Fethi Kooli

Exfoliation properties of acid-activated montmorillonites and their resulting organoclays.

The intercalation process of acid-treated montmorillonite clays by a cationinc surfactant (decyltrimethylammonuium) from a hydroxide solution was affected by the temperature of acid activation. Although the cation exchange capacity of the treated clay at 90 degrees C (0.74 mequiv g(-1)) was lower compared to that treated at room temperature (0.84 mequiv g(-1)), the uptaken amount of the surfactant (1.24 mmol g(-1)) and thus the basal spacing (3.83 nm) were higher. These values depended on the initial loading concentrations. However, when the clay was treated at room temperature, the uptaken amounts of surfactant (0.81 mmol g(-1)) and the basal spacing (2.20 nm) were lower. These values were independent of the initial loading concentration. The higher basal spacing (3.83 nm) was also affected by the type of the exchange medium and the washing solution by a mixture of ethanolic solutions. The intercalation of the surfactants occurred in two different ways, and was related to exfoliation properties of the acid activated clays. The intercalated surfactant exhibited different conformations in the interlayer space and different thermal stability.

The Janus-like behaviour of sulfur in substituted diquinoline inclusion crystal structures

The crystal structures of the methylene-bridged diquinolines 1,2 are compared to those of their newly synthesised thia-substituted analogues 9,10. As expected from our molecular design, neither non-brominated compound 1 nor 9 shows inclusion properties, but the dibrominated structures 2 and 10 act as versatile lattice inclusion host molecules. All our crystal structures of the methylene-bridged compounds 1,2 contain an (EF)6 centrosymmetric dimeric building block, built from three different types of aryl edge-face (EF) interactions. The crystal structures of the thia-compounds 9,10 also involve (EF)6 dimers, but fall into two distinct types. In one group, the sulfur atom effectively mimics the methylene group and isostructural compounds result across the two series. The second group is comprised of structures that are markedly dissimilar between the two series, even though the sulfur substituent does not play an overt role in the molecular packing. These similarities and differences are examined in crystal engineering terms.

Pillaring of a Layered Titanate With Alumina: Effect of Hydrolysis Solution

A layered titanate with a lepidocrocite-type structure has been pillared with Al 13 Keggin ions to prepare a porous and high-surface-area material. Pillaring was achieved by ion exchange of hexylammonium (HA-Ti) or tetrabuthylammonium (TBA-Ti) intercalated titanates with Keggin Al 13 complex. The thermal stability of the Al 13 intercalates depended on the amount of aluminum incorporated. The surface area and porosity can be tailored by controlling the amount of aluminum uptake and by the nature of base used to prepare the aluminium pillaring solution. In addition, the material derived from HA-Ti exhibited a sharp pore size distribution with an average diameter of 2 nm, while the pillared product obtained from TBA-Ti showed mostly a broad mesoporous distribution with an average pore diameter of 4 nm.