Ketonization of carboxylic acids over CeO2-based composite oxides

甲基异丙基酮

Ketonization of carboxylic acids over CeO2-based composite oxides

Ketonization of carboxylic acids over CeO2-based composite oxides

JournalofMolecularCatalysisA:Chemical227(2005)

Ketonization of carboxylic acids over CeO2-based composite oxides

231–239

KetonizationofcarboxylicacidsoverCeO2-basedcompositeoxides

OsamuNagashima,SatoshiSato ,RyojiTakahashi,ToshiakiSodesawa

DepartmentofAppliedChemistry,FacultyofEngineering,ChibaUniversity,Yayoi,Inage,Chiba263-8522,Japan

Received3September2004;receivedinrevisedform26October2004;accepted28October2004

Availableonline10December2004

Abstract

Theketonizationofpropanoicacidtoform3-pentanoneoverCeO2-basedcompositeoxidesattemperaturesof300–425 Cwasinvestigated.ACeO2-basedsolidsolution,CeO2–Mn2O3,waseffectivefortheketonization.Thecitrateprocesswasthemostappropriatemethodforpreparingawell-dispersedsolidsolution.Intheketonizationofpropanoicacidwithanotherlinearcarboxylicacid,anasymmetricketonetogetherwithtwosymmetricketoneswasformed,andtheketonecompositionwasapproximatedbyabinomialdistribution.Thereactivityofthecarboxylicacidwasslightlydecreasedasitschainlengthwasincreased.Incontrasttolinearaliphaticacids,branchedacidswerelessreactive.Methylgroupsubstituentsatthe -and -positionsofcarboxylicacidsdecreasedtheirreactivitiesinbothhomo-andcross-ketonization.Thelackofan -hydrogenortheincreaseinsterichindrancewassurmisedtobethecauseofthedecreaseinreactivity.©2004ElsevierB.V.Allrightsreserved.

Keywords:Ketonization;Carboxylicacid;CeO2;Mn2O3;Symmetricandasymmetricketones

1.Introduction

CeO2isasigni cantcomponentofautomobileexhaustcatalysts[1,2],workingasapromoterinthethree-waycatal-ysisduetoitsoxygenstoragecapacity[2].CeO2alsofunc-tionsasacatalystintheortho-selectivealkylationofphenolwithprimaryalcohols[3–5].WehaverecentlyfoundthatpureCeO2catalyzesthedehydrationof1,3-diolsintoallylicalcohols[6,7]andof1,4-butanediolinto3-buten-1-ol[8].Thesynthesisofketonesfromcarboxylicacidsintheva-porphaseiscalledketonization.Anumberofarticlesontheketonizationofcarboxylicacidsareavailable:severaloxides,suchasCr2O3[9,10],Al2O3[11,12],PbO2[12],TiO2[13–16],ZrO2[14,17–19],CeO2[19–24],ironox-ide[14,15,25–27],andmanganeseoxide[12,19,20,22,28],aswellasMg/Alhydrotalcites[29]catalyzetheketonizationofcarboxylicacids.Manyothercatalystshavebeenfoundsincethe19thcentury:BaCO3,MgO,ThO2,UO2,CdO,ZnO,NiO,Bi2O3,andSnO2havebeenintroducedinreferences[12,30].

Twomoleculesofcarboxylicacidsarerequiredtoformaketoneviaketonization,producingcarbondioxideandwater.The

Ketonization of carboxylic acids over CeO2-based composite oxides

generalreactionschemeisexpressedasfollows:

Correspondingauthor.Tel.:+81432903376;fax:+81432903401.E-mailaddress:satoshi@faculty.chiba-u.jp(S.Sato).

Intheabovereaction,RCOOHreactswithR COOHviacross-ketonization;ontheotherhand,twosymmetricketonesofRCORandR COR canbeformedviahomo-ketonization,namely,twodifferentcarboxylicacidsproducethreedifferentketones.Cross-ketonizationhasbeenreported[12,22–24].

Alcohols,aldehydes,andestersarealsoconvertedintoke-tonesthroughdimerizationinthepresenceofCeO2andZrO2[5,31–37].Inourpreviousstudy[35],1-propanol,propanalandpropylpropanoatewereconvertedinto3-pentanoneinthepresenceofCeO2–Fe2O3catalysts.Theintramolecularcondensationof1,6-hexanedioltoformcyclopentanonealsoproceedsoverCeO2–Mn2O3[36].IthasbeenprovedthatasolidsolutioncontainingCeO2iseffectiveforketoneforma-tion[35,36].Therefore,wefocusedontheutilityofCeO2-basedsolidsolutionsinproducingketonesfromcarboxylicacids.

1381-1169/$–seefrontmatter©2004ElsevierB.V.Allrightsreserved.doi:10.1016/j.molcata.2004.10.042

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