D iti f B T l dD iti f B T l d X lX lDecomposition of Benzene, Toluene andDecomposition of Benzene, Toluene and XyleneXyleneDecomposition of Benzene, Toluene and Decomposition of Benzene, Toluene and XyleneXyleneii At h i C Di hAt h i C Di husing anusing an Atmospheric Corona DischargeAtmospheric Corona Dischargeusing anusing an Atmospheric Corona DischargeAtmospheric Corona Discharge

Kohji NagaoKohji Nagao11 KohkiKohki SatohSatoh1,21,2 andand HidenoriHidenori ItohItoh11Kohji NagaoKohji Nagao , , KohkiKohki SatohSatoh ,, and and HidenoriHidenori ItohItoh1 Department of Electrical and Electronic Engineering Muroran Institute of Technology Muroran Hokkaido 050-8585 JapanDepartment of Electrical and Electronic Engineering, Muroran Institute of Technology, Muroran, Hokkaido 050-8585, Japan

22 Center of Environmental Science and Disaster Mitigation for Advanced Research, Muroran Institute of Technology, Muroran, Hokkaido 050-8585, JapanCe te o v o e ta Sc e ce a d saste t gat o o dva ced esea c , u o a st tute o ec o ogy, u o a , o a do 050 8585, Japa

E il 1624059@ it jEmail : s1624059@mmm.muroran-it.ac.jp@ jp

22.. ExperimentalExperimental apparatusapparatus andand conditionsconditions11.. IntroductionIntroduction 22.. ExperimentalExperimental apparatusapparatus andand conditionsconditions11.. IntroductionIntroductionR tl i ki d f VOC ( l til i d ) t i d i h tR tl i ki d f VOC ( l til i d ) t i d i h t ElectrodeElectrodeRecently, various kinds of VOCs (volatile organic compounds) contained in exhaust gas, Recently, various kinds of VOCs (volatile organic compounds) contained in exhaust gas, ElectrodeElectrode

•• AA multimulti needleneedle electrodeelectrode whichwhich consistsconsists ofof thirteenthirteenwhich are emitted from factories, automobiles etc, cause major environmental issues.which are emitted from factories, automobiles etc, cause major environmental issues. •• AA multimulti--needleneedle electrode,electrode, whichwhich consistsconsists ofof thirteenthirteenstainlessstainless--steelsteel needlesneedles ((5555 mmmm lengthlength andand 44 mmmm

, , j, , j

300250200150100500

stainlessstainless steelsteel needlesneedles ((5555 mmmm lengthlength andand 44 mmmmdiameter)diameter) andand aa planeplane electrodeelectrode mademade ofof stainlessstainlessPRTR (Pollutant Release and Transfer Register) data in 2006PRTR (Pollutant Release and Transfer Register) data in 2006[1][1]

300250200150100500 )) ppsteelsteel ((8080 mmmm diameter),diameter), areare placedplaced inin aa cylindricalcylindrical

( g )( g )

dischargedischarge chamberchamber..ThTh didi bb hh l il i dldl l dl dTolueneToluene (C(C66HH55CHCH33)) andand xylenexylene (C(C66HH44(CH(CH33))22))toluene (46%)toluene (46%)

•• TheThe distancedistance betweenbetween thethe multimulti--needleneedle electrodeelectrodeandand thethe planeplane electrodeelectrode isis fixedfixed atat 3535 mmmm

(( 66 55 33)) yy (( 66 44(( 33))22))areare emittedemitted toto thethe environmentenvironment inin thethe largestlargestxylenexylene (28%)(28%)

thlb andand thethe planeplane electrodeelectrode isis fixedfixed atat 3535 mmmm..ggvolumevolume..ethlbenzene

methylene chloride DischargeDischarge chamberchambermethylene chloridepoly oxyethylene = alkyl ether

