Cordierite monoliths were washcoated with slurries of different zeolites (ZSM5, b zeolite, mordenite, and Zeolite Y) in order to establish the relationship between washcoat characteristics and the powder and slurry properties. To achieve this objective, initially, the zeolite particle size was reduced to 2-3 lm by wet ball milling, and during this process the crystallinity and surface area of the powder were not significantly affected. The rheological behavior of the zeolite slurries is a function of the type of zeolite and solid content. The washcoat properties, such as loading, thickness, uniformity, and reproducibility, depend on the particle size of the powder, number of immersions, slurry concentration, slurry viscosity, and surface tension. The mechanical stability of the zeolite washcoat decreases with an increase in cumulative loading and slurry particle size. Addition of binder (colloidal silica) results in an improvement in zeolite loading and washcoat adherence.H. Du-contributing editor

No abstract

No abstract

in Wiley Online Library (wileyonlinelibrary.com).ZSM5 washcoated monoliths with zeolite loading ranging from 10 to 60 wt % were prepared, characterized, and examined for disproportionation of toluene. Toluene conversion increased with temperature and W/F Ao but decreased with washcoat thickness. The selectivity of the most desirable isomer (p-xylene) increased with a decrease in temperature, W/F Ao and washcoat thickness. The high selectivity to p-xylene indicates that the initially formed para isomer is easily removed from the zeolite pores in the thin washcoat to the bulk gas phase preventing further isomerization of the primary product. A reaction scheme has been proposed for this reaction and the kinetic parameters determined for the 10 wt % ZSM5 monolith. A one-dimensional reactor model was developed to predict the performance of the reactor for disproportionation of toluene. The model equations were coupled with a module to calculate the concentration profile in the washcoat by considering the effect of diffusion and reaction.

No abstract