Tổng hợp và đặc trưng xúc tác tẩm chất lỏng ion (SILP) imidazol chứa phức rodi mang trên các chất mang rắn cho phản ứng hydroformyl hóa etylen

Recently, a novel approach to immobilizing homogeneous catalysts on solid supports supported ionic liquid phase – SILP catalyst has been reported, in which the hydroformylation complex c

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ACKNOWLEDGEMENTS

This PhD thesis has been carried out at the Laborotory of Environmental Friendly Material and Technologies, Advance Institue of Sicence and Technology, Department of Organic and Petrochemical Technology, Laboratory of the Petrochemical Refinering and Catalytic Materials, School of Chemical Engineering, Hanoi University of Science and Technology The work has been completed under supervision of Associate Prof Dr Le Minh Thang and Associate Prof Tran Thi Nhu Mai

First of all, I would like to express my heartfelt thanks to my supervisor, Associate Prof

Dr Le Minh Thang and Associate Prof Tran Thi Nhu Mai, for their tremendous help and constructive suggestions throughout all my Ph.D candidate period

I would like to thank all teachers of Department of Organic and Petrochemical Technology and the technicians of Laboratory of Petrochemistry and Catalysis Material, Institute of Chemical Engineering for their guidance, and their helps in my work

I acknowledge Department of Chemistry, Technical University of Denmark and Prof Rasmus Fehrmann, Prof Ander Rijsager for helping in some measurement and synthesis and funding for my research

I cannot complete this acknowledgement without mention of my beloved family members who have put in their efforts and prayers for me to attain success in life

Do Van Hung

September, 2016

COMMITTAL IN THE THESIS

I assure that my scientific results are righteous They haven‟t been published in any scientific document I have responsibilities for my protestation and my research results in

the thesis

On behalf of Supervisors: PhD Student

Associate Professor, Doctor Le Minh Thang Do Van Hung

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CONTENT OF THESIS

LIST OF TABLES 7

LIST OF FIGURES 8

INTRODUCTION 11

1 LITERATURE REVIEW 12

1.1 Hydroformylation of alkenes 12

1.2 Catalysts for hydroformylation reaction 13

1.2.1 Cobalt catalyzed hydroformylation 15

1.2.2 Rhodium catalyzed hydroformylation 17

1.2.3 Heterogenization of homogeneous catalysts 18

1.3 Mechanism of hydroformylation reaction 21

1.3.1 Mechanism for Cobalt-Catalyzed Hydroformylation 21

1.3.2 Mechanism for Rhodium-Catalyzed Hydroformylation 22

1.3.3 Mechanism for Rhodium-Catalyzed Hydroformylation of ethylene 23 1.4 Application of hydroformylated products 24

1.5 Supported Ionic Liquid Phase Catalysts (SILP) 25

1.5.1 Ionic liquid (ILs) 27

1.5.2 Ligand 30

1.5.3 Rh complex 30

1.5.4 Supports for SILP catalysts 32

1.5.4.1 Amorphous silica (SiO 2 ) 32

1.5.4.2 Mesoporous Al 2 O 3 33

1.5.4.3 Mesoporous zirconium dioxide (ZrO 2 ) 34

1.5.4.4 Mesoporous MCM - 41 36

1.5.4.5 Mesoporous SBA - 15 36

1.6 Synthesis of SILP catalysts 38

1.7 Aim of the thesis 38

2 EXPERIMENT 40

2.1 Sythesis of the catalysts 40

2.1.1 Ligand Synthesis 40

2.1.2 Synthesis of Supports 42

2.1.2.1 ZrO 2 42

2.1.2.2 MCM – 41 43

2.1.2.3 SBA – 15 44

2.1.3 Catalysts synthesis 45

2.2 Physico – Chemical Experiment Techniques 48

2.2.1 X – ray Diffraction 48

2.2.1.1 Principle 48

2.2.1.2 Application in thesis 48

2.2.2 Characterization of surface properties by physical adsorption 49 2.2.2.1 Principle 49

2.2.2.2 Application in thesis 51

2.2.3 Infrared (IR) spectroscopy 51

2.2.3.1 Principle 51

2.2.3.2 Application in thesis 52

2.2.4 Temperature Programmed Techniques 52

2.2.4.1 Principle 52

2.2.4.2 Application in thesis 53

2.2.5 Transmission Electron Microscopy (TEM) 53

2.2.5.1 Principle 53

2.2.5.2 Application in this thesis 54

2.2.6 Scanning Electron Microscopy (SEM) 54

2.2.6.1 Principle 54

2.2.6.2 Application in this thesis 55

2.2.7 Nuclear magnetic resonance spectroscopy – NMR 55

2.2.7.1 Principle 55

2.2.7.2 Application in this thesis 56

2.3 Measurement of the catalyst 56

2.3.1 Micro reactor setup 56

2.3.2 The analysis of the reactants and products 57

3 RESULTS AND DISCUSSTIONS 60

3.1 Chracterization of support 60

3.1.1 Chracterization of MCM-41 60

3.1.2 Chracterization of SBA-15 63

3.1.3 Characterization of ZrO2 64

3.1.4 Characterization of commercial Al2O3 and SiO2 support 67

3.2 Characterization of ligand 68

3.2.1 FTIR spectra of ligand TPPTS 69

3.2.2 NMR spectra of ligand TPPTS 69

3.2.3 The influence of ligand to the catalytic acitivity 74

3.3 Characterization of support ionic liquid phase (SILP) catalysts 74

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3.3.1 FT – IR characterization 74

3.3.1.1 FT-IR of ionic liquid [BMIM][n-C 8 H 17 OSO 3 ] 74

3.3.1.2 FT – IR spectra of support ionic liquid phase (SILP) catalysts on different supports 75

3.3.2 TEM observation 79

3.3.3 Surface area and physical adsorption properties of SILP catalysts 83 3.4 Catalytic activity of SILP on SiO2 91

3.5 Catalytic activity of SILP on Al2O3 93

3.5.1 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/Al2O3 93

3.5.2 Influence of Ionic Liquid loading content on activity of SILP on Al2O3 96 3.6 Catalytic activity of SILP on ZrO2 97

3.6.1 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/ZrO2 97

3.6.2 Influence of Ionic Liquid loading content on activity of SILP on ZrO2 99 3.7 Catalytic activity of SILP on MCM-41 101

3.7.1 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/MCM-41 101

3.7.2 Influence of Ionic Liquid loading content on activity of SILP on MCM-41 101

3.8 Catalytic activity of SILP on SBA-15 103

3.8.1 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/SBA-15 103

3.8.2 Influence of Ionic Liquid loading content on activity of SILP on SBA-15 104

3.9 Influence of supports on catalytic activity of SILP 106

4 CONCLUSIONS 111

REFERENCES 113

LIST OF PUBLICATIONS 121

APPENDIX 122

ABBREVIATION

CTAB Cetyltrimetylamoni bromua C16H33N(CH3)3Br FBC Flourous Biphasic Catalysis

SAPC Supported Aqueous Phase Catalysis

SEM Scanning Electron Microscope

SILP Supported Ionic Liquid Catalysis

SLPC Supported Liquid Phase Catalysis

TEM Transmission Electron Microsope

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LIST OF TABLES

Table 1.1 Developments of hydroformylation catalysts 14

Table 1.2 Physico-chemical properties of ionic liquids and their beneficial impacts on catalysis [92] 28

Table 1.3 Application of SiO 2 as supports [42] 33

Table 2.1 Summary of the synthesized ligands 42

Table 2.2 Summary of the synthesized MCM-41samples 44

Table 2.3 Summary of the synthesized catalysts (Rh weight content is 0.2%, L/Rh molar ratio is 10) 47

Table 2.4 Temperature Program of the GC analysis method for the reaction 57

Table 2.5 Retention time of some chemicals 57

Table 3.1 Summary of synthesized zirconia samples 64

Table 3.2 Surface properties of SiO 2 and 0.2%Rh-10%Il-L/Rh=10SiO 2 83

Table 3.3 Surface properties of Al 2 O 3 and SILP catalyst on Al 2 O 3 84

Table 3.4 Surface properties of ZrO 2 and SILP on ZrO 2 catalysts 85

Table 3.5 Surface properties of MCM-41and SILP on MCM-41 catalysts 86

Table 3.6 Surface properties of SBA-15 and SILP catalysts on SBA-15 89

Table 3.7 TPD NH 3 profiles of Al 2 O 3 supports 95

Table 3.8 TPD NH 3 profiles of ZrO 2 supports 98

LIST OF FIGURES

Figure 1.1 Three stages of the catalyst development for the hydroformylation reaction [14] 14

Figure 1.2 Interaction of Co 2 (CO) 8 with H 2 and ligand [82] 15

Figure 1.3 Schematic representation of a supported liquid phase catalyst (SLPC)[48] 20

Figure 1.4 Cobalt-catalyzed hydroformylation reaction cycle [36, 103] 21

Figure 1.5 Mechanism for Rhodium-Catalyzed Hydroformylation [1, 84, 104, 103] 22

Figure 1.6 Wilkinson’s dissociative mechanism presented for rhodium-phosphine catalysed ethene hydroformylation [84,27] 23

Figure 1.7 Overview of the use of aldehydes [4, 15] 25

Figure 1.8 Illustration of supported ionic liquid phase catalyst [13] 26

Figure 1.9 Most common cations and anions of Ionic Liquids [48] 29

Figure 1.10 excess phosphine arises from the facile Rh-PPh 3 dissociation equilibrium [103, 104] 31 Figure 1.11 Various ways of acac to bond with metal [28] 32

