5258125Carbohydrazones as boiler water oxygen scavengers.docx

5258125Carbohydrazones as boiler water oxygen scavengers.docx

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5258125Carbohydrazonesasboilerwateroxygenscavengers

（1of1）

UnitedStatesPatent

5,258,125

Kelley, etal.

November2,1993

Carbohydrazonesasboilerwateroxygenscavengers

Abstract

Theinventionisdirectedgenerallytocontrollingcorrosioninboilersystemsandmoreparticularlytotreatingboilerwatertoremovedissolvedoxygenandtopassivatemetalsurfaces.

Inventors:

Kelley;DouglasG.（Naperville,IL）,Rogers;DeborahM.（Naperville,IL）,Swiecinski;FrederickJ.（Algonquin,IL）

Assignee:

NalcoChemicalCompany（Naperville,IL）

Appl.No.:

07/872,255

Filed:

April22,1992

CurrentU.S.Class:

210/750;210/757;252/188.28;252/392;422/16

CurrentInternationalClass:

C23F11/10 （20060101）;C23F11/14 （20060101）;C02F1/20 （20060101）;C02F001/20 （）;C02F001/70 （）

FieldofSearch:

210/750,757252/188.28,392422/16,17

ReferencesCited[ReferencedBy]

U.S.PatentDocuments

4269717

May1981

Slovinsky

4479917

October1984

Rothgeryetal.

4540494

September1985

Fuchsetal.

OtherReferences

Copper-CatalyzedAutoxidationofCarbohydrazide:

KineticsandMechanism,DavidR.CosperandDavidJ.Kowalski0888-5885/90/2629-1130AmericanChemicalSociety1990..

CarbodihydrazonesandOxalylDihydrazones,D.M.WilesandT.Suprunchuk,CanadianJournalofChemistry,vol.46,1968,pp.701-705..

ReactionsofCarbohydrazide.PartII.A.M.MunroandF.J.Wilson,Jo.ChemicalSociety1928--pp.1257-1261..

XVIII.-ReactionsofCarbohydrazide.PartI.AndrewC.Brown,EricC.Pickering,ForsythJ.Wilson--Jo.ChemicalSociety1927pp.107-113..

PrimaryExaminer:

Cintins;Ivars

Attorney,AgentorFirm:

Miller;RobertA.Barrett;JosephB.

Claims

Havingdescribedourinvention,weclaim:

1.AmethodforremovingdissolvedoxygenfromboilerwaterhavinganalkalinepHwhichcomprisesaddingtosaidboileranoxygenscavengingamountofatleastonecarbohydrazonecompoundselectedfromthegroupofcarbohydrazonecompoundsconsistingof:

##STR3##inwhichR.sub.1,R.sub.2,R.sub.3,R.sub.4,R.sub.5,R.sub.6,R.sub.7andR.sub.8are,individually,hydrogen,analkylgroup,asubstitutedalkylgroup,anarylgroup,andasubstitutedarylgroup.

2.Themethodaccordingtoclaim1whereinthecarbohydrazoneisaddedatalevelofatleast0.5molesofthecarbohydrazonepermoleofdissolvedoxygen.

3.Themethodofclaim1whereintheboilerwaterissubjectedtoadeaerationsteptoreducethelevelofdissolvedoxygenandthecarbohdrazoneisaddedtotheboilerwaterafterdeaeratingtoremoveremainingdissolvedoxygen.

4.Themethodofclaim1whereinthecarbohydrazoneisusedinconjunctionwithanoxidation-reductioncatalyst.

5.Themethodofclaim1inwhichthecarbohydrazoneisacetaldehydecarbohydrazone.

6.Themethodofclaim1inwhichthecarbohydrazoneisdihydroxyacetonecarbohydrazone.

7.Themethodaccordingtoclaim1inwhichthecarbohydrazoneismethyltetrazone.

8.Themethodaccordingtoclaim1inwhichthecarbohydrazoneisdimethyltetrazone.

9.Themethodaccordingtoclaim1inwhichthecarbohydrazoneishydroxymethyltetrazone.

10.Themethodaccordingtoclaim1inwhichthecarbohydrazoneisdihydroxymethyltetrazone.

11.AmethodofremovingdissolvedoxygenfromboilerwaterhavingalkalinepHandpassivatingboilersurfaces,themethodcomprisingthestepofaddingtotheboilerwateratleast0.5molesofacarbohydrazonepermoleofdissolvedoxygenalongwithfrom0.2toabout20%byweightbasedonthecarbohydrazoneofacatalystcapableofundergoingoxidation-reductionreactions.

12.Themethodofclaim11whereinthecatalystiscopper.

13.Themethodofclaim11whereinthecatalystishydroquinone.

14.Themethodofclaim11whereinthecatalystiscobalt.

15.Themethodofclaim11whereinthecatalystisdiethylhydroxylamine.

Description

INTRODUCTION

Efficientoperationofboilersandothersteam-runequipmentrequireschemicaltreatmentoffeedwatertocontrolcorrosion.Corrosioninsuchsystemsgenerallyarisesasaresultofoxygenattackofsteelinwatersupplyequipment,pre-boilersystems,boilers,andcondensatereturnlines.Unfortunately,oxygenattackofsteelisacceleratedbytheunavoidablehightemperaturesfoundinboilerequipment.SinceacidpH'salsoacceleratecorrosion,mostboilersystemsarerunatalkalinepH's.

Inmostmodernboilersystems,dissolvedoxygenishandledbyfirstmechanicallyremovingmostofthedissolvedoxygenandthenchemicallyscavengingtheremainder.Themechanicaldegasificationistypicallycarriedoutwithvacuumdegasifierswhichwillreduceoxygenlevelstolessthan0.5-1.0mg/Lorwithdeaeratingheaters,whichwillreduceoxygenconcentrationtotherangeof0.005-0.010mg/L.

