Support effect on conversion of quinoline over ReS2 catalyst

Article abstract of DOI:10.4067/s0717-97072016000400004

The conversion of quinoline over ReS₂ supported on γ-Al₂O₃, SiO₂, ZrO₂ and TiO₂ catalysts in a batch reactor at 300°C and 5 MPa of hydrogen pressure was studied. The catalysts were prepared by wet impregnation with a loading of 1.5 atoms of Re per nm2 of support. The catalysts were characterized by N₂ adsorption, X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). The Re(x)/supports catalysts displayed high activities for the conversion of quinoline, although negligible formation of N-free compounds (hydrodenitrogenation) were observed. The intrinsic activities of ReS₂ were modified by the support decreased in the order: Re/TiO₂ > Re/ZrO₂ > Re/SiO₂ > Re/γ-Al₂O₃. The highest activity displayed by the Re/TiO₂ catalyst was correlated with the Re dispersion and formation of ReS₂ species. Meanwhile, the lower conversion of quinoline over the Re/ZrO₂, Re/SiO₂ and Re/γ-Al₂O₃ catalysts was related to the combined effect of the textural properties of catalysts and the formation of ReS_(2-x) species on the supports.

Full text of DOI:10.4067/s0717-97072016000400004

J. Chil. Chem. Soc., 61, Nº 4 (2016)
SUPPORT EFFECT ON CONVERSION OF QUINOLINE OVER ReS CATALYST
2
a
b
b
a
c
d
R. BASSI , M. VILLARROEL , F. J. GIL-LLAMBIAS , P. BAEZA , J. L. GARCÍA-FIERRO , N. MARTÍNEZ ,
d
d
e, f, g*
P. OLIVERA , K. LEIVA , N. ESCALONA
a
Pontificia Universidad Católica de Valparaíso, Facultad de Ciencias, Instituto de Química, Casilla 4059, Valparaíso, Chile.
b
Universidad de Santiago de Chile, Casilla 40, Correo 33, Santiago, Chile
Instituto de Catálisis y Petroquímica, CSIC, Cantoblanco, 28049 Madrid, Spain.
c
d
Universidad de Concepción, Facultad de Ciencias Químicas, Casilla 160C, Concepción, Chile.
e
Departamento de Ingeniería Química y Bioprocesos, Escuela de Ingeniería, Pontificia Universidad Católica de Chile,
Avenida Vicuña Mackenna 4860, Macul, Santiago, Chile.
Departamento de Química Física, Facultad de Químicas, Pontificia Universidad Católica de Chile.
f
g
Centro de Investigación en Nanotecnología y Materiales Avanzados (CIEN-UC), Pontificia Universidad Católica de Chile, Santiago, Chile.
ABSTRACT
The conversion of quinoline over ReS supported on g-Al O , SiO , ZrO and TiO catalysts in a batch reactor at 300◦C and 5 MPa of hydrogen pressure was
2
2
3
2
2
2
2
studied. The catalysts were prepared by wet impregnation with a loading of 1.5 atoms of Re per nm of support. The catalysts were characterized by N adsorption,
2
X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). The Re(x)/supports catalysts displayed high activities for the conversion of
quinoline, although negligible formation of N-free compounds (hydrodenitrogenation) were observed. The intrinsic activities of ReS were modified by the support
2
decreased in the order: Re/TiO > Re/ZrO > Re/SiO > Re/g-Al O . The highest activity displayed by the Re/TiO catalyst was correlated with the Re dispersion
2
2
2
2
3
2
and formation of ReS species. Meanwhile, the lower conversion of quinoline over the Re/ZrO , Re/SiO and Re/g-Al O catalysts was related to the combined
2
2
2
2
3
effect of the textural properties of catalysts and the formation of ReS(2-x) species on the supports.
Keywords: Hydrodenitrogenation, ReS , quinoline, supports.
2
1
. INTRODUCTION
Chouzier et al. [9] studied (Ni, Co)-Mo binary and ternary nitrides in the
HDN of quinoline. They found that the active phase for monometallic nitrides
Recently, the quality of crude oil has declined due to the contents
of heavier nitrogen and sulfur organic compounds which hinder the
hydrotreating processes (HT), particularly hydrodesulfurization (HDS) and
hydrodenitrogenation (HDN). Moreover, stringent environmental regulations
have forced the oil industry to reduce the nitrogen and sulfur levels present in
fuels. In order to meet the required standards, it is essential to find catalysts
that are more active than the classical HT Ni(Co)-Mo/Al O catalysts. In this
was MoS formed on the surface of nitride particles. This was confirmed by
2
the poor activity of the nitride in the absence of sulfur. The authors reported
synergism for these bimetallic nitride systems, and indicated that the active
sites are probably some ensembles of metallic atoms on the surface of mixed
phases Co Mo N and Ni Mo N.
