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COMBINATORIAL MATERIALS
A four-year collaboration between Symyx Technologies and Dow Chemical has borne fruit in the discovery of a new class of single-site catalysts for olefin polymerization. The new amide-ether-based hafnium catalysts were found using a fully integrated high-throughput screening methodology [J. Am. Chem. Soc., 125, 4306 (2003)]. "The results are stunning," says one of the coauthors, Dow chemist James C. Stevens, because the new screening methodology enabled them to do in days or weeks what used to take many months or years.
The work uncovered many catalytically active metal-ligand combinations. One hafnium catalyst (complex 1) was found capable, under the right conditions, of polymerizing 1-octene with 100% conversion. Further experiments demonstrated that this complex can produce high-molecular-weight ethylene-1-octene copolymers. In the course of one day, the researchers then studied the activity at 130 °C of 96 other hafnium complexes containing related amine-ether ligands. They found that many of these catalysts are even better at copolymerizing ethylene and 1-octene than complex 1. In larger scale batch reactor experiments, complex 1 and a closely related hafnium complex were found to perform as well as or better than Dow's workhorse metallocene polyolefin catalyst system. Dow isn't necessarily "marching to commercialization" with any of the catalysts reported in the JACS paper, Stevens tells C&EN. "But we will be talking soon, I think, about another catalyst that's come out of this procedure that is going to be commercialized." |
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