Stabilized Ni-based catalysts for bio-oil hydrotreatment: Reactivity studies using guaiacol

Article abstract of DOI:10.1016/j.cattod.2013.10.023

The development of catalysts possessing high activity and high stability in the catalytic hydrotreatment of pyrolysis oils (bio-oil) is of great interest. NiCu bimetallic catalytic systems are very attractive for use in hydrotreatment process due to their low price and high activity in hydrogenation, hydrodeoxygenation and hydrocracking reactions. In the present work P-/Mo-containing agents were used to modify bimetallic catalytic system NiCu/SiO₂-ZrO₂ to improve its mechanical strength and stability in acidic medium. The modified catalysts were tested in hydrodeoxygenation (HDO) of guaiacol - a well-known model compound of bio-oil. HDO process has been carried out in an autoclave at 320 C, 17 MPa initial hydrogen pressure, reaction time 1 h. It was shown that phosphorus and molybdenum addition to the catalysts composition results in the decrease of guaiacol conversion and deoxygenation degree. The yield of undesirable gaseous reaction products (mainly methane) and coking of the catalyst were lower for the modified catalysts in contrast to the initial NiCu/SiO₂-ZrO ₂ system. The catalysts treatment in glacial acetic acid at 118 C showed that modification by P and Mo gives a significant improvement of catalysts stability in acidic medium (mass loss decreases from 53 wt.% to 1 wt.%). Also a significant improvement of bulk crushing strength has been observed for PMo-modified samples (from 0.5 MPa to 1.2 MPa).

Full text of DOI:10.1016/j.cattod.2013.10.023

Catalysis Today 220–222 (2014) 21–31
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Catalysis Today
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Stabilized Ni-based catalysts for bio-oil hydrotreatment:
Reactivity studies using guaiacol
M.V. Bykovaa,b,∗, D.Yu. Ermakova, S.A. Khromovaa,b, A.A. Smirnova,
M.Yu. Lebedeva, V.A. Yakovleva,c
a Boreskov Institute of Catalysis SB RAS, Pr. Akad. Lavrentieva, 5, Novosibirsk 630090, Russia
b Novosibirsk State University, Pirogova Str. 2, 630090, Novosibirsk, Russia
c UNICAT Ltd., Pr. Akad. Lavrentieva, 5, Novosibirsk 630090, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 April 2013
Received in revised form 3 October 2013
Accepted 7 October 2013
Available online 1 November 2013
The development of catalysts possessing high activity and high stability in the catalytic hydrotreatment
of pyrolysis oils (bio-oil) is of great interest. NiCu bimetallic catalytic systems are very attractive for use
in hydrotreatment process due to their low price and high activity in hydrogenation, hydrodeoxygena-
tion and hydrocracking reactions. In the present work P-/Mo-containing agents were used to modify
bimetallic catalytic system NiCu/SiO2–ZrO2 to improve its mechanical strength and stability in acidic
medium. The modified catalysts were tested in hydrodeoxygenation (HDO) of guaiacol—a well-known
model compound of bio-oil. HDO process has been carried out in an autoclave at 320 ◦C, 17 MPa initial
hydrogen pressure, reaction time 1 h. It was shown that phosphorus and molybdenum addition to the
catalysts composition results in the decrease of guaiacol conversion and deoxygenation degree. The yield
of undesirable gaseous reaction products (mainly methane) and coking of the catalyst were lower for
the modified catalysts in contrast to the initial NiCu/SiO2–ZrO2 system. The catalysts treatment in glacial
acetic acid at 118 ◦C showed that modification by P and Mo gives a significant improvement of catalysts
stability in acidic medium (mass loss decreases from 53 wt.% to 1 wt.%). Also a significant improvement
of bulk crushing strength has been observed for PMo-modified samples (from 0.5 MPa to 1.2 MPa).
© 2013 Elsevier B.V. All rights reserved.
Keywords:
Bio-oil
Hydrotreatment
Hydrodeoxygenation
Guaiacol
Modified Ni-based catalyst
1. Introduction
chemically unstable [6]. Co-processing of bio-oil and conventional
oil refinery products on the FCC units using traditional oil refinery
Currently the problem of the limited fossil energy sources
becomes more evident. Their rapid depletion is inevitable in future
due to the constant growth of a human energy demand. Motor
fuels production from plant biomass is a considerable alterna-
tive to fossil oils. Thermochemical treatment by pyrolysis is of
great interest among the approaches used for the biomass con-
version. The yield of a liquid pyrolysis products, so called bio-oil,
can come up to 70–80 wt.% in special reaction conditions, when
the elevated temperatures (450–550 ◦C) are combined with the
extremely short residence time (< 1 s) under oxygen-free atmo-
sphere [1,2]. The process being carried out at such conditions is
called fast pyrolysis. However, thus obtained bio-oil is not suitable
for the direct use as transport fuel due to the high water content
and the presence of different oxygen-containing organic com-
pounds in its composition (organic acids, aldehydes, ketons, sugars,
aromatics, etc.) [3–5]. Because of the chemical complexity fast
pyrolysis oils are corrosive, acidic (pH ≈ 2–3), and thermally and
equipment is of particular interest [7]. But before co-processing
an upgrading of the crude bio-oil is required to reduce its polar-
ity and increase its miscibility with non-polar petrochemicals. An
attractive way for the improvement of the bio-oil quality is catalytic
hydrotreatment (hydrodeoxygenation, HDO) [1,8–15]. Similarly to
the hydrotreating of fossil oils (hydrodesulfurization) [16,17] HDO
process is considered as an effective way for the selective oxygen
removal from the biomass pyrolysis products. The main chemi-
cal reactions are hydrocracking, decarbonylation, decarboxylation,
hydrodeoxygenation, cracking, and hydrogenation. However, the
catalytic hydrotreatment of pyrolysis oils is far from the commer-
cial scale in contrast to the conventional refining, and intensive
research is required. The focus of this paper concerns the catalytic
systems suitable for bio-oil hydrotreatment. The investigations
in this field started in 1980’s, and the first papers on the cat-
alytic hydrotreatment of oxygen-containing feed were published
[18,19]. The first catalytic systems used in HDO of bio-oil and its
model compounds were conventional sulfided NiMo and CoMo
alumina-supported desulfurization catalysts and noble metal based
catalysts (Pt, Pd, Rh, Ru) [20]. These catalytic systems possessed
high activity in target hydrodeoxygenation process, but some of
∗
Corresponding author. Tel.: +7 383 326 96 52; fax: +7 383 330 62 54.
E-mail address: bykova@catalysis.ru (M.V. Bykova).
0920-5861/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cattod.2013.10.023

22
M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
Table 1
Catalysts composition (measured by ICP-OES) and texture characteristics (BET method) after the reduction at 0.1 МPɑ Н2, Н2 flow rate–200 cm3/min (the reduction
temperature was selected according to the TPR analysis).
No.
Tred (◦C)
Active component (wt.%)
Stabilizing component ZrO2-SiO2, wt.%
ABET (m2/g)
Vꢀ (cm3/g)
<d> (Å)
Ni
Cu
Mo
P
1
2
3
4
5
400
500
500
500
500
52
48
48
42
39
5.6
5.2
5.1
4.5
4.2
12–27
11–25
11–25
9.7–22
8.9–20
188
115
139
135
113
0.19
0.12
0.17
0.16
0.15
41
42
47
46
53
8.8
4.9
4.7
7.1
10.1
9.7
their disadvantages were also revealed [20–23]. Conventional sul-
fided catalysts deactivated due to sulfur removal from the catalysts
composition and oxidation of the active sulfide phase. Addition of
sulfur-containing agents (H2S, CS2) to maintain catalyst activity
resulted in products contamination with sulfur [24,25]. The main
disadvantage of noble metal based catalysts is high cost that makes
their use in hydroprocessing of bio-oils economically unprofitable.
