Polymerization of olefins by metallocene catalysts

Transcription

1 Polymerization of olefins by metallocene catalysts Pasquale Longo Università di Salerno

2 Molecular Machine Ziegler Natta catalysts building some plastic materials (Poly-ethylene, Poly-propylene, Poly-styrene, etc. etc.) This ship is made of only synthetic materials!

3 USA production ( ) (1,000s of metric tons) year LDPE 560 1,923 3,307 5,069 7,042 HDPE ,998 3,780 6,333 PP ,655 3,773 7,139 PS 450 1,075 1,597 2,273 3,104 PVC 590 1,413 2,481 4,122 6,551 production went from 1.7 billion tons m in 1960 to a massive 30.1 billion tons m in 2000

4 PP strength - very low density - high stiffness - good tensile strength - inertness towards acids, alkalis and solvents - cost advantage - good injection-molding characteristics very suitable for the large-volume cost- and weight-conscious markets (automotive)

5 PP automotive applications Battery cases Bumpers Exterior trim Interior trim Fuel tanks Instrument panels Under-the-hood applications Wires and cables 1,700 components of 5,000 are made of plastics 10% of total weight. 60% of interior weight

6 Amminoacids Proteins Ala Ile Leu Trp Ile Ser Glu Phe Lys Gly His Ser Arg Lys Glu Pro His Pro Leu Phe Arg Gly Trp Ala Ala Glu Gly His Leu Ile Pro Trp Arg Lys Propylene Poly-propylene

7 Input (brick) Linus : Human machine Classic machine (Linus Van Pelt) Output (building)

8 Rybosom : Natural Machine Input (amino-acid) Output (protein) Molecular Machine (Rybosom) Glu Trp Pro His Gly Lys Arg Ile Leu Phe Ser Ile Gly Gly Ile Phe Gly Ile Phe Ser Gly Ile Lys Phe Ser Gly Ile Lys Arg Phe Ser Gly Ile Trp Lys Arg Phe Ser Gly Ile Trp Pro Lys Arg Phe Ser Gly Ile Trp Pro Lys Arg Ile Phe Ser Gly Ile Trp Pro Lys Arg Ile Leu Phe Ser Gly Ile Trp Pro His Lys Arg Ile Leu Phe Ser Gly Ile Trp Pro His Gly Lys Arg Ile Leu Phe Ser Gly Ile Glu Trp Pro His Gly Lys Arg Ile Leu Phe Ser Gly Ile

9 Input (propylene) Ziegler Natta Catalysts : Artificial Machine Molecular Machine (Ziegler-Natta catalysts) Output (poly-propylene)

10 Catalysts for plastic material production Winners of the Nobel Prize Karl Ziegler Giulio Natta Only italian Nobel prize winner for chemistry!

11 The motivations for awarding the prize to Natta Natural and biological catalysts had previously dominated the synthesis of stereoregular polymers. Prof. Natta ended this monopoly.

12 Propylene : INPUT Poly-propylene : OUTPUT Metallocene : tools

13 Propylene (CH 2 =CHCH 3 ) A H C 1 H H 3 C C 2 H B INPUT

14 The faces of propene are chiral A chiral object does not over-lay its mirror-image Louis Pasteur Mirror A A* Chirality = asymmetry Lord Kelvin

15 MILESTONES REACHED

16 Overview, history (1) First report in September 1955 using purple phases of TiCl 3 (α-ticl 3 and γ-ticl 3 ) and AlEt 3 (higher activity) or AlEt 2Cl (higher stereoselectivity). Solvay 1973: Added TiCl 4, which acted as a catalyst to convert β- TiCl 3 into an active phase of TiCl 3 (higher activity due to smaller particles).

17 Overview, history (2) Shell 1980: TiCl 4 supported on MgCl 2 in presence of AlEt 3 or AlEt 2 Cl. Active species still TiCl 3. Other remarks: Awarded Nobel price in s: Process attributed to Robert Banks and J. Paul Hogan Cerutti, L; International Journal for Philosophy of Chemistry, 1999 (5), 3-41

18 Mechanism Two complications Why Cl-vacancy? Why stereospecific? Cossee-Arlman postulate (1964)

19 Structure of the catalyst, overview Three phases of TiCl 3 Color Stucture Activity α-ticl 3 Purple Hexagonal layered structure Isotactic β-ticl 3 Brown Needle structure Little stereospecifity γ-ticl 3 Purple Cubic layered structure Like α-ticl 3

20 Structure of the catalyst, overview Schematic view of the structures of α-ticl 2, α-ticl 3 and ß-TiCl 3

21 Structure of the catalyst, active site (1) Cl-vacancies on the edges of the crystal. Electron Microscopy: active sites are on the edges Ti at the active sites in a square of Cl

22 Structure of the catalyst, active site (2) Square makes an angle of 55 with the base plane. Cl - s not equivalent: 3 stuck in crystal 1 bound by 2 Ti 3+ 1 loosely bound (to 1 Ti 3+ ) Vacancy and L not equivalent sites

