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ChineseJournalofCatalysis35(2014)16191640
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Review
Ammoniasynthesiscatalyst100years:Practice,enlightenmentandchallengeHuazhangLiu*InstituteofIndustrialCatalysisofZhejiangUniversityofTechnology,Hangzhou310014,Zhejiang,China
A R T I C L E I N F O
A B S T R A C T
Articlehistory:Received19March2014Accepted23April2014Published20October2014
Ammonia synthesis catalyst found byHaberBosch achieves its
history of 100 years. The
currentunderstandingandenlightenmentfromfoundationanddevelopmentofammoniasynthesiscatalystarereviewed,anditsfutureandfacingnewchallengeremainedtodayareexpected.Catalyticammoniasynthesistechnologyhasplayedacentralroleinthedevelopmentofthechemicalindustryduring
the20thcentury.During100years, ammonia synthesis catalysthas come
throughdiversifiedseedtimesuchasFe3O4basedironcatalysts,Fe1xObasedironcatalysts,rutheniumbasedcatalysts,anddiscoveryofaCoMoNsystem.Oftennewtechniques,methods,andtheoriesofcatalysishaveinitiallybeendevelopedandappliedinconnectionwithstudiesofthissystem.Similarly,newdiscoveriesinthefieldofammoniasynthesishavebeenextendedtoother
fieldsofcatalysis.Thereisnootherpracticallyrelevantreactionthatleadstosuchacloseinterconnectionbetweentheory,modelcatalysis,
andexperimentasthehighpressuresynthesisofammonia.Catalyticsynthesisammoniareactionisyetaperfectmodelsystemforacademicresearchinthefieldofheterogeneouscatalysis.Understanding
themechanismand the translation of the knowledge into technical
perfection hasbecomea fundamentalcriterionforscientificdevelopment
incatalysisresearch.Theneverendingstoryhasnotendedyet.Inadditiontoquestionsabouttheelementarystepsofthereactionandtheimportanceoftherealstructureandsubnitridesforthecatalystefficiency,aswellasthewideopenquestionaboutnewcatalystmaterials,therearealsodifferentchallengesthrowndownbytheoryfortheexperimentalistinthepredictionofabiomimeticammoniasynthesispathatroomtemperatureand
atmospheric pressure including electrocatalysis, photocatalysis and
biomimetic nitrogen fixation.
2014,DalianInstituteofChemicalPhysics,ChineseAcademyofSciences.PublishedbyElsevierB.V.Allrightsreserved.
Keywords:AmmoniasynthesiscatalystDiscoveryDevelopmentChallengePracticeEnlightenment
1. Theinventionandenlightenmentofammonia synthesiscatalyst
The ammonia synthesis industry has developed
rapidlysincethefirstammoniasynthesisdeviceovertheworldstartedtoproduceammonia
inSeptember9th,1913.Toearly2000s,theammoniasynthesisdeviceswithdailyproductioncapabilityof1000or2200tareworldwide.Ammoniasynthesishasbeenapillarof
chemical industryandamilestone in
thehistoryofconquestofnaturemadebyhumanbeings.
In theprocessof thisgreat invention,unprecedenteddifficulties
have been encountered [1]. In 1787, C. L. Bertholletproposed that
ammonia consisted of elemental nitrogen
andhydrogen.Manydistinguishedchemistsatthattime,
includingW.H.Nernst,W.Ostward,F.Haber,etc., immediatelycontributed
great efforts into research about ammonia synthesis byelemental
nitrogen and hydrogen.However, the first obstaclethey facedwas
chemical equilibrium. The law ofmass actionand the lawof chemical
equilibriumdidnot be found at
thattime,sothatconcentrationofammoniaintheequilibriumwas
*Correspondingauthor.Tel:+8657188320063;Fax:+8657188320259;Email:[email protected]:10.1016/S18722067(14)601182|http://www.sciencedirect.com/science/journal/18722067|Chin.J.Catal.,Vol.35,No.10,October2014
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1620 HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640
unclear.Atatmosphericpressure,ammoniawasonlygeneratedatvery low
temperature,but itdecomposedathigh
temperature.Therefore,manyscientistsevenbelievedthatthegenerationofammoniabytheelementalhydrogenandnitrogenwasaninsurmountableobstacle.
At that critical moment, Haber first proposed to use
highpressurereactiontechnique.However,itwasstillhardtorealizeindustrialscaleproductionduetolowconversionperpassofammonia.SoHaberabandonedthepopularstaticviewandadoptsadynamicmethodbyintroducinganimportantconcept,thereactionrate,whichusingspacetimeyieldtoreplacereaction
yield. Based on this important principle, he
developedclosedprocessflowandloopoperationtechnology.Thesethreetechnologiesandconceptof
reactionratewereagreat invention that provided the basis for the
construction of experimental apparatus to produce ammonia and
achieved the firstpressurized catalytic process in industrial
history. Thiswas amilestone in the development history of the
catalytic
processthatrepresentedthebeginningofaneweraofindustrialcatalysis.Onlya
fewyears later,methanol synthesis,FischerTropsch synthesis and
highpressure reaction technology in thepresence of heterogeneous
catalysts that appeared
subsequentlyhavebecomeessentialpracticesinthefieldoforganicchemistry,andpromoted
theentirechemicalandmaterial
industries.Habersunprecedentedcreationsestablishedthebasisfortheentirechemicalengineeringscience.
InFebruary1908,Haber
signedanagreementwithBadenAnilineandSodaCompany(BASF).BASFassigned
the taskofindustrialdevelopment toCarlBosch.Bosch
immediatelywasaware enough of the fact that he had to address
threemajorchallenges: designingmethods to produce lowcost
hydrogenandnitrogen;exploringanefficientandstablecatalyst;developing
equipment and materials for highpressure ammoniasynthesis.
Haberandotherscientistsenergeticallyexploredcatalysts.Haberdiscovered
thatosmiumanduraniumuraniumcarbidecatalystsdisplayedexcellentperformanceonammoniasynthesis.BASFCorporationacquiredpurchaserightsforosmiuminstock
all over theworld, a total of about 100 kg. Although
itsoundsincredibletoday,itdidfullyreflectthepassionofscientistsandentrepreneursat
that
time.However,HaberwasappointedthedirectoroftheInstituteofPhysicalChemistryand
ElectrochemistryKaiserWilhelmInstitutein1912,whichalsomarked the
end of Habers research activities in the field
ofammoniasynthesis.
Boschassignedthetaskonfindingefficientandstablecatalysts to his
assistant AlwinMittasch.Mittasch first
conductedextensivestudiesonmetalnitridesinanattempttofixthenitrogeninairbytheindirectroute.Althoughthattechniquewasunsuccessful
for the ammonia synthesis, it provided
valuableinformationonthecatalyticpropertiesofalmostall
themetalelementsinperiodictable.Herecognizedthatmanyofmetalsitselfpresentedonlylittleornocatalyticeffect,butanadditivecouldimprovetheircatalyticactivity.Basedonthesefindings,inFebruary1909hemadeanunprovenhypothesis:"thewinning
catalyst should be a multicomponents system" and
itneededaverylargenumberofteststodetermine.Forthisreason, BASF
produced a variety of model reactors for
catalysttests.From1909to1911, inaboutayearandahalf,2500ofdifferent
catalysts were tested at 6500 times. That
amazingcatalystselectiontrial,continueduntil1922beforeitwasover,with
a totalof 20000 timesof testing
forover5000differentcatalystsystems.
Ironhas been knownas an effective catalyst for
ammoniasynthesissincetheyearof1905.However,itwasprovedtobedisappointing
in BASFs initial experiments. Someday Mittaschs assistant Wolf
inadvertently used
SwedishproducedGallivareironoresampleswhichhadbeenplacedontheshelfofthelaboratoryafewyearstotestthesynthesisofammonia,andreceivedunexpectedresults.Hefoundthatifafewpercentof
alumina, a small amount of calcium oxide and
potassiumalkaliwerefusedintopureiron,asuitablecatalystforthesynthesisofammoniawasobtained.Thebestcatalystwasprovedtobeamulticomponentmixture,whichcomprisedthesimilarcomposition
of Gallivare magnetite. That is the
magnetitebasedfusedironcatalystwithasmallamountofpromoterwhichisstillusedtoday.Themixedcatalystisprovedtobesoeffectivethatevennowallammoniacatalystsintheworldarestillmanufacturedbasedonthisprinciple.
Haber,Bosch,Mittasch,andErtl these fourgreat scientistshavemade
a great contributionon the creation and development of ammonia
synthetic industry, among whom
Haber,Bosch,andErtlwereawardedtheNobelPrizeinChemistry.
Thesuccessfuldevelopmentofsyntheticammoniaindustry
FritzHaber(18681934)Laidthetheoreticalbasisonsynthesisofammonia,awardedthe1919NobelPrizeinChemistry.
CarlBosch(18741940)Realizedtheindustrialsynthesisofammonia,awardedthe1931NobelPrizeinChemistry.
AlwinMittasch(18691953)Themajordeveloperforfusedironcatalyst,whoproposedtheconceptofmixedcatalyst.
GerhardErtl
(1936)Greatcontributiononironcatalystsurfacechemistryresearch,awardedthe2007NobelPrizeinChemistry.
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HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640 1621
isnotonlyagreattechnicalachievementbutalsoamasterpieceof the
organizationwork,whichbecome a precedent in earlystage for today's
prevalent collaborative innovation
(teamwork).Inthecreationprocess,Haber,BoschandMittascsthegreat
creation, brilliant scientific ideas and innovative
spirit,thepassionandspiritofcooperationfromscientistsandentrepreneurs,aswellastheteamspiritofcooperationandcollaborativeinnovationamongchemists,engineers,physicists,materials
scientists and a variety of artisans group, areworthy
ofouradmirationandlearning.
