Thermoregulated poly(ethylene glycol) biphasic system with Pd nanoparticle catalysts for selective hydrogenation of cinnamaldehyde

Article abstract of DOI:10.1016/S1872-2067(12)60552-X

Poly(ethylene glycol) (PEG)-stabilized Pd nanoparticles were prepared by simple hydrogen reduction of PdNa₂Cl₄·xH ₂O in the presence of PEG₄₀₀₀ (PEG with an average molecular mass of 4000 g/mol). These were show

Full text of DOI:10.1016/S1872-2067(12)60552-X

ChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ674–678
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
ava i l a b l e a t w w w. s c i e n c ed 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
ꢀ
ꢀ
Communication
Thermoregulatedꢀpoly(ethyleneꢀglycol)ꢀbiphasicꢀsystemꢀwithꢀPdꢀ
nanoparticleꢀcatalystsꢀforꢀselectiveꢀhydrogenationꢀofꢀ ꢀ
cinnamaldehydeꢀ
NIUꢀMingming,ꢀWANGꢀYanhua
ꢀ
*,ꢀLIꢀWenjiang,ꢀJIANGꢀJingyang,ꢀJINꢀZilin
ꢀ
StateꢀKeyꢀLaboratoryꢀofꢀFineꢀChemicals,ꢀDalianꢀUniversityꢀofꢀTechnology,ꢀDalianꢀ116024,ꢀLiaoning,ꢀChinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Poly(ethyleneꢀglycol)ꢀ(PEG)‐stabilizedꢀPdꢀnanoparticlesꢀwereꢀpreparedꢀbyꢀsimpleꢀhydrogenꢀreduc‐
tionꢀ ofꢀ PdNa Cl ·xH Oꢀ inꢀ theꢀpresenceꢀofꢀ PEG4000ꢀ (PEGꢀ withꢀ anꢀ averageꢀ molecularꢀ massꢀ ofꢀ 4000ꢀ
Receivedꢀ31ꢀJanuaryꢀ2013ꢀ
Acceptedꢀ19ꢀFebruaryꢀ2013ꢀ
Publishedꢀ20ꢀAprilꢀ2013ꢀ
2
4
2
g/mol).ꢀTheseꢀwereꢀshownꢀtoꢀbeꢀefficientꢀandꢀrecyclableꢀcatalystsꢀforꢀtheꢀselectiveꢀhydrogenationꢀofꢀ
cinnamaldehydeꢀinꢀaꢀthermoregulatedꢀPEGꢀbiphasicꢀsystem,ꢀwhichꢀallowsꢀforꢀanꢀefficientꢀhomoge‐
neousꢀ catalyticꢀ reaction,ꢀ easyꢀ biphasicꢀ separationꢀ andꢀ catalystꢀ reuse.ꢀ Underꢀ optimizedꢀ reactionꢀ
conditions,ꢀtheꢀconversionꢀofꢀcinnamaldehydeꢀandꢀtheꢀselectivityꢀofꢀhydrocinnamaldehydeꢀ(HCAL)ꢀ
wereꢀ99%ꢀandꢀ98%,ꢀrespectively.ꢀTheꢀPEG4000‐stabilizedꢀPdꢀnanoparticleꢀcatalystꢀcouldꢀbeꢀeasilyꢀ
separatedꢀfromꢀtheꢀproductꢀbyꢀphaseꢀseparationꢀandꢀreusedꢀeightꢀtimesꢀwithoutꢀevidentꢀlossꢀof
activityꢀandꢀselectivity.ꢀ
Keywords:ꢀ
Thermoregulatedꢀpoly(ethyleneꢀglycol)
biphasicꢀsystemꢀ ꢀ
Selectiveꢀhydrogenationꢀ
Palladiumꢀ
©ꢀ2013,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
Nanoparticleꢀ ꢀ
Cinnamaldehyde
Overꢀtheꢀ pastꢀdecades,ꢀ solubleꢀ transition‐metalꢀnanoparti‐
clesꢀ inꢀ catalystsꢀ haveꢀ attractedꢀ growingꢀ interestꢀ becauseꢀ ofꢀ
