NCER Assistance Agreement Annual Project Summary

Date of Report: January 2, 2008

EPA Agreement Number: X-83254101-1

Center: Center for Environmental and Energy Research (CEER)

Project Title: Separation and Purification of Hydrogen From Mixed Gas Streams Using Hollow Glass Microspheres

Investigator(s): James E. Shelby

Institution of PI(s): Alfred University

Research Category: Congressionally Mandated Center

Project Period: September 2006 to August 2008

Objective of Research: In light of current fears surrounding global warming, the appeal of alternative fuel sources continues to grow. A major obstacle standing in the way of the hydrogen economy is the expense and difficulty of the purification and separation of hydrogen from mixed gases. Due to different permeabilities of gases through vitreous silica, it is believed that glass would make an exceptional membrane for gas separation, which has been proposed as far back as Barrer. Hollow glass microspheres have extremely thin walls which makes them ideal membranes for this application. The other exceptional benefit of using hollow glass microspheres is the ease at which they can be produced, using recycled glass frit from beer bottles. Other inorganic membrane materials used for this application often rely upon the fabrication of continuous palladium/palladium alloy films which selectively allow hydrogen to pass. As could be imagined, processing a membrane as such is no simple task, and if any pinhole is present in the film the membrane is rendered useless.

Progress Summary/Accomplishments: Four compositions of hollow glass microspheres (HGMS) have been studied to date, 3M Glass Bubbles (K25, K37, K46) and Mo-Sci Hollow Glass Spheres (GL-0237) along with one composition of solid glass microspheres from Mo-Sci (GL-0179).

The separation of hydrogen from mixed gases containing nitrogen (N₂), argon (Ar), carbon dioxide (CO₂), and helium (He) has been studied using residual gas analysis. The parameters analyzed at this point have been fill pressure, fill time, fill composition, variance of HGMS and residual gas analysis, separation via IR light, and the removal of adsorbed gases using IR light and furnace treatments.

The amount of hydrogen and helium released in all cases exhibits a linear relationship with the fill partial pressure, which is indicative of molecular diffusion. The other gases studied did not exhibit any trends with the fill partial pressure, which indicates mechanisms other than molecular diffusion. As the permeabilities of these gases in vitreous silica are orders of magnitude lower than that of hydrogen or helium, they should not diffuse into the hollow glass microspheres. Due to the elevated temperatures used for filling the microspheres (~400°C) it is plausible that these gases could be adsorbed to the microsphere surfaces. It has been shown by exposing the HGMS to air that various atmospheric gases adsorb to the surfaces of the microspheres. Low temperature heat and IR light treatments were utilized in an attempt to increase the purity of hydrogen released, and it was found that a significant amount of adsorbed gas can be removed before the controlled desorption of stored hydrogen.

Publications/Presentations:

Rich, J. S. and Shelby, J. E., Diffusion in Hollow Glass Microspheres for the Recovery and Purification of Hydrogen from H₂/Ar and H₂/CO₂ Gas Streams, MS&T Conf., Detroit, Michigan, September 20, 2007.

Rich, J. S. and Shelby, J. E., Recovery and Purification of Hydrogen From Mixed Gas Streams via Absorption into Hollow Glass Microspheres, GOMD Conf., Rochester, NY, May 21, 2007.

Rich, J. S. and Shelby, J. E., Separation of Hydrogen from Mixed Gases using Hollow Glass Microspheres, to be presented at Materials Innovations in an Emerging Hydrogen Economy Conf., Cocoa Beach, Fl, February 24-28, 2008.

Rich, J. S. and Shelby, J. E., Inorganic Membranes for the Recovery and Purification of Hydrogen from Mixed Gas Streams, to be presented at GOMD Conf., Tucson, Az, May 21, 2008.

Future Activities: The heat treatment cycles to remove adsorbed gases still need to be optimized, and more work must be done on the use of IR light for the separation of gases from hydrogen.

Supplemental Key Words: hydrogen, gas separation, membrane, gas permeability, gas diffusion, hydrogen fuel

Relevant Web Sites:

http://en.wikipedia.org/wiki/Hydrogen_economy

http://www.physicstoday.org/vol-57/iss-12/p39.html

http://www.uop.com/objects/SelOfHydroSepProc.pdf

htttp://ceer.alfred.edu