kinetics & catalysis of methane steam reforming in sofcs and reformers fuel cell center chemical...
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Kinetics & Catalysis of Kinetics & Catalysis of Methane Steam Reforming Methane Steam Reforming in SOFCs and Reformersin SOFCs and Reformers
Fuel Cell CenterChemical Engineering Department
Worcester Polytechnic InstituteWorcester, MA
Caitlin A. Callaghan (PhD), James Liu (MS candidate), Ilie Fishtik, and Ravindra Datta
Alan Burke, Maria Medeiros, and Louis Carreiro
Naval Undersea Warfare CenterDivision Newport
Newport, RI
Methane Steam ReformingMethane Steam Reforming•Consists of three reversible overall reactions (OR):
Rostrupnielsen J. R, Journal of Power Sources 105 (2002) 195-201
•Endothermic (reforming is favored by high temperature)
•Exothermic (favors low temperature while pressure is unaffected)
•Steam to Carbon ratio (P(H2O)/P(CH4) or S/C) around 3 are applied
Solid Oxide Fuel CellSolid Oxide Fuel Cell
Similar ORs and Chemistry
Microkinetic & Graph Theoretic Approach
• Develop Molecular Mechanisms
• Predict Kinetics of Elementary Reactions (UBI-QEP or Ab Initio)
• Draw Reaction Route (RR) Networks
• Microkinetic Analysis of Network
• Comparison with Experiment
• Design of better Catalysts
RR RR GraphsGraphs
A RR graph may be viewed as several hikes through a mountain range: Valleys are the energy levels of reactants and products Elementary reaction is a hike from one valley to adjacent valley Trek over a mountain pass represents overcoming the energy barrier
RRRR Graph Topology Graph Topology
A + B
C
s1 s2 s5
s3 s4
s5
s1 s2
s3 s4
s5
OR
s1: A + S A·Ss2: B + S B·Ss5: A·S + B·S C + 2SOR: A + B C
s3: A·S + B·S C·S + Ss4: C·S C + S
–s5: C + 2S A·S + B·S OR: 0 0
Full Route
s1: A + S A·Ss2: B + S B·Ss3: A·S + B·S C·S + Ss4: C·S C + Ss5: A·S + B·S C + 2S
Mechanism: A + B C
Empty Route
Rate, Affinity & ResistanceRate, Affinity & Resistance• DeDonder Relation:
• Reaction Affinity:
• Reaction Rate (Ohm’s Law):
1 1 expr
r r rr
A
!
1 1 1
ln ln ln lnqn n
i i o o k k i ii k i
AK P
RT
A
rR
A
(conventional)net reaction ratereaction affinity
RESISTANCE
ln1
rr
Rr r r
!
"!
forward reaction rate
Electrical AnalogyElectrical Analogy
Kirchhoff’s Current Law– Analogous to conservation of mass
Kirchhoff’s Voltage Law– Analogous to thermodynamic consistency
Ohm’s Law– Viewed in terms of the De Donder Relation
a b c d e 0r r r r r
ab
c
d
e
f g
i h
f g h i 0 A +A A A
Rr
A=
Example ofExample ofWGS ReactionWGS Reaction
E
Elementary Reaction
Steps E
!
!
