Biomass Depolymerization projects
Mesoporous Carbon Nanoparticles
This project focuses on enhancing biomass depolymerization through the use of reactive materials consisting of mesoporous carbons. Using miscanthus as a biomass source, investigators put particular emphasis on the cellulose and hemicellolose fractions of biomass while accounting for the presence of lignin. This approach leverages the reactive materials' known ability to absorb biomass and uses acid-functionalized carbons as glycosidic-bond hydrolysis catalysts, which convert cellulose to glucose in aqueous media. The project emphasizes the use of real biomass sources and practical process conditions.
Lignocellulosic biomass feedstocks typically contain 60% - 80% of cellulose and hemicellulose. Depolymerization of these carbohydrates has served as the bottleneck for biomass to fuels and chemicals transformations, and requires the hydrolysis of these carbohydrates into their monomeric sugar constituents. Our project is geared towards replicating, in a crude but practical way, the binding and catalytic domains of cellulases, using carbon materials. We demonstrated recently that mesoporous carbon nanoparticles strongly adsorb long-chain glucans and extracted xylan polysaccharides derived from Miscanthus biomass, and catalyze their depolymerization via catalytic hydrolysis. Our investigation focuses on commercial porous carbon material (MSC-30) and its post-synthetic modification. We have discovered the glucan adsorption capacity of MSC-30 has increased about 4 times higher in comparison to MCN. In addition, the catalysts are catalytically active for hydrolysis in pure water, and the glucose yield can be as high as an unprecedented 92% and above. The combination of experimental and computational studies also provides fundamental insights into the nature of adsorption of glucan oligomers in the internal porosity of carbon materials. Current research is focused on further enhancing these processes via design of carbon-based materials.
The Katz group leads in the development of mesoporous carbon nanoparticles (MCN) as materials for the adsorption and depolymerization of polysaccharides derived from biomass. Activity during the past year has been the first to demonstrate adsorption of long-chain beta-1-->4-xylan and beta-1-->4-glucan strands (i.e. more than 10 repeat units) to the interior MCN surface, despite a pore-aperture radius in the MCN that is smaller than the polysaccharide radius of gyration in aqueous solution. The group has also demonstrated the MCN-catalyzed depolymerization of long-chain xylan derived from Miscanthus into xylose, in yields exceeding 74 percent, under acetate-buffer conditions of pH 4.0. The group is also focused on leveraging these and other results for the depolymerization of polysaccharides from raw biomass using flow apparatus.
Our research group has been the first in the world to demonstrate the adsorption of long-chain biomass-derived polymer strands (i.e. glucans), within the confines of carbon mesopores that are smaller than the hydrodynamic radius of these strands. We demonstrate that the driving force for this strand unraveling and adsorption is a series of weak hydrophobic interactions between the strand and underlying carbon surface, similar to interactions previously observed in glycoproteins. This observation has significant repercussions on placing biomass-derived polymer strands into highly strained and constrained environments, which are predicted to favor their depolymerization. We have previously demonstrated the repercussions of similarly constrained environments surrounding adsorbed glucan strands, in our unique grafted glucans-on-inorganic-oxide class of materials. These glucan strands depolymerize under extraordinarily mild conditions of surface acidity and temperature. These results support current efforts, which are geared toward the discovery of mild catalytic methods for biomass depolymerization.
Hydrolysis Catalysis of Miscanthus Xylan to Xylose Using Weak-Acid Surface Sites, Po-Wen Chung, Alexandre Charmot, Olayinka A. Olatunji-Ojo, Kathleen A. Durkin, Alexander Katz, ACS Catalysis, V. 4, pp. 302-310, doi: 10.1021/cs400939p, 2014.
Glucan Adsorption on Mesoporous Carbon Nanoparticles: Effect of Chain Length and Internal Surface, Cedric Po-Wen Chung, Alexandre Charmot, Oz M. Gazit, Alexander Katz, Langmuir, doi: 10.1021/la3030364,September 28, 2012.
Dialkylimidazolium Ionic Liquids Hydrolyze Cellulose Under Mild Conditions, Oz M. Gazit, Alexander Katz, ChemSUSChem, doi: 10.1002/cssc.201100803, April 30, 2012.
Chemisorption and Dehydration of Ethanol on Silica: Effect of Temperature on Selectivity, Tatiana Luts, Alexander Katz, Topics in Catalysis, doi: 10.1007/s11244-012-9771-9, February 14, 2012.