a fundamental approach to the development of novel alkane

A Fundamental Approach to the Development of A Fundamental Approach to the Development of Novel Alkane Isomerization CatalystsNovel Alkane Isomerization Catalysts

Abteilung Anorganische ChemieFritz-Haber-Institut der Max-Planck-Gesellschaft

Faradayweg 4-6, 14195 Berlin

University of Reading June 4, 2007

FriederikeFriederike C. JentoftC. Jentoft

Alkane Alkane SkeletalSkeletal IsomerizationIsomerization

equilibrium at 300 K: 71 % isobutane

Common solid acid catalysts

Pt/AlCl3-Al2O3: 393-453 K, problems with Cl and H2O

Pt/zeolite: 533 K, unfavorable equilibrium

“New” low temperature isomerization catalyst

Pt/sulfated zirconia

acid catalyst

CH3

CH3CH2

CH2CH3

CH3

CH

CH3

Catalyst ComparisonCatalyst Comparison

after G.C. Anderson, R.R. Rosin, M.A. Stine, M.J. Hunter, UOP 2004

0 60 120 180 240 300 360 4200

100

200

300

400

500

SZ, 378 K

Rat

e of

isom

eriz

atio

n / µ

mol

g-1 h

-1

Time on stream / min

Promotion of Sulfated ZirconiaPromotion of Sulfated Zirconia

500 mg catalyst, fixed bed1 kPa n-C4 in N2, atm. pressure

80 ml min-1 total flowPt/sulfated zirconia: 353 KHolm, Bailey 1962, US Patent 3,032,599

"SZ" isomerizesn-butane at RT Hino, Arata, JACS 1979 & Chem. Comm. 1980


0 60 120 180 240 300 360 4200

100

200

300

400

500

SZ, 378 K

Rat

e of

isom

eriz

atio

n / µ

mol

g-1 h

-1


2% FeSZ, 323 K2% MnSZ, 323 K

Fe and Mn act as promoters of SZ Hollstein et al., US Patent 4,918,041 1990Hsu et al., Chem. Comm. 1992Lange et al., Catal. Lett. 1996

Pt/sulfated zirconia: 353 KHolm, Bailey 1962, US Patent 3,032,599



80 ml min-1 total flow

Indu

ctio

npe

riod Deactivation


0 60 120 180 240 300 360 4200

100

200

300

400

500

SZ, 378 K

Rat

e of

isom

eriz

atio

n / µ

mol

g-1 h

-1


2% FeSZ, 323 K2% MnSZ, 323 K

Fe and Mn act as promoters of SZ Hollstein et al., US Patent 4,918,041 1990Hsu et al., Chem. Comm. 1992Lange et al., Catal. Lett. 1996

Pt/sulfated zirconia: 353 KHolm, Bailey 1962, US Patent 3,032,599


SZ catalyzes cracking, alkylation, condensation, etherification, acylation, esterification, nitration, and oligomerizationG.D. Yadav, J.J. Nair, Microporous Mesoporous Mat. 33 (1999) 1-48


80 ml min-1 total flow

sulfated zirconia a solid superacid (>100% H2SO4) ?

Zr4+O

Zr

H

Initial IdeasInitial Ideas

tetragonal (?!) ZrO2

Brønsted-acidicOH-group

Lewis-acid sitecus metal cation

"ZrO2 (mp 2700°C) is a white, chemically, thermally, and mechanically stable compound" Riedel, Anorganische Chemie, deGruyter 2002, p. 776

S

O O

OO

Zr4+O

Zr

H

O O

OO

S





sulfate generates acidity



Brønsted-acidicOH-group S

O O

OO

Zr4+O

Zr

H

O O

OO

S S

O O

OO

Zr4+O

Zr

H

O O

OO

S



sulfate generates acidity




Mn and Fe increase acidity of the "solid superacid" sulf. ZrO2evidence: activity, TPD with (subst.) benzenesHsu et al., Chem. Comm. 1992; Lin et al., Chem. Comm. 1992

