Catalytic zeolite membrane reactors for CO-free hydrogen production
Advancing the chemical engineering fundamentals
Membranes and Membrane Science - II (T2-8b)
Keywords: CO-free hydrogen, zeolite catalytic membrane
In hydrogen production from hydrocarbons, final purification is required to reduce the amount of carbon monoxide to the desired level (e.g., less than a few tens ppm for PEM fuel cells). Among several approaches, without excessive hydrogen consumption, CO selective oxidation (Selox) is the most simple and cost-effective purification method [1]. A highly selective catalyst is necessary because of the high ratio of H2 to CO in the reformate stream. Typically, Pt–supported catalysts are used as fixed bed or monoliths [1–3]; catalytic membrane reactors (MRs) have been recently investigated in a few papers [4,5].
The use of a catalytic membrane, with a zeolite layer containing catalytic Pt clusters, has numerous advantages over conventional fixed bed reactors: the catalytic surface directly available, reduced by-pass and the small pressure drop.
In this work, tubular zeolite Pt–Y membranes were prepared and their catalytic performance for the CO Selox. was tested in a flow–through MR. Experimental results were collected at 200°C, with different feed compositions and pressures (up to 5 bar). The feed mixtures (CO, O2, H2, N2 and CO2) simulated a dry reformate gas stream (H2 c. 60%, CO c. 1%).
The catalytic MRs succeeded in bringing the outlet CO concentration within the range 50–10 ppm in one stage, starting from 1% (10,000 ppm) CO and using a low O2 amount (O2/CO feed ratio =1). Moreover, the good selectivity measured (ca. 50% at O2/CO = 1) is important for reduced hydrogen consumption (< 1%).
The results obtained indicate the potential for practical application of the catalytic MR for the CO Selox stage in a fuel processor for PEM fuel cells.
Acknowledgements
This work was performed also with the contribution of the Italian Ministry of University and Research, Progetto “FIRB-CAMERE RBNE03JCR5”.
References
[1] S.H. Oh and R.M. Sinkevitch, Journal of Catalysis 142 (1993) 254.
[2] M.J. Kahlich, H.A. Gasteiger, R.J. Behm, Journal of Catalysis 171 (1997) 93.
[3] R.K. Ahluwalia, et al., Catalysis Today 99 (2005) 271.
[4] Y. Hasegawa, A. Ueda, K. Kusakabe, S. Morooka, Applied Catalysis A 225 (2002) 109.
[5] P. Bernardo, C. Algieri, G. Barbieri, E. Drioli, Catalysis Today 118 (2006) 90.
Presented Wednesday 19, 16:40 to 17:00, in session Membranes and Membrane Science - II (T2-8b).
