Download Lecture 5 - Homogeneous catalysis: polymerization, Lewis acid/base catalysis

Catalysis
Lecture 5
Nikodem Kuźnik
Silesian University of Technology
Gliwice, Poland
Scope of the lecture
• Acylation/Alkylation – Friedel-Crafts’ Process
• Polymerization of olefins catalyzed by transition
metals
• Ring Opening Polymerization
• Phenol Synthesis
Catalytic Polymerization
R
1
R
R
2
1
R
1
R
1
R
1
R
1
catalyst
n
H
H
R
2
R
2
R
2
n
R
2
R
2
Transition metal Catalysts for olefin polymerization
Me
Cl
Me
Zr
Cl
Metallocenes Catalyst
(Single-Site Catalyst)
Zr
Cl
Cl
CrO3/silica
Phyllips catalyst
TiCl4+ AlEt2Cl/Al2Et3Cl3=-TiCl3+AlCl3
Zigler-Natta catalyst
Polymerization Mechanism
P
R
CH2 +
P
Ligand association
CH2
M
M
R
Chain growth
P
CH2
P
1,2-Insertion
R
H2C
M
M
R
Propagation of polymer chain
What is the role of the metal (M)?
Stereochemistry of polypropylene
(PP)
Me H Me H Me H Me H
Isotactic
Me
Z-N catalyst
n
Me H Me H Me H Me H
Syndiotactic
n
Me H Me H Me H Me H
n
Atactic
Mechanism for Isotactic Polymerization
P
H
Me
Zr
Zr
H
Me
Me H
Me
Zr
P
Me
P
H
Zr
Zr
H Me H Me H Me
Me
Cl
Cl
=
Cl
Zr
Cl
Me
Me
H
P
Zr
H
H Me H Me
H Me H Me
P
Zr Me
P
Mechanism for Syndiotactic Polymerization
P
H
Me
Zr
Zr
Me
Me Me H
Zr
P
P
Me H
H
Zr
Zr
Me H H Me Me H
Me
Zr
Cl
Cl
=
Cl
Zr
Cl
H
Me
Me
P
Me
Me
H
H Me Me H
Me
P
Zr
H
Me Me H
P
Ring-Opening Metathesis Polymerization
ROMP
Ring-Opening Metathesis Polymerization
ROMP
General idea:
Since 1976, 5000 tons/year CdF-Chimie (France),
norbornene is converted to polynorbornene (Norsorex):
Since 1980, Hüls - cyclooctene is converted to polyoctenamer (Vestenamer 8012):
Alkylation of Benzene
Friedel-Crafts Process
8.000.000 tons/year
(2-propyl)benzene
cumene
20.000.000 tons/year
ethylbenzene
H2C CH2
catalyst
catalyst
OH
Catalytic
alkylation
polysyrene
phenol
vinylbenzene
styrene
Alkylating and Acylating Agents and Catalysts
Acylating Agents
Alkylating Agents
Acyl Halides
Olefins
Carboxylic Acids
Alkyl halides H3C Cl H3C
Anhydrides
Alcohols, Ethers, Esters,...
H2C CH2
I C2H5
Cl
Acylation/Alkylation Catalysts (Friedel-Crafts Catalysts):
Acidic halides (Lewis Acids): AlCl3, AlBr3, BF3, ZnCl2, TiCl3, SnCl4,... Cocatalysts: HX, H2O, H2SO4
Metal Alkyls and Alkoxides: Al(OPh)3 - for industrial alkylation of phenol
Proton Acids: H2SO4, HF (anhydrous), CF3COOH, HCl, H3PO4
Acidic Oxides and Sulfides (heterogeneous): zeolites, metal oxides, heteropolyacids
Supported Acids and Cation-Exchange Resins
Basic and Organometallic Catalysts
Mechanism of Alkylation
Carbonium cation formation
R-CH=CH2 + HX + AlX3 →[R-HC-CH3][AlX4]RX + AlX3 → [R]+[AlX4]ROH + AlX3 → [R]+[AlX3OH]R =
alkyl
Electrophylic attac of carbonium cation on aromatic ring
R
H
+
R
CH3 +
CH3
+
+
H+
Mechanism of Acylation
Ethylbenzene Synthesis
Homogeneous oxidation with auxiliary
hydroperoxides
CH3
H3C
izobutene
MTBE
CH3
OH
R=CH(CH3)3
RH
ROOH
H2C CH2 CH3
catalyst
ROH + HC
CH2 CH3
O
R=PhCH=CH2
OH
CH CH2
-H2O
CH
CH3
styrene
Homogeneous oxidation - mechanism
[Mo6+]
[Mo6+ROOH]
+ ROOH
H2C CH CH3
H2C
CH CH3 + [Mo6+] + ROH
O
R'-OH
H
O
R
CH2
O
O
R'
O
O
O
O
Mo
CH
CH3
H
O
O
R
H3C
H3C
R
O
O
O
O
O
Mo
O
+
H
O
CH2
O-
CH
R'
CH3
O
H3C
O
O
O
O
Mo
O
O
O
Mo
O
H
O
O
R'
H3C
O R
CH2
H
CH2
CH
O
CH
CH3
R'
CH3
O
Phenol Synthesis
OOH
OH
+
AlCl3
O2
O
H2SO4
cumyl
hydroperoxide
+
phenol
7 ton/year
propenon
acetone
5 tons/year
Oxidation of Cumene - Autocatalysis
CH3
Ph
H
CH3
O2/initiators
spontaneus
homolytic
cleavge
CH3
Ph
OOH
.OH
CH3
+
Ph
.
O
CH3
CH3
CH3
Ph
CH3
.OH
autocatalysis
H
CH3
Ph
.
O
CH3
CH3
H2O
CH 3
Ph
Ph
.
CH3
CH3
OOH
Ph
CH 3
C
O2
CH3
CH3
Ph
H
CH3
CH3
Ph
OH
.
C O O
CH3