Figure 1.12 Schematic P-T phase diagram of ZrO 2 [78] 35

Figure 1.13 Three phases of ZrO 2 [78] 35

Figure 1.14 Synthesis of SBA-15 mesoporous silica [108] 37

Figure 1.15 Schematic view of Schlenk line 38

Figure 2.1 Setup for the synthesis of Ligand TPPTS-Cs 3 41

Figure 2.2 Scheme for the synthesis of ZrO 2 support 43

Figure 2.3 Scheme for the synthesis of SBA-15 support [108] 45

Figure 2.4 Schenk system to synthesize catalyst 45

Figure 2.5 Illustrates how diffraction of X-rays by crystal planes allows one to derive lattice by using Bragg relation 48

Figure 2.6 The BET plot 49

Figure 2.7 Isotherm adsorption 50

Figure 2.8 IUPAC classification of hysteresis loops (revised in 1985)[107] 51

Figure 2.9 Ways to perform vibration spectroscopy: Transmission infrared [53] 52

Figure 2.10 Experimental set-ups for temperature programmed (TP) reduction, oxidation and desorption The reactor is inside the oven, the temperature of which can be increased linearly in time [54] 53

Figure 2.11 Transmission electron microscopy with all of the components [53] 53

Figure 2.12 The interaction between the primary electron and sample in an electron microscope leads to a number of detectable signals [49] 54

Figure 2.13 Spin state of a nulear 55

Figure 2.14 A description of the transition energy for a 31 P nucleus 55

Figure 2.15 Scheme of the reactor set-up 56

Figure 2.16 Standard curve of propanal 59

Figure 3.1 XRD patterns of the MCM-41 synthesized from TEOS in acid condition (pH=2) 60

Figure 3.2 XRD patterns of the MCM-41 synthesized from TEOS in base condition (pH=10) with CTAB/TEOS ratio = 0.2, 0.25 0.3, H 2 O/TEOS = 24 60

Figure 3.3 XRD patterns of the MCM-41 synthesised from TEOS with CTAB/TEOS=0,25, H O/TEOS =8; 14; 18; 24; 30 61

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Figure 3.5 Nitrogen isotherm of the MCM-41.8 62

Figure 3.6 Pore distribution of MCM-41.8 62

Figure 3.7 XRD patterns of the SBA-15 synthesised from TEOS 63

Figure 3.8 Nitrogen isotherm of the 63

Figure 3.9 Pore distribution of SBA-15 63

Figure 3.10 The TEM image of SBA-15 64

Figure 3.11 SEM image of Z1.2 65

Figure 3.12 SEM image of Z1.3 65

Figure 3.13 XRD pattern of zirconia prepared by hydrothermal 66

Figure 3.14 Nitrogen isotherm of the ZrO 2 66

Figure 3.15 Pore distribution of ZrO 2 66

Figure 3.16 XRD pattern of SiO 2 67

Figure 3.17 Nitrogen isotherm of the SiO 2 67

Figure 3.18 Pore distribution of SiO 2 67

Figure 3.19 XRD pattern of γ-Al 2 O 3 68

Figure 3.20 Nitrogen isotherm of the Al 2 O 3 68

Figure 3.21 Pore distribution of Al 2 O 3 68

Figure 3.22 IR spectrum of synthesized TPPTS-Cs 3 ligand 69

Figure 3.23 NMR 1 H spFigure 3.23ectrum of synthesized TPPTS-Cs 3 ligand 1 70

Figure 3.24 NMR 31 P spectrum of synthesized TPPTS-Cs 3 ligand 1 70

Figure 3.25 NMR 1 H spectrum of synthesized TPPTS-Cs 3 ligand 2 71

Figure 3.26 NMR 31 P spectrum of synthesized TPPTS-Cs 3 ligand 2 71

Figure 3.27 NMR 1 H spectrum of synthesized TPPTS-Cs 3 ligand 3 72

Figure 3.28 NMR 31 P spectrum of synthesized TPPTS-Cs 3 ligand 3 72

Figure 3.29 The influence of ligand to the catalytic activity of catalysts 74

Figure 3.30 IR spectra of ionic liquid [BMIM][n-C 8 H 17 OSO 3 ] 75

Figure 3.31 IR spectra of SILP on MCM-41 76

Figure 3.32 IR spectra of SILP on SBA-15 76

Figure 3.33 IR spectra of SILP on ZrO 2 76

Figure 3.34 IR spectra of SILP on Al 2 O 3 77

Figure 3.35 IR spectra of 0.2%Rh–10%IL–L/Rh=10/SiO 2 77

Figure 3.36 IR spectra of used SILP on Al 2 O 3 78

Figure 3.37 IR spectra of used SILP on MCM-41 78

Figure 3.38 IR spectra of used SILP on SBA-15 79

Figure 3.39 TEM images of SILP catalysts 82

Figure 3.40 Pore distribution of SiO 2 and 0.2%Rh-10%Il-L/Rh=10 SiO 2 83

Figure 3.41 Pore distribution of Al 2 O 3 support and SILP catalysts on Al 2 O 3 support 84

Figure 3.42 Description of small pore filling by IL 84

Figure 3.43 Pore distribution of ZrO 2 support and SILP catalysts on ZrO 2 85

Figure 3.44 Pore distribution of MCM-41 support and SILP catalysts on MCM-41 support 88

Figure 3.45 Pore distribution of SBA-15 support and SILP catalysts on SBA-15 support 90

Figure 3.46 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/ SiO 2 at different reaction temperatures on time 91

Figure 3.47 The influence of reaction temperatures on the catalytic activity of L/Rh=10/SiO 2 92 Figure 3.48 Propanal selectivity of 0.2%Rh-10%IL-L/Rh=10/ SiO 2 at different reaction temperatures 93 Figure 3.49 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/Al 2 O 3 at different reaction temperatures 94 Figure 3.50 TPD NH 3 profiles of Al 2 O 3 supports 94 Figure 3.51 Propanal selectivity of 0.2%Rh-10%IL-L/Rh=10/Al 2 O 3 at different reaction temperatures 95 Figure 3.52 Catalytic activity of SILP on Al 2 O 3 catalysts with different IL loading 96 Figure 3.53 Selectivity of catalysts with diffrent IL loading content on Al 2 O 3 support 97 Figure 3.54 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/ZrO 2 at different reaction temperatures 98 Figure 3.55 TPD NH 3 profiles of ZrO 2 supports 98 Figure 3.56 Propanal selectivity of 0.2%Rh-10%IL-L/Rh=10/ZrO 2 at different reaction temperatures 99 Figure 3.57 Catalytic activity of SILP on ZrO 2 catalysts with different IL loading 100 Figure 3.58 Selectivity of catalysts with diffrent IL loading content on ZrO 2 support 100 Figure 3.59 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/MCM-41 catalyst at different reaction temperatures on time 101 Figure 3.60 Catalytic activity of SILP on MCM-41 catalysts with different IL loading 102 Figure 3.61 Propanal selectivity of SILP on MCM-41 catalysts with different IL loading 103 Figure 3.62 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/SBA-15catalyst at different reaction temperatures on time 104 Figure 3.63 Catalytic activity of SILP on SBA-15 catalysts with different IL loading 105 Figure 3.64 Propanal selectivity of SILP on SBA-15 catalysts with different IL loading 105 Figure 3.65 The catalytic activity of SILP with 10%IL, 0.2%Rh, L/Rh=10 on different supports 106 Figure 3.66 Activity comparison of catalysts with other IL content on different support: (a) 30%IL, (b) 40%Il, (c)50%IL, (d) 70%IL 108 Figure 3.67 Comparison of the best catalysts on different supports 109 Figure 3.68 Comparison of the catalysts with the same weight percent of IL 110

0.2%Rh-10%IL-11

INTRODUCTION

In recent years, two-phase catalysis has been emerged as a new field of catalyzed processes and has achieved industrial-scale importance in olefin hydroformylation Two-phase reactions have a number of advantages, for example, ease of separation of catalyst and product, catalysts can be tailored to the particular problem, use of special properties and effects of water as a solvent, and low environmental impact

Ionic liquids have received worldwide academic and industrial attention as substitutes for organic solvents in catalysis Beyond their very low vapour pressure, attractive features

of ionic liquids for catalysis included: their versatility, their capacity to dissolve a wide range of inorganic and some organic materials, their ability to act both as catalyst and solvent, their tendency to suppress conventional solvation and solvolysis phenomena, resulting in increased reaction rates and better selectivity (reduction of side reactions) Their potential to reduce pollution in industrial processes has led to investigation of ionic liquids as alternative reaction media for a variety of applications that conventionally use organic solvents

Recently, a novel approach to immobilizing homogeneous catalysts on solid supports (supported ionic liquid phase – SILP catalyst) has been reported, in which the hydroformylation complex catalyst was distributed in ionic liquid medium contained in pore system of a solid support This results to an excellent stability, reusability and even improved activity of hydroformylation catalyst Using these novel catalysts, the classical homogeneous hydroformylation becomes heterogeneous with solid catalysts in fixed bed reactors Hydroformylation on SILP catalysts has been applied for many hydrocarbons from C3 to C8 Since 2010, SILP catalysts on SiO2 support were firstly applied for the hydroformylation of ethylene and many promising results has been obtained

