1. Status of Hydrogen Separation Membrane Development* U. (Balu) Balachandran, T. H. Lee, L. Chen, and S. E. Dorris Energy Systems Division *Work supported by U.S. Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory’s Hydrogen & Syngas Program. Presented at the NHA Annual Hydrogen Conference, Sacramento, CA, April 1, 2008. E-mail: balu@anl.gov

2. NHA, April 1, 2008 2 Types of Hydrogen Separation Membranes Metallic membranes (Pd, Pd alloys, Group IV – V elements, etc.) Porous membranes (micro-, nano-porous materials) Polymeric membranes (low-temperature organic materials) Dense ceramic membranes (mixed-conductors) Dense ceramic/metal composite (cermet) membranes (this presentation)

3. NHA, April 1, 2008 3 Requirements Membranes must combine several structural and functional properties. high permeability and species selectivity sufficient mechanical, chemical, and thermal stability under applied operating conditions low foul rate long & reliable operation cost effective production Quite difficult for a single material to satisfy all the constraints

4. NHA, April 1, 2008 4 Objectives Develop dense ceramic & cermet membranes for separating hydrogen from mixed gases at commercially significant fluxes under industrially relevant operating conditions. Product streams from coal gasification and methane reforming are of particular interest. Membrane must: –have low cost –have high selectivity for H 2 –give industrially significant flux –withstand high pressure and temperature –be chemically stable in presence of steam, CO, CO 2, CH 4, H 2 S, Hg, halides, etc.

5. NHA, April 1, 2008 5 Advantages of Argonne’s Cermet Membrane Major concern for metallic membrane (free standing or supported) –Dissolved hydrogen tends to cause lattice expansion in metals leading to rupture –Cracking will cause total failure/loss of mechanical integrity of metallic membrane Argonne’s membrane is a ceramic/metal homogeneously mixed composite (cermet) –Ceramic phase blunts crack propagation and provides three-dimensional mechanical support –Argonne membranes have been tested at high pressures & temperature conditions

6. NHA, April 1, 2008 6 H 2 flux through ≈  m cermet membrane at 500 & 900°C (feed gas: 100% H 2 at ambient pressure) YSZ-Pd Cermet

7. NHA, April 1, 2008 7 H 2 Flux at High Feed Gas Pressures (≈300 psig) (Measured at Argonne and NETL) Measurements at NETL were made by M. Ciocco and R. Killmeyer Extrapolated values fall in line with values measured at high pressures at both Argonne and NETL. High pressure measurements were made on ≈0.8-mm-thick cermet membrane, and were scaled to 20  m thickness for comparison. 20  m thick

8. NHA, April 1, 2008 8 Pd/Pd 4 S phase boundary calculated for various H 2 concentrations using data from literature J. R. Taylor, Met. Trans., 16B, 143, 1985; O. Knacke, et al., Thermochemical Properties of Inorganic Substances I, Springer-Verlag, Berlin, 1991. Temperature (°C)

9. NHA, April 1, 2008 9 Pd/Pd 4 S Phase Boundary determined at Argonne Calculated data from literature: J. R. Taylor, Met. Trans., 16B, 143, 1985; O. Knacke, et al., Thermochemical Properties of Inorganic Substances I, Springer-Verlag, Berlin, 1991 Bars in red color summarize results obtained at Argonne by equilibrating samples at various temperatures with feed gas of 73% H 2 with 400, 190, & 60 ppm of H 2 S ( □ ); 10% H 2 with 50, 27, & 8 ppm H 2 S ( ◊ )

10. NHA, April 1, 2008 10 Pd/Pd 4 S phase boundary determined at Argonne Bars in colors summarize results obtained at Argonne by equilibrating samples at various temperatures with feed gas of: (Red) 73% H 2 with 400, 190, & 60 ppm of H 2 S; (Blue) 73% H 2, 0.5% CH 4, 6.2% CO 2, 7.8% CO, 400 ppm H 2 S. Temperature (°C)

11. NHA, April 1, 2008 11 Chemical Stability of ANL-3 Membrane Time (h) H 2 Flux (cm 3 /min-cm 2 ) ANL-3e (Thickness ≈ 0.20 mm; Temp. = 900°C) Feed Gas: 400 ppm H 2 S, 73% H 2, Balance He at ambient pressure ANL-3 HTM appears to be stable in 400 ppm H 2 S. YSZ-Pd Cermet

12. NHA, April 1, 2008 12 H 2 flux at 900°C in H 2 S-containing mixed-gas stream ( 61.3% H 2, 8.2% CH 4, 11.5% CO, 9.0% CO 2, 10% He, 100 ppm H 2 S ) ≈0.20-mm thick YSZ-Pd Cermet

13. NHA, April 1, 2008 13 Stability of Cermet Membrane in Mixed Gas Streams containing Steam (53% H 2, 10% CO, 8% CO 2, 1% CH 4, 21% H 2 O, bal. He)

14. NHA, April 1, 2008 14 Tubular HTM Membranes (a) (b) a) Porous alumina support tube pre-sintered for 5 h at 700°C in air. b) Pre-sintered porous alumina support tubes coated with ANL-3e HTM and then sintered for 5 h at 1400°C in air.

