Vapor-phase catalytic dehydration of butanediols to unsaturated alcohols over yttria-stabilized zirconia catalysts

Article abstract of DOI:10.1016/j.apcata.2019.02.013

Vapor-phase catalytic dehydration of butanediols (BDOs) such as 1,3-, 1,4-, and 2,3-butanediol was investigated over yttria-stabilized tetragonal zirconia (YSZ) catalysts as well as monoclinic zirconia (MZ). BDOs were converted to unsaturated alcohols with some by-products over YSZ and MZ. YSZ is superior to MZ for these reactions in a view point of selective formation of unsaturated alcohols. Calcination temperature of YSZ significantly affected the products selectivity as well as the conversion of BDOs: high selectivity to unsaturated alcohols was obtained over the YSZ calcined at high temperatures over 800 °C. In the conversion of 1,4-butanediol at 325 °C, the highest 3-buten-1-ol selectivity of 75.3% was obtained over the YSZ calcined at 1050 °C, whereas 2,3-butanediol was less reactive than the other BDOs. In the dehydration of 1,3-butanediol at 325 °C, in particular, it was found that a YSZ catalyst with a Y₂O₃ content of 3.2 wt.% exhibited an excellent stable catalytic activity: the highest selectivity to unsaturated alcohols such as 2-buten-1-ol and 3-buten-2-ol over 98% was obtained at a conversion of 66%. Structures of active sites for the dehydration of 1,3-butanediol were discussed using a crystal model of tetragonal ZrO₂ and a probable model structure of active site was proposed. The well-crystalized YSZ inevitably has oxygen defect sites on the most stable surface of tetragonal ZrO₂ (101). The defect site, which exposes three cations such as Zr⁴⁺ and Y³⁺, is surrounded by six O^2? anions. The selective dehydration of 1,3-butanediol to produce 3-buten-2-ol over the YSZ could be explained by tridentate interactions followed by sequential dehydration: the position-2 hydrogen is firstly abstracted by a basic O^2? anion and then the position-1 hydroxyl group is subsequently or simultaneously abstracted by an acidic Y³⁺ cation. Another OH group at position 3 plays an important role of anchoring 1,3-butanediol to the catalyst surface. Thus, the selective dehydration of 1,3-butanediol could proceed via the speculative base-acid-concerted mechanism.

Full text of DOI:10.1016/j.apcata.2019.02.013

Accepted Manuscript
Title: Vapor-phase catalytic dehydration of butanediols to
unsaturated alcohols over yttria-stabilized zirconia catalysts
Authors: Shota Ohtsuka, Takuma Nemoto, Rikako Yotsumoto,
Yasuhiro Yamada, Fumiya Sato, Ryoji Takahashi, Satoshi Sato
PII:
S0926-860X(19)30069-9
DOI:
Reference:
https://doi.org/10.1016/j.apcata.2019.02.013
APCATA 16983
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
9 October 2018
6 February 2019
9 February 2019
Please cite this article as: Ohtsuka S, Nemoto T, Yotsumoto R, Yamada Y, Sato F,
Takahashi R, Sato S, Vapor-phase catalytic dehydration of butanediols to unsaturated
alcohols over yttria-stabilized zirconia catalysts, Applied Catalysis A, General (2019),
https://doi.org/10.1016/j.apcata.2019.02.013
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A revisedmanuscriptfortheoriginalpapersubmittedtothejournalofAppliedCatalysisA:General
Re: APCATA-D-18-01983-R2
Vapor-phasecatalyticdehydrationofbutanediolstounsaturatedalcoholsover
yttria-stabilizedzirconiacatalysts
a
a
a
a
b
ShotaOhtsuka ,TakumaNemoto , RikakoYotsumoto ,YasuhiroYamada , FumiyaSato ,
b
a*
RyojiTakahashi ,SatoshiSato
a GraduateSchoolofEngineering,ChibaUniversity,Yayoi, Inage,Chiba, 263-8522, Japan
b GraduateSchoolofScienceandEngineering, EhimeUniversity, 2-5Bunkyocho, Matsuyama, Ehime,
790-8577, Japan
*
Correspondingauthor. Tel.+81432903376;Fax:+81432903401
E-mailaddress:satoshi@faculty.chiba-u.jp(S. Sato)
Graphical abstract
100
Selectivity to unsaturated alcohols
o
8
6
4
2
0
0
0
0
0
over Y-stabilized ZrO at 325 C
2
Conversion of 1,3-butanediol
O H
O H
O H
O H
H O
1
,3 -B u ta n ed io l
2 -B u ten -1 -o l 3 -B u ten -2 -o l 3 -B u ten -1 -o l
0
10
20
30
40
Time on stream / h
1

Highlights


Vapor-phasedehydrationofbutanediolswasstudiedoverY-stabilizedZrO
Unsaturatedalcoholswerepreferentiallyproducedinthedehydrationof1,3-butanedioloverY-stabilized
ZrO
CatalyticactivitywasgreatlyenhancedbycalcinationtemperatureofY-stabilizedZrO
2
catalystswithtetragonalphase.
2
.



2
catalysts.
o
Stable1,3-butanediolconversionwithhighunsaturatedalcoholsselectivityof96.9% wasobtainedat325 C.
Catalyticactivitywassensitivelydependentupontheflowrateofnitrogencarriergas.
Abstract
Vapor-phasecatalyticdehydrationofbutanediols(BDOs)suchas1,3-,1,4-,and2,3-butanediolwas
investigated over yttria-stabilized tetragonal zirconia (YSZ) catalysts as well as monoclinic zirconia (MZ).
BDOs were converted to unsaturated alcohols with some by-products over YSZ and MZ. YSZ is superior
to MZ for these reactions in a view point of selective formation of unsaturated alcohols. Calcination
temperature of YSZ significantly affected the products selectivity as well as the conversion of BDOs: high
o
selectivitytounsaturatedalcoholswasobtainedovertheYSZcalcinedathightemperaturesover800 C. In
o
the conversion of 1,4-butanediol at 325 C, the highest 3-buten-1-ol selectivity of 75.3% was obtained over
the YSZ calcined at 1050°C, whereas 2,3-butanediol was less reactive than the other BDOs. In the
o
dehydration of 1,3-butanediol at 325 C, in particular, it was found that a YSZcatalyst with a Y
2
O content
3
of3.2wt.%exhibitedanexcellentstablecatalyticactivity:thehighestselectivitytounsaturatedalcoholssuch
as 2-buten-1-ol and 3-buten-2-ol over 98% was obtained at a conversion of 66%. Structures of active sites
forthedehydrationof1,3-butanediolwerediscussedusingacrystalmodeloftetragonalZrO
2
andaprobable
modelstructureofactivesitewasproposed. Thewell-crystalizedYSZinevitablyhasoxygen defectsiteson
4+
themoststablesurfaceoftetragonalZrO (101).Thedefectsite,whichexposesthreecationssuchasZr and
2
3+
2-
Y , is surrounded by six O anions. The selective dehydration of 1,3-butanediol to produce 3-buten-2-ol
overtheYSZcouldbeexplainedbytridentateinteractionsfollowedbysequentialdehydration:theposition-
2-
2
hydrogen is firstlyabstracted bya basic O anion andthen the position-1 hydroxyl groupis subsequently
3+
orsimultaneouslyabstractedbyanacidicY cation.AnotherOHgroupat position3playsanimportantrole
2

of anchoring 1,3-butanediol to the catalyst surface. Thus, the selective dehydration of 1,3-butanediol could
proceedviathespeculativebase-acid-concertedmechanism.
Keywords:yttria-stabilizedzirconia;tetragonalphase;dehydration;butanediols;unsaturatedalcohols.
3

