Document vVwLJpBDMp1QmdMYQ3goM3bwm
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Fluorochemical Decomposition Processes - April 4,2001 David A. Dixon Theory, Modeling, and Simulation, William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA Overview tpfostchhluoofueelntofreppcomrnelornutorociafsacdhmlTileuyoehsiopmnndsirrsaseeoiemcssfca..arulidolkcTrsomsyshAcolienutbrohsmpsfiiursnoeilicmnffvnwiotiatnaothnrierrieaoyrokdstaeueegtissisnoeoccclaonroelldiumcrbepodtepgrrefosooor:tfanchudieinrmcsasedstsowsieuo,nssolntoatrrsbmrukeapcesitalsoreuitskndhtroeewoolyeaprnvytoehapmstmleeouoonliafysrdtotiysmeearilloieinnfrmwgspdpaoeersodcrgofoefrdllnautuuhdtocsaeasretiutosnditlaohifonlnoekfgrntyotmahlppmoesaedupitridhyfnlrfelewncousdianoa.nimyarceottsrieacasKlst,kitfoheyoooyenlrrf 1. thdIaefsiomgpmthhepcieentersatnaenotomutufrpgeitshehsire,suatethiuhniregcieinhnfielenmurnaootitrhnuiooeigcmnhaii.nrszbcyiOoinsnngtneeermwabmtyiiiluo-nlpsnrttceoopardmlrmsuoopccslteheosatsffevolme(yremti.hxgdaei.etnicpiogonrnmcoaipnnpaedesorrsrafeellto.suoniordTg,rehocnucaecsasme,rbettthoihnmenet/ekfieuinwnlecnglii,linrlnaeeebttriceaeo.rt).iitnohinges 2. IicnfocnCidnFiet4ri,oatntihsoenshmosyuoslsdttefmsut,lalybiltdesespcteorromfylpualoelrltoeoatlhkdeyerslptrecurocfmtliuoponoruonawldko,yulwldceorsmehpoaowdudnetddhsa.atsthaetriancceirnetroatitohne Thermal Decomposition Processes bmettbooenuxemavlriatodnieprwierehozirriainanglf2Imtlghn0uaae0rmnaatne0egndtsemae.ilbnutnpeetinCcemmtdtirwoonaeppmgeteraeureecrbarttnathueht.tiesue2ot(rr0nitepoe0wrsnm0ooyitppfshcteae3aernranm5ad0cthuto03ayhrns0deetd0srownoi0tuec4ioolap0lFcnr0bcast0aous,onrn0it-dnh3fFlee~u0a)ae80fcdlio0.neisrnmemaTgcFenayanttpaitot~oiitkcrneati1mhlsl6notepr5r,fee0etdasphrimearedostCeutwdtrnrhuu~eacaccssetttt1sieatpo9ibmrnmw2oo5vieavtosethiKefdra1elitro5asbhel0waeO~0sise32os0dhtraFaseserozatcaneittnnheraodgdeat pttbcdec(hh2hvoreyeao-paemcsttcnieheenepnnesotbdamhtsurefer.iTeuenersna)hecdckWlilehiisoscekatramehsneonalifbfoahysttiytnsermaeisttnvsartto.a.hierpadteblr3Iofteefoot-mcesccbDaemtdeiuhonnnenispenftactee)fedeto.ediderrmtradobheoTtomrpeunnberhrortiayeesn4tbk.eha-bdvuiecnnoaeamTegtncpnvhnodopdaeitamrsrsepsriowreoztpcahaarewoeecetalssspitiikoisotmhitwheennliaiossi)iidsntttneihdaoaabwtirtrlorofieheohfnrxiaeaitenidcycrgcatceghthciwpanioetorntitnintoeonleslncbns(mseodbeu,tsoprsrrsoseveefuwntanraaotaaekipghltntlhtoebumaydhrertosimeuoztct.ahscheoatwecdeOtnseurdltilnroilrloerienlcwatawbaueedlyderseehimrvicsanbotaavvpigoplntfiersenaooetimdognrcatideetphzseaniseeecrfrseadrifefsarbed,sa(astroitsauittectonnehranaedndedeslrt
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R fC F 20 R f' + F2C(0)
(1)
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Molecule C3F7SO2NH2 c 3f 7s o 2* c 3f 7s o 3c 3f7so 2oh c 3f 7s o 2f c3f 7so3'
Bond Cleavage Products
c c
23ff
75-*
++
Cs oF22nS0h22NH2
c c
23ff
75'-
++
Cs oF22SO2(singlet)
CC23FF75.* ++ SCOF32S(s0i3n*g(letrti)plet)
c c
32ff
75--
++
CSF022S0OH2OH
cc23ff57-* ++ CsoF22SfO2F
- Cc23fF57-. ++ CSF023S' O3'
B.E.(kcal/mol) 6835 768
2804 6845 6844 7889
~1900The conditions in most cement kiln incineration systems are very high
temperatures (up to
K). As the C-S bonds are o f the lowest energy, they will break
first under these high temperatures and will be the first to break at the lower temperatures
expected in the temperature ramp region in the incineration system. This will lead to
formation o f fluorocarbon radicals that will then decompose as discussed above. I f the
~20SO2R' group is SO3, then the C-S bond is extremely weak,
kcal/mole, and the
85compound will readily decompose. The C-C bond energy is still on the order o f
44kcal/mole. Also note that this is dissociation to the singlet ground state o f SO3. The
triplet is calculated to be kcal/mole higher in energy than the singlet which places the
S-C bond energy in the same range as those o f other compounds. (Our calculated singlet-
triplet energy difference is likely be too low.) The C-C bond for CF3CF2-CF2SO3 to form
triplet CF2SO3 is o f a comparable energy to other C-C bonds in this series. I f the S -R '
bond breaks first, for example in RfS02N(CH3)C2H40R (however, see below for a
discussion o f this point), then the radical R rS 0 2 will be formed. I f an RS2* fragment is
21 7formed, the C-S bond is very weak, only kcal/mole in CH3SO2 and an even lower
kcal/mol for CF3SO2. Cleavage o f the C-S bond in RfSC>2 will quickly lead to the
fluorocarbon radical chain decomposition described above and SO2 formation. The C-C
bond energy in RfSC>2 is again much higher than the C-S bond energy although lower
10than other C-C bond energies. If the SO2R' group is SO3', then the C-S bond is about 15 ~10to kcal/mole stronger than in the other compounds noted above but still kcal/mole
weaker than the C-C bond.
