There is great interest in reducing the size of zeolite particles, because this can improve their catalytic properties in various reactions. This work evaluates two faujasite-type X zeolites, one micrometric and one nanometric. Zeolites in the sodium form were exchanged ionically with methylammonium cations. The materials were then evaluated as catalysts in the Knoevenagel condensation reaction. Steric impediments restricted ion exchange in the micrometric zeolite and became more important with increasing cation volume. In the case of the nanometric sample, such impediments were less evident, because the smaller particle size provided greater access of exchanger cations, compared to the micrometric zeolite in which the sodium was inaccessible. The best catalytic performances were achieved with zeolites containing the monomethylammonium cation. The increased accessibility and diffusion of the reactants and products through the pores of the nanometric zeolite provided the best butyraldehyde conversions, independent of the exchanger cation. In order to increase accessibility to catalytic sites, several studies have been carried out in order to reduce the diameter of the particles of zeolites to the nanometer scale. This reduction can promote the increase in the activity of the catalysts in some reactions.