1. Introduction
It is well known that pure zirconia exhibits three polymorphs such as monoclinic, tetragonal, and
cubicphases[1].Themonoclinic,tetragonal,andcubicphasesarethermodynamicallystableatatemperature
of <1170 °C, 1170-2370 °C, and 2370-2680 °C (melting point), respectively. Because the phase transition
among these phases is reversible, the structures of high-temperature phases cannot be maintained at room
temperature. In addition, the phase transition from monoclinic to tetragonal causes large density change.
Therefore, pureZrO cannotbeused forhigh-temperatureapplications. Thetetragonaland thecubicphases
2
3+
3+
3+
2+
canbestabilizedbytheadditionofappropriatealiovalentcations, suchasY ,Sc , La , Ca , andsoon, at
the temperatures below melting point [2]. Among them, yttria-stabilized zirconia (YSZ) is widely used as
oxygen sensor, thermal barrier coatings, and solid oxide electrolyte ceramics due to the excellent strength,
thermalstability,andionicconductivityathightemperature[3-5].SinceYSZhasuniqueacid-basecharacter
and oxygen ion conductivity [6,7], it has been recently used as catalysts and catalyst supports for several
reactions: YSZ effectively works as a catalyst for the ketonization of carboxylic acid [6] and ethanol-to-
propylenereaction[7].
Unsaturatedalcohols(UOLs)such as3-buten-1-ol(3B1ol), 2-buten-1-ol(2B1ol), and3-buten-2-ol
(3B2ol) are currently manufactured from fossil-based feedstock. UOLs are valuable intermediates for the
synthesisofmedicaldrugs, agriculturalchemicals, andfunctionalpolymers[8-12]. UOLs arealsoproposed
asanintermediateforthesynthesisof1,3-butadiene,whichisanimportantbulkchemicalusedforproducing
rubbers and polymers [13-15]. 1,3-Butadiene is presently manufactured through the naphtha cracking. The
supply of 1,3-butadiene has been influenced by the unstable price of crude oil as well as the increment of
shalegas foradecade. Therefore, alternativeroutes forproducing1,3-butadieneareexpected. Torealizethe
low-carbon society via reducing the use of fossil sources, it is important that useful chemicals, as well as
energy, areproducedfromrecyclableresourcesofbiomass[14]. Butanediols(BDOs) suchas2,3-, 1,3-and
1
,4-butanediolscouldhavebeenformedfrombiomassthroughfermentation[16,17]. Inthesesituations,we
havestudied thevapor-phasecatalyticdehydrationofBDOstoUOLsoversolidcatalysts[18-31].
We have previously found that rare earth oxides such as CeO , Er , and Yb catalysts are
2
2
O
3
O
2 3
effectivefortheselectiveconversionofBDOstoUOLs[18-23]. Forthesereactions,thecrystallinephaseof
theoxides is oneoftheimportant factors fortheir catalytic activityandselectivityto eachproduct. Wehave
4

revealedthatthecatalyticactivityofrareearthoxidesforthedehydrationof1,3-butanediol(1,3-BDO)greatly
dependsonthecrystallinephaseaswellasthecrystallinesize[20]. Intheoreticalinvestigations[21,22],about
CeO
2
whichis especiallyeffectiveforthedehydrationof1,3-BDO, oxygendefectsitesonthecubicfluorite
(111) facets work as adsorption sites. In the dehydration of BDOs to UOLs, ZrO [24-26] and base-
CeO
2
2
modifiedZrO
et al. reported that 3B1ol selectivity of 68.9% at a 1,4-BDO conversion of 94.6% was obtained over CaO
supported on ZrO aerogel catalyst [32]. In thereport, monoclinicandtetragonal phases coexist in theCaO-
2
[27-32]arealsoeffectiveasacatalyst. Inthedehydrationof1,4-butanediol(1,4-BDO),Zhang
2
ZrO catalyst. In our previous work, a high 3B1ol selectivity of 89% at a 1,4-BDO conversion of 68% is
2
reported over CaO supported on monoclinic zirconia (MZ) catalyst, which prepared by an impregnation
method (CaO/MZ)[30]. In the activeCaO/MZ catalysts calcinedhigherthan 700 °C, a small diffraction of
2+
tetragonal ZrO
2
phase was observed with the major monoclinic one. It is considered that Ca diffused into
o
ZrO
2
latticeuponcalcinationover700 Cwiththechangeincrystalphasetotetragonal.
InthedehydrationofBDOsoverthemodifiedZrO
2
,itissuggestedthatthecrystallinephaseofZrO
2
isanimportantfactorfortheactivationofBDOsinthecatalyticdehydration.However,itisstillunclearwhich
crystalline phase is effective for these reactions. Therefore, in this paper, we examined the dehydration of
BDOssuchas1,3-,1,4-,and2,3-BDOs(Scheme1) overZrO
2
andyttria-stabilizedZrO
2
toclarifytheactive
crystallinephaseofZrO forthesereactions,inadditiontothedehydrationof1,5-pentanediol(1,5-PDO).We
2
alsodiscussedtheactivesitesforthedehydrationof1,3-BDOandthereactionmechanism.
O H
O H
O H
O H
H O
1
,3 -B D O
2 B 1 o l
3 B 2 o l
3 B 1 o l
O
O H
O H
H O
1
,4 -B D O
3 B 1 o l
T H F
5

O H
O H
O
O
O H
,3 -B D O
2
3 B 2 o l
bu tano ne
2 -m ethylp ro p anal
Scheme1Dehydrationofbutanediols.
2
. Experimental
.1Samples
ZrO(NO
2
3
)
2
·2H
2
O was purchased from Wako Pure Chemicals Industries, Ltd., and Y(NO
3
)
3
·5H O
2
was purchased from Sigma-Aldrich. A monocliniczirconia(MZ) and yttria-stabilizedzirconias with Y
2 3
O
contents of 3.2 and 13.8 wt.% (YSZ) were supplied by Daiichi Kigenso Kagaku Kogyo Co., Ltd., Japan.
The samples calcined in air at a prescribed temperature for 3 h wereused for the reactions. Hereafter, YSZ
samples with Y
2
O
3
contents of 3.2 and 13.8 wt.%, which correspond to 3.5 and 14.8 mol%, are expressed
o
as 3YSZ-T and 14YSZ-T, respectively, where T is the calcination temperature of the sample ( C). MZ-T
o
alsorepresentsMZsamplecalcinedatT C.
Another series of Y-contained ZrO
solution of ZrO(NO ·2H O and Y(NO
example,0.368gofY(NO ·5H Oand5.89gZrO(NO
2
was prepared through a hydrothermal (HT) process using a
·5H O. In the preparation of 3 mol% Y-containing ZrO , for
Oweredissolvedin20cm ofdistilledwater.
3
)
2
2
3
)
3
2
2
3
3
)
3
2
3
)
2
·2H
2
Then, pHvalueofthesolutionwas adjustedto10with25wt.%ammoniawater understirringwithout any
3
additivessuchasamine,fattyacid,andalcohol.Afterthesolutionhadbeentransferredinto100cm Teflon-
o
lined autoclave, HTtreatment was performed at 200 C for 24 h. The resulting precipitatewas centrifuged,
o
o
then washed, and dried at 110 C for 18 h, and calcined at 900 C for 3 h. Here, the Y-contained ZrO
2
is
namedasHT-ZrO
2
.
Reactantchemicalssuchas1,3-BDO,1,4-BDO,2,3-BDO,and1,5-PDOwerepurchasedfromWako
Pure Chemical Industries, Ltd., Japan. They were used for the catalytic reaction without any further
purification.
6

