SYNTHESIS AND CHARACTERIZATION OF SULPHATED AlMCM-41 AND ITS CATALYTIC ACTIVITY IN DIBENZOYLATION OF BIPHENYL WITH BENZOYL CHLORIDE

Transcription

1 SYNTHESIS AND CHARACTERIZATIN F SULPHATED AlMCM-41 AND ITS CATALYTIC ACTIVITY IN DIBENZYLATIN F BIPHENYL WITH BENZYL CHLRIDE NG ENG PH UNIVERSITI TEKNLGI MALAYSIA

2 PSZ 19:16 (Pind. 1/97) UNIVERSITI TEKNLGI MALAYSIA BRANG PENGESAHAN STATUS TESIS υ JUDUL: SYNTHESIS AND CHARACTERIZATIN F SULPHATED AlMCM-41 AND ITS CATALYTIC ACTIVITY IN DIBENZYLATIN F BIPHENYL WITH BENZYL CHLRIDE SESI PENGAJIAN: 2004/2005 Saya: NG ENG PH (HURUF BESAR) mengaku membenarkan thesis (PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut: 1. Tesis ini hakmilik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi. 4. **Sila tandakan ( ) SULIT TERHAD TIDAK TERHAD (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972) (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan) Disahkan oleh (TANDATANGAN PENULIS) (TANDATANGAN PENYELIA) Alamat Tetap: PRF. DR. HALIMATN HAMDAN 8, Taman Salad, (Nama Penyelia) Lunas, Kedah. Tarikh: 15 March 2006 Tarikh: 15 March 2006 CATATAN: * Potong yang tidak berkenaan ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD υ Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM).

3 I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award of the degree of Master of Science (Chemistry). Signature : Name of Supervisor : Prof. Dr. Halimaton Hamdan Date : 15 March 2006

4 BAHAGIAN A PENGESAHAN KERJASAMA* Adalah disahkan bahawa projek penyelidikan tesis ini telah dilaksanakan melalui kerjasama antara dengan Disahkan oleh: Tandatangan : Nama : Jawatan : (Cop Rasmi) *Jika penyediaan tesis / projek melibatkan kerjasama. Tarikh : BAHAGIAN B Untuk Kegunaan Pejabat Sekolah Pengajian Siswazah Tesis ini telah diperiksa dan di akui oleh: Nama dan Alamat Pemeriksa Luar : Prof. Madya Dr. Misni Bin Misran Fakulti Sains Universiti Malaya Kuala Lumpur Nama dan Alamat Pemeriksa Dalam I : Prof. Madya Dr. Salasiah Binti Endud Fakulti Sains UTM, Skudai Disahkan oleh Penolong Pendaftar di SPS : Tandatangan : Nama : GANESAN A/L ANDIMUTHU Tarikh :..

5 SYNTHESIS AND CHARACTERIZATIN F SULPHATED AlMCM-41 AND ITS CATALYTIC ACTIVITY IN DIBENZYLATIN F BIPHENYL WITH BENZYL CHLRIDE NG ENG PH 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

6 I declare that this thesis entitled SYNTHESIS AND CHARACTERIZATIN F SULPHATED AlMCM-41 AND ITS CATALYTIC ACTIVITY IN DIBENZYLATIN F BIPHENYL WITH BENZYL CHLRIDE is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree. Signature : Name : Ng Eng Poh Date : 15 March 2006

7 iii For the Lord God Almighty, My beloved family And My best friends

8 iv ACKNWLEDGEMENT 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 27 Al 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.

9 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.

10 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 Si 2 /Al 2 3 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 m 2 /g) and large quantities of Brönsted acid sites after characterizing with surface analyzer and pyridine infrared spectroscopy. 27 Al 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.

11 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). bjektif kajian ini adalah untuk meningkatkan keasidan mangkin yang digunakan dalam tindak balas pemangkinan dwibenzoilasi bifenil melalui modifikasi H-AlMCM-41. AlMCM-41 dengan nisbah Si 2 /Al 2 3 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 m 2 /g) dan kuantiti tapak asid Brönsted yang banyak selepas dicirikan dengan penganalisis permukaan dan spektroskopi inframerah piridina. 27 Al 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.

