High-efficiency catalytic performance over mesoporous Ni/beta zeolite for the synthesis of quinoline from glycerol and aniline

Article abstract of DOI:10.1039/c6ra26736j

A green route for the vapor-phase synthesis of quinoline from glycerol and aniline was developed in this work, employing Ni/mesoporous beta zeolite (denoted as Ni/Hβ-At) as a catalyst. The mesoporous beta zeolite was prepared by alkaline treatment. Various influencing factors were systematically investigated. Both mesopores and the type of acid sites of the catalyst played important functions in catalytic activity for the synthesis of quinoline. Mesopores facilitated the transport of bulky products from internal surface of the catalyst. Meanwhile, weak Br?nsted acid sites favored the dehydration of glycerol to acrolein and the existence of Lewis acid sites could accelerate the formation of quinoline. The Ni/Hβ-At catalyst exhibited the highest catalytic activity; and as high as a 71.4% yield of quinoline was obtained under the optimized reaction conditions. An enhanced ability of anti-deactivation was also displayed, due to the existence of mesopores on the Ni/Hβ-At catalyst facilitating the transport of bulky products and restraining the deposition of the coke. Meanwhile, it was found that the coke was main reason leading to catalyst deactivation and its performance was basically regenerated. The catalytic properties were slightly lower after 3 reaction-regeneration cycles. Finally, a feasible reaction pathway was proposed on the basis of the various products.

Full text of DOI:10.1039/c6ra26736j

RSC Advances
View Article Online
View Journal | View Issue
PAPER
High-efficiency catalytic performance over
mesoporous Ni/beta zeolite for the synthesis of
Cite this: RSC Adv., 2017, 7, 9551
quinoline from glycerol and aniline†
a
a
a
a
ab
An Li, Chen Huang, Cai-Wu Luo, Wen-Jun Yi and Zi-Sheng Chao*
A green route for the vapor-phase synthesis of quinoline from glycerol and aniline was developed in this
work, employing Ni/mesoporous beta zeolite (denoted as Ni/Hb-At) as a catalyst. The mesoporous beta
zeolite was prepared by alkaline treatment. Various influencing factors were systematically investigated.
Both mesopores and the type of acid sites of the catalyst played important functions in catalytic activity
for the synthesis of quinoline. Mesopores facilitated the transport of bulky products from internal surface
of the catalyst. Meanwhile, weak Brønsted acid sites favored the dehydration of glycerol to acrolein and
the existence of Lewis acid sites could accelerate the formation of quinoline. The Ni/Hb-At catalyst
exhibited the highest catalytic activity; and as high as a 71.4% yield of quinoline was obtained under the
optimized reaction conditions. An enhanced ability of anti-deactivation was also displayed, due to the
existence of mesopores on the Ni/Hb-At catalyst facilitating the transport of bulky products and
restraining the deposition of the coke. Meanwhile, it was found that the coke was main reason leading to
catalyst deactivation and its performance was basically regenerated. The catalytic properties were slightly
lower after 3 reaction–regeneration cycles. Finally, a feasible reaction pathway was proposed on the
basis of the various products.
Received 13th November 2016
Accepted 19th December 2016
DOI: 10.1039/c6ra26736j
www.rsc.org/advances
especially via vapor-phase process, due to the utilization of
glycerol as green raw material. It is known that glycerol is cheap,
1
. Introduction
Quinoline and quinoline derivatives constitute an important abundant, renewable and environment-friendly, and it has been
category of heterocyclic compounds and are widely used as currently manufactured on a large scale as the byproduct of
pharmaceuticals, fungicides, herbicides, corrosion inhibitors biodiesel process. Whereas, the exceeding output of bio-glycerol
19–21
1–5
and functional chemicals. However, the traditional liquid- has hindered further development of the biodiesel industry.
phase routes suffer from several limitations, such as, volatile Efficient utilization of bio-glycerol is of signicant necessity.
organic solvents, expensive or toxic feedstocks and complicated Therefore, the further development of vapor-phase Skraup
6
–12
recycling of catalysts.
Hence, the development of vapor- routes, utilizing bio-glycerol as raw material to manufacture
phase synthesis is of great interest. Although many vapor- quinolines, is green, sustainable, low-cost pathway and highly
phase syntheses of quinolines have been reported, most of desired.
them are not environment-friendly and uneconomical. For
instance, saturated/unsaturated aldehydes or acetones reacted phous silica-alumina, mixed metal oxides and zeolites, have
4,13,22,23
To date, different kinds of catalysts, such as, K10, amor-
13–15
with anilines to produce quinolines,
in which, however, been used for vapor-phase synthesis of quinolines.
aldehydes or ketones are toxic, expensive and prone to poly- However, the above-mentioned catalysts suffer from low cata-
merization which result in serious catalyst deactivation. The lytic activity and stability or high transport limitation, which
6,16–18
Skraup approach, as a typical quinolines synthetic route,
limited the further development of quinoline and its deriva-
presents more and more potential industrial importance tives. This is no doubt that the development of a novel and high-
performanced catalyst is highly necessitated.
Beta zeolite-based catalysts were effective catalysts for not
a
only the dehydration of glycerol to acrolein but also the gener-
College of Chemistry and Chemical Engineering, Key Laboratory of Chemometrics &
14,24
Chemical Biological Sensing Technologies, Ministry of Education, Hunan University, ation of quinolines from various raw materials.
Changsha, 410082, China. E-mail: zschao@yahoo.com; Fax: +86-731-88713257;
The can be
attributed to the advantages associated with beta zeolite, such
as adjustable acid sites, unique shape selectivity, excellent
hydrothermal stability, and especially appropriate pore size
matching with quinoline molecule size. Nevertheless, its single
micropores impose diffusion limitations and restrict the
Tel: +86-731-88713257
b
College of Materials Science and Engineering, Changsha University of Science &
Technology, Changsha, 410114, China
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c6ra26736j
1
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 9551–9561 | 9551

View Article Online
RSC Advances
Paper
transport of bulky products (like quinolines) from the active resultant suspension was ltrated immediately, washed with
ꢀ
sites in its internal surface. These drawbacks preclude practical deionized water until neutrality, and dried at 120 C for 12 h.
applications in synthesis quinolines reactions. One strategy is The obtained solid was redispersed into NH NO aqueous
4
3
preparation of beta zeolites with mesopores to facilitate diffu- solution; then, the resultant mixture was subjected to ion-
ꢀ
sion to the internal active sites. In recent years, mesoporous exchange at 90 C for 4 h under vigorous stirring and reux-
structured beta zeolites, which has advantages of both micro- ing conditions. Aerwards, the slurry was ltrated, and dried at
ꢀ
pores and mesopores, have been considerably used in various 120 C for 12 h. The above process from ion-exchange to drying
bulky molecular reactions, such as, conversion of synthesis gas steps was repeated for three times, with fresh 1.0 M NH
to C –C11 isoparaffins, isomerization of a-pinene or glucose, aqueous solution being employed in each run. Finally, the ob-
alkylation of benzene with isopropanol to cumene, benzoylation tained solid was calcined at 550 C for 4 h. The thus-prepared
4 3
NO
5
ꢀ
25–30
of naphthalene and desulfurization.
catalytic performance than the single microporous beta zeolite-
base catalysts. For example, 100% conversion of a-pinene with parent Hb was rst added into the mixture aqueous solution
5.4% selectivity of desired products was achieved by meso- containing a calculated amount of 0.2 M Ni(NO and excessive
They exhibited superior catalyst was denoted as Hb-At.
