Kinetic study of sesame stalk pyrolysis by thermogravimetric analysis

Sesame stalk is a promising agricultural residue for generating renewable bioenergy, but still remains undeveloped on account of the lack of reliable pyrolysis kinetic information. The novelty of present work lies in that it gives the first thorough examination of kinetic and thermodynamic parameters for pyrolysis of sesame stalk. Non-isothermal pyrolysis experiments in N2 via thermogravimetric analysis were conducted at 5–20 K/min with temperatures programmed from 350 to 900 K. Experimental results indicate that pyrolysis of sesame stalk seems to occur in multi-stage reactions, model-free kinetic analysis methods, including differential Friedman, integral Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Vyazovkin-Dollimore methods, are isoconversionally attempted to perform kinetic analysis of two-stage sesame stalk pyrolysis, respectively resulting in the mean activation energy of 136, 125, 128 and 125 kJ/mol for stage I and 140, 146, 150 and 146 kJ/mol for stage II. The master-plots method and differential composite method are integrated for determining pyrolysis mechanism, and the Ginstling−Brounshtein model is found to be the most appropriate and verified very well by experimental results. The averaged pre-exponential factors for two stages are determined to be 2.80 × 108 and 1.04 × 109 min−1, respectively. Besides, thermodynamic parameters in terms of ΔH, ΔG and ΔS are also evaluated for the whole pyrolysis process. The findings acquired from this study suggest sesame stalk is a promising biomass for sustainable bioenergy generation and kinetic and thermodynamic information is of significance for advancing the design of a sesame stalk pyrolysis reactor.