SummaryThe removal of the surfactant (EO20PO70EO20) by washing before final calcination is a critical step in the synthesis of silica SBA-15. In contrast to washing with pure water or ethanol, washing with water and ethanol may, depending on the quantity of solvent used, alter the homogeneity and order of the pores, but also lead to an increase of the surface area of SBA-15. A reduction of solvent volume and a controlled washing protocol allow the synthesis of high surface area SBA-15 materials with a narrow monomodal pore size distribution. For larger batch sizes the influence of the quantity of solvent on the quality of the SBA-15 is reduced.

The structure of molybdenum oxide supported by silica SBA-15 has been studied by visible Raman spectroscopy, diffuse reflectance UV-Vis spectroscopy and X-ray absorption spectroscopy in the dehydrated state obtained after thermal treatment at elevated temperatures (≥350°C). No dependence of the molybdenum oxide structure on preparation procedure or loading has been observed within the range of loadings studied in detail (0.2 to 0.8 Mo/nm 2 ). X-ray absorption spectroscopy (XAS) reveals that the dehydrated state consists of a mixture of monomeric and connected molybdenum oxide centres. While the presence of crystalline MoO3 can be excluded by Raman spectroscopy, tetrahedrally and octahedrally coordinated MoO4 and MoO6 units are identified by XAS. The MoO6 units possess connectivity similar to that of MoO3 building blocks, whereas the MoO4 units are isolated or connected to other MoxOy units. These results are supported by UV-Vis spectra showing intensity at wavelengths (>300 nm) typical for dimeric and/or oligomeric species.

The CO2 methanation performance of a Ni catalyst supported on a Lewis basic (Mg,Al)Ox mixed oxide derived from a (Ni,Mg,Al)‐hydrotalcite‐like (HTL) precursor was investigated. The HTL structure of the precursor, synthesized by pH‐controlled coprecipitation, was confirmed by using XRD. Reduction at 900 °C led to metallic Ni particles supported on a spinel‐type (Mg,Al)Ox matrix. Catalytic measurements between 210 and 400 °C revealed a reproducible CO2 conversion into CH4. Kinetic analysis of the data in the lower temperature range resulted in an apparent activation energy of (83±7) kJ mol−1 for this reaction. After a latency period of 10 h, the catalyst showed excellent long‐term stability for up to 50 h on stream under methanation conditions.

The structure of silica SBA-15-supported molybdenum oxide catalysts is investigated during selective oxidation of propylene at 500 °C using operando Raman spectroscopy. The active catalysts contain mixtures of dispersed molybdenum oxide species exhibiting monooxo and dioxo structure. An increase in molybdenum oxide loading results in a decrease of the ratio of dioxo and monooxo species from 3.8 to 1.9, as determined by quantitative analysis of Raman spectra. Additional in situ Raman studies at 500 °C reveal that the dioxo/monooxo ratio increases in the presence of steam at higher molybdenum oxide loadings. The observed structural changes are assigned to shifts in the equilibrium between dioxo and monooxo species resulting from hydration/dehydration of the catalyst. This study demonstrates that the detailed structure of nanostructured molybdenum oxide catalysts depends on temperature, gas-phase composition, and molybdenum oxide loading.