23 Stereospecifity, bonding of propylene L B V Ti B V V F B = B Ti L = Ti L B F F B Et AlEt 3 Ti V F H 3 C CH 2 Et HC Ti - F CH 2 CH 3 F H 3 C V CH Ti CH 2 Et Two possibilities: 1. Alkalyne moves back to vacancy 2. Alkalyne doesn t move back

24 Stereospecifity, Polymerization (1) F H 3 C V CH Ti CH 2 Et H 3 C CH H 2 C Ti F V Et H 3 C CH 2 H 3 C CH Et H 2 C HC Ti - F CH 2 CH 3 H 3 C CH H 3 C V CH 2 CH 2 Et R C H 3 C H 3 R F Ti CH 2 Polymer moves back to vacancy isotactic polypropylene

25 Stereospecifity, Polymerization (2) V H 3 C Et CH H 3 C H 2 C CH 3 H 3 C CH Et CH H 2 C CH 3 CH 3 HC HC CH2 Et CH 2 F Ti CH 2 F Ti CH 2 F Ti V C H 3 C H 3 R R Polymer doesn t back to vacancy syndiotactic polypropylene Experimental: Some syndiotactic PP at -70

26 Cossee s mechanism R R X X C 3 H 6 X X X X X X insertion X X X X R C 3 H 6 X X X X R

27 The Polymerization reaction Zr Polymer + CH 2 =CH 2 C C Zr Polymer C C Zr Polymer C5 C5 C5 C5 C5 C5 C C Zr C5 C5 Polymer Polymer C C C5 Zr Piet Cossee 1964 C5

28 Allegra said that CH 2 C CH 3 * P

29 Zambelli found that. Steric control C C C C C C C C C C C C C C C C C C C C a C C C C C C C C C C C C C C C C C b C C C

30 Hydrocarbons monomers Ethylene Propylene Styrene

31 Conseguence of Chirality The right foot can only wear right shoes. A Better (more reactive) A* Catalyst

32 Poly-propylene : OUTPUT

33 Poly-propylene Isotactic Polypropylene * * * * * * * * Syndiotactic polypropylene * * * * * Atactic Polypropylene * * * * * * * * * * *

34 Poly-propylene If only one face of propylene gives co-ordination to the catalyst A A A A A A * * * * * * * * Isotactic Polypropylene

35 Poly-propylene If propylene gives co-ordination to the catalyst alternatively with one and the other face A A A A* A* A* * * * * * * Syndiotactic Polypropylene * *

36 Poly-propylene If propylene can give co-ordination to the catalyst with both the faces A A A A* A* A* * * * * * * * Atactic poly-propylene *

37 Metallocenes : Molecular Tools

38 How is a Z/N metallocene catalyst made? Ancillary Ligands Group 4 Metal + = Metallocene

39 How is a Z/N metallocene catalyst made? The metal is of group 4.

40 How is a Z/N metallocene catalyst made? Which are the ligands?

41 How is a Z/N metallocene catalyst made????????? More than 10,000 ligands!

42 How is a Z/N metallocene catalyst?? made? Which are the other ligands?

43 How is a Z/N metallocene catalyst x x made? Which are the other ligands?

44 Activators Al(CH 3 ) 3 + H 2 O Al O CH 3 REPRESENTS A BREAKTHROUGH n B(C 6 F 5 ) 3 (C 6 H 5 ) 3 C + B(C 6 F 5 ) 4 - (C 6 H 5 ) 2 NH + B(C 6 F 5 ) 4 -

45 Cation Cp 2 MX 2 + MAO [Cp 2 M(CH 3 )] + + [MAOX] - + CH 3 Zr C5 C5

46 How is a Z/N metallocene catalyst made? Polimero Polymer chain Monomero Zr Which are the other ligands? C5 C5

47 How is a Z/N metallocene catalyst made? Ethylene C5 Polyethylene Zr C5 Which are the other ligands?

48 How is a Z/N metallocene catalyst made? Polypropylene Propylene Zr Which are the other ligands? C5 C5

49 The Tools at work: Fundamental reaction

50 The Fundamental reaction A chain of Snoopy kennels

51 The Catalytic Cycle

52 Polymerization reaction One monomer insertion is going on every millionth of a second. A metallocene has a very high reactivity: it can give 10,000-20,000 monomers insertion for macromolecules A metallocene has a very high activity: 1 g of metallocene can produce more than 1,000 kg of polymer before it becomes inactive.

53 The Tools at work: Formation of stereoregular polymers.

54 Stereoregular polymers.

55 The Symmetry of the King of diamonds (isospecific symmetry)

56 The Symmetry of the King of diamonds (isospecific symmetry) Better situation! Growing chain Growing chain

57 The Symmetry of the King of diamonds (isospecific symmetry) A* A Growing chain

58 Consequence of the Chirality The right foot can wear only right shoes! A A* Catalyst

59 The Symmetry of the King of diamonds (isospecific symmetry)? A* A or?? A* Better situation! A or? Growing chain Growing chain

60 The Symmetry of the King of diamonds (isospecific symmetry) A A Growing chain Growing chain?

61 The Symmetry of the King of diamonds (isospecific symmetry) + = Isotactic Poly-propylene A metallocene having the same symmetry of the King of diamonds produces an isotactic polymer.

