Isomorphous substitution of trivalent iron in mesoporous MCM-48 silicate molecular sieves: Synthesis, characterization and catalytic properties

Abstract

Trivalent iron-substituted MCM-48 (FeMCM-48) was synthesized and characterized by various analytical (XRD, N2 adsorption, TG-DTA and ICP-AES) and spectroscopic (DRUV-VIS, FTIR and ESR) techniques. An NH3-TPD study suggests the presence of high concentration of moderate Brønsted acid sites. The catalytic performance of the protonated catalyst (H-FeMCM-48) was evaluated for the tertiary-butylation of phenol, and the results indicate that the activity for the chosen reaction is comparable or slightly higher than H-FeMCM-41 but lower than their corresponding aluminium and gallium analogues. The observed lower activity is attributed to the low concentration of Brønsted acid sites in the iron analogues. On the other hand, the latter shows much higher para-tertiary-butyl phenol selectivity of as compared to many other catalysts reported so far.