Novel catalyst for low-temperature ethanol steam reforming; potential advance for on-board production of hydrogen for vehicles
Researchers at the A*STAR Institute of Chemical and Engineering Sciences in Singapore have developed a novel catalyst (iron-promoted rhodium on a calcium-modified aluminum oxide support) for CO-free hydrogen production via low-temperature ethanol steam reforming (ESR). The catalyst could advance the realization of small-scale on-board ethanol reformers for hydrogen-powered cars. A paper on their work appeared earlier this year in the journal Topics in Catalysis.
They investigated a series of 1 wt% Rh–x % Fe catalysts with various Fe loading (x = 0–10 wt%) and on different supports (Ca–Al2O3, SiO2 and ZrO2). The results showed that close interaction between Rh and Fe is required to reduce the CO selectivity to almost negligible values.
Rh–Fe supported on Ca–Al2O3 exhibited the best performance in terms of CO selectivity and hydrogen yield as compared to other supports.
This catalyst enables hydrogen to be generated more efficiently with less environmental damage as the reaction can occur at temperatures as low as 350 ˚C and produce almost no carbon monoxide as a byproduct. The presence of iron oxide enables carbon monoxide to be converted into carbon dioxide and hydrogen via the water–gas shift reaction. Thus, the iron promotion effect on the rhodium-based catalyst is the key to removing carbon monoxide—something that is exceedingly difficult to achieve on rhodium alone.
Additional benefits of ESR are the commercial advantages stemming from the catalyst being quite stable and having a long active lifetime. This means that the catalyst will permit long cycle lengths, minimize the regeneration frequency and reduce the operational downtime for on-board steam reformers.
Co-author Luwei Chen at the A*STAR Institute of Chemical and Engineering Sciences explained that these factors are “essential for maintaining profitable operations in reforming units. Similarly, a stable catalyst would reduce the operating cost for an on-board reformer.”
Chen noted that the catalyst will enable better operational flexibility in terms of economics and on-board reformer size (since carbon monoxide purification units can be removed), which she says will “make a significant impact in the design of efficient and simple on-board reactors.”
Choong, C. K. S., Chen, L., Du, Y., Wang, Z., Hong, L. & Borgna, A. (2014) “Rh–Fe/Ca–Al2O3: A unique catalyst for CO-free hydrogen production in low temperature ethanol steam reforming.” Topics in Catalysis 57, 627–636 doi: 10.1007/s11244-013-0221-0