Autothermal oxidative dehydrogenation of ethane to ethylene using SrxLa1.0Nd1.0Oy catalysts as ignitors

The behavior of SrxLa1.0Nd1.0Oy catalysts with different Sr loading (x = 0, 0.001, 0.01, 0.1, and 1.0) was examined regarding their application as ign itors for the autothermal oxidative dehydrogenation of ethane. Ethylene yie lds as high as 42% (S > 69%) were obtained at a contact time of similar to 45 ms (STP) as a result of the ignition of the reaction mixture on the cata lyst and the resultant occurrence of the thermal ethane pyrolysis. The cata lysts showed comparable performance; a slightly higher ethylene yield (45%) was obtained on a Sr0.1La1.0Nd1.0Ox catalyst on which the optimization of the reaction conditions was carried out by varying space velocity(1(.)10(4) -8(.)10(4) h(-1)), preheat temperature of the feed gas (100-600 degreesC), and ethane-to-oxygen ratio (2-5) in the absence and presence of 15% steam. Space velocity was found to be a significant factor in determining the maxi mal reaction temperature and hence the extent of thermal pyrolysis. The hig hest ethylene yield amounted to 56% (S = 71%) achieved at GHSV = 8.3(.)10(4 ) h(-1) (tau (STP) = similar to 45 ms), C2H6/O-2/N-2 = 2/1/1, and a preheat temperature of 600 degreesC corresponding to a maximal reaction temperatur e of 940 degreesC. The addition of steam resulted in some decrease of the m aximal temperature leading to a decrease in the ethylene yield by ca. 2%. N o significant effect of the steam addition on product distribution was obse rved. (C) 2001 Academic Press.