2.2.2. Metal modication. The above-obtained Hb-At or the
8
3 2
)
porous beta catalyst, whereas only 20.3% conversion was ob- urea. Aer being strongly stirred at room temperature for 1 h,
ꢀ
tained by the single microporous beta catalyst under the same the resultant suspension was heated to 90 C and subjected to
reaction conditions. The mesoporous structured beta zeolite resume strong stirring under reuxing condition for 4 h. Aer
can be achieved in various methods, such as by post-synthesis being cooled to room temperature, the solid was recovered by
treatment, by using surfactants as so templates or crystalli- ltration, washing with deionized water until neutrality, and
ꢀ
zation of amorphous aluminosilicates deposited onto hard drying at 120 C for 12 h. Finally, the solid obtained was
28–32
ꢀ
templates.
Among these methods, the alkaline post- calcined at 550 C for 4 h. The thus-prepared catalysts were
treatment have been proved to improve the porosity of beta denoted as Ni/Hb and Ni/Hb-At, respectively. Similarly, other
zeolite via selective extraction of silicon atoms from the M/Hb-At catalysts (M ¼ Mn, La, Cu, Zn and Fe) were also
framework without distinct change of the acidity and crystal- prepared with the same procedure as above for the preparation
linity. Moreover, this method is more simple, feasible and of Ni/Hb-At.
effective methods, which can be suitable for mass production
All the above-described catalysts were rst pressed into
without the complicated synthesis procedures and the disks, crushed, and sieved to 30–40 mesh before use.
employment of expensive templates. However, to the best of our
knowledge, mesoporous beta catalysts have never been reported
in the application of vapor-phase synthesis of quinolines.
2.3. Catalysts characterization
In this work, we reported a green and economic route for X-ray diffraction (XRD) was performed with a Bruker D8-
vapor-phase synthesis of quinoline from glycerol and aniline, Advance X-ray diffractometer, under the following conditions:
˚
for the rst time, using modied mesoporous beta zeolite as Cu target Ka ray (l ¼ 1.54187 A); scanning voltage 40 kV,
catalyst. Under the optimized conditions, as high as 71.3% yield scanning current 40 mA; scanning speed 0.2 s, scanning step
ꢀ
of quinoline was obtained over the Ni/Hb-At catalyst. The rela- 0.02 .
tionship between the structure and the performance of catalyst
Fourier transform infrared (FT-IR) spectroscopy was recor-
was discussed in detail. A feasible reaction pathway was ded on a Varian 3100 spectrometer equipped with a DTGS
proposed on the basis of various products.
detector. The catalyst was rst mixed with KBr (the weight ratio
of catalyst/KBr ¼ 1/100) by thoroughly grounding, and then, the
mixture was pressed into the sample holder and mounted in the
detection chamber of the spectrometer, before the FT-IR
determination. The data was recorded at a scanning number
2. Experimental
2.1. Chemicals
ꢁ1
of 32 and a resolution of 2 cm
-physisorption was conducted on
Autosorb-1 instrument at liquid-N temperature. Before
measurement, the specimen was in situ outgassed in the
.
All the chemicals of analytic purity were commercially available
and provided as follows: aniline, glycerol and ethanol (A.R.,
Sinopharm Chemical Reagent Co., Ltd.); nickel nitrate, sodium
hydroxide and urea (A.R., Xilong Chemical Co., Ltd.). Besides,
beta zeolite (Hb, Si/Al ¼ 25; Nankai University Catalyst Factory)
N
2
a Quantachrome
2
ꢀ
ꢁ8
instrument at 300 C for 12 h under a vacuum of 10 Torr. The
specic surface area was calculated by using the multipoint BET
equation, with the correlation coefficient being above 0.9999.
The micropore area and volume were estimated by the “t-plot”
micropore analysis method. The total pore volume was calcu-
ꢀ
was calcined at 550 C for 4 h to remove the absorbed water and
any residual organics prior to used directly as the catalyst and in
the subsequent process of other catalysts.
lated at relative pressure of P/P
coverage with nitrogen. The pore size distribution was deter-
.2.1. Alkali treatment. A 300 mL sample of 0.20 M NaOH mined by the BJH model employing desorption isotherm.
0
¼ 0.99, assuming full surface
2
.2. Catalyst preparation
2
ꢀ
aqueous solution was rst heated to 65 C and added to 15.0 g of
Temperature programmed desorption of NH3 (NH -TPD)
3
Hb. Then, the suspension was reuxed for 0.5 h at that was determined on a Micromeritics Autochem II 2920 instru-
temperature under vigorous stirring. Subsequently, the ment equipped with a thermal conductivity detector (TCD). The
9552 | RSC Adv., 2017, 7, 9551–9561
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
catalyst was rst pretreated at 400 C for 30 min in a ow of
RSC Advances
ꢀ
3
. Results and discussion
ꢁ
1
helium (99.99%) with a ow rate of 60 mL min , followed by
ꢀ
3.1. Catalyst characterization
cooling to 100 C. Then, ammonia was repeatedly pulse-injected
ꢁ1
in a stream of 10% NH /He with a ow rate of 50 mL min until Fig. 1 shows the XRD patterns for the fresh and deactivated
3
its saturation adsorption over the catalyst had been achieved. catalysts, in which the content of Ni supported on Ni/Hb and Ni/
ꢀ
Aer purging with helium at 100 C for 1.0 h, ammonia was Hb-At catalysts is ca. 10 wt%. For the fresh catalysts, all the XRD
ꢀ
ꢀ
desorbed by heated the catalyst from 100 C to 800 C at a rate of patterns are characteristic of Hb zeolite and contain no
ꢀ
ꢁ1
10 C min
.
diffraction peaks of Ni species for Ni-containing catalysts,
Thermogravimetry (TG) proles were recorded on a Dia- implying that the original structure of Hb zeolite is retained well
mond instrument (Perkin Elmer Corp.). The catalyst was heated aer alkali treatment and that Ni species are highly dispersed
ꢀ
33,34
from room temperature to 800 C in an air stream at a heating on Hb zeolite with very small dimension. Ha and Hong et al.
ꢀ
ꢁ1
ꢁ1
rate of 5 C min . The ow rate of air was 30 mL min
.
showed that zeolites containing fewer framework Al atoms per
unit cell showed a slight contraction in each cell parameter
relative to low Si/Al ratio zeolites. Aouali et al. found that the
35
2
.4. Catalytic performance evaluation
removal of silicon from the zeolites framework resulted in an
Catalytic performance test was carried out in a xed-bed stain- increase of the unit cell parameters since the framework Si/Al
less steel reactor (i.d. 8 mm) under atmospheric pressure at ratio was decreased. Thus, the desilication and dealumination
suitable reaction temperature. The reaction equipment for would theoretically cause the expansion and contraction of
vapor-phase synthesis of quinoline was homemade and its zeolite framework, respectively. As a result, the characteristic
36,37
schematic diagram was shown in Fig. S1.† The typical operated peak would shi slightly toward lower or higher angle.
