Transcript Chapter. 13 Zieglar-Natta Catalyst

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Chap 12. Zieglar-Natta Catalyst
Zieglar-Natta Catalyst
- Before Z-N Catalyst invention, PP composites were only atactic form
- After that, isotactic PP composites of extraordinary MW(>106) is synthesized
LDPE = HPPE
HDPE
This has less hardness,
stiffness and strength
compared to HDPE,
but better ductility,
Free radical
Use chromium
compounds.
Zieglar-Natta process
is recent application.
A few number of
branches
AlR3, AlHR2
10 billion lb/yr
PP
Natta
4 billion lb/yr
Characteristic conditions for PP
PP and solid catalysts are put together at 50℃ to 90℃ below 5atm.
After stopping of reaction, it is washed with H2O or ROH to remove the catalysts.
MW is on the control of chain transfer agent
E.g.) CO2, O2, H2, H2O, …
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Dr. Ziegler and Dr. Natta
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Zieglar-Natta Catalyst
Cl
open
Ti *
Cl
CH2=CHCH3
Cl
Cl
Monometallic
Bimetallic mechanism
Assumption: equal site reactivity
- Monometallic Corsee mechanism
CH2
Cl
CH2
Cl
Cl Ti
Cl
Cl
+
*
CH2=CHCH3
Cl Ti
Cl
Cl
CHCH3
*
CH2
HC CH3
H2C
Cl Ti
Cl
Cl
Cl
*
migration * open
Ti
isotactic
CH2
CH2CHCH3
H2C
Ti
CHCH3
CH2
syndio
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Zieglar-Natta Catalyst

Bimetallic

H2C
H2C CHCH3
CH2
Ti
Al
Ti
 CH2

Ti
TiCl
α-TiCl3
Al
R
R
CH2
CHCH3
CH
Al
R
CHCH3
CHCH3
H2C
CH2
Ti
Al
R
β-TiCl3
2 vacancy sites => atactic
1 vacancy site => isotactic
1 vacancy site => isotactic
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Zieglar-Natta Catalyst
This image shows the mechanism by which the Ziegler Natta catalyst polymerizes 1-propene.
The image was created by Christine Ann.
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A
Polymerization
rate
B
C
Time
Types of rate curves observed in Ziegler-Natta polymerization: (A) constant; (B)
decaying; and (C) decaying to constant
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Polyethylene Polymerization
A
B
E
D
C
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Chap 13. Polymerization Processes
Bulk polymerization
 Homogeneous polymerization
Solution Polymerization
Suspension polymerization
 Heterogeneous polymerization
Emulsion polymerization
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Bulk polymerization
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Solution Polymerization
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Suspension polymerization
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Emulsion polymerization
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Stages in Emulsion Polymerization
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