Fractionation and characterization of thermal extracts from lignite under ultrasonic-assisted extraction

Abstract Hypercoal (HPC) is promising feedstock for producing coal-based chemicals due to its extremely low ash content and high reactivity. However, the conventional methods for HPC preparation through thermal extraction under mechanical stirring are difficult to scale-up due to the low HPC yield and large consumption of solvent. This work conducted ultrasonic-assisted extraction (UAE) instead of mechanical stirring to enhance the efficiency of HPC production, and the effect of technological conditions on the HPC yield were examined. It was found that the UAE could remarkably enhance the HPC yield from 52.3% to 82.4%. Moreover, the ratio of soluble (HPC-S) to deposit (HPC-D) increased from 1.65 to 2.85, verifying the high efficiency and the capacity of altering the product distribution of UAE.