(NH4)2SiF6-modified ZSM-5 as catalysts for direct hydroxylation of benzene with N2O: 2. A comparative study with ferrisilicalite and dealuminated and iron-exchanged ZSM-5

The direct hydroxylation of benzene with nitrous oxide was studied over two HZSM-5 zeolites and over ferrisilicalite. HZSM-5 zeolite was dealuminated with (NH4)2SiF6 as described previously, with steam treatment, with high-temperature calcination, and with steam treatment and subsequent acid wash. Furthermore one sample was exchanged with aqueous Fe(NO3)3, treated with Na2S2O4, and acid-washed. The samples were characterized with regard to their elemental composition and textural, structural, and acid–base properties, using a variety of methods such ICP-AES, XRD, BET, NMR, FTIR, and 1H and 27Al MAS NMR. The catalytic performance was correlated to acid–base and textural properties of all the materials. Samples treated with (NH4)2SiF6, according to a method developed in our laboratory, combined high activity with excellent resistance to deactivation compared to the other examined materials.