Thermogravimetric kinetics of lignocellulosic biomass slow pyrolysis using distributed activation energy model, Fraser-Suzuki deconvolution, and iso-conversional method

Pyrolysis kinetics of pine wood, rice husk and bamboo (Bambusa chungii) were studied via thermo-gravimetric analysis technique under low heating rates. The result of model-free procedure showed that the lignocellulosic pyrolysis according to one-step reaction model is dominated by the diffusion effects. However, the complex features of variations are caused by the mechanism changes, which are hard to be determined. The distributed activation energy model (DAEM) kinetic results indicated that the activation energy distribution for pseudo components follows the orders of: E0(lignin) > E0(cellulose) > E0(hemicelluloses), σ(lignin) > σ(hemicelluloses) > σ(cellulose). The Fraser-Suzuki deconvolution fits better with the experimental data than DAEM. The pyrolysis mechanism of pseudo components after deconvolutions follows the theoretical models: third order model f(α) = (1 − α)3 for hemicelluloses and lignin, random scission model f(α) = 2(α1/2 − α) for cellulose. The apparent activation energy for pseudo hemicelluloses is 162.84 ± 26.45 kJ/mol for pine wood, 168.63 ± 28.47 kJ/mol for rice husk and 154.55 ± 26.49 kJ/mol for bamboo, respectively. The Eα value increases with the conversion with little deviation to its mean value. Similar Eα vs. α dependencies also are observed for pseudo celluloses, which has Eα of 188.14 ± 24.42 kJ/mol for pine wood, 206.71 ± 24.88 kJ/mol for rice husk and 190.45 ± 23.79 kJ/mol for bamboo, respectively.