Steam gasification of chars of ash-free coals extracted using 1-methylnaphthalene and N-methyl-2-pyrrolidone

Abstract Coal that contains >70 wt% carbon is possibly an economical option as fuel for highly efficient power generation system such as catalytic coal gasification and direct carbon fuel cell, when mineral ashes in coal are removed. In this work, ash-free coals (AFs) are prepared via thermal extraction of carbonaceous components in parent raw coal (PA) and chars of AFs are made by pyrolysis at 300–900 °C. Then, those are characterized concerning the compositional change associated with the extraction and carbonization condition, based on the steam gasification behavior. The composition of AF chars changes depending on the polarity of the extraction solvent. Chars of AF extracted using a polar solvent (N-Methyl-2-Pyrrolidone) show much higher gasification rate than that using a non-polar solvent (1-methylnaphthalene). The addition of K2CO3 catalyst to the AF chars improves the conversion rate significantly, showing that AFs can be a feedstock of the catalytic coal gasification. The effect of the pyrolysis temperature on the reactivity varies between the AFs, implying the difference in the aromaticity and the chemical composition. The property of the AF chars that can be somewhat adjusted by the extraction and pyrolysis condition possibly provides a custom-made product for a particular application including a precursor of the functional carbon materials.