ID
× COMMENTARY
Dorothy_LozowskiGetting ready
My local municipality recently mailed out a brochure titled “Are…
COVER STORYIN THE NEWSNEWSFRONTSCHEMENTATOR + Show More BUSINESS NEWSTECHNICAL & PRACTICALFEATURE REPORTFACTS AT YOUR FINGERTIPSTECHNOLOGY PROFILEENGINEERING PRACTICEEQUIPMENT & SERVICESFOCUSNEW PRODUCTS + Show More SHOW PREVIEWS

Comment Separation Processes

Liquid metal membranes improve on Pd membranes for separating hydrogen

By Scott Jenkins |

A liquid metal membrane with liquid gallium (Ga) sandwiched between two porous silicon carbide supports offers a pathway to improve the currently available membranes of solid palladium (Pd) metal for separating hydrogen after the steam reforming of methane.

Pd metal is effective at allowing hydrogen to pass while excluding other species, such as CO2 and CO, but Pd has limitations. Pd is costly and so must be spread into thin layers, which can crack easily, allowing all gases through. Also, Pd membranes are adversely affected by sulfur in the gas mixture. Researchers at Worcester Polytechnic Institute (WPI; Worcester, Mass.; www.wpi.edu) have developed a separation membrane that uses liquid Ga instead of solid Pd to separate hydrogen. The team has successfully demonstrated the system, known as a SLiMM (sandwiched liquid metal membrane), to separate H2 from gas mixtures of helium (see diagram).

Liquid metal membrane

When H2 contacts a Pd membrane, it dissociates into hydrogen atoms, which diffuse through the membrane and recombine on the other side. At the elevated temperatures at which steam methane reforming would be carried out, liquid Ga achieves the same dissociation of H2. “The hydrogen atoms then hop from one interstitial site to another, across the 200-µm-thick Ga layer,” says research team leader Ravindra Datta.

The gallium membranes offer several key advantages over Pd membranes. First, gallium’s cost is an order of magnitude lower than Pd, and the metal is non-toxic. Also, as Datta explains, “the liquid membrane is self-healing, so it can spontaneously repair any cracks or defects.” Further, he says “there is more interstitial space in a liquid metal than a solid, so the hydrogen atoms can diffuse through the material more easily.”

The WPI team plans to test its SLiMMs with real-world synthesis gas mixtures from steam-methane reforming.

Related Content

Chemical Engineering publishes FREE eletters that bring our original content to our readers in an easily accessible email format about once a week.
Subscribe Now
Purdue University Saves $400,000 Annually with Local Vacuum Networks
Bag filter Housings/Vessels
Innovative Backwashable Media Filter
Automated Vertical Tower Filter Press
Visit VACUUBRAND at ACS in San Francisco!

View More

Live chat by BoldChat