theirꢀhighlyꢀcatalyticꢀefficiencyꢀandꢀuniqueꢀproperties.ꢀHowev‐
er,ꢀasꢀwithꢀtraditionalꢀhomogeneousꢀcatalysts,ꢀoneꢀofꢀtheꢀmainꢀ
disadvantagesꢀofꢀsolubleꢀnanoparticleꢀcatalystsꢀisꢀtheꢀdifficultyꢀ
ofꢀrecoveringꢀtheꢀcatalystsꢀfromꢀtheꢀproducts.ꢀToꢀovercomeꢀthisꢀ
problem,ꢀ severalꢀ strategiesꢀ haveꢀ beenꢀ disclosed.ꢀ Theꢀ liq‐
uid/liquidꢀbiphasicꢀsystem,ꢀi.e.,ꢀaqueous/organicꢀbiphasicꢀsys‐
temꢀ [1−3],ꢀ ꢁluorous/organicꢀ biphasicꢀ systemꢀ [4−6],ꢀ andꢀ ionicꢀ
liquidꢀbiphasicꢀsystemꢀ[7−10]ꢀwereꢀmostꢀfrequentlyꢀused.ꢀ
Recently,ꢀ aꢀ thermoregulatedꢀ biphasicꢀ systemꢀ composedꢀ ofꢀ
PEGꢀandꢀorganicꢀsolventsꢀhasꢀbeenꢀdeveloped.ꢀThisꢀallowsꢀforꢀaꢀ
highlyꢀefficientꢀhomogeneousꢀcatalyticꢀreaction,ꢀeasyꢀbiphasicꢀ
separationꢀandꢀcatalystꢀreuseꢀbecauseꢀofꢀtheꢀthermoregulatedꢀ
phase‐transitionꢀpropertyꢀofꢀtheꢀsystem.ꢀThisꢀsystemꢀhasꢀbeenꢀ
employedꢀ forꢀ theꢀ hydroformylationꢀ ofꢀ olefinsꢀ andꢀ selectiveꢀ
hydrogenationꢀ ofꢀ 1,5‐cyclooctadieneꢀ byꢀ applyingꢀ theꢀ
PEG‐stabilizedꢀRhꢀorꢀPdꢀnanoparticlesꢀtoꢀtheꢀcatalystsꢀ[11,12].ꢀ
Theꢀselectiveꢀhydrogenationꢀofꢀcinnamaldehydeꢀisꢀusefulꢀasꢀtheꢀ
possibleꢀproductsꢀofꢀhydrocinnamaldehydeꢀ(HCAL)ꢀorꢀcinnam‐
ylꢀ alcoholꢀ (COL)ꢀ areꢀ usedꢀ inꢀ theꢀ synthesisꢀ ofꢀ fineꢀ chemicals,ꢀ
pharmaceuticalsꢀandꢀfragrances.ꢀHowever,ꢀmostꢀstudiesꢀonꢀthisꢀ
transformationꢀhaveꢀconcentratedꢀonꢀtransition‐metalꢀhetero‐
geneousꢀcatalystsꢀorꢀhomogeneousꢀcomplexꢀcatalystsꢀ[13−18].ꢀ
Asꢀaꢀcontinuationꢀofꢀpreviousꢀworksꢀandꢀtoꢀbestꢀuseꢀtheꢀther‐
moregulatedꢀ PEGꢀ biphasicꢀ systemꢀ containingꢀ solubleꢀ transi‐
tion‐metalꢀ nanoparticles,ꢀ thisꢀ studyꢀ focusedꢀ onꢀ
PEG4000‐stabilizedꢀ Pdꢀ nanoparticleꢀ catalyzedꢀ selectiveꢀ hydro‐
genationꢀofꢀcinnamaldehydeꢀinꢀaꢀthermoregulatedꢀPEGꢀbiphasicꢀ
system.ꢀ
*ꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+86‐411‐84986033;ꢀFax:ꢀ+86‐411‐84986033;ꢀE‐mail:ꢀyhuawang@dlut.edu.cnꢀ ꢀ ꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀofꢀChinaꢀ(21173031)ꢀandꢀtheꢀFundamentalꢀResearchꢀFundsꢀforꢀtheꢀCentralꢀ
Universities.ꢀ ꢀ
DOI:ꢀ10.1016/S1872‐2067(12)60552‐Xꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,Vol.ꢀ34,ꢀNo.ꢀ4,ꢀAprilꢀ2013ꢀ ꢀ ꢀ

ꢀ
NIUꢀMingmingꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ674–678ꢀ
ꢀ
ꢀ
ꢀ
Schemeꢀ1.ꢀHydrogenationꢀofꢀcinnamaldehyde.ꢀ
Room temperature
Org.
