The thermal degradation of cellulose and of different wood samples was studies by thermogravimetric analysis in a flow system, under nitrogen and air.
A model predicting the mass loss rate taking into account the various constituents of wood and for each constituent several successive or parallel reactions was established and used to interpret the experimental results obtained.
The pyrolysis of cellulose in nitrogen appears to obey a first order reaction with an activation energy of the order of 250kJ/mol. When carried out in air another reaction obeying a zero order with a similar activation energy competes with that obeying a first order.
In the case of wood we wee able to show that the maximum mass low rate corresponds to the decomposition of cellulose, the kinetic parameters used keeping the same value.
It was also established that activation energy values which erratically drift between 84 and 250 kJ/mol are due to the use of a single overall mechanism. According to heating rates lower or higher values are obtained and a more correct evaluation was obtained with the use of a finer monitoring of the thermal degradation.