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

CONTENT OF THESIS
LIST OF TABLES ................................................................7
LIST OF FIGURES ..............................................................8
INTRODUCTION................................................................11
1 LITERATURE REVIEW ................................................12
1.1
1.2

Hydroformylation of alkenes ........................................... 12
Catalysts for hydroformylation reaction ......................... 13

1.2.1
1.2.2
1.2.3

1.3

Mechanism of hydroformylation reaction ...................... 21

1.3.1
1.3.2
1.3.3
ethylene

1.4
1.5

Cobalt catalyzed hydroformylation .......................................... 15
Rhodium catalyzed hydroformylation ..................................... 17
Heterogenization of homogeneous catalysts ......................... 18
Mechanism for Cobalt-Catalyzed Hydroformylation .............. 21

Mechanism for Rhodium-Catalyzed Hydroformylation .......... 22
Mechanism for Rhodium-Catalyzed Hydroformylation of
23

Application of hydroformylated products ...................... 24
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 (SiO2) .......................................................... 32
1.5.4.2 Mesoporous Al2O3 ................................................................... 33
1.5.4.3 Mesoporous zirconium dioxide (ZrO2) ..................................... 34
1.5.4.4 Mesoporous MCM - 41 ............................................................ 36
1.5.4.5 Mesoporous SBA - 15 ............................................................. 36

1.6
1.7

Synthesis of SILP catalysts ............................................. 38
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 ZrO2......................................................................................... 42
2.1.2.2 MCM – 41................................................................................ 43
2.1.2.3 SBA – 15 ................................................................................. 44
2.1.3
Catalysts synthesis ................................................................... 45
3


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
2.3.2

Micro reactor setup ................................................................... 56
The analysis of the reactants and products............................ 57

3 RESULTS AND DISCUSSTIONS .................................60
3.1

Chracterization of support ............................................... 60

3.1.1
3.1.2
3.1.3
3.1.4

3.2

Chracterization of MCM-41 ....................................................... 60
Chracterization of SBA-15 ........................................................ 63
Characterization of ZrO2 ........................................................... 64
Characterization of commercial Al2O3 and SiO2 support ....... 67

Characterization of ligand ............................................... 68

3.2.1

FTIR spectra of ligand TPPTS .................................................. 69

3.2.2
3.2.3

NMR spectra of ligand TPPTS .................................................. 69
The influence of ligand to the catalytic acitivity ..................... 74

3.3 Characterization of support ionic liquid phase (SILP)

catalysts ........................................................................................ 74
4


3.3.1
FT – IR characterization ............................................................ 74
3.3.1.1 FT-IR of ionic liquid [BMIM][n-C8H17OSO3] ............................. 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
3.5

Catalytic activity of SILP on SiO2 .................................... 91
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
3.6.2
on ZrO2

3.7

Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/ZrO2 .................. 97
Influence of Ionic Liquid loading content on activity of SILP
99

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

5


ABBREVIATION
BET

Brunauer Emmet Teller

BMIM

1–Butyl–3–Methyl imidazolium

CTAB

Cetyltrimetylamoni bromua C16H33N(CH3)3Br

FBC

Flourous Biphasic Catalysis

GC

Gas Chromatography

IL

Ionic Liquid

IR

Infra Red

LHSV

Liquid Hourly Space Velocity

M41S

Mesoporous Materials

MCM

Mobil Composition of Mater.

NMR

Nuclear Magnetic Resonance.

S

Chất định hướng cấu trúc

SAPC

Supported Aqueous Phase Catalysis

SEM

Scanning Electron Microscope

SILP

Supported Ionic Liquid Catalysis

SLPC

Supported Liquid Phase Catalysis

TEM

Transmission Electron Microsope

TEOS

Tetraethoxysilicat

TOF

Turn Over Frequency

TPP

Triphenylphosphine.

TPPDS

Triphenylphosphin disunfonat

TPPMS

Triphenylphosphin monosunfonat

TPPTS

Triphenylphosphin trisunfonat

XRD

X–Ray Diffraction.