12 viii TABLE F CNTENTS CHAPTER TITLE PAGE TITLE DECLARATIN DEDICATIN ACKNWLEDGEMENT PREFACE ABSTRACT ABSTRAK TABLE F CNTENT LIST F TABLES LIST F FIGURES LIST F SYMBLS AND ABBREVIATINS LIST F APPENDICES ii iii iv v vi vii viiii ix xii xv xviii 1 INTRDUCTIN 1.1 Research Background and Problem Statement 1.2 bjectives of Research 1.3 Research Strategies 1.4 Scope of the Research LITERATURE REVIEW 2.1 The Importance of Solid Catalyst 2.2 Solid catalysts - Introduction to M41S family 6 7

13 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 EXPERIMENTAL 3.1 Starting Materials 3.2 Preparation of AlMCM Preparation of Protonated MCM-41 (H-AlMCM-41) 3.4 Synthesis of Sulphated AlMCM Characterization of MCM-41 Materials X-ray Powder Diffraction (XRD) Fourier Transform Infrared Spectroscopy (FTIR) Solid State Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) Spectroscopy Thermogravimetric and Differential Thermal Analysis (TG-DTA) Nitrogen Adsorption-Desorption Isotherm Analysis Fourier Transform Infrared Spectroscopy of Pyridine Adsorption Hammett Acidity Analysis 3.6 Dibenzoylation of Biphenyl Reaction over Sulphated AlMCM Dibenzoylation of Biphenyl Reaction over Various Types of Catalysts Synthesis of 4-PBP as authentic sample Synthesis of 4, 4 -DBBP as authentic Sample

14 x Calibration Curve for Authentic Sample 29 4 RESULTS AND DISCUSSIN 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 27 Al MAS NMR 4.6 Solid State 29 Si MAS NMR 4.7 Acidity Measurements Pyridine-FTIR Spectroscopy Hammett indication Analysis 4.8 Catalytic testing: Dibenzoylation of Biphenyl Effect of Catalyst Effect of Si 2 /Al 2 3 ratio Reaction Temperature Effect of Catalyst Loading 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 CNCLUSINS 5.1 Conclusions 69 REFERENCES 71 APPENDICES 77

15 xi LIST F TABLES N. TABLE TITLE PAGES 2.1 Comparison of the various phases of catalysts Amount of NaAl 2 added in preparing AlMCM The organic compounds used as Hammett Indicators GC-FID oven-programmed setup for identifying 4, 4 -DBBP GC-MSD oven-programmed setup for identifying 4, 4 -DBBP XRD data of various MCM-41 samples The textural properties of various protonated and sulphated 39 MCM-41 samples obtained form calculation and surface analyzer. 4.3 Peak areas of octahedral aluminium (Al oct ) and tetrahedral 45 aluminium (Al tet ) from 27 Al MAS NMR spectra 4.4 Peak areas of octahedral aluminium species in aluminium 45 sulphate (Al Al2(S4)3) and sulphated AlMCM-41 (Al Sulphated AlMCM-41) from 27 Al MAS NMR spectra. 4.5 Peak areas of silicon species in SCAL Pyridine FTIR data of protonated and sulphated MCM materials. 4.7 The results of acid strength of catalysts using Hammett 54 indicators. 4.8 Benzoylation and dibenzoylation of biphenyl with benzoyl 57 chloride over various types of catalysts at 180 o C for 24 h. 4.9 Amount of Brönsted acid active sites in SCAL-4 with different 61 loading and and its effect towards conversion of biphenyl Theoretical mass balance Experimental mass balance 67

16 xii LIST F FIGURES N. FIGURE TITLE PAGES 1.1 Two proposed reaction routes: (Route1) direct and (Route 2) 3 consecutive synthesis of the dibenzoylation of biphenyl using sulphated AlMCM-41 mesoporous materials and benzoyl chloride. 1.2 Flow diagram of research strategies Illustration of hexagonal honeycomb structure of mesoporous 9 MCM-41 with 2 nm to 10 nm pore size. 2.2 Formation of MCM-41 materials. (a) Coagulation of surfactants 9 process, (b) Combination of organic and inorganic materials, (c) MCM Framework of (a) SiMCM-41 and (b) AlMCM Generation of Brönsted acid sites Generation of Lewis acid sites Benzoylation of an aromatic compound using aluminium 13 trichloride as catalyst, leading to a stable Lewis complex. 2.7 Friedel-Crafts acylation showing a typical starting materials, 14 products and waste mass balance. 3.1 Range of 29 Si chemical shifts of Q n in solid silicate Proposed mechanism of interaction between pyridine molecules 24 with (a) Brönsted and (b) Lewis acid sites in MCM-41 molecular sieves. 3.3 Adsorption and desorption of pyridine apparatus for acidity study Quantitative calibration plot of biphenyl Quantitative calibration plot of 4-PBP Quantitative calibration plot of 4, 4 -DBBP. 31

