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SynthesisofASingle-PhaseSuperfineNa-YZeolitefromCoalFlyAsh*ZOULixiaa,DINGHuilingb,ZHENGLanpingb,HEMejuana,XUQiongaaStateKeyLaboratoryBreedingBaseofNuclearResourcesandEnvironment,EastChinaInstituteofTechnology,Nanchang,330013,Jiangxi,ChinabJiangxiscienceandtechnologynormaluniversity,Nanchang,Jiangxi,330000,Chinaaemail:lxzou1125@163.
comKeywords:superfine,zeolite-Y(FAZ),flyash(FA),crystallization,synthesisAbstract.
Theprocessforthesynthesisofflyash-basedsuperfinezeolites-Y(FAZ)werepresented,whichbasicallyincludedthealkalinefusiontreatmentofflyash(FA),thegelsformationbydissolvedandaged,followinghydrothermalcrystallization.
Adetailedinvestigationwascarriedouttodeterminetheeffectsofconditionsofsynthesissuperfinezeolite-Y.
Thecrystallizationstructureofzeolite-YwascharacterizedbyX-raydiffraction(XRD)andscanningelectronmicroscope(SEM).
Theexperimentalresultsshowthattheoptimizedconditions:Flyashbyalkalifusion(NaOH:flyashratio1.
2:1),anddissolvedof60Cusingdistilledwaterandagedof25Cfor22h.
Thefollowing,atconditionsof2.
2MNaOHsolution,liquid:solid=6.
5,theslurrywashydrothermalcrystallizedat100Cfor24h.
Synthesisofparticlesexhibitscompletelygrowncrystalsofzeolites-Yandcubicmorphologywithapproximatedimensionsof400mm.
Thecrystalinityofzeolite-Ywas88.
7%.
AttheadvantageofthispaperwastosynthesizesuperfineYzeolitethatusingonlyflyashasarawmateriaandwithoutusinganyothersiliconandaluminumsourceandanytemplateadditionundermildconditions.
IntroductionCoalashisgeneratedbycombustionofcoalinapowerstationasawasteproduct.
IthasbeenestablishedthatFAismainlycomposedofamorphousmaterial(aluminosilicateglasses)canbeconvertedtozeolitesinalkalisolutionsbyhydrothermaltreatment.
TherearemanyreportsforsynthesisofzeolitefromFA,forexample,faujasite,Na-Azeolite,phillipsiteandhydroxysodalite.
Thezeolite-Yhasbeusedinreceivedmuchattention.
Itisalsoreportedthatuseofzeolite-Ycanimprovecatalyticcrackingselectivity,reducecokeformation,increasetheyieldofdieseloilandpromotegasolinequality;itcanalsobeusedinthefinechemicalindustry.
Inthesynthesesofzeolite-Y,silicasourcesuchassodiumsilicatesolutionandSourceofaluminumarecurrentlyusedandthisrequirestheadditionofseedsorinitialsolutiontoprovidenuclei[1~4].
Theaimofthispaperwastosynthesizeasingle-phasesuperfinezeolite-YfromFA.
Andanysourceofsiliconandaluminumsourceandanyorganictemplatewithoutadditional.
TheproductsthusobtainedwerecharacterizedbyXRDandSEM.
Theformationconditionandprocessofasingle-phasezeolite-Yarediscussedinthisarticle.
ExperimentZeolitesynthesisAhomogenousmixturewaspreparedbypropergrindingandmixingofflyashandcausticsodain1:1.
2ratio.
Thismixturewasheatedatabout750Cforabout2h.
Then,thefusionsamplewascooled,milledandmixedthoroughlyusingdistilledwaterinabreaker.
Thebreakerwaskeptinawaterbathandstirredconstantlyforafewhours.
Theslurrywassubjectedtoultrasonicandagingforafewhours.
Thisamorphousalumino-silicategelwasformed.
