A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for Efficiently Synthesizing the High Value-Added 3-Methylindole by Aniline and Biomass-Derived Glycerin

Article abstract of DOI:10.1007/s10562-020-03308-7

Abstract: An excellent catalyst with a large number of weak acid centers and highly dispersed copper nanoparticles embedded in mesoporous SBA-15 carrier was successfully constructed for the purpose of efficient conversion of aniline with biomass-derived glycerin to the high value-added 3-methylindole, in which the catalyst of Cu/SBA-15 was modified with Al₂O₃, La₂O₃ and CoO in sequence. The modified carrier and the copper-based catalysts were studied by scanning electron microscopy and energy-dispersive X-ray (SEM–EDX) spectroscopy, nitrogen physical adsorption, ammonia temperature programmed desorption (NH₃-TPD), hydrogen temperature programmed reduction (H₂-TPR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG–DTA) and inductively coupled plasma (ICP) emission spectroscopy. The research found that the Cu/CoO/La₂O₃/Al₂O₃/SBA-15 catalyst exhibited a very good catalytic performance with 3-methylindole yield up to 73.3% and selectivity reaching 86.4%. Besides, only a 3.9% yield decreased after the catalyst was circulated seven times. The characterizations revealed that Al₂O₃ could enhance the polarity of the carrier, thereby the interaction between the active component and the composite carrier was strengthened and the dispersion of copper was increased significantly. Adding La₂O₃ to Cu/SBA-15-Al₂O₃ could weaken the acidity and inhibit the formation of carbon deposits. CoO promoter could increase the number of weak acid centers, which was conducive to a good dispersion of active component and the high selectivity of 3-methylindole. Furthermore, the reaction pathway of gas-phase synthesis of 3-methylindole from glycerin and aniline on Cu/CoO/La₂O₃/Al₂O₃/SBA-15 was explored. Graphic Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-020-03308-7

Catalysis Letters
https://doi.org/10.1007/s10562-020-03308-7
A Highly Dispersed Copper Nanoparticles Catalyst with a Large
Number of Weak Acid Centers for Efciently Synthesizing the High
Value‑Added 3‑Methylindole by Aniline and Biomass‑Derived Glycerin
Pinghui Sun1 · Shuyi Lin1 · Huimei Guo1 · Jianhui Su1 · Lei Shi1
Received: 6 May 2020 / Accepted: 30 June 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
An excellent catalyst with a large number of weak acid centers and highly dispersed copper nanoparticles embedded in
mesoporous SBA-15 carrier was successfully constructed for the purpose of efcient conversion of aniline with biomass-
derived glycerin to the high value-added 3-methylindole, in which the catalyst of Cu/SBA-15 was modifed with Al2O3, La2O3
and CoO in sequence. The modifed carrier and the copper-based catalysts were studied by scanning electron microscopy
and energy-dispersive X-ray (SEM–EDX) spectroscopy, nitrogen physical adsorption, ammonia temperature programmed
desorption (NH3-TPD), hydrogen temperature programmed reduction (H2-TPR), powder X-ray difraction (XRD), transmis-
sion electron microscopy (TEM), thermogravimetric and diferential thermal analysis (TG–DTA) and inductively coupled
plasma (ICP) emission spectroscopy. The research found that the Cu/CoO/La2O3/Al2O3/SBA-15 catalyst exhibited a very
good catalytic performance with 3-methylindole yield up to 73.3% and selectivity reaching 86.4%. Besides, only a 3.9% yield
decreased after the catalyst was circulated seven times. The characterizations revealed that Al2O3 could enhance the polar-
ity of the carrier, thereby the interaction between the active component and the composite carrier was strengthened and the
dispersion of copper was increased signifcantly. Adding La2O3 to Cu/SBA-15-Al2O3 could weaken the acidity and inhibit
the formation of carbon deposits. CoO promoter could increase the number of weak acid centers, which was conducive to a
good dispersion of active component and the high selectivity of 3-methylindole. Furthermore, the reaction pathway of gas-
phase synthesis of 3-methylindole from glycerin and aniline on Cu/CoO/La2O3/Al2O3/SBA-15 was explored.
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-020-03308-7) contains
supplementary material, which is available to authorized users.
* Lei Shi
shilei515dl@126.com
1
College of Chemistry and Chemical Engineering, Liaoning
Normal University, Dalian 116029, Liaoning, China
Vol.:(0123456789)
1 3

P. Sun et al.
Graphic Abstract
Keywords 3-Methylindole · Cu/SBA-15 · Al2O3 · La2O3 · CoO · Biomass-derived glycerin
vasodilator, anti-amine, anti-typhoid, anti-radiation and
anti-cancer drugs, etc. [17, 18]. So important that 3-MI
is, its synthesis methods, therefore, are widely concerned
[19, 20].
1 Introduction
With the continuous development of economy and industrial
production, the shortage of fossil fuels has become more
and more serious. So the efcient use of renewable bio-
mass resources to partially replace fossil fuels has received
widespread attention [1–3]. Biodiesel, as one of the typical
representatives of biofuels and a green energy source, has
the advantages of renewable, degradable and low pollution,
thereby the research about biodiesel production has attracted
most of the attention in recent years [4, 5]. However, the
production of biodiesel would emerge a large amount of by-
product glycerin [6]. How to efectively convert glycerin
to high value-added chemicals is a topic of great concern
to chemical researchers [7–9], which can improve the sus-
tainability and economic viability of biodiesel production.
And by now, a lot of high value-added chemicals have been
gained through various methods such as dehydration [8],
hydrogenolysis [9], etherifcation [10], carboxylation [11],
oxidation [12], transesterifcation [13], steam reforming of
glycerin [6] and, etc. [14].
Considering 3-MI synthesis methods, it can be known
that gas-phase syntheses [21–24] and liquid-phase syn-
theses [25–27] are the most commonly used methods. For
example, Campanati et al. [21] carried out the catalytic
reaction with aniline and 1,2-propanediol as raw materi-
als in a fxed bed at atmospheric pressure over ZrO2/SiO2,
however, 3-MI yield was merely 12%. Our research group
[22] used Ag/SiO2 as a catalyst for the reaction, and the
3-MI yield increased to 35%. Gopal et al. [23] gained a
30% 3-MI yield over CeHZ zeolite catalyst using indole
and methanol (1:6 molar ratio) as raw materials. Simoneau
et al. [25] reported the Fischer cyclization of allylamine
and 1-bromo-2-iodine-benzene catalyzed by Pd2dba3 with
Nao–(tBu) and PhCH3 as solvents, and a 85% yield of tar-
get product was obtained. For the liquid-phase syntheses,
the 3-MI yield is relatively high, but some disadvantages
exist such as complicated reagents, harsh reaction condi-
tions, expensive catalysts and high cost of product sepa-
ration [25–27]. Correspondingly, although the catalytic
efciency is not as good as that of the liquid-phase synthe-
ses, the gas-phase syntheses have the advantages of envi-
ronmental protection of raw materials, simple operation
conditions and easy separation of products, etc. Thereinto,
the gas-phase synthesis by using glycerin and aniline as
raw materials is currently the most promising method and
has attracted much attention because the reaction not only
can convert the biomass-derived glycerin into the high
In our recent research, it was discovered that glycerin
and aniline could be used to synthesize the high value-
added chemical of 3-methylindole (3-MI), in which Cu/
SiO2-Al2O3 was the catalyst and a 40% 3-MI yield was
obtained [15]. 3-MI is a crucial nitrogen-containing het-
erocyclic compound and has a wide range of application
in industry, medicine and agriculture, such as used as a
spices [16] and synthesizing dyes, feed additives, plant
growth agents, pesticides, herbicides, fungicides and anti-
infammatory drugs, stimulants, antihypertensive drugs,
1 3

