Reações de oxidação catalíticas · 2018. 6. 11. · Reações de oxidação catalítica – O...
Transcript of Reações de oxidação catalíticas · 2018. 6. 11. · Reações de oxidação catalítica – O...
Reaçõesdeoxidaçãocatalíticas
QFL5835-6Catálise:umavisãointegradaProfs:AtaualpaBraga,LianeM.Rossi,PedroVidinha
1
2
Selective oxidation remains one of the keysynthetic steps for the activation of a broad range ofsubstrates for the production of either finished products orintermediates for the preparation of pharmaceuticals,agrochemicals,aswellascommoditychemicals.
Epoxides,alcohols,ketones,aldehydes,
andacids
alkanesolefinsalcohols
?
3
IncontrasttohydrogenationreactionswhichareoftencarriedcatalyticallywithH2,therearerelativelyfewselectiveoxidationreactionsthatarecatalyzedusingO2.
4
WhyhydrogenationwithaheterogeneousmetalcatalystandH2isacommonplacelaboratoryprocedureandmostwouldnotconsiderdoingasimilaroxidationprocesswithO2asastandardlaboratoryprocedure?
• H2hastobeactivatedbychemisorptiononacatalystsurfacebeforeitcanbereactedwithasubstrateforhydrogenationtooccur
• O2initsgroundstateisadiradicaltripletspecies.Thisopensupthepossibilitiesofcompetingnon-catalyzedgasorliquidphasereactionsinwhichtripletdioxygenreactsdirectlywiththesubstratewithouttheinterventionofacatalyst
5
• Selectiveoxidationsusingstoichiometric
oxidants:Na2Cr2O7,KMnO4,MnO2,…
• Producestoichiometricamountsofverytoxicwaste,nolongertolerable.
6
• Mostindustrialoxidationprocessestendtouseeitherchlorineororganicperoxides.
• Oneproduceshugeamountsofchloridesaltsandlesser,butsignificant,amountsoftoxicchlorinatedorganicby-products.
• Thealternativeuseoforganicperoxidesisexpensive,andisalsoaccompaniedbytheformationofby-products—economicallydisadvantageousifthereisnomarketforthem.
Epoxidationwithchlorine
-Chlorine-hypochlorite-peroxyacids
7
SharplessEpoxidation
• Theoxidizingagentistert-butylhydroperoxide
Katsuki,T.;Sharpless,K.B.(1980)."Thefirstpracticalmethodforasymmetricepoxidation”J.Am.Chem.Soc.,1980,102(18),pp5974–5976
8
9
cleanandfreelyavailablefromairO2
• CATALYTICOXIDATIONS
Thereisarealneedfornewcatalyticprocessesthatusemolecularoxygen,especiallysinceenvironmentalfactorsareofparamountimportanceandweneedtodevelopatomefficientgreenprocesses.
10
Itissurprisingthattherehavebeenfewnewapproachesinthedesignofselectiveoxidationcatalystsusingmolecularoxygeninthepastfortyyears.1Themajoradvancesinselectiveoxidationweremarkedoutover50yearsago.
1G.J.Hutchings,Chem.Commun.,2008,1148–1164
• titaniumsilicaliteTS-1 àepoxidationofalkenes(H2O2)
• iron-dopedZSM-5zeolite àoxidationofbenzenetophenol(N2O)
Reaçõesdeoxidaçãocatalítica–O2
• Autoxidation mechanism
Radicalscavenger: butylatedhydroxytoluene(BHT).BHTisanantioxidantthatreactswithfreeradicals,delayingoxidativeprocesses.
Reaçõesdeoxidaçãocatalítica–O2
• Oxidation at metal or oxide surfaces
Redoxcatalysts:V,Mo,Fe• Lowselectivity:theoxygenatedproductsaremorereactivethanthe
startingmaterials,e.g.alkanes.
