Effect of ZrO2 in Ni2P/ZrO2-Al2O3 catalysts on hydrotreating reactions

Article abstract of DOI:10.1039/c5ra14498a

Catalysts 60% Ni/Al₂O₃ and 60% Ni/4% ZrO₂-Al₂O₃ were prepared, and it was found that the addition of ZrO₂ promoted reduction while maintaining the high dispersion of supported nickel. Upon phosphidation by triphenylphosphine (PPh₃) in the liquid phase, the two catalysts were converted into corresponding Ni₂P/Al₂O₃ and Ni₂P/ZrO₂-Al₂O₃ catalysts with highly dispersed Ni₂P particles (6.3 and 6.8 nm, respectively), high CO uptakes (305 and 328 μmol g^-1, respectively) and thus high activities for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation of tetralin to decalin. In particular, the Ni₂P/ZrO₂-Al₂O₃ was found to be significantly more active than the Ni₂P/Al₂O₃ for the HDS of DBT and hydrogenation of tetralin to decalin. Although the presence of ZrO₂ did not affect the heat of adsorption of CO on Ni₂P, it significantly increased the heat and uptake of adsorption of H₂ on Ni₂P, which might account for the increased activity of Ni₂P promoted by ZrO₂.

Full text of DOI:10.1039/c5ra14498a

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Effect of ZrO in Ni P/ZrO –Al O catalysts on
2
2
2
2 3
hydrotreating reactions
Cite this: RSC Adv., 2015, 5, 74312
ab
a
a
a
a
Junen Wang, Yamei Yuan, Abdalla Shuaib, Jun Xu and Jianyi Shen*
Catalysts 60% Ni/Al
ZrO promoted reduction while maintaining the high dispersion of supported nickel. Upon
phosphidation by triphenylphosphine (PPh ) in the liquid phase, the two catalysts were converted into
corresponding Ni P/Al and Ni P/ZrO –Al catalysts with highly dispersed Ni P particles (6.3 and
.8 nm, respectively), high CO uptakes (305 and 328 mmol g , respectively) and thus high activities for
the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation of tetralin to decalin. In
particular, the Ni P/ZrO –Al was found to be significantly more active than the Ni P/Al for the
HDS of DBT and hydrogenation of tetralin to decalin. Although the presence of ZrO did not affect the
heat of adsorption of CO on Ni P, it significantly increased the heat and uptake of adsorption of H on
Ni P, which might account for the increased activity of Ni P promoted by ZrO
2 3 2 2 3
O and 60% Ni/4% ZrO –Al O were prepared, and it was found that the addition of
2
3
2
2
O
3
2
2
2
O
3
2
ꢀ
1
6
Received 22nd July 2015
Accepted 25th August 2015
2
2
2
O
3
2
2 3
O
2
DOI: 10.1039/c5ra14498a
2
2
www.rsc.org/advances
2
2
2
.
ZrO was frequently used as a promoter for metal cata-
2
4–16
1
. Introduction
1
lysts.
The environmental protection laws in many countries require cerning ZrO
sulfur contents lower than 10 ppm in transportation fuels, and been reported that the addition of appropriate amounts of ZrO
thus the hydrotreating reactions of liquid fuels are becoming increased the reducibility of supported Ni in Ni/Al without
17–19
However, no studies have been reported so far con-
as a promoter for the Ni P/Al catalysts. It has
O
2 3
2
2
2
2 3
O
1,2
more important and difficult. It has been found that the decreasing the dispersion of supported Ni signicantly.
transition metal phosphides, especially Ni P, are highly active Apparently, the reducibility and dispersion of supported Ni
2
2
for the hydrodesulphurization (HDS), hydrodenitrogenation might decide the content and dispersion of supported Ni P
3
–8
(
HDN) and hydrogenation reactions,
and thus they may prepared by the phosphidation of supported Ni, and thus affect
P catalysts for the hydrotreating
become a new generation of commercial catalysts for hydro- the activity of resulted Ni
2
6,7
20,21
treating reactions.
reactions.
In this work, the catalysts 60% Ni
–Al were prepared by the phosphidation with PPh
3
Alumina is a preferred support since it possesses the strong
mechanical strengths, high temperature resistance, appropriate ZrO
2
P/Al
2
O
3
and 60% Ni
2
P/
in
2
2
O
3
pore structures and large surface areas. Thus, it was frequently liquid phase and compared for the hydrotreating reactions in
used as the support for the traditional NiMoS and CoMoS order to understand the effect of ZrO . It was found that the
catalysts. However, it was difficult to prepare highly dispersed presence of ZrO signicantly promoted the dissociative
Ni P/Al
catalysts with programmed temperature reduction adsorption of H on Ni P, leading to the higher activity of the
TPR) method since it required high temperatures and high Ni P/ZrO –Al than Ni
Recently, we prepared a 60% reactions.
2
2
2
2
O
3
2
2
(
2
2
2
O
3
2
P/Al
2
O
3
for the hydrotreating
9–12
loadings of phosphates.
Ni/Al
2
O
3
catalyst with the co-precipitation method. Aer the
, it was phosphided at 443 K with
pre-reduction at 723 K in H
2
triphenylphosphine (PPh ) in liquid phase and a Ni P/Al O 2. Experimental
3
2
2 3
1
3
catalyst with highly dispersed Ni P particles was obtained. The
2
2.1 Preparation of catalysts
ꢀ
1
Ni P/Al O catalyst adsorbed great amount of CO (305 mmol g
)
2
2 3
The 60% Ni/Al
different amounts of ZrO
co-precipitation method. The preparation procedure can be
2
O
3
and 60% Ni/ZrO
2 2 3
–Al O catalysts with
and thus exhibited the high activities for the HDS of dibenzo-
thiophene (DBT) and hydrogenation of tetralin to decalin.
2
(2–8 wt%) were prepared by the
1
5
found elsewhere.