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for…
value-added chemical of 3-MI, which reduces the produc-
tion cost of 3-MI remarkably, but also could promote the
production of biodiesel [28].
2.2 Preparation of SBA‑15 Carrier
and Copper‑Based Catalysts
According to the in-depth research of our research group,
it has been found that Cu-based catalysts are active in this
reaction. And in order to make the activity and selectivity
of the catalyst as superior as possible, the catalyst carrier
should have a high specifc surface area and a large amount
of weak acid centers [29–31].
SBA-15 carrier was hydrothermally prepared based on
the literature [40, 41] with a minor modifcation. A 4 g of
P123 (EO20PO70EO20) was dispersed in 160 mL (1.5 M)
hydrochloric acid solution. After the solution was stirred
thoroughly by the magnetic stirrer until the surfactant was
wholly dissolved and uniformly dispersed, a 8.5 g TEOS
was added into the above solution, and it was also stirred at
313 K for 24.0 h using a magnetic stirrer. Then the miscible
liquid underwent an additional aging at 353 K for 24.0 h,
and the suspension was fltered, washed. The sample was
calcined in a mufe furnace at 773 K for 6.0 h after air-dried.
Finally, the carrier of SBA-15 was obtained.
The mesoporous SBA-15 is a good alternative as a carrier
of heterogeneous catalyst because of its long-range ordered
channels, high specifc surface area, good hydrothermal sta-
bility and adjustable mesopore size [32–37]. And the unique
hexagonal arrangement makes it be very suitable for sup-
porting nano-scale metals [38, 39]. Therefore, in this paper,
we select SBA-15 as the catalyst carrier to construct an ef-
cient and inexpensive Cu-based catalyst. Considering the
polarity of SBA-15 is very small, the interaction between
SBA-15 and active components is very weak, which would
make copper particles move and aggregate easily on the
surface of the carrier, therefore, in this paper, the promot-
ers of Al2O3, La2O3 and CoO were added to the catalyst of
Cu/SBA-15 in order to improve the dispersion of the active
component and increase the activity and selectivity of the
catalyst. At the same time, SEM–EDX, N2 physical adsorp-
tion, NH3-TPD, H2-TPR, XRD, TEM, TG–DTA and ICP
characterization methods were used to explore the structure
and performance of the catalysts. Furthermore, the synthesis
mechanism of 3-MI by glycerin and aniline on Cu/CoO/
La2O3/Al2O3/SBA-15 was studied profoundly and a reason-
able pathway was proposed.
The catalyst of Cu/SBA-15 was obtained by equal volume
impregnation method. At room temperature, take a certain
amount of SBA-15 and immerse it in a suitable amount of
copper nitrate aqueous solution. After 15.0 h of impregna-
tion, dry it in a water bath of 368 K and next in an oven of
493 K for 4.0 h. Finally, place it in a mufe furnace, where
it was calcined at the temperature of 773 K for 4.0 h. Then
the catalyst precursor was prepared.
The catalyst of Cu/Al2O3/SBA-15 was acquired by
sequential impregnation. The SBA-15 carrier was first
soaked in a certain concentration of aqueous solution of
Al(NO3)3 for 15.0 h. The mixture was then dried and cal-
cined using the above method to obtain the modifed carrier
of Al2O3/SBA-15. Finally, the active component was loaded
on the composite carrier of Al2O3/SBA-15 and the loading
process was the same as the previous step.
The catalysts of Cu/La2O3/Al2O3/SBA-15 and Cu/CoO/
La2O3/Al2O3/SBA-15 were also prepared by the same
method as above and the loading sequence was Al2O3,
La2O3, CoO in order, in which the active component was
last loaded. For every SBA-15 supported copper-based cata-
lyst, the loading of copper was 6.53 wt%. Before the cata-
lytic reaction, the catalyst precursor (1.5 mL) was reduced at
513 K for 2.0 h with a mixture fow of H2 (15 mL min−1)-N2
(15 mL min−1), which was the optimum reduction condition
obtained by optimizing the reduction temperature, reduction
time and reduction gas ratio.
2 Experimental
2.1 Materials
Copper nitrate (Cu(NO3)2·3H2O, ≥ 99.0%), alu-
minium nitrate (Al(NO3)3·9H2O, ≥ 99.0%), lantha-
num nitrate (La(NO3)2·6H2O, ≥ 99.0%), cobalt nitrate
(Co(NO3)3·6H2O, ≥ 99.0%), aniline (C6H5NH2, ≥ 99.5%),
and n-hexanol (C6H13OH, ≥ 95.0%) were obtained from
Tianjin Damao Chemical Reagent Co., Ltd. (China).
Glycerin (C3H8O3, ≥ 99.0%) was obtained from Zhao-
qing Zhaolifang Trading Co., Ltd. Tetraethyl orthosili-
cate (TEOS, (C2H5O)4Si, ≥ 98.0%), hydrochloric acid
(HCl, 36% ~ 38%), acetol (C3H6O2, > 99.0%), 1,2-propan-
ediol (C3H8O2, >99.0%) and 3-MI (C9H9N, >98.0%) were
obtained from Tianjin Kemiou Chemical Reagent Co., Ltd.
(China). Pluronic P123 (Mn=5800, EO20PO70EO20) were
obtained from Beijing Reagent Co., Ltd. (China). The above
chemicals were not purifed before use.
2.3 Evaluation of Catalysts
The active measurement of catalyst was carried out in a
glass reactor of fxed-bed with the inside diameter of 12 mm,
which the reactor was placed vertically inside a tubular fur-
nace and the temperature was monitored by a thermocou-
ple with its tip located at the catalyst bed and connected
to a temperature indicator controller. The reactant solution
with glycerin/aniline molar ratio of 1:3 was pumped and
vaporized by the preheater and then entered the reactor,
1 3

