The catalytic performance and characterization of perovskitetype halo-oxide La1¡xSrxFeO3-δXσ (XDF, Cl) as well as La1-x SrxFeO3-δ(x=0-0.8) for the oxidative dehydrogenation of ethane (ODE) to ethene have been investigated. XRD results indicate that the catalysts had oxygen-deficient perovskite structures and TGA results demonstrated that the F-and Cl-doped perovskites were thermally stable. Under the reaction conditions of C2H6/O2/N2D 2/1/3.7, temperature=660℃C, and space velocityD6000 mL h¡1 g¡1, C2H6 conversion, C2H4 selectivity, and C2H4 yield were, respectively, 55.3, 45.1, and 24.9% over La0.6Sr0.4FeO3¡0.048; 76.8, 62.1, and 47.7% over La0.8Sr0.2FeO3¡0.103F0.216; and 84.4, 68.4, and 57.6% over La0.6Sr0.4FeO3¡0.103Cl0.164. Over the two halo-oxide catalysts, with an increase in space velocity, C2H6 conversion decreased, whereas C2H4 selectivity increased. Both La0.8Sr0.2FeO3-δ0.103F0.216 and La0.6Sr0.4FeO3-0.103Cl0.164 were durable within 40h of onstream ODE reaction. XPS results suggested that the presence of halide ions in the perovskite lattices promotes lattice oxygen mobility. It is apparent that the inclusion of For Cl-ions in La1¡xSrxFeO3-δ can reduce the deep oxidation of C2H4 and thus enhance C2H4 selectivity. Based on the results of O2-TPD and TPR studies, we suggest that the oxygen species that desorbed at temperatures ranging from 590 to 700℃ over the La0.8Sr0.2FeO3-0.103F0.216 and La0.6Sr0.4FeO3-0.103Cl0.164 catalysts are active for the selective oxidation of ethane to ethene.Byregulating the oxygen vacancy density and the oxidation states of B-site cations by implanting halide ions into oxygen vacancies in perovskite-type oxides (ABO3), one may obtain catalysts that are durable and selective for the ODE reaction.

The addition of BaBr2 (<70 mol%) to Ho2O3 could improve considerably both theC2H6 conversion andC2H4 selectivity of theODE (oxidative dehydrogenation of ethane) reaction. The use of BaO as a modifier was not suitable because the catalyst degraded rapidly due to BaCO3 formation. At 640℃, C2H6:O2:N2D2:1:4, and space velocity=6000mL h-1 g-1, C2H6 conversion of 70.6%, C2H4 selectivity of 80.2%, and C2H4 yield of 56.6% were observed over the 50 mol% BaBr2/Ho2O3 catalyst after a reaction time of 1 h.We conclude that the addition of BaBr2 to Ho2O3 can (i) enhance oxygen activation, (ii) protect a certain amount of active basic sites from CO2 poisoning, and (iii) suppress C2H4 deep oxidation. It is possible that the presence of Br¡ ions could have induced the formation of new active sites suitable for C2H4 generation. However, we observed continuous leaching of bromine during the ODE reaction, and the 50 mol% BaBr2/Ho2O3 catalyst gradually degenerated to a somewhat aged BaO/Ho2O3 catalyst. After 40 h of reaction, the C2H6 conversion, C2H4 selectivity, and C2H4 yield diminished to 51.8, 63.8, and 33.0%, respectively.

The catalytic performance and characterization of Ln1.85A0.15 CuO4–± and Ln1.85A0.15CuO4–±X¾ (LnDLa, Nd; ADSr, Ce; XDF, Cl) for the oxidative dehydrogenation of ethane (ODE) to ethene have been investigated. The hole-doped catalysts performed better than the electron-doped ones. Under the reaction conditions of temperature, 660±C; C2H6/O2/N2 molar ratio, 2/1/3.7; and contact time, 1.67£10¡4 h g mL¡1; La1.85Sr0.15CuO3.930Cl0.053 showed 82.8% C2H6 conversion, 73.2% C2H4 selectivity, and 60.6% C2H4 yield; Nd1.85Ce0.15CuO3.981F0.092 showed 72.1% C2H6 conversion, 61.8.0% C2H4 selectivity, and 44.6% C2H4 yield. The sustainable performance during a period of 60 h on-stream reaction at 660±C demonstrated that the F- and Cl-doped catalysts are durable. The results of X-ray powder diffraction indicated that the Sr-substituted cuprates were of T structure whereas the Ce-doped cuprates were of T0 structure. The results of X-ray photoelectron spectroscopic (XPS) studies revealed that there were Cu2C and Cu3C in the Sr-doped cuprate catalysts and CuC and Cu2C in the Ce-doped cuprate catalysts. The results of the XPS, thermogravimetric analysis (TGA), and 18O2-pulsing studies demonstrated that the incorporation of halide ions into the Ln1.85A0.15CuO4–± lattice promoted the activity of lattice oxygen. By comparing the results of XPS, TGA, and O2 temperature-programmed desorption with the catalytic performance of the catalysts, we conclude that (i) lattice O2¡ species at the surface are active for the selective oxidation of ethane; (ii) in excessive amount, O¡ species accommodated in oxygen vacancies are prone to induce the total oxidation of ethane; and (iii) a suitable Cu3C or CuC concentration and/or oxygen nonstoichiometry in Ln1.85A0.15CuO4-±X¾ are required for the best catalytic performance of the catalysts.

