synthesis and characterization of sulphated almcm-41...

SYNTHESIS AND CHARACTERIZATION OF SULPHATED AlMCM-41 AND

ITS CATALYTIC ACTIVITY IN DIBENZOYLATION OF BIPHENYL WITH

BENZOYL CHLORIDE

NG ENG POH

UNIVERSITI TEKNOLOGI MALAYSIA

SYNTHESIS AND CHARACTERIZATION OF SULPHATED AlMCM-41 AND

ITS CATALYTIC ACTIVITY IN DIBENZOYLATION OF BIPHENYL WITH

BENZOYL CHLORIDE

NG ENG POH

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Master of Science (Chemistry)

Faculty of Science

Universiti Teknologi Malaysia

MARCH 2006

iii

For the Lord God Almighty,

My beloved family

And

My best friends

iv

ACKNOWLEDGEMENT

To God be all the glory! Halleluyah! All praise, glory and thanks give to

Almighty God for His amazing grace and merciful that supported and led me

throughout the whole process of completing this research.

I would like to take this opportunity to express my appreciation to my

beloved supervisor, Prof. Dr. Halimaton bt. Hamdan who introduced me to the field

of mesomorphous materials. Her guidance, help, experience, advice and support

throughout this research is greatly appreciated. Heartfelt thanks also to my all

beloved lecturers especially, Dr. Hadi Nur who had given me worthy advices,

valuable suggestions and constructive discussions during conducting this research. Special thanks also go to Mr. Lim Kheng Wei for helping me to carry out the

27Al MAS NMR measurements. My special thanks also go to all the colleagues of

Zeolite and Porous Materials Group (ZPMG) for their help and support throughout

my project. I would like to extend my appreciation to the laboratory assistant, Pn.

Mek Zum, En. Azmi, Pn. Mariam and the other laboratory assistants for the help

offered to me. Last but not least, I would like to thank my parents and my friends

especially Daniel Lim for their support and caring.

v

PREFACE

This thesis is the result of my work carried out in the Department of Chemistry,

Universiti Teknologi Malaysia between Jun 2002 to September 2004 under the

supervision of Prof. Dr. Halimaton Handan. Part of my work described in this thesis

has been reported in the following publications:

1. Ng Eng Poh, Hadi Nur, Mohd Nazlan Mohd Muhid and Halimaton Hamdan,

(2005). “Sulphated AlMCM-41: Mesoporous Solid Brönsted Acid Catalyst

for Dibenzoylation of Biphenyl”, Catalysis Today (Accepted).

2. Ng Eng Poh and Halimaton Hamdan, (2005). “Structural Properties and

Surface Acidity Characterization of Sulphated AlMCM-41”, Poster

Presentation in International Science Congress (ISC), Putra World Trade

Centre, Kuala Lumpur Malaysia.

vi

ABSTRACT

Benzoylation of biphenyl with benzoyl chloride is an important acylation

reaction, producing monosubstituted product, 4-phenyl benzophenone (4-PBP) and

disubstituted product, 4, 4’- dibenzoylbiphenyl (4, 4’-DBBP). 4, 4’-DBBP is a

monomer used as a component in emitting layer in polymer light emitting (PLED)

devices. The objective of this study is to synthesize and characterize a highly active

sulphated AlMCM-41 acid catalyst by enhancing its acidity through sulphation.

Firstly, the AlMCM-41 with various SiO2/Al2O3 ratios was prepared by direct

synthesis, followed by conversion to H-AlMCM-41 via ion exchange of NaAlMCM-

41 with ammonium nitrate. Finally, sulphated AlMCM-41 was prepared by

impregnation of sulphuric acid in toluene. The sulphated MCM-41 materials possess

high surface area (>500 m2/g) and large quantities of Brönsted acid sites after

characterizing with surface analyzer and pyridine infrared spectroscopy. 27Al MAS

NMR indicates the presence of octahedrally coordinated extra-framework sulphated

aluminiums (EFAL) and aluminium sulphate. The Hammett indicators show that the

acid strength of the sulphated AlMCM-41 materials was stronger than sulphuric acid

and H-AlMCM-41 because of sulphate groups attached to aluminium atom in

sulphated AlMCM-41. The results of comparative study on the dibenzoylation of

biphenyl reaction indicate that only sulphated AlMCM-41 gives both

monosubstituted 4-PBP and disubstituted 4, 4’-DBBP with the highest activity

compared to sulphuric acid, H-AlMCM-41 and sulphated amorphous silica.