6


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 SiO2 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 SiO2 and 0.2%Rh-10%Il-L/Rh=10SiO2 ......................................... 83
Table 3.3 Surface properties of Al2O3 and SILP catalyst on Al2O3 .................................................. 84
Table 3.4 Surface properties of ZrO2 and SILP on ZrO2 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 NH3 profiles of Al2O3 supports ................................................................................ 95
Table 3.8 TPD NH3 profiles of ZrO2 supports .................................................................................. 98

7


LIST OF FIGURES
Figure 1.1 Three stages of the catalyst development for the hydroformylation reaction [14]. ....... 14
Figure 1.2 Interaction of Co2(CO)8 with H2 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-PPh3 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 ZrO2 [78] ................................................................. 35
Figure 1.13 Three phases of ZrO2 [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-Cs3................................................................. 41
Figure 2.2 Scheme for the synthesis of ZrO2 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 31P 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, H2O/TEOS = 24....................................................................... 60
Figure 3.3 XRD patterns of the MCM-41 synthesised from TEOS with CTAB/TEOS=0,25,
H2O/TEOS =8; 14; 18; 24; 30. ........................................................................................................ 61
Figure 3.4 The TEM image of MCM-41.8 ....................................................................................... 62

8

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 ZrO2 ...................................................................................... 66
Figure 3.15 Pore distribution of ZrO2.............................................................................................. 66
Figure 3.16 XRD pattern of SiO2 ..................................................................................................... 67
Figure 3.17 Nitrogen isotherm of the SiO2....................................................................................... 67
Figure 3.18 Pore distribution of SiO2 .............................................................................................. 67
Figure 3.19 XRD pattern of γ-Al2O3 ................................................................................................. 68
Figure 3.20 Nitrogen isotherm of the Al2O3 ..................................................................................... 68
Figure 3.21 Pore distribution of Al2O3 ............................................................................................ 68
Figure 3.22 IR spectrum of synthesized TPPTS-Cs3 ligand ............................................................. 69
Figure 3.23 NMR 1H spFigure 3.23ectrum of synthesized TPPTS-Cs3 ligand 1 ............................. 70
Figure 3.24 NMR 31P spectrum of synthesized TPPTS-Cs3 ligand 1 ............................................... 70
Figure 3.25 NMR 1H spectrum of synthesized TPPTS-Cs3 ligand 2 ................................................ 71
Figure 3.26 NMR 31P spectrum of synthesized TPPTS-Cs3 ligand 2 ............................................... 71
Figure 3.27 NMR 1H spectrum of synthesized TPPTS-Cs3 ligand 3 ................................................ 72
Figure 3.28 NMR 31P spectrum of synthesized TPPTS-Cs3 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-C8H17OSO3] ....................................................... 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 ZrO2 .......................................................................................... 76

Figure 3.34 IR spectra of SILP on Al2O3 ......................................................................................... 77
Figure 3.35 IR spectra of 0.2%Rh–10%IL–L/Rh=10/SiO2 .............................................................. 77
Figure 3.36 IR spectra of used SILP on Al2O3 ................................................................................. 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 SiO2 and 0.2%Rh-10%Il-L/Rh=10 SiO2 ....................................... 83
Figure 3.41 Pore distribution of Al2O3 support and SILP catalysts on Al2O3 support. .................... 84
Figure 3.42 Description of small pore filling by IL ......................................................................... 84
Figure 3.43 Pore distribution of ZrO2 support and SILP catalysts on ZrO2 .................................... 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/ SiO2 at different reaction temperatures
on time .............................................................................................................................................. 91

9


Figure 3.47 The influence of reaction temperatures on the catalytic activity of 0.2%Rh-10%ILL/Rh=10/SiO2 ................................................................................................................................... 92
Figure 3.48 Propanal selectivity of 0.2%Rh-10%IL-L/Rh=10/ SiO2 at different reaction
temperatures..................................................................................................................................... 93
Figure 3.49 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/Al2O3 at different reaction temperatures
.......................................................................................................................................................... 94
Figure 3.50 TPD NH3 profiles of Al2O3 supports............................................................................. 94
Figure 3.51 Propanal selectivity of 0.2%Rh-10%IL-L/Rh=10/Al2O3 at different reaction
temperatures..................................................................................................................................... 95
Figure 3.52 Catalytic activity of SILP on Al2O3 catalysts with different IL loading........................ 96
Figure 3.53 Selectivity of catalysts with diffrent IL loading content on Al2O3 support ................... 97
Figure 3.54 Catalytic activity of 0.2%Rh-10%IL-L/Rh=10/ZrO2 at different reaction temperatures
.......................................................................................................................................................... 98

