Selective Production of Aromatics by Catalytic Fast Pyrolysis of Furan with in Situ Dehydrogenation of Propane

Article abstract of DOI:10.1021/acscatal.8b04859

Catalytic fast pyrolysis (CFP) of furan was studied with the co-feeding of propane over ZSM-5, CrO_x/Al₂O₃, and mixed catalysts with both ZSM-5 and CrO_x/Al₂O₃ to combine the dehydrogenation of propane and CFP of furan in the presence of in situ generated propylene. With 15 vol % propane co-feeding, a slight increase in aromatic yield was observed over ZSM-5 catalyst. These enhancement was further improved by using mixed catalysts consisting of CrO_x/Al₂O₃ and ZSM-5 with different weight ratios. Over the best mixed catalyst with CrO_x/Al₂O₃ to ZSM-5 weight ratio of 2, a nearly 2-fold increase in the aromatic yield was obtained. The toluene selectivity was also increased from 37% to 50%. The increase in aromatic yield is directly dependent on the propane to total flow volume ratio. Moreover, the coke formation within ZSM-5 was also reduced, leading to a slower catalyst deactivation. From mechanistic studies, a two-step cascade reaction pathway was observed over the bifunctional mixed catalysts. It was proposed that propane dehydrogenates to propylene over CrO_x/Al₂O₃. The propylene then reacts with furan within ZSM-5 catalyst to selectively form aromatics. This work demonstrates a simple and economical strategy to further improve the CFP technique.

Full text of DOI:10.1021/acscatal.8b04859

Research Article
Cite This: ACS Catal. 2019, 9, 2626−2632
pubs.acs.org/acscatalysis
Selective Production of Aromatics by Catalytic Fast Pyrolysis of
Furan with In Situ Dehydrogenation of Propane
Xiaoduo Qi and Wei Fan*
Department of Chemical Engineering, University of Massachusetts Amherst, 686 North Pleasant Street, Amherst, Massachusetts
0
1003, United States
*
S Supporting Information
ABSTRACT: Catalytic fast pyrolysis (CFP) of furan was
studied with the co-feeding of propane over ZSM-5, CrOx/
Al O , and mixed catalysts with both ZSM-5 and CrO /Al O
2
3
x
2
3
to combine the dehydrogenation of propane and CFP of furan
in the presence of in situ generated propylene. With 15 vol %
propane co-feeding, a slight increase in aromatic yield was
observed over ZSM-5 catalyst. These enhancement was further
improved by using mixed catalysts consisting of CrO /Al O
3
x
2
and ZSM-5 with different weight ratios. Over the best mixed
catalyst with CrO /Al O to ZSM-5 weight ratio of 2, a nearly
x
2
3
2
-fold increase in the aromatic yield was obtained. The toluene
selectivity was also increased from 37% to 50%. The increase in
aromatic yield is directly dependent on the propane to total flow volume ratio. Moreover, the coke formation within ZSM-5 was
also reduced, leading to a slower catalyst deactivation. From mechanistic studies, a two-step cascade reaction pathway was
observed over the bifunctional mixed catalysts. It was proposed that propane dehydrogenates to propylene over CrO /Al O .
x
2
3
The propylene then reacts with furan within ZSM-5 catalyst to selectively form aromatics. This work demonstrates a simple and
economical strategy to further improve the CFP technique.
KEYWORDS: biomass, catalytic fast pyrolysis, aromatics, co-feeding of propane, in situ dehydrogenation, CrO /Al O
3
x
2
1
. INTRODUCTION
to increase the aromatic yield because of their bifunctional
16
nature. In addition to developing new zeolite catalysts, higher
aromatic yield can also be achieved by altering the chemistry
involved in CFP. The Diels−Alder reaction, which involves the
addition of alkenes to conjugated dienes to form cyclohexene
derivatives, has been proposed as an effective reaction pathway
Because of diminishing fossil fuel reserves and increasing
environmental concerns, lignocellulosic biomass has attracted
significant attention as an alternative carbon source to produce
1
−5
fuels and chemicals.
