US Patent 11858821 Method of silica pretreatment

The subject invention discloses an improved method for making pre-hydrophobated precipitated silica from rice hull ash silica. This process is renewable, highly efficient, and incorporates virtually all of the silica coupling agent used in making the pre-hydrophobated precipitated silica into the final product. The subject invention more specifically reveals a method for making pre-hydrophobated precipitated silica comprising: (1) dispersing silica into water under conditions of agitation to made an aqueous silica slurry; (2) adding a phase transfer agent to the aqueous silica slurry; (3) adding a silica coupling agent to the aqueous silica slurry; (4) maintaining the aqueous slurry at a temperature of at least 20° C. for a time which is sufficient for the silica coupling agent to react with the silica to produce the pre-hydrophobated precipitated silica; and (5) recovering the pre-hydrophobated precipitated silica from the aqueous silica slurry.