Abstract: Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques have been applied to investigate thermal degradation characteristics of tobacco stems (TS) and the structure of its charcoal at different carbonization temperatures, respectively. The effect of carbonization temperature on the structure of the tobacco stems-based charcoal (TSC) and carbonization mechanism of TS were discussed. Based on the results of TGA and XRD, a simple model of TS carbonization was derived. Experimental results show that weight loss during heating of dried TS in N₂ atmosphere starts below 433 K and is almost terminated at 943 K, and the maximum decomposition rate in the temperature range 470-660 K could be determined by differential thermogravimetric (DTG) curve, and almost 72.85% of the total weight loss occurs in 298-1 273 K. The XRD patterns of TSCs showed three broad peaks (002), (100) and (110),which are typical of turbostratic layering and non-graphitic carbon. With increasing of carbonization temperature, the interlayer spacing of aromatic layers (d₀₀₂) is decreasing, and the crystallite sizes L_c and L_a are changing in the ranges of 0.66-1.24 nm and 2.64-4.26 nm, respectively, which implied that there are about 2-4 graphene layers along c-axis and 10-18 aromatic rings along a-axis in crystallite of TSCs.

Key words: tobacco stems, thermogravimetric analysis, X-ray diffraction, carbonization mechanism