Application of Nonthermal Plasma to ChemicalApplication of Nonthermal Plasma to Chemical Conversion of CO2

Shigeru FUTAMURA

National Institute of Advanced Industrial Science and TechnologyAIST Tsukuba West, 16-1 Onogawa, Tsukuba,

Ib ki 305 8569 JIbaraki, 305-8569 Japan

Voice: +81 (29) 861-8497; FAX: +81 (29) 861-8866( ) ; ( )E-mail: s-futamura@aist.go.jp

Application of Nonthermal Plasma to Application of Nonthermal Plasma to Chemical SynthesisChemical SynthesisChemical SynthesisChemical Synthesis

N2 + 3 H2 2 NH3N2 + 3 H2 2 NH3

N2 + 2 H2 NH2 NH2N2 + 2 H2 NH2-NH2

H. Uyama et al., Plasma Chem. Plasma Process., 13(1) 11 (1993) ibid 14(4) 491 (1994)

2 CH O 2 CH OH

13(1), 117 (1993); ibid., 14(4), 491 (1994)

2 CH4 + O2 2 CH3OHA. Mizuno et al., IEEE Trans. Ind. Applicat., 34(5), , pp , ( ),

940 (1998); ibid., 35(5), 1205 (1999)

OutlineOutlineOutlineOutline

Introduction- Reforming reactions with NTPIntroduction

- CO2 as an oxidant in NTPExperimentalExperimentalResults and Discussion- Structure-dependent behavior- Temperature effectTemperature effect- Reaction mechanismSSummary

Time Profile for the Numbers of Papers Relevant to Time Profile for the Numbers of Papers Relevant to Plasma Processing of Chemical SubstancesPlasma Processing of Chemical Substances

16

14

16H2 productionFuel reforming

10

12

pap

ers Pyrolysis/gasification

Plasma-aided combustion

6

8

mb

er o

f

2

4Nu

0

994

995

996

997

998

999

000

001

002

003

004

005

006

199 199 199 199 199 199 200 200 200 200 200 200 200

Year

Endothermicities of NTP Reactions Investigated

EndothermicityΔHo (kJ l-1)R ti

Endothermicities of NTP Reactions Investigated

CO2 + H2O CO + H2 + O2 524.8

ΔHo (kJ mol 1)Reaction

CO2 CO + 0.5 O2

CH + CO 2 CO + 2 H

283.0

247 1CH4 + CO2 2 CO + 2 H2H2O H2 + 0.5 O2CH4 + H2O CO + 3 H2

247.1241.8205.94 2 2

CH OH CO 2 H 90 5CH3OH CO + 2 H2 90.5

Typical Reaction Modes of Catalytic Reforming Processes for Natural Gas

Reformer

Processes for Natural Gas

Steam reformingT 1000K

Natural

H2Temperature > 1000K, pressure > 2.0 MPa, Ni catalyst,Steam / C 2 5～3 0 Natural

gas

CO2

Steam / C 2.5 3.0[H2] / [CO] > 3.0

COCO2 reformingTemperature > 900K,

2 0 MPpressure > 2.0 MPa,steam or catalyst (Ir, Ru, Rh, sulfided Ni), [H2] / [CO] < 1 0[H2] / [CO] < 1.0

Partial OxidationTemperature > 1500K, pressure 3.0 ~ 7.0 MPa, pureoxygen, no catalyst, [H2] / [CO] < 2.0

L. Bromberg et al., “Low Power Compact Plasma Fuel Converter,” WO 01/33056 A1

R ti

H2 (10 %), CO (16 %), CO2 (6 %), and CH4 (0.7 %)from Gasoline (0 12 g/s) and

Fuelconverter

Reactionchamber

G

from Gasoline (0.12 g/s) and air (1.1 g/s)

Fl l h flDischarge

Gap Flame propagates along the gas flow in the AC power-driven plasmatron.

AConduit

I l t

Useful at higher pressuresIncreases in voltages for

breakdown and glow discharge

El d

Insulator

A: Conductive structure

breakdown and glow dischargesustenance.

