ix
TABLE OF CONTENTS
CHAPTER
1
TITLE
PAGE
TITLE
i
STATEMENT
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
PREFACE
v
ABSTRACT
vii
ABSTRAK
viii
TABLE OF CONTENTS
ix
LIST OF TABLES
xiv
LIST OF FIGURES
xvi
LIST OF SYMBOLS
xxiii
LIST OF APPENDICES
xxv
INTRODUCTION
1.1
Green Chemistry for Sustainable Development
1
1.2
Heterogeneous Catalysts
2
1.3
Research Background and Problem Statement
4
1.4
Research Objectives
6
1.5
Scope of the Study
6
1.6
Outline of the Thesis
7
x
2
EXPERIMENTAL
2.1
2.2
Chemical Analysis of Rice Husk Ash (RHA)
9
2.1.1
Determination of LOI (Loss of Ignition)
9
2.1.2
Determination of Silica
9
Synthesis
of
Materials
Via
Purely
A
Siliceous
Mixed
Si-MCM-48
10
Cationic-Neutral
Templating Route
2.3
Removal of Organic Templates
2.4
Synthesis
of
Aluminated
11
Cubic
Mesoporous
12
Preparation of Protonated Al-MCM-48 (H-Al-
14
Materials (Al-MCM-48)
2.5
MCM-48)
2.6
Charaterization of MCM-48 Molecular Sieves
15
2.6.1
15
Powder X-Ray Diffraction (XRD)
2.6.2 Fourier Transform Infrared Spectroscopy
16
(FTIR)
2.6.3 Magic Angle Spinning Nuclear Magnetic
16
Resonance (MAS NMR)
2.6.4
Nitrogen Adsorption Measurements
2.6.5 Field
Emission
Scanning
17
Electron
18
Microscopy (FESEM)
2.7
2.6.6 Acidity Measurement
18
Catalytic Testing
19
2.7.1 Activation of H-Al-MCM-48
19
2.7.2 Acylation
of
2-Methoxynapthalene
with
21
Acetyl Chloride over H-Al-MCM-48
3
OPTIMIZATION
OF
SYNTHESIS
AND
CHARACTERIZATION OF PURELY SILICEOUS
MESOPOROUS MOLECULAR SIEVES MCM-48
3.1
Introduction
23
xi
3.2
Proposed
Formation
Mechanisms
and
the
26
Evolution of Synthesis Routes for the M41S
Mesoporous Materials
3.3
Synthesis of MCM-48 Materials
29
3.4
Results and Discussion
32
3.4.1 Characterization of Rice Husk Ash (RHA)
32
3.4.2 Synthesis of Purely Siliceous Mesoporous
33
Materials
35
3.4.2.1 Effect of pH Value
Oxide/Silica
40
Surfactant/Silica
44
3.4.2.4 Effect of Water/Silica (H2 O/SiO 2 )
46
3.4.2.2 Effect
of
Sodium
(Na2 O/SiO 2 ) Ratio
3.4.2.3 Effect
of
(Sur/SiO 2 ) Ratio
Ratio
3.5
4
Conclusion
49
QUANTITATIVE
MEASUREMENT
COMPOSITION
OF
CUBIC
OF
MCM-48
PHASE
AND
HEXAGONAL MCM-41 PHASE MIXTURES BY
USING 13 C CP/MAS NMR
5
4.1
Introduction
50
4.2
Results and Discussion
52
4.3
Conclusion
59
TAILORING
THE
ALUMINOSILICATE
Al-MCM-48 MESOPOROUS MOLECULAR SIEVES
AS
CATALYSTS
FOR
FRIEDEL-CRAFTS
REACTION
5.1
Introduction
60
xii
5.2
61
Post-Synthesis Route to Mesoporous Al-MCM-48
Materials
5.3
Results and discussion
62
5.3.1 Post-Synthesis Alumination of Mesoporous
62
Si-MCM-48
5.3.2 Post-Synthesis Alumination of Si-MCM-48
73
Mesophase
5.3.3
5.4
6
Proposed Mechanism
84
Conclusion
CATALYTIC
87
ACTIVITY
OF
ALUMINATED
MCM-48 MOLECULAR SIEVES IN THE FRIEDELCRAFTS
ACYLATION
2-METHOXYNAPHTHALENE
OF
WITH
ACETYL
CHLORIDE
6.1 Introduction
88
6.2 Generation of Active Sites in Al-MCM-48
89
6.3 Characterizationof Acidity
93
6.4 Friedel-Crafts Acylation
94
6.5 Results and Discussion
97
6.5.1
Characterization of Acidity of Al-MCM-48
97
6.5.1.1 Temperature-Programmed
97
Desorption
of
Ammonia
(NH3 -
TPD)
6.5.1.2 Infrared
Spectroscopy
(IR)
of
100
with
109
Adsorbed Pyridine
6.5.2 Acylation
of
2-Methoxynapthalene
Acetyl Chloride
6.6
6.5.2.1 The Effect of Various Catalysts
111
6.5.2.2 The Effect of Solvent
114
Conclusion
120
xiii
7
GENERAL CONCLUSION AND
RECOMMENDATIONS
7.1
Main Results
121
7.2
Recommendations
124
REFERENCES
125
APPENDICES
141
xiv
LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Summary of synthesis conditions for Si-MCM-48 materials.