17 xiii 4.1 X-ray diffractogram patterns of uncalcined mesoporous MCM molecular sieves. (a) UNCAL-1, (b) UNCAL-2, (c) UNCAL-3 and (d) UNCAL X-ray diffractogram patterns of mesoporous MCM-41 materials 34 after calcinations at 550 o C for 10 h. (a) CAL-1, (b) CAL-2, (c) CAL-3 and (d) CAL X-ray diffractogram patterns of protonated MCM-41 materials 35 after ion exchange with NH 4 N 3 and calcination at 500 o C (a) HCAL-1, (b) HCAL-2, (c) HCAL-3 and (d) HCAL X-ray diffractogram patterns of sulphated MCM-41 materials (a) 35 SCAL-1, (b) SCAL-2, (c) SCAL-3 and (d) SCAL FTIR spectra of uncalcined mesoporous MCM-41 molecular 37 sieves. 4.6 FTIR spectra of calcined mesoporous MCM-41 molecular sieves FTIR spectra of sulphated mesoporous MCM-41 molecular sieves Modification of surface of MCM-41 through sulphation leads to 39 shrinkage of pore diameter. 4.9 Thermogravimetric analysis of uncalcined MCM-41 sample 40 (UNCAL-2) in nitrogen gas with 20 o C/min heating rate Thermogravimetric analysis of uncalcined MCM-41 samples with 41 various ratio of Si 2 /Al Thermograms of a series of protonated MCM-41 molecular sieves Thermogravimetric curves of sulphated AlMCM-41 materials Al NMR spectra of protonated MCM-41 molecular sieves (a) 44 HCAL-4, (b) HCAL-3, (c) HCAL-2 and (d) HCAL Al NMR spectra of sulphated MCM-41 molecular sieves (a) 44 SCAL-4, (b) SCAL-3, (c) SCAL-2 and (d) SCAL Si NMR spectrum of sulphated MCM-41 molecular sieves 48 (SCAL-4) The possible silicon species and Brönsted acid sites in sulphated 49 AlMCM The pyridine-ftir spectra of purely siliceous sulphated MCM-41 (SCAL-1) at (a) room temperature, (b) 150 o C, (c) 250 o C and (d) 50

18 xiv 350 o C The pyridine-ftir spectra of sulphated AlMCM-41 (SCAL-2) at 51 (a) room temperature, (b) 150 o C, (c) 250 o C and (d) 350 o C The pyridine-ftir spectra of sulphated AlMCM-41 (SCAL-3) at 51 (a) room temperature, (b) 150 o C, (c) 250 o C and (d) 350 o C The pyridine-ftir spectra of sulphated AlMCM-41 (SCAL-4) at 52 (a) room temperature, (b) 150 o C, (c) 250 o C and (d) 350 o C FTIR spectra of silanol groups of MCM-41 materials at 250 o C (a) 53 before treatment (HCAL-1) and (b) after treatment (SCAL-1) of sulphuric acid Dibenzoylation of biphenyl catalyzed by various types of catalysts Conversion of biphenyl over various ratio of Si 2 /Al 2 3 within h Yield of 4, 4 -DBBP over various ratio of Si 2 /Al 2 3 within 24 h Temperature effect towards dibenzoylation of biphenyl over 60 SCAL Effect of catalyst loading towards dibenzoylation of biphenyl over SCAL Effect of Biphenyl : Benzoyl Chloride molar ratio towards 62 dibenzoylation of biphenyl over SCAL Mechanism of how the electron density affects BP and 4-PBP in 63 attacking benzoylium ion Formation of 4-phenyl benzophenone (4-PBP) via electrophilic substitution Mechanism of production of 4, 4 -dibenzoyl biphenyl (4, 4-65 DBBP) Stoichiometrical chemical equation of dibenzoylation of biphenyl 66 reaction Hydrolysis of benzoyl chloride as side reaction in production of 68 benzoic acid and benzoic anhydrice Scheme proposed for the sulphated AlMCM-41 materials showing possible Brönsted acid sites. 68

19 xv LIST F SYMBL AND ABBREVIATINS 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

20 xvi % - Percent ~ - Approximately TG/DTA - Thermogravimetric and Differential Thermal Analysis TGA - Thermogravimetric Analysis DTA - Differential Thermal Analysis H o - 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 NH 4 H - Ammonium hydroxide min - Minute o C - Celsius h - Hour wt% - Weight percent g - Gram mg - milligram Si 2 /Al 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 Si 2 /Al 2 3 ratio UNCAL-2 - Uncalcined AlMCM-41 with Si 2 /Al 2 3 ratio 60 UNCAL-3 - Uncalcined AlMCM-41 with Si 2 /Al 2 3 ratio 30 UNCAL-4 - Uncalcined AlMCM-41 with Si 2 /Al 2 3 ratio 15 CAL-1 - Calcined MCM-41 with Si 2 /Al 2 3 ratio CAL-2 - Calcined AlMCM-41 with Si 2 /Al 2 3 ratio 60

