Patent GB-652355-A (GB)
Title: Improvements in the production of aliphatic dicarboxylic acids with long chains
IPC: C07C51/215
Filed: 1946-10-24
Abstract: Aliphatic dicarboxylic acids in which the carboxyl groups are separated by a chain of at least 4 carbon atoms, are prepared by oxidizing unsaturated aliphatic monocarboxylic acids containing the group =CH-(CH2)n-COOH, where n is at least 4, or esters of such acids, in the gaseous phase in the presence of an oxidation catalyst with air or other oxygen-containing gas, and isolating the desired aliphatic dicarboxylic acids from the reaction mixture by fractional crystallization from an inert organic solvent or by dissolving the reaction mixture in aqueous alkali and fractionally precipitating the desired aliphatic dicarboxylic acids by addition of an acid. Suitable starting materials are oleic acid, linoleic and linolenic acids either in pure state or as they occur naturally, for example, tall oil. Oxidation is preferably carried out at a temperature between 200 DEG  and 600 DEG  C.  Suitable catalysts are compounds of the metals belonging to the fourth to eighth vertical groups inclusive of the periodic system, e.g. compounds of titanium, vanadium, molybdenum, manganese, iron, cobalt, nickel and platinum; suitable carriers are porous or sintered substances such as aluminium oxide, clays containing aluminium oxide, silica, zeolites and pumice and metals such as copper, iron, nickel, aluminium and silver.  The oxidation may take place at reduced, ordinary or elevated pressures, but preferably at between 1/10 and 10 atmospheres.  The quantity of oxygen used may vary between the theoretical amount and sixty-fold thereof.  In examples: (1) evaporated oleic acid mixed with preheated air is passed over a catalyst consisting of titanium vanadate and titanium dioxide on aluminium oxide at between 400 DEG  and 500 DEG C., the products, mono-and di-carboxylic acids are condensed and azelaic acid isolated in 22 per cent by neutralizing with sodium hydroxide solution and fractionally precipitating with the aid of sulphuric acid; in a similar experiment using as catalyst vanadium pentoxide containing Fe2O3 and Os2O3 on pumice at 425-500 DEG  C., the yield is 32 per cent; (2) tall oil acid is treated as in (1) using vanadium pentoxide on pumice as catalyst, the yield of azelaic acid being 20 per cent; (3) evaporated methyl oleate and preheated air are passed over vanadium pentoxide on copper metal at 425-550 DEG C. and azelaic acid (21 per cent) and suberic acid (6 per cent) are recovered as in (1).  The Specification as open to inspection under Sect. 91 relates to the preparation of aliphatic dicarboxylic acids having long chains between the carboxyl groups by oxidizing long chain unsaturated aliphatic monocarboxylic acids or their esters with an oxygen containing gas in the vapour phase and in the presence of an oxidation catalyst and is not restricted to the above methods of isolating the desired products.  This subject-matter does not appear in the Specification as accepted.ALSO:Catalysts for use in the vapour phase catalytic oxidation of long chain unsaturated aliphatic monocarboxylic acids or their esters to yield aliphatic dicarboxylic acids (see Group IV (b)), comprise compounds of metals belonging to the fourth to eighth vertical groups inclusive of the periodic system, e.g. compounds of titanium, vanadium, molybdenum, manganese, iron, cobalt, nickel and platinum; suitable carriers are porous or sintered substances such as aluminium oxide, clays containing aluminium oxide, silica, zeolites and pumice and metals such as copper, nickel, iron, aluminium and silver.  Catalysts used in examples are (1) a mixture of titanium vanadate and titanium dioxide on 2-4 mm. particle size aluminium oxide; (2) vanadium pentoxide on silica (2-4 mm. size) or copper metal (1-4 mms size); (3) vanadium pentoxide containing 2-10 per cent of Fe2O3 and OsO3 on pumice