Therefore, the goal of this thesis was to synthesize SILP catalysts with different ionic liquid loading content on other supports (ZrO2, Al2O3, MCM-41, SBA-15) to compare with the catalysts on SiO2 These catalysts were applied for hydroformylation of ethylene It is expected that the optimized ionic liquid loading content on different supports will be found and the influence of the nature of the supports (surface area, pore size, acidity ) on the catalytic activity will be explored

The thesis contains four chapters The first chapter summarizes the literature review about the hydroformylation process, synthesis, the structure, the catalytic property of SILP catalyst

The second chapter introduces basic principles of the physico-chemical methods used in the thesis, catalyst synthesis and catalytic measurement

The most important chapter (chapter 3) focused on catalytic activity of hydroformylation of ethylene using synthesized SILP catalysts on different supports Furthermore, the influence of ionic liquid loading content and supports on the catalysts are investigated in detail in this chapter

The last chapters (chapter 4) summarizes general conclusion of the thesis

1 LITERATURE REVIEW

1.1 Hydroformylation of alkenes

Hydroformylation has been one of the most important homogenous catalysis processes that has been largely applied in industry nowadays It transforms olefins and syngas (CO/H2) into aldehydes in one single, atom economic step [1]

Otto Roelen discovered Hydroformylation in 1938 during an investigation of the origin

of oxygenated products occurring in cobalt catalyzed Fischer-Tropsch reactions [84] Roelen's observation that ethylene, H2 and CO were converted into propanal, and at higher pressures, diethyl ketone, marked the beginning of hydroformylation catalysis In the hydroformylation reaction, the elements of formaldehyde (H and CHO) are added across a double bond to give an aldehyde Both linear and branched products can be produced Depending on the catalyst and conditions, the aldehydes can be directly reduced to alcohols during the reaction [28, 80] This seminal work was based on cobalt carbonyl catalyst with harsh conditions and low reactivity The first rhodium-catalyzed hydroformylation was reported by Wilkinson group in the middle of 1960‟s It was found that rhodium complexes modified by phosphine ligands can make hydroformylation run at mild conditions with much higher activity and selectivity comparing to cobalt catalysts [24] The detailed studies on phosphine ligands revealed that the variations on phosphine ligands can significantly affect the reaction rate and selectivity Thus, modern research on hydroformylation focuses mainly on phosphorus ligands modified rhodium catalysts and its applications [89]

The first generation of hydroformylation catalysts was based on cobalt carbonyl without phosphine ligand [1] The conditions were harsh, as the reactivity of cobalt is low The second generation processes use rhodium as the metal and the first ligand-modified process came on stream in 1974 (Celanese) and more were to follow in 1976 (Union Carbide Corporation) and in 1978 (Mitsubishi Chemical Corporation), all using triphenylphosphine (TPP) The UCC process has been licensed to many other users and it is often referred to as the LPO process The third generation process concerns the Ruhrchemic-RhonePoulene process utilizing a two-phase system containing water-soluble rhodium-TPPTS in one phase and the product butanal in the organic phase The process has been in operation in Oberhausen since 1984 by Celanese, as the company is called today Since 1995 this process is also used for the hydroformylation of 1 –butene [1]

Hydroformylation has been widely applied in the synthesis of intermediates both for

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obtained through the hydroformylation reaction It is convenient to further convert aldehyde products into alcohols, amines, carboxylic acid derivatives, and other high valued chemicals Linear aldehydes are important raw materials for fine chemicals, in particular for detergents and polymer plasticizer Optically active aldehydes, produced by the asymmetric version of hydroformylation, are versatile intermediates for the synthesis of many biologically active compounds, pharmaceuticals and natural products [33]

1.2 Catalysts for hydroformylation reaction

The compounds of platinum group metals are known to be active in hydroformylation, but the main interest lies in catalysis by cobalt and rhodium compounds [1] Initially, hydroformylation was performed with cobalt based catalyst, but it was recognized that rhodium is by far the most active metal being used On the other hand platinum and ruthenium catalysts are mainly subjects of academic interest, not thoroughly investigated

by industrial researchers [1,77] The general accepted order of catalytic activity for the group VIII metals in hydroformylation reaction [30] is as

Rh >>>Co > Ir, Ru > Os > Pt > Pd > Fe > Ni The hydroformylation catalysts consist of a transition metal ion (M) which interacts with CO and hydrogen to form metal carbonyl hydride species, which is an active hydroformylation catalyst If complexes containing only carbonyl ligands are known as unmodified catalysts, on the other hand, introduction of tailor made ligand to the transition metals are known as modified catalysts Typical complexes are HCo(CO)4, HCo(CO)3PBu3and HRh(CO)(PR3)3 [35]

The improvement of the catalyst‟s performance has mainly been achieved by variation

of modifying ligand [64] Among the compounds, which are able to coordinate to a transition metal to form complexes, phosphines are most used and accepted ligands [64,9] Nitrogen containing ligands showed lower reaction rates than phosphine and carbon monoxide due to their stronger coordination to the metal centers A comparative study of Ph3R (where R= elements of Main Group V) in the hydroformylation of 1-dodecane [52] showed following order

Ph3P> Ph3N> Ph3As, Ph3Sb> Ph3Bi Catalysts that are used for industrial hydroformylation processes are cobalt and rhodium based metal complexes Cobalt-catalyzed hydroformylation is used since the 50s Cobalt processes are mostly used in the production of medium- to long chain olefins While Rhodium catalyst processes are used since the 70s Rhodium catalysts are more expensive than cobalt catalysts and have higher activity, but have lower activity in case of branched olefins Three developmental stages of hydroformylation catalysts can be visualized in Figure 1.1 Some of the most important industrially implemented oxo process based on Co and Rh catalysts are shown in Table 1.1

Figure 1.1 Three stages of the catalyst development for the hydroformylation reaction

[14]

Table 1.1 Developments of hydroformylation catalysts

Catalyst

Process

BASF, Rhurchemie process

Shell process Ruhrchemi

e process

Union Carbide process (LPO)

Rhône-Poulenc process

HRh(CO)(TPPTS)3

of catalyst separation and recycling

1.2.1 Cobalt catalyzed hydroformylation

The first catalyst used in hydroformylation was cobalt Initially, hydroformylation was performed with heterogeneous cobalt catalysts of the Fischer Tropsch type But it was established that the catalytic active species in the cobalt-catalyzed hydroformylation is the complex hydrido cobalt carbonyl; HCo(CO)4, a yellow liquid and strong acid (stable only under high CO/H2 pressure) is formed from precursors Co2(CO)8 Heck and Breslow (1960) [82] The Co2(CO)8 reacts with H2 under catalysis reaction conditions to form two equivalents of HCo(CO)4 Both species are extremely toxic, similar to Ni(CO)4

Figure 1.2 Interaction of Co 2 (CO) 8 with H 2 and ligand [82]

The stability of the HCo(CO)4 complex is strongly dependent upon the partial pressure

of syngas (200 - 300 bar) and temperature (110 - 180°C) as it produces metallic cobalt if the CO partial pressure is not kept high enough [9] The regioselectivity of HCo(CO)4 or HCo(CO)3 for producing the more valuable linear aldehydes varies with reaction conditions and alkene substrates used and can typically get linear to branched aldehyde ratios of 2 - 3 to 1 The ligand modification in HCo(CO)4 was significant progress in hydroformylation The replacement of carbon monoxide with trialkylphosphine such as PBu3 (Shell, 1964) enhances the selectivity towards linear aldehyde (n/b) and the stability

of cobalt carbonyl, leading to reduced carbon monoxide pressure [60] Instead of 200 - 300 bars of H2/CO pressure needed for HCo(CO)4, the monophosphine substituted complex

HCo(CO)3(PR3) needed only 50 - 100 bars of pressure, and could be run at higher temperatures without any decomposition of catalyst to cobalt metal However, the higher stability of the HCo(CO)3(PR3) catalyst, due to stronger Co - CO bonding means that this catalyst is less active than HCo(CO)4 (about 5–10 times slower) From a steric viewpoint the bulkier trialkylphosphine ligand favors formation of linear products While linear to branched ratios of only 2 - 3:1 are typically found for HCo(CO)4, higher regioselectivity of

6 - 7:1 occur for HCo(CO)3(PR3) Another advantage is that the separation of the products

by distillation is possible in contrast to unmodified cobalt catalysts Consequently, the phosphine modified cobalt catalyst system is still used by SHELL for the production of surfactant alcohols from internal linear olefins It suggested a renewed interest in modification of HCo(CO)4 by phosphorous based ligands as result hydroformylation with cobalt catalyst was developed and are in significant progress [29]

The discovery of hydroformylation of alkenes by Roelen occurred in fact accidentally, while he was studying the Fischer-Tropsch reaction with a heterogeneous cobalt catalyst in the late thirties That‟s why cobalt processes were first developed They are still mostly used in the production of medium to long chain olefins, whereas rhodium catalysts only dominate the hydroformylation of propene [12]

The classical oxo process using cobalt catalyst in solution operates at very high pressure (200 to 450 bar) and at a temperature from 140 to 180°C The active catalyst is in the form

of hydridotetracarbonyl cobalt HCo(CO)4 High pressure of CO is required to ensure catalyst stability during hydroformylation Typically the catalyst has to be decomposed before the reaction product can be recovered; therefore the process involves cumbersome and costly catalyst recycle

Most of industrial cobalt based processes are pretty similar, the main difference between them concerns the separation of products and catalyst