P. Sun et al.
meanwhile a certain fow rate of hydrogen, nitrogen or steam
was also introduced into the reaction system. The liquid
products were hourly collected from the reactor exit. The
space velocity (SV) of the reaction was 1700 h−1, and the
liquid hourly space velocity (LHSV) of aniline and glycerin
was 0.4 h−1.
away in 3.0 h at the same temperature in the helium fow
(35 mL min−1). Finally, the sample was heated to 973 K at a
9.6 K min−1 speed in a 35 mL min−1 He fow and stayed at
973 K for 0.5 h, in which the desorption data for the chem-
isorbed ammonia was collected.
H2-TPR experimental device is the same as the NH3-
TPD instrument. 100 mg catalyst precursor was flled and
heated to 573 K in N2 (30 mL min−1) fow and purged at the
temperature for 1.0 h to remove surface moisture and impuri-
ties, then the temperature was lowered to 313 K. Finally the
reduction was carried out in a mixed gas (30 mL min−1) of
H2-Ar (VH2/VAr of 1/9) from 313 to 873 K and maintained
the fnal temperature for 0.5 h, in which the data of hydrogen
consumption were collected.
2.4 Analysis of Products
In this paper, the products for the reaction of glycerin and
aniline were qualitatively detected by using a QP2010
GC–MS instrument (Shimadzu Corporation, Japan) with
DB-5MS column, in which the temperature was changed
from 373 to 533 K at a 15 K min−1 heating rate. The qualita-
tive analysis of 3-MI was proceeded on a 500 superconduct-
ing NMR spectrometer of Bruker and the result was shown
in Fig. S1.
The crystal structures of SBA-15 carrier and its supported
copper-based catalysts were detected on the Rigaku Smart-
lab 9 instrument using Cu-Kα radiation. The scan rate was
5° min−1. A 200 mA tube current and a 45 kV tube voltage
were used.
The reaction products were quantitatively determined
by gas chromatography with HP-5 capillary column and
N-hexanol was the internal standard. The glycerin conver-
sion, 3-MI yield or selectivity was calculated as follows.
Glycerin conversion:
Use a JEM-2000EX microscope to obtain the TEM
images of the catalysts, where the sample was ground down
and put into ethanol solvent to uniformly be dispersed by
ultrasonic treatment. The solution was then coated on a
porous carbon copper mesh, and the transmission image of
the sample was measured at 50 kV acceleration voltage.
The carbon deposits analyses for the used catalysts were
carried out on a 6300 Diamond TG–DTA thermogravimetric
instrument of PerkinElmer. A 7 mg sample was taken and
purged at 573 K in a N2 fow (20 mL min−1), then it was
dropped to 333 K. In the end, the sample was heated in
an air fow of 20 mL min−1 from 333 to 1073 K at a 10 K
min−1 rate.
nglycerin(initial) − nglycerin(final)
Conv.(%) =
× 100%
nglycerin(initial)
3-MI yield:
n3 − MI
Yield(%) =
× 100%
nglycerin(initial)
3-MI selectivity:
Yield
Sel.(%) =
× 100%
The amounts of Cu component of the fresh or used SBA-
15 supported Cu-based catalysts were tested by a Perkin
Elmer Optima 2100DV inductively coupled plasma (ICP)
emission spectroscopy, in which the RF power was 1300 W
and a nebulizer (sample) argon fow was 0.80 L/min.
Conv.
2.5 Characterization of Catalysts
The compositions and each element content of Cu/CoO/
La2O3/Al2O3/SBA-15 were examined using field-emis-
sion scanning electron microscopy of Germany Carl zeiss
Supra55 with energy-dispersive X-ray spectroscopy (EDS)
of UK Oxford X-MaxN. The acceleration voltage was 15 kV.
The N2 adsorption–desorption measurements of SBA-15
or its loaded Cu-based catalysts were accomplished using
a physical adsorption instrument of Micromeritics ASAP
2010, where the sample was evacuated under 10–5 mmHg
to purify at 573 K for 3.0 h.
2.6 Catalyst Regeneration
The deactivated catalyst sample of Cu/CoO/La2O3/Al2O3/
SBA-15 was regenerated at 773 K for 4.0 h in the mixed gas
fow with oxygen (3 mL min−1) and nitrogen (57 mL min−1)
after it was slowly heated to 773 K at 1 K min−1. Then the
cyclic activity test was conducted for the obtained sample.
3 Results and Discussion
The NH3-TPD measurement was proceeded in a
6 mm × 350 mm quartz tubular reactor. Under He (35 mL
min−1) gas fow, 150 mg catalyst to be tested was heated
from 293 to 773 K at a 9.6 K min−1 ramp rate, and impurities
were removed. Then, the sample was absorbed by NH3 at
373 K for 1.0 h, and the physically adsorbed NH3 was blown
3.1 Catalytic Performance
As is known to all, Cu-based catalysts are benefcial to the
gas-phase synthesis of 3-MI by glycerin and aniline [15,
1 3

