Fuel, Vol.210, 290-297, 2017
Comparison of three methods for extracting Liuhuanggou bituminous coal
Microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), and ultrasonic/microwave-assisted extraction (UMAE) were separately conducted on the extraction of Liuhuanggou bituminous coal (LBC) sequentially using petroleum ether, carbon disulfide (CDS), methanol, and isometric CDS/acetone mixture as solvents to afford extracts 1-4 (E-1-E-4) from MAE (E-M1-E-M4), UAE (E-U1-E-U4), and UMAE (E-UM1-E-UM4). The highest total extract yield of 10.6 wt% was obtained by UMAE, while MAE is the most effective for extracting highly condensed arenes from LBC. The carbon types in LBC mainly consist of aliphatic (22.2%) and aromatic (73.7%) carbons. Each aromatic cluster of LBC contains 2 or 3 aromatic rings on average. The molecular masses of E-U3, E-U4, E-M3, and E-M4 range from 200 to 1500 u, while those in E-UM3 and E-UM4 distribute from 100 to 900 u. E-UM2 is a promising feedstock to produce advanced aromatic polymers and E-UM3 could be converted to clean light oil by catalytic hydroconversion after removing heteroatom-containing species (HACSs). MAE and UMAE are ideal tools to obtain value-added chemicals for their high selectivity of extracting HACSs.
Keywords:Microwave-assisted extraction;Ultrasonic-assisted extraction;Ultrasonic/microwave-assisted extraction;Sequential extraction