•• TheThe cylindricalcylindrical dischargedischarge chamberchamber isis mademade ofofTheThe emissionemission volumevolume ofof benzenebenzene (C(C66HH66)) isispoly oxyethylene alkyl etherp-dichlorobenzene

stainlessstainless--steel,steel, withwith 197197 mmmm innerinner diameterdiameter andand300300 h i hth i htbenzenebenzene (4%)(4%)

TheThe emissionemission volumevolume ofof benzenebenzene (C(C66HH66)) isislessless thanthan thatthat ofof toluenetoluene andand xylenexylene,, butbut itit hashas

p d c o obe e e

300250200150100500300300 mmmm heightheight..( )( ) yy ,,

carcinogenicitycarcinogenicity andand teratogenicityteratogenicity..300250200150100500amount of emissions [kt/year] AppliedApplied voltagevoltage

g yg y g yg y

amount of emissions [kt/year]•• AA positivepositive DCDC highhigh voltagevoltage 2020 ~~ 2828 kVkV isis appliedapplied

toto thethe multimulti--needleneedle electrode,electrode, generatinggenerating aa streamerstreamercoronacorona dischargedischarge..

A h t d VOCVOC GasGas conditionconditionApproaches to decompose VOCsVOCs•• NitrogenNitrogen--oxygenoxygen mixturemixture isis usedused asas aa backgroundbackground gas,gas, andand thethe mixturemixture ratioratio isis NN22::OO22 == 8080::2020 %%..using dischargedischarge plasmasplasmas have gg ygyg gg gg 22 22•• InitialInitial gasgas pressurepressure inin thethe chamberchamber isis 10131013 hPahPa (atmospheric(atmospheric pressure),pressure), andand initialinitial concentrationsconcentrations ofof benzene,benzene, toluenetoluene andand xylenexylene areare 300300 ppmppm..

bb (C(C HH )) t l (Ct l (C HH CHCH )) ll (C(C HH (CH(CH )) ))attracted attention.

ConcentrationConcentration measurementmeasurementbenzenebenzene (C(C66HH66)) toluene (Ctoluene (C66HH55CHCH33)) xylenexylene (C(C66HH44(CH(CH33))22)) ConcentrationConcentration measurementmeasurement

•• ConcentrationsConcentrations ofof benzenebenzene toluenetoluene xylenexylene andand byby--productsproducts areare measuredmeasured byby aa FourierFourier TransformTransform InfraredInfrared SpectrophotometerSpectrophotometer (Shimadzu(ShimadzuObjectiveObjective ConcentrationsConcentrations ofof benzene,benzene, toluene,toluene, xylenexylene andand byby productsproducts areare measuredmeasured byby aa FourierFourier TransformTransform InfraredInfrared SpectrophotometerSpectrophotometer (Shimadzu,(Shimadzu,FTIRFTIR-- 89008900)) equippedequipped withwith aa gasgas cellcell (Infrared(Infrared Analysis,Analysis, 1010PA),PA), whichwhich hashas opticaloptical pathpath lengthlength ofof 1010 mm..

jjWW i ti ti ti t thth d itid iti h t i tih t i ti ff VOCVOC ii t h it h i DCDC di hdi h )) q ppq pp gg (( y ,y , ),), pp pp gg

MeasurementMeasurement ofof voltagevoltage andand currentcurrentWeWe investigateinvestigate thethe decompositiondecomposition characteristicscharacteristics ofof VOCsVOCs inin anan atmosphericatmospheric DCDC coronacorona dischargedischarge..C iC i i ii i ff bb ll ll dd bb dd dd bb i f di f d MeasurementMeasurement ofof voltagevoltage andand currentcurrent

A li dA li d ltlt ii dd bb hi hhi h ltlt bb (T kt i(T kt i PP60156015A)A)ConcentrationConcentration variationsvariations ofof benzene,benzene, toluene,toluene, xylenexylene andand byby--productsproducts areare measuredmeasured byby infraredinfrared