Exxon process

The Exxon process (previously called Kuhlmann process) is designed to convert higher alkenes The HCo(CO)4 catalyst reacts with syngas in the reactor under normal hydroformylation conditions The recycling of the catalyst involves two main steps: the recovery of sodium tetracarbonylcobaltate and its regenerative conversion into cobalt tetracarbonyl hydride After the reactor, the product mixture is treated with aqueous alkali

to convert HCo(CO)4 to water-soluble NaCo(CO)4, which is extracted as aqueous solution from the organic product phase Then the catalyst is regenerated by addition of H2SO4 The elegance of this process is that the cobalt catalyst is not decomposed by oxidation but it is left in the system as tetracarbonylcobaltate [1] In propylene hydroformylation, the process results in about 80 wt% of butyraldehydes, with ratio of linear/branched product (n/i ratio) from 3 to 4 [102]

Shell process

In the Shell process higher olefins are converted using a phosphine modified cobalt

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operated at lower pressure (25-100 bar) In this process the product mixture is distilled, the organic products leave the distillation column at the top and the catalyst is recovered at the bottom Before re-entering the reactor the catalyst recycle is upgraded with catalyst and phosphine ligand The drawback is that the process requires a larger reactor volume as the activity of the ligand modified catalyst is low (5 times lower than HCo(CO)4) [1] Although higher n/i ratios are obtained (equal to about 9), the selectivity to aldehydes is lower as hydrogenation side and secondary reactions occur to a greater extent giving both alkanes and alcohols [102]

BASF process

The BASF hydroformylation process of propene or higher olefins occurs under high pressure The catalyst is in the form of HCo(CO)4 This catalyst is separated from the liquid product by addition of oxygen and formic or acetic acid, leading to an aqueous solution which contains the cobalt mainly as formate or acetate The organic products are withdrawn in a phase separator and the cobalt solution is concentrated afterwards and sent

to the carbonyl generator The cobalt losses are compensated The best selectivity to linear aldehydes is claimed for low temperatures [32]

1.2.2 Rhodium catalyzed hydroformylation

The fundamental work by Wilkinson [23] showed that rhodium (Rh) complexes with PPh3 allowed the reaction to proceed at much lower pressures and the subsequent development of an industrial process in the 1970s represented a break-through for Rh catalysis Higher price of Rh was offset by mild reaction conditions, simpler and therefore cheaper equipment, high efficiency, and high yield of desire linear products

The most important industrial processes using rhodium as a metal catalyst are discussed below

UCC process

The Union Carbide Corporation (UCC) commercially applies the LPO (Low Pressure Oxo) process for the hydroformylation of propene in a liquid-recycle process The reaction takes place in a stainless steel reactor where the gas and propene are introduced via a feed line and a gas-recycle The catalyst is dissolved in high-boiling aldehyde condensation products The liquid product stream out of the reactor consists of dissolved gas, aldehydes, rhodium-phosphine catalyst complex, free phosphine ligand and the higher-boiling aldehyde condensation products In order to split all this complex mixture the product stream enters a separator and a flash evaporator, where the major part of inerts and unconverted reactants is separated overhead The flashed-off gases are compressed and returned to the reactor, whereas the liquid stream is heated and is fed to two distillation columns in series The vaporous aldehydes are later condensed and sent to the upgrading section

At the bottom the catalyst solution is separated and recycled in the reactor The whole UCC process is well described by Beller et al (1995) [13] The processes operated by

Celanese and Mitsubishi for butyraldehyde production resemble to the LPO process introduced by UCC

Ruhrchemie/Rhône-Poulenc process

Following the laboratory results on several biphasic catalytic reactions (hydroformylation, hydrocyanation and diene conversion) based on the idea of E Kuntz [58, 59] and patented by Rhône-Poulenc, a 100 000 tons/year capacity butyraldehyde plant (now increased to 300 000 tons/year capacity) was build in Oberhausen in 1984 based on this technology

It was the joint work of the Ruhrchemie AG (now part of Celanese AG) and Poulenc which gave the name Ruhrchemie/Rhône-Poulenc (RCH/RP) process, an aqueous biphasic hydroformylation process The RCH/RP unit is essentially a continuous stirred tank reactor, surmounted by a phase separator and followed by a stripping column Propylene with syngas is fed into the reactor containing the aqueous catalyst solution (rhodium/tri-sulfonated triphenylphosphine) After the reaction the crude aldehyde product passes into a decanter, where it is degassed and separated into the aqueous catalyst solution and the organic aldehyde phase The heat of the aqueous phase is then used to produce steam in a heat exchanger After separation the organic phase is passed through a stripping column, where the unreacted olefin is separated and sent back to the reactor The product mixture is then distilled into n- and iso- butyraldehyde (linear/branched) While the n/i ratio was about 8 for the UCC, it is equal to almost 19 for the RCH/RP process [15]

Rhône-The produced steam from the reactor is used in the reboiler of the distillation unit, which is a big advantage However the system is limited by the solubility of organic substrates in aqueous phase Long chain alkenes (higher than butene) cannot be hydroformylated economically by the RCH/RP process because of their low solubility in water

1.2.3 Heterogenization of homogeneous catalysts

A heterogenized catalyst is a homogeneous catalyst mostly attached via a covalent bond

to an insoluble support Silica is often used as support When functional groups are not present for attaching the catalyst to the support the catalyst needs to be modified, but it must be taken into account that this can influence the activity and selectivity Also the support can have an effect on activity and selectivity, because they can have catalytically active groups or groups that can interact with the catalyst in a beneficial or detrimental way [21]

There are several advantages which compensate the more difficult preparation of a catalyst, namely reusing the catalyst and less waste So expensive or difficult-to-obtain components, such as ligands or scarce metals, can be recovered Also the products can be

19

easier separated when the catalyst residues have been removed Another advantage is that more than one catalyst can be present in the reaction mixture on the same solid support or different supports, so that multi-stage reactions can be carried out in one pot Solid catalysts can also be used in reactors such as fixed or fluidized bed reactors, flow reactor, membrane reactor, etc The reactants flow over or through a bed or film of catalyst with reaction and separation being achieved at the same time

There are many possibilities to heterogenize homogeneous catalysts, namely covalent attachment, ionic attachment, ship in a bottle, entanglement and supported liquid phase The first and most common method is covalent attachment The advantage of covalent bonding of the catalyst to the support is its stability and the different ways of forming A drawback is the requirement of a binding site for the catalyst which can add complexity and change characteristics of the catalyst Another method is ionic attachment The heterogenization occurs because of the electrostatic attraction between the catalyst and support This method is ideal for charged catalysts and can be carried out easily The conditions are that the catalyst remains charged during the whole catalytic cycle and ion exchange is not allowed The next method is„ship in a bottle‟ The catalyst is prepared inside a cage-like pore which has greater dimensions so that the catalyst is entrapped It is

an effective immobilization method, but there is a restricted range and there are difficulties with diffusion Entanglement can be used when the catalyst is a nanoparticle Nanoparticles have the propensity to agglomerate, which results in decreasing activity This method prevents this and is based on the fact that many polysaccharides form gels under the appropriate conditions The catalyst can be entrapped and tangled up in this network of H-bonded polysaccharide strands The advantages of this method are that it is easily done and the polysaccharides are generally inexpensive The need for entanglement between the catalyst precursor and polymer and the limited thermal stability are serious drawbacks [21]

The last method for heterogenizing a homogeneous catalyst is supported liquid phase

(SLP) The SLP technique was discovered by Davis et al in 1989 by introducing a

supported aqueous-phase (SAP) catalyst by forming a thin layer of Rh-TPPTS dissolved in water onto high-surface-area hydrophilic silica TPPTS is the abbreviation for tri(m-sulfonyl)-triphenyl phosphine trisodium salt [90] This technique combines features of liquid-liquid biphasic catalysis and solid-liquid biphasic catalysis The important advantage

of thin film catalysis compared to biphasic catalysis is that the diffusion path is shorter, so the mass transfer limitations that occur are negligible [48] The principle of supported liquid phase catalyst (SLPC) is shown in Figure 1.3

Figure 1.3 Schematic representation of a supported liquid phase catalyst (SLPC)[48]

The concept is a homogeneous catalyst dissolved in a thin film of liquid on the surface and within the pores of a solid support Generally, the method is dissolving the homogeneous catalyst in a small amount of liquid phase and dispersing this over the solid support The SLPC appears as heterogeneous, but the homogeneous catalyst is dissolved in the liquid on the support, so it is acting as a homogeneous catalyst These results in an activity and selectivity comparable to homogeneous catalysts but no separation problems occur The most important requirement for SLP catalysts is that the catalyst doesn‟t leach out into the organic phase, because this results in deactivation of the catalyst Very low water miscibility and no dissolving of the catalyst in the organic phase are the conditions for the organic solvent

Horvath reported that SAP catalysts have good activity for the hydroformylation of higher alkenes, like hexane, octene and decene, but show deactivation via the loss of water

[90] For this reason, Mehnert et al used ionic liquids (ILs) instead of water and prepared

supported ionic liquid catalysts (SILC) Ionic liquids will be further discussed SILC were more active for the liquid-phase hydroformylation of 1-hexene than SAPC But a loss of

Rh occurs at high conversion, because of depletion of the supported ionic liquid layer into

the reaction medium(Shylesh, Hanna, Werner, & Bell, 2012) Mehnert et al introduced in

2002 SILP catalysis for slurry phase hydroformylation and hydrogenation reactions

Wasserscheid et al reported supported ionic liquid-phase (SILP) Rh-catalysts for the

vapor-phase hydroformylation of propene These catalysts were very stable and active under continuous gas-phase reaction conditions [90] ILs have more positive effects on the immobilization of the catalyst compared to water, for example higher reaction rate and selectivity There are two categories, namely SILP catalysts and solid catalysts with ionic liquid layer (SCILL) Many studies confirm that the use of SILP catalysts for hydroformylation of alkenes is promising [40]

