US 4,900,530 A · Process for the production of silicon tetrafluoride

Abstract

A continuous process is disclosed for the production, with a high yield, of high purity silicon tetrafluoride, starting from an aqueous solution of fluorosilicic acid, which comprises: (a) reacting an aqueous solution of fluorosilicic acid with concentrated sulphuric acid, carried out with a short residence time and preferably under fluido-dynamic conditions of turbulence, inside a reaction zone; (b) separating a gaseous stream containing silicon tetrafluoride from a liquid stream of aqueous sulphuric acid, carried out inside a separation zone, directly connected with the reaction zone; (c) washing said gaseous stream with concentrated and cold sulphuric acid carried out inside a washing zone, for the purpose of separating a gaseous stream of purified silicon tetrafluoride; and, possibly (d) further purifying said gaseous stream of purified silicon tetrafluoride by means of techniques of adsorption on an adsorbent solid material.

Claims7

Dependent claims

A process for the preparation of silicon tetrafluoride comprising:

(a) contacting a 12-20% (w/w) aqueous solution of fluorosilicic acid with 90-100% (w/w) of an aqueous solution of sulphuric acid at a contact time of at least 1 second, in a reaction zone, said reaction zone operating at a temperature of from 90.degree. C. to 120.degree. C. and under a pressure greater than 30 kPa, said contacting resulting in the liberation of a gaseous stream of silicon tetrafluoride;
(b) separating said gaseous stream of silicon tetrafluoride from a liquid stream of a diluted aqueous solution of sulphuric acid produced in a separation zone, said separation zone operating at a temperature of from 70.degree. C. to 120.degree. C. and connected directly with and positioned below said reaction zone;
(c) washing said gaseous stream of silicon tetrafluoride with cold sulphuric acid havng a concentration of at least 96% (w/w), in a washing zone;
said cold sulphuric acid having a temperature higher than the freezing point of said sulphuric acid to 10.degree. C., and
(d) contacting said stream of gaseous silicon tetrafluoride with activated charcoal.

2 more elements

Dependencies are inferred from the claim text.

Process for the production of silicon tetrafluoride

Life of this patent

Process for the production of silicon tetrafluoride

Life of this patent

Abstract

Claims7