UniteS ta tesPa tent[ 1 9 1Pence et.[ 1 1 1 4 , 2 2 0 , 6 3 2[ 4 5 ] S ep .2 , 1 9 8 0[ 5 4 ] REDUCTION OF NITROGEN OXIDESWITH CATALYTIC ACID RES IS TANT ALUlVlllNOS ILICATE MOLECULAR S IEVESAND AMMONIA Da lla sT.Pence;Thoma sR.Thoma s ,b oth ofId a ho Fa lls ,Id .The UnitedS ta tesofAmericaa srep res entedb ythe UnitedS ta tesDep a rtment ofEnerg y ,Wa s hing ton,[ 7 5 ] Inv entors :[ 7 3 ] As s ig nee:1 1 c.[ 2 1 ] Ap p 1 . No. : 5 0 4 , 7 9 3[ 2 2 ] Filed : S ep .1 0 , 1 9 7 4Rela tedUS .Ap p lica tion Da ta[ 6 3 ] Continu a tion- imp a rtof S er. No. 2 8 4 , 8 1 0 , Au g . 3 0 ,1 9 7 2 ,a b a nd oned .[ 5 1 ] Int.( 3 1 . 3 . . . . . . . . . . . . . . . . . . . . . . . .. . B0 1 J 8 /0 0 ;COlB 2 1 /0 0[ 5 2 ] US .Cl. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 4 2 3 /2 3 9 ;4 2 3 /2 3 7 ;4 2 3 /4 0 3[ 5 8 ] FieldofS ea rch . . . . . . . . . . . . .. . 4 2 3 /2 3 9 ,2 1 9 ,2 3 5 ,2 1 2 ,4 2 3 /2 1 3 2 ,2 1 3 . 5 ,2 1 3 . 7[ 5 6 ] Ref erencesCitedU. S .PATENT DOCUMENTS.2 , 9 7 5 , 0 2 5 3 /1 9 6 1 Cohn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 4 2 3 /2 3 93 , 0 3 3 , 6 4 2 5 /1 9 6 2 Bu ka taet a 1 . . . . . . . . . . . . .. . . .3 , 2 7 9 , 8 8 4 1 0 / 1 9 6 6 Nonnenma cher et a 1 .3 , 3 4 6 , 3 2 8 1 0 /1 9 6 73 , 4 4 9 , 0 6 3 6 /1 9 6 93 , 4 5 4 , 3 5 5 7 /1 9 6 93 , 4 7 6 , 5 0 8 1 1 /1 9 6 93 , 5 9 9 , 4 2 7 8 / 1 9 7 13 , 6 7 4 , 4 2 9 7 / 1 9 7 23 , 7 6 7 , 7 6 4 1 0 /1 9 7 3 Dolb ea r . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 4 2 3 /2 1 3 73 , 8 9 5 , 0 9 4 7 /1 9 7 5 Ca rter et a 1 . . . . . . . . . . . . . . . . . . . . . . . .. . 4 2 3 /2 3 9OTHER PUBLICATIONSPence eta 1 . NOX Ab a tement Us ing Ammoniaw ith Z eoliteCa ta ly s ts , Proceed ing s oftheAEC Pollu tion ControlConf erence, p p . 1 1 5 - 1 2 1 , Oa kRid g e 1 0 /2 5 /7 2 - 1 0 /2 7 /7 2 ,US AEC.Pence et a 1 . Ca ta ly tic Red u ction ofNitrog en Ox id es ,Atomic Energ yCommis s ion Relea s es , US . Pa tentsa ndPa tent Ap p lica tionsf or Licens ingp . 2 2 ,Ma y4 , 1 9 7 3 .Penceeta 1 . NOxAb a tement Us ing Ammoniaw ith Z eolite Ca ta ly s ts ,Nu clea r S cience Ab s tra cts ,v ol.2 8 ,p .2 5 4 ,Ab s tra ct No.2 6 3 2 ,Ju l. 3 1 , 1 9 7 3 .Pence et a 1 . Ca ta ly tic Red u ction ofNitrog en Ox id es , Atomic Energ yCommis s ion Relea s es ,U. S I Pa tentsa ndPa tent Ap p lica tionsf or Licens ing ,p .2 7 ,Au g .3 1 , 1 9 7 3 .Norton Bu lletin Z - 5 0 ;Norton Chemica l Prod u ctsDiv i s ion, Akron,Ohio,1 9 7 0 . 'Chemica l Ab s tra cts ,v ol. 6 5 , 1 9 6 6# l6 , 0 9 1 g .Ind u s tria la ndEng ineering Chemis try v ol. 5 3 , No. 3 ,Ma r.1 9 6 1 ,p p . 1 9 9 - 2 0 4 .Prima ryEx a miner- Bria n E.Hea rn Attorney ,Ag ent , or Firm - Ja mesE.Denny ;Dea n E.Ca rls on;Fra nk H.Ja cks on [ 5 7 ] ABS TRACT Nox iou snitrog en ox id esin aw a s te g a ss trea m s u ch a sthe s ta ck g a sf rom af os s il- f u el- ? red p ow er g enera tion p la nt or other ind u s tria l p la nt of f - g a ss trea m is ca ta ly ti ca lly red u cedto elementa l nitrog en a nd /or innocu ou snitrog en ox id esemp loy inga mmoniaa sred u cta nt in the p res ence ofaz eolite ca ta ly s t in the hy d rog en 9 r s od iu m f orm ha v ingp ore op ening sofa b ou t 3to1 0A.8Cla ims ,7Dra w ingFig u resUS a tentS ep .2 , 1 9 8 0 S heet1 of4 4 , 2 2 0 , 6 3 2NH3/MOM 5 5 . 0 f m5 6 3 5 0 02 . 0L0 0 L5 0m3/NOX 3 5 6 mm5 5 . 5 2 0 0 .@ g i' oichig ? w ei' ric Amou ni of NH3mm L2 0' 0o ( D O ' 6 )O S michiomei nc Amou ni' of NH34 , 2 2 0 , 6 3 2S ep .2 , 1 9 8 0 S heet 2of41 . 2 01 . 0 0. s o 1 8 . . %$ 0_ _ II BEIDDEPTH, I 2 5 0 3 5 0 4 5 0TEMPERATURE, C 2 5 0 3 5 0TEMPERATURE, C 4 5 0 7 Q EFFICIENCY 0 Pa tent S ep .2 , 1 9 8 0 S heet 3of 44 , 2 2 0 , 6 3 2FIE I0 0% EFFICIENCY | E1 | IIl . 5 L0 0S TOICHIOMETRICRATIO 6 0I0 08 0U3 l% H2 00 | O / H2 O TI5 % H2 O 1 . 0 L5 2 . 0S TOICHIOMETRICRATIO U a mtS ep . . 2 , 1 9 8 0 S heet4of 4 4 , 2 2 0 , 6 3 5 ?% EFFICIEHCY i)4 , 2 2 0 , 6 3 2I REDUCTION OF NITROGEN OXIDESWITH CATALYTIC ACID RES IS TANT ALUMINOS ILICATE MOLECULAR S IEVESAND AMMONIA CONTRACTUAL ORIGIN OF THE INVENTION Theinv entiond es crib ed hereinw a s ma d einthe cou rs eof , oru nd er, a contra ctw iththeUNITED S TATESATOMIC ENERGY COMMIS S ION.CROS SREFERENCE TO RELATED APPLICATIONSThisis acontinu a tion- in- p a rt ofou r a p p lica tion S er.Nu mb er 2 8 4 , 8 1 0? ledAu g .3 0 , 1 9 7 2 ,nowa b a nd oned .BACKGROUND OF THE INVENTION Thisinv entionrela tes totheca ta ly ticred u ctionofnitrog en ox id es .In more d eta il,the inv ention rela testo the ca ta ly tic red u ction ofnox iou snitrog en ox id esp resent in aw a s te g a ss trea m.In s tillmore d eta il,the inv en tion rela testo the ef f ectiv e elimina tion ofnitrog en oxid esa sas ou rce ofp ollu tion f rom f os s il- f u el- ? redp ow er g enera tionp la nts a nd otherind u s tria lp la ntof f - g a ss trea ms .Ititnowg enera llyrecog niz edtha t the a tmos p heric conta mina tiontha ta ccomp a nies ind u s tria ls ociety isone ofthe mos t s eriou sp rob lemsf a cingma nkinda ndtha tcerta innitrog en ox id escontrib u te hea v ilytothisp rob lem.There a rea tlea s t- s ix s ta b leox id es ofnitrog en b u t onlynitric ox id e ( NO)a ndnitrog en d iox id e ( N0 2 )a re trou b les ome f rom a p ollu tions ta nd p ointa ndthef or mu laNOX isg enera lly u s edto ref er to thes e tw o ox id es .In common w ith other ma j or a irp ollu ta ntsNOX a ris e chief lyf rom thep rod u ction ofenerg yinthe community , moe s p eci? ca lly b ythe? x a tionofa tmos p heric nitrog eninhig h- temp era tu rereg ions off u rna ces a ndinterna l comb u s tion eng ines .Another s ou rce ofNO, a sa tmos p heric p ollu ta ntsa re inorg a nic a ndorg a nic nitration rea ctionsin the chemica l p roces sind u s tries .Tra nsp ort, ind u s trya ndelectricity g enera tion a llcontrib u te to the p rob lem.The corros iv echa ra cterofw a s te g a s es conta iningnitrog en ox id esma ya ls o neces s ita te or a t lea s t rend er d es ira b lethe remov a l ofthes eox id esf rom w a s te g a ss trea ms ,ev en thou g h relea s e ofthe ox id esto the a tmo s p here ca n b e tolera ted .The p res ence ofNO, in aWa s te g a ss trea m ma yma ke it neces s a ryto