Chem. Rev., 113 (2013)

Catalysis with SR: Catalysis with SR: ex

ex--situ, in situ, in ––situ and situ and

in Operando conditions in Operando conditions

Department of Chemistry, University of Turin (Italy) Department of Chemistry, University of Turin (Italy)

in Operando conditions in Operando conditions

C. Lamberti C. Lamberti

A selection of several other examples: A selection of several other examples:

What does a catalyst do? What does a catalyst do?

‡

What does a catalyst do? What does a catalyst do?

What does a catalyst do? What does a catalyst do?

What does a catalyst do? What does a catalyst do?

The complexity of a catalyst: The complexity of a catalyst:

Nature of the support Nature of the support

Concentration of the active phase Concentration of the active phase

Deposition methods Deposition methods Addition of dopants Addition of dopants Addition of dopants Addition of dopants P, T P, T

Possible presence of spectators Possible presence of spectators

Aging effects Aging effects Poisoning Poisoning Deactivation Deactivation

A ve rage e ar th t em p er at u re ( ° C )

New researchs discover the actual cause of the global warming

Number of Pirats actives in the caribbean sea

A ve rage e ar th t em p er at u re (

A ve rage e ar th t em p er at u re ( ° C )

New researchs discover the actual cause of the global warming

Number of Pirats actives in the caribbean sea

A ve rage e ar th t em p er at u re (

The relevance of surfaces The relevance of surfaces

There is NO life on earth ! There is NO life on earth !

NO, it is a surface phenomenon ! NO, it is a surface phenomenon !

We avoided an invasion because aliens We avoided an invasion because aliens

had no surface sensitive techniques had no surface sensitive techniques

I

0 I1

x

Transmission techniques are basically Transmission techniques are basically

bulk techniques bulk techniques IR IR hard XAS hard XAS XRPD XRPD Transmission geometry

... but catalysis is related with surface sites

XPS; UPS; soft

MgO smoke

Mg(metal) + ½ O₂ →→→→ MgO

MgO morphology MgO morphology

(< 1 m2_/g)

MgO morphology MgO morphology

MgO sintered (40 m2_/g)

MgO morphology MgO morphology

MgO "Smoke"

MgO Sintered

CO on MgO at 60 K CO on MgO at 60 K

Spoto et al. Prog. Surf. Sci. 76 (2004) 71-146.

2200 2100 1600 1400 1200

MgO High Surf. Spoto et al. Prog. Surf. Sci. 76 (2004) 71-146.

CO on MgO at 60 K CO on MgO at 60 K Mg2+ 4c•••CO Mg2+ 5c•••CO MgO smoke MgO sintered 2200 2100 19 Mg2+ 3c•••CO MgO high surface area

CO on MgO at 60 K CO on MgO at 60 K 2200 2150 2100 (a) 0.2 a.u. A B S O R B A N C E MgO smoke IR transmission

Spoto et al. Surf.Sci. 540 (2003) L605;

Spoto et al. Prog. Surf. Sci. 76 (2004) 71-146. 2200 2100 T R A N S M IT T A N C E (b) MgO(001) single crystal IRAS

Heidberg, Surf. Sci. 331-333(1995)1467

High surface materials are reactive High surface materials are reactive

materials materials

Gold is known to be an inert material Gold is known to be an inert material

But gold But gold But gold But gold nanoparticles are nanoparticles are very active in very active in catalysis catalysis

12 16 20 24 N 1 N 2 N 3 N 4 C o o rd in at io n N u m b er 12 22 d (Å) 31 40 2 4 6 8 4 8 CO TCO ICO C o o rd in at io n N u m b er m

Tetrahedral unit Tetrahedral unit (SiO(SiO

4

4)) chainchain

The building

The building--up of a zeolitic frameworkup of a zeolitic framework

Microporous molecular sieve Microporous molecular sieve

ring ring

cage cage

Linde Type A

Sodalite

MOR

BEA

FAU MFI

95 100 400 600 800 1000 0.4 x TP A W e ig h t lo s s % 0.8

M. Milanesio, G. Artioli, A. F. Gualtieri, L. Palin and C. Lamberti. J. Am. Chem. Soc., 125 (2003) 14549-14558; ESRF Highlights 2003, 113-114

In situ template burning by XRPD In situ template burning by XRPD

85 90 Temperature (K) 0.0 W e ig h t lo s s % 4 6 8 10 12 (040) (202) (301) (102) (002) ₍₀₅₃₎ (352) (133) (303) (501) (200) (011) C o u n ts ( a .u .) T(K) 2θ(°) 973 573 GILDA BM8 GILDA BM8

