GB742159A - Production of pentaerythritol - Google Patents

Abstract

Pentaerythritol is produced in a batch process by the reaction of acetaldehyde with formaldehyde and a suitable inorganic base in an aqueous medium, wherein control of the reaction is facilitated by employing the formaldehyde and acetaldehyde in a molecular ratio substantially exceeding 4 : 1, preferably at least 10 : 1, and bringing the reagents together rapidly with agitation so as to ensure complete admixture within a period of less than 2 minutes. Preferably the initial temperature of the reagents is between 15 DEG and 40 DEG C., the reaction is stopped after between 45 and 250 minutes and the conditions are controlled so that the temperature reaches between 45 and 75 DEG C. The total initial concentration of aldehydes is preferably between 15 and 30 per cent by weight of the total mixture and from about 1.0 to 1.3 equivalents of inorganic base are used for each mol. of acetaldehyde. Suitable inorganic bases are sodium, potassium and calcium hydroxides. Pentaerythritol may be recovered by reducing the pH to between 7.5 and 6.5 by addition of acetic, formic, hydrochloric or sulphuric acid, distilling off excess formaldehyde and crystallizing out the product after concentration. Formaldehyde may be recovered by distillation at 10-30 p.s.i.g. or atmospheric pressure or by steam distillation, and recycled as feed. Detailed examples are given in which formaldehyde and acetaldehyde in mol. ratios of at least 10 : 1 are mixed with an inorganic base over a half minute. Comparative runs are described showing the decrease in yield and purity of the product when the reactants are added over 45 minutes and when in addition the ratio is reduced to 5 : 1 and excess formaldehyde is removed by alkaline condensation.