cons tru ct p ollu tion control eq u ip ment throu g h w hich the w a s te g a ss trea m p a s s esofa n ex p ens iv e corros ion- res is ta nt ma teria l s u ch a s s ta inles s s teel, w herea sa chea p er ma teria ls u cha sca rb ons teelcou ld b eu s ed if theNOX a reremov edb ef orethew a s te s trea menters thep ollu tioncontrol eq u ip ment.Ox id esofnitrog en p la yad u a l role ina irp ollu tion,? rs t a sap ollu ta nt in their ow n rig ht a nds econda sthe initia torofcomp lexp hotochemica l rea ctionsw ith hyd roca rb ons . Whilep hotochemica ls mogis themos t v is ib lea nd immed ia tely s eriou s cons eq u ence ofNOxp ollu tion, itis recog niz edtha t the p res ence ofNOxin thea tmos p here w illa d v ers elya f f ecttheenv ironment ev enthou g hnop hotochemica ls mogha s ev erb een d etected inthea rea , a nd theS ta teofCa lif ornia ha ses ta b lis heda n a d v ers elev el a b ov e w hich the concen tra tion ofNOxin the a tmos p here s hou ldnot b e p ermit~tedto ris e.Unf ortu na tely ,thisa d v ers elev el ha sb een s u b s ta ntia lly ex ceed ed inma ny cities of theUnited2 02 53 54 55 05 56 06 52S ta tesw hich ra rely ,ifev er,ha v e ap rob lem w ith p hoto chemica l s mog .It f ollow stha t ox id esofnitrog en s hou ldb e controlledin a llcitiesa nda rea sin w hich there is aconcentra tion ofind u s tryin ord er to red u ce the NO, a ndox id a nt concentra tion b elowthe a d v ers elev el.There a re tw o comp letelyd if f erent a p p roa chesto the controlofNOxemis s ion; the? rs tis tomod if y the s ou rceins u ch a w a ya s tored u cethef orma tionofox id esofnitrog en a ndthe other is d es troyor ca p tu re the nitrog en ox id esa lrea d yf ormed ,thereb yp rev entingthem f rom es ca p ingto the a tmos p here.Ma nymethod sf or red u cingNO, p ollu tion ha v e b een s u g g es teda ndaf ewa re inp ra ctica lu s e. S ome ofthe s u g g es tedmethod sinclu d e:Mod i? ca tion oforig ina l s ou rce 1 . Mob ile s ou rcesa . Cha ng esin eng ine d es ig n b . Ex ha u s t g a srecircu la tion 0 . Us e g a stu rb inesra ther tha n g a s oline or d ies el eng inesd .Us e electric motorsra ther tha n interna l comb u stion eng ines2 . S ta tiona rys ou rcesa . Cha ng esin f u rna ce d es ig n b . Tw o- s ta g e comb u s tion 0 . Cha ng e in ty p e off u el d . Inclu s ion ofa d d itiv esin the f u el Remov a l ofox id esofnitrog en a . S orp tion b yliq u id s ,f or ex a mp le,f errou ss u lf a te or ca lciu m hy d rox id e s olu tionsb .S orp tion b ys olid s ,f or ex a mp le,s ilicag el or molec u la r s iev es0 . Therma l red u ction b yb u rningin af u el- rich ? a me d . Va p orp ha s erea ctionw ithothercomp ou nd s .Metz ler inNAS A TMX- 2 2 5 7 ,Ma rch1 9 7 1 , p ro p os estha t a mmoniab e rea ctedd irectlyw ith ox id esofnitrog en. How ev er,p otentia llyex p los iv e s olida mmoniu m nitra te is area ction p rod u ct a ndcon trolled d ecomp os itionofthis a mmoniu m nitra te ha snot b een d emons tra ted .e. Ca ta ly tic red u ction to nitrog en w ith or w ithou t the a d d ition ofared u cingg a s .And ers on et a l. in Ind .Eng .Chem,5 3 , 1 9 9( 1 9 6 1 )s howtha t NOxca n b e s electiv ely red u cedb ya mmoniaemp loy ingp la ti nu m a sca ta ly s t anu mb er ofp rob lems ,how ev er,ha v e b een rep orted w ith this p roces s . Firs t, f ree ox y g en,ev eninrela tiv ely s ma lla mou nts , ha s atend encyto p ois on the ca ta ly s t a nd ,s econd ,d if ?cu lties ha v eb eenex p erienced inob ta ining the p rop er cond itionsto p rev ent ox id a tion ofa mmoniap rior to its u s e a sthe red u cingg a s .Thef ollow ing p a tents a ls od es crib ep roces s es in w hich a mmoniaisu s eda sared u cingg a sin the p res ence ofaca ta ly s t.Nonnenma cher U. S . Pa t. No. 3 , 2 7 9 , 8 8 4 - Us esV2 0 3 ,M0 2 0 3or W2 0 3a sca ta ly s t in p res ence of0 - 15 %ox y g en S how s 9 9 . 2 % remov a lw ith3 . 5 % ox y g en p res ent.Grif ? nget a l. U. S .Pa t. No.3 , 4 4 9 , 0 6 3 - Emp loy sacop p erconta ining ca ta ly s ts u cha s cop p erox id eor s u p p ort s u ch a ss ilicaa lu mina .Cohn et a l. U. S . Pa t. No.2 , 9 7 5 , 0 2 5 ~ S u g g es tsu s e ofap la tinu m g rou pmeta l inp res ence ofO~ 2 2 %ox yg en.In a d d ition Kea rb yet a l. - . - U. S .Pa t.No.3 , 4 7 6 , 5 0 8 ~ emp loy sz eolitesto d ecomp os e u nb u rnedhy d roca rb onsp res ent in ex ha u s t g a s esa nds ta tesin one ex a mp le tha t 4 , 2 2 0 , 6 3 23Ni- ex cha ng ed z eolites conv erted CO a nd NO u nd er red u cingcond itions .In s p ite ofthe tremend ou sef f ort tha t ha sb een a ndisb eingp u t intothis p rob lem, thef a ctrema instha tno s a tis f a ctory p roced u ref orp ra ctica la nd ef f icientre mov a l ofNO, f rom ef f lu entstha t conta in hig h lev elsofox y g en ( 3 to 2 0 % )is nowknow n f or es s entia llycom p letelyd es troy ingNOxp res ent inaw a s te g a ss trea m,s u cha s thes ta ckg a s g iv enof fb ya f os s il- f u el- f iredp ow er g enera tion p la nt.S UMMARY OF THE INVENTION Accord ingto the p res ent inv ention,nox iou snitrog en ox id esa rered u cedtoN2a nd /or N2 0b ymix ingthe s trea m conta iningnox iou snitrog en ox id es w ith ag a ss trea m conta ininga mmoniaa t atemp era tu re of2 5 0 to 5 5 0 C.a ndconta ctingthe s a me w ith az eolite ca ta ly s t in the hy d rog en or s od iu m f orm ha v ingp ore op ening sofa b ou t 3to1 0A.For ex a mp le,the nox iou snitrog en ox id esp res ent in s ta ck g a s esconta iningox y g en,w a ter v a p or a nds u lf u r d iox id e ma yb e red u cedto innocu ou ss u b s ta ncesb ymix ingthe s ta ck g a sw ith ag a sconta ininga n ef f ectiv eq u a ntityofa mmoniaa tatemp era tu re of2 5 0 to 5 5 0 C.in the p res ence ofaz eolite in the hy d ro g en or s od iu m f orm a sca ta ly s t.BRIEF DES CRIPTION OF THE DRAWING FIG.1isag ra p h in w hich the conv ers ion ef f icienciesf or the red u ction ofNOxp res ent in ad rya ir s trea m a ndp a s s ed throu g ha f ou r- inchz eoliteca ta ly s tb ed a tas u p er? ca l f a ce v elocityof1 0 0f t/min. a re p lotteda saf u nction ofthe ra tioofa mmoniaconcentra tion tothe NOxconcentra tion a ndtemp era tu re;FIG.2is as imila rg ra p h f or a n eig ht- inch ca ta