Rheological Properties of Biomass Deconstruction Process Using Ionic Liquid

Lignocellulosic  biomass must be pretreated  prior to enzymatic hydrolysis to improve sugar yields and saccharification efficiency.  Ionic liquid (IL) pretreatment  has shown great potential as a novel pretreatment technology with sugar yields as high as ~100%.  However, to improve process economics, higher biomass loading is necessary.  Biomass slurry in IL are highly viscous.  To decrease production cost, the biomass slurry should be pumpable and exhibit least resistance to flow.  Here we investigate rheological properties of neat IL, biomass slurry in ionic liquid through dissolution and regeneration processes.  Complex viscosities and modulus (both elastic and viscous) measurements provide a detail insight of biomass solubilization and cellulose regeneration process and pinpoint the onset of cellulose regeneration event.  By generating small-angle oscillatory frequency sweeps of pretreated switchgrass at various increased loading percentages we can characterize the nature of the slurry where the material has strong intermolecular association.  For a viscous material such as in the 3% pretreated switchgrass sample, the viscous modulus is dominant over the elastic modulus.  Just a slight increase in percent loading makes the slurry behave like a gel like structure and the elastic modulus is dominant over the viscous modulus.  All percent loading pretreated switchgrass show frequency dependence and shear thinning behavior.