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Paper Information

Journal:   JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TEHRAN)   MARCH 2009 , Volume 42 , Number 8 (118); Page(s) 975 To 982.
 
Paper: 

POLYMERIZATION OF ETHYLENE BY BI-SUPPORTED CATALYST MORPHOLOGY AND MOLECULAR WEIGHT

 
 
Author(s):  HAKIM SH.*, NEKOUMANESH HAGHIGHI MAHDI, AGHAEI NIAT M.
 
* IRAN POLYMER AND PETROCHEMICAL INSTITUTE, POLYMERIZATION ENGINEERING DEPARTMENT
 
Abstract: 

In the case of industrial gas phase, slurry, or bulk polymerization it is very essential to keep the active catalytic components on a support. That is to achieve a polymer product with defined particle morphology. In this study a SiO2/TiCl4/THF/MgCl2 type of Bi-Supported catalyst was synthesized. The focus of which was on morphology and molecular weight. The catalysts were made of two different supports (LC, PQ-MS-3050.( Due to lower mechanical strength of LC and its un-controllable smashing during catalyst synthesis or polymerization, a catalyst with a poor morphology was obtained. Silica PQ-MS-3050 particles are spherical and hence resulted in polymers with a great percent of spherical particles. Due to appropriate mechanical strength of PQ-MS-3050, an acceptable morphology of the product was obtained. Replication phenomenon and fragmentation were investigated for the two synthesized catalysts using polymer melt and polymer ash microscopy. Because of the better morphology of PQ-MS-3050 supported catalyst, it was selected for molecular weight studies. An increase in hydrogen and co-catalyst concentrations and temperature, the molecular weight decreases. Four active centers were determined for PQ-MS-3050 supported catalyst by de-convolution of molecular weight distribution curves. These curves were obtained from GPC analysis for two samples polymerized at two different pressures. It was seen that the molecular weight is constant for each of the Flory components and a bimolecular chain transfer to monomer exists. Also, an increase in ethylene concentration produces a gradual decrease of polymer fractions produced by the centres I, II and III and a progressive increase in the fraction produced by the centre IV. It was also shown that monomer pressure increases with molecular weight. Therefore the centres with higher molecular weight have higher kinetic constants and an increase in ethylene concentration causes further increase in the fraction of the Flory components.

 
Keyword(s): POLYMERIZATION, CATALYST, MORPHOLOGY, MOLECULAR WEIGHT, ETHYLENE
 
References: 
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