CFB8 - REM, 5/3/2005

Kinetics of the chemical looping reduction of CuO/bentonite by

methane (CH4)

Esmail R. Monazam1,2, Ranjani Siriwardane, Lawrence J. Shadle, George

Richard, Hanjing Tian2 , David E. Huckaby, and Stephen Carpenter2

National Energy Technology Laboratory

U. S. Department of Energy

3610 Collins Ferry Rd.

Morgantown, West Virginia 26507-08801REM Engineering Services, PLLC

3537 Collins Ferry Rd.

Morgantown, West Virginia 265052URS Energy & Construction, Inc.

3610 Collins Ferry Rd.

Morgantown, WV. 26505

CFB8 - REM, 5/3/2005

Objective

Extract kinetic parameters from experimental test data

using Thermo-gravimetric Analysis (TGA) and Mass

spectrometry (MS) on selected metal oxygen carrier

(Cu-based and Fe-based/Bentonite) developed at the

National Energy Technology Laboratory (NETL).

Thermo-gravimetric Analysis (TGA)–Used to record the change in mass of ~40 mg samples

over- time

Mass spectrometry (MS)

-Used to determining the elemental composition of a sample or molecule

CFB8 - REM, 5/3/2005

Chemical Looping

Combustion Products

CO2 , H2ODepleted Air

O2 , N2

Fuel

CnHm

MeO

Me

Air

O2 , N2

Air

Reactor

Fuel

Reactor

Oxygen is removed from air stream and transported to a fuel reactor via

a metal or other oxygen carrier. The metal must then be separated

from ash once oxygen is freed in the reactor and returned to the air

reactor

4 2 24 4 2CuO CH Cu CO H O

∆G=−590 kJ/mol, ∆H=−217 kJ/mol

2

2 2

2 2

2 2

4 2

2 4

Cu O CuO

Cu O Cu O

Cu O O CuO

Fuel Reactor

Air Reactor

CFB8 - REM, 5/3/2005

Typical mass and temperature measurement for

CuO/bentonite particle and 100% CH4 for reduction

and air for oxidation reactions

0

200

400

600

800

1000

30

32

34

36

38

40

42

44

0 500 1000 1500 2000T

emp

erat

ure

(oC

)

Mas

s (m

g)

Time (min)

dp=150-250 m

NETL TGA Data for Cu base sorbent

4 2 24 4 2CuO CH Cu CO H O

100% CH4, 800 oC

0.E+00

1.E-14

2.E-14

3.E-14

4.E-14

5.E-14

0

0.5

1

1.5

2

0 0.5 1 1.5 2

Conce

ntr

atio

n-C

H4

,CO

2

Conver

sion (

X)

Time (min)

T =900 oC

CH4

CO2

X

→

→

Conversion, X, and outlet gas analysis of CH4 and CO2

for the reduction of copper oxide (CuO) with methane

(100%CH4)

1 rr

ox r

m mX

m m

CFB8 - REM, 5/3/2005

Eight different rate equations

were indentified and examined,

including shrinking core model

(diffusion and reaction control),

linear, parabolic and cubic rate

laws, first and second order

global reaction rate, and Jonson-

Mehl-Avarmi (JMA) rate, to fit the

TGA experimental data for CuO-

bentonite/methane reduction

reaction. None of the models

gave satisfactory results over the

range of 750-900 oC with the

exception of JMA equation.

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

Conv

ersi

on (

X)

t/

Ideal diff. cont.

Ideal Rxn Cont.

Measured Exp. data

JMA rate

T=850 oC

Rate Analysis (Cu-base Reduction)

Typical curve fitting of experimental reduction data

using shrinking core model (diffusion and reaction

control) and JMA rates for 100% methane and 850 oC.

