Inderscience Publishers

Gold nano–particles supported on hematite and magnetite as highly selective catalysts for the hydrogenation of nitro–aromatics

0
The catalytic action of nano–sized Au particles supported on hematite (Fe
2
O
3
) and magnetite (Fe
3
O
4
) is compared in the continuous gas phase hydrogenation of p–chloronitrobenzene and m–dinitrobenzene. The catalysts were prepared by deposition–precipitation and have been characterised in terms of BET/pore volume, powder X–ray diffraction (XRD), temperature programmed reduction (TPR), H
2
chemisorption, high–resolution transmission electron microscopy (HRTEM) and X–ray photoelectron spectroscopy (XPS) measurements. XRD confirmed the formation Fe
2
O
3
, which was transformed into Fe
3
O
4
during TPR to 673 K with a concomitant decrease in BET area and pore volume. Post–TPR to 423 K, Au/Fe
2
O
3
exhibited well dispersed pseudo–spherical Au particles with mean diameter = 2.0 nm. HRTEM and XPS demonstrate the encapsulation of Au in the Fe
3
O
4
matrix after TPR to 423 K, which inhibited hydrogenation rate. Thermal treatment to 673 K resulted in the segregation of Au on the Fe
3
O
4
surface and the formation of nano–scale particles with mean diameter = 4.0 nm. Similar activities were recorded over both Au/Fe
2
O
3
and Au/Fe
3
O
4
with exclusive nitro–group reduction to yield p–chloroaniline and m–nitroaniline, a response that is discussed in terms of Au electronic character.

Keywords: gold nanoparticles, selective hydrogenation, p–chloronitrobenzene, p–chloroaniline, m–dinitrobenzene, m–nitroaniline, nanoscale supported gold, hematite, magnetite, Au/, Fe2O3, Au/, Fe3O4, temperature programmed reduction, HRTEM, XPS, catalysts, nitro–aromatics, nanotechnology

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