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목차
INTRODUCTION
MATERIALS
METHODS
RESULTS AND DISCUSSION
REFERENCES
MATERIALS
METHODS
RESULTS AND DISCUSSION
REFERENCES
본문내용
Different Cocatalyst ([M] = 0.33 mol/l)
Cocatalyst
Rp
(mol/mol Ti.s)b
kp
(l/mol.s)
[C*]
(mol %)
Al(CH3)3
Al(C2H5)3
MAO
0.88
2.59
4.90
222
393
674
1.2
2.0
2.2
a 50oC, 0.78 atm Pc3, Ti = 0.5 mmol, Al/Ti=50, 200 ml n-hexane
b Mole of propylene/mol of titanium sec.
From the kinetic results, the kinetic parameters of Al(C2H5)3 are higher than those of Al(CH3)3. It is attributed to the different interaction between catalytic titanium sites and cocatalysts. Al(CH3)3 lead to deactivate of catalytic titanium sites (Ti3+→Ti2+) more than Al(C2H5)3[10]. The higher activity of MAO over the other cocatalysts is due to its higher propagation rate constant. Murata et. al have claimed on the basis of kinetic results and XPS measurement that the high electron density of active Ti resulted in accelerated coordination of propylene into a titanium-polymer chain bond (increase of kp)[11]. From the results of kinetic study, the advantage of MAO as a cocatalyst may be its capability to act as an electron donor via oxygen to Lewis acidic sites in the catalyst.
REFERENCES
1. P. Pino and R. Mulhaupt, Angew. Chem., Int. Ed. Engl., 19, 857
(1980).
2. W. D. Song, K. J. Chu, H. S. Chang and S. K. Ihm, J. Mol. Catal., 84, 103 (1993).
3. K. Soga, T. Shiono and Y. Doi, Makromol. Chem., 189, 1531
(1988).
4. J. Boor Jr., Ziegler-Natta Catalysis and Polymerization, Academic
Press, New York (1979).
5. H. Sinn and W. Kaminsky, Adv. Organomet. Chem., 18, 99
(1980).
6. S. K. Ihm, K. J. Chu and J. H. Yim, Studies in Surface Science
and Catalysis (Edited by K. Soga and M. Terano), Vol.89, 299
(1994).
7. V. Busico, P. Corradini, A. Ferraro and A. Proto, Makromol.
Chem., 187, 1125 (1986).
8. P. J. T. Tait, Transition Metal Catalyzed Polymerizations, MMI
Press, Harwood Academic Publishers, New York, 115 (1983).
9. N. Kashiwa and J. Yishitake, Polymer Bulletin, 12, 99 (1984).
10. T.Keii, Kinetics of Ziegler-Natta Polymerization, Kodansa Press,
Tokyo (1972).
11. M. Murata, A. Nakano, H. Furuhashi and Imai, Studies in Surface
Science and Catalysis (Edited by T. Keii and K. Soga), Vol. 56,
165 (1990).
Fig.1 Kinetic Curves of Propylene Polymerization
as a Function of Time with Different Cocatalysts
Cocatalyst
Rp
(mol/mol Ti.s)b
kp
(l/mol.s)
[C*]
(mol %)
Al(CH3)3
Al(C2H5)3
MAO
0.88
2.59
4.90
222
393
674
1.2
2.0
2.2
a 50oC, 0.78 atm Pc3, Ti = 0.5 mmol, Al/Ti=50, 200 ml n-hexane
b Mole of propylene/mol of titanium sec.
From the kinetic results, the kinetic parameters of Al(C2H5)3 are higher than those of Al(CH3)3. It is attributed to the different interaction between catalytic titanium sites and cocatalysts. Al(CH3)3 lead to deactivate of catalytic titanium sites (Ti3+→Ti2+) more than Al(C2H5)3[10]. The higher activity of MAO over the other cocatalysts is due to its higher propagation rate constant. Murata et. al have claimed on the basis of kinetic results and XPS measurement that the high electron density of active Ti resulted in accelerated coordination of propylene into a titanium-polymer chain bond (increase of kp)[11]. From the results of kinetic study, the advantage of MAO as a cocatalyst may be its capability to act as an electron donor via oxygen to Lewis acidic sites in the catalyst.
REFERENCES
1. P. Pino and R. Mulhaupt, Angew. Chem., Int. Ed. Engl., 19, 857
(1980).
2. W. D. Song, K. J. Chu, H. S. Chang and S. K. Ihm, J. Mol. Catal., 84, 103 (1993).
3. K. Soga, T. Shiono and Y. Doi, Makromol. Chem., 189, 1531
(1988).
4. J. Boor Jr., Ziegler-Natta Catalysis and Polymerization, Academic
Press, New York (1979).
5. H. Sinn and W. Kaminsky, Adv. Organomet. Chem., 18, 99
(1980).
6. S. K. Ihm, K. J. Chu and J. H. Yim, Studies in Surface Science
and Catalysis (Edited by K. Soga and M. Terano), Vol.89, 299
(1994).
7. V. Busico, P. Corradini, A. Ferraro and A. Proto, Makromol.
Chem., 187, 1125 (1986).
8. P. J. T. Tait, Transition Metal Catalyzed Polymerizations, MMI
Press, Harwood Academic Publishers, New York, 115 (1983).
9. N. Kashiwa and J. Yishitake, Polymer Bulletin, 12, 99 (1984).
10. T.Keii, Kinetics of Ziegler-Natta Polymerization, Kodansa Press,
Tokyo (1972).
11. M. Murata, A. Nakano, H. Furuhashi and Imai, Studies in Surface
Science and Catalysis (Edited by T. Keii and K. Soga), Vol. 56,
165 (1990).
Fig.1 Kinetic Curves of Propylene Polymerization
as a Function of Time with Different Cocatalysts
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