Abstrakt
In this contribution, zeolites with different pore sizes and connectivity (MFI 10-10-10R, MTW 12R, Beta 12-12-12R) were prepared in bulk and hierarchical "nanosponge" form and with different composition (aluminosilicate, gallosilicate). Properties of the samples were characterized by X-ray diffraction, argon adsorption, transmission electron microscopy and adsorption of pyridine followed by FTIR spectroscopy.
Catalytic performance (conversion of reactants, yields of products and turn-over frequencies) of prepared materials was investigated in the Pechmann condensation of resorcinol with ethyl acetoacetate. The lowest conversion (less than 15%) over the MFI samples suggests that its 10R channels are too narrow for the products to escape from the framework and thus the reaction proceeds mainly on the crystal surface.
Conversion of reactants over MTW and Beta zeolites is higher (10%, 35%, 71% and 69% for bulk MTW, nanosponge MTW, bulk Beta and nanosponge Beta, respectively), however, undesired side-products are formed. The hierarchical form of MFI and MTW gives higher conversions and yields of products than their bulk counterparts.
Interestingly, the difference between bulk and hierarchical Beta is negligible. The overall performance of aluminosilicates and gallosilicates in the reaction is comparable.
Catalytic activity of the samples was determined mainly by their textural properties.