Electrodestructure

M. Czernichowski, “Electrically Assisted P ti l O id ti f Li ht H d bPartial Oxidation of Light HydrocarbonsBy Oxygen,” WO 99/11572

2: Electrodes2: Electrodes4: Gliding electric discharge12: High voltage connections14: Ceramic plate separating15a and 15b15a: Plasma zone15b: Post-plasma zone19: Metal Ni sticks keeping temp. lowp20: temp. resistance furnace

Syngas (H2/CO = 1.55 ~ 2.19)Syngas (H2/CO 1.55 2.19)from natural gasTemperature: 1238 ~ 1388KPressure: ~ 6 0 MPaPressure: ~ 6.0 MPaO2/HC: 0.25 ~ 0.65

Ferroelectric Packed-bed Reactor (FPR)

Effective reaction length 127 mm; gap distance 15 4 mm;Effective reaction length 127 mm; gap distance 15.4 mm;

BaTiO3 pellets: 1 mm in diameter; ε = 5000 at r. t.

Application of NTP to H2 Production and Fuel Reforming

H2 from(CH3)3N

Syngas fromCH4 + H2O 4)1)(CH3)3N

H2OCH3OH CH

CH4 + H2OCH4 + CO2

CH3OH + H2OCO H O

4)5)6)7)

1)2), 3)3)3)

1) Jpn. Patent No. 2,934,861 (1999)

CH4 CO2 + H2O 7)3)

2) Chem. Lett., 1314 (2001)

3) US Patent No. 6,884,326 B2 (2005);

Ger. Patent DE 10210112.4;Ger. Patent DE 10210112.4;

IEEE Trans. Ind. Applicat., 39(2), 340 (2003)

4) Jpn. Patent No. 3,834,614 (2006); Chem. Lett., 1108 (2002);

IEEE T I d A li 40(6) 1476 1481 (2005)IEEE Trans. Ind. Applicat., 40(6), 1476-1481 (2005)

5) IEEE Trans. Ind. Applicat., 40(6), 1515-1521 (2005);

Catal. Today, 115, 1-4, 211-216 (2006)

6) IEEE Trans. Ind. Applicat., 40(6), 1459-1466 (2004)

7) Stud. Surf. Sci. Catal., 153, 119-124 (2004)

Typical Landfill Gas Evolution

Gas temp.38 to 54oC

CH4

CO2

N2N2

Landfill Off-gas Collection and Treatment Systems, Department of the Army, U.S. Army Corps of Engineers, Washington DC, 20314-1000, 04/17/1995.

Application of NTP to Methane Reforming

CH4 H2, CO, CO2NTP Cat

H2, CO2150oC

Technical merits of NTP

150oC

1) Non-catalytic process2) High energies at short residence times2) High energies at short residence times3) Quick response4) System compactness) y p5) Easy operations

Technical challenges for NTP

1) Improvement of energy efficiency2) Power-up of the reactor system

Schematic Diagram of Experimental Set-up

High voltage amplifier

Oscilloscope

MFC

Reactor FTIR

Oscilloscope

Gas in Gas out

MFC

MFCGC

MFC

MFC

GC MS

(FID + TCD)

GC-MS

NOx GC

Humidifier

HC/N2

CO2/N2

N2

analyzer

Ozoneanalyzer

(FID)

Definitions for the Conversions of CnH2(n+1) andCO2, and the Yields of H CO and Byproductand the Yields of H2, CO, and Byproduct

Hydrocarbons (CmHl)

CCnHH2(n+1) conv. (mol%) =conv. (mol%) = 100 X {1 100 X {1 –– (C(CnHH2(n+1) concentration / concentration / Initial CInitial CnHH2(n+1) concentration)}concentration)}

COCO2 conv. (mol%) =conv. (mol%) = 100 X {1 100 X {1 –– (CO(CO2 concentration / concentration / Initial COInitial CO2 concentration)}concentration)}

HH2 yield (mol%) = 100 X Hyield (mol%) = 100 X H2 concentration /concentration /[([(n+1n+1) X Initial C) X Initial CnHH2(n+1) concentration]concentration]

CO yield (mol%) = 100 X CO concentration / CO yield (mol%) = 100 X CO concentration / Initial COInitial CO2 concentrationconcentration

CCmmHHll yield (mol%) = 100 X Cyield (mol%) = 100 X CmmHHll concentration / concentration / {({(n/mn/m) X Initial C) X Initial CnHH2(n+1) concentration}concentration}

(m,l) = (1,4), (2,6), (2,4), (2,2)(m,l) = (1,4), (2,6), (2,4), (2,2)