Based
procedures of catalyst evaluation were as follow: initially, the on the enlargement of the predominant peaks in the XRD
ꢁ
1

ows of glycerol aqueous solution and nitrogen (10 mL min
)
patterns, the diffraction peaks over Hb-At and Ni/Hb-At catalysts
ꢀ
were mixed in preheater at 260 C; similarly, the ows of aniline shi towards a lower angle, relative to that of the parent Hb one.
and nitrogen (10 mL min ) were mixed in another preheater at It indicates that the expansion of the Hb zeolite framework have
60 C. Then, the vaporized aniline and glycerol aqueous solu- occurred for the Hb-At and Ni/Hb-At catalysts. This result
ꢁ
1
ꢀ
2
tion were respectively fed into the reactor via the carried gas of conrms that desilication has occurred during the alkali treat-
nitrogen, and subsequently mixed on the top of catalyst bed and ment to the parent Hb zeolite. The diffraction intensity of the
reacted on the catalyst at suitable reaction temperature. The fresh catalysts shows an order of Hb ¼ Ni/Hb > Hb-At ¼ Ni/Hb-
liquid product mixtures were rst diluted with ethanol, passing At. This trend occurs because the framework of zeolite is des-
through a connecting tube enwrapped with thermal insulation tructed to a certain extent aer alkali treatment. Furthermore,
jacket, and then introduced into the condenser for the separa- for the deactivated catalysts, their diffraction intensities have
tion and collection of gas and liquid product mixtures.
almost no decrease relative to their corresponding fresh cata-
The liquid products mixtures was analyzed by a Varian lysts; thus, the framework structure of Ni/Hb and Ni/Hb-At
Saturn 2200/CP-3800 gas chromatography-mass spectrometry catalysts are considerably stable and difficult to be destructed at
(
GC-MS) equipped with two CP8944 capillary columns (VF-5, 30 high reaction temperature.
m ꢂ 0.25 mm ꢂ 0.25 mm), which were connected to a mass
detector and a ame ionization detector (FID) for the quanti-
tative and qualitative identications, respectively. The gas
product mixtures were also conducted on a on a PE Clarus500
GC instrument equipped with a thermal conductivity detector
(
TCD) and a HAYESEP DB 100/120 packed column (30  ꢂ 1/8
in. ꢂ 0.85 in. SS). In the qualitative analysis of liquid products
mixture, 3-nitrotoluene was added as internal standard. The
yield of quinoline was calculated based on the converted
aniline.
moles of aniline reacted
Conversion ðmol%Þ ¼
ꢂ %
moles of aniline input
moles of product defined
moles of aniline reacted
Selectivity ðmol%Þ ¼
ꢂ %
Yield (mol%) ¼ conversion ꢂ selectivity ꢂ %
Fig. 1 XRD patterns for the fresh and deactivated catalysts. (a) Hb; (b)
Ni/Hb; (c) deactivated Ni/Hb; (d) Hb-At; (e) Ni/Hb-At; (f) deactivated
Hb-At. (The inset shows the enlargement of the predominant peaks in
the XRD patterns.)
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 9551–9561 | 9553

View Article Online
RSC Advances
Paper
Fig. 2 shows the FT-IR spectra of the fresh and deactivated
catalysts. For the fresh catalysts, all the spectra exhibit the
characteristic vibrations of beta zeolite framework. The bands
ꢁ1
at ca. 1225, 1087 and 797 cm are characteristic of SiO tetra-
4
hedron units and can be assigned to the external asymmetric,
internal asymmetric and external symmetric stretching vibra-
tions of Si–O–T linkages for TO
4
(T ¼ Si and/or Al) tetrahe-
38–40
ꢁ1
dral.
The bands at ca. 1225 and 1087 cm reportedly shied
towards lower wavenumbers with decreasing Si/Al ratio of
zeolite, due to the slightly lower mass of silicon as compared to
4
0
ꢁ1
that of aluminum. The bands at 1225 and 1087 cm have
ꢁ1
moved to 1222 and 1083 cm for Hb-At and Ni/Hb-At catalysts,
respectively, relative to parent Hb one, indicating the decrease
in framework Si/Al ratio. The band at 943 cm is sensitive to
the framework Si/Al ratio and its intensity decreases when
It can be seen that the band
intensity at 943 cm slightly decreases for the Hb-At and Ni/
ꢁ1
41–43
framework desilication occurs.
ꢁ
1
Fig. 3
2
N -adsorption/desorption isotherm for the fresh and deacti-
Hb-At catalysts compared with those of the Hb and Ni/Hb ones. vated catalysts and corresponding pore size distributions analyzed by
BJH method. (a) Hb; (b) Ni/Hb; (c) deactivated Ni/Hb; (d) Hb-At; (e) Ni/
Hb-At; (f) deactivated Hb-At.
The results further conrm the deduction from the above XRD
characterization that alkali treatment to Hb zeolite leads to
ꢁ1
desilication. Besides, the bands at ca. 568 and 524 cm are
43,44
typical characteristic for beta zeolite,
which are presumably
assigned to the double six-ring (D6R) and double four-ring distributions analyzed by BJH method employing desorption
4
5,46
(
4
D4R) lattice vibrations of external linkage.
The band at ca. isotherm. For the fresh catalysts, the isotherms rise steeply at
ꢁ1
60 cm can be attributed to the internal T–O bending vibra- extremely low relative pressure, showing for the existence of
tion of TO4 tetrahedron. Furthermore, for the deactivated microporous. A pronounced hysteresis loop at P/P0 > 0.4 is
catalysts, the whole-band intensity decreases, to varying extent, present for Hb-At and Ni/Hb-At but almost absence for the Hb
particularly at ca. 568 and 524 cm . The phenomenon is and Ni/Hb, inferring that alkaline treatment to the parent Hb
consistent with the report that the whole-band intensity in FT- successfully generates mesopores. This occurrence is due to the
IR spectra of ZnO-FHZSM-5-At-acid catalyst decreases obvi- removal of silicon species from the external framework of the
ously aer deactivation. The decrease is presumably attributed parent Hb zeolite to generate mesopores to a certain extent
to the deposition of the coking on the surface of catalyst. during alkaline treatment. For the deactivated Ni/Hb and Ni/
Particularly, the drastic decrease of intensity at ca. 568 and 524 Hb-At catalysts, a notable difference can be noted that their
47
ꢁ1
48
ꢁ
1
cm may be due to the interaction between the coking located isotherm maintains a at rising trend at low relative pressure
in micropore with the nearby double-ring structure of zeolite.
and the hysteresis loop at P/P > 0.4 disappeared completely
0
Fig. 3 shows N -adsorption/desorption isotherm for the fresh relative to those for corresponding fresh ones. These results
2
and deactivated catalysts and corresponding pore size indicate that the microporous and mesoporous of the deacti-
vated catalysts have almost disappeared.
The detailed textural properties of various catalysts are listed
in Table 1. Compared to the pure Hb, the Hb-At possesses
a larger Vmeso, Vtotal and Sext, but smaller Vmic, Smic and SBET
.
This is due to the fact that the desilication resulted in gener-
ating the extra-framework species, thereby, blocking or covering
the pore structure. When the Ni species is supported on the Hb
and Hb-At respectively, their textural values, including Vmeso
,
Vmic, Vtotal, Sext, Smic, SBET, as well as Dmic, decrease to different
degree. For the deactivated Ni/Hb and Ni/Hb-At catalysts, SBET
and Vtotal decrease sharply, relative to the fresh ones. Mean-
while, their micropores disappear completely. The variation is
possible due to blocking mesopores and micropores by coking
substances with prolonging to the reaction time.
Fig. 4 shows the NH
vated catalysts. For the fresh catalyst, the T peak at ca. 142 C is
3
-TPD proles for the fresh and deacti-
ꢀ
1
present for all catalysts and assigned to weak acid sites relating
24,49
ꢀ
The T peak at ca. 277 C
2
to the terminal acid silanol groups.