ly s t b ed ;FIG.3is ag ra p h in w hich the a mmoniareq u iredf or 9 9 %conv ers ion ofa b ou t 5 0 0 0p p m N0 2p res ent inad rya ir s trea m a ndp a s s edthrou g h az eolite ca ta ly s t b eda t af a ce v elocityof1 0 0f t/min.is p lotteda saf u nction oftemp era tu re;FIG.4isas imila r g ra p h f or ahu mida ir s trea m ( d ewp oint of4 6 C. ) ;FIG.5is ag ra p h in w hich the a b a tement ef ? ciencyf or NO, ( 1 5 %NO,8 5 %N0 2 )p res ent inas imu la tedWa s te Ca lciner Fa cilitya tmos p here isp lotteda saf u nc tion ofex it b edtemp era tu re a nds toichiometric ra tio ofNH3to NOxf or a n eig ht- inch b edconta iningl/ 1 6 - inch hy d rog en mord enite ex tru d a te;FIG.6is as imila r g ra p h f or 1 0 0 %NO,a ndFIG.7is as imila r g ra p h f or 1 0 0 %NO a ndatw elv e inch b edconta ining - inch hy d rog en mord enite ex tru da te.S PECIFIC EMBODIMENTSOF THE INVENTION Und erthecond itions emp loy ed inou rinv ention,nox iou snitrog en ox id es a rered u cedtonitrou s ox id e a nd /or nitrog en.The d is trib u tion ofthe rea ction p rodu ctsa p p ea rsto b e af u nction ofthe ca ta ly s t b edtemp er a tu re a ndthe a ctiv ityofthe ca ta ly s t a sw ell a s ofthe p a rticu la r red u cingg a semp loy ed .Althou g h red u ction ofNO, to elementa l nitrog en is p ref era b le, N2 0is not a nu nd es ira b lep rod u ct, b eca u s eitd oes notf orm a n a nhy d rid e,isd if f icu lt to ox id iz e a ndisnot cons id eredto b e ap ollu ta nt.The ex a ctrea ctions inv olv ed inthep roces softhe ins ta nt inv ention a re d ep end ent on the comp os ition of4 05 06 06 54theg a s eou s mix tu re, a ndtheca ta ly ticb ed op era tingcond itions . How ev er,the p rob a b le rea ctionsa re:3 N2 O+2 NH3 >4 N2 +3 H2 O( 4 )The a mou nt ofa mmoniaemp loy edmu s t b e s u f f icient toef f ectcomp lete red u ction ofthe nitrog en ox id esto elementa l nitrog en a nd / or nitrou sox id e.The a mou nt ofa mmoniareq u iredw ill f a llin ara ng e b etw een s lig htlys u b s toichiometrica nd s lig htly s u p ers toichiometric b a s edon comp lete red u ction to nitrog en.Ifno or v erylittle ox y g en isp res ent in the w a s te g a ss trea m the s ma ll a mou ntsofred u cingg a s( CO a ndH2 )p res ent therein ma yred u ce ap a rt ofthe NOX s o tha t les s tha n as toi chiometric q u a ntityofa mmoniaw ou ldb e s u f ? cient.Ifa llor ama j or p rop ortion ofNOX is N0 2 ,the a mmoniama yred u ce thisto N2 0w hereb yles s tha n as toichio metric q u a ntityb a s edon comp lete red u ction tonitro g en is req u ired . Als o p a rticu la rly a thig hertemp eratu resthe z eolite ca ta ly s t w ill red u ce the N0 2to NO s o tha t les sa mmoniaisreq u ired .On the other ha nd ,p a rtic u la rlya t hig her temp era tu res ,comp etingrea ctionsma yma ke it neces s a ryto emp loyalittle more a mmonia . -The ex a cta mou nt ofa mmoniareq u ired is d eterminedb yon- line continu ou smea s u rement ofthe NOxin the p ro ces sef ? u ent. ,It isnot neces s a rytha t the entire red u cingg a ss trea m ha v e a red u cing comp os ition s incethep roces s is re ma rka b lytolera nt to the p res ence ofmolecu la r ox y g en or other ox id iz ingg a s .For ex a mp le,the p roces sis v eryef f ectiv eona irs trea ms conta ining u p to2 0 v olu me p ercent ox y g en.Thisis as ig nif ica nt a d v a nta g e ofthe p roces s , s incema nycu rrently p rop os edp roces s es re q u ire tha t the ex ha u s t s trea m ha v e av erylowox y g en content.Asw ill b e s how n hereina f ter the p roces sisa ls o ef f ec tiv eon hu mida irs trea ms a nd on s trea ms conta inings u lf u r d iox id e.Thisis v eryimp orta nt s ince ma nyind u stria lw a s teg a s s trea ms conta inw a terv a p ora nd / or s u lf u r d iox id e.The z eolitesu s ef u l in the p ra ctice ofthe ins ta nt inv en tiona rea lu minos ilica tes w ithf ra mew ork s tru ctu resenclos ingla rg e ca v itiesca lleds u p erca g es ,w hich a re ofex cep tiona llyla rg e a ndu nif orm s iz e. The f u nd a menta l s tru ctu ra lu nits ofz eolites a res ilicona nd a lu minu m a toms tetra hed ra lly coord ina ted w ithf ou rox y g en a toms . Beca u s e the ox y g en a tomsa re mu tu a llys ha redb etw een tetra hed ra lu nits a ndcontrib u tea nef f ectiv e u nitcha rg e to ea ch tetra hed ron,ea ch a lu minu m tetra he d ra lu nitp os s es s es anetneg a tiv echa rg e. Ca tions a sreq u iredin the f ra mew ork s tru ctu re to ma inta in cha rg e neu tra lity . The ca tionsa re u s u a lly ,b u t not a lw a y s ,s o d iu mions , a ndthenu mb er req u ired p eru nitcellisd icta tedb ythe s ilicon- to- a lu minu m ra tio ofthe z eolite.Thes e ca tionsca n b e rep la cedb yother ionsb yion- excha ng e p roced u res .The s ilicon- to- a lu minu m ra tioa ndthep a rticu la rca tiona reca teg oriz ed b ythety p eofz eolite. While a nyz eoliteex hib itingca ta ly tica ctiv itycou ldb e u s edex cep t f or thos e in w hich the s od iu m ha sb een ex cha ng edf or ca tionsw hich a re s o a ctiv e tha t the red u cingg a sd ecomp os esb ef ore itca n rea ct w ith the NOX inv iewofthe ind ica ted u tility ofz eolites inthe 4 , 2 2 0 , 6 3 235u nex cha ng eds od iu m orhy d rog en f orm a ndthes u bs ta ntia llylow er cos t thereoftha n ofex cha ng edz eolites ,u s e onlyofthe hy d rog en a nds od iu m f ormsofz eolitesiscontemp la tedin a ccord a nce w ith thisinv ention.One ofthe p rop ertiesofz eolitesis their ca p a b ilityofs electiv ely a d s orb ing certa inmolecu les inp ref erence to, or tothecomp lete ex clu s ionof , othermolecu les ;they , theref orea ref req u ently know n a s molecu la r s iev es . While w e d onotw is h tob e b ou ndb ya nymecha nis tic interp reta tion,it isb eliev edtha t the z eolitesofthe ins ta nt inv ention f u nction b ys electiv elya d s orbingb oth thenitrog en ox id esa ndthe a mmoniaw ithin the p ore inters ticesw here s trongelectros ta tic f orcesofthe p romote the rea ction ofthe nitrog en ox id e a ndthe red u cingg a s . The rea ction p rod u ctsthereb yp rod u cedthenex itf romthez eolitef ra mew ork s tru ctu re. The p oresofd if f erent know n z eolitesv a ryin d ia meter f rom a b ou t 3Ang s tromsto a b ou t 1 0Ang s