Download Catalysis

Ziegler-Natta Palladium and Nickel Catalysts for the
Transformation of Unsaturated Hydrocarbons
G. Myagmarsuren
National Research Laboratory for Environmental Catalysis,
Department of Chemical and Biomolecular Engineering,
Korea Advanced Institute of Science and Technology
Catalysis
• An acceleration of the rate of a process or
reaction, brought about by a catalyst,
usually
present
in
small
managed
quantities and unaffected at the end of the
reaction. A catalyst permits reactions or
processes to take place more effectively or
under milder conditions than would
otherwise be possible.
The basis for catalysis
A catalyst lower the
activation barrier for a
transformation, by
introducing a new
reaction pathway
– It does not change the
thermodynamics!!
Importance of catalysis
Synthetic chemical
- Many major
industrial chemicals
are prepared with
the aid of catalysts
- Many fine chemicals
are also made with
the aid of catalysts
– Reduce cost of
production
– Lead to better
selectivity and less
waste
Ethene
Sulfuric acid
Propene
1,2-Dichloroethane
Calcium hydroxide
Ammonia
Urea
Phosphoric acid
Chlorine
Ethylbenzene
Sodium carbonate
Sodium hydroxide
Styrene
Nitric acid
Ammonium nitrate
Hydrogene chloride
Acrylonitrile
Ammonium sulfate
Potassium oxide
Titanium oxide
Rank*
Catalytic process
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Hydrocarbon cracking; heterogeneous
SO2 oxidation; heterogeneous
Hydrocarbon cracking; heterogeneous
C2H4 + Cl2; heterogeneous
Not catalytic
N2 + H2; heterogeneous
NH3 precursor catalytic
Not catalytic
Electrolysis
Alkylation of benzene; homogeneous
Not catalytic
Electrolysis
Dehydrogenation of ethylbenzene;
heterogeneous
NH2 + O2; heterogeneous
Precursors catalytic
Precursors catalytic
HCN + C2H2; homogeneous
Precursors catalytic
Not catalytic
Heterogeneous versus
homogeneous










􀂋 A heterogeneous catalyst is material that is in a
different phase from the reactant and product
– For example, Pt/Al2O3 for hydrogenation
» Often used industrially for large scale chemical
manufacture. Can be cheap but catalytically active
species hard to pin down
􀂋A homogeneous catalyst is a substance that is in
the same phase as the reactant and product
– For example, Wilkinson’s catalyst [RhCl(PPh3)]for
hydrogenation
Industrial use of homogeneous
catalysis
C-C bond formation:
Polymerization and Oligomerization





Def: the fundamental process by which low molecular weight
compounds are converted into high molecular weight compounds.
n=2 – dimerization;
n=3 – trimerization;
n< 200 - oligomerization
n>200 up to millions – polymerization.
Low molecular weight
material (having two or
more reactive groups)
Catalyst
High molecular
weight material
Brief History
Karl Ziegler
1/2 of the prize
Federal Republic of Germany
•Since the end of 1952, a doctoral candidate, Holzkamp,
has been working on growth reaction with ethylene and
ethylaluminum in a steel pressure vessel (100°C, 100 atm).
In a routine experiment he was surprised to get almost
only 1-butene very fast. After a "strenuous investigation“,
Holzkamp discovered that the catalytic effect was due to
nickel present in the steel reaction vessel.
•At the end of October, Breil, another of Ziegler’s
collaborators, came to zirconium: a rapid and complete
polymerization occurred. Moreover, the infrared spectra
demonstrated that the polymer was linear.
•Heinz Martin tried the simplest possible conditions: no higher
pressure at all and no external heating. The result of the trial
was that Martin burst in Ziegler’s office waving a glass flask and
crying: "Es geht in Glass!“.
CATALYST: Titanium trichloride +
diethylaluminum chloride
Cl
Cl
Cl
Ti
(TiCl3)
Al
Cl
(Al(C2H5)2Cl)
H2C


Grocery bags, shampoo
bottles, toys, etc.
Simple structure than all
polymers.
Branched/low-density =
(LDPE)


Ziegler-Natta Catalyst
most popular plastic.