Greatsuccessonammoniaindustryhaschangedthehistoryofworld
foodproduction.According to the statistics
fromUNFoodandAgricultureOrganization(FAO),fertilizercontributesmorethan40%tofoodproduction.Thus,thecatalyticammoniasynthesistechnologyinventedbyHaberandBoschisconsidered
to be one of the greatest contributions to human beings. From the
technological invention to the present, theEarthspopulationhas
grownby4.2 times from1.7billionatthebeginning of the 20th
century,while foodproductionhasincreasedby7.8 times.Humans can
still produce ample foodandclothingunder the limited
landresources,mainly relyonsuch technology created by Haber and
Bosch. Now, 50% ofnitrogen in our body is from ammonia synthesis
[2], whichmean, if without such invention, 50% of people in the
Earthcannotsurvive.Chinaisalsounlikelytofeed20percentoftheworldspopulationbyonly7%ofarablelandallovertheworld.
After a century of development, catalytic synthesis of
ammoniahasmadetremendousprogress.Theproductioncapacityofsinglesetequipmenthasbeenimprovedfromtheoriginal5tofdailyammoniaproductiontothecurrent2200t.Thereaction
pressure has dropped to 1015MPa from the original100 MPa. The
energy consumption has decreased to 27.2
GJfromtheoriginal78GJ,whichisclosetothetheoreticalenergyconsumptionof20.1GJ.Butasthesecondlargestchemicals,theammoniaproductionstillconsumes2%oftotalenergysupplyintheworldandreleasesmorethan400MtofCO2,whichaccountsfor1.6%oftotalglobalCO2emissions.
2. Thedevelopmentandenlightenmentofammonia
synthesiscatalysts
The inventionof fused
ironcatalystcreatesacatalyticammoniasynthesisindustry.Ironcatalystsforammoniasynthesisbecomeoneofthemostsuccessfulandstudiedthoroughcatalystsintheworld.Withthedevelopmentofpetrochemical,coalchemical,
biochemical, polymer, materials, energy and
environment,therelativepositionofresearchonammoniasynthesiscatalystinthecatalyticdomaingraduallydeclines,anditisno
longerthemainaspectsofcatalysisresearch,but
therigiddemandforfooddecidestheirreplaceabletraditionalammoniaindustrycanonlyrelyontechnologicalprogresstoconstantlyevolve.
The catalyst of any progress can improve
thermodynamicefficiencyandlowerproductprices.Therefore,advancesofammonia
industryanditscatalysttechnologywillnotstop.Initially, the suitable
Fe catalyst was only found by F.
Haberfromabout5000triedcatalysts;currently, inorderto
furtherimprove theprocess and reduceenergy consumption, further
improvingthecatalystisstilltheonlyhope.
2.1.
DevelopmentofammoniasynthesiscatalystCurrentlyfusedironcatalystsstilloccupytheabsoluteposi
tion in industrywith tens of catalyst product types,
ofwhichmorethantenkindsaredevelopedbyChinese.NanjingChemicalIndustryCompanydevelopedtheA102ammoniasynthesiscatalyst
in 1951, which was the first Chinese
selfdevelopedammoniasynthesiscatalyst,andfollowedbysuccessfuldevelopmentoftypeA106andA109ammoniasynthesiscatalysts.In1979,
Zhejiang University of Technology successfully
developedtypeA1102lowtemperatureammoniasynthesiscatalyst[3].AfterthattheNanjingChemicalIndustryResearchInstitute,FuzhouUniversity,LinQuCatalystPlant,ZhengzhouUniversity,Hubei
Institute of Chemistry, etc. successfully developed typeA1101, A110
3, A1104, A1105Q (spherical) and
A1106catalysts,whichformedawidelyappliedA110catalystsfamilysince1980s[4].
CocontainingcatalystisanimportantdevelopmentforthetraditionalFe3O4basedfusedironcatalyst.TheBritishcompany
ICI applied patents on cobaltcontaining catalyst in
1978,andsuccessfullydeveloped741typecobaltcontainingcatalystin
1979. In 1985, Fuzhou University successfully
developedA201typecobaltcatalyst[5],thentheamountofcobaltinA201wasfurtherreducedandCeO2wasadded,whichwascalledasthe
typeA202 cobaltcontaining catalyst in1995 [6]. In addition, South
ChinaUniversity of Technology,Nanjing ChemicalCompany, Zhengzhou
University, also developed their
cobaltcontainingcatalysts[4,7].
Since rutheniumbased catalyst for ammonia synthesis isinvented
in the 1990s, most of scientists have shifted theirmain research
directions and attention to the studyof
rutheniumbasedcatalyst,andthusfusedironcatalystresearchhasbecome
less popular. Only a few of universities and
researchinstitutionsaroundtheworldarestillstudyingfusedironcatalysts,
such as Szczecin University of Technology in Poland[810], Fuzhou
University [11] and Zhejiang University ofTechnology [12]. Others
such as the Fritz Haber InstituteMaxPlanckSociety in Germany [13]
occasionally
publishedresearchpapersonironcatalystsforammoniasynthesis.
To 1970s, the fused iron catalyst was considered
wellconsolidatedandnospecial improvementwasstillexpected.The
industrial iron catalyst presently used is not basicallydifferent
from that developed 100 years ago [14]. It has becomemore difficult
to achieve significant progress. This willencourage people to seek
a major technological breakthroughonekindof jumpingordiscontinuous
technologicalprogress. Nearly 30 years, the discoveries of
Fe1xObasedcatalyst
system,rutheniumbasedcatalystandcobaltandmolybdenumbimetallicnitridecatalystareexpressingtheideaofseekingtechnicalbreakthroughs(Table1).
2.1.1. ThediscoveryofFe1xObasedammoniasynthesiscatalyst
Inthepastcentury,scholarsalwaysbelievedthatwhenthe
precursorof fused iron catalystswasFe3O4, catalysts
showedthehighest activity. Therefore, people confined their
thinking
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1622 HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640
onFe3O4 catalyst in thepast fused iron catalyst research
anddevelopment,andimprovedthecatalystactivityandlifejustbychangingthetypeandnumberofpromoter,whileignoringtheimpactofcatalystprecursorphase.Althoughresearchandimprovementhadbeendoingbyscientistsincountries,magnetitewasstillofthedominance[15].In1986ZhejiangUniversityofTechnology[1621]
inventedFe1xObasedcatalystwithWustitestructure,whichbroketheshackleofthetraditionalconclusion"thefusedironcatalystwithFe3O4asprecursorshowsthehighest
activity", and found a breakthrough in improving theperformanceof
fused iron catalystWustite catalyst system.
Itmarked80yearsofresearchonfusedironcatalystshadbeenmade a
substantial progress which kept the development
offusedironcatalystalive.Fe1xObasedammoniasynthesiscatalystismostactivefusedironcatalystintheworld.Thisdiscovery
causeswidespread concern and interest in domestic andforeign
scholars [13,14,22,23], and has been widely used inindustry.
The author [24] has the opportunity to witness the
constructionanddevelopmentofChinasammonia industry
fromthe1960s,anddevoteshislifetothedevelopmentofcatalyticammonia
technology.He contributeshis efforton thevariousresearch stages of
the catalystwhich start from Fe3O4based,cobaltcontaining
Fe3O4based, Fe1xObased to
rutheniumbasedcatalysts.HecreatedtheFe1xObasedcatalystanditstheory
system based on themonophase principle of iron oxides, and
collaboratedwith his colleagues to successfully
developnewindustrialcatalystsoftypeA1102,A301,ZA5,etc.,whichhavebecomeoneofmajorindustrialammoniasynthesiscatalystsinnearly30years.
2.1.2.
Thediscoveryofrutheniumbasedcatalystsforammoniasynthesis
The Fe3O4based iron catalyst was considered well consolidated
and no special improvement was still expected.Scientists abroad
started to look for nonferrous
noblemetalcatalysts.40yearsago,Ozakietal.[25]inareviewarticleproposed
that chemical adsorption of nitrogen and catalytic efficiency of
elements in ammonia synthesis and decompositioncould be associated,
and thus could obtain a
volcanoshapedcurvetoquantitativelydescriptthecatalyticefficiencyofmetalelements
in ammonia synthesis. In this graph, ruthenium,
osmium,andironareatthetopofthevolcanoshapedcurve.Under industrial
conditions, the use of Ru and Os catalysts
hasbeenclosetotheoptimumpoint.BoththeoreticalandpracticalstudiesinnearlyahundredyearshaveshownthatRu,OsandFearethebestpuremetalcatalysts.
The development of ruthenium catalyst has a long
history[26].Thefirstreportabouttheapplicationofrutheniumcatalyst
insynthesisofammoniawaspublishedin1917, inwhich
Mittasch,etc.believedthatcatalyticactivityofrutheniumcatalystsintheammoniaprocessisnotasgoodasthatofironcatalyst.Thenrutheniumcatalysthadnotbeenreportedina
longtimeperiod.In1969,Tamaru[27]proposedatransitionmetalelectrondonoracceptortype(EDA)ofammoniasynthesiscatalystsystem.Inthiscatalystsystem,theychosethealkalimetalpotassiumorsodiumaselectrondonors,transitionmetalssuchas
iron, ruthenium, osmium, cobalt, etc. as electron acceptorsand
staffwith electrons transport capability such as phthalocyanine,
polyphenylene quinone, graphite or graphitized
carbonascarriers,anditshowedhighcatalyticactivityinammonia
synthesisundermild conditions. In1972,Ozaki et al
[28]foundthatwhenrutheniumasanactivecomponent,potassiumasametalpromoter,
carbonas a catalyst carrier, the catalystsystemshowedhighactivity
forammoniasynthesis.Thatdiscovery once again sparked scientists
interest in studying
rutheniumcatalysts.Afterthat,researchersinJapan,Russia,UK,USA,Italyandothercountries,aswellasZhejiangUniversityofTechnology,
Fuzhou University, Xiamen University, Dalian
InstituteofChemicalPhysics(DICP)andotherunitsinourcountry[2932]putalargeamountofenergyintothedevelopmentof
ruthenium catalysts in order to replace traditionalironbased
catalysts. British Petroleum (BP) was
responsibleforloadingrutheniumcarbonylcompoundsongraphitecarboncarrierstobeanewRu/Ccatalyst.KelloggwasresponsiblefordevelopingtheammoniasynthesisprocessbyusingthatRu/Ccatalyst.With10yearsofjointefforts,theysuccessfullydevelopedin1992anewammoniasynthesisprocessKAAP(KelloggAdvanced
Ammonia Process) which was applicable to
Ru/Ccatalyst,andachieveditsindustrialapplications[3335].