3
3
2
3
On the other hand, Eijsbouts et al. [10] studied the reactivities of first-,
second-, and third-row transition metal sulfide (TMS) supported on activated
carbon in the HDN of quinoline. They found that the first-row transition
metal sulfides displayed low quinoline conversion to hydrocarbons. On the
other hand, the second- and third-row TMS formed a volcanic curve with
maxima at Rh/C and Ir/C catalysts, respectively. On this curve, Re/C presented
intermediate activity but with a high selectivity for propylbenzene. The ReS2
catalyst has been rarely studied for HDN reactions although a ReS /Al O
2
3
context, several researches have been carried out in order to either improve
the activity of classical sulfides catalysts or find alternative catalysts [1, 2, 3].
Liu et al. [1] studied the effects of the addition of fluorine and phosphorus
on Ni–Mo/Al O catalysts in the HDN of quinoline. They found that fluorine
2
3
and phosphorus promote the activity of Ni–Mo/Al O catalysts, attributing
2
3
this behavior to the promotion of weak and moderate acid sites, as well as the
enhancement of Mo dispersion.
2
2
3
catalyst exhibited a higher activity (1.6 times) than the Ni-Mo/Al O catalyst in
2
3
Deepa et al. [4] investigated the effect of supports on the HDN of
quinoline and 1,2,3,4-tetrahydroquinoline (THQ1) over Ni-Mo catalysts. The
highest quinoline conversion was displayed by Ni-Mo supported on a B-zeolite
dealuminated blend with Al O (Al O -DAl BEA-Al), followed by Ni-Mo/
the HDS of thiophene [11].
Escalona et al. [12] studied the simultaneous HDS and HDN reaction over
ReS /Al O catalyst. They found that the HDN/HDS selectivity increases with
2
2
3
increasing Re loading, which was attributed to changes in the acid sites of the
catalysts. A similar behavior was also observed in the simultaneous HDS and
2
3
2
3
Al O catalyst. On the other hand, the highest THQ1 conversion was presented
2
3
by Ni-Mo/Al O3 (DAl BEA-AL), followed by Ni-Mo/AlMCM-41 catalyst.
HDN over ReS /C catalysts [13].
2
2
The trend obtained was attributed mainly to differences in the acid strength of
supports used.
On the other hand, Laurenti et al. [14] studied the HDS of thiophene
over ReS supported on Al O , ZrO and TiO . They found that the ReS /ZrO
2
2
3
2
2
2
2
2
Yang and Satterfield [5] studied the effect of hydrogen sulfide on the HDN
of quinoline using NiMo/Al O catalyst. They found that the hydrogen sulfide
catalyst displayed the highest activity followed by ReS /Al O and ReS /TiO
2 2 3 2
catalysts, and that catalytic activity was strongly dependent on the sulfidation
mixture used, similar to previous findings by Escalona et al. [11].
2
3
inhibits hydrogenation and dehydrogenation reactions but markedly accelerates
hydrogenolysis reactions.
It is well known that the activity of transition metal sulfides strongly
depends on the type of support used. The support can influence the interaction
between its surface and the active phase, the dispersion, degree of sulfurization,
stability, and structure of the active phase, etc. [15, 16, 17, 18]. Therefore, the
aim of this work is to study the effect of support (TiO , Al O , SiO and ZrO )
Moreau et al. [6] studied HDN of quinoline using mechanical mixtures of
industrial pre-sulfided alumina-supported Ni-Mo and Co-Mo catalysts. They
found a substantial promotion effect, due mainly to the better hydrogenolysis
properties of the catalysts mixtures. The authors indicated that this effect could
be due to a novel active phase or due to a bifunctional mechanism.
