Application of sodium titanate nanotubes doped with vanadium (VNaTNT) as a heterogeneous catalyst for oxidation of sulfides at room temperature

Article abstract of DOI:10.1016/S1872-2067(15)61056-7

A heterogeneous titanate nanotube (TNT) catalyst containing TiO₂, Na, and V has been synthesized and used in the chemoselective oxidation of sulfides to the corresponding sulfoxides in the presence of 30% H₂O₂ in water. Some of the advantages of our method include excellent yields, heterogeneous conditions, simplicity, compatibility with a variety of functionalities, and ease of isolation of the products. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N₂ adsorption were used for structural and textural characterization of the catalyst (VNaTNT).

Full text of DOI:10.1016/S1872-2067(15)61056-7

ChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
ꢀ
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
ꢀ
ꢀ
Article
Applicationꢀofꢀsodiumꢀtitanateꢀnanotubesꢀdopedꢀwithꢀvanadiumꢀ
VNaTNT)ꢀasꢀaꢀheterogeneousꢀcatalystꢀforꢀoxidationꢀofꢀsulfidesꢀatꢀ
(
roomꢀtemperatureꢀ
MohammadꢀAliꢀDadvar,ꢀRaziehꢀFazaeliꢀ*
ꢀ
DepartmentꢀofꢀChemistry,ꢀShahrezaꢀBranch,ꢀIslamicꢀAzadꢀUniversity,ꢀ86145‐311,ꢀIranꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Aꢀheterogeneousꢀtitanateꢀnanotubeꢀ(TNT)ꢀcatalystꢀcontainingꢀTiO ,ꢀNa,ꢀandꢀVꢀhasꢀbeenꢀsynthesizedꢀ
2
Receivedꢀ31ꢀDecemberꢀ2015ꢀ
Acceptedꢀ4ꢀFebruaryꢀ2016ꢀ
Publishedꢀ5ꢀAprilꢀ2016ꢀ
andꢀusedꢀinꢀtheꢀchemoselectiveꢀoxidationꢀofꢀsulfidesꢀtoꢀtheꢀcorrespondingꢀsulfoxidesꢀinꢀtheꢀpresenceꢀ
ofꢀ30%ꢀH ꢀinꢀwater.ꢀSomeꢀofꢀtheꢀadvantagesꢀofꢀourꢀmethodꢀincludeꢀexcellentꢀyields,ꢀheterogene‐
ousꢀconditions,ꢀsimplicity,ꢀcompatibilityꢀwithꢀaꢀvarietyꢀofꢀfunctionalities,ꢀandꢀeaseꢀofꢀisolationꢀofꢀtheꢀ
O
2 2
products.ꢀFourierꢀtransformꢀinfraredꢀspectroscopy,ꢀX‐rayꢀdiffraction,ꢀscanningꢀelectronꢀmicroscopy,ꢀ
transmissionꢀelectronꢀmicroscopy,ꢀandꢀN
terizationꢀofꢀtheꢀcatalystꢀ(VNaTNT).ꢀ
2
ꢀadsorptionꢀwereꢀusedꢀforꢀstructuralꢀandꢀtexturalꢀcharac‐
Keywords:ꢀ
Sulfideꢀ
Sulfoxideꢀ
Sulfoneꢀ
©ꢀ2016,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
Supportedꢀvanadiaꢀcatalystꢀ
Nanotube
1
.ꢀ ꢀ Introductionꢀ
Amongꢀ allꢀ transition‐metalꢀ oxides,ꢀ TiO
sivelyꢀ studied,ꢀ makingꢀ itꢀ oneꢀ ofꢀ theꢀ mostꢀ investigatedꢀ com‐
poundsꢀinꢀmaterialsꢀscience.ꢀBulkꢀTiO ꢀisꢀknownꢀtoꢀbeꢀaꢀveryꢀ
2
ꢀ isꢀ theꢀ mostꢀ exten‐
Sulfoxidesꢀ andꢀ sulfonesꢀ [1],ꢀ ofꢀ whichꢀ someꢀ areꢀ importantꢀ
2
commodityꢀchemicalsꢀandꢀpharmaceuticalsꢀ[2], areꢀmostꢀcom‐
monlyꢀsynthesizedꢀbyꢀtheꢀstraightforwardꢀoxidationꢀofꢀsulfides.ꢀ
Thisꢀtransformationꢀhasꢀbeenꢀcarriedꢀoutꢀbyꢀvariousꢀmethodsꢀ
usefulꢀnon‐toxic,ꢀenvironmentallyꢀfriendly,ꢀcorrosion‐resistantꢀ
material,ꢀ itꢀ isꢀ frequentlyꢀ usedꢀ inꢀ paint,ꢀ whiteꢀ pigments,ꢀ andꢀ
sunblocksꢀ[16].ꢀTiO ‐basedꢀnanotubesꢀhaveꢀattractedꢀattentionꢀ
2
[
3–7].ꢀTheꢀuseꢀofꢀH
2
O
2
ꢀasꢀtheꢀfinalꢀoxidantꢀoffersꢀtheꢀadvantagesꢀ
becauseꢀofꢀtheirꢀpotentialꢀapplicationꢀasꢀhighlyꢀefficientꢀphoto‐
catalystsꢀ[17],ꢀinꢀlithiumꢀionꢀbatteriesꢀ[18],ꢀinꢀphotovoltaicꢀcellsꢀ
[19],ꢀandꢀinꢀenvironmentalꢀapplicationsꢀ[20].ꢀSol‐gelꢀprocessingꢀ
ofꢀ TiO2ꢀ hasꢀ beenꢀ extensivelyꢀ investigated,ꢀ andꢀ modernꢀ pro‐
cessesꢀhaveꢀbeenꢀdevelopedꢀtoꢀrefineꢀandꢀcontrolꢀtheꢀstability,ꢀ
asꢀwellꢀasꢀtheꢀphaseꢀformation,ꢀofꢀtheꢀcolloidalꢀprecursorsꢀ[21].ꢀ
Sodiumꢀ trititanateꢀ nanotubesꢀ haveꢀ recentlyꢀ beenꢀ synthesizedꢀ
usingꢀ aꢀ methodꢀ proposedꢀ byꢀ Refs.ꢀ [22,23],ꢀ viaꢀ hydrothermalꢀ
