Kinetics of formation of chromia promoted skeletal iron catalysts for the water gas shift reaction

Particles of Fe2Al5 (60–211 μm diameter) were leached at 10, 30 and 50 °C in 3 M NaOH containing varying amounts of sodium chromate in the range 0.005–0.05 M. The kinetics of leaching was fitted to solid-state kinetic models. The model best fitting the data was the Avrami–Erofeev model −ln(1 − α)1/1.5 = kt. Apparent activation energies were in the range 60–63 kJ mol−1. The BET surface areas of the promoted materials were high, with values in the range 57–91 m2 g−1. Catalysts were tested for the water–gas-shift (WGS) reaction at 350 °C and it was found that the chromium content of the catalysts had a significant effect on the WGS activity, which went through a maximum for a catalyst containing around 2 wt% chromium.

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► Chromate addition slows down the leaching kinetics of Fe2Al5.
► Cr is distributed throughout the skeletal structure of the leached material.
► Cr has a marked effect on WGS activity, suggesting it is a promoter.