CH2
Easier to make
Linear/high-density =
(HDPE)
CH2
CH2 n
In Italy, Giulio Natta also recognized that catalysts of the type
described by Ziegler were capable of polymerizing 1-alkenes
(alpha olefins) to yield stereo-regular polymers. By slightly
modifying the catalysts used by Ziegler, Natta was able to prepare
highly isotactic linear crystalline polymers from non-polar α-olefins
(e.g. propylene).
Giulio Natta
1/2 of the prize
Italy
CATALYST: Titanium tetrachloride + triethylaluminum
Cl
Al
Cl
Ti
Cl
Cl
(TiCl4)
(Al(C2H5)3)
Polypropylene tacticity
H
H
C
H
C
CH 3
H
H
C
C
H
CH 3
C
n
C
C
C
C
C
C
C
C
C
R
R
R
R
R
R
isotactic
R
C
Automobile and appliance
parts, rope, carpeting
Soft n’ sticky…not very good
for anything
C
C
R
C
C
C
C
R
C
C
C
C
R
C
C
C
R
R
syndiotactic
R
C
C
C
C
C
R
R
R
C
C
C
C
R
C
C
C
R
atactic
The way groups are arranged along the
backbone chain of a polymer.
The Nobel Prize in Chemistry 1963
"for their discoveries in the field of the chemistry and technology of high polymers"
Karl Ziegler
1/2 of the prize
Giulio Natta
1/2 of the prize
Federal Republic of
Germany
Italy
Max-Planck-Institut für
Kohlenforschung (MaxPlanck-Institue for Carbon
Research)
Mülheim/Ruhr, Federal
Republic of Germany
Institute of Technology
Milan, Italy
b. 1898
d. 1973
b. 1903
d. 1979
Robert L. Banks and J. Paul Hogan
(Phillips Petroleum Company
Crystallynie polypropylene and
polyethylelene with nickel oxide catalyst
)
Polymerization Apparatus
O
T
O
T
O
T
O
T
M
T
M
T
M
T
M
T
P
F
F
F
H2
F
N2
C3H6
C2H4
Vacuum
TC
Projected demand for catalyzed
polyolefins
Demand by Year (in tons)
Polymer
2000
2005
2101
Polyethylene
10 000 000
20 000 000
40 000 000
Polypropylene
1 500 000
7 000 000
20 000 000
Polystyrene
80 000
150 000
300 000
Cyclic olefins (e.g. PNB)
30 000
60 000
100 000
Ziegler-Natta Catalysts

Combination of a transition metal compound of an element
from groups IV to VIII, and an organometallic compound of a
metal from groups I to III.

Catalyst – Transition metal

Co-catalyst – Organometallic Compound, mainly alkyl or
alkylhalides of aluminium and boron, or methylaluminoxane.
Metal Catalysts for the
Transformations of Olefins
Late transition metals
Early transition
metals
Central
transition
metals
Four generations of catalysts for
-olefins polymerization
Innovation
Catalyst
First
generation
1957
Third
component
1964
Second
generation
1973
Third
generation
1980
Fourth
generation
1991
TiCl3 purple
phases
Cocatalyst
Result
Support
AlEt2Cl
–
Lewis bases
added
TiCl3 purple
phases at
lower
temperature
Stereo
selectivity
Morpholo
gy
+
Crystal
structure
analysis
+
Coordination
chemistry
Solid state
+
Activated
MgCl2
Al-oxane
activated
metallocene
complexes
Activity
Disciplinary
Makeup
++
+
Silica gel
+
(–)
Solid state
Materials
science
Coordination
chemistry
Important catalyst properties
•
•
•
•
•
•
•
•
•
Activity
– A reasonable rate of reaction is needed
􀂋Selectivity
– Byproducts should be minimized
􀂋Lifetime
– It is costly to replace the catalyst frequently
􀂋Cost
– The acceptable cost depends upon the catalyst
lifetime and product value
HOWEVER
Organometallic
compounds
(alkyl
or
alkylhalides) are highly reactive and many
ignite spontaneously upon exposure to the
atmosphere.
 Methylaluminoxane is mainly obtained by the
partial hydrolysis of trimethylaluminium (TMA)
and called as a
black box due to the lack of a
deep understanding of its structure.
Due to high production costs of MAO
and organoborane cocatalysts, it is
desirable to find the novel activators
which can be used as substitutes for MAO
and organoboranes.

