High-Temperature Water-Gas Shift Reaction over Cr-Free Fe-Al Catalysts Promoted with First Row Transition Metals

Hydrogen generation technologies have become increasingly important due to recent attention focusing on fuel cells. The water-gas shift reaction, which is performed in two stages as highand low-temperature shift, is of central significance to produce highpurity hydrogen. Generally, the high-temperature water-gas shift reaction (HTS) is conducted on Fe-Cr catalysts. However, these catalytic systems possess many drawbacks such as low activity at low temperatures, sintering of magnetite (Fe3O4), and a pyrophoric nature. Moreover, the use of Cr poses additional complications due to harmful effects of Cr on human health. Thus, development of Cr-free catalytic systems is necessary. Also, it is apparent that innovative chromium-free iron-based catalysts that can overcome those drawbacks would have a significant impact on widespread applications of fuel cell systems. Araujo and Rangel [1] investigated the catalytic performance of Al-doped Fe-based catalyst with small amounts of copper (%wt Cu ≈ 3) in the HTS reaction. The aluminium and copper-doped catalysts showed similar catalytic activity compared to the commercial Fe-Cr catalyst at 350 C and H2O/CO = 0.4. Costa et al. [2] subsequently examined the use of thorium instead of chromium in ironand copper-based catalysts for the HTS reaction. It was found that the thorium and copper-doped catalyst was more active than the commercial Fe-Cr catalyst at H2O/CO = 0.6 and 370 C. Its high activity was attributed to an increase in surface area by thorium.