PREPARATION, CHARACTERIZATION, AND PROPERTIES OF NEW ADSORPTIVE AND CATALYTIC MATERIALS

Abstract

Mobil's synthetic strategy of mesoporous MCM-41 materials, using a surfactant as a templating agent, has been shown in this thesis to be successfully extended, for the first time, to template M (K10 montmorillonite) into SM (surfactant-templated M). M usually has a surface area of around 200 m2/g. However, after M has been templated by a surfactant, the new SM material was found to have a surface area of 408 m2/g, which is much higher than M. The surfactant templating method has increased not only the surface area but also the pore volume and the available adsorptive and catalytic sites. This is shown by the increase of the pore volume and catalytic conversion of IPA of SM. The high thermal stability of SM is proposed to be due to the internally-available amorphous silica acting as the connecting bridge to connect the neighbouring broken clay layers of M, resulting in the formation of thermally-stable and catalytically-active SM. Based on this fundamental understanding that the internally-available amorphous silica in M might be as the bridge to connect the broken clay layers of M, externally-added fumed silica was further exploited in the surfactant treatment of M. The idea was to increase the amount of the broken clay layers of M to be bonded by silica so that the resulting mesoporous material would have more surface area and more available adsorptive and catalytic sites than M. We have successfully shown in this thesis that, in fact, using a surfactant as a synthetic template, the broken clay layers of M could be templated and bonded with the externally-added fumed silica to form SBM (silica-bonded M). SBM is found to be a new type of mesoporous clay material having very high surface area (736 m2/g), high thermal stability, and catalytic conversion of IPA. A series of synthetic [MgxNiy]-saponites, having two elements (Mg and Ni ions) in their octahedral position, were synthesized. Based on the results of XRD, IPA reaction, and porn structure, both Mg and Ni ions are suggested to be in the octahedral position, causing certain chemical interactions between the Mg and Ni ions in the octahedral sheet. The synthesis of [MgxNiy]-saponites may offer opportunities to synthesize crystalline clays with multi elements either in the octahedral or in the tetrahedral positions, which may have interesting catalytic properties.