Autothermal Oxidative Dehydrogenation of Ethane to Ethylene Using SrxLa1.0Nd1.0Oy Catalysts as Ignitors

Abstract

The behavior of SrxLa1.0Nd1.0Oy catalysts with different Sr loadings (x=0, 0.001, 0.01, 0.1, and 1.0) was examined regarding their application as ignitors for the autothermal oxidative dehydrogenation of ethane. Ethylene yields as high as 42% (S>69%) were obtained at a contact time of ∼45 ms (STP) as a result of the ignition of the reaction mixture on the catalyst and the resultant occurrence of the thermal ethane pyrolysis. The catalysts 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 (1·104–8·104 h−1), preheat temperature of the feed gas (100–600°C), 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 maximal reaction temperature and hence the extent of thermal pyrolysis. The highest ethylene yield amounted to 56% (S=71%) achieved at GHSV=8.3·104 h−1 (τSTP=∼45 ms), C2H6/O2/N2=2/1/1, and a preheat temperature of 600°C corresponding to a maximal reaction temperature of 940°C. The addition of steam resulted in some decrease of the maximal temperature leading to a decrease in the ethylene yield by ca. 2%. No significant effect of the steam addition on product distribution was observed.