(586c) Characterization and Kinetic Study of Fast Pyrolysis and Torrefaction Products From Woody Feedstocks Using Direct Py-GC/MS

Pyrolysis and torrefaction are complex thermal degradation pathways that can produce valuable biofuels products – pyrolysis for bio-oils and torrefaction for bio-coals.  Due to the complexity of these processes, decomposition mechanisms and product formations can vary based on the starting feedstock.  Yet, detailed mechanistic understanding of the native material degradation is essential for process/product formation control.  Current kinetic models and speciation as based around global phenomenological and empirical models, with little to no direct relation to actual decomposition mechanisms.  This presentation will present chemical speciation and models based on the product identification that provides new insights for model development.  Product speciation includes major gaseous and vapor products formed during both torrefaction (200-300˚C) and pyrolysis (500-700˚C).  The preliminary models are formed around observed products/product formation rates during torrefaction at fast heating rate (1000˚C/s).  The models were developed around temporal histories of two primary observed product groups during torrefaction: (1) CO, CO₂, H₂O and (2) organic acids (acetic acid, formic acid).  Group 1 products are likely formed through dehydration and deoxygenation reactions, followed by Group 2 formation through ring scission reactions, depolymerization, and other complex hemicelluloses degradation reactions.  The direct observation of these chemical groups leads to the proposed degradation mechanisms, and kinetic parameters.  This work was accomplished with the use of a Pyroprobe 5200 micropyrolysis reactor (CDS Analytical, Inc.) in-line with a Trace Gas Chromatograph Ultra (Restek Rxi-5ms capillary column) and Trace DSQ II Mass Spectrometer (Thermo-Fisher Scientific).