21 xvii CAL-3 - Calcined AlMCM-41 with Si 2 /Al 2 3 ratio 30 CAL-4 - Calcined AlMCM-41 with Si 2 /Al 2 3 ratio 15 HCAL-1 - Protonated MCM-41 with Si 2 /Al 2 3 ratio HCAL-2 - Protonated AlMCM-41 with Si 2 /Al 2 3 ratio 60 HCAL-3 - Protonated AlMCM-41 with Si 2 /Al 2 3 ratio 30 HCAL-4 - Protonated AlMCM-41 with Si 2 /Al 2 3 ratio 15 SCAL-1 - Sulphated MCM-41 with Si 2 /Al 2 3 ratio SCAL-2 - Sulphated AlMCM-41 with Si 2 /Al 2 3 ratio 60 SCAL-3 - Sulphated AlMCM-41 with Si 2 /Al 2 3 ratio 30 SCAL-4 - Sulphated AlMCM-41 with Si 2 /Al 2 3 ratio 15 MHz - Megahertz µs - Microsecond TMS - Tetramethyl silane BJH - Barrett, Joyner, Halenda mbar - millibar kpa - Kilopascal m/z - Mass over charge a o - Unit cell parameters t - Crystallite size W d - Pore diameter b d - Pore wall thickness

22 xviii LIST F APPENDICES APPENDICES TITLE PAGES A Calculation of the amount of pyridine adsorbed on the sample in 77 the acidity study of sulphated AlMCM-41 samples. 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, 83 (b) 150 o C, (c) 250 o C and (d) 350 o C. H The pyridine-ftir spectra of HCAL-2 at (a) room temperature, 84 (b) 150 o C, (c) 250 o C and (d) 350 o C. I The pyridine-ftir spectra of HCAL-3 at (a) room temperature, 85 (b) 150 o C, (c) 250 o C and (d) 350 o C. J The pyridine-ftir spectra of HCAL-4 at (a) room temperature, 86 (b) 150 o C, (c) 250 o C and (d) 350 o C. K Chromatogram of reactants at 0 h. 87 L Chromatogram of reactants and products. 88 M Data obtained from GC-FID Chromatograms (Friedel-Crafts 89 dibenzoylation of biphenyl with benzoyl chloride over SCAL-4). N Mass balance of dibenzoylation of biphenyl with benzoyl 90 chloride (Experimental) Mass balance of dibenzoylation of biphenyl with benzoyl chloride (Theoretical) 98

23 1 CHAPTER 1 INTRDUCTIN 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

24 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 CF 3 S 3 H, FS 3 H, H 2 S 4 and HF and by soluble Lewis acids such as TiCl 4, AlCl 3 and FeCl 3 [12]. These acids are very strong in terms of their catalytic activity. Unfortunately, some of the homogeneous catalysts such as TiCl 4, AlCl 3 and FeCl 3 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 AlCl 3 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 AlCl 3 in the presence of nitrobenzene at 120 o C, Equation

25 3 + Biphenyl Benzoyl chloride + AlCl 3 o 4-PBP (Equation 1.1) Reflux in CHCl 3 at 25 C (74%) + AlCl Benzoyl chloride + Biphenyl 3 o 4-PBP (Equation 1.2) Reflux in PhN 2 at 120 C (94.2%) 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. 2 Biphenyl C + Benzoylium ion + Route 1 (Direct) Route 2 (Consecutive) 4, 4'-dibenzoyl biphenyl (4, 4'-DBBP) Targeted product MCM-41 materials 4-Phenyl benzohenone (4-PBP) 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. 3

26 4 1.2 bjectives 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 Si 2 /Al 2 3 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

27 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 29 Si and 27 Al 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). 5

28 6 No Synthesis of MCM-41 materials Characterization Catalytic testing Modification and improvement Satisfy Yes Finish Synthesize catalysts in MCM-41 materials are characterized to Dibenzoylation of biphenyl, a The properties of catalytic various Si 2 /Al 2 3 ratio determine their: model reaction was carried out system will be improved in using direct synthesis Crystallinity - XRD to test the activity of the terms of Modification of MCM-41 Textural properties (specific surface catalysts. Acid strength materials area and pore volume) - N 2 adsorption- Amount of acid site desorption isotherm Specific surface area Functional groups - FTIR Acidity (type, density and strength) - Pyridine-FTIR, Hammett indicator Thermal stability, volatile matter - TG-DTA Aluminum environment in the structure - 27 Al MAS NMR Silicon environment in the structure - 29 Si MAS NMR Figure 1.2: Flow digram of research strategies. 6

29 7 CHAPTER 2 LITERATURE REVIEW 2.1 The importance of solid catalyst Catalysis has had a major impact on chemicals and fuels production, environmental protection and remediation, processing of consumer products and advanced materials manufacturing. A survey of British agency Frost and Sullivan revealed that the catalyst European market had reached to USD 3.7 billion turnover in 2000 with the 4 % of average increment per year and it illustrates that the critical role of this field in the fuel and chemical industry [18]. Homogeneous catalyst is referred as the catalyst that exists in the same phase with the reactants whereas heterogenous catalyst is a catalyst which has different phase with the reactants. Catalyst can be used either in gaseous, liquid or solid form. Usually, heterogeneous catalyst is more favorable in application because it is easy to isolate from the reaction mixture. nly a few heterogeneous catalysts in gaseous form are used commercially because of difficulty in handling and safety factors. However, the industries nowadays prefer to use solid form heterogeneous catalyst compared with liquid form homogeneous catalyst due to high corrosion of vessels caused by liquid form catalyst, difficulty in handling, leaking and spillage problems. Table 2.1 depicts the advantages and disadvantages of 3 phases of catalysts. 7

