Low-grade natural iron ore, limonite, is proposed as an inexpensive catalyst to increase the light liquid production from coal pyrolysis. Experiments were conducted at a pyrolyzer combined with gas chromatography/mass spectrometry (Py–GC/MS). It is found that limonite favors the formation of light aromatic hydrocarbons, while the aliphatics and oxygenated compounds in tar are significantly reduced. Tests with model compounds (C19 alkane and o-cresol) indicate that the increased light aromatics could result from the conversions of either oxygenated compounds or aliphatics promoted by limonite. Gaseous products are determined with online gas chromatography (GC). A strong correlation between COx and light aromatics is revealed in the catalytic pyrolysis process, indicating that COx could be seen as an index of light aromatic formation. There is a maximum value for the yield of liquids when the temperature is increased, which is quite different from the tests without limonite. It is postulated that pyrolytic ...