2.2Vapor-phasecatalyticreactions
The vapor-phase catalytic reaction was carried out in a fixed-bed flow reactor under an atmospheric
3
-1
o
pressure of N
2
carrier gas with a flow rate of30 cm min at atemperature between300 and 375 C. After
thecatalysthadbeenheatedinanN
2
flowattheprescribedreactiontemperaturefor1h, areactantBDOwas
-1
fed into the reactor at a liquid feed rate of 1.60 g h . The liquid effluent was collected in a dry ice-acetone
trap every hour. The products were identified by gas chromatography (GC) with a mass spectrometer
(GCMS-QP5050A, Shimadzu) with a capillary column (DB-WAX, a length of 30 m, JW Scientific), and
the quantitative analysis of the products was performed by a GC (FID GC-8A, Shimadzu) with a capillary
column (Inert Cap WAX-HT, an inner diameter of 0.53 mm and a length of 30 m, GL-Science). The
gaseousproducts wereanalyzed byanotherGC (TCDGC-8A, Shimadzu)withapackedcolumn(VZ-7, a
length of6 m, GL-Science). The catalytic reactionwas typicallycarriedout for5h toassurethestabilityof
catalytic activity. All the catalysts showed little decay in the initial period of 1 h so that we evaluated the
catalytic activitybyaveraging the data of conversion and selectivityin the initial 1-5 h excluding the first 1
h. Theselectivitytoeachproductwasdefinedasmol%.
2.3Characterizationofcatalysts
The Y content in HT-ZrO
2
samples was measured by X-ray Fluorescence (XRF) analysis using
EDX-900HS (Shimadzu). The continuous scanning X-ray diffraction (XRD) patterns were recorded on
New D8 ADVANCE (Bruker) using Cu Kα radiation (λ=0.154 nm) to identify the crystal phase of each
catalyst. The specific surface area (SA) of catalyst was calculated by the Brunauer-Emmett-Teller (BET)
o
method using the N
2
isotherm at -196 C. The thermogravimetry (TG) analysis of samples was carried out
usingThermoplus8120E2(Rigaku)fromtheroomtemperatureto900 °C atarateoftemperatureincrement
o
−1
of 5 Cmin .
To estimate the basicity of the catalysts, temperature-programmed desorption (TPD) profiles of
adsorbed CO were measured by a self-made apparatus using the change in the conductivity of 1/1000 N
2
NaOH solution, into which the desorbed CO
2
was bubbled with N
2
carrier gas [26, 29]. The measurement
adsorption at room temperature
o
conditions are the following: preheating the sample at 500 C for 1 h; CO
2
for 72 h; desorption temperatures controlled from the room temperature to 700 °C at a rate of temperature
7

o
−1
increment of 10 Cmin . The amounts ofbasicsites wereestimatedfrom neutralization-titration curves of
thedilutedNaOHsolution.
Toestimatetheacidityofthecatalysts,TPDofadsorbedNH
3
wasalsoperformedusingBELCATII
(Microtrac BEL Corp.) with thermal conductivity detector (TCD). The measurement conditions are the
o
o
following:preheatingthesampleat500 Cfor1h;NH
3
adsorptionat 100 Cfor1h;desorptiontemperatures
o
−1
controlledfrom 100 to 800 °C at an increment rateof 10 C min . TheTCD detector candetect water and
other gases such as oxygen as well as NH
3
iftheyaredesorbed from thecatalyst. Thus, we also performed
o
TPD experiment for the sample only preheated at 500 C without NH
3
adsorption as a blank profile. A
-TPD profile. The
-TPDprofileasafunctionoftemperature.
difference profile of TPD between NH
3
adsorption and the blank was adapted as a NH
3
amountsofacidicsiteswereestimatedfromtheintegraloftheNH
3
3. Resultsanddiscussion
3
.1. HT-ZrO catalystswithdifferentYcontents
2
2
In preliminary catalytic tests of Y-containing ZrO , an HT process was adapted to obtain well-
crystalized oxide particles of ZrO . Fig. 1 shows XRD profiles of HT-ZrO
2
2
catalysts with different Y
o
contents,whichwerecalcinedat900 C. ThecrystalstructureofZrO
2
withoutYshowedonlyamonoclinic
phase. A tetragonal phase of ZrO
andonlyatetragonalphaseexistedatYcontentshigherthan4mol%. Table1showsthecatalyticconversion
of1,3-BDOovertheHT-ZrO catalystswithdifferentYcontents.Thecatalystsampleshadarelativelyhigh
2
increased with increasing Y content, the monoclinic phase disappeared
2
2
-1
o
specificsurfaceareaof 10-35m g evenaftercalcinationat900 C. Theyshoweddifferentcatalyticactivity
depending on Y content. At Y content of 0 mol%, the monoclinic ZrO showed a low conversion and the
2
lowestselectivitytoUOLs.ThecatalyticactivitywasincreasedwithincreasingYcontentovertheHT-ZrO
2
catalysts:theselectivitytoUOLswasmaximizedataYcontentof3mol%,andtheconversionof1,3-BDO
was maximized at aYcontent of6mol%. Therefore, thecrystal phaseandthespecificsurfaceareaofHT-
ZrO
2
catalystsvariedwithYcontent, andalsotheircatalyticperformancevaried.
o
In the HT process followed by the calcination at 900 C, we confirmed that a well-crystalized
tetragonalzirconiawasobtainedwiththeyttriastabilizer. Indeed, Yspeciescouldbedispersedintozirconia
8

crystal lattice with the transformation. Then, in the following sections, we investigated effect of calcination
temperatureonthecommerciallyavailable3YSZand14YSZtogetherwithaMZcatalyst.
3
.2.Physicalpropertiesof3YSZ, 14YSZandMZcatalysts
In the present work, 3YSZ and 14YSZ samples as well as MZ sample were calcined at different
temperatures. Table 2 summarizes specific surface area (SA) of ZrO catalysts calculated by the BET
2
method. The specific surface area of these samples decreased with increasing the calcination temperature.
The specific surface area of 3YSZ-800 was about twice as large as MZ-800. Particle size, dBET, was
calculatedbythefollowingequationassumingthattheparticlewas a sphere: dBET = 6/(ρ×SA), whereρwas
a density of ZrO . Comparing the values of YSZs and MZ calcined at the same temperature, YSZs have a
2
smallerparticlesizeandalargerspecificsurfaceareathanMZdoes.
Fig. 2 shows the continuous scanning XRDpatterns of the YSZs calcined at various temperatures
as well as MZ. There is no obvious change in diffraction pattern by calcination for both YSZs and MZ
samples (profiles for MZ-600 and MZ-1000 not shown), while the diffraction peaks become sharp and
strong. This means the growth of crystallites in the samples bycalcination. In order to clarify the crystal
structuresofYSZ,weperformedRietveldrefinementforstepscanningXRDpatternsof3YSZand14YSZ
o
samples calcined at 1000 C. Fig. S1 and Table S1in supplementaryinformationshow therefined results.
Allpeaksintheprofileof3YSZ-1000and14YSZ-1000samples(Fig.S1) wereindexedastetragonalYSZ
phase(spacegroup:P4
inwhicha cubicphaseextendsinadirectiontoward[001],whilethatof14YSZisextremelyclosetocubic
phase (F m -3 m, No. 225). No diffractions assigned to other crystal phases such as Y was observed.
IndexesshowninFig.2areassignedfromtheRietveldrefinement(Fig.S1andTableS1).
2
/nmc,No.137-2).Therefinedstructureoftetragonalphasein3YSZisatypicalYSZ,
O
2 3
Aparticlesize,dXRD, wascalculatedfromthefullwidthathalfmaximumbySherrerformula,dXRD
Kλ/(βcosθ), where K (=0.9), λ, β, and θ are shape factor, X-ray wavelength, full width at half maximum,
=
and Bragg’s diffraction angle, respectively. The calculated dXRD values are also listed in Table 2. The
crystallite size simply increased as the calcination temperature increased. The crystallite size, dXRD, well
agrees with the particle size, dBET (Table 2), so that the individual catalyst particles are composed of a
crystallite. Fig. S2 displays the TEM images of 3YSZ samples calcined at different temperatures. The as-
9

