Analysis of Composition and Structure Characteristics of Heavy Hydrogenated Coal Tar and Its Subcomponents from Xinjiang, China

Low-temperature coal tar (LTCT) is the preferred raw material for the catalytic hydrogenation of coal tar. In order to study and popularize the technology of preparing fuel oil by hydrogenation of LTCT, it is necessary to research its composition and structural characteristics. Heavy hydrogenated coal tar (HHCT) from a company in Xinjiang, which is a mixture of hydrorefined tail oil distillate (>350 °C) and hydrotreated circulating tail oil (>350 °C). To make scientific and customized use of HHCT, the chemical composition and molecular structure characteristics of HHCT and its subcomponents were investigated by using elemental analysis (EA), infrared analysis (FT-IR), and nuclear magnetic resonance (1H NMR and 13C NMR) through fraction separation. Compared to other low-temperature coal tar (LTCT), the content of saturates (SA) in HHCT is 95.01 wt %, considerably higher than other LTCT samples, and the content of aromatics (AR), resins (RE), and asphaltenes (AS) is all much lower than other LTCT samples. Compared with the basic properties, elemental content, and refining performance of other crude oils, HHCT is good-quality oil with relatively small density, high H/C ratio, fewer heteroatoms, and low metal impurities, and is easy to refine and process. FT-IR and NMR results show that HHCT and SA are primarily constituted of long-chain n-alkanes possessing longer aliphatic chains and fewer branched chains. Aromatics are predominantly present in AR and mainly encompass bicyclic and tricyclic aromatics. HHCT and other fractions contain a small quantity of aromatic structures.