Chemicalscavengingoftheremainingdissolvedoxygeniswidelyaccomplishedbytreatingthewaterwithhydrazine.See,forexample,theKirk-OthmerEncyclopediaofChemicalTechnology,SecondEdition,Interscience,Publishers,VolumeII,page187.AsexplainedinKirk-Othmer,hydrazineefficientlyeliminatestheresidualoxygenbyreactingwiththeoxygentogivewaterandgaseousnitrogen.Inaddition,hydrazineisagoodmetalpassivatorsinceitformsandmaintainsanadherentprotectivelayerofmagnetiteoverironsurfaces.

Unfortunately,however,ithasbecomewidelyrecognizedthathydrazineisanextremelytoxicchemical.Asaresult,itislikelythatworkerexposuretothiscompoundwillbesubjectedtoextremelyseveretolerancesbygovernmentoccupationalhealthagencies.Itisthereforedesirabletoprovidealternateboilerwatertreatmentchemicalswhicharegenerallyfreeofthedangersinherentintheuseofhydrazine,butwhicheffectivelyscavengeoxygenandpassivatesteelsurfacesundertypicalboilerconditions.

AnimprovedoxygenscavengercompositionwhichovercomesmanyoftheproblemsdescribedaboveisthesubjectmatterofU.S.Pat.No.4,269,717,thedisclosureofwhichisincorporatedhereinbyreference.Thispatentteachesthatcarbohydrazide（CHz）isasuperiorboilerwateroxygenscavenger.Recently,CosperandKowalski（I&ECResearch,1990,29,1130）reportedthatthescavengingofoxygenbyCHzismosteffectivelycatalyzedbycupricions.

THEDRAWINGS

FIG.1comparesthepassivationeffectivenessofacetaldehydecarbohydrazoneversushydrazineandcarbohydrazide.

FIG.2illustratesthedecompositionofacetaldehydecarbohydrazonetohydrazine.

THEINVENTION

Theinventionisdirectedgenerallytocontrollingcorrosioninboilersystemsandmoreparticularlytotreatingboilerwatertoremovedissolvedoxygenandtopassivatemetalsurfaces.

OneaspectoftheinventionprovidesamethodforremovingdissolvedoxygenfromboilerwaterhavinganalkalinepH.Themethodcomprisesaddingtosaidboileranoxygenscavengingamountofatleastonecarbohydrazonecompoundselectedfromthegroupofcarbohydrazonecompoundsoftheformula:

##STR1##inwhichR.sub.1,R.sub.2,R.sub.3,R.sub.4,R.sub.5,R.sub.6,R.sub.7andR.sub.8arethesameordifferentandareselectedfromhydrogen,alkylgroups,substitutedalkylgroups,arylgroups,andsubstitutedarylgroups.

Accordingtoapreferredembodiment,thecarbohydrazoneisaddedatalevelofatleast0.5molesofthecarbohydrazonepermoleofdissolvedoxygen.Preferably,theboilerwaterissubjectedtodeaerationtoreducethelevelofdissolvedoxygenandthecarbohydrazoneisaddedtotheboilerwaterafterdeaerationtoremoveremainingdissolvedoxygen.Thecarbohydrazonemayalsobeusedinconjunctionwithanoxidation-reductioncatalyst.Preferredcarbohydrazonecompoundsareacetaldehydecarbohydrazone（ACHz）,dihydroxyacetonecarbohydrazone（DHACHz）,methyltetrazone（MTz）,dimethyltetrazone（DMTz）,hydroxymethyltetrazone（HMTz）,anddihydroxymethyltetrazone（DHMTz）.

AfurtheraspectoftheinventionprovidesamethodofremovingdissolvedoxygenfromboilerwaterhavingalkalinepHandpassivatingboilersurfacescomprisingaddingtotheboilerwateratleast0.5molesofthecarbohydrazonepermoleofdissolvedoxygenalongwithfrom0.2uptoabout20%byweightbasedonthecarbohydrazoneofacatalystcapableofundergoingoxidation-reductionreactions.Preferredcatalystsoftheinventionarecopper,hydroquinone,cobalt,anddiethylhydroxylamine.

Thecarbohydrazonesdescribedabovearereadilypreparedbyreacting,carbohydrazide（CHz）witheitheraldehydesorketoneshavingtheappropriatenumberofcarbonatomsinanalkylorsubstitutedalkylgroupdefinedbytheformulapreviouslyshown.

Typicalofthealdehydesthatmaybereactedwithcarbohydrazideareacetaldehyde,butyraldehyde,propionaldehyde,hydroxyacetaldehydeandthelike.Startingketonesareacetone,butanone,hydroxyethylketonedihydroxyacetoneandthelike.Incertaininstances,itispossibletoperformthereactionusingtwoormoredifferentaldehydesorketones.

Thereactionofanymolaramountofanaldehydeorketonefrom0.1to2withcarbohydrazideyieldsaproductwhichismoreactiveandstablethancarbohydrazideitself.Thealdehydesortheketonesreactedwithcarbohydrazidetoyieldthecorrespondingcarbohydrazone.Inthecaseof（ACHz）thiscompoundhasbeencharacterizedby.sup.13C-NMR,FTIRandelementalanalysis.Allofthesecompoundsarestableatroomtemperature.

ProductsformedinatypicalcarbohydrazonereactionareillustratedbytheACHzproductsshownbelow:

##STR2##

AlthoughACHzorMTzmaybeaddedtotheboilersystematanypoint,itismostefficienttotreattheboilerfeedwater,preferablyasitcomesfromthedegasifier.Residencetimespriortosteamformationshouldbemaximi