30 8 Table 2.1: Comparison of the various phases of catalysts. Type(s) Advantage(s) Disadvantage(s) Gas High activity towards reaction Leaking problem. due to kinetic factor. Difficulties in handling. Possible explosion hazard. Corrosive to vessels. Liquid High activity towards reaction Difficulties in separation. due to kinetic factor. Leaking and spillage problems. Difficulties in handling. Corrosive to vessels. Solid Safer to use. Difficult to contain high active High activity towards reaction component loading (dosage) to due to high surface area. further improve strength and Convenient to handle. impact. No leaking and spillage. Difficult to modify. Easy to use and separate. Leaching problem. Therefore, from Table 2.1 it is clear that among all types of catalysts, solid catalysts have many advantages and currently are of interest. 2.2 Solid catalysts - Introduction to M41S family Usually, a solid consisting of nanometer-sized cavities or pores has a high surface area. International Union of Pure Applied Chemistry (IUPAC) classifies pore sizes into three categories. Pores larger than about 50 nm in diameter are termed macropores while those less than about 2 nm are termed micropores whereas pores of intermediate size (2 nm < x < 50 nm) are classified as mesopores. Microporous zeolites are widely used as acid catalysts nowadays. Acid sites are generated by introducing metals such as aluminium [3, 4, 16] into the framework. 8

31 9 However, the zeolites with micropores still face many problems because they often suffer from diffusion limitation when applied to the chemical synthesis involving bulky molecules. Hence, the development of molecular sieves with pore diameter in the mesoporous range has been increasing in demand for its use in acid catalyzed reactions, particularly for the synthesis of large molecules for producing chemicals [19]. ne significant step forward came with the determination of the structure of zeolite β [20, 21] which has three-dimensional channels larger than most microporous zeolites and exhibits catalytic performances competitive with those widely used as catalysts on an industrial scale such as Y-type and ZSM-5 zeolites. Another significant step forward has come more recently with the discovery of the mesoporous M41S family in 1992 [22], which offer many opportunities over microporous materials by being more accessible to reactants. In 1992, Mobil researchers reported that a family of aluminosilicates (termed M41S) with pores larger than 2 nm could be synthesized in an ordered packing through liquid-crystal templating (LCT) mechanism shown in Figure 2.1 [23]. Firstly, the surfactant aggregates to form rod-like micelles. Next, the silicate anions will migrate and undergo polymerization, resulting in the formation of MCM-41 structure. (a) (b) (c) Fig. 2.1: Formation of MCM-41 materials. (a) Aggregation of surfactants process, (b) Combination of organic and inorganic materials, (c) MCM-41 [26]. 9

32 10 f particular interest is MCM-41, which has hexagonally-packed cylindrical pore channels containing surface areas greater than 1200 m 2 /g and uniform pore sizes that can be tailored from 2 to 10 nm in diameter available, making it attractive heterogeneous catalysts, catalyst supports, and nanocomposite host materials for a wide range of novel applications, Figure 2.2 [22, 24]. A study of mesoporous MCM- 41 materials however, is of interest to chemists nowadays. Since the introduction of MCM-41 with its unique characteristics, these materials have important uses in chemistry disciplines [25]. Figure 2.2: Illustration of hexagonal honeycomb structure of mesoporous MCM-41 with 2 nm to 10 nm pore size. Purely siliceous MCM-41 generally does not have catalytic ability because of the absence of the Al as active sites. Therefore, in order to obtain acidic mesoporous catalysts which are suitable for the synthesis of large hydrocarbons, a modification of their acid sites is necessary. In recent years, many efforts have been devoted towards the study of incorporating numerous kinds of metal or nonmetal compounds in MCM- 41 in order to enhance both the acid sites and strengths. For example, many researchers reported that by incorporating trivalent metals such as Al or Ga in the MCM-41, the Lewis and Brönsted acid characters can be generated and improved [9, 27-30]. n the other hand, the introduction of many metals other than Al and Ga, i.e. 10

