Hydrochloric Acid → 4,6-Diaminoresorcinol Dihydrochloride

Participants

Reaction Steps

In detail, the process according to the invention is carried out, for example, as follows: a suspension of Pd (5%)/activated carbon catalyst in 1 to 30% by weight hydrochloric acid is initially introduced into a hydrogenation autoclave of a material which is resistant to aqueous hydrochloric acid. Under preferred hydrogenation conditions (60 to 80° C.; 10 to 20 bar H2), a 10 to 80% by weight solution or suspension of 1,3-dibenzyloxy-4,6-dinitrobenzene in toluene is pumped in within the course of 30 to 90 minutes, the concentration of 1,3-dibenzyloxy-4,6-dinitrobenzene, relative to the total quantity of toluene and aqueous hydrochloric acid, being 5 to 20% by weight and the 1,3-dibenzyloxy-4,6-dinitrobenzene/palladium weight ratio being, for example, 85:1. After the absorption of hydrogen has ceased, the stirring of the reaction mixture is continued, for example for 60 minutes, at 60 to 80° C. and 10 to 20 bar H2, the stirrer is stopped and about 66% of the two-phase reaction mixture of toluene and aqueous 4,6-diamino-resorcinol dihydrochloride solution containing hydrochloric acid is forced out of the hydrogenation autoclave by means of nitrogen through a riser consisting of a corrosion-resistant material and provided with a frit into a receiver. After the organic solvent (toluene) has been separated off by simple phase separation, the stable 4,6-diaminoresorcinol dihydrochloride can be isolated from the resulting aqueous solution containing hydrochloric acid, if appropriate after stripping of toluene and clarification from activated carbon, in the usual manner, for example by concentrating the aqueous solution and/or by precipitation with concentrated hydrochloric acid and/or by introducing gaseous HCl and/or, if appropriate, by salting out, for example with NaCl, or in any desired manner known to those skilled in the art, if appropriate after previous addition of a stabilizer, for example SnCl2. In the same way, several hydrogenations can be carried out successively with the Pd (5%)/activated carbon catalyst employed without a decrease in the catalyst activity, which leads to a very low catalyst consumption.

Provenance & Evidence