Patent ID: 7417168

Claim:
A method for preparing hydroxylamine, which comprises the steps of: (i) pretreating an acidic buffer solution comprising an acidic buffer reagent, nitric acid or nitrates, and metal impurities, the pretreatment of the acidic buffer solution comprising the steps of: (a) adding a precipitant represented by formula (I) to the acidic buffer solution, [(A)aM(CN) 6 .xH 2 O] (I) wherein A is selected from the group consisting of IA metals and NH 4 , M is IIIB metals, a is an integer of 3 or 4, x is an integer of 0 to 10, and pH of the acidic buffer solution is less than 3.5, (b) reacting the precipitant with the metal impurities in the acidic buffer solution to form metal complexes, and (c) removing the metal complexes from the acidic buffer solution; and (ii) reducing nitrate ions provided by the nitric acid or nitrates in the acidic buffer solution with hydrogen in the presence of catalysts to give hydroxylamine.