Fe Fe

…extremely acidic sites can not be identifiedAdeeva et al., J. Catal. 1995; Wan et al., J. Catal. 1996

could not be confirmed

OutlineOutline

1. Preparation: calcination chemistry

2. Zirconia metastability

3. Zirconia - promoter interaction

4. Surface sites and reactivity

5. Summary

6. Outlook

Addition of PromotersAddition of Promoterscommercial hydrous zirconia

X-ray amorphous sulfated with (NH4)2SO4

dried at 383 K

sulf. ZrO2

“SZ”Mn-sulf. ZrO2

“MnSZ”Fe-sulf. ZrO2

“FeSZ”

promoter content: 0.5-5.0 wt% metal

Fe(III), Mn(II) nitrate

Incipient wetness

Calcination

sulfate content: 4.5 wt% SO3

Calcination ChemistryCalcination Chemistry

0 100 200 300 400 500300

400

500

600

700

800

900

Tem

pera

ture

/ K

Time / min

3 K/min

with Fe, Mnpure SZ

Water loss

Decomposition of NO3- and NH4

+

Crystallization / sintering of ZrO2

Volume: 17.1 ml

Endo-/exothermic reactions

Calcination Calcination ChemistryChemistry and Engineeringand Engineering

0 100 200 300 400 500300

400

500

600

700

800

900

Tem

pera

ture

/ K

Time / min

3 K/min

with Fe, Mnpure SZ

300 400 500 600 700 800300

400

500

600

700

800

900

1000

Water loss

Decomposition of NO3- and NH4

+

Crystallization / sintering of ZrO2

Sam

ple

bed

tem

pera

ture

/ K

Oven temperature / K

115 120 125 130 135 140 145 150 155 Heating time / min

Rapid overheating(up to 40-50 K/s)

Overshoot up to 300 K

“Glow phenomenon” not unique to formation of ZrO2: Ti, Fe, Cr oxides

20 g hydrous zirconia

780 800 820 840 860

750

800

850

900

950

1000

2%MnSZH

2.2 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min

Effect of the Calcined Amount: Effect of the Calcined Amount: MnSZMnSZ and and FeSZFeSZ

2.2 ml

780 800 820 840 860

750

800

850

900

950

1000

2%MnSZH

17.1 ml

8.4 ml

2.2 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min


Strong effect of batch size

Planned Tmax may be exceeded

2.2 ml

8.4 ml

17.1 ml




Promoters: influence calcination chemistry, Fe different than Mn

780 800 820 840 860

750

800

850

900

950

1000

2%FeSZH

2%MnSZH

17.1 ml

8.4 ml

2.2 ml2.2 ml

8.4 ml

17.1 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min

780 800 820 840 860

750

800

850

900

950

1000

2%MnSZH

17.1 ml

8.4 ml

2.2 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min

780 800 820 840 860

750

800

850

900

950

1000

2%MnSZH

2.2 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min

2.2 ml

8.4 ml

17.1 ml




Promoters: influence calcination chemistry, Fe different than Mn

780 800 820 840 860

750

800

850

900

950

1000

2%FeSZH

2%MnSZH

17.1 ml

8.4 ml

2.2 ml2.2 ml

8.4 ml

17.1 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min

0 100 200 300 400 500300

400

500

600

700

800

900

1000

Tem

pera

ture

/ K

Time / min

Samples calcined in large batches more active

0 120 240 360 480

0

2

4

6

8

10

12

14

17.1 ml batch 8.4 ml batch 2.2 ml batch

Yiel

d is

obut

ane

(%)


2%MnSZ

Influence on Catalytic Activity?!Influence on Catalytic Activity?!

