| 摘要 |
A process for preparing precipitated silica comprising a precipitation reaction between silicate and an acid, in which the acid used in at least one of the steps is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, acetic acid having a concentration of at least 90% by weight, formic acid having a concentration of at least 90% by weight, nitric acid having a concentration of at least 60% by weight, phosphoric acid having a concentration of at least 75% by weight, and hydrochloric acid having a concentration of at least 30% by weight. |
| 主权项 |
1. A process for preparing precipitated silica, comprising a reaction of a silicate with at least one acid, whereby a suspension of precipitated silica is obtained, followed by separation and drying of this suspension,
wherein said precipitation reaction is performed in the following manner:
(i) forming an initial stock comprising at least a portion of the total amount of the silicate involved in the reaction and an electrolyte, the concentration of silicate expressed as SiO2 in said initial stock being between 50 and 70 g/l,(ii) adding an acid to said initial stock to form a reaction medium until a pH value of the reaction medium of between 7 and 8.5 is obtained,(iii) adding an acid to the reaction medium and optionally simultaneously adding the remaining amount of the total amount of the silicate involved in the reaction, and(iv) adding an acid to the reaction medium, until a pH value of the reaction medium of between 4 and 6 is obtained, wherein the separation comprises filtration and washing using a filter equipped with a compacting means, wherein said obtained suspension of precipitated silica is dried by atomization,wherein, in at least step (iii), the acid used is a concentrated acid 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. |