21

1.3 Mechanism of hydroformylation reaction

1.3.1 Mechanism for Cobalt-Catalyzed Hydroformylation

The first catalyst used in hydroformylation was cobalt Under hydroformylation conditions at high pressure of carbon monoxide and hydrogen, a hydrido–cobalt–tetracarbonyl complex HCo(CO)4 is formed from precursors like cobalt acetate This complex is commonly accepted as the catalytic active species in the cobalt-catalyzed hydroformylation entering the reaction cycle according to Heck and Breslow (1960) (Figure 1.4) [36, 103]

Figure 1.4 Cobalt-catalyzed hydroformylation reaction cycle [36, 103]

The hydrido–cobalt–tetracarbonyl complex (I) undergoes a CO-dissociation reaction to form the 16-electron species HCo(CO)3 (II) This structure forms a π-complex (III) with the substrate and is a possible explanation for the formation of further (C =C) double bond isomers of the substrate In the next equilibrium reaction step, the π-complex is converted into the corresponding σ-complex (IV), which has the opportunity to add carbon monoxide

to form the 18 electron species (V)

In the next step of the reaction cycle, the carbon monoxide is inserted into the carbon–cobalt bond At this time, the subsequent aldehyde can be considered as preformed This step leads to the 16 electron species (VI) Once again, carbon monoxide is associated to end up in the 18 electron species (VII) In the last step of the reaction cycle, hydrogen is added to release the catalytically active hydrido–cobalt–tetracarbonyl complex (I) Likewise, the aldehyde is formed by a final reductive elimination step

The reaction cycle discussed is generally accepted for unmodified cobalt and unmodified rhodium catalysts But it has to be stressed here that to date no one has been able to prove the single steps conclusively; it is still a subject of research, with modern techniques like in situ spectroscopic methods and molecular modeling in conjunction with kinetic investigations

1.3.2 Mechanism for Rhodium-Catalyzed Hydroformylation

Extensive mechanistic studies have been reported among which the so-called dissociative mechanism proposed by Breslow and Heck is widely accepted as the catalytic cycle of hydroformylation Although it was first proposed for cobalt-catalyzed hydroformylation, this mechanism is applicable for rhodium complex-catalyzed hydroformylation with chelating monophosphines and diphosphines

Figure 1.5 Mechanism for Rhodium-Catalyzed Hydroformylation [1, 84, 104, 103]

In this mechanism, the trigonal bipyramidal complex 1 (18-electron species) is believed

to be a key active catalyst species which is formed by the reaction rhodium precursor with ligands (L) in the presence of CO and H2 The dissociation of one carbon monoxide from this complex generates a 16-electron coordinatively unsaturated species 2 The main catalytic cycle starts from the coordination of olefin to the rhodium center in the equatorial position, forming a trigonal bipyramidal hydrido olefin complex 3/3' The subsequent olefin insertion into the Rh-H bond generates tetragonal alkyl rhodium complexes 4 and 5 (leading to linear and brunched products, respectively), which was revealed to be the key step determining the regio- and enantioselectivity of the hydroformylation reaction Next, the coordination of carbon monoxide to the rhodium center generates trigonal bipyramidal complexes 6 and 7, respectively, which is followed by migratory insertion of the alkyl

23

group to one of the coordinated carbon monoxide yields tetragonal acyl complexes 8 and 9 Oxidative addition of molecular hydrogen affords tetragonal bipyramidal rhodium complexes 10 and 11 Finally, Reductive elimination yields the linear aldehyde 12 and the branched aldehyde 13, and regenerates the catalytically active species 2

1.3.3 Mechanism for Rhodium-Catalyzed Hydroformylation of ethylene

The mechanism on supported catalysts for hydorformylation shown in Figure 1.6 The active species are 16-electron hydrides of the general formula HRh(CO)x(PPh3)3-x (x = 1, 2) formed by the dissociation of CO from the 18-electron carbonyl hydride [31, 27] The basic steps in the hydroformylation reaction after the initial formation of the hydrido metal carbonyl are: (1) dissociation of CO to form the unsaturated 16-electron species, (2) coordination of alkene, (3) formation of the alkylmetal carbonyl species, (4) coordination

of CO, (5) insertion of CO to form the acylmetal carbonyl, (6) oxidative addition of hydrogen, and (7) cleavage of the acylmetal species by hydrogen to form the aldehyde and regeneration of the hydridometal carbonyl It is generally believed that the oxidative addition of hydrogen to the rhodium-acyl complex is the rate determining step [31] Leeuwen [1] has proposed that, roughly speaking, in phosphine catalyst systems the migratory insertion of the alkene into Rh-H is the rate-determining step under standard industrial process conditions

Figure 1.6 Wilkinson’s dissociative mechanism presented for rhodium-phosphine catalysed

ethene hydroformylation [84,27]

The reaction mechanism on supported catalysts follows a similar mechanism Olivé and Olivé [32] have suggested that the decisive difference between the homogeneous and the heterogeneous process is the availability of a free, mobile, very reactive hydrido-metal species in solution According to them, the last step (steps 6 and 7 in Scheme 2), the transformation of the acyl-metal species to the aldehyde, proceeds through reaction with a second catalyst species in homogeneous media, but in heterogeneous media the oxidative addition of molecular hydrogen to an acyl-metal species is the only means of formation of

Henrici-the aldehyde The hydrogenation of Henrici-the acyl intermediate was identified as Henrici-the rate determining step at 0.1 MPa on Rh/SiO2 [14] In some studies, the CO insertion selectivity

on supported unmodified metal catalysts, is related exclusively to the linearly adsorbed CO

on isolated Rh0 sites [47], whereas other studies show that reaction rate and selectivity for hydroformylation increases in the presence of Rh+ sites [18] Thus, the dispersion of the catalytic metal and the extent of reduction are the main factors determining the CO insertion activity, and thereby, the selectivity towards aldehyde formation According to Sachtler and Ichikawa [86], two types of active sites are responsible for aldehyde formation: isolated, partially oxidised metal crystallites for the migratory CO insertion into metal alkyl bonds, and fairly large metal ensembles for the dissociation of hydrogen Hedrick et al [38, 19] noticed that on a Mn-Rh/SiO2 catalyst, spill-over hydrogen from the metal to the silica surface plays a role in the hydrogenation of the acyl intermediate Thus, the hydrogenation of ethyl species to form ethane, and the hydrogenation of adsorbed acyl species to form propanal, are involved with two different types hydrogen: metal adsorbed hydrogen and hydrogen from Si-OH

1.4 Application of hydroformylated products

Main consuming industries of aldehydes are the plasticizer, polymer (n-butanal is converted to 2-ethylhexanol which is used in the production of dioctyl phthalate DOP, a plasticizer that is used in the poly vinyl chloride (PVC) applications) and detergent industry followed by solvents, chemical intermediates, flavors and fragrances and lubricants

Starting from mid 1950s hydroformylation gained an importance and over the recent years a steady and continuous growth in production capacity of aldehydes has taken place Production of aldehydes by the hydroformylation process is now well beyond 10 million metric tons annually

Aldehydes themselves are of little commercial interest, but they open a way to alcohols via hydrogenation, to carboxylic acids via oxidation, and to amines via reductive amination Aldolization is the starting point for branched alcohols, carboxylic acids, and amines with a double carbon number These products are mostly applied in the fine chemicals and pharmaceutical industry as lubricants, plasticizers, detergents, pharmaceutical intermediates, chiral auxiliaries for synthesis, agrochemicals, perfumery, food, clothing, fuel etc [4, 15] As an example of co-aldolization, the route to polyols is shown All reactions shown in Figure 1.7 are commercially employed, starting from propene (R = H)

25

Figure 1.7 Overview of the use of aldehydes [4, 15]

1.5 Supported Ionic Liquid Phase Catalysts (SILP)

The Supported Ionic Liquid Phase (SILP) Catalyst Concept was developed by Mehnert

et al [66] The concept was introduced in order to overcome the transport limitation drawbacks of homogenous IL catalyst systems By coating the IL as a thin film on a solid support, the accessible interphase area increases (comparable to values in heterogeneous catalysis) while the diffusion pathways decrease From the standpoint of thermodynamics, the IL film still acts like a bulk liquid Therefore, this concept bridges the gap between heterogeneous and homogenous catalysis

This principle was investigated by different research groups Mehnert et al studied hydrogenation reactions of olefins as well as Friedel Crafts reactions and hydroformylation reactions [66, 67, 68] The choice of IL for the catalyst system was mainly driven by the commercial availability They report overall conversions and yields, but no detailed kinetics of the investigated systems Virtanen et al use a different name for the same concept (Supported Ionic Liquid Catalysis, SILCA) They mainly looked into hydrogenation reactions of natural products [63, 97, 96] Beside a pure system optimization, they also studied detailed kinetics and general hydrogenation reactions of organic compounds [98] Riisager et al investigated hydroformylation reactions of 1-alkenes [2, 3] and carbonylation reactions They determined overall conversions and yields

as well as kinetics For the kinetic expressions, partial pressures of the reactants were used This research group is working closely associated with Haumann et al., who used SILP for various purposes Haumann et al also investigated hydroformylation reactions of 1-alkenes [73] Werner et al studied the Watergas-Shift-Reaction in SILP Catalyst Systems Joni et

al investigated Friedel Crafts alcylations of cumene as well as the isopropylation of toluene and cumene Beside classical reactive applications, Kuhlmann et al looked into separation science, namely the desulfurization of diesel using SILP [56, 57]

