Enhancement of hydrocarbon production and catalyst stability during catalytic conversion of biomass pyrolysis-derived compounds over hierarchical HZSM-5

Article abstract of DOI:10.1039/c6ra05356d

In order to promote hydrocarbon production and catalyst stability in catalytic fast pyrolysis (CFP) of biomass, HZSM-5 catalysts were treated with alkali solutions to introduce mesopores into the microporous system. Parent and hierarchical catalysts were tested in catalytic conversion of furan as an important intermediate from biomass fast pyrolysis (BFP). Controlled desilication with mole concentration of NaOH of 0.3 M resulted in sheet-like mesopores on the external sphere, enhancing mass transfer in the catalyst, and it specifically promoted the carbon yield of hydrocarbons by 21.6%. Though the coke content on these HZSM-5-0.3M catalysts increased gradually by 11.6%, the tolerance toward deactivation by coke deposition was improved. Cyclic tests of catalysis-regeneration process over hierarchical HZSM-5-0.3M over 20 cycles revealed that it can withstand long-running with a stable yield of hydrocarbons being achieved. Thus, hierarchical HZSM-5 is a suitable catalyst for CFP of biomass and its derivatives to hydrocarbons by this simple synthetic process.

Full text of DOI:10.1039/c6ra05356d

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: S. Shao, H. Zhang,
D. Shen and R. Xiao, RSC Adv., 2016, DOI: 10.1039/C6RA05356D.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Please do not adjust margins
RSC Advances
Page 1 of 9
View Article Online
DOI: 10.1039/C6RA05356D
Journal Name
ARTICLE
Enhancement of hydrocarbon production and catalyst stability
during catalytic conversion of biomass pyrolysis-derived
compound over hierarchical HZSM-5
Received 00th January 20xx,
Accepted 00th January 20xx
S. S. Shao, H. Y. Zhang*, D. K. Shen, R. Xiao*
DOI: 10.1039/x0xx00000x
In order to promote hydrocarbon production and catalyst stability in catalytic fast pyrolysis (CFP) of biomass, HZSM-5
catalysts were treated by alkali solution to introduce mesopores into microporous system. Parent and hierarchical
catalysts were tested in the catalytic conversion of furan as an important intermediate from biomass fast pyrolysis (BFP).
Controlled desilication with mole concentration of NaOH of 0.3 M (HZSM-5-0.3M) resulted in sheet-like mesopores on the
external sphere, enhancing mass transferring in catalyst, and it specifically promoted the carbon yield of hydrocarbons by
21.6%. Though coke content on HZSM-5-0.3M catalysts increased gradually by 11.6%, its tolerance toward deactivation by
coke deposition was improved. Cyclic tests of catalysis-regeneration process over hierarchical HZSM-5-0.3M with 20 cycles
revealed that it can withstand long-running with a stable yield of hydrocarbons being achieved. Thus, hierarchical HZSM-5
is a suitable catalyst for CFP of biomass and its derivates to hydrocarbons for its simple synthetic process.
recover the activity of catalysts, the deactivated catalysts are
www.rsc.org/
Introduction
usually regenerated in air atmosphere in which the combustion
temperature determines the result of regeneration. Regeneration
at low temperature may not remove the coke completely, while
higher temperature may bring about overheating and furthermore
break down the catalysts structure.11
Catalyst deactivation is the biggest barrier in CFP of biomass for
hydrocarbons that can be great sources of most liquid and gaseous
fuels.1-3 A high carbon yield (23.7%) of olefins and aromatic
hydrocarbons from pine wood catalytic pyrolysis in a fluidized bed
reactor has been achieved, but actually it is much lower than the
theoretical yield (more than 60%), which is mainly due to catalyst
deactivation caused by coke deposition.4 Among all studied
catalysts, ZSM-5, a three-dimensional micropore system that
consists of two perpendicularly intersecting channels of 10-
membered rings, i.e., straight channels (5.5 Å×5.1 Å) and zigzag
channels (5.6 Å×5.3 Å), is a well known catalyst in CPF because it
has moderate pore openings, internal pore space (i.e., pore
intersection, d=6.36 Å) and steric hindrance, all that favors aromatic
production.5, 6 In biomass zeolite-catalyzed hydrocarbon formation
reactions, loss of ZSM-5 catalyst activity is mainly due to coke
formation. Some high molecular weight oxygenates larger than
pore opening of ZSM-5 (like levoglucosan) cannot enter the pores of
microporous catalysts, and will polymerize and form coke on the
surfaces. Some small-molecule oxygenates with high activity (like
furans) can also polymerize and form coke in the presence of
external acid sites of the catalyst.7, 8 Coke deposition may result in
changes in pore structure and acid property. On one hand, it will
increase the effective diffusion length, block the pore mouth on the
surface of ZSM-5 and then inhibit the entering of pyrolysis vapor.
