The Hydrogen Permeability of Palladium-Copper Alloy Composite Membranes Over a Wide Range

of Temperatures and PressuresBret Howard, Rich Killmeyer, Kurt Rothenberger

US DOE NETL

Bryan Morreale, Mike CioccoParsons

Robert EnickORISE Faculty Fellow, Dept. of Chem. and Pet. Eng., Univ. of Pittsburgh

Felipe BustamanteResearch Assoc. DOE-University Student Partnership Program

Dept. of Chem. and Pet. Eng., Univ. of Pittsburgh

NETL’s Hydrogen Separation Team

Fossil Fuels to H2•Direct Production•Reformable Fuels

Hydrogen fromRenewableResources

Carbon BasedFuels

MissionInvestigate technologies to produce and separatehydrogen for downstream uses, both in advanced energy plant applications and in off-site applications.

VisionFossil fuels are viewed as the transition feedstocks for the production of hydrogen in the “Hydrogen Economy”.

Pd is Not Appropriate for Post-Gasifier Membrane Reactor Conditions

• Temperature range: 448-1173 K (175-900ºC)• Pressure range: 1-7 MPa (145-1000 psi)• Composition of Gasifier Effluent

− H2, CO2, CO, H2O• H2S (2000-10000 ppm): known to poison Pd• NH3 + HCN (0-3000 ppm)• COS (0-1000 ppm)• CH4 (0-50000 ppm)

Severe conditions are associated with coal gasification membrane reactors

Pd-Cu Alloys Have Been Proposed as Sulfur Resistant Hydrogen Membrane Materials

• Certain Pd-Cu alloys have high permeability• Certain Pd-Cu alloys may exhibit H2S resistance• Published literature focuses on the 60wt%Pd-40wt%Cu alloy at 623 K

(350ºC), low H2 partial pressure (0.1 MPa)

Project Objective

• Temperature range: 623-1173 K (350 - 900ºC)• PH2 range: 0.1-2.6 MPa (14 - 380 psi)• Composition (80-20, 60-40, 53-47, 40-60 wt% Pd-Cu)• Crystal structure (bcc, fcc, mixed bcc-fcc)

Evaluate the permeability of Pd-Cu alloys over a wide range of conditions encompassing those characteristic of gasification.

Goal: To Provide a performance baseline for Pd-Cualloys for ongoing poisoning resistance studies.

Composite Membrane Mechanism

Hydrogen

FuelGasStream

Pd-CuMembrane

Adsorption/Dissociation

AtomicDiffusion

Recombination/Desorption

PorousSupport

Membrane Holder

1 mm thick x 19 mm Dia.Porous Support.

Nickel AlloyWasher

0.1 mm Thick x ~ 13 mm Dia.Pd-Cu Alloy Membrane

Inconel Alloy 600 Holders19.1mm O.D. x 16.5 mm I.D.

RETENTATE(Feed side) PERMEATE

TI

GC

FCV FCV

PCV PCV

H2 Ar

Heater

Membrane

H2

H2

H2

H2

Ar/H2

Ar/H2

Ar

Ar

Heater

Heater

H2

Membrane PermeanceApparatus

NETL Hydrogen Separation Facilities• 3 H2 Membrane Test Units• Constructed FY99 to FY02• Temperatures to 900°C• Pressures to 1000 psi• Disk & tubular membranes• Feed gas flexibility• Membrane separation &

reactor configurations• “Clean” and “sulfur-laden”

gas feedstocks• Online analysis of

products by GC

300

400

500

600

700

800

900

1000

0 20 40 60 80 100

Weight % Palladium

Tem

pera

ture

(C)

(bcc)High Permeability

Mixed(bcc)+(fcc)

(fcc)Low Permeability

α’ α’’

Pd-Cu Phase Diagram*Red vertical lines represent compositions tested at NETL.

*Derived from: M. Henson, Constitution of Binary Alloys, (McGraw-Hill 1958), pp. 612-613.

53%Pd-47%Cu Alloy Permeance ThroughPhase Transition

Temp (C

)

40 60 80300

600

900

Pd wt%

fcc

fcc + bcc

bcc

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.0008 0.001 0.0012 0.0014 0.0016 0.0018

1/T [K-1]

Perm

eanc

e [m

ol /

m2 / s /

Pa0.

5 ]

977ºC 727ºC 560ºC 441ºC 352ºC 283ºC

bccfcc100% Pd53%Pd - 47%Cu,Run #153%Pd - 47%Cu,Run #2, Increasing T53%Pd - 47%Cu,Run #2, Decreasing T

60%Pd-40%Cu Alloy Permeance ThroughPhase Transition

Temp (C

)

40 60 80300

600

900

Pd wt%

fcc

fcc + bcc

bcc

fcc + bccfcc

977ºC 727ºC 560ºC 441ºC 352ºC 283ºC

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.0008 0.001 0.0012 0.0014 0.0016 0.0018

1/T [K-1]

Perm

eanc

e [m

ol /

m2 /

s / P

a0.5 ]

100% Pd60%Pd-40%Cu,Run #1, Increasing T60%Pd-40% Cu,Run #1, Decreasing T,non-steadystate60%Pd-40% Cu,Run #2

80%Pd-20%Cu and 40%Pd-60%CuAlloy H2 Permeance

Temp (C

)

40 60 80300

600

900

Pd wt%

fccfcc +bcc

bcc

977ºC 727ºC 560ºC 441ºC 352ºC 283ºC

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.0008 0.0010 0.0012 0.0014 0.0016 0.0018

1/T [K-1]

Perm

eanc

e [m

ol /

m2 /

s / P

a0.5 ]

100% Pd80% Pd - 20% Cu40% Pd - 60% Cu 100% Cu

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.0008 0.0010 0.0012 0.0014 0.0016 0.0018

1/T [K-1]

Perm

eanc

e [m

ol /

m2 / s /

Pa0.

5 ]

80%Pd-20%Cu Alloy H2 Permeance ShowingDecrease Caused by Intermetallic Diffusion

977ºC 727ºC 560ºC 441ºC 352ºC 283ºC

100% Pd80% Pd - 20% Cu80% Pd - 20% Cu – cooling from 900°C100% Cu

1

2345

6

7

8

Temp (C

)

40 60 80300

600

900

Pd wt%

fccfcc +bcc

bcc

Interface Between Membrane and Support

Adhesionpoints

Membranesurface

Poroussupport

Membranesurface

keV109876543210

Cou

nts

400

300

200

100

0

Intermetallic Diffusion Between Membrane and Support

Adhesionpoint

Membranesurface

Cr Fe Ni Cu

Pd EDS analysis

Cr, Fe and Ni from porous support have diffused from contact/adhesion points into Pd-Cu foil causing a flux decrease.

Conclusions• The Pd-Cu alloys exhibited predictable permeance. • 53Pd-47Cu and 60Pd-40Cu alloys exhibited a distinct drop in permeance

at the T associated with the bcc to fcc transition.• 80Pd-20Cu and 40Pd-60Cu alloys remained in the fcc region and

exhibited no discontinuities in permeance over the 350 to 900ºC range.• 60Pd-40Cu alloy yielded the highest permeance but only at 350ºC (bcc).• fcc permeance increases with %Pd.• A passivation layer is necessary for composite membrane applications

at high temperatures.

Future Work• Evaluate permeance in the presence of H2S.• Investigate membrane recovery after H2S exposure.• Evaluate permeance in the presence of major WGS gas components:

H2O, CO, CO2 and other gas impurities, such as NH3.• Evaluate thinner foil Pd-Cu membranes supported on porous substrates.• Consider other alloys.