•• AppliedApplied voltagevoltage isis measuredmeasured byby aa highhigh--voltagevoltage probeprobe (Tektronix(Tektronix PP60156015A)A)..•• DischargeDischarge currentcurrent isis calculatedcalculated byby voltagevoltage dropdrop acrossacross aa nonnon inductiveinductive resistanceresistance ((11 kkΩΩ)) whichwhich connectedconnected betweenbetween thethe planeplane electrodeelectrode andand

spectroscopyspectroscopy andand decompositiondecomposition processesprocesses ofof benzene,benzene, toluenetoluene andand xylenexylene isis examinedexamined onon thethe basisbasis ofof•• DischargeDischarge currentcurrent isis calculatedcalculated byby voltagevoltage dropdrop acrossacross aa nonnon--inductiveinductive resistanceresistance ((11 kkΩΩ),), whichwhich connectedconnected betweenbetween thethe planeplane electrodeelectrode andand

thethe earthearth..massmass balancebalance forfor carboncarbon atomsatoms.. thethe earthearth..[1] Ministry of the Environment[1] Ministry of the Environment：：The compendium of PRTR data on 2006 (released in 2008).The compendium of PRTR data on 2006 (released in 2008).

33 実験結果および考察実験結果および考察33.. 実験結果および考察実験結果および考察

(1) Infrared spectrum (C(1) Infrared spectrum (C66HH66 and Cand C66HH44(CH(CH33))22)) (3) Mass balance for carbon atoms(3) Mass balance for carbon atoms(1) Infrared spectrum (C(1) Infrared spectrum (C66HH66 and Cand C66HH44(CH(CH33))22)) (3) Mass balance for carbon atoms(3) Mass balance for carbon atoms2.02.0

C H CC HH CC HH CC HH CHCH CC HH (CH(CH ))1.51.5 C6H6 CC66HH66CC66HH66 CC66HH66

CC66HH66 CC66HH55CHCH33 CC66HH44(CH(CH33))22

pm]

2000pm]

pm]1.01.0 without discharge 66 66 66 66

2000s [pp C6H4(CH3)2

2000

s [pp

1500s [pp0.5

0 0.u.]0.5

0 0.u.]

2000

oms

1500oms1500

oms0.0

e [a

2 00.0

e [a

2 0 HCOOHHCOOHNN22OO OO33 COCO22 1500n at

o

n at

1000n at

ance 2.0

1 5ance 2.0

1 5 with discharge (10 kJ) COCO22

HCOOHHCOOHNN22OO OO33 COCO22HCNHCN

1000rbon

1000arbo

n

CO2

1000

arbo

n

CO2orba 1.5

1 0orba 1.5

1 0 with discharge (10 kJ) COCO22 COCO CC HH

HCNHCN1000

f ca

CO2CH3COOHPANf c

aCH3COOHPANf c

a

abs 1.0

0 5abs 1.0

0 5CC22HH22

500nt o

f PANHCHO500er

of PAN

HCHOCO500

er o

f

CO0.50.0

0.50.0 500

mou

n COHCOOH

HCNC2H2um

be HCNC2H2

HCOOHC H CHum

be HCNC2H2

HCOOHC6H6800 750 700 650 600

14000 3500 3000 2500 2000 1500 1000 500

10am

706050403020100

HCOOH 2 2

0nu

706050403020100

2 2C6H5CH30nu

706050403020100

2 2

wavenumber [cm-1]wavenumber [cm-1]706050403020100

input energy [kJ]706050403020100

input energy [kJ]706050403020100

input energy [kJ]2.02.0C H (CH ) CC HH (CH(CH )) p gy [ ]p gy [ ]p gy [ ]

1.51 0

CC66HH44(CH(CH33))221.51 0 without discharge

C6H4(CH3)2 CC66HH44(CH(CH33))22CC66HH44(CH(CH33))22

The number of carbon atoms [The number of carbon atoms [ppmppm]]1.00 5]

1.00 5]

without discharge

××number of carbon atoms in each of gaseous moleculesnumber of carbon atoms in each of gaseous molecules concentration [concentration [ppmppm]][[pppp ]]0.5

0 0a.u.