s1 0 1.5 106 CO + S CO·S 12.0 1014
s2 0 106 H2O + S H2O·S 13.6 1014
s3 25.4 1013 H2O·S + S OH·S + H·S 1.6 1013
s4 10.7 1013 CO·S + O·S CO2·S + S 28.0 1013
s5 0 1013 CO·S + OH·S HCOO·S + S 20.4 1013
s6 15.5 1013 OH·S + S O·S + H·S 20.7 1013
s7 0 1013 CO·S + OH·S CO2·S + H·S 22.5 1013
s8 1.4 1013 HCOO·S + S CO2·S + H·S 3.5 1013
s9 4.0 1013 HCOO·S + O·S CO2·S + OH·S 0.9 1013
s10 29.0 1013 H2O·S + O·S 2OH·S 0 1013
s11 26.3 1013 H2O·S + H·S OH·S + H2·S 0 1013
s12 1.3 1013 OH·S + H·S O·S + H2·S 4.0 1013
s13 0.9 1013 HCOO·S + OH·S CO2·S + H2O·S 26.8 1013
s14 14.6 1013 HCOO·S + H·S CO2·S + H2·S 14.2 1013
s15 5.3 4 1012 CO2·S CO2 + S 0 106
s16 15.3 1013 H·S + H·S H2·S + S 12.8 1013
s17 5.5 6 1012 H2·S H2 + S 0 106
s18 15.3 6 1012 H·S + H·S H2 + S 7.3 106
Adsorptionand
DesorptionSteps
Surface Energetics for Cu(111) Catalyst:
Activation energies: kcal/mol
Pre-exponential factors:atm-1s-1 (ads/des) s-1 (surface)
Constructing the Constructing the RRRR Graph Graph
1. Select the shortest MINIMAL FR
OR = s1+s2+s3+s15+s7+s18
s1 s2 s3 s15 s7 s18
s18 s7 s15 s3 s2 s1
1
Constructing the Constructing the RRRR Graph Graph
2. Add the shortest MINIMAL ER to include all elementary reaction steps
s4 + s6 – s7 = 0s5 + s8 – s7 = 0s5 + s9 – s4 = 0s6 + s16 – s12 = 0s8 + s16 – s14 = 0s16 + s17 – s18 = 0
2
s1 s2 s3 s15 s7 s18
s18 s7 s15 s3 s2 s1s4
s5
s4
s5s9
s9
s6
s6
s12
s12
s8
s8
s14
s14
s17
s17 s16
s16
All but 3 steps included!
s11
s5
s16
Constructing the Constructing the RRRR Graph Graph
3. Add remaining steps to fused RR graph
s3 + s16 – s11 = 0s6 + s10 – s3 = 0s3 + s13 – s8 = 0
3
s1 s2 s3 s15 s7 s18
s18s7 s15 s3 s2 s1s4
s5
s4
s9
s9
s6
s6
s12
s12
s8
s8
s14
s14
s17
s17 s16 s11
s10 s10
s13
s13
Constructing the Constructing the RRRR Graph Graph
4. Balance the terminal nodes with the OR4
s18
s4
s5
s15 s17
s9
s7
s16
s14
s12
s6
s18
s4
s5
s15s17
s9
s7
s16
s12
s8s14
s8
s1
s1
OR
OR
s2 s3
s3 s2
s11s10
s10
s13
s13
s11
s6
RR RR NetworkNetwork
R1
OR
OR
R1
R2 R3
R13
R15 R4 R12 R17
R2R3R15R4R12R17
R18
R18 R16R16
R6
R6 R11
R11
R9
R9 R14
R14
R5
R5
R8
R8R13
R7
R7
R10
R10
RRRR enumeration enumerationFR1: s1 + s2 + s3 + s7 + s15 + s18 = OR
FR2: s1 + s2 + s7 + s11 + s15 + s17 = OR
FR3: s1 + s2 + s3 + s4 + s6 + s15 + s18 = OR
FR4: s1 + s2 + s3 + s5 + s8 + s15 + s18 = OR
FR5: s1 + s2 + s4 + s6 + s11 + s15 + s17 = OR
FR6: s1 + s2 + s3 + s4 + s12 + s15 + s17 = OR
FR7: s1 + s2 + s3 + s5 + s14 + s15 + s17 = OR
FR8: s1 + s2 + s3 + s7 + s15 + s16 + s17 = OR
FR9: s1 + s2 + s5 + s8 + s11 + s15 + s17 = OR
FR10: s1 + s2 + s7 + s8 – s13 + s15 + s18 = OR
FR250: s1 + s2 + s4 – s10 – 2s13 + 2s14 + s15 + 2s17 – s18 = OR
