Influences of pore sizes on the catalytic activity of Fe-MCM-41 in hydroxylation of phenol

A series of Fe-MCM-41 with different pore sizes were synthesized by changing alkyl chain lengths of surfactants and the properties of the pore structures were characterized by XRD, BET, TEM and UV-visible techniques. The results show that the pore size, pore volume, a0 and regularity of Fe-MCM-41 increase as alkyl chain lengths of surfactants increase, while the content and the coordination state of iron species in catalysts remain constant. The pore sizes of Fe-MCM-41s have an important effect on their catalytic activity in the direct hydroxylation of phenol by H₂O₂. The conversion of phenol decreases as the pore sizes become larger, whereas the selectivity of diphenol rises.