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.

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 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.

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 redox behaviors, oxygen mobilities, and oxygen storage capacities of Ce0.6Zr0.4O2 (CZ), Ce0.6Zr0.35Y0.05O2 (CZY), and 0.5 wt%M/CZY (M=Pd, Pt, Rh) as well as the three-way catalytic performance of the noble metal-loaded CZY materials have been investigated. It is observed that at a space velocity of 60,000 h−1 and in an atmosphere close to the theoretical air-to-fuel ratio (i.e., 14.6), the CZY-supported precious metal catalysts showed good threeway catalytic activity. X-ray diffraction investigations revealed that there are two phases (cubic Ce0.75Zr0.25O2, major; cubic ZrO1.87, minor) in CZ, CZY, and 0.5 wt% M/CZY. These materials are porous and large in surface area. According to the results of Ce 3d X-ray photoelectron spectroscopic studies, the doping of Y3+ ions into the CZ lattice would cause the concentrations of oxygen vacancies and Ce3+ ions to increase. The results of H2(or CO)-O2 titration and temperature-programmed reduction–reoxidation experiments indicate the presence of a reversible redox behavior of Ce4+/Ce3+ couples. The results of 18O/16O isotope exchange studies show that in the presence of oxygen vacancies and noble metals, the mobility of lattice oxygen on/in CZY is promoted. Based on the above outcomes, we suggest that by incorporating Y3+ ions into CZ and loading Pd, Pt, or Rh on CZY, one can enhance (i) lattice oxygen mobility, (ii) Ce3+ ion concentration, and (iii) oxygen uptake capacity of the CZY solid solution, generating a class of materials suitable for the catalytic conversion of automotive exhaust.

The perovskite-type oxides La1−xSrxMO3 (M=Co0.77Bi0.20Pd0.03) have been investigated for three-way catalytic performance and characterized by means of temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalysts exhibited good activity in CO elimination: La0.8Sr0.2MO3 showed ca. 100% CO conversion at 160◦C, 60 000 h−1, and λ=1.00. Under similar reaction conditions, the activity for C3H6 elimination decreased in the order of La0.2Sr0.8MO3>La0.8Sr0.2MO3>La0.4Sr0.6MO3>La0.6Sr0.4MO3>LaMO3, while the activity forNOelimination decreased in the order of La0.8Sr0.2MO3>La0.2Sr0.8MO3>La0.4Sr0.6MO3>La0.6Sr0.4MO3>LaMO3. With x<0.6, La1−xSrxMO3 were single-phase and hexagonal in structure; at x=0.6 and 0.8, they were cubic and there was a trace amount of the La2O3 phase. The results of TPD, TPR, and XPS studies revealed the coexistence of over-stoichiometric oxygen vacancies in La0.8Sr0.2MO3, a criterion for good three-way catalytic performance.

The oxidative dehydrogenation (ODH) of propane was investigated on vanadia dispersed on alumina containing a nominal polymolybdate monolayer (4.8 Mo/nm2). Dehydrogenation rates and selectivities on these catalysts were compared with those on vanadia domains dispersed on alumina. At a given vanadia surface density, ODH reaction rates per gram of catalyst were about 1.5-2 times greater on MoOx-coated Al2O3 than on pure Al2O3 supports. The higher activity of vanadia dispersed on MoOx -coated Al2O3 reflects the greater reducibility of VOx species as a result of the replacement of V-O-Al with V-O-Mo bonds. The MoOx interlayer also increased the alkene selectivity by inhibiting propane and propene combustion rates relative to ODH rates. This appears to reflect a smaller number of unselective V2O5 clusters when alkoxide precursors are used to disperse vanadia onMoOx/Al2O3 as compared to the use of metavanadate precursor to disperse vanadia on pure Al2O3. At 613K, the ratio of rate coefficients for propane combustion and propane ODH was three times smaller on MoOx /Al2O3 than on Al2O3 supports. The ratio of rate constants for propene combustion and propane ODH decreased by a similar factor.