Thus, an important task is the development of the catalysts meeting
all the necessary requirements for use in bio-oil hydrotreatment.
They are the low cost, non-sulfided nature, high activity and stabil-
ity to coking, stability in corrosive media (against leaching) at high
temperatures and pressures, high thermal stability (e.g. against
agglomeration) and ability for multiple regeneration by coke com-
bustion. As an alternative for the sulfided catalysts and noble metal
based catalysts mentioned above, non-sulfided systems based on
transition metals (Ni, Fe, Co, Mo, etc.) were considered [8]: systems
with the metallic state of the active component [26–29], transition
metal oxides [8,27,30,31], transition metal phosphides [32–35] and
amorphous boron-containing catalysts [36–39], etc. They catalyze
hydrogenation and hydrodeoxygenation reactions and are cheaper
than noble metal based ones.
Recent works have shown that Ni–Cu bimetallic supported cat-
alysts are highly active in catalytic hydrotreatment of bio-oil and
its model compounds [26,29]. In terms of activity in the target pro-
cess these catalysts were comparable with the noble metal based
systems and better than commercial sulfided hydrotreating cata-
lysts [26]. The role of copper in these systems is to decrease the
reduction temperature of nickel oxide species followed by the for-
mation of NixCu1−x solid solution. Moreover Cu addition results
in the decrease of undesirable products yield (mainly CH4) during
hydrotreatment of oxygen-containing compounds [26]. However,
despite high activity of supported NiCu catalysts, they had a number
of disadvantages: low stability in acidic medium (active compo-
nent leaching), low thermal stability (active component particles
agglomeration) and tendency to coking [29]. Thus, one of the
prospective directions for further research is the development of
new Ni-based catalysts possessing high activity and improved sta-
bility in hydrodeoxygenation of oxy-organic compounds including
bio-oil. A possible way to improve catalysts is the use of modifying
additives.
stability of these alloys to corrosion is particularly high. Therefore
the aim of the present study was to investigate the effect of phos-
phorus and molybdenum as modifying additives on the stability
and activity of Ni-based catalysts. The initial catalytic system used
was sol–gel catalyst NiCu/SiO2–ZrO2. This catalyst was similar to
NiCu/SiO2 and NiCu/SiO2–ZrO2–La2O3 previously studied in HDO
of guaiacol, and their high activity was reported in [46].
2. Experimental
2.1. Catalyst preparation
At the first stage catalytic system NiCu/SiO2 was prepared
using sol–gel method described elsewhere [47]. The appropriate
amounts of commercial NiCO3·mNi(OH)2·nH2O, CuCO3·mCu(OH)2
were mixed with required amount of aqueous ammonia solution
(25% NH3) in ball mill. Afterwards, the suspension was filtered
out, dried in air at 120 ◦C for 12 h and calcined at 400 ◦C for 4 h.
Thus obtained nickel–copper mixed oxide system was crushed and
sieved (fraction 2-5 mm). After that the granules were impregnated
by commercial ethyl silicate-32 (ES) comprising SiO2 in amount
of 32%, which was used as the silica precursor without any addi-
tional treatment. The desired NiCu/SiO2 ratio was provided by
diluting ES with ethyl alcohol. Samples were dried at room tem-
perature, then at 120 ◦C for 12 h and calcined at 400 ◦C for 4 h. The
granules of NiCu/SiO2 catalyst thus prepared were impregnated
by ZrO(NO3)2 salt solution of required concentration to improve
catalyst mechanical strength and thermal stability [48]. Then the
catalysts was dried at 120 ◦C for 12 h and calcined at 400 ◦C for
4 h. Thus obtained catalytic system was modified by molybdenum-
and/or phosphorus-containing agents. The modification procedure
was performed by impregnating of NiCu/SiO2–ZrO2 system with
(NH4)6Mo7O24·4H2O and/or H3PO4 aqueous solution of required
concentration. After each impregnation stage the catalyst was dried
at 120 ◦C for 12 h followed by the calcination at 500 ◦C (4 h). At the
final stage the modified catalysts were reduced in a quartz reactor
in a hydrogen flow. The reduction temperature was chosen accord-
ing to the TPR analysis of the catalysts (see Section 3.1): 500 ◦C
in the case of Mo- and P-modified systems, 400 ◦C—non-modified
catalyst NiCu/SiO2–ZrO2. After 2 h of the reductive treatment the
catalyst was cooled down in a hydrogen flow. Upon reaching room
temperature hydrogen was switched to argon and the catalyst was
passivated by ethanol and dried at the room temperature.
According to the data available from the literature [32,40–43], P-
modified hydrotreating catalysts and catalysts based on transition
metal phosphides were intensively studied in hydrodesulfurization
(HDS) and hydrodenitrogenation (HDN) of crude oil and certain
sulfur- and nitrogen-containing compounds. The use of these cat-
alysts in hydrodeoxygenation processes is much less reported
[32–35]. According to [44], transition metal-rich phosphides have
physical properties similar to those of ordinary metallic compounds
like the carbides, nitrides, borides and silicides. They combine the
properties of metals and ceramics, and thus are good conductors
of heat and electricity, are hard and strong, and have high thermal
and chemical stability. On the other hand according to [45], Ni–Mo
alloys with the Mo content of 15 wt.% (in relation to nickel) possess
high stability in acids. When Mo content is higher than 20 wt.% the
Table 1 presents the chemical composition (measured by ICP-
OES) and texture characteristics (BET method) of catalysts used in
the present study. The catalysts were characterized in their reduced
form.
2.2. Catalytic hydrotreatment of guaiacol
The catalysts were tested in HDO of guaiacol on a high-pressure
set up (Autoclave Engineers, USA) in a sealed 300 mL stainless steel
batch reactor (EZE Seal type). Before the reaction, the catalysts (1 g,
0.05–0.1 mm fraction) were activated inside the reactor in a flow

M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
23
of 100% H2 (200 mL/min, 0.1 MPa), heating rate—10 ◦C/min. Upon
reaching the temperature of 400 ◦C the reactor was cooled down.
After the activation, 30 mL of guaiacol (Acros Organics, 99%) was
placed into the reactor at 0.1 MPa and 25 ◦C without access of air
to prevent the catalyst oxidation. After that, the reactor was pres-
surized to 11 MPa H2 at room temperature and then sealed. The
hydrogen-to-guaiacol molar ratio was kept the same in all experi-
ments. Further, the reactor was heated by an oven until the preset
temperature (320 ◦C), which led to a pressure increase up to 17 MPa.
The reaction duration was taken to coincide with the stirring time,
which was equal to 1 h. The stirring rate was 2000 rpm. The reaction
was accompanied with a gradual pressure decrease which was not
compensated by addition of hydrogen. After the reaction, the reac-
tor was cooled to the room temperature, and liquid and gaseous
products were analyzed.
where ϕi(%) is the fraction of i-product in the liquid phase, taking
into account unreacted guaiacol.
Product selectivities and yields were calculated according to Eqs.
(5) and (6), respectively:
ni
Si(%) =
· 100
(5)
A
· n0GUA · X
i
A
GUA
ni
· n0GUA
Wi(%) =
· 100 = Si · X,
(6)
A
i
A
GUA
where Ai and AGUA are stoichiometric coefficients in the reaction of
guaiacol conversion into i-product.