33 11 In, Fe, Ti, Zr etc. is another promising ways to generate acid character in MCM-41 mesoporous sieves [12, 29, 31-33]. 2.3 Generation of active sites in AlMCM-41 mesoporous materials Purely siliceous MCM-41 mesoporous materials generally are neutral in term of charge because of the +4 charge of Si in the Si 4 unit of the framework is electronically neutralized by the four 1 charges from the oxygen atoms. It is shown in Figure 2.3 (a). As a result, purely siliceous MCM-41 mesoporous materials do not exhibit acidity due to neutral charge and have no heterocation such as Al in the framework. However, the charge of framework of purely siliceous mesoporous materials is no longer neutral when lattice Si 4+ cations are replaced by lattice foreign cation such as Al 3+ cation. This phenomenon creates negatively charged framework of the mesoporous materials as illustrated in Figure 2.3 (b). (a) 4+ Si 0 Si Si Si Si 0 (b) 3+ Al -1 Si Al Si Si -1 Figure 2.3: Framework of (a) SiMCM-41 and (b) AlMCM-41. Typically, AlMCM-41 materials are synthesized in the sodium form. Therefore, it is a need to convert the Na + form to H + form in order to generate the 11

34 12 Brönsted acid sites as shown in Figure 2.4. It can readily be accomplished by ion exchanging Na + with NH 4 + followed by thermal decomposition of the NH 4 + into proton and ammonia [5]. Na Na Si Al Si Al NH 4 + exchange NH 4 NH 4 Si Al Si Al > 300 o C - NH 3 Brönsted acid sites H H Si Al Si Al Figure 2.4: Generation of Brönsted acid sites. The Lewis acid sites in aluminosilicate mesoporous materials are originated from extraframework Al species (EFAL) present in the form of Al 3+, Al +, Al(H) 2+, or charged Al x n+ y clusters within the materials [36]. EFAL species is the Al species that locates outside of the framework. There are two possible explanations about the generation of Lewis acid sites. The first approach was proposed by Lercher et al. [37] using infrared studies, stating that Lewis acidity is due to framework tricoordinated aluminium formed upon dehydroxylation as demonstrated in Figure 2.5 (a). The second explaination postulated by MAS NMR spectroscopy [38], which shows that 12

35 13 the presence of Lewis acid sites is associated with both octahedral and tetrahedral extra framework Al (EFAL) species, created by dehydroxylation of the hydrogen forms of aluminosilicate meterials as illustrated in Figure 2.5 (b). (a) Lewis acidity due to framework tricoordinated aluminium. H H Si Al Si Al Si - H 2 Si Al Si Al Si (b) Lewis acidity associated with both octahedral and tetrahedral EFAL. H H Si Al Si Al Si - H 2 Si Al Al + Si Si Figure 2.5: Generation of Lewis acid sites: 2.4 Generation of acid sites via sulphation Another method of modification and improvement of acid sites in MCM-41 is via sulphation whereby it is a method of introducing sulphate group onto the MCM- 41. Sulphation has received much attention recently [33-35]. Chen et al. [35] first reported the details of the synthesis and characterization of sulphuric acid impregnated mesoporous materials for the synthesis of β-naphthyl methyl ether and later M. Selvaraj et al. [33, 34] reported the synthesis, characterization of mesoporous 13

36 14 materials with different Si/Al ratios for synthesis of neroline. Usually sulphuric acid is used as sulphating agent [33-35]. The sulphuric acid is impregnated in MCM-41 materials in aqueous solution followed by drying and readily be used in reaction. Sulphation is simple and can generate Lewis acid site. Figure 2.6 illustrates the scheme proposed by M. Selvaraj for the sulphate-containing AlMCM-41 material showing possible Lewis acid sites. Impregnation by sulphuric acid enables the generation of Lewis acid sites on the surface of AlMCM-41 due to the inductive effect of the sulphate group and the aluminium ions is being non-framework. From this point of view, sulphation provides a promising solution to the enhancement of acidity and catalyzes Friedel-Crafts reaction that needs strong and large amount of acidity. 2- LA Si BA Al Si S S Si Al Si LA Figure 2.6: Scheme proposed for the sulphated AlMCM-41 material showing possible Lewis acid sites (LA) after sulpathating AlMCM-41 containing Brönsted acid site (BA). 2.5 Friedel-Crafts reactions and solid catalysts Friedel-Crafts reaction is an important synthesis techniques in organic chemistry. It is widely used not only in research but also in chemical production industries. ne of the reactions called acylation reaction is of interest due to the importance of preparing aromatic ketones as intermediate in the dyes [3], pharmaceutical and fragrance [4] industries. 14

