(137c) Stability Study of Dense Cermet Membranes for Hydrogen Separation

Lu, Y. - Presenter, Argonne National Laboratory
Dorris, S. E. - Presenter, Argonne National Laboratory
Lee, T. H. - Presenter, Argonne National Laboratory
Park, C. - Presenter, Argonne National Laboratory
Balachandran, U. - Presenter, Argonne National Laboratory


Argonne National
Laboratory is developing dense cermet (i.e. ceramic-metal composite) hydrogen
transport membranes (HTMs) for
separating hydrogen from mixed gases, particularly product streams generated
during coal gasification and/or methane reforming. Hydrogen separation with
these membranes is nongalvanic (i.e., it does not use electrodes or an external
power supply to drive the separation), and hydrogen separated from the feed
stream is of high purity, so post-separation steps are unnecessary.

These cermet membranes (60-70vol%
Pd with Y2O3-stabilized ZrO2) with
thickness of 10-20 mm were prepared by conventional ink/paste
painting and co-sintering techniques on a porous substrate (alumina or
zirconia). Nongalvanic hydrogen permeation flux in the temperature range of 400°C-600°C were measured. The chemical stability of
membranes was tested in various gas mixtures that contained H2, CO,
CO2, and/or H2S. The dense HTM demonstrated high
selectivity for H2 over CO and CO2. When tested in
a gas mixture that contained 30% CO2 and 1% CO at 400-600 °C. HTM
cermet membrane showed continuous slow performance degradation; however, the
observed flux degradation can be fully reversed. Because
H2S reacts with Pd-containing membranes to form palladium sulfide
(Pd4S), which impedes hydrogen permeation through the membranes, the
Pd/Pd4S phase boundary was determined in the temperature
range of 400-600°C using various feed gases with 10-50% H2 and
≈5-100 ppm H2S.  Tests
in H2S-containing atmospheres showed that the membrane is stable at 500°C in gases that contain 10% H2
and 15-20 ppm H2S for 200 hrs and at 550°C in gases that contain 10% H2
and 25-30 ppm H2S for 100 hrs. These results suggest that
Pd-containing cermet membranes are promising candidate for hydrogen
separation/purification under coal gasification conditions. The present
status of HTM development at Argonne will be presented in this talk.

Work supported
by the U.S. Department of Energy, Office of Fossil Energy, National Energy
Technology Laboratory's Clean Fuels Program, under
Contract DE-AC02-06CH11357.