Reaction temperature
Org.
Room temperature
Org.
Pd
PEG
Pd
PEG
PEG
ꢀ
Fig.ꢀ 1.ꢀ SchematicꢀillustrationꢀofꢀPEG4000‐stabilizedꢀPdꢀnanoparticleꢀcatalyzedꢀselectiveꢀhydrogenationꢀofꢀcinnamaldehydeꢀinꢀaꢀthermoregulatedꢀPEGꢀ
biphasicꢀsystem.ꢀ
Pdꢀ nanoparticlesꢀ stabilizedꢀ byꢀ PEG4000ꢀ wereꢀ prepared.ꢀ Aꢀ
mixtureꢀofꢀPdNa Cl ·xH Oꢀ(containingꢀ30%ꢀPd,ꢀ1.77ꢀmg,ꢀ0.005ꢀ
Theꢀ schematicꢀ illustrationꢀ ofꢀ selectiveꢀ hydrogenationꢀ ofꢀ
cinnamaldehydeꢀ inꢀ aꢀ thermoregulatedꢀ PEGꢀ biphasicꢀ systemꢀ
containingꢀPEG4000‐stabilizedꢀPdꢀnanoparticlesꢀisꢀshownꢀinꢀFig.ꢀ
1.ꢀAtꢀroomꢀtemperature,ꢀtheꢀlowerꢀPEGꢀphaseꢀcontainingꢀtheꢀPdꢀ
nanoparticlesꢀ wasꢀ immiscibleꢀ withꢀ theꢀ upperꢀ organicꢀ phaseꢀ
consistingꢀofꢀtolueneꢀandꢀn‐heptaneꢀwithꢀtheꢀcinnamaldehydeꢀ
substrateꢀ(leftꢀpanelꢀinꢀFig.ꢀ1).ꢀItꢀwasꢀnotedꢀthatꢀwhenꢀtheꢀtem‐
peratureꢀwasꢀelevatedꢀ graduallyꢀtoꢀtheꢀ reactionꢀtemperature,ꢀ
theꢀbiphasicꢀsystemꢀmergedꢀintoꢀaꢀsingleꢀphaseꢀandꢀtheꢀreac‐
tionꢀproceededꢀinꢀaꢀhomogeneousꢀphaseꢀ(centralꢀpanelꢀinꢀFig.ꢀ
1).ꢀFinally,ꢀbyꢀdecreasingꢀtheꢀtemperatureꢀtoꢀroomꢀtemperatureꢀ
afterꢀtheꢀreactionꢀwasꢀcompleted,ꢀtheꢀsystemꢀrecoveredꢀtoꢀbi‐
phasicꢀformꢀ(rightꢀpanelꢀinꢀFig.ꢀ1).ꢀTheꢀproductꢀandꢀtheꢀcatalystꢀ
wereꢀeasilyꢀcollectedꢀfromꢀtheꢀorganicꢀandꢀPEGꢀphase,ꢀrespec‐
tively.ꢀ Theꢀ recoveredꢀ catalystꢀ canꢀ beꢀ reusedꢀ withoutꢀ furtherꢀ
purificationꢀorꢀactivation.ꢀ
2
4
2
mmol)ꢀ andꢀ PEG4000ꢀ (2.0ꢀ g,ꢀ 0.5ꢀ mmol)ꢀ wasꢀ addedꢀ toꢀ aꢀ 75ꢀ mlꢀ
stainless‐steelꢀautoclave.ꢀTheꢀautoclaveꢀwasꢀflushedꢀthreeꢀtimesꢀ
withꢀ2.0ꢀMPaꢀhydrogenꢀandꢀstirredꢀunderꢀhydrogenꢀ(4.0ꢀMPa)ꢀ
atꢀ70ꢀ°Cꢀforꢀ2ꢀh.ꢀTheꢀreactorꢀwasꢀthenꢀcooledꢀtoꢀroomꢀtempera‐
