Oxidative Degradation Oxidative Degradation and the Oxidation-and the Oxidation-

Reduction Potential of Reduction Potential of ROC20 SolutionsROC20 SolutionsByBy

Fred ClosmannFred Closmann

January 10, 2008January 10, 2008

Summary of Topics Summary of Topics CoveredCovered

What is Oxidation-Reduction Potential (ORP)?What is Oxidation-Reduction Potential (ORP)? Why we want to Measure ORP?Why we want to Measure ORP? How ORP Can Help US?How ORP Can Help US? Review Preliminary Data (ROC20)Review Preliminary Data (ROC20) Other Findings – High Viscosity SolventOther Findings – High Viscosity Solvent Possible Future ExperimentsPossible Future Experiments

ORPORP

According to ASTM method, “the ORP According to ASTM method, “the ORP measurement establishes the ratio of oxidants measurement establishes the ratio of oxidants and reductants prevailing within a solution… and reductants prevailing within a solution… allows determination of the ability to oxidize allows determination of the ability to oxidize or reduce species in solution.”or reduce species in solution.”

Reacting species related by Nernst Equation.Reacting species related by Nernst Equation. Non-selective; all e-transfer reactions Non-selective; all e-transfer reactions

influence measurement.influence measurement. Gross measurement - not initially concerned Gross measurement - not initially concerned

with exact chemistry.with exact chemistry. Standardized method(s) (ASTM)Standardized method(s) (ASTM)

Standard Hydrogen Electrode

We are using Ag/AgCl reference

ORP ElectrodeORP Electrode

Flue Gas

10% CO2

5-10% O2

Absorber

40-70 °C

1 atm

Stripper

120 °C

1 atm

Cross

Exchanger

Where is the degradation most likely to occur?

Absorber

Packing

Reboiler

Gas w/ 1% CO2

CO2

H2O, O2

Solvent

= 0.4

Sump

Why Measure ORP?Why Measure ORP? Oxidative degradation can occur in the mass-Oxidative degradation can occur in the mass-

transfer controlled region (Goff).transfer controlled region (Goff). Allow us to know the potential for and rate of Allow us to know the potential for and rate of

degradation of solvents.degradation of solvents. Goal: Develop correlation between ORP and Goal: Develop correlation between ORP and

solvent degradation rate.solvent degradation rate. Secondary Goal: Understand catalytic effect of Secondary Goal: Understand catalytic effect of

metals on solvent oxidation.metals on solvent oxidation. Real-time data collection (on-line methods).Real-time data collection (on-line methods).

Experiments Conducted Experiments Conducted to-Dateto-Date

1.1. Baseline: ROC20 formulations (loaded to 0.3 mole/mole Baseline: ROC20 formulations (loaded to 0.3 mole/mole based on alkalinity) aerated/stirred in glass reactor at based on alkalinity) aerated/stirred in glass reactor at 53.5 53.5 °°C.C.

2.2. Loaded ROC20 solution augmented with 0.01 mM Cu Loaded ROC20 solution augmented with 0.01 mM Cu (added as cupric sulfate).(added as cupric sulfate).

3.3. Rapid shut-down of well-mixed/aerated reactor with Rapid shut-down of well-mixed/aerated reactor with loaded ROC20 to understand Oloaded ROC20 to understand O22 consumption (absence consumption (absence of copper).of copper).

4.4. Rapid start-up of reactor (aeration and mixing) from Rapid start-up of reactor (aeration and mixing) from quiescent state (absence of copper).quiescent state (absence of copper).

5.5. Viscosity measurements of loaded ROC20 solutionsViscosity measurements of loaded ROC20 solutions

Figure 1 - ORP Following Reactor Shut-Down

-300

-280

-260

-240

-220

-200

-180

-160

-140

0 15 30 45 60 75

Time (min)

OR

P (

mV

)

ORP Following Shut-down

Figure 2- ORP After Reactor Start-up

-290

-270

-250

-230

-210

-190

-170

-150

0 5 10 15

Time (min)

OR

P (

mV

)

Aeration/ORP Study No. 2ORP (mV)

Steady-State ResultsSteady-State Results

Solution Solution CharacteristicCharacteristic

ORP ORP (mV)(mV) T (°C)T (°C)

Viscosity Viscosity (cp)**(cp)**

ROC20ROC20 -179-179 53.553.5 17.8/10.517.8/10.5

ROC20 w/ 0.001 mM CuROC20 w/ 0.001 mM Cu -145-145 53.553.5 NMNM

ROC20 w/ 0.01 mM Cu*ROC20 w/ 0.01 mM Cu* -80-80 53.553.5 305/110305/110

pH 4/7 Quinhydrone StdpH 4/7 Quinhydrone Std+246/+6+246/+6

44 2323 NANA*ROC20 solution sat idle in reactor for 3 weeks.

**Viscosity measurements made at 25/40 °C.

•NM – Not measured, NA – Not Applicable.

Interpretation of ResultsInterpretation of Results Negative ORP not necessarily reduced Negative ORP not necessarily reduced

environment.environment. Oxygen depleted fast; 90% of ORP change occurs Oxygen depleted fast; 90% of ORP change occurs

in 24 minutes in quiescent reactor.in 24 minutes in quiescent reactor. Rapid increase (<3 min) in ORP to near-steady Rapid increase (<3 min) in ORP to near-steady

state condition (-185 mV) upon reactor start-up.state condition (-185 mV) upon reactor start-up. Copper increases ORP; consistent with previous Copper increases ORP; consistent with previous

observations related to formate production observations related to formate production (Sexton, 2007).(Sexton, 2007).

ROC20 became more viscous after sitting idle ROC20 became more viscous after sitting idle (305 cp vs. 18 cp at 25 °C); observation (305 cp vs. 18 cp at 25 °C); observation confirmed in experiment without Cu.confirmed in experiment without Cu.

Potential ORP Potential ORP ExperimentsExperiments

Change reactor conditions improved Change reactor conditions improved mixing/aeration, and absence of both.mixing/aeration, and absence of both.

Addition of metals species including Addition of metals species including Ferric/Ferrous Iron to ROC20 to observe iron Ferric/Ferrous Iron to ROC20 to observe iron shuttle effect on ORP.shuttle effect on ORP.

Addition of cobalt and nickel to investigate Addition of cobalt and nickel to investigate catalytic effects on ORP.catalytic effects on ORP.

Addition of Hydrogen Peroxide (HAddition of Hydrogen Peroxide (H22OO22) to create ) to create highly oxidative environment - measure ORP highly oxidative environment - measure ORP and degradation of ROC20.and degradation of ROC20.

Investigate Potential Investigate Potential ROC20 Polymerization ROC20 Polymerization

MechanismsMechanisms1.1. Recreate steps that lead to formation of highly Recreate steps that lead to formation of highly

viscous ROC20.viscous ROC20.2.2. Repeat with ROC20 and other solvents.Repeat with ROC20 and other solvents.3.3. Analysis using ORP, cation/anion chromatography, Analysis using ORP, cation/anion chromatography,

NMR, titration. NMR, titration. 4.4. Reversible condition? Heat to 120 °C to mimic Reversible condition? Heat to 120 °C to mimic

stripper operation.stripper operation.

5.5. Investigate COInvestigate CO22 stripping effects of experiments. stripping effects of experiments. Reload back to 0.3 m/m to reverse condition – Reload back to 0.3 m/m to reverse condition – (completed).(completed).

6.6. Literature review – formation of urea compound or Literature review – formation of urea compound or polymer based on ROC20; propose pathway to polymer based on ROC20; propose pathway to creation of polymer.creation of polymer.