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Oxidative Degradation and the Oxidation-Reduction Potential of ROC20 Solutions. By Fred Closmann January 10, 2008. Summary of Topics Covered. What is Oxidation-Reduction Potential (ORP)? Why we want to Measure ORP? How ORP Can Help US? Review Preliminary Data (ROC20)

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oxidative degradation and the oxidation reduction potential of roc20 solutions

Oxidative Degradation and the Oxidation-Reduction Potential of ROC20 Solutions

By

Fred Closmann

January 10, 2008

summary of topics covered
Summary of Topics Covered
  • What is Oxidation-Reduction Potential (ORP)?
  • Why we want to Measure ORP?
  • How ORP Can Help US?
  • Review Preliminary Data (ROC20)
  • Other Findings – High Viscosity Solvent
  • Possible Future Experiments
slide3
ORP
  • According to ASTM method, “the ORP measurement establishes the ratio of oxidants and reductants prevailing within a solution… allows determination of the ability to oxidize or reduce species in solution.”
  • Reacting species related by Nernst Equation.
  • Non-selective; all e-transfer reactions influence measurement.
  • Gross measurement - not initially concerned with exact chemistry.
  • Standardized method(s) (ASTM)
orp electrode
ORP Electrode

Standard Hydrogen Electrode

We are using Ag/AgCl reference

slide5

Where is the degradation most likely to occur?

Gas w/ 1% CO2

CO2

H2O, O2

Absorber

40-70 °C

1 atm

Stripper

120 °C

1 atm

Absorber

Packing

Cross

Exchanger

Sump

Reboiler

Flue Gas

10% CO2

5-10% O2

Solvent

 = 0.4

why measure orp
Why Measure ORP?
  • Oxidative degradation can occur in the mass-transfer controlled region (Goff).
  • Allow us to know the potential for and rate of degradation of solvents.
  • Goal: Develop correlation between ORP and solvent degradation rate.
  • Secondary Goal: Understand catalytic effect of metals on solvent oxidation.
  • Real-time data collection (on-line methods).
experiments conducted to date
Experiments Conducted to-Date
  • Baseline: ROC20 formulations (loaded to 0.3 mole/mole based on alkalinity) aerated/stirred in glass reactor at 53.5 °C.
  • Loaded ROC20 solution augmented with 0.01 mM Cu (added as cupric sulfate).
  • Rapid shut-down of well-mixed/aerated reactor with loaded ROC20 to understand O2 consumption (absence of copper).
  • Rapid start-up of reactor (aeration and mixing) from quiescent state (absence of copper).
  • Viscosity measurements of loaded ROC20 solutions
steady state results
Steady-State Results
  • *ROC20 solution sat idle in reactor for 3 weeks.
  • **Viscosity measurements made at 25/40 °C.
  • NM – Not measured, NA – Not Applicable.
interpretation of results
Interpretation of Results
  • Negative ORP not necessarily reduced environment.
  • Oxygen depleted fast; 90% of ORP change occurs in 24 minutes in quiescent reactor.
  • Rapid increase (<3 min) in ORP to near-steady state condition (-185 mV) upon reactor start-up.
  • Copper increases ORP; consistent with previous observations related to formate production (Sexton, 2007).
  • ROC20 became more viscous after sitting idle (305 cp vs. 18 cp at 25 °C); observation confirmed in experiment without Cu.
potential orp experiments
Potential ORP Experiments
  • Change reactor conditions improved mixing/aeration, and absence of both.
  • Addition of metals species including Ferric/Ferrous Iron to ROC20 to observe iron shuttle effect on ORP.
  • Addition of cobalt and nickel to investigate catalytic effects on ORP.
  • Addition of Hydrogen Peroxide (H2O2) to create highly oxidative environment - measure ORP and degradation of ROC20.
investigate potential roc20 polymerization mechanisms
Investigate Potential ROC20 Polymerization Mechanisms
  • Recreate steps that lead to formation of highly viscous ROC20.
  • Repeat with ROC20 and other solvents.
  • Analysis using ORP, cation/anion chromatography, NMR, titration.
  • Reversible condition? Heat to 120 °C to mimic stripper operation.
  • Investigate CO2 stripping effects of experiments. Reload back to 0.3 m/m to reverse condition – (completed).
  • Literature review – formation of urea compound or polymer based on ROC20; propose pathway to creation of polymer.
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