vii

ABSTRAK

Benzoilasi bifenil dengan benzoil klorida merupakan tindak balas pengasilan

yang penting, menghasilkan hasil penukargantian mono, 4-fenil benzofenon (4-PBP)

dan hasil penukargantian dwi, 4, 4’- dibenzoilbifenil (4, 4’-DBBP). 4, 4’-DBBP

merupakan monomer yang digunakan dalam lapisan pemancaran dalam peranti

pemancar cahaya polimer (PLED). Objektif kajian ini adalah untuk meningkatkan

keasidan mangkin yang digunakan dalam tindak balas pemangkinan dwibenzoilasi

bifenil melalui modifikasi H-AlMCM-41. AlMCM-41 dengan nisbah SiO2/Al2O3

disintesiskan melalui kaedah sintesis secara langsung, diikuti dengan menukarkannya

kepada bentuk H-AlMCM-41 melalui penukaran ion menggunakan ammonium

nitrat. Akhirnya, AlMCM-41 tersulfat disediakan melalui kaedah pengisitepuan

dengan asid sulfurik dalam toluena. Mangkin AlMCM-41 tersulfat mempunyai luas

permukaan yang tinggi (>500 m2/g) dan kuantiti tapak asid Brönsted yang banyak

selepas dicirikan dengan penganalisis permukaan dan spektroskopi inframerah

piridina. 27Al MAS NMR menunjukkan kehadiran Al tersulfat luar bingkaian yang

berkoordinatan oktahedra dan aluminium sulfat. Penunjuk Hammett menunjukkan

bahan MCM-41 tersulfat mempunyai kekuatan asid yang lebih tinggi daripada asid

sulfurik dan H-AlMCM-41. Keputusan tindak balas dwibenzoilasi bifenil

menunjukkan bahawa hanya AlMCM-41 tersulfat memberikan hasil penukargantian

mono (4-PBP) dan dwi (4, 4’-DBBP) dengan keaktifan tertinggi berbanding dengan

asid sulfurik, H-AlMCM-41 dan silika amorfus tersulfat.

viii

TABLE OF CONTENTS

CHAPTER

TITLE

TITLE

DECLARATION

DEDICATION

ACKNOWLEDGEMENT

PREFACE

ABSTRACT

ABSTRAK

TABLE OF CONTENT

LIST OF TABLES

LIST OF FIGURES

LIST OF SYMBOLS AND ABBREVIATIONS

LIST OF APPENDICES

PAGE

ii

iii

iv

v

vi

vii

viiii

ix

xii

xv

xviii

1 INTRODUCTION

1.1 Research Background and Problem Statement

1.2 Objectives of Research

1.3 Research Strategies

1.4 Scope of the Research

1

4

4

4

2 LITERATURE REVIEW

2.1 The Importance of Solid Catalyst

2.2 Solid catalysts - Introduction to M41S family

6

7

ix

2.3 Generation of Active Sites in AlMCM-41

Mesoporous Materials

2.4 Generation of acid sites via sulphation

2.5 Friedel-Crafts Reactions and Solid Catalysts

10

12

14

3 EXPERIMENTAL

3.1 Starting Materials

3.2 Preparation of AlMCM-41

3.3 Preparation of Protonated MCM-41

(H-AlMCM-41)

3.4 Synthesis of Sulphated AlMCM-41

3.5 Characterization of MCM-41 Materials

3.5.1 X-ray Powder Diffraction (XRD)

3.5.2 Fourier Transform Infrared Spectroscopy

(FTIR)

3.5.3 Solid State Magic Angle Spinning

Nuclear Magnetic Resonance (MAS

NMR) Spectroscopy

3.5.4 Thermogravimetric and Differential

Thermal Analysis (TG-DTA)