The reactivity of non-classical catalysts has also been studied for HDN and
HDS reactions. Ni-rich bimetallic phosphides incorporating different metals
displayed high activity in the simultaneous HDN of quinoline and HDS of
dibenzothiophene [2]. However, the HDS conversion and product selectivities
were dependent on the adsorption of N-containing compounds on the active
sites of catalysts [7, 8]. These results reiterated that the removal of nitrogen
from heterocyclic compounds is a more difficult process than the removal of
sulfur, and generally leads to deactivation of catalysts.
2
2
3
2
2
on conversion of quinoline using Re sulfide as active phase. The preparation of
Re sulfide catalysts was carried out with N /H S mixture, following a procedure
2
2
previously reported by Escalona et al. [14].
2.- EXPERIMENTAL
2.1 Catalyst preparation
The supported rhenium-based catalysts were prepared by incipient
wetness impregnation of an aqueous solution of NH ReO (Aldrich, 99%) on
4
4
3
170
e-mail: neescalona@ing.puc.cl

J. Chil. Chem. Soc., 61, Nº 4 (2016)
SiO (BASF D10-11), g-Al O (BASF D10-10), TiO (p25 Degussa) and ZrO
2.
2
2
3
2
The ZrO support was obtained by direct calcination of a commercial hydrous
2
Eq. (2)
zirconium Zr(OH) (MEL Chemicals) at 573 K for 3 h in a muffle furnace.
4
2
The catalysts were prepared with a loading 1.5 atoms of Re per nm of support.
The impregnated catalysts were left for maturation at room temperature for 24
h, dried at 393 K for 12 h, and then calcined at 573 K for 0.5 h. The calcined
samples were pre-sulfided at 673 K for 4 h under a flow of 10 % H S/N
where X is the percentage of product formation i, and X is the quinoline
conversion.
i
T
2
2
mixture. The Re content was determined by ICP-OES using the Re emission
line of 221.426 nm.
3
. RESULTS AND DISCUSSION
3
.1 Characterization of catalysts
2
.2 Characterization of the Catalysts
Figure 1 shows the N adsorption-desorption isotherms of the supports.
2
According to IUPAC classifications, all the isotherms belong to type IV which
The BET surface area (SBET) and total pore volume (V ) of the support and
the ReOx/support catalysts were determined from nitrogen isotherms at 77 K
using a Micromeritics-TriStar II 3020 instrument.
p
is typical of mesoporous materials [19]. Also, Fig. 1 shows that the g-Al O and
2
3
ZrO supports displayed a hysteresis loop, closely resembling a type H1, due
2
to capillary condensation which is typically associated to non-interconnected
X-ray powder diffraction (XRD) patterns were obtained by means of a
ink-bottle pores. Meanwhile, the TiO and SiO supports displayed a hysteresis
Rigaku diffractometer equipped with a nickel-filtered CuK α radiation (l =
2
2
1
loop resembling a type H3, suggestive of slit-shaped pores. The N adsorption-
1
.5418˚A).
XPS measurements were performed using a VG Escalab 200R electron
spectrometer equipped with a hemispherical electron analyzer and a Mg Kα
1253.6 eV) excitation source. Energy corrections were performed using
2
desorption isotherms of the catalysts (not shown here) were similar to their
respective supports. The textural properties from N2 adsorption-desorption
isotherms of the supports and catalysts are summarized in Table 1. The g-Al O
(
2
3
support possessed the highest surface area, followed by SiO , TiO and ZrO
the line of each support as internal reference. The samples were treated as
2
2
2
supports. Also, there was a slight decrease in textural properties of the supports
surface area and the total, micropore and mesopore pore volumes) after Re
previously stated, cooled to room temperature, flushed with N , stored in
2
(
flasks containing n-heptane, and transferred into the pretreatment chamber of
the spectrometer. The XPS analyses of these samples were categorized as pre-
reaction. After the HDN reaction, the spent catalyst was transferred into flasks
containing n-dodecane, and analyzed by XPS. The intensity of the peaks was
estimated by calculating the integral of each peak after subtracting an S-shaped
background and fitting the experimental curve to a combination of Gaussian/
Lorentzian lines.
impregnation, suggesting that pore mouth blockage was practically absent.