2.4. Catalyst stability
2.3. Analysis of the reaction products
2.4.1. Carbon deposition
The amount of coke deposited on the catalyst surface after
the reaction was determined using a thermogravimetric ana-
lyzer SHIMADZU-DTG-60H (Japan). Catalyst samples (0.01 g) were
heated in corundum crucibles with a constant heating rate of
10 ◦C/min from the ambient temperature to 600 ◦C. All measure-
ments were carried out under air (0.1 MPa).
Qualitative analysis of the guaiacol HDO liquid products
was carried out using an Agilent 7000B GC/MS spectrome-
ter equipped with a triple quadrupole analyzer and a HP-5ms
(J&W Agilent) quartz capillary column (stationary phase: 5%
phenyl–95% dimethylpolysiloxane, 30 m × 0.25 mm × 0.25 ␮m),
NIST.11 database was used for identification of components. Quan-
titative analysis of the liquid products was performed on a Chromos
2.4.2. Corrosion resistance
GCh 1000 chromatograph equipped with
a Zebron ZB-35HT
The catalyst resistance to corrosion in acidic medium was deter-
mined by the treatment with glacial acetic acid under the severe
conditions. The catalyst in reduced form (1 g) was placed in the
flask filled with glacial acetic acid (100 mL), and after treatment at
118 ◦C for 2 h was washed by the distilled water and dried at 80 ◦C.
The catalyst corrosion resistance was calculated from the sample
mass loss (wt.%) after the acidic treatment.
INFERNO capillary column (stationary phase: 35% phenyl–65%
dimethylpolysiloxane, 30 m × 0.32 mm × 0.25 m) and flame ioniza-
tion detector. The gas phase (H2, CO, CO2, CH4) was analyzed on
a Chromos GCh 1000 chromatograph equipped with two columns
packed with silochrome or activated carbon (3 m × 2 mm i.d.) and
with thermal conductivity and flame ionization detectors, respec-
tively.
The internal normalization was used for the quantitative anal-
ysis of the components in the reaction mixture (mole). The total
amount of carbon atoms in the liquid phase, number of carbon
atoms in the molecule and each component fraction were taken
into account. The last parameter was calculated as the certain chro-
matographic peak area divided to the sum of all peak areas (detector
2.4.3. Mechanical strength
Determination of the bulk crushing strength of the catalysts was
carried out using Shell method (SMS method 1471). This method
allows determination of the resistance to crushing of a catalyst
grains bed. The equipment consists of a sample-holding cell and
an automated press controlled by a stepping motor. A representa-
tive catalyst sample (size fraction 2.5–4 mm) was dried in an oven
at 120 ◦C during 2 h then sieved with sieve opening 425 ␮m, 20 cm3
of the catalyst was taken and placed in the cell. The fines obtained
at the different pressure stages were separated by sieving, and
weighed. Particles which pass through the mesh of a sieve of open-
ing 425 ␮m (sieve ASTM E.11 No. 40) are considered as “fines”. The
Bulk Crushing Strength is expressed in terms of the pressure neces-
sary to obtain 0.5% fines: P (MPa) = F/A, where F—force to be applied
on the catalyst in Newton to produce 0.5% fines, A—cross-sectional
area of the sample holder in mm2.
sensitivity coefficients ␰ were taken as 1).
i
The catalyst activity was estimated according to guaiacol con-
version XGUA (%) and deoxygenation degree HDO (%), which were
calculated as follows:
n0GUA − nfGinUaAl
XGUA(%) =
· 100 = X · 100
(1)
n0GUA
ꢀ
ꢀ
⎛
⎞
n0GUA · X · 2 −
ni · ai
ni · ai
⎜
⎜
⎟
⎟
⎠
i
i
HDO (%) =
· 100 = 1 −
· 100
n0GUA · X · 2
nGUA · X · 2
0
⎝
2.5. Catalysts characterization
(2)
Elemental composition of the catalysts was determined using
Optical Emission Spectrometry with Inductively Coupled Plasma
(ICP-OES). ICP-OES analysis was performed on an “Optima 4300
DV” optical emission spectrometer from Perkin Elmer (USA).
Texture characteristics of the catalysts were measured at the
liquid nitrogen temperature using an ASAP-2400 automated volu-
metric adsorption analyzer (Micromeritics Instrument. Corp., USA).
Before the analysis, the samples were de-gassed at 150 ◦C and pres-
sure 0.13 Pa for 4 h. The analysis time was varied depending on the
particular sample. The resulting adsorption isotherms were used
to calculate the specific surface area ABET, the total pore volume
Vꢀ (from ultimate adsorption at a relative pressure of P/P0 = 1), the
micropore volume V␮pore, and the mean pore size <d>.
Oeliminated (%) = XGUA · HDO/100,
where n0GUA is the initial amount of guaiacol (mole), nGUA
amount of guaiacol (mole), ni is the amount of i-product (mole)
in the liquid phase (except for unreacted guaiacol), and ai is the
number of oxygen atoms in the molecule of i-product.
The product distribution was calculated as follows:
(3)
final is the final
ni
ϕi(%) =
· 100,
(4)
ꢁ
k
i=jni

24
M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
The TPR studies were performed in a 10% H2 + 90% Ar mix-
CAT1-10Mo-5P and CAT1-10Mo-7P (650 ◦C and 750 ◦C, corre-
spondingly) also include the reduction of Mo6+ to Мо4+ and Mo4+ to
Мо0 besides the reduction of the nickel species and phosphates. It
should be noted that the TPR profiles in the present study similar to
those reported by Li et al. [34], but are somewhat shifted towards
the lower temperatures. It can be attributed to the presence of cop-
per in our catalytic systems that induces catalysts reduction at the
lower temperatures.
Thus, according to the TPR data, before use in HDO processes P-
and Mo-modified catalysts need to be reduced at higher tempera-
tures if compared with the non-modified system NiCu/SiO2–ZrO2
(CAT1). Moreover, an important observation has been made about
the shape of TPR profiles of P- and/or Mo-modified catalysts. They
reveal one intense peak in contrast to non-modified catalyst CAT1.
It indicates the strong interactions of the components of these sys-
tems. Otherwise several peaks could be expected on the TPR profiles
starting from 200 ◦C and corresponding to the reduction of Ni(II),
Cu(II), and P and Mo oxide forms. Taking into account the above
mentioned observations and the catalysts performance in guaiacol
HDO (Section 3.3) it can be assumed that the formation of NiMo
alloys as well as phosphides is possible on reducing the catalysts.
According to the TPR data, the following temperatures were cho-
sen for catalysts activation before use in guaiacol HDO: 400 ◦C for
non-modified system NiCu/SiO2–ZrO2 (CAT1) and 500 ◦C for P- and
Mo-modified catalysts. In the latter case the temperature was cho-
sen not to exceed 500 ◦C to prevent undesirable agglomeration of
active Ni particles [46].
ture at a flow rate of 30 mL/min. The catalyst sample weight was
varied according to the metal content (mmet = 50 mg). The sam-
ple was placed into a U-shaped quartz reactor and was heated to
800–900 ◦C at a constant heating rate of 6 ◦C/min in the reductive
medium. The outlet concentration of hydrogen was recorded using
a thermal conductivity detector.
Transmission electron microscopy analysis (TEM) was per-
formed on a JEM-2010 (JEOL, Japan) electron microscope with a
lattice resolution of 0.14 nm and an accelerating voltage of 200 kV.
