Transient analysis of reactions between NO and H2 with Pt-Al2O3 thin film catalyst

Abstract

Transient pulse techniques using time-of-flight mass spectrometry were used to investigate the reduction of NO by H 2 over Pt/Al 2 O 3 thin film. A typical result measured at 400 °C shows different behaviors of N 2 , NH 3 and N 2 O. Changing the temperature with corresponding numerical simulations, we elucidated that N 2 O was produced via a consecutive process of NO reduction with NH 3 molecules. A specially designed apparatus employing (1) pulse valves for injection of reactant molecules onto catalysts and (2) a time-of-flight mass spectrometer was used to investigate processes of NO + H 2 reaction using Pt-Al 2 O 3 thin film on Si substrate. First, the planar layer of the catalyst was located in a vacuum chamber and the reactants were supplied onto the surface by pulse valves. This process is considered to involve few consecutive reactions. There, the transient production of N 2 and NH 3 was observed simultaneously. Second, the reactants were supplied into the micro reactor filled with square pieces of planar catalysts spaced with SiC balls. Here, N 2 O was observed as well as NH 3 and N 2 . The experiments and the numerical simulation of the NO and H 2 reaction rates clearly elucidated some aspects of NO reduction passes, i.e., while N 2 and NH 3 were directly produced from N and H adatoms dissociated from NO and H 2 admolecules, N 2 O was produced via consecutive process of NO reduction with NH 3 molecules which were produced in transient reactions.