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Customized supports for Ziegler and Ziegler-Natta catalysts

Catylen® S 300

Catylen® S 300 for the fi rst time provides the manufacturers of Ziegler (polyethylene) and Ziegler-Natta (polypropylene) catalysts with a support material that is made in the exact particle size needed for each process. With this option, the Evonik product eliminates a complex and costly production step.

CUSTOMIZED SUPPORT MATERIAL

In the past, the process chain included few choices. Support materials for catalysts were shipped in a defined shape to catalyst manufacturers. The raw material then had to undergo a complex process before it could be used further. Evonik is now turning this principle on its head: Catylen® S 300 is the first support material made of magnesium ethanolate (Mg(OC2H5)2) that can be produced in exactly the right particle size for each catalyst manufacturer.

Both Ziegler and Ziegler-Natta catalysts have been used for the production of polyethylene and polypropylene since the mid-1950s. Today, these catalysts are used to manufacture approximately 56% of the globally produced polyethylene and 95% of the polypropylene. About 20% of Ziegler or Ziegler-Natta catalysts are based on magnesium alkoxides, especially magnesium ethanolate. These can then be suspended in hydrocarbons and reacted with titanium tetrachloride (TiCl4). As far back as 1953, Evonik has supplied magnesium ethanolate to catalyst manufacturers.

The needs of customers have always been our top priority. Evonik's product portfolio, which has been marketed under the brand name Catylen® S 100 since 2008, features various qualities of magnesium ethanolate, which diff er, e.g., with respect to purity, particle size distribution and content of fi ne particles. Based on the catalyst being produced and the targeted polymerization process, the customer is able to select the optimal raw material for their system. Evonik also off ers Catylen® S 200, a 30-percent solution of magnesium ethanolate and titanium tetra-n-butanolate (Mg2Ti(OR)8) in hexane. It is used, for example, for the production of polyethylene using slurry technologies.

CUSTOMIZED SUPPORT MATERIAL

Evonik's Catylen® S 300 for the first time off ers catalyst manufacturers a support material based on magnesium ethanolate, which is generated in precisely the particle size required for a specifi c process and thereby eliminates a complex production step. The microparticle size can be freely chosen within a range of 18 to 80 micrometers, which means they are up to 20 times smaller than the support material of the Catylen® S 100 series brand (about 650 to 700 micrometers). The narrow particle size distribution below 0.8 (D90-D10/D50) is an optimal prerequisite of a uniform final product.

Catalysts play a special role, particularly in the polymerization of polyolefins, since polymer particles adopt the shape of catalyst particles. This socalled replica effect ensures that the shape and size of particles as well as the particle size distribution of the catalyst is directly refl ected in the polymer.

The polymerization reaction takes place at the active centers that are distributed over the entire catalytic particle, both on the surface and in the interior. Since particles have to fragment and expand evenly in all directions, no uncontrolled breakup of catalyst particles must occur during this step. Aft er all, unintended fragments would ultimately have the eff ect of additional nucleation sources for new polymer particles, which would significantly interfere with their particle size distribution. Given the daily capacity of around 1,000 metric tons of polymer in modern facilities, the resulting system downtime would be extremely costly.

The products of the Catylen® S 300 brand now provide catalyst manufacturers with support substances that can be custom-tailored to every process. The technology underlying the manufacturing process combines a number of special chemical and engineering details to ultimately generate magnesium ethanolate support materials in the highest quality with narrowly defi ned production tolerances.

FULL RANGE OF COMPONENTS FROM A SINGLE SOURCE

Catylen® S 300 can be seen as the core element of a catalyst toolbox, as Evonik has continuously optimized its
facilities for the production of magnesium ethanolate and adapted them to market needs. In addition to the supsupport materials, Evonik also supplies a variety of organo silanes, which are indispensable as external donors in polypropylene production. They help to control molecular weight, molecular weight distribution, and tacticity – in other words, the integration of monomers into the polymer chain.