Catalytic decomposition of pyridine gas with fine particles of metallic iron formed from limonite

• An Australian natural limonite rich in α-FeOOH is employed as a catalyst.
• The limonite achieves nearly complete decomposition of 100 ppmv pyridine at 500 °C.
• N2 yield upon pyridine decomposition at 500 °C is greater than 80%.
• The limonite shows high activity with or without H2 reduction pretreatment.
• Iron nitrides may act as intermediates for the conversion of pyridine to N2.

Catalytic decomposition of 100 ppmv pyridine (C5H5N) with an Australian limonite ore, composed mainly of goethite (α-FeOOH), has been examined for hot gas cleanup with a fixed-bed quartz reactor at 300–500 °C under a large space velocity of 51,000 h−1. When α-FeOOH in the limonite is reduced with pure H2 at 500 °C, the transformation into nanoscale particles of metallic iron (α-Fe) occurs, and the catalyst achieves almost complete C5H5N decomposition in inert He at 500 °C and provides an N2 yield greater than 80% for at least 10 h. The limonite also exhibits a high catalytic activity at 500 °C, even without H2 reduction. Based on the results of N 1s X-ray photoelectron spectroscopy and temperature-programmed desorption measurements, it is probable that the limonite-catalyzed formation of N2 from pyridine proceeds through cycle mechanisms involving α-Fe and iron nitride species.

Figure optionsDownload high-quality image (157 K)Download as PowerPoint slide