Bayer Aktiengesellschaft

Covestro Deutschland Ag

Dieter Heitkamp

Helmut Fiege

Winfried Joentgen

Alfred Soppe

Thomas Runowski

Karl Heinz Neumann

Thorsten Leidig

Karl-Heinz Neumann

Jiyuan Sun

The present invention relates to an apparatus and a method for evaporating liquids containing potentially explosive impurities of lower volatility than the actual liquid compound. The set-up of the evaporator according to the invention allows its operation with complete evaporation of a liquid without formation of a liquid sump of not yet evaporated liquid.

Apparatus and method for evaporating liquids containing potentially explosive impurities

Hydroxypivalic acid is obtained from aqueous solutions by removal of the water by azeotropic distillation and subsequent crystallization from a solvent mixture which is composed of a polar and a non-polar component. The distillation is carried out under reduced pressure and at a maximum bottom temperature of 90.degree. C., until a residual water content of at least 0.1% of the total weight of the resulting solution is achieved.

Process for isolating hydroxypivalic acid from aqueous solution

Hydroxypivalic acid can be prepared by oxidation of hydroxypivalaldehyde with hydrogen peroxide by metering the hydrogen peroxide, as the oxidizing agent, into an aqueous hydroxypivalaldehyde reservoir in the temperature range from 60.degree. to 80.degree. C. such that a hydrogen peroxide concentration of 4% by weight, based on the total weight of the reaction mixture, is not exceeded, and ending the addition of hydrogen peroxide as soon as the concentration of hydroxypivalaldehyde in the reaction mixture falls below 1% by weight.

Process for the preparation of hydroxypivalic acid

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Burscheid, Germany

Dieter Heitkamp