Hydrogen Production with Mixed Protonic-Electronic Conducting Perovskite Membranes Eric D. Wachsman UF-DOE High Temperature Electrochemistry Center Department of Materials Science and Engineering University of Florida Gainesville, FL 32611 [email protected]UF-DOE HiTEC
34
Embed
Hydrogen Production with Mixed Protonic-Electronic ... Production with Mixed Protonic-Electronic Conducting Perovskite Membranes ... transport membrane ... for membrane thin filmSintered
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
UF-DOE HiTEC
Hydrogen Production with Mixed Protonic-ElectronicConducting Perovskite Membranes
Eric D. WachsmanUF-DOE High Temperature Electrochemistry Center
Department of Materials Science and EngineeringUniversity of Florida
Oxygen transport membrane•Exothermic oxidation of hydrocarbon feed gas
Concept - Autothermal Catalytic Membrane Reactorfor Production of Pure H2
CO2
Ultimately can produce pure H2 from anyhydrocarbon feed stock:
• Natural gas• Coal based syn gas• Biomass
UF-DOE HiTEC
Cost of Hydrogen Production from Natural Gas*
3.25 H2/CH4
CH4 ~ 0.20C$/m3
~$0.15/m3 H2
~0.015 ¢/liter H2
CH4 + 0.375 O2 + 1.25 H2O = CO2 + 3.25 H2
* Assumes 100% conversion and selectivity,air and water are free, and ignores capital cost
UF-DOE HiTEC
DOE’s Future Gen
• Hydrogen and electricity co-generation from coal• Zero emissions and CO2 capture
“Hydrogen Production from Fossil Fuels with Proton and Oxygen-Ion Transport Membranes,”E. D. Wachsman and M. C. Williams, Interface, Volume 13, No.3, Fall 2004
UF-DOE HiTEC
Outline
• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions
UF-DOE HiTEC
OXIDE-ION CONDUCTING MIEC’s
• Ionic and electronic conductivity results in O2 permeationlimited by oxide-ion conductivity σVo••
σi and σe of La0.8Sr0.2Co0.8Fe0.2O3-dTeraoka, et al (1998)
JO2 of La0.6Sr0.4Co0.8B0.2O3-dTeraoka, et al (1998)
Hydrocarbon Feed
O2 Permeation Membrane
O2, N2h•
Vo••
O2
Partially Oxidized Hydrocarbon Effluent
CnHm
CO, H2N2
UF-DOE HiTEC
OXIDE-ION vs. PROTONIC CONDUCTION
• Oxygen ions jump from a filled (OOx) to a vacant (VO
••) site• H-bonded protons form an OH group (OHO
•)• Protons move around OO
x and jump to neighboring OOx
VO••
OOx
MMx
OHO•
UF-DOE HiTEC
Partially Oxidized Hydrocarbon Feed
H2 Permeation Membrane
H2e’
OHo•
H2
CO, H2, CH4
CO, C2+
Hydrogen Depleted Effluent
SrCeO3-δ layer
Ni-GDC porous support
PROTONIC vs. OXIDE-ION CONDUCTORS
• Protonic conductors have comparable ionic conductivity butnegligible electronic conductivity
• H2 flux limited by electronic conductivity (σe’)
σi and σe of La0.8Sr0.2Co0.8Fe0.2O3-dTeraoka, et al (1998)Iwahara, et al.
UF-DOE HiTEC
• Add electronic conductivity by doping Ce sitewith multivalent cation (M3+/2+) that can bereduced to 2+– MCe” = MCe
