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T.E. Davies et al. / Applied Catalysis A: General 493 (2015) 17–24
O
lacey carbon coated 300 mesh copper grids. ATR FT-IR spectra
R1
R2
were obtained using a Perkin Elmer Spectrum Two spectrome-
ter. NH3-TPD experiments were carried out using a Quantachrome
ChemBet TPR/TPD Chemisorption Analyser. Prior to the measure-
ments, approximately 30 mg of sample was activated by heating
at 100 ◦C for 1 h. The sample was then cooled to room tempera-
ture before treating with ammonia for 30 min. Physically adsorbed
ammonia was removed by purging with helium at 90 ◦C for 1 h
before the NH3-TPD analysis. The NH3-TPD of the samples was
carried out by increasing the cell temperature linearly from 90 ◦C
to 900 ◦C with a heating rate of 20 ◦C min−1 and a helium flow
rate of 80 cm3 min−1. Elemental compositions were obtained with
a JOEL scanning electron microscope fitted with an EDX detec-
tor using a 20 keV accelerating voltage. MAS-NMR spectra were
obtained courtesy of the EPSRC National Solid State NMR Service,
Durham University. Aluminium spectra were obtained using a Var-
ian VNMRS system, with direct excitation (DE) and the results are
reported relative to an external 1 M aqueous Al(NO3)3 solution. Sili-
con spectra were obtained using a Varian Unity Inova spectrometer
with a DE or cross polarisation (CP) from protons and the results
are reported in ppm with respect to neat tetramethylsilane. Boron
spectra were obtained using a Varian VNMRS system and results
are reported relative to external BF3·Et2O.
H
LA
O
R3
H
O
R1
R2
R1
R2
R3
R3
O
R1
R2
H
H
R3
Scheme 1.
activity of large pore nanoporous alumino- and borosilicate mate-
rials produced by a modified EISA procedure and their ability to
efficiently catalyse the Meinwald rearrangement reaction of epox-
ides in dimethyl carbonate (DMC).
2. Materials and methods
2.1. General methods
Commercially available reagents were used without further
purification. Commercial zeolite materials were purchased in their
NH4 form and calcined at 500 ◦C for 3 h to provide the H+ form.
+
Nuclear magnetic resonance (NMR) spectra were recorded at
400 MHz in CDCl3 at 25 ◦C. High resolution mass spectra (HRMS)
were obtained courtesy of the EPSRC Mass Spectrometry Facility,
Swansea University, UK.
2.4. Catalyst testing and product analysis
All reactions were carried out in a stirred batch reactor. The cat-
alyst was removed from the sample by filtration through a Celite
plug, which was washed with DMC (2 mL × 2 mL) and the combined
solvents were removed under reduced pressure. Product mixtures
were analysed using 1H NMR and GC–MS techniques, and percent-
age conversions of reactions were determined by integration of the
relevant signals from crude 1H NMR spectra. Product distributions
from reactions involving ␣-pinene oxide were also determined by
GC analysis employing an FID detector with toluene as an external
standard. These samples were analysed using a Varian Star 3800 Cx
GC employing a 30 m CP-Wax 52 CB column. GC–MS analysis was
performed using a Varian 450GC and Varian 300MS employing a
VF-5ms capillary column (30 m, 0.25 mm i.d. and 0.25 m) and a
gradient temperature profile with an initial temperature of 50 ◦C
2.2. Catalyst preparation
rials, in addition to the unmodified silica material (S-1-(2.02)),
were synthesised as described previously using an evaporation-
induces self-assembly (EISA) method [26,27]. In addition, a number
of larger pore silicate materials were synthesised by a modification
of this EISA protocol as described previously [28]. A typical prepa-
ration for the synthesis of the large pore borosilicate B-13-(3.54)
catalyst is as follows: cetyltrimethylammonium bromide (4.0 g,
11 mmol) was dissolved in a solution of hydrochloric acid (2.5 mL,
0.1 M), ethanol (17.5 mL) and water (22.5 mL). Tetraethyl orthosili-
cate (25 mL, 112 mmol) was then added and the mixture stirred for
10 min at 40 ◦C. The solution was cooled to room temperature and
boric acid (553 mg, 8.95 mmol) was added in one portion. The mix-
ture was stirred for 20 min and then left to age at room temperature
for 24 h. The resultant white solid was crushed into a fine powder
and calcined in air at 550 ◦C for 6 h to remove the organic template
to give a fine white powder. All materials were stored at 140 ◦C for
at least 24 h prior to use.
for 3 min rising to 280 ◦C at a rate of 20 ◦C min−1
.
2.5. General procedure for the Meinwald rearrangement of
epoxides
The borosilicate catalyst B-13-(3.54) (25 mg) was added to a
solution of styrene oxide (60 mg, 0.5 mmol) in DMC (2 mL) and the
reaction heated to 40 ◦C with vigorous stirring. On completion of
the reaction, the catalyst was removed by filtration through a Celite
plug which was washed with DMC (2 mL × 2 mL) and the combined
solvents were removed under reduced pressure to afford phenylac-
etaldehyde as a colourless oil; ꢀmax (film)/cm−1 (neat) 2993, 1704,
1510, 1452 and 1127; 1H NMR (400 MHz; CDCl3) ı = 9.70 (1H, t,
J = 2.0 Hz), 7.30–7.10 (5H, m), 3.60 (2H, d, J = 2.0 Hz); MS (EI) m/z
121 (M+H)+; HRMS (EI) calculated for C8H8O (M)+ 120.0570, found
(M)+ 120.0568.
2.3. Catalyst characterisation methods
Specific surface areas were obtained by the BET method at liquid
nitrogen temperatures using a Micromeritics Gemini or a Quanta-
chrome Autosorb-1 automated gas sorption instrument. Samples
were degassed at 120 ◦C under a flow of helium for 2 h prior to
analysis. Pore sizes were obtained using a Quantachrome Autosorb-
1 automated gas sorption instrument. Samples were degassed at
120 ◦C under vacuum for 3 h prior to analysis. Pore sizes were calcu-
lated by applying the non-local density functional theory (NLDFT)
method to the N2 sorption at −196 ◦C employing Quantachrome
AS-1 software data reduction parameters. Low angle XRD pat-
terns were obtained using a Panalytical X’Pert Pro diffractometer.
Measurements were performed in transmission mode at room tem-
perature using monochromatic CuK␣1 radiation. TEM analysis was
performed on a Jeol 2100 operated at 200 kV. Samples were pre-
pared by dispersion in methanol by sonication and deposited onto
3. Results and discussion
3.1. Catalyst characterisation
All of the silicate materials generated displayed the expected
large surface areas and narrow pore size distributions (Table 1).
The nitrogen adsorption–desorption isotherms of all the materi-
als appears to be a transition from type IV (mesoporous materials)