OBJECTIVES
• To develop novel simple catalytic systems
for the transformation of unsaturated
hydrocarbons:
• Catalyst: Palladium and Nickel Complexes
• Cocatalyst: Simple Lewis Acid – Boron
Trifluorid (BF3) Compounds, e.g. BF3OEt2.
Processes
• Propene dimerization
• 1-Hexene izomerization
• Styrene dimerization
• Norbornene and derivative’s
polymerization
Three different mechanisms
for the C-C bond formation
1-butene
M-H
C 2H 4
C 2H 4
M
M
M-H
-H
Insertion pathway ( hydride)
1-butene
n+
[M]
(n+2)
M
M
(n+2)
 - H
or
1, 3 - H shift
[M]
n+
Oxidative coupling pathway
1-butene
+
n+
[M]
M
n-1
M
n-1
Cationic pathway
+ H+
n+
[M]
PROPENE DIMERIZATION
•Gasoline (80%)
•Polypropylene
•isopropanol, trimers
and tetramers for detergents,
propylene oxide, cumene,
and glycerine
Octane number
H3C CH3
CH3-CH2-CH2-CH2-CH2-CH2-CH3
CH3-C-C-CH3
n-heptane
H3C CH3
0
isooctane
100
Alkylation of propene dimers
to gasoline
RH
CH3CH2CH=CHCH2CH3
CH3CH2C-CCH2CH3
HEX
HR
CH3
2 CH2=CHCH3
CH3CH2CH=CCH3
H3C R
CH3CH2C-CCH3
MP
HR
H3C CH3
H3C CH3
CH3C-CCH3
CH3C=CCH3
DMB
HR
Palladium based systems
Catalyst components:

R1
R3
C
O
CH
O
C
+ n BF3OEt2
Pd
C
O
O
C
R2
R4
R1
R3
C
O
CH
C
+ PR3 + n BF3OEt2
Pd
C
R2
O
O
O
C
R4
•
IR, UV, 1H, 13C NMR, elemental
analysis: Palladium hydrides
(Pd-H) are responsible for catalytic
activity.
• Catalytic activity of 2500 mol
propene per mol Pd for an hour has
been achieved (CPd=0.0042 mol/l;
B/Pd=30;
500C;
toluene,
contineous supply of propene).
• This is 300 times higher than those
Ziegler-Natta palladium catalysts
described in the literature.
Nickel based systems
ESR, NMR, IR spectroscopy
(PPh3)4Ni(0)
+(2-4)BF3 OEt2
- Ph3P BF3
[(PPh3)3Ni(I)L]BF4
[(PPh3)Ni(I)L2]BF4
+160BF3 OEt2
+(40-60)BF3 OEt2
+(60-80)BF3 OEt2
- Ph3P BF3
- Ph3P BF3
- Ph3P BF3
[(PPh3)2Ni(I)L]BF4
+L
[(PPh3)2Ni(I)L2]BF4
Nicolloidal
L = OEt2, BF3 OEt2
Nickel based systems: Catalyst design
Ni(0)
Ni(I)
NiP4
HX,
BF3
[P2NiH]+A
BF3, L
[P2NiL]BF4
BF3, L
[PNiL2]BF4
HX,
BF3
[P2NiH]2+[A ]2
P=PR3; BF3=BF3OEt2; A=BF3X; L=unsaturated hydrocarbon
Ni(II)
Ni(III)
Efficiency of Nickel Catalysts

