Solvent Extraction of Bituminous Coals Using Light Cycle Oil: Characterization of Diaromatic Products in Liquids

Abstract

Many studies of the pyrolytic degradation of coal-derived and petroleum-derived aviation fuels have demonstrated that the coal-derived fuels show better thermal stability, both with respect to deposition of carbonaceous solids and cracking to gases. Much previous work at our institute has focused on the use of refined chemical oil (RCO), a distillate from the refining of coal tar, blended with light cycle oil (LCO) from catalytic cracking of vacuum gas oil. Hydroprocessing of this blend forms high concentrations of tetralin and decalin derivatives that confer particularly good thermal stability on the fuel. However, possible supply constraints for RCO make it important to consider alternative ways to produce an "RCO-like" product from coal in an inexpensive process. This study shows the results of coal extraction using LCO as a solvent. At 350 °C at a solvent-to-coal ratio of 10:1, the conversions were 30-50 wt % and extract yields 28-40 wt % when testing five different coals. When using lower LCO/coal ratios, conversions and extract yields were much smaller; lower LCO/coal ratios also caused mechanical issues. LCO is thought to behave similarly to a nonpolar, non-hydrogen donor solvent, which would facilitate heat-induced structural relaxation of the coal followed by solubilization. The main components contributed from the coal to the extract when using Pittsburgh coal are di-and triaromatic compounds.

Interactions of Illinois No. 6 Bituminous Coal with Solvents: A Review of Solvent Swelling and Extraction Literature

“…However, more recent results 57, 58, 60, 62, 63 using a flow reactor and/or hot filtration, thermal solvent extraction rose from 51.2 to 74.6 wt.% depending on solvent; these results met the expectation of >50% conversion, and by using a petroleum-generated solvent, the expensive solvent separation may not be required. 62,63 Researchers suggest that bond breaking is not taking place at 633K, but that the coal structure is "relaxing" with higher temperatures to release trapped molecules. 58,60 The contribution of bond cleavage to enhanced extraction yields at temperatures above 350 ˚C is not entirely clear.…”

“…Griffith et al worked to reduce the solvent: coal ratio from 10:1 to 5:1 and 3:1, but determined coal conversion decreased and mechanical problems at the lower solvent: coal ratios. [61][62][63] Compared to other coals, Illinois No. 6 yielded higher conversions; the high fluidity in Illinois No.…”

“…69 The goal of Griffith et al was to increase the 2-and 3-ring aromatic concentration in the liquid extracts using the solvent LCO; the extract would then be hydrotreated to produce a thermally stable jet fuel similar to JP-900. 62, 63 Griffith et al characterized the extracts from one of the coals reacted -the extract from Pittsburgh coal after reaction in LCO at 350°C for 60 min. The main result was that the coal contributed additional 2-and 3-ring aromatics to the product, with coal conversions ranging from 20-73% depending on the conditions used ( Table 7).…”

Thermoplasticity and strength improvement of coking coal by addition of coal extracts

“…In previous work, extractions have been performed using a flowing-solvent extractor with an aprotic solvent (light cycle oil) and in relatively high-pressure systems [8][9][10]. Instead, in this study, the extraction was performed at an applicable temperature and under normal atmospheric pressure, and this method may be workable and effective for industrial applications.…”

Analysis of Geting Bituminous Coal by Electrospray Ionization and Direct Analysis in Real Time Mass Spectrometry

“…Gasification (Zeng et al 2012), liquefaction (Inoue et al 2012), pyrolysis (Senneca et al 2011), extraction (Giray et al 2000;Griffith et al 2009;Shui, Wang, and Gao 2006), and oxidation (Yao et al 2010) of coals have been widely studied. For example, benzene polycarboxylic acids produced through the oxidation of coal were shown to be useful for synthesizing functional materials, medicine, and aircraft fuel (Yao et al 2010).…”