Hydrotalcites

The collected and refined know-how to produce alumina hydrates via the sol-gel technique is now used by Sasol to prepare other inorganic oxides or mixed oxides. The properties of these novel inorganic specialty materials are leading Sasol into new, interesting fields of research and application. One of these specialties is the hydrotalcite family (aluminium magnesium compounds) which are obtained by hydrolysis of heterometallic alcoholates.

PURAL MG

Compared to alumina hydrates (pH 8-9) hydrotalcites are even more alkaline by nature. Basicity is adjustable by increasing the Mg/Al ratio and/or incorporating anions other than OH-. As shown below, hydrotalcites have a double-layered metal hydroxide structure consisting of magnesium and aluminium hydroxide octahedrons interconnected via the edges. Additional interstitial anions between the layers compensate the charge of the crystal and determine the size of the interlayer distance (basal spacing).

While hydrotalcites are accessible through the corresponding metal salts [Miyata et al., Clay and Minerals, 25, 14-18 (1977)], the metal alcoholate route, patented by Sasol, has advantages over other ways of synthesis. Most important is that the Al/Mg ratio can be varied over a wide range. In addition, it is now possible to obtain hydrotalcites with a purity and a controlled anion content that have to date been unavailable.

The production facility is in Brunsbüttel (Germany).

Downloads of brochures: PURAL MG 30, 70; PURAL MG 63 HT