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Ziegler-Natta Catalysis Presented by: Mehrban ashiq Saad afzal Presented To: M.phil Inorganic- Analytical Chemistry 3 rd Semester Department of Chemistry,

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Presentation on theme: "Ziegler-Natta Catalysis Presented by: Mehrban ashiq Saad afzal Presented To: M.phil Inorganic- Analytical Chemistry 3 rd Semester Department of Chemistry,"— Presentation transcript:

1 Ziegler-Natta Catalysis Presented by: Mehrban ashiq Saad afzal Presented To: M.phil Inorganic- Analytical Chemistry 3 rd Semester Department of Chemistry, University of Gujrat, Pakistan. Course Title: Organo -Transition Chemistry Course code: CHEM-529 Instructor : Dr. Muhammad Ali Mohsin

2 Ziegler-Natta Catalysis Outline: Introduction Catalysis Activation Energy Ziegler-Natta Olefin Polymerization Ziegler's Discovery Mechanism Natta's Discovery PP Stereochemistry Different Catalyst system and % yield Conclusion

3 most popular plastic. Grocery bags, shampoo bottles, toys, etc. Simple structure than all polymers. Branched/low-density = (LDPE) Easier to make Linear/high-density = (HDPE) Ziegler-Natta Catalyst

4 Catalysis Catalysts increase reaction rate without themselves being changed Can accelerate a reaction in both directions Do not affect the state of equilibrium of reaction –simply allow equilibrium to be reached faster

5 Activation energy Molecules must be activated before they can undergo a reaction –Reactants must absorb enough energy from surroundings to destabilize chemical bonds (energy of activation) Transition state –Intermediate stage in reaction where the reactant molecule is strained or distorted but the reaction has not yet occurred

6 Zieglers Discovery 1953 K. Ziegler, E. Holzkamp, H. Breil & H. Martin Angew. Chem. 67, 426, 541 (1955); 76, 545 (1964). Problem Idea:

7 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. 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 Catalyst – Transition metal Co-catalyst – Organometallic Compound, mainly alkyl or alkylhalides of aluminium and boron, or methylaluminoxane. Co-catalyst – Organometallic Compound, mainly alkyl or alkylhalides of aluminium and boron, or methylaluminoxane.

8 Ziegler-Natta Catalysis of Alkene Polymerization A typical Ziegler-Natta catalyst is a combination of TiCl 4 and (CH 3 CH 2 ) 2 AlCl, TiCl 4 and (CH 3 CH 2 ) 2 AlCl, or or TiCl 3 and (CH 3 CH 2 ) 3 Al. TiCl 3 and (CH 3 CH 2 ) 3 Al. Ziegler-Natta Catalyst

9 Polymerization 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

10 Conventional Ziegler-Natta Catalyst Catalyst componentsTiCl 4 & AlEt 3 Organo aluminium compound reduces TiCl 4 to generate TiCl 3 Active phase TiCl 3 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

11 Mechanism of Coordination Polymerization Initiation Initiation Al(CH 2 CH 3 ) 3 + TiCl 4 ClAl(CH 2 CH 3 ) 2 + CH 3 CH 2 TiCl 3

12 Mechanism of Coordination Polymerization Initiation Initiation Al(CH 2 CH 3 ) 3 + TiCl 4 ClAl(CH 2 CH 3 ) 2 + CH 3 CH 2 TiCl 3 H2CH2CH2CH2C CH 2 CH 3 CH 2 TiCl 3 + H2CH2CH2CH2C CH 2

13 Mechanism of Coordination Polymerization Initiation Initiation CH 3 CH 2 TiCl 3 H2CH2CH2CH2C CH 2 TiCl 3 CH 3 CH 2 CH 2 CH 2

14 Mechanism of Coordination Polymerization propagation propagation TiCl 3 CH 3 CH 2 CH 2 CH 2 TiCl 3 CH 3 CH 2 CH 2 CH 2 H2CH2CH2CH2C CH 2

15 Mechanism of Coordination Polymerization propagation propagation TiCl 3 CH 3 CH 2 CH 2 CH 2 H2CH2CH2CH2C CH 2 TiCl 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2

16 Mechanism of Coordination Polymerization propagation propagation TiCl 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 H2CH2CH2CH2C CH 2 etc.

17 Termination

18 Catalytic cycle for polymerization of ethylene - Cossee-Arlman mechanism - Direct insertion of olefin across M-alkyl bond

19 Nattas Discovery 1954 Giulio Natta, P. Pino, P. Corradini, and F. Danusso J. Am. Chem. Soc. 77, 1708 (1955) Crystallographic Data on PP J. Polym. Sci. 16, 143 (1955) Polymerization described in French Isotactic Syndiotactic Ziegler and Natta won Nobel Prize in 1963

20 Automobile and appliance parts, rope, carpeting Soft n sticky…not very good for anything Polypropylene tacticity

21 - Before Z-N Catalyst invention, PP composites were only atactic form - After that, isotactic PP composites of extraordinary MW(>10 6 ) is synthesized LDPEHDPEPP This has less hardness, stiffness and strength compared to HDPE, but better ductility, Free radical 10 billion lb/yr Use chromium compounds. Zieglar-Natta process is recent application. A few number of branches AlR 3, AlHR 2 Natta 4 billion lb/yr Zieglar-Natta Catalyst

22 PP- Streochemistry Vs Properties PP Elastic HardnessMP Mech.props Modulus-Gpa Mpa°C Isotactic Stiff/Brittle Syndiotactic Robust, transparent Atactic < 0

23 Isotactic Polymerization

24

25 Syndiotactic Polymerization

26 Continue………….

27 Continue…..

28 Z-N catalysts- Generations catalyst First TiCl 3 and AlEt 2 Cl Second TiCl 3 + AlEt 2 Cl + Mono/Di ethers, Mono/Di esters Third TiCl 4 supported on MgCl 2 + Al-Alkyl + Phthalate esters -3 rd component MgCl 2 has layered structure; Ionic radii of Mg 2+ & Ti 3+ similar Structural compatibility Polymer yield > 30 Kg/g ; Isotacticity index % Fourth Morphology controlled catalysts Spherical polymer product-No extrusion

29 General Composition of Catalyst System and % Yield Main Group Metal alkyl Transition Metals Compounds% Yield of Polymer Al 2 Et 6 TiCl 4 48 AlBu 3 TiCl 4 60 Al 2 Et 6 TiCl* Al 2 Et 6 VCl 4 78 Al 2 Et 6 VCl 3 73 Al 2 Et 6 CrCl 3 36 Al 2 Et 6 TiCl [Et 2 Be] n TiCl* [Et 2 Mg] n TiCl* Et 2 ZnTiCl* [AlClMe 2 ] 2 TiCl* R.C.MEHROTRA,. A.SINGH. Organometallic Chemistry Revised Second Edition page(464)

30 Limitations we can't make poly(vinyl chloride) by Ziegler-Natta polymerization. When the catalyst and cocatalyst come together to form the initiating complex, radicals are produced during intermediate steps of the reaction. These can initiate free radical polymerization of the vinyl chloride monomer. Acrylates are out, too, because Ziegler-Natta catalysts often initiate anionic vinyl polymerization in those monomers.

31 Move forward homogeneous polymerization catalyst metallocene catalysis polymerization

32 Ziegler – Natta olefin polymerization homogeneous polymerization catalyst: Reactive intermediates such as A or B, alkyl olefin complexes, should be unsaturated

33 PP Stereochemistry- Effect of metal & ligand

34 Conclusion Linear high density ethene polymerization Isotactic propylene polymerization

35 Thanks


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