Althoughrutheniumcatalystsarehighlyactive,theirstronginhibitionofH2andthemethanationofcarbonmaterialofthecarriersinRucatalystunderconditionsofammoniasynthesiswhichresultsinlossofactivecarboncarrierandshorteningthelife
of catalyst, are weaknesses of the ruthenium
catalysts.Meanwhile,theRuandOsareveryexpensive,whichislackofcommercial
appealing compared to the thirdbest Fe
catalyst[36].OsandUareabandonedbyHaberintheearly20thcentury.Ru/Ccatalystisnotmuchadvantageinenergyefficiency(Table
2). From1992 to 2010, only 16 ammonia plants usedruthenium
catalysts. Therefore, it canbe said that theoreticalmeaning of
ruthenium catalysts is larger than its practicalmeaning.The
industry is still necessary to
findmoreefficientandcheapercatalyststhanrutheniumcatalysts.
2.1.3. ThediscoveryofCoMonitridecatalystforammonia synthesis
Nrskovetal[36]proposedanalloycatalystisdesignedbyinterpolation
in the periodic table. This catalyst
developmentstrategywasobtainedbysimplephysicalprinciples,soitsbasic
Table1Developmentofammoniasynthesiscatalysts.Developmentstage
Year Inventor Catalysttype Chemicalcomposition(1)Fe3O4basedcatalyst
1913 BASF,Germany S610,KM Fe3O4+Al2O3+K2O+CaO+(2)Fe1xObasedcatalyst
1986 ZhejiangUniv.ofTechnol.,China A301,ZA5
Fe1xO+Al2O3+K2O+CaO+(3)Rubasedcatalyst 1992 UKBP,Japan KAAP
RuBaK/AC
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HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640 1623
principlecouldbewidelyapplied.Accordingtothisprinciple,areasonable
assumption was that the elements which
reactedwithnitrogenveryactivelyandveryinactivelyinA.Ozakivolcanoshapedcurve
together formalloy
toconstructanewactivesurfaceinordertoachievethemostoptimalperformance.The
result showed that theactivityof
cobaltmolybdenumnitridecatalystwashigherthanthatofRuandOscatalysts;wasalso
better than the activity of either single component
forammoniasynthesis;wasevenbetterthanFeandRuatlowNH3concentration
[3741]. The discovery of
cobaltmolybdenumnitridecatalystisconsideredtobethelatestvertexsofarinthestudy
of ammonia synthesis catalyst according to
theoreticalpredictions[42,43].
TheexperimentsofErtl[44]andSomorjai[45]canimproveunderstanding
on ammonia synthesis and allow
quantitativetheoreticaldescriptionandpredictiononthereaction.First,onthebasisofbasicknowledgeonreactionpathwaysandtransition
state theory, thequantitativedescriptionof catalytic efficiency of
the elements in the ammonia synthesis can be obtained. It thus
canpredict the catalytic efficiencyof alloy
systems[36,46].ResearchresultsontheCoMoNsystem[36,47]confirm that
the both theory and experience in the choice ofcatalyst are equally
useful. This impressive success
storiesshowthataccordingtothetargetreactionprocess,anewcatalystsystemcanbedesignedbaseonpuretheory[36,48].Thus,thediscoveryofnonferrousandalloycatalystswillonceagainpromotethedevelopmentofheterogeneouscatalysisscience.
Herein,thatweneedtoconcerniswhattheresearchmethods of discovery
and development of catalyst for ammoniasynthesis can give
inspiration to us. During the invention ofammonia synthesis
catalyst,Mittasch, etc. used test screeningmethod which relied on a
large number of experiments
andwasacompletelynovelapproachatthattime.Thatmethodissoeffective
thatpeople are still following it. Thediscoveryofcobalt molybdenum
nitride catalyst provide us with anothernew research method, which
means that catalyst can be designedbypure theory, includingthe
interpolation
intheperiodictabletodesigncatalysts.Withunderstandingthetheoreticalknowledgeandregularitiesofcatalyticscienceindepth,aswell
as accumulation of a lot of information and
experience,especiallywith the development of computer technology,
designofcatalystbasedonthetheoryandinthe"molecular"levelchangestobepossible.Inrecentyears,avarietyofexpertsystemstoassistthedesignofcatalystshavedeveloped[4952].
2.2.
PeculiarityoffusedFecatalystandinspirationsfromitstheoryandpractice
The catalytic chemistry in ammonia synthesis has specialcharm.
so that attracts the attention and interest frommany
chemists., Many famous physical chemist and catalytic scientists
at the present age, such asW.H. Nernst,W. Ostward,
F.Haber,C.Bosch,M.I.Temkin,G.Ertl,P.Emmett,A.Nielsen,H.Topse,G.A.Samorjai,
J.A.Dumesic, J.K.Norskov,M.Boudart ,etc. have been attended or
involved in research of
catalyticammoniasynthesis[5358],andpublishedanumberofmonographs[24,5962].Thisisbecausethefusedironcatalystshavesomespecialproperties.
(1)Inthedevelopmentofthechemicalindustryinthe20thcentury,thecatalyticammoniatechnologyplayedacriticalrole[63].Theimportanceofthisindustryassociatedwiththatpeoples
strong interest on understanding of important scientificvalue and
technological progress on the ammonia synthesiscatalyst.Typically,
thedevelopmentofnew
technologies,newmethodsandnewtheorywhichwererelativetocatalysisusuallystartedfromthisreactionsystem,orwerefirstappliedtothis
reaction system. Similarly,newdiscoveries in the fieldofcatalytic
synthesis of ammoniawere often extended to
othercatalyticfields.Thedevelopmentoffinecharacterizationtechniques,
dynamic analysis and new theoretical models
havegreatlypromotedtotheindepthunderstandingofthefoundationofammoniasynthesiscatalysts.
Evenbeingconstantlyimprovedforcenturies,thenatureoffused iron
catalyst stillunchanged.Todate, all studieson thesynthesis of
ammonia have been based on this catalyst.
Forexample,thecompletionofwellknownBETadsorptiontheoryon the iron
catalyst;method for determining the active
componentofthecatalystsurfacebyselectivechemicaladsorptioninventedbyP.
Emmett; theworkbasedonnitrogen
selectiveadsorptiononFe(111)crystalfacelaidthefoundationofmetalcluster
catalysis theorywhichgradually formed in the1980s;the important
assumption of "crystal surfacewith the largestligand number shows
the greatest catalytic activity" and theconceptof
structuresensitive reactionsproposedbyG.A.
Somorjai;theconceptofstoichiometricnumberwasproposedbyJ.Horiutitoverifythekineticsmechanismofammoniasynthesisreaction;M.I.Temkintheoryandhisfamousammoniasynthesiskineticequation,wasthefirstsuccessfullyemployedandisnowstillbeingusedindesignofindustrialreactors,andalsolaidthefoundationforheterogeneouscatalyticreactionkinetics.Thesetheoriesandconcepts,
ledthedevelopmentofaseriesofbasic theory, laidthe foundation
forheterogeneouscatalysisscience.Historyofammoniasynthesisreactionandthecatalystisamicrocosmofthehistoryofheterogeneouscatalysis.
Temkins theory of catalytic reaction kinetics on
nonuniformsurfacenotonlyhasbeenprovenbydataofoverallreactionkineticsonammoniasynthesisusingironcatalyst,butalsomore
importantly, perhaps, can induce some very useful anduniversal
results. For example, firstly, Temkin equation is re
Table2Comparisonofironcatalystsandrutheniumcatalysts.Catalysttype
Resource Manufacturingcost(103*Yuan/m3)
Conditions Energyconsumption(GJ/t)T/C P/MPa H2/N2
Fe abundant 30 350525(wide) 1030 23 ~27Ru/AC scarce 1600
325450(narrow) 10 2 ~27
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1624 HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640
ducedbasedonatwostepmechanismorthosecanbesimplifiedasatwostepmechanism,andnonuniformityofthecatalystsurfacecanusuallybetreatasauniformsurfaceinthekinetics
of catalysis. Therefore it can be applied to any type ofcatalytic
reactions. Secondly, as formultiple sites
adsorption,thelargedifferenceoncatalyticactivityfromdifferentcatalystsis
driven from themultiple reasoning to active site, which isextremely
important to thediscussionof the structural
sensitivityofheterogeneouscatalyticreactions.Thirdly,theconceptofdistributionfunctiononactivesiteisintroducedinthederivation
of the Temkin theory, which can induce manywellknown adsorption
isotherms such as Freundlich, FrumkinTemkinexpressionsandtheir
formulas,andother lawsofadsorption rate such as Elovich equation.
It can deduce
thatoptimumactivesiteorbestactivecatalystshouldhavemoderate
affinity value, which means energy distribution is in
thecenterofactivesitesof thesurface.Theseresults canbeconsidered as
the Sabatier principle which best catalyst can beeasily formed
sufficiently stablebutnot too stable intermediates[64].
These theories provide valuable information for catalysisstudy
that, the affinity valuemustbe changed inorder to
getthebestcatalyst.Forexample,thefollowingthreemethodscanbe used
for the metal catalysts: First, changing the
exposedcrystalsurfaceortheparticlesizetoalterthesurfacestructure,whichincludesthechangesoftherelativedistributionratioofatoms
on the surface with different coordination
numbers;Second,forminganalloy(e.g.,copperisaddedintonickel)oraddingsurfaceimpurities(e.g.,sulfur,carbon,oxygenornitrogen)tothemodifiedmetalcatalysts[9];Third,accordingperiodictabletochangesmetalcomponentsinthecatalystinorderto
select the best catalyst, such as the discovery of cobaltmolybdenum
nitride catalyst. To make this
approachmeaningful,itmustassumethatreactionmechanismdoesnotchange.However,whentheactivityofacatalystincreasestoacertain
level, the further increaseof
thembecomesverydifficult.Tobreakthroughthislevel,ithastofindadifferentreactionmechanism.
