Understanding the Influence of Temperature On H2 Flux in the Presence of H2S On Pd-Based Ternary Alloy Membranes

Understanding the Influence of Temperature on H₂ Flux in the Presence of H₂S on Pd-based Ternary Alloy Membranes

A.E. Lewis¹, J. D. Way¹, S.D. Hopkins², H. Zhao²

¹Colorado School of Mines, Golden, CO

²Pall Corporation, Cortland, NY

               

                Palladium (Pd) based membranes are appealing for hydrogen separation applications [1-4].  The use of pure Pd has been limited due to poor chemical tolerance in the presence of carbon monoxide and hydrogen sulfide (H₂S), which are stream contaminants commonly found in coal-derived syngas [5-7].  Carbon species deactivate hydrogen dissociation sites on the Pd surface [8, 9].  H₂S can block hydrogen dissociation sites, and cause Pd-sulfide formation, which has lower hydrogen permeability than Pd [3, 10, 11].  The hydrogen flux of a pure Pd membrane was reduced by 71% in a gas mixture with only 4 ppm of H₂S in hydrogen  [7].   In order to enhance chemical stability, Pd is alloyed with other metals such as gold, copper, and platinum [7, 9, 12-18].  Although Pd-based binary alloys have been studied for over 50 years and have a presence in current literature, recent research has focused on Pd-based ternary alloys for improved chemical tolerance [19-21].  Fabrication and testing of these ternary alloys is in its infancy, but there are a few compositions with notably enhanced properties.  Pd₈₀Au₁₀Pt₁₀ alloy membranes fabricated by magnetron sputtering had a flux reduction of 21% when 20 ppm H₂S was added to a water-gas shift mixture at 673 K and 1.27 MPa feed pressure [20].  Pd₇₄Ag₁₄Au₁₂ showed no sulfide formation when exposed to 1000 ppm H₂S in hydrogen at 623 K [19].

                The purpose of this work is to further the understanding of the hydrogen permeation behavior of Pd-Au-Pt and Pd-Ag-Au ternary alloy membranes in the presence of H₂S at different temperatures.  The results will be compared to similar testing in literature.  The membranes will be prepared by sequential electroless deposition, annealed, pure-gas tested, and then tested in a gas mixture of 20 ppm H₂S in hydrogen at a feed pressure of 689.5 kPa and temperatures up to 773 K.  A Pd-Ag-Au alloy composite membrane was fabricated on a Pall AccuSep® substrate tube and subsequently annealed.  This Pd-Ag-Au alloy membrane had a pure-gas hydrogen permeance at 673 K of 1.29x10^-3 mol H/m²/s/Pa^0.5 which is comparable to that of pure Pd on a similar substrate [22].  The alloy was pure-gas tested up to 873 K and feed pressures of up to 689.5 kPa as seen in Figure 1.  The apparent activation energy of the Pd-Au-Ag alloy for hydrogen permeation derived from Figure 1 was 9.39 kJ/mol, which is a little less than that of pure Pd [23].  Figure 2 shows the hydrogen flow reduction at 773 K for the Pd-Au-Ag membrane.  When exposed to the gas mixture of 20 ppm H₂S in hydrogen for 24 hours at a feed pressure of 689.5 kPa, the hydrogen flux was reduced by 52%, 60%, and 75% at 773, 723, and 673 K, respectively.    

                The preliminary results of this study provide insight to the hydrogen flow reduction in the presence of H₂S.  The steep drop in hydrogen flux when the H₂S is introduced could be attributed to surface site-blocking.  Once the initial drop in hydrogen flow occurs, a steady state value is achieved.  This indicates that no sulfide has formed.  These results are similar to a test done on binary Pd-Au membranes by Chen, et al [24].  Once the H₂S is removed, the hydrogen flow begins to recover, which is further evidence no sulfide has formed.  Post-testing characterization is not yet complete to confirm this observation. This particular alloy exhibits a larger flow reduction with decreasing temperature, which may be an important finding for applications with operating temperatures above 673 K.

Figure 1. Pure-gas hydrogen flux of a 9 micron Pd-Au-Ag as a function of feed pressure and temperature.

Figure 2. Hydrogen flow of a 9 micron thick Pd-Au-Ag alloy membrane in 20 ppm H₂S in hydrogen gas mixture at 689.5 kPa feed pressure.

           

 

 

References

[1] M. Abdollahi, J. Yu, P.K.T. Liu, R. Ciora, M. Sahimi, T.T. Tsotsis, Hydrogen production from coal-derived syngas using a catalytic membrane reactor based process, J. Membr. Sci., 363 (2010) 160-169.

[2] A.C. Bose, Inorganic Membranes for Energy And Environmental Applications, Springer, New York, 2008.

[3] M.V. Mundschau, X. Xie, C.R. Evenson Iv, A.F. Sammells, Dense inorganic membranes for production of hydrogen from methane and coal with carbon dioxide sequestration, Catal. Today, 118 (2006) 12-23.

