Post on 09-Aug-2019
Catalyst Material Development for Internal Reforming SOFC Fuelled by Sustainable Biofuels
Kyushu University, Department of Mechanical EngineeringInternational Institute for Carbon-Neutral Energy Research (I2CNER)
Next-Generation Fuel Cell Research Center
Yusuke Shiratoriy-shira@mech.kyushu-u.ac.jp
2nd International Symposium on Solid Oxide Fuel Cells for Next Generation Power Plants
Imperial College London, Friday 19th April, 2013
2
Research background
3
Solid oxide fuel cell (SOFC)
Solid electrolyte
O212
H2, CO
H2O, CO2
2e-
2e-Anode (Ni-YSZ)
Cathode (LSM-YSZ)
Hydrocarbon(Chemical energy )
Air
Reforming
O2-
Anode contains excellent reforming catalyst, Ni.
All solid materials
Compact design is possible.
Practical fuels such as city gas, natural gas, biogas, biodiesel, gasoline and alcohol, etc., can be supplied directly to SOFC.
Operation mechanism of direct internal reforming SO FC
In principle, possiblePractically, chemical andthermomechanicalproblems will arise!
Direct Internal reforming SOFC
(DIRSOFC)
Direct Internal reforming SOFC
(DIRSOFC)
Internal reforming can occur.Internal reforming can occur.
High temp. operation in the temp. range between 600 and 900 °C
High temp. operation in the temp. range between 600 and 900 °C
Electricity
Problems in conventional DIRSOFC
4
790 ppm H2S
CH4
62.6 %
CO2
35.7 %
H2
99 ppm
N2
0.09 %
H2
O 1.62 %
H2
S < 0.5 ppm
Desulfurizer(FeO pellets)
Y. Shiratori, T. Ijichi, T. Oshima, K. Sasaki, “Internal Reforming SOFC Running on Biogas”, International Journal of Hydrogen Energy 35 (2010) 7905-7912.
Field test of internal reforming SOFC running on bi ogas
After test with real biogas
Severe cokingSevere coking
5
0 100 200 300 400 500 600 700 8000.0
0.2
0.4
0.6
0.8
1.0
1.2
Cel
l vol
tage
/ V
Time / h
Temp: 800 oCCurrent density: 200 mA cm-2
Real biogas(1.4 < CH4/CO2 < 1.7, H2S ≈ 0.2 ppm)
Simulated biogas(CH4/CO2 = 1.5)
Methane fermentation reactorPlace: Tosu-city, Saga, JapanReactor size: 144 m3
Biogas: Max 250 m3 / dayOutput: Max 60 kW level
Desulfurized biogas
Long term test of DIRSOFC with anode-supported button cell
Direct feed of biogas to SOFC is feasible!
Saga Prefecture
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
16
18
Time / h
CO formation
Rea
ctio
n ra
tes
/µm
ols-
1cm
-2
1 ppm H2S1 ppm H2S
Temp: 1000 oCFuel: Simulated biogas mixture (CH4/CO2 = 1.5)Cell type: Electrolyte-supported (Ni-ScSZ/ScSZ/LSM-ScSZ)Current density: 200 mA cm-2
0 2 4 6 8 10 12 14 16 18 200.0
0.2
0.4
0.6
0.8
1.0
1.2
Cel
l vol
tage
/ V
Time / h
0.00
0.05
0.10
0.15
0.20
0.25
0.30
Vol
tage
loss
es /
V
Anodic overvoltage
Anode-side IR drop
Cell voltage
CH4 consumption
CO2 consumption
100 mV, 9 % of initial cell voltage
40 % decrease
1 h
Y. Shiratori, T. Oshima, K. Sasaki, “Feasibility of Direct-biogas SOFC”, International Journal of Hydrogen Energy 33 (2008) 6316-6321.