37 15 Liquid phase Friedel-Crafts reactions traditionally have been catalyzed by strong Brönsted acids such as CF 3 S 3 H, FS 3 H, H 2 S 4 and HF and by soluble Lewis acids such as TiCl 4, AlCl 3 and FeCl 3 [12]. These acids have many important advantages. They are very active and readily available. Apart from that, they are cheap. Unfortunately, homogeneous catalysts such as TiCl 4, AlCl 3 and FeCl 3 are highly sensitive to moisture, corrosive and environmentally unfriendly [13]. They are often too powerful acid, giving lower yield of desired product with low selectivity and very significantly in the context of green chemistry, they may need to be used in reagent quantities because of their ability to form complex Lewis base products. For example, AlCl 3 is used as a catalyst in a benzoylation reaction as shown in Figure 2.6. CCl AlCl 3 R + + AlCl 3 Solvent R Figure 2.6: Benzoylation of an aromatic compound using aluminium trichloride as catalyst, leading to a stable Lewis complex. When the reaction is complete, the only possible way to separate the AlCl 3 is by a destructive water quenching, resulting in emission of about 3 equivalents of HCl; which need to be scrubbed off the gases leading to the production of 3 equivalents of salt waste. nce the organic product has been recovered, aluminous water remains, which must be disposed of. The overall process generates considerably more waste than product, Figure 2.7 [2]. 15

38 16 C R + AlCl 3 + RCCl H 2 3 HCl + Al(H) 3 3 NaH 3NaCl Substrates and reagents 1000 arbitrary weight units Products 290 arbitrary weight units Waste 710 arbitrary weight units Figure 2.7: Friedel-Crafts acylation showing a typical starting materials, products and waste mass balance. 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 [12, 15, 16] has been reported for the Friedel-Crafts reaction. Zeolites do seem to be a better alternative due to their shape selective properties. In addition, these materials are easy to separate from the product, environmentally friendly, small amount of hazardous corrosive wastes, high catalyst reusability, high thermostability, safer and easier to handle [14, 17]. 16

39 17 CHAPTER 3 EXPERIMENTAL 3.1 Starting Materials Rice husk ash (RHA) containing 97% of Si 2 was used as the silica source for MCM-41 while sodium aluminate (NaAl 2 ; Riedel-de-Haän ; 53 wt% Al 2 3 ) was used as aluminium source. Cetyltrimethylammonium bromide (CTABr) and acetic acid (Merck, 25 wt%) were used as surfactant and organic acid, respectively. Sodium hydroxide (NaH; Merck; 99%) and ammonium hydroxide (NH 4 H; Merck; 99%) were used as alkali bases. Doubly distilled water was used as a medium. Ammonium nitrate (Merck) was used as an ion-exchange agent to produce protonated mesoporous materials whereas sulphuric acid (H 2 S 4 ; Merck; v/v%) was the sulphating agent. All reagents were of analytical purity. Benzoyl chloride and biphenyl were used without further purification. The monosubstituted 4-phenyl benzophenone and disubstituted 4, 4 -benzoyl biphenyl were synthesized via homogeneous Friedel- Crafts reaction. These products were used as authentic samples. 3.2 Preparation of AlMCM-41 AlMCM-41 was prepared in the following way using published method [5]. In a typical synthesis, sodium silicate was prepared by dissolving 6.13 g of RHA and 2.00 g of NaH in 40.0 ml doubly distilled water at 80 o C for 2 h under stirring. The resulting solution was designated as solution A. Another solution B was prepared by mixing appropriate amount of NaAl 2 as shown in Table 3.1, 6.07 g of CTABr and 17

40 g of NH 4 H 25 wt% in 35.0 ml of doubly distilled water, followed by stirring at 80 o C for 30 min until a clear solution was obtained. For both solutions, viz. A and B were mixed together in a polypropylene bottle to give a gel with a mole ratio composition of 6 Si 2 : CTABr : 1.5 Na 2 : 0.15 (NH 4 ) 2 : 250 H 2 followed by vigorous stirring for 15 min. After stirring, the resulting gel was kept in an air oven for crystallization at 100 o C for 24 h. The gel was then cooled to room temperature and the ph of the gel was adjusted close to 10.2 by adding acetic acid 25 wt%. The subsequent 24 h heating and ph adjustment was repeated twice. The solid product was filtered, washed, neutralized and dried overnight at 100 o C. The solid sample was calcined at 550 o C in air for 10 h with a heating rate of 1 o C min -1 to remove the trapped organic template. Calcined solid powders with Si 2 /Al 2 3 ratios of, 60, 30 and 15 were labelled as CAL-1, CAL-2, CAL-3 and CAL-4, respectively. Table 3.1: Amount of NaAl 2 added in preparing AlMCM-41. Sample Si 2 /Al 2 3 ratios NaAl 2 weight (g) CAL CAL CAL CAL Preparation of Protonated AlMCM-41 (H-AlMCM-41) Calcined MCM-41 mesoporous materials (0.700 g) in Na + form was put into a 50 ml of 0.2 M NH 4 N 3 solution and stirred at 60 o C for 6 h. The solid was filtered, washed with deionized water and dried at 110 o C for 2 h. The ion exchange was 18

