Abstract: An improved process for the continuous preparation of hydroxylammonium salts by catalytic reduction of nitric oxide with hydrogen in a dilute aqueous solution of a mineral acid in the presence of a suspended noble metal catalyst at an elevated temperature in several reaction zones connected in series, wherein the improvement comprises maintaining a pH of <2.0 in the last reaction zone.

Abstract: A process for the preparation of hydroxylammonium salts by catalytic reduction of nitric oxide with hydrogen in a dilute aqueous solution of a mineral acid, in the presence of a suspended supported platinum catalyst, at elevated temperatures, wherein the reaction is carried out in a conventional manner, in one or more reaction zones, under superatmospheric pressure, and the exit gases produced are let down to a lower pressure, and are reacted, in a downstream reaction zone, with the reaction mixture, containing hydroxylammonium salt, the ammonium salt, the supported platinum catalyst and residual mineral acid, from the upstream reaction zone or zones, or with a fresh aqueous solution of the mineral acid, which contains the supported platinum catalyst in suspension.