(629x) Condensed-Phase Cellulose Pyrolysis

Authors: 
Mettler, M. S., Univeristy of Delaware
Dauenhauer, P. J., University of Massachusetts, Amherst


Fast pyrolysis of biomass converts solid biopolymers into a valuable liquid product (bio-oil) which can be further upgraded to fuels or chemicals. Much effort has been dedicated to developing processes and catalysts which maximize efficiency, throughput and/or bio-oil quality (e.g., [1-2]). While these efforts are important to developing thermochemical biorefineries of the future, the complex chemistry by which the biomass feedstock breaks down is still largely unknown. Global reaction kinetics for the pyrolysis of cellulose have been published (e.g., [3]), but the accuracy of these models is debated [4]. Additionally, recent work has indicated both indirectly (e.g., [5]) and directly [6] that solid biomass pyrolysis proceeds through a high temperature intermediate liquid before volatilizing into the final bio-oil constituents. In order to maximize the accuracy of pyrolysis experiments and prevent device-dependent results, it is important that mass and heat transport rates within the solid biomass and intermediate liquid be faster than the intrinsic reaction kinetics. In this work, we demonstrate an experimental technique whereby biomass pyrolysis can be studied in a kinetically-limited manner. By carefully controlling the size and shape of the biomass sample, we eliminate composition and thermal gradients. Additionally, volatiles, gases and char are characterized using multi-dimensional analytical techniques. Data from our experiments are consistent with recent results [7] that the first several cellulose oligomers (glucose, cellobiose, cellotriose, etc.) have different distributions of volatile organic products. Furthermore, we find that these oligomers differ in the fraction of the biomass which is converted to char and permanent gases. We believe that this novel experimental technique can contribute to the available experimental information on biomass pyrolysis and eventually lead to better chemical understanding and the creation of detailed kinetic models.

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