2017 Volume 60 Issue 3 Pages 146-153
Aluminosilicate and ferrisilicate with the MTW-type zeolite structure were hydrothermally prepared and used to catalyze the methylation of 2-methylnaphthalene (2-MN) under supercritical conditions in a batch-type reactor. Dimethylnaphthalene (DMN) and 1-methylnaphthalene (1-MN) yields increased with decreasing Si/Al ratio of the zeolite. In contrast, ferrisilicate with the MTW-type zeolite structure (Si/Fe=100) exhibited higher DMN selectivity and the β,β-DMN fraction in total DMNs was higher than that over aluminosilicate with MTW structure (Si/Al=100). Kinetic analysis of 2-MN methylation over MTW zeolites was conducted, to obtain the reaction rate constants and apparent activation energies. The activation energy for the methylation of 2-MN over aluminosilicate with MTW structure was 176 kJ mol−1, which was almost the same as that for the ferrisilicate with MTW structure. This indicates that the mechanism for methylation is independent of hetero-atoms species in the MTW zeolite framework. The introduction of Fe atoms into the framework significantly decreased the rate constant for the isomerization of 2-MN compared with that for the methylation of 2-MN. Therefore, ferrisilicate with MTW structure is effective for 2-MN methylation due to the decrease of the isomerization rate.
