High Selectivities to Ethylene by Partial Oxidation of Ethane

At least 85 percent selectivity to ethylene at greater than 70 percent conversion can be obtained by partial oxidation of ethane by adding large amounts of H(2) to the reaction mixture and using a platinum-tin catalyst operating at 950 degrees C with a contact time of approximately 10(-3) seconds. This system almost totally shuts off the reactions that form undesired CO and CO(2), which fall from 20 percent without H(2) to 5 percent when H(2) is added. Although a 2/1 H(2)/O(2) mixture should be explosive at high temperatures, no flames or explosions occur in the presence of ethane. The successive reactions on the catalyst generate more H(2) than used in the feed, so with recycle no additional H(2) would be needed. These results are unexpected because ethylene is a nonequilibrium product and entropy considerations argue that all reaction channels open at high temperatures so the products should approach equilibrium, which predicts only a few percent ethylene. This process is promising for the replacement of steam cracking in the production of ethylene.