High selectivities to ethylene by partial oxidation of ethane.

摘要

The oxidative dehydrogenation of ethane using Pt/alpha-Al2O 3 and various bimetallic catalysts operating at ∼1000°C and very short contact times is examined with H2 addition to the feed. When H2 is added with a Pt-catalyst, the ethylene selectivity rises from 65 to 72% but ethane conversion drops from 70 to 52%. However using a Pt-Sn/alpha-Al2O3 catalyst, the C2H 4 selectivity increases from 70 to greater than 85%, while the conversion remains ∼70%. The process produces as much H2 as is added to the feed so H2 can be conveniently recycled from the product stream, therefore no additional H2 input may be necessary. Effects of other metal promoters, sphere bed and fibermat supports, preheat, pressure, nitrogen dilution and flow rate are also examined. Deactivation of the Pt-Sn catalyst is examined and a simple method of regenerating activity in-situ is demonstrated.; Possible mechanisms to explain high selectivities to ethylene are discussed. Although the process can be regarded as a simple two step reaction sequence with the exothermic oxidation of hydrogen or ethane driving the endothermic dehydrogenation of ethane to ethylene, the exact contributions of heterogeneous or gas phase reactions are yet to be determined.; While the ethylene selectivity and ethane conversion obtained using a Pt-Sn catalyst with H2 recycle are at least comparable to those of steam cracking, oxidative dehydrogenation requires no additional heat input. Also, negligible coke, NOx, CO2, and other emissions are produced by oxidative dehydrogenation.