tureꢀ andꢀ depressurized.ꢀ Theꢀ PEG4000‐stabilizedꢀ Pdꢀ nanoparti‐
clesꢀobtainedꢀwereꢀusedꢀforꢀtheꢀselectiveꢀhydrogenationꢀofꢀcin‐
namaldehyde.ꢀ
Selectiveꢀhydrogenationꢀreactionsꢀwereꢀperformedꢀinꢀaꢀ75ꢀ
mlꢀ stainless‐steelꢀ autoclave.ꢀ Theꢀ PEG4000‐stabilizedꢀ Pdꢀ nano‐
particlesꢀ(0.005ꢀmmol),ꢀcinnamaldehydeꢀ(5ꢀmmol),ꢀtolueneꢀ(3.0ꢀ
g),ꢀ n‐heptaneꢀ (1.0ꢀ g)ꢀandꢀ n‐decaneꢀ(0.2ꢀg)ꢀwereꢀaddedꢀtoꢀtheꢀ
autoclaveꢀ andꢀ purgedꢀ threeꢀ timesꢀ withꢀ hydrogenꢀ atꢀ 2.0ꢀ MPa.ꢀ
Theꢀautoclaveꢀwasꢀthenꢀpressurizedꢀwithꢀhydrogenꢀtoꢀtheꢀde‐
siredꢀpressureꢀandꢀheldꢀatꢀaꢀsetꢀtemperatureꢀwithꢀstirringꢀinꢀaꢀ
thermostaticꢀoilꢀbathꢀ forꢀtheꢀdesiredꢀlengthꢀofꢀtime.ꢀAfterꢀtheꢀ
reaction,ꢀ theꢀ autoclaveꢀ wasꢀ cooledꢀ toꢀ roomꢀ temperatureꢀ andꢀ
depressurized.ꢀ Theꢀ upperꢀ organicꢀ phaseꢀ wasꢀ separatedꢀ fromꢀ
theꢀlowerꢀPEGꢀphaseꢀbyꢀphaseꢀseparationꢀandꢀanalyzedꢀbyꢀGCꢀ
andꢀGC‐MS.ꢀ ꢀ
Theꢀ optimalꢀ reactionꢀ conditionsꢀ forꢀ PEG4000‐stabilizedꢀ Pdꢀ
nanoparticleꢀcatalyzedꢀselectiveꢀhydrogenationꢀofꢀcinnamalde‐
hydeꢀinꢀaꢀthermoregulatedꢀPEGꢀbiphasicꢀsystemꢀwereꢀfirstꢀde‐
termined.ꢀAsꢀshownꢀinꢀTableꢀ1,ꢀtheꢀconversionꢀofꢀcinnamalde‐
hydeꢀ increasesꢀ withꢀ increasingꢀ temperatureꢀ (entriesꢀ 1−4).ꢀ Atꢀ
120ꢀ°C,ꢀtheꢀconversionꢀofꢀcinnamaldehydeꢀandꢀtheꢀselectivityꢀofꢀ
GasꢀchromatographyꢀanalysesꢀwereꢀperformedꢀonꢀaꢀTianmeiꢀ
7
890ꢀ GCꢀ instrumentꢀ (Shanghaiꢀ Techcompꢀ Instrumentꢀ Ltd,ꢀ
Shanghai,ꢀChina)ꢀequippedꢀwithꢀaꢀ50ꢀmꢀOV‐101ꢀcolumnꢀ(innerꢀ
diameterꢀ0.25ꢀmm)ꢀandꢀanꢀFIDꢀdetectorꢀ(N
ꢀasꢀaꢀcarrierꢀgas).ꢀ
Tableꢀ1ꢀ ꢀ
PEG4000‐stabilizedꢀPdꢀnanoparticleꢀcatalyzedꢀselectiveꢀhydrogenationꢀofꢀ
cinnamaldehyde.
