Maitra, Amarnath

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~-~.~:!NOTES7·5 througha column(0·5X4,0 cm) of 1·0 g ofthe exchanger(5·93meq.) and analysing50 mlfractionsof the effluentfor the nickelcontent,tillthe effiuent concentrationreachesthat cf theinfluent. It is interestingto note that the nickelsorbed,by thebreakthrough,is morethanthecapa-.city of the exchanger.Also the curveconsistsoftwo steps(curve1, Fig. 1). The columnwasthenwashedwith water. The sorbednickelwaselutedwith 34·2meq.of hydrochloricacid, followedbywater till free of acid. This effluentcontained23·1meq.of freeacidand10·28meq.of Ni2+. Sincethe excessacid (5,17meq.) consumedover thatrequired for regenerationof the exchangerintoH+form(5'93meq.)is nearlyequalto halfthemeq.ofnickeleluted,it is concludedthatnickelis presentmostly as NiOH+ by the time the exchangerisnearingexhaustion.Consideringthis dataandthetwo stepsin thesorptionprofile,it is inferredthatnickelis initially sorbedas Ni2of, whichtransformsto NiOH+with increaseof loading. This may beconsideredasanexampleof site-sharingon a cationexchanger.The reactionsmayberepresentedthus:2RCOO.NH4+Ni(NHsFH+H20~(RCOOhNi+3NH4'+OH- ...(1)(RCOO)zNi+Ni(NHs)2of+OH-+HzO~2RCOO.NiOH+NH: ...(2)When7·0meq.of Ni20f atpH 7,5wereequilibratedwith 2·70meq.of the exchanger,it wasobservedby a similar analysisof the exchangerthat 1·71and 0·78 meq. of Ni2+weresorbedas Ni20f andNiOH+ respectively.This lends further supportfor the transformationof Ni2+ speciesto NiOH+specieswith increaseof loading.When the exchangerof the samecapacitywastakenin Na+form,11·22meq.of Ni2+wassorbed,showing the formation of NiOH+ speciesto agreaterextentthanonNH~formof the exchanger.This is due to the greatertendencyof RCOO.Nato hydrolyseandprovidea higherconcentrationofOH- than RCOO.NH4.Though sorptionof nickel was decreasingwithincreaseof NH~concentrationin thesolutionphase(asexpected),sorptionof 75%and60%of 2·0and0'5mgof nickeltakenwasobservedin batchexperi-ments in the resenceof 2·0 g of ammoniumchloridein 100ml at pH 7·5,when equilibratedwith 0·25g of exchanger.Nickel can, therefore,be recovered most quantitativelyfrom spent.catalystsby em loying the exchangercolumnsinseries. Desorptinofnickelwithformicacid(curve2,Fig. 1)wasfoun to be asefficientas hydrochloricacid. This givesnickel formatefor obtainingtheactivecatalyst.Similar experi ents with a sulphonicacid ex·.changer(Dowex 0X 8, NH:n revealedthesorptionaswellasdesorptin to beconsiderablylessefficient,proving the greaer advantageof a weak cationexchangerfor th recoveryof nickel.The authorsar gratefulto Dr M. SankarDasandShri P. Muru aiyanfor usefuldiscussions.References1. SHKORBATOVA, T.. & RVZHOVA, L. 1., Chem.Abstr.,66 (1967),11799d.2. GULYAEVA, E. 1., Chem.Abstr., 54 (1960),5986i.3. GILMORE, A. J., Chem.Abstr., 74 (1971),1156S3k.~. KALOC, J., Chem.Abstr., 53 (1959),17388a.S. LAZAREV, A. 1. & LAZAREVA, V. T., ZavodskayaLab., 25(19S9),1301;Chem.Abstr., 54 (1960),8414h.6. YATSUK, V. V., GETSKIN, L. S., LYSENKO, V. 1. &PANTELEEVA, A. P., Chem.Abstr., 69 (1968),10885Or.7. YATSUK, V. V., LYSENKO,V. 1. & GETSKIN, L. S., Chem.Abstr., 69 (1968),108849x.8. WELCHER, F. J., The analyticalusesof etkylenediamine-tetraceticacid (D. Van Nostrand,New York), 1958,234.9. SANDELL, E. B., Colorimetricdeterminationof. tracesofmetals(Interscience,New York), 1959,668.CorrosionInhibitionCharacteristicsof