Co-adsorbents for sorption-enhanced steam

reforming of methane H.T.J. Reijers G.D. Elzinga J.W. Dijkstra W.G. Haije

P.D. Cobden R.W. van den Brink

Presented at the 5th Trondheim Conference on CO2 capture, Transport and Storage, 16-17 June 2009, Trondheim Norway

ECN-L--09-160 December 2009

Co-adsorbents for sorption-enhanced steam reforming of methane

Hendricus T.J. Reijers, Gerard D. Elzinga, Jan Wilco Dijkstra, W.G. Haije, Paul D. Cobden and Ruud W. van den Brink

www.ecn.nl

Introduction – Sorption enhancement

sorbent B

A

D(sorbed) C(gas)

Sorption Conversion enhancement by sorptive manipulation of concentration profiles

2 1-12-2009

A+B C+D

(catalyst)

sorbent

E

D(sorbed) E(gas)

E

D

Desorption

Sorption-Enhanced Reaction Process

CH4 + H2O 3 H2 + CO (∆H = 206 kJ/mol)

CO + H2O H2 + CO2 (∆H = - 41 kJ/mol)

CH4 + 2 H2O 4 H2 + CO2

3 1-12-2009

CH4 + H2O H2 + CO2

catalyst adsorbent catalyst adsorbent

Strategies for choosing Absorbent

• Start with available materials and see how they perform (bottom-up ). Examples: CaO, Li2ZrO3, Li4SiO4.• Derive materials requirements from systems

requirements: - CCR = 85% (Carbon Capture Ratio)

In general, two approaches are possible:

4 1-12-2009

- CCR = 85% (Carbon Capture Ratio)

- p = 25 bar - 3 < S/C < 4 - 600 °C < T < 800 °C

(top-down ).

Thermodynamic investigation, materials p*

1.E+04

1.E+08

p* (b

ar)

Li2SiO3

ZnOolivine

Li4SiO4

Li2ZrO3Ba2ZrO4

BaTiO3

MgO

5 1-12-2009

1.E-08

1.E-04

1.E+00

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

1000/T (1/K)

p* (b

ar)

CaO

BaZrO3

BaO

Ba2TiO4

Ba2ZrO4

Sr2ZrO4

Sr2TiO4

Thermodynamic investigation, materials p*

1.E+04

1.E+08

p* (b

ar)

Li2SiO3

ZnOolivine

Li4SiO4

Li2ZrO3Ba2ZrO4

BaTiO3

MgO

1/T

unsuitable

suitable

CCR = 85%

6 1-12-2009

1.E-08

1.E-04

1.E+00

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

1000/T (1/K)

p* (b

ar)

CaO

BaZrO3

BaO

Ba2TiO4

Ba2ZrO4

Sr2ZrO4

Sr2TiO4

CCR = 85%, p=25 bar S/C = 4

S/C = 3

Thermodynamic investigation, materials p*

1.E-02

1.E+00

(ba

r)

CaO

Ba2ZrO4

Sr2TiO4

BaO

7 1-12-2009

1.E-08

1.E-06

1.E-04

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

1000/T (1/K)

pC

O2 (

bar)

CaOSr2ZrO4

Ba2TiO4

preferred range of reaction

temperature

CCR = 85%, p=25 bar S/C = 4

S/C = 3

Preparation

24223 22 COTiOBaTiOBaCO +↔+

By solid-state reaction at 1450 °C:

8 1-12-2009

CO2 absorption

CO2 absorption reaction ∆H298 K (kJ/mol)

Stoichiometric CO2 uptake [wt%] [mol/kg]

33242 BaCOBaTiOCOTiOBa +↔+ -247 11 2.6

9 1-12-2009

33242

3223 BaCOTiOCOBaTiO +↔+ -131 19 4.3

32242 22 BaCOTiOCOTiOBa +↔+ -379 23 5.2

32 CaCOCOCaO ↔+ -170 78 18

SEM of Ba 2TiO4 particles

10 1-12-2009

Isotherm measurements1.E+03

p* (

bar)

BaTiO3+CO2 = BaCO3 + TiO2

Ba2TiO4+2CO2 = 2BaCO3 + TiO2

11 1-12-2009

1.E-05

1.E-01

0.8 0.9 1 1.1 1.2

1000/T (1/K)

p* (

bar)

Ba2TiO4+CO2 = BaCO3 + BaTiO3

solid circles: volumetric measurementopen circles: lab-scale reactor test

Comparison of TGA results for Ba 2TiO4 particles: a.r. (0.1 – 0.2 mm) and crushed (0.01 – 0.1 mm)

2

3

cap

acity

[wt%

]

