Abstract
Washcoated catalysts on honeycomb substrates are widely used as automotive catalysts, and it is well known that their catalytic performance is limited by gas transport resistance. In order to reduce the gas transport resistance, understanding the relationship between gas transport and pore properties is essential. Since a washcoat layer consists of porous metal oxide particles (e.g., Al2O3), the washcoat layer has two types of pores: primary pores, which are located inside the porous metal oxide particles themselves, and secondary pores, which are located among the porous metal oxide particles. We recently studied the effect of secondary pore connectivity on gas permeability by synchrotron X-ray computed tomography. Based on the results, we proposed a new model to predict the effective gas permeability of a washcoat layer by using parameters of the pore connectivity; however, the pore properties did not vary enough for this model to be validated. Therefore, in this research, we attempted to validate the model using a wide range of pore properties. In order to access various pore properties, 8 real washcoat layers and 12 virtual 3D structures were used. The pore properties of the real washcoat layers were determined using synchrotron X-ray computed tomography. The pore properties varied more widely in this study than in our previous study, thus allowing the model to be validated.
