Interest in energy storage technologies is still increasing in times of the excess of electricity that is generated by wind farms or solar plants. Solar electricity can be transformed to solar-hydrogen via water electrolysis. A crucial part of the energy storage technologies plays the efficient conversion of H 2 and CO 2 from renewable resources. Here, the process conditions for continuously catalytic hydrogenation of CO 2 to CH 3 OH under supercritical conditions over lab-synthesized Cu/ZnO/Al 2 O 3 catalysts were investigated. The impact of temperature (230 – 330 °C), residence time (0.5 - 2.2 s) at moderate pressure (150 bar) but even above the supercritical parameters of CO 2 showed a selective CO 2 hydrogenation. Higher H 2 concentrations, respectively higher H 2 :CO 2 -ratios (H 2 :CO 2 = 6), lead to an increased selectivity of CH 3 OH. A possible in situ phase separation of reaction products within the reactor due to the higher densities of the reaction mixture by the highered pressure could affect the kinectics and simplfy the down-stream processing. The combination of thermodynamic studies (phase separation phenomena) as well as the catalytic performance tests for the CO2 hydrogenation under supercritical conditions are discussed. Based on these data a process concept is presented.
Chemistry and Pharmacology
Process Engineering, Biotechnology, Nutrition Technology