3.5.5 Nitrogen Adsorption-Desorption

Isotherm Analysis

3.5.6 Fourier Transform Infrared

Spectroscopy of Pyridine Adsorption

3.5.7 Hammett Acidity Analysis

3.6 Dibenzoylation of Biphenyl Reaction over

Sulphated AlMCM-41

3.6.1 Dibenzoylation of Biphenyl Reaction

over Various Types of Catalysts

3.6.2 Synthesis of 4-PBP as authentic sample

3.6.3 Synthesis of 4, 4’-DBBP as authentic

Sample

15

15

16

17

17

17

18

19

21

22

23

26

26

28

28

29

x

3.6.4 Calibration Curve for Authentic Sample 29

4 RESULTS AND DISCUSSION

4.1 X-Ray Diffraction Analysis

4.2 Infrared Spectroscopy of AlMCM-41

Molecular Sieves

4.3 Nitrogen Adsorption Measurement

4.4 Thermal Analysis

4.5 Solid State 27Al MAS NMR

4.6 Solid State 29Si MAS NMR

4.7 Acidity Measurements

4.7.1 Pyridine-FTIR Spectroscopy

4.7.2 Hammett indication Analysis

4.8 Catalytic testing: Dibenzoylation of

Biphenyl

4.8.1 Effect of Catalyst

4.8.2 Effect of SiO2/Al2O3 ratio

4.8.3 Reaction Temperature

4.8.4 Effect of Catalyst Loading

4.8.5 Effect of Benzoyl Chloride : Biphenyl

Mole Ratio

4.9 Mechanism

4.10 Mass balance of Dibenzoylation of Biphenyl

with Benzoyl Chloride

4.11 Proposed Structure

32

36

38

40

43

47

49

49

53

55

55

58

59

60

62

63

66

68

5 CONCLUSIONS

5.1 Conclusions

69

REFERENCES 71

APPENDICES 77

xi

LIST OF TABLES

NO. TABLE TITLE PAGES

2.1 Comparison of the various phases of catalysts. 7

3.1 Amount of NaAlO2 added in preparing AlMCM-41. 16

3.2 The organic compounds used as Hammett Indicators. 26

3.3 GC-FID oven-programmed setup for identifying 4, 4’-DBBP. 27

3.4 GC-MSD oven-programmed setup for identifying 4, 4’-DBBP. 28

4.1 XRD data of various MCM-41 samples. 33

4.2 The textural properties of various protonated and sulphated

MCM-41 samples obtained form calculation and surface

analyzer.

39

4.3 Peak areas of octahedral aluminium (Aloct) and tetrahedral

aluminium (Altet) from 27Al MAS NMR spectra

45

4.4 Peak areas of octahedral aluminium species in aluminium

sulphate (AlAl2(SO4)3) and sulphated AlMCM-41 (AlSulphated

AlMCM-41) from 27Al MAS NMR spectra.

45

4.5 Peak areas of silicon species in SCAL-4 48

4.6 Pyridine FTIR data of protonated and sulphated MCM-41

materials.

52

4.7 The results of acid strength of catalysts using Hammett

indicators.

54

4.8 Benzoylation and dibenzoylation of biphenyl with benzoyl

chloride over various types of catalysts at 180 oC for 24 h.

57

4.9 Amount of Brönsted acid active sites in SCAL-4 with different

loading and and its effect towards conversion of biphenyl.

61

4.10 Theoretical mass balance 67

4.11 Experimental mass balance 67

xii

LIST OF FIGURES

NO. FIGURE TITLE PAGES

1.1 Two proposed reaction routes: (Route1) direct and (Route 2)

consecutive synthesis of the dibenzoylation of biphenyl using

sulphated AlMCM-41 mesoporous materials and benzoyl chloride.

3

1.2 Flow diagram of research strategies. 5

2.1 Illustration of hexagonal honeycomb structure of mesoporous

MCM-41 with 2 nm to 10 nm pore size.

9

2.2 Formation of MCM-41 materials. (a) Coagulation of surfactants

process, (b) Combination of organic and inorganic materials, (c)

MCM-41.

9

2.3 Framework of (a) SiMCM-41 and (b) AlMCM-41. 10

2.4 Generation of Brönsted acid sites. 11

2.5 Generation of Lewis acid sites. 12

2.6 Benzoylation of an aromatic compound using aluminium

trichloride as catalyst, leading to a stable Lewis complex.

13

2.7 Friedel-Crafts acylation showing a typical starting materials,

products and waste mass balance.

14

3.1 Range of 29Si chemical shifts of Qn in solid silicate. 21

3.2 Proposed mechanism of interaction between pyridine molecules

with (a) Brönsted and (b) Lewis acid sites in MCM-41 molecular

sieves.

24

3.3 Adsorption and desorption of pyridine apparatus for acidity study. 25

3.4 Quantitative calibration plot of biphenyl. 30

3.5 Quantitative calibration plot of 4-PBP. 30

3.6 Quantitative calibration plot of 4, 4’-DBBP. 31

xiii

4.1 X-ray diffractogram patterns of uncalcined mesoporous MCM-41

molecular sieves. (a) UNCAL-1, (b) UNCAL-2, (c) UNCAL-3

and (d) UNCAL-4.

