Characteristic of zeolite washcoats on cordierite monoliths for environmental applications

J.M. ZAMARO; M.A. ULLA; E.E. MIRÓ

Rio de Janeiro (Brasil)

Congreso; ENPROMER 2005. 2nd Mercosur Congress on Chemical Engineering and 4th Mercosur Congress on Process Systems Engineering; 2005

Several preparation variables were analyzed which might affect the characteristics of zeolite coatings on cordierite monolith structures obtained by washcoating. It was found that zeolite type, suspension concentration, number of immersions, solvent, particle size, and additives impinge on coating quality. When the suspension concentration is increased, a non-linear increment of the load is obtained. At the same time, the zeolite film thickness increases linearly at the channel centers but at a steadily slower rate at the corners, reaching a plateau after several immersions. This effect modifies the transversal geometry of the channel making it more circular. Besides, the load achieved after several immersions in diluted suspensions produces a greater homogeneity of the deposit. At microstructural level, zeolite deposition involves the anchoring of particles on the surface porosity of the cordierite support. For this reason, the characteristics of the zeolite particles and the support surface affect the level of insertion. For the zeolites under study (ZSM5, Mordenite and Ferrierite) a smaller size of the deposited aggregates provokes a higher mechanical stability of the deposit. The size of those aggregates and their intrinsic stability also seem to be influenced by the type of solvent employed. This latter variable can also be used to modify almost all the deposit characteristics here studied (load, thickness, geometry and stability). Finally, the addition of additives (SiO2) to the suspension improves the mechanical stability of the three zeolites under analysis.