Process for the preparation of low molecular weight polyhydroxyl compounds

In a process for the preparation of a mixture of low molecular weight polyhydric alcohols, hydroxyaldehydes and hydroxyketones comprising condensing formaldehyde in an aqueous reaction medium in the presence of metal compounds as catalysts and of compounds capable of enediol formation as co-catalysts, stopping the condensation of formaldehyde with itself by cooling and/or by inactivation of the catalyst with acids when the reaction mixture has a residual formaldehyde content of from 0 to 10% by weight, and removing the catalyst, the improvement wherein synthesis gases containing formaldehyde are continuously or discontinuously introduced at temperatures of between 10.degree. and 150.degree. C. into an absorption liquid comprising

• (a) 5 to 99% by weight of water,
• (b) 0.1 to 90% by weight of compounds capable of enediol formation as co-catalysts,
• (c) 0 to 20% by weight of soluble or insoluble metal compounds as catalysts optionally bound to high molecular weight carriers, and
• (d) 0to 60% by weight of one or more monohydric or higher hydric organic compounds having a molecular weight of from 32 to 10,000, and having a pH of 3 to 10, with the formaldehyde being condensed at the same time or, if the absorption solution contains no catalyst, the formaldehyde is condensed subsequently by addition of catalyst.