2
.3. Catalytic tests
The HDN of quinoline was carried out in an autoclave reactor operating in
-1
batch mode. The liquid reactant feed, consisting of quinoline (0.232 mol L ) in
−
1
decahydronaphthalene (decaline) (80 mL) with hexadecane (0.0341 mol L ) as
internal standard, was introduced into the reactor. Then, approximately 0.200
g of the selected catalyst was added. As previously indicated, the ReS (x)/
2
supports were prepared from the ex situ sulfidation and quickly transferred to
the reactor to prevent oxidation. The system was closed, and N was bubbled
2
-1
through the solution for 20 min with a flow of 100 mL min to purge any air
in the system. Still under N atmosphere, the reactor was heated to the reaction
2
temperature of 573 K with stirring. The reaction timer was initiated when the
reaction temperature was reached and the pressure was adjusted to 5 MPa
by H . The pressure was kept constant during the course of the experiment.
2
Condensed samples were taken periodically during the reaction and quantified
by a gas chromatograph (Perkin-Elmer - Clarus 400) equipped with a Flame
Ionization Detector (FID) and a CP-Sil 5 column (Agilent, 30 m x 0.53 mm x
1
.0 μm film thickness).
The specific rate for the total conversion of quinoline was deduced from
the initial slope of conversion as a function of time plot according to the
following equation:
Figure 1: Nitrogen adsorption – desorption isotherms of supports.
Figure 2 shows the XRD patterns of the calcined Re/support catalysts. The
patterns obtained were compared to JCPDS data files for phase identification
-
4
(
ReO : 010-0252, ReO : 041-0967, TiO : 01-086-1157; SiO : 01-087-0710,
3
2
2
Eq. (1)
ZrO : 037-1484, Al O : 010-0425). Figure 2a and 2b shows the presence of
2 2 3
-
ReO4 (main peaks 2q = 16.7; 25.4; 27.6; 30.4; 40.6; 41.3; 43.48; 47.2; 49.2;
0.9; 52.2) and ReO (main peaks 2q =34.8; 37.9; 59.0; 82.4; 85.5) species
5
−
1
−1
3
where r is the specific rate (mol g s ), b represents the initial slope of
the conversion vs. time plot (dimensionless), n is the initial moles of quinoline
mol), and m is the mass of catalyst (g). The intrinsic rate was calculated from
s
over SiO support. Also, it can be observed in Figs. 2a and 2b that the intensity
2
-
of the ReO peaks was higher than the intensity of the ReO peaks, suggesting
4
3
(
-
that ReO4 species is the main crystalline phase on this supports, in agreement
with Escalona et al. [12]. On the contrary, Fig. 2c shows no detected diffraction
peaks attributed to ReO4 and ReO species for the ZrO -supported catalysts,
the specific rate according to the following equation:
-
3
2
suggesting that either ReOx was highly dispersed on this support or that some
Eq. (2)
where r is
i
of the ZrO2 peaks may have masked the ReOx peaks. Meanwhile, Fig. 2d
-
shows that ReO4 species was detected on TiO support. Table 1 summarized
2
the intrinsic rate (represent the molecules of quinoline transformed per Re atom
-
the crystal size calculated by Scherrer equation. The ReO4 crystallite size
-1
-1
and second; and it is expressed as molec. Re at s ), and r is the specific rate
s
was similar on all supports, around 50 nm. However, this result contradicts a
previously reported study by Arnoldy et al. [20]; they found by XRD that the
ReOx particles size supported on Re(2.5)/SiO and Re(2.43)/g-Al O catalysts
(
[
expressed as moles of quinoline transformed per gram of catalyst per second
mol. gcat s ]), nRe represents the number of Re atoms per gram of catalyst,
-1 -1
2
2
3
and Nav is the Avogadro number.
was around 200 nm. This difference in ReOx particles size can be attributed
to the impregnation method used by Arnoldy et al. [20]. They used several
pore volume impregnation steps to reach high Re content, suggesting that this
procedure favor the formation of larger ReOx particles size.
The selectivities (%) were determined at 40% of quinoline conversion,
according to Eq. (2):
3
171

J. Chil. Chem. Soc., 61, Nº 4 (2016)
Table 1. Composition, textural properties and crystal size obtained from X-ray diffraction of ReOx(x)/support catalysts.
a
b
c
d
e
-
Re
Re surface density
(atoms nm )
S
Vp
Vm
Vo
3 -1
ReO4
BET
Samples
-2
2
-1
3
-1
3
-1
Content (%)
(m g )
(cm g )
(cm g )
(cm g )
Crystal size (nm)
γ-Al O3
---
9.8
--
---
1.5
---
211
202
41
0.55
0.35
0.09
0.07
0.31
0.26
0.09
0.08
0.46
0.25
0.07
0.05
0.22
0.19
0.06
0.06
0.09
0.09
0.02
0.02
0.09
0.06
0.03
0.02
---
50
2
Re(1.5)/ γ-Al O3
2
ZrO2
Re(1.5)/ ZrO2
SiO2
---
2.1
---
8.7
---
2.3
1.5
---
40
n.d.