Catalytic fast pyrolysis (CFP), which
directly converts biomass over solid catalysts in one integrated
reactor, is a promising technique for the production of
renewable aromatics such as benzene, toluene, and xylenes
17,18
to produce aromatics.
On the basis of this hypothesis,
Cheng and Huber studied the effect of propylene co-feeding
6
−8
on CFP of furan over ZSM-5 catalyst and reported an increase
from lignocellulosic biomass.
In this process, lignocellulosic
19
in the aromatic yields and higher selectivity to toluene. The
enhancement with the co-feeding of propylene was attributed
to the higher H/C ratio in the feed and the Diels−Alder
cycloaddition between furan and propylene. While the co-
feeding of propylene showed promising results, an inevitable
drawback of this method is the use of light alkene, which is also
a high-demand commodity chemical for producing polymers.
Hence, it is desired to use alkane as the co-feeding source and
integrate the dehydrogenation of alkane with CFP process.
Recently, shale gas has become an increasingly important
source of natural gas. Great opportunities have appeared for
using shale gas as the co-feeding chemical to produce
biomass is converted into pyrolysis gas at an intermediate
temperature. The produced pyrolysis gas then diffuses within
the micropores of zeolite catalysts where it undergoes various
reactions to form final products. While numerous studies have
been carried out to improve the efficiency of CFP technique,
the fast deactivation of zeolite catalysts and the low yields to
aromatics and olefins still remain as challenges of the CFP
7
,9−11
technique.
The fast catalyst deactivation is attributed to
the accumulation of coke formed inside the micropores of the
zeolite catalysts, which covers the active sites on the micropore
surface. To overcome the issue, hierarchical zeolites with short
diffusion lengths have been developed to improve the mass
transport within zeolite catalysts so that the formation of coke
20,21
renewable chemicals from biomass.
While shale gas is
12−14
within the micropores of zeolite catalysts can be reduced.
Other challenges of CFP are the low yields to desired products
e.g., aromatics and olefins) and the lack of flexibility to tune
Received: December 4, 2018
Revised: February 1, 2019
(
15
the product selectivity. Ga/ZSM-5 catalysts have been used
©
XXXX American Chemical Society
2626
DOI: 10.1021/acscatal.8b04859
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ACS Catalysis
Research Article
mostly made up of methane (∼90%) and ethane (∼10%), the
coupled with FID reactor. A plot-Q GC column was used to
separate light olefins from alkanes. The standard CFP reaction
conditions are as follows: temperature, 550 °C; total flow, 330
sccm; catalyst load, 80 mg for ZSM-5; 100 mg for CrOx/
Al O ; 120, 150, and 210 mg for mixed catalysts with CrO /
2
2
composition of propane can be as high as 5%, which
guarantees propane availability considering the total reserve of
shale gas.
In this work, we studied CFP of furan with co-feeding of
propane. The idea is to combine dehydrogenation of propane
and CFP of furan in the presence of both dehydrogenation
catalysts and zeolite catalysts. Improved aromatic yield, higher
selectivity to toluene, less coke formation, and slower catalyst
deactivation were achieved by using mixed catalysts consisting
2
3
x
Al O to ZSM-5 ratio of 0.5, 1, and 2, respectively. The
2
3
conversion, yield, and selectivity were calculated as described
in the Supporting Information.
3. RESULTS AND DISCUSSION
of CrO /Al O and ZSM-5. The effects of reaction parameters
x
2
3
Synthesized CrO /Al O sample was characterized using X-ray
x 2 3
including catalyst composition and the propane to total flow
volume ratio on the aromatic yield were studied. From
mechanistic studies, a typical two-step cascade reaction
pathway was observed over the bifunctional mixed catalysts.