Figure 3.55 TPD NH3 profiles of ZrO2 supports .............................................................................. 98
Figure 3.56 Propanal selectivity of 0.2%Rh-10%IL-L/Rh=10/ZrO2 at different reaction
temperatures..................................................................................................................................... 99
Figure 3.57 Catalytic activity of SILP on ZrO2 catalysts with different IL loading ....................... 100
Figure 3.58 Selectivity of catalysts with diffrent IL loading content on ZrO2 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

10


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. Twophase 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.

11


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
industries and research laboratories, due to the versatile functionality of the aldehydes
12


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)3PBu3
and 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.

13


Figure 1.1 Three stages of the catalyst development for the hydroformylation reaction
[14].
Table 1.1 Developments of hydroformylation catalysts
First stage
Catalyst

metal
Ligand
Process

Cobalt

Cobalt

Second stage
Rhodium

none
phosphines
none
BASF,
Ruhrchemi
Rhurchemie Shell process
e process
process

Third stage

Rhodium

Rhodium

phosphines

phosphines
RhurchemieRhône-Poulenc

process

Union Carbide
process (LPO)

Active
HCo(CO)3P
HRh(CO)(PPh3 HRh(CO)(TPP
HCo(CO)4
HRh(CO)4
catalyst
Ph3
)3
TS)3
species
Temperatur
150-180
160-200
100-140
60-120
110-130
e (°C)
Pressure
200-300
50-150
200-300
10-50
40-60
(bar)
Catalyst/alk

0,1-1
0,6
10-4-0,01
0,01-0,1
0,001-1
ene molar
ratio
Liquid
hourly space
0,5-2
0,1-0,2
0,3-0,6
0,1-0,2
>0,2
velocity
LHSV (h-1)
Aldehydes
Alcohols
Aldehydes
Aldehydes
Aldehydes
Products
High
High
Low
Low
Low
By-products
n/i of
80:20

88:12
50:50
92:8
>95:5
aldehydes
The first stage of hydroformylation was exclusively based on cobalt-based catalyst
having the pressure and temperature range between 240-300 bars and 150-200 °C because
of instability of cobalt carbonyl (BASF, Ruhrchemie process) [9]. Subsequently, the ligand
modification introduced by Shell (1964) was significant progress in hydroformylation [60].
The second stage of hydroformylation was the combined development in ligand
modification and appearance of rhodium as are placement for cobalt metal. It took almost a
decade of research before first rhodium catalyst based commercial process was launched in
1974 in Celanese [75], followed by Union Carbide Corporation (1976) [11] and the
14


Mitsubishi chemical corporation (1978) [76] using phosphine as a ligand (Union Carbide
process (LPO)).
In the third stage, the research was largely focused to design such a process wherein the
separation of products from reaction mixture is facile and easy. Hydroformylation can be
carried out in biphasic aqueous systems using a rhodium catalyst associated with the watersoluble ligand, sodium salt of tri sulfonated triphenyl phosphine (TPPTS). This system was
first used in 1984 by Ruhrchemie/Rhone-Poulenc in the industrial hydroformylation of
Propene (Ruhrchemie–Rhone–Poulene process) [25]. This procedure is much simpler and
more cost effective than those of the other oxo processes, mainly due to the new principle
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 Co2(CO)8 with H2 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
15


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
catalyst, which provides catalyst complex with higher stability and thus the process can be
16

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
17


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 RhônePoulenc 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].
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
18

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(msulfonyl)-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.

19


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].

20


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.
21


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
22

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. HenriciOlivé 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 hydridometal 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
23

the aldehyde. The hydrogenation of the acyl intermediate was identified as 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).

24


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 1alkenes [2, 3] and carbonylation reactions. They determined overall conversions and yields
25


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 indepth 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
hydrogen diffuse into the pore of the support and then dissolve in the thin film of IL. The
26


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
27