Practiceshowsthatthereisnootherreactionlikeammoniasynthesis
reaction, which can link the theories, models
andexperimentstogether.Theresultsobtainedinthelowpressureexperiments
canbe confirmedbyhighpressure
experiments;dynamicsresultingobtainedundertheultrahighvacuumconditioncanbeextrapolatedtotheindustrialconditions;studiesonasinglecrystalcanbedescribedbythetheory[44,65].Thissituationcannotonlybeenappliedtotheironcatalyst,butalsototherutheniumcatalystandCo3Mo3Ncatalyst.Moreover,therequiredtimetounderstandthesecatalysts
isgettingshorter,even though the structure and chemical composition
of catalystsbecomemore complex [13].Therefore, the catalytic
ammonia synthesis reaction is still an ideal model system
forstudyingtheoriesofheterogeneouscatalysis.
(2)Theammonia synthesis reaction isoneof the
simplestchemicalreactionswhichdoesntgenerateabyproductandisagreenchemicalreactionwith100%ofatomicutilization.Thecogeneration
of ammonia synthesiswith CO2 for urea or
ammoniumbicarbonateisacleanproductionprocesswithoutany
emission,whichisarareandmaturedindustrialtechnologyofcombining
theCO2 capture, storageanduse [66]; In industry,achieving the
ammonia synthesis reaction is one of
themostcomplexandtypicalchemicalprocess;Intheory,thereactionisable
to be completed at room temperature and
atmosphericpressurebutitpracticallyisverydifficulttobeachievedunlessat
high temperature and high pressure conditions.
Therefore,understanding the mechanism of the catalytic ammonia
synthesisreactionandconvertingit
intoaperfecttechnologyhasbeentheprimarystandardondevelopmentofcatalyticdomain.
(3) Themodern industrial iron catalysts are a
nanostructuredmetastablesubstance,which is
formedduringthesurprisinglycomplexsynthesisoftheoxideprecursor[67,68].Itsmetastabilityisalsothereasononsensitivityofoverheatstressgenerated
during the activation and oxidative activation ofmaterials. The
pathway to prepare nanostructures can be selected,
suchas,Fe3O4Fe1xO [6972], anda
seeminglyverysimplestructureoftheironcatalystisactuallyverycomplicated.Astartlingexampleisthatjustusingdifferentcatalystprecursors
causes a tremendous change in thenanostructuresofmetal
surface.Wustitebased catalyst has been
demonstratedtobemoreactivethanthemagnetitebasedcatalyst[23].Quantitativeanalysis[73]revealsthat,onlylessthan1%oftheironsurfaceof
the iron catalyst is involved in the
activationofnitrogen,andtheremaining99%oftheirononlyplaystheroleofa
support. If there can bemore exposed surface on iron, theactivityof
the catalystwill be greatly enhanced. For instance,scientists used
the iron catalyst as carrier, coated its
surfacewithnanoirontopreparecoatednanoironcatalyst.
(4)Ammoniasynthesiscatalystisthemoststablecatalystinallindustrialcatalysts.Thestructureofsuchmetastablematerialswithnanostructureisalmostunchangedevenbeingusedundertheharshreactionconditionsformorethan15years.Alotofresearchesandcharacterizationsregardingthispropertyhavebeenconducted,andmanymodelshavebeenproposedtoexplainthestabilityoftheactivesurfaceandmechanismofitsformation[10,55,7479].
(5)Thecatalyticsynthesisofammoniawhich
tightlyassociatedwithindustryisstillakeyreactionforcreatingnewlifeandaprototypemodelreactionthathelps
ingaininga fundamental understanding of catalysis in general and
therefore
ofconsiderablescientificandculturalimportance.Itismainlythisreasonthatdrivestheresearchinammoniasynthesisforward,especiallysinceevidenceforaknowledgebasedimprovementofacatalystwouldhaveastrongsignalingeffectonotherfieldsofcatalysisresearch[80].
For example, during ammonia synthesis process, from
thegasification, purification to the synthesis, the major
chemicalreactions are heterogeneous catalytic process, so the
catalystplays a very important role. Nine catalysts are used in
thesteam conversion ammonia synthesis byusingnatural gas ornaphtha
as rawmaterials,which includehydrocarbonhydrogenation catalyst,
steam reforming catalyst in first stage andsecond stage, high and
low temperature shift
catalyst,methanationcatalyst,ammoniasynthesiscatalyst,COselectiveoxidationcatalyst,etc.;thepartialoxidationprocessusingresidue
as rawmaterial and coal pressured gasification process
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HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640 1625
also use sulphurresistant CO shift catalysts, Claus sulfur
recoverycatalyst,CO2dehydrogenationcatalysts,variousdetoxification
catalyst and molecular sieve drying agents [81].Whichever the
ammonia synthesis process, shift catalyst
andammoniasynthesiscatalystareindispensableandarethecorecatalystinammoniaindustry.
This dozen of catalyst,most of them are basic catalysts
inotherchemicalprocesses,suchascoalchemical,petrochemical,naturalgaschemical,biochemical,energychemical,oilrefiningindustryaswellasenvironmentalprotectionandotherchemicalprocess.Inaddition,ammoniasynthesisindustryalsocontainsaseriesofhightechandcommonkeytechnologiesneedtobesolvedinemergingindustriesofstrategicimportance.Thecatalyticammoniasynthesisprocessitselfalsocontainsahugepotential
for energy saving. People will continue to improvethese catalysts.
Therefore, the development of synthetic ammonia catalysts will
promote the development of other
catalysts.Understandingammoniasynthesiscatalystsandprocesshasastronginspirationandreferenceonaseriesofcommon,keytechnologiesinthemodernchemicalindustry,energy,materials
and environmental protection fields, especially for energy saving
of traditional industries, modern coal chemicalindustry, hydrogen
production and clean energy and
otheremergingindustriesofstrategicimportance[82].
3.
ThechallengesoftheammoniasynthesiscatalystInthe21stcentury,ammoniasynthesiswascalledas"sun
setindustry".Somescientistsalsolamentallquietatthenitrogenfrontandthelowvisibilityofresearchinnitrogenfixationingeneral
[83]. In thisregard,
theGermanscientistR.Schlgl[13]publishedareportentitled"CatalyticSynthesisofAmmoniaANeverEndingStory?",pointedoutthestoryofcatalyticammoniasynthesisisneverover.
(1)Thenitrogencyclingisoneofmostimportantcyclinginnature to
sustain life on Earth. Ammonia is also an
essentialrawmaterialfortheoperationofmodernsociety,whichgivestheammoniaindustryexuberantvitality.Thesynthesisofthesematerials
requires ammonia as the activated state
nitrogen.Catalyticammoniasynthesisisanimportantpartofthenitrogencyclinginnature,alsoanimportantcomplementneededbyorganisms
(includinghumans), and currently theonlyway toobtain activated
state nitrogen in industrialscale. Currentlygenerating activated
state nitrogen through othermethods isstill only the subject of
scientific research. The production ofammonia requires the use of a
variety of carboncontainingfuels
toobtainH2gas,however,nomatterhowscarceenergysupplies and how
strict the environmental controls will be,the rigid demand for food
determines the ammonia industrymust relyon scientific and
technologicalprogress to face
thisgrimsituationandcontinueitsdevelopmentandpromotethecontinuousimprovementandinnovationonammoniasynthesiscatalyst
tomeet theneedsofhumansexistenceandsocialdevelopment.
Therefore,ammoniaindustryisanirreplaceabletraditionalindustrywithvitality.
(2)Ammoniaproductionofrawmaterialsandfuelsbothare
energy. Current global focuses on energy issues are
closelyrelativetotheammoniaindustry.TheemissionofCO2willalsobeseverelyrestrict,savingenergyandreducingemissionhavealways
been the major issues to the ammonia industry. Thecomprehensive
energy consumption of advanced ammoniaplant by using natural gas as
a raw material has reachedaround27.5GJ/t,with the process total
thermal efficiency
ofmorethan70%[84].Commercialironcatalystandrutheniumcatalyst both
can achieve the above benefits [85,86]. Any advancement in the
catalyst can improve the
thermodynamicefficiencyandreducethepriceoftheproduct[87].Itshouldbeemphasized
that, superficially, the energy loss mainly comesfrom the
transformation process and essentially should befrom synthesis of
ammonia. The power consumption
whichaccountsthetotalenergyconsumptionforabout30%ismainlyfortheserviceofsynthesis[88].Thehighpressureinammoniasynthesisisusedtoovercometheactivationbarrierofreaction,whichdependsonthecatalystactivity.Toovercomethisreaction
energy barrier we pay a how high price! Therefore, thedevelopment
of new catalyst for lowpressure ammonia synthesisismeaningful.
(3)HaberBoschnitrogenfixationprocessdoesnotinvolvetheuseofotherformsofenergyincatalyticreactions,suchaselectricenergy,lightenergy,etc.,neithertheroleofcatalystindifferentenergytransformation.Inrealityproductionpractice,thetransformationofotherformsofenergy,suchasthechemicalenergy,solar,wind,hydroandnuclearenergytransferringintoelectricenergy;orelectricenergy,lightenergytransferringintochemicalenergy;etc.issoextraordinarilyinteresting.
In the HaberBosch nitrogen fixation process which
usesheatenergyfromfossilfuelasthesoledrivingforce,evenintheammonia
plantwith themost advancedwaste heat
recoveryandcascadeutilizationofenergy(totalenergyefficiencyisupto74%),thereisnotonlymorethan20%oftheenergysavingpotential,butalsoconsumptionof
fossil fuels forat
least27.5GJ/tofenergy.Eveninthelimitstate(thetotalenergyefficiencyis100%),itstillhastoconsumefossilfuelsfor20.13GJ/tofenergy.
