Measurement of the effective diffusion coefficient of nitrogen monoxide through porous monolith-type ceramic catalysts

Abstract

This Research Note describes a straightforward experimental technique to measure the effective diffusion coefficient of nitrogen monoxide through the porous walls of a monolith-type ceramic catalyst. The method takes explicit advantage of the geometric shape of a monolith-type catalyst to measure the steady-state diffusion flux of nitrogen monoxide through the porous catalyst. It is found that the tortuosity factor of the commercial titania-supported catalysts used in this study and employed for the selective catalytic reduction of NO by NH3 ranges from 2.0 to 2.3.

An Experimental and Kinetic Modelling Study for Methane Oxidation over Pd-based Catalyst: Inhibition by Water

“…The effective diffusion coefficient was evaluated according to a modified Wakao-Smith random pore model for monolith catalysts used in selective catalytic reduction (SCR) of NO x as reported by the Tronconi group [42,43], where they determined the value to 5 × 10 −6 m 2 /s [42,44]. This value was successfully used in several models reported in literature [45][46][47].…”

Kinetic Modeling of Dynamic Aspects of the Standard NH3-SCR Reaction Over V2O5-WO3/TiO2and Fe-Zeolite Commercial Catalysts for the Aftertreatment of Diesel Engines Exhausts

“…Enthalpy balances for the gas and for the solid phase are included to account also for thermal effects. In addition, intra-phase diffusional limitations are accounted for by equations for diffusion-reaction of the gaseous reactants in the porous catalytic monolith wall or washcoat, with effective diffusivities evaluated from the catalyst morphological data according to a modified WakaoSmith random pore model [19]. The resulting set of model PDEs was solved numerically according to the method of lines, applying orthogonal collocation techniques to the discretization of the unknown variables along both the z (axial) and x (intraporous) coordinates, and integrating the resulting ODEs in time by Gear's algorithm for stiff systems.…”

Using temporal analysis of products and flux response technology to determine diffusion coefficients in catalytic monoliths

“…Since its initial conception, many modifications to the Wicke-Kallenbach system have been made which do allow the direct measurement of monoliths (Beeckman 1991;Hayes et al, 2001). However, the fundamental problem with the procedures cited is that the transport through the washcoat alone is not measured, but that the transport through both the monolith, e.g.…”