Catalyst components:
Ni(PPh3)4 + n BF3OEt2
Ni(acac)2 + PR3 + AlEt3 + BF3 + HX
Ni(acac)2 + PR3 + AlEt3 + HX + BF3

Astonishing 625 000
mol propene per mol
Ni for an hour,
[3-(allyl)Ni(PR3)]+[RAlX3]_
Activity
[PNiL2]BF4
270 000 mol propene per mol Pd for an hour
[P2NiH]2+[A ]2 200 000 mol propene per mol Pd for an hour
[P2NiH]+A
-
127 000 mol propene per mol Pd for an hour
Regioselectivity in Propene Dimerization
CH3
CH2=CHCH2CH2CH2CH3
M-CHCH2CH2CH2CH3
M
- MH
C2
CH3CH=CHCH2CH2CH3
CH3CH2CH=CHCH2CH3
CH2CHCH3
M-CH2CH2CH3
M
C1
CH3
CH3
- MH
M-CH2CHCH2CH2CH3
M
CH2=CHCH2CH2CH3
C1
CH3
CH3
M-H +
CH2CHCH3
CH3
CH3
M-CHCH2CHCH3
M
CH2=CHCH2CHCH3
CH3CH2CH=CCH3
- MH
CH3
C2
CH3CH=CHCHCH3
CH3
CH2CHCH3
M-CHCH3
M
C2
H3C CH3
M-CH2CH-CHCH3
M
- MH
H3C CH3
H3C CH3
CH2=C-CHCH3
CH3C=CCH3
C1
Dimerization vs. Double-bond isomerization!!!
1-Hexene isomerization
(Pd(acac)2 + 20BF3OEt2 system)
H
H
H
H
H
C
H
C
C
C
C
C
H
GLC method
H
H
H
H
H
1-Hexene
Isomerization of 1-hexene is more than
60 times faster than dimerization of
propene !!!
The dimerization products can
isomerize very fastly during their
formation!!!
H
C3H7
C
H3C
H
CH3
C3H7
C
H
H
C2H5
C
C2H5
Profile of isomer distributions versus time for the
isomerization of 1-hexene with Pd(acac)2 + 20BF3OEt2 catalyst.
(CPd=1.47x10-3 mol/dm3, C1-hexene=9.41x10-1 mol/dm3, B/Pd=20, T=100C, aging time 30 min)
trans-2-hexene
C
cis-2-hexene
C
H
C2H5
C2H5
C
C
H
trans-3-hexene
H
C
H
cis-3-hexene
Styrene dimerization
(Pd(acac)2 + 7BF3OEt2 system)

H2C
Source:
CH3
Importance:
CH
CH2
Cat.
- H2
Ethylbenzene
Styrene
(rank 10)
(rank 13)

H
2
C C
H
H
Reaction:
CH3
Pd(dik)2, BF3OEt2, PR3
T 0C
C
H
H
C C
H
trans-1,3-Diphenyl-1-butene
95%
-fine chemicals, e.g. pharmacologically
active Ibuprofen and Naproxen;
-lubricants;
-plasticizers;
-surfactants;
-detergents
Results on styrene dimerization
26
24
-3
Wx10 , mol St/(mol Pd x h)
22
20
4
18
Conversion of 75000 mol St per mol
Pd for 7 h
2
16
14
12
Selectivity of 95% to trans-1,3diphenyl-1-butene
10
8
6
5
4
2
1
3
6
0
0
30
60
90 120 150 180 210 240 270 300 330 360 390 420 450
Time, min
. Kinetic curves: Pd(acac)2 + 7BF3OEt2 system at 600C (1) and 700C (2);
Pd(acac)2 + 1PPh3 + 7BF3OEt2 system at 600C (3) and 700C (4); and
Pd(acac)2 + 2PPh3 + 7BF3OEt2 system at 600C (5) and 700C (6)
Palladium hydride mechanism
Norbornene polymerization

