Patent GB-586518-A (GB)
Title: Catalytic conversion of alicyclic ketonic compounds into aromatic amines
IPC: C07C37/50
Filed: 1944-04-25
Abstract: Aromatic amino compounds in particular 3,5-xylidene with or without minor amounts of hydroxy compounds (xylenols) and heterocyclic bases (collidines), are obtained by treating the vapours of isophorone with ammonia at an elevated temperature, in the presence of a dehydrogenation catalyst, e.g. an activated alumina which may be associated with a substantial but lesser amount of a dehydrogenating metal or metal compound. Advantageously the reaction temperature ranges from 400 DEG  C. to 650 DEG  C. and the mol. ratio of ammonia to isophorone ranges from about 2 : 1 to 20 : 1.  Specified aluminas are those which on heating are converted into alpha alumina through gamma alumina, e.g. alumina alpha trihydrate, alumina beta trihydrate, alumina alpha monohydrate, gamma alumina, gelatinous aluminium hydroxide and bauxite, e.g. Porocel.  Other specified catalysts are: chromium, nickel, iron, cobalt, manganese, vanadium, titanium, scandium, copper, zinc, zirconium, molybdenum, rubidiun, platinum rhodium, silver, cadmium, the rare earths, tantalum, osnium, iridium, gold palladium, and uranium used individually or in the form of mixtures or alloys thereof, e.g. alloys or mixtures comprising, e.g. silver and copper, chromium and copper, zinc and copper, nickel and aluminium, nickel and zinc, nickel and cobalt, their oxides, halides, sulphides, selenides, tellurides, phosphates, manganates, molybdates, chromates, bichromates.  They may be used with a carrier such as pumice, clay, diatonaceous earth, kieselguhr, or the aluminas specified above.  Inert diluents, e.g. nitrogen, and saturated hydrocarbons, e.g. methane, ethane and propane, may be used in the reaction mixture which may be treated intermittently, continuously or in batch.  In examples: (1) a vaporous mixture of ammonia and isophorone in a mol ratio of about 10 : 1 is heated at 500 DEG  C. and under atmospheric pressure in the presence of Porocel (an activated bauxite) to obtain a product consisting mainly of 3.5-dimethylaniline, together with other aromatic amines and hydroxy compounds; (2) as in (1) but using a catalyst such as alumina alpha monohydrate and gamma alumina; (3) as in (1) but using a catalyst consisting of ferric oxide incorporated in the surface of activated alumina and a mol ratio of 4 : 1; (4) three mixtures of ammonia and isophorone having mol ratios of ammonia to isophorone of 2 : 1, 6 : 1 and 10 : 1 respectively are heated at 500 DEG  C. with a gamma alumina catalyst to obtain increasing yields of aromatic amines xylidines and decreasing yields of aromatic hydroxy compounds; (5) as in (2) but using a mol ratio of about 9 : 1 at a pressure of 300 lbs. per sq. in. to obtain mainly 3,5-dimethylaniline and collidine aromatic hydroxy compounds; (6) as in (5) but using an activated bauxite catalyst and a mol ratio of 6 : 1.  In each example the xylidine is extracted with dilute sulphuric acid and the acid solution is neutralised to release the xylidine which is isolated by decantation; alternatively the reaction products may be conducted through a plurality of small-bore tubes together with dilute sulphuric or other acid solution, and the xylidene may be recovered as aforesaid, or, it may be isolated by fractionation. The unconverted isophorone may be recycled through the reaction zone. Hydrogen, methane and other gaseous by products may be collected. The Specification as open to inspection under Sect. 91 comprises also the use, as starting materials, of homologues of isophorone including homoisophorones, e.g. cyclic ketones wherein one or more of the methyl groups of isophorone have been substituted by other alkyl radiclas, e.g. ethyl, propyl, isopropyl, butyl, secondary butyl, isobutyl, tertiary butyl, amyl and hexyl.  Other diluents therein specified are hydrogen and steam.  This subject-matter does not appear in the Specification as accepted.