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for…
30, 31]. In addition, SBA-15 exhibits excellent performance
as a catalyst carrier [32, 33, 42]. Hence, we use SBA-15
supported Cu as the catalyst for this reaction, and added
an appropriate amount of Al2O3, La2O3 and CoO promot-
ers to make the catalyst performance more superior. For
the reaction, except the target product of 3-MI, many by-
products were also detected. Among them, N-methylani-
line (N-MA), N-ethylaniline (N-EA), N-isopropylaniline
(N-IPA), 2,5-dimethyl-1-phenyl-pyrrole (2,5-DMPP) and
2,3-dimethylindole (2,3-DMI) were the major by-prod-
ucts. In addition, there were other by-products with minor
amounts such as ethylic acid, N-propylaniline, propylene
glycol, indole, 3-ketoneindole, N-isopropylindole and N,N′-
dimethyl-N,N′-diphenyl-1,2-ethanediamine, etc. The activity
and selectivity for the catalysts of Al2O3, La2O3 and CoO
modifed Cu/SBA-15 were shown in Tables 1, 2 and 3.
First at all, glycerin conversion, the selectivity for 3-MI
and the by-products changed greatly when Al2O3 promoter
was added to Cu/SBA-15 (seen in Table 1). The glycerin
conversion was proportional to the content of Al2O3 added.
The selectivity of 3-MI presented an earlier increase and
later decreased trend with the increase of Al2O3 content.
For the generated by-products, the selectivity of N-MA, 2,5-
DMPP or 2,3-DMI increased with the increase of Al2O3 con-
tent, while N-EA or N-IPA selectivity decreased. When the
content of Al2O3 was 11.03 wt%, 3-MI selectivity reached
the better. From Table 2 it can be known that as the con-
tent of La2O3 increased, glycerin conversion decreased little
by little, and the target product selectivity also exhibited a
trend of going up frst and then declining. The selectivity
change trend of the major by-products was opposite to that
in Table 1. In Table 3, glycerin conversion, the selectivity
Table 1 Efect of Al2O3 content
Al2O3 con- Glycerin con- Product selectivity (%)
on the activity and selectivity of
Cu/Al2O3/SBA-15 catalyst
tent (wt%)
version (%)
3-MI
N-MA
N-EA
N-IPA
2,5-DMPP
2,3-DMI
Others
0.00
7.90
9.49
11.03
12.51
13.95
42.8
80.2
84.4
86.9
89.3
91.4
27.6
42.8
43.9
45.2
40.4
36.1
6.8
7.4
8.0
8.6
9.2
9.9
8.4
7.6
6.9
6.3
5.8
5.3
9.8
9.0
8.2
7.5
6.9
6.3
3.8
4.5
5.2
5.9
6.7
7.5
0.6
1.7
2.8
3.9
5.1
6.3
43.0
27.0
25.0
22.6
25.9
28.6
Reaction conditions: 513 K, H2 =15 mL min−1, N2 =25 mL min−1. The third hour results
Table 2 Efect of La2O3 content
on the activity and selectivity
of Cu/La2O3/Al2O3/SBA-15
catalyst
La2O3 con- Glycerin con- Product selectivity (%)
tent (wt%)
version (%)
3-MI
N-MA
N-EA
N-IPA
2,5-DMPP
2,3-DMI
Others
0.00
0.54
0.81
1.07
1.34
1.60
86.9
85.4
83.9
82.6
80.3
77.2
45.2
51.4
56.2
63.1
59.7
57.5
8.6
6.9
5.1
3.8
3.3
3.0
6.3
6.4
6.6
6.8
7.4
7.9
7.5
7.6
7.8
8.0
8.5
9.0
5.9
4.7
3.3
2.3
1.8
1.5
3.9
3.1
2.2
1.5
1.2
0.8
22.6
19.9
17.8
14.5
18.1
20.3
Reaction conditions: 513 K, H2 =15 mL min−1, N2 =25 mL min−1. Al2O3 content of 11.03 wt%. The third
hour results
Table 3 Efect of CoO content
on the activity and selectivity of
Cu/CoO/La2O3/Al2O3/SBA-15
catalyst
CoO con-
Glycerin con- Product selectivity (%)
tent (wt%) version (%)
3-MI
N-MA
N-EA
N-IPA
2,5-DMPP
2,3-DMI
Others
0.00
0.18
0.25
0.31
0.37
82.6
84.8
86.9
88.4
90.1
63.1
65.8
69.2
65.4
59.3
3.8
4.0
4.2
4.7
6.4
6.8
5.6
4.0
3.7
3.4
8.0
6.6
4.9
4.0
3.8
2.3
2.9
3.6
4.9
6.8
1.5
2.2
2.8
4.1
6.2
14.5
12.9
11.3
13.2
14.1
Reaction conditions: 513 K, H2 =15 mL min−1, N2 =25 mL min−1. Al2O3 content of 11.03 wt%, La2O3
content of 1.07 wt%. The fourth hour results
1 3

P. Sun et al.
for 3-MI and the major by-products showed the same change
trend as that in Table 1 with the increase of CoO content.
The optimal contents for La2O3 and CoO were 1.07 wt% and
0.25 wt%, respectively. And at this time, the activity and
selectivity of Cu/CoO/La2O3/Al2O3/SBA-15 catalyst were
optimal, which 3-MI yield reached 60.1%.
3.2 Characterization of Catalysts
3.2.1 SEM–EDX
Figure 2 presents the SEM images of Cu/CoO/La2O3/Al2O3/
SBA-15 with the optimal content of Al2O3, La2O3 or CoO
promoter, the content of each element and Si, O, Al, Cu,
La and Co element mappings. It can be seen that the dis-
tribution of each element was relatively uniform. And as
expected, the elements of silicon and oxygen were the most
abundant, followed by the elements of aluminium, copper
and lanthanum. The amount of cobalt element was least
because Co content was only 0.25 wt%.
Figure 1 shows the glycerin conversion (A) and 3-MI
yield (B) versus time on stream over Cu/SBA-15 and the
catalyst modifed with Al2O3, La2O3 and CoO promoter
(Al2O3 content: 11.03 wt%, La2O3 content: 1.07 wt%, CoO
content: 0.25 wt%). Over Cu/SBA-15, the conversion of
glycerin was low and as the reaction proceeded, it decreased
guadually. After adding the promoter of Al2O3, La2O3 and
CoO to Cu/SBA-15 in order, glycerin conversion increased
as a whole and it showed a slight downward trend versus
time on stream, but the falling range became smaller.
The 3-MI yield versus time on stream over Cu/SBA-15
and the catalyst modifed with Al2O3 or La2O3 gave the same
change trend, which the yield of target product showed an
upward trend within 1 to 3 h of reaction, and then began
to decline. Adding Al2O3 and La2O3 promoters increased
the yield of 3-MI greatly. After adding CoO to Cu/La2O3/
Al2O3/SBA-15, 3-MI yield increased further and the highest
yield of 60.1% was obtained at the fourth hour. It can clearly
be seen that the deactivation of Cu/La2O3/Al2O3/SBA-15
modifed with CoO was efectively suppressed, revealing the
stability of the catalyst was greatly improved.
3.2.2 N2 Physical Adsorption
The N2 adsorption–desorption isothermals and the pore
size distribution curves of SBA-15 and four copper-based
catalysts with the optimal content of Al2O3, La2O3 or CoO
promoter were shown in Fig. 3. It can be found from Fig. 3a
that all the fve samples have the same typical IV isotherm,
which was the representative feature of mesoporous mate-
rial [43, 44]. In the relative pressure of 0.4–0.7, the four
Cu-based catalysts had the H-1 hysteresis ring as well as
SBA-15 did, suggesting that the feature pore channels of the
SBA-15 carriers of the Cu-based catalysts were not dam-
aged after loaded the active component and promoters. The
hysteresis loops were deformed and migrated downward
slightly, indicating that their mesoporous sizes and ranges
had changed [45].
From Fig. 3b, two kinds of pore size distribution can
be seen on SBA-15, one was micropore at 1.9 nm, the
other was mesopore at 2.2 nm. When the active component
1 h
1 h
A
B
60
2 h
3 h
2 h
80
3 h
50
40
30
20
10
0
4 h
5 h
6 h
4 h
5 h
6 h
60
40
20
0
c
a
b
d
b
a
c
d
Catalyst
Catalyst
Fig. 1 The glycerin conversion (A) and 3-MI yield (B) versus time on stream over the catalysts of Cu/SBA-15 (a), Cu/Al2O3/SBA-15 (b), Cu/
La2O3/Al2O3/SBA-15 (c) and Cu/CoO/La2O3/Al2O3/SBA-15(d)
1 3

