Heterogeneous catalysis in protodecarboxylation and c c bond formation 1

In chapter 6, monometallic Ag/Al2O3 and Cu/Al2O3 catalyst, and bimetallic CuŸPd/Al2O3 catalysts were used in the study of decarboxylative cross-coupling of the potassium salt of 2-nitr

DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE

2013

DECLARATION

I hereby declare that this thesis is my original work and it has been written by

me in its entirety, under the supervision of A/P Stephan Jaenicke, Chemistry Department, National University of Singapore, between 01/08/2009 and 01/08/2013

I have duly acknowledged all sources of information which have been used in the thesis

This thesis has also not been submitted for any degree in any university previously

The content of the thesis has been partly published in:

(1) Xiu Yi Toy, Irwan Iskandar Bin Roslan, Gaik Khuan Chuah and Stephan Jaenicke, Catal Sci Technol., 2013, DOI: 10.1039/c3cy00580a

ACKNOWLEDGEMENT

This dissertation would not have been possible without the guidance and the help of several individuals who extended their valuable assistance in the preparation and completion of this study The 4 years of Ph.D research study have been a truly memorable learning journey

First and foremost, I would like to express my sincere appreciation to my supervisor Associate Professor Dr Stephan Jaenicke for giving me the opportunity to work on the project in his research lab His stimulating suggestions, encouragement and immense knowledge helped me greatly throughout the project

I would also like to thank Associate Professor Dr Chuah Gaik Khuan for her help and invaluable advices throughout my research and writing of this thesis

I truly appreciate all time she has taken to read and correct my writings and manuscript

My sincere thanks also goes to Madam Toh Soh Lian, Madam Tan Lay San and Miss Sabrina Ou from Applied Chemistry lab for all the help they have rendered during my work

This thesis would not have been possible without the help and support from

my fellow lab mates: Miss Nie Yuntong, Miss Ng Jeck Fei, Mr Do Dong Minh, Mr Fan Ao, Miss Liu Huihui, Mr Wang Jie, Miss Gao Yanxiu, Miss Han Aijuan, Mr Goh Sook Jin, Mr Sun Jiulong, Mr Irwan Iskandar Bin Roslan and Miss Angela Chian

I am also grateful to my parents and my family for their unconditional love, encouragement and motivation I would like to give my special thanks to my fiance for believing in me and giving me the moral support when it was most

required

Last but not least, I am indebted to the National University of Singapore for providing me with a valuable research scholarship and for funding the project

1.2.2 Ullmann reaction 23

Chapter 3: Homocoupling of aryl halides using

3.1.3 Examples of coupling reactions carried out in PEG

reaction medium

66

Chapter 4 Protodecarboxylation of carboxylic acids using

heterogeneous silver catalyst

97

4.3 Results and discussion 102

Chapter 5: Alumina supported copper catalyst for

protodecarboxylation of aromatic carboxylic acids

5.3.3.1 Cu weight loading 154

5.3.3.2 Effect of H2 pretreatment of the Cu/Al2O3

5.3.4 Study of reaction mechanism: kinetic rate expression

and nature of the reaction

157

Chapter 6: Heterogeneous catalysts for the decarboxylative

cross-coupling of aryl carboxylic acids and aryl

6.3.2.4 Effect of Cu loading, amount of catalyst and

ABSTRACT

Ullmann reaction and decarboxylative cross-coupling reactions are green alternatives for the formation of C-C bonds between aromatic compounds These methods do not require preformed organometallic reagents which improve their atom efficiency Since heterogeneous catalysts offer many advantages over homogeneous catalysts such as easy separation and recovery, the aim of this study is to develop and improve heterogeneous catalysts for the Ullmann reaction and decarboxylative cross-coupling In chapter 3, the development of a Pd(OAc)2-PEG-EG catalytic system for Ullmann coupling of bromobenzene is described In chapter 4 and 5, we present the use of alumina supported Ag and Cu catalysts for

protodecarboxylation of ortho-substituted aromatic benzoic acids In chapter 6,

monometallic Ag/Al2O3 and Cu/Al2O3 catalyst, and bimetallic CuŸPd/Al2O3

catalysts were used in the study of decarboxylative cross-coupling of the potassium salt of 2-nitrobenzoic acid and iodobenzene

LIST OF TABLES PAGE

bromobenzene using Pd-PEG catalysts

69

PEG 2000-Pd(OAc)2 with different additives and

reaction temperature

71

PEG of different average molecular weight

73

PEG 900 with varying amount of DMA

75

presence of 4g of PEG 900 and varying amounts of ethylene glycol (EG)

