Biomass Fractionation and its Effects on Pyrolysis Chemistry

Lignocellulosic biomass is a renewable resource for the production of fuels, chemicals and other materials. An improved understanding on chemical and molecular structures of biomass during thermochemical conversion is needed to drive better efficiency. However, separation of cellulose, hemicellulose and lignin (especially lignin) from a biomass is difficult not to cause serious alterations to the original structure. Furthermore, it is obviously unreasonable to divide components based on cellulose, hemicellulose and lignin to analyze the interplay among them during pyrolysis for biomass that utilizes its volatile species. In this work a mild fractionation by successive extraction (water followed by ethanol) was performed. This was followed by on-line and off-line pyrolysis product distribution detection combining comparison of actual yields with recombined yields (by weighted calculation of fractionated components) as well as pyrolysis kinetic analysis to evaluate the synergistic effect (promotion or inhibition) caused by the interplay among the fractionated components during pyrolysis. Results indicates that polycondensation to 2,2'-methylenebis-phenol and volatilization of (S)-3-(1-methyl-2-pyrrolidinyl) pyridine seemed to be both free from the interplay among components. The generation of CO2 was inhibited and the decomposition to produce furans, phenols and toluene was promoted to different degree by the interplay among components. Pyrolysis kinetic results showed that the conversion of 40% was a dividing line, below which the activation energy of Weighted was lower than that of Raw, above which, the activation energy of Weighted surpassed Raw, indicating that the synergistic pyrolysis between the components failed to play a significant role in promoting the devolatilization or the depolymerization, dehydration, and decarboxylation of small molecules, but could significantly promote the depolymerization of macromolecules and the subsequent decomposition reactions. Such results are critical to the advancement of biofuel research, improving bioprocessing methodology, and bioengineering efforts.