troms ,b u t f or a nyone z eolite, the p oresa re ofs u b s ta ntia llyu nif orm s iz e.Z eolitesu s ef u linthe p ra ctice ofthe ins ta ntinv ention ca n s u ita b lyha v e p oresra ng ingin s iz e f rom a b ou t 3to a b ou t 1 0Ang s tromsw hen s od iu m is the ca tion. Howev er,the p ore s iz e isa lteredb ythe ex cha ng e ofca tionsa td if f erents iz ea nd cha rg e. S u ita b lecommercia llya v a ila b le z eolites g enera llyha v e p a rticles iz esra ng ingf rom a b ou t 4 1to a b ou t 2 0mes h ( US .S ta nd a rdS eries ) .Ifd es ired ,the z eolite ma yb e d is p ers edw ith a n inert ca r rier s u ch a sa lu mina .Althou g hs y nthetica lly p rep a red z eolites a rep re f erred f oru s eina p p lica tionoftheins ta ntinv ention b eca u s e oftheir more u nif orm p rop erties , na tu ra l z eo litesca n b e u s ed .Na tu ra l z eolitesu s ef u l f or thisp u rp os e inclu d e, p rima rily , the f a u j a s ites , cha b a z ites , erionites ,a ndmord enites .The z eoliteu s edmu s t not b e s oa ctiv etha titw ill ox id iz ethea mmoniab ef ore itha stheop p ortu nityto rea ct w ith the corros iv e nitrog en ox id es .Thisreq u ire ment elimina tes z eolites w hich ha v e b eenca tionexcha ng edw ith meta lsw hich a re know n to b e ox id a tion ca ta ly s ts s u cha s thetra ns itionmeta ls a nd thenob le meta ls . For ex a mp le, 2 %p la tinu m ex cha ng edY- ty p e z eolite,as y nthetic f a u j a s ite w ith as lig htlyla rg er S i/Al ra tiotha n the X- ty p e, w a su s edw ith NO2 ( ~1 % )a nda mmoniain a n a ir s trea m a t a b ou t 3 0 0 C.The a mmoniaw a sox id iz edb y0 1b ef ore the N0 2cou ldb e red u ced .The z eolitema yb e ca tion ex cha ng edw ith a meta l w hich is not know n to b e a n ox id a tion ca ta ly s t s u ch a ss ilv era nd f u lly - ex cha ng ed s ilv erz eolite, ty p e X, ha sb een s how n to b e ef f ectiv e ( s ee b elow ) . Itis b eliev edhow ev er tha tthes ilv erta kes no p a rt intherea ction s ince itis clea r tha t z eolitesin the u nex cha ng edhy d ro g en or s od iu m f orm a re eq u a llyef f ectiv e.Unex cha ng edca ta ly s ts a reex cep tiona lly a d v a nta g eou snot onlyb e ca u s e theyw illnot ca ta ly z e ox id a tion ofthe a mmoniab u t a ls o b eca u s e theya re not p ois onedb ycons titu entss u ch a sS 0 ;w hich a re f req u entlyp res ent in ef f lu ent g a ss trea ms . Pref erred ca ta ly s ts a ccord ing tothep res ent inv entiona res y nthetichy d rog en mord enites s u cha sZ eolon 9 0 0 , ap rod u ct ofthe Norton Chemica l Com p a ny ,s ince the mord enitesa re more a cidres is ta nt tha n a re other z eolitesd u e to the hig her s ilicon to a lu minu m ra tiothereofa nds incehy d rog en mord enite is a p p a r ently ofs lig htly g rea ter s treng th tha n is s od iu m mor d enite.Asw illb ecome a p p a renthereina f terthehy d rog en mord enitesa re ef f ectiv e in ca ta ly z ingthe red u ction ofNO, ,w ith NH3ina irs trea msconta ining u pto1 5 , 0 0 0p p m N0 1 ,u pto2 0 %0 1 ,u pto 3 1 %w a ter,a ndu pto 02 53 03 54 55 563 0 0 0p p m 8 0 ; . All ofthes ev a ria b les , a s w ella s the rela tiv e p rop ortion ofNO a ndNO;inthe g a ss trea m,w ill ef f ect the temp era tu re a t w hich area s ona b le d eg ree of NO) ,a b a tementis a tta ined . How ev er, a ccep ta b le w orking cond itions ca nb ef ou nd reg a rd les s ofhowthes e p a ra metersv a ry .Althou g h thez eolites f u nctionef f ectiv ely f orp ro long edp eriod s ,their u s ef u l lif e, like tha t ofv irtu a llya ll ca ta ly s ts ,is , ofcou rs e,not ind e? nite.How ev er,u nlike ma nyofthe other ca ta ly s tsheretof ore p rop os edf or the red u ction ofthe corros iv e ox id esofnitrog en, the z eo lites ca n b e s u ita b lyres toredto s u b s ta ntia lly f u llca taly tica ctiv ityb yreg enera tion method sinclu d inghig h temp era tu re b u rn of f , i. e. hea tingto a b ou t 8 0 0 C.in the p res ence ofox y g en,or p u rg ingw ith hig h- p res s u re s tea m.The d eg ree ofreg enera tion a ndnu mb er ofreg en era tiv ecy cles p os s ib led ep endon thety p eofz eolite b a s e, ty p e a ndd eg ree ofex cha ng e,a ndthe ex tent a ndty p e ofconta mina nt on the ca ta ly s t b ed .Ev en w ithou t reg enera tion, thez eolites f u nctionef f ectiv ely f oralong erp eriod oftime tha n know n p riora rtnitrog en ox id e red u ction ca ta ly s ts .While itis know n tha t area ction p roceed sb etw een NOX a ndNH;in the a b s ence ofaca ta ly s t a ss how n in the p rior a rt, u s e ofaz eolite a sca ta ly s t ina ccord a nce w iththep res entinv entionp ermits g rea terrea ction ef ? ciency ,les s a mmoniacons u mp tion a ndens u resthe controlledtherma l d ecomp os ition on the ca ta ly s t ofthe p otentia llyex p los iv e a mmoniu m nitra te f ormedd u ringthe rea ction.One ofthe imp orta nt a d v a nta g esofthe p roces softhe ins ta nt inv ention is tha t v eryhig h conv ers ion ra tesa re a chiev ed . Und er a p p rop ria teop era ting cond itions , a sw ill b e d es crib ed ,es s entia llya ll, i. e. >9 8 % ,ofthe cor ros iv e nitrog en ox id esin the g a ss trea m w ill b e red u cedto elementa l nitrog en or N2 0 .Asp rev iou s lymentioned ,the p roces softhe ins ta nt inv ention ca n s u ita b ly b e ef f ected b yma inta ining the z eoliteca ta ly tic b eda tatemp era tu re ra ng ingf rom a t lea s t2 5 0 C. to a b ou t 5 5 0 C. The ex a ct temp era tu re req u iredto a tta in the d es iredred u ction d ep end son the ty p e ofz eolite,the comp os ition ofthe ef f lu ent g a s ,a ndres id ence time; g enera lly , there is no a d v a nta g e to exceed ing theminimu m temp era tu re. How ev er, if the concentra tionof u nb u rned hy d roca rb ons intheg a ss trea m is hig h, op era tion ofthe ca ta ly s t b eda t hig her temp era tu resw ill p rolongitsef f ectiv e lif e.The rea ction p res s u re is a ls o not critica l, p res s u resf rom a tmos p heric to a b ou t 1 5 0p s igb eingp a rticu la rlys u ita b le.The conta ct or res id ence time ofthe corros iv e nitro g en- ox id e- conta iningg a ss trea m p lu sthe red u cingg a sw iththez eoliteca ta ly s tca n b ea s lowa s a b ou t0 . 