On the other hand, coke species will cover lots of active sites,
Thanks to some developed effective methods, they can be used to
decrease the effective diffusion length and also increase the specific
surface area, improve the mass transfer ability of catalysts and thus
promote the production of hydrocarbons.12, 13 To shorten diffusion
pathways, nano-sized zeolites were proposed, thus improving the
mass transport in the zeolite channel.14, 15 Another popular method
is to introduce mesopores into microporous zeolite catalysts, the
diffusivity of the microporous channel and the accessibility of the
active sites are also greatly promoted.16-18 There are usually two
methods to introduce mesopores into the original microporous
system by desilication, namely templating and alkaline treatment. A
carbon source is impregnated with a zeolite precursor solution after
which the material is subject to a hydrothermal treatment to grow
the zeolite crystals, subsequently the carbon and the template are
burned away resulting in intracrystalline mesopores in the zeolite19.
Some templates are very expensive, which determines its limited
application in industry. Removal of silica from the crystal framework
with alkali solutions is an easily operated method that may cause
the appearance of mesoporosity.20-22 Selective dissolve and remove
of silica from the zeolite framework can be realized by alkaline
treatment. Silica extraction leads to the formation of structural
defects in the lattice.23, 24 Thus, desilication by alkaline treating is a
preferential method to introduce mesopores. These hierarchical
zeolites enhance the utilization of their active volume, and have
attained superior yield of targeted products in lots of catalysis
reaction.25
10
namely it leads to decrease of acid strength and amount.9, To
Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education,
Southeast University, Nanjing 210096, P.R. China
Email: hyzhang@seu.edu.cn, ruixiao@seu.edu.cn
To improve carbon yield of hydrocarbons in CFP of biomass and
1
J. Name., 2013, 00, 1-3 |
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 9
ARTICLE
Journal Name
promote the catalyst stability, alkali treatment was carried out on measurements were performed with a FEI Inspect F50 system at
View Article Online
DOI: 10.1039/C6RA05356D
HZSM-5 catalysts to introduce some mesopores into the 10kV. Prior to each measurement, the samples were prepared on a
microporous catalyst system. The hierarchical HZSM-5 catalyst carbon pad and sputtered with gold to obtain the necessary
showed better mass transfer. In our study, N2 adsorption and conductivity. The morphology and pore size of zeolites were also
transmission electron microscopy were used to investigate the examined by transmission electron microscopy (TEM) on a Tecnai
existence of mesopores, and the morphology was greatly G2 microscope operated at an electron acceleration voltage of 200
dependent on the treating conditions. The parent and hierarchical kV. A small amount of catalyst was dispersed in ethanol, sonicated,
HZSM-5 catalysts were employed in the catalytic conversion of and dispersed over a micrograte.
furan as an important intermediate from biomass fast pyrolysis. The The acidity of the catalysts was estimated by the NH3 temperature
effect on the hydrocarbon production was studied and the catalyst programmed desorption (TPD) technique. The sample was
performance in cycle runs of catalysis-regeneration process was pretreated at 600 °C in flowing He for 0.5 h. After pretreatment, the
discussed.
sample was cooled to 100 °C and saturated with NH3 gas. The
physical absorbed NH3 was then blown out. Finally, NH3-TPD was
carried out under a constant flow of He (20 mL/min). The
temperature was raised from 100 to 600 °C at a heating rate of 15
°C/min.
Experimental
Catalyst and desilication procedure
Deactivated catalysts were regenerated in air atmosphere of 50
mL/min in a thermogravimetric analyzer to determine coke content
by the weight loss during oxidation. Typically, 15 mg of sample was
placed in the alumina crucible and heated from ambient
temperature to 800 °C at a rate of 15 °C/min.
In this study, two series of HZSM-5 catalyst samples were compared:
A commercial catalyst (purchased from catalyst plant of Nankai
University, stated Si/Al ratio 25) and its hierarchical counterpart.
The hierarchical catalyst was prepared by desilication according to
the following procedure. 2 g parent sample was treated in stirred
aqueous NaOH solutions (0.1-1 M, 70 °C, 30 min, 33 mL solution per Catalyst tests
gram catalyst material). Mixture were washed and filtered for times
All catalytic tests were performed in a quartz glass fixed-bed reactor
until neutral, and the isolated solids were dried at 110 °C for 12 h.
All modified zeolites were converted to the protonic form by ion
exchange in aqueous NH4Cl solution (1 M, 80 °C, 4 h, 10 mL solution
per gram catalyst material, 3 consecutive treatments) and washed
for several times followed by calcination in air at 600 °C for 5 h.
These catalysts will be referred to as HZSM-5-P and HZSM-5-X,
respectively. X stands for the mole concentration of NaOH solutions.
It should be mentioned that Cl content of final modified catalysts
has been tested in the following section to eliminate the influence
of Cl on the catalytic performance.
described elsewhere.26 The catalyst bed was activated in a pure air
flow (200 mL/min) at 600 °C for 1 h prior to each run. Then, the
nitrogen flow was mixed with 1.68 g/h furan via a spring pump,
resulting in a weight hourly space velocity (WHSV) of 11.2 g furan
per gram catalysts per hour. All experiments were carried out under
atmospheric pressure and a furan partial pressure of Pfuran=12.30
Torr. After 20 minutes of catalysis reaction, furan feeding was
stopped and air was introduced into the reactor with flow rate of
500 mL/min for 30 minutes and it should be ensured the coke was
removed completely. During the coke combustion process, CO was
converted into CO2 in the copper converter which was full of copper
oxide and then trapped by the ascarite. The coke amount was
measured by the weight increase in the CO2 capturer. Product
analysis was performed using gas chromatography. The product
composition was determined with gas chromatography/mass
spectrometry (GC/MS) (Agilent, 7890A-5975C) equipped with HP-5
capillary column (30 m×0.25 mm×0.25 µm), and then quantified by
GC-Flame-ionisation detector/thermal-conductivity (FID/TCD) with
a Restek Rtx-VMS capillary column to qualify olefins and aromatics.