O O Si Si Si Si Al Al Si Si Al Al

Selectivity of the intermedite species

CH₂ CH₂ CH₃

Selectivity of the reactants

Selectivity of the products

CH₂

CH₃

Cu2+ NO Cu2+ O N₂ O₂ NO Cu+ NO Cu2+ O N₂O Cu+ -Cu+

Cu+--zeolites: Interests & Applicationszeolites: Interests & Applications

Iwamoto & Hamada, Catal. Today 1991, 10, 57 Lamberti et al, J. Phys. Chem. B, 1997, 101 , 344

NO₂ Cu2+ O N₂ NO NO N₂ NO NO NO -34

active catalysts for the direct active catalysts for the direct conversion of NOx into O

conversion of NOx into O 2 2 and N and N 2 2 Cu

Cu--exchanged zeolites exchanged zeolites are very

are very

Prestipino et al., Chem. Phys. Lett., 2002, 363 , 389 Llabrés i Xamena et al., J. Phys. Chem. B, 2003, 107, 7036

MFI MFI

2 4 6 8 10 12 14 -0.1 0.0 0.1 0.2 a) e x p . k χ ( k ) (Å -1 ) k (Å-1) 2 4 _b) m a g n it u d e o f F .T . (Å -4 ) 1.0 1.5 N o rm a liz e d µ x Bare Cu+ 1s→→→4p→ xyand 1s→→→→4pz

C. Prestipino, et al. Chem. Phys. Lett. 363 (2002) C. Prestipino, et al. Chem. Phys. Lett. 363 (2002) 389 389 N = 2.5 _±0.3 R = 2.00 _±0.02 Å 0 2 4 6 0 2 r (Å) c) m a g n it u d e o f F .T . (Å 2 4 6 8 10 12 14 -0.1 0.0 0.1 0.2 Sim. Exp. k (Å-1) k χ (k ) (Å -1 ) 8975 8980 8985 8990 8995 0.5 N o rm a liz e d

Energy (eV) C. Lamberti et al. C. Lamberti et al. J. Phys. Chem. B, 101 (1997) 344J. Phys. Chem. B, 101 (1997) 344

0.1 0.2 a) A b s o rb a n c e 0.1 0.2 I / I b) 0.5 1.0 N o rm a liz e d µ x N N 2 2 on Cu+on Cu+--ZSMZSM--55 Wavenumbers (cm-1) 2320 2300 2280 0.0 Wavenumbers (cm-1) 2320 2300 2280 0.0 C. Lamberti et al.

C. Lamberti et al. J. Phys. Chem. B, 101 (1997) 344J. Phys. Chem. B, 101 (1997) 344 C. Lamberti et al.

C. Lamberti et al. Phys. Chem. Chem. Phys., 5 (2003) Phys. Chem. Chem. Phys., 5 (2003) 45024502

8980 9000 9020

0.0 0.5

1s 4p

α = 90o Exp.

Geometry of the Cu+(CO) Geometry of the Cu+(CO)

3

3 complex in ZSMcomplex in ZSM--5: XANES spectra5: XANES spectra

8980 8985 8990 Cu+(CO)₃ Cu+(CO)₂ Cu+(CO) Cu+ Energy (eV) Formation of CuI(CO)

n _{CO to CuI}electron transfer from

0 1 2 3 4 Energy (Ry) α = 30o α = 42o α = 54o α = 70o B A

C. Lamberti, et al. Angew.

C. Lamberti, et al. Angew. Chem. Int. Ed., 39 Chem. Int. Ed., 39 (2000) 2138

0.05 Å-2

Experimental and Fit

Cu-O_F (g₂) Cu-C-O (g₂+g₃) Cu-C (g 2) Residual k 2 χ (k )( Å -2 )

Local structure of [CuI(CO)

2]+ adducts

hosted inside ZSM-5 zeolite

4 6 _{k (A}-1 8 10 12

)

0.0 0.2 - - - EXP ___ FIT Cu-C-O (MS) Cu-O Cu-C a) kχ(k)/Å-1 0.15 |FT|/Å -3 . . . EXP ___ FIT - - - residual b) Local structure of [CuI(CO) 3]+ adducts hosted inside ZSM-5 zeolite C. Lamberti, et al.

