Bull. Spec. CORESTA Congress, Brighton, 1998, p. 155, ST02

The effect of heating rate on the evolution of formaldehyde during cellulose pyrolysis

BANYASZ J.L.; LI S.; LYONS-HART J.
Philip Morris USA, Research Center, Richmond, VA, USA
The production of formaldehyde from the pyrolysis of cellulose has been found to be strongly dependent on heating rate. The study described here was undertaken with the objective of elucidating the mechanism of the reaction. The work was performed with a laser ablation system utilizing a 10 Watt CO2 gas laser. The evolved gases were analyzed via FTIR spectroscopy. Whatman filter paper was used as the substrate in all experiments. The laser was operated in the CW mode to achieve different heating rates by varying the on-time and the power setting. The focus was set to ablate an oval area approximately 3 x 11 mm in dimension. Real time thermal profiles were captured during ablation by use of small thermocouples placed in contact with the paper. The thermal profiles were chosen to obtain different heating rates with approximately the same end temperatures. The results showed that the formaldehyde produced was directly proportional to the initial heating rate while CO2 production and weight loss from the substrate remained constant. The laser ablation findings have been qualitatively confirmed by a rapid evolved gaz analysis (EGA) technique. The results can be accounted for by a mechanism comprised of concurrent reactions: one being the production of formaldehyde from a precursor the other a competing reaction which removes the precursor without producing formaldehyde.