Improvements in and relating to the production of amines

• Main Authors: WARD STANLEY, LAMB SIDNEY ARTHUR, HODGSON MAURICE ARTHUR ERIC
• Format: Patent
• Language: English
• Published: 21.07.1954

A continuous process for the production of alkylated aromatic amines comprises reacting an aromatic nitro compound and a dialkyl ketone with hydrogen under atmospheric or superatmospheric pressure and elevated temperature in the presence of catalyst comprising metallic copper. The process may be operated in the liquid or vapour phase. Mixed ketones may be used, to yield phenylene diamines having differing alkyl substituents. Suitable catalysts are copper on zinc oxide, copper on chromia, copper on alpha or gamma alumina, copper on mullite, copper on kieselguhr and reduced mixed copper oxide-magnesia - chromia containing metallic copper, copper on pumice and foraminate copper, e.g. foraminate copper/aluminium. Pelleted reduced copper oxide on chromia and copper on zinc oxide are preferred. Pelleting pressures of at least 15 tons per square inch are mentioned. Foraminate catalysts may be prepared by extraction, e.g. with aqueous alkali of up to 70 per cent of the aluminium from 1/4 inch to 5/16 inch granules of a copper aluminium alloy in which the weight ratio (Cu : Al) is 60 : 40. When using such catalysts mono-alkylated p-phenylene diamines are obtainable. Operating in the liquid phase temperatures of 100 DEG to 180 DEG C. (80 DEG to 250 DEG C. in the Provisional), preferably 120 DEG to 160 DEG C., and pressure 10 to 300, preferably 30 to 100, atmospheres are suitable. Inert solvents or excess ketone may be added. The space velocity is, e.g., 5 gram mols. of nitro compound per litre of bulk catalyst volume per hour. Heat developed in the reaction may be removed through the walls of the reactor, e.g. by a boiling liquid, or by recycling at least 50 per cent and preferably 85 per cent of reaction product. When ketones containing at least 4 carbon atoms are employed a cut comprising the ketone/water azeotrope obtained in distilling the product may be recycled and used for dissolving the nitro-compound, the water being thereby thrown out. In examples: (1) a mixture of p-nitroaniline, methyl ethyl ketone and recycled product is passed at N.T.P. with hydrogen over reduced copper chromite catalyst to give N,N-di-sec.-butyl-p-phenylene diamine, together with sec.-butanol, water, p-nitroaniline and p-phenylene diamine; (2) m-dinitrobenzene, acetone, recycled product and hydrogen passed over reduced copper chromite at 50 atmospheres and 110 DEG C. yield N,N1-diisopropyl-m-phenylene diamine together with small amounts of m-dinitrobenzene, m-nitroaniline, m-phenylene diamine, acetone, isopropanol and water; (3) p-nitroaniline, methyl ethyl ketone and recycled product passed with hydrogen over a foraminate copper aluminium catalyst (60 : 40 Cu : Al by weight) yielded a mixture of N-mono-and N,N1-di-sec.-butyl p-phenylene diamine (which were separated by precision fractional distillation) and small amounts of sec.-butanol, p - nitroaniline and p - phenylene diamine. Operating in the vapour phase suitable reaction conditions are 100 DEG to 285 DEG C. (350 DEG C. in the Provisional), 50 to 100 atmospheres, and at least the stoichiometric quantity of ketone. A table shows minimum hydrogen/liquid feed ratios for various temperatures and pressures in the vapour phase reaction of p-nitroaniline and methyl ethyl ketone to give N,N1-di-sec.-butyl-p-phenylene diamine. In vapour phase operation the catalyst may be employed as a fluidized bed. Other diamines that may be prepared are NN1 - diisopropyl - p - phenylene diamine from p - nitroaniline and acetone, N - sec. - butyl - p - phenylene diamine from p-nitro-aniline and methyl ethyl ketone, N,N1-diisopropyl-2,3,5,6-tetramethyl p-phenylene diamine from 2,3,5,6-tetramethyl - p - dinitrobenzene and acetone and N,N1 - di - (sec. - butyl) - m - phenylene diamine from dinitrobenzene and methyl ethyl ketone. The Provisional Specification refers to Specification 621,749. It also refers to using foraminate nickel catalysts in liquid phase operation and contains additional examples of a process similar to example (3) above.ALSO:Copper on zinc oxide, copper on chromia, copper on alpha- or gamma-alumina, copper on pumice and foraminate copper, e.g. foraminate copper/aluminium are specified as catalysts in a process for the production of alkylated aromatic amines by the reaction of an aromatic amine, a dialkyl ketone and hydrogen (see Group IV(b)). Preferred are pelleted reduced copper oxide on chromia and copper on zinc oxide, preferably formed using pelleting pressures of at least 15 tons per square inch. Foraminate catalysts are obtained by extraction, e.g. with aqueous alkali of up to 70 per cent. of the aluminium from 1/4 in. to 3/16 inch granules of a copper alloy in which the Cu:Al ratio is 60:40 by weight. In vapour phase operation the catalyst may be employed as a fluidized bed, copper on zinc oxide and copper magnesium chromite (i.e. reduced mixed copper oxide-magnesia-chromia containing metallic copper) preferrably to pass 200 mesh being specified. Specification 621,749 is referred to.