(529b) Spatio-Temporal Carbohydrate Characterization of Wood Particles During Fast Pyrolysis

Fast pyrolysis provides an inexpensive chemical process for converting lignocellulosic biomass including wood fibers and grasses to a liquid intermediate called bio-oil which can be transported and upgraded to chemicals and fuels.  The complexity of fast pyrolysis arises from the feedstock which is comprised of several biopolymers (cellulose, hemicellulose, and lignin) integrated within a cellular microstructure.  During rapid heating, cellulose and biopolymers rapidly degrade to a mixture of short-chain oligomers and eventually volatile components and aerosols which are collected as bio-oil [1,2,3].  When wood fibers are heated in pyrolysis, heat and mass transfer limitations within the cellular lignocellulosic structure produce dramatic temperature gradients, which ultimately dictate the local reaction conditions and the distribution of pyrolysis products.  The complexity of characterizing the reacting particle chemistry and transport phenomena requires a large number of kinetic parameters and has been identified as one of the major fundamental challenges in research of fast pyrolysis of biomass [4].

In this work, we aim to improve reaction-transport pyrolysis models of reacting woody biomass by demonstrating a new experimental technique that characterizes the composition of woody biomass as it pyrolyzes to bio-oil.  Using diffuse reflectance spectroscopy, the carbohydrate composition of Yellow Poplar (Liriodendron tulipifera) is characterized in position and time through a particle exhibiting heat transfer dominant in only one spatial dimension.  Compositional profiles exhibit a propagating reaction front consistent with heat-transfer limited (high Bi) pyrolysis conditions.  A range of reaction conditions are examined, and the resulting data are described using a one-dimensional reaction-transport model using existing lumped-kinetic reaction chemistry.  Sensitivity analysis of the resulting model and comparison of the prediction with experimental spatio-temporal compositional data allows for robust characterization of wood fiber pyrolysis.

References

[1] M.S. Mettler, D.G. Vlachos, P.J. Dauenhauer, Energy & Environmental Science 2012, 5, 7797-7809.

[2] V. Agarwal, P.J. Dauenhauer, G.W. Huber, S.M. Auerbach, Journal of the American Chemical Society 2012, 134(36), 14958-14972.

[3] A.R. Teixeira, K.G. Mooney, J.S. Kruger, C.L. Williams, W.J. Suszynski, L.D. Schmidt, D.P. Schmidt, P.J. Dauenhauer, Energy & Environmental Science 2011, 4, 4306.

[4] M.S. Mettler, D.G. Vlachos, P.J. Dauenhauer, Energy & Environmental Science 2012, 5, 7797-7809.