G Model
CATTOD-10272; No. of Pages5
ARTICLE IN PRESS
S.K. Moromi et al. / Catalysis Today xxx (2016) xxx–xxx
2
(
CBMM), ZrO ·nH O and H SnO (Kojundo Chemical Laboratory
with tetramethylsilane as an internal standard. All chemical shifts
2
2
2
3
◦
Co., Ltd.), respectively, at 500 C for 3 h.
A precursor of the 5 wt% Pt/C catalyst was prepared by impreg-
nation method; a mixture of carbon (Vulcan XC72) and aqueous
(ı) are reported in ppm and coupling constants (J) in Hz. All chem-
ical shifts are reported relative to tetramethylsilane and d-solvent
peaks (77.00 ppm, chloroform), respectively. Abbreviations used in
the NMR experiments: s, singlet d, doublet; t, triplet; m, multiplet.
GC–MS spectra were recorded by SHIMADZU QP2010.
HNO3 solution of Pt(NH ) 2(NO3)2 (Furuya Metal Co., Ltd.) was
3
◦
◦
evaporated at 50 C, followed by drying at 90 C for 12 h. The
reduced Pt/C catalyst, designated as Pt/C, was prepared by reduc-
tion of the precursor (Pt (NH ) (NO ) -loaded carbon) in a pyrex
3
2
3
2
2.4.1. 6-Methyl-quinoline (Table 3, entry 1) [18]
3
−1
◦
tube under H2 flow (20 cm min ) at 300 C for 0.5 h. The other
Pt catalysts were prepared by the same method as Pt/C. Carbon-
supported metal catalysts, designated as M/C (M = Rh, Pd, Ir, Ru,
Ni, Cu, Co, Ag), with metal loading of 5 wt% were prepared by
impregnation method by the similar manner as Pt/C using aque-
ous solution of metal nitrates (for Ni, Cu, Co, Ag) or IrCl ·nH O
1
H NMR (600.17 MHz, CDCl ), TMS: ı 8.51 (d, J = 2.70 Hz, 1H),
3
7
1
.73 (d, J = 8.94 Hz, 1H), 7.54 (d, J = 7.56 Hz, 1H), 7.12 (d, J = 8.22 Hz,
H), 7.05 (s, 1H), 6.98-6.87 (m, 1H), 2.09 (s, 3H); 13C NMR
3
2
(
150.91 MHz, CDCl ) ı 148.63, 146.11, 135.36, 134.39, 130.82,
or aqueous HNO solution of Rh(NO ) (Furuya Metal Co., Ltd.)
3
3
3 3
1
28.27, 127.44, 125.79, 120.17, 20.66; MS m/e 143.07.
or Pd (NH ) (NO ) (Kojima Chemicals Co., Ltd.). These cata-
lysts were reduced under H2 flow at 300 C for 0.5 h. Platinum
oxides-loaded carbon (PtOx/C) was prepared by calcination of the
3
2
3 2
◦
2.4.2. Quinoline (Table 3, entry 2) [16]
◦
Pt(NH ) (NO ) -loaded C in air at 300 C for 0.5 h.
3
2
3 2
2.2. Catalyst characterization
1
H NMR (600.17 MHz, CDCl ), TMS: ı 8.89 (d, J = 2.76 Hz, 1H),
3
8
7
.12-8.07 (m, 2H), 7.76 (d, J = 8.22 Hz, 1H), 7.68 (t, J = 7.56 Hz, 1H),
.50 (t, J = 7.56 Hz, 1H), 7.33–7.32 (m, 1H); C NMR (150.91 MHz,
Temperature programmed reduction by H2 (H -TPR) was car-
13
2
ried out by BELCAT (MicrotracBEL). PtOx/C (20 mg) in a quartz tube
CDCl ) ı 150.15, 148.02, 135.81, 129.22, 129.19, 128.03, 127.57,
3
◦
−1
was heated with a temperature ramp-rate of 10 C min in a flow
1
26.30, 120.83; MS m/e 129.04.
3
−1
of 5% H /Ar (20 cm min ). The effluent gas was passed through a
2
trap containing MS4 Å to remove water, then through the thermal
2.4.3. 2-Methyl-quinoline (Table 3, entry 3) [23]
conductivity detector, which detected the amount of H consumed
2
0
during the experiment. The number of surface Pt atoms on Pt/C,
◦
pre- reduced in H2 at 300 C for 0.5 h, was estimated from the
CO uptake of the samples at room temperature using the pulse-
adsorption of CO in a flow of He by BELCAT (MicrotracBEL). The
average Pt particle size was calculated from the CO uptake assum-
ing that CO was adsorbed on the surface of spherical Pt particles at a
stoichiometry of CO/(surface Pt atom) = 1/1. Transmission electron
microscopy (TEM) observation of Pt/C was carried out by a JEOL
JEM–2100 F TEM operated at 200 kV.