Coke content is the proportion between weight of coke and weight
of fresh catalyst.
Catalyst characterization
The parent and desilicated samples were characterized by several
techniques.
The structure of the ZSM-5 samples was determined through X-ray
powder diffraction (XRD) from Bruker using Cu Kα radiation at 40 kV
and 40 mA with a scanning speed of 0.02 °/min in the range of 5 °≤θ
≤80 °.
Energy Dispersive Spectrometer (EDS) was used to determine the
element content, and then Si/Al was obtained. Cl content helps to
make sure that little Cl was left. It was performed on a Vantage Ⅳ
system, Thermo Fisher Scientific, USA.
Nitrogen physisorption isotherms were measured using a Autosorb-
iQ gas adsorption analyzer (Quantachrome, USA) at -196 °C. Each
sample was outgassed at 200 °C for 6 h before measurement. The
specific surface area (SBET) was calculated by using the Brunauer-
Results and Discussion
Physicochemical characterization
Emmett-Teller equation (P/P0=0.05~0.20). The total pore volume The XRD powder pattern of parent and desilicated HZSM-5 are
(Vtotal) is taken as the total uptake at P/P0=0.995. The Barrett- shown in Fig. 1. Both types of catalysts displayed two diffraction
Joyner-Halenda (BJH) method was used to determine the micropore peaks in the range of 8~10 ° and 20~25 °, which are the
volume and micropore size distribution. And the mesoporous characteristic reflection of MFI topology. The intensity of refection
volume was obtained by subtracting the micropore volume from peaks decreased at higher NaOH concentration, while no big
the overall pore volume.
difference of intensity can be found when NaOH concentration was
Scanning electron microscopy (SEM) experiments were performed lower than 0.5 M. It suggested that effective size of the crystalline
to obtain the morphology of the fresh and modified catalysts. The has changed after severe alkali treatment.
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 9
RSC Advances
Please do not adjust margins
Journal Name ARTICLE
Table 1 Textural properties of parent and hierarchical HZSVMie-w5AcratitcalelyOstnsline
a
a
DOI: 10.1039/C6RA05356D
Vtotal
SBET
（m2/g）
Vmicro
（cm3/g）
HZSM-5-1M
Sample
Si/Alb
（cm3/g）
HZSM-5-0.8M
HZSM-5-0.5M
HZSM-5-0.3M
HZSM-5-P
239
244
262
271
291
312
0.11
0.14
0.16
0.17
0.2
22.28
21.13
21.89
19.45
17.67
15.31
HZSM-5-0.1M
HZSM-5-0.3M
HZSM-5-0.5M
HZSM-5-0.8M
HZSM-5-1M
0.12
0.11
0.10
0.09
0.08
HZSM-5-0.1M
HZSM-5-P
0.23
0.25
a Calculated by t-plot method
b calculated from EDS analysis
10
20
30
40
50
60
70
80
2(degrees)
recorded to see the changes of crystals after treatment (see Fig. 3).
The parent HZSM-5 showed uniform micropore distribution,
whereas it consists of sheet-like materials on the outer sphere of
HZSM-0.3M. For these samples treated with higher concentration
of NaOH solution, TEM images revealed clearly the appearance of
intracrystalline mesopores marked as the arrows. The morphology
of catalysts is greatly dependent on the treating conditions of
HZSM-5 catalysts. It has been widely accepted that when different
treating conditions are used, the grown sites, shape and size are
quite different, leading to catalyst crystals with different
morphology.28 Moderate alkali treating produced sheet-like pores
only on the outer sphere, and larger concentration of NaOH
concentration makes it easy to diffuse into the internal space for
serious corrosion and hollow mesopores creation, verified by BET
and TEM characterization.
Fig 1. XRD patterns of parent and hierarchical HZSM-5 catalysts
The nitrogen adsorption-desorption isotherms of HZSM-5-P and its
hierarchical counterparts are recorded in Fig. S1. The isotherm of
type I, characteristic of microporous structure, was presented in
parent HZSM-5, namely, high uptake was evident at low P/P0. The
hierarchical samples exhibited the characteristic of type IV
isotherms, obvious hysteresis loop corresponded to a gradual
uptake over the P/P0 range of 0.4~0.9, which revealed the presence
of mesopores especially for HZSM-5-1M.27 It can be furtherly
verified by the pore size distribution as shown in Fig. 2. For these
samples treated with NaOH concentration lower than 0.3 M,
mesopores with diameter size lower than 5 nm were produced,
while larger mesopores appeared with NaOH concentration higher
than 0.3 M. The BET surface area, total pore volume and micropore
volume derived from the isotherms are summarized in Table 1. The
BET surface area increased from 239 m2/g to 312 m2/g. Moreover,
the total pore volume increased by alkali treatment caused by the
presence of mesopores, and it is at the expense of micropore
volume because of the partial damage of micropore framework.