34

4.2 X-ray diffractogram patterns of mesoporous MCM-41 materials

after calcinations at 550 oC for 10 h. (a) CAL-1, (b) CAL-2, (c)

CAL-3 and (d) CAL-4.

34

4.3 X-ray diffractogram patterns of protonated MCM-41 materials

after ion exchange with NH4NO3 and calcination at 500 oC (a)

HCAL-1, (b) HCAL-2, (c) HCAL-3 and (d) HCAL-4.

35

4.4 X-ray diffractogram patterns of sulphated MCM-41 materials (a)

SCAL-1, (b) SCAL-2, (c) SCAL-3 and (d) SCAL-4.

35

4.5 FTIR spectra of uncalcined mesoporous MCM-41 molecular

sieves.

37

4.6 FTIR spectra of calcined mesoporous MCM-41 molecular sieves. 37

4.7 FTIR spectra of sulphated mesoporous MCM-41 molecular sieves. 38

4.8 Modification of surface of MCM-41 through sulphation leads to

shrinkage of pore diameter.

39

4.9 Thermogravimetric analysis of uncalcined MCM-41 sample

(UNCAL-2) in nitrogen gas with 20 oC/min heating rate.

40

4.10 Thermogravimetric analysis of uncalcined MCM-41 samples with

various ratio of SiO2/Al2O3.

41

4.11 Thermograms of a series of protonated MCM-41 molecular sieves. 42

4.12 Thermogravimetric curves of sulphated AlMCM-41 materials. 43

4.13 27Al NMR spectra of protonated MCM-41 molecular sieves (a)

HCAL-4, (b) HCAL-3, (c) HCAL-2 and (d) HCAL-1.

44

4.14 27Al NMR spectra of sulphated MCM-41 molecular sieves (a)

SCAL-4, (b) SCAL-3, (c) SCAL-2 and (d) SCAL-1.

44

4.15 29Si NMR spectrum of sulphated MCM-41 molecular sieves

(SCAL-4).

48

4.16 The possible silicon species and Brönsted acid sites in sulphated

AlMCM-41.

49

4.17 The pyridine-FTIR spectra of purely siliceous sulphated MCM-41

(SCAL-1) at (a) room temperature, (b) 150 oC, (c) 250 oC and (d)

50

xiv

350 oC.

4.18 The pyridine-FTIR spectra of sulphated AlMCM-41 (SCAL-2) at

(a) room temperature, (b) 150 oC, (c) 250 oC and (d) 350 oC .

51



51



52

4.21 FTIR spectra of silanol groups of MCM-41 materials at 250 oC (a)

before treatment (HCAL-1) and (b) after treatment (SCAL-1) of

sulphuric acid.

53

4.22 Dibenzoylation of biphenyl catalyzed by various types of catalysts 57

4.23 Conversion of biphenyl over various ratio of SiO2/Al2O3 within 24

h.

58

4.24 Yield of 4, 4’-DBBP over various ratio of SiO2/Al2O3 within 24 h. 59

4.25 Temperature effect towards dibenzoylation of biphenyl over

SCAL-4.

60

4.26 Effect of catalyst loading towards dibenzoylation of biphenyl over

SCAL-4.

61

4.27 Effect of Biphenyl : Benzoyl Chloride molar ratio towards

dibenzoylation of biphenyl over SCAL-4.

62

4.28 Mechanism of how the electron density affects BP and 4-PBP in

attacking benzoylium ion.

63

4.29 Formation of 4-phenyl benzophenone (4-PBP) via electrophilic

substitution.

64

4.30 Mechanism of production of 4, 4’-dibenzoyl biphenyl (4, 4’-

DBBP).

65

4.31 Stoichiometrical chemical equation of dibenzoylation of biphenyl

reaction.

66

4.32 Hydrolysis of benzoyl chloride as side reaction in production of

benzoic acid and benzoic anhydrice.

68

4.33 Scheme proposed for the sulphated AlMCM-41 materials showing

possible Brönsted acid sites.