-Hightemperature-Highlyactivecatalysts
• Oxidation with redox catalysts
• Industrialapplicationofcatalyticoxidationofalkanes:
Oxidationofbutanetomaleicanhydride((VO)2P2O7-VPO))
13
Fig.1.Selectivityinproductvs.D0HC–Hreactant–D0HC–HorC–Cproductat30%conversionfortheindicatedreactions[1]:1,ethylbenzenetostyrene;2,1-butenetobutadiene;3,acroleintoacrylicacid;4,toluenetobenzoicacid;5,ethanetoethylene;6,n-butanetomaleicanhydride;7,toluenetobenzaldehyde;8,propenetoacrolein;9,1-buteneto2-butanone;10,isobutanetoisobutene;11,methanoltoformaldehyde;12,methacroleintomethacrylicacid;13,propanetopropene;14,ethanoltoacetaldehyde;15,isobutenetomethacrolein;16,n-butaneto1-butene;17,benzenetomaleicanhydride;18,propanetoacrolein;19,methanetoethane;20,isobutanetomethacrylicacid;21,ethanetoacetaldehyde;22,methanetoformaldehyde;23,isobutanetomethacrolein.
Theroleofreactantandproductbondenergiesindetermininglimitationstoselectivecatalyticoxidations(AppliedCatalysisA:General137(1996)179-191)
ifthisbondenergydifference(weakestbondinreactantandproduct)islessthan30kJmol−1veryhighproductselectivityispossible,whereasfordifferencesgreaterthan70kJmol−1nearzeroselectivityisalwaysrecorded.
14
COoxidationM.Haruta1wasthefirsttoshowthatCOoxidationcouldbeperformedatambienttemperaturesbyusinggolddispersedonoxidesurfaces.
1Haruta,M.;Kobayashi,T.;Sano,H.;Yamada,N.ChemLett1987,405.
TheactivegoldcatalystswerecomposedofAunanoparticleshomogeneouslydispersedonmetaloxidesupportssuchasFe2O3,Co3O4,andNiO
• Oxidation by O2 chemisorption
15
COoxidation
M.Haruta,GoldBulletin2004,37/1–2,2716
17
COoxidationComparison with platinum:
18
COoxidationisanessentialgoalforfuelcelltechnologywhereresidualtracesofCOhavetoberemovedfromtheH2thatisusedasthefuelsource.However,thisrequirespreferentialoxidationofCOinthepresenceofCO2,H2OandamassiveexcessofH2.
COoxidation
• WhygoldissuchaneffectivecatalystfortheoxidationofCO?• WhatisthemechanismbywhichsupportedgoldnanocrystalsoxidizeCO?• Whatisthenatureoftheactivesiteandisitthesameforallsupportedgoldcatalysts?
19
COoxidationProposalshaveincludedthesizeandmorphologyofthegoldparticleanditsinterfacewiththesupport,themetaloxidationstate,andsupporteffects.EXAFS,XPS,Mössbauer,IRofCOadsorbed,O2adsorptionandthereactionofO2withCO,18O2isotopeexperiments,etc.-
MetallicAusurfacesarenecessaryforCOadsorptionandthattheperipheriesactasreactionzoneswithO2
20
AllattemptstoproducePOcommerciallybydirectoxidationofpropene,inasimilarwaytothesilverpromotedsynthesisofethyleneoxide,havetillnowbeenunsuccessfulandthemajorityofPOisstillmanufacturedbythechlorohydrinprocessandtheindirecthydroperoxideprocesses.
Propeneepoxidation
C.DellaPina,E.Falletta,L.PratiandM.Rossi,SelectiveoxidationusinggoldChem.Soc.Rev.,2008,37,2077–2095
21
Propeneepoxidation
Hayashi,T.;Tanaka,K.;Haruta,M.JCatal1998,178,566.
Haruta,Metal.Angew.Chem.Int.Ed.2009,48,7862–7866
Propeneepoxidation“Theresultingtitaniumhydroperoxidespecies(Ti–OOH)aretheactualreactionpartnersforthepropylene,whichisconvertedtopropyleneoxide.”