1s econdf or es s entia llycomp lete red u ction ofthe corro s iv enitrog enox id es . Long erconta cttimes a re, ofcou rs e,not ha rmf u l,b u t a sin v irtu a llya llp roces s esofthis ty p e , theminimu m ef f ectiv econta ct time, w hich ena b les thema x imu m throu g h- p u t ra te, is p ref era b le.The v olu me ra tio ofcorros iv e nitrog en ox id esthrou g h p ilot to z eolite a ls o is not critica l. We ha v e f ou ndtha t w ith q u a ntities ofz eolites a s lowa s 1 p a rt b yv olu me p er 1 0s ta nd a rdv olu mesofnitrog en ox id e throu g h- p u t p er minu te,es s entia llycomp lete red u ction ofthe corro s iv enitrog enox id es is a chiev ed . Asis a p p a rent, thisra tio ref ersto the nox iou snitrog en ox id e throu g h- p u t;thetota lg a s s trea mthrou g h- p u tca n, of cou rs e, b yma nyord ers ofma g nitu d eg rea ters inceinmos tg a ss trea ms ,inclu d ingp ow er- g enera ting - p la nt ef f lu entsa nda u tomob ileex ha u s t, thea mou ntofnox iou s nitrog en 4 , 2 2 0 , 6 3 27ox id esis u s u a llylow .For ex a mp le,the corros iv e nitro g en ox id e concentra tions inf os s il- f u el- p ow er- g enera t ing f a cilities , incinera tors , orothercomb u s tionu nit of f - g a s esa re u s u a llyles stha n 7 0 0p p m,w hile the ma x i mu m concentra tion ininterna lcomb u s tion eng ine exha u s t is les s tha n 4 0 0 0p p m a ndu s u a llyles s tha n 2 0 0 0p p m Asp rev iou s lymentioned ,toef f ectthe red u ction ofthe corros iv e nitrog en ox id es ,there mu s t b e p res ent a t lea s t a n ef f ectiv e a mou nt ofred u cingg a s .The req u ireda mou nt ofred u cingg a sca n b e a d d edto the g a ss trea m a t a nyp oint p rior to conta ctingthe g a ss trea m w ith the z eolite ca ta ly s t.The onlyreq u irement istha t as u f f icient q u a ntityofthe red u cingg a sb e f a irly w ell mix edw ith the g a ss trea m p rior to conta ctingthe z eolite ca ta ly s t.The inv ention ca n b e more f u llyu nd ers toodb yref er ence to the f ollow ingex a mp les .EXAMPLESA s eriesofp relimina ryex p erimentsw ere cond u ctedto a s certa in the ef f ectiv enes sofv a riou scommercia llya v a ila b le s y nthetic z eolitesa sca ta ly s tsf or the red u ction ofthecorros iv eox id esofnitrog en. Unles sotherw is e s ta ted , the p ercent comp os ition oftheg a s es ref ers to v olu me p ercents a nd a llinp u ttemp era tu res w erea t a mb ient temp era tu res( ~ 2 lC. ) .The f ollow inga b b rev ia tionsa re u s edin the ex a mp lesw hen ref erringto the ty p e ofz eolites :Na X Ty p e X z eolite,s od iu m ca tion,as y nthetic f a u j as ite- ty p e z eolite ma nu f a ctu redb yb oth Union Ca rb id e Corp .a ndGra ce Chemica l Corp ora tion.Ag X X- ty p e z eoliteinw hich thes od iu m ions ha v e b een rep la cedb yion ex cha ng e w ith s ilv er.AW5 0 0 - Arep roces s ed na tu ra lz eoliteconta iningmos tlys od iu m ca tions .Na Z A s y ntheticmord enite ca lled Z eolon ma nuf a ctu redb yNorton Chemica l Corp ora tion.( 1 )Ca ta ly s t Ma teria l 1 0 0 %Ag X 1 2 - 1 4mes h ~ 1 7cm3Op era tingCond itionsFlowra te 7 . 6l/min BedTemp - 2 0 0 to 2 5 0 C.Res id ence time ~ 0 . 1 5s ec Inp u t NO2 1 . 0 %Air rema ind er Ou tp u t ( 2 )Ca ta ly s t Ma teria l 1 0 0 %Na X 1 2 - 1 4mes h ~ 5 0cm3Op era tingCond itionsFlowra te 7 . 6l/min BedTemp . 2 7 5 to 3 2 5 C.Res id ence time 0 . 4s ec Inp u t NO2 - - l. 0 %1 02 003 51 5 05 5v 5 06 5l8. Air rema ind er Ou tp u tNOz -< 0 . 0 1 7NO< 0 . 0 1%N2 O 0 .8 %( 3 )Ca ta ly s t Ma teria l AW S OD- p rima rilys od iu m 1 1 2 - 1 4mes h ~5 0cm Op era tingCond itionsFlowra te- 7 . 6l/min Bedtemp . - 2 7 5 to 3 2 5 C.Res id ence time- 0 . 4s ec Ilnp u t NOZ 1 . 0 %NI- I3 ~ l. 9 %Air- rema ind er Ou tp u t NO2 < 0 . 0 1 %NO 7 /2 N2 +6 H2 0 ( 5 )In g enera tingthes e d a ta ,u pto s ev era l hou rsw ere u s edtoeq u ilib ra tetheNOx - NH3ca ta ly s ts y s tem. Asexp ected ,thes e d a taind ica te as ig ni? ca nt imp rov ement in conv ers ion ef ? ciencyw hen comp a ringthe res u ltsf rom the 8 - inch d eepca ta ly s t b edw ith thos e f rom the 4 - inch d eepb ed .Ef ? cienciesa shig h a s9 9 . 9 %w ere ob s erv eda t ca ta ly s t b edtemp era tu resin the ra ng e 3 0 0 to 4 0 0 C.The inf lu entNOxs trea ms w ere red u cedtoa tlea s t2p p m NOX,w hich w a sthe b a ckg rou ndlev el ofthe moni tor. Mea s u rements w erema d e f orb othNH3b rea k throu g h a ndox id a tion ofNH3to NO;a thig h NH] ,to NOX ra tiosa ndtemp era tu resin the ra ng e 4 0 0 to 4 5 0 C. , b u t no s ig ni? ca nta mou ntsofeithers p ecies w ere ob s erv ed .At the low er temp era tu resof3 0 0 to 3 5 0 C. ,s ma ll a mou ntsofNH3w ere ob s erv edto b rea kthrou g h the ca ta ly s t b edw hen the conv ers ion ef ? cienciesw ere in the ra ng e 9 9to 9 9 . 9 % .At ev en low er temp era tu res ,b elow3 0 0 C. ,cons id era b le a mou ntsofNH3w ere d e tectedin the ca ta ly s t b edef f lu ents ,b u t q u a ntita tiv e d a taw ere not collected .The a mou nt ofNH3req u iredto ob ta in 9 9 %conv er s ion ef f iciencyofNO, in d rya ir a t af a ce v elocityof1 0 0f t/min a nd4 -a nd8 - inch d eepb ed sisillu s tra tedin FIG.3 . The s toichiometryref ers toRea ction ( 5 ) . With the 8 - inch d eepb ed ,9 9 %conv ers ion ef ? cienciesw ere obta ined f rom 2 5 0 to 4 5 0 C.The 4 - inch d eepb edp er f ormednea rlya sw ell b u t req u ireds lig htlymore NH3 .In b oth b ed ss ome NH4 NO3w a sob s erv edin the ef f luentw hen theca ta ly s tb edw a sop era tedb elowa b ou t 2 7 5 to 3 0 0 C. ,b u t itw a snot p res ent a b ov e thistem p era tu re ra ng e.Cons id eringonlythea mou nt ofNH3req u ired , the p roces sw a smos t ef ? cient w hen the ca ta ly s t b edw a sop era tedinthe temp era tu re ra ng e of3 0 0 to3 5 0 C.There a re s ev era l rea s onsw hyconv ers ion ef ? cienciesof9 9 %w ere ob ta ineda t les stha n the a p p a rent s toichio metric a mou nt ofNH3 .Firs t, in the temp era tu re ra ng e ofa b ou t 2 7 5 to3 7 5 C. , incomp lete red u ction ofthe NO) ,occu rredres u ltingin s ome f orma tion ofN2 0in s tea dofa lltoelementa l nitrog en, thu s , req u iringles sNH3 .S econd ,w e ha v e ob s erv edtha t the z eolite ca taly s t w ill red u ce N0 2to NO ev en in the a b s ence ofNH3a