77

catalysed homocoupling 83

size of the supported silver catalysts 102

reaction mixture, initial rate and turnover frequency

of supported silver catalysts

116

acids using 10 wt % Ag/Al2O3

121

potassium nitrobenzoate using 10 wt % Ag/Al2O3

under different conditions

124

γ-Al2O3 (commercial and sol-gel), 10 wt %

141

Cu/Al2O3 WI catalyst, WI-SG catalysts with 1 wt %

to 15 wt.% Cu weight loadings

Cu LMM kinetic energy (KE) and the modifed Auger parameter, α’

143

(BE) of Cu 2p3/2 transitions, Cu LMM kinetic energy (KE) and the modified Auger parameter, α’ for Cu,

Cu2O and CuO

144

from the XPS measurements

147

Cu/Al2O3 WI catalyst for the optimisation of reaction conditions The 10.0 wt % Cu/Al2O3 WI catalyst was pretreated under flowing H2 at 300 oC for 2 h before use except for 1a

151

information

159

Pd, Cu and Al species 2.5 wt % Cu·1.0 wt % Pd/Al2O3

187

for bimetallic Cu·Pd catalysts prepared by selective adsorption with 1.0 and 5.0 wt % Cu

190

cross-coupling of 2-nitrobenzoic acid and iodobenzene using alumina supported metal catalysts

192

decarboxylative cross-coupling of potassium 2–nitrobenzoate and iodobenzene

194

Table 6.8 Optimisation of the ratio iodobenzene : potassium

2.5 wt.% Cu·1.0 wt % Pd/Al2O3 catalysts

204

LIST OF FIGURES

Figure 1.1 A plot of the calculated fraction of Au atoms at the

corner (red), edge (blue), and crystal face (green) of

a truncated octahedral gold nanoparticle The insert shows the top half of a truncated octahedral gold nanoparticle and the position of the corner, edge and surface atoms

4

Figure 1.2 Furfural hydrogenation pathways on Pt(111) surface 5

Figure 1.3 Examples of reactions of organometallic complexes 7

Figure 1.4 Formation of ammonia on a heterogeneous catalyst

Figure 1.5 Selective hydrogenation of crotonaldehyde to crotyl

alcohol

10

Figure 1.6 The surface-to-volume ratio decreases with

increasing volume of a particle 11

Figure 1.7 A schematic representation of the typical features of

a metal surface

12

Figure 1.8 Active phase distribution during impregnation, (a)

uniform; (b) shell, (c) white and (d) yolk

egg-13

Figure 2.1 Schematic diagram of the scattering of x-rays by a

crystalline material

42

Figure 2.2 A typical adsorption/desorption isotherm 45

Figure 2.3 Operating modes of TEM: (a) diffraction mode and

(b) imaging mode

51

Figure 2.4 The energy levels involved in the emission and

detection of the photoelectrons

53

Figure 2.5 (a) Emission of photoelectron and Auger electron; (b)

XPS spectrum collected from a silicon wafer

54

Figure 2.6 Wagner plot for B.E.XPS Cu 2p3/2 photoelectron and

K.E Cu LMM Auger electron

57

Figure 3.1 Conversion and selectivity of products obtained over

3 consecutive Pd-PEG-EG catalysed homocoupling reaction runs

77

Figure 3.2 Kinetic profile of Pd-PEG-EG catalysed

homocoupling reaction carried out in a closed system

78

in the presence of air with addition of fresh bromobenzene after 100 % conversion was achieved

Figure 3.3 Pd-PEG-EG catalysed homocoupling of

bromobenzene carried out in a closed system in the presence of (♦) no Cs2CO3, (■) 2 mmol Cs2CO3, and (▲) 4 mmol Cs2CO3

79

Figure 3.4 Kinetic profile of recycling test carried out in a

closed system in the presence of (□) air and (♦) N2

80

Figure 3.5 Total conversion and selectivities towards benzene,

biphenyl and terphenyl obtained in each of the 4 consecutive Pd-PEG-EG catalysed homocoupling reaction runs

81

Figure 3.6 TEM images of Pd nanoparticles formed in PEG-EG

(a) before reaction (stir 1 h at 120 oC), (b) after reaction at 120 oC for 24 h using 4 mmol of bromobenzene

82

Figure 3.7 (a) PEG-EG mixture and (b) PEG-EG immediately

after addition of Pd(OAc)2 and (c) PEG-EG after stirring with Pd(OAc)2 at 120 oC for 2 mins