SomeFuranDerivativesfromTheir QuantumChemicalValuesAMARNATH MAITRAChemistryDepartment,University of Delhi, Delhi 110007Received20 October1976;accepted14 December1976Quantumchemicalvaluessuchas ionizationpoten-tials andelectronaffinityof somefuranderivativeshavebeensuccessfullycorrelatedwiththeircorrOsioninhibitioncharacteristicsin aciddissolutionof iron.FURAN derivativeshavebeenusedas ccrrosicninhibitors in the ancdic disfeluticncf iren1.Vostaandcoworken,2,shavecocdatedthequantUD1chemicalparametersof a seriesof stIucturallyrelat-edcompoundswiththeircurasioninhibitioncharac-teristics. This paperreportsa correlaticnbetweensemequantumchemicalparameter~4suchasioniza-tion pctentialsand electrcnaffinitiesof furan andsomeof its derivativeswith their corrosioninhibi-tion characteristics.A cylindricalpieceof ircn (99·99%pure)mcuntedon teflon holderwas usedas the electrode.Theelectrodesurfacewas polishedsuccessivelywith150,250,360,and600emerypapersanddegreasedwithacetoneanddried. Discsurface(0'2cm2area)wasexposedto thesolutionandsatisfactorilytightsealswereprovidedbetweeniron surfaceandteflon.Triply distilledwaterwasused. Furan,furfuryl-amineandfuroicacid wereof AR grade~a!1dusedas such.The galvanostaticmethodusedfor steady·statepolarizationstudiesconsistedof a constantcurrentgeneratorand one vernier potentiometerhavingdifferentchannelsfor measuringcorrosioncurrentand corrosion pctentials. All experimentswerecarried out at 250+0.10• Corrosion·rates weremeasuredin termsof log icorr (currentdensity)in1M perchlcric acidcontainingO·lM inhibitorsolution.The relation betweeninhibition characteristicsand quantumchemicaldata showsthat log icorrmostly dependsupon the energyof the highestoccupiedmolecularorbital (HOMO) which is atheoreticalanalogueto the ionization potentialsof a substance.The lowestfreemolecularorbital(LFMO) which gives idea about electronaffinityof the moleculeis also shownto be dependenton the log icorrvalues (Fig. 1). It is observedthat the inhibition characteirsticincreaseswithincreasein theenergyof HOMO, i.e. with decreasein ionization potential. Thus the inhibition effi.•451jj0·4 0·8 12Reciprocal space velocity xll)4(",2rnirl.mol;')-log (1-x) vs reciprocalspacevelocityX10-4(m!min mole-l)o0.02-:tjIFig. 1- Plot ofINDIAN J. CHEM., VOL. 15A, MAY 1977MOLYEDA TES as catalysts,particuld.rlyfor theoxidationofpropylenetoacroleir.haveattractedconsiderableattention. In the presentcase, theoxidationof propyleneOna zincmolybdatecatalysthas been taken up with a view to studyirg thekineticsof oxidationas well as to characterizetheactivityof the catalyst.The oxidationhetsbeenstudiedush:f!a flow-typedifferentialmicro-reactorin the temperatureralge350 to 410°. The preparationof zinc molybdatecatalystandits physicalcharacterizationhavebeendescribedin ourearlierpaperl Thepurityofpropy-lene,obtd.illedby dehydratingpuredistilledisopropylalcohol over aluminacatalystat 350°, has beencheckedby gas chromatograph.Nitrogengashasbeenusedas a diluentalongwith the reactantgasmixture,oxygenard propylene.Keepingtbe total flow rate constantat 140 ml/min aswell as that of propyleneat 45ml/min,theflowrateof oxygenhasbeenvariedfrom 25 to 80ml/min at 3500 ard from the constantpercentageconversionof propylene(,.....,7·5%1 at varioll!'flowratesofoxygen,it hasbeendeducedthatthereactionis independentof the oxygenpartial pressure,i.e.the reactionis