FR251: s1 + s2 + s5 + 2s10 + 2s12 + s13 + s15 – 2s16 + s18 = OR
FR252: s1 + s2 + s5 + 2s10 + 2s12 + s13 + s15 + 2s17 – s18 = OR
ER1: s4 + s6 – s7 = 0
ER2: s4 – s5 – s9 = 0
ER3: s5 – s7 + s8 = 0
ER4: s6 – s8 + s9 = 0
ER5: s3 – s6 – s10 = 0
ER6: s3 – s8 + s13 = 0
ER7: s3 – s11 + s16 = 0
ER8: s6 – s12 + s16 = 0
ER9: s8 – s14 + s16 = 0
ER10: s9 + s12 – s14 = 0
ER115: s5 – s7 + s9 – s10 + s11 + s17 – s18 = 0
ER116: s4 – s7 – s10 – s13 + s14 + s17 – s18 = 0
ER117: s5 – s7 + s10 + s12 + s13 + s17 – s18 = 0
Quasi Equilibrium & RDSQuasi Equilibrium & RDS
Simulations based on energetics of Cu(111)
R1 R2 R3
R5
R15 R17
R12
R8
R16 R7
R4
AOR
n1 n2 n3 n4
n5
n6
n7 n8
n9 n10
R3
R7
R12
R5R8
R4
AOR
273 373 473 573 673 773 87310
-4
10-2
100
102
104
106
108
1010
1012
Temperature (K)
Res
ista
nce
(ra
te(s
-1))
R7(R5+R8)
R7+R5+R8
R16
273 373 473 573 673 773 87310
-10
10-5
100
105
1010
1015
Temperature (K)
Res
ista
nce
(1/
rate
(s-1))
R3
R15, R17
R2
R1
Reduced Rate ExpressionReduced Rate Expression
rOR = r8 + r10 + r15
where
(OHS is the QSS species.)
2
2
2 2 2
2
2
1/ 2H2 6 2 12 17 CO
3 2 H O 0 5 7 1 CO 12 1/216 17 4 2 12 17 CO 12 H CO H
1/ 2H3 4 2 12 17 CO
12 5 7 1 CO1/23 16 174 2 12 17 CO 12 H
( )( )
1
( )( )
OR
P k K K K Pk K P θ k k K P k
K K k K K K P k P P Pr
KPk k K K K Pk k k K P
K K Kk K K K P k P
2H O COP P
2
2
0 1/ 2H
1 H O 2 1/ 24 5
1
1 CO
PK P K P
K K
Simulation of Microkinetic Model Simulation of Microkinetic Model
Ni(111)
Fe(110)
Cu(111)Experimental Conditions
FEED:COinlet = 0.10H2Oinlet = 0.10CO2 inlet = 0.00H2 inlet = 0.00
Space time: 1.80 s
Other CatalystsOther Catalysts
PtPt PdPd
RhRh RuRu
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
600 650 700 750 800 850 900 950 1000
Temperature (K)
Co
nve
rsio
n o
f C
O, H
2
Feed 1, X(CO)
Feed 2, X(H2)
Feed 3, X(CO)
0
0.1
0.2
0.3
0.4
0.5
0.6
400 500 600 700 800 900 1000
Temperature (K)
Co
nve
rsio
n C
O, H
2
Feed 1, X(CO)
Feed 2, X(H2)
Feed 3 X(CO)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
400 500 600 700 800 900 1000
Temperature (K)
Co
nve
rsio
n o
f C
O, H
2
Feed 1, X(CO)
Feed 2, X(H2)
Feed 3, X(CO)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
600 650 700 750 800 850 900 950 1000
Temperature (K)
Co
nve
rsio
n o
f C
O,H
2
Feed 1, X(CO)
Feed 2, X(H2)
Feed 3, X(CO)
Example ofExample ofMSR ReactionMSR Reaction
Theoretical Thermodynamic Equilibrium Calculations
kmoles of species vs H2O/CH4 @ T=1000 K
0
0.5
1
1.5
2
2.5
3
3.5
4
0 0.5 1 1.5 2 2.5 3
H2O/CH4
km
ol
H2
H2O
CH4
CO
CO2
O2
Roine, A. HSC Chemistry; Ver. 4.1 ed.; Outokumpu Research: Oy, Pori, Finland.
