(587u) Mechanistic Studies On Char Formation From the Fast Pyrolysis of Lignin

Research interest in lignin conversion to liquid fuels has increased as the need for renewable fuels has become more prominent. One of the routes proposed for this transformation is through catalytic fast pyrolysis in which biomass is subjected to anaerobic thermal decomposition in the presence of a catalyst to produce bio-oil. However, one of the major drawbacks of using lignin as a feedstock is the recondensation of lignin fragments that can agglomerate to form solid char. Char represents a major problem for the viability of lignin pyrolysis processes in industrial applications as it can lead to extensive catalyst deactivation and reactor clogging. This research attempts to understand the role of hydroxyphenyl (H), guaiacyl (G), and syringyl (S) subunits in lignin and how they affect char agglomeration. Model compounds emulating H, G, and S (phenol, guaiacol, syringol) are pyrolyzed to determine the role of the methoxy functional group in the formation of char and compared to the pyrolysis of natural lignin. Py-GC/MS is used to analyze the resulting pyrolysis vapors through mass spectrometry. The resulting solid char is analyzed for characteristic functional groups using ATR FTIR spectroscopy. The chemical composition of the char is measured through CHNS/O elemental analysis to evaluate the mass balance of carbon in lignin biomass, char, and pyrolysis vapor. The comprehensive data on both the solid and vapor phase of lignin pyrolysis can suggest char formation mechanisms between monomeric lignin compounds, and it allows the evaluation of the degree of reactivity and char formation as a function of methoxy groups prevalent on a phenolic ring. The results from this project are intended to aid future biorefineries into selecting feedstocks with a range of phenolic monomer ratios that can simultaneously maximize transportation fuel production and minimize the amount of pyrolysis char generated.