Y. Cesteros et al., Effect of the alumina phase and its modification on Ni/Al2O3 catalysts forthe hydrodechlorination of 1,2,4-trichlorobenzene, APP CATAL B, 22(2), 1999, pp. 135-147
Citations number
79
Categorie Soggetti
Physical Chemistry/Chemical Physics","Environmental Engineering & Energy
Pure and mixed delta/alpha-aluminas were prepared and modified (treated wit
h HCl gas and aq HNO3) in order to be studied as supports of nickel catalys
ts for the hydrodechlorination reaction of 1,2,4-trichlorobenzene in the ga
s phase. All the samples were structurally characterized using XRD, BET, TP
R, SEM and TPD techniques. The catalytic activities for the hydrodechlorina
tion of 1,2,4 trichlorobenzene are higher for the catalysts containing the
modified supports (especially those treated with HNO3) and can be explained
by the reduction degree (TPR), the structure (BET area, TPD and SEM) and t
he number and type of catalytic active sites (H-2 TPD). The activity can be
related to the hydrogen available at the reaction temperature (423-523 K)
while the selectivity towards benzene can be explained in terms of the hydr
ogen desorbed at lower temperatures (350-500 K) which competes with the aro
matic compounds to be adsorbed on the surface of the catalyst. The selectiv
ity towards benzene is directly related to the activity for each catalyst.
Nevertheless, the most selective catalyst towards benzene is the one suppor
ted on a-alumina (73% of selectivity at 523 K) which is not the most active
. This may be correlated to the hydrogen desorbed at low temperatures. (C)
1999 Elsevier Science B.V. All rights reserved.