Briey, desired amounts of nickel,
aluminum and zirconium nitrates were dissolved in 100 mL
distilled water to form an aqueous solution and another
aqueous solution was obtained by dissolving desired amount of
sodium carbonate in 100 mL distilled water. The two solutions
were simultaneously added dropwise into a beaker containing
a
Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering,
Nanjing University, Nanjing 210093, China. E-mail: jyshen@nju.edu.cn; Fax: +86-25-
8
b
3594305; Tel: +86-25-83594305
College of Chemistry and Materials Science, Huaibei Normal University, Huaibei
35000, China
2
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200 mL distilled water at 353 K under vigorous stirring. The measurements. Microcalorimetric adsorption of CO was per-
precipitates were washed thoroughly with deionized water. The formed at 308 K and that of H at 308 and 423 K, respectively.
2

lter cakes were added into 200 mL n-butanol which was then
evaporated at 353 K. The samples were further dried in an oven
at 393 K for 12 h.
2
.3 Catalytic tests
The reactions of HDS of DBT, HDN of quinoline and hydroge-
nation of tetralin were performed in a x-bed reactor using a
feed containing 1.72% DBT (3000 ppm S), 0.185% quinoline
(200 ppm N), 5% tetralin and 0.5% n-octane (as an internal
standard) in balanced n-tetradecane (solvent) at different
temperatures (513–613 K) with the xed pressure (3.1 MPa),
The same phosphidation procedure was used as reported
21
previously. Typically, a supported nickel catalyst was placed in
a micro-reactor and pre-reduced in owing H (0.1 MPa and
0 mL min ) for 2 h at different temperatures (673–823 K).
2
ꢀ1
4
Then, the temperature was lowered to 443 K, at which the
catalyst was phosphided with PPh (2% in heptane) for 36 h
3
ꢀ
1
ꢀ1
LHSV (2 h ) and H /oil ratio (1500 (v/v)). The products were
collected aer 24 h when the activity was stabilized and
2
(
LHSV of 2 h and H /oil of 300 v/v). Aer the phosphidation,
2
2
the catalyst was heat-treated in H at 673 K for 3 h and then
analyzed on two gas chromatographs. One was equipped with
two SE-30 capillary columns connected to a ame ionization
detector (FID) and a ame photometric detector (FPD) for the
analysis of hydrocarbons and DBT, respectively. Another gas
chromatograph was equipped with a SE-54 capillary column
and a nitrogen–phosphorus detector (NPD) for the analysis of
quinoline.
cooled down to the rst reaction temperature (513 K), at which
model diesel was introduced into the reactor and the hydro-
treating reactions began.
2
.2 Characterization of catalysts
The adsorption of H and O was carried out in a home-made
volumetric apparatus. The catalysts were reduced in H at
23 K for 2 h and evacuated at 723 K for 1 h before the
2
2
2
7
3
. Results and discussion
measurements. The adsorption of H was performed at room
2
3
.1 Dispersion and reducibility of supported nickel
heated to 673 K at a rate of 10 K min and evacuated at 673 K In this work, the supported Ni catalysts were pre-reduced in H
for 1 h. The adsorption of O
was then performed at 673 K. The and then phosphided in situ at the relatively low temperature
uptakes of H and O
were obtained by extrapolating the (443 K) with PPh in liquid phase to obtain the corresponding
P catalysts. The content and dispersion of Ni P were mainly
2
temperature. Aer the adsorption of H , the samples were
ꢀ1
2
2
2
2
3
coverage of corresponding isotherms to P ¼ 0. The degree of Ni
2
2
reduction (reducibility), dispersion, active surface area and decided by the reducibility and dispersion of supported Ni
average particle size of supported nickel were calculated based before the phosphidation, and affected the activity of hydro-
on the amounts of H2 and O2 adsorbed and the amount of treating reactions of supported Ni
2
P catalysts. Thus, the prep-
nickel loaded. The detailed calculation formulae can be found aration of highly reduced and dispersed Ni catalysts was the
2
2
in the literature.
The supported Ni
essential prerequisite for the preparation of highly active Ni
in catalysts.
The 60% Ni/ZrO O catalysts containing different
2 3
2
P
2
P catalysts phosphided by using PPh
3
liquid phase were prepared separately for characterizations.
The phosphidation processes were the same as those above amounts of ZrO
2
–Al
2
were prepared by the co-precipitation method
(
Section 2.1). The phosphided catalysts were passivated for 12 h with an n-butanol drying process. In order to understand the
at room temperature under N containing about 0.5 vol% O
before they were characterized with different techniques.
effect of ZrO
Ni, the uptakes of H
2
on the reducibility and dispersion of supported
and O were measured at room tempera-
2
2
2
2
The surface area and pore structure were determined with a ture and 673 K, respectively, for these catalysts. The reducibility,
Micromeritics Gemini V 2380 autosorption analyzer at 77.3 K dispersion, particle sizes and active surface areas of supported
aer the samples were degassed in owing N
X-ray diffraction (XRD) patterns were collected on a Shi- results are shown in Table 1.
madzu XRD-6000 powder diffractometer (Japan) using a Cu Ka
It is seen that the uptakes of H
2 3
–Al catalysts than on the Ni/Al O
2
at 473 K for 5 h. nickel for these catalysts were calculated accordingly. The
2
and O
2
were higher on all the
. Among the
radiation (l ¼ 0.1541 nm) under the setting conditions of 40 kV Ni/ZrO
and 30 mA.
2
2
O
3
The chemical compositions of catalysts were determined by
an ARL-9800 X-ray uorescence spectrometer (XRF).
The morphologies of catalysts were performed on a JEOL
JEM-2100 transmission electron microscope (TEM) operated at
2 2 2 3 2
Table 1 Uptakes of adsorbed H and O on the Ni/Al O and Ni/ZrO –
Al
ZrO
was per- H adsorption (mmol g
2
O
3
catalysts reduced in H
2
at 723 K
2
content
0%
2%
4%
8%
200 kV.
