Reduction of 4-nitrotoluene over Fe-Mg-Al lamellar double hydroxides

Fe-Mg-Al lamellar double hydroxides (LDHs) are shown to be efficient catalysts in the heterogeneous reduction of 4-nitrotoluene to 4-aminotoluene using phenylhydrazine or hydrazine hydrate as reducing agent. Catalysts based on Fe(III) and/or Fe(II) as well as Mg(II) and/or Al(III) were prepared by precipitation of metal sulfates with Na,CO,. The samples were characterized by means of XRD, TG/MS, TPR, XPS and N-2 physisorption. The catalytic behavior was tested in a glass reactor under argon atmosphere at a temperature of 343 K using ethanol as a solvent. Selectivity to 4-aminotoluene amounted to 100% for all tested catalysts. Overall activity of the catalysts increased with increasing Mg(II) to Al(III) ratio and highest overall activity was obtained for an Al-free Mg-Fe(III) oxide/hydroxide. Highest specific rates referred to the Fe surface areas were observed for catalysts prepared from Fe(III) sulfate. The specific rate decreased with higher Fe(II) content of the precursor. (C) 1999 Elsevier Science B.V. All rights reserved.