Basic catalyzed Knoevenagel condensation by FAU zeolites exchanged with alkylammonium cations

This work concerns about ion exchange and basic properties evaluation of faujasite zeolites containing alkylammonium cations. The starting materials were sodium FAU zeolites with two Si/Al ratios (1.4 and 2.5) and alkylammonium cations with different degrees of substitution of methyl radical or alkyl chain length. Results showed that aqueous ion exchange equilibrium is readily achieved, even using (CH3)(4)N+ voluminous cation. Due to the lack of space to diffuse inside of some cavities, none of the organic cations completely exchanged sodium cations in the zeolite, being the exchange restricted to the large cavity. The maximum exchange degree diminishes with increase of the cation volume and aluminum content. Micropores volume decrease linearly with increasing exchange degree and with size of the compensation cation. These organic cations containing faujasites were evaluated as catalyst in the Knoevenagel condensation, leading to higher yields when Cs-FAU is used. This unique result opens news perspectives for application of these highly basic and low-cost molecular sieves. (C) 2007 Elsevier B.V. All rights reserved.