0.03
HZSM-5-1M
0.02
0.01
0.00
HZSM-5-0.8M
HZSM-5-0.5M
HZSM-5-0.3M
HZSM-5-0.1M
HZSM-5-P
0
2
4
6
8
10 12 14 16 18 20
Pore diameter(nm)
Fig. 2 BJH mesopore size distribution of parent and hierarchical HZSM-5
catalysts
Fig. 3 TEM images of parent and hierarchical HZSM-5
The morphology of parent and alkali treated HZSM-5 are scanned as
show in Fig. S2 by SEM. The surface of parent HZSM-5 was quite
smooth, while lots of gullies appeared due to alkali corrosion. And
partial catalysts framework collapsed at some extremely treating
conditions such HZSM-5-1M. To furtherly understand the the
influence of alkali treatment on the mesopore formation in
catalysts crystals and size distribution of pores, TEM images were
It has been tested in Table 1 that Si/Al ratio showed a very slight
decrease for HZSM-5-0.1M and HZSM-5-0.3M, and then decreased
sharply for samples with higher treating concentration of NaOH,
which proves that serious dealumination should be happening
accompanied with desilication by alkali treatment.29 The total acid
3
J. Name., 2013, 00, 1-3 |
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 9
ARTICLE
Journal Name
amount is proportional to the frammework Al content. Then the Mechanism of desilication and mesopore creation
View Article Online
DOI: 10.1039/C6RA05356D
hierarchical HZSM-5 catalyst was supposed to present very different
acid properties. To validate the above hypothesis, NH3-TPD was
conducted as shown in Fig. 4 finding the typical profiles with two
peaks from NH3-TPD analysis, of which the peak at low temperature
(PLT) was around 200 °C and that at high temperature (PHT) was
around 400 °C. Fig. 4(b) shows the area ratio between modified
samples and original catalyst (SM/SP) and area ratio between PHT and
PHT (SLT/SHT). PLT can be attributed to weak Lewis acid sites (e.g. extra
framework aluminum)30. The amount of PLT for HZSM-5-0.3M
decreased to 91% of parent HZSM-5, then decreased sharply for
HZSM-5-0.5M and HZSM-5-0.8M, and HZSM-5-1M finally showed
quite weak intensity of PLT. And PHT is usually related to ammonia
interacting with Brønsted type acid sites (e.g. framework
aluminum)30. An obvious gradual decrease of PHT indicated that
alkali treatment mainly brings about the decrease of acid strength
and amount of Brønsted aid sites. It indicated that alkali treatment
may damage not only Si but also frammework Al. For HZSM-5-0.3M,
the characteristic MFI topology did not change, which can be found
by XRD analysis. Though frammework Al was partially deprived, the
acid amount and strength is well kept for its catalysis for
hydrocarbons. Thus, it can be assumed that hierarchical HZSM-5
catalyst presented relatively weaker Brønsted acid sites rather than
Lewis acid sites compared with parent catalyst.
(a)
(F)
(E)
(D)
(b)
Fig. 5 Formation process of mesopores in HZSM-5 by alkaline treatment
(C)
(B)
(A)
Si-O-Al bond is usually thought to be weaker than Si-O-Si bond and
vulnerable to be attacked and hydrolyzed, yet it only applies to acid
treatment. In alkaline solutions, because of the negative charge of
-
AlO4 tetrahedron, the four-coordinated Al is protected from the
100
200
300
400
500
600
attack of OH-, and Si-O-Al is not easy to hydrolyze. Each four-
coordinated Al can protect four adjacent Si atoms from attack, thus
these Si-O-Si bonds without adjacent AlO4- tetrahedron are easily to
break, and then desilication happens with terminal Si-OH formation
during which coordination environment is steady.31 For these ZSM-5
catalysts with low Si/Al ratio, Al content and acid strength/amount
are high, and the inevitable dealumination is accompanied by loss
of four-coordinated Al. On one hand, when high concentration of
NaOH solution is used, both Si-O-Al bond and Si-O-Si bond break,
namely dealumination and desilication of framework both happens.
