Structural evolution of maize stalk/char particles during pyrolysis

The structural evolution characteristics of maize stalk/char particles during pyrolysis were investigated. The char was prepared by pyrolyzing at temperatures ranging from 200 to 900 oC. Maize stalk and chars were characterized by thermogravimetric analysis, ultimate analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), helium density measurement and N2 adsorption/desorption method. The char yield decreased rapidly with increasing temperature until 400 oC. As temperature increased, the char became progressively more aromatic and carbonaceous. The hydroxyl, aliphatic C–H, carbonyl and olefinic CC groups were lost at high temperatures. Below 500 oC, the removal of volatile matter made pore opening. High temperatures led to the occurrence of softening, melting, fusing and carbon structural ordering. The aromatization process started at ∼350 oC and continued to higher temperatures. The shrinkage of carbon structure occurred above 500 oC, which was concurrent with the aromatization process.