Comments on "Li, W., Song, Y., Yang, W.-B., Mathews, J.P., 2022. Structural transformations for a subbituminous coal, impact of temperature on gold-tube pyrolysis chars evaluated using HRTEM. Fuel 311, art. no. 122581.".

The manuscript under discussion is problematical owing to conflicting and contradictory coal rank indicators listed in the Methods section and in the title and text. The subbituminous rank as per the title does not match the high volatile A bituminous volatile matter or the Rock-Eval T max or the medium to low volatile bituminous vitrinite maximum reflectance. Further, the volatile matter and the Rock-Eval T max do not match the vitrinite maximum reflectance. Since the coal is said to have thermoplastic properties, the proper delineation of a subbituminous versus bituminous, i.e., non-caking versus caking coals, coal rank is critical for the proper interpretation of the results. [ABSTRACT FROM AUTHOR]