The direction of the papers here introduced is mostly limited to chemical considerations The transition metal catalysts and the ligands are optimized for the respective problem Further, only a part of the papers contains a proper modeling section This modeling is done without consideration of the VLE of the involved compounds However, for an in-depth understanding of SILP Catalyst Systems, solution thermodynamics play an important role

Figure 1.8 Illustration of supported ionic liquid phase catalyst [13]

In these SILP systems, a thin film of ionic liquid containing the homogeneous catalyst is immobilised on the surface of a high-area, porous support material, as depicted in Figure 1.8 SILP catalysts appear as solids, the active species dissolved in the liquid phase on the support, maintaining the attractive properties of ionic liquid homogeneous catalysts such as good dispersion of molecular reactant, and high activity Thus, SILP belonged to the group

of Supported liquid phase Catalysts (SLPC) It can be understood that the SILP concept combines the advantages of catalytic homogeneous process, and heterogeneous process technology SILP hydroformylation catalysis is an alternative way of performing immobilized hydroformylation catalysis

The principle is that the gaseous or vapor-phase ethylene, carbon monoxide and

27

homogeneous catalyst is present in this thin film, so the reaction occurs The formed aldehydes diffuse out of the thin film and the pore The main advantage of the SILP compared to classical biphasic systems is the IL film, because no mass transfer limitations occur when there are no other products in the pores of the support and there is more efficient utilization of the IL, because the IL surface has increased relatively to it volume SILP catalyst includes three components: solid support, an ionic liquid film, ligand and metal catalyst (commonly transition metal complex), which will be discussed below

1.5.1 Ionic liquid (ILs)

Ionic liquids have been generating increasing interest over the last decade It is a testament to the speed with which ionic liquids have caught the popular chemical imagination that in 1999 a monograph titled “Modern Solvents in Organic Synthesis”, could be published in which ionic liquids received no mention at all; a situation that would

be unimaginable now Much of this interest is centred on their possible use as “greener” alternatives to volatile organic solvents (see below) There is, however, also a more fundamental interest in how the unusual solvent environment that they provide for solute species might affect reactions conducted in them There have been a number of excellent ionic liquid reviews concerning their chemical and physical properties, and applications in synthesis and catalysis

Although it is only an arbitrary divide, ionic liquids are generally defined as salts that melt at or below 100 C to afford liquids composed solely of cations and anions In some cases the ionic liquids are free-flowing liquids at room temperature, in which case they can

be called ambient temperature ionic liquids Of course, these latter liquids have real advantages over higher melting salts in terms of the practicalities of handling [92]

The most important physical property of ionic liquids is that their vapour pressure is negligibly small at room temperature As a result, ionic liquids are odorless They do not evaporate, even when exposed to vacuum, and most of them do not combust, even when exposed to an open flame The fact that ionic liquids are non-volatile and non-flammable makes them safer and more environmentally benign solvents than the traditional volatile organic solvents Other properties of ionic liquids are inherent to salts in the liquid state and include wide liquid temperature range allowing excellent kinetic control in reactions, good thermal stability, high ionic conductivity and wide electrochemical window resulting

in high electrochemical stability of ionic liquids against oxidation or reduction reactions Furthermore, ionic liquids are good solvents for both organic and inorganic materials, polar and non-polar, which makes them suitable for catalysis [92] It is possible to tune the physical and chemical properties of ionic liquids by varying the nature of the anions and

cations In this way, ionic liquids can be made task-specific Table 1.2 gives a compilation

of some physico-chemical properties of ionic liquids with their beneficial impacts on catalysis

Table 1.2 Physico-chemical properties of ionic liquids and their beneficial impacts on

catalysis [92]

Properties of Ionic Liquids Benefits for catalysis

Very Low vapour pressure

Low melting point

Reasonable thermal stability

Large working liquid range of temperature

High heat conductivity (higher

than water)

Facilitates the management of large reactors

Permits a very rapid removal of the heat of the reaction Good ionic conductivity

Wide electrochemical window

Can be combined with electrochemical processes Can be combined with microwave irradiation

May be nonprotic May be used with organometallic compounds

May be protic May be used as both acidic catalyst and solvent

Adjustable coordination

properties

Ionic liquids have the potential to be polar yet weakly coordinating toward transition metal complexes; they may enhance reaction rates involving cationic electrophilic intermediates

Can exhibit Lewis acidity May act as both co-catalyst and solvent

Adjustable miscibility with

organic compounds (may be

hydrophobic or hydrophilic)

Unique ability to dissolve polar substances in a non aqueous environment

Good solvent for multiphase catalysis

May provide a solution to product separation from catalyst/solvent

High affinity for ionic

29

properties or their unique combinations of polarity/nucleophilicity e.g stabilization of ionic transition metal complexes Liquid-liquid biphasic catalysis and IL thin film catalysis are the most important concepts for IL in catalysis Figure 1.9 shows a list of typical cations and anions which form ionic liquids

Figure 1.9 Most common cations and anions of Ionic Liquids [48]

Selecting the most suitable IL for the given application has become easier over the past ten years, due to the higher amount of experimental data which have been gathered The relatively expensive ILs with functionalized, fluorinated, deuterated or chiral ions are potential for small scale applications with very high added value, like analytical applications, sensors, electrolytes, coatings The relatively low-priced anions, such as toluenesulfonates, octylsulfates and hydrogensulfates are used in bulk applications like synthesis, catalysis separation technologies, lubrication, formulation, etc ILs have diverse applications, e.g sensors, fuel cells, batteries, capacitors, thermal fluids, plasticizers, lubricants, ionogels, extractants and solvents in analysis, synthesis, catalysis and separation [48]

The nature of ILs is complex when not only the catalyst is dissolved, but also substrates, products and by-products [48] The conditions for the ionic liquid are as follows:

 Solubility of substrates and rapid mass transfer;

 Miscibility gap between the main product and by-products;

 Solvation of the catalyst, so that the catalyst is fully immobilized and no leaching occurs;

 No deactivation of the immobilized catalyst [48]

ILs have some drawbacks, e.g it is difficult to design a highly volatile, non-conductive

or absolutely nonpolar IL Despite their good commercial availability nowadays ILs are still 10-50 times more expensive than the organic solvents used in catalysis, so lifetime, stability, quantity and recovery have to compensate this The lack of information related to

utilizing ILs on industrial scale, like the compatibility with plant materials, sealings in pumps or disposing of spent IL, is a serious disadvantage Corrosion, swelling and embrittlement are other relevant effects which have to be taken into account [3, 48]

The environmental impact, toxicity and other detrimental reactions (e.g forming reactive and corrosive hydrogen fluoride) of halogen-containing anions have led to replace them by halogen-free low-melting IL One of those „greener‟ IL which is used for hydroformylation is [BMIM][n-C8H17OSO3] [65] Imidazolium- based ILs are selected because they stabilize transition-metal complexes and are immiscible with nonpolar solvents As a consequence of this immiscibility extraction methods can be used for separating the products instead of distillation) In particular the structures of the cations and anions of imidazolium-based ILs have influence on the activity and selectivity [106]

1.5.2 Ligand

Most of the current hydroformylation processes in industry are based on monophosphines catalyst Especially in the early stage of hydroformylation, monophosphorus ligands predominated both in academia and industry

rhodium-Other than triphenylphoshine, the earliest and most common monophosphorus ligand in hydroformylation, tris-m-sulfonatophenylphosphine (TPPTS), is one of the important ligands in the history of hydroformylation It was used in the Ruhrchemie, Rhône-Poulenc hydroformylation process by Celanese

The equilibrium constant of the ligand, the excess of ligand, the steric properties of the ligand, etc have strong influence on the activity and selectivity of the catalyst [9] The preference of the catalyst for ILs can be increased by incorporation of ionic groups in the ligand [11], because the affinity is relatively higher [16] The two main categories are phosphines (PR3) and phosphites (P(OR)3 Phosphites and phosphonates are seldom used themselves, but they represent two categories of used ligands [4] Modified rhodium catalysts are more active than their corresponding unmodified catalyst Phosphites are better π-acceptors than phosphines, which alleviate the CO dissociation during the catalytic cycle This results in higher reaction rates Phosphines work in a similar way and produce higher n/i-ratio

1.5.3 Rh complex

In 1965 Osborn, Young and Wilkinson reported that Rh(I)-PPh3 complexes were active and highly regioselective hydroformylation catalysts for 1-alkenes, even at ambient conditions Although Slaugh and Mullineaux had filed a patent in 1961 that mentioned Rh/phosphine combinations for hydroformylation, it was Wilkinson's work that really ignited serious interest in rhodium phosphine hydroformylation catalysts The initial catalyst system was derived from Wilkinson's catalyst, RhCl(PPh3)3, but it was rapidly discovered that halides were inhibitors for hydroformylation It was best, therefore, halide-

Pruett (at Union Carbide) quickly provided the next critical discovery that, along with the work of Booth and coworkers at Union Oil, allowed commercialization of the HRh(CO)(PPh3)2 technology They found that the use of rhodium with excess phosphine ligand created an active, selective, and stable catalyst system at 80-100 psig and 90°C Union Carbide, in conjunction with Davy Powergas and Johnson Matthey, subsequently developed the first commercial hydroformylation process using rhodium and excess PPh3

in the early 1970's

The need for excess phosphine arises from the facile Rh-PPh3 dissociation equilibrium shown below Loss of PPh3 from HRh(CO)(PPh3)2 generates considerably more active, but

less regioselective hydroformylation catalysts The addition of excess phosphine ligand

shifts the phosphine dissociation equilibrium back towards the more selective HRh(CO)(PPh3)2 catalyst This explains why higher CO partial pressures lower the product regioselectivity, in marked contrast to what is observed for HCo(CO)4-catalyzed hydroformylation

