Hydrodechlorination of 1,2,4-trichlorobenzene on nickel-based catalysts prepared from several Ni/Mg/Al hydrotalcite-like precursors

Several Ni/Mg/Al and Ni/Al hydrotalcite-like precursors have been prepared to study their catalytic properties in the hydrodechlorination of 1,2,4-tri chlorobenzene in the gas phase. All the samples were characterised by X-ray diffraction (XRD), BET, scanning electron microscopy (SEM), temperature-pr ogrammed desorption (TPD) and hydrogen chemisorption techniques. When the magnesium content increases in the catalysts, both the activity an d selectivity to benzene greatly increases and the deactivation of the cata lysts becomes slower. The highest TOF and selectivity to benzene values at 523 K (100%) are achieved by the catalyst which has the most content of Mg without any significant change in activity even at reaction times higher th an 500 min. This catalytic behaviour can be explained because the MgO modif ies the electronic properties of the nickel particle causing the hydrogen d esorption at lower temperatures and also adsorbs the HCl produced during th e hydrodechlorination reaction. (C) 2001 Elsevier Science B.V. All rights r eserved.