---
187
144
54
Re(1.5)/ SiO2
TiO2
1.5
---
47
---
*
Re(1.5)/TiO2
1.5
45
56
a
b
c
d
e
*
Determined from BET equation.
Calculated from the amount adsorbed at a relative pressure of 0.96.
Determined from Dubinin–Radushkevich (D–R) equation.
Difference between V and V .
p
p
-
ReO4 crystal size determined from Scherrer equation using 2q = 25.4°
ReO4 crystal size was calculated using 2q = 16.7°
-
Figure 2: X-ray diffraction of a) Re/SiO , b) Re/g-Al O , c) Re/ZrO and d) Re/TiO catalysts.
2
2
3
2
2
3
172

J. Chil. Chem. Soc., 61, Nº 4 (2016)
Table 2. XPS binding energies (eV) and surface atomic ratios of sulfided catalysts.
M 2p
Si, Al, Zr, Ti) (e.V.)
Re4f7/2
(e.V.)
S2p
(e.V.)
Catalysts
Re/M at
(
ReS (1.5)/SiO
103.4
74.5
41.2
161.8
162.0
0.041
0.034
2
2
4
4
1.6 (89)
3.3 (11)
ReS (1.5)/g-Al O
3
2
2
4
4
1.6 (88)
4.4 (12)
ReS (1.5)/ZrO
182.2
458.6
162.0
161.7
0.028
0.089
2
2
ReS (1.5)/TiO
41.0
2
2
Figure 3 shows the XPS spectra of Re/support catalysts with a surface
density of 1.5 atoms of Re per nm of supports. Curve fitting of spectra in
for ReS [12, 21, 22]. A single peak for S 2p peaks at 162 eV ± 0.4 indicates
the presence of S for all the sulfided catalysts. The BE of the Re 4f7/2 peaks
2
2
2-
Figures 3a and 3d revealed one doublet, each one containing the Re 4f 7/2 and
Re 4f 5/2 peaks, indicating the presence of one Re species. Meanwhile, curve
fitting of the spectra in Fig. 3b and 3c shows two partially overlapping doublets
containing the Re 4f 7/2 and Re 4f 5/2 peaks, indicating the presence of two Re
species. Table 2 summarizes the binding energies (BE) of the most intense Re
of the less intense doublet displayed by Re/g-Al O and Re/ZrO catalysts was
2
3
2
around 43.9 eV ± 0.3, which can be assigned to Re oxysulfide species [12, 13,
21, 22]. These results indicate that Re sulfidation was slightly incomplete, and
that the procedure used led to an estimated 90 % sulfidation for g-Al O - and
2
3
ZrO -supported catalysts. This result suggests a strong interaction between
2
4
f7/2 component of each doublet, its relative proportions (between parentheses)
and surface atomic ratio for Re/supports catalysts. Table 3 shows that the Re
f 7/2 components of the most intense doublet remained constant in all the
catalysts, at about 41.4 eV± 0.3, and corresponds closely to the values reported
ReOx species and these supports. On the other hand, the Re/TiO , and Re/SiO
catalysts displayed only a component of the Re 4f7/2 peak, indicating complete
Re sulfidation.
2
2
4
Figure 3: XPS of sulfides: a) Re/SiO , b) Re/g-Al O , c) Re/ZrO and d) Re/TiO
2
2
2
3
2
catalysts.
3
173

J. Chil. Chem. Soc., 61, Nº 4 (2016)
Figure 4: Quinoline conversion and yield of products over a) Re/SiO , b) Re/g-Al O , c) Re/ZrO and d) Re/TiO catalysts.
2
2
3
2
2
Table 2 also shows that Re/M atomic ratios for the ReS /supports catalysts.
2
This shows that Re/TiO catalysts displayed the highest Re/M atomic ratios,
2
followed by Re/SiO , Re/g-Al O and Re/ZrO catalysts. This trend suggests
2
2
3
2
that ReS was most highly dispersed on the TiO support, while it was poorly
2
2
dispersed on the ZrO support, as previously observed by Laurenti et al. [14].