Thisgelwasthensubjectedtocrystallizationbetween40C~100Cforabout10~30hinspeciallydesignedstainlessalloyautoclaveswiththinwallswhichallowafastheattransfer.
Thesolidcrystallineproductwasrecoveredbyfiltrationandwashedwithdistilled-deionizedwaterthoroughlyuntilthefiltratepHwas11,anddriedat80°Cfor24hinanairoven.
Characterization.
Thematerialsobtainedwerecharacterizedbyvariousconventionalmethods.
PowderX-raydiffraction(XRD)patternsweretakenonaRigakuX-raydiffractometerusingNi-filteredCuKRradiation(30kV,16mA).
ParticlemorphologywasobservedbyanHitachiscanningelectronmicroscope(SEM).
ResultsandDiscussionInfluenceofmolarratiosSiO2/Al2O3Fig.
1.
InfluenceofFig.
2Influenceofagingtemperatures:FAzeolite-YmolarratioSiO2/Al2O3:(1)80C,(2)50Cand(3)40Cfor24h;Fig.
4SEMspectrumofzeolite-Y(a)0.
9,(b)2.
0,(c)pureFA(4)at60Cfor2hand25Cfor22hFigure1showstheXRDpatternsofthesynthesizedsampleswereinvestigatedbychangingotherSiO2/Al2O3ratiofrom0.
9to3.
5andthecrystallizationtemperatureat100C.
ThepatternsofthematerialformedatSiO2/Al2O3=0.
9possessesmanydiffractionpeaks,whichcanbeassignabletozeolite-A.
WhentheratioofSiO2/Al2O3increase,newpeaksoffaujasiteappear(pattern(b)-(c)).
ThesyntheticfaujasitetypezeolitetakesintwoformswiththesamecrystalstructureatdifferentSiO2/Al2O3molarratio.
Onewaszeolite-XwithSiO2/Al2O3=2.
0andanotherwaszeolite-Yusingonlythestartingmaterialsflyash(SiO2andAl2O3ratioof2.
5~3.
5about).
InfluenceofagingconditionsIthasbeenestablishedthattheamorphousaluminosilicateinFAiseasiertodissolvethanthecrystallineonesuchasR-quartzandmulliteinalkalisolutions.
Toclarifythedetailedformationprocessofzeolite-Y,effectonthefinalproductofcrystallizationwerecharacterizedunderdifferentagingconditions.
InFigure2,ascanbeseen,thezeolite-Ywassynthesised,butthecrystallizationstrengthreductionwithtemperaturerise.
Thisisbecausethesiliconaluminumdissolvedeasilyformationgelunderhightemperature,depositedonthesurfaceofFA,furtherinfluenceinwhichthesiliconaluminumdissolved,resultdcrystallizationdecreased.
TheintensityofXRDpeakofthesample-(4)washighestwhichthatitwasdissolvedof60Candagedof25Cfor22h.
So,itwasusedasafixedagingconditioninthefollowingsynthesisexperiments.
InfluenceoftheconditionsofcrystallizationFig.
3(1)illustratestheXRDpatternsofthreesamplessynthesizedfromFAattheconditionof1M,2.
2Mand3MNaOHsolutionandcrystallizationfor24h.
AccordingtoXRDpatternsofthreesamplesobtained,onlysample(2.
2MNaOHsolution)wasconfirmedbypure-formzeolite-Ywithouttheformationofothertypesofzeolites.
HuiandChaopointedoutthatsynthesisofzeoliteYdependsontherateofgeldissolution[5],thenumberanddistributionofnucleiinpreparedinitialgel,andthecrystalgrowthrateduringhydrothermaltreatment.
ThestructuralformationofzeoliteYmaybeexplainedinturndependonotherfactorssuchassynthesistemperature,crystallizationtime,compositionmolarratiosofinitialgel,etc.
Fig.
