Propene polymerization with the one‐phase catalyst SiO₂/TiCl₄/Al(CH₂CH(Ch₃)₂)₃

Abstract

IntroductionTitanium containing active species in supported Ziegler-Natta catalysts are not accessible to direct observation. Therefore, special methods are utilized to describe the structure and characteristic properties at least of a fraction of the titanium amount.Electron spin resonance (ESR) measurements were used extensively for this purpose and attempts were made to reveal the relations between the ESR-active Ti(II1) population and the polymerization Chien and H u t ) studied the propene polymerization with a highly active MgCI, supported catalyst and found that isotactic poly(propy1ene) (PP) is formed on the ESR-active Ti(II1) species and atactic PP on the ESR-silent sites. The reaction of TiCl, with Al(i-C,H& was studied recently') by means of the ESR spectroscopy with the result that clusters of TiCl, are formed in the solution even at very low temperatures.In this paper, we carried out the propene polymerization with the simplified onephase catalyst SiO,/TiCl,/Al (i-C4H9)36) and the active sites for both atactic and isotactic polymerizations were correlated with the ESR results of the catalyst. Experimental partMaterials, preparation of the catalysts, polymerization and analytical procedures are described in a preceding paper ').The silica gel, grade 952 (Fuji Davison Co., Japan; Grace GmbH, Germany) and 175 (Grace GmbH, Germany), was dehydrated in a quartz glass vessel in a nitrogen stream at 400 or 600 "C for 6 h, then pumped for 1 h and cooled under nitrogen. The specific surface area of the silica gel was measured using the Brunauer-Emmett-Teller method to obtain 306 f 4 m2/g (grade 952) and 750 f 8 m2/g (grade 175). The pore volumes calculated using a nitrogen desorption isotherm were 1,6 * 0,l and 0,4 f 0,l cm3/g, respectively; the range of pore diameter distribution was 6 -30 nm with a mean value of 20 nm. The amount of ethane evolved during the reaction of these silica gel samples with a surplus of a triethylaluminium solution (0,5 mol/L) at 25 "C was 1,22 and 1,45 mmol/g, respectively, which can be equivalents of the surface hydroxy groups. The isotactic poly(propy1ene) fraction was determined by extraction with boiling heptane for 8 h using a Soxhlet type extractor. Results and discussionThe polymerization of propene was conducted on the one-phase catalyst system 6, SiO,/TiCI,/AI (i-C4H9), using different mole ratios AI/Ti (see Tab. 1). All polymerization runs exhibited a decay type of kinetic pattern with a maximum rate reached in 10-20 min, and practically a stationary rate in 2 h after starting the polymerization. The catalyst prepared at Al/Ti = 2, which showed the highest activity for the ethylene polymerization, gives also the highest activity for the propylene polymerization.Further increase in the AVTi mole ratio causes a decrease in activity accompanied by a remarkable increase in catalyst stereospecifity. Judging from the change of the catalyst color together with these results, it may be considered that most of the titanium species are separately located on the silica gel surface b...

Polymerization of propene with the MgCl2-supported dichlorobis (?-diketonato) titanium catalysts combined with methylaluminoxane or an ordinary alkylaluminum

“…1,2 of those catalysts together with the preliminary results To suppress the formation of such clustrates, we of propene polymerization with them. have already prepared the MgCl 2 -supported half titanocene (XTiCl 3 ; X Å cyclopentadienyl, pentamethyl cyclopentadienyl, indenyl, and heptamethylindenyl) cata-EXPERIMENTAL lysts and applied them to propene polymerization using an ordinary alkylaluminum as cocatalyst.…”

“…For reference, a similar supported catalyst was also prepared using Zr(acetylacetonato) 2 Cl 2 , which was proved to show a Conventional heterogeneous Ziegler-Natta catalysts very low activity. possess more or less different kinds of active species…”

“…Propene polymerization was conducted under atmo-RESULTS AND DISCUSSION spheric pressure in a 300 cm 3 2 Cl] and 100 for MAO, P Å 1 atm, n-heptane Å 100 cm 3 , 40ЊC, 1 h (runs 2, 9, 10: 0.5 h). b Iso.-part: isotactic-fraction, Ata.-part: atactic-fraction, C7-insol.…”

“…have already prepared the MgCl 2 -supported half titanocene (XTiCl 3 ; X Å cyclopentadienyl, pentamethyl cyclopentadienyl, indenyl, and heptamethylindenyl) cata-EXPERIMENTAL lysts and applied them to propene polymerization using an ordinary alkylaluminum as cocatalyst. 2 Cl 2 , and tested Chemical Co., Ltd. were purified by refluxing over CaH 2 them to propene polymerization. Those compounds for 24 h followed by distillation, and stored over molecucombined with MAO or an ordinary alkylaluminum lar sieves under dry nitrogen.…”

“…7 From such a viewpoint, we are now trying to find anHowever, it is not clear at the moment why Cat. 2 other kind of more promising electron donor. showed such a very low activity.…”