Colloids and Surfaces A: Physicochem. Eng. Aspects 251 (2004) 109–115
Zirconium and sulfated zirconium pillared clays: a combined
intercalation solution study and solid characterization
S. Ben Chaabene, L. Bergaoui
∗
, A. Ghorbel
Laboratoire de chimie des mat´ eriaux et catalyse, Facult´ e des Sciences de Tunis, Universit´ eElmanar,CampusUniversitaire,1060LeBelv´ ed` ere,Tunis,Tunisie
Received 25 August 2003; accepted 1 September 2004
Abstract
A new method to prepare pillared zirconium clay modified by sulfate was developed. This method was based on adding sulfates to zirconium
species before the pillaring process. First the intercalation solution was studied by
1
H NMR, conductivity and potentiometric techniques and
the effect of the reflux on this solution was examined. The intercalated clay was then characterized by DRX, N
2
-BET adsorption, chemical
analysis and mass spectrometry. On the base of the solution study and the solid study we can propose that intercalated species are more
probably octameric polycations with an advance hydrolysis degree. The addition of sulfate ion on the intercalation solution gives more than a
single mode of interaction between SO
4
2-
and Zr-polycation. The resulted intercalated clay shows a good thermal stability of the texture and
of the retained sulfur.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Pillared clay; Zirconium polycation; Sulfated zirconium polycation; Thermal stability
1. Introduction
Preparation of pillared clays (PILCS) consists of interca-
lated smectite clay with inorganic compounds. The interca-
lated species are able to prevent the collapse of the interlayer
spaces, giving a two-dimensional porous material [1–5]. The
most extensively studied materials are aluminium and zirco-
nium polynuclear complex ions. For zirconium pillared clay,
intercalated species are not well identified. In this work we try
to combine the intercalation solution study and the pillared
clay characterization to determine the nature of the interca-
lated species.
On the other hand, the modification of solids by sulfates
has been used to increase the acidity of some oxides. Sul-
fated zirconia is the most active member of this family [6–8].
Usually, sulfated zirconia pillared clay was prepared by im-
pregnation of the Zr pillared clay by SO
4
2-
[9–12]. Although,
catalysts prepared by this method show moderate acidity and
low thermal stability of sulfates.
∗
Corresponding author. Tel.: +216 71 872 600;
fax: +216 71 885 008/+ 216 71 704 329.
E-mail address: latifa.bergaoui@insat.mu.tn (L. Bergaoui).
In this work we present a new way of preparation of sul-
fated pillared clay inspired from a work in our laboratory
about the sulfation of titanium pillared clay [13]. It consists
of an initial sulfation by creation of sulfated species in the
ZrOCl
2
intercalation solution. First, the intercalation solution
was studied. Then, the effect of the sulfate precursor on the
textural properties of the obtained solids was discussed.
2. Progress report about ZrOCl
2
in solution
In spite of the complexity of these systems because of
the sensitivity of the Zr(IV) species to their environment and
the slowness with which the system reaches equilibrium, we
may try to put forward some hypotheses on the nature of these
species in solution on the base of recent progress.
Zirconium species in solution are built up from
[Zr
4
(
2
OH)
8
(H
2
O)
6
]
8+
tetramers [14–19]. Using NMR to
study the tetranuclear hydroxo zirconium complex in aque-
ous solution,
˚
Aberg and Glaser [20] have proposed that there
are two inert and two labile water molecules per Zr atom. The
release of the protons of labile water molecules makes the
0927-7757/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.colsurfa.2004.09.011