Polymerization of ethylene and propylene with chromium tristearate/diethylaluminum chloride/metal chloride catalysts

Abstract

A CrtCnH^COOls/AlEtsCl/MgC^catalyst was prepared by modifying the Battelle-type catalyst with MgCl2 dissolved in 2-ethyl-l-hexanol (2-EHA), and the polymerization of ethylene was carried out in toluene at 20-40 °C. The rate of polymerization markedly increased with increasing Mg/Cr molar ratio. The polyethylene obtained without MgCl2 had a very broad polydispersity, whereas the polyethylenes in the presence of MgCl2 had extremely high molecular weights with narrow polydispersities. The polymerization of ethylene was also performed with various types of metal chlorides under similar conditions. The activity of the catalyst was strongly dependent upon the metal chloride used as modifier. A clear correlation was observed between the activity and the electronegativity of the metal ion in the metal chloride.

Ethylene and propylene polymerizations with the MgCl2-supported tris(acetylacetonato)chromium-diethylaluminium chloride catalyst system

“…The Cr-(acac) 3 /MgCl 2 -DEAC catalyst system produced the highest molecular weight polypropylene with a fairly high activity, however, the resulting polymer contained a considerable amount of atactic polymer. Taking into account that the addition of suitable Lewis bases as internal and/ or external donors improves the isospecificity of ordinary Ziegler-Natta catalysts, [14] ethyl benzoate (EB), di-i-propyldimethoxysilane (DIPDMS), and dibutylphtalate (DNBP) were introduced as an external donor to the Cr-(acac) 3 /MgCl 2 -DEAC catalyst system. As expected, a drastic increase in catalyst activity and isospecificity was observed by adding ethylbenzoate (EB) as an external donor (Fig.…”

“…45 wt.-% of isotacticity. [10] Similar catalysts using b-diketonates as ligands were prepared by Asanuma et al and were used for ethylene homopolymerization and ethylene-propylene copolymerization. [11] More recently, we have investigated the propylene polymerization with the chromium(III) acetylacetonate (Cr(acac) 3 )/MgCl 2 -DEAC catalyst system and found that the addition of suitable Lewis bases like ethylbenzoate (EB) largely increases the polymerization activity as well as the isospecificity of the catalytic system.…”

Review of the Phillips Chromium Catalyst for Ethylene Polymerization

“…Although the primary commercial use of the Phillips catalyst is for the polymerization of ethylene and ethylene with α-olefins, the catalyst will also homopolymerize other unsaturates, including acetylenes [157,158,207] and α-olefins, such as propylene, butene and hexene [2,7,30,[324][325][326][327][328][329][330][331][332]. Like Ziegler-Natta catalysts, certain adjuvants can be used with Cr/silica to improve the stereoselectivity [333].…”