Supplementary Materials

Catalyst-assisted chemical looping auto-thermal dry reforming:

Spatial structuring effects on process efficiency

Jiawei Hua, Vladimir V. Galvitaa*, Hilde Poelmana, Christophe Detavernierb, Guy B. Marina

aLaboratory for Chemical Technology, Ghent University, Technologiepark 914, B-9052 Ghent, BelgiumbDepartment of Solid State Sciences, Ghent University, Krijgslaan 281, S1, B-9000 Ghent, Belgium*Corresponding author: V. V. Galvita: Vladimir.Galvita@UGent.be;

tel: +32-468-10-6004; fax: +32-9331-1759

List:

Fig. S1. EDX line-scan analysis for core-shell structured Ni/Zr@Zr catalyst and Fe/Zr@Zr

OSM.

Fig. S2. STEM micrograph and EDX element mapping of Fe, Zr, Si and Ni as well as these

elements combined for the as-prepared Fe/Zr@Zr-Si@Ni sample.

Fig. S3. 2D in-situ XRD pattern recorded during H2-TPR for the Fe/Zr@Zr-Ni@Zr bifunctional

catalyst as well as the diffraction peaks from 42.5° to 46.0° at the selected temperature.

Fig. S4. The XRD peaks from 42.5° to 46.5° at different time positions during the first

isothermal redox cycle over physical mixture of Ni/Zr@Zr and Fe/Zr@Zr, as well as

Fe/Zr@Zr-Ni@Zr bifunctional catalyst.

Fig. S5. XPS wide scans for the as-prepared, reduced and spent samples of Fe/Zr@Zr-Ni@Zr

bifunctional catalyst.

Fig. S6. Equilibrium lines of (CO+H2)/(CO2+H2O) ratio, CH4 and CO2 conversion, as well as the

iron/iron oxide system at different temperature during catalytic auto-thermal dry reforming

of methane.

Fig. S7. Reactivity of the Fe/Zr@Zr-Ni@Zr bifunctional catalyst during the CCAR process: the

space-time yields of the products vs. time on stream during the reduction and re-oxidation

half-cycle.

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Fig. S8. CO2 space-time yield (STY) during O2-TPO over the spent catalysts after 25 cycles of

CCAR from different reactor bed configurations.

Fig. S9. XRD patterns of the spent samples of Ni/Zr@Zr catalyst, Fe/Zr@Zr OSM and

Fe/Zr@Zr-Ni@Zr bifunctional catalyst after 25 cycles of CCAR in different reactor beds.

Fig. S10. BET specific surface area of fresh and spent samples after 25 CCAR cycles of a

physical mixture of Ni/Zr@Zr and Fe/Zr@Zr, as well as for the Fe/Zr@Zr-Ni@Zr bifunctional

catalyst.

2

Fig. S1

Fig. S1. EDX line-scan analysis for fresh core-shell materials: (a) Ni/Zr@Zr catalyst, (b) Fe/Zr@Zr OSM. The

upper figure show the X-ray scanning route through the particle.

3

Fig. S2

Fig. S2. STEM micrograph and EDX element mapping of Fe, Zr, Si and Ni as well as these elements combined for

the as-prepared Fe/Zr@Zr-Si@Ni sample.

4

Fig. S3

Temperature (°C)

Fe3O4

Ni + Fe

Ni-Fe alloy

Fe2O3

42.5 43.0 43.5 44.0 44.5 45.0 45.5 46.0

ZrO2

ZrO2

XRD in

tens

ity (a

.u.)

2-Theta ()

400°C 500°C 600°C 700°C

Ni-Fe alloy

Fe3O

4

Ni+Fe

Fig. S3. 2D in-situ XRD pattern recorded during H2-TPR for the Fe/Zr@Zr-Ni@Zr bifunctional catalyst as well as

the diffraction peaks between 42.5° and 46.0° at the selected temperatures (400 °C, 500 °C, 600 °C and 700 °C).

The background was processed by a linear subtraction.

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Fig. S4

42.5 43.0 43.5 44.0 44.5 45.0 45.5 46.0 46.5

XR

D in

tens

ity (a

.u.)

2-Theta ()

Fe3O

4Ni-Fe alloy

Ni+Fe(a)

ZrO2

ZrO2

42.5 43.0 43.5 44.0 44.5 45.0 45.5 46.0 46.5

Ni+Fe

ZrO2

ZrO2

(b)

XR

D in

tens

ity (a

.u.)

2-Theta ()

Fe3O

4 Ni-Fe alloy

Fig. S4. The XRD peaks from 42.5° to 46.5° at different time positions during the first isothermal redox cycle

over (a) physical mixture of Ni/Zr@Zr and Fe/Zr@Zr (data from Fig. 8c), and (b) Fe/Zr@Zr-Ni@Zr bifunctional

catalyst (data from Fig. 8d). The solid and dashed curve respectively show the main crystal phases of the samples

in the reduction and re-oxidation half-cycle. The inset figures show the selected time position, indicated by solid

or dashed line, which is located in the corresponding He purging period after each half-cycle to ensure a same

background intensity. The background was processed by a linear subtraction.