conductivity at much lowertemperature and higher PO2
J. Rhodes and E.D. Wachsman (2001).
UF-DOE HiTEC
• At high temperature (>750°C) permeation is bulk transport controlled– Flux is linear with 1/L
• At lower temperature permeation is surface kinetic controlled
0
0.001
0.002
0.003
0.004
0.005
0.006
600 650 700 750 800 850 900
100% H2 0.75 mm
90% H2 1.00 mm
90% H2 2.00 mm
HY
DR
OG
EN
FL
UX
(cc/c
m 2-m
in)
TEMPERATURE (oC)
0
0.001
0.002
0.003
0.004
0.005
0.006
0.4 0.6 0.8 1 1.2 1.4
HY
DR
OG
EN
FLU
X (
cc/c
m 2
-min
)
1/THICKNESS (mm)
850oC
800oC
750oC
Flux ~ 1/membrane thickness (L)
!! ++"= •••••••
//
2
/
22
/
//
2
/
22
ln)(2
ln4[1
22
H
HOO
O
OOOO
P
PHeVOHt
P
POVOHtOH
PdtttF
RTPdtt
F
RT
LJ ##
H2 Flux Relationship
UF-DOE HiTEC
Outline
• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions
UF-DOE HiTEC
Slurry coating for membrane thin filmCo-firing support and membrane thin filmSintered hydrogen membrane cell
Hydrogen Membrane Cell Fabrication
UF-DOE HiTEC
Fabrication of Membrane Reactor
UF-DOE HiTEC
Hydrogen Membrane Evaluation
All tubes are continuously leak checked by Ar tracer in feed gas
UF-DOE HiTEC
Hydrogen Permeation and Leak Testing
• Confirms membranes are leak free • Capable of producing 100% purity H2
UF-DOE HiTECHydrogen flux ~ PH2 1/4
Hydrogen Permeation
UF-DOE HiTEC
Activation energy of ~0.9 eV indicates flux limited by σe− σOH• activation energy ~ 0.5 eV
Hydrogen Permeation
0.9240.890.930.960.970.86Activation energy,E (eV)
average value10.600.350.200.075PH2 (atm)
UF-DOE HiTEC
H2 -3% H2O balance Ar / SrCe0.9Eu0.1O3 /He
Hydrogen Permeation
Membrane tubes produce7 cc/min of pure H2
UF-DOE HiTEC
H2 balance He / SrCe0.95Tm0.05O3 / 20% O2 balance He[1] S. Cheng, V. K. Gupta, and J. Y. S. Lin, Solid State Ionics 176 (2005) 2653.
4% H2 -3% H2O balance He / Ni-BaCe0.8Y0.2O3 / N2 with 100ppm H2[2] C. Zuo, T. H. Lee, S.-J. Song, L. Chen, S. E. Dorris, U. Balachandran, and M. Liu, Electrochem. Solid-State Lett., 8 (2005) J35
H2 -3% H2O balance Ar / SrCe0.9Eu0.1O3 /He
Hydrogen Permeation
Area normalized membraneflux comparable to best inliterature.
However…
UF-DOE HiTEC
Pure H2 produced directly by internal steam reforming CH4• H2 flux even higher than from comparable H2 feed
Hydrogen Production
CH4/H2O ~ 2
UF-DOE HiTEC• 3% CO and H2O balance He• Solid lines are H2O/CO=1, dashed lines are H2O/CO≈2
0
20
40
60
80
100
0
0.1
0.2
0.3
0.4
0.5
0.6
650 700 750 800 850 900 950
Temperature (oC)
Con
vers
ion
(%)
Hydrogen production and
Permeation Flux (cc/m
in)
H2 Permeation
Without H2 permeation
Thermodynamic calculation
With H2 permeation
Hydrogen Production
Water gas shift reaction: CO + H2O -> CO2 + H2
UF-DOE HiTEC
Outline
• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions
UF-DOE HiTEC
-4
-3.6
-3.2
-2.8
-2.4
5 10 15 20
Doping concentration of Eu on SrCeO3 (mol %)
900oC
800oC
700oC
600oC
0.49 eV
0.52 eV
0.87 eV
10 mol%
15 mol%
20 mol%
Activation Energy
Total conductivity maximum at ~10% Eu
Conductivity of Eu-doped SrCeO3
Log
σPr
oton
(Scm
-1)
UF-DOE HiTEC
-4.5
-4
-3.5
-3
-2.5
-2
10 15 20
900oC
800oC
700oC
600oC
Doping concentration of Eu (mol %)
-4.5
-4
-3.5
-3
-2.5
-2
10 15 20
Doping concentration of Eu (mol %)
900oC
800oC
700oC
600oC
Proton Conductivity Electron Conductivity
Proton vs. Electron ConductivityL
og σ
Prot
on (S
cm-1
)
Log
σE
lect
ron (
Scm
-1)
Increasing Eu concentration:• Decreases σOH•• Increases σe’
UF-DOE HiTEC
0
0.2
0.4
0.6
0.8
1
600 700 800 900
Temperature (oC)
Proton [Eu10]
Proton [Eu15]
Proton [Eu20]
Electron [Eu10]
Electron [Eu15]
Electron [Eu20]
Increased Electronic Transference NumberTr
ansf
eren
ce n
umbe
r
!
tOH
O
• ="
OHO
•
"OH
O
• +" # e
t # e =
" # e
"OH
O
• +" # e
H2 flux limited by electronic conductivity
UF-DOE HiTEC
Conclusions• High temperature protonic conductors offer tremendous potential for