High selectivities to ethylene by partial oxidation of ethane

At least 85 percent selectivity to ethylene at greater than 70 percent conv ersion can be obtained by partial oxidation of ethane by adding Large amoun ts of H-2 to the reaction mixture and using a platinum-tin catalyst operati ng at 950 degrees C with a contact time of similar to 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. A lthough 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 reacti ons on the catalyst generate more H-2 than used in the feed, so with recycl e no additional H-2 would be needed. These results are unexpected because e thylene is a nonequilibrium product and entropy considerations argue that a ll reaction channels open at high temperatures so the products should appro ach equilibrium, which predicts only a few percent ethylene. This process i s promising for the replacement of steam cracking in the production of ethy lene.