Zeigler-Natta Catalyst

A Powerpoint presentation on Zeigler Natta Catalyst.

1. ZEIGLER NATTA CATALYST

2. CONTENTS INTRODUCTION HISTORY MECHANISM EXAMPLE IMPORTANCE APPLICATION CONCLUSION

3. INTRODUCTION ZEIGLER NATTA catalyst is an important class of mixtures of chemical compounds remarkable for their ability to effect the polymerisation of Olefins ( hydrocarbons containing a double C-C bond ) to polymers of high molecular weights and stereoregular structures .

4. history Karl Zeigler of Germany in 1953 developed a series of catalysts that polymerise ethylene at low temperature and low pressures to give a polyethylene with a high molecular weight and very little branching. This polyethylene is denser, tougher and has a higher melting point than the polyethylene produced by the earlier high temperature and pressure method. Recognizing that Zeigler ’s catalysts were capable of polymerising 1- alkenes to yield stereoregular polymers, Guilio Natta of Itali in 1954 developed the edhodology to do it. In 1963, Zeigler and Natta jointly recieved the Nobel Prize for the discovery and developement of these catalyst systems.

5. Karl Zeigler ’s Discovery (1953) Guilio Natta ’s Discovery (1954)

6. MECHANISM A typical ZEIGLER NATTA Catalyst is a mixture of Titanium Tetrachloride and Triethyl Aluminium. The mechanism begins with the formation of a complex between Titanium and Aluminium.

7. In the above complex, Titanium has an empty orbital available for interaction with the pi elections in the monomer, thus allowing for the formation of a pi complex. The pi complex orients the methyl group away from the Titanium and towards the Aluminium. The pi complex then rapidly rearranges to form a bond between the CH2 group of propylene and the Titanium and giving second carbon of the propylene a positive charge.

8. The alkyl group of the aluminium transfers to the carbocation. This transfer happens so rapidly that the carbocation formed in the previous step doesnot have time to rearrange. Thus, the titanium stereospecifically inserts the propylene group between itself and the ethyl group.

9. The titanium complex continues to stereospecifically insert additional propylene monomers between itself and last ethyl group added to the chain. This repeating reaction forms the isotactic polymer.

10. To end the reaction, chemists destroy the complex by treating it with methanol.

11. EXAMPLE Propene can polymerize in three ways:

12. IMPORTANCE High efficiency. High Stability. High stereoregularity (tacticity 99%) High concentration of polymer product. Easy regeneration. Lower cost in production. Controls growth and formation of polymer product.

13. APPLICATION Production of high density polyethylene. Production of linear low density polyethylene. Production of thermoplastic polyolefins. Production of crystalline polypropylene. Production of carbon nanotube composites etc.

14. conclusion Ziegler-Natta polymerization is a great way to make polymers from hydrocarbon monomers like ethylene and propylene. But it doesn't work for some other kinds of monomers. For example, we can't make PVC by Ziegler-Natta polymerization. When the catalyst and co-catalyst come together to form the initiating complex, radicals are produced during intermediate steps of the reaction. These can initiate free radical polymerisation of the vinyl chloride monomer. 

15. REFERENCE Advanced Organic Chemistry- Arun Bahl | B.S Bahl www.britannica.com www.youtube.com

16. THANK YOU PRESENTED BY:- PRANJAL PROTIM GOGOI SIXTH SEMESTER ROLL NO:- 183 DEPARTMENT OF CHEMISTRY