Fig. 2 FT-IR spectra of the fresh and deactivated catalysts. (a) Hb; (b)
Ni/Hb; (c) deactivated Ni/Hb; (d) Hb-At; (e) Ni/Hb-At; (f) deactivated
Hb-At.
is identied evidently over Hb and Hb-At but virtually absent
over Ni/Hb and Ni/Hb-At; which can be ascribed to strong
9554 | RSC Adv., 2017, 7, 9551–9561
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
a
Table 1 The textural properties for various catalysts
2
ꢁ1
2
ꢁ1
2
ꢁ1
3
ꢁ1
3
ꢁ1
3
ꢁ1
Catalysts
S
BET (m g
)
S
ext (m g
)
S
mic (m g
)
V
total (cm g
)
V
mic (cm g
)
V
meso (cm g
)
Dmic (nm)
Dmes (nm)
Hb
483.7
419.0
389.7
339.4
53.6
168.2
227.0
107.8
189.2
53.6
315.5
193.0
281.9
150.2
0
0.40
0.51
0.39
0.48
0.09
0.18
0.15
0.11
0.15
0.09
0
0.25
0.40
0.24
0.39
0.09
0.18
0.61
0.61
0.60
0.59
—
4.81
—
Hb-At
Ni/Hb
Ni/Hb-At
Ni/Hb
Ni/Hb-At
4.76
DE
DE
65.1
65.1
0
0
—
—
a
Note: SBET, Sext and Smic refers to specic surface area, external surface area and micropore surface area, respectively, and SBET ¼ Sext + Smic; Vtotal
and Vmic refers to total pore volume and micropore volume, respectively; Dmic refers to micropore pore size calculated by the SF method; Dmes refers
to average mesopore pore size calculated by the BJH method; the pure Hb and Ni/Hb are inapplicable in the estimation of average mesopore size by
DE
the BJH method due to its microporous characteristic. Refers to the catalyst deactivation aer reacting for 6 h.
strong Brønsted acid sites almost disappears over Ni/Hb and Ni/
Hb-At. This is due to that Ni species attaching on zeolite create
Lewis acid sites, and meanwhile Ni-exchange to protons of
bridging Si–(OH)–Al groups partially result in a distinct
decrease in strong Brønsted acid sites. Furthermore, the
concentration of weak acid sites increases aer the addition of
Ni to Hb or Hb-At. This occurs probably due that some Ni
species dispersed on zeolite generate metal hydrate cation
2
+
50,51
Ni(H O)n due to the electrostatic eld of metal cations.
2
Subsequently, the splitting of water molecule occurs to form
+
Ni(OH) ; and as a result, new Brønsted acid sites form from this
process, as shown in eqn (1) and (2).
2
Ni + H
+
2+
n
2
O / Ni(H
2
O)
(1)
(2)
2
+
+
+
Ni(H O)
2
/ NiOH + H
n
3
Fig. 4 NH -TPD profiles for the fresh and deactivated catalysts. (a) Hb;
(
b) Hb-At; (c) Ni/Hb; (d) Ni/Hb-At; (e) deactivated Ni/Hb-At; (f)
regenerated Ni/Hb-At.
These new Brønsted acid sites should be related to weak
Brønsted acid sites, according to the study of Guzman et al.
52
Therefore, the addition of Ni species to zeolite increases both
Lewis acid sites and weak acid sites. For deactivated Ni/Hb-At
catalyst, concentration of original weak acid sites decreases
distinctly and that of Lewis acid sites almost disappear. The
result may be due that the substances cover acid sites and
subsequently block all micropores and some mesopores with
Brønsted acid sites relating to the bridging Si–(OH)–Al groups.
ꢀ
The T peak at ca. 448 C is highly distinct over Ni/Hb and Ni/
3
Hb-At; by contrast, the peak is absent over Hb and Hb-At. This
peak is attributed to Lewis acid sites deriving from Ni attached
to Hb zeolite with certain interactions. For the deactivated Ni/
Hb-At catalyst, two peaks containing the weak peak (T
1
) at ca.
ꢀ
ꢀ
142 C and the broad peak (T
4
) at the range of 430–580 C are
3
Table 2 NH -TPD results over various catalysts
present. The former peak belongs to the residual weak acid
sites. The latter one is presumably related to the signal of the
a
i
ꢀ
b
i
ꢁ1
T
( C) and A
(mmol g ) for various desorption peaks
coking at the high desorbed temperature, because the T peak
4
disappears and the T reoccurs aer regeneration of the deac- Catalyst
T1
A1
T2
A2
T3
A3
Atotal
3
tivated Ni/Hb-At catalyst.
Hb
146.0
141.2
145.0
140.7
135.8
148.0
0.86
0.91
0.91
1.21
0.19
1.12
277.2
277.2
277.2
277.2
—
0.16
0.18
0.03
0.03
—
—
—
454.0
443.3
—
—
—
0.38
0.27
—
1.02
1.09
1.32
1.51
0.19
1.39
Table 2 summarizes the strength and concentration of acid
Hb-At
sites, which corresponds respectively to the temperature at the
Ni/Hb
i i
maximum (T ) and integral area (A ) of the peaks. Aer alkaline
Ni/Hb-At
DE
RG
treatment, the resulting Hb-At shows increase slightly in Ni/Hb-At
concentrations of strong acid sites and change neglectable in
Ni/Hb-At
277.2
0.01
443.4
0.26
that of strong Brønsted acid sites, relative to the parent Hb. This
a
b
T
i
refers to the temperature at the maximum of desorption peak i.
A
i
increase is due to the fact that alkaline treatment leads to refers to the integral area of desorption peak i, and it means also the
concentration of acid site corresponding to the desorption peak i;
desilication; and as a result, more terminal acid silanol groups
are formed. When Ni is supported on Hb and Hb-At, respec-
A
total stands for the sum of the concentration of various acid site, i.e.,
P
DE
A
total
¼
A
i
.
Refers to the catalyst deactivation aer reacting for
RG
tively, concentration of weak acid sites increases and that of 6 h. Refers to the regeneration for the deactivated catalyst.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 9551–9561 | 9555

View Article Online
RSC Advances
Paper
increasing reaction time. This nding can be conrmed by the (including 3-hydroxypropanal, acrolein, hydroxyacetone and
above N adsorption–desorption, because the specic surface acetaldehyde) were well-detected by mass spectrum analysis.
2
2
ꢁ1
area remains just 65.1 m g and microporous surface area Thus, it infers that those byproducts are generated from
entirely disappears for deactivated Ni/Hb-At catalyst. Moreover, different intermediates reacting with aniline. For instance, 2-
microporous volume indeed disappears and mesoporous and 4-methylquinoline may be synthesized from aniline and
3
ꢁ1
14
volume decreases distinctly from 0.39 to 0.18 cm
g
. Aer acetaldehyde. 3-Methylindole may originate from the reaction
ꢀ
54
regeneration of deactivated Ni/Hb-At catalyst at 550 C for 4 h in of aniline and hydroxyacetone. In conclusion, both mesopores
air atmosphere, the concentration and strength of original weak and type of acid sites over catalyst play important role in cata-
acid sites and Lewis acid sites almost recover, whereas that of lytic activity for synthesis of quinoline, and as high as 71.4%
the additional acid sites (T ) disappears. Meanwhile, the yield of quinoline is achieved over the Ni/Hb-At catalyst.
4
regenerated Ni/Hb-At shows virtually high catalytic activity
Fig. 5 shows the effect of different metal (I) and the loading
similar to that of fresh Ni/Hb-At (see Fig. 8(II)). Thus, the results amount of Ni (II) supported on Hb-At, with the loading amount
indicate that catalyst deactivation originates by the deposition of different metal (I) supported on Hb-At of 10 wt%.
of coking substances rather than structure damage of the
catalyst.
(1) Different metal. Quinoline yield over these catalysts
containing metal species shows an order Ni > Fe > Zn > Cu > La >
Mn. Among all the catalysts, the introduction of Mn, La, Cu and
Zn to Hb-At, to varying extent, decreases quinoline selectivity
and yield in this reaction relative to the parent Hb-at catalyst.