68

xv

LIST OF SYMBOL AND ABBREVIATIONS

MCM-41 - Mobile Crystalline Material-41

RHA - Rice husk ash

Py - Pyridine

i.e. - Id est (that is)

BET - Brunauer-Emmett-Teller

GC - Gas chromatography

Å - Angstrom (10-10 meters)

kV - Kilovolts

α - Alpha

β - Beta

PDPV - Poly (4, 4’-diphenylene diphenylvinylene)

LED - Light emitting devices

IUPAC - International Union of Pure Applied Chemistry

LCT - Liquid-crystal templating

n - Diffraction order from n = 1, 2, 3, ….

d - Distance

2D - Two dimensions

λ - Lambda

θ - Theta

δ - Delta

FTIR - Fourier transform infrared

NMR - Nuclear magnetic resonance

MAS - Magic angle spinning

CP - Cross polarization

EFAL - Extra-framework aluminium

ppm - Part per million

xvi

% - Percent

~ - Approximately

TG/DTA - Thermogravimetric and Differential Thermal Analysis

TGA - Thermogravimetric Analysis

DTA - Differential Thermal Analysis

Ho - Hammett acidity function

µL - Microlitre

MS - Mass spectrometry

GC-MS - Gas chromatography combined with mass

spectrometry

4-PBP - 4-Phenyl benzophenone

4, 4’-DBBP - 4, 4’-dibenzoylbiphenyl

CTABr - Cetyltrimethylammonium bromide

NH4OH - Ammonium hydroxide

min - Minute oC - Celsius

h - Hour

wt% - Weight percent

g - Gram

mg - milligram

SiO2/Al2O3 - Silica over alumina ratio

mol - Mole

mmol - Millimole

m.p. - Melting point

mA - Milliampere o - Degree

cm-1 - Per centimeter

UNCAL-1 - Uncalcined MCM-41 with SiO2/Al2O3 ratio ∞

UNCAL-2 - Uncalcined AlMCM-41 with SiO2/Al2O3 ratio 60



CAL-1 - Calcined MCM-41 with SiO2/Al2O3 ratio ∞

CAL-2 - Calcined AlMCM-41 with SiO2/Al2O3 ratio 60

xvii



HCAL-1 - Protonated MCM-41 with SiO2/Al2O3 ratio ∞

HCAL-2 - Protonated AlMCM-41 with SiO2/Al2O3 ratio 60



SCAL-1 - Sulphated MCM-41 with SiO2/Al2O3 ratio ∞

SCAL-2 - Sulphated AlMCM-41 with SiO2/Al2O3 ratio 60



MHz - Megahertz

µs - Microsecond

TMS - Tetramethyl silane

BJH - Barrett, Joyner, Halenda

mbar - millibar

kPa - Kilopascal

m/z - Mass over charge

ao - Unit cell parameters

t - Crystallite size

Wd - Pore diameter

bd - Pore wall thickness

xviii

LIST OF APPENDICES

APPENDICES TITLE PAGES

A Calculation of the amount of pyridine adsorbed on the sample in

the acidity study of sulphated AlMCM-41 samples.

77

B Infrared spectrum of 4-phenyl benzophenone (4-PBP). 78

C Mass spectrum of 4-phenyl benzophenone (4-PBP). 79

D Infrared spectrum of 4, 4’-dibenzoyl biphenyl (4, 4’-DBBP). 80

E Mass spectrum of 4, 4’-dibenzoyl biphenyl (4, 4’-DBBP). 81

F Calculation of % conversion and % selectivity. 82

G The pyridine-FTIR spectra of HCAL-1 at (a) room temperature,

(b) 150 oC, (c) 250 oC and (d) 350 oC.

83

H The pyridine-FTIR spectra of HCAL-2 at (a) room temperature,

(b) 150 oC, (c) 250 oC and (d) 350 oC.

84

I The pyridine-FTIR spectra of HCAL-3 at (a) room temperature,

(b) 150 oC, (c) 250 oC and (d) 350 oC.

85

J The pyridine-FTIR spectra of HCAL-4 at (a) room temperature,

(b) 150 oC, (c) 250 oC and (d) 350 oC.

86

K Chromatogram of reactants at 0 h. 87

L Chromatogram of reactants and products. 88

M Data obtained from GC-FID Chromatograms (Friedel-Crafts dibenzoylation of biphenyl with benzoyl chloride over SCAL-4).