H

CO Rh OC PPh 3

H

CO Rh OC CO

of its stability and usability [3] Using acetylacetone (acac) as ligand has several benefits, it can be easily characterized by common techniques l103ike IR and 1H NMR spectroscopy,

it can be easily and safely manipulated and it is relatively low-priced There are various ways for acetylacetone to bond with a metal, which are displayed in Figure 1.11

Figure 1.11 Various ways of acac to bond with metal [28]

Rh(CO)2(acac) is bond like the anionic keto form shown as 4 in Figure 1.11 Due to the possibility of resonance the anion is formed, this results in delocalization The anion acts as

a bidentate chelate and forms a conjugated ring system The metal atom is not included in the conjugated system [28]

1.5.4 Supports for SILP catalysts

1.5.4.1 Amorphous silica (SiO 2 )

The silicon dioxide, also known as silica, is an oxide of silicon with a chemical formula

of SiO2 and has been known for its hardness since antiquity Silica has an exceptional place among the mineral oxides group From its crystallographic properties, synthesis modes and petrographic importance, it belongs to the silicate family Through its different structures,

it can be considered as the simplest of the tectosilicates Its framework is made of SiO4tetrahedra bound together by their tops and so sharing an oxygen atom Different crystalline structures are known: quartz, tridymite, cristobalite, coesite, keatite, stishovite, melanophlogite, fibrous or lamellar silicas In the amorphous state, silicon dioxide exists as anhydrous glass or hydrated colloidal silica Quartz and its varieties are certainly one of the main constituents of the earth's crust Numerous industrial applications taking advantage of the specific properties of that material have been and are still being developed Both crystalline and amorphous silicas are used in optic, electronic, ceramics or adsorption, chromatography, catalysis, etc

In catalysis field, amorphous silicas (like silica gel, mesoporous silica…) has been applied much in desiccant and catalyst support due to its high specific surface area (silica gel possesses surface area up to 800m2.g-1), high thermal stability (up to 700oC) and non ionic conductivity [42] However, Silica gel could possesses acidity because of silanol groups on the surface Acidity of silica gel is undesired in common because it could active

33

side-reactions that produce undesired products Among amorphous silicas, silica gel is the most popular because it is very easy to prepare and it also possesses very high surface area SiO2 is known as a support for catalysts in chemical reactions The surface area of SiO2

is hight about 200 – 800m2/g therefore SiO2 was applicated for vaviuos reactions: hydrogencation, polymerization, oxidation, reduction reactions…

Table 1.3 Application of SiO 2 as supports [42]

Pt/SiO2 Dehydro Cyclohexan to Benzen

Pd/SiO2

Hydrogenation CO to Methanol Rh/SiO2

20%Cu/SiO2

V2O5/SiO2 To product H2SO4

Cr2O3/SiO2 Polymer Etylen

V2O5-K2S2O7/SiO2 o-Xylen to Phthalic anhydride

Bi2MoO6/SiO2 Oxdication Propen to Acrolein

Nb2Mo3O11/SiO2 ODH

Al2O3/SiO2 Isomer

Bi2Mo2O9/SiO2 Selective oxidation

Catalytic SILP materials have been successfully applied in the continuous gas-phase hydroformylation of propene, 1-butene and in the carbonylation of methanol The silica-supported SILP Rh-bisphosphine hydroformylation catalyst exhibited good activities and excellent selectivities and was stable for more than 700 hours time on stream [2, 3, 73, 4]

Silica gel has already been commercialized, so it is very easy to find and use

1.5.4.2 Mesoporous Al 2 O 3

In 1950, Stumpf et al reported that apart from α-Al2O3( corundum), another six crystal structures of alumina occur: γ, δ, κ, η, θ, χ-Al2O3 The sequence of particular type formation under the thermal processing of gibbsite, bayerite, boehmite and diaspore is as follows [12]:

Gibbsite (Al(OH)3) → χ -Al2O3 → κ-Al2O3 → α-Al2O3

Bayerite (Al(OH)3) → η-Al2O3 → θ-Al2O3 → α-Al2O3

Boehmite (AlOOH) → γ-Al2O3 → δ-Al2O3 → θ-Al2O3 → α-Al2O3

The temperature of aluminum hydroxide formation is the basis of this system of classification The two groups of alumina are: low-temperature aluminas: Al2O3 nH2O (0<n<6) obtained by dehydrating at temperatures not exceeding 600oC (γ-group) This group belongs to: γ, η, χ-Al2O3, high-temperature aluminas: nearly anhydrous Al2O3obtained at temperatures between 900 and 1000oC (δ-group) This group belongs to: κ, θ and δ-Al2O3

All these structures are based on a more or less close-packed oxygen lattice with aluminum ions in the octahedral and tetrahedral interstices Low-temperature alumina is characterized by cubic close-packed oxygen lattices; however, high-temperature alumina is characterized by hexagonal close-packed lattices In terms of catalytic activity, high-temperature alumina is less active than low-temperature alumina This results from not only lower surface area (higher order and larger particle size) but also the different population of surface active sites of high-temperature alumina when compared to low-temperature ones [12]

The oxides of aluminium materials are widely used in ceramics, refractories and abrasives due to their hardness, chemical inertness, high melting point, non-volatility and resistance to oxidation and corrosion [109-93] The importance of alumina as catalyst or catalytic support has also been widely recognized for many chemical reactions [17-61] The most common form of alumina used for catalyst support is γ form, which possesses a surface area more than 300 m2/g, a pore size ranged from 30 to 120 Å and a pore volume from 0.5 ÷ 1 cm3/g

In its largest scale application, aluminium oxide is the catalyst for converting hydrogen sulfide waste gases into elemental sulfur in refineries It is also useful for dehydration

of alcohols to alkenes Aluminium oxide serves as a catalyst support for many industrial catalysts, such as those used in hydrodesulfurization and some polymerizations Aluminium oxdie was used as support for SILP for hydroformylation of propene The result show that Rh-SILP/Al2O3 catalyst had a lower initial activity and selectivity than the SiO2-based system but deactivated only slightly at prolonged reaction (55 h) [1]

1.5.4.3 Mesoporous zirconium dioxide (ZrO 2 )

Zirconium dioxide is knowed as white crystalline oxide of zirconium (or zirconia) It is very thermal stable with melting point of 2715°C

As shown in Fig 1.14, at ambient pressure zirconium dioxide exists in three modifications At room temperature only the monoclinic form is stable while tetragonal and cubic structures are found at higher temperatures (1373 K and 2573 K, respectively), although both can be quenched to ambient conditions Pure ZrO2 has a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at increasing temperatures

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Figure 1.12 Schematic P-T phase diagram of ZrO 2 [78]

Three phase structures of zirconia were shown in Figure 1.12, in cubic structure Zr surrounded by 8 oxygen atoms with fcc structure The baddeleyite (monoclinic) structure has been describe among others, in 1959 by McCullough and Trueblood [50], the Zr atom exists in a sevenfold coordination, whereas the oxygen atoms exist either in tetrahedral or triangular coordination In tetragonal structure, the eightfold coordination of Zr4+ ions is shown in (Figure 1.13) The lowest Zr-Zr distance is 3.5953 Å, whereas the second nearest

Zr neighbor is located at a distance of 3.60110 Å

Figure 1.13 Three phases of ZrO 2 [78]

ZrO2 have attracted much attention especially in ceramic field, because the cubic phase

of zirconia has a very low thermal conductivity, which has led to its use as a thermal barrier coating Zirconia is also used in oxygen sensors and fuel cell membranes because it has the ability to allow oxygen ions to move freely through the crystal structure at high temperatures Zirconia is a very special material because it has a high ionic conductivity but a low electronic conductivity Zirconia is also a semiconductor, The ZrO2 band gap is dependent on the phase (cubic, tetragonal, monoclinic, or amorphous) and preparation methods, with typical estimates from 5-7 eV

The surface area of ZrO2 is low (< 100 m2/g) Zirconia is chemically and thermally stable, combined with its unique amphoteric characteristic, makes it an ideal candidate for catalyst For example, the hydrogenation of aromatic carboxylic acids, the decomposition

of nitrous oxide, the isomerization of alkanes, and many other reactions As the same as aluminium oxdie zirconia oxdie was used as support for SILP for hydroformylation of propene The result show that Rh-SILP/ZrO2 catalyst had a lower initial activity and selectivity than the SiO2 and Al2O3 based system but deactivated only slightly at prolonged reaction (55 h) [1]

1.5.4.4 Mesoporous MCM - 41

MCM - 41, the simplest mesoporous molecular sieve, has been extensively studied It was first prepared by Mobil scientists using trimethyl alkyl ammonium halides CnH2n + 1-N(CH3)3+ X− (X = Cl or Br, n = 8 – 10, 12, 14, 16) surfactants as a template MCM is the abbreviation for Mobil Company of Matter The preparation of MCM - 41 is relatively easy

MCM-41 possesses high surface areas (> 700 m2/g), uniform pore size distribution (in the range 16 Å to 100 Å or more) and these uniform channels are in regular hexagonal array Due to its novel structure and preferable properties to conventional supports, MCM-