2
Unfortunately, HRTEM cannot be used to estimate the size of sulfide because
the lamellar structure decomposes into spherical metallic particles under
electron beam [14].
1
.2 Catalytic activity of catalysts
Figure 4 illustrates the conversion of quinoline and yield of products
over ReS /support catalysts as a function of time. It can be observed that
2
the main reaction product was 1,2,3,4 tetrahydroquinoline (THQ1), and that
decahydroquinoline (DHQ) was observed in minor amounts for all the catalysts.
The conversion of quinoline by the ReS (x)/supports catalyst can be depicted in
2
the reaction scheme shown in Figure 5, in agreement with previously reported
studies by several authors [4, 5, 6, 9, 10]. Figure 5 shows that the formation
of DHQ compound can be produced through hydrogenation of quinoline
(either via THQ1 or THQ5 intermediate compounds). However, THQ5 was
not detected under the experimental conditions used. Figure 6 illustrates the
products distribution calculated at 40 % of quinoline conversion.
The Re/SiO and Re/g-Al O catalysts displayed a higher yield to DHQ
2
2
3
compound than the Re/ZrO and Re/TiO catalysts, suggesting that SiO and
2
2
2
g-Al O supports slightly modified the active sites favouring the hydrogenation
2
3
route. In this sense, Laurenti et al. [14] studied the HDS of thiophene over
Re/ZrO , Re/TiO and Re/g-Al O catalysts, and suggested the formation of
2
2
2
3
ReS(2-x) under the reaction condition used. In other words, the authors proposed
the formation of a metallic character in ReS . In fact, C. Sepulveda et al. [23]
2
demonstrated by kinetic approach of competitive hydrogenation the presence
Figure 5: Reaction network for the conversion of quinoline.
of a metallic character on ReS supported on SiO and g-Al O . Therefore, the
2
2
2
3
higher yield to DHQ displayed by Re/SiO and Re/g-Al O catalysts could be
2
2
3
attributed to higher ReS metallic character on these supports.
2
3
174

J. Chil. Chem. Soc., 61, Nº 4 (2016)
Figure 6: Products distribution at 40% conversion of
quinoline for ReS (x)/supports catalysts.
2
Figure 7: a) Specific rate and b) intrinsic rate of ReS (x)/supports catalysts.
2
The negligible formation of N-free compounds observed for the Re/support
catalysts contrasts with the results reported recently by Fagar et al. [24] in the
HDN of quinoline over MoS catalyst. The MoS displayed high selectivity
TiO support, as suggested by XPS. On the contrary, the lower intrinsic activity
2
displayed by Re/g-Al O catalysts cannot be correlated with XPS results. This
2
3
catalyst presented a similar ReS dispersion to the Re/ZrO catalyst; however,
2
2
2
2
to THQ1 and C9 products. This behaviour can be due to an inhibitive effect
similar to those observed in the HDN of indole [25] and carbazol [26]. Laredo
et al. [25] studied, by kinetic approach mechanism, the inhibition of indole
and o-ethylaniline in the HDS of difenzothiophene (DBT) over commercial
Co-Mo/g-Al O catalyst at conditions commonly used in the hydrotreatment of
the Re/ZrO catalyst displayed an intrinsic activity about 4.5 times higher than
2
the Re/g-Al O catalyst. These results did not show a clear correlation between
2
3
the catalytic activity and the structure of the g-Al O -, ZrO - and SiO -supported
2
3
2
2
ReS catalysts, suggesting that other factors are involved in the conversion of
2
quinoline, such as the existence of an electronic effect induced on the active
phase by the support. Laurenti et al. [14] and Sepulveda et al. [23] reported
the formation of ReS(2-x) species under reaction condition over SiO , g-Al O -
2
3
diesel feedstock. They observed an unexpected self-inhibiting effect of indole
and o-ethylaniline in their hydrogenation process during DBT HDS. Similar
self-inhibitive effect was observed in the HDN of carbazol and the HDS of
DBT over Ni-MoP/g-Al O commercial catalyst [26]. These results suggest a
2
2
3
and ZrO -, while over TiO catalyst apparently this specie was not formed.