ꢀ
ꢀ
1
1
The microcalorimetric adsorption of CO and H
formed by using a Setaram Tian-Calvet C-80 heat-ux micro-
calorimeter, connected to a gas-handling system equipped with
2
)
)
881
930
1072
3722
28.8
84.7
3.5
959
2
O
2
adsorption (mmol g
3002
29.3
68.3
3.4
3207
29.0
73.0
3.5
3830
25.1
87.2
4.0
Dispersion (%)
Reducibility (%)
a
Baratron capacitance manometer for precise pressure
measurements. Passivated samples were re-reduced in owing
at 673 K for 3 h and evacuated at 673 K for 1 h before the
Ni particle size d (nm)
2
ꢀ1
Ni surface area (m g
)
69.0
72.8
83.9
75.1
H
2
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2 2 3 2
Ni/ZrO –Al O catalysts, the one with 4% ZrO exhibited the
ꢀ1
highest H2 uptake (1072 mmol g ). The further increase of
content of ZrO from 4 to 8% decreased the H uptake from
2
2
ꢀ1
1
072 to 959 mmol g . The active Ni surface area of supported Ni
reected the integrated effect of reducibility and dispersion of
Ni. Among the Ni/ZrO
possessed the highest active Ni surface area (83.9 m
signicantly higher than that of the Ni/Al
Thus, only the 60% Ni/4% ZrO –36% Al
were compared below and denoted as Ni/Al O and Ni/ZrO –
2
–Al
2
O
3
catalysts, the one with 4% ZrO
2
2
ꢀ1
ꢀ1
g
g
),
).
2
2
O
3
(69.0 m
2
2 3 2 3
O and 60% Ni/Al O
2
3
2
Al O , respectively. Aer the phosphidation, they were con-
2
3
verted into the 60% Ni P/Al O and 60% Ni P/4% ZrO –36%
2
2
3
2
2
Al
ZrO
From the data in Table 1, it is seen that the dispersion of
Ni/Al and Ni/ZrO –Al (4% ZrO ) was quite similar (29.3
and 28.8%, respectively), but the reducibility of Ni/ZrO –Al
was signicantly higher than that of Ni/Al O , leading to the
2
O
3
, respectively, and were denoted as Ni
2
P/Al
2
O
3
2
and Ni P/
2
–Al below.
2 3
O
2
O
3
2
2
O
3
2
2
2 3
O
2
3
signicantly increased active Ni surface area of the Ni/ZrO2–
Al O . However, the Ni particles were highly dispersed in both
2
3
the Ni/Al
2 3 2 2 3
O and Ni/ZrO –Al O with small average particle sizes
of 3.4 and 3.5 nm, respectively.
It should be mentioned that nickel species in the two cata-
lysts could not be completely reduced. The unreduced nickel
1
3
Fig. 1 XRD patterns of the Ni/Al
well as those of the Ni/ZrO –Al
Reaction conditions: T ¼ 513–613 K, P ¼ 3.1 MPa, LHSV ¼ 2 h and
/oil ¼ 1500 (v/v).
2
O
3
and Ni
2
P/Al
2
O
3
catalysts (a) as
2
cations were difficult to convert into Ni P during the phosphi-
21
2
2
O
3
and Ni P/ZrO
2
2 2 3
–Al O catalysts (b).
dation at 443 K. Instead, these unreduced nickel cations might
be converted into nickel suldes during the hydrotreating
reactions, leading to the increase of S contents in the used
catalysts.
ꢀ1
H
2
observed for the three samples, indicating its high dispersion in
ꢁ
ꢁ
the catalysts. Three broad diffraction peaks around 44.5 , 51.8
3
.2 Textural and structural properties of catalysts
ꢁ
and 76.4 for Ni (PDF 65-2865) appeared for the Ni/ZrO
2
–Al
2
O
3
.
ꢁ
The XRD patterns of the Ni/Al
Fig. 1(a). The diffraction peaks around 36.2 , 44.2 and 63.5
were attributed to Al
4
2
O
3
and Ni
2
P/Al
2
ꢁ
O
3
were shown in According to the broadening of Ni (111) peak at 44.5 and the
ꢁ
ꢁ
Scherrer equation, the average particle size of Ni formed in the
–Al was estimated to be about 3.5 nm, consistent
2
O
ꢁ
3
. Three broad diffraction peaks around Ni/ZrO
2
2 3
O
ꢁ
ꢁ
4.5 , 51.8 and 76.4 for Ni (PDF 65-2865) appeared for the with that (3.5 nm) estimated by the uptakes of H
2
and O
2
. Aer
ꢁ
Ni/Al
2
O
3
. According to the broadening of Ni (111) peak at 44.5
the phosphidation at 443 K, Ni
2
P with the diffraction peaks
ꢁ
ꢁ
ꢁ
ꢁ
and the Scherrer equation, the average particle size of Ni formed around 40.7 , 44.6 , 47.4 and 54.2 was formed. According to
in the Ni/Al O catalyst was estimated to be about 3.3 nm, in the broadening of Ni P (111) peak at 40.7 and the Scherrer
ꢁ
2
3
2
consistence with that (3.4 nm) estimated by the uptakes of H
and O
around 40.7 , 44.6 , 47.4 and 54.2 for Ni
2
2
equation, the average particle size of Ni P formed in the fresh
2
. Aer the phosphidation at 443 K, the diffraction peaks Ni
2
P/ZrO
P (PDF 65-1989) hydrotreating reactions, Ni
. According to the broadening indicating again that Ni P was stable during the hydrotreating
2
–Al
2
O
3
was estimated to be about 6.8 nm. Aer the
ꢁ
ꢁ
ꢁ
ꢁ
2
2
P was the only phase detected,
appeared for the fresh Ni
of Ni
average particle size of Ni
catalyst was estimated to be about 6.3 nm. Aer the hydro- Ni P/ZrO –Al O was estimated to be about 6.9 nm, which was
2
P/Al
ꢁ
2
O
3
2
2
P (111) peak at 40.7 and the Scherrer equation, the reactions. No nickel sulde phase was detected in the used
P formed in the fresh Ni
2
P/Al
2
O
3
Ni P/ZrO –Al O . The average particle size of Ni P in the used
2 2 2 3 2
2
2
2
2 3
treating reactions, Ni P was the only phase detected besides almost not changed as compared to that (6.8 nm) in the fresh
2
Al
reactions from 513 to 613 K. No nickel sulde phase was
detected by XRD in the used Ni P/Al although the studies 723 K was shown in Fig. 2(a). It was seen that metallic Ni
showed that S would be incorporated into the Ni P surfaces particles were well dispersed in the catalyst. The statistically
The average particle size averaged particle size of Ni particles in the Ni/ZrO –Al was
was estimated to be about 6.9 estimated to be about 3.8 nm, in consistence with that (3.5 nm)
nm, which was not changed signicantly as compared to that estimated by the Scherrer equation. The TEM image of the fresh
2
O
3
, indicating that Ni
2
P was stable during the hydrotreating catalyst.
