Influence of preparation conditions on the structure of MCM-41 and catalytic performance of Ru/MCM-41 in benzene hydrogenation

Article abstract of DOI:10.3184/174751914X13892022601610

The influence of the preparation conditions on the structures of mesoporous molecular sieve MCM-41 were studied. The prepared MCM-41 samples were characterised by nitrogen physical adsorption-desorption, powder X-ray diffraction, transmission electron microscopy, FT-IR spectroscopy, thermo gravimetric analysis, differential scanning calorimetry and water/benzene static adsorption technologies. Ru/MCM-41 catalysts were then prepared by double solvent impregnation method and tested for benzene hydrogenation to cyclohexene. The structure characteristics of MCM-41 have a great effect on cyclohexene selectivity in benzene hydrogenation process. Ruthenium supported on MCM-41 with moderate surface area, larger pore size and pore volume, better long-range-order of hexagonal mesoporous shows better catalytic performance for benzene hydrogenation to cyclohexene.

Full text of DOI:10.3184/174751914X13892022601610

90 RESEARCH PAPER
FEBRUARY, 90–95
JOURNAL OF CHEMICAL RESEARCH 2014
Influence of preparation conditions on the structure of MCM‑41 and
catalytic performance of Ru/MCM‑41 in benzene hydrogenation
Hongguang Liaoa, Donghong Ouyanga, Jing Zhanga, Yanjuan Xiaob, Pingle Liua*,Fang Haoa,
Kuiyi Youa and He′an Luoa
aSchool of Chemical Engineering, Xiangtan University, Xiangtan, 411105, P.R. China
bDepartment of Chemical Engineering, Hunan Chemical Vocational Technology College, Zhuzhou 412004, P.R. China
The influence of the preparation conditions on the structures of mesoporous molecular sieve MCM‑41 were studied. The
prepared MCM‑41 samples were characterised by nitrogen physical adsorption–desorption, powder X‑ray diffraction,
transmission electron microscopy, FT‑IR spectroscopy, thermo gravimetric analysis, differential scanning calorimetry and
water/benzene static adsorption technologies. Ru/MCM‑41 catalysts were then prepared by double solvent impregnation
method and tested for benzene hydrogenation to cyclohexene. The structure characteristics of MCM‑41 have a great effect
on cyclohexene selectivity in benzene hydrogenation process. Ruthenium supported on MCM‑41 with moderate surface area,
larger pore size and pore volume, better long‑range‑order of hexagonal mesoporous shows better catalytic performance for
benzene hydrogenation to cyclohexene.
Keywords: benzene hydrogenation, cyclohexene selectivity, MCM-41, Ru/MCM-41, preparation conditions
The novel route based on cyclohexene oxidation or hydration
is of considerable industrial and academic interest in the
syntheses of ε‑caprolactam and adipic acid, the important
intermediates for the manufactures of nylon-6 and nylon-66.
Compared with the current cyclohexane oxidation processes,
the route of cyclohexene has the advantages of higher yield,
environmental friendliness and atomic economy.1,2 Due to
the drawbacks of the conventional production methods of
cyclohexene from cyclohexanol, cyclohexane and halogenated
cyclohexane, such as expensive raw materials, poor
efficiencies, complicated operations and a large number of
by-products, numerous researchers have focused on the study
of selective hydrogenation of benzene to cyclohexene since
Hargod and Zwietering first obtained cyclohexene in benzene
hydrogenation over ruthenium black catalyst in 1963.3,4 Asahi
Chemical Industry Co. has succeeded in producing cyclohexene
from benzene hydrogenation over metallic ruthenium–zinc
catalyst on commercial scale in 1988.5 Thermodynamically,
it is much easier to produce cyclohexane by benzene
hydrogenation since it has smaller standard formation free-
energy than cyclohexene.6 Therefore, the key point for benzene
hydrogenation to cyclohexene with high selectivity lies in how
to promote the desorption of the formed cyclohexene from
the catalyst and inhibit its adsorption so as to prevent further
hydrogenation to cyclohexane.
