Chemical News

Monday, October 20, 2008

Crack Ethane to Ethylene - without a catalyst

The heart of the modern petrochemical industry is the steam cracker, whose function is to convert gaseous hydrocarbons (e.g., ethane and propane) or liquid hydrocarbons (e.g., naphtha) to olefins, primarily ethylene.

This cracking reaction is carried out in the absence of catalysts at extremely high temperatures, making it a very energy-intensive process. Much research has been devoted to improving the cracking process by performing it catalytically with the hope of being able to use lower temperatures. However, catalyst deactivation problems have prevented the commercialization of this method.

I. R. Little and I. A. B. Reid of Ineos describe the autothermal cracking of ethane to ethylene without the need for catalysts.

In one example, a feed stream comprising methane and oxygen was passed to a first reaction zone over a promoted palladium catalyst at 400 °C. The resulting product stream, containing H2, CO, CO2, and H2O at 1200 °C, was passed to a mixing zone where a second stream containing C2H6 and O2 at 450 °C was added. The residence time in the mixing zone was <5 ms. The mixed feed stream at 610 °C was maintained at an absolute pressure of 1.8 bar. The product stream exited the second reaction zone at 770 °C and was cooled with a water quench to 600 °C within <50 ms of formation. The conversion of ethane was 68.1%, and the selectivity to ethylene was 77.2%

Source: CAS - Patent Watch