150
6 Conversion of Methane to Aromatic Hydrocarbons
Fig. 6.2 Transient reaction of 4 wt% Mo/H-ZSM-5 with methane at 950 K (Reprinted with
permission from ref [93]. Copyright 2020 American Chemical Society)
However, unsupported molybdenum compounds (Mo, MoO 2 , MoO 3 , Mo 2 C, and
MoC (1-x) ) gave H 2 , H 2 O, and CO 2 as products were detected, Only a trace amount of
ethane was formed [100]. Therefore, Mo species such as Species (II–VI) are reduced
to lower-valent Mo species during the induction period and then further reduced to
Mo carbidic carbon, which must be supported on an H
+ -exchanged zeolite such as
H-ZSM-5 to obtain catalytic activity for the formation of aromatic hydrocarbons, as
will be discussed in the next section.
6.7 Active Species and Reaction Mechanism
for the Formation of Aromatic Hydrocarbons
The most investigated metal for the MDA reaction is Mo, because of its superior
activity. However, as mentioned in Sect. 6.4.4, in addition to Mo, several other metals
can be used to modify H
+ -exchanged zeolites for the catalysis of the MDA reaction.