86

Figure 3.8 X-ray diffractograms of Pd-EG-PEG carried out at

120 oC taken (a) at every hour for 5 h from 2 Theta = 30-90 o, (b) at 6 h from 2 Theta = 38-42 o

86

Figure 3.9 Typical GC-MS spectrum of the homocoupling of

Figure 3.10 GC spectrum of the homocoupling of chlorobenzene 95

Figure 3.11 GC spectrum of homocoupling of iodobenzene 96

Figure 3.12 GC spectrum of homocoupling of

1-chloro-4-bromobenzene

96

Figure 4.1 Chelating agents used in protodecarboxylation

reactions: 1: 1,10-phenanthroline, 2: 2,2’ bipyridyl 98 Figure 4.2 X–ray diffractograms of 10 wt % Ag supported on

(a) SiO2 (b) Al2O3 (c) MgO (d) TiO2 and (e) ZnO

The positions of the silver lines are indicated with a star *

103

Figure 4.3 Nitrogen adsorption and desorption isotherms for

Al2O3 supported silver catalysts with 10 wt % Ag loading Insert: pore size distribution

104

Figure 4.4 X-ray diffraction patterns of (a) calcined Al2O3

support, and the catalysts with (b) 5 wt % Ag, (c) 10 wt % Ag, (d) 15 wt % Ag, (e) 20 wt % Ag (traces are offset by 1000 counts) The positions of the silver lines are indicated with a star *

104

Figure 4.5 TEM images of (a) 5 wt %, (b) 10 wt %,

(c) 15 wt %, (d) 20 wt % Ag/Al2O3

106

Figure 4.6 XPS spectra for 5-15 wt % Ag/Al2O3 108

Figure 4.7 Kinetic profile of model reaction catalysed by

10 wt % Ag/Al2O3 with different catalyst pretreatment

112

Figure 4.8 Kinetic profile of model reaction catalysed by fresh

and recycled 10 wt % Ag/Al2O3 113

Figure 4.9 Kinetic profiles of the model reaction carried out

using 5-20 wt % Ag/Al2O3 and AgOAc

114

Figure 4.10 Plot of initial rate against silver loading of the

supported silver catalysts 114

Figure 4.11 Kinetic profile of protodecarboxylation of

2-nitrobenzoic acid carried out at (u) 100 oC, (n) 110 oC, (▲) 120 oC, (Ÿ) 130 oC

118

Figure 4.12 Arrhenius plot of ln k against 1/T 119

Figure 4.13 Ortho-substituent coordinating to a surface Agδ +

centre during the decarboxylation process

120

Figure 4.14 Kinetic profiles of 10 wt % Ag/ Al2O3-catalysed

protodecarboxylation of (u) 2-nitrobenzoic acid (2 mmol), with K2CO3 (0.3 mmol); (n) 2-nitrobenzoic acid (2 mmol), without K2CO3;

(▲) Potassium 2-nitrobenzoate (2 mmol) without AcOH; (Ÿ) Potassium 2-nitrobenzoate (2 mmol) with AcOH (2 mmol)

124

Figure 4.15 Influence of added potassium salts: Kinetic profiles

of the protodecarboxylation of 2-nitrobenzoic acid catalysed by 10 wt % Ag/ Al2O3 in the presence of (u) 0.3 mmol of KCl; (n) 0.3 mmol of K2SO4; and (▲) 0.3 mmol of K2CO3; (l) 0.3 mmol of KOH, (×) 0.6 mmol of KOH

125

Figure 4.16 Effect of alkali metal carbonates on

protodecarboxylation of 2-nitrobenzoic acid 127

Figure 4.17 Plot of initial rate against mol % of K2CO3 used 128

Figure 4.18 N2 adsorption and desorption isotherms of the

5-20 wt % Ag/Al2O3. Insert: Pore size distribution 132

Figure 4.19 XRD pattern of (a) fresh 10 wt % Ag/Al2O3 and

(b) recycled 10 wt % Ag/Al2O3

132

Figure 4.20 N2 adsorption and desorption isotherms of (n) fresh

and (▲) recycled and recalcined 10 wt % Ag/Al2O3

133

Figure 4.21 Pore size distribution of (n) fresh and (▲) recycled

and recalcined 10 wt % Ag/Al2O3

133

Figure 4.22 HPLC spectrum of a typical test reaction carried out

using 2-nitrobenzoic acid as substrate, K2CO3 as base, 10 wt % Ag/Al2O3 as catalyst at 120 oC The spectrum was recorded for 30 mins to ensure that no other products are formed