treatmentꢀ ofꢀ theꢀ titaniaꢀ precursorꢀ withꢀ concentratedNaOHꢀ
aqueousꢀsolutionꢀ(10ꢀmol/L).ꢀ
thatꢀitꢀisꢀaꢀcheap,ꢀenvironmentallyꢀbenign,ꢀandꢀreadilyꢀavailableꢀ
reagentꢀ andꢀ producesꢀ waterꢀ asꢀ theꢀ onlyꢀ by‐productꢀ [8].ꢀ Itꢀ isꢀ
worthꢀnotingꢀthatꢀmetalꢀcatalystsꢀareꢀessentialꢀforꢀtheꢀproduc‐
tionꢀofꢀsulfoxidesꢀinꢀhighꢀyieldsꢀandꢀselectivities.ꢀThereꢀareꢀsev‐
eralꢀreportsꢀonꢀsomeꢀmetal‐containingꢀcatalysts,ꢀsuchꢀasꢀVꢀ[9],ꢀ
Tiꢀ[10],ꢀ Cuꢀ[11],ꢀAgꢀ[12],ꢀFeꢀ[13],ꢀBiꢀ[14],ꢀandꢀWꢀ[15]ꢀ forꢀtheꢀ
oxidationꢀofꢀsulfidesꢀtoꢀsulfoxides.ꢀUnfortunately,ꢀmostꢀofꢀtheseꢀ
reagentsꢀ areꢀ notꢀ satisfactoryꢀ forꢀ medium‐ꢀ toꢀ large‐scaleꢀ syn‐
thesisꢀbecauseꢀofꢀtheꢀlowꢀcontentꢀofꢀeffectiveꢀoxygen,ꢀtheꢀfor‐
mationꢀ ofꢀ environmentallyꢀ unfavorableꢀ co‐products,ꢀ andꢀ highꢀ
cost.ꢀ
Vanadiumꢀhasꢀbeenꢀshownꢀtoꢀplayꢀanꢀimportantꢀroleꢀinꢀoxi‐
dationꢀ reactions.ꢀ Forꢀ example,ꢀ V‐SBA‐15,ꢀ V‐MCM‐41,ꢀ
*ꢀCorrespondingꢀauthor.ꢀTel:ꢀ+98‐31‐53292035;ꢀFax:ꢀ+98‐31‐53213095.ꢀE‐mail:ꢀfazaeli@iaush.ac.irꢀ
DOI:ꢀ10.1016/S1872‐2067(15)61056‐7ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ37,ꢀNo.ꢀ4,ꢀAprilꢀ2016ꢀ ꢀ ꢀ

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MohammadꢀAliꢀDadvarꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501ꢀ
495ꢀ
V‐MCM‐48,ꢀ andꢀ V‐MCFꢀ areꢀ someꢀ interestingꢀ V‐containingꢀ
mesoporousꢀ silicaꢀ oxidationꢀ catalystsꢀ withꢀ uniformꢀ poreꢀ sizeꢀ
andꢀhighꢀsurfaceꢀareaꢀthatꢀofferꢀaꢀlargeꢀconcentrationꢀofꢀacces‐
sibleꢀ andꢀ well‐definedꢀ activeꢀ centers,ꢀ oftenꢀ incorporatedꢀ intoꢀ
theꢀsilicaꢀframeworkꢀ[24–29].ꢀ ꢀ
tionꢀmethod.ꢀAꢀmethanolꢀsolutionꢀofꢀNH
contentꢀofꢀ(4–16)ꢀwt%ꢀwasꢀcontactedꢀwithꢀtheꢀNaTiO ꢀsupportꢀ
4
VO
3
ꢀtoꢀachieveꢀaꢀfinalꢀVꢀ
2
atꢀ60ꢀ°Cꢀ[22,23],ꢀandꢀtheꢀmethanolꢀwasꢀrotaryꢀevaporatedꢀuntilꢀ
completeꢀdryness.ꢀTheꢀcatalystsꢀwereꢀthenꢀdriedꢀovernightꢀinꢀ
airꢀatꢀ120ꢀ°C,ꢀfollowedꢀbyꢀcalcinationꢀatꢀ400ꢀ°Cꢀforꢀ4ꢀh,ꢀandꢀtheꢀ
catalystsꢀareꢀdenotedꢀasꢀV(x)NaTNT,ꢀwhereꢀtheꢀxꢀisꢀtheꢀVꢀmassꢀ
fractionꢀ(%).ꢀ ꢀ
Inꢀthisꢀarticle,ꢀweꢀreportꢀonꢀanꢀalcoholꢀimpregnationꢀmethodꢀ
forꢀ theꢀ synthesisꢀ ofꢀ orderedꢀ sodiumꢀ trititanateꢀ nanotubesꢀ
(
NaTNT)ꢀ dopedꢀ withꢀ vanadiumꢀ (VNaTNT)ꢀ byꢀ NaOHꢀ andꢀ
NH VO ꢀ ((4–13)ꢀ mol%).ꢀ Theꢀ compositionꢀ andꢀ crystallinityꢀ ofꢀ
theseꢀstructuresꢀwereꢀdeterminedꢀbyꢀpowderꢀX‐rayꢀdiffractionꢀ
XRD),ꢀscanningꢀelectronꢀmicroscopyꢀ(SEM),ꢀtransmissionꢀelec‐
tronꢀmicroscopyꢀ(TEM),ꢀN ꢀadsorption‐desorptionꢀanalysis,ꢀandꢀ
thermalꢀ gravimetricꢀ (TG)ꢀ analysis.ꢀ Theꢀ catalyticꢀ activityꢀ ofꢀ
VNaTNTꢀ isꢀ reportedꢀ forꢀ theꢀ oxidationꢀ ofꢀ sulfidesꢀ withꢀ H
Schemeꢀ1).ꢀ ꢀ
4
3
2.2.ꢀ ꢀ Synthesisꢀofꢀsulfoxidesꢀandꢀsulfonesꢀ
(
H
2
O ꢀ(8ꢀmmol)ꢀwasꢀaddedꢀinꢀoneꢀportionꢀtoꢀaꢀstirredꢀsus‐
2
2
pensionꢀofꢀtheꢀselectedꢀsulfideꢀ(1ꢀmmol)ꢀandꢀVNaTNTꢀhetero‐
geneousꢀcatalystꢀinꢀwaterꢀ(5ꢀmL).ꢀTheꢀresultingꢀslurryꢀwasꢀthenꢀ
stirredꢀatꢀroomꢀtemperatureꢀforꢀ30ꢀmin.ꢀEthanolꢀ(10ꢀmL)ꢀwasꢀ
usedꢀtoꢀfilterꢀoffꢀandꢀwashꢀtheꢀcatalyst.ꢀEthylꢀacetateꢀ(5ꢀmL)ꢀwasꢀ
addedꢀandꢀtheꢀresultingꢀsolutionꢀwasꢀdriedꢀonꢀanhydrousꢀso‐
diumꢀsulfateꢀandꢀtheꢀsolventsꢀremovedꢀinꢀvacuoꢀtoꢀaffordꢀtheꢀ
crudeꢀ product.ꢀ Thisꢀ wasꢀ thenꢀ purifiedꢀ byꢀ columnꢀ chromatog‐
raphyꢀusingꢀsilicaꢀgelꢀandꢀ10%ꢀEtOAcꢀinꢀhexaneꢀasꢀtheꢀeluentꢀtoꢀ
affordꢀ pureꢀ sulfoxide.ꢀ Sulfonesꢀ wereꢀ synthesizedꢀ byꢀ aꢀ similarꢀ
2 2
O ꢀ
(
2
.ꢀ ꢀ Experimentalꢀ ꢀ
Chemicalsꢀusedꢀwereꢀallꢀofꢀreagentꢀgrade.ꢀReactionꢀcoursesꢀ
andꢀ productꢀ mixturesꢀ wereꢀ monitoredꢀ byꢀ thinꢀ layerꢀ andꢀ gasꢀ
chromatographies.ꢀ Aꢀ Perkinꢀ Elmerꢀ Spectrumꢀ 65ꢀ spectropho‐