It has been found that ruthenium is the most effective
catalyst with exclusive cyclohexene selectivity in benzene
hydrogenation.7 Unsupported ruthenium based alloy catalyst8–13
and supported ruthenium catalyst14–27 are used in liquid
phase hydrogenation of benzene to cyclohexene. In recent
years, ruthenium supported on mesoporous molecular sieve
catalysts has also been applied in benzene hydrogenation
to cyclohexene.28–32 The research has mainly focused on the
effects of the promoters or reaction solvents on the performance
of ruthenium catalyst. Ru–La supported on zirconia modified
MCM-41 catalysts were prepared and used for benzene
hydrogenation in our previous work.33 The results show that
the cyclohexene selectivity increases to a certain degree with
the hydrophilic modification of zirconia to MCM-41 and the
improvement of ruthenium dispersion. However, the interaction
between ruthenium and the ordered mesoporous structure
of MCM-41 has not been discussed in depth. MCM-41 has
become one of the most popular mesoporous silica materials
for its interesting physical properties including the hexagonal
unidimensional channels, high specific surface area, specific
pore volume and high thermal stability.34–38 Studies show that the
high dispersity and small particle size of the ruthenium active
component favour cyclohexene formation.26,30,39,40 The unique
features of MCM-41 may show great potential for obtaining a
highly dispersed metal catalyst with defined particle size, which
may be beneficial for increasing cyclohexene selectivity in the
benzene hydrogenation process. The uniform mesoporous
channel structure and abundant pore volume of MCM-41 may
be helpful to the desorption of the formed cyclohexene. We
now report the influences of the preparation conditions on the
structures of mesoporous molecular sieve MCM-41 and the
catalytic performance of the ruthenium supported on MCM-41
catalyst as tested in the benzene hydrogenation process.
Results and discussion
Effects of crystallisation conditions on the structures of MCM-41
The nitrogen adsorption–desorption isotherms and pore size
distributions of MCM-41 prepared at different crystallisation
temperatures are shown in Fig. S1 (available in the Electronic
Supplementary Information, ESI).
According to the IUPAC classification, the isotherm of each
sample crystallised at 100–140 °C shows the typical type IV
isotherm with the hysteresis loop of H1. A sudden uptake of
the adsorbed amount occurs at the relative pressure between
0.3 and 0.4, representing capillary condensation of nitrogen
within the uniform mesoporous structure. The pore sizes of
these samples are distributed in the range 2–3 nm. While the
crystallisation temperature is above 160 °C, the isotherms of the
samples become type II with the hysteresis loops of H3 and the
pore size distributions clearly broaden. As shown in Table S1
(ESI), the BET surface areas of all samples decrease gradually
with the increment of crystallisation temperature. Especially,
the BET surface areas and pore volumes decrease observably
when the crystallisation temperature is above 160 °C, which
indicates that the ordered mesoporous structures of the samples
are possibly destroyed.
The XRD (powder X-ray diffraction) pattern of each sample
(see Fig. S2, ESI) crystallised at 100–140 °C shows three
Bragg peaks indexed as (100), (110) and (200), which are
typical diffraction peaks of MCM-41. The Bragg peaks clearly
* Correspondent. E-mail: liupingle@xtu.edu.cn

JOURNAL OF CHEMICAL RESEARCH 2014 91
decrease when the crystallisation temperature is above 160 °C,
further confirming that the ordered mesoporous structures are
destroyed at such high crystallisation temperature.
