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: [email protected]
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.