tometerꢀwasꢀusedꢀtoꢀobtainꢀinfraredꢀspectraꢀ(400–4000ꢀcm )ꢀ
fromꢀKBrꢀpellets.ꢀCuꢀK ꢀ(0.154056ꢀnm)ꢀradiationꢀwithꢀautomat‐
methodꢀusingꢀ5ꢀmol%ꢀofꢀVNaTNTꢀinꢀCH
CN.ꢀ
3
−1
α
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
icꢀcontrolꢀwasꢀusedꢀtoꢀobtainꢀpowderꢀXRDꢀpatternsꢀonꢀBrukerꢀ
D8ꢀ ADVANCEꢀ andꢀ PW1830ꢀ instruments.ꢀ Adsorp‐
tion/desorptionꢀofꢀnitrogenꢀatꢀliquidꢀnitrogenꢀtemperatureꢀwasꢀ
usedꢀtoꢀdetermineꢀBrunauer‐Emmett‐Tellerꢀ(BET)ꢀspecificꢀsur‐
faceꢀ areasꢀ andꢀ poreꢀ volumesꢀ ofꢀ theꢀ catalystsꢀ withꢀ aꢀ Mi‐
cromeriticsꢀ BELSORPꢀ miniꢀ ΙΙꢀ instrument.ꢀ Theꢀ samplesꢀ wereꢀ
outgassedꢀatꢀ350ꢀ°Cꢀforꢀ12ꢀhꢀunderꢀaꢀvacuumꢀofꢀ1ꢀꢀ10 ꢀPaꢀ
priorꢀtoꢀtheꢀadsorptionꢀmeasurements.ꢀCatalystꢀporeꢀsizesꢀwereꢀ
obtainedꢀ fromꢀ theꢀ peakꢀ positionsꢀ ofꢀ theꢀ distributionꢀ curvesꢀ
determinedꢀbyꢀtheꢀadsorptionꢀbranchesꢀofꢀtheꢀisotherms.ꢀAꢀJoelꢀ
JEMꢀ2010ꢀscanꢀtransmissionꢀelectronꢀmicroscopeꢀwasꢀusedꢀtoꢀ
obtainꢀtransmissionꢀelectronꢀmicrographs.ꢀToꢀperformꢀtheꢀTEMꢀ
measurements,ꢀtheꢀsampleꢀwasꢀsuspendedꢀinꢀethanolꢀandꢀsup‐
portedꢀonꢀaꢀcarbonꢀcoatedꢀcopperꢀgrid.ꢀAꢀShimadzu,ꢀMPC‐2200ꢀ
UV‐Visꢀ spectrophotometerꢀ operatingꢀ withinꢀ theꢀ rangeꢀ ofꢀ
3.1.ꢀ ꢀ Physico‐chemicalꢀcharacterizationꢀ
Fig.ꢀ1ꢀshowsꢀFourierꢀtransformꢀinfraredꢀ(FT‐IR)ꢀspectraꢀofꢀ
theꢀNaTNT,ꢀV(4)NaTNT,ꢀandꢀV(13)NaTNTꢀsamples.ꢀTheꢀvibra‐
tionalꢀ modeꢀ observedꢀ atꢀ 896ꢀ cm−1ꢀ inꢀ theꢀ spectrumꢀ ofꢀ theꢀ
−4
NaTNT
fromꢀ aꢀ distortedꢀ TiO
[24].ꢀTheꢀwavenumberꢀofꢀthisꢀvibrationalꢀmodeꢀincreasesꢀfromꢀ
ꢀ
referenceꢀ isꢀ assignedꢀ toꢀ stretchingꢀ ofꢀ theꢀ Ti–Oꢀ bondsꢀ
6
ꢀ octahedronꢀ whoseꢀ oxygenꢀ isꢀ unsharedꢀ
−1
896ꢀinꢀNaTNTꢀtoꢀ908ꢀcm ꢀinꢀ V(13)NaTNT.ꢀThisꢀ confirmsꢀin‐
corporationꢀofꢀvanadiumꢀintoꢀtheꢀtrititanateꢀstructures.ꢀCrystal‐
lineꢀV
2
O ꢀisꢀformedꢀinꢀtheꢀVNaTNTꢀsamples,ꢀasꢀimpliedꢀbyꢀtheꢀ
5
−1
appearanceꢀofꢀaꢀtypicalꢀbandꢀofꢀV
2
O ꢀatꢀca.ꢀ970–976ꢀcm .ꢀThisꢀ
5
suggestsꢀthatꢀtheꢀvanadiumꢀspeciesꢀareꢀisolatedꢀinꢀtheꢀVNaTNTꢀ
samples,ꢀorꢀatꢀleastꢀhighlyꢀdispersedꢀonꢀtheꢀTNTꢀsurface.ꢀ
Fig.ꢀ 2ꢀ showsꢀ XRDꢀ patternsꢀ ofꢀ sodiumꢀ titanateꢀ nanotubesꢀ
NaTNTꢀandꢀVNaTNT.ꢀTheꢀresultsꢀindicateꢀthatꢀtheꢀNaTNTꢀsam‐
190–900ꢀnmꢀatꢀaꢀresolutionꢀofꢀ2.0ꢀnmꢀwasꢀusedꢀtoꢀobtainꢀDRUVꢀ
spectra.ꢀ ꢀ
2.1.ꢀ ꢀ PreparationꢀofꢀV(x)NaTNTꢀ
VNaTNTꢀ catalystsꢀ wereꢀ preparedꢀ byꢀ anꢀ alcoholꢀ impregna‐
O
O
S
VNaTNT (5 mol %), CH CN
VNaTNT (3 mol %), H O
3
2
S
S
(1)
H
2
O
2
(15 mol%), r.t.
H O (8 mol%), r.t.
2
2
O
1
2
3
976
972
(2)
S
Br
S
9
08
S
S
9
04
(3)
1a
1b
1c
1d
S
O
S
S
CH3
896
900
O
O N
2
1000
800
700
600
500
H C
3
1
1g
Wavenumber (cm )
1
e
1f
Schemeꢀ1.ꢀOxidationꢀofꢀsulfidesꢀ(1)ꢀtoꢀsulfoxidesꢀ(2)ꢀandꢀsulfonesꢀ(3)ꢀinꢀ
theꢀpresenceꢀofꢀVNaTNTꢀcatalyst.ꢀ
Fig.ꢀ 1.ꢀ FT‐IRꢀ spectraꢀ ofꢀ NaTNTꢀ andꢀ V(x)NaTNTꢀ materialsꢀ withꢀ twoꢀ
differentꢀxꢀvalues.ꢀ(1)ꢀV(13)NaTNT;ꢀ(2)ꢀV(4)NaTNT;ꢀ(3)ꢀNaTNT.ꢀ

496ꢀ
MohammadꢀAliꢀDadvarꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501ꢀ
(a)
(b)
Na
Na
2
Ti
Ti
3
O
O
7
2
5
11
2 5
V O
(
1)
(2)
(c)
(d)
10
20
30
/( )
40
50
o
2
Fig.ꢀ2.ꢀXRDꢀpatternsꢀofꢀ(1)ꢀNaTNTꢀandꢀ(2)ꢀVNaTNT.ꢀ
plesꢀstudiedꢀshowꢀgoodꢀcrystallinityꢀand
ꢀ
displayꢀcharacteristicꢀ
peaksꢀatꢀ2ꢀ=ꢀ10.5°,ꢀ24.2°,ꢀ28.4°,ꢀandꢀ48.2°,ꢀcommonlyꢀassoci‐
atedꢀ withꢀ monoclinicꢀ layeredꢀ sodiumꢀ trititanateꢀ (Na Ti ,ꢀ
JCPDS‐ICDDꢀ cardꢀ 31‐1329).ꢀ Theseꢀ correspondꢀ toꢀ theꢀ (001),ꢀ
2
O
3 7
(201),ꢀ(111),ꢀandꢀ(020)ꢀcrystalꢀplanes,ꢀrespectively.ꢀ
Fig.ꢀ2(2)ꢀshowsꢀXRDꢀpatternꢀofꢀVNaTNT.ꢀTheꢀresultsꢀindicateꢀ
Fig.ꢀ3.ꢀSEMꢀimagesꢀofꢀ(a,ꢀb)ꢀV(4)NaTNTꢀandꢀ(c,ꢀd)ꢀV(13)NaTNT.ꢀ
