Patent ID: 9695053
Date: 2017-07-04
CPC Classifications: C01B

Claim:
1. A process for preparing precipitated silica, the process comprising: reacting-a silicate with at least one acid using the following steps, whereby a silica suspension is obtained: (i) preparing an aqueous precipitated silica suspension (1) forming an initial stock comprising a silicate and an electrolyte, the silicate concentration expressed as SiO (2) adding an acid to said stock to form a reaction medium until a value of the pH of the reaction medium of at least approximately 7 is obtained, (3) simultaneously adding an acid and a silicate to the reaction medium, and (4) stopping the addition of the silicate used in step (3) while continuing the addition of an acid to the reaction medium, until a value of the pH of the reaction medium of between 2.5 and 5.3 is obtained, whereby an aqueous precipitated silica suspension exhibiting a pH of between 2.5 and 5.3 is obtained, and (ii) bringing said aqueous precipitated silica suspension into contact with an acid and a silicate to form a reaction medium, so that the pH of the reaction medium is maintained between 2.5 and 5.3, separating precipitate from the silica suspension; and drying the precipitate, wherein step (2) comprises adding, for x minutes, a dilute acid followed by adding, after x minutes, a concentrated acid, wherein x is between 10 and 25, wherein said concentrated acid is selected from the group consisting of sulfuric acid with a concentration of at least 80% by weight, acetic acid with a concentration of at least 90% by weight, formic acid with a concentration of at least 90% by weight, nitric acid with a concentration of at least 60% by weight, phosphoric acid with a concentration of at least 75% by weight, and hydrochloric acid with a concentration of at least 30% by weight.