b ov e a b ou t 3 0 0 C. ,b u t the ef ? ciencyofthe rea ction d oesnot a p p ea r to b e a p p recia b le u ntil a b ou t 3 5 0 C. ;a t 4 0 0 C.the conv ers ion ef f iciencyofN0 2to NO isa b ou t 9 0 % .Theref ore,thes e tw o p roces s estendto red u ce the a mou ntofNH3req u ired f orcomp letered u ctionofNO, ,to N2 .Als o,w hen the ca ta ly s t b edw a sop era teda b ov e 4 0 0 C. , la rg eex ces s es , 3 0to5 0 %a b ov e tha t req u ired f or9 9 %conv ers ion, cou ldb e u s ed w ithou t b eing d etected intheef f lu ent, ind ica ting theex ces sNH3w a sb eingox id iz edin the ca ta ly s t b ed .How ev er,ina s mu ch a s nos ig ni? ca nta mou ntsofN0 2 , NO,or N2 0w ere ob s erv edin the ef f lu ent a t thes e cond itions ,theox id a tion p rod u ct mu s t b e N2 , a ndthered u ction rea ctionsofthe NO, to N;b yNH3occu rsin p ref erence to ox id a tion ofNH;. . . a t lea s tov er the temp era tu re ra ng e s tu d ied ,4 0 0 to 4 5 0 C.Beca u s e s ev era l rea ctionsma yta ke p la ce concu rrently , theex a ct d es crip tion ofthe ov era ll p roces smecha nis m is not clea r,b u t the net res u lt is av eryef f icient red u ction p roces sw ith no a dv ers e b y - p rod u cts .FIG.4s how sthe res u ltsoftes tscond u ctedin hu mid i ? eda irs trea msw ith a llother cond itionsthe s a me a s3 56 06 51 0thos e ofthe d rya ir s trea m s how n in FIG.3 . Althou g h no d if ? cu ltyw a s encou nteredin ob ta iningg rea ter tha n 9 9 %NOxconv ers ion ef f iciency inthehu mid i? eda ir s trea m,more NH3w a sreq u iredtha n w ith the d rya ir tes ts .The error b a rss how n in FIGS .3a nd4ind ica te the u ncerta inty intheN0 2s ta nd a rd . The s ta nd a rd w a sa s s u medto b e 4 7 5 0p p m N0 2w ith a n u p p er limitof5 1 0 0p p m a ndalow er limit of4 4 0 0p p m.Other s y s tem a ticmea s u rementerrors a renotb eliev ed toex ceedi5 % .The f ollow ingtes ts w ere p erf ormedon as imu la tedtes t a tmos p here ty p ica l ofcoa l- ? redp ow er p la nts .The ca ta ly tic ef f ect ofthe hy d rog en f orm ofZ eolon 9 0 0on therea ctionef f iciency ofNO a nd NH3w a ss tu d iedin af lows y s tem.A v ertica l 2 . 2 - inch i. d . q u a rtztu b e conta ininga 1 2 - inch b edofthe ~ inch ex tru d a te ca ta ly s t w a shea tedto 3 5 0 C.w ith atu b e f u rna ce. A s imu la ted f lu eg a s , w hichw a sp rehea ted totheb edtemp era tu re, w a sp a s s edthrou g h the b eda tara teof2 . 6 5f t3 /min ( mea s u reda t 7 0 F.a nd1 a tm) ,p rod u cingas u p er? cia l f a ce v elocityof1 0 0f t/min. The tes tg a scons is tedof0 . 3 %8 0 ; ,0 . 0 5 %NO,1 2 %C0 2 ,7 %H2 0a ndthe rema ind er a ir. Comb u s tion s ta ck g a s esu s u a llyconta in3 to7 %0 2a s comp a redw ith the1 6 %u s edhere; how ev er,thehig h f lowra te ofthe tes tmix tu re ma d e the u s e ofb ottledN2imp ra ctica l.Theref ore,p la nt a irw a su s edres u lting inthehig her 0 2content. The w a ter v a p or content w a smonitoredw ith ap s y chrome ter, a ndrota metersw ere u s edto mea s u re the req u iredf low oftheotherg a s es tha tma d e u pthetes ta tmo s p here. Thermocou p les p os itioned ev ery tw oinchesa long thev ertica la x is oftheb edind ica ted tha tthe temp era tu re g ra d ient w a sles s tha n 6 8 F. throu g hou t the tes t b ed .The p res s u re d ropa cros sthe b edw a s1 2 . 9inchesofH2 0 .Af tertheb edha db eenex p os edtothetes ta tmo s p here f or1 2hou rs ,the NH3w a sintrod u cedu p s trea m ofthe b ed .At ? rs t,as ix - hou r eq u ilib ra tion p eriodw a sreq u iredto a tta inacons ta nt ef f lu entNO rea d ing ; b u t therea f ter, onlyone hou r w a sneed edw ith ea ch s ma ll cha ng e in the inf lu ent NH3concentra tion.The tes t w a scond u ctedcontinu ou s lyf ora b ou t2 0 0hou rs . Du ringthis time ad es iredin? u ent concentra tion ofNH3w a ss elected ,a ndNO ef f lu ent d a tacollectedf or three to s ixhou rsb ef ore cha ng ingto a nother s etting . Ef f lu ent NO,N0 2 ,N2 0 ,a ndNH3concentra tion d a taw ere collectedthrou g hou t the tes t p eriod .The NO a b a tement ef ? cienciesofthis p roces s , a s af u nction ofthe in? u ent NH3concentra tion,a re g iv en in Ta b le 1 .TABLE 1 .Nitric ox id e a b a tement ef f iciencyv ers u sNH3. concentra tion a t ab edtemp era tu re of6 6 0 F. ,in? u ent NO concentra tion of5 0 0p p m,a nds p a ce v elocityof6 0 0 0hr 1 .in? u entEf f lu entAb a tementS toichiometric NH3 ( p p m) NO ( p p m) ef f iciency( 7 0 ) a mou nt ofNH;3 3 4 4 1 . 9 9 1 . 6 t 1 . 3 1 . 03 6 7 2 4 . 3 9 5 . 2 i 1 . 4 1 . 14 0 0 7 . 7 9 8 . 5 i 0 . 2 1 . 24 6 7 6 . 9 1 . 4 9 8 . 6 i 0 . 2Da tacollectionw a slimited toin? u ent lev els ofNH3w hich y ield ed g rea tertha n9 0 %remov a l ofNO.Asind ica tedin colu mn three,the d a taw ere hig hlyrep ro d u cib le,a ndno d ecrea s e in ca ta ly s t a ctiv ityw a snoted4 , 2 2 0 , 6 3 21 1d u ringthe Z OO- hou r tes t p eriod .Und er thes e cond itions ,the ma x imu m a b a tement ef f iciencyofthe s y s tem,w hich occu rredw ith a2 0 %ex ces sofNH3 ,w a sa b ou t 9 8 . 5 % .The s toichiometric ca lcu la tionsw ere b a s edon the rea c tion 3 N0 +2 NH3 >3 H7 _ O+5 /2N2 ( 6 )w hich isa s s u medto b e the p red omina nt one occu rring .The othermonitored s p ecies , N0 2 , N2 0 , a nd NH3 ,w ere not d etectedin the ef f lu ent a t a nytime. A w hite cry s ta lline comp ou ndw a sob s erv edin the ef ? u ent.Thisma teria lw a sa na ly z ed b y x - ra y cry s ta llog ra p hy a ndd etermined tob ea mix tu reof a mmoniu m b is u lf a te ( NH4 HS O4 )a nda mmoniu m s u lf a te[ ( NH4 ) 2 S O4 ] .The res u ltsofthes e tes t d a tas howthe z eolite ca ta ly s t to ex hib itarema rka b le a b ility tos electiv ely p romote theNO NI- I3rea ctioninthe p res ence ofp otentia llyinterf ering p roces s es , s u ch a s p rema tu re ox id a tionofNH3b y0 2 ,b lockingofa ctiv e s itesb yhig h concentrationsofH2 0a ndCO2 ,a ndca ta ly s t p ois oningb y$ 0 2 .The f orma tion ofN0 2isnot kinetica llyf a v oreda nyw herein the tes t or s a mp lings y s tem.Ca lcu la tionsind i ca te tha tles s tha n1 %of5 0 0p p m NO ina irw illb e conv ertedto NO;in 4s ec a t 6 8 F.a ndin 1 2s ec a t 6 6 8 F.The res id ence time ofthe tes t g a sisa b ou t 4s ec tota l inthe tes ta p p a ra tu sa nds a mp lings y s tem. Theref ore,N0 1s hou ldnot ha v e b een ob s erv ed ;s u ch w a sthe ca s e.Itw a scons id eredp os s ib le tha t the rea ction 4 NO+NH3 +5 /2N2 O+3 /2H2 0 ( 7 )w ou ldcomp ete w ith rea ction ( 6 ) , b u t thes e d a taind i ca te tha tthis rea ctionoccu rsonlya s a n intermed ia te s tep ,ifa t a ll.The a b s ence ofNH3in the ef f lu ent,w hen the inf lu ent s toichiometric ra tio ofNH3 /NO w a s1 . 