The samples for the TEM study were prepared by the ultrasonic
dispersing in ethanol and consequent deposition of the suspen-
sion upon a “holey” carbon film supported on an aluminum grid.
Local elemental analysis was performed with the EDX method on
an energy-dispersive X-ray Phoenix spectrometer equipped with a
Si(Li) detector with an energy resolution of 130 eV.
3. Results and discussion
3.1. Catalysts characterization by temperature-programmed
reduction
All the catalysts were characterized by the temperature-
programmed reduction technique (Fig. 1) to determine the optimal
temperature of the catalyst preliminary reduction. TPR profiles of
the catalysts used in the present study are given on Fig. 1. TPR
profile of the initial non-modified catalyst NiCu/SiO2–ZrO2 (Fig. 1,
CAT1) reveals peaks in the temperature range of 225–300 ◦C which
correspond to Ni(II) reduction in the presence of copper [49]. The
reduction of weakly bound NiO also takes place in this temper-
ature region, as the defective structure facilitates the reduction
at lower temperatures as compared to well-crystallized bulk NiO
[50]. A broad reduction peak with the maximum at 400 ◦C (Fig. 1,
CAT1) most likely indicates the strong metal-support interaction
as a result of the formation of hardly reducible nickel silicates
[46,47]. When P and Mo are added to the catalyst NiCu/SiO2–ZrO2
(CAT1) the maximum of hydrogen consumption (Fig. 1, CAT1,
CAT1-5P, CAT1-9Mo, CAT1-10Mo-5P, CAT1-10Mo-7P) shifts to the
higher temperatures (150–350 ◦C higher). Moreover, as opposed
to non-modified catalyst whose TPR profile shows several peaks,
TPR profiles of the modified systems reveal just one intense broad
peak. For the samples CAT1-9Mo, CAT1-5P/CAT1-10Mo-5P, and
CAT1-10Mo-7P this peak is centered at 550 ◦C, 650 ◦C, and 750 ◦C,
correspondingly.
3.2. Catalysts characterization by transmission electron
microscopy
Fig. 2 presents TEM images of the catalysts after the reduction
and passivation by ethanol: A, B are for CAT1 (400 ◦C), C, D for CAT1-
5P (500 ◦C), and E, F images correspond to CAT1-10Mo-7P (500 ◦C).
CAT1 (Fig. 2A and B) has a lamellar structure probably consist-
ing of oxide–silicate species typical for sol–gel Ni-based catalytic
systems [46]. Moreover, well-defined Ni metallic particles charac-
terized by higher density are observed for CAT1 (Fig. 2A and B)
with an average size of about 10 nm. Fig. 3 shows EDX data for the
catalysts CAT1, CAT1-5P, and CAT1-10Mo-7P after their reduction
to make a better distinction between active component particles
and the support. In the case of CAT1 (Fig. 3A) which has the sim-
plest chemical composition among the catalysts concerned, nickel
and copper are uniformly distributed over the catalyst. Area No. 2
most likely corresponds to the metal particle as it contains smaller
amount of Si (atomic %) if compared with areas No. 1 and 3, and
has considerably higher density. Zirconium is non-uniformly dis-
tributed over the catalyst due to its preparation technique. The
fragments with oxide–silicate lamellar structure also remain on
the TEM images of P- and Mo-modified catalysts (Fig. 2C–F). But
the catalysts morphology markedly changes, as the formation of
well-crystallized particles is observed (dark areas on Fig. 2C–F).
According to the EDX data (Fig. 3B and C), these are most likely
phosphide particles, for example No. 1, 3 and 4 on the Fig. 3B. In
the case of P-containing catalyst CAT1-5P (Fig. 2C and D and Fig. 3B)
these particles (100–150 nm) have a structure of Ni3P, Ni12P5 and
contain copper as well. Area No. 2 (Fig. 3B) most probably corre-
sponds to the mixed oxide phases containing Si, Zr, Ni, Cu, and
P with complex composition based on its amorphous structure
and EDX data. In the case of CAT1-10Mo-7P phosphide particles
also contain copper and molybdenum (Fig. 3C, Areas No. 3–5).
Areas No. 1 and 2 on the Fig. 3C most probably correspond to the
mixed oxide species containing Si, Zr, Ni, Cu, P and Mo. It should
be also noted that CAT1-10Mo-7P is inferior to CAT1-5P in the
amount of phosphide particles as well as their size. The possible
explanation is incomplete reduction of CAT1-10Mo-7P under the
According to [34], a small peak at 270 ◦C on CAT1-9Mo TPR pro-
file (Fig. 1) can be attributed to the reduction of weakly bounded
NiO, and the reduction of Cu(II) species. Besides the reduction of
Mo6+ to Мо4+ can contribute to this peak. The latter broad intense
peak at 550 ◦C (Fig. 1, CAT1-9Mo) is related to the co-reduction of
Mo4+ to Mo0 (probably Mo6+ to Мо4+ as well) and Ni2+ to Ni0. It
should be taken into account that in the case of non-modified cat-
alyst CAT1 a strong interaction was observed between nickel oxide
and SiO2 accounted for by the silicates formation. From the shift of
the peak towards the higher temperatures in the case of CAT1-9Mo
(150 ◦C higher than that of CAT1) it can be assumed that a strong
interaction occurs between nickel and molybdenum oxide species
in this catalyst as well.
As it was noted for CAT1-9Mo the TPR profiles of CAT1-5P, CAT1-
10Mo-5P and CAT1-10Mo-7P reveal small peaks at 310–320 ◦C
(Fig. 1) which can be attributed to the reduction of weakly
bound NiO, CuO, and Mo6+ to Мо4+ (for Mo-containing samples
CAT1-10Mo-5P and CAT1-10Mo-7P). According to [34], a broad
intense peak at 650 ◦C on the TPR profile of P-containing sample
CAT1-5P corresponds to the reduction of nickel oxide forms and
high thermally stable P–O bond. Broad peaks in TPR profiles of

M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
25
Fig. 1. TPR profiles of CAT1 (NiCu/SiO2–ZrO2), CAT1-5P, CAT1-9Mo, CAT1-10Mo-5P and CAT1-10Mo-7P.
selected conditions (500 ◦C). According to the TPR analysis (Section
3.1), much higher temperatures are required for full reduction of
CAT1-10Mo-7P as compared to CAT1-5P (Fig. 1). As it can be noticed
from Fig. 2, the metallic particles in non-modified catalytic sys-
tem CAT1 are more dispersed than nickel phosphides particles in
modified catalysts. This indicates that more intense agglomera-
tion of active component takes place in the latter case due to the
higher reduction temperature applied (500 ◦C). These observations
are also in agreement with the catalysts activity in hydrotreat-
ment of guaiacol, which is discussed in the next Section 3.3. It
should be noted that total and detailed identification of all the
phases presented in the modified catalysts is complicated when
using TEM analysis. These catalytic systems possess a non-uniform
structure due to the complexity of their chemical composition and
to their multi-step preparation process. The following phases were
identified in P- and Mo-modified catalysts: CuO, NiO, MoO3, ZrO2
oxides, Ni2CuO3 mixed oxide, nickel phosphides with a structure
of Ni3P, Ni12P5 and probably with incorporated copper and molyb-
denum, NiMo and NiCu metallic particles, Ni3(PO4)2, and NiMoO4.
Moreover, mixed oxide phases containing Ni, Cu, P and Mo with
complex composition were found in the modified samples. For
this reason the images at a higher resolution are not displayed
here.