o
received3YSZand3YSZcalcinedat800and1000 Chadtheparticlesizeof10-20,15-30, and40-50nm,
respectively. These sizes are consistent with the results shown in Table 2, indicating that the particles
observed in TEM indicate the primary particles. There is no clear difference in the shape of the particles
amongthem.
Fig. 3a depicts the TPD profiles of CO
2
adsorbed on 3YSZ calcined at different temperatures
together with MZ-800. It can be seen that the amount of basic sites simply decreases with increasing the
calcination temperature as the specific surface area decreases. Fig. S3 depicts the TPD profiles of NH
3
adsorbed on 3YSZ and MZ-800 with and without NH adsorption. Because the NH -TPD used a TCD
3
3
detector, waterand othergases suchas oxygen canbedetectediftheyare adsorbed. Inthesamples without
o
NH
3
adsorption(Fig.S3),abroaddesorptionsignalobservedattemperaturesof400-800 Cwascomposed
of water, whichdisappeared inanindividualexperimentafterthedesorbedgashadbeenflowedinazeolite
filterforH Oremoval.Thus,thebroadpeakintheblankTPDwasconfirmedtobeattributedfromthewater
2
desorbed from the catalyst sample. Fig. 3b depicts the NH -TPD profiles obtained from the difference
3
profiles for 3YSZ and MZ-800. The amounts of basic and acidic sites are also summarized in Table 2
together with the density of basic and acidic sites. Their amounts varied with the calcination temperature.
ThebasedensityofYSZcatalystsisalmostconstant, andthisindicatesthatthesurfacedensityofbasicsites
isindependentofthecalcinationtemperature.ThiswillbediscussedintheSection3.5.
3.3. DehydrationofseveralbutanediolsoverYSZandMZcatalysts
In the dehydration of 1,3-BDO at 325°C, the conversion of 1,3-BDO and the selectivity to UOLs
were changed with calcination temperature (Fig. 4). Details of the selectivityto each product were listed in
the supplemental information of Table S2. A maximum value of the 1,3-BDO conversion was obtained
over 3YSZ-900. In 3YSZ samples, the selectivity to UOLs became higher as the calcination temperature
o
increased up to 900 C, and then became almost constant at calcination temperatures higher than 900°C. It
is notedthat ahigh temperatureof900°C, which had thehighest aciddensity(Table2), wouldberequired
toconstructtheactivecentersonthe3YSZ.Athigherthan900°C ofcalcination,theconversionof1,3-BDO
decreased with increasing the calcination temperature due to the decrease of the specific surface area. In
o
1
4YSZsamples,amaximumconversionwasobtainedatcalcinationof800 C.Changesincatalyticactivity
1
0

of3YSZand14YSZwithcalcinationtemperatureweresimilartoeachother, while3YSZshowedslightly
higher selectivity. The highest selectivity to UOLs of 97.6% was obtained at the 1,3-BDO conversion of
62.4% over 3YSZ-900. In contrast, no significant increment was observed in both the selectivity to UOLs
as well as the 1,3-BDO conversion for the MZ samples. As for the by-products through dehydrogenation
such as butanone and 3-buten-2-one (Table S2), the selectivity to these products over YSZ samples
decreased with increasing the calcination temperature. The calcination at high temperatures reduces the
dehydrogenation ability of YSZ samples so that the dehydration ability is enhanced at high calcination
temperatures.
Fig. 5 shows the changes in the catalytic activity of YSZ and MZ catalysts for the dehydration of
1,4-BDOwithcalcinationtemperature.Inasimilarlywaytothe1,3-BDOconversion,theconversionof1,4-
BDO and selectivity to 3B1ol over 3YSZ were changed with calcination temperature, while details of the
selectivity are summarized in Table S3. The selectivity to 3B1ol increased with increasing the calcination
temperature,whiletheselectivitytoTHFdecreased.Theconversionof1,4-BDOdecreasedwithincreasing
thecalcinationtemperature, becauseofthedecreaseinspecificsurfacearea. In thecomparisonoftetragonal
and monoclinic zirconia calcined at 500 °C, we had considered that MZ was more effective than YSZ for
the dehydration of 1,4-BDO [27]. But the catalytic activity of 3YSZ, as well as 14YSZ, was drastically
changedbycalcination,anditwasfoundthat3YSZand14YSZcatalysts weremoreeffectivefortheUORs
productionthanMZwhentheywerecalcinedattemperatureshigherthan750°C.Itissuggestedthat3YSZ
and 14YSZ are superior to MZ as a catalyst for this reaction. In the dehydration of 1,4-BDO, 3YSZ and
14YSZshowa similarchangeinthecatalyticactivitywithcalcinationtemperature,but3YSZshowsaslight
highselectivity.Thehighestselectivityto3B1olof75.3%wasobtainedatthe1,4-BDOconversionof26.1%
over3YSZ-1050.Inourpreviouswork,a high3B1olselectivityof89%atthe1,4-BDOconversionof68%
was obtained overCaO/MZ[30]. Forthedehydration of1,4-BDO, the activityof3YSZis not sufficient at
all, whereas it is suggested that 3YSZ is promising as catalyst support for CaO. Since monoclinic and
tetragonal phases coexist in the CaO/MZ [30], further improvement of activity would be expected by
unifyingthecatalystsurfacetoa tetragonalphasewhichwasadvantageousforthedehydrationof1,4-BDO.
WewillexaminethecatalyticactivityofCaO-supportedonYSZnearfuture.
1
1

