Colloidal Alumina Particles Research Articles

New routes to the preparation of pillared montmorillonite catalysts

Clay catalysts have been prepared using reagents different from the aluminum chlorhydrate solution usually employed to pillar smectite minerals. Colloidal alumina, alumina-coated silica and solutions containing chlorhydrated complexes of zirconium and aluminum produced pillared bentonites which, upon calcination at 400 °C, formed microporous two-dimensional structures with 200 – 500 m 2 g −1 Langmuir surface area and basal spacing between 17 and 18 Å. These pillared clays contain both Bronsted and Lewis acid sites; above 300 °C, pyridine is retained predominantly on Lewis centers. The presence of zirconia seems to enhance Brönsted acidity, whereas pillaring with colloidal alumina particles increases the catalyst Lewis acidity. Cracking activity for gas oil conversion depends mainly on the surface area generated by pillaring. Pillared bentonites are more active but less selective than similarly prepared pillared hectorite catalysts.

Complexation of trace metals by adsorbed natural organic matter

The adsorption behavior and solution speciation of Cu(II) and Cd(II) were studied in model systems containing colloidal alumina particles and dissolved natural organic matter. At equilibrium a significant fraction of the alumina surface was covered by adsorbed organic matter. Cu(II) was partitioned primarily between the surface-bound organic matter and dissolved Cu-organic complexes in the aqueous phase. Complexation of Cu 2+ with the functional groups of adsorbed organic matter was stronger than complexation with uncovered alumina surface hydroxyls. It is shown that the complexation of Cu(II) by adsorbed organic matter can be described by an apparent stability constant approximately equal to the value found for solution phase equilibria. In contrast, Cd(II) adsorption was not significantly affected by the presence of organic matter at the surface, due to weak complex formation with the organic ligands. The results demonstrate that general models of trace element partitioning in natural waters must consider the presence of adsorbed organic matter.

Pliable Paper made from Inorganic Material using Colloidal Aluminas as Binder

Pliable asbestos paper was prepared from asbestos fibers using fibrous colloidal aluminas as binder. The results are as follows. (1) The properties (tensile strength, pliability) of asbestos paper were influenced by forms of colloidal alumina particles.(2) Forms of colloidal alumina particles were influenced by mol ratio of Al : stabilized ions. (3) Asbestos paper using colloidal alumina binder was superior in tensile strength to the asbestos paper with organic binding agents, and was inflammable and smokeless.