ꢀ
LIꢀBingꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ798–807ꢀ
GraphicalꢀAbstractꢀ
ꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2013,ꢀ34:ꢀ798–807ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(12)60557‐9
SynthesisꢀofꢀSAPO‐35ꢀmolecularꢀsieveꢀandꢀitsꢀcatalyticꢀpropertiesꢀinꢀ
theꢀmethanol‐to‐olefinsꢀreactionꢀ
SAPO‐35
LEV)
(
Coke species
(CH3)2
LIꢀBing,ꢀTIANꢀPeng,ꢀLIꢀJinzhe,ꢀCHENꢀJingrun,ꢀYUANꢀYangyang,ꢀSUꢀXiong,ꢀ
(CH3)3
FANꢀDong,ꢀWEIꢀYingxu,ꢀQIꢀYue,ꢀLIUꢀZhongmin*ꢀ
ꢀ
DalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences;ꢀ ꢀ
UniversityꢀofꢀChineseꢀAcademyꢀofꢀSciencesꢀ
(
CH3)2
ꢀ
SAPO‐34
CHA)
(
(
CH3)3
SAPO‐35ꢀ wasꢀ hydrothermallyꢀ synthesizedꢀ usingꢀ hexamethyleneimineꢀ asꢀ
theꢀtemplate.ꢀTheꢀcokeꢀspeciesꢀinꢀtheꢀMTOꢀreactionꢀoverꢀbothꢀSAPO‐35ꢀandꢀ
SAPO‐34ꢀwereꢀinvestigatedꢀandꢀcorrelatedꢀwithꢀtheirꢀcageꢀsize.ꢀ
5
10
15
20
25
30
35
40
45
50
Retention time (min)
ꢀ
isꢀaꢀhydrocarbonꢀpoolꢀactiveꢀcenter,ꢀonꢀwhichꢀtheꢀmethylationꢀ
hydrothermallyꢀ synthesized.ꢀ Theꢀ yieldꢀ ofꢀ solidꢀ sampleꢀ in‐
ofꢀmethanol/diethylꢀetherꢀoccurredꢀtoꢀformꢀethyleneꢀandꢀpro‐
pylene,ꢀ whileꢀ theꢀ resultingꢀ lessꢀ methylatedꢀ benzeneꢀ isꢀ
re‐methylatedꢀtoꢀstartꢀaꢀnewꢀcatalyticꢀcycleꢀ[15,16,24–27].ꢀInꢀ
theꢀpresentꢀexperiments,ꢀinꢀtheꢀinitialꢀstageꢀofꢀreactionꢀtheꢀex‐
istenceꢀ ofꢀ someꢀ hydrocarbonꢀ poolꢀ activeꢀ speciesꢀ (multiplyꢀ
methylatedꢀbenzenes)ꢀwereꢀobservedꢀinꢀSAPO‐34,ꢀwhereasꢀtheꢀ
cokeꢀ speciesꢀ wasꢀ dominatedꢀ byꢀ lessꢀ methylatedꢀ benzenesꢀ inꢀ
SAPO‐35.ꢀWithꢀincreasedꢀreactionꢀtime,ꢀatꢀtheꢀstageꢀofꢀnearlyꢀ
completeꢀdeactivation,ꢀtheꢀmainꢀcokeꢀspeciesꢀinꢀSAPO‐34ꢀwereꢀ
bulkyꢀ aromaticꢀ hydrocarbonsꢀ suchꢀ asꢀ phenanthreneꢀ andꢀ py‐
reneꢀ(generatedꢀfromꢀringꢀcondensationꢀbyꢀhydrogenꢀtransferꢀ
fromꢀmethylbenzeneꢀandꢀmethylnaphthalene),ꢀ whileꢀtheꢀ cokeꢀ
speciesꢀ inꢀ SAPO‐35ꢀ wereꢀ methylbenzene,ꢀ naphthaleneꢀ andꢀ
methylnaphthalene.ꢀ Theꢀ differenceꢀ inꢀ theꢀ cokeꢀ speciesꢀ ofꢀ
SAPO‐35ꢀandꢀSAPO‐34ꢀisꢀprobablyꢀrelatedꢀtoꢀtheirꢀstructures.ꢀ
Theꢀ CHAꢀ cageꢀ ofꢀ SAPO‐34ꢀ (0.67ꢀ nmꢀ ×ꢀ 0.67ꢀ nmꢀ ×ꢀ 1.0ꢀ nm)ꢀ isꢀ
largerꢀthanꢀtheꢀLEVꢀcageꢀofꢀSAPO‐35ꢀ(0.63ꢀnmꢀ×ꢀ0.63ꢀnmꢀ×ꢀ0.73ꢀ
nm).ꢀTheꢀsmallerꢀcageꢀofꢀSAPO‐35ꢀrestrictedꢀtheꢀformationꢀofꢀ