C. Lamberti, et al. AngewAngew. . Chem. Int. Ed., 39 (2000) 2138Chem. Int. Ed., 39 (2000) 2138

4 6 8 10 12 14 r/Å residual k/Å-1 2.5 5.0 7.5 0.00 Cu+ _{complexes N}

CO RCu-OF (Å) RCu-C (Å) RC-O (Å) θθθθCu-C-O (°)

Cu+ - _{2.00 ± 0.02} - -

-Cu+(CO)₂ 1.8 _± 0.3 2.11 _± 0.03 1.88 _± 0.02 1.12 _± 0.03 170 _± 10 Cu+_(CO)

3 3 (fixed) - 1.93 ± 0.02 1.12 ± 0.03 180 ± 10

Y Y

Cu+

Cu+--Y: IR spectroscopy of CO at 80 KY: IR spectroscopy of CO at 80 K

0.2 A.U.

Low P

CO 2 bands: 2 Cu+ sites? Medium P

CO 4 bands: 4 Cu+ sites? High P CO 3 bands: ??????????? 42 B 2200 2180 2160 2140 2120 2100 2080 Wavenumber (cm -1 ) Increasing P CO

Cu+

Cu+--Y:EXAFS data: GILDA BM8 @ ESRFY:EXAFS data: GILDA BM8 @ ESRF

0.0 0.2

It was not possible to refine the EXAFS data neither assuming one single Cu+ site nor assuming two different Cu+ environments

43 2.5 5.0 7.5 10.0 12.5 -0.2 k χ (k ) k (Å-1)

Cu+-Y still remains a puzzle

Cu+

Cu+--Y: in situ XRPD data @ ESRF (80 K)Y: in situ XRPD data @ ESRF (80 K)

II II*

I*

2 Cu+ sites available for CO

44 Turnes Palomino, et al.,

Turnes Palomino, et al., J. Phys. J. Phys. Chem. B, 2000Chem. B, 2000, , 104104,, 40644064 λλλλ = 0.62992(1) Å

Cu+

Cu+--Y: XRPD explains EXAFS dataY: XRPD explains EXAFS data

II

II*

I*

45 Turnes Palomino, et al.,

Turnes Palomino, et al., J. Phys. J. Phys. Chem. B, 2000Chem. B, 2000, , 104104,, 40644064

5.0 7.5 10.0 12.5 k χ (k ) 0.1 Å -1 ... Fit: I* + II*+ II ___ Experimental k (Å-1) II II* I*

Cu+

Cu+--Y:XRPD interaction with CO at 80 KY:XRPD interaction with CO at 80 K

II II* I* + CO 46 λλλλ = 0.62992(1) Å

One single Cu+ sites available for CO at high P

CO

Turnes Palomino, et al.,

Cu+

Cu+--Y: Y: XRPD explains XRPD explains IRIR datadata

0.2 A.U. 2200 2150 2100 2143 Wavenumber (cm-1) 2135 2168 _{O O} C C I Cu O C I Cu 2148 2178 2159 Two II sites Two II sites 2200 2150 2100 2143 Wavenumber (cm-1) 2135 2168 O O O C C I Cu O C I Cu 2148 2178 2159 One II site 47 B 2200 2180 2160 2140 2120 2100 2080 Wavenumber (cm -1 ) Increasing P CO

Turnes Palomino, et al.,

Turnes Palomino, et al., J. Phys. J. Phys. Chem. B, 2000Chem. B, 2000, , 104104,, 40644064

II II* I* O O O C C _C I Cu (2138) 2165 2188

MFI MFI

1.0 1.5 N o rm a liz e d µ x 2 Cu+(NO)₂ A b s o rb a n c e Cu+(NO) 2 1s→→→→4p x1s→→→→4pyand 1s→→→→4pz Bare Cu+ 1s→→→4p→ xyand 1s→→→→4pz

Prestipino et al., Chem. Phys. Let. 363 (2002) 389

8975 8980 8985 8990 8995 0.5 N o rm a liz e d Energy (eV) 1900 1850 1800 1750 1700 0 1 _Cu2+_(NO) NO...NO A b s o rb a n c e wavenumber (cm-1) oxydation

