Patent ID: 8845919
Filing Date: 2014-09-30
Classification: B82Y,C01G,C01P,C04B,C09C,Y10T

Abstract:
1. A process for producing an iron-silicon oxide particle, comprising: combining (a1) a first stream comprising 10 to 40% by weight, calculated as SiO (a2) a second stream, in vaporous form or in aerosol form, comprising 60 to 90% by weight of an iron compound, which is at least one of oxidizable and hydrolyzable, calculated as Fe to obtain a mixture in a mixing zone of a reactor comprising, in succession, a mixing zone, combustion zone, cooling zone, and solids removal zone; b) transferring the mixture, at least one hydrogenous combustion gas, and an oxygen-comprising gas into the combustion zone separately from one another, and igniting them in the combustion zone, and allowing them to react to completion at an adiabatic temperature of 700 to 2500° C. and a mean residence time of 10 ms to 10 s, to obtain a reaction mixture; c) cooling the reaction mixture to a temperature of 200 to 400° C. by feeding water into the cooling zone; subsequently, d) removing at least one solid from gaseous or vaporous substances in the solids removal zone; and thermally treating the iron compound, which is in aerosol form, before introducing the iron compound into the mixing zone, thereby producing an iron-silicon oxide having: (a) a core-shell structure, comprising a shell and an enveloped particle comprising a core; (b) a BET-surface area of 10 to 80 m (c) a thickness of the shell of 2 to 30 nm; (d) a content of iron oxide of 60 to 90% by weight; and (e) a content of silicon dioxide of 10 to 40% by weight, based in each case on the enveloped particle, wherein: a proportion of iron, silicon, and oxygen is at least 99% by weight, based on the enveloped particle, the core is crystalline, comprising iron oxides, and the iron oxides comprise haematite, magnetite, and maghemite, the shell consists of amorphous silicon dioxide, and at least one compound consisting of the elements silicon, iron, and oxygen is present between shell and core.