Non-thermal plasma-chemical CO2 utilization: COx polymer formation

Robert Geiger

Advisor: Dr. David Staack

Texas A&M Mechanical Engineering

Plasma Engineering & Diagnostics Laboratory (PEDL)

Outline

• Introduction– Background– History– Industrial Prospects– Non-Thermal Plasma– Objectives

• Thermodynamic and Kinetic Analysis– Thermodynamic Properties– Thermodynamic Equilibrium of Carbon Oxides– Kinetics

• Experimental Setup and Results– DBD Reactor and Setup– Plasma Parameters and Optical Emission Spectroscopy– Overall Kinetics– Characterization of Products

• Conclusions

Hydrocarbon Utilization

CH4 (CxHy)

•Combustion•Fischer Tropsch•Ethanol•Hydrogen

H=393.5 kJ/mol CO2H=241 kJ/mol H2O

H=110 kJ/mol CO2

CO2

H2O

CO H2

CO

1/2

Petrochemicals Higher HydrocarbonsCarbon Oxide Polymers

(Matthias Ballauff, et. al Angew. Chem. Int. Ed. 2004, 43)

Combu

stio

n

Partial Combustion

Upgrading

Plasma

Polymerization

Plasma Dissociation

Carbon Monoxide at Really High Pressures

Lipp M J et al 2005 Nat. Mater. 4 211

V V Brazhkin 2006 J. Phys.: Condens. Matter 18 9643

Carbon Oxides

• CO

• CO2

• C3O2 Carbon Suboxide

?

(Matthias Ballauff, et. al Angew. Chem. Int. Ed. 2004, 43)

Thermodynamic Equilibrium

CO CO2, C3O2 (g)

CO CO2, C3O2 (g), (C3O2)n (s)

CO CO2, C3O2 (g), (C3O2)n (s), C(gr)

Case 1:

Case 2:

Case 3:

Kinetics

Proposed mechanism from several sources

McTaggart FK PIasma Chemistry in Electrical Discharges (1967)

KineticsPathway for C3O2 polymer formation1) C + CO + m C2O + m k1 = 1.5 * 10-31 [cm6/molecule2*s]2) C2O + CO C3O2 k2 = 4.33 * 10-15 [cm3/molecule*s]3) n(C3O2) (C3O2)n k3 = 6.6 * 10-14 [cm3/molecule*s]

Pathway for C(gr) formation4) C + C C2 k4 = 2.16 * 10-11 [cm3/molecule*s]5) C2 C(gr)

• The pathway of C3O2 formation should be faster than the pathway to solid carbon formation

• C3O2 Monomer and Polymer formation are more favorable at low temperatures and high pressures

• C3O2 should formation favor low [C]/[CO]

Plasma Generation

Plasma Chemistry

Kinetic Model in Development

Still need to add• CO* reactions• C(s) reactions• Surface reactions

Kinetic Model in Development

Kinetic Model in Development

CO

CO2

C3O2

C3O2(p)

•Const T•Te = 1 eV•ne = 1013 cm-3

•ne = const

EXPERIMENTAL SECTION

Experimental Setup

Power Supply:•Vmax ~ 10 kV•Imax ~ 40 mA•Freq ~ 25 – 30 kHz•P ~ 40W-150W

DBD Reactor

Color Variations

Deposition Rate

Increasing FlowFlow appears to change power density distribution

180 sccm 870 sccm 1700 sccm

~ 30W ~50W ~100W

Increasing PowerPower increases deposition rate and film darkness

Gas temperature and surface temperature do not cause the different film colors.

FTIR – Comparison with High Pressure Film

(High Pressure Film FTIR data taken from: Lipp M J et al 2005 Nat. Mater. 4 211)

Film Properties

•C:O ~ 1.5 - 3.5 (XPS)•Solubility

•Water (Hydrates)•Insoluble

•Acetone•Ethanol

Solubility allows for spin coating and layer by layer film growth

Before After

Hydration

C:O ~ 1.9 1.7

Emission Spectroscopy

300 350 400 450 500 550 600 650w (nm)

C2 - SPECAIRCO - Our ModelExperimental

Angstrom CO Bands (B1Σ+ – A1π)

C2 Swan Bands (d3π– a3π)

Herzberg CO Bands (C1Σ+ – A1π)

Emission Spectroscopy - Temperature

471.5 472 472.5 473 473.5 474 474.5

0

0.5

1

wavelength (nm)

Inte

nsity

(A

.U.)

Trot

= 408K

Tvib

= 1962K

FWHM = 0.271nm

RMSE = 1.66%

ExperModel

Future Work

• Determine the polymer structures (NMR) and chain length

• Characterize polymers and determine their properties

• Complete the kinetic model and compare with experimental

• Determine optimum production parameters

Conclusion• CO Plasma

– Interesting films can be formed as fast as 1 mg/min at 50W with solely carbon and oxygen atoms

– These films appear similar in structure to high pressure CO polymers not C3O2

– Increased power darkens the film and increases deposition rate

– Color changes do not alter the FTIR– A kinetic model in under development– The C2 swan, CO angstrom and CO Herzberg bands

enables temperature measurements in the visible range

• CO2 Plasma– Micro-glow discharge showed best results– High power density and rapid quenching are thought to be

desirable

References

• Lipp M J et al 2005 Nat. Mater. 4 211• V V Brazhkin 2006 J. Phys.: Condens. Matter 18 9643• McTaggart FK PIasma Chemistry in Electrical Discharges

(1967)• P.C.Cosby, J. Chem. Phys. 98,9560(1993).• K.M.D’Amico,and A.L.S.Smith, J.Phys.D: Appl. Phys. 10,261

(1977)

Questions?

Email: rpg32@tamu.edu