2-Ethylhex-2-Enal → 2-Ethylhexanol

Participants

Reaction Steps

Heptane occurs as by-product in very limited amounts, from the hydrogenation via decarbonylation of 2-ethylhexenal and 2-ethylhexanal. The recovery of pure 2-ethylhexanol in the third stage occurs distillatively via the separation of a fraction of the first runnings by means of a first running column and separation of a distillation residue in a main product column. Although the separation of the components with boiling points below that of 2-ethylhexanol can take place at normal or slightly reduced pressure, industrially, due to the high boiling point of 2-ethylhexanol, the entire distillation is carried out at a reduced pressure of 50 to 200 torr. However, it is not possible under these conditions to separate 2-ethylhexanol completely from the higher boiling components in the main product column. The bottom product of the main product column must therefore be redistilled in a further column, the last runnings column, in order to separate the 2-ethylhexanol in the residue from the higher boiling components. A temperature below 180° C. is usually maintained in the bottom product with this distillation (last runnings distillation). At the head of the column, the remaining 2-ethylhexanol is obtained together with small amounts of the higher boiling substances as a last runnings fraction. This is recycled to the hydrogenation or distillation and is thereby subjected to a further distillation, so that finally, 2-ethylhexanol is almost completely separated from the higher boiling substances, which are removed at the bottom of the last runnings column. They consist of the reaction products of 2-ethylhexenal with itself or with n-butyraldehyde and constitute oxygen-containing compounds with more than 8 carbon atoms. The boiling points of the reaction products lie above that of 2-ethylhexanol.

Provenance & Evidence