2
ꢀ
GC‐MSꢀ measurementsꢀ wereꢀ performedꢀ onꢀ anꢀ HPꢀ 6890ꢀ
GC/5973ꢀMSDꢀinstrumentꢀ(withꢀaꢀ30ꢀmꢀHP‐5MSꢀcolumn,ꢀinnerꢀ
diameterꢀ0.25ꢀmm;ꢀHeꢀasꢀaꢀcarrierꢀgas).ꢀTheꢀtransmissionꢀelec‐
tronꢀmicroscopyꢀ(TEM)ꢀimagesꢀwereꢀtakenꢀwithꢀaꢀTecnaiꢀG 20ꢀ
Spiritꢀ microscopeꢀ atꢀ anꢀ acceleratingꢀ voltageꢀ ofꢀ 120ꢀ kVꢀ (FEIꢀ
company).ꢀICP‐AESꢀanalysesꢀofꢀPdꢀwereꢀcarriedꢀoutꢀonꢀanꢀOp‐
timaꢀ2000ꢀDVꢀ(PerkinꢀElmer,ꢀUSA).ꢀ
Tempera‐ Pressure Timeꢀ Conver‐ HCALꢀselec‐ HCOLꢀselec‐
Entry
ꢀ
tureꢀ(°C)
80ꢀ
(MPa)ꢀ
4.0ꢀ
4.0ꢀ
4.0ꢀ
4.0ꢀ
1.0ꢀ
2.0ꢀ
3.0ꢀ
4.0ꢀ
4.0ꢀ
4.0ꢀ
(h)ꢀ sionꢀ(%)ꢀ tivityꢀ(%) tivityꢀ(%)
1ꢀ
2ꢀ
7ꢀ
7ꢀ
7ꢀ
7ꢀ
7ꢀ
7ꢀ
7ꢀ
4ꢀ
5ꢀ
6ꢀ
36ꢀ
70ꢀ
89ꢀ
99ꢀ
70ꢀ
82ꢀ
90ꢀ
36ꢀ
70ꢀ
92ꢀ
>99ꢀ
ꢀ 99ꢀ
ꢀ 98ꢀ
ꢀ 98ꢀ
ꢀ 97ꢀ
ꢀ 98ꢀ
ꢀ 97ꢀ
ꢀ 98ꢀ
ꢀ 97ꢀ
<1ꢀ
1ꢀ
2ꢀ
2ꢀ
3ꢀ
2ꢀ
3ꢀ
2ꢀ
3ꢀ
3ꢀ
2ꢀ
100ꢀ
110ꢀ
120ꢀ
120ꢀ
120ꢀ
120ꢀ
120ꢀ
120ꢀ
120ꢀ
3
ꢀ
4
ꢀ
5
ꢀ
6
ꢀ
Cinnamaldehydeꢀ hasꢀ twoꢀ reactiveꢀ sitesꢀ forꢀ hydrogenationꢀ
7ꢀ
8
ꢀ
(C=CꢀandꢀC=Oꢀbonds).ꢀSelectiveꢀhydrogenationꢀofꢀtheꢀC=Cꢀbondꢀ
9
ꢀ
yieldsꢀ hydrocinnamaldehydeꢀ (HCAL),ꢀ whileꢀ selectiveꢀ hydro‐
genationꢀ ofꢀ theꢀ C=Oꢀ bondꢀ deliversꢀ cinnamylꢀ alcoholꢀ (COL).ꢀ Ifꢀ
hydrogenationꢀtakesꢀplaceꢀatꢀbothꢀC=CꢀandꢀC=Oꢀbonds,ꢀhydro‐
cinnamylꢀalcoholꢀ(HCOL)ꢀwillꢀformꢀ(Schemeꢀ1).ꢀ ꢀ
10ꢀ
ꢀ 97ꢀ
Reactionꢀconditions:ꢀPEG4000ꢀ2.0ꢀgꢀ(containingꢀ5.0×10 3ꢀmmolꢀPd),ꢀtolu‐
eneꢀ 3.0ꢀ g,ꢀ n‐heptaneꢀ 1.0ꢀ g,ꢀ n‐decaneꢀ 0.2ꢀ gꢀ (internalꢀ standard),ꢀ cin‐
namaldehyde/Pdꢀ=ꢀ1000ꢀ(molarꢀratio).ꢀ


ꢀ
NIUꢀMingmingꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ674–678ꢀ
Theꢀ leachingꢀ ofꢀ Pdꢀ wasꢀ detectedꢀ byꢀ ICP‐AESꢀ andꢀ theꢀ resultsꢀ
Conversion of cinnamaldehyde
Selectivity for hydrocinnamaldehyde
indicatedꢀthatꢀtheꢀleachingꢀofꢀPdꢀwasꢀunderꢀtheꢀminimumꢀde‐
tectableꢀamountꢀ(0.003ꢀμg/ml).ꢀ
100
PEG4000‐stabilizedꢀPdꢀnanoparticleꢀcatalystsꢀinꢀaꢀthermoreg‐
ulatedꢀ PEGꢀ biphasicꢀ systemꢀ wereꢀ shownꢀ toꢀ beꢀ highlyꢀ active,ꢀ