3.2. Catalytic performance evaluation
Table 3 shows catalytic performance of various catalysts for On the contrary, quinoline yield over Ni/Hb-at and Fe/Hb-At are
vapor-phase synthesis of quinoline from aniline and glycerol. higher than that of Hb-At, with the highest quinoline yield ob-
Meanwhile, the productivity of quinoline in terms of weight tained over Ni/Hb-At. As active component in catalysts, nickel is
55–58
time yield also displays in Table S1.† When Hb and Hb-At are widely applied in hydrogenation/dehydrogenation reaction.
employed as catalyst, respectively, aniline conversion, quinoline For instance, Liang et al. proposed that dehydrogenation could
selectivity and yield increase over Hb-At relative to that over Hb. be accelerated via the synergistic effect of Ni active species and
58
This enhanced catalytic activity over the Hb-At is mainly acid–base sites. Moreover, some researchers thought that the
attributed to the existence of mesopores facilitating diffusion of cooperation of Lewis acid sites (Ni as the acid center) and
bulky products (such as quinoline) from internal surface of Brønsted acid sites over the Ni/HZSM-5 catalyst contributes to
53
catalyst. When Ni species are supported on Hb or Hb-At, quin- the aromatization process. Therefore, according to the reac-
oline selectivity and yield increase distinctly over Ni/Hb or Ni/ tion mechanism on synthesis quinoline from aniline and glyc-
Hb-At, respectively. It is known that the addition of Ni to zeolite erol (Scheme 1), the addition of Ni on Hb-At could contribute to
not only generates Lewis acid sites but also eliminates strong aromatization process and particularly enhance the dehydro-
Brønsted acid sites, as shown by the above characterization genation process from 1,2-dihydrogenquinoline to quinoline.
results. It indicates Lewis acid sites are preferable active sites on As a result, the yield of quinoline increases evidently over the Ni/
quinoline selectivity over the strong Brønsted acid sites. This Hb-At catalyst.
occurs probably due that side reactions (such as acrolein poly-
(2) Loading amount of Ni. Aniline conversion change little
merization) are readily occurred over strong Brønsted acid sites with increasing Ni loading weight from 0 wt% to 15 wt%. By
while the aromatization process (Scheme 1) could be acceler- contrast, quinoline selectivity and yield rst increase and then
ated via the synergistic effect of Lewis acid sites (Ni as acid decrease gradually, reaching to their largest values at 10 wt% Ni
53
center) and acid–base sites. In addition, the valuable byprod- loading weight. It indicates that an appropriate amount of Ni
ucts of alkylquinolines (including 2- and 4-methylquinoline) species attached on zeolite can increase quinoline yield
and 3-methylindole are also produced. Considering that we effectively.
entered single starting material of glycerol into the reactor
Fig. 6 illustrates the effect of reaction conditions for vapor-
under standard operating condition, intermediate products phase synthesis of quinoline over the Ni/Hb-At catalyst,
Table 3 Catalytic performance for synthesizing quinoline from aniline and glycerol over various catalysts
Selectivity (%)
a
b
Catalyst
Aniline conversion (%)
Quinoline
Alkylquinoline
3-Methylindole
Other
Quinoline yield (%)
Hb
93.3
95.0
97.1
96.0
54.2
64.5
57.3
74.3
5.4
6.1
5.9
6.8
5.0
2.9
5.8
4.3
35.4
26.5
31.0
14.6
50.6
61.2
55.6
71.4
Ni/Hb
Hb-At
Ni/Hb-At
a
b
Alkylquinoline: 2- and 4-methylquinoline. Other: ethylquinoline, diemethylquinoline, indole, ethylaniline, N-ethylaniline, coking and etc.
ꢁ1
ꢀ
Reaction condition: catalyst weight ¼ 1.0 g; LHSV (aniline) ¼ 0.13 h , reaction temperature ¼ 470 C; molar ratio of aniline/glycerol ¼ 1/4;
concentration of glycerol ¼ 20 wt%; TOS ¼ 2 h.
9556 | RSC Adv., 2017, 7, 9551–9561
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
Scheme 1 Proposed catalytic mechanistic pathways to form quinoline and by-products on modified-zeolite catalyst (h.r.t ¼ high reaction
temperature; B ¼ Brønsted acid sites; w. B ¼ weak Brønsted acid sites; L ¼ Lewis acid sites; e–k.t ¼ enol–keto tautomersim).
Fig. 5 Effect of the different metal (I) and loading amount of Ni (II) supported on Hb-At. Reaction condition: catalyst weight ¼ 1.0 g; temperature
ꢀ
ꢁ1
¼
470 C; molar ratio of aniline/glycerol ¼ 1/4; LHSV (aniline) ¼ 0.13 h ; concentration of glycerol aqueous solution ¼ 20 wt%.
including temperature (I), liquid hourly space velocity (LHSV) of due that generation of quinoline requires two steps from glyc-
aniline (II), molar ratio of glycerol/aniline (III) and concentra- erol and aniline, as shown by eqn (3) and (4).
tion of glycerol (IV). These reactions have been conducted
ꢁ
2H2O
HOꢁ CH
2
ꢁ CHðOHÞꢁ CH
2
OH ꢀꢀꢀꢀꢀ ꢀꢀ ! CH
2
]CHCH]O
according to a procedure of condition gradual optimization,
which is described as follows: initially, the temperature is varied
to achieve its optimized value while maintaining the others
conditions constant; then, the LHSV, molar ratio of glycerol/
aniline and concentration of glycerol are sequentially opti-
mized by replacing the other conditions with their optimized
values. The above effect of reaction conditions can be inter-
preted as follows:
Cat:
(3)
PhNH þ CH ]CHCH]O ꢀꢀꢀꢀꢀ ꢀꢀ ! C H N ðquinolineÞ (4)
First, the dehydration of glycerol generates intermediate
acrolein; then, acrolein further reacts with aniline to yield
2
2
9
7
Cat:
2
3
(
1) Reaction temperature. On one hand, aniline conversion is quinoline. According to the previous literatures, relative low
ꢀ
ꢀ
ꢀ
ca. 56% at 320 C. With the increase of temperature, aniline reaction temperature at approximately 280 C to 350 C favors
5
9,60
conversion increase rapidly, reaching ca. 81% as its maximum glycerol dehydration to acrolein,
whereas high reaction
ꢀ
ꢀ
ꢀ
at 440 C, and then decreases slightly. On the other hand, temperature about 400 C to 500 C is preferred for the gener-
14,23
quinoline selectivity and yield rst increase with the elevation of ation of quinoline.