Propane first dehydrogenates to propylene over CrO /Al O ,
diffraction (XRD) technique and compared to γ-Al O . The
2
3
XRD patterns are shown in Figure 1. γ-Al O shows typical
2
3
x
2
3
which further reacts with furan within the micropores of ZSM-
to form aromatics. The results observed in this work support
5
a simple and economical method to improve the current CFP
technique toward longer catalyst lifetime and higher aromatic
production.
2
. EXPERIMENTAL METHODS
.1. Catalyst Preparation. Five different catalysts were
prepared and studied in this work: CrO /Al O (10 wt % Cr)
2
x
2
3
as the dehydrogenation catalyst, commercial ZSM-5 (Zeolyst
CBV 3024E) as the CFP catalyst, and mixtures of these two
phases as co-feeding catalysts. Three co-feeding catalysts with
different CrO /Al O to ZSM-5 weight ratios (0.5, 1, and 2)
x
2
3
were prepared, denoted as CrZSM_0.5, CrZSM_1, and
CrZSM_2, respectively.
Figure 1. XRD patterns of γ-Al O and CrO /Al O (10 wt % Cr).
2
3
x
2
3
CrO /Al O (10 wt % Cr) was synthesized by incipient
x
2
3
wetness impregnation of Cr precursor on γ-Al O . Cr(NO ) ·
2
3
3 3
9
H O (0.4 g) was dissolved into 0.5 mL of deionized water.
XRD peaks with no indication of impurities. No Cr O peak
2 3
2
The solution was then added into 0.5 g of γ-Al O dropwise
with vigorous stirring. The product was dried overnight at 80
was observed for the CrO /Al O sample, suggesting that
CrO is well dispersed on the γ-Al O support.
x 2 3
2
3
x 2 3
°
C and calcined at 500 °C for 30 h. ZSM-5 zeolite was
To find optimum reaction conditions, propane dehydrogen-
ation reactions over CrO /Al O were first carried out at
purchased from Zeolyst (CBV3024E). Three catalysts with
x
2
3
different CrO /Al O to ZSM-5 weight ratios (0.5, 1, and 2)
different temperatures ranging from 450 to 600 °C. As shown
x
2
3
were prepared by mixing CrO /Al O with ZSM-5. Specifi-
in Table S1, CrO /Al O catalyst shows low activity (<2%)
x
2
3
x
2
3
cally, 100 mg of ZSM-5 was always used and CrO /Al O was
when the temperature is lower than 550 °C and high cracking
product formation (i.e., methane and ethylene) at 600 °C.
Hence, 550 °C was chosen as the optimum reaction
temperature for propane dehydrogenation to ensure sufficient
activity and selectivity for propylene formation. When the
weight hourly space velocity (WHSV) was adjusted, the
product distribution was compared at similar propane
x
2
3
weighed accordingly (50, 100, and 200 mg for weight ratio of
.5, 1, and 2, respectively). Thereafter, two phases were placed
into a mortar and ground for 20 min for a uniform mixture.
.2. Catalyst Characterization. Powder X-ray diffraction
XRD) patterns were recorded on X’pert Powder (PAN-
0
2
(
alytical) diffractometer system equipped with a Cu Kα
radiation (operation at 40 kV, 30 mA, λ = 0.15418 nm) and
a Ni filter. The measurement was carried out from a 2θ range
of 10° to 70° with a scanning step size of 0.02°.
conversion (5−7%) over different catalysts including CrO /
x
Al O , ZSM-5, and mixed catalysts, as shown in Figure 2 and
2
3
Table S4. The CrO /Al O catalyst shows >90% propylene
x
2
3
2
.3. CFP Reaction. CFP reactions were carried out in a
selectivity. This result is expected as CrO /Al O has been
x 2 3
continuous flow quartz fixed-bed reactor placed into a
proportional integral derivative (PID) controlled furnace.