CFB8 - REM, 5/3/2005

Rate Analysis (Cu-base Reduction)

( )(1 )nktX e

n~kinetic exponent which depends on the

mechanism of growth and the dimensionality of

the crystal

k ~reaction rate constant, whose

temperature dependence is generally

expressed by the Arrhenius equation ,

( / )

0

E RTk k e

0

0.2

0.4

0.6

0.8

1

0 0.4 0.8 1.2 1.6 2

Co

nv

ers

ion

(X

)

Time (min)

750

800

850

900

T (oC)

Effect of reaction temperature and fitting of

Jonson-Mehl-Avarmi (JMA) equation

Jonson-Mehl-Avarmi (JMA) equation100% CH4

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

Xre

du

ctio

n

Time (Min)

T=850 oC

20%50%

100% CH4

Effect of methane concentration on reduction

for T=850 oC

CFB8 - REM, 5/3/2005

Rate Analysis (Cu-base Oxidation)

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6

Xre

du

cti

on

Time (Min)

R1

R2

R3

R4

R5

R6

R7

R8

R9

R10

T=850 oC20% CH4

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

Xre

du

ctio

n

Time (Min)

R1

R2

R3

R4

R5

R6

R7

R8

R9

R10

T=850 oC50% CH4

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5

Xre

du

ctio

n

Time (Min)

R1

R2

R3

R4

R5

R6

R7

R8

R9

R10

T=850 oC100% CH4

Reduction’s conversion increases as cycle

increased at given temperature

CFB8 - REM, 5/3/2005

0

1

2

3

0 2 4 6 8 10 12

n

# of Cycles

750

800

850

900

T (oC)

Effect of Cycles on n and k of JMA rate (CuO/CH4)

100% CH4

Diffusion controlled growth All shapes growing from small dimensions

Increasing nucleation rate >2.5

Constant nucleation rate 2.5

Decreasing nucleation rate 1.5-2.5

Zero nucleation rate 1.5

100% CH4-There is a slight increase (~10%)

in n with increasing cycles @ T= 750, 800,

and 850 oC (1.7-1.93 ) and about 30%

increase for T=900 oC (1.6-2.1) average

n=1.9.

50% CH4, n=1.6-1.74 for all T with average

n=1.66)

Rate constant, k, also increases (~20%) with

increasing cycles @ T= 750, 800, and 850 oC

and about 37% increase for T=900 oC.

0

1

2

3

0 2 4 6 8 10 12

k (m

in-1

)

# of Cycles

750

800

850

900

100% CH4

CFB8 - REM, 5/3/2005

y = -4484.2x + 4.2648

y = -4354.3x + 4.2504

y = -4316.1x + 4.0824

y = -4313.3x + 3.6573

y = -4358.7x + 3.1394

-1.4

-1

-0.6

-0.2

0.2

0.6

1

0.0008 0.00085 0.0009 0.00095 0.001

ln(d

X/d

t)

1/T (K-1)

0.2

0.4

0.6

0.8

0.9

X

Arrehenius plot for CuO/bentonite and CH4reaction

Kinetics Parameters for Reduction of Cu-base Sorbent

100%

CH4

Temperature and CH4 concentration dependence

of the rate constant, k (1/min.).

0

1ln( ) ln

dX Ek

dt R T

-1.5

-1

-0.5

0

0.5

1

0.0008 0.00085 0.0009 0.00095 0.001

ln(k

) (m

in-1

)

1/T (K-1)

E=36.5 kJ/mole

E=38.74 kJ/mole100% CH4

50%

E=36.56 kJ/mole

20%

Plot of ln(dx/dt) vs 1/T shows that activation

energy is uniform as a function of conversion

4

( 4482.34/ ) 0.654(1/ min) 91CH

Tk e y

CFB8 - REM, 5/3/2005

11

(1 )[ ln(1 )] ndX

kn X Xdt

0

0.5

1

1.5

2

0 0.5 1 1.5 2

dX

/dt

(min

-1)

Time (min)

750

800

850

900

T (oC)dX/dt,max

Rate Analysis (Cont.)

Effect of reaction temperature on the rate reduction of

CuO/bentonite particle and CH4 reaction

0.E+00

1.E-14

2.E-14

0

0.5

1

1.5

2

0 0.5 1 1.5 2

Co

nce

ntr

atio

n-

CO

2

Xr&

dX

r/d

t (m

in-1

)Time (min)

T =900 oC

dXr/dt

CO2

Xr

→

Rate reduction of CuO/bentonite particle and CO2

production

CFB8 - REM, 5/3/2005

-20

-10

0

10

20

30

40

0 2 4 6 8 10 12

(O,C

uO

-T,M

ass

lost

)x1

00

/ O

,Cu

O

Cycle #

750

800

850

900

100% CH4100% CH4

-20

-10

0

10

20

30

40

0 2 4 6 8 10 12

(O,C

uO

-T,M

ass

lost

)x10

0/O

,CuO

Cycle #

750

800

850

900

50% CH4

Mass balance during reduction of CuO with methane

CFB8 - REM, 5/3/2005

Reduction kinetics test

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100

Xre

du

ctio

n

Time (s)

model

exp

750 oC800

850

900

100% CH4

0

0.2

0.4

0.6

0.8

1

1.2

0 40 80 120 160 200

Xre

du

ctio

n

Time (s)

750 oC

850

900

50% CH4

Comparison between kinetic model predictions and experimental data at several

temperatures.