Therefore,theintroductionofelectricenergy,solarenergy,andradiationenergyintoammoniasynthesistoassisttheactivationofnitrogenmoleculeor
change the reactionpathways,and the study of the role of a catalyst
in the
transformationbetweendifferentformsofenergy,areinthepracticalandtheoreticalsignificance.
(4) As everyone knows, focus and difficulties of
catalyticchemistryresearchistheactivationofthemoststableofseveralsmallmoleculesinnature(CO2,H2O,CO,CH4,H2,N2,O2).Nitrogen
molecule is one of hardest activated elemental
substancesandchemicalbond.ThedissociationenergyofNNtriplebondisthe942kJ/mol,anditsbreakrequireshighenergy.Howtoactivatenitrogenmoleculeisakeytheoreticalissuestonitrogenfixation.Nitrogenmoleculehasalsobecomeoneofthe
prototype molecules in chemistry and catalysis
researchwithatypicalrepresentativesignificance.
(5)Thestandardequilibriumconstantofammoniasynthesisreactionat25Cisashighas6.8105.Therefore,theammoniasynthesisatroomtemperatureandunderatmospheric
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1626 HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640
pressure is theoretically possible, but the reaction rate is
almostimpossibletobedetected.Thisisanewchallenge.Sincenitrogen
fixation is important for human survival and development, achieving
ammonia synthesis atnormal
temperatureandpressurehasbeenthegoalwithrelentlesspursuitbyhumanbeings.
In summary, reducing energy consumption of the
existingammoniatechnology,lookingfornewwaysandmeansofammoniasynthesis,exploringthepossibilityofammoniasynthesisatnormaltemperatureandpressure,etc.,arethenewchallengesfacedbythecatalyticammoniatechnology.
Thekeytoachieveammoniasynthesisatnormaltemperature and pressure
is the activation of nitrogenmolecule
andformsandwaystoprovideenergy.
3.1. ActivationofnitrogenmoleculeThe process of converting the
free state of nitrogen in air
intonitrogencompoundsisknownasnitrogenfixation,includingchemicalandbiologicalnitrogenfixation.Therearemainlythreewaystochemicallyactivatenitrogenmolecule:
(1)Reductionmethod,byusingareducingagenttogiveN2electrons.
Catalytic ammonia synthesis belongs to reductionmethod.
(2) Oxidationmethod, by using an oxidizing agent to
taketheelectronsawayfromnitrogenmolecule.SincethefirstionizationenergyofN2ishigh,suchastrongoxidanthasnotbeenfoundtoformasuitablecatalyticcycle.
(3)physicalchemicalmethod(activationmethod),byusingstrongconditionssuchashighVoltwithdischarge,plasmaandotherphysicalmeanstoexcitetheN2moleculefromthegroundstatetothehighenergystate,oreventakeitaparttomakeitbecomeanitrogenatomoranitrogenioninordertoreactwithothersubstances.Forexample:arcmethodandcalciumcyanamidemethod
at early stage. Enormous energy consumptiongreatly limits the
industrialapplicationof these
twomethods.Inrecentyears,ammoniasynthesisbytheplasma[8992],themagnetic
induction method [93] and other studies are
alsoactive,buttheyarestillintheexploratorystage.
Thus, the catalytic reduction method occupies
undisputeddominance,whichisalsocurrentlytheonlyindustrialscaleofchemicalnitrogen
fixationmethod.Aftera long timeresearchand exploration, under the
catalysis of ruthenium
andFe1xObasedcatalysts,theinitialactivetemperatureofthecatalystscanbereducedtoabout200C[94].Forexample,intheindustrialprocessofhighpurityammonia,byusingZA5catalyst,undertheconditionsof8MPaofpressureandthereactiontemperatureattheinletandexitofreactoris215Cand363Crespectively,
thenetvalueofammonia is
themorethan10%,whichhasmettheeconomicrequirementfornetvalueofammonia
in industry, the key is the development of the
correspondinglowpressuresprocess.Butitisexpectedlydifficulttofurtherdevelophigheractivity
catalystunder lower temperatures.
Theresearchoncatalyticammoniasynthesis,whichlastsfora century,
is the study of the activation of N2 and its nature.Many kinds of
modern physicalchemical instruments have
beenusedtostudythemechanismofactivationofN2.However,sofar,itstilliscontroversialabouttheactivationofnitrogenonironcatalysts,which
is everbelonging
todissociativeadsorptionormolecularadsorption.Themostofexperimentssupportthedissociativeadsorption[70,9597].Forexample,toFecatalysts,G.Ertl[98]proposedamechanismofcatalyticammoniasynthesisreactionandpotentialenergydiagramofitsthermodynamicsandkineticsbasedonN2dissociativeadsorption(Fig.1).ThisisoneofrepresentativeachievementswhenG.ErtlwontheNobelPrizeinChemistryin2007[99].
M.Boudart[80]consideredthatFigure1gavealotofguidance.Toreallyunderstandthemechanismofcatalyticreaction,itshouldbeabletoprovideakindofthermalchemicalkineticprofiles
as clear as that of ammonia catalytic reaction
shownFig.1.Theoristsaretryingtocalculatealotofmissingenergyvalueoftheelementarystepsinthecatalyticcycle[100].
TherearealsomanyexperimentstosupporttheN2molecularadsorption[65,101106].Forexample,Liaoetal.[107,108]studied
bothmechanisms of ammonia synthesis, the
associativeandthedissociative,onironcatalystssurfacebyusingthemolecule
design system for heterogeneous catalysis basedonreactive
energetics, the Bond Order ConservationMorse Potential
(BOCMP)approachandantideuterium
isotopeeffect[109].Thecalculationsshowedthattheactivationenergybarrier
of ratedetermining step (rds) on associativemechanismwas below to
that of rds on dissociativemechanism, but theactivation energy
barrier of reaction was significantly
lowerthanthatofrdsondissociativemechanism.Itcouldbeinferredthattherearetwocompetingreactionpathwaysonthesurfaceoftheironcatalyst.
In the ammonia synthesis by using iron catalyst, the
stoichiometricnumberrdsofoverall
reactionandratedeterminingstepwhicharedetectedfromtransferofthechemicaltracers
canbeequal to1or2 (Fig.2).Bothvalueshavebeen
reportedintheexperimentalwork.Horiutietal.[110,111]foundthatrds=2nearequilibrium.Tanaka[112]
foundthatrdsofsynthesisreactionequals to2away
fromtheequilibrium,buttherdsofdecompositionreactionequalsto1.rds=2isgoodfor
the ratedetermining step in step2of Fig. 2(a), butmanyevidences
indicates that thenitrogenadsorption isratedetermining
step,whererds equals to1.However it
cannotdeterminewhethertheadsorptionisdissociationornotwhenrds=
Fig.1.Mechanismandpotentialenergydiagramofammoniasynthesisoniron[98].TheenergyisinkJ/mol.
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HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640 1627
1. It is conceivable that the reaction sequence shown in
Fig.2(b)exists,whereinthefirsttwostepsareconsideredtobethepathwaythroughwhichthenitrogenaserealizesnitrogenfixation.
If so,rds still equals to1.However, the evidenceon thedissociative
adsorption of nitrogen on iron catalyst is nowoverwhelming. The
dissociation on iron catalysts andnondissociation on the
nitrogenase respectively just
characterizeindustrialcatalysisathightemperatureandenzymecatalysisatlowtemperature.Therefore,inordertoimprovetheactivityoftheironcatalystonammoniasynthesis,itmayneedto
essentially change thenatureof each step in the
ironcatalyzedreactionsequence[10].
Thus,theproblems,suchastheactivatedformsofN2showninFigs.1and2,thebasicstepsofammoniasynthesisreactionand
the real structure etc., still containmany science
implies.Thenewandefficientmethodonactivationofnitrogenmoleculeisstillbeingexplored[57].Theactivationofnitrogenmoleculeisstillachallengeinchemistryandcatalysisscience,andstillhastheoreticalandpracticalsignificance.
3.2. Newchallengesintheoryofcatalyticammonia
Althoughtheheatvalueandtheeffectiveenergy(exergy)of
ammoniais21.29and20.13GJ/t,respectively,theactualenergy
consumption ismuchhigher. Sonomatterwhatmaterialsand process are
used to synthesize ammonia, the providedeffective energy cannot be
less than 20.13 GJ/t. In the HaberBosch process of nitrogen
fixation, because the
effectiveenergyvalueoftherawmaterialismorethaneffectiveenergyvalueoftheproduct,idealworkoftheprocessispositive.Eachproductionof1tonofsaturated
liquidammonia,
theoretically,isexternalworkprocess(Table3).Forexample,theammoniasynthesisprocessbyusingpureH2andN2asrawmaterialscanprovide0.63GJ/tofexternalwork,butdirectlyusingthewaterandairasrawmaterialsforthenitrogenfixationprocessmust
consumeexternalworkof20.31GJ/tatleast.Thecomparisonshows that
themain energy loss of the process derives fromextractions of
nitrogen in air and the hydrogen in water.Therefore, if other forms
of energy, such as
electric,lightenergy,etc.,canbeintroducedintonitrogenfixationprocesstotakethehydrogenoutofwater,thenthereactionpathwaycanbechanged.Althoughatleast20.31GJofelectricworkneeds
to be consumed, electric energy can be derived
fromrenewableenergysources,suchassolar,wind,hydroornuclearenergy.Ifnitrogenfixationprocessdonothavetousefossilfuels,thatwillbeacompletelyrevolutiontoammoniaindustry!
Therefore,introducingtheelectricenergy,solarenergy,etc.intonitrogen
fixationprocess, changing the reaction
pathwayorbiomimeticsynthesisisoneofthemajorchallengesthrowndowntocatalyticscientistsandhasgreattheoreticalandpracticalsignificance.
