Kinetics of isothermal and non-isothermal degradation of cellulose: model-based and model-free methods

BACKGROUND: The kinetics of the thermal decomposition of cellulosic materials is of interest from the viewpoint of flame retardancy for safety, optimization of incineration processes and reducing energy production from fossil sources and associated pollution. One essential step in these processes is the thermal degradation through mass and energy transport, which determines the rate of evolution of various types of products from cellulosic materials. RESULTS: Kinetic parameters have been detertimined using various model-based and model-free methods in the thermal degradation of cellulose up to 700 degrees C in helium atmosphere. The values of the activation energy obtained in isothermal processes and non-isothermal processes have been found to be not far from each other. From the integral method, the random nucleation (F-1)-type mechanism has been found most probable for cellulose degradation having an activation energy, E., in the range 156.5-166.5 kJ mol(-1), InA = 20-23 min(-1), for first-order reaction during its decomposition process at heating rates of 2, 5 and 10 degrees C min(-1). Based on the high correlation coefficient, many types of mechanisms seem equally good for non-isothermal degradation of cellulose. CONCLUSION: The linear correlation coefficient has a limitation for verifying the correctness of a reaction mechanism in the study of degradation kinetics. Therefore, the correctness of a mechanism should be considered on the basis of comparing the kinetic parameters obtained from isothermal as well as non-isothermal methods. (c) 2008 Society of Chemical Industry.