0 120 240 360 480

02468

10121416 17.1 ml batch

8.4 ml batch 2.2 ml batch

Yiel

d is

obut

ane

(%)


2%FeSZ

A. Hahn, F.C. Jentoft et al., Chem. Commun. 2001

780 800 820 840 860

750

800

850

900

950

1000

2%FeSZH

2%MnSZH

17.1 ml

8.4 ml

2.2 ml2.2 ml

8.4 ml

17.1 ml

Sam

ple

bed

tem

pera

ture

/ K


165 170 175 180 185 190Heating time / min

1 kPa n-C4, 338 K

Active phase formed during overheating – non equilibrium state

Improved reproducibility; extrinsic parameter decisive: calcined amount

Rapid genesis of active phase during overheating

Large batch calcination produce most active catalysts

Calcination Calcination -- SummarySummary

Improved reproducibility; extrinsic parameter decisive: calcined amount

Rapid genesis of active phase during overheating

Large batch calcination produce most active catalysts

Calcination Calcination -- SummarySummary

0.01.02.03.04.05.06.07.08.09.0

10.0

0.002 0.0022 0.0024 0.0026 0.0028 0.003 0.0032 0.0034

Temperature-1 / K-1

ln k

norm

(Fe,Mn)SZ literatureFeSZ, MnSZ large boat

303 K

373 K Arrhenius-type graph

Rate constants from literature

Assuming 1st order in n-butane

F.C. Jentoft et al., invited article in preparation for Angew. Chemie

Zirconia Phase ChemistryZirconia Phase Chemistry

Tetragonal / cubic phase stabilized by doping with of Y3+, Mg2+, Ca2+

Sulfate also stabilizes tetragonal phase

Tetragonal phase more active than monoclinic phaseC. Morterra, G. Cerrato, F. Pinna, M. Signoretto, J. Catal. 157 (1995) 109W. Stichert and F. Schüth, J. Catal. 174 (1998) 242

monoclinicmonoclinic tetragonaltetragonal cubiccubic1223 - 1473 K >2473 K

MetastableMetastable Nature of Active SitesNature of Active Sites

After calcination, powders are clumped together

Samples are being ground or milled to obtain fine powder

Samples are pressed for catalysis, transmission spectroscopy, vacuum methods

27 28 29 30 31 32 33 340.0

0.5

1.0

1.5

2.0

2.5

3.0

untreated

T

M M

Inte

rnal

sta

ndar

d no

rmal

ized

Diffraction angle Cu Kα 2θ / °

Grinding of Grinding of 0.5% 0.5% MnSZMnSZ: XRD and Catalysis: XRD and Catalysis

XRD

27 28 29 30 31 32 33 340.0

0.5

1.0

1.5

2.0

2.5

3.0

untreated

T

M M

Inte

rnal

sta

ndar

d no

rmal

ized



ZrO2 affected by mechanical stress, transformation of t-ZrO2 to m-ZrO2E.D. Whitney, Trans. Faraday. Soc. 1965 (footnote!)

Grinding: strong operator influence

27 28 29 30 31 32 33 340.0

0.5

1.0

1.5

2.0

2.5

3.0

untreated ground, operator 1 ground, operator 2

T

M M

Inte

rnal

sta

ndar

d no

rmal

ized


27 28 29 30 31 32 33 340.0

0.5

1.0

1.5

2.0

2.5

3.0

untreated

T

M M

Inte

rnal

sta

ndar

d no

rmal

ized



0 2 4 6 8 10 12 140

50

100

150

200

250

ground, operator 1

0.5% MnSZ, untreated

Rat

e of

isom

eriz

atio

n / µ

mol

g-1 h

-1Time on stream / h

Catalytic performance also altered!