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for…
Fig. 2 SEM images (a), content
of each element (b), elemental
mappings of Si (c), O (d), Al
(e), Cu (f), La (g) and Co (h) on
Cu/CoO/La2O3/Al2O3/SBA-15
with Al2O3 content of 11.03
wt%, La2O3 content of 1.07 wt%
and CoO content of 0.25 wt%
Cu was loaded on SBA-15, the amount of the mesopore
increased, while the number of the micropore decreased.
With the sequential addition of Al2O3, La2O3 and CoO
promoters, the number of the micropore remarkably went
down and the amount of the mesopore obviously aug-
mented. This may be because a part of aluminum in the
SBA-15 skeleton reacted with aluminum nitrate or cobalt
nitrate with certain acidity, while a part of silicon in the
SBA-15 skeleton reacted with lanthanum nitrate with
1 3

P. Sun et al.
400
350
300
250
200
150
100
50
6
5
4
3
2
1
0
A
B
Cu/CoO/La2O3/SBA-15-Al2O3
Cu/La2O3/SBA-15-Al2O3
Cu/SBA-15-Al2O3
Cu/SBA-15
SBA-15
SBA-15
Cu/SBA-15
Cu/SBA-15-Al O
2
3
Cu/La O /SBA-15-Al O
2
0
3
2 3
Cu/CoO/La O /SBA-15-Al O
2
3
2
3
-50
0.0
0.2
0.4
0.6
0.8
)
1.0
2
4
6
8
10
Relative Pressure
(
P/P
Pore diameter (nm)
o
Fig. 3 N2 adsorption–desorption isotherms (a) and the pore size
distribution curves (b) of the samples of SBA-15, Cu/SBA-15, Cu/
Al2O3/SBA-15, Cu/La2O3/Al2O3/SBA-15 and Cu/CoO/La2O3/Al2O3/
SBA-15 with Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt%
and CoO content of 0.25 wt%
certain basicity after immersing SBA-15 in the solution
of aluminum nitrate, cobalt nitrate or lanthanum nitrate
for a period of time (15 h), which resulted in the increase
of pore size [46].
d
c
3.2.3 NH3‑TPD
The presence of acid centers is good for the adsorption of
reactants of aniline and glycerin on the catalyst, but too
strong acidity is not conducive to the desorption of 3-MI,
which would cause a decrease in the yield and selectivity of
3-MI [30]. What’s more, for the reaction of carbon-contain-
ing compounds, the strong acid centers will cause the forma-
tion of a large amount of carbon deposits, while the carbon
deposits produced by weak acid centers are less. Therefore,
this reaction requires a large number of weak acid centers.
Figure 4 displays the NH3-TPD profles of Cu/SBA-15 and
the modifed catalysts with the optimal content of Al2O3,
La2O3 and CoO. On Cu/SBA-15, only a broad desorption
peak corresponding to medium-strong acid existed, no weak
acid center appeared. After the promoter of Al2O3 was added
into Cu/SBA-15, two large desorption peaks pertained to
weak acid centers appeared, which was very benefcial to the
high selectivity of target product [15, 31]. With the addition
of La2O3, the acidity of the catalyst weakened and the num-
ber of weak acid centers declined, which could cut down the
formation of carbon deposits. It’s gratifying that the addition
of CoO could also greatly increase the number of weak acid
centers, which was benefcial to the further improvement for
the selectivity of the target product.
b
a
400
500
600
700
800
900
Temperature
ꢀ ꢁ
K
Fig. 4 NH3-TPD profles of Cu/SBA-15 (a), Cu/Al2O3/SBA-15 (b),
Cu/La2O3/Al2O3/SBA-15 (c) Cu/CoO/La2O3/Al2O3/SBA-15 (d) with
Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt% and CoO
content of 0.25 wt%
3.2.4 H2‑TPR
The mutual efect between active component and carrier is
one of many factors that afect the catalyst performance and
H2-TPR profle of the catalyst is a good proof to reveal the
interaction. Figure 5 shows H2-TPR profles of CuO/SBA-
15, CuO/Al2O3/SBA-15, CuO/La2O3/Al2O3/SBA-15, CuO/
CoO/La2O3/Al2O3/SBA-15 and the composite carriers with-
out CuO (Al2O3 content: 11.03 wt%, La2O3 content: 1.07
wt%, CoO content: 0.25 wt%). There was no reduction peak
1 3

