INVESTIGATION OF INSTABILITY OF OXIDATION OF H2 AND NH3 + H2 PLATINUM

Abstract Kinetics of oxidation reactions of H2; and mixture H2 + NH3 on Pt has been studied at atmospheric pressure using a compensative electrothermography method. Existence of multiple steady states of catalyst activity and of isothermal critical phenomena is demonstrated for the system H2 + O2. Regions of reaction occurence are singled out and studied. Relaxation autooscillations of activity are detected. The phenomena observed are interpreted in terms of the hypothesis of branching-chain surface process. The study of critical phenomena in the mixture H2 + NH3; points to a common nature of active centres at oxidation of H2 and NH3 on Pt. A possible explanation of physical nature of active centres (a.c.) in the branching-chain surface process is proposed; the hypothesis suggests that a.c. are represented by catalyst adatoms.