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Fig. S5

0100200300400500600700800900

XPS

inte

nsity

(a.u

.)

binding energy (eV)

O1s

Ni2p

Fe2p+ Ni Auger

C1s

Zr3p

Zr3d

Si2s Si2p

OKLL

Zr3s

Fig. S5. XPS wide scans for the as-prepared (blue line), reduced (green line) and spent (red line) samples of

Fe/Zr@Zr-Ni@Zr bifunctional catalyst. The spent sample was collected after 25 CCAR cycles.

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Fig. S6

200 300 400 500 600 700 800 9000

1

2

3

4

5

6

7

8

9

Conversion (%

)

FeO / Ni

Fe / Ni

(CO

+H2)

(CO

2+H2O

) (m

ol/m

ol)

Temperature (C)

Fe3O

4 / Ni

-20

0

20

40

60

80

100

Fig. S6. The ratio between reducing (CO+H2) and oxidizing gases (CO2+H2O) as a function of temperature during

catalytic auto-thermal dry reforming of methane. Solid lines: Equilibrium lines of the iron/iron oxide system at

different temperatures and reduction capacities in the presence of (CO+H 2)/(CO2+H2O). Dashed lines:

Equilibrium value of the (CO+H2)/(CO2+H2O) ratio (blue curve), CH4 (red curve) and CO2 (green curve)

conversion at different reaction temperatures during reforming of a feed mixture with molar ratio CH4:CO2:O2 =

1:1:0.2. The thermodynamic calculations were executed by minimization of the Gibbs free energy of the system

at given conditions, such as pressure, temperature and initial reactants composition, performed with the

EkviCalc software [72].

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Fig. S7

0 40 80 1200.0

0.5

1.0

1.5

2.0

CO

2 STY

(mol

s-1

kg-1Fe2O

3 )C

O S

TY (m

olC

O

s-1

kg-1 Fe

2O3)

TOS (s)

0

5

10

15

20

25

30

STY

(mol

s-1

kg-1 N

i)

Reduction half-cycle

Re-oxidation half-cycle

COH2

CO2

CH4 H2O O2

0

5

10

15

20

Fig. S7. Reactivity of the Fe/Zr@Zr-Ni@Zr bifunctional catalyst during the CCAR process at 750 °C. Reduction half-cycle (upper figure): space-time yields of CH4, CO2, O2, CO, H2 and H2O as products vs. time on stream during catalytic auto-thermal dry reforming of CH4 and the reduction of the Fe/Zr@Zr OSM core (reactant: mixture of CH4:CO2:O2 = 1:1:0.2, 150 mL min⋅ -1); Re-oxidation half-cycle (lower figure): space-time yield of CO and CO2

during re-oxidation of Fe to Fe3O4 (reactant: 90% CO2/Ar, 150 mL min⋅ -1).

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Fig. S8

100 200 300 400 500 600 700 800 9000

20

40

60

80

100

CO

2 STY

(mols

-1k

g-1 Ni)

Temperature ( C)

NiFe_D1 NiFe_S2 BCFe_D3

Fig. S8. CO2 space-time yield (STY) during O2-TPO over the spent catalysts after 25 cycles of CCAR from different

reactor bed configurations. The samples were heated from room temperature to 900 °C with a ramp rate of 10

°C∙min-1. Gas flow: 60 mL∙min-1 of 10% O2/He.

10

Fig. S9

20 25 30 35 40 45 50 55 60

Fe

Ni

Inte

nsity

(a.u

.)

2-Theta()

(a)

20 25 30 35 40 45 50 55 60

Ni+Fe

Inte

nsity

(a.u

.)

2-Theta()

(b)

20 25 30 35 40 45 50 55 60

Fe

BC

Inte

nsity

(a.u

.)

2-Theta()

(c)

Fig. S9. XRD patterns of the spent samples of Ni/Zr@Zr catalyst (labeled as Ni), Fe/Zr@Zr OSM (Fe) and Fe/Zr@Zr-Ni@Zr bifunctional catalyst (BC) after 25 cycles of CCAR in different reactor beds: NiFe_D1 (a), NiFe_S2 (b) and BCFe_D3 (c). The symbols represent: (∆) -Alα 2O3, (●) m-ZrO2, ( ) t-ZrO◊ 2, ( ) Fe∨ 3O4 and ( ) Ni.∗ The residual -Alα 2O3 originates from the inert diluent in the reactor bed which cannot be removed completely from the spent samples.

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Fig. S10

0

5

10

15

20

25

30

35

After CCAR

BE

T-S

SA

(m2

g-1)

Fresh Fresh After CCARFig. S10. BET specific surface area of fresh and spent samples after 25 CCAR cycles of a physical mixture of

Ni/Zr@Zr and Fe/Zr@Zr (black column), as well as for the Fe/Zr@Zr-Ni@Zr bifunctional catalyst (red column).

The error bars represent the standard deviation based on three repeat tests.

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