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.

Vanadium oxides supported on γ-Al2O3, SiO2, TiO2, and ZrO2 were studied on their molecular structures and reactive performances for soot combustion. To investigate the effect of different alkali metals on the structures and reactivities of supported-vanadium oxide catalysts, they were doped into the V4/TiO2 catalyst which had the best intrinsic activity for soot combustion in the selected supported vanadium oxide catalysts. The experimental results demonstrated that the catalytic properties of these catalysts depended on the vanadium loading amount, support nature, and the presence or the absence of alkali metals. The spectroscopic analysis (FT-IR and UV–vis) and H2-TPR results revealed that the higher activity of alkali-promoted vanadium oxide catalysts could be related to the ability of alkali metal promoting the redox cycle of the active vanadyl species. TG results showed that adding alkali to Vm/TiO2 catalyst was beneficial to lowering their melting points. Low melting points could ensure the good surface atom migration ability, which would improve the contact between the catalyst and soot. Due to the alkali metal components promoting the redox ability and the mobility of the catalysts, alkali-modified vanadium oxide catalysts could remarkably improve their catalytic activities for soot combustion. The catalytic activity order for soot combustion followed Li > Na > K > Rb > Cs in the catalyst system of alkali-V4/TiO2, and the reason why it followed this sequence was discussed.

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.

Several systems of vanadium oxide and K-promoted vanadium oxide catalysts which supported on different carries with the variations of V contents and K contents were prepared by incipient-wetness impregnation method. Their catalytic performances for diesel soot catalytic oxidation were investigated with temperature-programmed oxidation reaction (TPO). Spectroscopic techniques (FT-IR and UV–vis DRS) were utilized to determine the structure of VOx species for vanadia supported on γ-Al2O3, SiO2, TiO2, and ZrO2. Thermal analysis techniques, including thermogravimetrical (TG-DTA) analyses and temperature-programmed reduction (TPR), were used to characterize the thermal behavior and redox properties of K promoting vanadium oxide catalysts, respectively. The results showed that the structure of supportedvanadia catalysts depends on the support materials and also on the V loading. At high V loading, VOx species exists predominantly as polyvanadate species and V2O5. The catalytic activities of the catalysts for soot oxidation are correlated to their redox property and the mobility of surface atoms. The catalytic activity for soot oxidation orders as Ti > Zr > Si > Al, and the sequence for selectivity to CO2 formation (Sco2) is Ti > Zr > Si ~Al for the catalysts over different supports. Adding potassium into supported vanadia catalysts can improve the catalytic activity of soot oxidation. And when n(K):n(V):n(Ti) = 4:4:100 the catalyst of K4V4/TiO2 gives the best activity for soot combustion, i.e., the lowest reaction temperature.

A comparative study on the effects of alkali metal on the structures, physico-chemical properties and catalytic behaviors of silica-supported vanadium catalysts for the selective oxidation of ethane and the complete oxidation of diesel soot was reported.