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Abstract

In this thesis, ordered mesoporous carbons (OMCs) have been prepared using the hard-templating approach. Hexagonal and cubic OMCs of the CMK-n (n = 3,5,8,9) family with different textural parameters were synthesized through the nanocasting replication of ordered mesoporous silica (SBA-15 and KIT-6). In particular, the different structural characteristics of the volume-templated CMK-3 carbon and the surface-templated CMK-5 carbon were intensively investigated using low angle X-ray diffraction (XRD), nitrogen sorption analysis, high resolution transmission electron microscopy (HR-TEM) and high-resolution scanning electron microscopy (HR-SEM). Furthermore, XRD patterns of simulated CMK-3 and CMK-5 carbons were calculated and compared with experimentally obtained XRD patterns.
For practical application, the surface of porous carbons usually needs to be modified according to specific requirements. In this thesis a detailed study on surface and structure modification of OMCs via a liquid phase chemical oxidation approach using nitric acid (HNO₃) is discussed. The presence of oxygen containing functional groups on the carbon surface was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR) and X-ray photoelectron spectroscopy (XPS). As compard to CMK-5, CMK-3 and CMK-8 carbons are structurally more stable during the oxidation treatment.
The modified surfaces were then further reacted with different amine molecules via an organic reaction route. CMK-5-type OMCs have two pore systems differing from each other allowing the development of a bifunctional mesoporous carbon. In this thesis a possibility to modify the two different surfaces of CMK-5 carbons by a spatially controlled functionalization method is presented. OMCs were employed for the selective deposition of nanoparticles within the mesoporous pore system of confined nanospace in OMCs. CMK-5 carbons with high iron loadings of more than 12 wt% could be achieved with a single impregnation step. The current interest in the synthesis of such nanostructured materials is driven by their great potential for the development of supported catalysts with excellent performance.
Iron-based nanoparticles supported on OMCs and their C-SBA-15 composite materials were found to be an excellent catalyst for ammonia (NH₃) decomposition reaction, with the activity depending clearly on catalyst loading and reaction temperature. Complete ammonia decomposition was achieved at 700 °C with space velocities as high as 60000 cm³g_cat^-1h^-1.
Finally, Pd-based catalysts supported on various OMCs were investigated for the selective oxidation of alcohols. The partial oxidation of multifunctional organic compounds is important for the syntheses of many fine chemicals and pharmaceutical intermiates. In this thesis the influence of different carbon supports, as well as the influence of different preparation methods on the catalytic activity of the selective oxidation of cinnamyl alcohol were investigated. The best catalysts showed high selectivities (>97%) to the desired product cinnamaldehyde.