3.3. Catalytic activity in guaiacol HDO
A series of catalysts was tested in hydrotreatment of guaia-
col which is a well-known model compound of bio-oil [33,51–56].
All the experiments were performed at least twice and were well
reproducible. The standard deviations of the values obtained were
not more than 5%. The experimental results allowed us to estimate
the effect of molybdenum and phosphorus addition on the cata-
lyst activity. The experimental results are presented in Table 2.
Guaiacol conversion (XGUA, %) and deoxygenation degree (HDO,
%) were calculated according to the analysis of gaseous and liq-
uid reaction products. XGUA and HDO values were used to calculate
the percent of oxygen eliminated during the reaction (Oeliminated
,
%). This value is suitable to estimate the efficiency of HDO process
and to compare catalysts activity. As it is shown in Table 2, cata-
lyst modification by molybdenum and phosphorus results in the
decrease of activity, phosphorus addition causing more obvious
decline. For example, guaiacol conversion, deoxygenation degree

26
M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
Fig. 2. TEM images of the reduced catalysts: A,B—CAT1 (400 ◦C), C,D—CAT1-5P (500 ◦C), E,F—CAT1-10Mo-7P (500 ◦C). Reduction temperature is indicated in brackets.
Fig. 3. TEM images and EDX data of the reduced catalysts: A—CAT1 (400 ◦C), B—CAT1-5P (500 ◦C), C—CAT1-10Mo-7P (500 ◦C). Reduction temperature is indicated in brackets.

M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
27
and percent of eliminated oxygen for the catalysts CAT1-5P and
CAT1-10Mo-5P are approximately the same (Table 2). The com-
parison of catalysts CAT1-9Mo, CAT1-5P with initial non-modified
system CAT1 (NiCu/SiO2–ZrO2) shows more appreciable decrease
of catalyst activity in the case of P-modified sample. Moreover, cata-
lyst CAT1-10Mo-7P with the highest phosphorus content possessed
the lowest activity.
It is likely that the decrease of the catalytic activity of PMo-
modified catalysts can be attributed to the less amount of metallic
Ni. The results of the TPR study (see Section 3.1) confirm this
assumption. It is shown that Mo addition to NiCu/SiO2–ZrO2
(CAT1) composition results in rising of the catalyst reduction
temperature by 150 ◦C. Addition of phosphorus and increasing
its content result in higher reduction temperatures (250–350 ◦C
higher than that for CAT1). As it was mentioned above, the fol-
lowing reduction conditions were chosen for the catalysts in the
present study: 400 ◦C for non-modified system; 500 ◦C—for PMo-
modified catalysts. Thus, the TPR data and conditions used for
the catalysts activation allow one to assume that the portion of
Ni in its active metallic state in the catalyst composition should
comply the following order: CAT1 > CAT1-9Mo > CAT1-5P ≈ CAT1-
10Mo-5P > CAT1-10Mo-7P. This is in agreement with their catalytic
activity (Table 2). Taking into account the reduction temperatures
and more intense agglomeration of active component particles
(TEM, Fig. 2), lower catalytic activity can be expected for the mod-
ified samples. It is likely that nickel oxide species interacting with
phosphorus species are more difficult to reduce than Ni(II) being in
contact with molybdenum oxide species. On the other hand, high
temperature can have a negative effect on the active component
particles dispersion and hence catalytic activity. In this respect it
can be difficult to choose the appropriate reduction conditions.
The decrease of the gaseous products yield (mainly CH4) was
observed in the HDO of guaiacol over PMo-modified catalysts. This
is advantageous due to less amount of hydrogen being consumed
for the gaseous products formation. The mass balance was calcu-
lated with respect to the initial number of carbon atoms in 30 mL of
guaiacol (mole %). It was shown that the gaseous products content
decreased from 9.9 to 1.5–2.8% when using PMo-modified catalysts.
The catalysts stability to coking was improved in the case of mod-
ified samples as well. As shown in Table 2, the amount of carbon
deposits (coke) on the modified catalysts after the reaction becomes
lower. The decrease of the gaseous products yield and higher
stability to coking observed for P- and Mo-modified Ni-based cat-
alyst is remarkable. Deactivation due to coking has proven to be a
pronounced problem of hydrotreatment catalysts resulting in the
blockage of catalysts pores and active sites. Carbon is principally
formed through polymerization and polycondensation reactions
on the catalytic surface, forming polyaromatic species [8,11]. Car-
bon deposition on the catalyst depends on the process conditions
(temperature, etc.), properties of the catalyst surface and chemical
nature of the reactants. It was reported that oxygen contain-
ing hydrocarbons with unsaturated bonds (aromatic fragments)
have the highest affinity for carbon formation by polymerization
reactions on the catalysts surfaces [21]. Coking increases with
increasing acidity of the catalyst influenced by both Lewis and
Brønsted acid sites. Lewis acid sites bind species to the catalyst sur-
face. Brønsted sites donate protons to reactant molecules, forming
carbocations which are believed to be responsible for coking [21].
Moreover, it is known that coke builds up effectively on the metallic
Ni phase of catalysts, Cu addition prevents this process due to modi-
fication of the Ni ensemble environment (by Cu–Ni alloy formation)
[57]. It is likely that P and Mo additives have similar effect on the
Ni-based catalysts from the present study. The role of additives
is to change distances between active Ni sites and thereby sup-
press polymerization reactions (coking) being structure-sensitive
reactions.

28
M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
because the activity of the catalyst with higher phosphorus con-
tent becomes lower. The amount of condensation products in the
liquid phase decreases in the presence of the modified catalysts
as well (Table 2). All these results indicate that phosphorus and
molybdenum apparently are incorporated into the catalysts active
component, and in this respect the changes in products selectivity
are observed. This assumption is in agreement with the TEM anal-
ysis data (Section 3.2), it was shown that in P- and Mo-modified
catalysts the formation of nickel phosphides and NiMo metal par-
ticles was observed.
The yields (Wi, %) of guaiacol conversion products detected by
GC-MS are given in Table 3. The yield of cyclohexane is the high-
est among the reaction products over all the catalysts tested. In the
case of CAT1 and CAT1-9Mo catalysts the active sites responsible for
hydrodeoxygenation and hydrogenation reactions are Ni0 metallic
centers. For P-containing catalysts CAT1-5P, CAT1-10Mo-5P, and
CAT1-10Mo-7P the active sites are most probably located on the
surface of the phosphide particles and bear a small positive charge
Ni␦+. According to [34,58], Ni sites in phosphides possess high activ-
ity in hydrogenolysis and hydrogenation reactions. Besides it was
shown on Fig. 5 that P-containing samples in the present study
possess higher selectivity towards the formation of O-free hydro-
genation products if compared with CAT1 and CAT1-9Mo, even
though the guaiacol conversion was lower for P-containing cata-
lysts. This should clearly indicate that Ni sites with and without
phosphorus are different in their nature.
Fig. 4. Selectivities (Si, %) of the main products of guaiacol conversion at 320 ◦C, PH
(Treaction) = 17 MPa, reaction time 1 h.
