Process for the preparation of aqueous formaldehyde solutions

摘要

In a process for the preparation of aqueous formaldehyde solutions, which comprises the following steps: a) reaction of a methanol/water/air mixture in the form of a vapour on a catalyst at elevated temperature, b) absorption of the reaction mixture in one or more absorption steps arranged in series, with the formation of a methanol-containing aqueous formaldehyde solution and c) removal of a fraction which contains essentially methanol and water by means of fractional distillation, the methanol/water/air mixture which is required for the reaction is vaporised with the aid of the heat absorbed from the formaldehyde solution obtained in the absorber by means of indirect heat exchange, and/or at least part of the vapours obtained during the fractional distillation step is condensed using liquid water. This condensate together with fresh methanol and air is fed to the vaporiser arranged upstream of the catalyst stage.