GB757564A - Continuous production of pentaerythritol - Google Patents

Abstract

Pentaerythritol is prepared by a continuous process of condensing acetaldehyde with formaldehyde comprising forming an aqueous stream containing acetaldehyde, a substantial excess of formaldehyde and an inorganic base, the inorganic base being introduced in a manner such that thorough mixing is effected in less than 2 minutes, passing the aqueous stream through a reaction zone in which it remains for a time sufficient for reaction to proceed to the desired extent, acidifying the effluent from the reaction zone, continuously distilling formaldehyde from the acidified effluent and recovering a pentaerythritol containing liquor. Suitable inorganic bases are for example, sodium hydroxide, calcium hydroxide or potassium hydroxide. A preferred starting mixture contains (by weight) 3 per cent of acetaldehyde, 20 per cent of formaldehyde and 77 per cent of water and it is desirable that the formaldehyde should contain less than 1 per cent of methanol based on the total weight of the mixture. The preferred reaction temperature is 130-140 DEG F. The alkaline mixture leaving the reactor should be acidified, for example, by addition of acetic acid, formic acid, sulphuric acid or hydrochloric acid, to prevent side reactions. The reaction liquor is then distilled to separate aqueous unreacted formaldehyde as distillate, leaving behind an aqueous solution of pentaerythritol and other non-volatile reaction products. Preferably some of the formaldehyde-containing distillate is recycled. After the distillation the pentaerythritol-containing liquor may be concentrated and cooled to crystallize out the pentaerythritol which may be further purified by recrystallization or otherwise.