thatꢀtheꢀVNaTNTꢀsamplesꢀshowꢀgoodꢀcrystallinityꢀand
theꢀcharacteristicꢀpeaksꢀforꢀNa Ti ,ꢀNa Ti 11,ꢀandꢀV
crystallineꢀphasesꢀofꢀNa Ti ꢀandꢀNa Ti 11ꢀareꢀgenerallyꢀcon‐
sideredꢀ characteristicꢀ forꢀ titanateꢀ nanotubularꢀ structuresꢀ
24,25].ꢀTheꢀpresenceꢀofꢀsodiumꢀinꢀtheꢀinterlayerꢀspacesꢀofꢀtheꢀ
ꢀ
displayꢀ
2
O
3 7
2
5
O
2 5
O .ꢀTheꢀ
2
O
3 7
2
5
O
Fig.ꢀ 3ꢀ showsꢀ theꢀ SEMꢀ imagesꢀ ofꢀ V(4)NaTNTꢀ andꢀ
V(13)NaTNTꢀcatalysts.ꢀV(x)NaTNTꢀexhibitsꢀaggregationꢀofꢀreg‐
ularꢀtube‐shapedꢀparticles,ꢀcommonlyꢀobservedꢀinꢀpureꢀtitanateꢀ
nanotubeꢀ materialꢀ [28].ꢀ Theꢀ externalꢀ diameterꢀ sizeꢀ ofꢀ theꢀ
nanotubesꢀbecomeꢀsmallerꢀandꢀtheꢀparticlesꢀtendꢀtoꢀaggregateꢀ
afterꢀincreasingꢀtheꢀVꢀloadingꢀfromꢀ4%ꢀtoꢀ13%,ꢀasꢀindicatedꢀbyꢀ
theꢀSEMꢀmicrographs.ꢀ ꢀ
Fig.ꢀ4(a)ꢀshowsꢀtheꢀSEM‐EDXꢀspectrumꢀofꢀtheꢀV(13)NaTNTꢀ
sample,ꢀ whichꢀ showsꢀ theꢀ presenceꢀ ofꢀ V,ꢀ Na,ꢀ Tiꢀ andꢀ Oꢀ asꢀ ele‐
mentsꢀ inꢀ theꢀ V(13)NaTNTꢀ structures.ꢀ Accordingꢀ toꢀ theꢀ ener‐
gy‐dispersiveꢀX‐rayꢀ(EDX)ꢀspectrumꢀandꢀitsꢀdataꢀinꢀTableꢀ1,ꢀitꢀ
canꢀ beꢀ concludedꢀ thatꢀ aꢀ sufficientꢀ amountꢀ ofꢀ Naꢀ andꢀ Vꢀ wasꢀ
[
trititanateꢀstructureꢀisꢀconfirmedꢀbyꢀtheꢀpresenceꢀofꢀaꢀpeakꢀatꢀ
aboutꢀ2ꢀ=ꢀ10.5°ꢀ[26].ꢀ ꢀ
Aꢀnumberꢀofꢀnewꢀsharpꢀreflectionsꢀareꢀobservedꢀalongꢀwithꢀ
theꢀsignalsꢀcorrespondingꢀtoꢀtheꢀNa
beꢀascribedꢀtoꢀtheꢀpresenceꢀofꢀdifferentꢀlayeredꢀsodiumꢀtitan‐
atesꢀ(Na Ti 11)ꢀwithꢀaꢀmonoclinicꢀlattice.ꢀConversionꢀofꢀTNTsꢀ
toꢀ largerꢀ nanostructures,ꢀ suchꢀ asꢀ nanoribbonsꢀ andꢀ nanorodsꢀ
27],ꢀisꢀsuggestedꢀbyꢀtheꢀappearanceꢀofꢀtheꢀNa Ti 11.ꢀThisꢀisꢀinꢀ
goodꢀagreementꢀwithꢀtheꢀSEMꢀimagesꢀ(Fig.ꢀ3).ꢀ ꢀ
2 3 7
Ti O ꢀphase,ꢀandꢀthisꢀcanꢀ
2
5
O
[
2
5
O
(b)
(c)
(d)
6000
5000
4000
3000
2000
1000
0
Ti K
α
(a)
V L
NaKα
α
Ti L
α
O K
α
(e)
(f)
(g)
V K
Ti Kβ
α
V K
β
0
5
5
10
keV
keV
Fig.ꢀ4.ꢀ(a)ꢀEDX‐SEMꢀandꢀ(b)ꢀTEMꢀimageꢀofꢀV(13)NaTNT,ꢀ(c–g)ꢀSEM‐EDXꢀmicrographsꢀandꢀdistributionꢀmapsꢀofꢀelementsꢀinꢀV(13)NaTNT.ꢀParticlesꢀrichꢀ
inꢀOꢀ(green),ꢀNaꢀ(orange),ꢀTiꢀ(blue),ꢀandꢀVꢀ(red)ꢀareꢀpresent.ꢀ

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MohammadꢀAliꢀDadvarꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501ꢀ
497ꢀ
adsorption‐desorptionꢀisothermsꢀofꢀVNaTNT(Fig.ꢀ6(a)),ꢀasꢀwellꢀ
ꢀ
Tableꢀ1ꢀ
Effectꢀ ofꢀ differentꢀ conditionsꢀ inꢀ theꢀ oxidationꢀ ofꢀ diphenylꢀ sulfidesꢀ toꢀ
sulfoxidesꢀafterꢀ0.5ꢀh.ꢀ
asꢀ theirꢀ hysteresisꢀ loops,ꢀ areꢀ similarꢀ toꢀ thoseꢀ previouslyꢀ re‐
portedꢀ forꢀ sodiumꢀ titanateꢀ nanotubesꢀ synthesizedꢀ fromꢀ lowꢀ
surfaceꢀareaꢀanataseꢀprecursorsꢀ[28–30].ꢀTheꢀporeꢀsizeꢀdistri‐
butionꢀcurvesꢀ(Fig.ꢀ6(b))ꢀshowꢀthatꢀtheꢀsampleꢀcontainsꢀthreeꢀ
typesꢀofꢀpores.ꢀTheꢀfirstꢀtypeꢀmayꢀbeꢀascribedꢀtoꢀaꢀsmallerꢀpor‐
tionꢀofꢀmesoporesꢀ(aboutꢀ3–5ꢀnmꢀinꢀdiameter)ꢀattributedꢀtoꢀtheꢀ
nanotubes.ꢀTheꢀsecondꢀtypeꢀ(aboutꢀ10–15ꢀnmꢀinꢀdiameter)ꢀcanꢀ
beꢀascribedꢀtoꢀtheꢀparallelꢀassemblyꢀofꢀtheꢀnanotubes,ꢀandꢀtheꢀ
thirdꢀtypeꢀ(aboutꢀ35ꢀnmꢀinꢀdiameter)ꢀmayꢀresultꢀfromꢀrandom‐
lyꢀassembledꢀnanotubesꢀ[23,28,29,31].ꢀ ꢀ
ꢀ
a
Entryꢀ
Catalystꢀ
—ꢀ
TNTꢀ
x/%ꢀ
—ꢀ
3ꢀ
3ꢀ
3ꢀ
3ꢀ
3ꢀ
3ꢀ
3ꢀ
3ꢀ
3ꢀ
4ꢀ
5ꢀ
H
2
O :sulfideꢀ Yield ꢀ(%)
8:1ꢀ
2
1ꢀ
ꢀ 3ꢀ
11ꢀ
23ꢀ
38ꢀ
27ꢀ
66ꢀ
75ꢀ
87ꢀ
80ꢀ
98ꢀ
85ꢀ
64ꢀ
2
ꢀ
8:1ꢀ
8:1ꢀ
8:1ꢀ
8:1ꢀ
8:1ꢀ
8:1ꢀ
8:1ꢀ
8:1ꢀ
8:2ꢀ
8:2ꢀ
8:2ꢀ
3
ꢀ
2 5
V O ꢀ
4
ꢀ
V
2
O
5
/TiO
NaTNTꢀ
2
ꢀ
5
ꢀ
6
ꢀ
V(4)NaTNTꢀ
V(7)NaTNTꢀ
V(13)NaTNTꢀ
V(15)NaTNTꢀ
V(13)NaTNTꢀ
V(13)NaTNTꢀ
V(13)NaTNTꢀ
7
ꢀ
8
ꢀ
9
ꢀ
Theꢀ thermalꢀ behaviorꢀ ofꢀ theꢀ NaVTNTꢀ isꢀ illustratedꢀ inꢀ Fig.ꢀ
10ꢀ
11ꢀ
12ꢀ
7(a).ꢀTGꢀprofileꢀdisplaysꢀtwoꢀmassꢀlossꢀevents,ꢀasꢀobserved.ꢀTheꢀ
initialꢀmassꢀlossꢀofꢀ2.21%ꢀwasꢀobservedꢀatꢀtemperaturesꢀbelowꢀ
