Co3O4, NiCo2O4 and LaCo2O4 catalysts were synthesized by the citric acid-ligated method. These catalysts containing Co-oxide active components can largely lower the temperature of sool combustion under tight contact conditions. Under the conditions of loose contact NiCo2O4 cannot promote soot combustion, but LaCo2O4 can effectively promote soot combustion because the nanometric perovskite-type catalyst LaCoO3 produced in the LaCo2O4 sample.

The nanometric La2-xKxCuO4 oxide catalysts with K2NiF4-type structure were prepared by auto-combustion method using citric acid as a ligand and an adjusting agent of particle-size and morphology. The structures and physico-chemical properties of these perovskite-like oxides were examined by means of XRD, FT-IR, H2-TPR and chemical analysis. The catalytic activities for the simultaneous removal of soot and NOx were evaluated by a technique of the temperature-programmed oxidation reaction (TPO). In the La2-xKxCuO4 catalysts, the partial substitution of K for La at A-site leads to the increase of the concentrations of Cu3+ and oxygen vacancy. Thus, it enhances the catalytic activity for simultaneous removal of NOx and diesel soot, and the optimal substitution amount of potassium x is equal to 0.5 among these samples. T10, T50, T90 are 376, 438,487 ℃ and PN2 is 22%, respectively, for simultaneous removal of NOx and soot particulates over the La1.5K0.5CuO4 catalyst under loose contact conditions between the catalyst and soot.

The oxidation of ethane by oxygen was studied over silica catalysts supporting different amounts of vanadium with and without cesium. Three different catalytic properties of the product selectivity were observed, aldehyde formation, oxidative dehydrogenation (ODH), and combustion, depending upon the vanadium loading amount and the presence or the absence of cesium. A very low loading of vanadium (V:Si=0.02–0.1 at.%) and the addition of Cs (Cs:Si=1 at.%) on silica were found to be important for the formation of aldehyde. Not only acetaldehyde but also acrolein were observed in the aldehyde formation from ethane. On the other hand, catalysts with medium and high vanadium loadings (V:Si=0.5–20 at.%) gave a dehydrogenated product, ethene, when Cs was not added to the catalysts. The addition of cesium to the catalysts with medium and high vanadium loadings changed the catalytic property from ODH to combustion. The different types of vanadyl species were identified by UV–visible and IR measurements in samples with different vanadium loadings. It was estimated that isolated vanadyl species with tetrahedral coordination, which were found mainly on the catalysts with vanadium loading lower than 0.5 at.%, became the active site for the aldehyde formation through the interaction with Cs. As a plausible reaction path giving acrolein from ethane, cesium-catalyzed cross-condensation between acetaldehyde and formaldehyde, formed in the reaction, was proposed. Polymeric vanadyl species with octahedral coordination and vanadium–oxygen clusters with dioxo tetrahedral coordination were detected in the samples with medium (0.5–5.0 at.%) and high (10 and 20 at.%) vanadium loadings, respectively. Both species show the ODH catalytic property without cesium, but they bring about a deep oxidation of ethane if cesium is added to the catalysts.

Selective oxidation of ethane by oxygen was examined over silica catalysts supporting cesium and bismuth. Aldehydes of C1–C3 were obtained with total selectivity of about 40% at ethane conversion lower than 5%. The catalytic performance was strongly dependent upon the bismuth loading on the catalysts. The higher turn-over-rate and the higher selectivity to aldehydes were observed at the Bi loadings lower than 0.5%. Characterization of the catalysts showed that isolated or highly dispersed Bi on the catalyst surface was indispensable for the high aldehyde yield. Cesium also plays an important role for the high ethane reactivity and the high aldehyde selectivity. A reaction pathway was proposed in which ethane is oxidized into acetaldehyde, but not through ethylene, and acrolein is formed through a cross-condensation of acetaldehyde and formaldehyde.

Many samples containing different elements M in the system of M/SiO2 (M:Si=1:1000, molar ratio) or Cs/M/SiO2 (Cs : M : Si=10:1:1000, molar ratio) were prepared and screened for the oxidation of ethane by use of oxygen as oxidant. It has been found that the elementsM(M=V, Bi, In, Ga, P, Zr, Zn, La) can give good aldehyde yields in the Cs/M/SiO2 system. The promoting effects of different alkali metals (Li, Na, K, Rb, Cs) on the catalytic performance of V/SiO2 (V:Si=1:1000) in ethane oxidation were investigated. Among them, cesium gave the best promoting effect on V/SiO2 for aldehyde formation. The presence of alkali metals increases the basicity and neutralizes the acid site of catalyst; thus it enhances the selectivity to acetaldehyde and controls the formation of formaldehyde. Increase in basicity promotes the cross-aldol condensation of acetaldehyde and formaldehyde to give acrolein. The pathway for acrolein formation is mainly through the cross-aldol condensation of acetaldehyde and formaldehyde over Cs/V/SiO2 catalysts.