ISSN:
0887-624X
Keywords:
VCl3
;
propylene polymerization
;
Ziegler-Natta catalyst
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Solvay type S-VCl3 catalyst has 7% of catalytically active vanadium sites ([C*]) with kp (rate constant of propagation) = 31 (M s)-1 for ethylene polymerization. Addition of a comonomer, propylene of 4-methylpentene-1 (4-MP) significantly raised the ethylene polymerization activity. S-VCI3 catalyst has very small amounts of catalytically active vanadium for propylene polymerizations: [Ci*] = 0.19% with kp,i = 857 (M s)-1 and [Ca*] = 0.45% with kp,a = 23 (M s)-1 for isospecific and nonspecific sites, respectively. Addition of a conomer, ethylene or 4-MP. lowered the propylene polymerization activity. S-VCI3 is more easily reduced to the divalent ion by AIR3 than S-TiCl3. Methyl-p-toluate moderates the reducting power of AIR3; it increase the productivity and stereoselectivity of the S-YiCl3 catalyst, VCI3 supported on MgCl2 (CW-V catalyst) has enhanced rate constant of propylene polymerization but has the opposite effects on the S-TiCl3 Catalyst. VCI3 supported on MgCl2 (CW-V catalyst) has enhances rate constant of propylene polymerization but only a minute fraction of the supported vanadiums are catalytically active: [Ci*] = 0.019% and kp,i = 1580 (Ms)-1, [Ca*] = 0.057% and kp,i = 58 (M s)-1. This is compared with far greater number of catalytically active titanium sites in the TiCl3 supported on MgCl2 catalyst: [Ci*] = 6% and kp,i = 200 (M s)-1, [Ca*] = 6% and kp,a = 16(M s)-1. Therefore, both the S-VCI3 and CW-V catalysts are highly stereoselective but low in efficiency with respect to the utilization of the vanadium ion in the catalysis.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1991.080291213
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