A HYDROGEN NITRIC-OXIDE CELL FOR THE SYNTHESIS OF HYDROXYLAMINE

A H-2-NO fuel cell was designed for the synthesis of hydroxylamine in the gas phase. The hydroxylamine produced was trapped in an aqueous so lution of H2SO4 held in a silica-wool disk used as an electrolyte barr ier for H-2 and NO. Among the cathode electrocatalysts tested, iron-ph thalocyanine (Fe-Pc) impregnated in graphite was the most favorable on e for selective synthesis of hydroxylamine. Active carbon and carbon w hiskers used to support the Fe-Pc enhanced the formation of hydroxylam ine remarkably. The carbon itself slightly catalyzed the formation of N2O and NH2. Excluding the effects of the support, Fe-PC catalyzed the electrochemical synthesis of hydroxylamine with high selectivity (equ ivalent to 100%). Applied voltage across the cell did not appreciably enhance the formation of hydroxylamine. The reaction under short-circu it conditions was most favorable for the synthesis of hydroxylamine. I t is suggested that the reduction of NO occurs on the Fe-2+ site of Fe -Pc with protons and electrons transferred from the anode. The very se lective synthesis of hydroxylamine over Fe-Pc must be ascribed to an F e-2+ site isolated by phthalocyanine ring. This isolation prohibits bo th the formation of N2O through the intramolecular elimination of H2O from the adjacent NHO intermediates and the formation of N-2 and NH2 t hrough the breaking of N-O bonds.