selectiveꢀandꢀrecyclableꢀforꢀtheꢀselectiveꢀhydrogenationꢀofꢀcin‐
namaldehydeꢀtowardsꢀHCAL.ꢀConsideringꢀtheꢀextensiveꢀappli‐
cationsꢀofꢀPdꢀnanoparticleꢀcatalysts,ꢀtheꢀthermoregulatedꢀPEGꢀ
biphasicꢀ systemꢀ containingꢀ PEG‐stabilizedꢀ Pdꢀ nanoparticlesꢀ
shouldꢀfindꢀmoreꢀusesꢀinꢀotherꢀcatalyticꢀreactions.ꢀ
80
60
40
20
0
Referencesꢀ
0
1
2
3
4
5
6
7
8
[1] Denicourt‐Nowickiꢀ A,ꢀ Ponchelꢀ A,ꢀ Monflierꢀ E,ꢀ Roucouxꢀ A.ꢀ Daltonꢀ
Recycling number
Trans,ꢀ2007:ꢀ5714ꢀ
Fig.ꢀ2.ꢀRecyclingꢀ efficiencyꢀofꢀPEG4000‐stabilizedꢀPdꢀ nanoparticleꢀ cata‐
lystsꢀforꢀtheꢀselectiveꢀhydrogenationꢀofꢀcinnamaldehyde.ꢀ ꢀ
[2] ZahmakıranꢀM,ꢀÖzkarꢀS.ꢀNanoscale,ꢀ2011,ꢀ3:ꢀ3462ꢀ
[3] LiꢀKꢀX,ꢀWangꢀYꢀH,ꢀJiangꢀJꢀY,ꢀJinꢀZꢀL.ꢀCatalꢀCommun,ꢀ2010,ꢀ11:ꢀ542ꢀ
[4] ChechikꢀV,ꢀCrooksꢀRꢀM.ꢀJꢀAmꢀChemꢀSoc,ꢀ2000,ꢀ122:ꢀ1243ꢀ
[5] Moreno‐MañasꢀM,ꢀPleixatsꢀR,ꢀVillarroyaꢀS.ꢀOrganometallics,ꢀ2001,ꢀ
20:ꢀ4524ꢀ
HCALꢀwereꢀ99%ꢀandꢀ98%,ꢀrespectively.ꢀTheꢀeffectsꢀofꢀhydrogenꢀ
pressureꢀonꢀtheꢀreactionꢀwereꢀstudied.ꢀInꢀtheꢀrangeꢀofꢀ1.0−4.0ꢀ
MPa,ꢀ theꢀ conversionꢀ ofꢀ cinnamaldehydeꢀ increasedꢀ withꢀ in‐
creasingꢀ hydrogenꢀ pressureꢀ (entriesꢀ 4−7).ꢀ Itꢀ isꢀ alsoꢀ evidentꢀ
fromꢀTableꢀ1ꢀ(entriesꢀ4,ꢀ8−10)ꢀthatꢀprolongingꢀreactionꢀtimesꢀ
ledꢀtoꢀanꢀincreasedꢀconversionꢀofꢀcinnamaldehyde.ꢀInꢀallꢀinves‐
tigatedꢀcases,ꢀtheꢀselectivityꢀofꢀHCALꢀwasꢀhigherꢀthanꢀ97%ꢀandꢀ
noꢀCOLꢀwasꢀobserved.ꢀComparedꢀwithꢀpreviouslyꢀreportedꢀPd,ꢀ
Rh,ꢀRuꢀorꢀIrꢀcatalystsꢀ[17−20],ꢀPEG4000‐stabilizedꢀPdꢀnanoparti‐
cleꢀ catalystsꢀ inꢀ aꢀ thermoregulatedꢀ PEGꢀ biphasicꢀ systemꢀ areꢀ
moreꢀactive.ꢀ
TheꢀrecyclingꢀefficiencyꢀofꢀPEG4000‐stabilizedꢀPdꢀnanoparti‐
cleꢀcatalystsꢀwasꢀalsoꢀinvestigated.ꢀAfterꢀtheꢀreaction,ꢀtheꢀupperꢀ
organicꢀ phaseꢀ wasꢀ separatedꢀ fromꢀ theꢀ lowerꢀ cata‐
lyst‐containingꢀ phaseꢀ byꢀ simpleꢀ phaseꢀ separation.ꢀ Theꢀ lowerꢀ
catalyst‐containingꢀphaseꢀwasꢀdirectlyꢀusedꢀinꢀtheꢀnextꢀreactionꢀ
