Halo-oxide ACuO(2-delta)X(sigma) (A = Sr0.63Ca0.27, X = F, Cl) catalysts active and durable for ethane selective oxidation to ethene

The catalytic performance and characterization of ACuO(2-delta) (A = Sr0.63 Ca0.27) and ACuO(2-delta)X(sigma) (X = F, Cl) catalysts have been investiga ted for the oxidative dehydrogenation of ethane (ODE) to ethene. The result s of X-ray diffraction indicated that the three catalysts are single-phase and tetragonal infinite-layer in structure. The incorporation of fluoride o r chloride ions in the ACuO(2-delta) lattice can significantly enhance C2H6 conversion and C2H4 selectivity. At C2H6/O-2/N-2 molar ratio = 2/1/3.7 and space velocity = 6000 mi h(-1) g(-1), we observed 73.5% C2H6 conversion, 6 7.2% C2H4 selectivity, and 49.4% C2H4 yield at 660 degreesC over ACuO(1.901 )F(0.088), and 87.4% C2H6 conversion, 74.4% C2H4 selectivity, and 65.0% C2H 4 yield at 680 degreesC over ACuO(1.950)Cl(0.036) With the decrease in C2H6 /O-2 molar ratio, C2H6 conversion increased, whereas C2H4 selectivity decre ased. Within 48 h of on-stream ODE reaction, the two halide-doped materials exhibited sustainable catalytic performance. Based on the results of X-ray photoelectron spectroscopy, O-2 temperature-programmed desorption, and C2H 6 and C2H6/O-2/N-2 (2/1/3.7 molar ratio) pulse studies, we conclude that (i ) the incorporation of halide ions into the ACuO(2-delta) lattice could enh ance lattice oxygen activity, and (ii) in excessive amount, the O- species accommodated in oxygen vacancies and desorbed below 600 degreesC tend to in duce ethane complete oxidation, whereas the lattice oxygen species desorbed above 600 degreesC are active for ethane selective oxidation to ethene. By regulating the oxygen vacancy density and Cu3+ population in the halo-oxid e catalyst, one can generate a durable catalyst with good performance for t he ODE reaction. (C) 2001 Elsevier Science B.V. All rights reserved.