]0.50 0a.

u.]

××number of carbon atoms in each of gaseous moleculesnumber of carbon atoms in each of gaseous molecules concentration [concentration [ppmppm]]0.0

ce [a

2 0COCO22

0.0

ce [a

2 0 HCOOHHCOOHNN22OO OO33

banc 2.0

1.5 HCNHCNbanc 2.0

1.5 with discharge (10 kJ) COCO22 CHCH33COOHCOOH

InIn benzenebenzene decomposition,decomposition, thethe totaltotal numbernumber ofof carboncarbon atoms,atoms, whichwhich isis presentedpresented asas thethe toptop lineline ofofsorb 1.5

1.0 CC22HH22sorb 1.5

1.0g ( ) 22 COCOHCHOHCHO PANPAN PANPAN

33

p ,p , ,, pp ppstackedstacked graph,graph, decreasesdecreases monotonouslymonotonously withwith thethe increaseincrease ofof inputinput energy,energy, andand thenthen becomesbecomes constantconstant..ab 0.5

CC22HH22ab 0.5 stackedstacked graph,graph, decreasesdecreases monotonouslymonotonously withwith thethe increaseincrease ofof inputinput energy,energy, andand thenthen becomesbecomes constantconstant..800 750 700 650 600

0.04000 3500 3000 2500 2000 1500 1000 500

0.0

InIn toluenetoluene andand xylenexylene decomposition,decomposition, thethe totaltotal numbernumber ofof carboncarbon atomsatoms decreasesdecreases withwith thethe increaseincrease ofof800 750 700 650 600b [ -1]

4000 3500 3000 2500 2000 1500 1000 500b [ -1] yy p ,p ,

inputinput energy,energy, onceonce tendstends toto increase,increase, andand thenthen becomesbecomes constantconstant..wavenumber [cm ]wavenumber [cm ]

inputinput energy,energy, onceonce tendstends toto increase,increase, andand thenthen becomesbecomes constantconstant..COCO22,, CO,CO, HCOOH,HCOOH, CC22HH22 andand HCNHCN areare producedproduced fromfrom benzene,benzene, toluenetoluene andand xylenexylene inin thethe

ItIt isis likelylikely thatthat gaseousgaseous unknownunknown byby productsproducts containingcontaining carboncarbonatmosphericatmospheric DCDC coronacorona dischargedischarge.. ItIt isis likelylikely thatthat gaseousgaseous unknownunknown byby--productsproducts containingcontaining carboncarbonatomsatoms existexist inin toluenetoluene andand xylenexylene decompositiondecomposition

pp gg

atomsatoms existexist inin toluenetoluene andand xylenexylene decompositiondecomposition..HCHO,HCHO, PANPAN andand CHCH33COOHCOOH areare producedproduced fromfrom toluenetoluene andand xylenexylene..

(2) Concentration variations of benzene, toluene,(2) Concentration variations of benzene, toluene, xylenexylene and byand by--productsproducts (4) Infrared spectrum and absorbance variations of unknown products(4) Infrared spectrum and absorbance variations of unknown products(2) Concentration variations of benzene, toluene, (2) Concentration variations of benzene, toluene, xylenexylene and byand by productsproducts (4) Infrared spectrum and absorbance variations of unknown products(4) Infrared spectrum and absorbance variations of unknown products

0 61 0(input energy : 10 kJ)600

m]

COm]

COm]

C 0.6unknown product (at 1200 cm-1)

1.0

0 5 C6H6ppm CO

1200ppm CO2300

ppm C6H6

C H CH HCOOHHCOOH0.5

u ow p oduct (at 00 c )C6H5CH3

0.5

]

C6H6400on

[p

on [p

200on [p C6H5CH3

C H (CH )

HCOOHHCOOH

0 4u.]