theꢀhydrocarbonꢀpoolꢀactiveꢀspeciesꢀ(multiplyꢀmethylatedꢀben‐
zene)ꢀandꢀdeactivatedꢀcokeꢀspeciesꢀ(macromolecularꢀfused‐ringꢀ
aromaticꢀhydrocarbon).ꢀAlso,ꢀitꢀhasꢀaꢀsmallerꢀaccommodationꢀ
capacityꢀ forꢀ deactivatedꢀ cokeꢀ species,ꢀ whichꢀ thusꢀ resultedꢀ inꢀ
theꢀ rapidꢀ deactivation.ꢀ Theꢀ lackꢀ ofꢀ hydrocarbonꢀ poolꢀ activeꢀ
speciesꢀ alsoꢀ ledꢀ toꢀ theꢀ relativelyꢀ lowꢀ ethyleneꢀ andꢀ propyleneꢀ
selectivityꢀ withꢀ SAPO‐35.ꢀ Moreover,ꢀ itꢀ isꢀ worthꢀ notingꢀ thatꢀ
duringꢀ theꢀ reaction,ꢀ theꢀ organicꢀ compoundsꢀ depositedꢀ inꢀ
SAPO‐35ꢀalwaysꢀcontainedꢀaꢀsmallꢀamountꢀofꢀsaturatedꢀcyclo‐
alkaneꢀadamantaneꢀcompounds.ꢀInꢀourꢀrecentꢀresearchꢀonꢀtheꢀ
cokeꢀspeciesꢀinꢀSAPO‐34ꢀinꢀtheꢀMTOꢀreactionꢀ[28],ꢀweꢀreportedꢀ
thatꢀ adamantaneꢀ compoundsꢀ areꢀ theꢀ cokeꢀ speciesꢀ inꢀ theꢀ lowꢀ
creasedꢀwithꢀtheꢀincreaseꢀofꢀSiꢀcontentꢀinꢀtheꢀsynthesisꢀgel.ꢀTheꢀ
crystallinityꢀofꢀtheꢀsampleꢀincreasedꢀfirstꢀandꢀthenꢀdecreasedꢀasꢀ
theꢀ Siꢀ contentꢀ increased.ꢀ 0.3Siꢀ sampleꢀ exhibitedꢀ theꢀ highestꢀ
crystallinity.ꢀ Theꢀ Siꢀ incorporationꢀ degreeꢀ showedꢀ aꢀ droppingꢀ
trendꢀ whenꢀ theꢀ silicaꢀ contentꢀ rose.ꢀ Theꢀ surfaceꢀ ofꢀ SAPO‐35ꢀ
crystalsꢀwithꢀaꢀhighꢀsilicaꢀcontentꢀwasꢀrough.ꢀInꢀparticular,ꢀ1.0Siꢀ
showedꢀtheꢀcharacteristicꢀofꢀaꢀcore‐shellꢀstructure,ꢀwhichꢀcouldꢀ
beꢀ dueꢀ toꢀ secondaryꢀ crystallizationꢀ onꢀ theꢀ roughꢀ surface.ꢀ
SAPO‐35ꢀ showedꢀ fastꢀ deactivationꢀ thanꢀ SAPO‐34ꢀ inꢀ theꢀ MTOꢀ
reaction,ꢀandꢀaꢀhigherꢀsilicaꢀcontentꢀwillꢀcauseꢀfasterꢀdeactiva‐
tion.ꢀTheꢀmainꢀreasonꢀisꢀthatꢀtheꢀhigherꢀBrönstedꢀacidꢀconcen‐
trationꢀinꢀtheꢀsampleꢀwithꢀhigherꢀsilicaꢀcontentꢀledꢀtoꢀmoreꢀsideꢀ
reactionsꢀ suchꢀ asꢀ cokeꢀ depositionꢀ andꢀ hydrogenꢀ transfer.ꢀ Byꢀ
comparingꢀandꢀanalyzingꢀtheꢀdepositedꢀcokeꢀspeciesꢀformedꢀinꢀ
SAPO‐35ꢀandꢀSAPO‐34ꢀduringꢀtheꢀMTOꢀreaction,ꢀweꢀconcludedꢀ
thatꢀtheꢀsmallerꢀcageꢀofꢀSAPO‐35ꢀlimitedꢀtheꢀgenerationꢀofꢀhy‐
drocarbonꢀ poolꢀ activeꢀ speciesꢀ (polymethylbenzens)ꢀ andꢀ mac‐
romolecularꢀcokeꢀspeciesꢀ(polyaromaticꢀhydrocarbons).ꢀMore‐
over,ꢀtheꢀsmallerꢀcageꢀofꢀSAPO‐35ꢀhadꢀaꢀlowerꢀcapacityꢀtoꢀac‐
commodateꢀdepositedꢀcokeꢀspecies.ꢀTheseꢀtwoꢀreasonsꢀresult‐
edꢀinꢀtheꢀfasterꢀdeactivationꢀofꢀSAPO‐35.ꢀ
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[