of each sample also shows type IV with hysteresis loop of
H1 as shown in Fig. S9, representing capillary condensation
of nitrogen within the uniform mesoporous structure. The
hydrophilic index of every sample increases with the increment
of the mole ratio of Al to Si (see Table S5). The reason may be
the formation of new hydroxyl species like hydroxy-bridged of
Si(OH)Al and the change of polarity of bridge oxogroup by the
introduction of Al.42
When the TMB is added to the CTAB solution, it quickly
enters into the hydrophobic region of the micelles, leading to
an increase of the micelle diameter so as to further amplify the
pore size of MCM-41. Higher relative pressure at the closure
point of the hysteresis loop indicates bigger pore size. As shown
in Fig. S11 and Table S6, the pore sizes of the samples increase
with the increasing of the amount of TMB. It can be seen from
Fig. S12 that the Bragg peaks of each sample turn to lower
angle with the increasing of the amount of TMB, indicating
the increment of the lattice parameters. However, while the
mole ratio of TMB to CTAB increases to 4:1, the pore size
distribution of the sample presents broadening trend, which
could mean the partial collapse of the mesoporous structure.
The nitrogen adsorption–desorption isotherms and XRD
patterns of MCM-41 prepared under different crystallisation
times are shown in Fig. S3 and Fig. S4 respectively. The
isotherm of each sample shows the typical type IV isotherm
with the hysteresis loop of H1 and the small angle XRD pattern
of each sample exhibits three Bragg peaks indexed as (100),
(110) and (200), which indicates the prepared samples are
typical MCM-41 materials. Furthermore, both of the samples
crystallised for 2 days and 5 days exhibit narrower pore size
distribution and stronger intensity of Bragg peaks, representing
better long-range-order of hexagonal mesoporous structure.
Table S2 shows that the effect of crystallisation time on BET
surface area of MCM-41 is much greater than those of pore size
and pore volume.
MCM-41 can be prepared at a broad range of pH.41 As
shown in Table S3, the distinctions of the texture properties
of all samples crystallised at pH of 9.0 to 12.0 are not obvious.
However, the sample crystallised at pH of 10.5 shows relatively
narrower pore size distribution (see Fig. S5) and stronger
intensity of Bragg peaks (see Fig. S6).
The effect of calcination temperature on the structures of MCM-41
The TG-DSC (thermo gravimetric and differential scanning
calorimetry) pattern of as-synthesised MCM-41 is shown in
Fig. 2. This shows that a conspicuous exothermic peak exhibits
between 500 °C and 600 °C, attributed to the decomposition
The effects of material ratio on the structures of MCM-41
The effects of the mole ratios of CTAB (cetyl trimethyl
ammonium bromide) to SiO2, Al to Si and TMB (mesitylene) to
CTAB were examined.
The CTAB is used as the template to form a hexagonal
lyotropic liquid-crystal of cylindrical micelle, surrounded by a
continuous region of water. The inorganic compounds formed
by the hydrolysis of TEOs (tetraethoxysilane) occupy the
continuous water region to create inorganic walls between the
surfactant cylinders. With a low concentration of CTAB, the
hydrolytic polymerisation of TEOs is dominant, and thus leads
to smaller pore size and volume in MCM-41. The amount and
stability of the micelles increase with the increment of CTAB
concentration, which may be helpful to form regular and rich
pore structure in MCM-41. However, over high concentration
of CTAB would result in an exorbitant density of micelle and
the space between the micelles decreases greatly, which is
unfavourable to form the ordered array of silicon species. It can
be seen from Table S4 that the BET surface area of each sample
firstly decreases and then increases with the increment of the
mole ratio of CTAB to SiO2 from 0.16 to 0.98, while the pore
volume shows the opposite trend. The prepared MCM-41 with
the mole ratio of CTAB to SiO2 of 0.32 shows the moderate BET
surface area of 501 m2 g–1 and larger pore volume of 1.97 cm3·g–1
with three strongest intensity of Bragg peaks (see Fig. S8).
The introduction of transition metal ions (Al, Ti, Fe, V, Zr, etc.)
during the preparation process of mesoporous molecular sieve
may improve the physical structures and chemical properties.42–44
In this work, Al was incorporated to MCM-41 by one-step in-
situ hydrothermal synthesis method using NaAlO2 as precursor.