89

N Mass balance of dibenzoylation of biphenyl with benzoyl chloride (Experimental)

90

O Mass balance of dibenzoylation of biphenyl with benzoyl chloride (Theoretical)

98

1

CHAPTER 1

INTRODUCTION

1.1 Research Background and Problem Statement

Catalyst is defined as a substance that increases the rate of reaction without

being appreciably consumed in the process [1]. Catalyst increases the reaction rate by

offering other route of reaction with lower activation energy of the reaction system.

There are many chemical reactions which need this substance in order to enhance the

reaction rate. The presence of this substance is essential not only for enhancing

reaction rate but also decreasing energy consumption and minimizing the waste

production.

Today, catalysts play a vital role in the chemical industries, with a total

contribution of ~20% of world GNP [2]. Apart from that, there are approximately

80% of the industrial reactions such as acylation, oxidation, hydrogenation,

epoxidation etc. use catalysts. Among the reactions, Friedel-Crafts acylation

(benzoylation) reaction is of interest in industries due to the importance of preparing

aromatic ketones as intermediate in the dyes [3], pharmaceutical and fragrance [4]

industries. An example of benzoylation reaction which has been studied is the

benzoylation of biphenyl with benzoyl chloride [5-8]. More attention has been

centered on it because of its applications. The monosubstituted product, 4-

benzoylbiphenyl or 4-phenyl benzophenone (4-PBP) is used in the synthesis of

antifungal bifonazole agent [7]. The 4-PBP is also an intermediate in the synthesis of

fructone, an apple scent used in fragrant, detergents [9] and photo initiator [7] whereas

the disubstituted product, 4, 4’- dibenzoylbiphenyl (4, 4’-DBBP) is used as a

1

2

monomer in producing poly (4, 4’-diphenylene diphenylvinylene) or PDPV, an

attractive polymer for electroluminescence because it has very high

photoluminescence efficiency in solid state along with good solubility in common

organic solvents [10]. As a result, it is used as an emitting layer in polymer light

emitting (PLED) [11].

Liquid phase Friedel-Crafts reactions traditionally have been catalyzed by

strong Brönsted acids such as CF3SO3H, FSO3H, H2SO4 and HF and by soluble Lewis

acids such as TiCl4, AlCl3 and FeCl3 [12]. These acids are very strong in terms of

their catalytic activity. Unfortunately, some of the homogeneous catalysts such as

TiCl4, AlCl3 and FeCl3 are highly sensitive to moisture, corrosive and

environmentally unfriendly [13]. In industrial processes, the reaction brings another

disadvantage to this system where it has a difficulty in product purification due to

production of large amount of side products [14]. Therefore, a demand for searching

an alternative is a need to overcome this problem.

Recently, the use of solid acid catalysts such as zeolites [3, 4, 7] and

mesoporous materials [15, 16] has been reported for the acylation reaction. Zeolites

and mesoporous materials are known for their shape selective properties and they

have been used widely in a variety of acid and base catalyzed shape selective

reactions. In addition, these materials are easy to separate from the product,

environmentally unfriendly, small amount of hazardous corrosive wastes, high

catalyst reusability, high thermostability, safer and easier to handle [14, 17].

Current research on the production of 4, 4’-DBBP via homogeneous and

heterogeneous systems is still facing difficulties. For example, Walczak et al. [15]

were only able to prepare 4-PBP in 74% of yield by treatment of benzoyl chloride

with AlCl3 in chloroform at room temperature, followed by addition of biphenyl into

refluxing solution, Equation 1.1. Another researchers, viz. Han et al. [7] synthesized

94.2 % yield of 4-PBP by stirring benzoyl chloride with biphenyl and AlCl3 in the

presence of nitrobenzene at 120 oC, Equation 1.2.

2

3

+ Biphenyl oReflux in CHCl3 at 25 C Benzoyl chloride + AlCl3 4-PBP (Equation 1.1)

(74%)

Recently, the first attempt to synthesize 4, 4’-DBBP using H-AlMCM-41 as

heterogeneous catalyst with 100% selectivity was reported, however with very low

conversion (0.05%) [5]. According to the researchers, these unsatisfactory results

might be due to low amount of Brönsted and Lewis acid sites as well as its acid

strength. In addition, the reaction condition such as effect of temperature, solvent used,

reactants and catalyst loaded also contribute to these results. In view from the above,

it is of importance to (i) develop a new catalyst or modify the existing catalyst in

order to enhance the amount and the strength of acidity of the materials and (ii)

improve reaction condition for the selective synthesis of 4, 4’-DBBP. By taking the

actions suggested, it is expected that the activity of the catalyst will be improved.

