Herstellung und Charakterisierung von keramik- und metallgestützten Membranschichten für die CO$_{2}$-Abtrennung in fossilen Kraftwerken

The separation of CO$_{2}$ in fossil fuel power plants has become a very important issue due to the contribution of this greenhouse gas to global warming. Thin microporous membranes are promising candidates for separating CO$_{2}$ from gas flow before being exhausted into the atmosphere. The membrane demands are good permeation and separation properties and high stability under operation conditions. Novel sol-gel derived materials composed of TiO$_{2}$/ZrO$_{2}$ and stabilized SiO$_{2}$ seem to be promising due to their good chemical stability and microporous character, especially for the separation of H$_{2}$ and CO$_{2}$. Metallic substrates should be preferred as membrane support because they exhibit practical advantages combining good mechanical stability and the benefit of facilitated joining. The present thesis deals with the development of sol-gel derived microporous membrane layers on ceramic and metallic supports for the separation of CO$_{2}$. In this context, the optimized preparation of high-quality membranes with TiO$_{2}$/ZrO$_{2}$ and Ni, Co, Zr, Ti doped SiO$_{2}$ top layers is presented. These multilayered membranes consist of a graded pore structure to provide a smooth transition of the pore size from the support to the functional layer. Due to the good surface properties, the ceramic substrates only need one interlayer, whereas the rough metallic substrates exhibiting larger pores require a total of three interlayers to obtain an enhanced surface quality. On both types of supports, crack-free functional layers with a thickness below 100 nm were deposited by dip-coating. The unsupported and supported sol-gel materials used for the top layers were investigated in terms of structural properties by thermal analysis, sorption measurements, X-ray diffraction and electron microscopy. Gas permeation tests with He, H$_{2}$, CO$_{2}$ und N$_{2}$ were carried out to determine the membrane performance with regard to permeation rates and separation properties. Ceramic supported stabilized SiO$_{2}$ membranes exhibit a 100 % separation of He and H$_{2}$ towards larger gas molecules such as CO$_{2}$ and N$_{2}$. This occurs when all the manufacturing steps which include sol preparation and layer deposition under cleanroom conditions are optimized. In contrast, the layers are not applicable for separation of CO$_{2}$ and N$_{2}$ by reason of very low or no flow rates. The microporous TiO$_{2}$/ZrO$_{2}$ functional layers show a lack of viable permeation and separation properties suggesting a low pore volume. The metal supported membranes with SiO$_{2}$ based functional layer demonstrate a selectivity of H$_{2}$/CO$_{2}$ up to 50 and exhibit a very good separation performance compared to similar membranes in literature. Ceramic supported SiO$_{2}$ based functional layers prepared by Rapid Thermal Processing (RTP) with a deposition and calcination time of one hour were investigated to reduce the membrane production time. Gas permeation results show a 100 % separation of H$_{2}$ towards CO$_{2}$ and N$_{2}$ confirming the excellent layer quality. The results are an important contribution to the optimized preparation of high-quality microporous membrane layers exhibiting a high potential for CO$_{2}$ separation in fossil fuel power plants. The successful layer deposition on metallic substrates and the significantly reduced heat treatment time by using RTP are a further step of development in membrane technology