Table3showstheeffectofcalcinationtemperatureofZrO catalystsinthedehydrationof2,3-BDO.
2
No such drastic changes as shown in Figs. 4 and 5 was observed in the dehydration of 2,3-BDO.
Furthermore, the reactivity of 2,3-BDO over 3YSZ, 14YSZ, and MZ catalysts at 325 °C was lower than
those of the other butanediols. In the dehydration of 2,3-BDO, 14YSZ was superior to 3YSZ and MZ in
termsofthe3B2olselectivity.Furthermore,asfortheselectivitytoeachproduct,theselectivitytoacetoinas
a dehydrogenated product was almost constant, whichis different from thefact inthe reaction of 1,3-BDO
that thedehydrogenated products over YSZsamples decreasedwithincreasingthecalcinationtemperature
(TableS2). In addition, in thedehydrationof1,5-PDO, as showninTableS4, thereactivityof 1,5-PDOis
quite similar to that of 2,3-BDO. This suggests that effective phase of ZrO is different depending on the
2
position of OH group of BDOs, and that the mechanism of the dehydration of 2,3-BDO and 1,5-PDO is
differentfromthat of1,3-BDOand1,4-BDO.
Fig. 6 shows the changes in theformation rateofUOLs perunit surfaceareainthedehydrationof
BDOs as well as 1,5-PDO with calcination temperature. The formation rate of UOLs per unit surface area
canbedefinedastheintrinsicactivityofcatalystsample. In thedehydrationof1,3-BDOand1,4-BDOover
YSZcatalysts,theformationratesofUOLsincreasedwithincreasingthecalcinationtemperatureofYSZin
a similar way. In contrast, in the dehydration of 2,3-BDO and 1,5-PDO over YSZ, the formation rate
remainedalmostunchangedevenwhenthecalcinationtemperaturewasincreased. In thedehydrationof1,5-
PDO,we havereportedthatMgO/MZismoreeffectivethanCaO/MZ[33]. Nemecetal.havereportedthat
2+
a cation with an ionic radius smaller than zirconium such as Mg is hard to dissolve in zirconia and to
stabilize the tetragonal phase when it is added into zirconia [34]. The addition of Mg into zirconia makes it
difficultforthetetragonalstructuretobestabilizedascomparedwiththeadditionofCaintheXRDpatterns.
For the dehydration of 2,3-BDO, we reported that BaO/MZ and CaO/MZ were effective [31]. These are
additiveelementsthatcouldstabilizeeithertetragonalorcubicphase. 14YSZwasbetterthanMZand3YSZ
intermsoftheformationrateof3B2olinthedehydrationof2,3-BDO.Sincethecrystallinephaseof14YSZ
is tetragonal, which is close to cubic, cubic zirconia could also improve the catalytic activity. There is still
roomfordiscussiononthedehydrationof2,3-BDO.
Fig. 7summarizes anintrinsicactivityofYSZ-900andMZ-600aswellastheselectivitytoUOLs
compared with other catalysts reported in the conversion of 1,3-BDO. CeO shows the highest formation
2
1
2

rate of UOLs [19-20] with a selectivityto UOLs of 94.1 % at a conversion of 72.8 %, while Lu
2
O shows
3
thesecondhighestUOLsselectivityof93.9%ataconversionof29.0%[19].AmongtheYSZcatalystswe
tested, 3YSZ-900 showed the highest UOLs selectivity of 98.1 % at a conversion of 66.2 %, as shown in
Table 4. Thus, it was found that 3YSZ catalysts were the most selective for UOLs formation in the
2
-1
dehydrationof1,3-BDO. Becausethespecificsurface area (34.3m g )of3YSZ-900is muchhigherthan
o
2 -1
thoseofCeO
2
andLu
2
O calcinedat1000 C,whichare13.2and14.1m g ,respectively[35],theintrinsic
3
activityof3YSZ-900islowerthantherareearthoxides(Fig.7).Inthedehydrationof1,4-BDO,ontheother
hand, the 3B1ol selectivity of 64.6 % (Table S3) over 3YSZ-900 is lower than that of CaO-modified MZ
o
calcinedat800 C(89.3%ataconversionof95.2%[30]), whichisthebestcatalyticperformanceas faras
weknow.
3.4.CatalyticactivityofYSZin thedehydrationof1,3-BDOunderdifferentreactionconditions
Table4showstheeffectofN carriergasflowrateonthedehydrationof1,3-BDOover3YSZ-900
2
at 325°C. The conversion of 1,3-BDO depended on the flow rate, although the stable conversion was
obtained at a constant carrier gas flow rate. The highest conversion of 1,3-BDO was attained at a flow rate
3
-1
of 60 cm min . Fig. S4 depicts TG profiles for the fresh 3YSZ-900 and the samples used in an N
2
carrier
3
-1
3
-1
gasof7.5and30cm min for5h.Intheflowrateof 30cm min ,itwasfoundthattheamountofdeposited
3
-1
carbonwas halfofthatat7.5cm min . Becausealowcarriergasflowratemeansahighpartialpressureof
the reactant of 1,3-BDO, carbon deposition readily occurs at a high partial pressure of 1,3-BDO. It is
suggestedthatthe highpartialpressureof1,3-BDOwouldaffectthechemicalstepsincludingtheadsorption
of 1,3-BDO and the desorption of the product UOLs although clear explanation cannot be made. It should
benotablethatthecarriergasflowratesignificantlyaffectsthecatalyticactivityandthecarbondeposition.
Table 5 shows the effect of reaction temperature on the catalytic activity of 3YSZ-900 for the
dehydrationof1,3-BDO.The1,3-BDOconversionincreasedwithincreasingthereactiontemperature.The
selectivitytoUOLsdecreasedwithincreasingthereactiontemperature,whiletheselectivityto1,3-butadiene
(BD), ethanol, and 2-butanone (MEK) increased. We observed other by-products including propylene,
acetone, and unidentified products, which were also increased at higher reaction temperatures. Thus, high
temperatureswouldinducethefurtherdehydrationandthedecompositionofUOLs.
1
3

Table 6 shows the conversion of 1,3-BDO and the selectivity to each product over 3YSZ-900 at
3
25°C at different contact times of W/F, where W and F are catalyst weight and feed rate of 1,3-BDO,
respectively. Theconversionof1,3-BDOincreasedwithincreasingW/F. Onthecontrary, theselectivityto
UOLsdecreasedwithincreasingW/F,whiletheselectivitytoBD,ethanol,and2-butanone(MEK)increased.
It is suggested that secondary dehydration, isomerization, dehydrogenation, decomposition, and
polymerizationofUOLswouldproceedathighW/F, resultinginthedecreaseofselectivitytoUOLs.
Fig. 8 shows a long run test of the dehydration of 1,3-BDO over 3YSZ-900 at 325 °C. The 1,3-
BDO conversion and theselectivityto UOLs weremaintainedat a highlevel during 38 h. The colorofthe
usedcatalystwaschangedfromwhitetolightgray.TGanalysesoffreshandused3YSZ-900catalystswere
performed to confirm the carbon deposition (Fig. S5). The difference in the weight change, which was
calculatedbysubtractingtheweightlossatthetemperatures200-400°Cofthefreshcatalystfromthatofthe
usedone, would beattributed to carbon deposition. Theweight ofcarbon depositedon3YSZ-900afterthe
38-h reaction was only 1.2 wt.%. Thus, the negligible carbon deposition would cause the stable catalytic
activity.
3.5.Speculationontheactivecenterforthedehydrationof1,3-BDO
In Section 3.2, we have characterized the base-acid property of 3YSZ and MZ-800. The samples
have basic and acid sites whose amounts and their density vary with the calcination temperature. In the
previous study, the catalytic activity of Er
containing CO and NH [19]. Thus, we examined poisoning experiments using CO
reaction (Table S5). Over 3YSZ-900 and MZ-600, however, neither CO nor NH acted as a poison. 1,3-
BDOmightbeadsorbedontheactivesitesmorestronglythanCO andNH . Becausethestrongadsorptive
2
O
3
for the dehydration of 1,3-BDO was reduced in a carrier gas
2
3
2
and NH during the
3
2
3
2
3
interactionbetween1,4-BDOandanactiveCaO/MZcatalystwasobserved[33],wehavestillroomforthe
further research. This results seemingly indicate that the reaction is not catalyzed by base and acid. Thus,
unfortunately,wecannotconcludethebase-acidsitesplayanactivecenterinthedehydrationof1,3-BDOat
thepresenttime.
We have previously reported that rare earth oxides such as CeO
2
, Er
2
O
3
, and Yb
2
O catalysts are
3
effectivefortheselectiveconversionof1,3-BDOtoUOLs[18-20].Thecrystallinephaseoftheoxidesisthe
1
4