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for…
Cu(111)
Cu(200)
Cu(222)
a
b
c
g
f
d
e
a'
b'
c'
d
c
b
a
d'
450
480
510
540
570
600
630
660
30
40
50
60
70
80
Temperature (K)
Fig. 5 H2-TPR profles of Al2O3/SBA-15 (a), La2O3/Al2O3/SBA-15
(b), CoO/Al2O3/SBA-15 (c), CuO/SBA-15 (d), CuO/Al2O3/SBA-15
(e), CuO/La2O3/Al2O3/SBA-15 (f), CuO/CoO/La2O3/Al2O3/SBA-15
(g) with Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt% and
CoO content of 0.25 wt%
Fig. 6 XRD patterns of the fresh or used Cu/SBA-15 (a, a′), Cu/
Al2O3/SBA-15 (b, b′), Cu/La2O3/Al2O3/SBA-15 (c,c′′) Cu/CoO/
La2O3/Al2O3/SBA-15 (d, d′) with Al2O3 content of 11.03 wt%, La2O3
content of 1.07 wt% and CoO content of 0.25 wt%
on the curve of a, b or c, only a reduction peak appeared
on the curve of d, e, f or g, indicating that the reduction
peak belonged to the reduction of CuO. CuO reduction
peak shifted to the direction of high temperature after add-
ing Al2O3, revealing that CuO was difcult to be reduced.
This indicated that the promoter of Al2O3 could enhance the
interaction force between CuO and the composite carrier.
Adding the promoter of La2O3, however, brought about the
reduction peak to shift to a low temperature, illustrating that
the addition of La2O3 made CuO acquire electrons more
easily and be reduced with easy. When CoO was added into
CuO/La2O3/Al2O3/SBA-15, the reduction temperature of
CuO increased from 509 to 517 K, meaning that the inter-
action between the carrier and CuO enhanced again. The
above reduction phenomenon can be explained by the result
of NH3-TPD. Since the acidity of the catalyst raised after
adding the promoter of Al2O3 or CoO, that is, the polarity of
the catalyst molecule increased, which made the interaction
force between CuO and the composite carrier enhanced, so
CuO was difcult to be reduced. On the contrary, the acidity
of the catalyst weakened after adding the promoter of La2O3,
that is, the polarity of the catalyst molecule decreased, which
brought about the force between CuO and the composite
support weakened, therefore CuO was reduced easily.
that three typical difraction peaks appeared at 2θ of 43.3,
50.5 and 74.5° on Cu/SBA-15 catalyst, pertained to the char-
acteristic difraction refection of (111), (200) and (220) of
copper crystal [47]. When Al2O3 promoter was added, the
difraction peaks of copper crystal had completely disap-
peared. This was due to the fact discussed in NH3-TPD
and H2-TPR that the addition of promoter Al2O3 enhanced
the force of copper and composite carrier, which hindered
the aggregation of copper particles and made them be
dispersed on the carrier. After adding La2O3 promoter to
Cu/Al2O3/SBA-15, the intensity of the difraction peak of
copper increased a little, which can be explained from the
fact that the interaction between Cu and the composite car-
rier reduced a bit as the addition of La2O3, so Cu particles
aggregated slightly. The addition of CoO made the difrac-
tion peak of Cu disappear again, illustrated the Cu particles
were highly dispersed once more. The reason was naturally
related to the increase of the force between Cu and the com-
posite carrier.
Comparing the XRD patterns of fresh Cu-based catalysts,
the intensity of the difraction peaks of Cu crystal obviously
enhanced on every used catalyst, which was attributed to
the Cu sintering during the reaction. And on Cu/SBA-15,
the sintering of Cu particles was most severe. Adding the
promoter Al2O3 or CoO could signifcantly inhibit the sin-
tering of Cu particles, while La2O3 promoter could not play
the role. It was still due to the increase and decrease of the
force of copper with the carrier after the addition of the three
promoters.
3.2.5 XRD
In order to further explore the efect of Al2O3, La2O3 and
CoO on the Cu dispersity, we performed the XRD measure-
ment of the catalysts and Fig. 6 shows the patterns of the
fresh and used copper-based catalysts. It can be observed
1 3

P. Sun et al.
Fig. 7 TEM images of the fresh and used Cu/SBA-15 (a, a′), Cu/Al2O3/SBA-15 (b, b′), Cu/La2O3/Al2O3/SBA-15 (c, c′) and Cu/CoO/La2O3/
Al2O3/SBA-15 (d, d′) with Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt% and CoO content of 0.25 wt%
3.2.6 TEM
manifesting that the sintering of Cu particles was efectively
inhibited. Among them, Al2O3 and CoO played a very good
role in improving the dispersion of Cu particles and inhibit-
ing their sintering, which was also identifed with the results
of XRD. It’s interesting, it can be seen in images b′, c′ and
d′, a considerable part of the Cu particles were restricted in
the SBA-15 strip-shaped channels, where they presented a
channel streamline shape. So, it can be concluded that the
composite SBA-15 carrier could limit the aggregation and
sintering of active component to a certain extent.
For the sake of knowing the Cu particles size and the chan-
nel of SBA-15 carrier after loaded copper and three pro-
moters on SBA-15 before and after the reaction, the TEM
measurement (Fig. 7) of the fresh and the used Cu-based
catalysts were proceeded (Al2O3 content: 11.03 wt%, La2O3
content: 1.07 wt%, CoO content: 0.25 wt%). The long-range
uniform ordered strip channels can be observed after SBA-
15 was loaded the active component Cu and three promot-
ers. The Cu particles average diameter was 18.4 nm on the
fresh Cu/SBA-15. The addition of Al2O3 reduced the average
diameter of Cu particles to 4.8 nm, indicating that the pro-
moter of Al2O3 improved the dispersion of Cu particles obvi-
ously. After adding La2O3 promoter to Cu/Al2O3/SBA-15,
however, the average diameter of Cu particles augmented to
8.3 nm. After CoO promoter was doped to Cu/La2O3/Al2O3/
SBA-15, the average diameter of Cu particles declined to
5.4 nm. The change of the average diameter of Cu particles
is consistent with the aggregation of copper particles shown
in XRD patterns.
3.2.7 TG–DTA
For the reaction with carbon compounds as raw materials,
the acid centers will cause the formation of carbon deposits,
which would reduce the catalyst activity until it is deac-
tivated [48]. From the weight loss of the used Cu-based
catalysts in Fig. 8, we can know the carbon deposits of the
catalysts happened during the reaction. There was an obvi-
ous mass loss on Cu/SBA-15. After adding the promoter
of Al2O3, the weight loss enhanced distinctly, revealed that
Al2O3 facilitated the formation of carbon deposits. After
adding La2O3 promoter to Cu/Al2O3/SBA-15, the weight
loss decreased signifcantly. And the addition of CoO, how-
ever, increased the weightlessness again, indicating that CoO
could not inhibit the formation of carbon deposits. The phe-
nomenon was related to the acidity of catalyst. When Al2O3
From the image a′ it can be known that the average diam-
eter of Cu particles on the used Cu/SBA-15 catalyst aggre-
gated to 30.7 nm, illustrating that Cu particles were severely
sintered. With the sequential addition of Al2O3, La2O3 and
CoO promoters, the average diameters of Cu particles on
the used catalysts were 9.2, 13.1 and 10.0 nm, respectively,
1 3

