X. Wang, H. Wang, K. Zhao et al.
Journal of Catalysis 394 (2021) 18–29
was developed with USY zeolite as catalyst under organic ligand-
free conditions (Scheme 2).
with Ar. The reaction was carried out at 160 °C (reaction tempera-
ture) for 12 h with a magnetic stirring speed of 500 rpm/min. After
the reaction finished, the press tube was cooled to room tempera-
ture and 0.5 mmol triphenylmethane was added. Subsequently, the
reaction mixture was diluted with 8 mL of methanol and cen-
trifuged. Then, 0.75 mL of the supernatant liquid was taken and
treated with hydrochloric acid (12 mol/L, 5–6 drops). Finally, the
mixture was concentrated by a rotary evaporator and 0.5 mL CDCl3
was added for quantitative analysis by 1H NMR.
The scale-up experiments were performed in a 100 mL mag-
netic stirred autoclave equipped with a PID temperature controller.
A mixture of styrene (25.0 mmol, 2.6 g), aniline (30.0 mmol, 2.8 g),
USY (1.0 g), toluene (50 mL) were added and exchanged with Ar.
The reaction was carried out at 160 °C (reaction temperature) for
12 h with a magnetic stirring speed of 500 rpm/min.
2. Experimental section
2.1. Catalyst preparation
All solvents and chemicals were obtained commercially and
used as received.
Zeolites with different structures and different chemical compo-
sitions were purchased from different companies. MOR (Si/Al = 25, H
type), ZSM-5 (Si/Al = 27, H type), SAPO-11 (Si/Al = 0.5, H type), USY
(Si/Al = 11, H type) and USY (Si/Al = 5.4, H type) were purchased from
Nankai University Catalyst Co., Ltd. b (Si/Al = 30, H type) was
received from Shandong Qilu Huaxin High-Tech Co., Ltd. NaY was
purchased from J&K Scientific Ltd. HY was prepared by ion exchange
3 times, NaY in 1 mol/L NH4NO3 solution (Solid-liquid ratio = 1:20) at
80 °C for 24 h, then calcined at 550 °C for 3 h. All zeolites without spe-
cial descriptionin this articlewere calcinedfor 3 h at a heatingrate of
10 °C/min to 550 °C from room temperature.
3. Results and discussion
3.1. Screening of different zeolites for hydroarylation of styrene and
aniline
2.2. Catalyst characterization
In order to verify our conjecture, we selected various zeolites
with different structures and morphologies for hydroarylation of
styrene and aniline as a model reaction (Table 1). Meanwhile,
we calculated the molecular sizes of reactants and products the-
oretically. It was found that the equivalent diameters of styrene,
aniline, 2-(1-phenylethyl)aniline, 4-(1-phenylethyl)aniline and
N-(1-phenylethyl)aniline are 8.34 Å, 8.04 Å, 9.94 Å, 9.92 Å and
9.92 Å (Fig. 1). Obviously, the computational results revealed that
the pore diameter of the zeolite should be greater than 9.94 Å for
the products leaving the pore. Initially, low yields were obtained
on the small pore size zeolites for the hydroarylation of styrene
and aniline (entries 1–3, Table 1), such as ZSM-5 (Framework
Type: MFI, Maximum diameter of a sphere: 6.36 Å [45]), MOR
(Framework Type: MOR, Maximum diameter of a sphere: 6.7 Å
[45]) and SAPO-11 (Framework Type: AEL, Maximum diameter
of a sphere: 5.64 Å [45]). Gratifyingly, a promising yield of 36%
was observed when b (Framework Type: BEA, Maximum diameter
of a sphere: 6.68 Å [45]) was used, but selectivity for hydroami-
nation was 58% (entry 4, Table 1). Then, we systematically inves-
tigated the performance of Y-type zeolite (Framework Type: FAU,
Maximum diameter of a sphere: 11.24 Å [45]). When using NaY,
5% yield and 40% selectivity for hydroarylation could be obtained
(entry 5, Table 1). Surprisingly, the yield and the selectivity of
hydroarylation were improved after ion exchange 3 times (entry
6, Table 1). To our delight, USY (Si/Al = 11) significantly increased
the yield and selectivity to 68% (entry 7, Table 1). As the Si/Al
ratio decreased to 5.4 and there was no pretreatment of USY,
the yield and hydroarylation selectivity were 65% and 68%,
respectively (entry 8, Table 1). With the increase in the calcina-
tion temperature of USY, such as USY(5.4)-400 (Si/Al = 5.4, calci-
XRD measurements were conducted by using a STADIP auto-
mated transmission diffractometer (STOE) equipped with an inci-
dent beam curved germanium monochromator with CuKa1
radiation and current of 40 kV and 150 mA, respectively. The
XRD patterns were scanned in the 2 Theta range of 5-80°.
