Zeolite reaction conditions impact

Reactions for the synthesis of fine chemicals differ in many aspects from the hydrocarbon reactions that constitute today the major application of zeolites and other micro- or mesoporous catalysts, as they often involve the transformation of molecules with several functional groups. Chemoselectivity is therefore of prime importance. These reactions are generally operated in rather mild conditions and condensed media (rather than vapour phase) to avoid undesired secondary reactions. The use of solvents can have major impacts on the activity and selectivity of these catalysts as they may affect the adsorption and desorption of reactants and products on these catalysts. 

Under these conditions, the zeolite HY was very stable. During the first cycle (Table 14.7) we have observed a slight dealumination of the HY zeolite, probably by dissolution of extraframework alumina and generation of mesopores, because we did not observed any impact on the integrity of the catalyst. After the first cycle, the kinetics of the reaction increased and then stabilized. 

The scope of this paragraph is to analyze the impact of internal washcoat diffusion on the performance of zeolite-based catalysts both by experimental and simulation results. In the first part, an experimental study of mass transfer limitations in Fe- and Cu-zeolite catalysts performed by Metkar et al. [40] is presented. The authors investigated catalysts with different washcoat loadings, washcoat thicknesses, and lengths under various SCR reactions in order to identify the presence of diffusion limitations throughout an extended temperature range. In the second part, the flow-through catalyst model, presented in Sect. 13.2, was employed to reproduce the test conditions of the fore-mentioned experiments. 

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