1
H NMR (600.17 MHz, CDCl ), TMS: ı 8.03 (d, J = 8.28 Hz, 1H),
3
7
1
.80 (d, J = 8.28 Hz, 1H), 7.59 (d, J = 7.56 Hz, 2H), 7.34 (t, J = 6.90 Hz,
H), 7.05 (t, J = 6.18 Hz, 1H), 2.64 (s, 3H); C NMR (150.91 MHz,
CDCl ) ı 158.13, 147.18, 135.35, 128.68, 127.95, 126.82, 125.77,
24.93, 121.22, 24.65; MS m/e 143.07.
13
3
1
2
.4.4. Indole (Table 3, entry 4) [14]
2.3. Catalytic tests
Typically, 5 wt% Pt/C was used as the standard catalyst. After
◦
1H NMR (600.17 MHz, CDCl3), TMS: ı 8.09 (s, NH, 1H), 7.65
the H -reduction of the catalyst at 300 C, catalytic tests were car-
2
ried out using a batch-type reactor without exposing the catalyst to
air as follows. A mixture of 6-methyl 1,2,3,4-tetrahydroquinoline
(d, J = 8.28 Hz, 1H), 7.38 (d, J = 8.28 Hz, 1H), 7.19 (m, 2H), 7.12 (t,
J = 7.20 Hz, 1H), 6.55 (s, 1H); 13C NMR (150.91 MHz, CDCl3) ı 135.74,
127.82, 124.10, 121.96, 120.71, 119.79, 111.00, 102.60; MS m/e
117.10.
(
1.0 mmol) and n-dodecane (0.29 mmol) in o-xylene (1.5 mL) was
injected to the pre-reduced catalyst inside the reactor (cylindrical
glass tube) through a septum inlet, followed by filling N . Then, the
2
resulting mixture in a 15 mL of closed reflux system under 1 atm
N2 was magnetically stirred and was heated to reflux tempera-
3. Result and discussion
◦
ture; the bath temperature was 160 C and reaction temperature
3.1. Catalyst characterization
◦
was ca. 144 C. The yield of 6-methyl-quinoline was determined by
+
GC (Shimadzu GC–14 B with Ultra ALLOY capillary column UA -1
Fig. 1 shows temperature programmed H2-reduction (H2-TPR)
profile of Pt(NH3)2(NO3)2- loaded carbon as the precursor of Pt/C.
The H2-TPR profile shows H2 consumption peaks below 250 C
of Frontier Laboratories Ltd., N ) using n-dodecane as an internal
2
◦
standard. Typically, the error in the yield determined by GC was
±
1.5%. To determine the isolated yield of 6-methyl-quinoline, 6-
assignable to the reduction of Pt(II) to metallic Pt. This indicates that
the standard Pt/C catalyst pre-reduced at 300 C contains metallic
◦
methyl-quinoline was isolated by column chromatography using
silica gel 60 (spherical, 63–210 m, Kanto Chemical Co. Ltd.) with
hexane/ethylacetate (90/10) as the eluting solvent, followed by
analyses by GC–MS and 1H and C NMR. The hydrogenation of
Pt. Fig. 2 shows a representative TEM image and Pt size distribution
of Pt/C. The average diameter of Pt particles for 98 particles was
2.9 ± 0.8 nm, and the volume-area mean diameter of Pt particles
was 3.5 ± 0.8 nm. The volume-area mean diameter (TEM analy-
sis) was consistent with the mean diameter estimated by the CO
adsorption experiment (3.2 nm) within the experimental error of
TEM analysis, which supprted the TEM reults. Summarizing the
above characterization results, we conclude that Pt species in the
standard Pt/C catalyst are present as 3.5 nm sized Pt metal nanopar-
ticles.
13
3
◦
quinoline was carried out by a stainless autoclave (28 cm ) at 160 C
under 3 bar H2.
2.4. NMR and GC–MS analysis
by JEOL-ECX 600 operating at 600.17 and 150.92 MHz, respectively
Please cite this article in press as: S.K. Moromi, et al., Acceptorless dehydrogenation of N-heterocycles by supported Pt catalysts, Catal.