C6H5CH3 C6H4(CH3)2

0.0a.u.

ratio800

ratio200

ratio C6H4(CH3)2

PANPANunknown productsunknown products 0.4[a.u 6 4( 3)2

ce [ 1.0

C H CH200en

tr

400entr

100entr PANPANunknown productsunknown products

0.3ance

banc

0.5C6H5CH3on

ce400

once100

once

0.3

orba

bsor

b

0 00

co

504030201000

co

504030201000

co

50403020100 0.2

absoab 0.0

1 050403020100

input energy [kJ]50403020100

input energy [kJ]50403020100

input energy [kJ]

0 1

a1.0

0 5 C6H4(CH3)24

m]

HCN6

m]

C H

input energy [kJ]input energy [kJ]input energy [kJ]600

m]

HCOOH 0.10.5 C6H4(CH3)23pp

m HCN

ppm C2H2

ppm HCOOH

0.0504030201001400 1350 1300 1250 1200 1150 1100

0.03

on [p4on [p400on [p

50403020100input energy [kJ]

1400 1350 1300 1250 1200 1150 1100b [ -1]

2ratio

ratio

ratio

input energy [kJ]wavenumber [cm ]1cent

r

2

cent

r

200

cent

r

1

conc

conc

conc In toluene and In toluene and xylenexylene decomposition, unknown absorptiondecomposition, unknown absorption--peaks exist.peaks exist.

0

c

504030201000

c

504030201000

c

50403020100 ThTh kk d td t h ih i th lth l f df d tt bb50403020100input energy [kJ]

50403020100input energy [kJ]

50403020100input energy [kJ] TheThe unknownunknown productsproducts havinghaving methylmethyl groupgroup areare foundfound toto bebe

i dii di ddp gy [ ]p gy [ ]

3.0

m]

HCHO

p gy [ ]30

m]

CH COOH10

m]

PANintermediateintermediate productsproducts..

[ppm HCHO

[ppm CH3COOH

8[ppm PAN

2.0on [ 20on [

6on [

(5)(5) Decomposition processes of benzene, toluene and Decomposition processes of benzene, toluene and xylenexyleneratio

ratio6

4ratio ( )( ) p p ,p p , yy

1.0

cent

r

10

cent

r4

cent

r

Benzene,Benzene, toluenetoluene andand xylenexylene areare chieflychieflyCC66HH66conc

conc2

conc Benzene,Benzene, toluenetoluene andand xylenexylene areare chieflychiefly

convertedconverted toto COCO viavia COCO andand HCOOHHCOOH byby thetheCC66HH66 COCO HCOOHHCOOH0.0

c

504030201000

c

50403020100

0

c

50403020100 convertedconverted toto COCO22 viavia COCO andand HCOOHHCOOH byby thetheatmosphericatmospheric DCDC coronacorona dischargedischargeCC22HH22 HCNHCN50403020100

input energy [kJ]50403020100

input energy [kJ]50403020100

input energy [kJ] atmosphericatmospheric DCDC coronacorona dischargedischarge..22 22p gy [ ] p gy [ ]p gy [ ]

COCOT lT l dd ll dd COCO iiHCHOHCHO PANPANConcentrationsConcentrations ofof benzene,benzene, toluenetoluene andand xylenexylene decreasedecrease withwith thethe increaseincrease ofof inputinput energyenergy.. COCO22TolueneToluene andand xylenexylene areare convertedconverted toto COCO22 viaviaHCHOHCHO PANPAN

CHCH COOHCOOHCOCO COCO dd HCOOHHCOOH jj d td t ff bb t lt l dd ll ii thth di hdi h HCHO,HCHO, PAN,PAN, CHCH33COOHCOOH andand unknownunknownCHCH33COOHCOOHunknown productsunknown productsCC66HH55CHCH33