134

Figure 4.23 Kinetic profiles for protodecarboxylation of

2-nitrobenzoic acid over (u) 10 wt % Ag/Al2O3, (×)

Ag2O (commercial) and (n) Ag powder

134

Figure 5.1 Powder XRD patterns of 10 wt % Cu/Al2O3 : (a) WI

catalyst without H2 pretreatment, (b) WI catalyst with H2 pretreatment, (c) WI-SG catalyst with H2

pretreatment ( + : lattice plane of γ-Al2O3; * : lattice planeof metallic Cu, # : lattice plane of CuO)

138

Figure 5.2 N2 adsorption and desorption isotherms of 10 wt %

Cu/Al2O3 : (u)WI and (▲) WI-SG catalyst

139

Figure 5.3 Pore size distribution of 10 wt % Cu/Al2O3 : (u)WI

and (▲) WI-SG catalyst

139

Figure 5.4 Powder XRD patterns of γ-Al2O3 supported with

(a) 1.0 wt % Cu, (b) 2.5 wt % Cu, (c) 5.0 wt % Cu, (d) 10.0 wt % Cu, and (e) 15.0 wt % Cu ( + : lattice plane of γ-Al2O3, * : lattice planeof metallic Cu)

141

Figure 5.5 Cu XPS spectrum of (a) 1.0 wt %, (b) 2.5 wt %,

(c) 5.0 wt %, (d) 10.0 wt % and (e) 15.0 wt % Cu/Al2O3 WI-SG catalyst (dotted lines indicate the peak maxima detected)

143

Figure 5.6 The Cu LMM Auger peak of (a) 1.0 wt %,

(b) 2.5 wt %, (c) 5.0 wt %, (d) 10.0 wt % and (e) 15.0 wt % Cu/Al2O3 WI-SG catalyst (dotted lines indicate the 2 peak maximum observed.)

146

Figure 5.7 TEM images and Cu particle size distribution of (a)

1.0 wt %, (b) 2.5 wt %, (c) 5.0 wt %, (d) 10.0 wt %, (e) 15.0 wt % Cu/Al2O3

148

Figure 5.8 Plot of ion current for CO2 (m/z= 44) against

temperature for 2.5 wt % Cu/Al2O3 WI-SG catalyst (a) without pretreatment; (b) after H2 pretreatment for 2 h at 150 oC; (c) after H2 pretreatment for 2 h at

300 oC

149

Figure 5.9 Kinetic profile of protodecarboxylation of

2-nitrobenzoic acid carried out in the presence of (♦) Li2CO3, (■) Na2CO3, (▲) K2CO3, (x) Cs2CO3

152

Figure 5.10 Kinetic profile of protodecarboxylation reaction

carried using 10 wt % Cu/Al2O3 WI and WI-SG catalyst

153

Figure 5.11 Kinetic profile protodecarboxylation of

2-nitrobenzoic acid carried using Cu/Al2O3 WI-SG catalyst with 1.0 wt % to 15.0 wt % Cu loading

154

Figure 5.12 Plot of initial rate of reaction (mmol/mmolcath)

against weight loading of copper (%)

154

Figure 5.13 Kinetic profile of protodecarboxylation of

2-nitrobenzoic acid using (♦) 2.5 wt % Cu/Al2O3

WI-SG catalyst without pretreatment; (■) 2.5 wt % Cu/Al2O3 WI-SG catalyst after H2 pretreatment for

2 h at 150 oC; (▲) 2.5 wt % Cu/Al2O3 WI-SG catalyst after H2 pretreatment for 2 h at 300 oC

156

Figure 5.14 Optimised structure of Cu2O (111) and (100)

surface: (a) side view of Cu2O (111) and (b) side view of Cu2O (100) The red, brick red and yellow spheres represent oxygen, coordinatively saturated copper (CuCSA) and coordinatively unsaturated copper (CuCUS) atoms The white line defines the uppermost layer

157

Figure 5.15 Leaching test at 165 oC - Kinetic profile for the

protodecarboxylation of 2-nitrobenzoic acid carried out (▲) without hot filtration and (■) with hot filtration after 0.5 h

163

Figure 5.16 Leaching test at 150 oC- Kinetic profile of

protodecarboxylation of 2-nitrobenzoic acid carried out (▲) without hot filtration and (■) with hot filtration after 2 h

165