125ꢀ°Cꢀasꢀaꢀresultꢀofꢀtheꢀlossꢀofꢀphysicallyꢀabsorbedꢀwater.ꢀTheꢀ
secondꢀ massꢀ lossꢀ ofꢀ 2.77%ꢀ wasꢀ betweenꢀ 230ꢀ andꢀ 570ꢀ °Cꢀ
(mostlyꢀatꢀaroundꢀ430ꢀ°C),ꢀwhichꢀcanꢀbeꢀattributedꢀtoꢀtheꢀre‐
movalꢀ ofꢀ unhydrolyzedꢀ isopropoxideꢀ ligandsꢀ bondedꢀ inꢀ theꢀ
titaniumꢀ[32–34].ꢀApproximatelyꢀ95.02%ꢀofꢀtheꢀstartingꢀmassꢀ
remainedꢀ afterꢀ theꢀ secondꢀ stage.ꢀ Theꢀ applicabilityꢀ ofꢀ theꢀ
VNaTNTꢀacrossꢀaꢀwideꢀtemperatureꢀrangeꢀisꢀdemonstratedꢀbyꢀ
theꢀTGAꢀresults.ꢀ
aꢀIsolatedꢀyields.ꢀ
ꢀ
loadedꢀ intoꢀ theꢀ NaTNT.ꢀ Fig.ꢀ 4(b)ꢀ showsꢀ TEMꢀ imagesꢀ ofꢀ
VNa/TiO .ꢀ Theꢀ VNaTNT sampleꢀ wasꢀ foundꢀ toꢀ includeꢀ nano‐
2
ꢀ
tubularꢀstructures,ꢀeitherꢀasꢀrandomꢀgroupsꢀorꢀalignedꢀbunch‐
es.ꢀElementalꢀmappingꢀhasꢀbeenꢀperformedꢀforꢀV,ꢀNa,ꢀTi,ꢀandꢀO,ꢀ
togetherꢀ withꢀ SEMꢀ imaging,ꢀ EDXꢀ mappingꢀ (Fig.ꢀ 4(c–g)),ꢀ andꢀ
EDXꢀlinearꢀscanningꢀofꢀVNaTNTꢀ(Fig.ꢀ5),ꢀtoꢀcheckꢀtheꢀuniformityꢀ
ofꢀtheꢀelementalꢀcompositionꢀandꢀdistributionꢀthroughoutꢀtheꢀ
VNaTNTꢀ samples.ꢀ ꢀ Theꢀ componentsꢀ areꢀ heterogeneouslyꢀ dis‐
tributedꢀthroughoutꢀtheꢀTNT,ꢀasꢀshownꢀbyꢀEDXꢀmapsꢀandꢀlinearꢀ
scans.ꢀ
Aꢀ DRUV‐Visꢀ spectrumꢀ ofꢀ theꢀ VNaTNTꢀ sampleꢀ isꢀ shownꢀ inꢀ
Fig.ꢀ7(b).ꢀTheꢀspectrumꢀshowsꢀoneꢀintenseꢀabsorptionꢀbandꢀatꢀ
247ꢀnm.ꢀThisꢀbandꢀisꢀattributedꢀtoꢀchargeꢀtransferꢀtransitionsꢀ
associatedꢀ withꢀ O ꢀ toꢀ V5+ꢀ [35].ꢀ Indeed,ꢀ thisꢀ bandꢀ closelyꢀ re‐
2−
Fig.ꢀ 6ꢀ showsꢀ theꢀ N
Barret‐Joyner‐Halendaꢀ (BJH)ꢀ poreꢀ sizeꢀ distributionsꢀ ofꢀ
VNaTNT.ꢀ Aꢀ typicalꢀ type‐IVꢀ adsorptionꢀ isothermꢀ withꢀ aꢀ re‐
markableꢀhysteresisꢀloopꢀis
theꢀ presenceꢀ ofꢀ meso‐ꢀ andꢀ macropores.ꢀ Theꢀ shapeꢀ ofꢀ theꢀ N2ꢀ
2
ꢀ adsorption‐desorptionꢀ isothermsꢀ andꢀ
semblesꢀthatꢀfoundꢀforꢀNH VO3ꢀ[36],ꢀindicatingꢀanꢀisolatedꢀtet‐
4
5+
rahedralꢀenvironmentꢀofꢀV ꢀinꢀtheꢀVNaTNTꢀmatrix,ꢀwhichꢀisꢀinꢀ
goodꢀagreementꢀwithꢀtheꢀliteratureꢀ[37].ꢀOnꢀtheꢀotherꢀhand,ꢀtheꢀ
bandꢀatꢀ247ꢀnmꢀmayꢀalsoꢀbeꢀassignedꢀtoꢀaꢀdistortedꢀtetrahedralꢀ
ꢀ
shownꢀbyꢀVNaTNT.ꢀThisꢀconfirmsꢀ
5+
arrangementꢀofꢀV ꢀ(asꢀaꢀresultꢀofꢀimmobilizing/anchoringꢀonꢀ
(
a)
90
80
70
60
50
40
30
20
10
0
(b)
O
Ti
Na
V
2
0
1
3
m
(
c)
80
Ti
(d)
60
40
20
0
O
Na
V
4
0
1
2

3
m
Fig.ꢀ5.ꢀSEMꢀimageꢀandꢀEDXꢀlinearꢀscanꢀalongꢀVNaTNTꢀ(a,ꢀb)ꢀfreshꢀcatalyst,ꢀandꢀ(c,ꢀd)ꢀreusedꢀcatalystꢀafterꢀtheꢀsixthꢀrun.ꢀ

498ꢀ
MohammadꢀAliꢀDadvarꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501ꢀ
40
30
20
10
0
(
a)
(
b)
0
.002
.001
Adsorption
Desorption
0
Adsorption
Desorption
0.000
0.0
0.2
0.4
0.6
0.8
1.0
0
10
20
/nm
30
40
p/p
0
r
p
2
Fig.ꢀ6.ꢀ(a)ꢀN ꢀadsorption‐desorptionꢀisothermsꢀandꢀ(b)ꢀporeꢀsizeꢀdistributionsꢀcalculatedꢀbyꢀtheꢀBJHꢀmethodꢀofꢀV(13)NaTNT.ꢀ
1
0.0
1.8
3
85
(b)
(
a)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
247
9
9
9
9
9
9
9
.9
.8
.7
.6
.5
.4
.3
2
.21%
2
.77%
Residue 95.02%
0.0
200
0
100 200 300 400 500 600 700 800
300
400
500
600
700
800
900
o
Temperature ( C)
Wavelength (nm)
Fig.ꢀ7.ꢀ(a)ꢀTGꢀcurveꢀandꢀ(b)ꢀDRUV‐VisꢀspectrumꢀofꢀV(13)NaTNT.ꢀ
theꢀporeꢀwindowsꢀofꢀtheꢀTNT),ꢀinꢀaꢀsimilarꢀmannerꢀtoꢀthatꢀre‐
portedꢀ forꢀ variousꢀ vanadium‐loaded/graftedꢀ amor‐
phous/mesoporousꢀsilicaꢀmaterialsꢀ[37,38].ꢀ ꢀ Theꢀfundamentalꢀ
3.2.ꢀ ꢀ Catalyticꢀactivityꢀ
absorptionꢀedgeꢀofꢀTiO
nmꢀ[39].ꢀ
2
ꢀappearedꢀinꢀtheꢀUVꢀregionꢀatꢀaboutꢀ385ꢀ
3.2.1.ꢀ ꢀ Oxidationꢀofꢀsulfidesꢀtoꢀsulfoxidesꢀandꢀsulfones
Oxidation wasꢀcarriedꢀoutꢀinꢀmethanol,ꢀn‐hexane,ꢀdichloro‐
methane,ꢀ acetonitrile,ꢀ ethanol,ꢀ acetone,ꢀ andꢀ H Oꢀ toꢀ checkꢀ theꢀ
2
feasibilityꢀofꢀtheꢀVNaTNTꢀsystemꢀinꢀanꢀorganicꢀmediumꢀ(Fig.ꢀ8).ꢀ