Deactivation of anode by 1 ppm H 2S measured at 1000 oC
Electrochemical deactivation Catalytic deactivation
6
R1━COOCH3
R2━COOCH3
R3━COOCH3
CH2━COO━R1
┃
CH━COO━R2
┃
CH2━COO━R3
3CH3OH
CH2━OH ┃
CH━OH┃
CH2━OH
+ +→
Fatty oil MethanolFatty Acid Methylester(FAME)⇒⇒⇒⇒ BDF Glycerol
Biodiesel fuels
Name Formula Degree of unsaturation
Composition / wt %
Palm Jatropha SoybeanWaste-cooking
Discarded fish
Palmitic acid methyl ester C17H34O2 0 39.9 13.7 10.7 34.9 27.2
Stearic acid methyl ester C19H38O2 0 4.35 6.65 3.19 4.51 7.52
Oleic acid methyl ester C19H36O2 1 40.4 40.5 22.4 36.9 35.4
Linoleic acid methyl ester C19H34O2 2 12.0 31.5 53.9 8.9 8.8
Linolenic acid methyl ester C19H32O2 3 0.21 0.17 5.28 0.31 0.44
Tri-glyceride 0.4 0,4 0.1 6 6
Sulfur S 1ppm 7ppm ≦1ppm 3ppm 8ppm
7
BDFs derived from Palm, Jatropha, Soybean, Waste-cooking, Discarded fish oils
8
Measured compositions of anode off-gas for the internal steam reforming of practical-BDFs (soybean- , jatrropha- and palm-BDF ) and reference FAMEs (oleic- and linoleic-FAME ) on Ni-ScSZ anode
(a) 800 oC
H2
CO
CO2
CH4
C2H4
0 5 10 15 20 50 55 60 65 70 75
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Equilibrium
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Equilibrium
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Equilibrium
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Concentration in anode off gas / %
0 5 10 15 20 50 55 60 65 70 75
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Equilibrium
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Equilibrium
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
Equilibrium
Oleic-FAME
Jatropha-BDFPalm-BDF
Soybean-BDF
Linoleic-FAME
0 5 10 15 20 50 55 60 65 70 75
(b) 700 oC
0 5 10 15 20 50 55 60 65 70 75
Concentration in anode off gas / %
H2
CO
CO2
CH4
C2H4
Internal steam reforming of biodiesel
SOFC
Methane fermentation
Test cell simulating real SOFC
We demonstrated “Generation of electricity from garbage” and “Generation of electricity from vegetable oils” using lab-scale solid oxide fuel cell.
DIRSOFC running on biofuels
Biogas Palm-biodiesel
“Visualization of SOFC in operation”
in
Local cooling caused by endothermic reforming
out
Biofuels
① Crack formation
Operating temp.: 800 oCCurrent density: 0.2 A cm-2
Time / h0 200 400 600 800
Cel
l vol
tage
/ V
0.0
0.2
0.4
0.6
0.8
1.0Biogas
Palm-BDF
are pronounced at the cooled area.
Y. Shiratori et al., Int. J. Hydrogen Energy 35 (2010) 7905-7912.
I. Feasibility study-Efforts toward the realization of DIRSOFC running on biofuels-I. Feasibility study-Efforts toward the realization of DIRSOFC running on biofuels-
II. Practical study-Clarification of thermomechanical problems in the internal reforming operation-II. Practical study-Clarification of thermomechanical problems in the internal reforming operation-
“Direct Internal reforming SOFC running on biofuels”
Button cell operation was possible.Rather high degradation rate due to
coking on the anodeBiogas :::: ~3.0%/1000h
Palm-BDF :::: ~15%/1000h
Button cell test
② Impurity poisoning ③ Carbon deposition5
mm
Crack in dense electrolyte
①
5 mm
Ni dust
NiScSZ C
③
Cel
l vol
tage
/ V
1 ppm H 2S
0 2 4 6 8 10 12 14 16 18 20 220.0
0.2
0.4
0.6
0.8
1.0
1.2
Time / h
Cell voltage
Fuel: BiogasOperating temp.: 800 oCCurrent density: 0.2 A cm-2
②
Blockage of diffusion path by deposited carbon
Previous studies 9
Direct internal reforming operation is currently impossible.
Temperature homogenization in the cell is necessary!
10
Development of flexible catalyst material“Paper-structured catalysts (PSCs)”
11Microstructure of paper-structured catalyst (PSC)
YSZ fiber (Zf)
Ni or Ni-MgO
Inorganic binder(Al2O3 (As) or ZrO2 (Zs) or CeO2 (Cs))
Al2O3 fiber (Af) SiO2-Al2O3 fiber (Cf)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.01 0.1 1 10 100 1000
dV/ d
(logD
)/ c
m3
g-1
Pore diameter / µm
ZfCfZs paper
Cermet anode
Compacted powder
5 µm
Ni
ScSZConventional anode
Pore diameter: 1 µmPorosity: 32 %
Conventional cermet anode ((((Ni-ScSZ))))
Flexible fiber network
50 µm
Paper-structured catalyst
Pore diameter: 17 µmPorosity: 83 %
Paper-structured catalyst (PSC)
12
H2
N2
H2O
MFC
Reactor
BDF
Evaporator
Upper furnace
Lower furnace
800 oC
600 oC
MFC
6 µl min-1
21 µl min-1
50 ml min-1
150 ml min-1
S/C = 2.0-3.5
Micro pump
Micro pump
Water trap
Gaschro
2 PSCs
T.C. was placed between the two papers.