Thus, a relatively low reaction tempera-
temperature, achieving ca. 56% and 46%, respectively, as their ture promotes the former step but restricts the latter one. As
ꢀ
maximums at 470 C, and then decreases evidently. This occurs a result, low aniline conversion and quinoline selectivity are
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 9551–9561 | 9557

View Article Online
RSC Advances
Paper
Fig. 6 Effect of temperature (I), LHSV of aniline (II), molar ratio of glycerol/aniline (III) and concentration of glycerol (IV) over the Ni/Hb-At
catalyst. aniline conversion (-C-), quinoline selectivity (-:-) and quinoline yield (---).
obtained at low reaction temperature. However, at excessively either acrolein itself or acrolein with other intermediates suffers
ꢀ
higher reaction temperature (beyond 500 C), the concentration from polymerization to generate the coking substances at high
of acrolein decreases distinctly and then further restrain quin- reaction temperature. On the other hand, other active interme-
oline yield. In conclusion, the reaction temperature profoundly diates besides acrolein also participate in the reaction with
affects quinoline selectivity and yield, and the optimized reac- aniline to generate other heterocyclic aromatic compounds, such
ꢀ
tion temperature is 470 C in this reaction.
as alkylquinolines and alkylindole. Accordingly, the increase in
(2) LHSV of aniline. With the increase of LHSV, quinoline the molar ratio of glycerol/aniline increases the concentration of
yield increases, reaching the highest value at the LHSV ¼ 0.13 generated acrolein, and in turn, that of the quinoline, arriving to
ꢁ
1
h
, and then decreases. The residence time of the reactants on its maximum yield at the molar ratio of glycerol/aniline ¼ 4.
the catalyst decreases with the elevation of LHSV. If the LHSV is Whereas the molar ratio of glycerol/aniline exceeds 4, an exces-
lower, the residence of reactants on surface of catalyst becomes sively high concentration of generated acrolein may lead to
longer, and then the reaction is conducted more completely. a larger extent of the side reactions in acrolein polymerization or/
However, more side reactions also occur because the long and its copolymerization with other active intermediate
staying of intermediate acrolein on the surface of catalyst compounds. Thus, an optimized molar of glycerol/aniline (¼4)
increases the chances of acrolein polymerization to generate was obtained in our reaction.
coking substance, which can block pore channel of catalyst and
(4) Concentration of glycerol. With the increase of glycerol
further restrain the effective diffusion of bulky products from concentration, aniline conversion, quinoline selectivity and yield
catalyst surface. Therefore, although aniline conversion increase evidently, reaching to their largest values at 20 wt%
increases, quinoline selectivity decreases, further reducing glycerol aqueous solution, and then, decreases to varying degree.
quinoline yield. If the LHSV is too higher, the contact time The above results may be due to the increased glycerol concen-
between the reactants and catalyst is shorter, indicating that tration increasing the opportunity for contact between aniline
active sites of catalyst cannot perform more effectively catalytic and generated acrolein. Therefore, the positive reaction accel-
function in this reaction, due to hurried movement of the erates, and quinoline yield increases. However, at excessively
reactants from catalyst surface. Accordingly, the increase of high glycerol concentration (beyond 20%), generated acrolein
LHSV value promotes quinoline yield; however, an excessively themselves can accelerate polymerization; and meanwhile, more
high LHSV value exerts a negative inuence on quinoline yield. side reactions between aniline and other intermediate products
(
3) Molar ratio of glycerol/aniline. With the increase of the occur. Thus, quinoline yield decreases at excessively high
molar ratio of glycerol/aniline from 2 to 4, aniline conversion concentration of glycerol aqueous concentration.
increases from ca. 81% to 96%, arriving to its maximum, and Fig. 7 shows the stability of the Ni/Hb and Ni/Hb-At catalysts
then decrease slightly. Quinoline selectivity and yield exhibit (I) and the regenerability of Ni/Hb-At (II).
a similar tendency relative to aniline conversion. This phenom-
(1) Stability. For Ni/Hb-At, quinoline yield is 71.36% at TOS ¼
enon is due accompanied generation of other intermediate 2 h, and then decreases generally from 64.39% to 48.71% with
compounds (such as, hydroxyacetone, 3-hydroxypropionaldehyde prolonging the reaction time from 3 h to 4 h. The decreasing
and acetaldehyde) during glycerol dehydration. On one hand, trend accelerates rapidly with further increasing reaction time
9558 | RSC Adv., 2017, 7, 9551–9561
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
Fig. 7 The stability of the Ni/Hb and Ni/Hb-At catalysts (I) and regenerability of Ni/Hb-At (II). Reaction condition: catalyst weight ¼ 1.0 g;
ꢀ
ꢁ1
temperature ¼ 470 C; LHSV (aniline) ¼ 0.13 h ; molar ratio of aniline/glycerol ¼ 1/4; concentration of glycerol aqueous solution ¼ 20 wt%.
ꢀ
to 5 h. Finally, 15% yield of quinoline is obtained for the longest loss prior to 300 C is attributed to the desorption of water, and
ꢀ
ꢀ
reaction time of 6 h employed in this work. In contrast, quin- the decrease in weight from 300 C to 800 C is caused by
oline yield over Ni/Hb is 61.22% at TOS ¼ 2 h, and decreases by burning off the coking substances. The rate of weight loss in
increasing reaction time to 3 h. With further prolonging reac- deactivated Ni/Hb-At is lower than that in deactivated Ni/Hb,
tion time from 3 h to 4 h, quinoline yield decreases violently further implying that the former possesses stronger anti-
from 48.81% to 13.98%. Finally, only 6.99% and 5.53% quino- deactivated ability by imposing the transport of bulky prod-
line yields are obtained respectively at TOS ¼ 5 h and 6 h. ucts from internal surface of catalyst and restraining the
Therefore, catalytic activity and the life of Ni/Hb-At are higher deposition of carbon due to the existence of mesopores.
than these of Ni/Hb. The result indicates that Ni/Hb-At
Table 4 shows the result about a comparison of the yield of
possesses stronger ability of anti-deactivation than the Ni/Hb. desired quinoline between in this work and those reported in
13,14,23
The enhanced ability of anti-deactivation benets from the the patents and literatures.
One can see that, among
existence of mesopores on Ni/Hb-At, which imposes the trans- various synthetic routes, the yield of quinoline is the highest;
port of bulky products from internal surface of catalyst and and its route is green and economic in this work, relative to
restraining the deposition of carbon.
other routes utilizing allyl alcohol, acrolein or aldehydes as raw
(2) Regenerability of Ni/Hb-At. Although the serious catalyst materials. Considering the abundant sources, high yield of
deactivation occurs with prolonging reaction time, the catalytic quinoline and desired regeneration of catalyst, this green
activity of the deactivated Ni/Hb-At can recover near to that of synthetic route developed in this work for synthesis of the
ꢀ
the fresh one via calcining at 550 C for 4 h in the presence of desired quinoline, co-employing mesoporous Ni/Hb-At as cata-
air. The result further veries that catalyst deactivation is lyst with simple preparation and low cost, presents the potential
reversible deactivation in this reaction, which is caused by importance of industrial manufacture.
deposition of coking substances rather than devastating the
structure of catalyst.
Fig. 8 displays the thermogravimetric proles over deacti-
vated Ni/Hb and Ni/Hb-At. In the recorded proles, the weight
3
.3. Reaction mechanism
As shown eqn (3) and (4), the generation of quinoline from
aniline and glycerol requires two steps, involving glycerol
dehydrating to acrolein and subsequent condensation of
aniline and acrolein over active sites. Therefore, acrolein
generated from glycerol dehydration is essential intermediate
Table 4 Comparison with different reagents with aniline for vapor-
phase synthesis of the desired quinoline
Reagents
Catalysts
Yield/%
Ref.
b
Allyl alcohol
Acrolein
Al
Al
2
O
O
3
3
/SiO
/SiO
2
1
13
13
b
2
2
15
Acetaldehyde
BEA* zeolite
Al /SiO
16
67
14
13
a
b
2
CH O/MeCHO
2
O
3
2
Glycerol
Glycerol
CuO–ZnO/Al
Ni/HBeta-At
2
O
3
65
71.4
23
In this work
a
b
CH
2
O: formaldehyde; MeCHO: acetaldehyde.
The yield of 8-
methylquinoline referring to the reaction of different reagents with
Fig. 8 TG profiles for the deactivated catalysts. (a) deactivated Ni/Hb; ortho-toluidine.
b) deactivated Ni/Hb-At.
