Pd
A Metallic Advantage
The system has proven astonishingly effective. In phase one
of the DOE trials, the WPI membrane achieved an H2 purity
level of 99.89 percent during the entire 200-hour test period,
a level that had never been seen before with coal gas. In a
paper published last year in the International Journal of
Hydrogen Energy, the research team called it "a breakthrough" — not a term scientists use lightly.
"There is no material in nature more efficient in separating hydrogen than palladium," says Andreas Matzakos,
principal concept engineer at Shell Oil Company, which
sponsored the WPI work for seven years and is now using
the WPI technology to produce hydrogen for cars powered
22 > wpi.edu/+research
by fuel cells. Calling the research "brilliantly executed," he
added, "Moreover, it can stand the temperature found in
common reactors, and it enables process intensification: the
ability to do more steps in a smaller volume."
Matzakos is referring to another advantage of the metallic membranes that WPI has developed. Unlike polymer
membranes, which are also used for gas separation, the
metal structures can sustain the high temperatures needed
for coal gasification and natural gas reforming, a process
for extracting hydrogen from methane. When using organic
membranes, on the other hand, the gas must be cooled before
it can be separated.
"That's energy loss," Ma notes. "That's cost."
The membrane's heat tolerance is what appeals to Praxair,
the largest producer of industrial gases in the Americas and
one of the largest hydrogen producers in the world, which
is hoping to commercialize WPI's technology for use in
hydrogen production. Raymond P. Roberge, senior vice
president and chief technology officer at Praxair, says the
membrane's ability to function at higher temperatures
will make it much more economical than conventional
technology, which requires many separate steps.
"Researchers have been looking for methods to cleanly
separate hydrogen from other gases at high temperature for
some time with limited success," says Roberge, a 1972