3.2.1. ThestudiesofelectrocatalysiscatalystsElectrocatalysis can
promote the thermodynamic non
spontaneousreactionN2+3H2O=2NH3+1.5O2(K298=10120)tooccurbyelectricenergy,thusexpandstheammoniasynthesisresearchfield;Italsoallowstheammoniasynthesisreactionwhichislimitedbytheequilibriumisnotorlessaffectedbythethermodynamicequilibrium.Therefore,theintroductionoftheelectricenergyintoammoniasynthesisprocesstoactivateactivationofnitrogenmoleculeor
change the
reactionpathwayhasbeenoneoftheconcernedresearchareas.Electrochemicalsynthesis
method has similar efficiency with that of existingmethods and is a
desirable method to synthesize ammoniaunder normal temperature and
pressure [114]. For
example,fortheelectrochemicalprocessofammoniasynthesisatahightemperature
(570 C) and atmospheric pressure, the
conversionofhydrogeniscloseto100%.Thus,inrecentyears,studiesof
electrochemical method for ammonia synthesis at normaltemperature
and pressure ammonia are also very active
Step
1 N2 + 2 * N2 *
2 N2 * + H2 *
3 N2H2 * + H2 N2H4*
2NH3 + *
N2 + 3H2 2NH3
4
i1
1
1
1
N2H2 *
N2H4 * + H2
Step
1 N2 + 2 * 2N *
2 N * + H * NH * + *
3 NH * + H * NH2 * + *
NH2 * + H * NH3 + 2 *
H2 + 2 * 2H *
N2 + 3H2 2NH3
4
5
i1
2
2
2
3
(a) (b)
Fig.2.ThemechanismsofN2dissociativeadsorption(a)andmolecularadsorption(b)andtheirstoichiometricnumber.
Table3Theoreticalenergyconsumptionofammoniasynthesis[113].Rawmaterial
Totalreactionequationofprocess H=Hv
Theoreticalenergyconsumptionofprocess(GJ/t)
Theoreticalenergyconsumptioofproduct(GJ/t)
Water,air H2O+N2NH3+O2 21.26 20.31 20.13Water,air,coal
C+H2O+(N2+O2)NH3+CO2 0.80 0.19 20.13Water,air,naturegas
CH4+H2O+(N2+O2)NH3+CO2 1.85 0.94 20.13Water,air,lightoil
C9H2O+H2O+(N2+O2)NH3+CO2 1.41 1.65 20.13PureH2andN2 H2+N2NH3 3.95
0.63 20.13
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1628 HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640
[115118].Themainelectrocatalystswhichhavebeenstudiedinclude
iron phthalocyanine catalystloaded gas diffusion electrodes,the
ceramic solid electrolyte and the molten salts(LiCl/KCl/CsCl) and
so on. Using solid electrolytes with highprotonconductivityat
roomtemperature to improve the current efficiency and the stability
of electrodes is an
importantdirectionforfutureresearchonelectrochemicalammoniasynthesis[87,119,120].
Lowcurrentefficiencyisthekeytoinfluencetheefficiencyandproductcostsofelectrochemicalammoniasynthesis.Withtheindepthstudyoftheelectrochemicalammoniasynthesis,ifcurrent
efficiency and conversion rates can be
significantlyimprovedsothatthecostoftheelectrochemicalammoniasynthesis
can be focused on consumption of electric energy,
theelectrochemical ammonia synthesis in the remote districts
ofsufficient
inelectricenergy,oreffectivelyconvertingsolarenergy,windandwaterenergyintoelectricityisexpectedtohaveitsplace.Especiallywhentheenergycrisisinthefutureleadstopricesofoil,naturegasandcoaletc.raisesharplywhichresultsincostsofHaberBoschammoniasynthesisgrowingexponentially,theelectrochemicalammoniasynthesiswillberegardedasausefulalternative.Therefore,thestudyofelectrochemicalammoniasynthesisstillhaspotentialapplication[115].
3.2.2. ResearchonphotocatalyticammoniasynthesiscatalystsThemost
familiarphotocatalyticreaction isnaturalphoto
synthesis:CO2+H2OCH2O+O2.Greenplantsabsorbsunlightbychlorophyll(photosensitizer),convertCO2andH2ObyplantenzymestocarbohydrateandreleaseO2.Photosynthesisisthemostimportantwaytoconvertsolarenergyintochemicalenergy.Themostcriticalstepincomplexprocessofphotosynthesis
is thesubstances inphotosyntheticreactioncenterabsorbphoto energy
to release electrons which are transferred
intocellstocausechemicalsynthesisreactionsothatsolarenergyisstoredup[121].
Atroomtemperatureandatmosphericpressureusingwaterasahydrogensourceandsolarenergyasenergy,aphotocatalyticwaytodirectly
transformthenitrogen inair
intoammonia:N2+3H2O2NH3+1.5O2,needtoresolvethesolarenergyinputandphotocatalystsofproblems.
These two reactions are both thermodynamically
nonspontaneousreactions,andN2isactivatedtheharderthanCO2,but their
photocatalysis are both theoretically
achievable.WhicheverthenaturalCO2reductionreactionorartificialwater
reduction (producing H2) and oxidation (producing
O2)reaction,isaverycomplexcatalyticprocessthatusuallyoccursthroughmultipleelectronspathway,
andcombinationsofelementaryreactions.MichelandDeisenhoferwhocowinnersoftheNobelPrizeinChemistryin1988[122,123]usedtheoretical
calculations to conclude that the common effect of asymmetric
nuclear Frankcondon factors and the electronic couplingis
likelythemainreasonforunidirectionelectrontransfer.Thestudyresultsofmechanismofphotosynthesisand
itscenter structure will provide inspiration for
photocatalyticammoniasynthesis.
The researchonphotocatalysishasmore than50yearsof
history [124].Most of the photocatalyst used as
thematerialhavingsemiconductorcharacteristics
,suchasdifferentseriesof metaldoped TiO2 and WO3 series [125], and
CdS/GaPPt,Fe2O3Nd2O3catalystandsoon[126132].Currentlypeopleareconstantlydevelopingmoreeffectivecatalystandthenewmethods
for ammonia synthesis at normal temperature andpressure [133135].
This shows that people are exploring tothislongtermgoal.
3.2.3.
Studiesonchemicalsimulationofnitrogenaseammoniasynthesis
Innature,thereisamicroorganism,whichcomprisesacatalystwith a
special abilitynitrogenase, that can directly
reducethenitrogeninairtoammoniaatnormaltemperatureandpressure
conditions. Its nitrogen fixation capacity is
thousandfoldofHaberBoschchemicalnitrogenfixationprocess.Itis
estimated that today the biological fixation of
nitrogenreached200milliontons,coveringabout48%ofthecombinednitrogen
in earth surface (the remaining 52% is provided
bycatalyticammoniasynthesis).Biologicalnitrogenfixation,bothitsrequiredconditionsandnitrogenfixationcapability,ismuchhigherthanchemicalnitrogenfixation.Biologicalnitrogenfixation
can be divided into biological and biomimetic
chemistrynitrogenfixation.
Biomimetic chemistry nitrogen fixation uses
chemicalmethodstosimulatethefunctionofnitrogenaseinvivotoprepare
fine chemical catalyst in order to achieve ammonia
synthesisatnormaltemperatureandpressure.Thisisachallengefacingcatalysisscientists.Itisboththeoreticallyandpracticallysignificanceonstudiesaboutmechanismofbiologicalnitrogenfixation.
It can provide an important basis for the chemicalsimulationof
biologicalnitrogen fixation.To achievenitrogenfixation by nitrogen
fixation microbes, there are three basicconditions [136]: (l)
nitrogenase; (2) MgATP2; (3) electrondonors, such as reduced
ferredoxin, reduced flavodoxin, orartificial Na2S2O4 to provide
electrons for N2 reduction. The1970s1980s,agroupofChinesescientists
ledbyfamousscientistsAoqingTang, Jiaxi Lu andQirui Cai indepthly
studiedthe nitrogenase and its chemical simulation [137], and
proposed amodel of the active center of the nitrogenase [138].After
continuous efforts of scientists around the world, thechemical
simulation of nitrogenase has been developed, andnitrogen
fixationmolecular genetics has been created, whichhave made
biological nitrogen fixation research
significantprogress.SincetheAmericanscholarReesetal[139143]clarifiedthethreedimensionalstructureofnitrogenaseactivecentralatomclustersandpolypeptidesaround,
thestudiesaboutchemical simulation of biological nitrogen fixation
are onceagain on the rise [144151]. Meanwhile, the development
ofselectiveenzymeswillbearichsourceofcatalystsfororganicchemistry
and biotechnology [152]. Although no
satisfactorypracticalresulthasbeenachievedsofar,
theresearchandexploration for biological nitrogen fixation and
biomimetic ammoniasynthesiswillnotbestopped.
In addition, in the biological azotobacter nitrogen
fixationmethod,mainlynonleguminouscropsareinoculatedbyrhizobiumusingbioengineeringtechnologyto
introducethenitro
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HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640 1629
genase genes and other related genes so that it can
achieveselfprovidednitrogen [153].With thedevelopmentofbreeding
transgenic technology to achieve nonleguminous
cropswithinoculationofrhizobiumforselfprovidednitrogenandalarge
number of planting leguminous and other oil
plants(nitrogencontaining 7%8%), and reducing the amount
ofchemicalnitrogenfertilizerisonewaytosolvenegativeeffectsof a lot
of fertilizer application in the agricultural production[154].
4. ConclusionsAmmonia synthesis in catalytic chemistry is
charismatic.
Fused iron catalysts have some special properties which
arebeyondcomparetoanumberofothercatalysts.Theammoniasynthesis
reaction of high industrial relevance is also a
keyreactionforcreatingnewlifeandaprototypicalmodelreactionthathelpsingainingafundamentalunderstandingofcatalysisin
general and therefore of considerable science and
cultureimportance.Understandingof themechanismof catalytic ammonia
synthesisandconverting it into theperfect technologyhas been a
basic standard in the catalytic domain,
especiallysinceevidenceforaknowledgebasedimprovementofacatalyst
would have a strong signaling effect on other fields ofcatalysis
research.Therefore, it is still an idealmodel
systemforheterogeneouscatalysisresearch.