(
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 9551–9561 | 9559

View Article Online
RSC Advances
Paper
during this reaction, and the degree of glycerol to acrolein process consists of dehydration of glycerol to acrolein and
signicantly affects quinoline yield. On one hand, in the former subsequent condensation of acrolein and aniline to quinoline,
step, the strength and type of acid sites on solid acid catalyst which are affected signicantly by the texture and acid proper-
perform a crucial function in formation of intermediate acro- ties of the catalyst. The main points are summarized as follows:
lein. For instance, Brønsted acid sites (especially weak/
Mesopores are successfully generated by alkaline treatment
moderately Brønsted acid sites) were effective active and selec- on Hb zeolite via desilication from the framework of zeolite,
3
7,61–64
tive sites of acrolein,
readily result in acrolein polymerization simultaneously.
Contrarily, Lewis acid sites could catalyze glycerol dehydration species on zeolite eliminates strong Brønsted acid sites and
whereas strong Brønsted acid sites which can facilitate the transport of bulky products (such as
65
quinoline) from internal surface of catalyst. The addition of Ni
61
to produce hydroxyacetone. On the other hand, for the latter produces Lewis acid sites. Both mesopores and type of acid sites
step, the addition of Lewis acid sites can effectively promote the over catalyst play crucial function in catalytic activity for
formation of quinoline on the basis of the catalytic evaluation synthesis of quinoline.
(Table 3), probably due to the synergistic inuence of Lewis acid
The Ni/Hb-At catalyst with mesopores structure, possessing
sites (Ni as the acid center) and Brønsted acid sites to promote abundant weak Brønsted acid sites and appropriate Lewis acid
53,58
the aromatization process.
Besides, it is noted that hydrox- sites, exhibits the highest catalytic activity; and as high as 71.4%
yacetone and 3-hydroxypropanal could be cracked to generate yield of quinoline is achieved under the optimized reaction
66,67
acetaldehyde at high reaction temperature.
conditions. Meanwhile, an enhanced ability of anti-deactivation
Thus, the proposed catalytic mechanistic pathways relating to of the Ni/Hb-At catalyst is displayed, because the existence of
forming quinoline and other valuable heterocycle byproducts mesopores facilitates the transport of bulky products from
from aniline and glycerol are provided in Scheme 1. The internal surface of catalyst and restrains the deposition of the
formation of quinoline is that glycerol rstly dehydrates to coke. Catalyst deactivation is caused mainly by the deposition of
generate acrolein mainly over the weak Brønsted acid sites on coking substances rather than structure damage of the catalyst;
the catalyst, followed by reacting with aniline to yield quinoline and the desired catalytic property is obtained aer 3 reaction–
over the Brønsted and/or Lewis acid sites on the catalyst through regeneration cycles.
Michael addition process, intramolecular aromatization and
23
dehydrogenation reactions (pathway 1). Furthermore, 2- and 4-
methylquinoline derive from the reaction of aniline and acetal-
Acknowledgements
dehyde, whereas their reaction routes are different. As reported This work was supported by the National Natural Science
14
by Brosius et al., 2-methylquoniline is produced from the Foundation of China (Grant 21376068), Program for New
Michael addition of aniline with the a,b-unsaturated aldehyde Century Excellent Talents in University, the Ministry of Educa-
crotonaldehyde (generated from the condensation of acetalde- tion of P. R. China, and the Program for Fu-Rong Scholar in
hyde) and subsequent ring-closing electrophilic aromatic Hunan Province, P. R. China.
substitution (pathway 2). By contrast, 4-methylquinoline origi-
nates from the reaction between aniline and acetaldehyde to
form enamine, which subsequently reacts with another acetal-
References
dehyde to yield product via intramolecular electrophilic
aromatic substitution (pathway 3). Besides, a certain amount of
hydroxyacetone is produced from glycerol dehydration over
1 D. G. Markees, V. C. Dewey and G. W. Kidder, J. Med. Chem.,
1970, 13, 324–326.
2 A. A. Alhaider, M. A. Abdelkader and E. J. Lien, J. Med. Chem.,
1985, 28, 1394–1398.
68
Lewis acid sites on catalyst. According to the report of Cui et al.,
hydroxyacetone was readily transformed to 2-hydroxyl-1-
propanal via enol–keto tautomerism, followed by forming
a Schiff's base via N-alkylation of aniline and subsequent intra-
molecular aromatization to produce 3-methylnidol (pathway 4).
In conclusion, the reaction pathways of the above products are
affected sensitively by strength and type of acid sites of catalyst.
Weak Brønsted acid sites favor the dehydration of glycerol to
acrolein, whereas Lewis acid sites retard the former step (eqn (3))
but accelerate the latter one (eqn (4)) via the synergistic effect
with Brønsted acid sites. Therefore, the mesoporous Ni/Hb-At
catalyst, possessing abundant weak Brønsted acid sites and
appropriate Lewis acid sites, exhibits brilliant catalytic activity on
synthesis of quinoline from aniline and glycerol.
3 M. Isobe, T. Nishikawa, N. Yamamoto, T. Tsukiyama, A. Ino
and T. Okita, J. Heterocycl. Chem., 1992, 29, 619–625.
4 M. Campanati, A. Vaccari and O. Piccolo, Catal. Today, 2000,
60, 289–295.
5 V. V. Kouznetsov, L. Y. V. Mendez and C. M. M. Gomez, Curr.
Org. Chem., 2005, 9, 141–161.
6 Z. H. Skraup, Monatsh. Chem., 1880, 1, 316–318.
7 O. Doebner and W. V. Miller, Bioresour. Technol., 1881, 14,
2812–2817.
8 W. J. Boyle and F. Mares, Organometallics, 1982, 1, 1003–
1006.
9 Y. Tsuji, K. T. Huh and Y. Watanabe, J. Org. Chem., 1987, 52,
1673–1680.
1
0 C. S. Cho, J. S. Kim, B. H. Oh, T. J. Kim, S. C. Shim and
N. S. Yoon, Tetrahedron, 2000, 56, 7747–7750.
1 B. C. Ranu, A. Hajra and U. Jana, Tetrahedron Lett., 2000, 41,
531–533.
4
. Conclusions
1
A green route for vapor-phase synthesis of quinoline from
glycerol and aniline are developed in this work. The reaction 12 H. Yalgin, D. Luart and C. Len, J. Flow Chem., 2016, 6, 80–85.
9560 | RSC Adv., 2017, 7, 9551–9561
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
1
1
1
1
1
1
1
2
3 C. H. Mcateer, R. D. Davies and J. R. Calvin, US Pat., 40 L. Shirazi, E. Jamshidi and M. R. Ghasemi, Cryst. Res.
,700,942, 1997. Technol., 2008, 43, 1300–1306.
4 R. Brosius, D. Gammon, F. Vanlaar, E. Vansteen, B. Sels and 41 F. Goovaerts, E. F. Vansant, P. De Hulsters and J. Gelan,
P. Jacobs, J. Catal., 2006, 239, 362–368. J. Chem. Soc., Faraday Trans., 1989, 85, 3687–3694.
5 S. Kamiguchi, I. Takahashi, H. Kurokawa, H. Miura and 42 M. Maache, A. Janin, J. C. Lavalley, J. F. Joly and E. Benazzi,
T. Chihara, Appl. Catal., A, 2006, 309, 70–75. Zeolites, 1993, 13, 419–426.
6 H. Saggadi, D. Luart, N. Thiebault, I. Polaert, L. Estel and 43 I. Kiricsi, C. Flego, G. Pazzuconi, W. O. Parker Jr, R. Millini,
5
C. Len, Catal. Commun., 2014, 44, 15–18.
7 H. Saggadi, D. Luart, N. Thiebault, I. Polaert, L. Estel and
C. Len, RSC Adv., 2014, 4, 21456–21464.
8 H. Saggadi, I. Polaert, D. Luart, C. Len and L. Estel, Catal.
Today, 2015, 255, 66–74.
