Patent ID: 6797249
Filing Date: 2004-09-28
Classification: C01B

Abstract:
A process for the production of amorphous silica from quartz having a silica content of at least 90% comprising:a) heating said quartz with CaCl2, at a temperature in the range of about 900Â° C. to about 1,200Â° C., wherein the wt/wt ratio of CaCl2 to the quartz is greater than 3 and in the presence of water vapor, in excess of the stoichiometric amount needed for the reaction: xCaCl2+ySiO2+xH2Oâ†’(CaO)xÂ·(SiO2)y+2xHCl wherein x is greater than y to obtain a conversion of said quartz to calcium silicates in excess of 99.9% and wherein said calcium silicate is primarily in the form of dicalcium silicate of the formula (CaO)2Â·(SiO2); b) Leaching said calcium silicates with HCl to form a solution of CaCl2 with insoluble silica; c) Separating said insoluble silica from solution; and d) Recycling the CaCl2 solution from step â€œcâ€  to step â€œaâ€ .