same cubic phase of either fluorite of CeO
2
or bixbyite of Ln
2
O
3
. In the case of CeO , we reported that the
2
UOLs selectivity increased with increase in crystallite sizes induced by calcination at high temperatures
together with the increment of the formation rate per unit surface area [20]. In theoretical investigations,
oxygendefectsitesonthecubicfluoriteCeO with(111)facetsworkasadsorptionsitesfortheactivationof
2
1
,3-BDO[21,22].Also,(222)facetsofcubicEr
23, 36].
In the present study, to discuss the active center of YSZ for the dehydration of 1,3-BDO, the
crystallinemodeloftetragonal ZrO phasewas presentedin Fig. S6, whichdipicts several cross sections of
2
O
3
provideadsorptionsitesforthedehydrationof1,4-BDO
[
2
tetragonal ZrO
tetragonalZrO
tobe(101)of tetragonal ZrO
2
. Figs. 9a and 9b, which are the top threelayers of Fig. S6d and S6c, show a (101) facet of
withandwithoutanoxygendefect,respectively. ThemoststablefacetsofZrO arereported
, whichiscrystallographicallythesamefacetsas cubicZrO (111)[37-39]. In
2
2
2
2
a simplecompositional calculation ofYSZ, whichis expressedbyZr(1-x)
YSZ with a Y content of 3.5 mol% contains oxygen vacancy in 0.72% of oxygen-occupied sites of the
bulk YSZ crystallite. This means that 1 out of 139 oxygen-occupied sites must be vacant in 3YSZ. In the
present YSZ, it is speculated that oxygen defect sites on the (101) facets of tetragonal ZrO provide
x
Y O2(1-0.5x), wherexismol%ofY,
3
2
adsorption sitesof1,3-BDO, in asimilarwaytothecubicCeO [21,22]. Onthestable(222)facetsofcubic
2
rareearthoxidessuchasYb
vacancies occupythe one fourth of surface oxygen anion sites [20, 36]. Therefore, it is reasonable that Y3+
ionsinYSZcouldinducetheformationofoxygenvacanciesonthestablefacesoftetragonalZrO (101),as
shownin Fig. 9a. Therefore, three cations such as Zr andY couldbe exposed ontheoxygen defect site
2
O
3
, whichisalsoactivefortheselectivedehydrationof1,3-BDO[19], oxygen
2
4+
3+
2-
ofthe(101)surfaceoftetragonalZrO andthedefectissurroundedbysixO anions, asseeninFig. 9a.
2
4+
3+
In an analogous way to CeO
2
[20, 21], it is considered the exposed Zr and Y would act as the
2-
adsorptionpointsforOHgroupsof1,3-BDO, whileanO anioncancoordinateahydrogenatposition2of
2-
3+
1
,3-BDO, asillustratedin Fig. 10. Intheformation of3B2ol, forexample, O and Y extractthehydrogen
4+
andtheOH group ofposition 1 of1,3-BDO, respectively, where Zr acts as ananchoroftheadsorption of
position-3OH. In themechanism illustrated in Fig. 10, the abstractionofposition-2hydrogen andposition-
2-
3+
1
OH group could proceed simultaneously. It is speculated that the basic site of O induced by the Y
substitutedinZrO playsanimportantrolefortheabstractionofposition-2 Hatomfrom1,3-BDO.Although
2
1
5

CO
between Ce and Ce is speculated to play an important role in the dehydration of 1,3-BDO [20, 21].
Because both Y and Zr do not have such redox property as CeO has, the reaction can be explained by the
2
as well as NH
3
did not poison the surface of 3YSZ (Table S5). In the case of CeO , the redox cycle
2
3+
4+
2
aforementionedbase-acidconcertedmechanism, andotherwise-unexplained.
In thereactionmechanismforthedehydrationofotherdiols, anessentialroleofoxygendefectsiteof
YSZ catalysts would be the same as that of 1,3-BDO. Because a difference in the reactants is distance
between OH group and another OH group, the distance could affect the adsorption structure on the oxygen
defectsiteofYSZ. TheadsorptionstructureinFig. 10couldbestabilizedwithringcoordinationofaseven-
3+
4+
2-
4+
2-
membered-ringcoordinationofY OCCCOZr aswellas2six-memberedringsofO HCCOZr andO
3+
HCCOY . In a similar manner, 1,4-BDO has the adsorption structure with an eight-membered-ring
3+
4+
2-
4+
2-
3+
coordination of Y OCCCCOZr and 2 six-membered rings of O HCCOZr and O HCCOY . In
3+
4+
contrast,1,5-BDOwouldformnine-membered-ringcoordinationofY OCCCCCOZr , whichisunstable
with the strained structure. In the case of 2,3-BDO, the adsorption structure has 3 six-membered-ring
3+
4+
2-
4+
2-
3+
coordination such as Y OCCOZr , O HCCOZr , and O HCCOY , in which each coordination could
be stable but the adsorption structure of 2,3-BDO with the 3 six-membered rings would be highly strained.
Thus, the reactivity of 1,5-PDO and 2,3-BDO is lower than the others. However, we need further
investigationonthebase-acidconcertedmechanismforthedehydrationofBDOsinthenearfuture.
4. Conclusions
Vapor-phasecatalyticdehydrationofBDOs wasinvestigatedoverYSZcatalystsaswellasMZ. It
issuggestedthatYSZissuperiortoMZasacatalystforthedehydrationof1,3-BDOand1,4-BDO. Drastic
changesinactivitywithcalcinationtemperaturewereobservedinthedehydrationof1,3-BDOand1,4-BDO
over YSZ catalysts, while no significant changes were observed in the dehydration of 2,3-BDO and 1,5-
PDO. In the dehydration of 1,3-BDO at 325°C, the UOLs selectivity exceeded 98% at the 1,3-BDO
conversion of 66% over 3YSZ calcined at 900°C, and the catalytic activity was stable for at least 38 h.
Especially, the UOLs selectivityover 98%is thehighest valuewe evenobtained inthe dehydrationof1,3-
BDO, which is superior to an excellent CeO
2
catalyst. In addition, the flow rate of nitrogen carrier gas
significantlyaffectsthecatalyticactivityandthecarbondepositioninthedehydrationof1,3-BDO.
1
6

