August 18, 2003
Volume 81, Number 33. p. 15
Chemical and Engineering News
by MITCH JACOBY
High-purity hydrogen can be produced from oxygen-containing organic compounds using a simple water-based catalytic process developed at the University of Wisconsin, Madison. Researchers there have shown that the carbon monoxide content of the H2 produced in their single-reactor reforming process can be controlled as a function of the process conditions.
A key requirement of hydrogen used in fuel cells and other applications is that it be free of CO, because this oxide tends to poison catalysts. Thus, the products of reforming reactions, which include H2 and CO, must be subjected to CO-cleanup treatments to produce fuel-cell-grade hydrogen. The water-gas shift reaction, which converts CO + water to CO2 + H2, is commonly used to reduce CO levels. But that reaction needs to be run separately from typical steam-reforming reactions because the two processes require different conditions.
The competing requirements make fuel-cell hydrogen generators complex engineering systems--an undesirable feature, especially for portable applications such as automobiles. But now, Wisconsin chemical engineering professor James A. Dumesic and graduate student Rupali R. Davda have demonstrated that oxygenates such as ethylene glycol can be used to make high-purity hydrogen in an aqueous-phase system that consists of a single reactor [Angew. Chem. Int. Ed., published online June 18, http://www3.interscience.wiley.com/cgi-bin/abstract/104539925/start].
The group showed that through judicious choice of temperature and pressure, an ethylene glycol solution can be converted to hydrogen containing as little as about 60 ppm of CO. The work builds on another study in which Dumesic's group found that biomass-derived compounds can be converted to hydrogen and CO at about 500 K using an alumina-supported platinum catalyst [Nature, 418, 964 (2002)].
REFORMATION Researchers can produce hydrogen from ethylene glycol and clean up unwanted CO in a single reactor using the water-gas shift reaction.