Patent Watch

May 14, 2012

Make cyclododecatriene with an improved catalyst system. Cyclododecatriene (CDT) is an unusual molecule that consists of a 12-membered ring with three double bonds. CDT is used to make laurolactam, an intermediate in the manufacture of nylon-12. The automotive industry prefers nylon-12 to other polymers for making automobile fuel lines because it is stable to ethanol-containing gasoline.

J. Herwig and colleagues disclose a catalyst system that allows butadiene to be converted to CDT in high yields. The catalyst system consists of TiCl4 and ethylaluminum sesquichloride (EtAlCl2·Et2AlCl) dissolved in benzene with traces of moisture and ammonia.

In one example, the feed to the reactor is 1.5 kg/h butadiene, 0.5 kg/h benzene, 0.34 g/h TiCl4, and 7.9 g/h EtAlCl2·Et2AlCl. The moisture in the reactor is set at 115 ppm by preconditioning the butadiene and benzene with water; the ammonia content is set at 80 ppm by metering it separately. The reactor temperature is maintained at 60 °C.

Under these conditions, butadiene conversion is >99% with 93.7% selectivity to CDT. Selectivities to butadiene dimers, heavier oligomers, and polymers are 2.9%, 1.1%, and 2.3%, respectively. After workup, CDT purity is ≥99%. (Evonik Degussa GmbH [Essen, Germany]. US Patent 8,168,841, May 1, 2012; Jeffrey S. Plotkin)

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CDT plant explosion

Evonik Industries makes ≈40% of the world’s CDT. An explosion at its Marl, Germany, plant on March 31 killed two workers and shut down CDT production until at least December. This is causing a problem for automobile manufacturers, who are scrambling to find a replacement for nylon-12 for this critical application.)