Low-rank coals such as lignite and sub-bituminous coal have high oxygen content,volatile matter and reactivity,and aresuitable for using in the preparation of high value-added oxygenated chemicals such as phenols,esters and ketones,thus realizing the high-efficiency and low-carbon utilization of low-rank coals. Thermal extraction is the key method for the selective separation of phenols,estersand ketones from low-rank coals under mild conditions. The thermal extraction process involves the breaking and reforming of chemicalbonds. Research progress on thermal extraction to separate phenols,esters and ketones in low-rank coals was summarized in terms of thestructures and types of low-rank coal,solvent types,extraction temperatures and extraction methods. The mechanisms of selective thermalextraction of phenols,esters and ketones in low-rank coals by different solvents were summed up. The current status of the application ofdifferent analytical methods were also illustrated. Structural models of low-rank coals have not been unified,while the widely acceptedhost-guest model suggests that separation of oxygenated structures can be achieved by directed interruption of covalent and non-covalentbonds among coal molecules. The type and number of chemical bonds among coal molecules and the lithotype of coal are different fordifferent degree of coalification,thus the organic matter extracted from different types of low rank coals varies considerably. Comparedwith high-boiling solvents,low-boiling solvents are more suitable for selective thermal extraction of low-rank coals because of theirsuitable extraction yield and easy separation from thermal extraction products; however,conventional solvents exhibit a limited range ofproperties for thermal extraction. The design of ionic liquids with suitable extraction yield (≤30%) and high selectivity for oxygenated functional groups is the future development direction. In addition,analytical methods such as precision instrumentation and pre-treatment of thermal extraction products are useful for a full understanding of the thermal extraction process,however,it is necessary tointroduce more advanced analytical methods and establish cost-effective purification methods in view of the complexity of thecomposition of thermal extraction products. For practical industrial applications,advanced processes and equipment need to be developedand evaluated for techno-economics.

梁鹏(1976—),男,山西长治人,教授,博士生导师。E-mail:liangpeng202@hotmail.com

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LIANG Peng,HAO Meilu,QIN Xizhuang. Research progress on selective thermal extraction and product analysis of low-rank coal[J].Clean Coal Technology,2025,31(2):165−177.