Acid and redox activity of template-free Al-rich H-BEA* and Fe-BEA* zeolites

Abstract

Al-rich template-free BEA* zeolite (Si/Al 4.6) was synthesized and its structure was analyzed in comparison with the conventional H-BEA* zeolite of Si/Al 11.3 using XRD, N2 sorption, SEM, FTIR, 27Al 3Q and 29Si MAS NMR spectroscopy, and DFT calculation of the deprotonation energies. The Al-rich H-BEA* exhibited a high concentration of Brønsted and Lewis sites, both of high acid strength, although AlSiAl sequences were present in the framework. In Al-rich Fe-BEA* the exchanged Fe ions, Fe–oxo species, and Fe–oxo oligomers were identified by UV–vis spectroscopy. Cracking of n-decane, alkylation of benzene with benzyl alcohol and hydroamination of styrene with aniline to (anti)Markovnikov phenyl-[2-phenylethyl]amine over H-BEA*, and decomposition of N2O and NH3-SCR-NOx over Fe-BEA* were investigated in relation to the concentration and nature of acid and Fe-redox sites. The high concentration of Al-related active sites and the highly regular structure of Al-rich beta zeolite are directly manifested in enhanced activity compared with conventional Si-rich beta zeolite.