In thedehydration of1,4-BDOat325°C, thehighestselectivityto3B1olof75.3%atthe1,4-BDO
conversionof26.1%wasobtainedover3YSZcalcinedat1050°C.Thecatalyticactivity,however,isinferior
tothepreviouslyreportedCaO/MZcatalyst.Inthedehydrationof2,3-BDOat325°C,thehighestselectivity
to3B2olof54.3% atthe2,3-BDOconversionof8.9%wasobtainedover14YSZcalcinedat1000°C.Inthe
dehydration of 1,5-PDO at 325°C, the highest selectivity to 4P1ol of 37.9% at the 1,5-PDO conversion of
1
0.3% was obtained over MZ calcined at 800°C. The reactivity of 2,3-BDO and 1,5-PDO over YSZ and
MZ catalystsat325°C waslowerthanthatof1,3-BDOand1,4-BDO.
Structuresofactivesitesfor1,3-BDOwasdiscussedusingacrystalmodeloftetragonalZrO
probable model structure of active sites was proposed. Oxygen defect sites are inevitably generated on the
stable faces of tetragonal ZrO (101), as seen in Fig. 9a. A defect site, which exposes three cations such as
2
anda
2
4+
3+
2-
4+ 3+
2-
Zr andY ,issurroundedbysixO anions. TheexposedZr , Y ,andO wouldcomposeanadsorption
siteforthetridentatecoordinationofa1,3-BDOmolecule, whichincludesaninteractionbetweenaposition-
2-
2
hydrogenof1,3-BDOandanO anionontheedgeofthedefectandotherinteractionsbetweenOHgroups
3+
4+
of1,3-BDOandY and Zr cationsonthedefect. ThecatalyticreactionovertheYSZcouldbeexplained
bytridentatecoordinationfollowedbythereactionsequencethattheposition-2hydrogenisfirstlyabstracted
2-
byabasicO anionandthentheposition-1hydroxylgroupissubsequentlyorsimultaneouslyabstractedby
3+
an acidic Y cation to produce 3-buten-2-ol. Another OH group at position 3 plays an important role of
4+
anchoring 1,3-BDO to the catalyst surface through the interaction with the exposed Zr cation. Thus, it is
speculated that the selective dehydration of 1,3-butanediol over YSZ catalyst proceeds via a base-acid
concertedmechanismthroughtridentatecoordination, asshowninFig.10.
Acknowledgments
ThisworkwassupportedbyJSPSKAKENHIKIBANBGrantNumberJP18H01784.
1
7

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1
9

o
Table1Dehydrationof1,3-butanediolat325 CoverHT-ZrO
2
catalystswithdifferentYcontents.
Selectivity(mol%)
Y
Ycontent
content byXRF
mol%) (mol%)
Conv.
SA
m g )
(E)-
(Z)- UOLs
2
-1
(
(%) 3B1ol 3B2ol
MVK MEK others
(
2B1ol 2B1ol total
0
2
3
4
6
9
0
2.2
3.1
4.1
6.1
9.1
11.9
10.0
17.9
21.8
21.3
24.1
32.0
34.8
5.6
33.6
49.6
46.8
62.8
58.5
51.7
42.5
7.6
3.5
2.9
2.5
3.3
4.6
19.8
39.6
43.5
43.4
45.3
44.9
44.0
17.7
35.2
41.1
39.6
38.9
35.3
30.5
4.5
8..7
9.7
9.7
8.8
8.0
7.4
84.5
91.1
97.8
95.6
95.5
91.5
86.5
7.7
2.7
1.0
1.5
1.4
2.2
3.3
4.0
3.3
0.8
1.5
1.8
3.4
5.5
3.8
2.9
0.4
1.4
1.3
2.9
4.7
12
o
Thesampleswerepreparedbyhydrothermaltreatmentofthecorrespondingprecipitatesat200 Cfollowedby
o
calcinationat900 Cfor3h.
3
-1
Reactionconditions:N flowrate,30cm min ;catalystweight,0.5g.
2
3
B1ol,3-buten-1-ol;3B2ol,3-buten-2-ol;2B1ol,2-buten-1-ol;MEK,butanone;MVK,3-buten-2-one.Othersinclude
1-butanol,acetoneandsomeunidentifiedproducts.
Table2PhysicalpropertiesofYSZandMZcalcinedatdifferenttemperatures
S
BET
Particlesize
Basicity
Acidity
Catalysts
2
-1
2
-1
(μmolg-1)
(μmolg-1)
(
m g )
d
BET(nm)
(m g )
As-received3YSZ
81.8
70.0
63.7
61.6
52.9
43.2
34.3
26.9
19.7
14.6
78.0
72.4
50.7
39.0
26.8
12.9
15.1
16.6
17.1
20.0
24.5
30.8
39.3
53.6
72.4
13.5
14.6
20.8
27.1
39.4
22.4
24.1
27.3
29.4
31.4
36.3
41.7
47.9
58.8
67.8
11.6
12.4
13.7
17.6
27.3
-
-
135 (1.9) a
175 (2.5)
3
YSZ-600
YSZ-700
YSZ-750
YSZ-800
YSZ-850
YSZ-900
YSZ-950
YSZ-1000
YSZ-1050
4YSZ-600
4YSZ-700
4YSZ-800
4YSZ-900
4YSZ-1000
127 (2.0)a
133 (2.1)
3
3
3
3
-
-
76 (1.4)a
201 (3.8)
-
-
49(1.4)a
194 (5.7)
3
3
3
3
-
-
33 (1.7)a
67 (3.4)
-
-
-
-
-
-
-
-
-
-
-
-
1
1
1
1
1
MZ-600
MZ-800
MZ-1000
37.0
25.0
13.4
28.5
42.3
78.8
29.5
39.7
68.7
-
46 (1.8)
-
-
53 (2.1)
-
a
-2
Numberintheparenthesisrepresentsthesurfacedensityofbasicandacidicsites(μmol m ).
2
0

Table3Dehydrationof2,3-BDOoverYSZandMZcatalystscalcinedatdifferenttemperatures
Conv. Selectivity/mol%
Catalysts
/
mol%
23.4
15.0
14.6
6.0
29.3
19.1
8.9
3B2ol
15.2
23.3
37.7
35.3
34.5
46.7
54.3
12.0
28.9
20.9
MEK
22.0
25.6
19.9
24.6
25.4
17.8
16.6
45.3
34.0
41.0
acetoin
29.8
26.6
30.2
32.0
23.8
22.7
23.0
17.0
20.4
29.9
MPA
MPO
6.5
6.7
3.4
2.8
1.9
1.7
0.6
4.8
2.8
2.7
others
10.0
6.8
1.8
5.0
6.1
5.5
3.1
9.1
3
3
3
3
1
1
1
YSZ-600
16.5
11.0
7.0
0.3
7.4
5.6
2.4
11.8
7.8
0.0
YSZ-800
YSZ-900
YSZ-1000
4YSZ-600
4YSZ-800
4YSZ-1000
MZ-600
MZ-800
MZ-1000
28.4
16.8
4.7
6.1
5.5
Conversionandselectivityareaveragedbetween1-5 h.
3
-1
Reactionconditions: N
B2ol,3-buten-2-ol;MEK;butanone,acetoin,3-hydroxy-2-butanoe;MPA,2-methylpropanal,MPO,2-methyl-1-
propanol. Othersinclude1,3-butadieneandsomeunidentifiedproducts.
2
flowrate,30cm min catalystweight,0.5 g; reactiontemperature,325°C.
3
Table4Changeinconversionof1,3-BDOandselectivityover3YSZ-900underN carriergaswith
2
differentflowrates.
Carrier
gasrate
cm min )
Conv.
Selectivity(mol%)
(Z)- UOLs
2B1ol 2B1ol total
(E)-
(%) 3B1ol 3B2ol
acetone ethanol MEK Others
3
-1
(
7
.5
32.8
57.5
62.4
66.2
61.7
53.8
2.6
1.8
1.8
1.8
2.1
2.3
44.5
44.5
44.5
45.7
46.3
49.4
32.2.
41.0
41.5
40.5
38.1
35.8
13.7 93.0
0.4
0.1
0.3
0.1
0.1
0
3.1
0.9
0.6
0.5
0.7
0.8
2.5
1.1
0.8
0.5
0.7
0.8
1.0
0.9
0.7
0.8
1.6
2.0
15
9.8
9.8
97.0
97.6
98.1
96.8
96.3
30
60
10,1
10.3
8.8
90
120
Conversionandselectivityareaveragedbetween1-5 h.
Reactionconditions:catalystweight,0.5g; reactiontemperature,325°C.
MEK,butanone;MVK,3-buten-2-one.Othersinclude1-butanolandsomeunidentifiedproducts
2
1

