Investigation of Primary and Secondary Reactions during the Pyrolysis of Different Celluloses

A micropyrolyzer/GC-MS/FID system was used to investigate the primary and secondary reactions of cellulose pyrolysis when sample weight, particle size, length scale, feedstock, crystallinity, and chain length were varied. Initial work involved estimating the heating rate of the sample to reaction temperature in the system. The sample heating rate was found to be an order of magnitude lower than pyrolysis reaction time. It was also found that with larger samples mass transfer limitations existed, leading to secondary reactions including the formation of secondary char and gas, as well as the dehydration/decomposition of levoglucosan to low molecular weight products, furans, dehydrated pyranose, and char. The char from cellulose pyrolysis was found to catalyze the secondary reactions. Using a system that minimized transport limitations, celluloses of differing crystallinity, chain length, and feedstock source were pyrolyzed. Similar product distributions were found for each sample, indicating that the formation of primary products was not influenced by crystallinity, chain length, or feedstock.