+ NH

TS

TS--1: Interest & Applications1: Interest & Applications

N O H O OH OH Ph-OH 1:1 o:p NH3 RC 2 H CH RC 2 H CH O

Higly active and Higly active and selective catalyst selective catalyst for

for oxidation oxidation

reactions using reactions using hydrogen peroxide hydrogen peroxide 53 RR'CHNH2 R NOH2 NOH RR'C RR'CHOH R NH2 R S2 R SO2 R CH2 2 O RR'C R CHOH2 + O R C2 + H O_{2 2} 30% hydrogen peroxide hydrogen peroxide as oxidizing agent as oxidizing agent: : Industrial plants in Industrial plants in Europe and Japan Europe and Japan

Notari, Adv. Catal. 1996, 41, 253,

Mantegazza, et al. J. Mol. Catal. A 1999, 146, 223 Bordiga et al. Angew. Chem. Int. Ed., 2002, 41, 4734 Bonino et al., J. Phys. Chem. B, 2004, 108, 3573

95 100 400 600 800 1000 0.4 x T P A W e ig h t lo s s % 0.8 M. Milanesio, G. Artioli, A. F. Gualtieri, L. Palin and C.

Lamberti. J. Am. Chem. Soc., 125 (2003) 14549-14558;

ESRF Highlights 2003, 113-114

In situ template burning by XRPD In situ template burning by XRPD

85 90 Temperature (K) 0.0 W e ig h t lo s s % 4 6 8 10 12 (040) (202) (301) (102) (002) ₍₀₅₃₎ (352) (133) (303) (501) (200) (011) C o u n ts ( a .u .) T(K) 2θ(°) 973 573 GILDA BM8 GILDA BM8

O₂ Feed line

Catalyst

Instrumental set-up

In situ template burning by XRPD GILDA BM8 In situ template burning by XRPD GILDA BM8

Heat gun The reactor

TS-1 _Fe-MFI

T_s = start of the template decomposition T_b = start of the template burning

T_f = end of the template burning

T_{s T} s evolution of the lattice parameters thermal expansion template decomposition template burning

volatile fragments diffuse out of the channels

coke elimination

annealing of defective T sites

nearly isotropic TE

very anisotropic TE

M. Milanesio, G. Artioli, A. F. Gualtieri, L. Palin and C. Lamberti. J. Am. Chem. Soc., 125 (2003) 14549; ESRF Highlights 2003, 113-114

0.2 norm µx 2 Å-4 0.1 Å-1 before TS

TS--1: XAFS data @ ESRF BM8 GILDA1: XAFS data @ ESRF BM8 GILDA

4980 5000 5020

Photon Energy (eV)

1 2 3 R (Å) 5.0 7.5 10.0 12.5 in vacuo + H 2O + NH 3 k (Å-1) S. Bordiga et al.

S. Bordiga et al. J. Phys. ChemJ. Phys. Chem., ., 20022002, , 106106,, 9892; A. Zecchina et al., 9892; A. Zecchina et al., Topics in Catal.Topics in Catal., , 20022002, , 21,21, 6767

before

TS

TS--1: XAFS data @ ESRF BM8 GILDA1: XAFS data @ ESRF BM8 GILDA

Zecchina et al.,

Zecchina et al., Topics in Catal.Topics in Catal., , 20022002, , 21,21,67; F. Bonino, et al. 67; F. Bonino, et al. J. Phys. Chem. BJ. Phys. Chem. B, , 2004,2004,108108, 3573 , 3573 Prestipino et al.

C o u n ts ( a .u ) νννν(O-O): 898 cm-1 Breathing mode Ti-O₂: 595 cm-1 (NH₄)₃TiF₅O₂ 1064 and 442 nm TS-1 TS-1 + H O

Electronic and vibrational transitions involving Ti

Electronic and vibrational transitions involving Ti--peroxo speciesperoxo species

300 400 500 1500 2000 % R Wavelength (nm) 442 nm 442 nm 1200 1000 800 600 400 C o u n ts ( a .u ) Raman shift / cm-1 S. Bordiga, et al

S. Bordiga, et al Angew. Angew. Chem., Chem., 20022002, , 4141, 4734, 4734

Sil Sil + H₂O₂ 442 nm νννν(O-O) H₂O₂: 875 cm-1 TS-1 + H₂O₂ 442 nm Breathing mode Ti-O₂: 620 cm-1

The PVC [-CH₂-CHCl-]_n

• A wide use polymeric material

• It used in electronic, • It used in electronic, building,farmaceutic, and in several different kind of applications