,
We also have calculated -SO2-N bond and N-C bond energies in related model
systems. These models were chosen to get higher accuracy without having to use
85 298additivity corrections. The N-C bond strength in CH3NH2 is kcal/mol at K based 3 2on the latest results from experiment and theory. For the model system CF3SO2NH2, we
obtain the following bond energies at the G -MP level:
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CF3SO2NH2
- NCFH32**++ *SS0022NCHF23
6789..35 kkccaall//mmooll
tsTChthrFeoe3fnorCgale-ldoSriwctbhaiolnanngisdtahnteeonthteCerag-sGSy3sbit-saoMbnciPodlin2zasislinesgevtexeanpl:stecwthteietdh.Ct3hFFeo7vrraathldueiecsmals)ohdaoenwldnstyhasebteomSv-eNC(Fsbl3oiSgn0hd2tlNeynHsetrCrgoHyn3gi,sewrcealesafitrnhlyde
CF3S02NHCH3
CF3S02NH + *CH3 94.3 kcal/mol
-> CF3S02* + *NHCH3 78.4 kcal/mol
tTeoxhpeceshceatnergdees.uslotsfaarefecwonksciastle/mntowl dituhethtoosreemdoistceussusebdstiatbuoevnet.efTfehcetsmboudtenlosylasrtgeemrscmhaingghetsleaarde
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TD-DFT Calculated Excitation Energies of CF3SO2NH2
Exfncnitfa)tion 177 161 157 156 Conclusions
Excitation Energy ('eV') 7.00 7.69 7.90 7.93
Oscillator Strength f 0.0008 0.0228 0.0066 0.0051
Based on the above assessment o f the thermal destruction o f fluorochemicals, the
following conclusions may be drawn:
1. The C-S bond should break first under high temperature conditions leaving the
SC^R' Rf Rf R'substituted
or the SO2 radicals and the and radicals respectively.
2 Rf. The radical will then follow normal fluorocarbon combustion pathways via C(0)F2
to form CO2 and HF.
3. The SO2R' radical will likely decompose to SO2 and R ' with the R ' radical following
its normal decomposition path.
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4. tIefmRpfe-SraCt>u3resis. formed, it will quickly decompose to Rf and SO3 at very low 5. AaeIfnftfyCictFshiie4egnntwuliyfpaispcdaeeanrcdtodofmelpudeporoarasitnteirnadagtcesedotrebtmghyaap-spterraioatndtcduuarcnnetossseaCorrFvfe4ecgeiaesmsnepearrnaemttseeadknr.iktlnearst ft(oh-re1c9oo0um0tlpeKtl,e)ti,et dCiseFc4uonmlsihkpoeoulsylidtitohbnae.t 6. tcfuTiinlopmuhcnpoeietenraeorecwncretagainltriltdinbiombeooneenefr/tiitfetnhutsmogeeolpapdeersoenarpramtseaituouctirin.trneseagnIocnittfsoeiamtmshhdspepidugelieehitrnitaoeictennuinn,rdmoeeieurtigragnawrthiniamo.idglnlaiezt.bOsiioneynngsebt.eebwmsyta-Opiinnfnrtosetthdeterumomccuthsesmaftoovefreamnmltstahoiktxeiioilhnnnlagovinasaesgnreudltsohntrneegnpseopiaadsrssreoinptbthhceleeeer References 1. T38sa5n. g, W.S.; Burgess, Jr., D.R.; Babushok, V. Combust Sci and Tech. 1998, 139, 2. PC10hu3yrs,ti.s1s10,96L93.;8A,C1.0u;9rRt,isa7sg7,h6La4v.. aAch.;arRi,agKh.a;vRacehdaferim, ,KP.;. RC.e;dPfeompl,e,P.J.CA.; .P./.opCleh,emJ.. AP.hyJs.. C1h9e9m7., 3. MSCPhaIetEmsu.2zA0a0,w0ian,,3pN9r.e9s9Ns,.(;327M050;o1rM)i.,aSts.;uzYaawnao,,NE..;NO.;kIaszhaiktain, iS, .A; .I;shDitiaxnoin,,AD..; AD.i;xUond,a,DT. .AJ.. PPrhoycs..
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