On the other hand, excessive alkali treatment may lead to direct
falling off of the integral Al quadridentate. Therefore, alkali
treatment of HZSM-5 is a selective desilication process at moderate
conditions, while Si-O-Al may also be cut when severe treating
condition is used. The bond breaking process of alkali treatment is
described in detail in Fig. 5(a). The schematic diagram of formation
process of mesopores in HZSM-5 is presented in Fig. 5(b). Alkali
corrosion begins from the outer sphere of HZSM-5 following the
guide of Si atoms. The sheet-like pores were firstly formed,
indicated by TEM images.32 Further diffusion of OH- will permeate
into the inner micropores and result in alkali corrosion around
Temperature(C)
(a)
1.0
3.0
2.5
2.0
1.5
1.0
PLT
0.8
0.6
0.4
0.2
0.0
PHT+PLT
PHT
0.0
0.2
0.4
0.6
0.8
1.0
Concentration of NaOH solution used in desilication(M)
(b)
Fig. 4 NH3-TPD analysis of parent and hierarchical HZSM-5 catalysts: (A)
HZSM-5-P, (B)HZSM-5-0.1M, (C)HZSM-5-0.3M, (D)HZSM-5-0.5M,
(E)HZSM-5-0.8M, (F)HZSM-5-1M,
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 9
RSC Advances
Please do not adjust margins
Journal Name ARTICLE
them.33 Hollow mesopores with average diameter around 8 nm
were formed when the concentration of NaOH solutions was 0.5 M.
Finally, excessive treating led to framework collapsing and
involuntary loss of acid sites. The average diameter of HZSM-5-1M
is mainly around 10 nm. Thus, the degree of alkali treatment must
be well controlled and the targeted mesopore shape can be realized,
sheet-like or hollow.
24
80
View Article Online
Olefins+aromatic hydrocarbons
DOI: 10.1039/C6RA05356D
70
Aromatic hydrocarbons
60
22
20
18
50
40
Catalytic conversion of biomass derivates over hierarchical HZSM-
5 catalyst
Olefins
30
Catalytic conversion of furan as an important biomass-derived
compound was investigated over parent and desilicated HZSM-5
catalysts to find out the optimal post-treating condition for
maximizing the production of hydrocarbons. Fig. 6 shows the results
of catalytic tests for the parent and hierarchical HZSM-5 catalysts
performed at the pyrolysis temperature of 600 °C. Fig. 6(a) presents
the general olefins and aromatic hydrocarbon yield and distribution
with the change of concentration of NaOH solution in desilication.
Moderate alkaline treating will lower diffusion limitation, decrease
the strong acid and increase the concentration of acid sites on the
external level.34 Carbon yield of olefins and aromatic hydrocarbons
reached a maximum of 23.3%. It showed an improvement of 21.6%
compared with the parent HZSM-5 catalyst. The excellent
performance of hierarchical HZSM-5 may be attributed to the
synthesis of mesopore that will promote the diffusion of reactants
and products, and get easier access to acid sites in the
micropores.35 However, too severe desilication produced redundant
mesopores, led to bad selectivity and less acid sites to meet the
fundamenal catalysis reaction. The framework even collapsed at
extreme treating conditions. In Fig. 6(b), the curves describe carbon
yield of olefins as a function of time over the treated catalysts and
also a comparison with the parent catalyst. It is obvious that the
initial carbon yield increased with the increasing concentration of
NaOH solution in desilication, accompanied by higher surface area
and acid density on the external sphere. Carbon yield of olefins
increased to a maximum value in a short time which is usually name
“induction period” and then decreased sharply due to coke
deposition. It is found that the length of induction period is closely
related to alkali treating conditions. The presence of mesopore, the
shape and size of mesopores as well may influence the formation of
active sites. Unfortunately, the detailed mechanism of the
relationship is still unknown.
0.0
0.2
0.4
0.6
0.8
1.0
Concentration of NaOH solution used in desilication(M)
(a)
16
HZSM-5-P
HZSM-5-0.5M
HZSM-0.1M
HZSM-5-0.8M
HZSM-5-0.3M
HZSM-5-1.0M
14
12
10
8
6
4
2
0
2
4
6
8
10 12 14 16 18
Time(min)
(b)
Fig. 6 Catalytic performance of hierarchical HZSM-5 catalysts
Table 2 Product distribution in the catalytic conversion of furan over HZSM-5
Parent 0.1M
0.3M
0.5M
0.8M
1M
Carbon yield（mol%）
Olefins
5.41
6.74
8.78
7.10
5.12
3.82
Aromatic
hydrocarbons
13.79
14.25 14.57 15.65 14.66 13.31
Coke content
（wt%）
7.07
7.43
7.89
7.99
8.53
9.91
In desilication process, the introduction of mesopores will also
change the shape selectivity of catalysts dependent on the size of
gate between mesopore and micropore and the change of diffusion
limitation. The detailed product distribution was listed in Table 2, in
which HZSM-5-0.3M showed larger selectivity to ethylene and
smaller selectivity to naphthene. When using concentration of
NaOH solution lower than 0.3 M, the sheet-like channels will
shorten the diffusion pathway. The contact time of furan in the
catalyst decreased, which is insufficient for olefin aromatization,
and thus the selectivity to olefins increased. For these hierarchical
HZSM-5 catalysts like HZSM-0.5M, HZSM-0.8M and HZSM-1M, the
hollow mesopores provided enough space for aromatization.
Therefore, alkali treatment is a useful method for promotion of
olefins in catalytic conversion of furan.
