3.2. Catalytic activity of catalyst
To evaluate the catalytic performance of Fe-Mor and Fe-M-Mor, the
benzylation of benzene by benzyl chloride was chosen. The reaction
was firstly carried out under a mild reaction temperature (343 K). The
used amount of the catalyst is 50 mg. Fig. 4 shows the catalytic activities
of Fe-Mor and Fe-M-Mor with reaction time. It can be seen that
Fe-M-Mor quickly gave a reactive ability after an induction period of
10 min. The BC conversion nearly reached 100% in a reaction time of
10 min. Among the products, only the diphenylmethane (DPM) can
be observed. Comparatively, Fe-Mor took a long induction period of
about 50 min and the BC conversion reached 60% after 40 min. The apparent
reaction rate constant for Fe-M-Mor (155.4×10−3 min−1
) is
about ten times as that for Fe-Mor (14.7×10−3 min−1
) (Table 2).
This result indicates that Fe-M-Mor is a more active catalyst than
Fe-Mor in the benzylation. The reaction induction period seemed to depend
on the catalytic activity. The higher the activity is, the shorter the
induction period. This phenomenon has been observed in earlier work
Choudhary et al. think that the reaction induction period was
caused by the presence of moisture in reaction mixture and the catalysts
are activated during the initial reaction period. However, further study
need be done to understand the reason of induction period clearly.