Solventsꢀwithꢀhighꢀhydrogenꢀbondingꢀcapacity,ꢀsuchꢀasꢀmetha‐
nolꢀ andꢀ water,ꢀ favorꢀ theꢀ formationꢀ ofꢀ sulfideꢀ withꢀ highꢀ
chemoselectivityꢀ [40],ꢀ asꢀ clearlyꢀ indicatedꢀ inꢀ Tableꢀ 2ꢀ andꢀ inꢀ
Tableꢀ2ꢀ
Oxidationꢀ ofꢀ sulfidesꢀ toꢀ sulfoxidesꢀ andꢀ sulfonesꢀ usingꢀ theꢀ
V(13)NaTNT/H
2
O ꢀsystem.ꢀ
2
a
Yieldꢀ ꢀ(%)–Timeꢀ(h)ꢀ
Sulfideꢀ
ꢀb
Sulfoneꢀ3ꢀcꢀ
Sulfoxideꢀ2 ꢀ
98–0.5ꢀ
98–0.5ꢀ
98–1.0ꢀ
98–1.0ꢀ
98–1.2ꢀ
96–1.2ꢀ
92–1.8ꢀ
1aꢀ
1bꢀ
1cꢀ
1dꢀ
1eꢀ
1fꢀ
96–1.5ꢀ
97–1.5ꢀ
98–2.0ꢀ
98–1.5ꢀ
92–2.0ꢀ
92–2.0ꢀ
86–3.0ꢀ
1
gꢀ
aꢀ
Isolatedꢀyields.ꢀ
bꢀReactionꢀconditions:ꢀSulfideꢀ(2ꢀmmol),ꢀH
2 2
O ꢀ(8ꢀmmol),ꢀV(13)NaTNTꢀ(3ꢀ
mol%),ꢀH
2
Oꢀ(5ꢀmL),ꢀr.t..ꢀ
cꢀ
Fig.ꢀ8.ꢀSolventꢀeffectꢀonꢀtheꢀconversionꢀrateꢀandꢀselectivityꢀofꢀdiphenyl
sulfideꢀoxidationꢀusingꢀH ꢀcatalyzedꢀbyꢀV(13)NaTNT.ꢀ
Reactionꢀconditions:ꢀSulfideꢀ(2ꢀmmol),ꢀH
CNꢀ(5ꢀmL),ꢀr.t..ꢀ
2
O2ꢀ(15ꢀmmol),ꢀV(13)NaTNTꢀ
O
2 2
(5ꢀmol%),ꢀCH
3

ꢀ
MohammadꢀAliꢀDadvarꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501ꢀ
499ꢀ
PhSOMe (>96 %)
+
PhCOOH (0 %)
H O
2
2
H O
2
PhSMe
+
PhCHO
VNaTNT/ H O2
2
H O, r.t., 1.5 h
2
Schemeꢀ 2.ꢀ Formationꢀ ofꢀ methylphenylꢀ sulfoxideꢀ fromꢀ theꢀ catalyzed
oxidationꢀofꢀmethylphenylꢀsulfideꢀandꢀbenzaldehyde.ꢀ
-
O
- NH4+
NH4+
O
O
O
V
V
agreementꢀwithꢀourꢀstudies.ꢀ
Aꢀsetꢀofꢀpreliminaryꢀexperimentsꢀonꢀdiphenylꢀsulfideꢀwereꢀ
nextꢀperformedꢀtoꢀexamineꢀtheꢀeffectsꢀofꢀdifferentꢀamountsꢀofꢀ
O
O
O
NaTNT
NaTNT
VNaTNTꢀinꢀH Oꢀatꢀ25ꢀ°Cꢀ(Tableꢀ1).ꢀNoꢀsignificantꢀoxidationꢀwasꢀ
2
observedꢀinꢀtheꢀabsenceꢀofꢀVNaTNTꢀinꢀaꢀblankꢀexperimentꢀ(Ta‐
bleꢀ1,ꢀentryꢀ1)ꢀandꢀonlyꢀaꢀlowꢀyieldꢀofꢀsulfoxideꢀwasꢀobtainedꢀinꢀ
S
theꢀ presenceꢀ ofꢀ H
fide:H :VNaTNTꢀwasꢀfoundꢀtoꢀbeꢀ2:8:3ꢀforꢀcompleteꢀconver‐
sionꢀofꢀsulfidesꢀtoꢀsulfoxides.ꢀTheꢀresultsꢀareꢀpresentedꢀinꢀTableꢀ
.ꢀ
2
O2ꢀ afterꢀ 6ꢀ h.ꢀ Theꢀ optimalꢀ ratioꢀ ofꢀ sul‐
(or)
R
R
O
S
S
R
R
O
2 2
solvent: H O
2
R
R
solvent: CH CN
O
S
3
O
2
R
R
Toꢀ examineꢀ theꢀ scopeꢀ andꢀ limitationsꢀ ofꢀ thisꢀ procedure,ꢀ
severalꢀfunctionalizedꢀsulfidesꢀwereꢀselectedꢀ(Tableꢀ2).ꢀDialkylꢀ
1a),ꢀarylꢀalkylꢀ(1b),ꢀandꢀdiarylꢀ(1c)ꢀsulfidesꢀcouldꢀbeꢀoxidizedꢀ
Schemeꢀ3.ꢀSimplifiedꢀcatalyticꢀmechanismꢀforꢀtheꢀoxidationꢀofꢀsulfidesꢀ
inꢀtheꢀpresenceꢀofꢀH /VNaTNTꢀsystem.ꢀ
O
2 2
(
toꢀ theꢀ correspondingꢀ sulfoxidesꢀ inꢀ excellentꢀ yields.ꢀ Sulfidesꢀ
withꢀelectron‐withdrawingꢀ(1d,ꢀ1e)ꢀorꢀdonatingꢀ(1f)ꢀsubstitu‐
entsꢀgaveꢀtheꢀcorrespondingꢀsolfoxidesꢀinꢀexcellentꢀyieldsꢀwithꢀ
highꢀpurity.ꢀImportantly,ꢀthisꢀmethodꢀisꢀcompatibleꢀwithꢀfunc‐
tionalꢀgroups,ꢀsuchꢀasꢀestersꢀ(1g).ꢀOxidationsꢀcouldꢀtypicallyꢀbeꢀ
haltedꢀatꢀtheꢀsulfoxideꢀstageꢀwithoutꢀover‐oxidationꢀtoꢀtheꢀsul‐
fone.ꢀ ꢀ
step,ꢀtheꢀformationꢀinꢀtheꢀactiveꢀsiteꢀofꢀaꢀperoxovanadiumꢀspe‐
ciesꢀ(IV)ꢀ[5],ꢀwhichꢀisꢀaꢀmuchꢀstrongerꢀoxidantꢀthanꢀH ꢀ[3,5].ꢀ
Theꢀrecoveryꢀandꢀreusabilityꢀofꢀtheꢀcatalystꢀhaveꢀbeenꢀstud‐
ied.ꢀItꢀwasꢀobservedꢀthatꢀtheꢀcatalystꢀcanꢀbeꢀeasilyꢀrecoveredꢀ
O
2 2
quantitativelyꢀbyꢀsimpleꢀfiltrationꢀafterꢀtheꢀadditionꢀofꢀCHCl ꢀtoꢀ
3
theꢀreactionꢀmixture.ꢀTheꢀwetꢀcatalystꢀwasꢀrecycledꢀandꢀchar‐
acterizedꢀbyꢀneutronꢀactivationꢀanalysisꢀ(NAA),ꢀXRD,ꢀandꢀFT‐IRꢀ
spectroscopy.ꢀTheꢀreusabilityꢀtestꢀwasꢀcarriedꢀoutꢀunderꢀopti‐
mizedꢀreactionꢀconditions.ꢀWhenꢀtheꢀsolidꢀcatalystꢀwasꢀusedꢀforꢀ
1,ꢀ 2,ꢀ 3,ꢀ 4,ꢀ andꢀ 5ꢀ cycles,ꢀ theꢀ conversionꢀ wasꢀ 98%,ꢀ 98%,ꢀ 96%,ꢀ
94%,ꢀandꢀ90%,ꢀrespectively.ꢀTherefore,ꢀitꢀisꢀpossibleꢀtoꢀreuseꢀ
theꢀcatalystꢀwithoutꢀsignificantꢀlossꢀinꢀitsꢀactivity.ꢀFurthermore,ꢀ
noꢀremarkableꢀdifferencesꢀinꢀtheꢀmorphologyꢀofꢀtheꢀfreshꢀcata‐
lystꢀandꢀtheꢀspentꢀoneꢀcouldꢀbeꢀobserved.ꢀThisꢀmayꢀbeꢀfurtherꢀ