As shown in Fig. 1, the FT-IR spectrum of each sample with
different mole ratios of Al to Si exhibits the antisymmetric and
symmetric stretching vibration peaks of M–O–M (M represents
Si or Al) at the wavenumbers of about 1087 cm–1 and 798 cm–1,
which confirms that the introduction of Al does not destroy the
skeleton structure of MCM-41. Meanwhile, the intensities of
the antisymmetric and symmetric stretching vibration peaks of
each sample increase and the wavenumbers of the peaks migrate
to the low frequency with the increment of the mole ratio of Al
to Si, ascribing to the formation of Al–O–M with longer bond
length of Al–O. The nitrogen adsorption–desorption isotherm
Fig. 1 FT‑IR spectra of MCM‑41 prepared at different mole ratios of Al to
Si: (a) 0.2, (b) 0.05, (c) 0.02, (d) 0.
Fig. 2 TG‑DSC curves of as‑synthesised MCM‑41.

92 JOURNAL OF CHEMICAL RESEARCH 2014
of the template molecule. As shown in Fig. 3, the nitrogen
adsorption–desorption isotherm of each sample calcinated at
550 °C to 750 °C is typical of type IV with hysteresis loop of
H1 and narrow pore size distribution. Meanwhile, the XRD
pattern of every sample calcinated at 650 °C and 750 °C shows
three obvious Bragg peaks revealing the long-range order of
the hexagonal mesoporous structure (see Fig. 4), which is also
confirmed by the TEM (transmission electron microscopy)
images (see Fig. 5). However, when the calcination temperature
is above 850 °C, the hysteresis loop of the isotherm of the
sample transfers to type H3 and the pore size distribution
clearly broadens as well as the Bragg peaks of the low angle
XRD pattern of the sample disappear gradually. Thus, the over
high calcination temperature may cause partial collapse of the
mesoporous structure of MCM-41 and lead to the remarkable
decrease of the surface area and pore volume of MCM-41 (see
Table S7 and Fig. 3).
for liquid phase hydrogenation of benzene to cyclohexene
under the conditions of 4.0 MPa and 423 K with the agitation
rate of 800 rpm in a Teflon-lined stainless-steel autoclave using
aqueous ZnSO4 as solvent. The TEM images of Ru/MCM-41
catalyst shown in Fig. 5 indicate that Ru particles disperse on
the surface of MCM-41 uniformly with the particle size of
about 2 nm. The loading of Ru does not disturb the ordered
mesoporous structure of MCM-41.
The effects of the preparation conditions of MCM-41
such as crystallisation temperature, crystallisation time and
crystallisation pH on the catalytic performance of Ru/MCM-41
are discussed. The influence of the crystallisation pH on the
catalytic performance of Ru/MCM-41 is not obvious. The
influences of the crystallisation temperature and crystallisation
time of MCM-41 on the catalytic performance are shown in
Tables 1 and 2. As discussed in the previous section, MCM-41
crystallised at 140 °C for 2 days with crystallisation pH of 10.5
has moderate BET surface area of 569 m2 g–1, larger pore size of
2.5 nm and pore volume of 0.65 cm3 g–1, as well as better long-
range order of hexagonal mesoporous structure. A ruthenium
catalyst supported on this MCM-41 shows higher cyclohexene
selectivity in benzene hydrogenation. The larger the BET
surface area of MCM-41, the more active sites of ruthenium,
which leads to further hydrogenation of the formed cyclohexene
to cyclohexane. Meanwhile, larger pore size and more ordered
mesoporous structure are beneficial to the desorption of the
formed cyclohexene, so as to avoid further hydrogenation to
produce cyclohexane.
Catalytic performance
Ru/MCM-41 catalysts were prepared based on the above
MCM-41 by double solvent impregnation method and tested
The effects of material ratios of MCM-41 on the catalytic
performance of Ru/MCM-41 are shown in Tables 3 to 5.
