Acidity study of X zeolites modified by nickel and/or chromium cations in the case of binary and ternary exchanges

S. Bendenia (1) , I. Batonneau-Gener (2) , J.D. Comparot (2) , K. Marouf-Khelifa (1) , H. Hammoudi (1) , A. Khelifa (1)

1 Département de Mécanique
2 Zéolithes

A series of Ni(x)-, Cr(x) and CrNi(x)-exchanged X zeolites (x being the ion-exchange degree) was prepared and characterised by nitrogen adsorption, XRD. DTA/TGA and pyridine adsorption-desorption followed by IR spectroscopy. The objective is mainly to estimate quantitatively the number, strength and nature of acid sites and their dependence on the type of cation and its exchange level. A comparison between the binary and ternary exchanges was also established. The crystallinity and micropore volume losses were more significant for Cr(x)X and CrNi(x)X. The concentration of Lewis acid sites decreases with increasing the exchange degree for Cr(x)X and Ni(x)X, while it increases up to 39% for CrNi(x)X. An increase of the concentration of Bronsted sites was obtained. The fact that both the Lewis and Bronsted acidities markedly decrease between 423 and 623 K, proves that the available acid sites are overall weak. The pyridine desorption from the protonic sites is easier with CrNi(39)X than with Cr(39)X and Ni(40)X at 623 K, indicating a decrease in the strength in the case of ternary exchange. (C) 2012 Elsevier Inc. All rights reserved.

Domaines: Catalyse; Chimie organique; Autre

S. Bendenia, I. Batonneau-Gener, J.D. Comparot, K. Marouf-Khelifa, H. Hammoudi, et al.. Acidity study of X zeolites modified by nickel and/or chromium cations in the case of binary and ternary exchanges. Microporous and Mesoporous Materials, 2012, 159, pp.111-118. ⟨10.1016/j.micromeso.2012.04.026⟩. ⟨hal-00819237⟩