ZrO2 affected by mechanical stress, transformation of t-ZrO2 to m-ZrO2E.D. Whitney, Trans. Faraday. Soc. 1965 (footnote)

Grinding: strong operator influence

27 28 29 30 31 32 33 340.0

0.5

1.0

1.5

2.0

2.5

3.0

untreated ground, operator 1 ground, operator 2

T

M M

Inte

rnal

sta

ndar

d no

rmal

ized


B. Klose, F.C. Jentoft et al., J. Catal. 2003

1 kPa n-C4, 338 K

Stability during LongStability during Long--Term StorageTerm Storage

Storage Conditions

Laboratory"Berliner Luft"

glovebox "tropical" 313 K, saturated H2O vapor

Stability of Sulfated ZirconiaStability of Sulfated Zirconia

0 5 10 15 20 250

10

20

30

40

Isob

utan

e / µ

mol

g-1 h

-1

Time on stream / h

fresh glovebox laboratory tropical

} after 6 months 373 K

B.S. Klose, F.C. Jentoft et al., in preparation

SZ

Stability of Sulfated ZirconiaStability of Sulfated Zirconia

Tropical, 6 months: loss of 90% activity, 21% monoclinic phase

0 5 10 15 20 250

10

20

30

40

Isob

utan

e / µ

mol

g-1 h

-1

Time on stream / h

fresh glovebox laboratory tropical

} after 6 months 373 K

20 30 40 50 60 70

M M

2 months

**

**

**

*

*

Inte

nsity


6 months

T

fresh

B.S. Klose, F.C. Jentoft et al., in preparation

SZ SZ, tropical

Only fraction of tetragonal material active, particularly prone to phase transformation

Ion Scattering Spectroscopy: Surface CompositionIon Scattering Spectroscopy: Surface Composition

No Mn on surface at typical promoter contents

600 800 1000 1200 1400 1600 1800 2000

10000 cts

MnFe

Zr

OS

2.0% MnSZ 3.5% MnSZ 2.0% FeSZ

Inte

nsity

/ a.

u.

Energy / eV

XRD: Phase Composition and PromotersXRD: Phase Composition and Promoters

20 30 40 50 60 700.0

0.5

1.00.0

0.5

1.0

20 30 40 50 60 70

2.0% FeSZ, 923 K

Inte

nsity

(nor

mal

ized

)


MM

**

*

*

*

*

*

**

*

*

*

*

*

**

SZ, 923 K

Fe, Mn stabilize tetragonal / cubic phaseJ. Stöcker, Ann. Chim. 1960

XRD: Phase Composition and PromotersXRD: Phase Composition and Promoters

Unit cell of tetragonal ZrO2 shrinks with increasing Mn content, isolated Mn2+ in EPR spectrum

0 1 2 3 4 5 6 7 8 9 10

66.4

66.6

66.8

67.0

67.2SZ

FeSZ

MnSZ

Tetr

agon

al u

nit c

ell v

olum

e / Å

3

Promoter content / mol%20 30 40 50 60 70

0.0

0.5

1.00.0

0.5

1.0

20 30 40 50 60 70

2.0% FeSZ, 923 K

Inte

nsity

(nor

mal

ized

)


MM

**

*

*

*

*

*

**

*

*

*

*

*

**

SZ, 923 K

Fe, Mn stabilize tetragonal / cubic phaseJ. Stöcker, Ann. Chim. 1960

Analysis of FeAnalysis of Fe--Species in Species in FeSZFeSZ with XANESwith XANES

7.10 7.15 7.20 7.25 7.300.00

0.05

0.10

0.15

0.20

non-washed

Fe K edge near edge spectra of 2% FeSZ

Fluo

resc

ence

Yie

ld

Photon Energy, keV

Surface species can be washed offwith oxalic acid, ca. 42%

7.10 7.15 7.20 7.25 7.300.00

0.05

0.10

0.15

0.20

2, 3

4

1

non-washed

Fe K edge near edge spectra of 2% FeSZ

Fluo

resc

ence

Yie

ld

Photon Energy, keV7.10 7.15 7.20

0.0

0.5

1.0

1.5

Difference spectrum Fe2O3 reference

Abs

orpt

ion

/ Flu

ores

cenc

e Yi

eld

Photon Energy, keV

EPR and Mössbauer: only Fe3+

3-4 species, Fe2O3 and isolated Fe3+ model FeSZ

F.C. Jentoft et al., J. Catal. 2004

Preparation Method and Distribution of PromotersPreparation Method and Distribution of Promoters

solutions, ZrO(NO3)2 + Fe(III), Mn(II) nitrates

coprecipitationNH4OH

0 100 200 300 400 500300

400

500

600

700

800

900

Tem

pera

ture

/ K

Time / min

calcination 923 K

"FeZ, MnZ"

