Pd Membrane Characterization Chi Lo In collaboration with Esther Wilcox and Eva Krauss Advisor: Will Medlin
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Pd Membrane Characterization
Chi Lo In collaboration with Esther Wilcox and Eva Krauss
Advisor: Will Medlin
Hydrogen Purification with Pd Membranes n Hydrogen
dissociatively adsorbs on the metal surface
n Hydrogen atoms diffuse through the metal
n On permeate side, Hydrogen molecules recombine
H H
Pd Membrane
H H
H H
H H
Permeate Side
Retentate Side H H
H H
S
O
O O C
O C
Sulfur Poisons Pd Membranes
n Sulfur bonds strongly to Pd blocking sites for H2 adsorption
n Over time, sulfur restructures the metal surface
1µm
1µm
a
b
SEM images of metal surfaces (a) 20% Cu 80% Pd (b) 30% Cu 70% Pd after H2S exposure. Note: Stronger restructuring with increased Cu%
Alloys Improve Pd Membranes n Cu, Ag, and Au – Pd alloys
can improve H2 permeation ¨ Prevent “hydrogen
embrittlement” ¨ Sulfur resistance ¨ Lower costs
n Research Objective ¨ Gain a fundamental
understanding of the surface effects of sulfur on Pd alloys
Pd alloy membrane (40% Pd 60% Cu
composition)
What is to come…
n Permeation Experiments ¨ Problems
n Reactor set-up n Membranes
n AFM imaging ¨ Trends and Conclusions
Permeation Experiment Equipment
Mass Spec
Furnace
Mass Flow Controllers
Reactor
Flow and Temperature Readings taken by National Instruments LabVIEW 7.1 Mass Spec Signal
Taken by WinMPA
Reactor Types
n C-ring reactor
n O-ring reactor
49.7% Pd 50.3% Ag 2000A H2S Permeation Experiment
1.0E-13
1.0E-12
1.0E-11
1.0E-10
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Time (sec)
Mas
s Spe
c Sig
nal
49.7% Pd 50.3% Ag (1/23/07)
Top and Bottom: 100
sccm He
Top: 25 sccm H2 75 sccm H2S in N2
Bottom: 100 sccm He 100°C
10.1% Pd 89.9% Cu 2000A H2S Permeation Experiment
1.0E-13
1.0E-12
1.0E-11
1.0E-10
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Time (sec)
Mas
s Spe
c Si
gnal
HeH2H2SN2
H2S Experiments Conclusion
n Membranes fail quickly and allow other gases to permeate
n New membranes are needed
AFM (Atomic Force Microscope) n Creates a topographical
map of the membrane surface
n Study deformation trends of membranes for the different alloy compositions
100% Pd
60% Pd 40 % Cu
64.8% Pd 35.2% Cu
54.8% Pd 45.2% Cu
28.1% Pd 71.9% Cu
AFM Conclusions
n Deformation of membranes following H2S exposure
n Number of pyramids per area and size correlates with alloy ¨ Increased reconstruction with
increasing Cu percentage n Additional AFM images for more
trend analysis
Reflections on Senior Thesis
n Laboratory experience n Learned to use equipment and software n Would have been nice for permeation
experiments to work to finish AFM imaging
n Would have changed nothing