GB271044A - Improved process for concentrating volatile aliphatic acids - Google Patents

Abstract

271,044. Holzverkohlungs Industrie Akt.-Ges. May 17, 1926, [Convention date]. Acids, concentrating and distilling. - In the concentration of volatile aliphatic acids such as acetic acid or propionic acid by distillation in the presence of alkali bisulphate or other water combining substances, the vapour mixtures passing off during the distillation are brought into contact with sodium bisulphate or salt mixtures containing this; the dilute acid may be treated with water combining substances before distillation. For example, 100 parts of 10 per cent acetic acid are treated with 200 parts sodium bisulphate and distilled, and the distillation vapours are passed throuah a column charged with granular sodium bisulphate, the acid from the column having a concentration of 80-90 per cent. The process is particularly suitable for the concentration of impure dilute solutions such as pyroligneous acid; the raw acid is first treated with sodium bisulphate to enable the oily and tarry constituents to be separated in known manner, and the vapours passing off during the subsequent distillation are brought into contact with sodium bisulphate. The small quantity of acid remaining m the dilute solution may be recovered by esterification. Specification 28595/02, [Class 2, Acids and salts, Organic &c.], is referred to. The Specification as open to inspection under Sect. 91 (3) (a) also states that the concentration of the dilute acid may be effected by adding to the dilute acid before distillation water combining substances such as sulphuric acid, or salts thereof, e.g. sodium bisulphate, or mixtures of salts, or mixtures of acids and salts, and then subjecting the mixture to distillation, or the dilute acid may be distilled and the vapour mixtures brought into contact with such substances, or both methods may be employed in combination. For example, 100 parts of 10 per cent acetic acid ara treated with 50 parts of 70 per cent sulphuric acid and the distillation vapours sprayed with 70 per cent sulphuric acid, the acetic acid passing from the column having a concentration of about 90 per cent. This subject-matter does not appear in the Specification as accepted.