Table5Dehydrationof1,3-BDOover3YSZ-900atdifferentreactiontemperatures.
Reaction Conv.
Temp.
Selectivity(mol%)
(E)-
2B1ol 2B1ol
36.3
41.5
32.6
20.5
(Z)-
UOLs
total
(%)
3B1ol 3B2ol
BD
ethanol
MEK others
(
3
3
3
°C)
00
25
50
75
9.1
2.7
1.8
2.3
3.9
41.1
44.5
44.5
45.9
15.7
9.8
12.9
9.8
95.8
97.6
92.3
80.0
0.1
0.0
1.2
9.8
1.3
0.6
2.0
2.4
0.6
0.7
2.7
2.5
2.2
1.0
1.8
5.3
62.4
93.7
99.6
3
3
-1
Reactionconditions:N
2
flowrate,30cm min ;catalystweight,0.5g.
BD,1,3-butadiene;MEK,butanone;MVK,3-buten-2-one.Othersinclude1-butanol,acetoneandsomeunidentified
products.
Table6Dehydrationof1,3-BDOover3YSZ-900atdifferentcontacttime.
Conv.
(%)
Selectivity(mol%)
W/F
h)
(
2
38.7
41.5
34.5
28.6
E)-
(Z)-
UOLs
total
97.1
97.6
89.1
84.8
(
3B1ol 3B2ol
BD
ethanol MEK others
B1ol 2B1ol
0
.16
.31
.63
.25
24.8
62.4
73.5
96.2
1.9
1.8
1.8
2.6
38.7
41.5
34.5
28.6
14.6
9.8
12.4
11.3
0.2
0.0
0.5
3.1
0.8
0.6
3.8
2.7
0.5
0.8
3.5
4.6
1.4
1.0
3.1
4.8
0
0
1
3
-1
Reactionconditions:N
2
flowrate,30cm min ;reactiontemperature,325°C.
BD,1,3-butadiene;MEK,butanone;MVK,3-buten-2-one.Othersinclude1-butanol,acetoneandsomeunidentified
products.
2
2

Y content
:
tetragonal
(
mol%)
0
2
3
4
6
9
1
2
2
0 30 40 50 60 70 80
 /degree
2
Fig.1XRDpatternsofHT-ZrO
2
withdifferentYcontents.
o
Thesampleswerecalcinedat900 C.
2
3

3YSZ-1000
3YSZ-800
3
YSZ-600
14YSZ-1000
1
1
4YSZ-800
4YSZ-600
MZ-800
2
0
30
40
50
60
70
2
θ/degree
Fig.2XRDpatternsofYSZandMZcalcinedatdifferenttemperatures
2
4

(a)
(b)
3
YSZ-1000
3
YSZ-1000
3
YSZ-900
YSZ-800
3
YSZ-900
YSZ-800
3
3
3
YSZ-700
YSZ-600
3YSZ-700
3YSZ-600
3
MZ-800
600
M-Z800
0
200
400
200
400
600
800
o
Temperature/ C
Temperature /°C
Fig.3TPDprofilesof(a)CO
2
and(b)NH adsorbedon3YSZcalcinedatdifferenttemperaturesaswellas
3
MZ-800.
2
5

1
00
100
80
60
40
20
0
1
,3-BDO
3
1
YSZ
8
6
4
2
0
0
0
0
0
4YSZ
1
4YSZ
3
YSZ
MZ
MZ
1
,3-BDO
6
00 700 800 900 1000 1100
600 700 800 900 1000 1100
Calcination temperature / °C
Calcination temperature / °C
Fig.4Dehydrationof1,3-BDOoverYSZandMZcatalystscalcinedatdifferenttemperatures
Conversionandselectivityareaveragedbetween1-5 h.
3
-1
Reactionconditions:N
2
flowrate,30cm min ;catalystweight,0.5g; reactiontemperature,325°C.
100
100
3
YSZ
1
,4-BDO
3
YSZ
14YSZ
80
80
60
40
20
0
60
40
20
0
14YSZ
MZ
1
,4-BDO
MZ
6
00 700 800 900 1000 1100
600 700 800 900 1000 1100
Calcination temperature / °C
Calcination temperature / °C
Fig. 5Dehydrationof1,4-BDOoverYSZandMZcatalystscalcinedatdifferenttemperatures
Conversionandselectivityareaveragedbetween1-5 h.
3
-1
Reactionconditions:N flowrate,30cm min ;catalystweight,0.5g; reactiontemperature,325°C.
2
2
6

3
YSZ
1
,3-BDO
1,4-BDO
0.6
0.4
0.2
0
0.6
0.4
0.2
0
3
YSZ
14YSZ
14YSZ
MZ
MZ
6
00 700 800 900 1000 1100
Calcination temperature / °C
600 700 800 900 1000 1100
Calcination temperature / °C
0
.2
.1
0
0
.2
.1
0
2
,3-BDO
1
,5-PDO
0
0
1
4YSZ
MZ
3
YSZ
3
YSZ
MZ
1
4YSZ
600 700 800 900 1000 1100
6
00 700 800 900 1000 1100
Calcination temperature / °C
Calcination temperature / °C
Fig.6ChangesintheformationrateofUOLsoverYSZandMZcalcinedatdifferenttemperatures
2
7

5
4
3
2
1
0
100
80
60
40
20
0
3
YSZ-900
MZ-600
4
+
Ce
Lu
Yb
3
YSZ-900
Er
Y
Sc
Tb
Tm
+
Dy
4
Zr
Pr
Ho
Eu
Nd
Sm
La
MZ-600
Gd
0
.07
0.08
0.09
0.1
0.11
Ionic radius / nm
o
Fig.7Comparisonof3B1olformationrateat325 Camongthecatalystsreportedpreviously.
Squaresrepresenttheformationrateof3UOlsandcirclesindicatetheselectivitytoUOLs. Thedataforrare
o
earthoxideswerecitedfromRef. [19],inwhichthecatalystswerecalcinedat1000 C.
100
UOLs select.
8
6
4
2
0
0
0
0
0
1
,3-BDO conv.
0
10
20
30
40
Time on stream / h
Fig.8Changeintheconversionandselectivityinalongrunreactionover3YSZ-900.
3
-1
Reactionconditions:N flowrate,30cm min ;catalystweight, 0.5g; reactiontemperature,325°C.
2
2
8

Fig.9Topviewofsurfacestructureof(101)faceofYSZ(a)withand(b)withoutanoxygendefectsite
modeledbyVESTA3[40].
2-
4+
3+
LargewhiteballsrepresentO , andSmallblueballsareeitherZr orY . Thetopandthethirdlayersare
2-
composedofO anions, andthesecondlayeriscomposedofthecations.
O H
H
H
+
O H
O H
O H
O H
O H
H
+
H 2 O
H
H
4 +
4
+
4 +
4 +
Z r
O H
Z r
Z r
Z r
2
-
2 -
2
-
3 +
3 +
3 +
2
-
3 +
O
O
O
Y
Y
Y
O
Y
A d so rp tio n
D isso ciatio n
D eso rp tio n
R eg eneratio n
Fig.10 Proposedreactionmechanismintheformationof3B2OLfromof1,3-BDOoverbase-acid
concertedactivesitesonthesurfaceofYSZcatalysts.
2
9