2
It can be also noticed from Table 3 that the yield of methyl
substitution products (mainly methylguaiacols) is higher for P-
containing catalysts. According to Zhang et al. [54], it can be favored
by higher Lewis acidity of catalyst. The guaiacol molecule could
adsorb strongly on the acid sites of catalyst surface due to its polar
C–O bond and free p electron pair of the oxygen atom followed
by the heterolytic scission of the CH3–O bond. Then the positively
charged methyl group could be transferred to aromatic ring, which
results in the methylated products formation. In accordance with
Zhang et al. [54] and Li et al. [34], it is very likely that in the present
study the reduced metal sites Ni␦+ act as Lewis acid cites in the
phosphide-containing catalysts (CAT1-5P, CAT1-10Mo-5P, CAT1-
10Mo-7P) and are responsible for their activities towards methyl
substitution. The lack of such metal species with a small positive
charge in CAT1 and CAT1-9Mo may give a reasonable explanation
for their lower selectivities towards methyl substitution products.
The yield of the aromatic ring condensation products (con-
denses) becomes lower for modified catalysts which correlates
with their improved stability to coking (Table 2).
According to the data presented in Table 3 and data avail-
able from the literature, guaiacol conversion scheme over P-
and/or Mo-modified NiCu/SiO2–ZrO2 was suggested (Fig. 6). At
first guaiacol can be transformed by hydrodeoxygenation (HDO)
reactions into phenol and anisole. Phenol molecule can be fur-
ther converted by two routes: (i) hydrodeoxygenation (HDO) with
benzene formation; (ii) benzene ring hydrogenation (HYD) and
further dehydration–hydrogenation with the cyclohexane produc-
tion. Methylcyclopentane was also detected among the reaction
products, which likely could be due to the isomerization of cyclo-
hexene. Anisole is converted by hydrodeoxygenation (HDO) into
benzene with further hydrogenation (HYD) to cyclohexane. The
second route is anisole demethylation and methyl substitution
(MET) with o-cresole formation and subsequent conversion into
toluene and methylcyclohexane. Condenses can be formed from
guaiacol and other aromatic products by a variety of reactions.
Therefore, the corresponding reaction routes were not included
in the proposed scheme for simplification. The methyl substitu-
tion reactions are also shown among guaiacol conversion routes.
Although 1-hydroxycyclohexene was not identified by GC-MS anal-
ysis it was included into the reaction scheme as an intermediate
Fig. 5. Aliphatic-to-aromatic product selectivities ratio (total deoxygenation prod-
ucts) in HDO of guaiacol at 320 ◦C, PH = 17 MPa, reaction time 1 h.
2
Table 2 also presents H2 consumption data—the amount of
hydrogen (%) consumed during the reaction with respect to the
initial amount of hydrogen in the reactor. As it can be noticed from
the Table 2 this value complies the following order: CAT1 ≈ CAT1-
9Mo > CAT1-10Mo-5P > CAT1-10Mo-7P ≈ CAT1-5P, which is not in
line with the catalysts activity, but it conforms with the gaseous
products yield (see Table 2, Gas phase). This is reasonable because
a significant amount of hydrogen is consumed for methane forma-
tion.
The liquid reaction products distribution also changes for P-
and Mo-modified catalysts. Fig. 4 presents the selectivity of the
main liquid reaction products of guaiacol HDO. The selectivity
towards aliphatic products (cyclohexane and methylcyclopentane)
formation increases over phosphorus-containing catalyst CAT1-5P
as compared to CAT1. The selectivity towards the aromatic prod-
ucts formation increases (samples CAT1 and CAT1-9Mo, CAT1-5P
and CAT1-5P-10Mo) when Mo is used as an additive. Aliphatic-to-
aromatic products selectivity ratios (oxygen-free products, Si, %)
can be a more representative parameter in this case (Fig. 5). One
can see that Saliph/Sarom ratio is lower for molybdenum-containing
sample (Fig. 5, CAT1 and CAT1-9Mo). As opposed to it a marked
increase of Saliph/Sarom ratio is observed when using phosphorus as
an additive (Fig. 5, samples CAT1 and CAT1-5P). Saliph/Sarom ratio
decrease is observed when Mo is added to the P-modified sys-
tem (Fig. 5, CAT1-5P and CAT1-10Mo-5P). For the CAT1-10Mo-7P
sample the selectivity towards the aliphatic products formation
becomes unexpectedly lower than for CAT1-10Mo-5P. This is

M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
29
Table 3
Yields (Wi, %) of guaiacol HDO products. The process was performed in the autoclave at 320 ◦C and initial hydrogen pressure of 17 MPa, reaction time—1 h, mGUA:mcat = 33:1.
No.
Product
CAT1
CAT1-9Mo
CAT1-5P
CAT1-10Mo-5P
CAT1-10Mo-7P
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Methylcyclopentane
Cyclohexane
Benzene
Cyclohexene
Methylcyclohexane
Toluene
5.4
67
2.9
62
6.8
67
0.6
0.3
–
–
–
–
0.6
0.1
0.2
0.5
2.6
0.9
5.1
67
2.3
0.6
–
–
–
–
0.7
1.2
0.3
0.4
1.8
0.4
3.9
49
2.1
0.3
–
–
–
–
1.5
2.4
0.7
1.0
1.6
0.5
11.9
0.3
1.4
0.5
0.3
0.3
0.8
1.9
–
14.8
0.8
0.5
1.6
0.5
0.4
0.7
1.5
0.3
1.3
0.2
1.1
Cyclohexanol
Cyclohexanone
Methoxybenzene
Phenol
Methylcyclohexane-1,2-diols
1,2-Dimethoxybenzene
Methylguaiacols
Condenses
0.3
0.5
3.7
Table 4
product for cyclohexanone formation through the keto-enol tau-
tomerism [46]. Therefore this compound was placed in brackets
(Fig. 6).
Catalysts mass loss after the treatment in glacial acetic acid (118 ◦C, 2 h) and the
bulk crushing strength determined by the Shell method (SMS 1471). Catalysts were
tested in reduced form.
Guaiacol conversion over the transition metal phosphide cata-
lysts was previously reported by Zhao et al. [33]. The main products
of the reaction carried out at 300 ◦C, atmospheric pressure in a
packed bed reactor over Ni2P/SiO2 were aromatic compounds:
phenol, benzene, anisole, toluene. On the contrary in the present
study the main products were aliphatic compounds (cyclohexane,
methylcyclopentane). The most likely explanation is the difference
between contact times as well as hydrogen pressures used in both
studies. In the present work the hydrogen pressure was 11 MPa
(25 ◦C) and contact time of 1 h, and Zhao et al. performed their
experiments under the atmospheric pressure and contact time of
20.2 min.
Tred (◦C)
Mass loss (%)
Bulk crushing
strength (MPa)
a
Catalyst
CAT1-10Mo-7P
CAT1-10Mo-5P
CAT1-5P
CAT1-9Mo
CAT1 (NiCu/SiO2–ZrO2)
500
500
500
500
400
1.0
1.0
16.7
12.2
53.0
1.15
1.20
0.60
0.65
0.52
aReduction temperature.
done to find out whether the addition of modifiers would improve
the catalysts stability. The samples reduced at 500 ◦C (400 ◦C for
non-modified CAT1) and passivated by ethanol were tested.
The stability to corrosion of the modified samples as well as
non-modified CAT1 is given in Table 4.