The chemistry of PVC The chemistry of PVC

Direct chlorination (FeCl₃): C₂H₄ + Cl₂ →→→→ C₂H₄Cl₂

The oxychlorination reaction (CuCl₂) : C₂H₄ + 2HCl + ½ O₂ →→→→ C₂H₄Cl₂ + H₂O

The cracking of 1,2-dichloroethane:

Understanding the basic reactions Understanding the basic reactions

Catalyst: CuCl₂/γ-Al₂O₃

Evolution of the XANES spectra after interaction with reactants

a) Reduction of CuCl₂ to CuCl by C₂H₄ :

2CuCl₂ + C₂H₄ → C₂H₄Cl₂ + 2CuCl µ x N o rm a liz z a to attivato + C 2H4 (a) 0.2 + C 2H4 + O 2 (b) activated 2 2 4 2 4 2

b) Re-oxidation of CuCl by oxygen:

2CuCl + ½ O₂ → Cu₂OCl₂

c) Closure of the catalytic cycle by re-chlorination by HCl yielding CuCl₂ :

Cu₂OCl₂ + 2HCl → 2CuCl₂ + H₂O

G. Leofanti et al.

G. Leofanti et al. J. Catal.,J. Catal., 189189 (2000) 91(2000) 91; ; J. Catal.,J. Catal., 189189 (2000) 105(2000) 105;;

J. Catal.,

J. Catal., 202202 (2001) 279(2001) 279; ; J. Catal.,J. Catal., 205205 (2002) 275(2002) 275

8975 9000 9025 8975 9000 9025 Energia (eV) Energia (eV) + C 2H4 µ x N o rm a liz z a to + O 2 +HCl (c) 2 Energy (eV) Energy (eV)

Understanding the basic reactions Understanding the basic reactions

Catalyst: CuCl₂/γ-Al₂O₃

Evolution of the XANES spectra after interaction with reactants

a) Reduction of CuCl₂ to CuCl by C₂H₄ :

2CuCl₂ + C₂H₄ → C₂H₄Cl₂ + 2CuCl 4 + C₂H₄ + O₂ + HCl FT (Å -4 ) 2 2 4 2 4 2

b) Re-oxidation of CuCl by oxygen:

2CuCl + ½ O₂ → Cu₂OCl₂

c) Closure of the catalytic cycle by re-chlorination by HCl yielding CuCl₂ :

Cu₂OCl₂ + 2HCl → 2CuCl₂ + H₂O 1 2 0 2 _Cu-Cl Cu-O FT (Å

R(Å) _{G. Leofanti et al. G. Leofanti et al. J. Catal.,J. Catal., 189189 (2000) 91(2000) 91; ; J. Catal.,J. Catal., 189189 (2000) 105(2000) 105;;}

J. Catal.,

The use of additives in the industrial catalysts The use of additives in the industrial catalysts

Fixed bed reactors Potassium

Base catalyst: CuCl₂/γγγγ-Al₂O₃

P3 R E A C PRODUCTS OUTPUT K/Cu=0.17

Fluid bed reactors Magnesium

Other additives : Li, Cs, Ce, La

P1 P2 C T O R REACTANTS INPUT K/Cu=0.50 K/Cu=0.75

Second goal:

Determination of the

rate determining step

GOALS and TECHNIQUES GOALS and TECHNIQUES

First goal:

The study of the effects of

additives rate determining step

Of the ethylene oxychlorination

reaction

additives

and of their concentration

dispersive XAS

Different X

Different X--ray absorption techniques ray absorption techniques

Classical monochromatic geometry Dispersive Geometry 8950 9000 9050 µ x

Energia [eV]_{Energy (eV)}

0.2 0.4 0.6 0.8 1.0 1.2 8950 9000 9050 9100 9150 Energ ia (eV ) Tem pera_tura (K) 400 500 600 µ x n o rm a liz z a to

Experiment description @ ID24 Experiment description @ ID24

500 550 600 650 I0 e C u re f I0 e C u re f S to p a c q u is iz io n i X A S T e m p e ra tu ra [ K ] Composition of the reactant flux: N₂ 13cc/min. C₂H₄ 100cc/min. HCl 36.1cc/min. Te m p e ra tu re ( K ) I0 a n d C u re f I0 a n d C u re f S to p a cq u is it io n 0 20 40 60 80 350 400 450 ESPERIMENTO STANDARD S to p a c q u is iz io n i X A S I 0 e C u re f I 0 e C u re f T e m p e ra tu ra [ K ] Tempo [min.] 2 4 HCl 36.1cc/min. O₂ 7.6cc/min. • Ramp up from 373 to 623 K • Isotherm at 623 K