[4] P. Pinacci, M. Broglia, C. Valli, G. Capannelli, A. Comite, Evaluation of the water gas shift reaction in a palladium membrane reactor, Catal. Today, 156 (2010) 165-172.

[5] A. Li, W. Liang, R. Hughes, The effect of carbon monoxide and steam on the hydrogen permeability of a Pd/stainless steel membrane, J. Membr. Sci., 165 (2000) 135-141.

[6] H. Li, A. Goldbach, W. Li, H. Xu, PdC formation in ultra-thin Pd membranes during separation of H2/CO mixtures, J. Membr. Sci., 299 (2007) 130-137.

[7] D.L. McKinley, Metal alloy for hydrogen separation and purification, U.S. Patent 3,350,845, (November 7, 1967).

[8] J.P. Collins, R.W. Schwartz, R. Sehgal, T.L. Ward, C.J. Brinker, G.P. Hagen, C.A. Udovich, Catalytic Dehydrogenation of Propane in Hydrogen Permselective Membrane Reactors, Ind. Eng. Chem. Res., 35 (1996) 4398-4405.

[9] A.E. Lewis, D.C. Kershner, S.N. Paglieri, M.J. Slepicka, J.D. Way, Pd-Pt/YSZ Composite Membranes for Hydrogen Separation from Synthetic Water-Gas Shift Streams, J. Membr. Sci., (Accepted on February 17, 2013).

[10] B.D. Morreale, B.H. Howard, O. Iyoha, R.M. Enick, C. Ling, D.S. Sholl, Experimental and Computational Prediction of the Hydrogen Transport Properties of Pd4S, Ind. Eng. Chem. Res., 46 (2007) 6313-6319.

[11] C.P. O'Brien, A.J. Gellman, B.D. Morreale, J.B. Miller, The hydrogen permeability of Pd4S, J. Membr. Sci., 371 (2011) 263-267.

[12] S.K. Gade, S.J. DeVoss, K.E. Coulter, S.N. Paglieri, G.k.O. Alptekin, J.D. Way, Palladium-gold membranes in mixed gas streams with hydrogen sulfide: Effect of alloy content and fabrication technique, J. Membr. Sci., 378 (2011) 35-41.

[13] A. Kulprathipanja, G.O. Alptekin, J.L. Falconer, J.D. Way, Pd and Pd-Cu membranes: inhibition of H2 permeation by H2S, J. Membr. Sci., 254 (2005) 49-62.

[14] P.M. Thoen, F. Roa, J.D. Way, High flux palladium-copper composite membranes for hydrogen separations, Desalination, 193 (2006) 224-229.

[15] R. Bhandari, Y.H. Ma, Pd-Ag membrane synthesis: The electroless and electro-plating conditions and their effect on the deposits morphology, J. Membr. Sci., 334 (2009) 50-63.

[16] S.K. Gade, Palladium-gold membranes for hydrogen separations: development, characterization, and optimization, in:  Chemical Engineering, Colorado School of Mines, Golden, 2009, pp. 127.

[17] A. Kulprathipanja, G.O. Alptekin, J.L. Falconer, J.D. Way, Effects of Water Gas Shift Gases on Pd-Cu Alloy Membrane Surface Morphology and Separation Properties, Ind. Eng. Chem. Res., 43 (2004) 4188-4198.

[18] M. Kajiwara, S. Uemiya, T. Kojima, Stability and hydrogen permeation behavior of supported platinum membranes in presence of hydrogen sulfide, Int. J. Hydrogen Energy, 24 (1999) 839-844.

[19] F. Braun, J.B. Miller, A.J. Gellman, A.M. Tarditi, B. Fleutot, P. Kondratyuk, L.M. Cornaglia, PdAgAu alloy with high resistance to corrosion by H2S, Int. J. Hydrogen Energy, 37 (2012) 18547-18555.

[20] K.E. Coulter, J.D. Way, S.K. Gade, S. Chaudhari, G.O. Alptekin, S.J. DeVoss, S.N. Paglieri, B. Pledger, Sulfur tolerant PdAu and PdAuPt alloy hydrogen separation membranes, J. Membr. Sci., 405-406 (2012) 11-19.

[21] T.A. Peters, T. Kaleta, M. Stange, R. Bredesen, Development of ternary Pd-Ag-TM alloy membranes with improved sulphur tolerance, J. Membr. Sci., 429 (2013) 448-458.

[22] O. Hatlevik, S.K. Gade, M.K. Keeling, P.M. Thoen, A.P. Davidson, J.D. Way, Palladium and palladium alloy membranes for hydrogen separation and production: History, fabrication strategies, and current performance, Sep. Purif. Technol., 73 (2010) 59-64.

[23] B.D. Morreale, M.V. Ciocco, R.M. Enick, B.I. Morsi, B.H. Howard, A.V. Cugini, K.S. Rothenberger, The permeability of hydrogen in bulk palladium at elevated temperatures and pressures, J. Membr. Sci., 212 (2003) 87-97.

[24] C.-H. Chen, Y.H. Ma, The effect of H2S on the performance of Pd and Pd/Au composite membrane, J. Membr. Sci., 362 (2010) 535-544.