GB805249A - Catalytic reduction of aromatic dinitro compounds - Google Patents

Abstract

Aromatic diamines are prepared by reducing the corresponding dinitro compounds with hydrogen in the presence of a nickel or platinum metal hydrogenation catalyst, the process being characterized in that a solution of the dinitro compound, liquid at reaction temperature and pressure, is introduced into the hydrogenation zone, the solvent being one that will dissolve all the products of the reaction also, i.e. the diamine and the water, so that there is only one liquid phase in the hydrogenation zone throughout the whole reaction, the diamine being recovered from the solution when it has been removed from the hydrogenation zone. Specified solvents are morpholine, N-alkyl morpholines, butyrolactone, ethylenediamine, piperidine, N-alkyl piperidines, pyridine, N:N-dialkylamides, pyrollidone, methyl pyrollidone lower alkyl ethers of ethylene glycol and diethylene glycol and an aqueous solution of the aromatic diamines which are formed in the reduction containing about 15 to about 50 per cent of water. The invention also includes the reduction of aromatic dinitro compounds to the corresponding mononitro monoamino compounds. The reaction is carried out under conventional conditions for such reductions, i.e. 20-100 DEG C. and 25-150 lb./sq. inch gauge pressure. Specified catalysts are platinum black, platinum oxide, "Raney" nickel (Registered Trade Mark), palladized charcoal, platinized charcoal, nickel on kieselguhr or platinum or palladium on alumina. The reduction may be carried out batchwise or continuously. In examples: (i) m-dinitrobenzene is dissolved in m-phenylenediamine and water and reduced in the presence of 5 per cent palladized charcoal; (ii) as (i) using dimethylformamide; (iii) as (ii) but using nickel or kieselguhr; (iv) as (i) using the methyl ether of ethylene glycol and 10 per cent palladized charcoal; (v) as (iv) using pyrollidone; (vi) as (i) using butyrolactone; (vii) as (i) using methyl pyrollidone; (viii) as (i) using pyridine; (ix) as (ii) using 0.3 per cent palladized silica gel; (x) as (ix) using 0.5 per cent palladized alumina; (xi) as (ii) using a mixture of dinitrotoluenes; (xii) as (xi) using the ethyl ether of ethylene glycol and 1 per cent palladized charcoal; (xiii) as (iv) using "Raney" nickel; (xiv) as (iv) using 2:4-dinitro toluene and 5 per cent palladized charcoal; (xv) as (xiv) using o-dinitrobenzene; (xvi) as (xv) using a mixture of dinitrotoluenes; (xvii) as (xvi) using 0.5 per cent platinized alumina; (xviii) as (xv) using dinitroethylbenzene; (xix) m-dinitro benzene is reduced to m-nitroaniline using the methyl ether of ethylene glycol as solvent and a 10 per cent palladized charcoal catalyst.