Product Distributions for the COProduct Distributions for the CO22--ReformingReformingof CHof CH44, C, C33HH88, and C, and C55HH1212

HCHC REDRED(kJ/L)(kJ/L)

Conv.Conv.(mol%)(mol%)

Product yield (mol%)Product yield (mol%)

HH22 COCO CHCH44 CC22HH66 CC22HH44 CC22HH22

CH4 0.810.81 1717 9.19.1 17.717.7 -- -- -- --

C3H8 0.830.83 2929 12.412.4 16.116.1 5.25.2 0.90.9 0.80.8 1.01.0

C5H12 0 760 76 6363 11 211 2 26 326 3 5 85 8 0 50 5 1 11 1 1 61 6C5H12 0.760.76 6363 11.211.2 26.326.3 5.85.8 0.50.5 1.11.1 1.61.6

[HC] = 0.5 %, [CO2] = 1.0 %, in N2, 298K, Q = 0.2 L/min.

Temperature Effect on HC Conversion in the CO2 Reforming

80

60

70

80

%)

CH4 298K

CH4 373K

CH4 433K

50

60

n (m

ol% CH4 433K

C3H8 298K

C3H8 373K

30

40

vers

ion

C3H8 433K

C5H12 298K

C5H12 373K

10

20

HC

con

C5H12 373K

C5H12 433K

FPR

0

10

0 00 0 50 1 00

H FPR, [HC] = 0.5 %, [CO2 ] = 1.0 %,in N2,0.00 0.50 1.00

Reactor energy density (kJ/L)

in N2,Q = 0.2 L/min.

Bond Dissociation Energies of CBond Dissociation Energies of C--O, HO, H--C, and C, and CC--C in the Substrates and COC in the Substrates and CO

B dB d BDE (kJ lBDE (kJ l 11))BondBond BDE (kJ molBDE (kJ mol--11))

CC--OO 1,083.91,083.9,,

O=CO=COO 532.2532.2

HH CCHH 438 9438 9HH--CCHH33 438.9438.9

HH--CCHH22CHCH22CHCH33 423.3423.3

HH--CCH(CHH(CH33))22 399.6399.6

HH CCHH C(CHC(CH )) 418 8418 8HH--CCHH22C(CHC(CH33))33 418.8418.8

CCHH33--CCHH22CHCH33 363.4363.4

CCHH33--CC(CH(CH33))33 338.2338.2

Relationship between CO2 Conversion andCO Yield

25

) CO2 298K

20

mol

%) CO2 298K

CO 298K

CO2 433K

15

yiel

d ( CO 433K

10

sion

or

FPR

5

Con

vers FPR,

[CO2] = 1.0 %,in N2,Q = 0 2 L/min

0

0 00 0 50 1 00

C Q = 0.2 L/min.

0.00 0.50 1.00Reactor energy density (kJ/L)

CO2 Conversion in the Presence of Hydrocarbons at 298K

20

15ol%

) FPR, [HC] = 0.5 %,[CO2] = 1.0 %,in N2,Q 0 2 L/ i

10

15io

n (m

Q = 0.2 L/min.

10

nver

si

None

CH4

5

O2

co C3H8

C5H12

0

0 00 0 50 1 00

C

0.00 0.50 1.00Reactor energy density (kJ/L)

CO2 Conversion in the Presence of Hydrocarbons at 433K

10

8ol%

) FPR, [HC] = 0.5 %,[CO2] = 1.0 %,in N2,Q 0 2 L/ i

6

ion

(m

None

Q = 0.2 L/min.

4

nver

si CH4

C3H8

C5H12

2

O2

co

0

0 00 0 20 0 40 0 60

C

0.00 0.20 0.40 0.60Reactor energy density (kJ/L)

Plasma-assisted Cleavage of Covalent Bonds

HH

H HH C

HH

H HH C

HH

HCC

H

H CH

HCH

HH

H C H

H CH

HCH

HH

H H C HH

Methane Propane Neopenatne

HSecondary Decomposition Induced by Radicals

Methane Propane Neopenatne

HH

H HH C

HH

H HH C H

HCC

H

H CH

C HH

H C H

H CH

C HH

H C HH

Processes of Hydrocarbon Decomposition

CH4 + e* • CH3 + H • + e

• CH3 + • CH2CH3 + e

(1)

(2)