Prior to reaction, the catalyst bed was heated to the reaction
temperature and equilibrated for 30 min under He flow (100
sccm). After calcination, the He stream was switched to bypass
the reactor. Furan was then fed into He carrier flow using a
syringe pump (Fisher KDS100) and allowed to equilibrate for
well-known for its superior performance as an industry
23
dehydrogenation catalyst. Dehydrogenation of propane
over ZSM-5 produced a significant amount of cracking
products including 24% selectivity to methane and 45%
selectivity to ethylene, suggesting that the ZSM-5 catalyst is
not ideal for propane dehydrogenation, possibly because of the
24
strong acidity of ZSM-5 catalyst. In the case of mixed
catalysts, the samples with higher CrO /Al O to ZSM-5
3
0 min. For co-feeding reactions, the furan/He flow was mixed
x
2
3
with co-feeding stream using a three-way tee. After 30 min
bypass, the feed stream was switched into the reactor, and after
weight ratios promote the dehydrogenation reaction, resulting
in an increase in propylene selectivity from 73% to 94% (Table
S4). In all cases, the aromatic selectivity is negligible (<3%), as
shown in the Supporting Information (Table S4).
1
min, an online gas chromatograph (GC) was started. The
products were characterized using an online Agilent 7890A GC
2
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indicating the lack of activity of CrO /Al O for converting
x
2
3
furan and propane into aromatics. A 19% increase in aromatic
yield from 14.4% to 17.1% was observed by the co-feeding of
propane over ZSM-5. The improvement is largely enhanced
with the use of mixed catalysts (40% increase over
CrZSM_0.5, 60% increase over CrZSM_1, and 94% increase
over CrZSM_2, respectively). It is clear that the co-feeding of
propane can improve the aromatic yield from CFP of furan
(
Table S2), especially with the presence of CrO /Al O in the
x 2 3
mixed catalyst. It should be noted that when only propane is
fed into the reaction (green bars), the aromatic yield is much
lower as compared to those of furan and furan/propane co-
feeding. This suggests that the studied catalysts are not active
for propane aromatization under the reaction conditions.
Therefore, it is reasonable to conclude that the increase in
aromatic yield with the co-feeding of propane is not from the
direct propane aromatization, but from the reactions involving
CFP of furan. For clarity, the enhancement of aromatic yield
Figure 2. Propane dehydrogenation over different catalysts. (Reaction
conditions: temperature, 550 °C; propane feed, 15 vol %; total flow,
was calculated and plotted against CrO /Al O to ZSM-5
3
30 sccm; catalyst loading, 100 mg.)
x
2
3
weight ratio, as shown in Figure 3b. As discussed, ZSM-5
catalyst shows less enhancement as compared to the mixed
catalysts. This is due to the lack of ability of ZSM-5 to
selectively dehydrogenate propane to propylene. With similar
ZSM-5 loading, the enhancement becomes more profound at
higher CrO /Al O to ZSM-5 weight ratios, because of more
CFP reactions of furan with and without the co-feeding of
propane were performed over different catalysts at 550 °C.
Figure 3a shows the aromatic yield using furan, furan/propane,
x
2
3
dehydrogenation reaction occurring over CrO /Al O . The co-
x
2
3
feeding of propane shows no effect on aromatic yield over
CrO /Al O . In this case, even though propylene is selectively
x
2
3
produced, there are no active sites available on CrO /Al O to
x
2
3
catalyze further reactions between propylene and furan. The
results in Figure 3 suggest the necessity of two different active
sites that can simultaneously catalyze dehydrogenation and
CFP reaction.