What is Norbornene?
Norbornene is a bicyclic olefin.
CH2 = CH2
Norbornene possesses ring strain,
thus the molecule contains a highly
reactive double bond.
Norbornene is manufactured via the
Diels-Alder reaction of
cyclopentadiene and ethylene.
It is a colorless substance which
melts at 460C.
DCPD
+ CH2=CH2
Norbornene
Norobornene polymerization routes
Cationic or
Radical
Little is known about the cationic and
radical polymerization. The product is
a low molecular weight oligomer with
2,7-enchainity.
n
n
ROMP
n
Vinylic
The best known polymerization is ROMP.
The polymer contains one double bond in
each repeating unit.
The vinylic polymerization is less developed
than ROMP. The polymer has 2,3-enchainity.
n
Application of norobornene saturated
polymers
High optical transparency in the IR region
– data and telecommunication waveguide materials
High optical transparency in the visible (400-700 nm) region
-plastic display substrate
Amorphous nature and subsequent low birefringenece
-optical lenses
High optical transparency in the UV region and
good reactive ion-etch resistance
-photoresist matrix material
Chip fabrication
157 nm photolithgraphy
Application (contd.)
Low dielectric constant and high Tg
-electronics packaging
Sharp decomposition temperature
and low char yield
-interlayer dielectrics in semiconductors
Norbornene polymerization over
Pd(acac)2 + 25BF3OEt2 system
Reaction conditions:
[Pd]=5.0x10-6 M; NB/Pd=22 350;
B/Pd=25; 250C
13C, 1H
Polymer structure: 2,7-enchainity!!!
7
NMR, IR
2
1
L. Goodall et al. BF Goodrich Co., USA, 1999
3
4
6
5
Activity – 20 220 kg NB/(mol Pd  h) !!!
A.Greiner et al. 20564 kg NB/(mol Pd  h)
MAO/Ni=60 000, 200C: Macromol. Rap.
Commun., 20 (1999) 232
Carbocationic mechanism!!!
What are Functionalized
Norbornenes?
X
Source: Diels-Alder reactions
Exo isomer is much more reactive than endo.
Common substituents:
Exo isomer (more reactive)
(20%)
Alkyl (R), Acetate (OC(O)R), Alcohol (OH), Aldehyde
(C(O)H), Anhydride (RC(O)O(O)R), Epoxide
CH2C(O)CH), Ester (CO2R), Ether (OR), Nitrile (CN),
Silyl Ether (Si(OR)3), Ketone (C(O)R), Phenyl (Ar)
X
Endo isomer (less reactive)
80%
Polymerization of Alkylnorbornenes over
Pd(acac)2 + 25BF3OEt2 Catalyst System
Problem arises:
The conversion is 20% at 250C for 48 h. It means that the only exo-isomer
is reacted. Increase of reaction temperature resulted in drastic drop of activity
due to low thermal stability of the system.
Idea:
Addition of Lewis base PR3 and increase of reaction temperature
Pd(acac)2+nPPh3+25BF3OEt2 Catalyst System
And what happened?
Reaction conditions:
[Pd]=5.0x10-6 M; NB/Pd=4500;
B/Pd=25; P/Pd=2; 650C
•The activity is 2680 kg BuNb/(mol Pd  h), which is
comparable to that for most active known catalysts !!!;
•The introduction of PPh3 switches the carbocationic
polymerization mechanism to the coordination Ziegler-Natta
mechanism !!! Polymer has 2,3-enchainity !!!
Switching mechanism
13C
NMR spectra
2,7-enchainity
+
+
Pd
Pol
P
Pd
P
2,3-enchainity
Summary

The combinations of readily available Pd and Ni compounds with simple
Lewis acid BF3 can lead to industrially important catalytic systems. Activities
of these systems are comparable with that of most sophisticated Ziegler-Natta
systems.

The switching of catalytic reaction mechanism is much more common
phenomenon for transition metal catalysis than it is considered so far.

Those catalysts active in the oligomerization of open chain compounds are
presumably active in the polymerization of cyclic compounds.
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graduate students – Master and
Doctor Candidates, the Real
Heroes
of
the
SCIENCE
HYSTORY !!!