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for…
Table 4 Copper amount of the fresh or used SBA-15 supported Cu-
based catalysts
Catalyst
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
Copper amount (wt%)
Fresh
Used
catalyst
catalyst
Cu/SBA-15
Cu/Al2O3/SBA-15
Cu/La2O3/Al2O3/SBA-15
Cu/CoO/La2O3/Al2O3/SBA-15
6.47
6.45
6.51
6.48
5.89
6.27
6.22
6.26
Used Cu/SBA-15
Used Cu/Al2O3/SBA-15
Used Cu/La2O3/Al2O3/SBA-15
Used Cu/CoO/La2O3/Al2O3/SBA-15
which was difcult to be oxidized was more. After adding
La2O3 to the catalyst of Cu/Al2O3/SBA-15, both exothermic
peaks moved towards the lower temperature, meaning that
the carbon deposition type of the catalyst changed from the
coke which was difcult to be oxidized at a higher tempera-
ture to the coke which was easy to be oxidized at a lower
temperature. When CoO was added to Cu/La2O3/Al2O3/
SBA-15, the exothermic peaks shifted to the high tempera-
ture again, demonstrating that the generated coke was more
regular and more difcult to be oxidized.
300
450
600
750
900
1050
Temperature (K)
Fig. 8 TG results of the used catalysts of Cu/SBA-15, Cu/Al2O3/
SBA-15, Cu/La2O3/Al2O3/SBA-15 and Cu/CoO/La2O3/Al2O3/SBA-
15 with Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt% and
CoO content of 0.25 wt%
a
3.2.8 ICP
b
Table 4 shows the copper amounts of the fresh or used SBA-
15 supported copper-based catalysts (Al2O3 content: 11.03
wt%, La2O3 content: 1.07 wt%, CoO content: 0.25 wt%).
0.58, 0.18, 0.29 and 0.22 wt% loss of copper component
were tested by ICP on Cu/SBA-15, Cu/Al2O3/SBA-15, Cu/
La2O3/Al2O3/SBA-15 and Cu/CoO/La2O3/Al2O3/SBA-
15 after 6 h of reaction. Obviously, the result was closely
related to the efect of Al2O3, La2O3 or CoO promoter and
it was in good agreement with the above discussion result.
c
d
450
600
750
900
1050
Temperature
(K)
3.3 Optimization of Reaction Conditions
Fig. 9 DTA profles of the used catalysts of Cu/SBA-15 (a), Cu/
Al2O3/SBA-15 (b), Cu/La2O3/Al2O3/SBA-15 (c) and Cu/CoO/La2O3/
Al2O3/SBA-15 (d) with Al2O3 content of 11.03 wt%, La2O3 content
of 1.07 wt% and CoO content of 0.25 wt%
The reaction conditions such as reaction temperature,
hydrogen fow rate and steam fow rate were optimized
over Cu/CoO/La2O3/Al2O3/SBA-15 (Al2O3 content: 11.03
wt%, La2O3 content: 1.07 wt%, CoO content: 0.25 wt%).
From the data in Table 5, as the reaction temperature grad-
ually augmented, the conversion of glycerin increased, the
selectivity of 3-MI presented the trend of increasing frst
and decreasing. Among the by-products, N-MA, N-EA and
N-IPA showed a downward trend, while 2,5-DMPP and
2,3-DMI exhibited an upward trend. When the reaction
temperature was 523 K, the selectivity of target product
achieved 71.9%. In Table 6, with the increase of hydrogen
fow rate, the variation trend of glycerin conversion and
3-MI selectivity was the same as that in Table 5, while
the selectivity change trend of the major by-products was
opposite. When the fow rate of hydrogen was 10 mL
or CoO was added, the acidity of the catalyst increased, so
more carbon deposits were formed. On the contrary, when
La2O3 was added, the acidity of the catalyst was weakened,
therefore the amount of the carbon deposition was less.
Figure 9 is DTA profles of the Cu-based catalysts after
6 h of reaction. Obviously, after adding the promoter of
Al2O3 to Cu/SBA-15, the type of carbon deposit of the
catalyst changed. Although the exothermic peak at 647 K
still existed, a new exothermic peak at 773 K appeared, and
the area of this exothermic peak was much larger than that
at 647 K, indicating that the amount of the carbon deposit
1 3

P. Sun et al.
Table 5 Efect of reaction
temperature on the activity and
selectivity of Cu/CoO/La2O3/
Al2O3/SBA-15
Reaction tem- Glycerin con- Product selectivity (%)
perature (K)
version (%)
3-MI
N-MA
N-EA
N-IPA
2,5-DMPP
2,3-DMI
Others
503
513
523
533
82.4
86.9
88.6
91.2
67.1
69.2
71.9
67.4
4.5
4.2
3.5
2.9
4.8
4.0
3.0
2.1
6.0
4.9
3.5
2.4
3.4
3.6
4.6
5.8
1.5
2.8
3.8
6.2
12.7
11.3
9.7
13.2
Reaction conditions: H2 =15 mL min−1, N2 =25 mL min−1. Al2O3 content of 11.03 wt%, La2O3 content of
1.07 wt% and CoO content of 0.25 wt%. The fourth hour results
Table 6 Efect of H2 fow rate
in reaction mixed gases on the
activity and selectivity of Cu/
CoO/La2O3/SBA-15-Al2O3
catalyst
V (H2)
Glycerin con- Product selectivity (%)
version (%)
(mL min−1
)
3-MI
N-MA
N-EA
N-IPA
2,5-DMPP
2,3-DMI
Others
5
86.1
87.9
88.6
91.2
73.3
77.1
71.9
67.4
2.6
3.1
3.5
3.8
2.4
2.7
3.0
3.4
2.4
3.0
3.5
3.9
5.5
5.0
4.6
4.3
3.2
3.5
3.8
4.2
10.6
5.6
9.7
10
15
20
13.0
Reaction conditions: 523 K, Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt% and CoO content of
0.25 wt%. The fourth hour results
Table 7 Efect of steam fow
rate in reaction mixed gases on
the activity and selectivity of
Cu/CoO/La2O3/Al2O3/SBA-15
catalyst
Vsteam
Glycerin con- Product selectivity (%)
version (%)
(mL min−1
)
3-MI
N-MA
N-EA
N-IPA
2,5-DMPP
2,3-DMI
Others
0
8
10
12
87.9
86.2
84.8
83.6
77.1
83.3
86.4
83.4
3.1
2.8
2.5
2.2
2.7
2.3
1.9
1.6
3.0
2.3
1.8
1.5
5.0
4.1
3.2
2.6
3.5
3.0
2.6
2.2
5.6
2.2
1.6
6.5
Reaction conditions: 523 K, H2 =10 mL min−1, Al2O3 content of 11.03 wt%, La2O3 content of 1.07 wt%
and CoO content of 0.25 wt%. The fourth hour results
min−1, 3-MI selectivity reached 77.1%. Since an appro-
priate amount of steam is benefcial to removing carbon
deposits generated during the reaction and improving
the target product selectivity, the infuence of the steam
fow rate was explored. In Table 7, when the steam fow
rate was 10 mL min−1, 3-MI selectivity reached the top
of 86.4% with the yield up to 73.3%. The excess steam
resulted in a reduction for the target product selectivity
because the chemical reaction equilibrium would shift to
the direction of the reactants.
100
80
60
40
20
0
Conv.
Yield
Sel.
3.4 Reusability of Cu/CoO/La2O3/Al2O3/SBA‑15
Catalyst
The reusability of Cu/CoO/La2O3/Al2O3/SBA-15 (Al2O3
content: 11.03 wt%, La2O3 content: 1.07 wt%, CoO con-
tent: 0.25 wt%) was tested. The catalyst underwent the
regeneration after each run, and was reduced in situ
again prior to activity test. Figure 10 shows the seven
1
2
3
4
5
6
7
Used times
Fig. 10 Resuability study of Cu/CoO/La2O3/Al2O3/SBA-15 catalyst
1 3

