Effective diffusivities and pore-transport characteristics of washcoated ceramic monolith for automotive catalytic converter

Multi-scale modelling of reaction and transport in porous catalysts

“…2 the overall, bimodal pore size distribution of the reconstructed catalytic layer corresponds well to the experimentally determined pore size distribution for the washcoated catalyst of the Pt/ -Al 2 O 3 type (cf. Starý et al, 2006). Hence two types of the pores can be clearly distinguished: the small meso-pores inside the -Al 2 O 3 micro-particles, and the larger macro-pores forming the space between the individual -Al 2 O 3 micro-particles.…”

“…The pore-size maximum is located around r = 4 nm, which is in good agreement with the experimentally obtained pore size distribution (cf. Starý et al, 2006). A key property of the porous supported catalyst is the magnitude of accessible surface of Pt particles-it determines the number of active sites for heterogeneous catalytic reactions (Ertl, 2002;Chorkendorff and Niemantsverdriet, 2003).…”

“…The discretisation and numerical solution methods are discussed in more elsewhere (Ko cí et al, 2007a). Values of overall effective diffusion coefficients D eff k in typical -Al 2 O 3 -based porous washcoat used in monolith converters of automobile exhaust gases were evaluated experimentally by, e.g., Starý et al (2006) and Zhang et al (2004). The measured values for CO at 298 K vary from 1 × 10 −7 to 1 × 10 −6 m 2 s −1 ; the higher value seems to be more typical.…”

Evaluation of local pore sizes and transport properties in porous catalysts

“…The purpose of the present work is to characterise a porous medium by its local pore radii and compare obtained output pore size distribution with results evaluated by virtually capillary condensation method (Štěp anek et al, 1999, 2007) and experimentally measured pore size distribution (Starý et al, 2006). The second aim is to extend our methodology for the continuum-based modelling of reaction-diffusion problems in virtual porous media also to situations where diffusion is predominantly in the Knudsen regime.…”

Preparation and properties of nanophase (Ce, Zr, Pr)O2-doped alumina coating on cordierite ceramic honeycomb for three-way catalysts

“…The cordierite ceramic substrate (2MgO • 2Al 2 O 3 • 5SiO 2 ) has high mechanical strength, a small pressure drop and a low thermal expansion coefficient (Zotin et al, 2005), but the specific surface area of the cordierite ceramic honeycomb is small (<1m ). In order to improve the catalytic activity, a coating material of high specific surface area should be deposited on the surface layer of the cordierite ceramic honeycomb (Hirohumi et al, 2001;Stary et al, 2006). γ-Alumina is a coating material that is currently being used to expand the specific surface area (Yue et al, 2005;Aguila et al, 2008).…”