Recovery of Large Amount of Levoglucosan Produced by the Fast Pyrolysis of Acid Infused Biomass From the Reactor

We have previously shown that infusion of mineral acids converts alkali and alkaline earth metals in biomass into thermally-stable salts, reducing their catalytic activity during fast pyrolysis.  The suppression of metal-catalyzed ring breaking reactions allows depolymerization to dominate pyrolysis reactions, resulting in enhanced yields of levoglucosan (LG). In a bench scale fluid bed pyrolyzer, however, the large amount of LG formed by the fast pyrolysis of acid infused switchgrass at 500°C led to bed agglomeration. It was inferred that the agglomeration was caused by LG polymerization and charring taking place at about 270°C and 280°C respectively. Analytical pyrolysis studies using micropyrolyzer/GC/FID showed that temperatures between 350 and 400°C are more suitable for collecting LG from acid-infused biomass. The present work explored various techniques such as low temperature pyrolysis and higher sweep gas flow rates to improve the recovery of LG using a bench scale fluid bed and auger reactors.