Full Papers
Synthesis of mesoporous alu-
mina
Table 9. Scope of the oxidative esterification of substituted benzyl alcohols with methanol catalyzed by Au/
Al O -3-800.
2 3
[a,b]
Mesoporous alumina materials
were synthesized by the evapora-
tion-induced self-assembly method
[11b]
using an established procedure
Entry
1
Product
Entry
2
Product
Entry
3
Product
Entry
4
Product
with some modifications. Alumi-
num isopropoxide, Pluronic P123,
and TIPB were used as the precur-
sor, template, and swelling agent,
respectively. Three different TIPB/
P123 weight ratios (1, 2, and 3)
were used in the synthesis of mes-
oporous alumina. In general, TIPB
5
9
6
7
8
(
6.0 g) was added to a solution of
Pluronic P123 (2.0 g) in ethanol
40 mL) and stirred vigorously at
(
RT under air for 1 h. Aluminum iso-
propoxide (4.08 g), concentrated
HCl (3.2 mL), and citric acid (0.9 g)
were added, and the resulting mix-
ture was stirred vigorously at RT
under air for 12 h. The reaction
mixture was transferred to a Petri
dish and evaporated in an oven at
10
11
12
13
14
4
58C for 24 h and at 608C for 48 h.
[a] Reaction conditions: Au/Al
2
O
3
-3-800 (1 mol%), 1 (0.2 mmol), K
2
CO
3
(0.2 mmol) and MeOH/hexanes (1:4,
The white solid was calcined at
0
.8 mL, purged with O
2
for 5 min), RT, 14 h, under O
2
. [b] Isolated yield. [c] 0.5 mol% Au catalyst.
500, 600, 700, or 8008C under air
for 4 h with a heating rate of
À1
1
8Cmin . The mesoporous alumi-
na materials were labeled as Al O -
2
3
Characterization
a-b, in which a and b represent the TIPB/P123 weight ratio and the
calcination temperature, respectively. The six mesoporous alumina
materials (Al O -3-500, Al O -3-600, Al O -3-700, Al O -3-800, Al O -
2
TEM was performed by using a FEI Tecnai G F20 electron micro-
scope operated at 200 kV with the software package for automat-
ed electron tomography. For TEM studies, a drop of the nanomate-
rial solution was dispensed onto a 3 mm carbon-coated copper
grid. Excess solution was removed by an absorbent paper, and the
sample was dried under air in an oven at 808C. EDX analysis of the
2
3
2
3
2
3
2
3
2
3
2
-800, and Al O -1-800) were characterized by TEM, TEM-EDX, XRD,
2 3
and N adsorption–desorption isotherms.
2
Synthesis of Au/mesoporous alumina nanocatalysts
2
nanomaterials was performed by using the FEI Tecnai G F20 elec-
Mesoporous alumina (0.200 g) in water (4.4 mL) was sonicated for
tron microscope equipped with an EDX detector. XPS analysis was
conducted by using a VG ESCALAB MKII spectrometer. The powder
XRD patterns were collected by using PANalytical X’Pert PRO and
3
0 s to disperse the solids. HAuCl4 aqueous solution (0.0186 mL,
0.58m) was added with vigorous stirring, followed by the addition
of l-lysine (0.5 mL, 0.53m). The suspension was stirred vigorously
at RT under air for 30 min. NaBH aqueous solution (0.25 mL,
4
Bruker D8 ADVANCE X-ray diffractometers using CuK irradiation
a
1
13
(
l=1.5406 ). H and C NMR spectra were collected in CDCl by
3
using a Bruker AV-400 spectrometer at 258C. Chemical shifts were
reported in ppm from tetramethylsilane with the solvent reso-
nance as the internal standard. GC–MS analysis was performed by
using a Shimadzu GCMS-QP2010 spectrometer. ICP-MS analyses
0.35m) was added dropwise, followed by HCl aqueous solution
(0.25 mL, 0.3m). The resulting reddish suspension was stirred at RT
under air for 18 h. The Au/mesoporous alumina was collected by
centrifugation (10000 rpm for 20 min), washed twice with deion-
ized water (10 mL) and once with acetone (10 mL), and dried at RT
under vacuum overnight. The material was characterized by TEM,
TEM-EDX, XRD, and ICP-MS.
were performed by using a PerkinElmer Elan DRC II. N adsorption–
2
desorption isotherms were measured at 77 K by using a Micromerit-
ics Tristar system, and the sample was degassed at 1808C for 12 h
before analysis. The surface area was calculated using the BET
method using adsorption data in a relative pressure range of 0.06–
0
.3. The pore size and total pore volume were derived from the ad-
Synthesis of amides
sorption isotherm using the Barrett–Joyner–Halenda (BJH) model.
TGA was conducted by using a PerkinElmer Pyris 1 thermogravimet-
ric analyzer, and the samples were heated at 108Cmin from 25–
The general procedure for the direct amidation of substituted
benzyl alcohol with amine was as follows. A mixture of the Au/
Al O -3-800 nanocatalyst (1 mol% Au), amine (0.2 mmol), substitut-
À1
2
3
9
008C in flowing air.
ed benzyl alcohol (0.4 mmol), lithium hydroxide (0.4 mmol), and
deionized water (0.8 mL, purged with O for 5 min) were added to
2
a 10 mL glass vial equipped with a rubber septum. The headspace
in the glass vial was purged with O , and the reaction mixture was
2
subjected to sonication to disperse the catalyst. The reaction mix-
ChemSusChem 2015, 8, 1916 – 1925
1924
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