Ion Exchange for the Production of Cellulosic EthanolA.Hammervold, C. Cochran, J. Belsher, K. Childress

Sponsored by Trillium FiberFuels, Inc.

Introduction Project Focus

Pretreatment Fermentation

Cellulosic ethanol is ethanol derived from straw and wood biomass

Breakdown into simple

sugars

1. Mechanical Breakdown

2. Steam Explosion3. Strong Acid

Treatment4. 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 fermentationCalcium ions are known to poison the enzyme used for isomerization

Ion exchange is an effective means of Ca2+ removal

The project focuses on the design and scale-up of two ion exchange columns

cellulase enzymecannot access

cellulose

Pre-Treatment

“lignocellulose”

lignin (25%)

cellulose (50%)(glucose polymer)

hemicellulose (25%)(xylose polymer)

cellulase enzymecan access

cellulose

Figure 1: Benchtop ion exchange column designed and built for the removal of Ca2+ from straw hydrolysate

Operating ParametersGovernment grant specifies Trillium FiberFuels, Inc. to be able to process 200 L/day of straw hydrolysate

Ca2+ must be removed to a concentration below 2.0 ppm

Inlet Ca2+ Concentration

100-500 ppm Predicted

Benchtop Column Diameter

0.75 inches Specified

Wet Resin Volume 25 mL Specified

Xylose Concentration

50-100 g/L Predicted

Effluent Ca2+ Concentration < 2.0 ppm

ICP/API Calcium test

kit

Effluent pH 4-7.5 Vernier Probe

Scale-up production

200 L/day Desired

Scale-up flow 10 L/hr Desired

Column DesignIsomerization 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. Ca2+ exchange with H+ on active sites

3. pH is significantly reduced due to addition of protons

4. Exchange capacity :1.8 eq/L5. 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/L4. 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.

AcknowledgementsSteve Potochnik and all the others at Trillium FiberFuels, Inc.

Dr. Azizian for ICP useDr. Harding

Acid hydrolysate was used for a more accurate process model

Acid hydrolysate has proton concentrations that are much greater than Ca2+ concentrations

High cation concentration pushes Ca2+ off the resin bead, causing simultaneous treatment and regeneration

The team could not obtain a feasible column design using acid hydrolysate

Theoretical Scale-UpTeam was asked to scale up for 50 L of a 400 ppm Na+, 400 ppm Ca2+, and 400 ppm K+ solutionCation column will need to have 4.5 L of resin and the anion column will need to have 5.5 L of resinCation resin volume was verified by benchtop model

STOCK SOULTION

EFFLUENT

7 % NAOH

7 % HCL

DI WATER

DI WATER

22

4

26

4

48