The TEM image of the Ni/ZrO
2
2 3 2
–Al O pre-reduced in H at
2
2 3
O
2
23,24
during the hydrotreating reactions.
of Ni P in the used Ni P/Al
2
2 3
O
2
2
2 3
O
(6.3 nm) in the fresh catalyst.
Ni P/ZrO –Al O catalyst prepared by the phosphidation with
2
2
2 3
The XRD patterns of the Ni/ZrO
2
–Al
2
O
3
and Ni
2
P/ZrO
2
–Al
2
O
3
3 2
PPh at 443 K was shown in Fig. 2(b). The highly dispersed Ni P
were shown in Fig. 1(b). No diffraction peaks for ZrO
2
were particles were formed in the catalyst with the statistically
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averaged particle size of about 6.7 nm, agreeing well with that to be about 0.43 and 0.61, respectively, in the fresh Ni
6.8 nm) estimated by the Scherrer equation. and Ni P/ZrO –Al O . Aer the hydrotreating reactions, the P/Ni
Aer the hydrotreating reactions from 513 to 613 K, the used ratios were measured to be about 0.39 and 0.53, respectively, in
Ni P/ZrO –Al O catalyst was collected and characterized. The the used Ni P/Al O and Ni P/ZrO –Al O , which were appar-
2 2 3
P/Al O
(
2
2
2 3
2
2
2
3
2
2
3
2
2
2 3
TEM image of the used Ni
The Ni P particles were still highly dispersed in the catalyst with fresh ones. The decrease of P/Ni ratios might be explained by
the average size of about 7.3 nm, in consistence with that the incorporation of S into the Ni P surfaces and the leaching of
6.9 nm) estimated by the Scherrer equation. As compared with some oxidized forms of phosphorus from the catalyst. The
the average size of Ni P particles in the fresh Ni P/ZrO –Al content of S was signicantly higher in the used Ni P/Al
6.7 nm), the increase of size of Ni P particles during the (5.5%) than in the Ni P/ZrO –Al O (1.3%). The lower S content
2 2 2 3
P/ZrO –Al O was shown in Fig. 2(c). ently decreased as compared to the corresponding data in the
2
2
(
2
2
2
2
O
3
2
2 3
O
(
2
2
2
2 3
hydrotreating reactions was not signicant.
in the used Ni P/ZrO –Al O might be associated with the
2 2 2 3
Table 2 shows the chemical compositions of the catalysts. higher reducibility of Ni/ZrO –Al O .
2
2
3
The contents of Ni were measured to be about 62.5 and 61.3%,
respectively, in the Ni/Al and Ni/ZrO –Al
ZrO about 3.8% in the Ni/ZrO –Al , close to the values the unreduced Ni in the catalyst. These unreduced Ni
desired. Aer the phosphidation, the P/Ni ratios were measured cations might react with H S formed during the hydrotreating
The P/Ni ratio in the Ni
2
P/Al
2
O
3
was signicantly lower than
2
O
3
2
2 3 2
O while that of the stoichiometric ratio of Ni P (0.5). This might be caused by
2
+
2+
2
2
2 3
O
2
reactions to form nickel suldes and thus increased the content
of S. In addition, S might be incorporated into Ni P surfaces to
2
form NiP S species, which was considered as the active phase
x
y
24–26
for the hydrotreating reactions.
ZrO –Al was higher than the stoichiometric ratio of Ni
0.5). Besides the P in Ni P, other forms of P might deposit in
The P/Ni ratio in the Ni P/
2
2
2
O
3
2
P
(
2
the catalyst during the phosphidation, leading to the higher
P/Ni ratios.
Table 3 lists the information about the surface areas, pore
parameters, phosphide phase, particle sizes and CO coverage
for the catalysts studied in this work. The surface area, pore
2
ꢀ1
volume and pore size of Ni/Al O were measured to be 325 m g
,
2
3
3
ꢀ1
1.01 cm
g
and 9.3 nm, respectively, which were higher
2
ꢀ1
than the corresponding data of Ni/ZrO
0
2
–Al
.76 cm g and 8.8 nm, respectively). However, the differences
of these data for the two fresh Ni P catalysts were small. The
used Ni P/Al and Ni P/ZrO –Al even exhibited the similar
surface area, pore volume and pore size, respectively.
2 3
O (267 m g ,
3
ꢀ1
2
2
2
O
3
2
2
2 3
O
3.3 Surface properties probed by the adsorption of CO and
H
2
Microcalorimetric adsorption of CO was performed on the
catalysts. The results were shown in Fig. 3. It is seen that the CO
ꢀ1
uptakes were high (828 and 815 mmol g , respectively), and the
initial heats for the adsorption of CO were similar (112 and
ꢀ
1
1
2 3 2 2 3
14 kJ mol , respectively), on the Ni/Al O and Ni/ZrO –Al O .