CFB8 - REM, 5/3/2005

Rate Analysis (Cu-base Oxidation)

rdOxd

oxd rd

m mX

m m

Conversion rate decreases as temperature increases

2

2 2

2 2

2 2

4 2

2 4

Cu O CuO

Cu O Cu O

Cu O O CuO

0.0

0.2

0.4

0.6

0.8

1.0

0 10 20 30 40

Conver

sion (

X)

Time (min)

750

800

850

900

T (oC)

0.0E+00

2.0E-14

4.0E-14

6.0E-14

8.0E-14

1.0E-13

1.2E-13

1.4E-13

0 20 40 60

Ga

s C

on

cen

tra

tio

n C

O2,

O2

Time (min)

750

800

850

900

T (oC)

O2

CO2

Effect of reaction temperature on oxidation

conversion for Cycle #5

Effect of reaction temperature on CO2 and O2

gas concentration

100% CH4 reduction

CFB8 - REM, 5/3/2005

Rate Analysis (Cu-base Oxidation)

rdOxd

oxd rd

m mX

m m

Conversion rate decreases as temperature increases

2

2 2

2 2

2 2

4 2

2 4

Cu O CuO

Cu O Cu O

Cu O O CuO

Effect of reaction temperature on oxidation

conversion for Cycle #5

Effect of reaction temperature on CO2 and O2

gas concentration

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20

XO

xd

Time (Min)

750

800

850

900

T (oC)

50%CH4

0.0E+00

2.0E-14

4.0E-14

6.0E-14

8.0E-14

1.0E-13

1.2E-13

1.4E-13

0 10 20 30 40 50 60

Gas

Co

ncentr

ati

o (

O2,C

O2)

Time (min)

750

800

850

900

T (oC)

O2

CO2

CFB8 - REM, 5/3/2005

0.0E+00

2.0E-14

4.0E-14

6.0E-14

8.0E-14

1.0E-13

1.2E-13

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25 30

Gas

Conce

ntr

atio

n

Conv

ersi

on (

X)

Time (min)

O2

CO2

Cycle #5 Oxid.T=850 oC

100% CH4 Red.

0.0E+00

2.0E-14

4.0E-14

6.0E-14

8.0E-14

1.0E-13

1.2E-13

1.4E-13

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25 30

Gas

Co

nce

ntr

atio

n

Co

nver

sio

n (

X)

Time (min)

O2

CO2

Cycle #5 Oxid.T=850 oC

50% CH4 Red.

0.0E+00

2.0E-12

4.0E-12

6.0E-12

8.0E-12

1.0E-11

1.2E-11

1.4E-11

1.6E-11

1.8E-11

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Gas

Co

ncen

trati

on

Co

nvers

ion

(X

)

Time (min)

O2

CO2

Cycle #5 Oxid.T=850 oC

20% CH4 Red.

Effect of methane concentration during reduction

process on oxidation of Cu

0

0.2

0.4

0.6

0.8

1

1.2

0 4 8 12 16 20

XO

xid

ati

on

Time (Min)

100% CH4

50%

20%

T=850 oC

Oxidation’s conversion is for higher Ch4

concentration during reduction

CFB8 - REM, 5/3/2005

Rate Analysis (Cu-base Oxidation)

y = 6465.1x - 7.5157R² = 0.9582

-3

-2.5

-2

-1.5

-1

-0.5

0

0.0008 0.00085 0.0009 0.00095 0.001

ln(k

) (m

in-1

)

1/T (K-1)

E=53.75 kJ/mole

y = 2483x - 3.2434

-3

-2.5

-2

-1.5

-1

-0.5

0

0.0008 0.00085 0.0009 0.00095 0.001

ln(k

) (m

in-1

)

1/T (K-1)

E=20.64 kJ/mole

50% CH4 reduction20% CH4 reduction

CFB8 - REM, 5/3/2005

Fuel Reactor Analysis

For reaction aA(g) +bB(s)=cR(g)+dS(s)

4 2 24 4 2CH CuO Cu CO H O

Gas phase mass transport4CH

g

dmaR

dy

Where “a” is contact area between solid and gas per

unit volume of bed

6(1 )

p

ad

Solid phase mass transport

,(1 )

CuO mix

g

dmabR

dy

"0.6*( )1

3

oxyr o s oAA

s s CuO

MWm m Rdm dX dXR

A dt A dt MW dt

CFB8 - REM, 5/3/2005

Summary

Completed kinetics rate CuO/bentonite sorbent{1}

-Rate of reaction increases as temperature increased.