Preparation Method and Distribution of PromotersPreparation Method and Distribution of Promoters

solutions, ZrO(NO3)2 + Fe(III), Mn(II) nitrates

coprecipitationNH4OH

0 100 200 300 400 500300

400

500

600

700

800

900

Tem

pera

ture

/ K

Time / min

calcination 923 K

"FeZ, MnZ"

Distribution of promoters on surface and into zirconia lattice strongly preparation dependent

Promoter valences, zirconia crystallite size also influence unit cell

0 1 2 3 4 5 6 7 8 9 1065.8

66.0

66.2

66.4

66.6

66.8

67.0

67.2

FeZ, MnZ, coprecipitated

MnSZ, impregnated

FeSZ, impregnated

Tetr

agon

al u

nit c

ell v

olum

e / Å

3

Promoter content / mol%F.C. Jentoft et al., J. Catal. 2004

Sulfation of Sulfation of CoprecipitatedCoprecipitated Materials & CatalysisMaterials & Catalysis

Active material can be generated via coprecipitation

0 200 400 6000

100

200

300

400

500

1.8MnSZ, coprecipitated and spray-dried

1.8MnSZ, coprecipitated and oven-dried

2.0MnSZ, incipient wetness impregnationIs

obut

ane

form

atio

n ra

te /

µmol

g-1 h

-1


1 kPa n-C4, 338 K

Zirconia Solid State Chemistry SummaryZirconia Solid State Chemistry Summary

O2-

O2-

O2-

Zr4+

O2-

O2-

O2-

O2-

O2-

Zr4+

O2-

Zr4+ Zr4+

Zr4+

O2-

O2-

Zr4+

O2-

Zr4+

Zr4+ Zr4+

Active tetragonal phase formed during glow - defects? O vacancies?


O2-

O2-

O2-

Zr4+

O2-

O2-

O2-

O2-

O2-

Zr4+

O2-

Zr4+ Zr4+

Zr4+

O2-

O2-

Zr4+

O2-

Zr4+

Zr4+ Zr4+

Mn3+

Mn3+


Incorporation of promoters Mx+ with x<4 into lattice: O vacancies

Many Mx+ promoters known: Cr, Mn, Fe, Co, Ni, Al, Ga


O2-

O2-

O2-

Zr4+

O2-

O2-

O2-

O2-

O2-

Zr4+

O2-

Zr4+ Zr4+

Zr4+

O2-

O2-

Zr4+

O2-

Zr4+

Zr4+ Zr4+

Mn3+

Mn3+




Active phase metastable (monoclinization)


O OO O

SOO

SO

O2-

O2-

O2-

Zr4+

O2-

O2-

O2-

O2-

O2-

Zr4+

O2-

Zr4+ Zr4+

Zr4+

O2-

O2-

Zr4+

O2-

Zr4+

Zr4+ Zr4+

Mn3+

Mn3+

OH




Active phase metastable (monoclinization)How is the surface chemistry affected?

