Figure 4. (a) Effects of zeolite shell thickness on
K-ZnFe2O4@K-ZSM-5 catalytic performance;(b) Paraffins composition over composite catalysts with
different shell thickness; (c) Detailed product distribution
over composite catalysts with different shell thickness.
TG analysis of spent ZnFe2O4 and
zeolites was shown in Figure S11. The spent
K-ZnFe2O4 have more more obvious degree
of carbonization than spent Na-ZnFe2O4,
and the rising curve is the process by which iron-carbon compounds is
converted to ferrites. When K-ZnFe2O4 is
coupled with different ZSM-5, there are more iron-carbon compounds on
K-ZSM-5 after the reaction, not only carbon deposits in H-ZSM-5. With
the introduction of K-ZSM-5, Na-ZnFe2O4has more carbon deposition resulting in reduced activity, and
K-ZnFe2O4 is not easily sintered.
Among different zeolite treated by K ion exchange startegy, the
K-ZnFe2O4@K-ZSM-5 exhibited an excellent
performance of CO2 hydrogenation. The catalytic
performances of K-ZnFe2O4 coupled with
different kinds of K-modified zeolites were shown in Figure S12 and
Table S7. The introduction of K-ZSM-5 in composite system displayed the
best C5+ hydrocarbons selectivity, which indicates that
ZSM-5 with K ion exchange promoted the secondary reaction of olefins to
form gasoline-range products due to its unique acidic and pore
structure.