Ion exchange and catalytic properties of methylammonium FAU zeolite

Ion exchange of methylammonium cations (Me) in Na-Y zeolite (FAU) and the properties of the resulting Me-Y material (Me=(CH3)iNH4-i+;i=0–4) was studied. Results indicated that the ion exchange equilibrium can quickly be reached, even when voluminous tetramethylammonium cations are used. XRD results indicated that the cation distribution along zeolite crystals is uniform but, due to stereo-spatial reasons, methylammonium cation cannot replace all sodium cations present in the zeolite: the ion exchange of organic cations is restricted to the supercavity. XRD also shows that as the voluminous methylammonium cations are incorporated in compensation sites, they produce an expansion of the unit cell of the Faujasite. Physisorption of nitrogen evidences that as the ion exchange level increases, the volume of micropores available in the zeolite crystals decreases proportionally. For the first time, the Me-Y zeolites, containing methylammonium cations in charge compensation sites, were evaluated as basic catalysts in Knoevenagel condensation, producing much higher yields than the ones obtained with cesium faujasite. These unique results open new perspectives for the use of these low-cost organic containing zeolites, in processes when the presence of basic sites is necessary.