Chemical Industry-The Fact Sheet 70000 products 10 Million direct employees 50 Million indirect employees Wide range of products/processes / feed-stocks Enabling better quality of life Annual growth rate 2.4 % Global enterprise valued at $2.2 Trillion …… and growing
30
Embed
Chemical Industry-The Fact Sheet 70000 products 10 Million direct employees 50 Million indirect employees Wide range of products/processes / feed-stocks.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Chemical Industry-The Fact Sheet
70000 products
10 Million direct employees
50 Million indirect employees
Wide range of products/processes
/ feed-stocks
Enabling better quality of life
Annual growth rate 2.4 %
Global enterprise valued at $2.2 Trillion …… and growing
Chemical Industry- Products pattern
Polymers constitute 20 % of Mega Chemical Industry
ABS- Acrylonitrile-Butadiene-Styrene co-polymer PAN-Strong fibre character PBR- Rubber-Elasticity-shock absorber PS - Tough & hard
The co-polymer has very high strength & toughness
Block
Random
Graft
Polymers- Finger prints
Catalyst & Process controlled Reflected in
Regioselectivity Melting point
Cis/Trans Isomerism Crystallization temp.
Stereoselectivity Glass Transition temp.
Mol. Wt distributuion Modulus
Polydispersity Crystallinity
Viscosity
Morpohology
Hardness
Stiffness
Transparency
Catalysts & process dictate the property of polymer
Polymers-The journey
Monomer
Type of polymerization
Type of process/reactor
Reaction conditions
Type of catalyst
Polymer resin Processing
End Product
Type of Processing, Processing aids,Machinery
Co-monomer(s)
Co-catalystsDonors etc.
History of PE & PP(1933)
(1955)
Propylene polymerization on similar catalysts by Natta (1956) - 3 generations of catalysts
Silica supported chromia catalyst for ethylene polymerization Banks & Hogan- Phillips (1958)- Low pressure/Temp process
Metallocene catalysts- Kaminsky (1989) Post metallocene catalysts
Ziegler & Natta awarded Nobel prize in 1963 Global consumption- PP - 45 Mill.MT; Value- $65 Billn. (2007) PE - 65 Mill.MT (2008)
monomer
initiation
Ethylene (C2H4) forms polyethylene (PE)in the presence of free radical R• (catalyst or initiator)
propagation
Free radical ploymerization- Ethylene
Ploy ethylene – Types Vs Properties
PE MW Density Tensile strength Branching Mill. g/cc MPaHDPE 0.2-0.5 > 0.941 43 LowLDPE 0.1 0.91-0.940 24 Med & ShortLLDPE 0.1 0.91-0.925 37 Short
Co-monomers for LLDPE → 1-Butene/1-Hexene/1-Octene
PE by free radical route
• Extensive branching
• Long and short branches
• Lower crystallinity 30-60%
• Density 0.91-0.925
• Vary P, T during synthesis
UHMWPE – MW- 3-6 Million
Surface structure of Chromium based PE catalysts
1.CrO3/ Silica- Phillips
2.Chromocene/Silica- Union Carbide
Choice of silica (~300 m2/g), Cr loading (1%), promoters & pretreatment (calcination, pre-reduction) of the catalysts are crucial
30-40 % of PE is produced by Phillips process
Z-N- Polymerization of ethylene
Catalytic cycle for polymerization of ethylene - Cossee-Arlman mechanism- Direct insertion of olefin across M-alkyl bond
Processes for Polyethylene
Processes for PE production
High Pressure
Autoclave
Tubular
Low Pressure
Slurry phase
Gas phase
Solution phase
Conventional Ziegler-Natta Catalyst
• Catalyst components TiCl4 & AlEt3
• Organo aluminium compound reduces TiCl4 to generate TiCl3
• Active phase TiCl3• Different crystalline forms- α , β, γ , & δ• β Chain structure; α , γ , & δ have layer structure• Activity & Isotacticity differs• α – Hexagonal Close packed – hcp of Cl ions• γ - Cubic close packed –ccp of Cl ions• Ti ions occupy Octahedral holes of Cl- matrix
Stereochemistry of PP- a) Three different orientation of methyl groups in PPbackbone b) Stereo chemical relationship between two adjacent methyl groups
Z-N Polymerization-Stereochemistry
PP Stereochemistry- Effect of metal & ligand
PP- Streochemistry Vs Properties
PP Elastic Hardness MP Mech.props
Modulus-Gpa Mpa ° C
Isotactic 1.09 125 160-170 Stiff/Brittle
Syndiotactic 125-131 Robust, transparent
Atactic 0.15 1.4 < 0
Polymerization of propylene- Reaction scheme
Polymerization of propylene- Steps
1. Replacement of one Cl by alkyl group of Al alkyl
2. Bonding of Propylene to a vacant site
3. Insertion of propylene into Metal-alkyl bond- Initiation
4. Creation of vacant site for propylene adsorption
5. Repetition of steps 2,3 & 4 leading to chain growth/propagation
6. Catalyst configuration decides the configuration of added propylene
7. Termination of polymer chain with hydrogen- Termination
Streochemistry of active site
TiCl
Cl
Cl CH3
P
Cl
4 Bridging Cl1Terminal Cl replaced by alkyl 1 Vacant site for propylene adsorption
--------
----
-----------
-----------
--------
---
----------
C
C
CH3
HH
124.3°
1.336Å
1.501ÅH
Polypropylene- Stereoregulation
Methyl group of the incoming propylene prefers a trans position vis-à-vis the polymer chain-p – Right ; cis orientation as shown on left is not favoured
M P +
1
3
2
1
2P
3
M
M
3 1
P2
M
3
12
P
1,2 Insertion
2,1 Insertion
3,1 Insertion
Possible insertion modes for Propylene across Metal-Alkyl bond- Different orientations of methyl group