Data logger
20 mm
T.C.
Fuel(simulated biogas)CH4 : CO2 = 1 : 1
Off-gas
800 or 750 oC
Paper-structured catalyst
to GC
Experimental setup for biofuel reforming
Dry reforming of methane Steam reforming of BDF
♦ CH4 conv.♦ H2 production rate♦ CO production rate♦ Temp. decrease
13Performance of PSC for dry reforming of methane
♦ Simple processing♦ Easy handling♦ High catalytic activity♦ Catalytic function easily adjustable ♦ Applicable to various devises♦ Available under SOFC operating condition♦ Tolerant to thermal shock
Features of PSCComparison with conventional anode
Paper-structured catalyst (PSC) exhibited
considerably higher catalytic activity than
that of conventional SOFC anode.
0.0
0.2
0.4
0.6
0.8
1.0
Conversion
and selectivity / -
Equilibrium at 800 o
C
Ni-YSZ anode support (200 mA cm-2
) at 800 o
C
(W/F = 8.4 g-cat h mol-1
)
PSC at 800 o
C (W/F = 0.17 g-cat h mol-1
)
Fuel: simulated biogas (CH4
/CO2
= 1)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.80.0
0.2
0.4
0.6
0.8
1.0
1.2
Current density / A cm-2
Cel
l vol
tage
/ V
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Pow
er d
ensi
ty /
Wcm
-2
14
2 cm
Self-made anode-supported cellPSC
Biogas
Ni-MgO/ZfCfZsAnode support: Ni-YSZ Electrolyte: YSZ
CH4/CO2= 1
45 %LHV (at Uf = 78 %)
Performance of DIRSOFC fuelled by simulated biogas
Temp. : 750 oCFuel : CH4/CO2 = 1Current density : 200 mA cm-2
Uf: 14 %
♦ Maximum power density of 820 mW cm-2
♦ Degradation rate of 1.4 %/1000 h♦ No coking
Temp. : 750 oCFuel : CH4/CO2 = 1
15
Molecular formula
Degree of unsaturation
wt %
Palmitic acid C17H34O2 0 39.9
Stearic acid C19H38O2 0 4.35
Oleic acid C19H36O2 1 40.4
Linoleic acid C19H34O2 2 12.0
Linolenic acid C19H32O2 3 0.21
Tri-glyceride 0.4
Sulfur S 1ppm
Palm oil-BDF
0 10 20 30 40 50
50
60
70
80
H2
conc
entr
atio
n / %
Ni-MgO/ZfAfAs
Fuel: Palm BDF (S/C = 3.5)Temp: 800 oCGHSV = 3900 h-1
Time / h
Ni/ZfAfZswith MgO
Ni only
45
55
65
75
0
1
2
3
4
5
Ni-MgO/ZfAfZs
Ni-MgO/ZfAfCs
C2H
4co
ncen
trat
ion
/ %
♦ Ni loaded PSC exhibited insufficient catalytic activity for steam reforming of BDF, deactivated rapidly accompanied by the formation of C2H4.♦ MgO addition was quite effective to improve catalytic activity.♦ Choice of inorganic binder is very important to achieve stable performance.♦ Ni-MgO loaded PSC using CeO2 sol as an inorganic binder, Ni-MgO/ZfAfCs, can stably convert palm-BDF to produce H2.
Performance of PSC for the steam reforming of BDF
S/C = 3.5
O0 20 40 60 80 100
0
20
40
60
80
100
H
0
20
40
80
100
C
Carbon deposition
region
S/C = 3.0S/C = 2.0
S/C = 0
Oleic-FAME (C19H36O2)
Oleic-FAME(C19H34O2)+ steam + N2
Ni-MgO loaded PSC
Perovskite containing PSC
20 mm
800 oC
Evaporator
dry air
H2, CO, CO2, CH4C2H4 and steam
600 oC
PSC
800 oCSOFC
16Experimental setup for BDF fuelled SOFC
Ni-YSZ anode-supported cell
0.0 0.2 0.4 0.6 0.8 1.0 1.20.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
Cel
l vol
tage
/ V
Current density / A cm-2
Oleic-FAME , (S/C = 2.0)
Palmitic-FAME /Oleic-FAME = 1 (S/C = 2.0)
Temp.: 800 oC
with PSC
with PSCPalm-BDF(S/C = 3.5)
17
IV curves in the feed of biodiesel fuels
Performance of SOFC fuelled by biodiesel
without PSC
Palmitic-FAME (C16:0)
Oleic-FAME (C18:1)
♦ By applying PSC, quite large current density of above 1.0 A cm-2 was obtained at 0.7 V.
