US 7,622,097 B2Granted

Process for hydrothermal production of sodium silicate solutions and precipitated silicas

AssigneeThe National Titanium Bioxide Co., Ltd. (CRISTAL)

InventorsFadi Mohammed Saeed Trabzuni, Hassan Moenes El Dekki, Chathangat Cheroolil Gopalkrishnan

Life of this patent

Estimating the term…

Loading patent…

Abstract

A method is provided for treating silica sand scrubs (SSS) generated and accumulated as waste in the chloride manufacturing process of titanium dioxide pigment. A hydrothermal process is used to produce sodium silicate solutions of modulus 3.0 to 3.8, and precipitated silicas. In some embodiments, the process uses two specific principal reaction stages. A sodium silicate solution having a low SiO2:Na2O molar ratio, in the range from 2.0 to 2.8, is first produced by reaction of the SSS, as a cost-effective SiO2 source, with aqueous caustic soda. The conversion of this intermediate sodium silicate solution of low modulus to a high SiO2:Na2O molar ratio is made possible by using a SiO2 source that is prepared as precipitated amorphous silica from the intermediate sodium silicate solution produced above.

Claims18

Dependent claims

A method for hydrothermal production of an aqueous sodium silicate solution having a SiO2:Na2O molar ratio of at least 3.0:1, said method comprising the steps of:

(i) manufacturing titanium dioxide, wherein the manufacturing comprises generating a waste product, the waste product comprising a precursor solid silica source;
(ii) collecting the waste product;
(iii) exfoliating and removing titanium dioxide particles adhering to the surface of the precursor solid silica source of the collected waste product, to form cleaned silica;
(iv) producing an intermediate sodium silicate solution by a hydrothermal fusion reaction of the cleaned silica with a caustic soda in an autoclave;
(v) forming an amorphous silica source by transposing the SiO2 content of the intermediate sodium silicate of step (iv) by a separate precipitation process;
and
(vi) dissolving the amorphous silica provided in step (v) in the intermediate sodium silicate solution of step (iv) and raising the SiO2:Na2O molar ratio to result in a high modulus sodium silicate solution.

4 more elements

Dependencies are inferred from the claim text.