COCO22,, COCO andand HCOOHHCOOH areare majormajor productsproducts fromfrom benzene,benzene, toluenetoluene andand xylenexylene inin thethe coronacorona dischargedischarge..productsproducts..unknown productsunknown products66 55 33

CC66HH44(CH(CH33))22COCO isis aa gaseousgaseous endend productproduct andand COCO andand HCOOHHCOOH areare intermediateintermediate productsproducts pp66 44(( 33))22COCO22 isis aa gaseousgaseous endend product,product, andand COCO andand HCOOHHCOOH areare intermediateintermediate productsproducts..

44 C l iC l i44.. ConclusionsConclusionsDecomposition processes of benzene toluene andDecomposition processes of benzene toluene and xylenexylene in nitrogenin nitrogen oxygen mixture gas in an atmospheric DC corona discharge are investigatedoxygen mixture gas in an atmospheric DC corona discharge are investigatedDecomposition processes of benzene, toluene and Decomposition processes of benzene, toluene and xylenexylene in nitrogenin nitrogen--oxygen mixture gas in an atmospheric DC corona discharge are investigated.oxygen mixture gas in an atmospheric DC corona discharge are investigated.COCO22,, CO,CO, HCOOH,HCOOH, CC22HH22 andand HCNHCN areare producedproduced fromfrom benzene,benzene, toluenetoluene andand xylenexylene inin thethe atmosphericatmospheric DCDC coronacorona dischargedischarge..22 22 22 pp yy pp ggHCHOHCHO PANPAN andand CHCH33COOHCOOH areare foundfound toto bebe intermediateintermediate productsproducts fromfrom toluenetoluene andand xylenexyleneHCHO,HCHO, PANPAN andand CHCH33COOHCOOH areare foundfound toto bebe intermediateintermediate productsproducts fromfrom toluenetoluene andand xylenexylene..C t tiC t ti ff bb t lt l dd ll dd t lt l ithith thth ii ff i ti tConcentrationsConcentrations ofof benzene,benzene, toluenetoluene andand xylenexylene decreasedecrease monotonouslymonotonously withwith thethe increaseincrease ofof inputinput energyenergy..InIn benzenebenzene decomposition,decomposition, thethe totaltotal numbernumber ofof carboncarbon atoms,atoms, whichwhich isis presentedpresented asas thethe toptop lineline ofof stackedstacked graph,graph, decreasesdecreases withwith thethe increaseincrease ofof inputinput energy,energy, andand thenthen becomesbecomes constantconstant..p ,p , ,, pp pp g p ,g p , pp gy,gy,InIn toluenetoluene andand xylenexylene decompositiondecomposition thethe totaltotal numbernumber ofof carboncarbon atomsatoms decreasesdecreases withwith thethe increaseincrease ofof inputinput energyenergy onceonce tendstends toto increaseincrease andand thenthen becomesbecomes constantconstantInIn toluenetoluene andand xylenexylene decomposition,decomposition, thethe totaltotal numbernumber ofof carboncarbon atomsatoms decreasesdecreases withwith thethe increaseincrease ofof inputinput energy,energy, onceonce tendstends toto increase,increase, andand thenthen becomesbecomes constantconstant..B l dB l d ll hi fl d COhi fl d CO i CO d HCOOH d l di CO d HCOOH d l d ll d COd CO i HCHO PAN CHi HCHO PAN CH COOH d k d b h h i DC di hCOOH d k d b h h i DC di hBenzene, toluene and Benzene, toluene and xylenexylene are chiefly converted to COare chiefly converted to CO22 via CO and HCOOH, and toluene and via CO and HCOOH, and toluene and xylenexylene are converted to COare converted to CO22 via HCHO, PAN, CHvia HCHO, PAN, CH33COOH and unknown products by the atmospheric DC corona discharge.COOH and unknown products by the atmospheric DC corona discharge.