♦ The addition of saturated FAME, here palmitic FAME, had the positive impact on the cell performance due to the suppression of C2H4 formation.
0 10 20 80 90 1000.5
0.6
0.7
0.8
0.9
1.0
Cel
l vol
tage
/ V
Time / h
without PSC (S/C = 3.5)
Temperature: 800 oCFuel: Oleic-FAMECurrent density: 0.2 A cm-2
with PSC (S/C = 2.0)
Degradation rate: 2.4 % / kh
Galvanostatic measurements
SOFC without PSC after 15 h test
SOFC with PSC after 100 h test
By the application of PSC, remarkably stable cell voltage was obtained even under the severe operating condition prone to carbon deposition.
5 µm
Agglomezated Ni Carbon fiberYSZ
Metal dust
18Stability of SOFCs with and without PSC
PSC serves as an anti-coking agent.10 µm
Microstructure of Ni-YSZ
19
Temperature homogenization in a planar reaction field using PSC technology
Suppression of temperature gradient using PSC techn ology
CathodeElectrolyte(YSZ)Inorganic fiber network Void ~20µm
Nano-sized metal catalyst
Ionic conductive fiber
SOFC
“Paper converting biogas to syngas”
PSC Install in a energy conversion device
Biogas
Final goalDevelopment of
internal reforming SOFC running on biofuels
Catalytic activity for reforming reactionLow High
⇒Temperature homogenization in a cell
Anode active layer (Ni-YSZ)
Array of PSCs with different catalytic activity
・ No carbon deposition・ Tolerant to deactivation by contaminants
・ Suppression of catalyst agglomeration・ Enhanced gas diffusivity
Electricity
Development of functionally-graded catalytic reacti on fieldSupported by Industrial Technology Research Grant Program in 201 1 from New Energy and Industrial Technology Development Organi zation (NEDO) of Japan
20
Monitoring of dry reforming methane to build a kine tic model 21
♦ Temperature decrease is easily adjustable by controlling Ni precursor concentration in the impregnation process of PSC.
Temperature change caused by the dry reforming of methane
0 200 400 600 800 1000-20
-15
-10
-5
0
5
0.02M Ni (0.15wt% Ni)
Temp: 800 oC
0.05M Ni (0.38wt% Ni)
0.1M Ni (0.76wt% Ni)
Time / s
Tem
pera
ture
dec
reas
e / o
C
T.C. was placed between the two papers.
Data logger
20 mm
♦ CH4 conv.♦ H2 production rate♦ CO production rate♦ Temp. decrease
T.C.
Fuel(simulated biogas)CH4 : CO2 = 1 : 1
Off-gas
800 or 750 oC
Paper-structured catalyst
to GC
Methane dry reforming test
CH4:CO2:N2(ml min-1) = 20:20:20
22Sensitivity analysis
Elementary reactions, Blaylock et al., J. Phys. Chem. C, 113 (2009) 4898
*: vacant site on the Ni surface.i*: adsorbed chemical species
According to the sensitivity analysis by changing activation energies in the base mechanism,
Recombination reactions of CH* with oxygenated adsorbants, Rx. 15 and 16, were found to be the most sensitive to the conversion and selectivity in dry reforming of methane.
Second sensitive reaction was CO2* decomposition, which is the reverse reaction of Rx. 35.
Reaction 15 : CH* + O* = CHO* + *, Ea = 101 kJ mol-1
Reaction 16 : CH* + OH* = CHOH* + *, Ea = 73 kJ mol-1
Reaction 35 : O* + CO* = CO2* + *, Ea = 124 kJ mol-1
23
H2 formation rate
0.01 0.1 1 100
10
20
30
40
50
60
70
80
0.01 0.1 1 100
10
20
30
40
50
60
70
80H
2pr
oduc
tion
rate
/ m
l min
-1
Ni concentration / M Ni concentration / M
H2
prod
uctio
n ra
te /
ml m
in-1
Temp: 800 oC
20:20:20
CH4:CO2:N2(ml min-1) = 40:40:40
20:20:20
40:40:40
20 : 20 : 20 ex.20 : 20 : 20 cal.40 : 40 : 40 ex.40 : 40 : 40 cal.
0.01 0.1 1 100
10
20
30
40
50
60
70
80
0.01 0.1 1 100
10
20
30
40
50
60
70
80
Ni concentration / M Ni concentration / M
CO
pro
duct
ion
rate
/ m
l min
-1
CO
pro
duct
ion
rate
/ m
l min
-120:20:20
40:40:40
40:40:40
20:20:20
Fuel: CH4/CO2 = 120 : 20 : 20 ex.20 : 20 : 20 cal.40 : 40 : 40 ex.40 : 40 : 40 cal.
