GB283112A - Improvements in process for the manufacture of acetal - Google Patents

Abstract

283,112. Soc. Anon. des Distilleries des Deux-SÞvrÚs. Jan. 3, 1927, [Convention date]. Acetal.-In the production of acetal by treating alcohol and acetaldehyde with a catalyst such as hydrochloric, sulphuric, toluene-sulphonic, or acetic acid, hydrogen phosphide, calcium chloride or certain metallic salts, the reaction mixture is treated to remove first the acetaldehyde with part of the alcohol, then the alcohol and water by means of an insoluble liquid forming an azeotropic mixture, leaving the acetal behind, and the aceotropic mixture is then treated to recover the auxiliary liquid and the alcohol. The process is described with the use of an acid catalyst (hydrochloric acid), and when the reaction is finished the acid is neutralized by sodium bicarbonate until a slight alkalinity is shown by bromo-thymol blue prior to distillation. In an example, 45 grs. of gaseous hydrochloric acid (used as a solution of 22‹ B.) is employed with 92 kilos of alcohol and 46 kilos of acetaldehyde. The reagents are placed in a reaction vessel having a cooling-coil 2, and the neutralized product is discharged to, a vessel 3, from which it is fed continuously to a still 4, which is arranged so that the free acetaldehyde, possibly with some alcohol, is distilled over and caught in a condenser 6 from which part is returned to the still 4 by a pipe 7 and the rest is collected in a tank 8 for use again. At the bottom of the still 4 the acetal collects with some alcohol, and the sodium chloride separates and is removed at 11. The liquor from the bottom of the still 4 is vaporized and taken by a pipe 9 to a still 10 which contains some benzene distributed over its upper part. An azeotropic mixture of benzene, alcohol, and water escapes to a condenser 12, from which a part is returned to the still 10 and the rest goes by a pipe 14 to a washing-column 15, to which water is supplied by a pipe 18. The acetal collects in the lower part of the still 10 and is withdrawn by a pipe 16 to a cooler 17. The benzene separates in the column 15 and returns to the still 10 by a pipe 19, and the diluted alcohol passes from the bottom of the column 15 by a pipe 20 to a still 21. from which concentrated alcohol is delivered by a pipe 22 to a tank 23, the residual water being discharged by a pipe 24. The Specification as open to inspection under Sect. 91 (3) (a) states that the condensation is effected with from one-fifth to one-tenth of the quantity of catalyst employed in the known processes. This subject-matter does not appear in the Specification as accepted.