Ethylene
Propylene
Butylene
10.13
7.41
9.57
15.72 19.81 12.58
8.18
7.91
4.91
6.85
2.76
1.99
9.06
5.22
8.63
5.56
9.04
5.38
Benzene
Toluene
Xylene
8.25
12.47
4.21
3.40
5.62
9.19
15.32
9.84
7.35
12.52
10.47 16.93 14.17 14.27 14.31
3.55
7.20
6.44
5.64
10.20 13.20 17.60 20.10
6.12 5.92 6.41 6.32
4.32
6.06
5.06
Benzofuran
Indene
5
J. Name., 2013, 00, 1-3 |
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 9
ARTICLE
Journal Name
30
650
To understand coking behavior of hierarchical HZSM-5, coke
content of deactivated catalysts were analyzed by thermal analysis
as shown in Fig. 7. It showed mass loss of deactivated catalysts
during coke combustion. First of all, total coke content of catalysts
are of some differences among all catalysts. Compared with the
parent one, the treated catalysts almostly had more coke content,
and this observation can also be found in other coked catalyst with
View Article Online
DOI: 10.1039/C6RA05356D
HZSM-5-P
640
25
20
15
10
630
HZSM-5-0.3M
37
hierarchical structure.36, This suggests that the mesopores may
620
act as space for coke to form and accumulate.38 Though more coke
were deposited on the hierarchical catalysts, carbon yield of
hydrocarbon was higher compared with parent catalyst, which
indicated its higher tolerance toward coke deposition. Actually, not
only the coke content of all catalysts differed from each other, but
also the combustion temperature ranges were different as shown in
Fig. S3. Major coke was deprived from 400 °C to 800 °C, while some
weak peaks appeared at the temperature range of 100~400 °C for
HZSM-5-0.5M, HZSM-5-0.8M, HZSM-5-1M. It means that either the
location of coke or the chemical species of coke were different from
three other catalysts. Kaskel found that deactivated hierarchical
materials showed higher porosities, and assumed that coke in the
mesoporous area was more loose and porous.39
HZSM-5-P
610
HZSM-5-0.3M
600
0
5
10
15
20
Number of cycle
Fig. 8 Cycle performance of parent and hierarchical HZSM-5 catalyst
because of the appearance of mesopores in HZSM-5, which
provided more chances for the contact between reactant and
catalysts acid sites. The parent HZSM-5 catalyst showed more
serious overheating than HZSM-5-0.3M. On one hand, the loose and
porous coke determines its relatively lower burning temperature.39
Svelle and Schmidt reported that coke distribution of microporous
HZSM-5 showed a gradient over the catalyst particle and the
carbonaceous molecules mainly deposited in the microporous near-
surface area that led to the rapid deactivation of catalysts, while
hierarchical HZSM-5 catalysts showed a homogeneous distribution
10
8
6
over the whole particle due to the improved accessibility of active
4
sites and higher catalyst utilization.19,
Therefore, the more
40
uniform deactivation of the desilicated catalyst due to a complex
interplay among alterations of porosity, activity, and rate of
deactivation upon desilication, makes combustion gas easily diffuse
out of catalysts channels.40 Actually, accurate temperature within
the catalyst particle was much higher than the detected value. Thus,
lots of heat during coke combustion resulted in extraction of the
framework Al to generate octahedrally coordinated Al species out
of the zeolite framework.41 Dealumination happened, and deprived
aluminum retained in the pores. Generally, the mesopores in
treated HZSM-5 catalyst will decrease the burning temperature and
also the particle interior temperature, weaken the dealumination
effect, and finally promote the stability via cycles. Coke content was
also recorded online during regeneration. The coke amount
determined by combustion online only includes carbon, while TG
analysis of deactivated catalysts in air can determine the amount of
full composition including carbon, hydrogen and oxygen. Previous
study revealed that coke species at high temperature (>400 °C) are
mainly hydrogen-poor carbon species with no oxygen42. Therefore,
coke amount obtained by the above method may be just a little
smaller than TG analysis. Coke content of original catalysts and
those used for cycles has been added in Fig. S4. It is obvious that
coke content decreased with the increasing cycle numbers, and the
decrease rate of parent ZSM-5 catalysts seems higher. For parent
ZSM-5, high burning temperature leads to hotspot in catalyst
particles and then dealumination may happen43, 44. Dealumination is
usually accompanied by the decrease of strong acid sites which
easily causes serious coke formation41. Thus the decrease of coke
content with cycle numbers is understandable. Hierarchical catalyst
(HZSM-5-0.3M) showed relatively combustion temperature and
thus lower degree of dealumination, which determines its slighter
2
0
0
100 200 300 400 500 600 700 800 900
Temperature(C)
Fig. 7 Regeneration of deactivated HZSM-5 catalysts of different alkali
treating conditions
(□, HZSM-5-P; ◯, HZSM-5-0.1M; △, HZSM-5-0.3M; ▽, HZSM-5-0.5M;
◁, HZSM-5-0.8M; ▷, HZSM-5-1M)
Cycle run of catalysis-regeneration process
To determine the cycle performance of hierarchical catalysts, cyclic
tests were conducted with 20 catalysis-regeneration cycles
consisting of 20 min catalytic reaction followed by 30 min catalyst
regeneration. The catalytic condition was the same as section 3.3,
and the regeneration was performed with air flow rate of 200
mL/min. The variation of carbon yield of hydrocarbons as a function
of cycle number for the catalyst HZM-5-P and HZSM-5-0.3M is
shown in Fig. 8.
