Thermochemische Beständigkeit von keramischen Membranen und Katalysatoren für die H$_{2}$-Abtrennung in CO-Shift-Reaktoren

The Watergas-shift reaction is a process for hydrogen production, which can be applied in IGCC power plants. One goal of current research is to find more energy efficient ways to separate the product gases after the shift and hydrogen permeable membranes appear to be a promising alternative. In cooperation with the IEK-1, several membrane and catalyst materials were tested for their thermochemical stability in gasification-related conditions. In the first part various barium zirkonates and lanthanum tungstate are exposed to gas atmospheres that simulate the gas compositions before and after the watergas-shift reaction. Powder samples were analyzed by powder diffraction and sintered samples by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Exposures were performed with and without adding impurities. The observed effects include carbonization for lower temperatures and specifically for the barium zirconates the formation of zirconium rich phases and barium chloride compounds. Additionally, a CO-shift reactor with a planar lanthanum tungstate membrane had been build. In the second part, activity tests have been performed with three iron based catalysts and molybdenum carbide in a temperature range of 200 °C – 900 °C. While the iron catalysts reduced to active phases, the molybdenum carbide gradually oxidized. In the next step the iron catalysts were tested in a temperature range of 400 °C – 900 °C while adding the contaminants H$_{2}$S, HCl, KCl and NaCl. The influence of HCl could be observed until 700 °C and up to 600 °C for H$_{2}$S. With KCl and NaCl contaminations however, next to no changes in the CO-conversion were observed. In the last part, tubular silica membranes were tested for stability in water steam, with H$_{2}$S- and HCl-contamination and under temperature cycling. The hydrogen selectivity decreased significantly when the H$_{2}$O-CO-ratio reaches 1. Adding H$_{2}$S or HCl contaminants did not yield a measureable influence. Higher temperatures did negatively influence the selectivity of the membrane