22
23
Oxidationofhigheralkenes
G.J.Hutchings,Chem.Commun.,2008,1148–1164
ComparingthecatalyticactivityofAuandPtnanoparticles
• Oxidationofn-propanal • Oxidationofaldehydes
S.Biellaetal.,J.Mol.Catal.A:Chem.(2003)197,207.
Oxidationofalcohols• Michele Rossi et al.
24
Effectofsupportongoldcatalysis
A.Cormaetal.,Angew.Chem.Int.Ed.(2005)44,4066
5nmCeO2
Oxidationof3-octanol
• Avelino Corma et al.
25
ComparingthecatalyticactivityofAuandPdnanoparticles
Substrate T(°C) Catalyst Ketoneyield(%) TOF(h−1)
1-Phenylethanol 160 Au/CeO2 33 12,480
Pd/CeO2 >95 32,558
120 Au/CeO2 >95 1511
Pd/CeO2 91 645
3-Octanol 120 Au/CeO2 >95 2337
Pd/CeO2 3 63
Pd/CeO2▲,Au/CeO2■ePd/apatite♦A.Abadetal.Tetrahedron(2006)62,6666.
• Avelino Corma et al.
3-Octanol
1-Phenylethanol
26
27
• G. H. Hutchings, et al.
D.I.Enache,D.W.Knight,andG.J.Hutchings,CatalysisLetters,103,2005,43.
Oxidation of benzyl alcohol – effect of support
28
• G. H. Hutchings, et al.
DanI.Enache,etal.Science311,362(2006)
ComparingthecatalyticactivityofAu,PdandAuPdnanoparticles
TiO2-supportedAu-PdalloynanocrystalsgivesignificantlyenhancedactivityforalcoholoxidationusingagreenchemistryapproachwithO2undermildsolvent-freeconditions
29
(A)Au(4d)andPd(3d)spectrafora2.5weight%Au–2.5weight%Pd/TiO2catalystafterdifferentheattreatments:(a)uncalcinedor(b)calcinedat673Kinair.(B)MontageshowingtheADF-STEMimageofabimetallicparticleandthecorrespondingMSA-processedSTEM-XEDSmapsoftheAu-M2,Pd-La,O-Ka,andTi-Kasignals.AlsoshownisareconstructedMSA-filteredAu-Pd-Ticompositionmap(Ti,red;Au,blue;andPd,green).
DanI.Enache,etal.Science311,362(2006)
30 DanI.Enache,etal.Science311,362(2006)
Bimetallicnanomaterialsforthedesignofadvancedcatalysts
• High atomic structural complexity:
• Distribution of metal domains?
• Composition (bulk and surface)?
• Composition homogeneity among particles
• Atomic rearrangement and restructuring under heating/working conditions
(a)alloy,(b)cluster-on-cluster,(c)core-shell
31
32
Heterogeneous catalysis = surface catalysis1
Sólido
Gas Liquid
1BruceC.GatesandTobinJ.Marks,DefragmentingCatalysis(editorial),Angew.Chem.Int.Ed,2012,51,11644
1) Adsorption 2) Reaction 3) Desorption
Solidcatalyst
33
Heterogeneous catalysis = surface catalysis1
Sólido
Gas Liquid
1BruceC.GatesandTobinJ.Marks,DefragmentingCatalysis(editorial),Angew.Chem.Int.Ed,2012,51,11644
Solidcatalyst
Extremelysensitivetosurfaceandsubsurfacecomposition?Howtocontrol(andknow)thesurfacecompositionofbimetalliccatalysts?
Biorefineryplatformmolecules
34JGallo,J.Braz.Chem.Soc.,Vol.28,No.9,1586-1607,2017.
H2O2
Anthraquinone process
H2 + O2
J.Am.Chem.Soc.,2016,138(2),pp574–586
DirectsynthesisofH2O2
35