It is obvious that reaction stability of HZSM-5-0.3M was much
better than parent HZSM-5 catalyst, in particular, carbon yield of
hydrocarbons almost kept constant after 10 cycles while it
decreased continuously for parent one. The highest temperature
the thermocouple detected after air flowed in was named burning
temperature. Burning temperature of each cycle was also recorded
in Fig. 8, in which burning temperature of parent HZSM-5 was
around 645 °C, while that of HZSM-5-0.3M was 40 °C lower than
parent HZSM-5 catalyst. First, it is understandable that carbon yield
of hydrocarbons of HZSM-5-0.3M was higher than that of HZSM-5-P
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 9
RSC Advances
Please do not adjust margins
Journal Name ARTICLE
decrease of coke content.
15. Y. M. Ni, A. M. Sun, X. L. Wu, G. Hai, J. L. Hu, T. VLiiewanAdrticGle.OXn.linLei,
Micropor. Mesopor. Mat., 2011, 143, 435-442.
DOI: 10.1039/C6RA05356D
16. H. Mochizuki, T. Yokoi, H. Imai, S. Namba, J. N. Kondo and T.
Tatsumi, Appl. Catal. A-Gen., 2012, 449, 188-197.
17. K. Y. Nandiwale, S. K. Sonar, P. S. Niphadkar, P. N. Joshi, S. S.
Deshpande, V. S. Patil and V. V. Bokade, Appl. Catal. A-Gen., 2013,
460, 90-98.
Conclusion
Catalytic conversion of furan as an important intermediate from
BFP was conducted on a micro-mesoporous HZSM-5 catalyst by
alkali treatment for hydrocarbons. The prepared sample of HZSM-5-
0.3M with sheet-like mesopores presented the best catalytic
performance with carbon yield of hydrocarbons boosted to 21.6%.
The appropriate desilicated HZSM-5 catalyst showed higher
selectivity to olefins, and more serious coke deposition but higher
tolerance toward coking. Moreover, the cyclic tests of catalysis-
regeneration process indicated that hierarchical HZSM-5 zeolites
are potentially suitable for long-term operation. The hierarchical
HZSM-5 catalyst successfully combined the high selectivity of
microporous system and promoted mass transfer of mesopores in
CFP of biomass for hydrocarbon production.
18. W. C. Yoo, X. Zhang, M. Tsapatsis and A. Stein, Micropor.
Mesopor. Mat., 2012, 149, 147-157.
19. A. H. Janssen, I. Schmidt, C. Jacobsen, A. J. Koster and K. P. De
Jong, Micropor. Mesopor. Mat., 2003, 65, 59-75.
20. K. A. Tarach, J. Tekla, W. Makowski, U. Filek, K. Mlekodaj, V.
Girman, M. Choi and K. Gora-Marek, Catal. Sci. Technol., 2015, 10-
1039.
21. D. Li, J. Yang, W. Tang, X. Wu, L. Wei and Y. Chen, RSC Adv.,
2014, 4, 26796-26803.
22. H. Zhu, G. Li, X. Lv, Y. Zhao, T. Huang, H. Liu and J. Li, RSC Adv.,
2014, 4, 6535-6539.
23. L. L. Su, L. Liu, J. Q. Zhuang, H. X. Wang, Y. G. Li, W. J. Shen, Y. D.
Xu and X. H. Bao, Catal. Lett., 2003, 91, 155-167.
Acknowledgement
24. J. S. Jung, J. W. Park and G. Seo, Appl. Catal. A-Gen., 2005, 288,
149-157.
The authors acknowledge the financial support of the National
Natural Science Foundation of China (Grant No. 51306036,
51561145010 and 51525601), the National Basic Research Program
of China (973 Program, Grant 2012CB215306), the Jiangsu Natural
Science Foundation (Grant No. BK20130615) and the Scientific
Research Foundation of Graduate School of Southeast University
(YBJJ1324).
25. D. Verboekend and J. Pérez-Ramírez, Catal. Sci. Technol., 2011,
1, 879-890.
26. S. S. Shao, H. Y. Zhang, Y. Wang, R. Xiao, L. J. Heng and D. K.
Shen, Energ. Fuel., 2015, 29, 1751-1757.
27. A. Koekkoek, W. Kim, V. Degirmenci, H. Xin, R. Ryoo and E.
Hensen, J. Catal., 2013, 299, 81-89.
28. Z. J. Hu, H. B. Zhang, L. Wang, H. X. Zhang, Y. H. Zhang, H. L. Xu,
W. Shen and Y. Tang, Catal. Sci. Technol., 2014, 4, 2891-2895.
Reference
1. P. S. Rezaei, H. Shafaghat and W. M. A. W. Daud, RSC Adv., 2015,
5, 65408-65414.
2. A. Veses, M. Aznar, I. Martínez, J. D. Martínez, J. M. López, M. V.
Navarro, M. S. Callén, R. Murillo and T. García, Bioresour. Tech.,
2014, 162, 250-258.
29. W. P. Zhang, X. W. Han, X. M. Liu and X. H. Bao, Micropor.
Mesopor. Mat., 2001, 50, 13-23.