Analyzed kinetics rate Fe-based/bentonite sorbent

CFB8 - REM, 5/3/2005

Publications

1. Esmail R. Monazam1,2, Ranjani Siriwardane, Lawrence J. Shadle, George Richard,

Hanjing Tian2 , David E. Huckaby, and Stephen Carpenter2 “Kinetics of the chemical

looping reduction of CuO/bentonite by methane (CH4) “ submitted for internal review

CFB8 - REM, 5/3/2005

Performance and Kinetics of a Solid Amine Sorbent for Carbon Dioxide Removal

Esmail R. Monazam+, Lawrence J. Shadle, Ranjani Siriwardane, Daniel

Fauth, James S. Hoffman, McMahan L. Gray, and Henry Pennline

National Energy Technology Laboratory+REM Engineering Services, PLLC

Morgantown, West Virginia

CFB8 - REM, 5/3/2005

Objective

To characterize a solid supported amine CO2 sorbent (Amine/Bentonite ,

and PEI/Silica) developed at the National Energy Technology Laboratory

(NETL).

- Investigate the kinetics of the CO2 uptake from

experimental data using thermo-gravimetric analyzer (TGA)

and volumetric adsorption apparatus on selected solid

supported amine.

Thermo-gravimetric Analysis (TGA)–Used to record the change in mass of ~60 mg samples of

(amine/bentonite) over time

Volumetric Adsorption Apparatus- equilibrium absorption - Pressure measurements before and after the exposure of the sample

chamber to CO2

CFB8 - REM, 5/3/2005

Reaction of CO2 + Amine (R1R2NH),

Formation of zwitterion;

1 1

1

,

1 2 2 1 2 ( )K k

kR R NH CO R R NH COO zwitterion

Proton removal step of the zwitterion by amine;

2 2

2

,

1 2 1 2 1 2 1 2 2( )K k

kR R NH COO R R NH R R NCOO carbamate R R NH

(1)

(2)

Combining Eqs (1) and (2) resulted;

3 1 2

1 2

1 2

1 2 2 1 2 2 1 22K K K

k k

k k

R R NH CO R R NH R R NCOO

(3)

(R1=CH2CH2OH=C2H4OH) R2=H for MEA, R2=R1 for DEA

CFB8 - REM, 5/3/2005

Reaction of CO2 + Amine (R1R2NH),

2 , 1 2 1 2 1[ ][ ] [ ]CO zwitr k CO R R NH k Z

2

1 2 2 2

1

1 1 2 1 2

1e

CO

R R NH CO COr

k

k k k R R NH

1

1 1 2 1 2

1

1

[ ]

appkk

k k k R R NH

2 1 2 2 2CO app er k R R NH CO CO

kapp=apparent rate coefficient for the reaction

between CO2 and amine (m3/kmol.s)

Overall reaction rate (kmole/m3.s)

CFB8 - REM, 5/3/2005

Effect of reaction temperature on

Amine/bentonite particle and CO2

reaction

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4

Time (min)

X=

(m-m

o)/

(mf-m

o)

30

40

50

60

80

Temperature (oC)

Mean particle size : 70 m

Particle B

0

20

40

60

80

100

120

0 50 100 150 200 250 300

Time (min)

Tem

pera

ture

(oC

)

56

57

58

59

60

61

62

63

Mass (

mg)

Introduction

of CO2

Typical temperature and mass

measurements during TGA

experiment

Experimental data:Amine/bentonite (TGA)

Rate of reaction increases as

temperature increases

CFB8 - REM, 5/3/2005

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3

Time (min)

Co

nve

rsio

n,X

TGA Exp.

