GB982643A - Continuous process for the manufacture of halogenated aldehydes, ketones and acids - Google Patents

Abstract

Aldehydes, ketones and carboxylic acids, which may be partially halogenated, are halogenated in the a -position to the aldehyde, ketone or carboxyl group by reaction in a continuous process in the presence of water and at a temperature below 200 DEG C. with a metal halide in a high valency state which is converted by the reaction to a lower valency state and the reduced metal halide is continuously converted from the lower valency state to the higher valency state by reaction with oxygen or a gas containing free oxygen and a hydrogen halide containing the same halide, the organic halogenation product being continuously isolated from the reaction mixture. The regeneration of the metal halide may take place in the same reaction stage as the halogenation or may take place in a subsequent reaction stage, the regenerated metal halide being recycled in the latter case. The process may be carried out at or above atmospheric pressure (i) by reacting the carbonyl compound or organic acid with the metal halide in aqueous solution and simultaneously passing oxygen or a gas containing free oxygen through the reaction mixture and adding aqueous hydrohalic acid at the rate at which halogen is consumed; the halogenated product, water and unreacted starting material are removed and the unreacted starting material recycled; (ii) the aqueous metal halide is reacted with the carbonyl compound or carboxylic acid and in a subsequent stage the reaction product, unreacted starting material and some water are removed; after addition of aqueous hydrohalic acid the catalyst is regenerated by means of oxygen or a gas containing free oxygen, e.g. air, and returned to the reactor with fresh starting material; or (iii) a porous inert carrier is impregnated with aqueous metal halide (see Division B1) and the carbonyl compound or carboxylic acid is passed over the catalyst with steam, hydrogen halide and oxygen or a gas containing free oxygen at a temperature such that the catalytic mass contains water; the resultant mixture is separated and unreacted starting material is recycled. The aldehyde or ketone may also be produced in the reaction medium by catalytic oxidation of an olefine in the presence of a noble metal halide. Specified starting materials are acetaldehyde, propionaldehyde, butyraldehyde acetone, methyl ethyl ketone, cyclohexanone, acetophenone, acetic acid, propionic acid, phenylacetic acid, malonic acid and monochloroacetone. The process may be used for producing fluorine, chlorine, bromine or iodine compounds, but preferred metal halides are cupric and ferric chlorides and bromides. Metal halides which are sparingly soluble in water in their lower valency states may render more soluble by the incorporation of other substances which promote solubility (see Division B1). In Examples: (1) acetone is treated with cupric chloride and water to give monochloracetone and asymmetrical dichloroacetone, the catalyst being regenerated by the action of air and concentrated hydrochloric acid in a separate stage; (2) acetone steam and air are passed over a catalytic mass containing silica gel, cupric chloride and lithium chloride to give monochloroacetone; (3) monochloroacetone, steam and air are passed over the catalyst of (2) to give a ,a -dichloroacetone; (4) acetic acid, steam and air are passed over the catalyst of (2) to give monochloroacetic acid; (5) acetone, steam and air are passed over a catalyst containing ferric bromide and silica gel to give monobromoacetone; (6) acetaldehyde, steam, aqueous hydrochloric acid and a gas mixture containing oxygen, ethylene and inert components are passed under pressure into a reactor containing a catalyst which contains palladous chloride, copper ions, chromic ions, chloride ions and acetate ions to yield monochloroacetaldehyde; the same catalyst, except for palladous chloride-converts acetaldehyde to mono- and dichloro, acetaldehyde.ALSO:Catalysts for the halogenation of aldehydes, ketones or carboxylic acids (see Division C2) comprise either (i) a porous inert carrier such as active carbon, silica gel or aluminium oxide, impregnated with an aqueous solution of a metal halide in a high valency state which is converted by the halogenation reaction to a lower valency state, or (ii) an aqueous solution of a metal halide of the above type plus a perchlorinated organic acid or a metal halide which is not capable of introducing halogen atoms other than the desired halogen atoms into the organic molecule. The second type of catalyst is used when the metal halide of lower valency state is sparingly soluble in water, for example cuprous chloride, and specified additives are an alkali metal chloride such as sodium, potassium or lithium chloride, chromium chloride or iron chloride, or an excess of cupric chloride and/or a perchlorinated organic acid such as trichloroacetic acid. Specified metal chloride catalysts are CuCl2, CuBr2, FeBr3 and FeCl3. A noble metal halide may be present in addition to the above components. Examples are given.