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Shanxi Institute of Coal Chemistry: New progress achieved in the advanced utilization of coal liquefaction residues Author/Source: Modern Coal Chemical Engineering Date: 2020-04-02 Clicks: 51 The advanced utilization of coal liquefaction residues, which are the main by-products of the coal liquefaction process, has a significant impact on the resource efficiency and economic viability of this process; it represents an important aspect in improving coal direct liquefaction technology. The typical composition of coal liquefaction residues includes: heavy oil, aromatics, proto-aromatics, and **furan-insoluble substances (including unreacted coal and minerals). Both asphaltene and proto-asphaltene molecules are primarily composed of carbon atoms. Their basic structural units consist of condensed aromatic rings as the core, with various alkyl side chains or cycloalkane rings attached to these rings; they have a high degree of aromaticity and high carbon content, tend to polymerize or cross-link, and are thus suitable as precursors for the preparation of carbon materials. Recently, the team led by Researcher Song Yan from the Shanxi Coal Chemistry Research Institute used aromatic hydrocarbons or pre-aromatic hydrocarbons present in coal liquefaction residues as carbon sources. Through electrospinning combined with non-fusing and carbonization treatments, flexible porous nanocarbon fiber non-wovens were successfully produced. Methods such as pretreatment with nitric acid combined with air-based non-fusing processes, as well as the addition of benzoic acid to the spinning solution, were employed to effectively prevent fiber fusion during the non-fusing process. It elucidated the evolution patterns of the structure and morphology of the products obtained through processes such as electrospinning, non-fusing, and carbonization, and explored the applications of this non-woven fabric in novel electrochemical energy storage devices such as supercapacitors, lithium-ion batteries, and potassium-ion batteries (ACS Sustainable Chem Eng, 2019, 7 (6): 5742-5750) ； Energy Fuels, 2020, 34 (2): 2445-2451; patent application numbers: 201711362163.4, 201810491436.3, 201810641716.8, 201810641705.X, and 201811315964.X). Since 2011, this team has been working on the preparation and structural modification of flexible nanocarbon fiber nonwovens. Using thermosetting phenolic resin as the carbon source and polyvinyl alcohol as a spinning aid, they successfully produced porous nanocarbon fiber nonwovens through electrospinning, curing, and carbonization processes (Mater Lett, 2012, 76: 211-214) ； Patent authorization numbers: CN201110319102.6 and CN201110319111.5). The specific surface area and pore structure of nanocarbon fiber nonwovens were regulated by adding pore-forming agents to the spinning solution or through subsequent activation treatments, resulting in the preparation of nanocarbon fiber nonwovens rich in micropores or mesopores, which improved their electrochemical properties to a certain extent (Carbon, 2013, 51: 290-300, Chem Eng J, 2014, 249: 216-225, J Electrochem Soc, 2014, 161 (9): A1330-A1337, RSC Adv, 2015, 5 (51): 40884-40891, New Carbon Materials, 2012, 27(2): 129-134). By using nitrogen-rich precursors as a carbon source or ammonia for post-treatment, nitrogen-containing functional groups were introduced into the fabricated flexible nanocarbon fiber nonwovens, thereby improving their electrochemical properties (Int J Electrochem Sci, 2012, 7: 7587 – 7599; J Colloid Interface Sci, 2013, 395: 217-223; Electrochim Acta, 2015, 185: 40-51; New Carbon Materials, 2015, 30(4): 295-301). By adding graphene oxide to the spinning solution, nanocarbon fiber nonwovens with a graphitized structure were prepared, thereby improving their electrochemical properties (Electrochim Acta, 2017, 247: 1060-1071). Furthermore, composite electrode materials with high specific capacity and long cycle life were prepared by introducing metal oxides or metal sulfides with high theoretical specific volumes. When used as a cathode material for supercapacitors, it exhibits a specific capacity of up to 1088.5 F g-1 at a current density of 1 A g-1; even when the current density is increased to 20 A g-1, it still retains a capacity of 860.3 F g-1. When used as a negative electrode material for lithium-ion batteries, it still exhibits good performance (Appl Surf Sci, 2018, 434: 49-56; Appl Surf Sci, 2019, 465: 635-642). The above work was completed with the support of projects such as the National Natural Science Foundation, the Shanxi Provincial Natural Science Foundation, the Shanxi Provincial Key R&D Program, and the Outstanding Young Talent Fund of the Shanxi Institute of Coal Chemistry.