41 19 repeated three times. The solid powder was then calcined at 550 o C at the rate of 1 o C min -1 for 5 h. The solid powders of H-AlMCM41 with Si 2 /Al 2 3 ratio of, 60, 30 and 15 were labeled as HCAL-1, HCAL-2, HCAL-3 and HCAL-4, respectively. 3.4 Synthesis of Sulphated AlMCM-41 Sulphated AlMCM-41 samples were prepared the following way g of H- AlMCM-41 was transferred to a round bottom flask containing 10 ml of toluene and 30 µl H 2 S wt%. The mixture was stirred at 50 o C for 1 h and dried at 130 o C for 12 h. The sulphated samples with Si 2 /Al 2 3 ratios of, 60, 30 and 15 were designated as SCAL-1, SCAL-2, SCAL-3 and SCAL-4, respectively. 3.5 Characterization of MCM-41 Materials X-ray Powder Diffraction (XRD) X-ray diffraction is a powerful method to define the crystallographic structure of MCM-41 materials whereby no other means is feasible or even possible. Each of the zeolite materials has their own specific pattern that can be used as references for the determination of solid crystal phase and it is used as fingerprint for every zeolites. This technique can identify the phase present in the sample and signify whether the solid sample is amorphous or crystalline phase. Amorphous phases will produce no diffraction peak at all and small particles will produce broad diffraction lines, whereas a crystalline particle gives a sharp and strong diffraction lines. The degree of crystallinity can also be determined by referring to peak intensity. The purity of solid crystal can be measured by comparing the X-ray diffractogram pattern of sample with X-ray diffractogram pattern of standard that can be attained from International Zeolite Association (IZA). The presence or absence of some peaks of the diffractogram 19

42 20 indicates to the existence of other crystal phase or zeolite was contaminated with other phases [39]. The crystallite size for MCM-41 can be easily determined by using the Scherrer equation shown as follow [40]. t = 0.9 λ / (B cos θ) (Equation 3.1) where t is the average crystallite size in nm, B is the full width at half maximum of diffraction peak, λ is the wavelength of X-ray and θ is the diffraction angle. Equation 3.2. The unit cell parameters for MCM-41 can be determined by applying the a o 100 = 2 d / 3 (Equation 3.2) where a o is the unit cell parameter in Å and d is the interplanar spacing In this study, the MCM-41 mesoporous materials were characterized by means of X-ray Powder Diffraction (XRD) using a Bruker Advance D8 using Siemens 5000 diffractometer with Cu K α radiation (λ = Å, 40 kv, 40 ma). First, the powder samples were ground and spread on a sample holder. The samples were scanned in the range from 2θ = 1.5 o 10.0 o with step size of 0.02 o Fourier Transform Infrared Spectroscopy (FTIR) FTIR is a very powerful analytical tool because it reveals information about molecular vibrations that cause a change in the dipole of moment of molecules [41]. In zeolite chemistry, it is employed to study the aluminoslicate framework, hydroxyl group and also foreign molecules adsorbed in the zeolites. Normally, FTIR provides meaningful information in the mid-infrared region ( cm -1 ) which attributed to the framework vibrations of zeolite which tetrahedral linked of Si 4 or Al 4. FTIR 20

43 21 also can be used to determine the hydroxyl group in zeolite. In air, the water vapour will interact with the H group in zeolites through hydrogen bonding and give a broad band around cm -1. For determination of H group of zeolites, the samples have to be heated at high temperature under vacuum to eliminate water vapour trapped in zeolite framework [42]. Sulphate functional group shows several signals in IR spectra. The stretching vibration of the S= bond gives band at 1071 cm -1 while the absorption band at 1180 cm -1 is due to symmetric vibrations of Si S bridges. Apart from that, sulphate group also demonstrates a band at 888 cm -1 which is due to symmetric S stretching vibrations. The S 2 deformation can also be detected in the region 580 cm -1 [43, 44]. In this research, infrared spectra were acquired by using a Perkin Elmer Spectrum ne FT-IR spectrometer with a 4 cm -1 resolution and 10 scans in the mid IR region ( cm -1 ). KBr pellet method was used in which the solid samples were finely pulverized with dry KBr in the ratio of 1:100 and the mixture was pressed in a hydraulic press (5000 psi) to form a transparent pellet. The pellet was put in a sample holder and the spectrum of the pellet was measured Solid State Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) Spectroscopy In recent years, theory and practice have been developed for the NMR study of solids. NMR is a powerful spectroscopic technique, which can be used for a number of applications in various branches of chemistry. ne of the applications of NMR is to characterize zeolites and mesoporous materials concerning structure elucidation and the short range ordering (local environment). Usually, solid state NMR spectroscopy is performed using a number of special techniques, including magic-angle spinning (MAS), cross polarization (CP), special 2D experiments and enhanced probe electronics in order to obtain a high resolution 21