The catalytic performance and characterization of YBa2Cu3O7-δ and YBa2Cu3O7-δXσ for the oxidative dehydrogenation of ethane (ODE) to ethene have been investigated. Under the reaction conditions of temperature=680℃, C2H6/O2/N2 molar ratioD2/1/3.7, and contact timeD1.67£10¡4hgml¡1, YBa2Cu3O7¡0.21F0.16 showed 84.1% C2H6 conversion, 81.8% C2H4 selectivity, and 68.8% C2H4 yield; YBa2Cu3O7¡0.18Cl0.13 showed 92.5% C2H6 conversion, 72.0% C2H4 selectivity, and 66.6% C2H4 yield. The sustainable performance during a period of 40h on-stream reaction at 680℃ demonstrated that the F- and Cl-doped catalysts are durable. X-ray powder diffraction results indicated that the undoped YBa2Cu3O7-δ and halide-doped YBa2Cu3O7-δXσ were of triple-layered oxygen-deficient perovskite-type orthorhombic structure. The results of the X-ray photoelectron spectroscopy, thermal treatment, thermogravimetric analysis, and 18O2-pulsing studies indicated that the incorporation of halide ions into the YBa2Cu3O7-δ lattice enhanced the activity of lattice oxygen. According to the O2 temperature-programmed desorption and temperature-programmed reduction results, we conclude that the oxygen species desorbed at 610-710℃ are active for the selective oxidation of ethane and those desorbed below 610℃ are active for the total oxidation of ethane; a suitable oxygen nonstoichiometry and Cu3C concentration in YBa2Cu3O7-δXσare required for the best catalytic performance of the catalysts.

Perovskite-type oxides La1−xA′xCo1−yBiyO3−δ (A′x=Ba0.2, Sr0.4; y=0, 0.2) and La1−xSrxMO3−δ (M =Co0.77Bi0.20Pd0.03, x=0, 0.2, 0.4) and perovskite-like oxides La1.867Th0.100CuO4−δ, Nd2−xA xCuO4−δ (A′x=Ba0.4, Ce0.2), and YBa2Cu3O7−δ have been investigated as catalysts forCOoxidation, NO removal, andN2Odecomposition, respectively. X-ray diffraction results revealed that (i) all of these materials were single phase, and (ii) the crystal structures of La1−xA′xCo1−yBiyO3−δ, La1−xSrxMO3−δ, La1.867Th0.100CuO4−δ, Nd2−xA′xCuO4−δ, and YBa2Cu3O7−δ were cubic, orthorhombic, tetragonal (T structure), tetragonal (T′structure), and orthorhombic, respectively. The results of chemical analysis indicated that (i) there were Co4+/Co3+ ions in La1−xA′xCoO3−δ (A′x=Ba0.2, Sr0.4), Co2+/Co3+ and Bi5+/Bi3+ ions in La1−xA′xCo0.8Bi0.2O3−δ(A′x=Ba0.2, Sr0.4) and La1−xSrxMO3−δ, Cu2+/Cu3+ ions in La1.867Th0.100CuO4−δ, Nd2CuO4−δ, Nd1.6Ba0.4CuO4−δ, and YBa2Cu3O7−δ; and (ii) after pretreatments in H2 or helium at certain temperature, Cu+/Cu2+ ion couples appeared in these cuprate samples. Oxygen isotope exchange experiments indicated that the lattice oxygen mobility in the Bi-doped catalysts were much higher than that in the Bi-free ones. TPR results showed that lattice oxygen in the former samples could be reduced at temperatures lower than those in the latter samples. In the oxidation of CO, the Bi-incorporated catalysts performed much better than the corresponding Bi-free catalysts, the Sr-substituted perovskites showed higher catalytic activities than the Ba-substituted ones; among La1−xSrxMO3−δ, La0.8Sr0.2MO2.90 exhibited the best catalytic activity. The improved catalytic performance due to the Sr (or Ba)- and Bi-doping is believed to be associated with the enhancements in oxygen vacancy density and Con+/Co(n+1)+ (n=2, 3) and Bi3+/Bi5+ couple redox ability as well as in lattice oxygen mobility. In the elimination of NO over La1−xSrxMO3−δ, La0.8Sr0.2MO2.90 performed the best. The 300℃-reduced La1.867Th0.100CuO4− catalyst that possessed dual cationic and anionic defects and Cu+/Cu2+ couple showed