2
2
Therefore, the formation of ReS(2-x) over g-Al O , ZrO and SiO2 supports
2
3
2
3
2
possible retardation in the formation of N-free compounds in the batch reactor.
In fact, reaction of these same catalysts in continuous flow reactor (elimination
of self-inhibiting effect) showed high formation of N-free compounds (data
not show here).
could favor the HYD pathway but decrease the quinoline conversion. This
behavior contrasts results previously observed for the conversion of thiophene,
suggesting that this species disfavor the adsorption of quinoline over the active
site. However, in the case of ZrO support the intrinsic rate was higher than Re/
2
Figure 7 shows the activity expressed as the initial rate (per gram of
catalysts) and intrinsic initial rate (by metal atom) of all the catalysts evaluated
SiO and Re/g-Al O catalysts, this behavior is not clear. Future research should
be aimed at clarifying this possible electronic effect (exact ReOx nature) versus
Re dispersion on the HDN reaction over this active phase.
2
2
3
in this study. Fig. 7a shows that the Re/SiO catalyst displayed the highest initial
2
rate followed by Re/Al O , Re/ZrO and Re/TiO catalysts. This behaviour can
2
3
2
2
be a function of Re atoms surface loading due to differences in the surface area
of supports. Regarding the intrinsic activity, Fig. 7b shows that the ReS /TiO
4. CONCLUSIONS
2
2
2
catalyst displayed the highest intrinsic activity, followed by Re/ZrO , Re/SiO
The ReS (1.5)/supported catalysts are highly active in the conversion of
2
2
and Re/g-Al O catalysts. Similar trend was observed previously by Laurenti et
quinoline but exhibit negligible activity on the formation of N-compounds
in a batch reactor. This behavior was attributed mainly to a self-inhibitive
effect by some of the products from quinoline conversion in the batch reactor.
2
3
al. [14] in the conversion of thiophene. The highest intrinsic activity observed
over the Re/TiO catalyst can be attributed to higher ReS dispersion on the
2
2
3
175

J. Chil. Chem. Soc., 61, Nº 4 (2016)
The highest activity presented by the ReS /TiO catalyst was attributed
10.- Eijsbouts S, De Beer V.H.J, Prins R., J. Catal 127, 619 (1991).
11.- Escalona N, Vrinat M, Laurenti D, Gil Llambías F. J., Appl. Catal. A:Gen
322, 113 (2007).
12.- Escalona N, Ojeda J, Cid R, Alvez G, López Agudo A, Fierro J.L.G, Gil-
Llambías F.J. Appl. Catal. A:Gen 232, 45 (2002)
2
2
to the combined effect of Re dispersion and the formation of ReS species.
2
Meanwhile, the activity trends displayed over the Re/g-Al O , Re/SiO and
2
3
2
Re/ZrO catalysts cannot be related to any structural and textural properties
2
of the catalysts, suggesting that the support can be involved in modifying the
active site by electronic effect. The Re/SiO and Re/g-Al O catalysts displayed
13.- Escalona N, Ojeda J, Yates M, Lopez Agudo A, Fierro J.L.G and Gil–
Llambías F. J. Applied. Catal. A:Gen 240,151 (2003).
2
2
3
a higher yield to DHQ compound than the Re/ZrO2 and Re/TiO catalysts.
2
The results were attributed to higher ReS metallic character over Re/SiO and
14.- Laurenti D, Thoa K.T, Escalona N, Massin L, Vrinat M, Gil Llambías F. J.
Catal Today 130, 50 (2008).
15.- Cáceres C.V, Fierro J.L.G, Lázaro J, López Agudo A, Soria J., J. Catal.
2
2
Re/g-Al O catalysts favouring of yield to DHQ compound but decreasing the
2
3
quinoline conversion.
1
22, 113 (1990)
ACKNOWLEDGMENTS
16.- Hédoire C.-E, Louis C, Davidson A, Breysse M, Maugé F, Vrinat M., J.
Catal. 220, 433 (2003).
The authors thank CONICYT-Chile for FONDECYT Nº 1130749 grant.
17.- Breysse M, Afanasiev P, Geantet C, Vrinat M., Catal. Today 86, 5 (2003)
1
8.- Laurenti D, Phung-Ngoc B, Roukoss C, Devers E, Marchand K, Massin
L, Lemaitre L, Legens C, Quoineaud A.-A, Vrinat M., J. Catal. 297, 165
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