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Pyrolysis Decomposition Kinetics of Cellulose-Based Materials by Constant Heating Rate Micropyrolysis

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posted on 21.01.1997, 00:00 by John G. Reynolds, Alan K. Burnham
Fibrous, powdered fibrous, and acid-washed celluloses, newsprint, and paper dunnage were examined by Pyromat micropyrolysis to determine volatile organic compound evolution kinetic parameters. For the cellulose samples, the interpolated Tmax values (temperature of maximum evolution rate for a constant heating rate) indicate the fibrous cellulose is the least reactive. The fibrous cellulose samples have activation energies and frequency factors around 43 kcal/mol and 5 × 1012 s-1. A three-parameter nucleation kinetic model gave the best fits to the reaction profile, which is narrower than a first-order reaction. Newsprint and dunnage were also examined. The interpolated Tmax values indicate that dunnage is more reactive than the newsprint, and both are more reactive than the cellulose samples. Newsprint and paper dunnage have energy distributions that are similar but shifted from each other. Because of the diversity in chemical structure in the papers, the best fits were found using a discrete energy distribution method, which uses parallel first-order reactions. The newsprint has a principal activation energy of 43 kcal/mol and a frequency factor of 5 × 1012 s-1, consistent with cellulose being the predominant component. The dunnage has a principal activation energy of 40 kcal/mol and a frequency factor of 9 × 1011 s-1. Pyrolysis−MS measurements indicate that the difference between the total mass loss and organic evolution profiles is only a few degrees and cannot account for the 15−20 °C difference between decomposition temperatures measured by Pyromat and some TGA results in the literature.