evidenceꢀforꢀtheꢀstabilityꢀofꢀtheꢀcatalyst.ꢀWhenꢀtheꢀreactionꢀwasꢀ
carriedꢀoutꢀinꢀMeOH,ꢀafterꢀsixꢀrunsꢀtheꢀvanadiumꢀwasꢀleachedꢀ
fromꢀtheꢀsupport,ꢀasꢀprovenꢀbyꢀSEMꢀandꢀEDXꢀlinearꢀscanningꢀ
alongꢀtheꢀVNaTNTꢀ(Fig.ꢀ4(c)ꢀandꢀ4(d)),ꢀandꢀbyꢀNAAꢀandꢀinduc‐
tivelyꢀcoupledꢀplasmaꢀopticalꢀemissionꢀspectrometryꢀ(ICP‐OES)ꢀ
resultsꢀ(Vꢀremovedꢀisꢀ0.87ꢀwtꢀ%,ꢀwithꢀdeviationꢀinꢀtheꢀrangeꢀofꢀ
0.12).ꢀThisꢀledꢀtoꢀdeactivationꢀofꢀtheꢀheterogeneousꢀcatalyst.ꢀ
Toꢀshowꢀtheꢀmeritꢀofꢀtheꢀpresentꢀworkꢀinꢀcomparisonꢀwithꢀ
recentlyꢀreportedꢀprotocolsꢀ[44],ꢀweꢀcomparedꢀtheꢀresultsꢀwithꢀ
respectꢀ toꢀ theꢀ amountsꢀ ofꢀ catalystꢀ used,ꢀ reactionꢀ time,ꢀ andꢀ
yieldsꢀofꢀtheꢀproductsꢀ(Tableꢀ3).ꢀComparisonꢀofꢀVNaTNTꢀwithꢀ
theseꢀcatalysts,ꢀforꢀselectiveꢀoxidationꢀofꢀsulfidesꢀtoꢀsulfoxides,ꢀ
showsꢀthatꢀtheꢀactivityꢀofꢀVNaTNTꢀseemsꢀtoꢀbeꢀhigherꢀthanꢀorꢀ
equalꢀtoꢀotherꢀknownꢀcatalystsꢀ(Tableꢀ3).ꢀ
Itꢀ isꢀ evidentꢀ thatꢀ theꢀ H
2
O /VNaTNTꢀ systemꢀ allowsꢀ theseꢀ
2
transformationsꢀ toꢀ proceedꢀ withꢀ excellentꢀ selectivity,ꢀ highꢀ
yield,ꢀ andꢀ underꢀ mildꢀ conditions.ꢀ Furthermore,ꢀ theꢀ useꢀ ofꢀ
H
2
O
2
/VNaTNTꢀ makesꢀ thisꢀ methodꢀ simple,ꢀ inexpensive,ꢀ con‐
venient,ꢀ andꢀ practical.ꢀ Additionally,ꢀ aꢀ competitiveꢀ
/VNaTNTꢀ catalyzedꢀ oxidationꢀ reactionꢀ ofꢀ equimolarꢀ
H
2 2
O
amountsꢀ ofꢀ methylphenylꢀ sulfideꢀ andꢀ benzaldehydeꢀ atꢀ roomꢀ
temperatureꢀleadsꢀtoꢀtheꢀselectiveꢀformationꢀofꢀmethylphenylꢀ
sulfoxideꢀ inꢀ highꢀ yield,ꢀ whereasꢀ benzaldehydeꢀ remainsꢀ un‐
changedꢀ(Schemeꢀ2).ꢀ
Theꢀchemoselectiveꢀoxidationꢀofꢀsulfidesꢀtoꢀsulfonesꢀwasꢀal‐
soꢀ investigatedꢀ toꢀ furtherꢀ demonstrateꢀ theꢀ efficiencyꢀ andꢀ ap‐
plicabilityꢀofꢀtheꢀH
forꢀtheꢀreaction,ꢀspecifiedꢀinꢀTableꢀ3,ꢀwereꢀfoundꢀusingꢀCH
solventꢀ atꢀ ambientꢀ temperatureꢀ (sulfide:H :VNaTNTꢀ =ꢀ
:15:5).ꢀApplicationꢀofꢀaꢀsmallerꢀamountꢀofꢀoxidizingꢀagentꢀgaveꢀ
2 2
O /VNaTNTꢀsystem.ꢀTheꢀoptimalꢀconditionsꢀ
3
CNꢀ
O
2 2
2
aꢀ mixtureꢀ ofꢀ sulfoxideꢀ andꢀ sulfone.ꢀ Itꢀ wasꢀ foundꢀ thatꢀ aꢀ wideꢀ
varietyꢀofꢀdiaryl,ꢀdialkyl,ꢀandꢀarylalkylꢀsulfidesꢀhaveꢀbeenꢀoxi‐
dizedꢀ toꢀ theirꢀ correspondingꢀ sulfonesꢀ inꢀ excellentꢀ yieldsꢀ inꢀ
CH CNꢀatꢀroomꢀtemperature,ꢀasꢀshownꢀinꢀTableꢀ2.ꢀBasedꢀonꢀaꢀ
3
varietyꢀofꢀstudies,ꢀaꢀmechanism,ꢀdepictedꢀinꢀSchemeꢀ3,ꢀhasꢀbeenꢀ
proposedꢀ [3].ꢀ Theꢀ catalyticꢀ cycleꢀ involves,ꢀ asꢀ aꢀ fundamentalꢀ
Tableꢀ3ꢀ
ComparisonꢀofꢀVNaTNTꢀwithꢀotherꢀcatalystsꢀforꢀtheꢀoxidationꢀofꢀPhSMe.ꢀ
a
Entryꢀ ꢀ
Reagentꢀ
Oxidovanadium(V)ꢀcomplexes/H
Oxido‐bridgedꢀdinuclearꢀvanadium(V)ꢀSchiffꢀbaseꢀcomplexes/H
vanadium(V)ꢀcomplexesꢀwithꢀtridentateꢀSchiffꢀbaseꢀligands/H
V@Cr‐MIL(101)ꢀ
Conditionꢀ
Timeꢀ(min)ꢀ Yieldꢀ ꢀ(%)
Ref.ꢀ
[41]ꢀ
[42]ꢀ
[43]ꢀ
[44]ꢀ
1
2
3
4
5
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2
O
2
ꢀ
CH
2
CH
2
CH
2
Cl
2
Cl
2
Cl
2
/MeOH,ꢀr.t.ꢀ
/MeOH,ꢀr.t.ꢀ
/MeOH,ꢀr.t.ꢀ
30ꢀ
30ꢀ
30ꢀ
60ꢀ
30ꢀ
88ꢀ
88ꢀ
84ꢀ
98ꢀ
98ꢀ
2
O
2
ꢀ
2
O
2
ꢀ
EtOH,ꢀr.t.ꢀ
O,ꢀr.t.ꢀ
VNaTNT/H
2
O
2
ꢀ
H
2
thisꢀwork
aꢀYieldꢀrefersꢀtoꢀtheꢀcorrespondingꢀsulfoxide.ꢀ

500ꢀ
MohammadꢀAliꢀDadvarꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ494–501ꢀ
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2016,ꢀ37:ꢀ494–501ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(15)61056‐7
Applicationꢀofꢀsodiumꢀtitanateꢀnanotubesꢀdopedꢀwithꢀvanadiumꢀ(VNaTNT)ꢀasꢀaꢀheterogeneousꢀcatalystꢀforꢀoxidationꢀofꢀsulfidesꢀ
atꢀroomꢀtemperatureꢀ
ꢀ
MohammadꢀAliꢀDadvar,ꢀRaziehꢀFazaeli*ꢀ
IslamicꢀAzadꢀUniversity,ꢀIranꢀ
O
O
S
VNaTNT (5 mol %), CH CN
VNaTNT (3 mol %), H O
3
2
S
S
H O (15 mol%), r.t.