The MCM-41 with the mole ratio of CTAB to SiO2 of 0.32
has the moderate BET surface area of 501 m2 g–1 and better
long-range-order of hexagonal mesoporous structure. And
the corresponding Ru/MCM-41 gives the best cyclohexene
selectivity (see Table 3). The hydrophilic index of MCM-41
has been improved in a certain degree with the introduction
of Al (see Table S5). Ru based catalyst prepared from stronger
hydrophilic support can be easily surrounded by a stagnant
Fig. 3 N2 adsorption–desorptionisothermsandBJHporesizedistributions
(inset) of MCM‑41 prepared at different calcination temperatures: (a)
550 °C, (b) 650 °C, (c) 750 °C, (d) 850 °C, (e) 900 °C.
Fig. 4 XRD patterns of MCM‑41 prepared at different calcination
temperatures: (a) 550 °C, (b) 650 °C, (c) 750 °C, (d) 850 °C, (e) 900 °C.
Fig. 5 (A) and (B) TEM images of MCM‑41; (C) and (D) TEM images of Ru/
MCM‑41.

JOURNAL OF CHEMICAL RESEARCH 2014 93
water layer, which is favourable for the desorption of the
formed cyclohexene so as to increase the selectivity.22,24 Thus
Ru supported on the MCM-41 with the mole ratio of Al to Si of
0.05 gives the best yield of cyclohexene (see Table 4). The pore
diameter increases and the BET surface area decreases with the
increment of mole ratio of TMB to CTAB. However, the long-
range-order of hexagonal mesoporous structure is destroyed
in a certain degree when the mole ratio of TMB to CTAB
increases to 4:1. Thus Ru supported on the MCM-41 with the
mole ratio of TMB to CTAB of 3:1 gives the highest yield and
selectivity of cyclohexene (see Table 5).
AsshowninTable6,undertheoptimumpreparationconditions
of crystallisation temperature of 140 °C, crystallisation time of
2 days, crystallisation pH value of 10.5, mole ratio of CTAB to
SiO2 of 0.32, mole ratio of Al to Si of 0.05, mole ratio of TMB to
CTAB of 3 and calcination temperature of 750 °C, the prepared
MCM-41 has an ordered hexagonal mesoporous structure with
the BET surface area of 598 m2 g–1, pore size of 5.0 nm and
pore volume of 2.59 cm3 g–1. The corresponding Ru/MCM-41
catalyst exhibits the best result of cyclohexene selectivity of
71.7% and benzene conversion of 44.9%.
Experimental
RuCl3·xH2O (Ru wt%=37.1%) and cyclohexene were purchased
from Shanghai Jiuyue Chemical Industry Corporation Limited.
Benzene, cyclohexane, NaAlO2, ZnSO4·7H2O, TEOs, CTAB, TMB,
ammonia solution (25–28 wt%) and ethanol were purchased from
Tianjin Guangfu Fine Chemical Research Institute. All reagents were
analytical grade. H2 (99.99%) was provided by Zhuzhou Diamond Gas
Company.
Synthesis of MCM-41
Mesoporous molecular sieve MCM-41was prepared by a hydrothermal
synthesis method. Typically, CTAB (1.5 g) was dissolved in the
deionised water (80 g), and a certain amount of TMB was added to the
solution. When the pH was adjusted to the desired value by ammonia
solution (25 wt%), TEOs (5 g) was added slowly to the solution over a
period of 10 min with vigorous stirring and then a certain amount of
NaAlO2 aqueous solution was added dropwise into the formed gel.
The mixture was stirred for 1 h followed by transferring to a Teflon-
lined autoclave for crystallisation. The aged sample was filtered and
washed with deionised water and ethanol. Finally, the sample was
dried at 363 K for 12 h and calcinated for 5 h in air with a heating rate
of 1 K min–1.
