Ammonia desorption behavior

Y. Shimizu, T. Okamoto, Y. Takao, M. Egashira, Desorption behavior of ammonia from Ti02-based specimens-ammonia sensing mechanism of doublelayer sensors with Ti02-based catalyst layers , Journal of Molecular Catalysis A Chemical, 155, 183-191, (2000). 

Ammonia adsorption/desorption— The interaction of NH3 with the catalyst surface is obviously important for SCR applications, as it is well known that the DeNOx performances and the dynamics of SCR converters are governed by the reactivity of adsorbed NH3. The adsorption-desorption behavior of NH3 (R.1-R.2 in Table 18.1) was first studied performing isothermal NH3 feed... 

The hydrothermal deactivation of Y zeolite containing 0, 4, 7 and 12 wt.% of REO and its effects on catalytic activity, stability and selectivity were investigated. The Y zeolites were hydrothermally deactivated at 788°C in three consecutive cycles of two hours each. The fresh and deactivated zeolites were characterized by measuring Unit Cell Size (UCS) and surface area. The acidic properties were measured by the Temperature Programmed Desorption (TPD) of ammonia and IR-pyridine desorption. In order to correlate structural, textural and acid properties with catalytic behavior, the zeolites were evaluated in the conversion of cyclohexane. The Hydrogen Transfer Index (HTI) measured as a ratio of paraffins to olefins is a parameter of the selectivity. It was found that the REO was incorporated into zeolite structure up to high concentrations modifying to some extent XRD deflection, the acidic properties and the HTI ratio. After deactivation, the acidity and HTI were diminished and the Lewis/Bronsted acid ratio was modified. HTI decreased as REO concentration increased. 

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