62 Polymerization reaction as a catalytic cycle.

63 C 2 symmetric metallocene Mt chain chain Mt m m m m m m m

64 Allegra By utilizing C2 symmetric stereorigid metallocene Allegra s conclusion was verified and an isotactic polypropylene was obtained. The two sites of cationic catalyst with the C 2 -symmetry are homotopics, and perform isotactic polymerization of propene. An eventual back-skip reaction of the chain, before a following monomer insertion, does not influence the polymerization stereochemistry. Mt chain chain Mt

65 How is a Z/N metallocene catalyst made????????? More than 10,000 ligands have been synthesized

66 Symmetry of Chess (syndiospecific symmetry)

67 Symmetry of Chess (syndiospecific symmetry) Better situation Growing chain Growing chain

68 Symmetry of Chess (syndiospecific symmetry)? A* A or?? A* Better situation! A or? Growing chain Growing chain

69 Symmetry of Chess (syndiospecific symmetry) Growing chain Growing chain

70 Symmetry of Chess (syndiospecific symmetry) A A* Growing chain Growing chain?

71 symmetry of Chess (syndiospecific symmetry) + = Syndiotactic Poly-propylene A metallocene having chess symmetry produces a syndiotactic polymer

72 C s Symmetric Metallocene Mt chain chain Mt r r r r r r r

73 The comparison of the symmetries King of diamonds Growing chain Chess Growing chain

74 Mechanism. The syndiospecificity of catalysts having Cs - symmetry was the first experimental evidence that Cossee s chain migratory insertion was operative. Mt chain chain Mt

75 Mechanism Occasional meso (m) diads defects provide evidence for back-skip reactions of the chain, according to the hypothesis of Cossee and Arlman which suggested that the growing alkyl group moves back to its original position after each incorporation of a new monomeric unit. r r m m r r r

76 Mechanism of Cossee and Arlman R R X X C 3 H 6 X X X X X X insertion R X X X X back -sk ip X X X X R

77 Cossee and Arlman The presence of tert-butyl group forbids the growing chain to be located in the inward position, close to tert-butyl group, thus, after each monomer insertion, the growing chain skips back to the less crowded outward position. Hence, insertion always takes place with the same face, because it occurs each time on the same site of the catalyst that becomes isospecific. Mt chain m m m m m m m

78 Summary. Metallocenes are molecular tools that change input molecules (alkenes) into output molecules (polymers). Monomer Ethylene Polymer Polyethylene Propylene Polypropylene

79 Summary. Metallocenes are intelligent and change prochyral monomers (propylene) into stereoregular polymers (polypropylene iso- or syndiotactic) Monomer Symmetry King of Diamonds Polymer isotactic polypropylene propylene Chess syndiotactic polypropylene

80 Possible polypropylene from metallocenes: ZrX 2 atactic polypropylene ZrX 2 hemisotactic polypropylene ZrX 2 isotactic polypropylene TiPh 2 isotactic block polypropylene ZrX 2 syndiotactic polypropylene ZrX 2 atactic - isotactic block polypropylene

81 C 1 Symmetric Metallocene Mt chain chain Mt R or S R R or S R R or S R R or S R

82 Elastomeric polypropylene + Zr P + Zr P

83 2-(1-cyclopentadienyl)2-(1-phenyl)propano titanium trichloride (CH 3 ) 2 C(Cp)(Ph)TiCl MAO atattico atactic a at T T = = 50 C Propylene Isotactic at T = - 60 C (CH 3 ) 2 C(Cp)(Ph)TiCl 3 Cp 2 TiCl 2 CpTiCl 3 [m]=0.76 [m]=0.85 [m]=0.51 Longo, P.; Amendola, A.G.; Fortunato, E.; Boccia, A.C.; Zambelli, A.; Macromol. Rapid Commun. 2001, 22, 339.

84 Active specie + + Ti P Ti P high temperature low temperature Longo, P.; Amendola, A.G.; Fortunato, E.; Boccia, A.C.; Zambelli, A.; Macromol. Rapid Commun. 2001, 22, 339.

85 2-(1-indenyl)2-(1-naphtyl)propano zirconium trichloride CH 3 CH 3 C ZrCl 3 + MAO

86 Hapto-flexible catalysts C. De Rosa, F. Auriemma, G. Circielli, A. C. Boccia, P. Longo Macromolecules, 36, 3465, 2003

87 Ethylene-Propylene Rubber Common uses: Automotive applications 44% Roofing membrane 18% Oil additives 10% Wires and cables 8% Other (Gaskets, seals, coated fabric, footwear, rug underlay) 20%.

88 THE END