12
2.2
Sample codes for Al-MCM-48 with different concentration
13
of sodium aluminate prepared by post-synthesis alumination
of mesoporous Si-MCM-48.
2.3
Sample codes for Al-MCM-48 with different Si/Al ratio
14
prepared by post synthesis alumination of Si-MCM-48
mesophase.
3.1
Surfactant packing parameter g, expected structure and
31
examples for such structures.
5.1
Unit cell parameters of Al-MCM-48 prepared from the
66
purely siliceous Si-MCM-48 with different concentrations of
NaAlO 2 aqueous solution. The unit cell parameter has been
calculated from the interplanar spacing using the formula
ao =d211 √6.
5.2
Sorption properties of the parent Si-MCM-48 and the
aluminated samples prepared via post-synthesis alumination
of mesoporous Si-MCM-48.
73
xv
5.3
Unit cell parameters of Si-MCM-48 and Al-MCM-48
prepared from post-synthesis alumination.
75
The unit cell
parameter has been calculated from the interplanar spacing
using the formula ao =d211 √6.
5.4
Sorption properties of Si-MCM-48 and Al-MCM-48.
82
6.1
Total acid amount of H-Al-MCM-48 materials determined by
100
NH3 -TPD.
6.2
Number of Brönsted and Lewis acid sites in the samples.
110
6.3
GC Data for the Acylation Products.
111
6.4
Catalytic Activities of Various Catalysts for the Acylation of
112
2-Methoxynaphthalene with Acetyl Chloride.
xvi
LIST OF FIGURES
TITLE
FIGURE NO.
1.1
Development
of
publications
PAGE
on
ordered
mesoporous
3
materials since 1990.
1.2
Flowchart of the research design.
8
2.1
Experimental setup for acidity study .
20
2.2
GC-FID and GC-MS oven-programme setup.
21
3.1
Schematic structural illustrations of M41S family (a)
24
hexagonal MCM-41; (b) cubic MCM-48; (c) lamellar
MCM-50.
3.2
Schematic
of
possible
mechanistic
pathways
for
the
26
formation of MCM-41: (1) Liquid crystal phase initiated
and (2) silicate anion initiated.
3.3
Schematic diagram of the transformation mechanism from
27
lamellar to hexagonal mesophase.
3.4
Schematic showing of interfacial interactions for surfactant
28
micelles in cooperatively assembly.
3.5
Illustration of the regions of generic surfactant.
30
xvii
3.6
XRD diffractogram of RHA obtained from an open burning
34
site.
3.7
FTIR spectrum of RHA obtained from open burning site.
34
3.8
XRD diffractograms of (a) as-synthesized mesoporous
37
materials; (b) calcined mesoporous materials with various
pH value.
3.9
XRD diffractograms of (a) as-synthesized mesoporous
41
materials; (b) calcined mesoporous materials with various
Na2 O/SiO 2 ratios.
3.10
XRD diffractograms of (a) as-synthesized mesoporous
45
materials; (b) calcined mesoporous materials with various
Sur/SiO 2 ratios.
3.11
XRD diffractograms of (a) as-synthesized mesoporous
47
materials; (b) calcined mesoporous materials with various
H2 O/SiO 2 ratios.
4.1
X-ray diffraction (XRD) patterns of mesophases MCM-48
53
and/or MCM-41 prepared by difference of the Na2 O/SiO 2
ratio; (a) 0.20, (b) 0.25, (c) 0.30, (d) 0.35 and (e) 0.40.
XRD pattern (f) was obtained by mixing samples (a) and
(e) with the composition of 50:50.
4.2
13
C CP/MAS NMR spectra of mesophases MCM-48 and/or
MCM-41 prepared with various Na2 O/SiO 2 ratios; (a) 0.20,
(b) 0.25, (c) 0.30, (d) 0.35 and (e) 0.40. A contact time of 1
ms was applied.
55
xviii
4.3
Integrated intensity ratio of the C5 –C14 and C1 peaks
56
(normalized to percentage of mesophases MCM-48 and
MCM-41), calculated from Figure 4.2, of MCM-48 and/or
MCM-41 prepared with various Na2 O/SiO 2 ratios; (a) 0.20,
(b) 0.25, (c) 0.30, (d) 0.35 and (e) 0.40.