4 0 ,a ndthe p resence ofa mmoniu m b is u lf a te a nds u lf a te in the ef f lu ent ind ica te tha t the f ollow ingrea ctionsa re comp etingw ith rea ction ( 6 ) :Und er thes e cond itionsitis a p p a rent tha t the rea ction b etw een NH3a ndNO iskinetica llymore f a v ora b le tha n b etw een NH3a nd8 0 ; ,es p ecia llyw hen one cons id erstha t the in? u ent S Og /NO ra tio is a b ou t 6 . The f ormation ofthe a mmoniu m b is u lf a te a nds u lf a te a srea ction p rod u ctsw a snot s u rp ris ing .In p rev iou sinv es tig a tionsthep os s ib ility ofS O;a b a tementb ya mmoniainthe a b s ence ofNO w a sex a mined , a ndaconv ers ion ef ?ciencyofa b ou t 8 0 %ofthe S 0 ;to a mmoniu m s u lf a te w a sob ta ined . The s u lf a te/b is u lf a tep rod u ct ra tiow ill d ep endin p a rt on the a mou nt ofNH3w hich isa v a ila b le f or rea ction w ith S 0 3 .Thu saconcep tu a llya ttra ctiv e a nd s imp lecomb ined NOx S OX a b a tements y s tem w ou ldinv olv e inj ection ofNH3u p s trea m ofas ing le b edofmord enite ma inta ined a ta b ou t 6 6 0 F. Thiscou lds imu lta neou s lyca ta ly z e the red u ction ofNOxto N2a ndconv erttheS 0 , ,top a rticu la tea mmoniu m s u lf a teor a mmoniu m b is u lf a tew hichcou ld b eremov ed w ith electros ta tic p recip ita tion.Fu rther tes ts w ere ca rriedou t on ates ta tmos p here conta ining 3 1 %H2 0 ,5 %CO2a nd2 %CO w hich isty p ica loftheef f lu entg a s f romtheWa s teCa lciner 2 5. 3 03 54 56 5Fa cilitya t the Na tiona l Rea ctor Tes t S ta tion.The f ol low ingex p erimenta l cond itionsw ere u s ed :( a )Ca ta ly s t hy d rog en f orm ofZ eolon 9 0 0 .( b )BedDep th l2in w ith the 5 in ex tru d a te a nd8 in w ith theH1 6in in ex tru d a te.( c)Tes t Atm 3 l%H2 O+5 %CO2 +2 %CO+a ir.( d )Temp era tu re Ra ng e 3 0 0 to 5 5 0 C.a t the b edex it.( e) Fa ce Velocity l0 0f t/min a t s cf m.( f )Res id ence Time 0 . 6s ec in the l2 - in b eda nd0 . 4s ec inthe 8 - in b ed .( g )NOX Concentra tion- - u s u a llya b ou t 5 0 0 0p p m b u t u pto1 5 , 0 0 0p p m.( h)BedPres s .Drop 3 0to 4 2mm Hgin the temp eratu re ra ng e 3 0 0 to 5 5 0 C.( i)BedTemp era tu re Gra d ients a b ou t a4 0 C.increa s e in the d irection ofg a sf loww ith 5 0 0 0p p m NOxa nd1 0 0 C.w ith 1 5 , 0 0 0p p m NOX.FIGS .5a nd6illu s tra te the d a taob ta inedf rom the eig ht inch b ed .Asind ica ted ,p u re N0 2tes t a tmos p heresw ere not ob ta ina b le. Thisis p rob a b lyd u e tos ome therma l d is s ocia tion in the p rehea tings ta g e ofthe g a s . Th d a taind ica te ap ronou ncedd if f erence in the b eha v ior ofNO a ndN0 2b etw een 3 0 0 a nd3 8 0 C.The rea ction ef ?cienciesf or NO a re more temp era tu re d ep end ent tha n f orN0 2 . Als o, b etter a b a tementef ? ciencies a reobta ined f orN0 2w ithreg a rd s tob othma x imu m ef f i ciencya ndNH3req u ireda tcomp a ra b le temp era tu res . Other d a taw a sa ls o collectedw ith the eig ht inch b ed :( a ) Grea ter tha n 9 9 %a b a tement of 1 5 , 0 0 0 p p m "N0 2w a sob ta inedw ith a n ex it b edtemp era tu re of5 5 0 C.( b ) Below3 5 0 C. a b ou t 2 0 %ofthe in? u ent N0 2a pp ea reda sN2 0in the ef ? u ent.Ab ov e 4 4 0 N2 0w a snot d etecteda nda t no temp era tu re w a sN2 0d etectedw hen the in? u ent conta inedonlyNO.( 0 )An ef f ecton a b a tement ef ? ciencya saf u nction ofCO or CO;concentra tion w a snot ob s erv ed .( d )A w a ter ef f ect w a sob s erv ed .At 3 8 0 C.the ma x i mu m N0 2a b a tement ef ? ciencies w ere 9 7 , 9 9 . 3 a nd9 9 . 9 %f oraw a ter v a p or content of3 1 , 1 0a nd1 %res p ectiv ely .FIG. 7 illu s tra tes thed a ta ob ta inedu s ingthe1 2 - inch b ed .A comp a ris on ofthisd a taw ith FIG.6ind ica te tha t ma x imu m ob ta ina b le ef f icienciesa re a b ou t the s a me b u t tha t cons id era b lymore NH3is req u iredw hen u s ingthe la rg er ex tru d a te.Ofp erha p sg rea ter interes t isthe w a ter ef f ecton the cu rv es . There is ap os itiv e ef f ect a tlows toichiometric ra tio w hich cha ng esto aneg a tiv e ef f ect a tthe hig her ra tios a s thew a ter content is increa s ed . The ma x imu m ob ta ina b le ef ? ciencyis not g rea tly a ff ecteda t the hig h temp era tu re b u t v erymu ch s o a t the low er temp era tu re.Itw illb e noted tha tthed a tainFIG.7 ind ica teama x imu m ef ? ciencys omew here b etw een 8 0a nd9 3 %f or 7 %w a ter content a t3 5 0 C.The d a taf rom ex a m p les d es crib ed a b ov e ind ica tes a n ef ? ciencyofb etter tha n 9 8 %w hen the b edw a sop era teda t 3 5 0 C.a ndthe ef ? u ent conta ined5 0 0p p m NO a ndg rea ter tha n 9 9 %ef ? ciencyb etw een 3 0 0 a nd4 5 0 C.f or 5 0 0 0p p m NO;in a ir+ 1 0 %H2 O.While s ome ofthe d if f erencesa re d u e to d if f erencesin the tes t a tmos p here,itis p os s ib le tha t theex itb ed temp era tu res intheea rliertes ts w ere s lig htlyhig her ( p os s ib lyu pto5 0 ) tha n the mea s u redtemp era tu resd u e tola ck ofs op his tica tedtemp era tu re mea s u ringd ev ices .Ba s edon the a b ov e d a tarecommend edtemp era tu resofop era tion a re:( 1 )For aw a s te g a ss trea m ty p ica l ofthe Wa s te Ca lciner Fa cilityef ? u ent cons is tingofa ir, 3 0v olu me p ercent 4 , 2 2 0 , 6 3 21 3w a ter v a p or,5v olu me p ercent CO,2v olu me p ercent CO,0 . 9v olu me p ercent N0 2a nd0 . 4v olu me p ercent ( 2 )For aw a s te g a ss trea m ty p ica l ofap a rticu la r ind u stria lw a s te g a s s trea m cons is ting ofa ir, 1 0 v olu me p ercent w a ter v a p or, a nd0 . 5 v olu me p ercent NO 2 - ~ 3 5 0 C.( 3 ) For aw a s te g a ss trea m ty p ica l ofaf os s il- f u el- ? redp ow er p la nt cons is tingofa ir,7v olu me p ercent w a ter v a p or. 0 . 3 v olu me p ercent S 0 2 , 1 2 v olu me p ercent CO2a nd0 . 