• Ramp down from 623 back to 373 K

Standard experiment Time (min) Te m p e ra tu re ( K ) I0 a n d C u re f I0 a n d C u re f S to p a cq u is it io n

Description of the experimental set

Description of the experimental set--up @ ID24up @ ID24

X-rays Exausted gas Flow detector candles Bottles cell

XAFS cell and positioning motors Mass spectrometer Exhaust gases elimination Zoom on the cell DETECTOR spectrometer

Base catalyst CuCl

Base catalyst CuCl₂₂//γγ--AlAl₂₂OO₃₃

Ramp up: Cu(II) Cu(I)

1.0 1.2 x n o rm a liz z a to _0.6 0.8 1.0 1.2 x n o rm a liz z a to Punti isosbestici 0.06 0.08 0.10 0.12 0.14 0.16 x )/ d E [ e V -1 ] 0.05 eV-1 Cu(II) Cu(I) x )/ d E [ e V -1 ] C. Lamberti,

C. Lamberti, et al.et al. Angew. Angew. Chem. Int. Ed.,Chem. Int. Ed., 4141

(2002) 2341 (2002) 2341--23442344 0.2 0.4 0.6 0.8 1.0 8950 9000 9050 9100 9150 Energ ia (eV ) Tem pera tura _(K) 400 500 600 µ x n o rm a liz z a to 8950 9000 9050 0.2 0.4 0.6 µ x n o rm a liz z a to Energia [eV] Punti isosbestici XANES spectra 8970 8980 8990 9000 9010 -0.04 -0.02 0.00 0.02 0.04 d ( µ x )/ d E [ e V Energy [eV]

First derivative spectra

8955 8970 8985 9000 400 500 600 d ( µ x )/ d E [ e V Te_m pe ratu ra [_K] Energ ia [eV ]

K

K--CuClCuCl₂₂//γγ--AlAl₂₂OO_{3 3} catalystcatalyst

Ramp up: Cu(II) Cu(II)+Cu(I)

0.8 1.0 1.2 x n o rm a liz z a to 0.8 1.0 1.2 x n o rm a liz z a to 0.04 0.06 0.08 0.10 0.12 0.14 0.16 CuI /d E [ e V -1 ] CuII x )/ d E [ e V -1 ] C. Lamberti,

C. Lamberti, et al.et al. Angew. Angew. Chem. Int. Ed.,Chem. Int. Ed., 4141

(2002) 2341 (2002) 2341--23442344 0.2 0.4 0.6 0.8 1.0 1.2 8950 9000 9050 9100 9150 0.2 0.4 0.6 0.8 Energ ia (eV ) 500 400 600 Tem pera tura _(K) µ x n o rm a liz z a to 8950 9000 9050 0.2 0.4 0.6 µ x n o rm a liz z a to Energia [eV] XANES spectra 8970 8980 8990 9000 9010 -0.04 -0.02 0.00 0.02 0.04 CuII residuo d µ /d E [ e V Energia [eV] 8950 9000 9050 CuI 600 500 400 Te mp era tura _(K ) d ( µ x )/ d E [ e V Energ ia (eV

CuCl₂/γγγγ-Al₂O₃

• Totally reduced at the end of the ramp up

• Not re-oxidized during the ramp down • The activity of the catalysts starts with the reduction, within our accurancy (±10 K) Comparison between K

Comparison between K--CuClCuCl₂₂//γγ--AlAl₂₂OO_{3 3} and CuCland CuCl₂₂//γγ--AlAl₂₂OO₃₃

600 550 500 450 400 0 10 20 30 400 450 500 550 600 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 C o n v e rs io n e O 2 [ % ] F ra z io n e d i C u (I I) Temperatura [K] Temperature (K) K-CuCl₂/γγγγ-Al₂O₃

• Partially reduced at the end of the ramp up

• Re-oxidized during the ramp down • The activity starts before the reduction

C. Lamberti,

C. Lamberti, et al.et al. Angew. Angew. Chem. Int. Ed.,Chem. Int. Ed., 4141

(2002) 2341 (2002) 2341--23442344 Temperatura [K] -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 600 550 500 450 400 0 10 20 30 400 450 500 550 600 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 F ra z io n e d i C u (I I) C o n v e rs io n e O 2 [ % ] Temperatura [K] Temperature (K) Temperature (K)