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K. Bachari, R.M. Guerroudj / C. R. Chimie 15 (2012) 317–323
of p-acetylanisole and 4-acetylveratrole, which are com-
mercially important products and are being used as the
precursors of a sun protector and of a component in an
insecticide formulation [10], respectively. Different cata-
lysts including zeolites [11–18], heteropoly acids [19,20],
sulfated metal oxides [21] and AlSBA-15 [22], have been
investigated for the Friedel-Crafts alkylation and acetyla-
tion reactions. Indeed, in the present study we have
studied the liquid phase of acetylation of 1,2-dimetho-
xybenzene with acetic anhydride over Ni-MCM-41 cata-
lysts synthesized by microwave irradiation method.
calculated by the Barrett-Joyner-Halenda (BJH) method.
Transmission electron microscopy (TEM) morphologies of
samples were observed on a Philips TEMCNAI-12 with an
acceleration voltage of 100–120 kV. The nickel content in
the samples was determined by the inductively coupled
plasma (ICP) technique (Vista-MAX, Varian). The density
and strength of the acid sites of the different Ni-MCM-41
samples were determined by the temperature pro-
grammed desorption (TPD) of pyridine. About 100 mg of
the materials were evacuated for 3 h at 523 K under
vacuum (P < 10ꢀ5 kPa). Thereafter, the samples were
cooled to room temperature under dry nitrogen followed
by exposure to a stream of pyridine in nitrogen for 30 min.
Subsequently, the physisorbed pyridine was removed by
heating the sample to 393 K for 2 h in a nitrogen flow. The
TPD of pyridine was performed by heating the sample in a
nitrogen flow (50 mL/min) from 393 to 873 K with a rate of
2. Experimental
2.1. Synthesis of the catalysts
M-H synthesis of Ni-MCM-41 mesoporous molecular
sieves with different Si/Ni ratios (Si/Ni = 80, 50, 10) was
performed using a MARS5 (CEM Corp., Matthews, NC, USA)
microwave digestion system. This system operates at a
maximum power of 1200 W and the power can be varied
from 0 to 100% and is controlled by both pressure and
10 K/min using a high-resolution thermogravimetric
analyzer coupled with a mass spectrometer (SETARAM
setsys 16MS). The observed weight loss was used to
quantify the number of acid sites assuming that each mole
of pyridine corresponds to one mole of protons.
temperature to
a
maximum of 350 psi and 513 K,
2.3. Catalytic testing
respectively. A 2.45 GHz microwave frequency was used
which is the same as that used in domestic microwave
ovens. The syntheses were carried out in double-walled
digestion vessels, which have an inner liner and cover,
made up of Teflon PFA and an outer strength vessel shell of
Ultem polyetherimide. In a typical synthesis, 21.32 g of
sodium metasilicate (Na2SiO3 9H2O, CDH) was dissolved in
60 g of water. The reaction mixture was stirred for 2 h.
Meanwhile, cetyltrimethylammonium bromide (5.47 g,
CTABr, OTTO Chemie) and nickel nitrate were dissolved
in 20 g of distilled water. Then, the resultant solution was
added dropwise to the sodium metasilicate solution. The
final mixture was stirred for 1 h. The pH of the gel was
adjusted by using 2 M sulfuric acid (H2SO4; 98% Merck) and
it was stirred for another 3 h. Thus obtained gel was
allowed to crystallize under M-H conditions at 373 K for
2 h. The crystallized product was filtered off, washed with
warm distilled water, dried at 383 K and finally calcined at
813 K in air for 6 h.
Acetylation of 1,2-dimethoxybenzene with acetic an-
hydride has been carried out under liquid phase condi-
tions. The liquid phase reaction set up consists of two
necked 50 mL round bottom flask duly fitted with a
condenser in one end for cooling and another vent is closed
with Teflon septum for collecting samples by glass syringe
at regular intervals. The whole system was kept in a
thermostated oil bath attached with a magnetic stirrer
coupled with a heating plate. In a typical reaction, the
catalyst was added to a solution of 2.6 g 1,2-dimethoxy-
benzene (18.9 mmol), 0.4 g acetic anhydride (3.8 mmol)
and 50 mL chlorobenzene together with 1 g nitrobenzene
as internal standard. Then, the reaction mixture was
heated to the required temperature and the samples were
collected with regular intervals of time. The collected
samples were analyzed periodically by a gas chromato-
graph (HP-6890) equipped with a FID detector using a DB-
5 capillary column. The products were confirmed with GC-
MS (HP-5973) analysis.
2.2. Characterization techniques
The X-ray diffraction (XRD) patterns of samples were
recorded with a powder XRD instrument (Rigaku D/max
3. Results
2500PC) with Cu K
a
radiation (
l
= 0.15418 nm). It was
3.1. Characterization of the samples
operated at 40 kV and 50 mA. The experimental conditions
correspond to a step width of 0.028 and the scan speed of
The small angle XRD patterns of Ni-MCM-41 (Si/Ni = 80,
50, 10) synthesized by the microwave irradiation method
are shown in Fig. 1. The Ni-MCM-41 (80) sample gives a
very strong (100) peak followed by (110) and (200) lower
intensity peaks. All three distinct Bragg reflections at low
angles were indexed on a hexagonal lattice. However,
when the nickel content ratio increased from 50 to 10, the
intensities of the long range ordered peaks were gradually
reduced. However, compared with the pattern of the
typical MCM-41 mesoporous molecular sieve [23], it can
be noted that the d100 spacing in Ni-MCM-41 samples is
18/min. The diffraction patterns were recorded in the 2
u
range of 1–108. Fourier transform infrared spectra of
samples were recorded on a Nexus FT-IR 470 spectrometer
made by Nicolet Corporation (USA) with KBr pellet
technique. The effective range was from 400 to
4000 cmꢀ1. Specific surface area and pore size were
measured by using a NOVA2000e analytical system made
by Quantachrome Corporation (USA). The specific surface
area was calculated by the Brunauer-Emmett-Teller (BET)
method. The pore size distribution and pore volume were