30. M. Rutkowska, D. Macina, N. Mirocha-Kubień, Z. Piwowarska
and L. Chmielarz, Appl. Catal. B-Environ., 2015, 174, 336-343.
31. C. Doremieux-Morin, A. Ramsaran, R. Le Van Mao, P. Batamack,
3. K. G. Wang and R. C. Brown, Green Chem., 2013, 15, 675-681.
L. Heeribout, V. Semmer, G. Denes and J. Fraissard, Catal. Lett.,
1995, 34, 139-149.
32. F. S. Xiao, L. F. Wang, C. Y. Yin, K. F. Lin, Y. Di, J. X. Li, R. R. Xu, D.
4. H. Y. Zhang, T. R. Carlson, R. Xiao and G. W. Huber, Green Chem.,
2012, 14, 98-110.
5. E. L. Kunkes, D. A. Simonetti, R. M. West, J. C. Serrano Ruiz, C. A.
S. Su, R. Schlögl and T. Yokoi, Angew. Chem., 2006, 118, 3162-3165.
33. J. C. Groen, J. A. Moulijn and J. Pérez-Ramírez, J. Mat. Chem.,
2006, 16, 2121-2131.
Gärtner and J. A. Dumesic, Science, 2008, 322, 417-421.
6. T. P. Vispute, H. Y. Zhang, A. Sanna, R. Xiao and G. W. Huber,
Science, 2012, 330, 1222-1227.
34. J. R. García, M. Bertero, M. Falco and U. Sedran, Appl. Catal. A-
Gen., 2015, 503, 1-8.
7. Á. Ibarra, A. Veloso, J. Bilbao, J. M. Arandes and P. Casta O, Appl.
Catal. B-Environ., 2016, 182, 336-346.
8. H. Y. Zhang, M. M. Luo, R. Xiao, S. S. Shao, B. S. Jin, G. M. Xiao,
M. Zhao and J. Y. Liang, Bioresour. Tech., 2014, 155, 57-62.
35. J. S. Kim, Y. Y. Lee and T. H. Kim, Bioresour. Tech., 2016, 199,
42-48.
36. M. Choi, K. Na, J. Kim, Y. Sakamoto, O. Terasaki and R. Ryoo,
Nature, 2009, 461, 246-249.
9. D. Chen, K. Moljord and A. Holmen, Micropor. Mesopor. Mat.,
2012, 164, 239-250.
37. J. Kim, M. Choi and R. Ryoo, J. Catal., 2010, 269, 219-228.
38. A. J. Foster, J. Jae, Y. T. Cheng, G. W. Huber and R. F. Lobo, Appl.
Catal. A-Gen., 2012, 423, 154-161.
39. F. Schmidt, M. R. Lohe, B. Büchner, F. Giordanino, F. Bonino and
S. Kaskel, Micropor. Mesopor. Mat., 2013, 165, 148-157.
40. F. L. Bleken, K. Barbera, F. Bonino, U. Olsbye, K. P. Lillerud, S.
Bordiga, P. Beato, T. V. W. Janssens and S. Svelle, J. Catal., 2013,
307, 62-73.
10. K. G. Wang, K. H. Kim and R. C. Brown, Green Chem., 2014, 16,
727-735.
11. S. Vitolo, B. Bresci, M. Seggiani and M. G. Gallo, Fuel, 2001, 80,
17-26.
12. C. A. Mullen and A. A. Boateng, ACS Sustain. Chem. Eng., 2015,
7, 1623-1631.
13. S. S. Shao, H. Y. Zhang, L. J. Heng, M. M. Luo, R. Xiao and D. K.
Shen, Ind. Eng. Chem. Res., 2014, 53, 15871-15878.
14. M. Firoozi, M. Baghalha and M. Asadi, Catal. Commun., 2009,
10, 1582-1585.
41. Y. H. Kim, K. H. Lee and J. S. Lee, Catal. Today, 2011, 178, 72-78.
42. H. Y. Zhang, S. S. Shao, R. Xiao, D. K. Shen and J. M. Zeng, Energ.
7
J. Name., 2013, 00, 1-3 |
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 8 of 9
ARTICLE
Journal Name
Fuel., 2014, 28, 52-57.
View Article Online
DOI: 10.1039/C6RA05356D
43. J. C. Zhang, H. B. Zhang, X. Y. Yang, Z. Huang and W. L. Cao, J.
Nat. Gas Chem., 2011, 20, 266-270.
44. A. T. Aguayo, A. G. Gayubo, A. Atutxa, M. Olazar and J. Bilbao, J.
Chem. Technol. Biot., 1999, 74, 1082-1088.
8
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 9
RSC Advances
View Article Online
DOI: 10.1039/C6RA05356D
Alkali treated ZSM-5 with sheet-like mesopores showed higher yield of hydrocarbons in CFP of biomass, withstanding long-running over
catalysis-regeneration cycles.
30
25
20
15
10
650
640
630
620
610
600
HZSM-5-P
HZSM-5-0.3M
HZSM-5-P
HZSM-5-0.3M
0
5
10
15
20
Number of cycle