15. NHA, April 1, 2008 15 HTM Tube Test Assembly H 2 permeation exceeded 150 cc/min in small tubes in the temperature range 600 - 900°C at ambient pressure. (≈8 cm long; 0.9 cm OD; ≈24 cm 2 surface area)

16. NHA, April 1, 2008 16 Fracture Toughness of the HTM Membrane (YSZ/Pd Cermet) Temperature [°C] K* IC [MPa(m) -1/2 ] 207.79 257.98 6006.58 9005.22 10005.24 11004.64 12004.72 Al 2 O 3 tubes2.50 Measured by K. Salama & G. Majkic at University of Houston

17. NHA, April 1, 2008 17 Summary Developed dense cermet membranes that nongalvanically separate hydrogen from mixed-gas streams (gasification/reforming). Highest H 2 flux (≈66 scfh/ft 2 at 900°C and ≈42 scfh/ft 2 at 500°C) was measured on ≈15-  m-thick HTM using feed of 1 atm H 2. Flux >400 scfh/ft 2 (>200 cc/min/cm 2 ) can be achieved with hydrogen pressure at ≈350 psi in feed gas. Measurements made at high pressures both at Argonne & NETL support this conclusion. Hydrogen permeation exceeding 150 cc/min (300 scfh) were measured in short (≈8 cm long) tubular membranes at 600°C (at ambient pressure feed). Cermet membranes were stable in the range 500-800°C in simulated syngas mixtures containing ≈20% steam. Flux was stable for ≈1200 h in feed stream with 400 ppm H 2 S at 900°C. Regeneration of sulfur poisoned cermet membrane was observed. High temperature mechanical properties were measured.

18. NHA, April 1, 2008 18 Acknowledgements This work is supported by the U.S. Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory's Hydrogen & Syngas Technology Program. NETL Project Manager: Richard Dunst (ph: 412-386-6694; richard.dunst@netl.doe.gov) NETL Technology Manager: Dan Cicero (ph: 304-285-4826; daniel.cicero@netl.doe.gov)

19. NHA, April 1, 2008 19 Argonne’s Approach to H 2 Membrane Development Feed CO 2 CO H 2 etc. H+H+ H2H2 H2H2 H+H+ e-e- H /H / ANL-2 Mixed Conductor With Metal H+H+ H2H2 H2H2 H+H+ e-e- ANL-1 Feed CO 2 CO H 2 etc. High Flux High Selectivity Good Mechanical Integrity Structural Ceramic With Hydrogen Transport Metal H2H2 H2H2 H H ANL-3 Feed CO 2 CO H 2 etc. Single-Phase Mixed Conductor Low  e- Low Flux Poor Mechanical Integrity H+H+ e-e- H2H2 ANL-0 Feed CO 2 CO H 2 etc. H2H2 e-e- e-e- H /H / (Dorris, Lee, and Balachandran, U.S. Patent 6,569,266, May 27, 2003)

20. NHA, April 1, 2008 20 Stability of Cermet Membrane in Steam (0.22 mm-thick-ANL3e, feed pH 2 = 0.5 atm, T = 600 o C) YSZ-Pd Cermet

21. NHA, April 1, 2008 21 Cross-Sectional Views at Two Magnifications of HTM Film on Porous Alumina Tube HTM film thickness ≈60 µm

22. NHA, April 1, 2008 22 Schematic of Experimental Setup

23. NHA, April 1, 2008 23 H 2 Permeation Rate vs. Temperature (ambient pressure measurement) Temperature (°C) Flux (mol/s-cm 2 ) Flux (cm 3 /min-cm 2 ) ANL-3a (≈40 µm) 100% H 2 feed Al 2 O 3 -Pd Cermet

24. NHA, April 1, 2008 24 H 2 Flux vs. Inverse HTM Thickness H 2 Flux (cm 3 /min-cm 2 ) 1/Thickness (cm -1 ) H 2 Flux (scfh/ft 2 ) Feed Gas: 80% H 2 /He at Ambient Pressure ANL-3e @ 900°C Flux data indicate that reducing HTM thickness should increase H 2 flux.