Process for the Preparation of Finely Divided Precipitated Silica

A process for preparing finely divided precipitated silica by neutralization.

A process for the preparation of precipitated silica having more than 75% particles finer than 10 nm on 5 kg batch scale has been developed. In the process neutral grade sodium silicate solution was treated with mineral acid and silica sol in different steps under controlled rate in presence of electrolyte.

• The process involves step wise neutralization of sodium silicate solution with mineral acids or acidic silica sol and simultaneous addition of acid and sodium silicate solution is not required.
• Simple neutralization procedure is adopted wherein the rate of addition of diluted acid and acidic silica sol is only to be controlled.
• Acidic Silica sol preparation step involves only addition of sodium silicate solution to the acid solution at room temperature and does not involve the use of cation exchange resin.
• Neutralization of alkali present in alkali metal silicate solution with mineral acid can be completed in short duration.
• No post-synthesis treatment is given to get finely divided particles and narrow size distribution of the precipitated silica.