The distribution of aromatic products at similar furan
conversions (53−62%) is shown in Figure 4. CFP of furan over
ZSM-5 catalyst shows that benzene and toluene are the major
aromatics with an equal selectivity of 33% (Figure 4). This
observation was consistent with the literature reporting CFP of
25
furan over ZSM-5. Larger aromatics including xylenes,
styrenes (styrene and methylstyrenes), alkylbenzenes (ethyl-
benzene and 1,2,4-trimethylbenzene), indenes (indene and
methylindenes), and naphthalenes (naphthalene and methyl-
naphthalenes) are present in much smaller percentages. This
result is largely due to the shape selectivity imposed by the
microporous structure of ZSM-5 catalyst, which is favorable for
19
the formation of molecules with six-membered carbon rings.
The co-feeding of propane with furan results in a slightly
increased selectivity to toluene from 33% to 37% over ZSM-5
catalyst. More profound increase was observed by introducing
Figure 3. (a) Aromatic yield from CFP of furan, furan/propane, and
propane over different catalysts. (b) Aromatic yield enhancement with
different catalysts. (Reaction conditions: temperature, 550 °C;
propane feed, 15 vol %; total flow, 330 sccm; furan feed, 0.5 mL/h;
catalyst loading, 80 mg for ZSM-5; 100 mg for CrO /Al O ; 120, 150,
CrO /Al O catalyst (from 37% to 43%). Among mixed
x
2
3
catalysts, the selectivity to toluene shows strong dependence
on the CrO /Al O to ZSM-5 weight ratio, increasing from
x
2
3
43% to 50% as the ratio increases from 0.5 to 2. CFP reaction
x
2
3
and 210 mg for mixed catalysts with CrO /Al O to ZSM-5 weight
has been proposed to proceed via a “hydrocarbon pool”
x
2
3
26
ratio of 0.5, 1, and 2, respectively.)
mechanism, where benzofuran, formed either by Diels−Alder
27
28
cycloaddition or ring-opening reaction, is a key inter-
mediate for the production of aromatics. In this work, the
increase in toluene selectivity resulting from propane co-
feeding can be explained by the participation of produced
propylene through two possible mechanisms. The first
mechanism is the direct Diels−Alder cycloaddition of furan
and propylene to toluene, which was proposed by Cheng and
and propane as feedstocks. The yield was compared at similar
furan conversions (53−62%) with the feedstocks being furan
and furan/propane. For CrO /Al O catalyst, the furan
x
2
3
conversion is low because of the lack of catalytic active site
for CFP. The propane conversions are also similar (5−7%) in
all cases (Tables S3 and S4). Over CrO /Al O catalyst,
x
2
3
19
negligible aromatic yield was observed for all feedstocks,
Huber. The second possible mechanism is the addition of
2
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more propylene was available for furan to form aromatics,
19
leading to higher aromatic production and furan conversion.
To confirm the reaction pathway during CFP of furan with
propane co-feeding, we intentionally shut off the dehydrogen-
ation step by switching the co-feeding chemical from propane
to propylene. In this study, the propylene to total flow volume
ratio was set to be 0.8 vol %. This amount of propylene in the
feed is similar to the amount of produced propylene from 15
vol % propane co-feeding at 5% conversion. The 5%
conversion of propane was observed in furan/propane co-
feeding reaction under the same reaction conditions (Table
S3). The role of CrO /Al O in the mixture catalyst was also
x
2
3
investigated by changing the catalyst from CrZSM_2 to pure
ZSM-5 with propylene co-feeding. Both results are shown in
Figure 6. It can be seen from Figure 6a that the aromatic yield
Figure 4. Distribution of aromatic products in CFP of furan with
propane over different catalysts. The result for CFP with only furan is
also shown for comparison. The conversion of furan is controlled
between 53% and 62%. (Reaction conditions: temperature, 550 °C;
propane feed, 15 vol %; total flow, 330 sccm; furan feed, 0.5 mL/h;
catalyst loading, 80 mg for ZSM-5; 120, 150, and 210 mg for mixed
catalysts with CrO /Al O to ZSM-5 weight ratio of 0.5, 1, and 2,
x
2
3
respectively.)
propylene in the hydrocarbon pool which may enhance the
29,30
selectivity to toluene.