higher DeNO activity than the fresh one; the redox action between Cu+ and Cu2+ is an essential process for NO decomposition. In the decomposition of N2O, the 800 ◦C-treated Nd2−xA xCuO4−δ (A'x=Ba0.4, Ce0.2) and YBa2Cu3O7− samples were superior in catalytic performance to their fresh counterparts; oxygen vacancies were favorable for the formation of the crucial N2O2 2− intermediate species in N2O activation, and the redox Cup+/Cu(p+1)+ (p=1 and 2) couples involved in the N2O decomposition processes. The DeN2O activity over the Ce- or Ba-doped catalyst was much better than that over the undoped catalyst (Nd2CuO4−δ). This behavior is intimately related to the oxygen nonstoichiometry and copper ion redox properties. According to the outcome of our experiments, we conclude that there is a strong correlation either between the structural defect (mainly oxygen vacancies) and catalytic activity or between the redox [Con+/Co(n+1)+ (n=2, 3), Bi3+/Bi5+, and Cup+/Cu(p+1)+ (p=1 and 2) couples] ability and catalytic performance of these materials for CO and NOx removal. The generation of oxygen vacancies by A-site replacements favors the

The 30 mol% MO (MDMg, Ca, Sr, Ba)-, 30 mol% BaCO3-, and 30 mol% BaX2 (XDF, Cl, and Br)-promoted Y2O3 catalysts have been investigated for the oxidative dehydrogenation of ethane reaction. Adding BaO or BaX2 to Y2O3 could significantly enhance the C2H4 selectivity. We also found that the doping of BaX2 into Y2O3 could considerably reduce C2H4 deep oxidation. Among these catalysts, 30 mol% BaCl2/Y2O3 performed the best. It was stable within a reaction period of 40 h, giving aC2H6 conversion, aC2H4 selectivity, and a corresponding C2H4 yield of ca. 72, 74, and 53%, respectively, at 640±C and 6000 mL h-1g-1 space velocity. X-ray photoelectron spectroscopy and chemical analysis of halides indicated that the Cl- ions were uniformly distributed in 30 mol% BaCl2/Y2O3 whereas the halide ions in 30mol% BaF2/Y2O3 and 30 mol% BaBr2/Y2O3 were not. With the increase of space velocity, the C2H6 conversion decreased and the C2H4 selectivity increased at 640±C over the 30 mol% BaCl2/Y2O3 catalyst.We observed that Cl leaching was not significant in 30 mol% BaCl2/Y2O3. However, gradual Br leaching was observed over 30 mol% BaBr2/Y2O3. X-ray powder diffraction and CO2 temperature-programmed desorption (CO2-TPD) results demonstrated that the 30 mol% BaCl2/Y2O3 catalyst is durable and is resistant to CO2 poisoning whereas the 30mol% BaO/Y2O3 and BaX2 (XDF and Br)/Y2O3 catalysts are readily poisoned by CO2 due to BaCO3 formation. O2-TPD studies showed that the addition of BaO (or BaX2) toY2O3 could obviously enhance the adsorption of oxygen molecules.We consider that such enhancement is closely associated with the defects generated due to ionic exchanges between the BaO (or BaX2) and the Y2O3 phases. Among the three 30 mol% BaX2/Y2O3 catalysts calcined at 900℃, 30 mol% BaCl2/Y2O3 showed a cubic Y2O3 lattice most significantly enlarged and a BaX2 lattice most pronouncedly contracted. In situ laser raman results indicated that there were dioxygen adspecies such as O22-, O2n/2- (1<n<2), O- 2, and O2δ/2- (0<±<1) on the 30 mol% BaO/Y2O3 and 30mol% BaX2/Y2O3 catalysts. Electron paramagnetic resonance results indicated that there were monoxygen O¡ and dioxygen O2- species on Y2O3, 30 mol% BaO/Y2O3, and 30 mol% BaX2/Y2O3.We suggest that the O2- O2n/2-, O2δ/2-, and O2/2- species participate in the selective oxidation of ethane to ethene whereas the O- species were responsible for the deep oxidation of ethane.

