Computational Analysis of the Pyrolysis of ..beta..-O4 Lignin Model Compounds: Concerted vs. Homolytic Fragmentation: Abstract No. ENFL-491

The thermochemical conversion of biomass to liquid transportation fuels is a very attractive technology for expanding the utilization of carbon neutral processes and reducing dependency on fossil fuel resources. As with all such emerging technologies, biomass conversion through gasification or pyrolysis has a number of obstacles that need to be overcome to make these processes cost competitivewith the refining of fossil fuels. Our current efforts have focused on the investigation of the thermochemistry of the linkages between lignin units using ab initio calculations on dimeric lignin model compounds. All calculations were carried out using M062X density functional theory at the 6-311++G(d,p) basis set. The M062X method has been shown to be consistent with the CBS-QB3 method whilebeing significantly less computationally expensive. To date we have only completed the study on the b-O4 compounds. The theoretical calculations performed in the study indicate that concerted elimination pathways dominate over bond homolysis reactions under typical pyrolysis conditions. However, this does not mean that concerted elimination will be the dominant loss process for lignin.Bimolecular radical chemistry could very well dwarf the unimolecular pathways investigated in this study. These concerted pathways tend to form stable, reasonably non-reactive products that would be more suited producing a fungible bio-oil for the production of liquid transportation fuels.