Patent GB-736417-A (GB)
Title: Improvements in or relating to the production of halogen-substituted organic compounds
IPC: C07B39/00
Filed: 1952-08-20
Abstract: Halogen-substituted organic compounds are obtained by reacting an organic compounds consisting of an alcohol, ether, aldehyde, ketone, ester, thioalcohol, thioether, thioester, or amine, with an ammonium or organic substituted ammonium halide (but excluding iodides) containing at least one H atom attached to the N atom at a temperature of 250 DEG  C. to 500 DEG  C. in the presence of a dehydrochlorination type catalyst of acidic to mildly alkaline character.  The ammonium chloride used may be that recovered as by-product in the ammonia-soda process for the manufacture of soda ash.  In addition to ammonium chloride there may be used ammonium fluoride, ammonium bromide and the corresponding organic substituted ammonium halides, e.g. methylamine hydrochloride, diethyl ammonium chloride, trimethylammonium chloride, dimethylammonium bromide, pyridine hydrochloride and aniline hydrofluoride.  The catalyst may be a metallic oxide, silicate, or chloride, alumina being preferred. Other materials specified include bauxite, silica, titania, magnesium silicate, aluminium silicate and various activated earths and silicates.  Fuller's earth and clays treated with phosphoric acid or acid phosphate salts may also be used.  The materials may be promoted with zinc chloride, ferric chloride, aluminium chloride, calcium chloride or other inorganic metal halides or with active carbon impregnated with zinc chloride.  Metal halides (other than iodides) of Groups 1 and 2 of the Periodic Table are valuable catalysts when used in melt form.  The metal halide may be fused with the ammonium halide.  Suitable halides are cuprous chloride, zinc chloride, sodium chloride and potassium chloride.  The process is preferably effected at 350-400 DEG  C. and it is preferred to employ an excess of the organic starting material, e.g. molar ratios of 1 : 1 up to 5 : 1 of the organic material to the ammonium halide.  Amines and ethers produced as by-products particularly in the reaction between ammonium chloride and an alcohol may be recycled to the reaction zone.  The process may be carried out at atmospheric, elevated or reduced pressure.  Specified starting materials are aliphatic alcohols, e.g. methanol, ethanol, isopropanol, isoamyl alcohol, lauryl alcohol and octadecanol; alicyclic alcohols, e.g. cyclohexanol, ac-tetrahydronaphthol, cholesterol, terpineol, borneol; aromatic substituted alcohols, e.g. diphenyl carbinol, phenyl methyl carbinol and phenyl benzoyl carbinol; heterocyclic substituted alcohols, e.g. di-alphathienyl carbinol and pyridyl carbinol; ethers, e.g. dimethyl-, diethyl-, and di-isopropyl ethers, beta, beta-dichloroethyl ether, methyl secondary butyl ether and cyclic ethers such as tetrahydrofuran, tetrahydropyran, ethylene oxide and propylene oxide; aldehydes, e.g. formaldehyde, acetaldehyde and benzaldehyde, ketones, e.g. acetone, methyl ethyl ketone and acetophenone; esters, e.g. ethyl acetate (which is converted to ethyl halide) isopropyl butyrate, methyl benzoate, dioctyl phthalate, and tricresyl phosphate; mercaptans, thioethers and thioesters, e.g. n-butyl mercaptan, benzyl mercaptan, trichloromethyl mercaptan (which is converted to CCl4) diethyl sulphide, and amyl thioacetate; amines including primary, secondary, and tertiary amines such as methylamine, dimethylamine, triethylamine, piperazine, and morpholine.  The conversion may be carried out in the vapour phase, e.g. by passing the vapours of the organic material through a heated bed of ammonium halide and passing the mixed vapours through a bed of heated catalyst.  Alternatively, an inert gas stream may be passed through the ammonium halide and admixed with the organic vapours and the mixed vapours passed through a bed of catalyst, or a finely divided solid ammonium halide or a mixture thereof with finely divided catalyst may be suspended by a stream of organic vapours sufficiently superheated to vaporize the ammonium halide and the reaction may be completed in an additional reaction zone.  The vapour phase operation may be carried out batchwise but is preferably carried out continuously by replenishing the supply of the ammonium halide and organic material to the vaporizers.  In another method of carrying out the process the ammonium halide and catalyst are suspended as a slurry in an organic liquid heat transfer medium and maintained at reaction temperature while the organic material is introduced in the vapour or liquid state, the organic halide formed being removed as vapour.  Specified heat transfer agents are chlorinated diphenyl, diphenyl, diphenyl oxide, mixtures of diphenyl and diphenyl oxide, ditolylethane, terphenyl, and highly aromatic petroleum oils.  The slurry operation may be made continuous by the addition continuously or intermittently of fresh catalyst and ammonium halide to the slurry, the organic material being injected continuously and the gaseous products separated from the liquid medium.  The preferred catalyst is alumina which is preferably activated before use, e.g. by heating at about 200 DEG  C. for 15 hours.  Three specific types of procedure for reacting an alcohol with ammonium chloride are described and illustrated.  In the first type both the reactants are vaporized separately before reaction; in the second, liquid alcohol is introduced into a slurry of ammonium chloride in a high boiling organic heat transfer medium which is heated before or after the introduction of the alcohol so as to vaporize the alcohol and ammonium chloride which are then reacted in the vapour phase in a separate reactor containing the catalyst whilst the third method illustrates the slurry method of operation in which both the catalyst and ammonium chloride are slurried in the heat transfer agent.  Examples describe the conversion of methanol, dimethyl ether and methylamine into methyl chloride, of ethanol and ethyl acetate into ethyl chloride, of isopropanol into isopropyl chloride, of n-butyl sulphide to n-butyl chloride, of tetrahydrofuran to butylene dichloride, and of paraldehyde and lauryl alcohol respectively to chlorine-containing products.  In each case the ammonium halide used is ammonium chloride and the use of various catalysts is described.  An example is also given for the conversion of ethanol to ethyl bromide using ammonium bromide.