Microwave pyrolysis of corn cob and characteristics of the pyrolytic chars

Microwave pyrolysis is a new process for converting biomass to bio-oil, syngas, and solid char. In this study, pyrolysis of corn cob was performed in an inert environment at atmospheric pressure and temperatures ranging from 300 to 600°C. The aim of this work was to study the effect of pyrolysis conditions on the characteristics of the solid char residue. The char was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, elemental analyzer, BET surface area analysis, and inductive coupled plasma. The char yield from pyrolysis decreased significantly to 23% with an increase in temperature to 600°C. SEM analysis indicated that pyrolysis of corn cob led to a stepwise accumulation of inorganic matter onto the exposed surface, and some organic matter melted, resulting in the formation of hollow cavities by the evolving volatiles. Fourier transform infrared spectroscopy results showed a continuous decrease in the intensity of the hydroxyl group stretch with temperature and the aromatic group to be at maximum at 600°C. Elemental analysis indicated both H/C and O/C ratio decreased continuously with increasing temperature to 450°C then became constant at higher temperatures.