J. Liu et al.
low energy density, high viscosity, and low stability [8–10].
Therefore, phenolic bio-oils, consisting of phenolic mol-
ecules such as phenol, guaiacol, syringol, and their deriva-
tives, require significant deoxygenation to convert into
conventional transport alkane fuels [9, 11]. Phenolic com-
pounds are generally regarded as important model com-
pounds for bio-oils [5], and hydrodeoxygenation is deemed
to be the most effective method for bio-oil upgrading [12].
The conventional hydrodeoxygenation studies have
focused on NiMo and CoMo sulfide catalysts that are
industrial hydrotreating catalysts developed for removal
of sulfur, nitrogen and oxygen from petrochemical feed-
stocks. However, these catalysts may be less suitable for
hydrodeoxygenation of bio-oil due to sulfur contamina-
tion, coke accumulation, and water-induced catalyst deac-
tivation [13–15]. An alternative approach based on sulfur-
free catalysts, liquid acids (e.g., phosphoric acid, acidic
ionic liquids) mixed with metals have been developed for
hydrodeoxygenation via consecutive hydrogenation and
dehydration steps. However, these homogeneous acids add
complexity when regenerating the reaction systems, which
is energy-consuming [4, 16]. Recently, aluminosilicate zeo-
lites (e.g., ZSM-5, Beta and Y), as typical solid acids, com-
bined with metals have been used to catalyze the hydrode-
oxygenation of phenolic compounds to alkanes [17–19].
Additionally, zeolite based catalysts exhibiting high stabil-
ity, easy separation, and abundant acidic sites, are regarded
to be one of the most promising catalysts in the application
of bio-oil upgrading. However, conventional zeolite cata-
lysts often suffer from slow diffusions of bulky reactants/
products in their channel systems, as a result of their small
pore size (<1.5 nm) [20, 21]. Therefore, the production of
relatively bulky bioalkanes is a challenge in the hydrodeox-
ygenation of phenolic bio-oil over zeolite-based catalysts.
Mesoporous zeolites, with hierarchical porous struc-
tures containing both micro- and mesopores, have attracted
much attention as a new type of promising catalytic mate-
rials [22–24]. The mesoporous zeolite based catalysts
have exhibited unique catalytic properties in many reac-
tions because of their efficient mass-transport property
compared with the conventional zeolites [25]. For exam-
ple, mesoporous ZSM-5-supported metal sulfide catalysts
biomolecules [28]. However, mesoporous zeolites sup-
ported inexpensive Ni catalyst is rarely reported for con-
version of biomass, although it is a promising bifunctional
catalyst for industrial application due to the high activity
for hydrodeoxygenation of biomass and lower cost.
In this work, a facile method was used for synthesizing
mesoporous ZSM-5 (MZSM-5) at low cost. To enhance the
hydrodeoxygenation activity, the HMZSM-5 zeolite mixed
with a 25 wt% fraction of γ-Al O (Al-HMZSM-5) was
2
3
designed as a more effective catalyst support. The phenol
hydrodeoxygenation activities of Ni catalysts supported on
ZSM-5, MZSM-5, γ-Al O and mixed Al-MZSM-5 zeolite
2
3
materials were compared to try to establish a relationship
between activity and catalyst structure. Meanwhile, the
physicochemical properties of the catalysts, such as their
acidity, surface area, and pore structure, have been evalu-
ated by various techniques.
2 Experimental
2.1 Catalyst Preparation
All reagents used were of analytical grade and were used
as-purchased without further purification. Mesoporous
ZSM-5 zeolite (MZSM-5) and conventional micropo-
rous ZSM-5 were prepared by our previously reported
approach [27]. MZSM-5 was synthesized hydrothermally
from an aluminosilicate gel with a molar composition of
Al O /50SiO /8.9Na O/0.02RCC/1950H O, where RCC
2
3
2
2
2
was a random cationic copolymer that contained quater-
nary ammonium groups and was used as mesoscale tem-
plate [23]. ZSM-5 was synthesized under the same condi-
tions except for the absence of RCC. Furthermore, H-type
+
zeolites (HZSM-5 and HMZSM-5) were obtained by NH
4
ion exchange. The Na-type MZSM-5 and ZSM-5 were
treated with 1.0 mol/L NH Cl aqueous solution at 80 °C for
4
5 h under stirring, in a ratio of 1.0 g solid sample to 20 mL
NH Cl solution. After filtration, washing, drying at 120 °C
4
overnight, and calcination at 450 °C in air for 4 h, the pro-
cess was repeated again.
γ-Al O powder was obtained by calcining commer-
2
3
(
NiMoS/MZSM-5 and CoMoS/MZSM-5) exhibited high
cial pseudo boehmite in air at 450 °C for 2 h. A mixture
activity in the deep hydrogenation of bulky aromatic phen-
anthrene [26]. The ZSM-5-based catalysts with mesopores,
as highly selective Fischer–Tropsch catalysts, gave much
higher selectivity to C –C isoparaffins than the conven-
of HMZSM-5 and γ-Al O (Al-HMZSM-5) was prepared
2
3
by mixing 25 wt% γ-Al O (100–120 mesh) with 75 wt%
2
3
HMZSM-5 (80–100 mesh) in excess distilled water under
vigorous stirring at room temperature, followed by drying
in air at 120 °C for 12 h and calcination at 450 °C for 4 h.
Then, supported nickel catalysts (Ni/HZSM-5, Ni/
HMZSM-5, Ni/Al-HMZSM-5 and Ni/γ-Al O ) were
5
11
tional ZSM-5-based catalysts [27]. Mesoporous Y zeo-
lite-supported Pd nanoparticles was more active in the
hydrodesulfurization of 4,6-dimethyldibenzothiophene
than conventional zeolite-based catalysts [24]. Recently,
mesoporous ZSM-5-supported Ru or Pt metals were
used as highly efficient catalysts for upgrading phenolic
2
3
prepared by an incipient wetness impregnation method
using aqueous solutions containing required amounts of
nickel nitrate (the nominal Ni loading of 10.0 wt%). After
1
3