20 : 20 : 20 ex.20 : 20 : 20 cal.40 : 40 : 40 ex.40 : 40 : 40 cal.
20 : 20 : 20 ex.20 : 20 : 20 cal.40 : 40 : 40 ex.40 : 40 : 40 cal.
Temp: 800 oCFuel: CH4/CO2 = 1
Temp: 750 oC
Fuel: CH4/CO2 = 1
Temp: 750 oC
Fuel: CH4/CO2 = 1
Reaction rate of dry reforming of methane
CO formation rate
24CH4 conversion vs temperature decrease
0.0 0.2 0.4 0.6 0.8 1.0-35
-30
-25
-20
-15
-10
-5
0
0.0 0.2 0.4 0.6 0.8 1.0-35
-30
-25
-20
-15
-10
-5
0
Tem
pera
ture
dec
reas
e / K
CH4 conversion / - CH4 conversion / -
20:20:20
40:40:40
20:20:20
40:40:40
Tem
pera
ture
dec
reas
e / K
Correlation between methane conversion and local te mperature decrease caused by the dry reforming of methane
♦ Calculated results were well accorded with experimental ones.♦ Kinetic simulation model build in this study can precisely predict local temperature decrease if a certain methane conversion is given.
Using the established model a functionally-graded reaction field leading to uniform temperature distribution in a planar reactor during biogas reforming can be designed.
20 : 20 : 20 ex.20 : 20 : 20 cal.40 : 40 : 40 ex.40 : 40 : 40 cal.
20 : 20 : 20 ex.20 : 20 : 20 cal.40 : 40 : 40 ex.40 : 40 : 40 cal.
Temp: 800 oCFuel: CH4/CO2 = 1
Temp: 750 oCFuel: CH4/CO2 = 1
Ni
YSZ plate
Ceramic bond
Simulated biogas(CH4/CO2 = 1)
Off-gasto gaschro
Inorganic fiber
PSC strip
Biogas
25
The array of PSC strips Measurement of temp. distribution
Before test
0.04M Ni0.5M Ni+1.0M Mg
0.1M Ni+0.5M Mg0.065M Ni
CH4/CO2= 1
♦Temperature homogenization ♦ Suppression of carbon deposition♦ Avoidance of destruction of the adjacent ceramic material♦ Stabilization of planar reformer
ThermographyParameter・ CH4/CO2 ratio・ Air/Biogas ratio・ Furnace temp.
Design of functionally-graded reaction field
Off-gas
Objective5 cm
5 cm
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0-100
-80
-60
-40
-20
0
20
Tem
pera
ture
dec
reas
e / o
C
Distance / cm
Fuel: Simulated biogas(CH4/CO2 = 1), 180ml min-1
Furnace temp: 800 oC
in out
Exp. I, One PSC(uniform catalyst )
Exp. II, PSC array(functionally graded)
Temperature homogenization
Exp. II
Calculation
Exp. I
Calculation
in out in out
26
Line distribution
♦ Temp. gradient caused by the dry reforming of methane was reduced down to 1/4 by the application of PSC array at the same CH4 conversion.♦ Sever coking occurred in the Exp. I caused by the strong temperature decrease by 90 oC, which can thermodynamically induce carbon formation.
Temperature distribution during dry reforming of me thane
0.5M Ni/ZfCfZs(3.8 wt% Ni)
0.04
M N
i
0.5M
Ni+
1.0M
Mg
0.1M
Ni+
0.5M
Mg
0.06
5M N
iCH4 conv. = 91 % CH4 conv. = 91 %
after 100 h
PSC
After test (35 h)
Coking
4 different PSCs
in out in out
4 cm
4 cm
No coking
27
♦ Inorganic fiber network including YSZ fiber which acts as catalyst support was created by the simple paper-making process.
♦ Novel Ni-loaded paper-structured catalysts (PSCs) with excellent catalytic activity for the reforming of biofuels were designed and developed.
♦ The significant advantages of the PSCs are their high mechanical flexibility and material workability to be easily applied to SOFC.
♦ So far, a functionally-graded reaction field which leads to uniform temperature distribution during biofuel reforming resulting in stable operation of planar reactor such as SOFC was successfully developed.
Summary
Acknowledgements 28
This study was supported by Industrial Technology Research Grant Program in 2011 from New Energy and Industrial Technology Development Organization (NEDO) of Japan.