Experimental study on microwave pyrolysis of an Indonesian low-rank coal

Microwave pyrolysis of an Indonesian lignite is investigated in this study. The effects of experimental parameters, such as microwave receptor/coal ratio, residence time, temperature, microwave power level, and coal particle size, on the yield and characteristics of coal pyrolysis products were studied systematically. Fe3O4 was used as the microwave receptor. The compositions of oil products from the microwave pyrolysis were analyzed using gas chromatography-mass spectrometry. The experimental results showed that a higher microwave power led to higher heating rates and higher volatile matter yields. The yield of gaseous and oil products increased with increasing the microwave receptor/coal ratio and microwave power. The oil products were complex mixtures of organic compounds with a variety of chemical groups. The yields of aromatic compounds, including phenol and naphthalene, increased significantly with the pyrolysis time. The oil products contained 17.27% saturated aliphatic species, while the aromatic compounds accounted for 45.5%, and polar groups formed 25.84% of pyrolysis oil. As pyrolysis proceeded, Fe3O 4 was reduced to elemental Fe at the later stages of microwave pyrolysis, as evidenced by X-ray diffraction and energy-dispersive X-ray analyses. Scanning electron microscopy analysis showed that the morphology of the microwave receptor (Fe3O4) changed as a result of reduction. © 2013 American Chemical Society