Table 1 The effects of crystallisation temperature on catalytic performance
Table 4 The effects of mole ratio of Al to Si on catalytic performance
Selectivity/%
Crystallisation
Selectivity/%
Conversion/%
n
Conversion/%
Al/nSi
temperature/°C
Cyclohexene
Cyclohexane
Cyclohexene
Cyclohexane
100
120
140
160
180
49.5
48.1
43.6
45.6
38.2
26.9
38.0
51.1
42.8
22.9
73.1
62.1
48.9
57.1
77.1
0.2
0.05
0.02
0
45.8
48.0
42.3
38.1
55.0
59.6
61.7
57.2
45.1
40.4
38.3
42.9
Reaction conditions: stirring rate, 800 rpm; PH2 =4.0 MPa; T=423 K; 30 mL
of 0.3 M ZnSO4 aqueous solution; 10 mL of benzene; 0.2 g of catalyst.
Preparation conditions of MCM‑41: crystallisation temperature of 140 °C,
crystallisation time of 2 days, crystallisation pH of 10.5, mole ratio of CTAB
to SiO2 of 0.32, mole ratio of TMB to CTAB of 0 and calcination temperature
of 550 °C.
Reaction conditions: stirring rate, 800 rpm; PH2 =4.0 MPa; T=423 K; 30 mL
of 0.3 M ZnSO4 aqueous solution; 10 mL of benzene; 0.2 g of catalyst.
Preparation conditions of MCM‑41: crystallisation time of 2 days,
crystallisation pH of 10.5, mole ratio of CTAB to SiO2 of 0.16, mole ratio of
Al to Si of 0, mole ratio of TMB to CTAB of 0 and calcination temperature
of 550 °C.
Table 5 The effects of mole ratio of TMB to CTAB on catalytic performance
Table 2 The effects of crystallisation time on catalytic performance
Selectivity/%
Selectivity/%
Crystallisation
n
Conversion/%
TMB/CTAB
Conversion/%
Cyclohexene
Cyclohexane
time /day
Cyclohexene
Cyclohexane
0
48.0
45.6
45.9
47.1
59.6
63.2
66.9
60.1
40.3
36.9
33.1
39.9
0
1
2
5
10
37.6
41.9
43.6
40.6
41.3
46.5
47.3
51.1
60.5
60.8
53.5
52.8
48.9
39.5
39.3
1:1
3:1
4:1
Reaction conditions: stirring rate, 800 rpm; PH2 =4.0 MPa; T=423 K; 30 mL
of 0.3 M ZnSO4 aqueous solution; 10 mL of benzene; 0.2 g of catalyst.
Preparation conditions of MCM‑41: crystallisation temperature of 140 °C,
crystallisation time of 2 days, crystallisation pH of 10.5, mole ratio of CTAB
to SiO2 of 0.32, mole ratio of Al to Si of 0.05 and calcination temperature
of 550 °C.
Reaction conditions: stirring rate, 800 rpm; PH2 =4.0 MPa; T=423 K; 30 mL
of 0.3 M ZnSO4 aqueous solution; 10 mL of benzene; 0.2 g of catalyst.
Preparation conditions of MCM‑41: crystallisation temperature of 140 °C,
crystallisation pH of 10.5, mole ratio of CTAB to SiO2 of 0.16, mole ratio of
Al to Si of 0, mole ratio of TMB to CTAB of 0 and calcination temperature
of 550 °C.
Table 6 The effects of calcination temperature on catalytic performance
Table 3 The effects of mole ratio of CTAB to SiO2 on catalytic performance
Selectivity/%
Calcination
Conversion/%
temperature/°C
Cyclohexene
Cyclohexane
Selectivity/%
n
Conversion/%
CTAB/nSiO
Cyclohexene
Cyclohexane
550
650
750
850
900
45.9
44.5
44.9
35.2
31.9
66.9
65.7
71.7
72.1
35.3
33.1
34.3
28.3
28.0
64.8
2
0.16
0.32
0.65
0.98
43.6
45.8
47.0
41.0
51.1
55.0
51.3
50.5
48.9
45.1
48.6
49.5
Reaction conditions: stirring rate, 800 rpm; PH2 =4.0 MPa; T=423 K; 30 mL
of 0.3 M ZnSO4 aqueous solution; 10 mL of benzene; 0.2 g of catalyst.
