(678a) Understanding Diffusion and Catalyst Deactivation in the Chemical Funneling of Lignin Derived Monomers over Zeolites

Stellato, M., Georgia Institute of Technology
Bommarius, A. S., Georgia Institute of Technology
Sievers, C., Georgia Institute of Technology
Pinho Oncken, M., University of Campinas
Realff, M., Georgia Institute of Technology
To design biorefineries capable of competing with established petroleum processes for producing organic chemicals, it is imperative that the use of all fractions of the biomass feed is optimized. Cellulose and hemicellulose have been investigated for use in many chemical and biological processes to generate bio-based organic molecules. However, lignin (the aromatic polymer occupying interstitial space between cellulose fiber bundles) has historically been underutilized as a low quality fuel rather than as a potential platform for aromatic organics. This attitude towards lignin has changed in recent years and new approaches are quickly being generated to try and make effective use of this resource in addition to cellulose and hemicellulose.

For these processes to utilize the entirety of the lignin stream in as cost effective a manner as possible, close attention must be paid to catalyst design and function. Understanding precisely how these catalysts behave on stream and what properties lead to longer catalyst activity will lead us to design better catalysts and reactor systems. The focus of this talk will be on exploring the effects of lignin-based aromatics, particularly oxygen containing species such as phenols, catechols, and guaiacols, on the kinetics of alkyl side chain cracking from lignin oligomers. We show that unusually fast deactivation is caused by strongly bound oxygenates, which hinder diffusion into and out of zeolite pores. We model how these road-blocking aromatics change diffusion within the zeolites and how this impacts conversion and catalyst lifetime. Finally, we study the influence of deactivation on the distribution of model lignin depolymerization products and propose process options, which allow for consistent activity and reliable conversion of such mixtures into easily separable products. This chemical funneling will be crucial for avoiding energy intensive separation in pursuit of drop-in petroleum replacement chemicals from biorefineries.