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Title:
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High temperature H2/CO2 separation using cobalt oxide silica membranes
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Author(s):
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Smart, S.; Vente, J.F.; Diniz da Costa, J.C.
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Published by:
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Publication date:
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ECN
Biomass & Energy Efficiency
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28-8-2012
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ECN report number:
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Document type:
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ECN-W--12-034
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Article (scientific)
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Number of pages:
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10
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Published in: International Journal of Hydrogen Energy (Elsevier), , 2012, Vol.37, p.12700 -12707.
Abstract:
In this work high quality cobalt oxide silica membranes were synthesized on alumina supports using a solegel, dip coating method. The membranes were subsequently connected into a steel module using a graphite based proprietary sealing method. The sealed membranes were tested for single gas permeance of He, H2, N2 and CO2 at temperatures up to 600 _C and feed pressures up to 600 kPa. Pressure tests confirmed that the sealing system was effective as no gas leaks were observed during testing. A H2 permeance of 1.9 _ 10_7- molm_2 s_1 Pa_1 was measured in conjunction with a H2/CO2 permselectivity of more than 1500, suggesting that the membranes had a very narrow pore size distribution and an average pore diameter of approximately 3 A° . The high temperature testing demonstrated that the incorporation of cobalt oxide into the silica matrix produced a structure with a higher thermal stability, able to resist thermally induced densification up to at least 600 _C. Furthermore, the membranes were tested for H2/CO2 binary feed mixtures between 400 and 600 _C. At these conditions, the reverse of the water gas shift reaction occurred, inadvertently generating CO and water which increased as a function of CO2 feed concentration. The purity of H2 in the permeate stream significantly decreased for CO2 feed concentrations in excess of 50 vol%. However, the gas mixtures (H2, CO2, CO and water) had a more profound effect on the H2 permeate flow rates which significantly decreased, almost exponentially as the CO2 feed concentration increased.
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