1. Ion Exchange for the Production of Cellulosic Ethanol A.Hammervold, C. Cochran, J. Belsher, K. Childress Sponsored by Trillium FiberFuels, Inc. IntroductionProject Focus Pretreatment Fermentation  Cellulosic ethanol is ethanol derived from straw and wood biomass Breakdown into simple sugars 1.Mechanical Breakdown 2.Steam Explosion 3.Strong Acid Treatment 4.Strong Base Treatment 1.Enzymatic Breakdown 1.Yeast Fermentation  The production of cellulosic ethanol requires less energy than starch based ethanol Production Wood Structure Trillium FiberFuels, Inc. Process  Lignin physically inhibits enzyme access to sugar polymers  Traditionally, cellulosic ethanol production is focused on the breakdown of cellulose to glucose  Increased demands require a more efficient means of ethanol production  Breakdown of hemicellulose to xylose could increase ethanol yields by 20-40% depending on biomass  Trillium FiberFuels is using agricultural residue (i.e. rye grass straw) as their feedstock  Biomass contains a multitude of ions such as calcium and magnesium  Xylose must be isomerized prior to fermentation  Calcium ions are known to poison the enzyme used for isomerization  Ion exchange is an effective means of Ca 2+ removal  The project focuses on the design and scale-up of two ion exchange columns Figure 1: Benchtop ion exchange column designed and built for the removal of Ca 2+ from straw hydrolysate Operating Parameters  Government grant specifies Trillium FiberFuels, Inc. to be able to process 200 L/day of straw hydrolysate  Ca 2+ must be removed to a concentration below 2.0 ppm Inlet Ca 2+ Concentration 100-500ppmPredicted Benchtop Column Diameter 0.75inchesSpecified Wet Resin Volume25mLSpecified Xylose Concentration 50-100g/LPredicted Effluent Ca 2+ Concentration< 2.0ppm ICP/API Calcium test kit Effluent pH4-7.5Vernier Probe Scale-up production 200L/dayDesired Scale-up flow10L/hrDesired Column Design  Isomerization enzyme works most efficiently at a neutral pH  Cation resin exchanges calcium and sodium ions for protons, therefore significantly decreasing the effluent pH  Anion resin is required to increase the pH to above 4.0 1.Calcium ions poison the isomerization enzyme 2.Ca 2+ exchange with H + on active sites 3.pH is significantly reduced due to addition of protons 4.Exchange capacity :1.8 eq/L 5.Regenerant: 7% HCl Cation Exchange Anion Exchange 1.Xylose isomerization requires neutral pH for highest efficiency 2.No actual ion exchange takes place – organics and acids absorb to the resin 3.Exchange capacity: 1.6 eq/L 4.Regenerant: 4% NaOH Resin Specifications Flow Rate and Breakpoint Column Design  Changing the flow rate of the feed solution alters the shape of the breakthrough curve  Two different test solutions were created: one using DI-water and one using tap water. Figure 3: ICP data shows that there is a significant difference in resin capacity between Trillium tap water and DI water. The process goal is to maintain a calcium ion concentration below 2 ppm, represented by the black line. Data also shows that the superficial velocity has a large influence over capacity. Acid Hydrolysate  Previous system modeling was done with a xylose-calcium solution Figure 4: Column design using theoretical values for resin capacities. All dimensions are in inches. The flow rate is 225 ml/min or 0.05 cm/s. Pumps will need to be rated for a 14.7 psi pressure drop. Acknowledgements  Steve Potochnik and all the others at Trillium FiberFuels, Inc.  Dr. Azizian for ICP use  Dr. Harding  Acid hydrolysate was used for a more accurate process model  Acid hydrolysate has proton concentrations that are much greater than Ca 2+ concentrations  High cation concentration pushes Ca 2+ off the resin bead, causing simultaneous treatment and regeneration  The team could not obtain a feasible column design using acid hydrolysate Theoretical Scale-Up  Team was asked to scale up for 50 L of a 400 ppm Na +, 400 ppm Ca 2+, and 400 ppm K + solution  Cation column will need to have 4.5 L of resin and the anion column will need to have 5.5 L of resin  Cation resin volume was verified by benchtop model