run.ꢀUnderꢀtheꢀidenticalꢀreactionꢀconditionsꢀtoꢀentryꢀ4ꢀinꢀTableꢀ
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[
[
[
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[
[
[
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slightꢀincreaseꢀofꢀparticleꢀsizeꢀfromꢀoriginalꢀ(1.9ꢀ±ꢀ0.5)ꢀnmꢀtoꢀ
3
73:ꢀ76ꢀ ꢀ
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4
[
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[
Theꢀleachingꢀofꢀtransition‐metalꢀnanoparticleꢀcatalystsꢀisꢀaꢀ
significantꢀconcernꢀinꢀtheseꢀtransformations.ꢀThisꢀpaperꢀstud‐
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contentꢀinꢀtheꢀupperꢀorganicꢀphaseꢀatꢀtheꢀendꢀofꢀtheꢀreaction.ꢀ
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CatalꢀCommun,ꢀ2012,ꢀ24:ꢀ65ꢀ
ꢀ
(
a)
(b)
(c)
(d)
(
1.9  0.5) nm
30
20
10
0
30
20
10
0
(2.0  0.5) nm
0
.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2
0
.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6
Diameter (nm)
Diameter (nm)
ꢀ
Fig.ꢀ3.ꢀTEMꢀimagesꢀ(a,ꢀc)ꢀandꢀparticleꢀsizeꢀhistogramsꢀ(b,ꢀd)ꢀofꢀPEG4000‐stabilizedꢀPdꢀnanoparticlesꢀ(200ꢀparticles).ꢀ(a,ꢀb)ꢀNewlyꢀprepared;ꢀ(c,ꢀd)ꢀAfterꢀ
eightꢀrecycles.ꢀ

ꢀ
NIUꢀMingmingꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ674–678ꢀ
GraphicalꢀAbstractꢀ
ꢀ
ꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2013,ꢀ34:ꢀ674–678ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(12)60552‐X
Thermoregulatedꢀpoly(ethyleneꢀglycol)ꢀbiphasicꢀsystemꢀwithꢀPdꢀnanoparticleꢀcatalystsꢀforꢀselectiveꢀhydrogenationꢀofꢀ ꢀ
cinnamaldehydeꢀ
ꢀ
NIUꢀMingming,ꢀWANGꢀYanhua*,ꢀLIꢀWenjiang,ꢀJIANGꢀJingyang,ꢀJINꢀZilinꢀ
DalianꢀUniversityꢀofꢀTechnologyꢀ
Poly(ethyleneꢀglycol)‐stabilizedꢀPdꢀnanoparticlesꢀwereꢀdemonstratedꢀtoꢀbeꢀefficientꢀandꢀrecyclableꢀcatalystsꢀforꢀtheꢀselectiveꢀhydrogena‐
tionꢀofꢀcinnamaldehydeꢀinꢀaꢀthermoregulatedꢀPEGꢀbiphasicꢀsystem.ꢀ