H O (8 mol%), r.t.
2
2
2
2
O
3
1
2
ꢀ
Sodiumꢀtitanateꢀnanotubeꢀdopedꢀwithꢀvanadiumꢀ(VNaTNT)ꢀhasꢀbeenꢀsynthesized,ꢀandꢀitꢀshowedꢀexcellentꢀcatalyticꢀperformanceꢀforꢀtheꢀ
2 2
chemoselectiveꢀoxidationꢀofꢀsulfidesꢀinꢀtheꢀpresenceꢀofꢀ30%ꢀH O ꢀinꢀwater.ꢀFT‐IR,ꢀXRD,ꢀSEM‐EDX,ꢀTEM,ꢀTG,ꢀBETꢀandꢀDRUVꢀwereꢀusedꢀforꢀ
characterizationꢀofꢀtheꢀVNaTNT.ꢀ
rus,ꢀ Sulfurꢀ andꢀ Siliconꢀ andꢀ theꢀ Relatedꢀ Elements,ꢀ 2014,ꢀ 189,ꢀ
1
423–1432.ꢀ ꢀ
5] V.ꢀConte,ꢀA.ꢀColetti,ꢀB.ꢀFloris,ꢀG.ꢀLicini,ꢀC.ꢀZonta,ꢀCoord.ꢀChem.ꢀRev.,ꢀ
011,ꢀ255,ꢀ2165–2177.ꢀ
6] R.ꢀFazaeli,ꢀH.ꢀAliyan,ꢀM.ꢀMasoudinia,ꢀZ.ꢀHeidari,ꢀJ.ꢀMater.ꢀChem.ꢀEng.,ꢀ
4.ꢀ ꢀ Conclusionsꢀ
[
[
[
[
2
Sodiumꢀtitanateꢀnanotubesꢀdopedꢀwithꢀvanadiumꢀ(VNaTNT)ꢀ
wereꢀ synthesizedꢀ byꢀ theꢀ hydrothermalꢀ treatmentꢀ ofꢀ aꢀ titaniaꢀ
nanotubeꢀprecursorꢀusingꢀaꢀalkaliꢀsolutionꢀ(10ꢀmol/L)ꢀcontain‐
2
014,ꢀ2,ꢀ46–55.ꢀ
ꢀ
7] R.ꢀFazaeli, H.ꢀAliyan,ꢀM.A.ꢀAhmadi,ꢀS.ꢀHashemian,ꢀCatal.ꢀCommun.,ꢀ
ingꢀbothꢀNaOHꢀandꢀalcoholicꢀNH
4
VO .ꢀVanadiumꢀwasꢀfoundꢀtoꢀ
3
2012,ꢀ29,ꢀ48–52.ꢀ
playꢀ anꢀ importantꢀ roleꢀ inꢀ theꢀ oxidationꢀ reactions;ꢀ therefore,ꢀ
vanadiumꢀwasꢀaddedꢀtoꢀtheꢀsodiumꢀtitanateꢀnanotubesꢀtoꢀim‐
proveꢀ theꢀ catalyticꢀ performance.ꢀ VNaTNTꢀ isꢀ anꢀ excellentꢀ het‐
erogeneousꢀ systemꢀ forꢀ promotingꢀ theꢀ highlyꢀ chemoselectiveꢀ
8] J.ꢀFujisaki,ꢀK.ꢀMatsumoto,ꢀK.ꢀMatsumoto,ꢀT.ꢀKatsuki,ꢀJ.ꢀAm.ꢀChem.ꢀ
Soc.,ꢀ2011,ꢀ133,ꢀ56–61.ꢀ ꢀ
[9] A.ꢀM.ꢀKhenkin,ꢀG.ꢀLeitus,ꢀR.ꢀNeumann,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.,ꢀ2010,ꢀ132,ꢀ
11446–11448.ꢀ
andꢀ rapidꢀ oxidationꢀ ofꢀ functionalizedꢀ sulfidesꢀ withꢀ H
2 2
O ꢀ atꢀ
[10] J.ꢀS.ꢀGao,ꢀH.ꢀC.ꢀGuo,ꢀS.ꢀZ.ꢀLiu,ꢀM.ꢀWang,ꢀTetrahedronꢀLett.,ꢀ2007,ꢀ48,ꢀ
8453–8455.ꢀ
roomꢀ temperatureꢀ inꢀ H O.ꢀ Itꢀ isꢀ noteworthyꢀ thatꢀ theꢀ reactionꢀ
2
[
[
[
11] R.ꢀDas,ꢀD.ꢀChakraborty,ꢀTetrahedronꢀLett.,ꢀ2010,ꢀ51,ꢀ6255–6258.ꢀ
12] R.ꢀDas,ꢀD.ꢀChakraborty,ꢀSynthesis,ꢀ2011,ꢀ277–280.ꢀ
13] D.ꢀ Chakraborty,ꢀ P.ꢀ Malik,ꢀ V.ꢀ K.ꢀ Goda,ꢀ Appl.ꢀ Organomet.ꢀ Chem.,ꢀ
toleratesꢀoxidativelyꢀsensitiveꢀfunctionalꢀgroupsꢀandꢀtheꢀsulfurꢀ
atomꢀisꢀselectivelyꢀoxidized.ꢀ
2
012,ꢀ26,ꢀ21–26.ꢀ
Acknowledgmentsꢀ
[
14] P.ꢀMalik,ꢀD.ꢀChakraborty,ꢀTetrahedronꢀLett.,ꢀ2012,ꢀ53,ꢀ5652–5655.ꢀ
15] R.ꢀFazaeli,ꢀH.ꢀAliyan,ꢀS.ꢀP.ꢀForoushani,ꢀZ.ꢀMohagheghian,ꢀZ.ꢀHeidari,ꢀ
IranꢀJ.ꢀCatal.,ꢀ2013,ꢀ3,ꢀ129–137.ꢀ ꢀ
[
WeꢀgratefullyꢀthankꢀShahrezaꢀBranch,ꢀIslamicꢀAzadꢀUniver‐
sityꢀforꢀfinancialꢀsupport.ꢀ
[
16] P.ꢀ Roy,ꢀ S.ꢀ Berger,ꢀ P.ꢀ Schmuki,ꢀ Angew.ꢀ Chem.ꢀ Int.ꢀ Ed.,ꢀ 2011,ꢀ 50,ꢀ
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