Method of producing aminophenol using a rhodium/carbon catalyst with synergistic quantities of rhodium, trichloride or rhodium tribromide

Claim 1

A method of preparing aminophenol comprising the steps of: a. hydrogenating a nitrobenzene substantially to completion by feeding hydrogen to a reaction mixture containing the nitrobenzene in the presence of aqueous sulfuric acid and a hydrogenation catalyst which comprises platinum group metal wherein from 10 to 80% of said platinum group metal is in the form of a rhodium salt selected from the group which consists of RhCl 3 and RhBr 3 and from 20 to 90% of said platinum group metal is in the form of elemental Rh, Pt, Pd or Ru and wherein the balance of said catalyst comprises carbon to produce a para-aminophenol in an aqueous phase containing the latter at a temperature of from 80 to 110° C and at 1 to 3 atmospheres; b. terminating hydrogen feed to said reaction mixture: c. thereafter charging the reaction mixture with a quantity of fresh nitrobenzene as required to repeat step (a); d. thereafter premitting said aqueous phase to separate from the nitrobenzene phase; e. next removing said aqueous phase from said reactor while retaining said nitrobenzene phase and said catalyst therein; f. thereafter adding fresh sulfuric acid to the reactor; g. repeating steps (a) through (f) in succession to transform nitrobenzene semicontinuously into said para-aminophenol; and h. recovering the para-aminophenol thus formed from the aqueous phases removed from said reactor.

Claim 2

A method of preparing aminophenol comprising the steps of: a. hydrogenating a nitrobenzene substantially to completion by feeding hydrogen to a reaction mixture containing the nitrobenzene in the presence of aqueous sulfuric acid and a hydrogenation catalyst which comprises platinum group metal wherein from 10 to 80% of said platinum group metal is in the form of a rhodium salt selected from the group which consists of RhCl 3 and RhBr 3 and from 20 to 90% of said platinum group metal is in the form of elemental Rh, Pt, Pd or Ru and wherein the balance of said catalyst comprises carbon to produce a para-aminophenol in an aqueous phase containing the latter at a temperature of from 80 to 110° C and at 1 to 3 atmospheres; b. terminating hydrogen feed to said reaction mixture: c. thereafter charging the reaction mixture with a quantity of fresh nitrobenzene as required to repeat step (a); d. thereafter premitting said aqueous phase to separate from the nitrobenzene phase; e. next removing said aqueous phase from said reactor while retaining said nitrobenzene phase and said catalyst therein; f. thereafter adding fresh sulfuric acid to the reactor; g. repeating steps (a) through (f) in succession to transform nitrobenzene semicontinuously into said para-aminophenol; and h. recovering the para-aminophenol thus formed from the aqueous phases removed from said reactor.