S. Rakass, H. Oudghiri-Hassani, P. Rowntree and N. Abatzoglou Effects of Temperature and CH4:H2O molar ratio, on theoretical equilibrium values
0%10%20%30%40%50%60%70%80%90%
100%
300 350 400 450 500 550 600 650 700
Teemperature C
CH
4 c
on
vers
ion
(%
)
CH4:H2O = 1:2
CH4:H2O = 2:2
CH4:H2O = 3:2
CH4:H2O = 4:2
Rakass, S. Journal of Power Sources xxx(2005) xxx-xxxRoine, A. HSC Chemistry; Ver. 4.1 ed.; Outokumpu Research: Oy, Pori, Finland.
Froment et al. Mechanism forFroment et al. Mechanism forMethane Steam ReformingMethane Steam Reforming
s1: CH4 + S = CH4.S
s2: H2O + S = O.S + H2 s3: CO.S = CO + S s4: CO2
.S = CO2 + Ss5: H.S + H.S = H2
.S + S s6: H2
.S = H2 + S s7: CH4
.S + S = CH3.S + H.S
s8: CH3.S + S = CH2
.S + H.Ss9: CH2
.S + O.S = CH2O.S + Ss10: CH2O.S + S = CHO.S + H.Ss11: CHO.S + S = CO.S + H.Ss12: CHO.S + O.S = CO2
.S + H.Ss13: CO.S + O.S = CO2
.S + S
Xu, J.; Froment, G. F. , AIChE Journal, 1989, 35, 88
MSR RR Network
s2
s3
s4
s12
s12
s13
s3
s2
OR3
OR3
OR1
OR1
IR
IRs4
s13
s11
s11
OR2
OR2
OR4OR4
OR1: -CH4 - H2O + CO + 3H2 = 0
OR2: -CH4 - 2H2O + CO2 + 4H2 = 0
OR3: -H2O - CO + CO2 + H2 = 0
OR4: -CH4 - CO2 + 2CO + 2H2 = 0
Rostrupnielsen J. R , Journal of Catalysis 144, 38-49 (1993)
Activities of Metals for Steam Reforming
Ni CatalystThermodynamic Steadystate 2:1 ratio of Steam to Methane
0
10
20
30
40
50
60
70
80
90
573 673 773 873 973 1073 1173
Temperature K
ml/m
in
H2
CO
CH4
CO2
Thermodynamic
0
1
2
3
4
5
6
7
573 673 773 873 973 1073 1173
Temperature K
km
ol
H2
H20
CH4
CO
CO2
Ni ExperimentalResults
Theoretical Equilibrium Calculations of MSR
Roine, A. HSC Chemistry; Ver. 4.1 ed.; Outokumpu Research: Oy, Pori, Finland.
Rhodium Catalyst
Experimental Results
0
10
20
30
40
50
60
70
80
90
300 350 400 450 500 550 600 650
Temperature K
ml/m
in . H2
CO
CH4
CO2
Future Work
• Combine both WGSR and MSR Network together• Determine promising catalyst candidates for
reforming based upon RR graph theory.• Perform MSR and ATR studies
Benefits to the NavyBenefits to the Navy
Extend fundamental understanding of reaction mechanisms involved in logistics fuel reforming reactions
Gather data on air-independent autothermal fuel reformation with commercially available catalysts
Develop new catalytic solutions for undersea fuel processing
Develop relationship between ONR and WPI
For more information….
WPI – Worcester, MACaitlin Callaghan – [email protected], http://alum.wpi.edu/~caitlin
James Liu – [email protected]
Ilie Fishtik – [email protected]
Ravindra Datta – [email protected]
NUWC – Newport, RIAlan Burke - [email protected]