Further studies are required to
understand the reaction pathways for toluene formation in the
CFP process.
The effect of propane to total flow volume ratio on the
aromatic yield was investigated, as shown in Figure 5. The
Figure 6. Aromatic yield from CFP of furan with the co-feeding of
propane and propylene over CrZSM_2 and ZSM-5 catalyst.
(Reaction conditions: temperature, 550 °C; total flow, 330 sccm;
catalyst load, 210 mg for CrZSM_2 and 80 mg for ZSM-5; propane
feed, 15 vol %; propylene feed, 0.8 vol %; furan feed, 0.5 mL/h).
does not change from switching the co-feed (left two
columns). It suggests that, with similar propylene concen-
tration in the stream, shutting off the dehydrogenation step
does not affect the aromatic yield from the following CFP
reaction. This result supports that, in the case of propane co-
feeding reaction, propylene is the intermediate and the role of
propane is to produce propylene to further react with furan. In
the case of propylene co-feeding, removing CrO /Al O in the
Figure 5. Aromatic yield from CFP of furan with propane co-feeding
at different propane to total flow volume ratios over CrZSM_2
catalyst. (Reaction conditions: temperature, 550 °C; total flow, 330
sccm; catalyst load, 210 mg; furan feed, 0.5 mL/h.)
aromatic yield was observed to be directly proportional to the
amount of propane as cofeed. With 20 vol % propane co-
feeding, we observed a 2.5-fold enhancement in the aromatic
yield. The furan conversion, as shown in Table S6, also
increases when more propane was fed (from 57.2% to 61.8%
with propane to total flow volume ratio increasing from 5% to
x
2
3
mixed catalyst does not affect the aromatic yield (right two
columns) either, suggesting that CrO /Al O itself has no
x
2
3
activity on CFP reaction of furan. Figure 6b presents the
aromatic product distribution using different co-feeds and
catalysts. Similarly, aromatic selectivity does not change with
switching the co-feed or removing the CrO /Al O . In all
1
5%). As the aromatic yield produced from propane itself is
x
2
3
negligible, these trends signify a possible cascade reaction
pathway where propane first converts to propylene, which
reacts with furan to form aromatics. As more propane was fed,
cases, the toluene becomes the dominant aromatic product as
compared to the CFP for furan. This further supports the
cascade reaction pathway.
2
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The reaction scheme of furan CFP with the co-feeding of
propane can be visualized in Figure 7. The reaction follows a
comparison of reaction results using mixed and stacked
catalyst beds. We observed that both aromatic yield and
toluene selectivity were similar using the two configurations. It
further suggests the absence of synergy effects between CrOx/
Al O and ZSM-5 so that the proximity of these two catalysts
2
3
does not affect the reaction results. In the stacked catalyst
configuration, the furan/propane mixture first passes through
the CrO /Al O layer, where propane selectively dehydrogen-
x
2
3
ates to propylene. It should be noted that furan also reacts over
CrO /Al O , but with much less conversion and aromatic yield
x
2
3
as compared to those on ZSM-5. In the layer of ZSM-5,
propylene and furan react within the micropores of ZSM-5
catalyst to form aromatics.
Figure 9 shows the change of furan conversion over
CrZSM_2 catalyst as a function of time on stream with and
Figure 7. CFP of furan with the co-feeding of propane is proposed to
follow a cascade reaction scheme. Propane is first dehydrogenated to
propylene over CrO /Al O . The propylene then reacts with furan
within the micropore of ZSM-5 catalyst to selectively produce
aromatics.
x
2
3
typical cascade reaction pathway consisting of two independ-
ent catalytic steps catalyzed by two different catalysts. First,
dehydrogenation of propane is catalyzed over CrO /Al O ,
x
2
3
converting propane to propylene. Propylene then enters the
micropores of ZSM-5 and react with furan to produce
aromatics. As being discussed earlier, the first step can be
removed by replacing the propane with propylene as the co-
feed. In this case, CrO /Al O has no effect on the production
x
2
3
of aromatics. From our study, direct reactions between
propane and furan and synergetic interactions between
CrO /Al O and ZSM-5 were not observed.
