CH 3NH 2 decomposition and oxidation on polycrystalline platinum: Steady-state kinetics and oscillations

Abstract

Steady-state rates of decomposition and oxidation of methylamine on polycrystalline platinum between 600 and 1500 K have been studied in a mixed reactor with methylamine and oxygen partial pressures from 0.2 to 6 Torr. HCN and H 2 are the dominant products (>98%) in excess methylamine. In excess oxygen, CO, N 2O, NO, and H 2O increase but HCN remains the major product up to a twofold excess of oxygen. Less than 2% of CH 4, NH 3, CO 2, or C 2N 2 is produced under any conditions. Reaction rates rise rapidly up to ~950 K, and most reactions appear to become flux limited by ~1100 K. The reaction probability of methylamine at high temperature varies from 0.025 in a 4 1 methylamine excess to 0.010 in 2 1 oxygen excess. The reaction probabilities of oxygen are ~0.003 and are independent of methylamine pressure. These results suggest that CH 3NH 2 → HCN is the dominant reaction channel even in excess oxygen and that oxygen mostly reacts with atomic hydrogen but does not significantly affect the CN bond in CH 3NH 2. Oscillations of wire temperature and reactor pressure occur at excess methylamine, while multiple steady states are observed in excess oxygen. These are caused by heat effects of the endothermic decomposition reaction and the exothermic oxidation reaction.