3XRDpatternsofFAYindifferentatcontidionsof1)alkalinityconcentration,2)crystallizationtime,3)crystallizationtemperatures,4)theratioofliquidtosolidThealumino-silicatefusedmassgelobtainedisamorphousandchangestothecrystallinestatewhensubjectedtohydrothermalcrystallization.
TheresultspresentedinFig.
3(2,3)revealsthatcrystallizationtemperatureandtimeinfluenceszeoliticcrystallinity.
Percentcrystallinityofzeolite-Yincreasessignificantlyuntilupto100Cfor24h.
Thecrystallizationtimeincreasesto30h,theotherpeakstoformed.
Therefore,crystallizationcontidionsidentifiedas100Cfor24hintheexperiment.
Fig.
3(4)showstheXRDpatternsofsamplesproducedusingdifferentmolarratiosofliquidtosolidunderthesamesyntheticconditions.
TheXRDpatternsindicatethatallsamplesexhibitazeolite-Ystructure.
Notably,thesamples-2(liquid:solid=6.
5)showsignificantlyhigherbroadeneddiffractionpeaks,withhigheryieldofcrystallization.
Therelativecrystalinitiescalculated[6]forsamples-1(liquid:solid=8.
5)andsamples-2arefoundtobe74.
7%and88.
7%,respectively.
MorphologicalstudiesTheSEMphotographsinFig.
3depictthesampletransformationofFAintoZeolite-Y.
Sampleszeolite-Yarefairlyuniformincrystalsize,andtheindividualaggregatesarecomposedofcloselypackednanocrystals,andhavesmalleraverageaggregatesizes.
Thisisprobablybecauselessuniformcrystallizationoccurredingel.
Forthesampletheaverageparticle(aggregate)sizewasestimatedfromatleast400nmparticlesintheSEMimages.
ConclusionsSynthesisofFAZisdirectlyrelatedtoextractionofsilicatesandaluminatesformFAusingsodiumhydroxide.
Fromtheinformationpresentedinthispaper,Si4+andAl3+ionsareelutedfromfusingFAbydissolutionofamorphousmaterialduringtheagingandcrystallizationtoformasingle-phaseYtypezeoliteintheautoclave.
TheYtypezeolitewerecharacterizationbyXRDandSEMpatterns,thefollowingconclusionscanbedrawn.
AhomogenousfusionmixturewaspreparedbypropergrindingandmixingofFAandcausticsodain1:1.
2ratio.
Thismixturewascalcinedatabout750Cforabout2h.
Thensamplewasdissolvedat60Candagedat25Cfor22h,tobegelformation.
Thegelandwaterastheratioofliquidtosolidis6.
5,in2.
2MNaOHsolutiontocrystallizationfor24hat100Cusingtheautoclave.
Themaximumpurityofzeolite-Ywasobtained,crystalinitycalculatedforsampleswas88.
7%.
SO,theSiO2andAl2O3ratioof2.
5~3.
5inFAfavoursformationofZeolite-Y.
OnmodificationoftheactualSiO2andAl2O3ratio,byincreasingsodiumsilicateorsodiumaluminatecontent,itwaspossibletosynthesisezeolite-Xorzeolite-AatSiO2/Al2O3of2.
0or0.
9respectively.
Theimportantfeatureofthisnovelprocedureistoproducesuperfinezeolite-Yandcrystalinity88.
7%inonevesselwithoutusinganyothersiliconandaluminumsourceandanytemplateaddition.
ThehighvolumeutilizationofFAforzeoliteproductiontechnologycomparedtoothermediumrlowvalueutilization,thisproductiontechnologyhasadvantagesofvalueaddition,offeringanedgeoverotherflyashutilisationtechnologiescurrentlyused.
AcknowledgmentThisstudywassupportedinpartbyJiangxiProvincialDepartmentofscienceandtechnologysupportprograminchina(20122BBG70084-2).
ThehelpandcooperationrenderedbythemanagementofFengchengThermalPowerStationincollectingflyashforthisresearchworkisgreatlyacknowledged.
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