IR, XPS, NMR, UV/Vis...shift of bands(probe/surface)

desorption TTDS/TPD

adsorption Δ Hcalorimetry

+ NH3

Probing Sites by ChemisorptionProbing Sites by Chemisorption

O2-

Zr4+

O2-O2-

Zr4+

Zr4+

O2-

Zr4+

Zr4+ Zr4+

OH

NH H

H

O2-

Zr4+

O2-O2-

Zr4+

Zr4+

O2-

Zr4+

Zr4+ Zr4+

OH NH H

H

Novel Concept: Evaluation of IR IntensitiesNovel Concept: Evaluation of IR Intensities

2

⎟⎠⎞

⎜⎝⎛∂∂

∝r

I μ

Extinction coefficients as a measure of polarization of adsorbed molecule

Intensified vibrations ↔ activated bonds (reaction begin)

V.B. Kazansky, I.R. Subbotina, A.A. Pronin, R. Schlögl, F.C. Jentoft, J. Phys. Chem. B 110 (2006) 7975V.B. Kazansky, I.R. Subbotina, F.C. Jentoft, J. Catal. 240 (2006) 77V.B. Kazansky, I.R. Subbotina, F.C. Jentoft, R. Schlögl, J. Phys. Chem. B 110 (2006) 17468

δ+ δ-

C H

2. Evaluation of IR Intensities

Site

1. Hydrocarbons as probe molecules

SpectroscopicSpectroscopic and Adsorption and Adsorption DataData

3050 3000 2950 2900 2850 2800 2750 2700 2650

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4 0.001 0.004 0.009 0.021 0.061 0.087 0.201 0.418 0.673 0.926 2.164 4.424 6.886 9.370

Abs

orba

nce

Wavenumber / cm-1

p / hPa2965

2940

28962868

0.000

0.050

0.100

0.150

0.200

0 2 4 6 8 10Pressure / hPa

Ads

orbe

d am

ount

/ m

mol

g-1

y = 1614.8xR2 = 0.999

0

5

10

15

20

25

30

0 0.005 0.01 0.015 0.02Adsorbed amount / mmol g-1

Ban

d ar

ea 3

050-

2650

cm

-1/ c

m-1

Measurement on SZ catalysts obscured by scattering effects

Neopentane C(CH3)4 on FeSZ, 308 K

Activation of Hydrocarbons by ZeolitesActivation of Hydrocarbons by Zeolites

Ethane, CH stretching vibrations

IMEC in km/mol km/mol

gas phase gas phase 169169

NaYNaY 100100

CaYCaY 260260

Activation of hydrocarbon by cations in zeolite (faujasite)

IR intensities can be used as new criterion to evaluate activation of hydrocarbons on surfaces

Possibilities for Reaction InitiationPossibilities for Reaction Initiation

+

ads

+

ads

hydride-

transfer

reaction cyclen-butane isomerization

Possibilities for Reaction InitiationPossibilities for Reaction Initiation

+

ads

+

ads

hydride-

transfer

reaction cyclen-butane isomerization

H H ++ H+

very strong Brønsted acid

- H2

- H2O

reduced catalyst

oxidizedcatalyst

oxidative dehydrogenation (stoichiometric?)possible oxidizing agents: S, Zr, promoters

+ H+

strong Brønsted acid

- H-

strong Lewis acid

nn--Butane Isomerization over Butane Isomerization over MnSZMnSZ: In Situ XAS: In Situ XAS

No change of Mn valence during reaction (after activation in He)

No correlation of Mn valence to catalytic performance

No stoichiometric redox reaction involving MnR.E. Jentoft, F.C. Jentoft et al., PCCP 2005

0 20 40 60 80 1002.3

2.4

2.5

2.6

2.7

2.8

Ave

rage

Mn

vale

nce


0

1

2

3

4

2% MnSZ at 333 K1 vol% n-butane

Con

vers

ion

to is

obut

ane

(%)

1 kPa n-C4, 333 K

2600 2580 2560

Wavenumbers / cm-1

Kub

elka

-Mun

k fu

nctio

n

2583 2570

0.00

2 KM

5400 5300 5200 5100

5228

0.00

2 K

M

Kub

elka

-Mun

k fu

nctio

nWavenumber / cm-1

4000 3500 3000 2500 2000

28702965

0.2

KM

3485

2352

2417

20442768

3062

35843631

Kub

elka

-Mun

k fu

nctio

n

Wavenumber / cm-1

Diffuse Reflectance IR SpectroscopyDiffuse Reflectance IR SpectroscopyReaction of SZ with Reaction of SZ with nn--ButaneButane

Batch mode experiment: heating of SZ in n-butane, spectra recorded at RTFormation of H2O, CO2, H2S, and unsaturated hydrocarbons

B.S. Klose, F.C. Jentoft, I.R. Subbotina, V.B. Kazansky, R. Schlögl, Langmuir 2005

CO2

1 kPa n-C4, 573 K / RT

H-C=C H2O

H2S

Redox chemistry involving sulfate!