4

6

upt

ake

rate

[wt%

/min

]

conditions:

adsorption: CO 2, 2 hrsdesorption: N 2, 1 hr, 1000 °C

0.35

0.4

0.45

0.5

Load

ing

CaO, 600 °C < T < 700 °C:5 - 10 wt%/min30 - 60 wt%

12 1-12-2009

0

1

500 600 700 800 900 1000

T [°C]

CO

2 ca

paci

ty [w

t%]

0

2

CO

2 up

take

rat

e [w

t%/m

in]

solid line: capacity

dashed line: rate

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200

Time

Load

ing

Comparison of TGA results for Ba 2TiO4 particles: a.r. (0.1 – 0.2 mm) and crushed (0.01 – 0.1 mm)

2

3

cap

acity

[wt%

]

4

6

upt

ake

rate

[wt%

/min

]

conditions:

adsorption: CO 2, 2 hrsdesorption: N 2, 1 hr, 1000 °C

crushed particles

13 1-12-2009

0

1

500 600 700 800 900 1000

T [°C]

CO

2 ca

paci

ty [w

t%]

0

2

CO

2 up

take

rat

e [w

t%/m

in]

solid line: capacity

dashed line: rate

particles a.r.

Cyclic performance in lab-scale experiment

6

8

cap

acity

[mol

/kg]

conditions:1 g Ba 2TiO4

adsorption: 5% CO 2, 29% H2O, balance N 2

600 °C, 1 atm, 30 mL/mindesorption: 29% H2O, balance N2 850 °C, 1 atm, 100 mL/min

CaO

14 1-12-2009

0

2

4

0 5 10 15 20 25 30 35 40

Cycle number

CO

2 ca

paci

ty [m

ol/k

g]

850 °C, 1 atm, 100 mL/min

Ba2TiO4

Desorption of CO 2 for various temperatures

2

3

flow

[ml/m

in]

950 °C

conditions:1 g Ba2TiO4

adsorption: 5% CO 2, 29% H2O, balance N 2

600 °C, 1 atm, 30 mL/min

15 1-12-2009

0

1

0 10 20 30 40

Time [min]

CO

2 flo

w [m

l/min

]

900 °C

850 °C

600 °C, 1 atm, 30 mL/mindesorption: 29% H2O, balance N2 1 atm, 100 mL/min

Tandem configuration of CaO and Ba 2TiO4

Making use of the good properties of both:• CaO: good kinetics, good capacity, cheap• Ba2TiO4: low CO2 equilibrium pressure, co-adsorbent

Ba TiO – catalystCaO – catalyst

16 1-12-2009

H2O

CH4

Ba2TiO4 – catalystfor polishing

CaO – catalystfor bulk reaction

Comparison of lab-scale SERP experiments: CaO-only bed and CaO-Ba 2TiO4 tandem bed

3

4

5

/CO

con

cent

ratio

n [%

]

75%

100%

con

vers

ion

CO2

CH4 conv

conditions:

17 1-12-2009

0

1

2

0 10 20 30 40 50 60

Time [min]

Wet

CO

2/C

H4/

CO

con

cent

ratio

n [%

]

0%

25%

50%

CH

4 co

nver

sion

CH4

CO

conditions:1 g CaO, 1 g cat7.1% CH4, 29% H2O, balance N 2

600 °C, 1 atm, 25 mL/min

Comparison of lab-scale SERP experiments: CaO-only bed and CaO-Ba 2TiO4 tandem bed

3

4

5

/CO

con

cent

ratio

n [%

]

75%

100%

con

vers

ion

CO2

CH4 conv

solid line: CaO + Ba 2TiO4

dashed line: only CaOconditions:1st bed: 0.95 g CaO, 0.98 g cat

18 1-12-2009

0

1

2

0 10 20 30 40 50 60

Time [min]

Wet

CO

2/C

H4/

CO

con

cent

ratio

n [%

]

0%

25%

50%

CH

4 co

nver

sion

CH4

CO

1st bed: 0.95 g CaO, 0.98 g cat2nd bed: 0.37 g Ba 2TiO4, 0.02 g cat7.1% CH4, 29% H2O, balance N 2

600 °C, 1 atm, 25 mL/min

Conclusions

• Based on thermodynamic calculations, Ba2TiO4 fulfills the system requirements: CCR = 85% at p = 25 bar, 600 °C < T < 800 °C, 3 < S/C < 4, while CaO does not.• The measured adsorption isotherm agrees with the

literature.•

19 1-12-2009

literature.• The observed stability of Ba2TiO4 in cyclic experiments

is better than for CaO.• For short contact times, the kinetics and the capacity of

CO2 adsorption for Ba2TiO4 is not so good as for CaO.• A tandem configuration of CaO and Ba2TiO4 offers a

trade-off between system requirements and economy.

Acknowledgement

This work was funded by

SenterNovem in the C-Clear project

20 1-12-2009