The BET surface area measurements were performed on a Quan-
tachrome IQ2 at the temperature of 77 K. The pore size distribution
was calculated from the adsorption–desorption isotherm by using
the DFT method. Prior to measurements, the samples were
degassed at 300 °C for 3 h, at a rate of 10 oCÁminÀ1
.
Py-IR spectra of samples were analyzed by a Bruker VERTEX 70
FTIR spectrometer. The samples were weighed and pressed into
transparent disk with a diameter of 15 mm. Then, the sample
was heated at 400 °C under vacuum for 1 h, and cooled to 150 °C
then pyridine was chemisorbed for 10 min. After this step, the
sample was evacuated and analyzed by FTIR.
NH3-TPD was performed on a chemisorption analyzer equipped
with a thermal conductivity detector (TCD). The chemisorption
analyzer was TP-5080D from Tianjin Xianquan Industrial and Trad-
ing Co., Ltd. The weighed sample (100 mg) was pretreated at 400 °C
for 1 h under He (40 mLÁminÀ1) and cooled to 100 °C. The NH3 gas
(30 mLÁminÀ1) was introduced instead of He at this temperature
for 0.5 h to ensure the saturation adsorption of NH3. The sample
was then purged with He for 1 h (40 mLÁminÀ1) until the signal
returned to the baseline as monitored by a thermal conductivity
detector (TCD). The desorption curve of NH3 was acquired by heat-
ing the sample from 100 °C to 700 °C at 10 oCÁminÀ1 under He with
the flow rate of 40 mLÁminÀ1
.
27Al MAS NMR were carried out on a Bruker AVANCE III 600
spectrometer at a resonance frequency of 156.4 MHz using a
4 mm HX double-resonance MAS probe at a sample spinning rate
of 14 kHz. 27Al MAS NMR spectra were recorded by small-flip angle
nation temperature
= = 5.4,
400 ◦C), USY(5.4)-550 (Si/Al
calcination temperature = 550 ◦C), USY(5.4)-800 (Si/Al = 5.4, cal-
◦
cination temperature = 800 C), the yield can be up to 82% and no
hydroamination product was observed (entries 9–11, Table 1).
Noteworthy, hydroamination products will be observed when
the reaction temperature decreased (entry 12, Table 1) but not
at high temperature (entry 13, Table 1). The impact of the solvent
on the reactivity of this reaction was further investigated, and it
was found that toluene was the optimal choice (Table S1). Mean-
while, the volume of toluene and the amounts of USY were also
optimized (Table S2 and S3), and 2 mL toluene and 40 mg USY
were proved to be the optimal. It should be noted that the cata-
lyst can be reused at least 10 times without apparent deactivation
(entry 14, Table 1).
technique with a pulse length of 0.68 ls (<p/12) and a 1 s recycle
delay. The chemical shift of 27Al was referenced to 1 M aqueous Al
(NO3)3.
NMR spectra were measured using a Bruker ARX 400 or ARX
100 spectrometer at 400 MHz (1H) and 100 MHz (13C).
2.3. Typical procedure for hydroarylation of amines and alkenes
A mixture of alkene (1.0 mmol), amine (1.2 mmol), USY (40 mg),
toluene (2 mL) were added into a 38 mL press tube and exchanged
20