CH3CH2CH3 + e*3 2 3

H • + CH3CHCH3 + e

( )

(3)•

CH3C(CH3)3 + e*

• CH3 + • C(CH3)3 + e (4)

CO2 + e* CO + O • + e

H • + • CH2C(CH3)3 + e (5)

(6)

SH + O • S • + • OH [SH = CH4, CH3CH2CH3, CH3C(CH3)3]

CH + R • • CH + RH (R •: H • O • • OH)

(7)

(8)CH4 + R • • CH3 + RH (R •: H •, O •, • OH)

CH3CH2CH3 + R • CH3CHCH3 + RH

(8)

(9)•

CH3C(CH3)3 + R • • CH2C(CH3)3 + RH (10)

Effects of Hydrocarbon Structure and Effects of Hydrocarbon Structure and Temperature on HTemperature on H22 YieldYield

18

16

18CH4 298K

CH4 373K

CH4 433K

FPR, [HC] = 0.5 %, [CO2] = 1.0 %,

12

14

l%)

CH4 433KC3H8 298K

C3H8 373K

C3H8 433K

in N2, Q = 200 mL/min.

8

10

ield

(m

o C3H8 433K

C5H12 298KC5H12 373K

C5H12 433K

4

6H2

y C5H12 433K

0

2

0

0.00 0.20 0.40 0.60 0.80 1.00 1.20Reactor energy density (kJ/L)

Processes of H2 Formation

CH4 + e* • CH3 + H • + e

CH CH CH + e*

• CH3 + • CH2CH3 + e

(1)

(2)

CH3CH2CH3 + e*

H • + CH3CHCH3 + e

• CH + • C(CH ) + e

(3)

(4)

•

CH3C(CH3)3 + e*

• CH3 + • C(CH3)3 + e

H • + • CH2C(CH3)3 + e

(4)

(5)

CH4 + H • • CH3 + H2

CH3CH2CH3 + H • CH3CHCH3 + H2

(6)

(7)•

CH3CH2CH3 H CH3CHCH3 H2

CH3C(CH3)3 + H • • CH2C(CH3)3 + H2

(7)

(8)

H d d• CH2CH3 + H • H2 + CH2=CH2

CH3CHCH3 + H • H2 + CH2=CHCH3

(9)

(10)•

Hydrogen donors better than propane and neopentane

• C(CH3)3 + H • H2 + CH2=C(CH3)2 (11)

Stoichiometric Syngas CompositionStoichiometric Syngas Composition

Reaction [H2] / [CO]

CH4 + CO2 2 H2 + 2 CO 1.00

Reaction [H2] / [CO]

C3H8 + 3 CO2 4 H2 + 6 CO 0.67

C5H12 + 5 CO2 6 H2 + 10 CO 0.60

HC StructureHC Structure--dependent Composition ofdependent Composition ofSynthesis Gas at 433K (I)Synthesis Gas at 433K (I)

3.0CH4 Sine

2.5

CH4 Sine

CH4 Square

CH4 Triangle

C3H8 Sine

C3H8 S

2.0

CO

] (-

)

C3H8 Square

C3H8 Triangle

C5H12 Sine

C5H12 SquareFPR [HC] = 0 5 % [CO2] = 1 0 % in N2

1.0

1.5

[H2 ]

/ [C C5H12 Triangle

FPR, [HC] = 0.5 %, [CO2] = 1.0 %, in N2, 433K, Q = 200 mL/min.

0.5

0.00.00 2.00 4.00 6.00 8.00

Reactor energy density (kJ/L)

HC StructureHC Structure--dependent Composition ofdependent Composition ofSynthesis Gas at 433K (II)Synthesis Gas at 433K (II)

1.0

0.8

FPR, [CO2] / [C in HC] = 2.0, in N2, 433K, Sine, Vp-p 14.0 kV, Q = 200 mL/min.

0.6

O]

(-)

CH4

C3H8

Q

0.4

H2]

/ [C

O

C5H12

0.2

[H

0.0

0.00 5.00 10.00 15.00 20.00 25.00Reactor energy density (kJ/L)

Effect of HC Structure on Carbon Balance

5000

in the CO2 –Reforming at 298K

4000

FPR, [HC] = 0.5 %, [CO2 ] = 1.0 %, 298K, in N2,

3000

(pp

m)

298K, in N2, Q = 0.2 L/min.