Catalytic ammonia technology plays a central role in
thedevelopmentofthechemicalindustryinthe20thcentury.Humansneedfood,andfoodneedsnitrogen,sothestoryofcatalyticammonia
synthesis isneverend.Ammonia
isalsoanessentialrawmaterialfortheoperationofmodernsociety,whichgivesexuberantvitalitytoammoniaindustry,andwillcontinueto
promote the improvement and innovation on catalyst for
ammonia synthesis. In the 21st century, catalytic
ammoniatechnologywillfacenewchallengesintheoryandpracticeandinnewapplicationofammonia.Reducingtheenergyconsumptionofexistingcatalyticammoniasynthesistechnology,
introducing electric energy, light energy into ammonia
synthesisprocess,lookingfornewwaysofammoniasynthesis,exploringelectrocatalysis,
photocatalysis and chemical simulation
biologicalnitrogenfixationonammoniasynthesisatnormaltemperatureandpressureareconcernedresearchfield.
References
[1]
TimmB.In:Proceedingsof8thInternationalCongressonCatalysis.Vol.1.Weinheim:VerlagChemie,1984.I7
[2] HuXD. In: The15thNational Conference onCatalysis of
China.Guangzhou:SouthChinaUniversityofTechnology,2010
[3] Zhejiang
InstituteofChemicalEngineering.ChemFertilizerCatal,1979,1:1
[4]
XiangDH,LiuHY.HandbookofChemicalFertilizerCatalysts.Beijing:ChemIndPress,1992.226
[5]
WeiKM,WangR,ChenZZ,YeBH,ZhengQ,YuXJ.ChemFertilizerInd,1985,(3):10
[6] WeiKM,YuXJ,WangR,LinJX,WeiMD.IndCatal,1995,(3):14[7]
LinWM,HuangCR,GanSF,CaoBL,LiZP,ZhongHB.Guang
dongChemInd,1984,(2):6[8]
FigurskiMJ,ArabczykW,LendzionBielunZ,KaleczukRJ,Lenart
S.ApplCatalA,2003,247:9 [9]
PelkaR,KielbasaK,ArabczykW.CentEurJChem,2011,9:240
[10] LendzionBielun Z, Jedrzejewski R, Ekiert E, Arabczyk W.
ApplCatalA,2011,400:48
[11] YuXJ,LinBY,LinJX,WangR,WeiKM.JRareEarths,2008,26:711
[12] ZhengYF,LiuHZ,LiuZJ,LiXN. JSolidStateChem,2009,182:2385
[13] SchlglR.AngewChemIntEd,2003,42:2004
GraphicalAbstractChin.J.Catal.,2014,35:16191640
doi:10.1016/S18722067(14)601182Ammoniasynthesiscatalyst100years:Practice,enlightenmentandchallengeHuazhangLiu*ZhejiangUniversityofTechnology
0 2 4 6 8 10
12
14
16
18
20
22
400 oC
Fe1-xO
(N
H3)
/ %
Fe2+/Fe3+
Fe3O4
P = 15 MPa, SV = 30000 h1425 oC
Theachievementandprogressoftheammoniasynthesiscatalystsintheoryandpracticeduringabout100years,andanewchallengeinfaceofabiomimeticammoniasynthesispathatroomtemperatureandatmosphericpressure,includingelectrocatalysis,photocatalysisandbiocatalysis,arepresented.Understandingthemechanismandthetranslationoftheknowledgeintotechnicalperfectionhasbecomeafundamentalcriterionforscientificdevelopmentincatalysisresearch.
-
1630 HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640
[14] Pernicone N, Ferrero F, Rossetti I, Forni L, Canton P,
Riello P,FagherazziG,SignorettoM,PinnaF.ApplCatalA,2003,251:121
[15] Shen J. Chemical Fertilizer Engineering Series:
AmmoniaSynthesis.Beijing:ChemIndPress,2001.49
[16] LiuHZ,LiXN.SciChina(SerB),1995,38:529[17]
LiuHZ,LiXN,HuZN.ApplCatalA,1996,142:209[18]
LiuHZ,LiXN.IndEngChemRes,1997,36:335[19]
LiuHZ,LiXN.StudSurfSciCatal,2000,130:2207[20]
GuanS,LiuHZ.IndEngChemRes,2000,39:2891[21]
LiuHZ,LiuCB,LiXN,CenYQ.IndEngChemRes,2003,42:1347[22]
LendzionBielun Z, ArabczykW, FigurskiM.ApplCatalA, 2002,
227:255[23] PerniconeN.CATTECH,2003,7:196[24] Liu H Z. Ammonia
Synthesis Catalysts: Innovation and Practice.
Singapore:WorldSciPublishingCo.Ltd.,2013[25]
OzakiA,AikaK.In:AndersenJR,BoudartMeds.Catalysis,Science
andTechnology.Heidelberg:Springer,1985.88[26]
BielawaH,HinrichsenO,BirknerA,MuhlerM.AngewChemIntEd,
2001,40:1061[27] SudoM, IchikawaM, SomaM,OnishiT,TamaruK.
JPhysChem,
1969,73:1174[28] AikaK,HoriH,OzakiA.JCatal,1972,27:424[29]
WanXN,ZhuH,XiaWQ,LiuHZ.ChinJCatal,2000,21:276[30]
LiangCH,WeiZB,XinQ,LiC.ApplCatalA,2001,208:193[31]
WanLH,LinYJ,JiangJ,ChenHB,LinYZ,ChenSZ,LiaoDW.J
XiamenUniversity(NaturSci),1999,38:148[32]
LiuGZ,ZhengXL,XuJX,WeiKM.IndCatal,2004,12(6):44[33] Forni
L,Molinari D, Rossetti I, PerniconeN.ApplCatalA, 1999,
185:269[34]
RossettiI,PerniconeN,ForniL.ApplCatalA,2001,208:271[35]
BrownDE,EdmondsT, JoynerRW,McCarroll J J,TennisonSR.
CatalLett,2014,144:545[36]
JacobsenCJH,DahlS,ClausenBS,BahnS,LogadottirA,NrskovJ
K.JAmChemSoc,2001,123:8404[37]
KojimaR,AikaK.ApplCatalA,2001,219:141[38]
KojimaR,AikaK.ApplCatalA,2001,219:157[39]
KojimaR,AikaK.ApplCatalA,2001,218:121[40]
KojimaR,AikaK.ApplCatalA,2001,215:149[41]
KojimaR,AikaK.ChemLett,2000:514[42]
KojimaR,AikaK.ApplCatalA,2001,209:317[43]
KojimaR,AikaK.ChemLett,2000:912[44]
ErtlG.JVacSciTechnolA,1983,1:1247[45]
StronginDR,CarrazzaJ,BareSR,SomorjaiGA.JCatal,1987,103:
213[46] LogadottirA,RodTH,NorskovJK,HammerB,DahlS,JacobsenCJ
H.JCatal,2001,197:229[47] JacobsenCJH.ChemCommun,2000:1057[48]
ThomasJM,ZamaraevKI.AngewChemIntEd,1994,33:308[49]
ZhengQF.[PhDDissertation].Hangzhou:ZhejiangUnivTechnol,
2012[50] HechtD.DrugDevelopRes,2011,72:53[51] Horiguchi J,
Kobayashi S, Yamazaki Y, Nakanishi T, Itabashi D,
OmataK,YamadaM.ApplCatalA,2010,377:9[52]
HuangK,ZhanXL,ChenFQ,LDW.ChemEngSci,2003,58:81[53]
AparicioLM,DumesicJA.TopCatal,1994,1:233[54]
BoudartM.TopCatal,1994,1:405[55]
SomorjaiGA,MatererN.TopCatal,1994,1:215[56]
TamaruK.In:JenningsJRed.CatalyticAmmoniaSynthesis.New
York:PlenumPress,1991.Chapter1[57]
RosenthalD.PhysStatusSolidA,2011,208:1217[58] Nielsen A. An
Investigation on Promoted Iron Catalysts for the
SynthesisofAmmonia.3rdEd.Copenhagen:JulGjellerupsForlag,
1968[59]
AndersonJR,BoudartM.Catalysis,ScienceandTechnology.Ber
lin:SpringerVerlag,1983[60]
JenningsJR.CatalyticAmmoniaSynthesis,FundamentalandPrac
tice.NewYork:PlenumPress,1991[61]
AikaK,ChristiansenL.AmmoniaCatalysisandManufacture.Ber
lin:SpringerVerlag,1995[62] TopseH,BoudartM,Norskov JK.Ammonia
Synthesis andBe
yond.Amsterdam:BaltzerSciPublishers,1994[63]
JacobsenCJH,DahlS,HansenPL,TrnqvistE,JensenL,Topse
H,PripDV,MenshaugPB,ChorkendorffB.JMolCatalA,2000,163:19
[64]
BoudartM,DjegaMariadassouG.KineticsofHeterogeneousCatalyticReactions.Princeton:PricetonUnivPress,1984
[65] AlstrupI,ChorkendorffI,UllmannS.JCatal,1997,168:217[66]
Jing Y, Arons D J S. Resource, Energy, Environment, Socie
tyScientific and Engineering Principles for Circular
Economy.Beijing:ChemIndPress,2009
[67] SchlJgl R. In: Ertl G, KnJzinger H,Weitkamp J eds. Handbook
ofHeterogeneousCatalysis.Weinheim:WileyVCH,1997.1697
[68] HolmeB,SkaugsetP,TaftoJ.ApplCatalA,1997,162:149[69]
JedynakA,KowalczykZ,SzmigielD,ZielinskiJ.Pol JChem,2001,
75:1801[70] GuanS,LinHZ.IndEngChemRes,2000,39:2891[71]
JacobsenCJH,JiangJZ,MorupS,ClausenBS,TopsoeH.CatalLett,
1999,61:115[72]
YunusovSM,KalyuzhnayaES,MahapatraH,PuriVK,Likholobov
VA,ShurVB.JMolCatalA,1999,139:219[73]
LiuHZ,LiXN,ShzykiS,OhnishiR, IchikawaM. JChem IndEng
(China),2000,51:462[74] Arabczyk W, Narkiewicz U, Moszynski D.