Figure 1.3 shows two possible routes to drive the reaction to obtain targeted product 4,

4’-DBBP either via direct or consecutive route.

C

O

2

OO

Biphenyl

Benzoylium ion

MCM-41 materials

4, 4'-dibenzoyl biphenyl(4, 4'-DBBP)

Targeted productO

4-Phenyl benzohenone (4-PBP)

Route 1(Direct)

Route 2(Consecutive)

+

+

Figure 1.1: Two proposed reaction routes: Route1 (direct) and Route 2 (consecutive)

synthesis of the dibenzoylation of biphenyl using sulphated AlMCM-41

mesoporous materials and benzoyl chloride.

+ AlCl3 oBenzoyl chloride + Biphenyl 4-PBP (Equation 1.2)

Reflux in PhNO2 at 120 C (94.2%)

3

4

1.2 Objectives of Research

The objectives of the research are:

1. To synthesize and characterize a highly active sulphated AlMCM-41

heterogeneous acid catalyst.

2. To relate the acidity to the structural characteristic of the catalyst.

3. To study the catalytic properties of the developed catalyst in

dibenzoylation of biphenyl reaction (model reaction).

4. To study the effect of reaction parameters on the production of 4, 4’-

DBBP.

1.3 Research Strategies

The flow diagram shown in Figure 1.2 describes about research strategies.

Generally the studies involve synthesis, modification, catalytic testing and

optimization. Characterizations are carried out by various techniques as listed. The

catalytic activity was tested in a model reaction – dibenzoylation of biphenyl reaction.

The modification, characterization and catalytic activity testing processes were

repeated until a suitable catalyst was discovered.

1.4 Scope of Research

The work reported in this study focuses on the synthesis of sulphated

AlMCM-41 with various of SiO2/Al2O3 ratio using amorphous rice husk ash as silica

source and sodium aluminate as aluminium source. MCM-41’s template namely

cetyltrimethyl ammonium bromide (CTABr) was used as structure directing agent.

The modification was followed by conversion to H-AlMCM-41 via ion exchange of

NaAlMCM-41 with ammonium nitrate solution followed by calcination and lastly

impregnated with sulphuric acid in order to obtain sulphated AlMCM-41.

4

5

5

Characterization of each sample was carried out using Fourier Transform

Infared (FTIR) spectrometer to study the molecular bondings while the crystalinity

and crystallite size of the samples were analyzed by means of X-ray Diffraction

analysis (XRD). Furthermore, characterization of the samples was also conducted

using 29Si and 27Al Magic Angle Spinning NMR (MAS NMR) spectrometers to study

the silicon and aluminum environments in the structure whereas the textural properties such

as specific surface area, pore volume, pore diameter and pore wall thickness was measured by

using nitrogen gas adsorption-desorption analysis. The thermal stability and volatile

matter in the MCM-41 samples were determined by utilizing thermogravimetry and

differential thermal analysis. The acid strength and the type of acid sites were measured

using Hammett indicators and Fourier Transform Infrared spectroscopy (FTIR) using

pyridine as the probe base molecule.

The final part in this study is to test the catalytic capability of sulphated

AlMCM-41 towards Friedel-craft dibenzoylation of biphenyl with benzoyl chloride as

the benzoylating agents. The reaction was performed in a batch reactor and the

products were separated and analyzed quantitatively by gas chromatography (GC) and

the identification of products were carried out using gas chromatography with mass

spectrometry detector (GC-MSD).

6

6

Finish

MCM-41 materials are characterized to

determine their:

Crystallinity - XRD

Textural properties (specific surface

area and pore volume) - N2 adsorption-

desorption isotherm

Functional groups - FTIR

Acidity (type, density and strength) -

Pyridine-FTIR, Hammett indicator

Thermal stability, volatile matter -

TG-DTA

Aluminum environment in the

structure - 27Al MAS NMR

Silicon environment in the structure -29Si MAS NMR

The properties of catalytic

system will be improved in

terms of

Acid strength

Amount of acid site

Specific surface area

Modification and improvement Yes

Satisfy

No

Characterization

Catalytic testing

Synthesis of MCM-41 materials

Figure 1.2: Flow digram of research strategies.

Dibenzoylation of biphenyl, a

model reaction was carried out

to test the activity of the

catalysts.

Synthesize catalysts in

various SiO2/Al2O3 ratio

using direct synthesis

Modification of MCM-41

materials

73

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