9 M. Ayoub and A. Z. Abdullah, Renewable Sustainable Energy
Rev., 2012, 16, 2671–2686.
C. Perego and G. Bellussi, J. Phys. Chem., 1994, 98, 4627–
4634.
44 J. Perez-Pariente, J. A. Martens and P. A. Jacobs, Appl. Catal.,
1987, 31, 35–64.
45 P. A. Jacobs, H. K. Beyer and J. Valyon, Zeolites, 1981, 1, 161–
168.
46 A. Corma, M. T. Navarro, F. Rey, J. Rius and S. Valencia,
Angew. Chem., 2001, 113, 2337–2340.
0 J. Calero, D. Luna, E. D. Sancho, C. Luna, F. M. Bautista,
A. A. Romero, A. Posadillo, J. Berbel and C. Verdugo- 47 C. S. Blackwell, J. Phys. Chem., 1979, 83, 3251–3257.
Escamilla, Renewable Sustainable Energy Rev., 2015, 42, 48 C.-W. Luo, X.-Y. Feng, W. Liu, X.-Y. Lia and Z.-S. Chao,
1
437–1452.
1 T. K. Amin, N. A. S. Amin and H. Hezaveh, Renewable 49 Y. T. Kim, K. D. Jung and E. D. Park, Microporous Mesoporous
Sustainable Energy Rev., 2014, 40, 28–59. Mater., 2010, 131, 28–36.
2 M. Campanati, P. Savini, A. Tagliani, A. Vaccari and 50 P. Tynj ¨a l ¨a and T. T. Pakkanen, J. Mol. Catal. A: Chem., 1996,
O. Piccolo, Catal. Lett., 1997, 47, 247–250. 110, 153–161.
3 B. M. Reddy and I. Ganesh, J. Mol. Catal. A: Chem., 2000, 151, 51 Q. Shu, B. Yang, H. Yuan, S. Qing and G. L. Zhu, Catal.
89–293. Commun., 2007, 8, 2159–2165.
4 B. O. D. Costa, M. A. Peralta and C. A. Querini, Appl. Catal., A, 52 A. Guzman, I. Zuazo, A. Feller, R. Olindo, C. Sievers and
Microporous Mesoporous Mater., 2016, 235, 261–269.
2
2
2
2
2
2
2
2
2
3
2
2
014, 472, 53–63.
J. A. Lercher, Microporous Mesoporous Mater., 2005, 83,
309–318.
53 C. Yin, R. Zhao and C. Liu, Energy Fuels, 2003, 17, 1356–1359.
5 J. Jin, X. Ye, Y. Li, Y. Wang, L. Li, J. Gu, W. Zhao and J. Shi,
Dalton Trans., 2014, 43, 8196–8204.
6 C. Yin, D. Tian, M. Xu, Y. Wei, X. Bao, Y. Chen and F. Wang, 54 Y. Chen, C. H. Xu, C. Q. Liu, X. Li, J. Y. Liu, Y. Cao and
J. Colloid Interface Sci., 2013, 397, 108–113. J. Yang, Heteroat. Chem., 2013, 24, 263–270.
7 F. Tian, Y. Wu, Q. Shen, X. Li, Y. Chen and C. Meng, 55 J. A. Anderson, L. Daza, S. Damyanova, J. L. G. Fierro and
Microporous Mesoporous Mater., 2013, 173, 129–138. M. T. Rodrigo, Appl. Catal., A, 1994, 113, 75–88.
8 Y. Wu, F. Tian, J. Liu, D. Song, C. Jia and Y. Chen, 56 E. Heracleous, A. F. Lee, K. Wilson and A. A. Lemonidou, J.
Microporous Mesoporous Mater., 2012, 162, 168–174. Catal., 2005, 231, 159–171.
9 F. Tian, X. Yang, Y. Shi, C. Jia and Y. Chen, J. Nat. Gas Chem., 57 A. Kant u¨ rk Figen, Int. J. Hydrogen Energy, 2013, 38, 9186–
012, 21, 647–652. 9197.
0 K. Cheng, J. Kang, S. Huang, Z. You, Q. Zhang, J. Ding, 58 G. Liang, L. He, H. Cheng, W. Li, X. Li, C. Zhang, Y. Yu and
2
W. Hua, Y. Lou, W. Deng and Y. Wang, ACS Catal., 2012, 2,
41–449.
1 J. C. Groen, S. Abell ´o , L. A. Villaescusa and J. P ´e rez-Ram ´ı rez,
Microporous Mesoporous Mater., 2008, 114, 93–102.
F. Zhao, J. Catal., 2014, 309, 468–476.
59 Y. T. Kim, K. D. Jung and E. D. Park, Appl. Catal., A, 2011,
393, 275–287.
4
3
3
3
3
3
60 R. Liu, T. F. Wang and Y. Jin, Catal. Today, 2014, 233, 127–132.
2 D. Verboekend, G. Vil ´e and J. P ´e rez-Ram ´ı rez, Cryst. Growth 61 P. Lauriol-Garbey, J. M. M. Millet, S. Loridant, V. Belli `e re-
Des., 2012, 12, 3123–3132. Baca and P. Rey, J. Catal., 2011, 281, 362–370.
3 B. H. Ha, J. Guidot and D. Barthomeuf, J. Chem. Soc., Faraday 62 Y. L. Gu, N. Y. Cui, Q. J. Yu, C. Y. Li and Q. K. Cui, Appl.
Trans., 1979, 75, 1245–1253. Catal., A, 2012, 429–430, 9–16.
4 Y. Hong and J. J. Fripiat, Microporous Mater., 1995, 4, 323– 63 L. G. Possato, R. N. Diniz, T. Garetto, S. H. Pulcinelli,
34. C. V. Santilli and L. Martins, J. Catal., 2013, 300, 102–112.
5 L. Aouali, J. Teanjean, A. Dereigne, P. Tougne and 64 S. R. Ginjupalli, S. Mugawar, P. Rajan N, P. K. Balla and
3
D. Delafosse, Zeolites, 1988, 8, 517–522.
V. R. C. Komandur, Appl. Surf. Sci., 2014, 309, 153–159.
65 X. Zhang, C. W. Luo, C. Huang, B. H. Chen, D. G. Huang,
J. G. Pan and Z. S. Chao, Chem. Eng. J., 2014, 253, 544–553.
66 E. Tsukuda, S. Sato, R. Takahashi and T. Sodesawa, Catal.
Commun., 2007, 8, 1349–1353.
3
3
6 C. W. Luo and Z. S. Chao, RSC Adv., 2015, 5, 54090–54101.
7 C. W. Luo, C. Huang, A. Li, W. J. Yi, X. Y. Feng, Z. J. Xu and
Z. S. Chao, Ind. Eng. Chem. Res., 2016, 55, 893–911.
8 A. Vimont, F. Thibault-Starzyk and J. C. Lavalley, J. Phys.
Chem. B, 2000, 104, 286–291.
3
3
67 L. Cheng and X. P. Ye, Catal. Lett., 2009, 130, 100–107.
9 I. Othman, R. M. Mohamed, I. A. Ibrahim and 68 Y. X. Cui, X. S. Zhou, Q. Sun and L. Shi, J. Mol. Catal. A:
M. M. Mohamed, Appl. Catal., A, 2006, 299, 95–102. Chem., 2013, 378, 238–245.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 9551–9561 | 9561