Bayer Aktiengesellschaft

Peter Schmidt

Hans-Dieter Block

Hans-Heinrich Moretto

Wolfgang Ohlendorf

Werner Ludovici

Uwe Brekau

Peter Schober

Roland Kleinstuck

Andreas Nickel

Michael Batz

Karl-Friedrich Thom

Hermann Sicius

Gerhard Jonas

Alex Burger

Michael Immenkeppel

Hans-G Unter Fr Ohlen

A process is provided for the preparation of aqueous silica sols having a particle size of 27 to 72 nm. by adding fresh acidic silica sol into the reactors of a multi stage cascade reactor wherein the reactors contain aqueous solution of colloidal silica sol of a pH of 8 or above. Each successive stage of the cascade reactor is supplied with overflow from the preceding stage. Alkaline compounds, such as alkaline sodium silicate solution, alkaline potassium silicate solution, sodium hydroxide solution or potassium hydroxide solution, are introduced into the first reactor or first reactors so that a pH value in the range of 8 to 12.5 is established in the reactors.

Continuous preparation of silica sols which contain large particles

A process for the recovery by distillation of tributyl phosphate (TBPO) from spent hydraulic oils, which are employed particularly in aircraft used for civilian air traffic.

Process for the recovery of tributyl phosphate from spent hydraulic oils

A process for the removal of organic impurities and dissolved salts from hydrazine hydrate and aqueous solutions thereof by distillation of the hydrazine hydrate under reduced pressure, passing the hydrazine hydrate vapor through an adsorbent, and condensing the vapor.

Process for the removal of impurities from hydrazine hydrate

Process for the production and concentration of alkaline silica sols containing nonaggregated, spherical SiO.sub.2 particles with a diameter of .gtoreq.1 nm starting with SiO.sub.2 concentrations of 4-8% by weight, using microporous membrane filters.

Process for the production and concentration of silica sols

The present invention relates to a process for eliminating 1-phosphono-1-carboxycyclopentan-3-one (ketone) from, or reducing its content in, an aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid, characterized in that the solution is adjusted to a pH value of &gt; 6 using an aqueous inorganic base, particularly sodium hydroxide, and aqueous bleaching liquor is subsequently added in a molar ratio of NaOCl to ketone of &gt;5:1.

Process for eliminating 1-carboxy-1-phosphonocyclopentan-3-one from, or

Activated carbon is produced by an improved process which comprises subjecting a mash comprising carbon-containing combustibles, phosphoric acid and water to a rapid thermal pretreatment at temperatures of from 80.degree. to 250.degree. C. in the presence of steam and oxygen followed by activation at temperatures of from 250.degree. to 550.degree. C. for no more than 30 minutes.

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Leverkusen, Germany

Peter Schmidt