Curve fit (Eq. 9)

Mean particle size:70 m

Temperature:40 oC

Particle B

Curve fitting to experimental data to obtain k and n

( ( ) )

( )

o

f o

m t mX

m m

(1 )ndXk X

dt1

11 1 (1 ) nX kt n

T (K) k (s-1

) n

303 0.014 0.88

308 0.016 0.88

313 0.022 1.01

318 0.019 0.99

323 0.019 1.05

333 0.023 1.17

353 0.035 1.48

363 0.037 1.41-5

-4.5

-4

-3.5

-3

0.0025 0.0027 0.0029 0.0031 0.0033 0.0035

1/T (0K

-1)

ln (

k)

1687.6ln 1.37k

T

CFB8 - REM, 5/3/2005

Volumetric Adsorption data- Adsorption Equilibrium

2

2

2

max( )CO

eq CO

CO

dK

dC

2

2 max 1 eq COK C

CO e

Experimental variation of CO2 loading with equilibrium partial

pressureCurve fitting of experimental data to obtain Keq

CFB8 - REM, 5/3/2005

max

2

max

1

1 2eqeq

COK

max 1.923 .0048T

(Alatiqi et al., 1994)

Variations of CO2 concentration with CO2 loading

y = -0.0048x + 1.9272R² = 0.8062

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

300 320 340 360 380 400

ma

x

T (oK)

Equil. Exp.

TGA

CFB8 - REM, 5/3/2005

1batX e

a~scale parameter

b~shape parameter

Weibull distribution function

Experimental data:PEI/silica, 196C (TGA)

Effect of reaction temperature on PEI/silica particle with CO2 reaction

Rate of reaction decreases as temperature

increased.

Typical temperature and mass measurements

during TGA experiment (10%CO2, 40 oC)

CFB8 - REM, 5/3/2005

0

0.2

0.4

0.6

0.8

1

0.0 0.5 1.0 1.5 2.0

Co

nv

ers

ion

(X

)

Time (min)

T=40 C

T=60 C

T=80 C

T=100 C

T=110 C

Effect of reaction temperature on immobilized PEI sorbent

particle and CO2 reaction using 100% CO2

( ) o

f o

m t mX

m m

(1 )batX e

0

0.4

0.8

1.2

1.6

2

0.0 0.5 1.0 1.5 2.0

dX

/dt

Time (min)

T=40 C

T=60 C

T=80 C

T=100 C

T=110 C

Effect of temperature on reaction rate

2

662

0.6930.42 (1 ) ln(1 )TCO

dXe y X X

dt

For b=2

Rate Analysis

CFB8 - REM, 5/3/2005

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.0E+00 1.0E-05 2.0E-05 3.0E-05 4.0E-05 5.0E-05

(mo

le C

O2/m

ole

am

ine

)

[CCO2] mol/CC

40 oC

60

80

100

2 2ln( ) ln( )e eq CO eq CO

RTK C B K C

H

2ln( ) ln( )e eq COB K B C

Temkin’s model assumes that the heat of adsorption of all

molecules in the layer would decrease linearly with coverage

0.0

1.0

2.0

3.0

4.0

-14 -13 -12 -11 -10

(mo

le C

O2/m

ole

am

ine

)

Ln[CCO2] mol/CC

40 oC

60

100

80

Adsorption Equilibrium-TGA data

CFB8 - REM, 5/3/2005

Summary

Completed kinetics rate Amine/bentonite sorbent (1, 2)

-Rate of reaction increases as temperature increased.

Completed kinetics rate PEI/silica sorbent (3)

-Rate of reaction appear to be faster at lower temperatures (apparent negative

activation energy)

CFB8 - REM, 5/3/2005

Publications

Esmail R. Monazam, Lawrence J. Shadle, and Ranjani Siriwardane “Equilibrium and

Absorption Kinetics of Carbon Dioxide by Solid Supported Amine Sorbent “AIChE J. 2011,

DOI 10.1002,

Esmail R. Monazam, Lawrence J. Shadle, and Ranjani Siriwardane “Performance and Kinetics

of a Solid Amine Sorbent for Carbon Dioxide Removal” Accepted for publication Ind. & Eng.

Chem. Res. (July 2011) ie-2011-01214q

Esmail R. Monazam, Lawrence J. Shadle, Daniel Fauth, James S. Hoffman, McMahan L. Gray,

and Henry Pennline “Kinetics Analysis of Carbon Dioxide Capture on Immobilized Amine on

Meso-Porous Silica” AIChE J. 2011, submitted.