x
2
3
We also carried out CFP of furan with propane co-feeding
using a stacked bed configuration. In this setup, 150 mg of
CrO /Al O was loaded on the top of 80 mg of ZSM-5 without
Figure 9. Time-on-stream study of CFP of furan and furan/propane
over CrZSM_2. (Reaction conditions: temperature, 550 °C; propane
feed, 15 vol %; total flow, 330 sccm; catalyst loading, 210 mg; furan
feed, 0.5 mL/h.)
x
2
3
any mixing. The CrO /Al O to ZSM-5 weight ratio was kept
x
2
3
at 2:1. The goal of this study is to see how the proximity of two
catalysts can change reaction results. Detailed reaction
breakdown is listed in Table S9. Figure 8 shows the
Figure 8. Comparison of aromatic yield and product selectivity from CFP of furan with propane co-feeding using different bed configurations.
Reaction conditions: temperature, 550 °C; total flow, 330 sccm; catalyst load, 210 mg; propane feed, 15 vol %; furan feed, 0.5 mL/h.)
(
2
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without the co-feeding of propane. As expected, furan
conversion decreases continuously with time on stream in
both cases because of coke accumulation within the micro-
pores of ZSM-5 catalyst. When only furan was fed, furan
conversion drops from 57% to 26% after 5 min, and the
catalyst is completely deactivated after 15 min. As discussed in
the Introduction, the rapid deactivation of catalyst has been
AUTHOR INFORMATION
■
*
Corresponding Author
E-mail: wfan@ecs.umass.edu (W.F.).
ORCID
Xiaoduo Qi: 0000-0001-6298-2618
Wei Fan: 0000-0002-8581-2651
Notes
10,31
well-known as a major drawback for CFP process,
and a
complete deactivation of ZSM-5 within a similar time on
1
2
The authors declare no competing financial interest.
stream has been observed from our previous study. In the
case of propane co-feeding, however, the loss of activity occurs
less rapidly. After the first 5 min, the catalyst retains 87% of its
activity as furan conversion decreases from 63% to 55%. At 15
min time on stream, instead of losing all the activity in the
previous case, the same catalyst still shows 26% of furan
conversion. The coke formed within zeolites at high temper-
atures has been reported to be polyaromatics because of the
ACKNOWLEDGMENTS
■
The authors are thankful for the support from the Catalysis
Center for Energy Innovation, an Energy Frontier Research
Center funded by the U.S. Department of Energy, Office of
Science, and Office of Basic Energy Sciences under award
number DE-SC0001004.
32
oligomerization of aromatic species. This more selective
formation of aromatics leads to a lower degree of
oligomerization, leading to less deposit of polyaromatics.
Besides propylene, the dehydrogenation of propane also
produces hydrogen, which can potentially react with furan via
hydrodeoxygenation (HDO) reaction to remove the oxygen
atom in the furan ring. In this work, we have tested CFP of
furan with the co-feeding of hydrogen (15 vol %) over
CrZSM_2 catalyst, but no HDO products were observed, as
shown in Figure S1. It suggests that the mixed catalyst cannot
catalyze the HDO reaction under the reaction conditions. The
effect of ethane co-feeding was also investigated. While the
CrO /Al O can selectively dehydrogenate ethane to ethylene
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2
(
8
(
x
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3
(Table S1), no significant enhancement in the aromatic yield
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shown in Figure S2(b) does not change with ethane co-feeding
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though ethylene can be produced, it is not as active as
propylene for further reaction with furan. This result is
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(
1
9
ethylene.
(
4
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x
2
3
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Al O . The dominant aromatic product was also tuned from
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x
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ASSOCIATED CONTENT
Supporting Information
■
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