1700 1650 1600 1550

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Kub

elka

-Mun

k fu

nctio

n

Wavenumber / cm-1

16301600

In Situ DRIFTS: Flow ExperimentsIn Situ DRIFTS: Flow Experiments

Bands at 1600, 1630 cm-1 increase

Range of C=C stretching vibrations, but corresponding CH vibrations not observed

Water bending vibration

Time on stream

1 kPa n-C4, 323 K

1700 1650 1600 1550

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Kub

elka

-Mun

k fu

nctio

n

Wavenumber / cm-1

16301600

Spectral and Catalytic InformationSpectral and Catalytic Information

Bands at 1600, 1630 cm-1 increase

Range of C=C stretching vibrations, but corresponding CH vibrations not observed

Water bending vibration

- H2O + H+

0 1 2 3 4 5 60

50

100

150

200

Rat

e of

isom

eriz

atio

n / µ

mol

g-1 h

-1

Time / h

+

ads

Rate proportional to number of intermediates?

Estimate number of intermediates from band area

Time on stream

MnSZ, 1 kPa n-C4, 323 K

0

10

20

30

40

50

0 10 20 30 40 50 60

0

50

100

150

200

250

Isob

utan

e fo

rmed

/ µm

ol g

-1 h

-1

Band area increase / cm-1

SZ, 358 K

MnSZ, 323 K

Correlation of Spectral and Catalytic InformationCorrelation of Spectral and Catalytic Information

Rate of isomerization proportional to amount of water formed (induction period)

Amount of water formed≅ number of „carbenium ions“

B.S. Klose, F.C. Jentoft et al., J. Catal. 2005

ODH one activation pathway

5400 5350 5300 5250 5200 5150 5100

5228

52380.00

2 K

M

MnSZ

SZ

Kub

elka

-Mun

k fu

nctio

n

Wavenumber / cm-1

Diffuse Reflectance IR: Diffuse Reflectance IR: EffectEffect of Promotersof Promoters

Promoters (Mn) increase reducibility = oxidizing power of sulfate

3100 3000 2900 2800 2700 2600 25000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

no butane

butaneRT373 K

SZ

2966

2767

2940

2875

Kub

elka

-Mun

k fu

nctio

n

Wavenumber / cm-1

3100 3000 2900 2800 2700 2600 25000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

butaneRT373 K

no butane

MnSZ

2764

29402966

2875

Kub

elka

-Mun

k fu

nctio

n

Wavenumber / cm-1

2910

573 K373 K

Summary: Catalyst DevelopmentSummary: Catalyst Development

Bulk Properties:phase compositionsurface area, morphology

Surface Properties:acidity

Mixed oxide/solid solution

Geometric structure:phase compositionlattice constants

Electronic structure:oxygen vacanciesStructure

Reactivity

Reactivity

OxideZrO2, TiO2, Fe2O3, CeO2, …

Promoter cationsMx+, x < 4…

Oxo-anionsSO4

2-, WO42-…

Current Work & OutlookCurrent Work & Outlook

Novel catalysts

Preparative efforts to vary defect chemistry of zirconia

Promotion by Ga (et al.)

In situ electron paramagnetic resonance (TU Munich)

Deactivation phenomena

Stabilization of catalytic activity through Pt & H2

Identification of carbonaceous deposits

In situ UV-vis spectroscopy

a fundamental approach to the development of novel alkane

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