E.i. Dupont De Nemours and Company

Scott Rickbeil Frerichs

Stephan Claude De La Veaux

Juergen Kurt Plischke

Jodi Lynn Witt

Christian Normand

Douglas Eric Spahr

William Harvey Morrison, Jr

Juergen K Plischke

There is described a process for preparing metal oxide particles which are substantially free of coarse tail from an oxidizing agent and a vaporous metal reactant in a flow reactor; comprising, (a) directing a flow of the metal reactant into a contacting region of the flow reactor; comprising (a) passing a flow of oxidizing agent through a high temperature zone of the flow reactor to form a flow of hot oxidizing agent and directing the flow of the hot oxidizing agent onto the contacting region of the flow reactor at a flow condition sufficient to form a reaction stream comprising a flow of hot oxidizing agent, a flow of metal reactant and a diffusive flow of the hot oxidizing agent and the metal reactant, the temperature of the hot oxidizing agent being at least sufficient to initiate oxidation of the metal reactant in the diffusive flow; (c) passing the reaction stream into a reaction zone of the flow reactor, while simultaneously introducing a flow of an upper cooling fluid substantially coaxially with the reaction stream to form a fluid curtain which surrounds the reaction stream; (d) maintaining the fluid curtain while the metal oxide particles form within the diffusive flow of the reaction stream and until at least a major portion of the reaction stream is cooled to a temperature below the temperature at which metal oxide particles coalesce; and (e) separating the metal oxide particles from the reaction stream.

Process for making metal oxide nanoparticles

There is described an apparatus for making metal oxide particles which are substantially free of coarse tail from an oxidizing agent and a metal reactant in a flow reactor. The apparatus can be a concentric tubular flow reactor comprising a substantially funnel-shaped reactant contacting region located adjacent to a reaction zone which is able to direct a flow of a hot oxidizing agent towards a flow of the metal reactant to form a reaction stream which flows downstream into a reaction zone, whereby the hot oxidizing agent of the reaction stream is able to surround the flow of metal reactant sufficient to prevent the metal reactant from contacting the wall of the reactant contacting region and forming scale on the wall. A cooling fluid conduit being able to direct a flow of a cooling fluid into the reaction zone to flow coaxially with the reaction stream and to form a fluid curtain between the reaction stream and a baffle, which defines at least a portion of the reaction zone, while the metal reactant and hot oxidizing agent within the reaction stream react to form the metal oxide nanopowder prevents scale from forming on the baffle.

Apparatus for making metal oxide nanopowder

The disclosure is directed to a method for reducing the chemical activity and photo activity of titanium dioxide nanoparticles comprising adding an amorphous alumina-stabilizing agent, specifically an anion, such as citric acid, to an aqueous slurry of the titanium dioxide nanoparticles; treating the aqueous slurry with a source of alumina, such as a solution of sodium aluminate, to form alumina-treated titanium dioxide nanoparticles; recovering the alumina-treated inorganic nanoparticles, wherein the nanoparticles have a particle size of about 50 to about 300 nm; and milling the nanoparticles to form nanoparticles having a particle size about 15% smaller than silica-treated inorganic nanoparticles milled under similar conditions. The titanium dioxide nanoparticles described herein are useful in cosmetic, coating and thermoplastic compositions.

Lower-energy process for preparing passivated inorganic nanoparticles

Growing community of inventors

Hockessin, DE, United States of America

Scott Rickbeil Frerichs