The initial heat of adsorption of CO on Ni is sensitive to the
surface density of electron charges on Ni which were affected by
27
the surface acidity and basicity of supports. It was higher on
Ni/MgO than on Ni/Al O due to that MgO is an electron donor
2
3
while Al
adsorption of CO on the Ni/Al
that ZrO was neither an electron donor nor an electron
2
O
3
is an electron acceptor. The similar heats for the
2
O
3
and Ni/ZrO –Al indicated
2
2 3
O
2
acceptor to Ni.
2
The initial heats of adsorption of CO on the catalysts Ni P/
Al
2
O
3
, Ni
2
P/MgAlO and Ni
2
P/MgO were determined to be 95,
ꢀ
1
13
99 and 95 kJ mol
,
respectively, indicating that the initial
heat of adsorption of CO on Ni P was not sensitive to the surface
acidity and basicity of supports. The data in Fig. 3 showed that
the initial heats for the adsorption of CO on the Ni P/Al O and
2 2 3
2
Fig. 2 TEM images of the Ni/ZrO
b) and used Ni P/ZrO –Al
(c) catalysts. Reaction conditions: T ¼
13–613 K, P ¼ 3.1 MPa, LHSV ¼ 2 h and H
2 2 3 2 2 2 3
–Al O (a), fresh Ni P/ZrO –Al O
(
5
2
2
2 3
O
ꢀ1
2
/oil ¼ 1500 (v/v).
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Table 2 Chemical compositions analyzed by XRF for the Ni/Al
O
2 3
2
, Ni/ZrO –Al
O , Ni
2 3 2
P/Al O
2 3
and Ni P/ZrO –Al
2 2 2
O
3
catalysts
Catalyst
Ni (wt%)
P (wt%)
S (wt%)
ZrO
2
(wt%)
Al
2
O
3
(wt%)
P/Ni (atom)
Ni/Al
Ni/ZrO
Fresh Ni
Fresh Ni
Used Ni
Used Ni
2
O
3
62.5
61.3
49.9
46.2
48.6
46.6
—
—
11.3
14.9
10.1
13.1
—
—
—
—
5.5
1.3
—
3.8
—
3.5
—
3.4
37.5
34.9
38.8
36.4
35.5
35.5
—
—
0.43
0.61
0.39
0.53
2
–Al
2
O
P/Al
P/ZrO
3
2
2
O
3
2
2
–Al
2
O
3
2
P/Al
2
O
3
2
P/ZrO
2
–Al
2
O
3
ꢀ
1
Ni
indicating that ZrO
electron acceptor to Ni
signicantly greater on the Ni P/ZrO –Al O (328 mmol g
2
P/ZrO
2
–Al
2
O
3
were similar (95 and 94 kJ mol , respectively),
was neither an electron donor nor an
P. However, the uptake of CO was
2
2
ꢀ
1
)
2
2
2 3
than on the Ni P/Al O , owing to the more Ni P content in the
2
2
3
2
Ni P/ZrO –Al O than in the Ni P/Al O .
2
2
2
3
2
2 3
Aer the hydrotreating reactions, the initial heats for the
ꢀ
1
adsorption of CO were measured to be 62 and 61 kJ mol on
the used Ni P/Al , and Ni P/ZrO –Al with the saturation
2
2
O
3
2
2
2 3
O
ꢀ
1
coverage of 68 and 71 mmol g , respectively. The heats and
coverages for the adsorption of CO were both signicantly
decreased as compared to those on the fresh catalysts, which
Fig. 3 Differential heat versus coverage for the adsorption of CO at
might be caused by the incorporation of S into the Ni P surfaces
2
3
08 K on the catalysts Ni/Al
Al (,), Ni P/ZrO –Al
ZrO –Al
and the higher CO uptakes indicated the more active sites of LHSV ¼ 2 h and H /oil ¼ 1500 (v/v).
2
O
3
(B), Ni/ZrO (C), fresh Ni
2
–Al
2
O
3
2
P/
P/
during the hydrotreating reactions. The number of active sites
2
O
3
2
2
O
2 3
(-), used Ni P/Al O (O) and used Ni
(:). Reaction conditions: T ¼ 513–613 K, P ¼ 3.1 MPa,
2
2 3
2
28,29
2
on Ni P surfaces is usually probed by the adsorption of CO,
2
2
O
3
ꢀ1
2
Ni
tions. However, it could not be explained why the Ni
Al was more active than the Ni P/Al for the hydrotreating was performed at 423 K, the initial heats were increased to 55
reactions according to the heats and coverages for the adsorp- and 69 kJ mol with the uptakes of 75 and 108 mmol g for the
tion of CO on the used Ni P/ZrO –Al O and Ni P/Al O .
adsorption of H2 on the Ni P/Al O and Ni P/ZrO –Al O ,
2
P and thus the better activities for the hydrotreating reac-
2
P/ZrO
2
–
2
O
3
2
2 3
O
ꢀ1
ꢀ1
2
2
2
3
2
2
3
2
2
3
2
2
2 3
H must be participated in the hydrogenation reactions, and respectively. The signicant increase in the heats and uptakes
2
the microcalorimetric adsorption of H is frequently used to with temperature indicated that the adsorption of H on Ni P
2 2
30
2
probe the surface properties of metallic nickel. However, the was an activation process which required activation ener-
P has not been gies.1
5,31,32
microcalorimetric adsorption of H
2
on the Ni
2
In addition, the initial heat and uptake for the
reported before. In this work, the microcalorimetric adsorption adsorption of H at 423 K were signicantly higher on the Ni P/
2
2
2 2 2 3 2 2 2 3
2 2 3 2 2 3 2
of H on the Ni P/Al O and Ni P/ZrO –Al O was performed ZrO –Al O than on the Ni P/Al O , indicating that ZrO
and the results are shown in Fig. 4. The initial heats for the promoted the dissociative adsorption of H on Ni P. Previously,
2
2
ꢀ
1
adsorption of H at 308 K were 40 and 43 kJ mol with the we observed the promotion effect of ZrO on the adsorption of
2
2
ꢀ1
15
saturation coverages of 54 and 43 mmol g , respectively, on the H on cobalt.