3.4. Catalysts stability
The catalysts stability to corrosion in acidic medium was studied
by the catalysts treatment in glacial acetic acid at 118 ◦C. This was
As it is shown in Table 2 (Section 3.3), non-modified cat-
alytic system CAT1 possesses the highest activity in guaiacol HDO
O
HO
HO
HO
OH
OH
1-Hydroxy-
Cyclohexanone
HYD
cyclohexene
D
Y
Methylcyclopentane
HO
HO
D
Y
H
CH3
Methylcatechols
CH3
H
Methylcyclohexane-
HYD
HYD
1,2-diols
-H2O
MET
H
O
D
Phenol
D
Cyclohexanol
Cyclohexene
Cyclohexane
H
O
H3CO
OCH3
HO
OCH3
MET
HYD
O
T
D
H
D
E
1,2-Dimethoxybenzene
HO
Guaiacol
H
Benzene
M
O
H3CO
HO
H3C
H3C
CH3
OCH3
MET
HDO
HYD
CH3
Methylguaiacols
Anisole
-Cresol
Toluene
Methylcyclohexane
o
Fig. 6. Reaction network for guaiacol hydrotreatment over P- and/or Mo-modified NiCu/SiO2–ZrO2.

30
M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
(highest XGUA, HDO degree, Oeliminated). On the contrary CAT1 treat-
ment in acetic acid showed the highest mass loss indicating that
non-modified system is the least stable (mass loss more than
50 wt.%). When molybdenum and phosphorus were added the sta-
bility of catalyst was significantly improved. According to the data
in Table 4, the mass loss of CAT1-9Mo and CAT1-5P samples is
35–40% lower than that of CAT1. When both P and Mo are used to
modify the catalyst its stability becomes even higher. This is evident
from the mass losses of samples CAT1-10Mo-5P and CAT1-10Mo-
7P which are close to 1 wt.%. Thus, the dissolving of these catalysts
in the acidic medium is almost prevented and the positive effect of
modifiers is clear. Along with increased stability the activity of the
modified catalysts is also quite high, though it is lower than that of
non-modified system (Table 2). For example, the mass loss of CAT1-
10Mo-5P catalyst in the acidic medium is about 1 wt.% (Table 4) and
guaiacol conversion is 81%, HDO degree is 95% (Table 2).
In the case of CAT1-9Mo an improved stability to corrosion can
be explained by the formation of Ni–Mo alloys. Ni–Mo alloys with
more than 15 wt.% Mo content are known to have high stability
against the metal leaching [45]. When Mo content is higher than
20 wt.% the stability of such alloys is especially high. In the present
study the certain amount of molybdenum was added to CAT1 to
produce catalysts CAT1-9Mo, CAT1-10Mo-5P, and CAT1-10Mo-7P
with Mo content 15.5, 19.4 и 20.1%, correspondingly (with respect
to Mo + Ni). In the case of P-modified catalyst CAT1-5P an improved
stability to corrosion can be due to the formation of nickel phos-
phides. Though the most interesting effect was observed in the case
of simultaneous modification by P and Mo (samples CAT1-10Mo-
5P and CAT1-10Mo-7P) which resulted in the highest stability to
corrosion. As well as in two previous cases the explanation can be
both the formation of Ni–Mo alloys and phosphides.
The catalysts mechanical stability was also investigated by mea-
suring the catalysts bulk crushing strength using Shell method (SMS
1471). The active forms of catalysts (after reduction and passiv-
ation) were examined.
As it is shown in Table 4, the mechanical properties of CAT1-
5P and CAT1-9Mo samples became slightly higher if compared
with the initial CAT1. This is evident from the growth of bulk
crushing strength. And again the best results were obtained for
simultaneously PMo-modified systems. Bulk crushing strength of
CAT1-10Mo-5P and CAT1-10Mo-7P shown in Table 4 are two times
higher (1.2 MPɑ) than the same parameter for CAT1 (0.52 МРɑ).
Such a difference in the catalysts properties is essential.
Thus, it was shown that Ni-based catalysts become much more
stable in organic acids after modification by P and Mo, which
is very important for bio-oil hydrotreatment processes. Besides,
the mechanical properties of the catalysts become significantly
improved. This is quite essential for the processes carried out in
fixed-bed continuous flow reactors. Although it was noted that
modification has a negative effect on the catalysts activity in gua-
iacol HDO, their improved stability is more valuable. The results
obtained show that PMo-modified Ni-based catalysts can be con-
sidered as promising systems for use in hydrotreatment of pyrolysis
oils.
that modified samples possessed less activity than that of initial
non-modified CAT1. Regardless high activity in target HDO pro-
cess CAT1 had a number of disadvantages. The yield of undesirable
gaseous products (mainly CН4) as well as coking of the catalyst sur-
face were the highest over this sample. The catalyst treatment by
glacial acetic acid has shown a significant mass loss (53 wt.%) for
CAT1 indicating its low stability in acidic reaction medium. More-
over, it was noted that CAT1 had the lowest mechanical strength
(bulk crushing strength of 0.52 MPa) among the catalysts tested.
When modifying CAT1 with P- and Mo-additives the mechanical
strength and stability to corrosion in the acidic medium were signif-
icantly improved. Thus, the bulk crushing strength increased from
0.52 to 1.2 MPa, catalysts mass loss after treatment by glacial acetic
acid decreased considerably from 53 to 1 wt.%. Besides, catalysts
testing in HDO of guaiacol has shown that Р- and Мо-modification
resulted in the decrease of undesirable gaseous products yield
(from 9.9 to 1.5%) and in the reduction of the catalysts coking
as well. The results obtained show that PMo-modified Ni-based
sol–gel catalysts with the high Ni loading are promising systems
for use in hydrotreatment of pyrolysis oils.
Acknowledgment
The work was supported by Skolkovo Foundation Grant Agree-
ment No. 64.
References
[1] A.V. Bridgwater, Biomass Bioenergy 38 (2012) 68–94.
[2] L. Zhang, C.C. Xu, P. Champagne, Energy Convers. Manag. 51 (2010) 969–982.
[3] L. Ingram, D. Mohan, M. Bricka, P. Steele, D. Strobel, D. Crocker, B. Mitchell, J.
Mohammad, K. Cantrell, C.U. Pittman Jr., Energy Fuels 22 (2008) 614–625.
[4] M. Garcia-Perez, A. Chaala, H. Pakdel, D. Kretschmer, C. Roy, Biomass Bioenergy
31 (2007) 222–242.
[5] A. Oasmaa, E. Kuoppala, Y. Solantausta, Energy Fuels 17 (2003) 433–443.
[6] Q. Lu, W.-Z. Li, X.-F. Zhu, Energy Convers. Manag. 50 (2009) 1376–1383.
[7] F.d.M. Mercader, M.J. Groeneveld, S.R.A. Kersten, N.W.J. Way, C.J. Schaverien,
J.A. Hogendoorn, Appl. Catal. B 96 (2010) 57–66.
[8] P.M. Mortensen, J.-D. Grunwaldt, P.A. Jensen, K.G. Knudsen, A.D. Jensen, Appl.
Catal. A 407 (2011) 1–19.
[9] A.K. Hossain, P.A. Davies, Renew. Sustain. Energy Rev. 21 (2013) 165–189.
[10] P. Azadi, O.R. Inderwildi, R. Farnood, D.A. King, Renew. Sustain. Energy Rev. 21
(2013) 506–523.
[11] Z. He, X. Wang, Catal. Sustain. Energy 1 (2012) 28–52.
[12] Q. Bu, H. Lei, A.H. Zacher, L. Wang, S. Ren, J. Liang, Y. Wei, Y. Liu, J. Tang, Q. Zhang,
R. Ruan, Bioresour. Technol. 124 (2012) 470–477.
[13] T.V. Choudhary, C.B. Phillips, Appl. Catal. A 397 (2011) 1–12.
[14] E. Butler, G. Devlin, D. Meier, K. McDonnell, Renew. Sustain. Energy Rev. 15
(2011) 4171–4186.
[15] D.A. Bulushev, J.R.H. Ross, Catal. Today 171 (2011) 1–13.