41 provides an ideal support for the heterogeneous catalysis Corma et al first time reported

a MCM-41 supported Ti catalyst for the oxidation reactions of bulky substrates [20] Reddy et al reported the vanadium-containing MCM-41 for oxidation reactions [81] Long

et al reported the Pt/MCM-41 exhibited a superior specific reaction rate for selective catalytic reduction of NO over other Pt supported catalysts using traditional supports [62] One of the chief reasons for the high activity shown by these MCM-41 supported transition metal catalysts is that the metals can disperse well on the support surface due to the high surface areas provided by MCM-41 Recently, Kawiís group reported many papers on MCM-41 supported rhodium catalysts for hydroformylation reactions [43-45] For example, aminated MCM-41 tethered Rh4(CO)12 and Rh(PPh3)3Cl were used to catalyze hydroformylations of 1-octene and styrene [44] It was reported that the addition of PPh3greatly enhance the catalytic performances of the supported catalysts especially for the

Rh4(CO)12 based catalysts The supported Rh(PPh3)3Cl seemed to be more active than Rh(PPh3)3Cl for the hydroformylation of 1-octene In another paper [43], Kawi et al reported that the aminated MCM-41 tethered Rh4(CO)12 exhibited high activity and stability for cyclohexene which was a relative inter substrate for hydroformylation

1.5.4.5 Mesoporous SBA - 15

SBA-15 is one member of a family of mesoporous silicas that make ideal candidates for catalyst supports by covalent grafting It is an ordered, amorphous silica material first created by Zhao and Stucky in 1998, in an effort to increase the material‟s thermal stability via increased wall thickness relative to MCM type materials The improved hydrothermal

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materials have important applications in a wide variety of fields such as separation, catalysis, adsorption and advanced nanomaterials

Figure 1.14 Synthesis of SBA-15 mesoporous silica [108]

Figure 1.14 shows the preparation of SBA-15 materials in a template process in acidic conditions with poly (alkaline oxide) tri-block co-polymers In acidic, aqueous solution, a structure directing agent (triblock copolymer of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide)) is dissolved to form micelles These block copolymers self-assemble to form unidirectional, cylindrical micelles in hexagonal arrays Tetraethylorthosilicate (TEOS) is added to the solution, which polymerizes around the organic micelles forming the pore walls of the material Finally, after filtration and washing, the material is calcined to combust the organic structure directing agent, leaving the mesoporous SBA-15 silica [108]

SBA-15 possesses larger range of uniform pore size distribution which is 50 to 300 Å Characteristic XRD diffraction patterns of SBA-15 show three diffraction peaks at 2θ angle 0.5~2º BET surface area of SBA-15 is around 600~1000 m2/g and the pore size is around 8 nm The silica wall thickness of SBA-15 ranges from 31 to 64 Å, which is much than that of MCM-41 (commonly 10 to 15 Å) And its channels are also hexagonally highly ordered [108] SBA-15 as support for impregnation of cobalt catalyst to catalyze Fischer-Tropsch synthesis of CH4, SBA-15 supported Wilkinson‟s catalyst for hydrogenation reactions of styrene, 1-hexene and cyclohexene, SBA-15 supported Pd(0) catalyst for hydrogenation reactions [99, 51]

Although SBA-15 has not been reported for being used as support for hydroformylation reactions, SBA-15 has been used for Fischer-Tropsch reactions and hydrogenation reactions which are very close to hydroformylation on the basis of the reaction conditions and the substrates and transition metals involved Let us to think of applying SBA-15 as

support for hydroformylation with the aim to synthesize a highly active, selective, stable catalyst combining advantages from homogeneous and heterogeneous catalytic systems

1.6 Synthesis of SILP catalysts

The general method for the preparation of SILP is impregnation The catalyst precursor and the ligand are first dissolved in a small amount of a volatile organic solvent (e.g., methanol, acetone, acetonitrile, tetrahydrofuran, dichloromethane and chloroform) that dissolves both the catalyst complex and the IL, and then the IL is added Next, this solution

is mixed with the support material (such as SiO2, TiO2, Al2O3, ZrO2, MCM-41, SBA-15, active carbon), and upon stirring, the volatile solvent is removed by evaporation under reduced pressure Alternatively, the homogeneous catalyst and the IL are impregnated on a support that already contains a monolayer of covalently anchored IL fragments In both cases, the homogeneous catalyst is dissolved in the IL film

During the synthesis of SILP catalysts, it should be paid attention that there must be no contamination of gaseous oxygen and water, therefore, the system must be filled with inert gases (such as Ar) prior to use because Rh complexes are very sensitive with water and oxygen That is why the synthesis must be done by standard Schlenk or Air-free technique

as described in Figure 1.15

Figure 1.15 Schematic view of Schlenk line

These techniques prevent the compounds from reacting with components of air, usually water and oxygen; less commonly carbon dioxide and nitrogen A common theme among these techniques is the use of a high vacuum to remove air, and the use of an inert gas: preferably argon, but often nitrogen

1.7 Aim of the thesis

The supported ionic liquid phase (SILP) technology is a fundamental, new approach to

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modification of a porous solid by dispersing a thin film of ionic liquid onto it Researches

on SILP catalysts appeared since 2002 In the world, The use of catalytic SILP materials has been reviewed recently [71] covering Friedel-Crafts reactions [88–94], hydroformylations (Rh-catalyzed) [72], hydrogenation (Rh-catalyzed) [70,105], Heck reactions (Pd-catalyzed) [34], and hydroaminations (Rh-, Pd-, and Zn-catalyzed) [16] That

is the reason why this thesis chooses to study Rh-SILP catalyst for the hydroformylation Since TPPTS-Cs was known as a phosphine ligand resulting in the catalysts with good activity, it was choosen as a ligand for SILP catalysts The TPPTS ligand has never been synthesized in Vietnam Thus, this thesis aims to study the synthesis of this ligand The influence of pH during the synthesis was investigated to find the good synthesis condition

As seen from previous sections, SILP catalysts have been studied for many hydroformylation processes of hydrocarbons from C3-C8 In Vietnam, the hydroformylation of ethylene to propanal has been studied for SILP on SiO2 [74] The influences of IL contents (10-50% pore volume), Rh contents (0.2-0.5 wt%), Rh/ligand ratios (3-10) on the catalytic activities have been investigated quite thoroughly It has been concluded that when IL loading increased, the catalytic activity increased but the stability

of the catalyst at high reaction temperatures decreased Thus, the IL loadings of 20-30%V pore were found to be most active while the IL loading of 10%V pore resulted in the most stable catalyst When the ratio of ligand to rhodium increased, the catalytic activity decreased The samples with the ratios from 3-10 were found to have good activity When rhodium-loading contents increased, the catalytic activity increased but when the rhodium loading contents reached to a certain value, the activity didn‟t increased any more Thus, the rhodium loading content of 0.5%wt was enough to form the catalytst with highest activity compared to ones with other rhodium loading contents However, for economic reason, the catalyst with 0.2%wt Rh is suitable to ensure a reasonable activity

The characterizations of the catalysts before and after the reactions revealed that the decrease of activities observed at high reaction temperatures may be due to the IL dilutions

by byproducts and the redistribution of IL on the surface and pores

Although the hydroformylation of ethylene on SILP catalyst on SiO2 has been studied, this reaction has not been studied on SILP catalyst on other supports and there is no comparison of the catalytic activity of the SILP catalyst on different supports Since the catalyst with 0.2%wt Rh, L/Rh=10 on SiO2 has been found exhibited good activity, in this thesis, SILP catalyst with 0.2%Rh, L/Rh=10 on different supports (SiO2, Al2O3, ZrO2, MCM-41, SBA-15) were synthesized, characterized and tested for the hydroformylation of ethylene It is also the first time that SILP catalyst for hydroformylation is synthesized on SBA-15 support The purpose of the thesis is the investigation of optimized IL content on different supports to find best conditions of the reaction and optimal catalyst for hydroformylation of ethylene

During the sythesis of TPPTS-Cs3 the following chemicals were used:

 Cesium hydroxide monohydrate (CsOH·H2O) (95%, Aldrich);

 Methanol (CH3OH) (99%, Merck)

TPPTS-Cs3 was synthesized form octylamine at the laboratory as following procedure:

P(C6H5)3+ 3SO3(H2SO4) P(C6H4SO3H)3P(C6H4SO3H)3+ 3NH2C8H17 [H3NC8H17]3[P(C6H4SO3)3]

octylamine

[H3NC8H17]3[P(C6H4SO3)3] + 3CsOH P(C6H4SO3Cs)3+ 3NH2C8H17

However, the synthesis was not successful because in the neutralization reaction with CsOH (the last reaction), pH of the solution is always 13, which is pH of cesium hydroxide solution (5%) itself That means that the neutralization reaction did not occur It may be due to the reaction of P(C6H4SO3H)3 and NH2C8H17 did not successful because the reactivity of NH2C8H17 is week Therefore, the use of octylamine was stopped, instead high reactivity amine – trioctylamine was used

TPPTS-Cs3 was synthesized form trioctylamine at the laboratory as following procedure:

P(C6H5)3+ 3SO3(H2SO4) P(C6H4SO3H)3P(C6H4SO3H)3+ 3N(C8H17)3 [HN(C8H17)3]3[P(C6H4SO3)3]

trioctylamine

[HN(C8H17)3]3[P(C6H4SO3)3] + 3CsOH P(C6H4SO3Cs)3+ 3N(C8H17)3

TPPTS-Cs 3 , M=Cs