4.4
X-Ray diffraction (XRD) patterns of mesoporous (a)
57
MCM-48 and (b) MCM-41 after reinsertion of CTABr.
4.5
13
C CP/MAS NMR spectra of mesoporous (a) MCM-48
58
and (b) MCM-41 after reinsertion of CTABr. A contact
time of 1 ms was applied.
5.1
XRD patterns of the parent Si-MCM-48 and its aluminated
samples
through
secondary
synthesis
with
63
different
concentrations of NaAlO 2.
5.2
Mechanism of post-synthesis alumination of mesoporous
65
MCM-41.
5.3
FTIR spectra of the parent and samples prepared via postsynthesis
of
mesoporous
Si-MCM-48
with
67
different
concentrations of NaAlO 2 ; (a) purely siliceous Si-MCM-48
(MP-5), (b) 0.10 M, (c) 0.25 M, and (d) 0.50 M.
5.4
27
Al MAS NMR spectra of Al-MCM-48 prepared via post-
68
synthesis alumination of mesoporous Si-MCM-48 with
different concentrations of NaAlO 2.
5.5
N2 adsorption-desorption isotherms and its BJH pore size
distribution curve (inset) of the parent Si-MCM-48 and its
aluminated samples through post-synthesis alumination of
mesoporous Si-MCM-48 with different concentrations of
NaAlO 2 ; (a) purely siliceous Si-MCM-48 (MP-5),
70
xix
(b) 0.10M, (c) 0.25 M, and (d) 0.50 M.
5.6
The α s plots of (a) Si-MCM-48, (b) 010Al-MCM-48, (c)
72
025Al-MCM-48, and (d) 050Al-MCM-48.
5.7
XRD patterns of the (a) as-synthesized and (b) calcined Al-
74
MCM-48 via post-synthesis alumination.
5.8
FTIR spectra of aluminosilicates Al-MCM-48 samples
77
prepared by post-synthesis alumination with various Si/Al
ratios; (a) 20, (b) 30, (c) 50, and (d) 100.
5.9
27
Al MAS NMR spectra of the calcined aluminosilicate Al-
78
MCM-48 samples prepared by post-synthesis alumination
with various Si/Al ratios; (a) 20, (b) 30, (c) 50, and (d) 100.
5.10
N2 adsorption-desorption isotherms and their corresponding
79
pore size distribution curve (inset) of aluminosilicate AlMCM-48 samples prepared by post-synthesis alumination
with various Si/Al ratios; (a) 20, (b) 30, (c) 50, and (d) 100.
5.11
The α s plots of aluminosilicate Al-MCM-48 samples
81
prepared through post-synthesis alumination with different
Si/Al ratios; (a) 20, (b) 30, (c) 50, and (d) 100.
5.12
FESEM micrograph of Si-MCM-48.
83
5.13
FESEM micrograph of Al-MCM-48-50.
83
5.14
Proposed
85
mechanism
of
post-synthesis alumination of
Si-MCM-48 mesophase.
5.15
Schematic
illustration
secondary mesopores.
of
formation
mechanism
of
86
xx
6.1
(a) Framework of Si-MCM-48, and (b) Framework of
90
Al-MCM-48.
6.2
Generation of Brönsted acid sites.
91
6.3
Generation of Lewis acid sites; (a) Lewis acidity due to
92
framework tricoordinated aluminium, and (b) Lewis acidity
associated with both octahedral and tetrahedral EFAL.
6.4
Mechanism of acylation of aromatics in the presence of
95
aluminium chloride.
6.5
The active positions of 2-methoxynaphthalene.
97
6.6
NH3 -TPD spectra of samples prepared through post-
98
synthesis alumination of Si-MCM-48 mesoporous materials
with different concentration of NaAlO 2 .
6.7
NH3 -TPD spectra of samples prepared through post-
99
synthesis alumination of Si-MCM-48 mesophase with
different Si/Al gel ratios.
6.8
FTIR spectra in the hydroxyl region of (a) Si-MCM-48, (b)
102
010AlMCM-48, (c) 025AlMCM-48, and (d) 050AlMCM48 recorded at 400 o C under 10-5 mbar pressure.
6.9
FTIR spectra in the hydroxyl region of (a) Si-MCM-48, (b)
103
Al-MCM-48-20, (c) Al-MCM-48-30, (d) Al-MCM-48-50,
and (e) Al-MCM-48-100 recorded at 400 o C under 10-5
mbar pressure.
6.10
FTIR spectra in the hydroxyl region after pyridine
desorption at 150 o C; (a) Si-MCM-48, (b) 010Al-MCM-48,
(c) 025Al-MCM-48, and (d) 050Al-MCM-48.
