On-line catalyst addition: Oxidation of ethane to ethylene

The current commercial process for producing ethylene is steam cracking of ethane. Ethane is heated until it pyrolyzes into ethylene. This process consumes large amounts of methane, operates at 800°C and has residence times of about one second. It also forms significant quantities of solid carbon, or coke, which leads to steam addition to inhibit its formation.; In comparison, our group has investigated partial oxidation of ethane to ethylene using a millisecond contact time reactor operating at about 1000°C. By adding oxygen and using a Pt-coated alumina foam monolith in a quartz tube, combustion reactions provide sufficient energy to crack the remaining ethane into ethylene, without coking. Adding Sn improves results, and adding H ₂ to the feed increases selectivity even more.; However, time dependence studies show a slow decrease in activity, which occurs due to Sn loss. To counter this, SnCl₂ solution is added in-situ by dripping it onto the upstream catalyst face, thus regenerating it without reactor shutdown. This on-line addition also allows for screening of various metals and examination of the dynamic behavior of the reactor system.; On-line addition of Pt creates superior results to catalyst preparation by incipient wetness, especially when combined with H₂ addition. This may be since on-line addition keeps almost all Pt on the front face of the monolith, and SEM results indicate on-line addition creates rougher Pt particles than those formed through incipient wetness. Continued work with this apparatus may lead to a better understanding of the mechanism of ethylene formation.