GB790759A - Trimethylolethane - Google Patents

Abstract

Trimethylolethane is produced by a process comprising continuously forming an aqueous alkaline solution of formaldehyde and propionaldehyde, passing it first through a region in which its components react to form trimethylolethane, then through a region in which the pH of the solution is reduced to no more than 7, and next through a region in which unreacted formaldehyde is distilled off, and recovering trimethylolethane in crystal form from the solution. The preferred alkali is sodium hydroxide. Preferably an excess of formaldehyde is used, e.g. about 5 to 15 mols. of formaldehyde for each mol. of propionaldehyde. Advantageously the reaction vessel is operated adiabatically. The solution leaving the reaction vessel is alkaline, generally having a pH of 9.8 to 10.5. The pH is reduced to not more than 7 by the addition of acid materials, e.g. formic acid, acetic acid, sulphuric acid or phosphoric acid. The mixture is then distilled under pressure and advantageously the formaldehyde distilled off is recycled to the mixing zone. After the distillation the aqueous reaction mixture containing trimethylolethane and sodium formate is treated for the recovery of crystalline trimethylolethane. In one procedure it is separated by adding an organic solvent for the trimethylolethane, e.g. an alcohol such as n-propyl alcohol or isopropyl alcohol, and separating the organic phase from the aqueous phase. The trimethylolethane may be recovered from the organic phase by heating it in the presence of added water to remove the organic solvent and crystallizing out trimethylolethane from the aqueous solution so produced. Alternatively the trimethylolethane may be separated from the reaction mixture by heating the mixture and evaporating water therefrom until the water content is about 30 to 40 per cent by weight and then cooling so that the trimethylolethane crystallizes out. The crude crystals so obtained may be freed from sodium formate by treatment with a solvent for trimethylolethane such as methanol, ethanol, propanol or isopropanol. These two methods of separating trimethylolethane from the reaction mixture may be combined together. Specification 790,760 is referred to.