Catalytic reduction of aromatic mononitro compounds

摘要

Compounds of the general formula: wherein X is an alkyl substituent of 1 to about 18 carbon atoms and n has a value 0 to 5 are reduced in the liquid phase and in the absence of added solvent to the corresponding amino compound with hydrogen in the presence of a noble metal catalyst of the platinum group having a surface area of at least 150 sq. in./gm at 25 DEG to 125 DEG C. while maintaining the water of reaction as a well dispersed separate liquid phase in the reaction zone during the reaction. The reaction may be carried out in a batchwise manner but is preferably carried out continuously by continuously introducing the nitro compound, catalyst and hydrogen into the reaction zone, continuously withdrawing amino reduction product at a rate equal to the feed input of the reactants, and withdrawing water of reaction from the reaction zone only as amino product is withdrawn. Specified nitrobenzenes which may be used as starting material are nitrobenzene, orthonitrotoluene, para-nitrotoluene, orthonitro ethyl benzene, para-nitro ethyl benzene, the nitroxylenes e.g. 4-nitro-o-xylene, 5-nitro-m-xylene and 2-nitro-p-xylene, nitro(2)-mesitylene, 5-nitro-1,2,3,4-tetramethyl benzene and 3-nitro-1,2,4,5-tetramethy benzene. The catalyst is usually employed on a suitable carrier, e.g. carbon or alumina, in a concentration of from 0.1% to 10% by weight based on the weight of the support. The reaction may be carried out pressures from atmospheric to 150 p.s.i.g. or even higher. U.S.A. Specifications 1,111,502, 1,174,245,2,292,879 and 2,458,214 are referred to.