A new class of solid Lewis acid catalysts based on interlayer expansion of layered silicates of the RUB-36 type with heteroatoms

Interlayer expanded zeolites are derived from layered zeolite precursors by inserting a tetrahedrally coordinated atom (T-atom) in between the precursor layers. To achieve this expansion, a Si source like dichlorodimethylsilane or diethoxydimethylsilane is typically used. In the interlayer expansion of the layered zeolite precursor RUB-36, an Fe salt instead of a silylating agent was used to fill up the linking sites in between the layers. The obtained material showed a shift of the first XRD reflection similar to that of RUB-36 interlayer expanded with dichlorodimethylsilane, indicating an increase in interlayer distance. Diffuse reflectance UV-vis spectra and EPR characterization proved the incorporation of isolated Fe sites. Using FTIR spectroscopy with pyridine and acetonitrile as probe molecules, it was found that the incorporation of Fe results in an increase in Lewis acidity. The material was successfully used as a catalyst in the acylation of anisole with acetic anhydride and in the alkylation of toluene with benzyl chloride. The Fe incorporation proved to be remarkably stable. In spite of the HCl production during the alkylation reaction, no leaching was observed and the catalyst could be reused after regeneration.