The performance and characterization of the SrCl2-promoted REOx (REDCe, Pr, Tb) catalysts have been investigated for the oxidative dehydrogenation of ethane (ODE) reaction. The doping of SrCl2 to REOx significantly reduced C2H4 deep oxidation and enhanced C2H4 selectivity and C2H6 conversion. It has been shown that the catalytic performance increases in the order of 30mol% SrCl2/CeO2<30mol% SrCl2/Pr O1.83<40mol% SrCl2/TbO1.75.We observed that Cl leaching was modest in the latter two catalysts but gradual Cl loss was observed over the first catalyst. Within a reaction period of 60 h, the first catalyst degraded, whereas the latter two catalysts were stable. The C2H6 conversion, C2H4 selectivity, and C2H4 yield measured 1 h after the start of the ODE reaction were, respectively, 72.6, 68.8, and 49.9% for 30mol% SrCl2/CeO2, 79.1, 71.4, and 56.5% for 30mol% SrCl2/PrO1.83, and 82.6, 75.8, and 62.6% for 40mol% SrCl2/TbO1.75 at 660

The SrCl2-promoted Ln2O3 (LnDSm and Nd) catalysts have been investigated for the oxidative dehydrogenation of ethane (ODE) to ethene. With the doping of SrCl2 into Ln2O3, the C2H4 selectivity and C2H6 conversion were enhanced considerably. We also found that the addition of SrCl2 to Ln2O3 could markedly reduce the deep oxidation of C2H4. The 40 mol% SrCl2/Ln2O3 catalysts were stable for 60 h of on-stream ODE reaction. Under the reaction conditions of temperatureD640 C and space velocityD6000 ml h−1 g−1, 40 mol% SrCl2/Sm2O3 showed 80.3% C2H6 conversion, 70.9% C2H4 selectivity, and 56.9% C2H4 yield while 40 mol% SrCl2/Nd2O3 gave 63.8% C2H6 conversion, 74.3% C2H4 selectivity, and 47.4% C2H4 yield. X-ray photoelectron spectroscopic and chemical analysis of chloride indicated that the Cl-anions were evenly distributed in the 40 mol% SrCl2/Ln2O3 catalysts. We observed that Cl-leaching was insignificant. The results of temperature-programmed desorption of oxygen and temperature-programmed reduction studies demonstrated that the addition of SrCl2 to Ln2O3 enhanced the activation of oxygen molecules. We believe that such improvement is closely associated with the defects formed during the exchanges of ions between the SrCl2 and Ln2O3 phases. X-ray powder diffraction results revealed that the Ln2O3 lattices were enlarged, whereas the SrCl2 lattices contracted in the 40mol% SrCl2/Ln2O3 catalysts. In situ Raman results indicated that there were dioxygen adspecies such as O2 2−, O2 n- (1<n<2), O2−, and O2- (0<1) on the 40 mol% SrCl2/Ln2O3 catalysts. Electron paramagnetic resonance (EPR) results indicated that there were dioxygen O2- and mono-oxygen O− adspecies present on the SrCl2-doped catalysts. Based on the results of in situ Raman and EPR studies as well as the catalytic activity data, we suggest that the O2 2-, O2 n-, O2-, and O2-adspecies favor the selective oxidation of C2H6 to C2H4, whereas the O- adspecies is responsible for the deep oxidation of C2H6.