GB353071A - Process and apparatus for the production of acetaldehyde - Google Patents

Abstract

In the catalytic oxidation of ethyl alcohol in the vapour form to acetaldehyde by means of air or other oxygen-containing gases in the presence of steam serving as a temperature regulator, use is made of copper or silver catalysts in the form of wire gauze, wire pieces, granules, turnings, borings, tetrahedra, Raschig rings, spirals of wire or tape, coiled gauze, disciform bodies formed by rolling up together a smooth and a corrugated piece of metal tape, or bundles of thin metallic tubes.ALSO:Acetaldehyde is obtained from ethyl alcohol by contacting the alcohol vapour mixed with air or other oxygen-containing gases with catalysts consisting of copper, silver, or the vanadates of these metals at temperatures of 420-450 DEG C. in the case of copper, 450-500 DEG C. in the case of silver, and 360-400 DEG C. in the case of silver or copper vanadate, in the presence of steam serving as a temperature regulator. The steam is derived from aqueous alcohol of less than 95 per cent strength, or from a separate source in equivalent amount. The proportion of steam may be from 10 per cent by weight of the alcohol when the vanadates of copper or silver are used as catalysts, to 50 or 60 per cent when metallic silver is used. The proportion of oxygen to ethyl alcohol may be greater than, equal to, or less than the amount theoretically required for the oxidation. Some of the residual gases from the reaction may, if desired, be added to the mixture as a diluent. The copper or silver catalysts may be deposited in finely-divided condition on carriers such as asbestos or pumice, or may be in the form of wire gauze, wire pieces, granules, turnings, borings, tetrahedra, Raschig rings, spirals of wire or tape, coiled gauze, disciform bodies formed by rolling up together a smooth and a corrugated piece of metal tape, or bundles of thin metallic tubes. The vanadates of copper or silver when used may be deposited on pumice. In an example, a mixture of air, ethyl alcohol vapour, and water vapour is formed by leading air from a perforated inlet through 85 per cent alcohol in a vessel heated to 60-70 DEG C. The vapour mixture is then heated to about 90 DEG C. in a pipe which leads into the reaction chamber, and is provided with a wire gauze spiral to prevent backfiring should the mixture undergoing reaction ignite. The catalyst in the reaction chamber consists of silver wire gauze sheets. The vapours leaving the reaction chamber pass to a condenser. The condensate goes to a tank, and the uncondensed gases to a scrubber in which they are finally freed from acetaldehyde vapour by means of 20 per cent aqueous alcohol. The lower part of the scrubber is provided with baffles traversed by cooling coils, the upper section being filled with Raschig rings or the like sprinkled with water. The exit liquor from the scrubber goes to the tank containing the original condensate, and the contents of this tank are then conveyed to a rectifying column and auxiliary condensers &c. to be separated into pure acetaldehyde and aqueous alcohol, which latter may be returned in part to the scrubber and in part to the reaction chamber.