A Highly Dispersed Copper Nanoparticles Catalyst with a Large Number of Weak Acid Centers for…
Scheme 1 Reaction pathway for
+
the gas–solid synthesis of 3-MI
NH2
fast
by glycerin and aniline on Cu/
OH
CoO/La2O3/Al2O3/SBA-15
O
- 2H2O
O
H 2
-
Acetol
OH
HO
OH
N
H
+
OH
-
Glycerin
H
2O
NH2
3-MI
,
OH
+
H
2
- 2H2O , - H2
slow
1,2-PDO
repeatability data about the fourth hour results of the reac-
tion under the optimum reaction conditions over Cu/CoO/
La2O3/Al2O3/SBA-15 catalyst. Only a 3.9% of 3-MI yield
decreased when the catalyst was circulated seven times,
indicating that it had a good practicality.
product of 3-MI. Because the main product for the hydrog-
enolysis of glycerin was acetol and no acetol was tested in
the reaction of glycerin with aniline, it can be deduced that
the reaction of acetol with aniline was fast, while the conver-
sion reaction of 1,2-PDO with aniline was slow.
3.5 Reaction Pathway Research
4 Conclusion
To gain a clear idea of the reaction mechanism is what chem-
ical researchers devote to do. In order to make clear the reac-
tion pathway of the aniline with glycerin to 3-MI through
gas-phase synthesis over the Cu/CoO/La2O3/Al2O3/SBA-15
catalyst, we did a series of investigations. First of all, we per-
formed a GC–MS analysis to the reaction products. Except
the target product of 3-MI, a 1.9% 1,2-propanediol (1,2-
PDO) yield was also obtained. According to the relevant
literature [49–52], glycerin can form 1,2-PDO through the
hydrogenolysis over Cu-based catalysts. To test this, we have
specifcally done the hydrogenolysis of glycerin over the cat-
alyst of Cu/CoO/La2O3/Al2O3/SBA-15. Only a 18.3% 1,2-
PDO yield was obtained, while a large amount of acetol with
the yield of 74.2% was detected. It has been reported [53,
54] that acetol could convert into 1,2-PDO, so the catalytic
conversion of acetol was further proceeded on the catalyst,
however, no 1,2-PDO was found. Since the related literature
reported that 1,2-PDO can also be converted to 3-MI with
aniline [55], the reaction of 1,2-PDO with aniline over Cu/
CoO/La2O3/Al2O3/SBA-15 was carried out and the result
confrmed this view. Moreover, in order to know whether
the large amount of acetol produced in the hydrogenolysis
of glycerin can be reacted with aniline to form 3-MI, we also
carried out the reaction of acetol and aniline over the Cu/
CoO/La2O3/Al2O3/SBA-15 catalyst. It was found that acetol
was completely converted and a 80.6% 3-MI was produced.
Based on the above research, a possible pathway for
the gas-phase synthesis of 3-MI by glycerin with aniline
was proposed, as shown in Scheme 1. Acetol and 1,2-PDO
were frst produced through glycerin hydrogenolysis on the
catalyst of Cu/CoO/La2O3/Al2O3/SBA-15. Then, acetol as
well as 1,2-PDO reacted with aniline to generate the target
3-MI was efciently synthesized in a low-cost and green way
over Cu/SBA-15 modifed with Al2O3, La2O3 and CoO using
biomass-derived glycerin and aniline as raw materials. Dur-
ing the reaction, the Cu/CoO/La2O3/Al2O3/SBA-15 catalyst
exhibited predominant activity and selectivity. Through a
series of characterization results it can be clearly known
that the promoters of Al2O3 and CoO could enhance the
acidity of the catalyst, thus the interaction force between
Cu and the composite carrier increased, and thereby the Cu
particles dispersity was higher and the sintering resistance
was better. Moreover, the high selectivity of 3-MI benefted
from a large number of weak acid centers after the addi-
tion of Al2O3 and CoO. The promoter of La2O3 weakened
the acidity of the catalyst, which promoted the reduction of
CuO and inhibited the formation of carbon deposits. Under
the optimized reaction conditions with reaction temperature
of 523 K and H2 or steam fow rate of 10 mL min−1, over
Cu/CoO/La2O3/Al2O3/SBA-15 (Al2O3 content: 11.03 wt%,
La2O3 content: 1.07 wt%, CoO content: 0.25 wt%), the opti-
mum yield and selectivity of 3-MI were 73.3% and 86.4%,
respectively. When the catalyst was reused 7 times, the yield
of 3-MI still reached 69.4%, revealing the catalyst has excel-
lent stability. Through the study on the reaction pathway it
was concluded that glycerin could produce acetol and 1,2-
PDO by hydrogenolysis on Cu/CoO/La2O3/Al2O3/SBA-15
catalyst. Acetol could fast react with aniline to form 3-MI.
Although 1,2-PDO could also react with aniline to produce
the target product, the rate was a little slow.
1 3

P. Sun et al.
Acknowledgements We are gratefully thankful to the fnancial sup-
ported by the National Natural Science Foundation of China (Grant
No. 21576128).
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