Abatement of Aniline in Supercritical Water Using Oxygen as the Oxidant

Abatement of aniline in supercritical water was explored in a tubular-flow reactor using oxygen as the oxidant. The effects of the reaction temperature, oxidant stoichiometric ratio, residence time, and initial aniline concentration on the product distribution were investigated. Aniline was primarily hydrolyzed to phenol and ammonia, and thereby, abatement of aniline was converted into the co-oxidation of phenol and ammonia in supercritical water. Phenol was the main carbon-containing intermediate, and ammonia was the exclusive nitrogen-containing intermediate on the pathway to the end products N₂, N₂O, and NO₃^–. Owing to the adsorption of aniline and catalysis on the reactor wall (made of Hastelloy C-276), the disappearance of ammonia during aniline supercritical water oxidation (SCWO) was markedly faster than that during SCWO of ammonia alone. Ammonia was mainly converted to N₂ (heterogeneous mechanism), and low levels of N₂O and NO₃^– were also produced (homogeneous mechanism)