2
2 2 3 2 2 2 3
fresh Ni P/Al O and Ni P/ZrO –Al O . When the adsorption
a
Table 3 Textural and structural properties of the Ni/Al
2
O , Ni/ZrO
3
2
–Al
2
O
3 2 2
, Ni P/Al O
, and Ni P/ZrO –Al
3 2 2 2
O
3
catalysts
S
BET
Pore volume
Pore size
(nm)
XRD
phase
d
CO uptake
CO ads. heat
2
ꢀ1
3
ꢀ1
ꢀ1
ꢀ1
Catalyst
(m g
)
(cm g
)
(nm) by XRD
(mmol g
)
(kJ mol
)
Ni/Al
Ni/ZrO
Fresh Ni
Fresh Ni
Used Ni
Used Ni
2
O
3
325
267
154
173
164
168
1.01
0.76
0.68
0.67
0.55
0.52
9.3
8.8
13.1
12.2
10.9
10.1
Ni
Ni
3.3
3.5
6.3
6.8
6.9
6.9
828
815
305
328
68
112
114
95
94
62
2
2 3
–Al O
2
P/Al
P/ZrO
2
O
3
Ni
2
Ni
2
Ni
2
Ni
2
P
P
P
P
2
2
–Al
2
O
3
2
P/Al
2
O
3
2
P/ZrO
2
–Al
2
O
3
71
61
a
ꢁ
The particle size (d) was estimated by the Scherrer equation according to the full width at half maximum (FWHM) of the peak at 44.5 (Ni) or at
ꢁ
4
0.7 (Ni
2
P) in the XRD patterns shown in Fig. 1.
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Fig. 4 Differential heat versus coverage for the adsorption of H
2
at Fig. 6 Conversion of DBT, quinoline and tetralin on the Ni
P/ZrO –Al
catalysts. Reaction conditions: T ¼ 513–613 K,
P ¼ 3.1 MPa, LHSV ¼ 2 h and H
2 2 3
P/Al O
3
2 2
08 and 423 K on the fresh Ni P/Al O
3
and Ni
2
P/ZrO
2
–Al
2
O
3
catalysts. and Ni
2
2
2 3
O
ꢀ1
2
/oil ¼ 1500 (v/v).
Fig. 5 compares the adsorption of H at 423 K on the fresh
2 3
and used Ni P/Al and Ni P/ZrO –Al O catalysts. The initial
heats and coverages for the adsorption of H2 on the used
catalysts were signicantly decreased as compared to those on
the fresh ones, indicating that the incorporation of S into
2
2
2
O
3
2
2
The difference in the activity of HDS of DBT was apparent over
the two catalysts at the lower temperatures. At 513 K, the
conversion of DBT was 62.4 and 80.9%, respectively, over the
Ni P/Al O and Ni P/ZrO –Al O . Thus, the Ni P/ZrO –Al O was
2
2
3
2
2
2
3
2
2
2 3
the Ni
2
P surfaces during the hydrotreating reactions might
signicantly more active than the Ni P/Al O for the HDS of
2
2 3
suppress the adsorption of H
kJ mol , respectively) and uptakes (53 and 49 mmol g
respectively) were similar and low for the adsorption of H
2
on Ni
2
P. The heats (23 and 25
ꢀ
1
ꢀ1
DBT.
The conversion of quinoline was 100% over the Ni
and Ni P/ZrO –Al at the temperatures from 513 to 613 K,
,
2
2 3
P/Al O
2
on
2
2
2 3
O
the two used catalysts. Thus, the different surface properties
of the used Ni P/Al O and Ni P/ZrO –Al O could not be
indicating that the difference of activity over the two catalysts
for the HDN of quinoline could not be distinguished under the
reaction conditions.
2
2
3
2
2
2 3
distinguished according to the adsorption of H2 at 423 K.
The difference in heats for the adsorption of H on the used
2
The conversion of tetralin over the Ni P/Al O and Ni P/
2
2
3
2
2 2 3 2 2 2 3
Ni P/Al O and Ni P/ZrO –Al O might be observed at the
ZrO –Al O increased with the increase of reaction tempera-
2
2 3
higher temperature and pressure.
tures from 513 to 613 K. At the low reaction temperatures, the
conversions of tetralin were quite low over the two catalysts.
However, when the temperature was increased to 613 K, the
conversion of tetralin was determined to be about 42.4 and
3
.4 Catalytic properties
Fig. 6 shows the conversions of HDS of DBT, HDN of quinoline
and hydrogenation of tetralin over the Ni P/Al and Ni P/
ZrO –Al O catalysts at different reaction temperatures. It is
5
5.8%, respectively, over the Ni
Thus, the Ni P/ZrO –Al was signicantly more active than
the Ni P/Al O for the hydrogenation of tetralin to decalin.
2 2 3 2 2 2 3
P/Al O and Ni P/ZrO –Al O .
2
2
O
3
2
2
2
2 3
O
2
2 3
2
2 3
seen that the conversion of DBT increased with the increase of
reaction temperature. At 593 and 613 K, the conversions of DBT
were 100% over the Ni P/Al O and Ni P/ZrO –Al O catalysts.
2 2 3 2 2 2 3
The HDS of DBT usually undergoes through two pathways.