Langmuir, 1999, 15:
5785[75] ArabczykW,NarkiewiczU,KaluckiK.Vacuum,1994,45:267[76]
SilvermanDC,BoudartM.JCatal,1982,77:208[77]
HolmeB,TaftJ.JCatal,1995,152:243[78]
ArabczykW,NarkiewiczU,MoszynskiD.ApplCatalA,1999,182:
379[79] HerzogB,HereinD,SchliSglR.ApplCatalA,1996,141:71[80]
BoudartM.TopCatal,2000,13:147[81] YuZH,ZhuBC,
ShenCDetal.ProcessAnalysis forLargeSyn
theticAmmoniaPlant.Beijing:ChinaPetrochemPress,1993[82]
LiuHZ.ChemIndEngProgr,2013,32:1995[83] LeighJ.ChemBr,2001,37:23[84]
DybkjaerI.In:NielsenAed.Ammonia,CatalysisandManufacture.
Heidelberg:Springer,1995.199[85]
MittaschA.ZElektrochemAmgewPhysChem,1930,36:569[86]
MittaschA.AdvCatal,1950,2:81[87]
MarnellosG,StoukidesM.Science,1998,282:98[88]
LiuHZ.ChemIndEngProgr,2011,30:1147[89] Mizushima T, Matsumoto K,
Ohkita H, Kakuta N. Plasma Chem
PlasmaProcess,2007,27:1[90]
YuanJH,ZhongXJ,TanSY.JChemIndEng,2008,29(4):7[91]
CarrascoE,JimnezRedondoM,TanarroI,HerreroVJ.PhysChem
ChemPhys,2011,13:19561[92]
KubotaY,KogaK,OhnoM,HaraT.PlasmaFusionRes,2010,5:042[93]
YahyaN,PuspitasariP,NoordinNH.DefectDiffusionForum,2013,
334335:329[94]
LiuHZ,HuZN,LiXN,CenYQ,FuGP.JChemIndEng(China),
2001,52:1063[95]
PorE,HaaseG,CitriO,KosloffR,AsscherM.ChemPhysLett,1991,
188:553[96] KatzG,KosloffR.JChemPhys,1995,103:9475
-
HuazhangLiu/ChineseJournalofCatalysis35(2014)16191640 1631
[97] VandervellHD,VaughKC.ChemPhysLett,1990,171:462[98]
ErtlG.CatalRevSciEng,1980,21:201[99]
ErtlG.AngewChemIntEd,2008,47:3524
[100] RappeAK,GoddardWA. In:TruhlarDGed.PotentialEnergySurfaces
andDynamics Calculations.NewYork: Plenum, 1981.661
[101]
MortensenJJ,HansenLB,HammerB,NrskovJK.JCatal,1999,182:479
[102] ShenHB,LiaoYY,ZhangHB,TsaiKR.ChinChemLett,1993,4:457
[103] ZhangHB,SchraderGL.JCatal,1986,99:461[104]
SpencerMS.CatalLett,1992,13:45[105]
SeiyamaT,TanabeK.Proceedingsofthe7thInternationalCon
gressonCatalysis.NitrogenFixation.Tokyo,1980[106]
BowkerW.TopCatal,1994,1:265[107]
SunJ,XuM,LiaoDW.ComputApplChem,2004,21:245[108]
HeiMJ,ChengHB,LinYJ,HongQ,LinYZ,YiJ,LiaoDW,TsaiK
R.JXiamenUniv(NaturSci),1997,36:879[109] Lin JD,
LiaoDW,ZhangHB,WanHL, TsaiKR.Chin JCatal,
2010,31:153[110]
EnomotoS,HoriutiJ.JResInstCatal(HokkaidoUniv),1953,2:
87[111] EnomotoS,Horiuti J. JRes InstCatal (HokkaidoUniv),
1954,3:
185[112] TanakaK.JResInstCatal(HokkaidoUniv),1966,13:119[113]
Liu H Z. Ammonia Synthesis Catalysts: Practice and Theory.
Beijing:ChemIndPress,2007[114]
RodTH,LogadottirA,NorskovJK.JChemPhys,2000,112:5343[115]
ZhangSY.ChemistryOnline,2001,c01005[116]
SkulasonE,BligaardT,GudmundsdottirS,StudtF,Rossmeisl J,
AbildPedersen F, VeggeT, JonssonH,Norskov
JK.PhysChemChemPhys,2012,14:1235
[117] CuiYC,LiuRQ.JXinjiangUniv,2010,27:473[118]
NeurockM.In:15thInternationalCongressonCatalysis.Munich,
Germany,2012[119]
MurakamiT,NohiraT,OgataYH,ItoY.ElectrochemSolidState
Lett,2005,8:E1[120]
YiokariCG,PitselisGE,PolydorosDG,KatsaounisAD,Vayenas
CG.JPhysChemA,2000,104:10600[121] MalatoS. In:15th
InternationalCongressonCatalysis.Munich,
Germany,2012[122] Deisenhofer
J,EppO,MikiK,HuberR,MichelH.Nature,1986,
318:618[123] MichelH,EppO,DeisenhoferJ.EMBOJ,1986,5:2445[124]
Herrmann J. In: 15th International Congress on Catalysis. Mu
nich,Germany,2012[125] MaedaK. In:15th
InternationalCongressonCatalysis.Munich,
Germany,2012[126]
XuHB,YangWS,GuoQ,DaiDX,ChenMD,YangXM.JAmChem
Soc,2013,135:10206
[127]
YamauchiM,AbeR,TsukudaT,KatoK,TakataM.JAmChemSoc,2011,133:1150
[128] NodaY,LeeB,DomenK,KondoJN.ChemMater,2008,20:5361[129]
RaoNN,DubeS,Manjubala,NatarajanP.ApplCatalB,1994,5:
33[130] IleperumaOA,TennakoneK,DissanayakeWDDP.ApplCatal,
1990,62:L1[131] SchrauzerGN,GuthTD.JAmChemSoc,1977,99:7189[132]
YamauchiM,AbeR.EPPatent2474356A1.2012[133]
DomenK.In:15thInternationalCongressonCatalysis.Munich,
Germany,2012[134] LiC. In:15th
InternationalCongressonCatalysis.Munich,Ger
many,2012[135]
PerianaR.In:15thInternationalCongressonCatalysis.Munich,
Germany,2012[136]
GroupofNitrogenFixationatJilinUniversity.ProgressinChem
icalSimulationofBiologicalNitrogenFixation.Beijing:SciPress,1973
[137] Research Group of Nitrogen Fixation at Fujian Institute of
theStructureofMatter,CAS.ProgressinChemicalSimulationofBiologicalNitrogenFixation.Beijing:SciPress,1976
[138]
ZhouTJ,WanHL,WangNQ,LiaoDW,TsaiKR.JXiamenUniv(NaturSci),1987,26:195
[139] WangYS,LiJL.ProgrNaturSci,2000,10:481[140]
KimJ,ReesDC.Nature,1992,360:553[141]
KimJ,ReesDC.Science,1992,257:1677[142] Howard
JB,ReesDC.Proceedingsof theNationalAcademyof
SciencesoftheUnitedStatesofAmerica.2006,103:17088[143]
ReesDC,TezcanFA,HaynesCA,WaltonMY,AndradeS,Einsle
O,HowardJB.PhilosophicalTransactionsoftheRoyalSocietyA,2005,363:971
[144]
HamiltonTL,LangeRK,BoydES,PetersJW.EnvironMicrobiology,2011,13:2204
[145] ChengQ.JIntegrativePlantBiology,2008,50:786[146]
TuczekF.NachrichtenausderChem,2006,54:1190[147]
deMatosNogueiraE,OlivaresFL,JapiassuJC,VilarC,VinagreF,
BaldaniJI,SilvaHemerlyA.PlantSci,2005,169:819[148]
StudtF,TuczekF.AngewChemIntEd,2005,44:5639[149]
DixonR,KahnD.NatureRevMicrobiol,2004,2:621[150]
GehringC,VlekPLG.BasicApplEcol,2004,5:567[151]
VintherFP.PlantSoil,1998,203:207[152]
ReetzMT.In:15thInternationalCongressonCatalysis.Munich,
Germany,2012[153] WangTF.ChemIndEngProgr,2001,(8):6[154]
WuHY.ChemEngDesign,2002,12(4):3
Pagenumbersrefertothecontentsintheprintversion,whichincludeboth
theEnglishandChinese versions of thepaper.The online
versiononlyhastheEnglishversion.ThepageswiththeChineseversionareonlyavailableintheprintversion.
Ammonia synthesis catalyst 100 years: Practice, enlightenment
and challenge1. The invention and enlightenment of ammonia
synthesis catalyst2. The development and enlightenment of ammonia
synthesis catalysts2.1. Development of ammonia synthesis
catalyst2.1.1. The discovery of Fe1xObased ammonia synthesis
catalyst2.1.2. The discovery of rutheniumbased catalysts for
ammonia synthesis2.1.3. The discovery of CoMo nitride catalyst for
ammonia synthesis
2.2. Peculiarity of fused Fe catalyst and inspirations from its
theory and practice
3. The challenges of the ammonia synthesis catalyst3.1.
Activation of nitrogen molecule3.2. New challenges in theory of
catalytic ammonia3.2.1. The studies of electrocatalysis
catalysts3.2.2. Research on photocatalytic ammonia synthesis
catalysts3.2.3. Studies on chemical simulation of nitrogenase
ammonia synthesis
4. ConclusionsReferences