104
xxi
6.11
FTIR
spectra
in
the
hydroxyl region after pyridine
105
desorption at 150 o C (a) Si-MCM-48, (b) Al-MCM-48-20,
(c)
Al-MCM-48-30,
(d)
Al-MCM-48-50,
and
(e) Al-MCM-48-100.
6.12
Structures showing interaction of (a) silanols with Lewis
106
acid sites and (b) Al-OH groups by H-bonding (represented
by arrows).
6.13
FTIR spectra of adsorbed pyridine on Si-MCM-48 and
samples
prepared
through
post-synthesis
107
alumination
mesoporous Si-MCM-48 evacuated at 25 o C, 150 o C, 250
o
C, and 400
o
C. (H, Hydrogen bonded pyridine; B,
Brönsted bound pyridine; L, Lewis bound pyridine).
6.14
FTIR spectra of adsorbed pyridine on samples prepared
108
through post-synthesis alumination Si-MCM-48 mesophase
evacuated at 25 o C, 150 o C, 250 o C, and 400 o C. (H,
Hydrogen bonded pyridine; B, Brönsted bound pyridine; L,
Lewis bound pyridine).
6.15
Effect of solvents on conversion of 2-methoxynaphthalene
116
over Al-MCM-48-20.
6.16
Effect of solvents on selectivity of the products from
116
acylation of 2-methoxynaphthalene over Al-MCM-48-20
catalyst.
6.17
Products of acylation of 2-methoxynaphthalene catalysed
117
by H-Al-MCM-48.
6.18
Proposed
mechanism
of
the
Acylation
of
2-methoxynaphthalene with acetyl chloride over Brönsted
acid sites in Al-MCM-48.
118
xxii
6.19
Proposed
mechanism
of
the
acylation
of
2-methoxynaphthalene with acetyl chloride over Lewis
acid sites in Al-MCM-48.
119
xxiii
LIST OF SYMBOLS
RHA
rice husk ash
LOI
loss of ignition
L
litre
mL
millilitre
o
Celsius
C
K
Kelvin
g
gram
min
minute
h
hour
MCM
Mobile Composition Material
M
molar
Si/Al
silicon-to-aluminium ratio
Si-MCM-48
purely siliceous MCM-48
Al-MCM-48
aluminosilicate MCM-48
XRD
X-Ray diffraction
FTIR
Fourier Transform Infrared
27
Al MAS NMR
27
Al magic-angle-spinning nuclear-magnetic-resonance
C CP/MAS NMR
13
C cross-polarization magic-angle-spinning nuclear-
13
magnetic-resonance
TPD
temperature-programmed desorption
FESEM
field emission scanning electron microscopy
d
inter-planar spacing
Cu-Kα
X-ray diffraction from copper Kα energy levels
λ
wavelength
kV
kilovolt
mA
milliampere
2θ
Braggs angle
xxiv
KBr
kalium bromide
TMS
tetramethylsilane
s
second
Hz
Hertz
CaF2
calcium fluoride
I.D.
internal diameter
GC
gas chromatrography
GC-MS
gas chromatrograpy-mass spectrometry
FID
flame ionization detector
IUPAC
International Union of Pure and Applied Chemistry
AlO 4
aluminate, framework aluminium in zeolite
SiO 4
siliceous; framework silicon in zeolite
TEM
transmission electron microscopy
LCT
liquid crystal templating
g
surfactant packing parameter
BET
Brunauer, Emmett and Teller
Si-OH
silanol group
EFAL
extra framework aluminium
ao
unit cell parameter
N2
nitrogen
P/P o
relative pressure; obtained by forming the ratio of the
equilibrium pressure and the vapor pressure Po of the
adsorbate at the temperature where the isotherm is
measured.
PSD
pore size distribution
BJH
Barrett, Joyner and Halenda
αs
alfa-S
Rt
retention time
TON
turnover number
ms
millisecond
xxv
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Calculation of the amount of pyridine adsorbed on
141
the sample in the acidity study of secondary
aluminated Al-MCM-48 samples.
B
Quantitative gas chromatography calibration plot
142
of 2-methoxynaphthalene by using naphthalene as
internal standard.
C
Calculation of % conversion, % selectivity, and
143
turnover number (TON).
D
An example of chromatogram for liquid products
of
conversion
of
2-metoxynaphthalene
144
in
nitrobenzene.
E
An example of chromatogram for liquid products
of
conversion
of
2-metoxynaphthalene
145
in
dichloroethane.
F
An example of chromatogram for liquid products
of
conversion
cyclohexane.
of
2-metoxynaphthalene
in
146
xxvi
G
Mass
spectra
of
methoxynaphthalene
and
(a)
(b)
2-acetyl-6-
147
1-acetyl-7-
methoxynaphthalene.
H
Quantitative calculation of phase composition via
integrated intensity ratio of the C5 –C14 and C1
peaks
of
mesophases.
13
C
CP/MAS
NMR
spectra
of
148