One is the direct desulfurization pathway (DDS) with the
formation of biphenyl (BP) as the desulfurization product, while
another is the indirect desulfurization pathway, i.e., the one for
the desulfurization aer an aromatic ring in DBT is hydroge-
nated (HYD), with the formation of cyclohexylbenzene (CHB) as
the desulfurization product. Fig. 7(a) shows the different
selectivities for the HDS of DBT at different temperatures. With
the increase of reaction temperature, the selectivity to BP
decreased while that to CHB increased. The two catalysts
exhibited mainly the DDS pathway at the lower reaction
temperatures while mainly the HYD pathway at the higher
2 2 2 3
reaction temperatures. In addition, the Ni P/ZrO –Al O
exhibited the higher activity of HYD pathway, i.e., the higher
activity for the hydrogenation of aromatic rings in DBT than the
Ni P/Al O .
2
2 3
Propylbenzene (PB) and propylcyclohexane (PCH) were the
products of HDN of quinoline. The selectivities to these prod-
ucts are shown in Fig. 7(b). It is seen that PCH was the main
Fig. 5 Differential heat versus coverage for the adsorption of H
2
at 423
K on the fresh and used Ni P/Al and Ni P/ZrO –Al catalysts.
2
2
O
3
2
2
2 3
O
ꢀ1
Reaction conditions: T ¼ 513–613 K, P ¼ 3.1 MPa, LHSV ¼ 2 h and H
2
/
oil ¼ 1500 (v/v).
product of HDN on the Ni
P catalysts, i.e., the aromatic ring
2
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Table 4 Turnover frequencies (TOF) of HDS of DBT and hydrogena-
2 2 3 2 2 2 3
tion of tetralin to decalin on the Ni P/Al O and Ni P/ZrO –Al O
catalysts
HDS of DBT at 513 Hydrogenation of tetralin
ꢀ4
ꢀ1
ꢀ4 ꢀ1
Catalyst
K (10
s
)
to decalin at 613 K (10
s )
Ni
Ni
2
P/Al
P/ZrO
2
O
3
4.8
5.9
12.0
16.5
2
2
2 3
–Al O
During the hydrotreating reactions, sulfur atoms would
incorporate into the Ni P to form Ni–P–S surface species as the
2
active sites for the hydrotreating reactions, and thus the TOF
values calculated according to the CO uptakes on the used
catalysts might be more appropriate to reect the real intrinsic
13
activities of Ni P catalysts. The turnover frequencies (TOF) for
2
the HDS of DBT (513 K) and the hydrogenation of tetralin to
decalin (613 K) were calculated according to the CO uptakes on
the used Ni
are shown in Table 4. The Ni
signicantly higher TOF values than the Ni
of DBT and hydrogenation of tetralin to decalin, indicating that
the Ni P/ZrO –Al possessed higher intrinsic activities, prob-
2
P/Al
2
O
3
and Ni
2
P/ZrO
2
–Al
P/ZrO
2
O
3
catalysts. The results
–Al exhibited the
P/Al for the HDS
2
2
2 3
O
2
2 3
O
2
2
2 3
O
ably owing to that the addition of ZrO promoted the dissociative
2
adsorption of H on Ni P and thus the sites of Ni P in the Ni P/
2
2
2
2
ZrO –Al O were more active than those in the Ni P/Al O .
2
2
3
2
2 3
4. Conclusions
Following conclusions can be drawn from the above results:
1) The addition of ZrO promoted the reducibility while
maintained the high dispersion of nickel in the Ni/ZrO –Al
Thus, the Ni/ZrO –Al possessed the highly dispersed
metallic nickel particles (3.5 nm) with the high active Ni surface
(
2
2
2 3
O .
2
2 3
O
2
ꢀ1
area (83.9 m g ).
2) The phosphidation of pre-reduced Ni/Al
Al O with PPh resulted in the corresponding Ni P/Al O and
(
2 3 2
O and Ni/ZrO –
Fig. 7 Selectivity of HDS of DBT (a), HDN of quinoline (b) and
2
3
3
2
2 3
hydrogenation of tetralin (c) on the Ni
2 2 3 2 2 2 3
P/Al O and Ni P/ZrO –Al O
Ni P/ZrO –Al O catalysts. The addition of ZrO increased the
catalysts. Reaction conditions: T ¼ 513–613 K, P ¼ 3.1 MPa, LHSV ¼
2
2
2
3
2
ꢀ1
2
h
2
and H /oil ¼ 1500 (v/v).
CO uptake without changing the initial heat, indicating that the
surface electron density of Ni P was not changed upon the
addition of ZrO
2
2
.
without the N atom in quinoline was easily hydrogenated on
Ni
catalysts, but slightly higher on the Ni
ZrO –Al , probably owing to that the Ni
more g-Al and thus possessed stronger surface acidity.
Tetralin might be hydrogenated to decalin (HYD) or dehy- values.
drogenated to naphthalene (DHYD) over the Ni P catalysts.
(4) The XRD and TEM results showed that the particle sizes
During the hydrogenation of tetralin, both trans- and cis-decalin of Ni P in the Ni P/Al O and Ni P/ZrO –Al O were almost not
(3) The Ni P/ZrO –Al O exhibited the signicantly higher
2
2
2
3
2
P. In addition, the selectivity to PCH was similar over the two activity than the Ni P/Al O for the HDS of DBT and hydroge-
2
2
3
2
P/Al
2
O
3
than on the Ni
2
P/ nation of tetralin to decalin. In particular, the Ni P sites in the
2
2
2
O
3
2
P/Al contained Ni P/ZrO –Al O might be signicantly more active than those
2 3
O
2
2
2 3
2
O
3
in the Ni P/Al O for the reactions according to their TOF
2 2 3
2
2
2
2
3
2
2
2 3
might be formed. Fig. 7(c) shows the selectivities to decalin and changed aer the hydrotreating reactions. Thus, the greatly
naphthalene over the Ni P/Al and Ni P/ZrO –Al catalysts decreased heats and uptakes for the adsorption of CO and H on
2
2
O
3
2
2
2 3
O
2
at different reaction temperatures. It is seen that the trans- the used catalysts might be caused by the incorporation of
decalin was the main product, and naphthalene was also S into the Ni P surfaces during the hydrotreating reactions.