Preparation conditions of MCM‑41: crystallisation temperature of 140 °C,
crystallisation time of 2 days, crystallisation pH of 10.5, mole ratio of CTAB to
SiO2 of 0.32, mole ratio of Al to Si of 0.05 and mole ratio of TMB to CTAB of 3.
Reaction conditions: stirring rate, 800 rpm; PH2 =4.0 MPa; T=423 K; 30 mL
of 0.3 M ZnSO4 aqueous solution; 10 mL of benzene; 0.2 g of catalyst.
Preparation conditions of MCM‑41: crystallisation temperature of 140 °C,
crystallisation time of 2 days, crystallisation pH of 10.5, mole ratio of Al to Si
of 0, mole ratio of TMB to CTAB of 0 and calcination temperature of 550 °C.

94 JOURNAL OF CHEMICAL RESEARCH 2014
Catalyst preparation
This work was supported by the NSFC (21276218), program for
New Century Excellent Talents in University (NCET-10-0168),
SRFDP (20124301110007), Project of Scientific Research
Fund of Hunan Provincial Education Department(13k043) and
Project of Hunan Provincial Science & Technology Department
(2012FJ1001).
Ru/MCM-41 catalyst was prepared by double solvent impregnation
method. Typically, MCM-41 (1.0 g) was dispersed in cyclohexane
(24 mL) with stirring for 15 min. 2 mL of aqueous solution containing
0.2696 g of RuCl3·xH2O was added dropwise into the above solution
and stirred for 10 min. After the decantation of the supernatant, the
remaining black solid was dried at 373 K for 12 h, and then reduced at
573 K for 4 h under 40 mL min–1 of 25 vol.% H2/N2.
Received 27 September 2013; accepted 12 December 2013
Paper 1302205 doi: 10.3184/174751914X13892022601610
Published online: 5 February 2014
Catalyst characterisation
Specific surface area, pore volume and pore size distribution of the
samples were obtained by the nitrogen adsorption–desorption on a
Quantachrome NOVA-2200e automated gas sorption system.
XRD patterns were determined under a D/max2500 TC diffractometer
using Cu–Kα radiation (λ=1.542 Å). The tube voltage was 40 kV, the
current was 300 mA, and the scan range was 2θ=5–90° or 0.5–8° with a
scanning rate of 1° min–1.
The microstructures of the samples were observed by TEM on a JEM-
2100 electron microscope working under 200 kV. The samples were
deposited on a copper grid coated with a holey carbon film.
The IR spectra of the samples were measured by FT-IR spectrometer on a
Nicolet-380 spectrometer and the wavenumber range was 4000–400 cm–1.
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The influence of the crystallisation conditions, material ratios
and calcination temperature on the structures of mesoporous
molecular sieve MCM-41 were studied in detail. The prepared
MCM-41sampleswerecharacterisedbyN2 physicaladsorption–
desorption, XRD, TEM, FT-IR, TG-DSC and water/benzene
static adsorption technologies. Ru/MCM-41 catalysts were
then prepared by double solvent impregnation method and
tested in benzene hydrogenation to cyclohexene. It has been
found that the structure characteristics of MCM-41 have great
effects on cyclohexene selectivity in benzene hydrogenation
process. Under the optimum preparation conditions of
crystallisation temperature of 140 °C, crystallisation time of 2
days, crystallisation pH value of 10.5, mole ratio of CTAB to
SiO2 of 0.32, mole ratio of Al to Si of 0.05, mole ratio of TMB to
CTAB of 3 and calcination temperature of 750 °C, the prepared
MCM-41 has ordered hexagonal mesoporous structure with
the BET surface area of 598 m2 g–1, pore size of 5.0 nm and
pore volume of 2.59 cm3 g–1. The corresponding Ru/MCM-41
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