0 5v olu me p ercent NO 3 5 0 C.In g enera l temp era tu resofop era tion ca n ra ng e f rom 2 5 0 or 3 0 0 to 5 5 0 C.w ith the minimu m b eingd ep en d ent u p on the comp os ition ofthe w a s te g a ss trea m.Ins u mma ry , z eoliteca ta ly s ts of f erthef ollow inga d v a nta g esov er other ca ta ly s ts : ( l) the s y nthetic z eo lites d o not ca u s e the p rema tu re ox id a tion ofa mmoniaev en a t ox y g en concentra tionsa shig h a s2 0 %a ndtem p era tu resa shig h a s4 0 0 C. ,( 2 )the p roces sisop era b le ov er aw id er temp era tu re ra ng e, 2 5 0 5 5 0 C. ( 3 ) the u s e ofz eolite ca ta ly s tsreq u ire onlynea r- s toichiometric q u a ntities ofa mmoniacomp a redw ith la rg eex ces s esu s u a llyreq u iredf or other ca ta ly s ts ,( 4 )the ca ta ly s tsa re not s u s cep tib le to p ois oningb yconta mina nt g a s esa ndp erf orm w ell ev en in hig hlyhu mida tmos p heres ,a nd( 5 )theyp rov id e v eryhig h ef f iciencies , g rea ter tha n 9 9 % ,f or NO, c red u ction a t s p a ce v elocitiesa ndca ta ly s t b edp res s u re d rop stha t a re p ra ctica l f or ind u s tria l a p p lications .In a d d ition to b einghig hlyef f icient,the p roces selim ina testhe f ollow ingd is a d v a nta g esa s s ocia tedw ith liqu id s cru b b erp roces s es : ( 1 ) d is p os a lofliq u id w a s tesg enera tedin the s cru b b ingp roces s ,( 2 )the req u irement f or eq u imola r mix tu resofNO a ndN0 2to ens u re g oodremov a lef f iciencies , ( 3 ) rela tiv ely low throu g hp u t ra tes ,a nd( 4 )the needto rehea t the trea tedg a sto ob ta in g oodd is p ers a l ofthe s ta ck d is cha rg e.Als o the p roces sd oesnot req u ire the hig h energ yreq u irementsofther ma l d ecomp os ition method s .Fina lly ,the p roces ss hou ldw ith minor mod i? ca tion b e u s ef u lf orcomb inedS 0 2a ndNO) ,remov a l f rom w a s te g a ss trea ms .The emb od imentsofthe inv ention in w hich a n ex clus iv ep rop erty orp riv ileg eis cla imed a red e? ned a sf ollow s :1 . A p roces s f or conv ertingmore tha n 9 8 %ofthe nox iou s nitrog enox id es p res enting a s eou s ef f lu entsconta ining 3 to2 0v olu me p ercent ox y g en toN2a ndN2 0comp ris ingmix ingthe g a s eou sef ? u ent w ith ag a ss trea m conta ininga n ef f ectiv e a mou nt ofa mmoniaa ndconta cting the mix edg a s esw ith aca ta ly s tcons is tinges s entia lly ofas y nthetic hy d rog en mord enite ha v ingp ore op ening sof3to 1 0A,the temp era tu re ofthe ca taly s t b edb eing2 5 0 5 5 0 C.a t the b edex it.2 . A p roces sa ccord ingto cla im 1w herein the g a s e ou sef f lu ent conta ins1 6to 2 0 %ox y g en.3 . A p roces sa ccord ingto cla im 1w herein the g a s e ou sef f lu entis s ta ck g a sf rom af os s il- f u el- f lred p ow er p la nt inclu d ingthe f ollow ing :7v olu me p ercent w a ter 1 02 02 53 54 04 55 05 56 06 51 4v a p or,1 2v olu me p ercent CO1 ,0 . 3v olu me p ercent S 0 2a nd0 . 0 5v olu me p ercent NO,a nd3to 7v olu me p ercent 0 2a ndthe b edtemp era tu re is 3 5 0 C.a t the b edex it.4 . A p roces sa ccord ingto cla im 1w herein the g a s e ou sef f lu ent iss ta ck g a sf rom anu clea r p roces s ingp la nt ha v ingthe f ollow inga p p rox ima te comp os ition:3 0v ol u me p ercentw a terv a p or, 5 v olu me p ercentC0 2 , 2v olu me p ercent CO,0 . 9v olu me p ercent N0 2 ,0 . 4v ol u me p ercentNO,theb a la nceb eing a ira ndtheb edtemp era tu re is 4 0 0 - 5 0 0 C.a t the b edex it.5 . A p roces sa ccord ingto cla im 1w herein the g a s e ou sef ? u ent iss ta ck g a sf rom a n ind u s tria l p la nt ha v inga p p rox ima tely thef ollow ing comp os ition: 1 0 v olu me p ercent w a ter v a p or,0 . 5v olu me p ercent N0 2 ,the b a l a nce b einga ir a ndthe b edtemp era tu re is 3 5 0 C.a t the b edex it.6 . A p roces sf or s electiv elyred u cingox id esofnitro g en p res entinamix tu re ofg a s es conta ining ox y g en,red u cib leox id es ofnitrog ena nda n inert' g a s , w hich comp ris esconta ctingin area ction z one s a idmix tu re ofg a s es a nda n a p p rox ima telys toichiometrica mou nt ofa mmoniab a s ed onred u ctionofthenitrog enox id esp res ent to nitrog en a t atemp era tu re of2 5 0 to 5 5 0 C.in the p res ence ofaca ta ly s t cons is tingofa n a cidres ista nta lu minos ilica temolecu la rs iev eha v ing s u b s ta n tia lly u nif orm intercry s ta lline p oresw hereb ys electiv e red u ction ofthe ox id esofnitrog en to nitrou sox id e a ndnitrog en is ef f ected .7 . A p roces sf or s electiv elyred u cingox id esofnitro g en in amix tu re ofg a s esconta iningu pto 2 0 %ox y g en,u pto1 . 0 %NO or N0 2a ndthe rema ind er a n inert g a s ,w hichcomp ris es conta cting ina rea ctionz ones a idmix tu re ofg a s esa nda n a p p rox ima telys toichiometric a mou nt ofa mmoniab a s ed on red u ctionofnitrog en ox id es p res enttonitrog ena tas p a ce v elocity ofles stha n 3 6 , 0 0 0hr 1a ndatemp era tu re w ithin the ra ng e of2 5 0 C.to 5 5 0 C.in the p res ence ofaca ta ly s t cons is tingofa n a cidres is ta nt a lu minos ilica te molecu la r s iev e com p os itionha v ing s u b s ta ntia lly u nif ormintercry s ta lline p oresw ith d ia metersofa b ou t 3to 1 0A,w hereb ys elec tiv e red u ction ofthe ox id esofnitrog en to nitrou sox id e a ndnitrog en is ef f ected .8 . A p roces sf or s electiv elyred u cingox id esofnitro g en in amix tu re ofg a s esconta iningu pto 2 0 %ox y g en,f rom atra ce to 2 %ox id esofnitrog en a ndthe rema ind er a n inert g a s , w hich comp ris esconta ctingin area ction z one s a idmix tu re ofg a s esa nda n a p p rox ima telys toi chiometric a mou nt ofa mmoniab a s edon red u ction ofnitrog en ox id esp res ent to nitrog en a t as p a ce v elocityofles stha n 3 6 , 0 0 0hr * 1a nda t atemp era tu re w ithin the ra ng e of2 5 0 C.to 5 5 0 C.in the p res ence ofaca ta ly s t cons is tingofa n a cidres is ta nt a lu minos ilica te molecu la r s iev ecomp os itionha v ings u b s ta ntia lly u nif orminter cry s ta llinep ores w ithd ia meters of a b ou t3 - 1 0 A,w hereb ys electiv e red u ction ofthe ox id esofnitrog en to nitrou sox id e a ndnitrog en is ef f ected .* * * # = 1 4