phase hydrocracking reaction, but the lack of systematic investigation in previous studies blocks further application of this mixing strategy.…”

“…43 Figure 6 also shows that the H 2 consumption and total yield of gas and light oil obtained from the CTAR reaction were higher than those from the MRAR reaction, while the coke yield was smaller, which is basically consistent with the results in the literature. 26 The reason is that the weaker colloidal stability of CTAR makes it more susceptible to the reaction than MRAR and that compared with the relatively stable MRAR asphaltene micelles, 44 coal tar has asphaltene with a higher degree of aromaticity, more heteroatoms and heterocycles, more and shorter branches, lower average relative molecular weight, and weaker association 18,30 and some TI, which can promote the hydrogenation reaction and inhibit the coke formation. 26−28 Thus, compared with petroleum-based heavy oil, coal tar asphaltene is not easy to polycondense at high temperature to produce a carbonaceous mesophase 45 and subsequently form coke.…”

Study on the Hydroconversion Law of Coal-Based Heavy Fractions with Different Catalyst Contents Based on an Improved Separation Method

“…However, existing research − has suggested that considerable heavy fractions in coal tar (e.g., asphaltene and resin) are easy to produce aggregates or trigger free radical reaction through molecular force for their highly condensed and multi heteroatom structure. As a result, heavy fractions are incompletely converted into light components in the processing process.…”