[16] F. Trejo, M.S. Rana, J. Ancheyta, A. Rueda, Fuel 100 (2012) 163–172.
[17] M.S. Rana, E.M.R. Capitaine, C. Leyva, J. Ancheyta, Fuel 86 (2007) 1254–1262.
[18] E. Furimsky, Catal. Rev. Sci. Eng. 25 (1983) 421–458.
[19] E.O. Odebunmi, D.F. Ollis, J. Catal. 80 (1983) 56–64.
[20] D.C. Elliott, Energy Fuels 21 (2007) 1792–1815.
[21] E. Furimsky, F.E. Massoth, Catal. Today 52 (1999) 381–495.
[22] M. Badawi, J.F. Paul, S. Cristol, E. Payen, Y. Romero, F. Richard, S. Brunet, D.
Lambert, X. Portier, A. Popov, E. Kondratieva, J.M. Goupil, J. El Fallah, J.P. Gilson,
L. Mariey, A. Travert, F. Maugé, J. Catal. 282 (2011) 155–164.
[23] M. Badawi, S. Cristol, J.-F. Paul, E. Payen, C. R. Chimie 12 (2009) 754–761.
˙
[24] O.I. S¸ enol, E.-M. Ryymin, T.-R. Viljava, A.O.I. Krause, J. Mol. Catal. A 277 (2007)
107–112.
[25] O.I. Senol, T.-R. Viljava, A.O.I. Krause, Appl. Catal. A 326 (2007) 236–244.
[26] V.A. Yakovlev, S.A. Khromova, O.V. Sherstyuk, V.O. Dundich, D.Y. Ermakov, V.M.
Novopashina, M.Y. Lebedev, O. Bulavchenko, V.N. Parmon, Catal. Today 144
(2009) 362–366.
4. Conclusion
[27] S. Echeandia, P.L. Arias, V.L. Barrio, B. Pawelec, J.L.G. Fierro, Appl. Catal. B 101
(2010) 1–12.
[28] Y. Xu, T. Wang, L. Ma, Q. Zhang, W. Liang, Appl. Energy 87 (2010) 2886–2891.
[29] A.R. Ardiyanti, S.A. Khromova, R.H. Venderbosch, V.A. Yakovlev, H.J. Heeres,
Appl. Catal. B 117–118 (2012) 105–117.
[30] D.R. Moberg, T.J. Thibodeau, F.G. Amar, B.G. Frederick, J. Phys. Chem. C 114
(2010) 13782–13795.
[31] V.M.L. Whiffen, K.J. Smith, Energy Fuels 24 (2010) 4728–4737.
[32] S.T. Oyama, X. Wang, Y.-K. Lee, W.-J. Chun, J. Catal. 221 (2004) 263–273.
[33] H.Y. Zhao, D. Li, P. Bui, S.T. Oyama, Appl. Catal. A 391 (2011) 305–310.
[34] K. Li, R. Wang, J. Chen, Energy Fuels 25 (2011) 854–863.
In the present study P- and Mo-containing agents were used
to modify Ni-based catalyst NiCu/SiO2–ZrO2 (CAT1) with high Ni
loading. This catalyst was similar to sol–gel systems NiCu/SiO2 and
NiCu/SiO2–ZrO2–La2O3 previously studied in HDO of guaiacol, and
their high activity was reported about. Modified catalysts were
produced by impregnating CAT1 with (NH4)6Mo7O24·4H2O and/or
H3PO4 aqueous solutions followed by calcination and reduction in
H2. Catalysts testing in hydrodeoxygenation of guaiacol has shown

M.V. Bykova et al. / Catalysis Today 220–222 (2014) 21–31
31
[35] X. Duan, Y. Teng, A. Wang, V.M. Kogan, X. Li, Y. Wang, J. Catal. 261 (2009)
232–240.
[48] P.D.L. Mercera, J.G.v. Ommen, E.B.M. Doesburg, A.J. Burggraaf, J.R.H. Ross, Appl.
Catal. 71 (1991) 363–391.
[36] W. Wang, Y. Yang, H. Luo, T. Hu, W. Liu, Catal. Commun. 12 (2011) 436–440.
[37] W. Wang, Y. Yang, H. Luo, H. Peng, B. He, W. Liu, Catal. Commun. 12 (2011)
1275–1279.
[38] W.-Y. Wang, Y.-Q. Yang, J.-G. Bao, H.-A. Luo, Catal. Commun. 11 (2009)
100–105.
[39] W.-y. Wang, Y.-q. Yang, H.-a. Luo, W.-y. Liu, Catal. Commun. 11 (2010) 803–807.
[40] S.T. Oyama, J. Catal. 216 (2003) 343–352.
[41] C. Stinner, R. Prins, T. Weber, J. Catal. 202 (2001) 187–194.
[42] P. Rayo, J. Ramírez, P. Torres-Mancera, G. Marroquín, S.K. Maity, J. Ancheyta,
Fuel 100 (2012) 34–42.
[49] A. Crucq, L. Degols, G. Lienard, A. Frennet, Stud. Surf. Sci. Catal. 17 (1983)
137–147.
[50] B. Mile, D. Stirling, M.A. Zammitt, A. Lovell, M. Webb, J. Catal. 114 (1988)
217–229.
[51] R.N. Olcese, J. Francois, M.M. Bettahar, D. Petitjean, A. Dufour, Energy Fuels 27
(2013) 975–984.
[52] R. Olcese, M.M. Bettahar, B. Malaman, J. Ghanbaja, L. Tibavizco, D. Petitjean, A.
Dufour, Appl. Catal. B 129 (2013) 528–538.
[53] J. Sun, A.M. Karim, H. Zhang, L. Kovarik, X.S. Li, A.J. Hensley, J.-S. McEwen, Y.
Wang, J. Catal. 306 (2013) 47–57.
[43] S.K. Maity, G.A. Flores, J. Ancheyta, M.S. Rana, Catal. Today 130 (2008)
374–381.
[54] X. Zhang, T. Wang, L. Ma, Q. Zhang, Y. Yu, Q. Liu, Catal. Commun. 33 (2013)
15–19.
[44] S.T. Oyama, T. Gott, H. Zhao, Y.-K. Lee, Catal. Today 143 (2009) 94–107.
[45] I.V. Semenova, G.M. Florianovich, A.V. Khoroshilov, Corrosion and Corrosion
Protection, Fizmatlit, Moscow, 2002.
[46] M.V. Bykova, D.Y. Ermakov, V.V. Kaichev, O.A. Bulavchenko, A.A. Saraev, M.Y.
Lebedev, V.A. Yakovlev, Appl. Catal. B 113–114 (2012) 296–307.
[47] M.A. Ermakova, D.Y. Ermakov, Appl. Catal. A 245 (2003) 277–288.
[55] C.R. Lee, J.S. Yoon, Y.-W. Suh, J.-W. Choi, J.-M. Ha, D.J. Suh, Y.-K. Park, Catal.
Commun. 17 (2012) 54–58.
[56] Y.-C. Lin, C.-L. Li, H.-P. Wan, H.-T. Lee, C.-F. Liu, Energy Fuels 25 (2011) 890–896.
[57] J.-H. Lee, E.-G. Lee, O.-S. Joo, K.-D. Jung, Appl. Catal. A 269 (2004) 1–6.
[58] J.A. Cecilia, A. Infantes-Molina, E. Rodríguez-Castellón, A. Jiménez-López, S.T.
Oyama, Appl. Catal. B 136–137 (2013) 140–149.