Soaking aqueous ammonia (SAA) pretreatment of corn stover was carried out at three temperatures (30, 50, and 70 ºC) and three concentrations of ammonia solution (5, 15, and 25 wt.%). The delignification kinetic model, based on three first-order reactions, was applied to describe the kinetic behavior of lignin removal from corn stover during SAA pretreatment. The first, second, and third terms were based on the initial, bulk, and residual phases of delignification, respectively. The results showed that the model fitted well with the data obtained from the experiments. The activation energies for the delignification reactions were estimated as 61.05 and 59.46 kJ/mol in the bulk and residual phases, respectively. Delignification selectivity increased with increasing reaction temperature.
The pyrolysis characteristic of bituminous coal (BC) and raw cornstalk (RC) were investigated through thermogravimetric analysis from environment temperature to 900 °C with 5, 15 and 25 °C/min. The distributed activation energy model (DAEM) was applied to estimate the kinetic parameters of samples. The average activation energy (E
a) of BC, RC and the blended sample (mBC/mRC=6/4) were 304.56, 207.77 and 226.26 kJ/mol, respectively. The heat energies of the experiment to be needed was lower than that of calculation during co-pyrolysis, comparing with the theoretical calculation E
a. To further researcher the thermal behavior during co-pyrolysis, the closeness of change in Enthalpy (ΔH) values vs. E
a values for the blend indicated that activated complex formation may be favored because of lower potential energy barrier. Moreover, Gibbs free energy (ΔG) for the blend varied from 108.40 to 275.93 kJ/mol, the pyrolysis process was converted to disordered-state from ordered-state, considering the changes of Entropies (ΔS) loss.
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