Decrystallization of cellulose is necessary during thermochemical pretreatment of biomass to facilitate cost effective conversion of biomass to biofuels. Currently, most reported solvents for pretreatments that can completely decrystallize cellulose are expensive and/or difficult to recycle. Alternatively, we have found that partial decrystallization of cellulose is possible using anhydrous liquid ammonia that can enhance enzymatic hydrolysis rates by up to five-fold. Ammonia is inexpensive and readily recoverable due to its high volatility unlike other exotic solvent systems. However, effective pretreatment with anhydrous ammonia alone requires high operating pressures and temperatures. Inclusion of suitable hydrogen-bonding co-solvent species along with ammonia has been shown to remarkably facilitate complete dissolution of cellulose chains that upon precipitation with an anti-solvent results in the formation of highly amorphous cellulose. In addition, inclusion of suitable co-solvents can also reduce vapor pressure of ammonia by nearly 30-fold to greatly reduce the pretreatment severity compared to conventional ammonia based pretreatments. However, we currently have a poor understanding of the mechanism of cellulose dissolution in such ammonia based solvent systems and the role of water in the dissolution process. Here, I will discuss results from an in-situ small-angle neutron scattering (SANS) investigation of cellulose pretreatment with ammonia based solvent systems to better understand the mechanism of cellulose dissolution. The impact of this pretreatment method on enzymatic deconstruction of cellulose will be highlighted as well. Insights into the mechanism of cellulose dissolution have allowed us to develop more efficient thermochemical pretreatments that will ultimately enable production of low-cost biofuels and biochemicals.

In-situ small-angle neutron scattering investigation of cellulose dissolution

256th National Meeting (2018)

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