Efficient Two-Step Utilization of Organic Matter in Shengli Lignite for Producing Chemicals and Supercapacitor Electrode Materials

Conversion of organic matter in lignite into chemicals and high-performance carbon materials is a promising approach for clean and efficient utilization of lignite. Herein, Shengli lignite (SL) is subjected to supercritical ethanolysis, followed by ultrasonic extraction with isometric carbon disulfide/acetone for separating SL into soluble organic matters (SOMs) and insoluble extraction residue (ER) with highly condensed aromatic structures. According to the analyses with gas chromatography/mass spectrometry (GC/MS) and Orbitrap MS, the SOMs were mainly composed of oxygen-containing compounds, such as arenols, aliphatic esters, and aromatic esters, which can be used as feedstock for producing value-added chemicals. The ER was used as a carbon precursor to produce three-dimensional porous carbon materials (PCMs) through precarbonization and activation with KOH using nano-ZnO as an in situ template. The prepared PCMs possessed high stability, large specific surface area, and abundant oxygen-doped carbon, showing a high specific capacitance of 300 F g–1 at 0.5 A g–1 in a three-electrode system, and the capacitance retention was 100% after 10,000 cycles of charge and discharge at 5 A g–1 in a two-electrode system.