2
formed as the dehydrogenation product. The selectivity to
naphthalene was increased with the increase of reaction cantly increased the heats and uptakes for the adsorption of H2
temperature.
over the catalysts. In addition, the Ni P/ZrO –Al O exhibited
(5) Increase in the temperature from 308 to 423 K signi-
2
2
2 3
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the signicantly higher heat and uptake than the Ni
2
P/Al
2
O
3
for 13 J. Wang, Y. Fu, H. Chen and J. Shen, Chem. Eng. J., 2015, 275,
89–101.
the adsorption of H at 423 K, demonstrating that the presence
2
of ZrO signicantly promoted the adsorption of H on Ni P, 14 N. Rahemi, M. Haghighi, A. A. Babaluo, M. F. Jafari and
2
2
2
which might account for the higher activities for the hydro-
treating reactions on the Ni P/ZrO –Al than on the Ni P/Al
P. Estifaee, J. Ind. Eng. Chem., 2013, 19, 1566–1576.
15 L. Chen and J. Shen, J. Catal., 2011, 279, 246–256.
2
2
O
2 3
2
2 3
O .
1
1
1
1
2
2
2
2
2
2
2
2
6 S. Damyanova, L. Petrov, M. A. Centeno and P. Grange, Appl.
Catal., A, 2002, 224, 271–284.
7 T. de Freitas Silva, C. G. M. Reis, A. F. Lucr ´e dio, E. M. Assaf
and J. M. Assaf, Fuel Process. Technol., 2014, 127, 97–104.
8 C. Guo, Y. Wu, H. Qin and J. Zhang, Fuel Process. Technol.,
Acknowledgements
Financial supports from NSFC (21273105), MSTC (2013AA031703)
and the fundamental research funds for central universities are
acknowledged.
2014, 124, 61–69.
9 N. Srisiriwat, S. Therdthianwong and A. Therdthianwong,
Int. J. Hydrogen Energy, 2009, 34, 2224–2234.
0 Y. Zhao, M. Xue, M. Cao and J. Shen, Appl. Catal., B, 2011,
References
1
04, 229–233.
1 J. Wang, H. Chen, Y. Fu and J. Shen, Appl. Catal., B, 2014,
60–161, 344–355.
2 S. Hu, M. Xue, H. Chen and J. Shen, Chem. Eng. J., 2010, 162,
71–379.
3 A. E. Nelson, M. Sun and A. S. M. Junaid, J. Catal., 2006, 241,
80–188.
4 S. T. Oyama, X. Wang, Y. K. Lee and W. J. Chun, J. Catal.,
004, 221, 263–273.
5 K. A. Layman and M. E. Bussell, J. Phys. Chem. B, 2004, 108,
0930–10941.
6 K. A. Layman and M. E. Bussell, J. Phys. Chem. B, 2004, 108,
5791–15802.
7 J. Zhao, H. Chen, J. Xu and J. Shen, J. Phys. Chem. C, 2013,
17, 10573–10580.
1
2
3
W. Fu, L. Zhang, T. Tang, Q. Ke, S. Wang, J. Hu, G. Fang, J. Li
and F.-S. Xiao, J. Am. Chem. Soc., 2011, 133, 15346–15349.
B. Pawelec, R. M. Navarro, J. M. Campos-Martin and
J. L. Fierro, Catal. Sci. Technol., 2011, 1, 23–42.
A. Infantes-Molina, C. Moreno-Leon, B. Pawelec,
J. L. G. Fierro, E. Rodriguez-Castellon and A. Jimenez-
Lopez, Appl. Catal., B, 2012, 113, 87–99.
1
3
1
4
5
J. R. Hayes, R. H. Bowker, A. F. Gaudette, M. C. Smith,
C. E. Moak, C. Y. Nam, T. K. Pratum and M. E. Bussell, J.
Catal., 2010, 276, 249–258.
J. A. Cecilia, A. Infantes-Molina, E. Rodriguez-Castellon and
A. Jimenez-Lopez, J. Catal., 2009, 263, 4–15.
2
1
1
6
7
8
S. T. Oyama, J. Catal., 2003, 216, 343–352.
R. Prins and M. E. Bussell, Catal. Lett., 2012, 142, 1413–1436.
X. Zhang, Q. Zhang, A. Zhao, J. Guan, D. He, H. Hu and
C. Liang, Energy Fuels, 2010, 24, 3796–3803.
1
28 S. T. Oyama and Y.-K. Lee, J. Catal., 2008, 258, 393–400.
29 G.-N. Yun and Y.-K. Lee, Appl. Catal., B, 2014, 150, 647–655.
30 J. Zhao, H. Chen, X. Tian, H. Zang, Y. Fu and J. Shen, J.
Catal., 2013, 298, 161–169.
9
P. A. Clark and S. T. Oyama, J. Catal., 2003, 218, 78–87.
1
1
1
0 S. J. Sawhill, K. A. Layman, D. R. van Wyk, M. H. Engelhard,
C. Wang and M. E. Bussell, J. Catal., 2005, 231, 300–313.
1 K.-S. Cho, H.-R. Seo and Y.-K. Lee, Catal. Commun., 2011, 12,
31 J. M. Zowtiak and C. H. Bartholomew, J. Catal., 1983, 83,
1
07–120.
2 C. H. Bartholomew and R. J. Farrauto, J. Catal., 1976, 45, 41–
3.
470–474.
3
2 J. A. Cecilia, A. Infantes-Molina, E. Rodriguez-Castellon and
5
A. Jimenez-Lopez, Appl. Catal., B, 2009, 92, 100–113.
This journal is © The Royal Society of Chemistry 2015
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