DOI: 10.1039/C5CC03087K
Page 3 of 4
Journal Name
ChemComm
COMMUNICATION
followed by aromatization over the MoOx species. Both the 2) As a weak solid acid, the SiO support may also participate the
2
rearrangement and the cracking of C alkenes can be promoted by reaction by promoting the rearrangement or cracking of C alkenes
9
9
acid sites. From these reactions, carbocation intermediates will be which is the essential step in the conversion of isophorone to C -C9
8
produced. Because the stability of carbocation decreases in the order aromatic hydrocarbons.
of tertiary carbocation > secondary carbocation > primary carbo-
1
00
cation, the rearrangement and cracking reaction are preferred at the
carbon which is connected with two methyl groups (labelled with *
in Scheme 1). For the rearrangement of methyl group, the ortho-
migration is relatively easier than the meta-migration. As the result,
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0
1
,2,4-trimethylbenzene and 1,2,3-trimethylbenzene are produced as
the major C aromatic hydrocarbons.
60
9
The effect of MoO content on the performance of the MoO /SiO
Carbon yield of C -C aromatic hydrocarbons (%)
8 9
x
x
2
catalyst was also studied. From the results illustrated in the entry 1
and entries 13-16 of Table 1, the isophorone conversion and the
carbon yield of C -C aromatic hydrocarbons increase with the
Carbon yield of C9 cycloalkenes (%)
Conversion of isophorone (%)
4
0
in-situ calcinlation
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9
increment of MoO content, reach the maximum when MoO content
x
x
20
0
is about 15 wt%, then stabilize. Over the 15 wt% MoO /SiO2
x
catalyst, the isophorone is completely converted, high carbon yield
of C -C aromatic hydrocarbons (~80%) was achieved (Table 1,
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9
2
5
8
11 14 17 20 24
Time (h)
2
5
8
entry 15).
To figure out the role of SiO support in the transformation of
isophorone to C -C aromatic hydrocarbons, we also investigated the
catalytic performances of the SiO support and the physical mixture
2
Figure 1. Isophorone conversion and carbon yields of different products
over the 15 wt% MoO /SiO catalyst as the function of reaction time.
Reaction conditions: 723 K, 0.1 MPa H , 2.0 g catalyst, isophorone flow rate:
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9
x
2
2
2
-
1
-1
of MoO and SiO (denoted as MoO + SiO catalyst). To facilitate
x
2
x
2
0.04 mL min , hydrogen flow rate: 80 mL min .
the comparison, the contents of Mo and Si in the MoO + SiO2
x
Finally, we also studied the stability of the MoO /SiO catalyst in
catalyst were controlled the same as those in the 15 wt% MoO /SiO2
x
2
x
the conversion of isophorone to C -C aromatic hydrocarbons. From
catalyst. From entries 18-19 of Table 1, the SiO has low activity for
8
9
2
the results show in Figure 1, the carbon yield of C -C aromatic
the conversion of isophorone to C -C aromatic hydrocarbons. In
8
9
8
9
hydrocarbons over the 15 wt% MoO /SiO catalyst decreased with
contrast, the activity of the MoO + SiO catalyst is between those of
x
2
x
2
the reaction time during the 24 h continuous test. The opposite trend
the 15 wt% MoO /SiO and the MoO (or SiO ) catalysts. Based on
x
2
x
2
was observed for the carbon yield of C alkenes. After being in-situ
above results, we believe that there is synergism effect between SiO2
and MoO species in the conversion of isophorone to C -C aromatic
9
calcined in air flow at 773 K for 3 h, the activity of the 15 wt%
x
8
9
MoO /SiO catalyst almost restored to its initial level. According to
hydrocarbons. The promotion effect of SiO on the MoO catalyst is
x
2
2
3
these results, we believe that some carbon deposition may occur
during the conversion of isophorone, which leads to the deactivation
of catalyst. The carbon deposited on the catalyst can be removed by
not unique. As we can see from Table S4 and Table S5 in supporting
information, the carbon yields of aromatic hydrocarbons over the
physical mixtures of MoO and solid bases (such as MgO and MgAl-
x
calcination in air flow. As the result, the activity of the MoO /SiO
HT) are even lower than that over MoO . In contrast, higher carbon
x
2
x
catalyst was restored to its initial value. Such a speculation was
verified by the TG-MS analysis of the spent MoO /SiO (see Figure
yields (49.0-61.3%) of jet fuel range C -C11 aromatic hydrocarbons
7
can be achieved over the physical mixtures of MoO and solid acids
x
2
x
S9 of the supporting information).
(
including SiO , acidic active carbon, H-β and H-ZSM-5) than that
2
over MoO (32.9%). Compared with the physical mixture of MoOx
x
and weak solid acids (such as SiO and acidic active carbon), higher Conclusions
2
carbon yields of toluene and C -C aromatic hydrocarbons were
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11
A new route was developed for the sustainable synthesis of jet-
fuel range C -C aromatic hydrocarbons with the isophorone
produced when the physical mixture of MoO and strong solid acids
x
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9
(such as H-β and H-ZSM-5) were used as the catalysts. These results
which can be obtained from lignocellulose. Among the
investigated catalysts, the MoO /SiO demonstrated the best
further confirmed that acid sites on the supports (or catalysts) can
promote the rearrangement or cracking reaction, which is beneficial
for the generation of jet fuel range aromatic hydrocarbons.
x
2
performance. The synergism effect of the partial reduced MoOx
species and SiO support is important for the transformation of
2
Moreover, we also characterized the MoOx and MoO /SiO2
x
isophorone to C -C aromatic hydrocarbons. This work offers a
8
9
catalysts by NH -TPD. Before the NH -TPD tests, the catalysts were
3
3
potential solution to the shortage of current bio-jet fuel at
density and volumetric heating value.
reduced by hydrogen at 723 K for 1 h. From the results illustrated in
Table S6 in supporting information, we can see that the amounts of
acid sites on the surfaces of MoO /SiO catalysts are evidently
x
2
Acknowledgements
higher than those on bulk MoO catalyst. This may be another reason
x
for the higher activity of the MoO /SiO2 catalysts. With the
x
This work is supported by the Natural Science Foundation of
China (No. 21106143; 21277140; 21202163; 21476229) and
increasing of MoOx content, the amount of acid sites over the
MoO /SiO catalyst initially increase, then stabilize when MoOx
x
2
100-talent project of Dalian Institute of Chemical Physics
content is greater than 15 wt%. Such a variation trend is consistent
what we observed for the activity of these catalysts in the conversion
of isophorone to jet fuel range aromatic hydrocarbons.
Basing on the above information, the beneficial effect of SiO2
support can be rationalized by two reasons: 1) Dispersion effect.
(
DICP).
Notes and references
a
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics,
Such an effect will lead to the generation of more acid sites which is Chinese Academy of Sciences, Dalian 116023, China. E-mail:
beneficial for the production of jet fuel range aromatic hydrocarbons.
lining@dicp.ac.cn, taozhang@dicp.ac.cn; Fax: + 86 411 84691570.
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