zeroorderwith respectto oxygen.In orderto evaluatetheorderwithrespectto propy-ler.e, the percentageconversionof propylenehasbeenevaluatedat threedifferenttemperatureswithvariousflow ratesof propylene.The plot of [-log(l- x)J vs reciprocalspacevelocity(Fig. 1) hasbeenfoundto be linear at allthe threetemperatures,thus showingthat the re-action is first order with respectto propylene.From the rate values, the activationenergyforthe reactionhas beenfound to be 9·3 kcal/mole.The major detectableproductsformedfrom theoxidation of propyleneon ZnMo04 are acrolein,waterar.d carbondioxide. The catalysthas beenfound to possessconsiderableactivity (60% selec-tivity) for partialoxidationof propyleneto acrolein.Carbondioxidecan be formedeitter by directcombustionof propylene or by oxidationof acroleinor througha~1Yotherintermediatespeciesthat maybe obtainedduringthe oxidation. The percentageca.rbondioxideformedat variouscontacttimesandtemperatures(Table1) hasbeenfoundto be almostconstant throughout,thus sho'wingthat (i) theB0·6 0·8-1l'4 -0·6 . -0'8-';'1·0 -1·2H.O.M·0 l f. M . 0ependenceof HOMO (curveA) and LFMOof inhibitorson log icorr[1, furan; 2 furfuryl-amine;and3, furoicacid]tudieson the Oxidationof PropylenebyZinc Molybdate2'N2·1E ~«:l, 1'9-0.-"!1'1',50Fig. 1-(curveB)ciencyi creaseswith the easeof ionizationof themolecul. This impliesthat the moleculeis actingas an eectrondonorwhenit is adsorbedoverthemetal dace and thus retardscorrosion. Furanlies bet eenfurfurylamineandfuroicacidin corro-sion in ibition properties,indicatingthat electrondensit on the heterocyclicoxygenatom is thedetermning factor for the inhibition effect.Car-boxyli group in furoic acid reducesthe electrondensit overcyclicoxygenatomwhereasmethylene-aminogroup, due to hyperconjugativeffectandinductve effect, increasesit. This. presumptionis to omeextent,corroboratedby the dependenceof en rgy of LFMO orbitalsuponlog icorr(Fig. 1)This orrelationshowsthat efficientinhibitorsarebad cceptorof electrons. On the other handit ma beremarkedthateasilyreduciblecompoundsstim ate corrosioninsteadof inhibitingit.Th author thanksDr J. Nagchoudhurifor herkind help in HMO calculations.Refe~nces1. V IDYANATHAN, H. & HACKERMAN, N., Carras.Sci., 11(1971),737.2. V STA, J. & EUASEK, J., Corros.Sci., 11 (1971),223.3. V STA, J. & ELIASEK, J., Werk. Korros., 23 (1972),487.4. S REITWEISER, A. (Jr), Molecularorbitaltheoryfor organicchemists(John Wiley,New York), 1961,117.T. K. VARADARAJAN, B. VISWANATHAN &M. V. C. SASTRI*Departmentof Chemistry,IndianInstituteof TechnologyMadras600036Received9 August 1976;accepted8 February 1977'hekineticsof the oxidationof propyleneoveraz~c molybdatecatalysthavebeenstudiedin thet mperaturerange350to 410°Cwith thevariationofp opyleneand oxygenpartial pres ures.using afferentialflow-typereactor.The reactionhasbeenfflUndto befirst orderwithrespecto propyleneanderoorderwith respecto oxy~enpartialpressure.*Present address:Head, MaterialsScienceResearchentre,Indian Instituteof Technology,Madras600036.rS2I!'I) II r f !II" 111"11 (;111(!/1 ,.~ "If Ii I"

Corrosion Inhibition Characteristics of Some Furan Derivatives from Their Quantum Chemical Values

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Corrosion Inhibition Characteristics of Some Furan Derivatives from Their Quantum Chemical Values

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