2000

Δ[C

O]

1000 CH4C3H8C5H12

0

0 5000 10000 15000 20000{ X Δ[C H2( 1)] + Δ[CO2]} ( )- {n X Δ[CnH2(n+1)] + Δ[CO2]} (ppm)

Effect of C3H8 Concentration on Carbon

0 80

Balance in the CO2 -Reforming

0.80

0.60

(%)

0.40

Δ[C

O]

C3H8 0.125 %C3H8 0.25 %

0.20C3H8 0.50 %C3H8 1.0 %

FPR, CO2 2.0 %, in N2,

0.00

0.00 0.40 0.80 1.20 1.60 2.00 2.40

298K, Q = 0.2 L/min.

- {3 X Δ[C3H8] + Δ[CO2]} (%)

Effect of Temperature on Carbon Balance in the CO2

12000

Reforming of Aliphatic Hydrocarbons at 433K

10000

12000

pm

)

8000

du

cts]

(p

FPR, [HC] = 0.5 %, [CO2 ] = 1.0 %, 433K in N2

6000

the

pro

d 433K, in N2, Q = 0.2 L/min.

2000

4000

al C

in t

CH4

0

2000

Δ[T

ota

C3H8C5H12

0 5000 10000 15000 20000- {n X Δ[CnH2(n+1)] + Δ[CO2]} (ppm)

Effect of [C5H12] / [CO2] on Carbon Balance in the

12000

CO2 Reforming of C5H12 at 433K

10000

12000

pp

m) FPR, 433K, in N2,

Q = 0.2 L/min.

8000

du

cts]

(p

6000

the

pro

d

[C5H12] / [CO2] = 0.5

[C5H12] / [CO2] = 0.1

2000

4000

tal C

in

0

2000

Δ[T

o t

0 5000 10000 15000 20000- {5 X Δ[C5H12] + Δ[CO2]} (ppm)

Processes of CO Formation

SH + e* S • + H • + e [SH = CH4, CH3CH2CH3, CH3C(CH3)3] (1)

CO2 + e* CO + O • + e

SH + O • S • + • OH

(2)

(3)

S

S' • CO

( )

(4)- H

O • - H

S •

Olefins Aldehydes, Ketones (5)O •- H

O(6)Aldehydes, Ketones CO

O •- H

Potential of Nonthermal Plasma in Various Potential of Nonthermal Plasma in Various T f Ch i l R tiT f Ch i l R tiTypes of Chemical ReactionsTypes of Chemical Reactions

SubstrateSubstrate Concn.Concn. Temp.Temp. CatalystCatalyst Conv.Conv.SubstrateSubstrate Concn.Concn. Temp.Temp. CatalystCatalyst Conv.Conv.

ClCl2C=CCC=CCｌｌ2a) 1,000 1,000

303K303K NoNo 98 %98 %Cl2C=CHCl

,,ppmppm

303K303K NoNo 98 %98 %

PhHPhHb)PhHPhHb),

PhCHPhCH3

200 ppm200 ppm 303K303K MnOMnO2 90 %90 %

CH3OH c) 1.0 %1.0 % 303K303K No 99 %99 %

CHCH CHCH CHCHCHCH3CHCH2CHCH3

with CO2d)

1.0 %1.0 % 433K433K NoNo 60 %60 %

a) IEEE Trans. Ind. Applicat., 33(2), 447-453 (1997); b) ibid., 37(5), 447-453 (2001); c) ibid., 40(6), 1459-1466 (2004); d) ibid., 41(6), 1515-1521 (2005).

SummarySummaryyy

H2 and CO are obtained as the major products in the CO reforming of methane propane andthe CO2-reforming of methane, propane, and neopentane in nonthermal plasma (NTP).Their reactivities are greatly affected by theirTheir reactivities are greatly affected by their chemical structures and reaction temperature.CO2 reactivity is not affected by reaction 2 y ytemperature. CO is quantitatively obtained from CO2 in the absence of the counterpart hydrocarbon. T t ff t th H i ld i tlTemperature effect on the H2 yield is greatly affected by the chemical structures of the aliphatic hydrocarbons (HCs).hydrocarbons (HCs). The molar ratio of H2 to CO, and the carbon balance are affected by the chemical structures of yHCs, [HC] / [CO2], and reaction temperature.